JP3344330B2 - Internal combustion engine - Google Patents

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 determined that the amount of _x and smoke generated was as small as possible. However, this way there is a limit to the EGR rate to decrease of the NO _x and NO _x and the amount of smoke produced be determined so that the amount of generation is possible less smoke, actually still substantial amount of the NO _x
At present, smoke is generated.

However, if the EGR rate is made larger than the maximum allowable limit in the course of research on the combustion of a diesel engine, the smoke rapidly increases as described above. However, the amount of generated smoke has a peak, and the peak exceeds this peak. EGR
When the rate is further increased, the smoke starts to decrease rapidly, and when the EGR rate is increased to 70% or more during idling operation, and when the EGR gas is cooled strongly, the smoke is reduced when the EGR rate is increased to about 55% or more. It 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, in this new combustion, the fuel injection timing and the air-fuel ratio at which stable combustion can be obtained are limited to relatively narrow ranges. That is, when the fuel injection timing is advanced, the injected fuel is heated by the compressed high-temperature gas for a long time, so that the temperature of the fuel and the surrounding gas becomes high at the time of combustion, and as a result, smoke is generated or a certain level or more. Noise will be generated. On the other hand, if the fuel injection timing is delayed, most of the fuel does not burn because the temperature of the injected fuel does not rise so much, and thus poor combustion occurs. On the other hand, when the air-fuel ratio is increased, the oxygen concentration around the fuel particles increases, so that the temperature of the fuel during combustion and the gas around the fuel increases, thereby producing smoke or generating noise above a certain level. become. On the other hand, when the air-fuel ratio is reduced, insufficient oxygen is generated, resulting in poor combustion.

Therefore, in order to obtain good combustion under new combustion, it is necessary to maintain the fuel injection timing and the air-fuel ratio within optimum ranges. However, the temperature of the fuel and its surrounding gas during combustion varies greatly depending on the ambient temperature, atmospheric pressure, humidity, etc., and as a result the ambient temperature, atmospheric pressure, and humidity change, the fuel injection timing and air-fuel ratio are determined in advance. Even if the temperature is kept within the specified optimum range, smoke is generated, noise of a certain level or more is generated, or combustion failure occurs.

Accordingly, in the present invention, the combustion pressure in the combustion chamber is detected, and it is determined from the change in the combustion pressure whether or not good combustion is being performed. State, or when it is determined that the combustion state has caused combustion failure, control the fuel injection timing or air-fuel ratio so that smoke or noise above a certain level does not occur, or combustion failure does not occur. I have.

[0012]

That SUMMARY OF THE INVENTION In the first aspect, reached the peak generation amount of the gradually increasing the amount of inert gas in the combustion chamber soot increases gradually, the combustion chamber of an inert gas
As the amount of fuel further increases, the fuel
Temperature of the fuel and its surroundings is lower than the soot formation temperature.
In an internal combustion engine where soot is hardly generated , the amount of inert gas supplied into the combustion chamber is made larger than the amount of inert gas at which the amount of generated soot becomes a peak, and fuel is injected into the combustion chamber. A fuel injection valve, a combustion pressure sensor for detecting the combustion pressure in the combustion chamber, and whether smoke or noise of a certain level or more is generated based on the combustion pressure detected by the combustion pressure sensor, or a combustion failure. a determination unit or the determining has occurred, to reduce the or air delay the fuel injection timing when the smoke or the appropriate level of noise is determined to have occurred, it is determined that combustion failure occurs Control means for advancing the fuel injection timing or increasing the air-fuel ratio.

In the second invention, in the first invention, when it is determined that smoke or noise of a certain level or more is generated, the fuel injection timing is delayed, and the fuel injection timing is delayed to the allowable limit timing. If it is determined that smoke or noise of a certain level or more is still generated, the air-fuel ratio is made smaller than the target air-fuel ratio.
In the second invention in the third invention, the air-fuel ratio is large when it is determined that combustion failure occurs when the air-fuel ratio is smaller than the target air-fuel ratio, the air-fuel ratio to the target air-fuel ratio If it is determined that poor combustion still occurs even if the fuel injection timing is increased, the fuel injection timing is advanced.

According to a fourth aspect, in the first aspect,
The control means controls the air-fuel ratio by controlling the amount of intake air. In a fifth aspect of the present invention based on the first aspect, when the first peak of the combustion pressure appears at the compression top dead center and the second peak of the combustion pressure appears after the compression top dead center, When the combustion pressure at the peak is higher than the combustion pressure at the first peak by a predetermined pressure or more, it is determined that smoke is occurring.

In a sixth aspect, in the first aspect,
The judging means judges that noise of a certain level or more is generated when the pressure change rate of the combustion pressure after the compression top dead center exceeds a predetermined allowable upper limit.
In the seventh invention, in the first invention, the determination means is:
When the pressure change rate of the combustion pressure after the compression top dead center becomes lower than a predetermined allowable lower limit, it is determined that poor combustion has occurred.

According to an eighth aspect, in the first aspect,
The determining means determines that poor combustion has occurred when the minimum value of the pressure change rate of the combustion pressure after the compression top dead center occurs before a predetermined crank angle. In a ninth aspect based on the first aspect, the determining means determines that a combustion pressure at a crank angle after a predetermined crank angle from the compression top dead center is smaller than a combustion pressure at a crank angle before the predetermined crank angle from the compression top dead center. When the pressure is not higher than a predetermined pressure, it is determined that poor combustion has occurred.

In a tenth aspect based on the first aspect, the judging means determines the combustion pressure after the compression top dead center from the pressure in the combustion chamber at the same crank angle during motoring operation over a predetermined crank angle range. Also, when the pressure is not higher than a predetermined pressure, it is determined that poor combustion has occurred. In an eleventh aspect based on the first aspect, the judging means is configured such that an integral value of the combustion pressure within a certain crank angle range from the compression top dead center to the compression top dead center is equal to or smaller than the compression top dead center to the compression top dead center before the compression top dead center. If the combustion pressure is not higher than the integral value of the combustion pressure within a certain crank angle range by a predetermined value or more, it is determined that poor combustion has occurred.

In a twelfth aspect based on the first aspect, the judging means determines that an integral value of the combustion pressure within a predetermined crank angle range after the compression top dead center is at the time of motoring operation within the crank angle range. When the pressure is not higher than the integral value of the pressure in the combustion chamber by a predetermined value or more, it is determined that poor combustion has occurred. In a thirteenth aspect based on the first aspect, the judging means includes a crank angle range in which the pressure change rate of the combustion pressure is continuously higher than the pressure change rate of the combustion chamber pressure during the motoring operation after the compression top dead center. The integral value of the difference between the pressure change rate of the combustion pressure and the pressure change rate of the pressure in the combustion chamber within this crank angle range is smaller than a predetermined value, or the crank angle range is predetermined. When it is smaller than the range, it is determined that poor combustion has occurred.

