JP2000087806A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly match an EGR(Exhaust Gas Recirculation) rate with a desired EGR rate. SOLUTION: A first combustion that an EGR gas amount in a combustion chamber 5 is larger than an EGR gas amount that a soot generation amount is peaked and soot is hardly generated and a second combustion that the EGR gas amount in the combustion chamber 5 is smaller than the EGR gas amount that the soot generation amount is peaked, are selectively performed. When the first combustion is performed, the downstream pressure of a throttle valve 20 is controlled to a desired pressure that an EGR rate is set to a desired EGR rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

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

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

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

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

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

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

[0009]

However, under this new combustion, the amount of EGR gas has a great influence on the combustion,
Thus, there is an optimum EGR rate that enables good combustion for the operating state of the engine. Therefore, in order to ensure good combustion under this new combustion, it is necessary to control the EGR rate to an optimum EGR rate according to the operating state of the engine.

Since the EGR rate is expressed by EGR gas amount / (EGR gas amount + intake air amount) as described above,
If the R gas amount and the intake air amount are known, the EGR rate can be obtained. If the EGR rate can be obtained, the EGR rate can be obtained by controlling the EGR gas amount or the intake air amount, or controlling both the EGR gas amount and the intake air amount. Can be controlled to an optimal EGR rate according to the operating state of the engine.

However, in this case, it is difficult to detect the amount of EGR gas recirculated into the intake passage as a practical matter, and therefore, it is difficult to detect the amount of EGR gas by some other method.
It is necessary to control the R rate to an optimal EGR rate according to the operating state of the engine.

[0012]

SUMMARY OF THE INVENTION Therefore, in the first invention, in an internal combustion engine, when the amount of recirculated exhaust gas supplied into the combustion chamber is increased, the amount of soot generated gradually increases and reaches a peak. In addition to supplying recirculated exhaust gas into the intake passage, the amount of recirculated exhaust gas supplied to the combustion chamber is made larger than the amount of recirculated exhaust gas at which soot generation is peaked, and the intake air supplied to the combustion chamber. Intake air amount control means for controlling the amount to a predetermined amount of intake air according to the operating state of the engine, pressure detection means for detecting pressure in the intake passage, and exhaust based on the pressure in the intake passage. Recirculation exhaust gas amount control means for controlling the amount of recirculation exhaust gas so that the gas recirculation rate becomes the target exhaust gas recirculation rate.

That is, if the intake air amount or EGR gas amount decreases, the pressure in the intake passage decreases, whereas if the intake air amount or EGR gas amount increases, the pressure in the intake passage increases. That is, the pressure in the intake passage is determined by the sum of the intake air amount and the EGR gas amount. By the way, in the first invention, the intake air amount is controlled by the intake air amount control means to the predetermined intake air amount. Therefore, at this time, the EGR gas amount is determined by the predetermined EGR gas amount from the pressure in the intake passage. It can be determined whether or not there is, that is, whether or not the EGR rate has reached the target EGR rate.

In this case, if the pressure in the intake passage is lower than the pressure in the intake passage when the EGR rate is the target EGR rate, the EGR gas amount is insufficient. If the EGR gas amount is increased, the EGR rate becomes the target EGR rate. On the other hand, if the pressure in the intake passage is higher than the pressure in the intake passage when the EGR rate is the target EGR rate, the EGR gas amount is excessive. In this case, the EGR gas amount Is decreased, the EGR rate becomes the target EGR rate. That is, by controlling the EGR amount based on the pressure in the intake passage, the EGR rate is set to the target EG.
R rate can be controlled.

In the second invention, in the first invention,
Storage means for pre-storing a target pressure in the intake passage according to an engine operating state required for setting the exhaust gas recirculation rate to the target exhaust gas recirculation rate; The amount of recirculated exhaust gas is controlled so that the internal pressure becomes the target pressure. In the third invention, 2
In the second aspect, the recirculation exhaust gas amount control means includes an exhaust gas recirculation control valve disposed in an exhaust gas recirculation passage connecting the engine exhaust passage and the engine intake passage, and controlling the recirculation exhaust gas amount. The means controls the opening of the exhaust gas recirculation control valve so that the pressure in the intake passage becomes the target pressure.

In a fourth aspect, in the first aspect,
An intake air amount detecting means for detecting an intake air amount, and an air-fuel ratio control means for controlling an air-fuel ratio to a target air-fuel ratio according to an operating state of the engine based on the detected intake air amount. . In a fifth aspect based on the fourth aspect, there is provided a calculation means for calculating a fuel injection amount, wherein the air-fuel ratio control means sets a ratio between the detected intake air amount and the calculated fuel injection amount to be a target air-fuel ratio. Thus, the intake air amount is corrected.

In the sixth invention, in the fourth invention,
Air-fuel ratio detection means for detecting the air-fuel ratio is provided, and the air-fuel ratio control means corrects the intake air amount so that the detected air-fuel ratio becomes the target air-fuel ratio. In a seventh aspect based on the fourth aspect, the air-fuel ratio control means calculates a fuel injection amount necessary for setting the air-fuel ratio to the target air-fuel ratio based on the detected intake air amount.

In the eighth invention, in the first invention,
The intake air amount control means includes a throttle valve disposed in the engine intake passage, and the throttle valve is controlled so that the amount of intake air supplied into the combustion chamber becomes a predetermined amount of intake air according to the operating state of the engine. Is controlled. According to a ninth aspect, in the first aspect, a storage means for storing the injection timing is provided, and the injection timing is controlled based on the stored injection timing.

In a tenth aspect based on the ninth aspect, a combustion pressure detecting means for detecting a combustion pressure in the combustion chamber is provided, and the injection timing is controlled based on the combustion pressure. According to an eleventh aspect based on the first aspect, the vehicle further comprises a rotation speed control means for controlling the engine speed to the target idling speed during the engine idling operation.

In a twelfth aspect based on the eleventh aspect, the engine speed control means maintains the engine speed at the target idling speed by controlling the fuel injection amount. According to a thirteenth aspect, in the eleventh aspect, the rotation speed control means controls the intake air amount to maintain the engine rotation speed at the target idling rotation speed.

According to a fourteenth aspect, in the first aspect, the intake air amount control means includes a throttle valve disposed in the engine intake passage, and expands an inner wall surface of the intake passage around the throttle valve outward. As the throttle valve opens from the fully closed position, the flow path area between the valve element periphery of the throttle valve and the intake passage inner wall portion increases as the throttle valve opens from the fully closed position. The shape is such that it gradually increases.

According to a fifteenth aspect, in the first aspect, the exhaust gas recirculation rate is about 55% or more. In a sixteenth aspect based on the first aspect, a catalyst having an oxidizing function is disposed in the engine exhaust passage. 17
In 16 th invention in 27th aspect, the catalyst is an oxidation catalyst, consisting of one at least of the three-way catalyst or _the NO _x absorbent.

In an eighteenth aspect based on the first aspect, in the first aspect, the amount of recirculated exhaust gas supplied into the combustion chamber is larger than the amount of recirculated exhaust gas at which the generation amount of soot reaches a peak, and soot is hardly generated. A switching means is provided for selectively switching between combustion and second combustion in which the amount of recirculated exhaust gas supplied into the combustion chamber is smaller than the amount of recirculated gas at which the amount of soot generation reaches a peak.

In a nineteenth aspect based on the eighteenth aspect, the operating range of the engine is divided into a first operating range on the low load side and a second operating range on the high load side. Is performed, and the second combustion is performed in the second operation region.

[0025]

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

On the other hand, the exhaust port 10 is connected to the exhaust manifold 2.
The exhaust turbine 2 of the exhaust turbocharger 15 via the
3 and an outlet of the exhaust turbine 23 is connected via an exhaust pipe 24 to a catalytic converter 26 having a built-in catalyst 25 having an oxidizing function. Exhaust manifold 22
Inside, an air-fuel ratio sensor 27 is arranged. Exhaust pipe 28 connected to the outlet of catalytic converter 26 and throttle valve 2
The downstream of the air suction pipe 17 is connected to the air suction pipe 17 via an EGR passage 29, and a stepping motor 3
An EGR control valve 31 driven by zero is disposed. Further, E flowing through the EGR passage 29 is provided in the EGR passage 29.
An intercooler 32 for cooling the GR gas is provided. 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 lane 34. Fuel is supplied into the common lane 34 from a fuel pump 35 of an electrically controlled variable discharge amount, and the fuel supplied into the common lane 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 lane 34 is attached to the common lane 34 so that the fuel pressure in the common lane 34 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 36. The discharge amount of the fuel pump 35 is controlled.

The electronic control unit 40 is composed of a digital computer, and has a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a CPU (Microprocessor) 44, an input port 45, An output port 46 is provided. The output signal of the mass flow detector 21 is input to the input port 45 via the corresponding AD converter 47, and the output signals of the air-fuel ratio sensor 27 and the fuel pressure sensor 36 are also input to the input port via the corresponding AD converter 47, respectively. 45 is input. A combustion pressure sensor 36 for detecting a pressure in the combustion chamber 5 is disposed in the combustion chamber 5, and an output signal of the combustion pressure sensor 36 is connected to an input terminal I of a peak hold circuit 49. The output terminal O of the peak hold circuit 49 is input to the input port 4 via the corresponding AD converter 47.
A pressure sensor 3 for detecting the absolute pressure in the air suction pipe 17 is provided in the air suction pipe 17 downstream of the throttle valve 20.
The output signal of the pressure sensor 37 is input to the input port 45 via the corresponding AD converter 47.

