JP3758514B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device for an internal combustion engine.
[0002]
[Prior art]
Particulates mainly composed of soot are contained in the exhaust gas of internal combustion engines, particularly diesel engines. Since particulates are harmful substances, it has been proposed to arrange a filter for collecting particulates in the engine exhaust system before release into the atmosphere. Such a filter is required to burn off the collected particulates in order to prevent an increase in exhaust resistance due to clogging.
[0003]
In such filter regeneration, ignition and combustion occur when the particulates reach approximately 600 ° C., but the exhaust gas temperature of the diesel engine is considerably lower than 600 ° C. at normal times, and usually means such as heating the filter itself. is required.
[0004]
In Japanese Patent Publication No. 7-106290, if a platinum group metal and an alkaline earth metal oxide are supported on a filter, the particulates on the filter are about 400 ° C., which is the exhaust gas temperature of a diesel engine at normal times. It is disclosed that it burns continuously.
[0005]
However, even if this filter is used, the exhaust gas temperature is not always about 400 ° C, and a large amount of particulates may be released from the diesel engine depending on the operating state. Particulates that could not be burned out in time may gradually accumulate on the filter.
[0006]
In this filter, if particulates are accumulated to some extent, the ability to burn out the particulates is extremely reduced, so that the filter can no longer be regenerated by itself. In this way, simply placing this type of filter in the engine exhaust system may cause clogging relatively early, resulting in a significant reduction in engine output.
[0007]
In order to solve this problem, it is conceivable to reverse the exhaust upstream side and the exhaust downstream side of the filter periodically or irregularly. By this reversal, both sides of the filter collection wall can be used as collection surfaces, so the amount of particulate collection on each collection surface is reduced and the particulate burnout capability is maintained high, and the filter has a particulate filter. Curing can be made difficult to deposit.
[0008]
However, in order to reverse the exhaust upstream side and the exhaust downstream side of the filter, the flow path is switched by the valve body, and the exhaust gas may bypass the filter during the switching.
[0009]
[Problems to be solved by the invention]
By the way, it is common to provide a turbocharger to increase the engine output. Thus, if the turbine of the turbocharger is arranged on the upstream side or downstream side of the filter, the pressure loss in the particulate filter is reduced by the exhaust gas bypassing the filter during the above-described switching of the valve body. In addition, the exhaust pressure on the downstream side of the turbine decreases or the exhaust pressure on the upstream side increases, and in any case, the differential pressure between the upstream side and the downstream side of the turbine is increased, so the boost pressure by the compressor increases. To do. As a result, the fuel injection amount automatically increases and torque fluctuation occurs.
[0010]
Such torque fluctuation is not limited to the case where the reverse rotation means as described above is provided, but for example, the exhaust gas may intentionally bypass the filter depending on the engine operating state or the filter state. This is also a problem that occurs in such cases.
[0011]
Accordingly, an object of the present invention is to provide an exhaust emission control device for an internal combustion engine including a turbocharger that can prevent torque fluctuation when exhaust gas bypasses a particulate filter.
[0012]
[Means for Solving the Problems]
  According to a first aspect of the present invention, there is provided an exhaust emission control device for an internal combustion engine comprising a particulate filter disposed in an engine exhaust system for collecting particulates, the internal combustion engine comprising a turbocharger and intake air amount suppression means. When the exhaust gas bypasses the particulate filter, the intake air amount suppression means suppresses an increase in the intake air amountHowever, at the time of high rotation and high load, the increase in the intake air amount is not suppressed by the intake air amount suppression means, and the increase in the fuel injection amount accompanying the increase in the intake air amount is suppressed.It is characterized by that.
[0013]
According to a second aspect of the present invention, there is provided the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, wherein the intake air amount suppression means increases the supercharging pressure of the turbocharger. It is characterized by suppressing.
[0014]
According to a third aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine according to the first aspect, wherein the intake air amount suppression means increases the supercharging pressure of the turbocharger. On the other hand, an increase in the intake air amount is suppressed by making it difficult to supply intake air into the cylinder.