According to a fourteenth aspect, in the first aspect, there is provided an exhaust gas recirculation device for recirculating exhaust gas discharged from the combustion chamber into the engine intake passage, wherein the inert gas comprises recirculated exhaust gas. . According to a fifteenth aspect, in the fourteenth aspect, the exhaust gas recirculation rate is approximately 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. In 16 th invention is a 17 th invention, the catalyst consists of one at least of the oxidation catalyst, three-way catalyst or _the NO _x absorbent. In an eighteenth aspect based on the first aspect, the first combustion in which the amount of inert gas supplied into the combustion chamber is larger than the amount of inert gas at which the amount of generated soot reaches a peak and soot is hardly generated; There is provided switching means for selectively switching the second combustion in which the amount of inert gas supplied into the combustion chamber is smaller than the amount of inert gas at which the amount of generation reaches a peak.

According to a nineteenth aspect, in 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.

[0022]

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.

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. Catalytic converter 26
The exhaust pipe 28 and the air suction pipe 17 downstream of the throttle valve 20 are connected to each other through an EGR passage 29. An EGR control valve 31 driven by a step motor 30 is provided in the EGR passage 29. Be placed. Also,
EGR flowing in the EGR passage 29 is provided in the EGR passage 29.
An intercooler 32 for cooling the 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 rail 34. Fuel is supplied from the electric control type variable discharge fuel pump 35 into the collen rail 34, and the fuel supplied into the common rail 34 is supplied to the fuel injection valve 6 through each fuel supply pipe 33. A fuel pressure sensor 36 for detecting the fuel pressure in the common rail 34 is attached to the common rail 34, and the fuel pump 35 is controlled so that the fuel pressure in the common rail 34 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 36. Is controlled.

The electronic control unit 40 is composed of a digital computer, and is connected to a 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 fuel pressure sensor 36 is input to the input port 45 via the corresponding AD converter 47. A combustion pressure sensor 37 for detecting the pressure in the combustion chamber 5 is disposed in the combustion chamber 5, and an output signal of the combustion pressure sensor 37 is supplied to an input port 45 via a corresponding AD converter 47. And the other end is connected to the input terminal I of the 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.

The accelerator pedal 50 includes an accelerator pedal 5
A load sensor 51 that generates an output voltage proportional to the depression amount L of 0 is connected, and the output voltage of the load sensor 51 is input to the input port 45 via the corresponding AD converter 47. 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 °. 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 shows the throttle valve 2 when the engine is under low load operation.
Change in the output torque when changing the air-fuel ratio A / F (abscissa in FIG. 2) by changing the opening and the EGR rate of 0, and smoke, HC, CO, a change in emission of the NO _x It shows the experimental example shown. As can be seen from FIG. 2, in this experimental example, the smaller the air-fuel ratio A / F, the higher the EGR rate. When the air-fuel ratio A / F is smaller than the stoichiometric air-fuel ratio (≒ 14.6), the EGR rate is 65% or more.

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

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

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

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

Summarizing these considerations based on the experimental results shown in FIG. 2 and FIG. 3, 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.

By the way, the temperature of the fuel and its surrounding when the process of producing hydrocarbons is stopped in the state of the soot precursor, that is, the above-mentioned certain temperature depends on various factors such as the type of fuel, 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 the 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 are set to a temperature lower than the temperature at which the soot is generated. Need 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 is required to absorb a sufficient amount of heat to do so. . 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. 5 shows the relationship between the EGR rate and smoke when EGR gas is used as the inert gas and the degree of cooling of the EGR gas is changed. That is, in FIG. 5, a curve A indicates that the EGR gas temperature is substantially 9
Curve B shows the case where the EGR gas is cooled by a small cooling device, and curve C shows the case where the temperature is maintained at 0 ° C.
Indicates a case where the EGR gas is not forcibly cooled.

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

As shown by the curve C in FIG.
When the R gas is not forcibly cooled, the EGR rate becomes 5
The soot generation amount peaks near 5%, and in this case, if the EGR rate is set to approximately 70% or more, soot is hardly generated. FIG. 5 shows the amount of smoke generated when the engine load is relatively high. When the engine load decreases, the EGR rate at which the amount of soot peaks slightly decreases, and the EGR rate at which soot is hardly generated is reduced. Also lowers slightly. As described above, the lower limit of the EGR rate at which almost no soot is generated varies depending on the degree of cooling of the EGR gas and the engine load.

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

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

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

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

[0046] However through the EGR passage 29 as shown in Figure 1 of the supercharger inlet side, i.e. the required load and recirculate the EGR gas into the air intake pipe 17 of an exhaust turbocharger 15 than L ₀ In large areas, the EGR rate can be maintained at or above 55 percent, for example, 70 percent, and thus the temperature of the fuel and its surrounding gas can be maintained below the temperature at which soot is produced. That is, if the EGR gas is recirculated so that the EGR rate in the air suction pipe 17 becomes, for example, 70%, the EGR rate of the suction gas boosted by the compressor 16 of the exhaust turbocharger 15 also becomes 70%. The temperature of the fuel and the surrounding gas can be maintained at a temperature lower than the temperature generated by the soot to the extent that the pressure can be increased by the compressor 16. Therefore, the operating range of the engine that can generate low-temperature combustion can be expanded. In this case, the required load is L ₀
When the EGR rate is set to 55% or more in a larger region, the EGR control valve 31 is fully opened and the throttle valve 20 is slightly closed.

As described above, FIG. 6 shows the case where the fuel is burned under the stoichiometric air-fuel ratio. However, even if the air amount is smaller than that 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. 6, that is, even if the average value of the air-fuel ratio is 17 to 18 lean, soot generation is prevented. while the generation amount of the NO _x can be around or less 10 ppm.

That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but since the combustion temperature is suppressed to a low temperature, the excess fuel does not grow to soot, thus producing soot. 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 the low-temperature combustion is being performed, regardless of the air-fuel ratio within a certain air-fuel ratio range, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio, no soot and would lean is generated, 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.

The fuel and surrounding gas temperature during combustion in the combustion chamber can be suppressed to a temperature lower than the temperature at which the growth of hydrocarbons stops halfway, only when the engine is operating at low load and the calorific value due to combustion is relatively small. It is. 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. 7 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. 7, the vertical axis TQ indicates the required torque, and the horizontal axis N indicates the engine speed. In FIG. 7, X (N) represents a first operating region I and a second operating 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 performed, soot is hardly generated, and the unburned hydrocarbon is replaced with the precursor of soot or the state before the soot. 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. Next, the operation control in the first operation region I and the second operation region II will be schematically described with reference to FIG.

FIG. 8 shows the opening degree of the throttle valve 20, the opening degree of the EGR control valve 31, the EGR rate, the air-fuel ratio, the injection timing, and the injection amount with respect to the required torque TQ. As shown in FIG. 8, 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. The opening degree of the EGR control valve 31 is gradually increased from near full close to full open as the required load L increases.
Further, in the example shown in FIG.
The R ratio is approximately 70%, and the air-fuel ratio is a slightly lean air-fuel ratio.