A load sensor 51 for generating an output voltage proportional to the depression amount L of the accelerator pedal 50 is connected to the accelerator pedal 50, and the output voltage of the load sensor 51 is supplied to an input port via a corresponding AD converter 47. 45 is input. The input port 45 is connected to a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, by 30 °. Further, an output pulse of the vehicle speed sensor 53 representing the vehicle speed is input to the input port 45. On the other hand, the output port 46 is connected to the reset input terminal R of the fuel injection valve 6, the throttle valve control step motor 19, the EGR control valve control step motor 30, the fuel pump 35 and the peak hold circuit 49 via the corresponding drive circuit 48. Connected.

FIG. 2 is an enlarged view around the throttle valve 20. Referring to FIG. 2, the inner wall portion 17a of the air suction pipe 17 around the throttle valve 20, that is, the intake passage 38
The inner wall portion 17a of the intake passage 38 is bulged outward, and in the embodiment shown in FIG.
7a has an arc-shaped cross section. When the cross-sectional shape of the inner wall surface portion 17a of the intake passage 38 is formed in an arc shape as described above, compared to the case where the air suction pipe 17 has a cylindrical shape over the whole, the throttle valve 20 opens when the throttle valve 20 opens from the fully closed position. The flow passage area between the peripheral edge of the valve body of the valve 20 and the inner wall surface portion 17a gradually increases. In other words, the change in the flow path area with respect to the rotation angle of the throttle valve 20 is smaller than when the air suction pipe 17 is entirely cylindrical. As a result, minute control of the intake air amount by the throttle valve 20 becomes possible.

FIG. 3 shows another embodiment of the shape of the inner wall portion 17a of the intake passage 38. In this embodiment, the intake passage 38
Has a V-shaped cross section. Also in this embodiment, the change in the flow path area with respect to the rotation angle of the throttle valve 20 is smaller than in the case where the air suction pipe 17 has a cylindrical shape over the entirety.
It is possible to finely control the intake air amount by 0.

FIG. 4 shows the throttle valve 2 when the engine is under low load operation.
Change in the output torque when changing the air-fuel ratio A / F (abscissa in FIG. 4) by changing the opening and the EGR rate of 0, and smoke, HC, CO, a change in emission of the NO _x It shows the experimental example shown. As can be seen from FIG. 4, in this experimental example, the EGR rate increases as the air-fuel ratio A / F decreases, and when the air-fuel ratio is equal to or lower than the stoichiometric air-fuel ratio (≒ 14.6), the EGR rate is 65% or higher.

As shown in FIG. 4, when the air-fuel ratio A / F is reduced 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 O _x is considerably reduced. On the other hand, at this time, HC,
The amount of generated CO starts to increase.

FIG. 5 (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. 5 (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. 5 (A) and FIG. 5 (B), in the case of FIG. 5 (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
When the amount of smoke generation is almost zero at 5.0 or less, FIG.
As shown in ₍₁₎ , the generation amount of NOx is considerably reduced. N
That the generation amount of O _x produced falls means that the combustion temperature in the combustion chamber 5 is reduced, thus the combustion temperature in the combustion chamber 5 becomes low when the soot is hardly generated I can say. The same can be said from FIG. That is, in the state shown in FIG. 5B 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. 6 are thermally decomposed when the temperature is increased in a state of lack of oxygen to form a soot precursor, and then mainly, Soot consisting of a solid aggregate of carbon atoms is produced. In this case, the actual soot generation 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 generation amount of soot becomes almost zero, the emission amounts of HC and CO increase as shown in FIG. 4, but HC at this time is a soot precursor or a hydrocarbon in a state before it. .

Summarizing these considerations based on the experimental results shown in FIGS. 4 and 5, when the combustion temperature in the combustion chamber 5 is low, the amount of soot generation becomes almost zero. Is discharged from the combustion chamber 5. As a result of further detailed experimental study on this, if the temperature of the fuel and the surrounding gas in the combustion chamber 5 is lower than a certain temperature, the growth process of the soot is stopped halfway, that is, the soot is It was found that no soot was generated, and soot was generated when the temperature of the fuel and its surroundings in the combustion chamber 5 exceeded a certain temperature.

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

Once soot has been produced, it cannot be purified by post-treatment using a catalyst having an oxidizing function. On the other hand, the soot precursor or the hydrocarbon in a state before the soot can be easily purified by a post-treatment using a catalyst having an oxidation function. Considering the post-treatment with 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.

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

That is, if there is only air around the fuel, the evaporated fuel immediately reacts with oxygen in the air and burns. In this case, the temperature of the air separated from the fuel does not rise so much, and only the temperature around the fuel becomes extremely high locally. That is, at this time, 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 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, the endothermic effect becomes stronger as the specific heat of the inert gas increases, and 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. 7 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. 7, the 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. 7, when the EGR gas is cooled strongly, the amount of soot generation peaks when 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. 7, when the EGR gas is slightly cooled, the amount of soot generation peaks at a point where the EGR rate is slightly higher than 50%. In this case, the EGR rate is increased to about 65% or more. If so, almost no soot is generated.

As shown by the curve C in FIG.
When the R gas is not forcibly cooled, the EGR rate becomes 5
The soot generation amount peaks near 5%, and in this case, if the EGR rate is set to approximately 70% or more, soot is hardly generated. FIG. 7 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 is peaked slightly decreases, and the EGR rate at which soot is hardly generated is reduced. Also lowers slightly. 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. 8 shows a mixture of EGR gas and air necessary to make the temperature of fuel during combustion and the surrounding gas temperature lower than the temperature at which soot is generated when EGR gas is used as the inert gas. It shows the gas amount, the ratio of air in the mixed gas amount, and the ratio of EGR gas in the mixed gas. In FIG. 8, the vertical axis indicates the total intake gas amount drawn into the combustion chamber 5, and the dashed line Y indicates the total intake gas amount that can be drawn into the combustion chamber 5 when supercharging is not performed. ing. The horizontal axis indicates the required load.

Referring to FIG. 8, 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. 8, the ratio between the air amount and the injected fuel amount is the stoichiometric air-fuel ratio. On the other hand, in FIG. 8, the ratio of the EGR gas, that is, the amount of the EGR gas in the mixed gas is set so that when the injected fuel is burned, the temperature of the fuel and the surrounding gas is lower than the temperature at which soot is formed. The required minimum EGR gas amount is shown. This EGR gas amount is approximately 55% or more in terms of the EGR rate. In the embodiment shown in FIG.
0% or more. That is, the total intake gas amount sucked into the combustion chamber 5 is indicated by a solid line X in FIG. 8, and the ratio of the air amount to the EGR gas amount in the total intake gas amount X is shown in FIG.
When the ratio is as shown in the following, the temperature of the fuel and the surrounding gas is lower than the temperature at which soot is generated, and thus no soot is generated. Further, the NO _x generation amount at this time is around 10 p.pm or less.
The amount of O _x generated is extremely small.

When the fuel injection amount increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the surrounding gas at a temperature lower than the temperature at which the soot is generated, the heat generated by the EGR gas is required. Must be increased. Therefore, as shown in FIG. 8, 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 supercharging is not performed, fuel
The upper limit of the total intake gas amount X sucked into the firing chamber 5 is Y.
Therefore, in FIG.₀Territory larger than
In the region, the EGR gas ratio increases as the required load increases.
The air-fuel ratio can be maintained at the stoichiometric air-fuel ratio unless reduced.
Can not. In other words, it is necessary when there is no supercharging.
Load demand is L₀Air-fuel ratio in the larger area than theoretical
When trying to maintain the fuel ratio, the required load increases.
As a result, the EGR rate decreases, and thus the required load becomes L ₀Than
In areas where the fuel and the surrounding gas temperature are
It will not be possible to maintain a temperature lower than the temperature produced. When
As shown in FIG.
Air suction of the inlet side of the feeder, that is, the exhaust turbocharger 15
When the EGR gas is recirculated in the pipe 17, the required load becomes L₀
EGR rate of 55% or less in the larger area
Above, for example, 70%.
The temperature of the fuel and its surrounding gas to the temperature at which soot is produced.
It can be maintained at a lower temperature. That is, air
The EGR rate in the suction pipe 17 is, for example, 70%
If the EGR gas is recirculated so that
Suction by the compressor 16 of the charger 15
The EGR rate of the gas is also 70%, thus
The fuel and its
Ambient gas temperature lower than that generated by soot
Can be maintained. Thus causing low temperature combustion
The operating area of the engine
And Required load is L₀EGR rate in a region larger than
Is set to 55% or more, the EGR control valve 31
Fully opened, throttle valve 20 slightly closed
Can be

As described above, FIG. 8 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. 10p.p. the generation amount of the NO _x even while preventing generation of soot by
m or less, and even if the air amount is larger than the air amount shown in FIG. 8, that is, even if the average value of the air-fuel ratio is lean from 17 to 18, the generation of soot is prevented. while the generation amount of the NO _x can be around or less 10 ppm.