[0016]
  And claims according to the invention4The exhaust gas purification apparatus for an internal combustion engine according to claim 1 is the exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein an increase in pressure loss in the particulate filter accompanying an increase in the amount of particulate collection in the particulate filter is achieved. On the other hand, it is characterized by comprising a supercharging pressure lowering suppression means for suppressing a decrease in the supercharging pressure of the turbocharger.
[0017]
  And claims according to the invention5An exhaust emission control device for an internal combustion engine according to claim 1,4The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein when the particulate collection amount is predicted or detected to be equal to or greater than a set collection amount, the fuel injection amount is suppressed to a set injection amount or less.
[0018]
  And claims according to the invention6The exhaust gas purification apparatus for an internal combustion engine according to claim 1 is the exhaust gas purification apparatus for the internal combustion engine according to claim 1, wherein liquefaction of hydrocarbons discharged from the cylinders is upstream of the turbine of the turbocharger in the engine exhaust system. In order to suppress this, a heat retaining means is provided.
[0019]
  And claims according to the invention7The exhaust gas purification apparatus for an internal combustion engine according to claim 1 is the exhaust gas purification apparatus for the internal combustion engine according to claim 1, wherein liquefaction of hydrocarbons discharged from the cylinders is upstream of the turbine of the turbocharger in the engine exhaust system. In order to suppress this, a heating means is provided.
[0020]
  And claims according to the invention8An internal combustion engine exhaust gas purification apparatus according to claim 17In the exhaust gas purification apparatus for an internal combustion engine according to any one of the above, a reversing means for reversing the exhaust upstream side and the exhaust downstream side of the particulate filter by switching the valve body from one of the two shut-off positions to the other. In the particulate filter, the collected particulate is oxidized, and the particulate filter has a collection wall for collecting the particulate, and the collection wall is a first collection surface. And a second collection surface, and the first reverse of the collection wall for collecting the particulates by reversing the exhaust upstream side and the exhaust downstream side of the particulate filter by the reversing means. The collection surface and the second collection surface are used alternately, and the exhaust gas is discharged from the partition while the valve body is switched from one of the two shut-off positions to the other. Characterized by bypassing the filter.
[0021]
  And claims according to the invention9An exhaust emission control device for an internal combustion engine according to claim 1,8In the exhaust gas purification apparatus for an internal combustion engine according to the item 1, the active oxygen releasing agent is supported on the collection wall, and the active oxygen released from the active oxygen releasing agent oxidizes the particulates.
[0022]
  And claims according to the invention10An exhaust emission control device for an internal combustion engine according to claim 1,9In the exhaust gas purification apparatus for an internal combustion engine according to claim 1, the active oxygen release agent takes in oxygen when excess oxygen is present in the surrounding area and retains oxygen, and when the surrounding oxygen concentration decreases, the retained oxygen is converted into the form of active oxygen. It is characterized by being discharged with
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic longitudinal sectional view of a four-stroke diesel engine equipped with an exhaust emission control device according to the present invention, FIG. 2 is an enlarged longitudinal sectional view of a combustion chamber in the diesel engine of FIG. 1, and FIG. It is a bottom view of the cylinder head in the diesel engine of. Referring to FIGS. 1 to 3, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5a is a cavity formed on the top surface of the piston 4, and 5 is formed in the cavity 5a. The combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is a pair of intake valves, 8 is an intake port, 9 is a pair of exhaust valves, and 10 is 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 an air cleaner 14 via an intake duct 13. A throttle valve 16 driven by an electric motor 15 is disposed in the intake duct 13. On the other hand, the exhaust port 10 is connected to the exhaust manifold 17.
[0024]
As shown in FIG. 1, an air-fuel ratio sensor 21 is disposed in the exhaust manifold 17. The exhaust manifold 17 and the surge tank 12 are connected to each other via an EGR passage 22, and an electrically controlled EGR control valve 23 is disposed in the EGR passage 22. A cooling device 24 for cooling the EGR gas flowing in the EGR passage 22 is disposed around the EGR passage 22. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 24, and the EGR gas is cooled by the engine cooling water.