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

During the idling operation, the throttle valve 20 is closed to almost fully closed, and at this time, the EGR control valve 31 is also closed to almost fully closed. 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. 8, the EGR rate is reduced stepwise from approximately 70% to 40% or less, and the air-fuel ratio is increased stepwise. That is, the EGR rate at which the EGR rate generates a large amount of smoke
The engine operating range is the first because it jumps over the rate range (Fig. 5).
A large amount of smoke does not occur when changing from the operating region I to the second operating region II.

In the second operation region II, the 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 FIG. 8 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 gradually reduced as the required torque TQ increases. In addition, this operation area II
In this case, 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. 9A shows the relationship between the required torque TQ, the depression amount L of the accelerator pedal 50, and the engine speed N. In FIG. 9A, each curve represents an equal torque curve, the curve indicated by TQ = 0 indicates that the torque is zero, and the remaining curves are TQ = a, TQ
The required torque gradually increases in the order of Q = b, TQ = c, TQ = d. The required torque TQ shown in FIG.
As shown in (B), the ROM is previously stored in the form of a map as a function of the depression amount L of the accelerator pedal 50 and the engine speed N.
42. In the embodiment according to the present invention, FIG.
A required torque TQ corresponding to the depression amount L of the accelerator pedal 50 and the engine speed N is first calculated from the map shown in FIG. 8B, and the fuel injection amount and the like are calculated based on the required torque TQ.

FIG. 10 shows the air-fuel ratio A / F in the first operating region I. In FIG. 10, 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. 10, the air-fuel ratio is lean in the first operating region I, and further, in the first operating region I, the lower the required torque TQ, the more 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,
Accordingly, as shown in FIG. 10, the air-fuel ratio A / F increases as the required torque TQ decreases. 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. 11A shows the injection amount Q in the first operation region I, and FIG. 11B shows the reference injection start timing θS in the first operation 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. 1 (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.

Further, the throttle valve 20 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F according to the operating state of the engine shown in FIG. 10 and setting the EGR rate to the target EGR rate according to the operating state of the engine is set. The target opening degree 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. 12 (A), and the air-fuel ratio is determined according to the operating state of the engine. 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 degree SE of the EGR control valve 31 required for setting the R rate
As shown in FIG. 12 (B), the ROM
Is stored within.

FIG. 13 shows the target air-fuel ratio when the second combustion, that is, the normal combustion by the conventional combustion method is performed. In FIG. 13, 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. 14A shows the injection amount Q in the second operation region II, and FIG. 14B shows the injection start timing θS in the second operation region II. As shown in FIG. 14A, 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. 5 (A), the EGR necessary for setting the air-fuel ratio to the target air-fuel ratio shown in FIG. 13 is stored in the ROM 42 in advance as a function of the required torque TQ and the engine speed N. FIG. 15 shows the target opening SE of the control valve 31.
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.

When the first combustion, that is, the low-temperature combustion is being performed, basically, the injection amount is set to the injection amount Q calculated from the map shown in FIG. FIG. 12B shows the reference injection start timing θS calculated from the map shown in FIG. 12B, the opening of the throttle valve 20 is the target opening ST calculated from the map shown in FIG. 12A, and the opening of the EGR control valve 31 is shown in FIG. 12 (B) to the target opening SE Tosureba smoke is calculated from the map shown is not generated, the noise does not become more than a certain level, good low temperature combustion that does not cause combustion failure is performed.

However, even if the injection amount, the injection timing, the opening of the throttle valve 20 and the opening of the EGR control valve 31 are made to correspond to the values on the corresponding maps as described above, the atmospheric temperature, atmospheric pressure, humidity equal or smoke or a certain level or more noise is generated since the gas temperature of the fuel and its surroundings is changed at the time of combustion and changes, combustion failure or cause.

Therefore, according to the present invention, the combustion pressure in the combustion chamber 5 is detected by the combustion pressure sensor 37, and based on the combustion pressure, it is determined whether or not smoke or noise of a certain level or more is generated. It is determined whether or not smoke or noise of a certain level or more is occurring. If it is determined that the injection start timing is delayed or the air-fuel ratio is reduced, it is determined that poor combustion has occurred. Sometimes, the injection start timing is advanced or the air-fuel ratio is increased.

That is, if the injection start timing is delayed when smoke or noise of a certain level or more is generated, the temperature of fuel and the surrounding gas during combustion is reduced, so that smoke is not generated and noise is reduced. descend. On the other hand, if the air-fuel ratio is reduced at this time, the oxygen concentration around the fuel particles is reduced, so that the temperature of the fuel and the gas around the fuel during combustion is reduced, so that no smoke is generated and the noise is reduced. Therefore, as described above, when it is determined that smoke or noise of a certain level or more is generated, the injection start timing is delayed or the air-fuel ratio is reduced.

On the other hand, if the injection start timing is advanced when poor combustion occurs, the whole fuel will burn well, and thus good combustion will be obtained. on the other hand,
At this time, if the air-fuel ratio is increased, the oxygen concentration around the fuel particles increases, so that the whole fuel burns satisfactorily, and thus good combustion can be obtained. Therefore, as described above, when it is determined that poor combustion has occurred, the injection start timing is advanced or the air-fuel ratio is increased.

In the embodiments of the present invention described below, when it is determined that smoke or noise of a certain level or more is generated, the injection start timing is first delayed, and still the smoke or the certain level is still present. When it is determined that the above noise is occurring, the air-fuel ratio is reduced. Also, when it is determined that poor combustion occurs in a state where the air-fuel ratio is reduced, first, the air-fuel ratio is increased, and when it is still determined that poor combustion still occurs, the injection start timing is advanced. Can be

Next, an embodiment according to the present invention will be specifically described. First, a method of determining whether or not smoke has occurred based on the combustion pressure detected by the combustion pressure sensor 37 will be described with reference to FIG. That is, when good low-temperature combustion without generation of smoke is being performed, the combustion pressure gradually changes as shown in FIG. More specifically, the combustion pressure once peaks at TDC as shown by P ₀ ,
_As shown by ₁ , the peak again occurs after the top dead center TDC. The peak pressure P ₁ is generated by the combustion pressure, and when good low-temperature combustion is being performed, the amount of increase of the peak pressure P ₁ with respect to the peak pressure P ₀ , that is, the differential pressure ΔP between the peak pressure P ₀ and the peak pressure P ₁ (= P ₁ −P ₀ ) becomes 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, if the pressure rise after ignition becomes large, the combustion temperature becomes high. At this time, low-temperature combustion is no longer performed, and thus a large amount of smoke is generated. Therefore, in the embodiment according to the present invention, the differential pressure ΔP
When (= P ₁ −P ₀ ) exceeds a predetermined upper limit, the injection timing is delayed so that the differential pressure ΔP becomes smaller.