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

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

By the way, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber can be suppressed to a temperature lower than the temperature at which the growth of hydrocarbons is stopped halfway, only when the engine is operating at low load and the calorific value due to combustion is relatively small. Can be Therefore, in the embodiment according to the present invention, the first combustion, that is, the low-temperature combustion is performed by suppressing the temperature of the fuel during combustion and the gas temperature around the same at or below the temperature at which the growth of hydrocarbons stops halfway during the low load operation in the engine. In addition, the second combustion, that is, the combustion that is usually performed conventionally, is performed during the high load operation of the engine. Here, the first combustion, that is, the low-temperature combustion, has a larger amount of the inert gas in the combustion chamber than the amount of the inert gas at which the soot generation amount is at a peak, as is clear from the description so far. The second combustion, that is, the combustion that has been 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. 9 shows a first operation region I in which the first combustion, that is, low-temperature combustion is performed, and a second combustion region II in which the second combustion, that is, combustion by the conventional combustion method, is performed. I have. In FIG. 9, the vertical axis TQ indicates the required torque, and the horizontal axis N indicates the engine speed. In FIG. 9, X (N) indicates a first operation region I and a second operation region II.
, And Y (N) indicates a second boundary between the first operation region I and the second operation region II.
The determination of the change of the operating region from the first operating region I to the second operating region II is made based on the first boundary X (N),
Of the operating range from the operating range II to the first operating range I is determined based on the second boundary Y (N).

That is, when the operating state of the engine is in the first operating region I
The required torque TQ when low-temperature combustion is being performed
Exceeds the first boundary X (N) which is a function of the engine speed N, it is determined that the operating region has shifted to the second operating region II,
Combustion is performed by a conventional combustion method. Next, a second boundary Y (N) in which the required torque TQ is a function of the engine speed N
If it becomes lower than this, 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 torque 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 torque side of the second operating region II, and at this time, the required torque TQ
This is because even if the temperature becomes lower than (N), low-temperature combustion cannot be performed immediately. That is, the low-temperature combustion does not immediately start unless the required torque TQ becomes considerably low, that is, when the required torque TQ becomes lower than the second boundary Y (N). The second reason is that the first operating region I and the second operating region II
This is because hysteresis is provided for a change in the operating region during the period.

By the way, when the operating state of the engine is in the first operating region I and low-temperature combustion is being carried out, soot is hardly generated, but the unburned hydrocarbon is replaced with the precursor of soot or the state before it. It is discharged from the combustion chamber 5 in the form. At this time, the unburned hydrocarbon discharged from the combustion chamber 5 is oxidized well by the catalyst 25 having an oxidizing function. Catalyst 2
As 5, an oxidation catalyst, a three-way catalyst, or a NO _x absorbent can be used. _The NO _x absorbent absorbs NO _x when the mean air-fuel ratio in the combustion chamber 5 of the lean, the combustion chamber 5
The average air-fuel ratio in the internal has a function of releasing NO _x becomes rich.

This NO _x absorbent uses, for example, alumina as a carrier and, for example, potassium K, sodium N
a, lithium Li, at least one selected from alkali metals such as cesium Cs, alkaline earths such as barium Ba and calcium Ca, rare earths such as lanthanum La and yttrium Y, and noble metals such as platinum Pt. Is carried.

In addition to the oxidation catalyst, the three-way catalyst and the NO
_{The x} absorbent also has an oxidizing function, so that a three-way catalyst and a NO _x absorbent can be used as the catalyst 25 as described above. FIG. 10 shows the output of the air-fuel ratio sensor 27. As shown in FIG. 10, 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, with reference to FIG.
The operation control in the second operation region II will be schematically described. FIG. 11 shows the opening of the throttle valve 20, the opening of the EGR control valve 31, and the EGR with respect to the required torque TQ.
The ratio, the air-fuel ratio, the injection timing, and the injection amount are shown. FIG.
As shown in FIG. 1, in the first operating region I where the required torque TQ is low, the opening of the throttle valve 20 is gradually increased from almost fully closed to about 2/3 as the required load L increases, and EGR is performed. The opening of the control valve 31 is gradually increased from near full closure to full opening as the required load L increases. In the example shown in FIG. 11, in the first operation region I, the EGR rate is approximately 70%, and the air-fuel ratio is a slightly lean air-fuel ratio.

In other words, in the first operation 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. At this time, the air-fuel ratio is controlled to the target lean air-fuel ratio by correcting the opening of the EGR control valve 31 based on the output signal of the air-fuel ratio sensor 27. In the first operation region I, fuel injection is performed before the compression top dead center TDC. In this case, the injection start timing θS is delayed as the required load L is increased, and the injection completion timing θE is delayed as the injection start timing θS is delayed.

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

On the other hand, when the operating state of the engine is in 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. 11, 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. 7).
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 second combustion, that is, the conventional combustion is performed. In this combustion method generates little soot and NO _x, but the heat efficiency is higher than the low temperature combustion, thus as the operating region of the engine is shown in Figure 11 from the first operation area I changes to the second operating region II Thus, the injection amount is reduced stepwise. In the second operation 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 equal to the required torque TQ.
Are gradually reduced as they become higher. In addition, this operating area
In II, the EGR rate decreases as the required torque TQ increases, and the air-fuel ratio decreases as the required torque TQ increases. However, the air-fuel ratio is a lean air-fuel ratio even when the required torque TQ increases. In the second operation region II, the injection start timing θS is set near the compression top dead center TDC.

FIG. 12A shows the relationship between the required torque TQ, the depression amount L of the accelerator pedal 50, and the engine speed N. In FIG. 12 (A), each curve represents an equal torque curve, a curve indicated by TQ = 0 indicates that the torque is zero, and the remaining curves are represented by TQ =
The required torque gradually increases in the order of a, TQ = b, TQ = c, and TQ = d. Required torque T shown in FIG.
Q is an accelerator pedal 50 as shown in FIG.
Is stored in the ROM 42 in advance in the form of a map as a function of the depression amount L and the engine speed N. In the embodiment according to the present invention, the accelerator pedal 5 is obtained from the map shown in FIG.
First, a required torque TQ corresponding to the depression amount L of 0 and the engine speed N is calculated, and the fuel injection amount and the like are calculated based on the required torque TQ.

FIG. 13 shows the air-fuel ratio A / F in the first operating region I. In FIG. 13, A / F = 15.
The curves indicated by 5, A / F = 16, A / F = 17, and A / F = 18 have air-fuel ratios of 15.5, 16, 17, and 18, respectively.
And the air-fuel ratio between the curves is determined by proportional distribution. As shown in FIG. 13, the air-fuel ratio is lean in the first operation region I, and in the first operation region I, as the required torque TQ decreases, the air-fuel ratio A /
F is made lean.

That is, the lower the required torque TQ, the smaller the amount of heat generated by combustion. Therefore, as the required torque TQ decreases, low-temperature combustion can be performed even if the EGR rate is reduced. As the EGR rate decreases, the air-fuel ratio increases,
Therefore, as shown in FIG. 13, as the required torque TQ decreases, the air-fuel ratio A / F increases. Air / fuel ratio A / F
As the fuel torque increases, the air-fuel ratio A / F increases as the required torque TQ decreases in order to make the air-fuel ratio as lean as possible.

FIG. 14A shows the injection amount Q in the first operation region I, and FIG.
Indicates the reference injection start timing θS in FIG. FIG.
As shown in FIG. 1A, the injection amount Q in the first operating region I is stored in the ROM 42 in advance in the form of a map as a function of the required torque TQ and the engine speed N.
As shown in FIG. 4 (B), the reference injection start timing θS in the first operation region I is also stored in the ROM 42 in advance in the form of a map as a function of the required torque TQ and the engine speed N.

The throttle valve 20 required to set the air-fuel ratio to the target air-fuel ratio A / F according to the operating state of the engine shown in FIG. 13 and to set the EGR rate to the target EGR rate according to the operating state of the engine. The target opening ST is stored in advance in the ROM 42 in the form of a map as a function of the required torque TQ and the engine speed N as shown in FIG. The target air-fuel ratio A /
F and the EGR rate is the target EG corresponding to the operating state of the engine.
The target opening SE of the EGR control valve 31 required for setting the R rate
As a function of the required torque TQ and the engine speed N as shown in FIG.
Is stored within.

Further, in the present invention, the air-fuel ratio is set to the target air-fuel ratio A / F shown in FIG.
The pressure PM in the air suction pipe 17 downstream of the throttle valve 20 when the rate is set to a target EGR rate according to the operating state of the engine
0 as a function of the required torque TQ and the engine speed N as shown in FIG.
2 is stored.

FIG. 16 shows the target air-fuel ratio when the second combustion, that is, the normal combustion by the conventional combustion method is performed. In FIG. 16, A / F = 24 and A / F = 3.
Curves indicated by 5, A / F = 45 and A / F = 60 indicate target air-fuel ratios 24, 35, 45, and 60, respectively. FIG. 17A shows the injection amount Q in the second operation region II, and FIG. 17B shows the injection start timing θS in the second operation region II. As shown in FIG. 17A, the injection amount Q in the second operation region II is equal to the required torque T
Q in advance in the form of a map as a function of
The injection start timing θS in the second operating region II is also stored in the ROM 42 in advance as a function of the required torque TQ and the engine speed N as shown in FIG. Have been.

The target opening degree ST of the throttle valve 20 required for setting the air-fuel ratio to the target air-fuel ratio shown in FIG.
As shown in FIG. 8 (A), a map is stored in the ROM 42 in advance as a function of the required torque TQ and the engine speed N, and the EGR necessary for setting the air-fuel ratio to the target air-fuel ratio shown in FIG. The target opening degree SE of the control valve 31 is shown in FIG.
As shown in (B), it is stored in the ROM 42 in advance in the form of a map as a function of the required torque TQ and the engine speed N.

In the first operating region I, the injection amount is set to the injection amount Q calculated from the map shown in FIG. 14A, and the opening of the throttle valve 20 is set to the target opening shown in FIG. ST, and the opening degree of the EGR control valve 31 is shown in FIG.
Assuming the target opening SE shown in FIG.
And the EGR rate is the target EGR corresponding to the required torque TQ and the engine speed N at that time.
Rate. In addition, the injection amount Q shown in FIG.
In this state, the air-fuel ratio becomes the target air-fuel ratio A / F shown in FIG.
At this time, the intake air amount is a target intake air amount according to the required torque TQ and the engine speed N at this time. At this time, the EGR gas amount is also a target EGR gas amount according to the required torque TQ and the engine speed N at this time.