[0025]
On the other hand, each fuel injection valve 6 is connected to a fuel reservoir, so-called common rail 26, via a fuel supply pipe 25. Fuel is supplied into the common rail 26 from an electrically controlled fuel pump 27 with variable discharge amount, and the fuel supplied into the common rail 26 is supplied to the fuel injection valve 6 through each fuel supply pipe 25. A fuel pressure sensor 28 for detecting the fuel pressure in the common rail 26 is attached to the common rail 26, and a fuel pump 27 is set so that the fuel pressure in the common rail 26 becomes a target fuel pressure based on an output signal of the fuel pressure sensor 28. The discharge amount is controlled.
[0026]
An electronic control unit 30 receives an output signal from the air-fuel ratio sensor 21 and an output signal from the fuel pressure sensor 28. Further, a load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and an output signal of the load sensor 41 is also input to the electronic control unit 30. For example, an output signal of a crank angle sensor 42 that generates an output pulse every 30 ° rotation is also input. Thus, the electronic control unit 30 operates the fuel injection valve 6, the electric motor 15, the EGR control valve 23, and the fuel pump 27 based on various signals.
[0027]
As shown in FIGS. 2 and 3, in the embodiment according to the present invention, the fuel injection valve 6 is composed of a hole nozzle having six nozzle ports, and the nozzle port of the fuel injection valve 6 is equiangularly slightly downward with respect to the horizontal plane. Fuel F is injected at intervals. As shown in FIG. 3, two of the six fuel sprays F are scattered along the lower surface of the valve body of each exhaust valve 9. 2 and 3 show the time when fuel injection is performed at the end of the compression stroke. At this time, the fuel spray F advances toward the inner peripheral surface of the cavity 5a, and is then ignited and combusted.
[0028]
FIG. 4 shows a case where additional fuel is injected from the fuel injection valve 6 when the lift amount of the exhaust valve 9 is maximum during the exhaust stroke. That is, as shown in FIG. 5, the main injection Qm is performed near the compression top dead center, and then, the additional fuel Qa is injected in the middle of the exhaust stroke. In this case, the fuel spray F traveling in the direction of the valve body of the exhaust valve 9 is directed between the rear surface of the umbrella portion of the exhaust valve 9 and the exhaust port 10. That is, in other words, of the six nozzle ports of the fuel injection valve 6, two of the nozzle ports discharge the fuel spray F when additional fuel Qa is injected while the exhaust valve 9 is open. It is formed so as to face between the rear surface of the umbrella portion of the valve 9 and the exhaust port 10. In the embodiment shown in FIG. 4, the fuel spray F collides with the back of the umbrella part of the exhaust valve 9 at this time, and the fuel spray F that collides with the back of the umbrella part of the exhaust valve 9 is reflected on the back of the umbrella part of the exhaust valve 9. To the exhaust port 10.
[0029]
Normally, no additional fuel Qa is injected, and only main injection Qm is performed. FIG. 6 shows the change in output torque when the air-fuel ratio A / F (horizontal axis in FIG. 6) is changed by changing the opening degree and EGR rate of the throttle valve 16 during engine low load operation, and smoke, HC , CO, NO_xThe experiment example which shows the change of the discharge amount of is shown. As can be seen from FIG. 6, in this experimental example, the EGR rate increases as the air-fuel ratio A / F decreases, and the EGR rate is 65% or more when the air-fuel ratio is less than the theoretical air-fuel ratio (≈14.6).
[0030]
As shown in FIG. 6, when the air-fuel ratio A / F is decreased by increasing the EGR rate, the EGR rate becomes around 40% and the amount of smoke generated increases when the air-fuel ratio A / F becomes about 30 To start. Next, when the EGR rate is further increased and the air-fuel ratio A / F is decreased, the amount of smoke generated increases rapidly and reaches a peak. Next, when the EGR rate is further increased and the air-fuel ratio A / F is reduced, the smoke suddenly decreases, the EGR rate is increased to 65% or more, and when the air-fuel ratio A / F is near 15.0, the smoke becomes almost zero. . That is, almost no wrinkles occur. At this time, the output torque of the engine slightly decreases, and NO_xThe amount of generation is considerably low. On the other hand, the generation amount of HC and CO starts increasing at this time.