Next, the control of the retard flag R1 indicating that the injection start timing should be retarded will be described with reference to FIG. FIG. 17 shows an interrupt routine that is performed every fixed crank angle. Referring to FIG. 17, first, in step 100, the current crank angle is set to CA1.
(FIG. 16). Crank angle is C
In the case of A1, the routine proceeds to step 101, where the output voltage of the peak hold circuit 49 is read. At this time, the output voltage of the peak hold circuit 49 represents the peak pressure P ₀ ,
Therefore, in step 101, so that the peak pressure P ₀ is read. Next, at step 102, 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 103, it is determined whether or not the current crank angle is CA2 (FIG. 16). When the crank angle is CA2, the routine proceeds to step 104, 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 104, the peak pressure P ₁ is read. Next, at step 105, 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 106, a differential pressure ΔP (= P ₁ −P ₀ ) between the peak pressure P ₀ and the peak pressure P ₁ is calculated.

[0079] Then whether the differential pressure [Delta] P in step 107 is larger than the upper limit value [Delta] P _max is determined. ΔP> Δ
If _Pmax , the routine proceeds to step 108, where the retard flag R
1 is set. This [Delta] P ≦ [Delta] P _max to become the retard flag R1 is reset for. When the retard flag R1 is set, the injection start timing is retarded.
> While in ΔP _max, so that the injection start timing continues to be retarded.

Next, the combustion pressure sensor 37 will be described with reference to FIG.
A method for determining whether or not noise above a certain level is generated based on the combustion pressure detected by the method will be described. That is, as described with reference to FIG.
₁ smoke is generated when higher against P _0. However, as shown in FIG. 18, the combustion pressure P ₁ is not so large as compared with P ₀ , so that no smoke is generated. However, since the combustion starts rapidly after the compression top dead center (TDC). In some cases, the pressure change rate dP / dθ of the combustion pressure per unit crank angle dθ may increase. Such a change in the combustion pressure occurs when the air-fuel ratio becomes too lean.

After the compression top dead center (TDC), if the pressure change rate dP / dθ increases, the noise increases. Therefore, in the embodiment according to the present invention, when the pressure change rate dP / dθ exceeds the allowable upper limit after the compression top dead center (TDC), the injection start timing is delayed in order to reduce the noise to a certain level or less. Next, control of the retard flag R2 indicating that the injection start timing should be retarded will be described with reference to FIG. Note that the routine shown in FIG. 19 is executed by interruption every fixed crank angle.

Referring to FIG. 19, first, at step 200, the current crank angle θ is changed to the compression top dead center TDC.
And CA3 (FIG. 18).
When TDC ≦ θ ≦ CA3, the routine proceeds to step 201, in which the combustion pressure P ₁ in the previous interruption routine is subtracted from the current combustion pressure P to obtain a pressure change rate dP of the combustion pressure.
/ Dθ (= P-P ₁ ) is calculated. Then step 2
02, the pressure change rate dP / dθ is the maximum value (dP / dθ)
_It is determined whether it is greater than _max . dP / dθ>
If (dP / dθ) _max , the routine proceeds to step 203, where dP / dθ is set to (dP / dθ) _max . Next, at step 204, the current crank angle θ is set to CA3 (FIG. 18).
Is determined, and when θ = CA3, the routine proceeds to step 205.

In step 205, it is determined whether or not the maximum value (dP / dθ) _{max of the} pressure change rate is larger than the allowable maximum value MAX. When (dP / dθ) _max > MAX, the routine proceeds to step 206, where the retard flag R2 is set, and then proceeds to step 208. On the other hand, (dP
/ Dθ) _max ≤ MAX, the retard flag R2 is reset, and the routine proceeds to step 208. Step 208
Then, (dP / dθ) _max is cleared. Retard flag R
When 2 is set, the injection start timing is retarded. Thus, while (dP / dθ) _max > MAX, the injection start timing continues to be retarded.

Next, the combustion pressure sensor 37 will be described with reference to FIG.
A method for determining whether or not combustion failure has occurred based on the combustion pressure detected by the method will be described. FIG. 20 shows the combustion pressure P and the pressure change rate dP / dθ of the combustion pressure P at the limit where poor combustion occurs. The broken line indicates the pressure change rate dP _m / d [theta] of the combustion chamber pressure P _m and the combustion chamber pressure P _m during motoring operation in FIG. 20. As shown in FIG. 20, when low-temperature combustion is performed, the peak of the combustion pressure P does not always appear after the compression top dead center (TDC). It decreases smoothly after the point (TDC). Therefore, at this time, the pressure change rate dP / dθ also changes relatively slowly. Such changes in the combustion pressure P and the pressure change rate dP / dθ tend to appear particularly when the air-fuel ratio is small.

[0085] On the other hand, always higher than the combustion chamber pressure P _m during motoring operation the combustion pressure P is shown by a broken line when the low temperature combustion is being performed. Further, while the combustion chamber pressure P _m during motoring operation, as shown in FIG. 20 is relatively rapidly reduced after compression top dead center, the combustion pressure P is total when low temperature combustion is being performed , And the rate of decrease of the combustion pressure P becomes large some time after the compression top dead center. Therefore the minimum value of the pressure change rate dP / d [theta] when the limit combustion failure occurs is larger than the minimum value of the pressure change rate dP _m / d [theta] at the time of motoring operation,
The crank angle which the pressure change rate dP / d [theta] becomes the minimum value is retarded from the crank angle at which the pressure change rate dP _m / d [theta] becomes the minimum value.

Accordingly, the combustion pressure P and the pressure change rate dP / d
It can be determined from the change in θ whether or not it is the limit at which poor combustion occurs. In the first embodiment according to the present invention, when the pressure change rate dP / dθ becomes smaller than a predetermined allowable lower limit value MIN between the compression top dead center (TDC) and CA4 (FIG. 20), poor combustion occurs. It is determined that this has occurred, and at this time, the injection start timing is advanced.

Next, a routine for executing the first embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 21, first, in step 300, it is determined whether or not the crank angle θ is between the compression top dead center TDC and CA4 (FIG. 20). When the TDC ≦ θ ≦ CA4 pressure change rate dP / dθ (= P-P 1) is calculated by subtracting the combustion pressure P ₁ at the time of the previous interruption willing from the current combustion pressure P in step 301.
Next, at step 302, it is determined whether or not the pressure change rate dP / dθ is smaller than a minimum value (dP / dθ) _min . dP / dθ <(dP / dθ ) mi dP / dθ is the minimum value the routine proceeds to step 303 when the _n (dP / _dθ)
min . Next, at step 304, the crank angle θ
Is determined to be CA4 (FIG. 20), and θ = C
When it becomes A4, the process proceeds to step 305.

In step 305, it is determined whether or not the minimum value (dP / dθ) _{min of the} pressure change rate is smaller than the allowable lower limit value MIN. When (dP / dθ) _min <MIN, the routine proceeds to step 306, where the advance angle flag is set.
Next, the routine proceeds to step 308. On the other hand, (dP / d
θ) When _min ≧ MIN, the routine proceeds to step 307, where the advance flag is reset, and then proceeds to step 308. In step 308, (dP / dθ) _min is cleared. When the advance flag is set, the injection start timing is advanced , so that the injection start timing continues to be advanced while (dP / dθ) <MIN.