By the way, the pressure in the air suction pipe 17 downstream of the throttle valve 20 is reduced by the air suction pipe 1 downstream of the throttle valve 20.
7 is determined by the amount of intake air flowing into the chamber 7 and the amount of EGR gas. Therefore, as described above, when the intake air amount and the EGR gas amount have respectively reached the target values, the pressure in the air suction pipe 17 downstream of the throttle valve 20 has a pressure corresponding to these target values. It matches the target pressure PM0 shown in FIG. 15C according to the required torque TQ and the engine speed N.

However, in practice, variations in the dimensions of parts, aging, the throttle valve 19 or the EGR control valve 3
Even if the injection amount, the opening of the throttle valve 20 and the opening of the EGR control valve 31 are determined based on the corresponding map due to the clogging of 1, the air-fuel ratio does not exactly match the air-fuel ratio shown in FIG. The rate deviates from the target EGR rate. Therefore, in the first embodiment according to the present invention, the target intake air amount necessary for setting the air-fuel ratio to the target air-fuel ratio A / F from the target injection amount Q is calculated, and the mass of the intake air detected by the mass flow rate detector 21 is calculated. The opening of the throttle valve 20 is corrected so that the flow rate (hereinafter, simply referred to as the intake air amount) becomes the target intake air amount, whereby the air-fuel ratio accurately matches the target air-fuel ratio.

As described above, in the first embodiment, the air-fuel ratio is made to exactly match the target air-fuel ratio, that is, the intake air amount is made to exactly match the target intake air amount. If it matches the EGR gas amount, the pressure in the air suction pipe 17 downstream of the throttle valve 20 will match the target pressure PM0 shown in FIG. In other words, at this time, if the pressure in the air suction pipe 17 downstream of the throttle valve 20 deviates from the target pressure PM0 shown in FIG.
It does not match the GR gas amount, and thus the EGR rate does not match the target EGR rate.

Therefore, in the embodiment according to the present invention, the pressure downstream of the throttle valve 20 is reduced to the target pressure P shown in FIG.
If it is deviated from M0, EG is adjusted so that the pressure downstream of the throttle valve 20 becomes the target pressure shown in FIG.
The opening degree of the R control valve 31 is controlled so that the EGR rate matches the target EGR rate. Also, the first
In the embodiment, the engine speed is controlled so that the engine speed becomes the target idling speed during the engine idling operation. In the first embodiment, the control of the engine speed is performed by controlling the fuel injection amount. Even in this case, the air-fuel ratio is controlled to be the target air-fuel ratio. Also,
The opening of the EGR control valve 31 is controlled so that the pressure in the air suction pipe 17 downstream of the throttle valve 20 becomes the target pressure,
Thus, the EGR rate is controlled so as to become the target EGR rate.

In this case, maintaining the pressure in the air suction pipe 17 downstream of the throttle valve 20 at the target pressure has two meanings. One is to ensure good low-temperature combustion by controlling the EGR rate to the target EGR rate. The other is to suppress the vibration of the engine body 1 by keeping the pressure in the combustion chamber 5 at the start of compression low. Next, the operation control will be described with reference to FIG.

Referring to FIG. 19, first, in step 100, 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 region of the engine is the first operating region I, step 1
In step 01, it is determined whether the required load L has become larger than the first boundary X1 (N). When L ≦ X1 (N), the routine proceeds to step 103, where the operation control I for executing the first combustion is performed. A routine for executing the operation control I is shown in FIGS. 20 and 21.

On the other hand, in step 101, L> X
When it is determined that (N) has been reached, the routine proceeds to step 102, where the flag I is reset.
The operation control II for executing the second combustion is performed. A routine for executing the operation control II is shown in FIG.
2 is shown. When the flag I is reset, in the next processing cycle, the process proceeds from step 100 to step 104, where it is determined whether or not the required load L has become lower than the second boundary Y (N). When L ≧ Y (N), the routine proceeds to step 106, where the second combustion is performed. On the other hand, when it is determined in step 104 that L <Y (N), the routine proceeds to step 105, where the flag I is set, and then proceeds to step 103 to perform low-temperature combustion.

Next, the operation control I for executing low-temperature combustion will be described with reference to FIG. Referring to FIG. 20, first, in step 200, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 15A, and then in step 201, the target opening ST of the EGR control valve 31 is calculated from the map shown in FIG. The target opening SE is calculated. Next, at step 202, the injection amount Q is calculated from the map shown in FIG. Next, step 203
Then, it is determined whether or not the engine is idling. For example, when the depression amount of the accelerator pedal 50 is zero and the vehicle speed is zero, it is determined that the engine is idling.

When the engine is not idling, the routine jumps to step 208 to jump to the target air-fuel ratio t shown in FIG.
(A / F) is calculated. Next, at step 209, a target intake air amount tGa required for setting the air-fuel ratio to the target air-fuel ratio t (A / F) is calculated based on the injection amount Q and the target air-fuel ratio t (A / F). Next, at step 210, the actual intake air amount G detected by the mass flow
a is taken. Next, at step 211, it is determined whether or not the actual intake air amount Ga is larger than the target intake air amount tGa.

When Ga> tGa, the routine proceeds to step 212, where a constant value a is subtracted from the correction amount ΔST for the throttle valve opening, and then the routine proceeds to step 214. On the other hand, when Ga ≦ tGa, the routine proceeds to step 213, where a constant value a is added to the correction amount ΔST.
Proceed to 14. In step 214, a value obtained by adding the correction value ΔST to the target opening degree ST of the throttle valve 20 (= ST + ΔS
T) is the final opening degree ST of the throttle valve 20.
Therefore, when Ga> tGa, the opening of the throttle valve 20 is decreased, and when Ga ≦ tGa, the opening of the throttle valve 20 is increased, whereby the actual intake air amount Ga is set to the target intake air amount tGa. The air-fuel ratio is set to the target air-fuel ratio t (A / F).

In step 215, the target pressure PM0 in the air suction pipe 17 downstream of the throttle valve 20 is calculated from the map shown in FIG. Next, at step 216, it is determined whether the pressure PM in the air suction pipe 17 detected by the pressure sensor 37 is higher than the target pressure PM0. When PM> PM0, the routine proceeds to step 217, where E
The constant value b is subtracted from the correction value ΔSE for the GR control valve 31, and then the routine proceeds to step 219. In contrast, P
If M ≦ PM0, the routine proceeds to step 218, where the correction value Δ
The constant value b is added to SE, and the process proceeds to step 219.

At step 219, a value obtained by adding the correction value ΔSE to the target opening degree SE of the EGR control valve 31 (= SE + ΔS
E) is the final opening degree SE of the EGR control valve 31.
Therefore, when PM> PM0, the opening of the EGR control valve 31 is decreased, and when PM ≦ PM0, the opening of the EGR control valve 31 is increased, whereby the EGR rate is set to the target EGR rate. Next, the routine proceeds to an injection timing control routine shown in FIG.

On the other hand, if it is determined in step 203 that the engine is idling, step 20 is executed.
4 and the engine speed N becomes the target idling speed N _0.
Is determined. N> when the N ₀ is a constant value C is subtracted from the correction value ΔQ for the injection amount proceeds to step 205, then the routine proceeds to step 207. On the other hand, when N ≦ N _0, the routine proceeds to step 206, where a fixed value C is added to the correction value ΔQ.
Proceed to.

In step 207, a value (= Q + ΔQ) obtained by adding the correction value ΔQ to the injection amount Q calculated from the map is set as the final injection amount Q. Therefore, when N> N ₀ , the injection amount is decreased, and when N ≦ N ₀ , the injection amount is increased, whereby the engine speed N is set to the target idling speed N ₀ . Next, in steps 208 to 214, the intake air amount is set to the target intake air amount and the air-fuel ratio is set to the target air-fuel ratio t (A / F).
Next, in steps 216 to 219, the pressure PM downstream of the throttle valve 20 is set to the target pressure PM0. At this time, the EGR rate becomes the target EGR rate.

Next, before describing the injection timing control routine shown in FIG. 25, a method of controlling the injection timing will be described with reference to FIG. In the embodiment according to the present invention, whether or not good low-temperature combustion is being performed is determined based on the pressure in the combustion chamber 5 detected by the combustion pressure sensor 36. That is,
When good low-temperature combustion is being performed, the combustion pressure changes slowly as shown in FIG. Specifically, the combustion pressure once peaks at the top dead center TDC as indicated by P ₀ , and then peaks again after the top dead center TDC as indicated by P ₁ . Peak pressure P ₁ is caused by the combustion pressure, good amount of increase in peak pressure P ₁ to the peak pressure P ₀ when the low temperature combustion is being performed, i.e., the peak pressure P ₀ and the differential pressure ΔP between the peak pressure P ₁ (= P ₁ -P
₀ ) is relatively small.

On the other hand, for example, a region where the density of the fuel particles is high is locally formed, and as a result, the combustion temperature increases as the pressure rise after ignition increases. At this time, low-temperature combustion is no longer performed, and thus a large amount of soot is generated. Therefore, in the embodiment according to the present invention, the differential pressure ΔP (= P
_{When (1−} P ₀ ) exceeds a predetermined upper limit α, the injection timing is delayed so that the differential pressure ΔP decreases.