[0031]
FIG. 7A shows a change in combustion pressure in the combustion chamber 5 when the air-fuel ratio A / F is near 21 and the amount of smoke generated is the largest, and FIG. 7B shows that the air-fuel ratio A / F is 18. A change in the combustion pressure in the combustion chamber 5 when the amount of smoke generated in the vicinity is almost zero is shown. As can be seen by comparing FIG. 7A and FIG. 7B, the case of FIG. 7B where the amount of smoke generated is almost zero is shown in FIG. 7A where the amount of smoke generated is large. It can be seen that the combustion pressure is lower than the case.
[0032]
The following can be said from the experimental results shown in FIGS. That is, first, when the air-fuel ratio A / F is 15.0 or less and the amount of smoke generated is almost zero, as shown in FIG._xThe amount of generated is significantly reduced. NO_xThe reduction in the amount of generation means that the combustion temperature in the combustion chamber 5 has decreased, and therefore it can be said that the combustion temperature in the combustion chamber 5 is low when soot is hardly generated. The same can be said from FIG. That is, in the state shown in FIG. 7B where almost no soot is generated, the combustion pressure is low, and therefore the combustion temperature in the combustion chamber 5 is low at this time.
[0033]
Second, when the amount of smoke generated, that is, the amount of soot is substantially zero, the HC and CO emissions increase as shown in FIG. This means that the hydrocarbons are discharged without growing to the soot. That is, linear hydrocarbons and aromatic hydrocarbons as shown in FIG. 8 contained in the fuel are thermally decomposed to form soot precursors when the temperature is raised in an oxygen-deficient state. A soot made of a solid in which carbon atoms are assembled is produced. In this case, the actual soot formation process is complicated, and it is not clear what form the soot precursor will take, but in any case the hydrocarbons shown in FIG. After that, it will grow up to heels. Therefore, as described above, when the generation amount of soot becomes almost zero, the emission amount of HC and CO increases as shown in FIG. 6. At this time, HC is a precursor of soot or a hydrocarbon in the previous state. .
[0034]
Summarizing these considerations based on the experimental results shown in FIGS. 6 and 7, the amount of soot generated becomes almost zero when the combustion temperature in the combustion chamber 5 is low, and at this time, the soot precursor or the previous state Hydrocarbons are discharged from the combustion chamber 5. As a result of repeated experimental research on this in detail, when the temperature of the fuel in the combustion chamber 5 and the gas surrounding it is below a certain temperature, the soot growth process stops midway, that is, soot It was found that soot was not generated at all, and soot was generated when the temperature of the fuel in the combustion chamber 5 and the surrounding temperature became below a certain temperature.
[0035]
By the way, when the hydrocarbon generation process stops in the state of soot precursor, the temperature of the fuel and its surroundings, that is, the above-mentioned certain temperature changes depending on various factors such as the type of fuel, the air-fuel ratio and the compression ratio. I can't say how many times, but this certain temperature is NO_xTherefore, this certain temperature is NO._xIt can be defined to some extent from the amount of occurrence. That is, as the EGR rate increases, the temperature of the fuel during combustion and the surrounding gas decreases, and NO_xThe amount of generation decreases. At this time NO_xWhen the amount of generation becomes around 10p.p.m or less, soot almost disappears. Therefore, the above mentioned temperature is NO_xThis is almost the same as the temperature when the amount of generated is around 10p.p.m or less.
[0036]
Once soot is produced, it cannot simply be purified by post-treatment using a catalyst having an oxidizing function. In contrast, soot precursors or hydrocarbons in the previous state can be easily purified by post-treatment using a catalyst having an oxidation function. Like this, NO_xIt is extremely effective for purifying exhaust gas to reduce the generation amount of hydrocarbons and to discharge hydrocarbons from the combustion chamber 5 in the state of soot precursor or in front thereof.