Next, an operation control routine will be described with reference to FIG. Referring to FIG. 20, first, in step 400, 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, the routine proceeds to step 401, where the required load L is reduced to the first boundary X1 (N).
It is determined whether or not it has become larger. L ≦ X1
In the case of (N), the routine proceeds to step 403, where the first combustion is performed.

That is, in step 403, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 12A, and then in step 404, the target opening ST of the EGR control valve 31 is calculated from the map shown in FIG. SE is calculated. Next, at step 405, the injection amount Q is calculated from the map shown in FIG. 11A, and then at step 406, the reference injection start timing θS is calculated from the map shown in FIG. 11B.

Next, at step 407, the retard flag R1
Alternatively, it is determined whether at least one of R2 is set. When either the retard flag R1 or R2 is set, the routine proceeds to step 408, where the retard control of the injection start timing is performed. This retard control is shown in FIG. On the other hand, the retard flag R1 or R2
If none of the above is set, step 409
Then, it is determined whether or not the advance angle flag is set. When the advance flag is set, the routine proceeds to step 410, where advance control is performed. This advance angle control is shown in FIG.

On the other hand, in step 401, L> X
When it is determined that (N) has been reached, the routine proceeds to step 402, where the flag I is reset.
And the second combustion is performed. That is, step 413
15A, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 15A, and then, in step 414, the target opening SE of the EGR control valve 31 is calculated from the map shown in FIG. Next, at step 415, FIG.
The injection amount Q is calculated from the map shown in (A), and then, in step 416, the injection start timing θS is calculated from the map shown in FIG.

When the flag I is reset, in the next processing cycle, the routine proceeds from step 400 to step 411, where it is determined whether or not the required load L has become lower than the second boundary Y (N). When L ≧ Y (N), step 413
And the second combustion is performed. On the other hand, step 411
When it is determined that L <Y (N), the routine proceeds to step 412, where the flag I is set. Then, the routine proceeds to step 403, where low-temperature combustion is performed.

Next, the retard control performed in step 408 of FIG. 22 will be described with reference to FIG. Referring to FIG. 23, first, at step 420, a constant value α is subtracted from the correction value ΔθS for the injection start timing. Next, at step 421, the reference injection start timing θS
Is added to the correction value ΔθS to calculate the final injection start timing θS (= θS + ΔθS). Next, at step 422, the final injection start timing θS is set to an allowable limit timing θS that is predetermined according to the operating state of the engine.
_It is determined whether or not it has become smaller than _min , that is, whether or not it has become late.

When θS ≦ θS _min , the routine proceeds to step 423, where θS _min is made the final injection start timing θS, and then at step 424, an A / F control flag indicating that the air-fuel ratio is being controlled is set. Is done. Next, at step 425, a constant value β is subtracted from the correction value ΔST for the target opening of the throttle valve 20. Next, at step 426, the correction value ΔST is added to the target opening degree ST of the throttle valve 20 to obtain the final throttle valve 2.
A target opening ST of 0 (= ST + ΔST) is calculated.

That is, when at least one of the retard flags R1 and R2 is set, the injection start timing θS is delayed, and even if the injection start timing θS is delayed to the allowable limit timing θS _{min, the} retard flag R1 is still set. Alternatively, when R2 is set, the opening of the throttle valve 20 is reduced. When the opening of the throttle valve 20 is reduced, the amount of intake air is reduced, and thus the air-fuel ratio is reduced.

Next, the advance angle control performed in step 410 of FIG. 22 will be described with reference to FIG. Referring to FIG. 24, first in step 430, A
It is determined whether the / F control flag is set. If the A / F control flag is set, the routine proceeds to step 431, where a fixed value β is added to the correction value ΔST for the target opening of the throttle valve 20. Next, at step 432, the final throttle valve 2 is added by adding the correction value ΔST to the target opening ST of the throttle valve 20.
A target opening ST of 0 (= ST + ΔST) is calculated. Next, at step 433, it is determined whether or not the correction value ΔST has become zero or negative. Step 4 when ΔST ≦ 0
The process proceeds to 34, where ΔST is made zero, and then step 435
In, the A / F control flag is reset.

When the A / F control flag is reset, the routine proceeds from step 430 to step 436, where a fixed value α is added to the correction value ΔθS for the injection start timing. Next, at step 437, the correction value ΔθS is added to the reference injection start timing θS.
Is added to obtain the final injection start timing θS (=
θS + ΔθS) is calculated. That is, if the air-fuel ratio is smaller than the target air-fuel ratio when the advance flag is set, the opening of the throttle valve 20 is increased, thereby increasing the air-fuel ratio. In this case, even if the air-fuel ratio is increased to the target air-fuel ratio, if the advance flag is still set, the injection start timing θS is advanced.

Next, with reference to FIG. 25, a description will be given of a second embodiment of the method for determining whether or not combustion failure has occurred based on the combustion pressure. As described above, when low-temperature combustion is performed at the limit where poor combustion occurs, as shown in FIG. 25, the crank angle θk at which the pressure change rate dP / dθ becomes the minimum after the compression top dead center (TDC) is determined by motoring. Pressure change rate dP _m / dθ of combustion chamber pressure during operation
Is a constant crank angle Δθ than the crank angle θo at which
Only late. Therefore, in the second embodiment, θo corresponding to the engine operating state is stored in advance, and when θk becomes smaller than θo + Δθ, that is, when θk becomes earlier than the predetermined crank angle (θo + Δθ). The advance flag is set.

Next, a routine for executing the second embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 26, first, at step 500, it is determined whether or not the crank angle θ is between the compression top dead center TDC and CA4 (FIG. 25). Rate of pressure change dP / dθ (= P-P 1) is calculated by subtracting the combustion pressure P ₁ at the time of the previous interruption from the current combustion pressure P proceeds to step 50 1 when the TDC ≦ θ ≦ CA4 .
Next, at step 502, it is determined whether or not the pressure change rate dP / dθ is smaller than the minimum value (dP / dθ) _min . When dP / dθ <(dP / dθ) _min , the routine proceeds to step 503, where dP / dθ is the minimum value (dP / dθ).
is _min, and then at step 504, the crank angle θ in this case are .theta.k. Next, at step 505, it is determined whether or not the crank angle θ has become CA4 (FIG. 25). When θ = CA4, the routine proceeds to step 506.

In step 506, it is determined whether or not θk is smaller than the sum (θo + Δθ) of θo according to the operating state of the engine and a constant value Δθ. When θk <θo + Δθ, the routine proceeds to step 507, where the advance angle flag is set, and then proceeds to step 509. On the other hand, θk ≧ θo +
When Δθ, the process proceeds to step 508 to reset the advance flag, and then proceeds to step 509. Step 5
In 09, (dP / dθ) _min is cleared. When the advance angle flag is set, the injection start timing is advanced , so that the injection start timing continues to be advanced while θk <θo + Δθ.