As shown in FIG. 23A, the upper limit α decreases as the required torque TQ increases.
As shown in (B), the upper limit α decreases as the engine speed N increases. The upper limit value α is stored in the ROM 42 in advance in the form of a map as a function of the required torque TQ and the engine speed N as shown in FIG.

If good low-temperature combustion is not performed and combustion failure occurs, the peak pressure P ₁ becomes lower than the peak pressure P ₀ . Therefore, in the embodiment according to the present invention, the differential pressure ΔP (= P ₁ −
When P ₀ ) becomes negative, the injection timing is advanced so that good low-temperature combustion is performed. Next, a method of detecting the differential pressure ΔP will be described with reference to FIGS. FIG. 24 shows a crank angle interrupt routine.
First, in step 300, the current crank angle is C
A1 (FIG. 22) is determined. When the crank angle is CA1, the routine proceeds to step 301, where the output voltage of the peak hold circuit 49 is read. At this time, the output voltage of the peak hold circuit 49 indicates the peak pressure P ₀ , and therefore, in step 301, the peak pressure P ₀ is read. Next, at step 302, a reset signal is input to the reset input terminal R of the peak hold circuit 49, whereby the peak hold circuit 49 is reset.

Next, at step 303, it is determined whether or not the current crank angle is CA2 (FIG. 22). When the crank angle is CA2, the routine proceeds to step 304, where the output voltage of the peak hold circuit 49 is read. At this time, the output voltage of the peak hold circuit 49 indicates the peak pressure P ₁ , and therefore, in step 304, the peak pressure P ₁ is read. Next, at step 305, a reset signal is input to the reset input terminal R of the peak hold circuit 49, whereby the peak hold circuit 49 is reset. Next, at step 306, the pressure difference ΔP (= P ₁ −P ₀ ) between the peak pressure P ₀ and the peak pressure P ₁ is calculated.

Next, the injection timing control routine shown in FIG. 25 will be described. Referring to FIG. 25, first, at step 400, the reference injection start timing θS is calculated from the map shown in FIG. 14B. Then step 40
At 1, it is determined whether or not the differential pressure ΔP (= P ₁ −P ₀ ) is greater than zero. When ΔP ≧ 0, the routine proceeds to step 406, where the upper limit value α is calculated from the map shown in FIG. Next, at step 407, it is determined whether or not the differential pressure ΔP is smaller than the upper limit α. When ΔP <α, the processing cycle is completed. That is, when 0 ≦ ΔP <α, the processing cycle is completed.

On the other hand, if it is determined at step 407 that ΔP ≧ α, the routine proceeds to step 408, where a constant value e is added to the correction value Δθ for the reference injection start timing θS. Next, at step 409, the correction value Δθ is subtracted from the reference injection start timing θS, whereby the injection start timing θ
S is slowed down. Next, at step 410, the allowable maximum retard timing θ _min is calculated. This allowable maximum retard timing θ
_{The min} is stored in advance in the ROM 42 as a function of the required torque TQ and the engine speed N as shown in FIG. Then whether step 411, the injection start timing θS becomes later than the allowable maximum retard timing theta _{mi n,} i.e. theta
It is determined whether or not S <θ _min . complete the processing cycle if θS ≧ θ _min. On the other hand, θS <θ
_{When it reaches min} , the routine proceeds to step 412, where the injection start timing θS
Is the maximum allowable retardation timing θ _min .

On the other hand, if it is determined in step 401 that the differential pressure ΔP is negative, the routine proceeds to step 402, where a fixed value e is subtracted from the correction value Δθ. Next, step 403
Then, the correction value Δθ is subtracted from the reference injection start timing θS,
At this time, the injection start timing θS is advanced. Next, at step 404, it is determined whether or not the correction value Δθ is larger than zero. When Δθ ≧ 0, the processing cycle is completed.
On the other hand, if ΔQ <0, the routine proceeds to step 405, where the injection start timing θS is set to the reference injection start timing obtained from the map of FIG.

In order to perform low temperature combustion, the throttle valve 2
When the differential pressure ΔP becomes larger than the upper limit α when the opening degree of the EGR control valve 31 and the opening degree of the EGR control valve 31 are controlled, the injection start timing is gradually delayed. Is gradually advanced. Thereby, good low-temperature combustion can always be performed. Next, referring to FIG.
The routine of the operation control II for executing the second combustion performed in step 106 will be described.

Referring to FIG. 27, first, at step 5
At 00, the target fuel injection amount Q is calculated from the map shown in FIG.
It is said. Next, at step 501, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. Next, at step 502, the target opening degree SE of the EGR control valve 31 is calculated from the map shown in FIG.
The opening of the EGR control valve 31 is set as the target opening SE.

Next, at step 503, the intake air amount Ga detected by the mass flow detector 21 is taken. Next, at step 504, the fuel injection amount Q and the intake air amount Ga
Is used to calculate the actual air-fuel ratio A / F. Next, at step 605, the target air-fuel ratio t (A / F) shown in FIG. 16 is calculated. Next, at step 606, the actual air-fuel ratio A / F
Is larger than the target air-fuel ratio t (A / F). When A / F> t (A / F), step 507 is executed.
Then, the correction value ΔST of the throttle opening is decreased by the constant value α, and then the routine proceeds to step 509. On the other hand, when A / F ≦ t (A / F), step 608 is executed.
And the correction value ΔST is increased by a constant value α,
Next, the routine proceeds to step 509. In step 509, the final target opening ST is calculated by adding the correction value ΔST to the target opening ST of the throttle valve 20. That is,
The opening of the throttle valve 20 is controlled so that the actual air-fuel ratio A / F becomes the target air-fuel ratio t (A / F). Next, at step 510, the injection start timing θS is calculated from the map shown in FIG.

FIG. 28 shows another embodiment for executing the operation control II. Referring to FIG. 28, first, in step 600, the target fuel injection amount Q is calculated from the map shown in FIG. 17A, and the fuel injection amount is set as the target fuel injection amount Q. Next, in step 601, FIG.
The target opening S of the throttle valve 20 is obtained from the map shown in FIG.
T is calculated, and the opening of the throttle valve 20 is set to the target opening ST. Next, in step 602, FIG.
The target opening SE of the EGR control valve 31 is calculated from the map shown in FIG.

Next, at step 603, the intake air amount Ga detected by the mass flow detector 21 is taken. Next, at step 604, the fuel injection amount Q and the intake air amount Ga
Is used to calculate the actual air-fuel ratio A / F. Next, at step 605, the target air-fuel ratio t (A / F) shown in FIG. 16 is calculated. Next, at step 606, the actual air-fuel ratio A / F
Is larger than the target air-fuel ratio t (A / F). If A / F> t (A / F), step 607 is executed.
Then, the correction value ΔSE for the EGR control valve opening is increased by a constant value α, and then the routine proceeds to step 609. On the other hand, when A / F ≦ t (A / F), the routine proceeds to step 608, where the correction value ΔSE is decreased by the constant value α, and then the routine proceeds to step 609. Step 60
9, a correction value ΔSE is added to the target opening SE of the EGR control valve 31.
Is added to calculate the final target opening degree SE. That is, the actual air-fuel ratio A / F is equal to the target air-fuel ratio t (A /
The opening of the EGR control valve 31 is controlled so as to satisfy F). Next, at step 610, the injection start timing θS is calculated from the map shown in FIG.

FIG. 29 and FIG. 30 show a second embodiment of the operation control I. In this embodiment, the intake air amount is controlled so that the actual air-fuel ratio detected by the air-fuel ratio sensor 27 at the time of low-temperature combustion becomes the target air-fuel ratio. Referring to FIGS. 29 and 30, first, at step 700, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG.
The target opening SE of the EGR control valve 31 is calculated from the map shown in FIG. Next, in step 702, FIG.
The injection amount Q is calculated from the map shown in FIG. Next, at step 703, it is determined whether or not the engine is idling. As described above, for example, when the depression amount of the accelerator pedal 50 is zero and the vehicle speed is zero, it is determined that the engine is idling.

When the engine is not idling, the routine jumps to step 708 to jump to the target air-fuel ratio t shown in FIG.
(A / F) is calculated. Next, at step 709, it is determined whether or not the actual air-fuel ratio A / F detected by the air-fuel ratio sensor 27 is larger than the target air-fuel ratio t (A / F). When A / F> t (A / F), the routine proceeds to step 710, where the constant value a is subtracted from the correction amount ΔST for the throttle valve opening, and then the routine proceeds to step 712. On the other hand, when A / F ≦ t (A / F), step 711 is executed.
Then, the constant value a is added to the correction amount ΔST, and then the process proceeds to step 712. In step 712, a value obtained by adding the correction value ΔST to the target opening degree ST of the throttle valve 20 (= S
T + ΔST) is the final opening degree ST of the throttle valve 20. Therefore, when A / F> t (A / F), the opening of the throttle valve 20 is reduced, and A / F ≦ t (A / F).
In the case of F), the opening degree of the throttle valve 20 is increased, whereby the actual intake air amount Ga is set to the target intake air amount tGa, and the air-fuel ratio is set to the target air-fuel ratio t (A / F).

In step 714, the target pressure PM0 in the air suction pipe 17 downstream of the throttle valve 20 is calculated from the map shown in FIG. Next, at step 715, it is determined whether the pressure PM in the air suction pipe 17 detected by the pressure sensor 37 is higher than the target pressure PM0. When PM> PM0, the process proceeds to step 715 and E
The fixed value b is subtracted from the correction value ΔSE for the GR control valve 31, and then the routine proceeds to step 717. In contrast, P
When M ≦ PM0, the routine proceeds to step 716, where the correction value Δ
The constant value b is added to SE, and the process proceeds to step 717.