[0037]
Now, in order to stop the growth of hydrocarbons in a state before soot is generated, it is necessary to suppress the temperature of the fuel and the surrounding gas in the combustion chamber 5 to a temperature lower than the temperature at which soot is generated. There is. In this case, in order to suppress the temperature of the fuel and the gas around it, it has been found that the endothermic effect of the gas around the fuel when the fuel burns has a very large influence.
[0038]
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 away from the fuel does not increase so much, and only the temperature around the fuel becomes extremely high locally. That is, at this time, the air away from the fuel hardly performs the endothermic action of the combustion heat of the fuel. In this case, since the combustion temperature becomes extremely high locally, the unburned hydrocarbons that have received this heat of combustion produce soot.
[0039]
On the other hand, the situation is slightly different when fuel is present in a mixed gas of a large amount of inert gas and a small amount of air. In this case, the evaporated fuel diffuses around and reacts with oxygen mixed in the inert gas and burns. In this case, since the combustion heat is absorbed by the surrounding inert gas, the combustion temperature does not rise so much. 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 action of the inert gas.
[0040]
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 soot is generated, an amount of inert gas that can absorb a sufficient amount of heat is required. Therefore, if the amount of fuel increases, the amount of inert gas required increases accordingly. In this case, the greater the specific heat of the inert gas, the stronger the endothermic action. Therefore, the inert gas is preferably a gas having a large specific heat. This point, CO₂Since EGR gas has a relatively large specific heat, it can be said that it is preferable to use EGR gas as an inert gas.
[0041]
FIG. 9 shows the relationship between the EGR rate and smoke when EGR gas is used as the inert gas and the cooling degree of the EGR gas is changed. That is, in FIG. 9, curve A shows the case where EGR gas is cooled strongly and the EGR gas temperature is maintained at about 90 ° C., and curve B shows the case where EGR gas is cooled by a small cooling device. Curve C shows the case where the EGR gas is not forcibly cooled.
[0042]
As shown by curve A in FIG. 9, when the EGR gas is cooled strongly, soot generation peaks when the EGR rate is slightly lower than 50%. In this case, the EGR rate is increased to about 55% or more. If you do, almost no wrinkles will occur. On the other hand, as shown by the curve B in FIG. 9, when the EGR gas is slightly cooled, the amount of soot generated peaks when the EGR rate is slightly higher than 50%. In this case, the EGR rate is almost 65% or more. If this is done, almost no wrinkles will occur.
[0043]
Further, as shown by the curve C in FIG. 9, when the EGR gas is not forcibly cooled, the amount of soot generated reaches a peak when the EGR rate is around 55%. In this case, the EGR rate is approximately 70%. If the percentage is exceeded, almost no wrinkles occur. FIG. 9 shows the amount of smoke generated when the engine load is relatively high. When the engine load is reduced, the EGR rate at which the amount of soot reaches a peak slightly decreases, and the EGR rate at which soot hardly occurs. The lower limit is also slightly reduced. Thus, the lower limit of the EGR rate at which soot hardly occurs varies depending on the degree of cooling of the EGR gas and the engine load.
[0044]
FIG. 10 shows the amount of mixed gas of EGR gas and air necessary for making the temperature of the fuel and the surrounding gas lower than the temperature at which soot is generated when EGR gas is used as the inert gas. And the ratio of the air in this gas mixture amount, and the ratio of the EGR gas in this gas mixture are shown. In FIG. 10, the vertical axis indicates the total intake gas amount sucked into the combustion chamber 5, and the chain 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, and Z1 indicates the low load operation region.
[0045]
Referring to FIG. 10, the ratio 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. 10, the ratio between the air amount and the injected fuel amount is the stoichiometric air-fuel ratio. On the other hand, in FIG. 10, the ratio of EGR gas, that is, the amount of EGR gas in the mixed gas is used to make the temperature of the fuel and its surrounding gas lower than the temperature at which soot is formed when the injected fuel is burned. The minimum EGR gas amount is shown. This EGR gas amount is approximately 55% or more in terms of EGR rate, and is 70% or more in the embodiment shown in FIG. That is, if the total intake gas amount sucked into the combustion chamber 5 is a solid line X in FIG. 10, the ratio of the air amount and the EGR gas amount in the total intake gas amount X is a ratio as shown in FIG. The temperature of the fuel and the surrounding gas is lower than the temperature at which soot is produced, and so no soot is produced. Also, NO at this time_xThe amount generated is around 10p.p.m or less, so NO_xThe amount of generated is extremely small.