Next, a third embodiment of a method for determining whether or not combustion failure has occurred based on the combustion pressure will be described with reference to FIG. Than the combustion chamber pressure P _m when the combustion pressure P is motoring operation after the compression top dead center (TDC) as shown in FIG. 27 in the case where the low temperature combustion is performed in the incomplete combustion occurs limitations as described above Slightly higher. Therefore, in this embodiment, the crank angle ATDCθa after a certain crank angle Δθa from the compression top dead center TDC
Combustion failure occurs when the combustion pressure P (A) is not higher than the combustion pressure P (B) at a crank angle BTDCθa at a predetermined crank angle Δθa before the compression top dead center TDC by a predetermined pressure ΔP ₀ or more. Is determined, and at this time, the advance angle flag is set.

Next, a routine for executing the third embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 28, first, at step 550 , it is determined whether or not crank angle θ is BTDC θa before compression top dead center (FIG. 27). The crank angle θ is BTDC θa
In step 551, the routine proceeds to step 551, where the combustion pressure P
Is defined as P (B). Next, at step 552, it is determined whether or not the crank angle θ is ATDC θa after the compression top dead center (FIG. 27). When the crank angle θ is ATDC θa, the routine proceeds to step 553, where the combustion pressure P at that time becomes PDC.
(A). Next, the routine proceeds to step 554.

At step 554, the combustion pressure P (A) is obtained by adding a constant value ΔP ₀ to the combustion pressure P (B) (P (B) + Δ
It is determined whether it is smaller than P ₀ ). P (A) <P
If (B) + ΔP _0, the routine proceeds to step 555, where the advance angle flag is set. On the other hand, P (A) ≧ P
When (B) + ΔP _0, the routine proceeds to step 556, where the advance angle flag is reset. When the advance flag is set, the injection start timing is advanced , so that P (A) <P (B) +
While ΔP ₀ , the injection start timing continues to be advanced .

Next, with reference to FIG. 29, a fourth embodiment of a method for judging whether or not a combustion failure has occurred based on the combustion pressure will be described. As described above, when low-temperature combustion is performed at the limit where poor combustion occurs, as shown in FIG. 29, CA5 to CA6 after compression top dead center (TDC).
In the predetermined crank angle range, the combustion pressure P (θ) at each crank angle becomes higher than the combustion chamber pressure P _m (θ) during the motoring operation by a constant pressure k or more. Therefore, in this embodiment, the combustion pressure P (θ) after the compression top dead center (TDC) is over the predetermined crank angle range of CA5 to CA6, and the pressure P _m ( When it is not higher than θ) by a predetermined pressure k or more, it is determined that poor combustion has occurred, and at this time, the advance angle flag is set.

Next, a routine for executing the fourth embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 30, first, at step 600, the crank angle θ is set to CA5 and CA5 after the compression top dead center (TDC).
6 (FIG. 29). CA5
When ≦ θ ≦ CA6, the routine proceeds to step 601, where the pressure P _m (θ) in the combustion chamber during the motoring operation at the current crank angle is calculated. In addition, this combustion chamber pressure P _m
(Θ) is stored in the ROM 42 in advance. Next, at step 602, the combustion pressure P at the current crank angle θ
(Θ) is taken. Next, at step 663, the pressure difference (P (θ) between the combustion pressure P (θ) and the pressure P _m (θ) in the combustion chamber.
−P _m (θ)) is greater than a constant value k. If CA5 ≦ θ ≦ CA6, P (θ) −P
when it becomes _{m (θ)} ≦ k flag K is set the routine proceeds to step 6 04. Next, at step 605, it is determined whether or not the crank angle θ has become CA6 (FIG. 29). When θ = CA6, the routine proceeds to step 606.

At step 606, it is determined whether or not the flag K is set. Advance flag goes to step 60 7 is set when the flag K is set, then the routine proceeds to step 609. Advance flag proceeds to step 608 when the flag K is not set, on the contrary Ru is reset. In step 609, the flag K is reset. When the advance flag is set, the injection start timing is advanced , and therefore, while the flag K is kept set, the injection start timing continues to be advanced .

Next, a fifth embodiment of the method for judging whether or not combustion failure has occurred based on the combustion pressure will be described with reference to FIG. Than the combustion chamber pressure P _m the combustion pressure P during motoring operation after the compression top dead center (TDC) as shown in FIG. 31 when the low temperature combustion is performed in incomplete combustion occurs limitations as described above Get higher. Therefore, in this embodiment, a constant crank angle range Δ from the compression top dead center TDC to ATDC θb after the compression top dead center is obtained.
The integral value AΣP of the combustion pressure P within θb is equal to the compression top dead center T
When the combustion pressure P is not higher than the integral value B 燃 焼 P of the combustion pressure P within a predetermined crank angle range Δθb from DC to BTDC θb before compression top dead center by a predetermined value f or more, it is determined that poor combustion has occurred. The corner flag is set.

Next, a routine for executing the fifth embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 32, first, at step 650, it is determined whether or not crank angle θ is between BTDC θb before compression top dead center and TDC (FIG. 31). BTDCθb
If <θ <TDC, the routine proceeds to step 651, where BΣP
Is added to the current combustion pressure P. This addition operation of the combustion pressure is performed when BTDC θb <θ <TDC, so that BΣP is the combustion pressure P at BTDC θb <θ <TDC.
Represents the integral value of.

Next, at step 652, it is determined whether or not the crank angle θ is between TDC and ATDC θb after compression top dead center (FIG. 31). When TDC ≦ θ ≦ ATDCθb, the routine proceeds to step 653, where the current combustion pressure P is added to AΣP. The effect of adding the combustion pressure is TDC ≦ θ ≦
ATDC θb, so that AΣP is equal to TD
It represents the integral value of the combustion pressure P when C ≦ θ ≦ ATDCθb. Next, at step 654, the crank angle θ is set to AT
It is determined whether DC θb (FIG. 31) has been reached, and θ = A
When it becomes TDCθb, the process proceeds to step 655.

At step 655, it is determined whether or not the integral value AΣP is smaller than the sum (BΣP + f) of the integral value BΣP and the constant value f. When AΣP <BΣP + f, the routine proceeds to step 656, where the advance angle flag is set, and then proceeds to step 658. In contrast, AΣP ≧ BΣP + f
In the case of, the process proceeds to step 657 to reset the advance angle flag, and then proceeds to step 658. Step 658
In this case, B @ P and A @ P are cleared. When the advance flag is set, the injection start timing is advanced , and therefore AΣP
While <BΣP + f, the injection start timing continues to be advanced .

Next, with reference to FIG. 33, a sixth embodiment of the method for judging whether or not combustion failure has occurred based on the combustion pressure will be described. In this embodiment, as shown in FIG. 33, a peak Pt of the combustion pressure P is formed after the compression top dead center, unlike the embodiments described above. Such a change in the combustion pressure P occurs when the air-fuel ratio is relatively large. In this case, an area ΔS surrounded by a curve indicating the combustion pressure P and a curve indicating the pressure P _{m in} the combustion chamber during motoring operation.
Becomes lower than a certain value when poor combustion occurs. Therefore, in this embodiment, CA7 to CA8 after compression top dead center (TDC)
Pressure P within a predetermined crank angle range
Integrated value .SIGMA.P of is determined to be defective combustion when not higher predetermined value S or than the integral value .SIGMA.P _m of the combustion chamber pressure P _m during motoring operation occurs within the crank angle range, the When the advance flag is set.