At step 717, a value obtained by adding the correction value ΔSE to the target opening degree SE of the EGR control valve 31 (= SE + ΔS
E) is the final opening degree SE of the EGR control valve 31.
Therefore, when PM> PM0, the opening of the EGR control valve 31 is decreased, and when PM ≦ PM0, the opening of the EGR control valve 31 is increased, whereby the EGR rate becomes the target EGR rate. Next, the routine proceeds to an injection timing control routine shown in FIG.

On the other hand, if it is determined in step 703 that the engine is idling, the routine proceeds to step 70.
4 and the engine speed N becomes the target idling speed N _0.
Is determined. When N> N _0, the routine proceeds to step 705, where the fixed value C is subtracted from the correction value ΔQ for the injection amount, and then the routine proceeds to step 707. On the other hand, when N ≦ N _0, the routine proceeds to step 706, where a fixed value C is added to the correction value ΔQ, and then step 707
Proceed to.

In step 707, a value obtained by adding the correction value ΔQ to the injection amount Q calculated from the map (= Q + ΔQ) is used as the final injection amount Q. Therefore, when N> N ₀ , the injection amount is decreased, and when N ≦ N ₀ , the injection amount is increased, whereby the engine speed N is set to the target idling speed N ₀ . Next, in steps 708 to 712, the intake air amount is set to the target intake air amount, and the air-fuel ratio is set to the target air-fuel ratio t (A / F).
Next, in steps 714 to 717, the pressure PM downstream of the throttle valve 20 is set to the target pressure PM0. At this time, the EGR rate becomes the target EGR rate.

FIG. 31 to FIG. 35 show a third embodiment of the operation control I. In this embodiment, the target air-fuel ratio A / F is predetermined as a function of the intake air amount Ga and the engine speed N as shown in FIG. Based on the air amount Ga and the target air-fuel ratio A / F, a fuel injection amount Q necessary for setting the air-fuel ratio to the target air-fuel ratio A / F is calculated.

In this embodiment, the target pressure PM0 in the air suction valve 17 downstream of the throttle valve 20 is also shown in FIG.
As shown in FIG. 33, a map is previously stored in the ROM 42 as a function of the intake air amount Ga and the engine speed N, and the injection start timing θS is also shown in FIG. It is stored in the ROM 42 in advance in the form of a map as a function of the engine speed N. Note that the target pressure PM0 and the injection start timing θS
And RO in the form of a map as a function of the engine speed N
It may be stored in M42.

In this embodiment, the engine speed is controlled to the target idling speed by controlling the opening of the throttle valve 20 during the engine idling operation, that is, by controlling the amount of intake air. Next, the operation control I will be described with reference to FIGS. 34 and 35.
Referring to FIG. 34 and FIG. 35, first, step 8
At 00, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG.
In FIG. 1, the target opening degree SE of the EGR control valve 31 is calculated from the map shown in FIG. Then step 80
In 2, it is determined whether or not the engine is idling. As described above, for example, when the depression amount of the accelerator pedal 50 is zero and the vehicle speed is zero, it is determined that the engine is idling.

When the engine is not idling, the routine jumps to step 807, where the actual intake air amount Ga detected by the mass flow detector 21 is taken. Next, at step 808, the target air-fuel ratio t (A
/ F) is calculated. Next, at step 809, based on the intake air amount Ga and the target air-fuel ratio t (A / F), the fuel injection amount Q necessary for setting the air-fuel ratio to the target air-fuel ratio t (A / F).
Is calculated.

Next, at step 810, the air suction pipe 17 downstream of the throttle valve 20 is obtained from the map shown in FIG.
Is calculated. Then step 81
In 1, the air suction pipe 17 detected by the pressure sensor 37 is used.
It is determined whether the internal pressure PM is higher than the target pressure PM0. When PM> PM0, the routine proceeds to step 812, where the correction value ΔSE for the EGR control valve 31 is changed to a fixed value b
Is subtracted, and then the process proceeds to step 814. On the other hand, when PM ≦ PM0, the routine proceeds to step 813, where the fixed value b is added to the correction value ΔSE.
Proceed to 4.

In step 814, a value obtained by adding the correction value ΔSE to the target opening degree SE of the EGR control valve 31 (= SE + ΔS
E) is the final opening degree SE of the EGR control valve 31.
Therefore, when PM> PM0, the opening of the EGR control valve 31 is decreased, and when PM ≦ PM0, the opening of the EGR control valve 31 is increased, whereby the EGR rate becomes the target EGR rate. Next, the routine proceeds to an injection timing control routine shown in FIG.

On the other hand, when it is determined in step 802 that the engine is in the idling operation, step 80
Proceeding to 3, the engine speed N becomes the target idling speed N ₀
Is determined. When N> N _0, the routine proceeds to step 804, where the constant value a is subtracted from the correction value ΔST for the throttle valve opening, and then step 806
Proceed to. On the other hand, when N ≦ N ₀ , step 80
The routine proceeds to 5, where a fixed value a is added to the correction value ΔST, and then the routine proceeds to step 806.

In step 806, a value obtained by adding the correction value ΔST to the target opening ST of the throttle valve 20 (= ST + ΔS
T) is the final opening degree ST of the throttle valve 20.
Therefore, when N> N ₀ , the opening of the throttle valve 20 is decreased, and when N ≦ N ₀ , the opening of the throttle valve 20 is increased, whereby the engine speed N is set to the target idling speed N _0. You. Then step 8
From step 07 to step 809, the air-fuel ratio becomes the target air-fuel ratio t.
(A / F), and then in steps 810 to 814, the pressure PM downstream of the throttle valve 20 is set to the target pressure PM0. At this time, the EGR rate becomes the target EGR rate.

In the first embodiment (FIGS. 20 and 21) and the second embodiment (FIGS. 29 and 30) of the operation control I, the injection amount Q and the target air-fuel ratio t are determined based on the required torque TQ and the engine speed N. (A / F) is calculated, and the intake air amount Ga is controlled based on the injection amount Q and the target air-fuel ratio t (A / F) so that the air-fuel ratio becomes the target air-fuel ratio t (A / F). . Therefore, in this case, as long as the actual injection amount matches the calculated injection amount Q, the intake air amount Ga becomes the target intake air amount according to the required torque TQ and the engine speed N.

However, in the third embodiment of the operation control I (FIGS. 34 and 35), the intake air amount is controlled based only on the throttle valve opening and the EGR control valve opening. If clogging occurs, the actual intake air amount Ga deviates from the target intake air amount. In the third embodiment, even if the actual intake air amount Ga deviates from the target intake air amount, the target air becomes the target air-fuel ratio t (A / F) and the target air becomes such that the EGR rate becomes the target EGR rate. The fuel ratio is determined based on the intake air amount Ga and the engine speed N, and the target pressure PM downstream of the throttle valve 20 is determined.
0 is determined based on the intake air amount Ga and the engine speed N.

It is also possible to arrange the throttle valve 20 downstream of the compressor 16 of the exhaust turbocharger 15 and connect the EGR passage 29 to an intake passage downstream of the throttle valve 20. In this case, the pressure sensor 37 is arranged in the intake passage downstream of the throttle valve 20 and the throttle valve 2
The degree of opening of the EGR control valve 31 is controlled such that the pressure in the intake passage downstream of 0 becomes the target pressure PM0.

[0119]

As described above, the EGR rate can be made to exactly match the target EGR rate.

[Brief description of the drawings]

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

FIG. 2 is an enlarged side sectional view around a throttle valve.

FIG. 3 is an enlarged side sectional view around a throttle valve showing another embodiment.

FIG. 4 is a diagram showing the amounts of smoke and NO _x generated, etc.

FIG. 5 is a diagram showing a combustion pressure.

FIG. 6 is a diagram showing fuel molecules.

FIG. 7 is a diagram showing a relationship between a generation amount of smoke and an EGR rate.

FIG. 8 is a diagram showing a relationship between an injection fuel amount and a mixed gas amount.

FIG. 9 is a diagram showing a first operation region I and a second operation region II.

FIG. 10 is a diagram showing an output of an air-fuel ratio sensor.

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

FIG. 12 is a diagram showing a required torque.

FIG. 13 is a diagram showing an air-fuel ratio in a first operation region I.

FIG. 14 is a diagram showing a map of an injection amount and the like.

FIG. 15 is a view showing a map of a target opening of the throttle valve and the like.

FIG. 16 is a diagram showing an air-fuel ratio in the second combustion.

FIG. 17 is a diagram showing a map of an injection amount and the like.

FIG. 18 is a view showing a map of a target opening of the throttle valve and the like.

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

FIG. 20 is a flowchart showing a first embodiment for executing operation control I;

FIG. 21 is a flowchart showing a first embodiment for executing operation control I;

FIG. 22 is a diagram showing a combustion pressure and the like.

FIG. 23 is a diagram showing an upper limit α.

FIG. 24 is a diagram showing a crank angle interrupt routine.

FIG. 25 is a flowchart for controlling the injection timing.

FIG. 26 is a diagram showing a map of an allowable maximum retard timing.

FIG. 27 is a flowchart for executing operation control II.

FIG. 28 is a flowchart showing another embodiment for executing the operation control II.

FIG. 29 is a flowchart showing a second embodiment for executing the operation control I.

FIG. 30 is a flowchart showing a second embodiment for executing the operation control I.

FIG. 31 is a diagram showing an air-fuel ratio in a first operation region I.