[0046]
If the amount of fuel injection increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the surrounding gas at a temperature lower than the temperature at which soot is generated, the amount of heat absorbed by the EGR gas Must be increased. Therefore, as shown in FIG. 10, the amount of EGR gas must be increased as the amount of injected fuel increases. That is, the amount of EGR gas needs to increase as the required load increases.
[0047]
On the other hand, in the load region Z2 of FIG. 10, the total intake gas amount X necessary for preventing the generation of soot exceeds the total intake gas amount Y that can be sucked. Therefore, in this case, in order to supply the total intake gas amount X necessary for preventing the generation of soot into the combustion chamber 5, it is necessary to supercharge or pressurize both the EGR gas and the intake air, or the EGR gas. When EGR gas or the like is not supercharged or pressurized, the total intake gas amount X coincides with the total intake gas amount Y that can be sucked in the load region Z2. Therefore, in this case, in order to prevent the generation of soot, the amount of air is slightly decreased to increase the amount of EGR gas, and the fuel is burned under a rich air-fuel ratio.
[0048]
As described above, FIG. 10 shows the case where the fuel is burned under the stoichiometric air-fuel ratio, but even if the air amount is smaller than the air amount shown in FIG. 10 in the low load operation region Z1 shown in FIG. That is, even if the air-fuel ratio is rich, NO is generated while preventing the generation of soot._xCan be reduced to around 10 p.pm or less, and even if the air amount is made larger than the air amount shown in FIG. 10 in the low load region Z1 shown in FIG. Even if the value is lean from 17 to 18, NO_xCan be reduced to around 10 p.p.m or less.
[0049]
That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but the combustion temperature is suppressed to a low temperature, so that the excess fuel does not grow to soot, and so no soot is generated. At this time, NO_xHowever, only a very small amount is generated. On the other hand, even 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 is high. Not generated at all. In addition, NO_xHowever, only a very small amount is generated.
[0050]
Thus, in the engine low load operation region Z1, regardless of the air-fuel ratio, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio is lean, no soot is generated._xThe amount of generated is 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.
[0051]
By the way, the temperature of the fuel during combustion in the combustion chamber and the surrounding gas can be suppressed to a temperature below the temperature at which the growth of hydrocarbons stops midway only when the heat generated by combustion is small and the engine load is relatively low. Therefore, in the embodiment according to the present invention, when the engine load is relatively low, the temperature of the fuel during combustion and the surrounding gas temperature are suppressed to a temperature below the temperature at which hydrocarbon growth stops halfway, so that the first combustion, that is, low temperature combustion is performed. When the engine load is relatively high, the second combustion, that is, the combustion normally performed conventionally is performed. Here, the first combustion, that is, low temperature combustion, as is clear from the above description, the amount of inert gas in the combustion chamber is larger than the worst inert gas amount at which the amount of soot generation is maximum, and soot is almost generated. The second combustion, that is, the combustion that is normally performed in the past, is combustion in which the amount of inert gas in the combustion chamber is smaller than the worst inert gas amount that generates the largest amount of soot. Say.
[0052]
FIG. 11 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. In FIG. 11, the vertical axis L indicates the amount of depression of the accelerator pedal 40, that is, the required load, and the horizontal axis N indicates the engine speed. In FIG. 11, X (N) indicates the first boundary between the first operation region I and the second operation region II, and Y (N) indicates the first operation region I and the second operation region. A second boundary with region II is shown. The change determination of the operation region from the first operation region I to the second operation region II is performed based on the first boundary X (N), and the change from the second operation region II to the first operation region I is performed. The change determination of the operation region is performed based on the second boundary Y (N).