Next, a routine for executing the sixth embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 34, first, in step 700, CA7 and CA after the compression top dead center (TDC) are determined.
8 (FIG. 33). CA7
When ≦ θ ≦ CA8, the routine proceeds to step 701, where the current combustion pressure P is added to ΔP. This addition operation of the combustion pressure is performed when CA7 ≦ θ ≦ CA8, and thus ΔP represents the integral value of the combustion pressure P when CA7 ≦ θ ≦ CA8. Next, at step 70 2 crank angle θ is CA8
It is determined whether or not (FIG. 33) has been reached. When θ = CA8, the routine proceeds to step 703.

[0114] integral value in step 703 .SIGMA.P _m is than the sum of the CA7 during motoring operation and the integral value .SIGMA.P _m of the combustion chamber pressure P _m within the crank angle range of CA8 a constant value S (ΣP _m + S) It is determined whether it is smaller.
The integral value ΣP _m of the pressure P _{m in} the combustion chamber is determined in advance by RO
It is stored in M42. When ΣP <ΣP _m + S, the routine proceeds to step 704, where the advance angle flag is set, and then proceeds to step 706. On the other hand, mP ≧ ΣP _m
In the case of + S, the process proceeds to step 705 to reset the advance angle flag, and then proceeds to step 706. Step 7
At 06, $ P is cleared. When the advance angle flag is set, the injection start timing is advanced , so that ΣP <ΣP _m + S
, The injection start timing continues to be advanced .

Next, based on the combustion pressure, referring to FIG.
Seventh implementation of a method for determining whether poor combustion has occurred
An example will be described. FIG. 35 shows the combustion pressure P as in FIG.
Is changed, and in this case, good low-temperature combustion is performed.
Has been performed, the compression top dead center as shown in FIG.
After (TDC), the pressure change rate dP / dθ of the combustion pressure P
Is the combustion chamber pressure P during motoring operation. _mPressure change rate
dP_m/ Dθ over the crank angle range Δθ
Become larger. However, if combustion failure occurs, dP
/ Dθ> dP_mA curve showing dP / dθ when / dθ
dP_mThe area ΔdS surrounded by the curve indicating / dθ is
Becomes smaller than the constant value h, or dP / dθ> dP_m
/ Dθ is smaller than the constant value J.
It will be cheap.

In this embodiment, the compression top dead center (TD
Pressure change rate in the combustion chamber pressure P _m at the rate of pressure change dP / d [theta] of the combustion pressure is motoring operation after C) dP _m /
The crank angle range Δθ that is continuously higher than dθ is calculated, and the pressure change rate dP / dθ of the combustion pressure and the pressure change rate dP _m of the combustion chamber pressure P _m within the crank angle range Δθ are calculated.
/ Dθ is smaller than a predetermined value h or when the crank angle range Δθ is smaller than a predetermined range J, it is determined that poor combustion has occurred. The advance flag is set.

Next, a routine for executing the seventh embodiment will be described with reference to FIG. This routine is executed by interruption every fixed crank angle.
Referring to FIG. 36, first, at step 750, it is determined whether or not the crank angle θ is between the compression top dead center TDC and CA9 (FIG. 35). When TDC <of theta ≦ CA9 pressure change rate dP / dθ (= P-P 1) is calculated by subtracting the combustion pressure P ₁ at the time of the previous interruption from the current combustion pressure P proceeds to step 751.
Next, at step 752, the pressure change rate dP _m / of the pressure in the combustion chamber during the motoring operation at the current crank angle.
dθ is calculated. This pressure change rate dP _m / dθ is stored in the ROM 42 in advance.

[0118] rate of change of pressure and then the pressure change rate dP / d [theta] at step 75 3, the combustion pressure P combustion chamber pressure dP _m /
It is determined whether it is greater than dθ. dP / dθ> d
If P _m / dθ, the routine proceeds to step 754, where dP / d
The difference Δd between θ and dP _m / dθ (= dP / dθ−dP _m / d
θ) is calculated. Next, at step 755, the difference Δd is added to ΔdS, and then at step 756, the crank angle t from when an interrupt is performed until the next interrupt is performed.
Is added to Δθ. Therefore, ΔdS calculated in step 755 and Δθ calculated in step 756 indicate the area ΔdS and the crank angle range Δθ shown in FIG. 35, respectively.

Next, at step 757, it is determined whether or not the crank angle θ has reached CA9 (FIG. 35).
When it reaches 9, the process proceeds to step 758. Step 7
At 58, it is determined whether or not ΔdS is larger than a constant value h. The process jumps to step 760 when ΔdS ≦ h, and proceeds to step 759 when ΔdS> h. c7
At 59, it is determined whether or not Δθ is larger than the fixed value J. When Δθ ≦ J, the process proceeds to step 760, where Δθ ≧
In the case of J, the process proceeds to step 761.

At step 760, the advance flag is set, and then the routine proceeds to step 762. On the other hand, in step 761, the advance flag is reset, and then the process proceeds to step 762. In step 762, ΔdS and Δθ
Is cleared. When the advance flag is set, the injection start timing is advanced , so that the injection start timing continues to be advanced while ΔdS ≦ h or Δθ ≦ J.

[0121]

According to the present invention, it is possible to maintain good low-temperature combustion by judging whether smoke or noise of a certain level or more has occurred or combustion failure has occurred based on the combustion pressure detected by the combustion pressure sensor. Can be.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing a combustion pressure.

FIG. 4 is a diagram showing fuel molecules.

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

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

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

FIG. 8 is a view showing an opening degree of a throttle valve and the like.

FIG. 9 is a diagram showing a required torque.

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

FIG. 11 is a diagram showing a map of an injection amount and the like.

FIG. 12 is a view showing a map of a target opening of a throttle valve and the like.

FIG. 13 is a diagram showing an air-fuel ratio in the second combustion.

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 a throttle valve and the like.

FIG. 16 is a diagram showing a combustion pressure and the like.

FIG. 17 is a diagram showing a crank angle interrupt routine.

FIG. 18 is a diagram showing a combustion pressure and the like.

FIG. 19 is a diagram showing a crank angle interrupt routine.

FIG. 20 is a diagram for explaining a first embodiment of a method for determining whether or not combustion failure has occurred.

FIG. 21 is a flowchart for executing the first embodiment.

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

FIG. 23 is a flowchart for executing advance control.

FIG. 24 is a flowchart for executing advance control.

FIG. 25 is a diagram for explaining a second embodiment of a method for determining whether or not combustion failure has occurred.

FIG. 26 is a flowchart for executing the second embodiment.

FIG. 27 is a diagram for explaining a third embodiment of the method of determining whether or not combustion failure has occurred.

FIG. 28 is a flowchart for executing the third embodiment.

FIG. 29 is a diagram for explaining a fourth embodiment of the method of determining whether or not combustion failure has occurred.