FIG. 32 is a view showing a map of a target opening degree of a throttle valve and the like.

FIG. 33 is a view showing a map of a target pressure and the like in an intake passage downstream of a throttle valve.

FIG. 34 is a flowchart showing a third embodiment for executing the operation control I.

FIG. 35 is a flowchart showing a third embodiment for executing the operation control I.

[Explanation of symbols]

 6 Fuel injection valve 20 Throttle valve 31 EGR control valve 37 Pressure sensor

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 31, 1999 (1999.3.3)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

On the other hand, fuel injectors 6 are connected through a fuel supply pipe 33 the fuel reservoir, a so-called common rail 34. The common rail is to Le 34 is supplied with fuel from a variable discharge fuel pump 35 of the electrically controlled, common rail
The fuel supplied to the fuel tank 34 is supplied to the fuel injection valve 6 through each fuel supply pipe 33. The common rail 34 is mounted a fuel pressure sensor 36 for detecting the fuel pressure in Como <br/> Nre Le 34, the target fuel fuel pressure common rail 34 based on the output signal of the fuel pressure sensor 36 The discharge amount of the fuel pump 35 is controlled so as to be a pressure.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

The electronic control unit 40 is composed of a digital computer, and has a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a CPU (Microprocessor) 44, an input port 45, An output port 46 is provided. The output signal of the mass flow detector 21 is input to the input port 45 via the corresponding AD converter 47, and the output signals of the air-fuel ratio sensor 27 and the fuel pressure sensor 36 are also input to the input port via the corresponding AD converter 47, respectively. 45 is input. The combustion chamber 5 is arranged a combustion pressure sensor 3 7 for detecting the pressure in the combustion chamber 5, the output signal of the combustion pressure sensor 3 7 is connected to the input terminal I of a peak hold circuit 49. The output terminal O of the peak hold circuit 49 is input to the input port 45 via the corresponding AD converter 47. Further, the throttle valve 20 downstream of the air suction pipe 17 is mounted a pressure sensor 3 8 for detecting the absolute pressure in the air suction pipe 17, AD converter 47 the output signal of the pressure sensor 3 8 corresponding Through the input port 45.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

FIG. 2 is an enlarged view around the throttle valve 20. Referring to FIG. 2, the inner wall portion 17a of the air suction pipe 17 around the throttle valve 20, i.e., the intake passage 3 9
The inner wall portion 17a of which is caused to bulge outward, the inner wall portion of the intake passage 3 9 in the embodiment shown in FIG. 2 1
7a has an arc-shaped cross section. When the throttle valve 20 is opened from the fully closed position as compared with the case in this way the cross-sectional shape of the inner wall portion 17a of the intake passage 3 9 air suction pipe 17 when the arc shape throughout having a cylindrical shape The flow passage area between the valve element peripheral edge of the throttle valve 20 and the inner wall surface portion 17a gradually increases. In other words, the change in the flow path area with respect to the rotation angle of the throttle valve 20 is smaller than when the air suction pipe 17 is entirely cylindrical. As a result, minute control of the intake air amount by the throttle valve 20 becomes possible.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

[0031] shows another embodiment of the shape of the inner wall portion 17a of the intake passage 3 9 3. Intake passage 3 9 In this example
Has a V-shaped cross section. Also in this embodiment, the change in the flow path area with respect to the rotation angle of the throttle valve 20 is smaller than in the case where the air suction pipe 17 has a cylindrical shape over the entirety.
It is possible to finely control the intake air amount by 0.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction contents]

When supercharging is not performed, fuel
The upper limit of the total intake gas amount X sucked into the firing chamber 5 is Y.
Therefore, in FIG.₀ Territory larger than
In the region, the EGR gas ratio increases as the required load increases.
The air-fuel ratio can be maintained at the stoichiometric air-fuel ratio unless reduced.
Can not. In other words, it is necessary when there is no supercharging.
Load demand is L₀ Air-fuel ratio in the larger area than theoretical
When trying to maintain the fuel ratio, the required load increases.
As a result, the EGR rate decreases, and thus the required load becomes L ₀ Than
In areas where the fuel and the surrounding gas temperature are
It will not be possible to maintain a temperature lower than the temperature produced. When
As shown in FIG.
Air suction of the inlet side of the feeder, that is, the exhaust turbocharger 15
When the EGR gas is recirculated in the pipe 17, the required load becomes L₀ 
EGR rate of 55% or less in the larger area
Above, for example, 70%.
The temperature of the fuel and its surrounding gas to the temperature at which soot is produced.
It can be maintained at a lower temperature. That is, air
The EGR rate in the suction pipe 17 is, for example, 70%
If the EGR gas is recirculated so that
Suction by the compressor 16 of the charger 15
The EGR rate of the gas is also 70%, thus
The fuel and its
Ambient gas temperature lower than that generated by soot
Can be maintained. Thus causing low temperature combustion
The operating area of the engine
And Required load is L₀ EGR rate in a region larger than
Is set to 55% or more, the EGR control valve 31
Fully opened, throttle valve 20 slightly closed
It is.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction contents]

[0069] FIG. 14 (A) shows the injection amount Q in the first operating region I, FIG. 14 (B) shows the reference injection start timing θS in the first operating region I. FIG.
As shown in FIG. 1A, the injection amount Q in the first operating region I is stored in the ROM 42 in advance in the form of a map as a function of the required torque TQ and the engine speed N.
As shown in FIG. 4 (B), the reference injection start timing θS in the first operation region I is also stored in the ROM 42 in advance in the form of a map as a function of the required torque TQ and the engine speed N.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0076

[Correction method] Change

[Correction contents]

However, in practice, variations in the dimensions of parts, aging, the throttle valve 20 or the EGR control valve 3
Even if the injection amount, the opening of the throttle valve 20 and the opening of the EGR control valve 31 are determined based on the corresponding map due to the clogging of 1, the air-fuel ratio does not exactly match the air-fuel ratio shown in FIG. The rate deviates from the target EGR rate. Therefore, in the first embodiment according to the present invention, the target intake air amount necessary for setting the air-fuel ratio to the target air-fuel ratio A / F from the target injection amount Q is calculated, and the mass of the intake air detected by the mass flow rate detector 21 is calculated. The opening of the throttle valve 20 is corrected so that the flow rate (hereinafter, simply referred to as the intake air amount) becomes the target intake air amount, whereby the air-fuel ratio accurately matches the target air-fuel ratio.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0080

[Correction method] Change

[Correction contents]

Referring to FIG. 19, first, in step 100, 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 region of the engine is the first operating region I, step 1
The program proceeds to 01 and it is determined whether or not the required torque TQ has become larger than the first boundary X1 (N). TQ ≦ X1
In the case of (N), the routine proceeds to step 103, where the operation control I for executing the first combustion is performed. A routine for executing the operation control I is shown in FIGS. 20 and 21.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0081

[Correction method] Change

[Correction contents]

On the other hand, in step 101, TQ > X
When it is determined that (N) has been reached, the routine proceeds to step 102, where the flag I is reset.
The operation control II for executing the second combustion is performed. A routine for executing the operation control II is shown in FIG.
2 is shown. When the flag I is reset, in the next processing cycle, the process proceeds from step 100 to step 104, where it is determined whether or not the required torque TQ has become lower than the second boundary Y (N). When TQ ≧ Y (N), the routine proceeds to step 106, where the second combustion is performed. On the other hand, when it is determined in step 104 that TQ <Y (N), the routine proceeds to step 105, where the flag I is set, and then proceeds to step 103 to perform low-temperature combustion.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Next, the operation control I for executing low-temperature combustion will be described with reference to FIGS . 20 and 21 . Referring to FIG. 20 and FIG.
At 0, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG.
In FIG. 15B, the EGR control valve 3
One target opening SE is calculated. Then step 202
Then, the injection amount Q is calculated from the map shown in FIG. Next, at step 203, it is determined whether or not the engine is idling. For example, the accelerator pedal 50
It is determined that the engine is idling when the depression amount of the vehicle is zero and the vehicle speed is zero.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0085

[Correction method] Change

[Correction contents]

In step 215, the target pressure PM0 in the air suction pipe 17 downstream of the throttle valve 20 is calculated from the map shown in FIG. Then the pressure PM in the air suction pipe 17 detected by the pressure sensor 3 8 at step 216 whether or not higher than the target pressure PM0 is determined. When PM> PM0, the routine proceeds to step 217, where E
The constant value b is subtracted from the correction value ΔSE for the GR control valve 31, and then the routine proceeds to step 219. In contrast, P
If M ≦ PM0, the routine proceeds to step 218, where the correction value Δ
The constant value b is added to SE, and the process proceeds to step 219.

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0089

[Correction method] Change

[Correction contents]

Next, before describing the injection timing control routine shown in FIG. 25, a method of controlling the injection timing will be described with reference to FIG. Whether in an embodiment according to the present invention has been made good low temperature combustion is determined based on the pressure in the combustion chamber 5 detected by the combustion pressure sensor 3 7. That is,
When good low-temperature combustion is being performed, the combustion pressure changes slowly as shown in FIG. Specifically, the combustion pressure once peaks at the top dead center TDC as indicated by P ₀ , and then peaks again after the top dead center TDC as indicated by P ₁ . Peak pressure P ₁ is caused by the combustion pressure, good amount of increase in peak pressure P ₁ to the peak pressure P ₀ when the low temperature combustion is being performed, i.e., the peak pressure P ₀ and the differential pressure ΔP between the peak pressure P ₁ (= P ₁ -P
₀ ) is relatively small.