FIG. 30 is a flowchart for executing the fourth embodiment.

FIG. 31 is a diagram for explaining a fifth embodiment of the method of determining whether or not combustion failure has occurred.

FIG. 32 is a flowchart for executing the fifth embodiment.

FIG. 33 is a diagram for explaining a sixth embodiment of the method of determining whether or not combustion failure has occurred.

FIG. 34 is a flowchart for executing the sixth embodiment.

FIG. 35 is a diagram for explaining a seventh embodiment of the method of determining whether or not combustion failure has occurred.

FIG. 36 is a flowchart for executing the seventh embodiment.

FIG. 37 is a flowchart for executing the seventh embodiment.

[Explanation of symbols]

 6 fuel injection valve 20 throttle valve 31 EGR control valve 37 combustion pressure sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 385 F02D 41/04 385J 41/40 41/40 E F02M 25/07 550 F02M 25/07 550G 570 570D (72) Inventor Masato Goto 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Yoshi ▲ saki Koji 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hiroki Murata Aichi 1 Toyota Town, Toyota City, Japan Toyota Motor Corporation (56) References JP-A-7-4287 (JP, A) JP-A 8-177654 (JP, A) JP-A 8-86251 (JP, A) JP-A-9-287527 (JP, A) JP-A-9-287528 (JP, A) JP-A-54-20203 (JP, A) JP-A-9-317568 (JP, A) JP-A-3 100362 (JP, A) JP flat 11-36923 (JP, A) JP flat 9-14026 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) F02D 41/00 - 41 / 40

Claims (19)

(57) [Claims] 1. A generation amount of the gradually increasing the amount of inert gas in the combustion chamber soot reached the peak gradually increased, the combustion chamber
As the amount of inert gas is increased further,
The temperature of fuel and surrounding gas during combustion is lower than the temperature of soot formation.
In an internal combustion engine in which soot is hardly generated due to the lowering of the soot, the amount of inert gas supplied into the combustion chamber is made larger than the amount of inert gas at which the amount of soot generation reaches a peak, and fuel is directed toward the combustion chamber. A fuel injection valve for injecting, a combustion pressure sensor for detecting the combustion pressure in the combustion chamber, and whether smoke or noise of a certain level or more is generated based on the combustion pressure detected by the combustion pressure sensor, or determining means for determining whether defective combustion is occurring, reducing the or air delay the fuel injection timing when the smoke or the appropriate level of noise is determined to have occurred, combustion non <br/> An internal combustion engine provided with control means for advancing the fuel injection timing or increasing the air-fuel ratio when it is determined that goodness has occurred. 2. When it is determined that smoke or noise of a certain level or more is generated, the fuel injection timing is delayed, and even if the fuel injection timing is delayed to an allowable limit time, the fuel is still smoked or at a certain level or more. 2. The internal combustion engine according to claim 1, wherein the air-fuel ratio is made smaller than the target air-fuel ratio when it is determined that noise is occurring. Wherein the air-fuel ratio is large when the combustion failure is determined to occur when the air-fuel ratio is smaller than the target air-fuel ratio, still it is largely air-fuel ratio is to the target air-fuel ratio combustion 3. The internal combustion engine according to claim 2, wherein the fuel injection timing is advanced when it is determined that a failure has occurred. 4. The internal combustion engine according to claim 1, wherein said control means controls an air-fuel ratio by controlling an intake air amount. 5. In a case where a first peak of the combustion pressure appears at the compression top dead center and a second peak of the combustion pressure appears after the compression top dead center, the determination means determines that the combustion pressure at the second peak is lower. The internal combustion engine according to claim 1, wherein it is determined that smoke has occurred when the pressure is higher than a combustion pressure at the first peak by a predetermined pressure or more. 6. A method according to claim 1, wherein said determining means determines that noise of a certain level or more is generated when a pressure change rate of the combustion pressure after the compression top dead center exceeds a predetermined allowable upper limit. 2. The internal combustion engine according to 1. 7. The method according to claim 1, wherein said determining means determines that poor combustion has occurred when the pressure change rate of the combustion pressure after the compression top dead center is lower than a predetermined allowable lower limit. An internal combustion engine as described. 8. The system according to claim 1, wherein the determination unit determines that poor combustion has occurred when the minimum value of the pressure change rate of the combustion pressure after the compression top dead center occurs before a predetermined crank angle. 2. The internal combustion engine according to 1. 9. The combustion engine according to claim 1, wherein the combustion pressure at a crank angle after a predetermined crank angle from the compression top dead center is a predetermined pressure compared with a combustion pressure at a crank angle before the predetermined crank angle from the compression top dead center. The internal combustion engine according to claim 1, wherein it is determined that poor combustion occurs when the temperature is not higher than the above. 10. The determination means according to claim 1, wherein the combustion pressure after the compression top dead center is higher than the pressure in the combustion chamber at the same crank angle during the motoring operation by a predetermined pressure over a predetermined crank angle range. 2. The internal combustion engine according to claim 1, wherein it is determined that poor combustion occurs when there is no combustion. 11. The determination means according to claim 1, wherein an integral value of the combustion pressure within a predetermined crank angle range from the compression top dead center to the compression top dead center is within the predetermined crank angle range from the compression top dead center to the compression top dead center. 2. The internal combustion engine according to claim 1, wherein it is determined that poor combustion has occurred when the combustion pressure is not higher than an integral value of the combustion pressure by a predetermined value. 12. The determination means according to claim 1, wherein the integral value of the combustion pressure in a predetermined crank angle range after the compression top dead center is smaller than the integral value of the pressure in the combustion chamber during the motoring operation in the crank angle range. 2. The internal combustion engine according to claim 1, wherein it is determined that poor combustion has occurred when the temperature is not higher than a predetermined value. 13. The crank angle range in which the pressure change rate of the combustion pressure after the compression top dead center is continuously higher than the pressure change rate of the pressure in the combustion chamber during the motoring operation, is calculated. The integral value of the difference between the pressure change rate of the combustion pressure and the pressure change rate of the pressure in the combustion chamber within the crank angle range is smaller than a predetermined value, or the crank angle range is smaller than a predetermined range. 2. The internal combustion engine according to claim 1, wherein it is determined that poor combustion sometimes occurs. 14. An exhaust gas recirculation device for recirculating exhaust gas discharged from a combustion chamber into an engine intake passage, wherein the inert gas comprises recirculated exhaust gas.
An internal combustion engine according to claim 1. 15. The internal combustion engine of claim 14, wherein the exhaust gas recirculation rate is greater than or equal to about 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 inert gas supplied into the combustion chamber is larger than the amount of inert gas at which the generation amount of soot is at a peak and almost no soot is generated, and the generation amount of soot is at a peak. 2. The internal combustion engine according to claim 1, further comprising switching means for selectively switching between the second combustion in which the amount of inert gas supplied into the combustion chamber is smaller than the amount of inert gas. 19. The 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, and a second operation is performed. Second in the area
19. The internal combustion engine according to claim 18, wherein combustion of the internal combustion engine is performed.