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Next, at step 503, the intake air amount Ga detected by the mass flow detector 21 is taken. Next, at step 504, the fuel injection amount Q and the intake air amount Ga
Is used to calculate the actual air-fuel ratio A / F. Next, at step 605, the target air-fuel ratio t (A / F) shown in FIG. 16 is calculated. Next, at step 606, the actual air-fuel ratio A / F
Is larger than the target air-fuel ratio t (A / F). When A / F> t (A / F), step 507 is executed.
Then, the correction value ΔST of the throttle opening is decreased by the constant value α, and then the routine proceeds to step 509. Step 5 08 when contrast of A / F ≦ t (A / F)
And the correction value ΔST is increased by a constant value α,
Next, the routine proceeds to step 509. In step 509, the final target opening ST is calculated by adding the correction value ΔST to the target opening ST of the throttle valve 20. That is,
The opening of the throttle valve 20 is controlled so that the actual air-fuel ratio A / F becomes the target air-fuel ratio t (A / F). Next, at step 510, the injection start timing θS is calculated from the map shown in FIG.

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0104

[Correction method] Change

[Correction contents]

In step 714, the target pressure PM0 in the air suction pipe 17 downstream of the throttle valve 20 is calculated from the map shown in FIG. Then the pressure PM in the air suction pipe 17 detected by the pressure sensor 3 8 at step 715 whether or not higher than the target pressure PM0 is determined. When PM> PM0, the process proceeds to step 715 and E
The fixed value b is subtracted from the correction value ΔSE for the GR control valve 31, and then the routine proceeds to step 717. In contrast, P
When M ≦ PM0, the routine proceeds to step 716, where the correction value Δ
The constant value b is added to SE, and the process proceeds to step 717.

[Procedure amendment 15]

[Document name to be amended] Statement

[Correction target item name] 0112

[Correction method] Change

[Correction contents]

Next, at step 810, the air suction pipe 17 downstream of the throttle valve 20 is obtained from the map shown in FIG.
Is calculated. Then step 81
1 air suction pipe 17 detected by the pressure sensor 3 8,
It is determined whether the internal pressure PM is higher than the target pressure PM0. When PM> PM0, the routine proceeds to step 812, where the correction value ΔSE for the EGR control valve 31 is changed to a fixed value b
Is subtracted, and then the process proceeds to step 814. On the other hand, when PM ≦ PM0, the routine proceeds to step 813, where the fixed value b is added to the correction value ΔSE.
Proceed to 4.

[Procedure amendment 16]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

It is also possible to arrange the throttle valve 20 downstream of the compressor 16 of the exhaust turbocharger 15 and connect the EGR passage 29 to an intake passage downstream of the throttle valve 20. The pressure sensor 3 8 is disposed in the throttle valve 20 downstream of the intake passage in this case, the throttle valve 2
The degree of opening of the EGR control valve 31 is controlled such that the pressure in the intake passage downstream of 0 becomes the target pressure PM0.

[Procedure amendment 17]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 18]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 19]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 20]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 21]

[Document name to be amended] Drawing

[Correction target item name] Fig. 25

[Correction method] Change

[Correction contents]

FIG. 25

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 21/08 301 F02D 21/08 301B 301D 41/02 351 41/02 351 41/04 360 41/04 360C 385 385J 41/14 310 41/14 310N 41/16 41/16 Z 45/00 301 45/00 301F (72) Inventor Koji Saki ▼ 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Takekazu Ito 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Hiroki Murata 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Tsukasa Abe Aichi 1 Toyota Town, Toyota-shi, Toyota F-term in Toyota Motor Corporation (reference) 3G062 AA01 AA05 BA04 BA05 BA06 EA11 ED08 ED10 FA13 GA01 GA02 GA04 GA05 GA06 GA08 GA10 GA15 GA21 3G084 AA01 BA02 BA03 BA05 BA09 BA13 BA15 BA20 BA24 DA10 DA12 EA02 EB02 EB08 EB12 FA05 FA07 FA10 FA11 FA13 FA17 FA18 FA21 FA26 FA32 FA33 FA37 3G091 AA10 AA11 BA02 AB02 AB02 AB02 AB02 DC03 EA01 EA02 EA05 EA06 EA07 EA08 EA09 EA12 EA34 EA39 FA07 FA11 HB05 HB06 3G092 AA02 AA06 AB03 BA01 BA03 BA04 BB01 BB06 DB03 DC01 DC08 DE01S DE03S DE06S EA06 EA07 HA01 H03 HA03 HA03 HA03 HA03 HA03 HA03 HA03 HA03 HA03 HA03 HA03 HA04 HA06 HA11 JA24 JA25 JA26 JA27 KA06 LA01 LB11 LC04 MA01 MA11 MA14 MA18 NC02 PA01A PA11A PA17A PB03A PB05A PB08A PC01A PD15A PE01A PE03A PE06A PF01A PF03A

Claims (19)

[Claims] When the amount of recirculated exhaust gas supplied to a combustion chamber is increased, the amount of soot generated gradually increases and the recirculated exhaust gas is supplied into an engine intake passage of an internal combustion engine that reaches a peak. At the same time, the amount of recirculated exhaust gas supplied to the combustion chamber is made larger than the amount of recirculated exhaust gas at which the generation amount of soot becomes a peak, and the amount of intake air supplied to the combustion chamber is predetermined according to the operating state of the engine. Intake air amount control means for controlling the intake air amount to be controlled, pressure detection means for detecting pressure in the intake passage, and a target exhaust gas recirculation rate based on the pressure in the intake passage. An internal combustion engine having recirculation exhaust gas amount control means for controlling the amount of recirculation exhaust gas such that And a storage means for storing in advance a target pressure in the intake passage according to an engine operating state necessary for setting the exhaust gas recirculation rate to the target exhaust gas recirculation rate. 2. The internal combustion engine according to claim 1, wherein the amount control means controls the amount of recirculated exhaust gas so that the pressure in the intake passage becomes the target pressure. 3. An exhaust gas recirculation control valve disposed in an exhaust gas recirculation passage connecting an engine exhaust passage and an engine intake passage, wherein said recirculation exhaust gas amount control means includes: 3. The internal combustion engine according to claim 2, wherein the amount control means controls the opening of the exhaust gas recirculation control valve so that the pressure in the intake passage becomes the target pressure. 4. An intake air amount detection means for detecting an intake air amount, and an air-fuel ratio control means for controlling an air-fuel ratio to a target air-fuel ratio according to an operation state of the engine based on the detected intake air amount. The internal combustion engine according to claim 1, comprising: 5. An air-fuel ratio control means for calculating a fuel injection amount, wherein the air-fuel ratio control means controls an intake air amount so that a ratio between the detected intake air amount and the calculated fuel injection amount becomes a target air-fuel ratio. The internal combustion engine according to claim 4, which corrects the following. 6. An air-fuel ratio detecting means for detecting an air-fuel ratio, wherein said air-fuel ratio control means corrects an intake air amount such that the detected air-fuel ratio becomes a target air-fuel ratio. Internal combustion engine. 7. The internal combustion engine according to claim 4, wherein said air-fuel ratio control means calculates a fuel injection amount required for setting the air-fuel ratio to a target air-fuel ratio based on the detected intake air amount. 8. An intake air amount control means includes a throttle valve disposed in an engine intake passage, wherein an amount of intake air supplied to the combustion chamber is equal to a predetermined amount of intake air corresponding to an operation state of the engine. 2. The internal combustion engine according to claim 1, wherein the opening of the throttle valve is controlled such that the opening degree of the throttle valve is controlled. 9. It has a storage means for storing an injection timing,
The internal combustion engine according to claim 1, wherein the injection timing is controlled based on the stored injection timing. 10. The internal combustion engine according to claim 9, further comprising a combustion pressure detecting means for detecting a combustion pressure in the combustion chamber, wherein an injection timing is controlled based on the combustion pressure. 11. The internal combustion engine according to claim 1, further comprising rotation speed control means for controlling the engine rotation speed to a target idling rotation speed during engine idling operation. 12. The internal combustion engine according to claim 11, wherein said rotational speed control means maintains the engine rotational speed at a target idling rotational speed by controlling a fuel injection amount. 13. The internal combustion engine according to claim 11, wherein said rotation speed control means maintains the engine rotation speed at a target idling rotation speed by controlling an intake air amount. 14. An intake air amount control means includes a throttle valve disposed in an engine intake passage, and causes an intake passage inner wall surface around the throttle valve to expand outward and to expand outward. The shape of the inner wall portion of the intake passage that has been made is such that the flow passage area between the valve body periphery of the throttle valve and the inner wall portion of the intake passage gradually increases as the throttle valve opens from the fully closed position. The internal combustion engine according to claim 1. 15. The internal combustion engine of claim 1, wherein the exhaust gas recirculation rate is approximately equal to or greater than 55 percent. 16. The internal combustion engine according to claim 1, wherein a catalyst having an oxidation function is disposed in the engine exhaust passage. 17. The method according to claim 17, wherein the catalyst is an oxidation catalyst, a three-way catalyst or NO.
17. The internal combustion engine of claim 16, comprising at least one of the _x absorbents. 18. The first combustion in which 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 is at a peak and little soot is generated, and the amount of generated soot is at a peak. 2. The internal combustion engine according to claim 1, further comprising a switching unit that selectively switches between a second combustion in which an amount of recirculated exhaust gas supplied to the combustion chamber is smaller than an amount of recirculated gas that becomes the second combustion. 19. 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 a first combustion is performed in the first operating region. Second in the area
The internal combustion engine according to claim 18, wherein combustion of the internal combustion engine is performed.