[0053]
That is, when the engine operating state is in the first operating region I and low-temperature combustion is being performed, if the required load L exceeds the first boundary X (N) that is a function of the engine speed N, the operating region is It is determined that the operation has shifted to the second operation region II, and combustion by the conventional combustion method is performed. Next, when the required load L becomes lower than the second boundary Y (N) that is a function of the engine speed N, it is determined that the operating region has shifted to the first operating region I, and low temperature combustion is performed again.
[0054]
FIG. 12 shows the output of the air-fuel ratio sensor 21. As shown in FIG. 12, the output current I of the air-fuel ratio sensor 21 changes according to the air-fuel ratio A / F. Therefore, the air-fuel ratio can be known from the output current I of the air-fuel ratio sensor 21. Next, operation control in the first operation region I and the second operation region II will be schematically described with reference to FIG.
[0055]
FIG. 13 shows the opening degree of the throttle valve 16, the opening degree of the EGR control valve 23, the EGR rate, the air-fuel ratio, the injection timing, and the injection amount with respect to the required load L. As shown in FIG. 13, in the first operation region I where the required load L is low, the opening degree of the throttle valve 16 is gradually increased from nearly fully closed to about half-open as the required load L increases, and the EGR control valve 23 As the required load L increases, the degree of opening is gradually increased from near full close to full open. Further, in the example shown in FIG. 13, in the first operating region I, the EGR rate is approximately 70%, and the air-fuel ratio is a slightly lean air-fuel ratio.
[0056]
In other words, the opening degree of the throttle valve 16 and the opening degree of the EGR control valve 23 are controlled so that the EGR rate becomes approximately 70% in the first operation region I and the air / fuel ratio becomes a slightly lean air / fuel ratio. The air-fuel ratio at this time is controlled to the target lean air-fuel ratio by correcting the opening degree of the EGR control valve 23 based on the output signal of the air-fuel ratio sensor 21. 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 also delayed as the injection start timing θS is delayed.
[0057]
During the idling operation, the throttle valve 16 is closed to near full close. At this time, the EGR control valve 23 is also closed to close to full close. When the throttle valve 16 is closed to close to the fully closed state, the pressure in the combustion chamber 5 at the start of compression becomes low, so the compression pressure becomes small. When the compression pressure is reduced, the compression work by the piston 4 is reduced, so that the vibration of the engine body 1 is reduced. That is, during idling operation, the throttle valve 16 is closed to close to the fully closed state in order to suppress vibration of the engine body 1.
[0058]
On the other hand, when the engine operating region changes from the first operating region I to the second operating region II, the opening of the throttle valve 16 is increased stepwise from the half-open state to the fully-open direction. At this time, in the example shown in FIG. 13, the EGR rate is decreased in a step-like manner from approximately 70% to 40% or less, and the air-fuel ratio is increased in a step-like manner. That is, since the EGR rate exceeds the EGR rate range (FIG. 9) that generates a large amount of smoke, a large amount of smoke is generated when the engine operating region changes from the first operating region I to the second operating region II. There is no.
[0059]
Conventional combustion is performed in the second operation region II. In this combustion method, soot and NO_XHowever, when the engine operating region is changed from the first operating region I to the second operating region II, the injection amount is reduced stepwise as shown in FIG. I'm damned.
[0060]
In the second operation region II, the throttle valve 16 is held in a fully open state except for a part thereof, and the opening degree of the EGR control valve 23 is gradually reduced as the required load L increases. In this operation region II, the EGR rate decreases as the required load L increases, and the air-fuel ratio decreases as the required load L increases. However, the air-fuel ratio is made a lean air-fuel ratio even when the required load L increases. In the second operation region II, the injection start timing θS is set near the compression top dead center TDC.
[0061]
FIG. 14 shows the air-fuel ratio A / F in the first operating region I. In FIG. 14, the curves indicated by A / F = 15.5, A / F = 16, A / F = 17, and A / F = 18 have air-fuel ratios of 15.5, 16, 17, and 18, respectively. Time is shown, and the air-fuel ratio between the curves is determined by proportional distribution. As shown in FIG. 14, the air-fuel ratio is lean in the first operation region I, and in the first operation region I, the air-fuel ratio A / F is leaner as the required load L becomes lower.
[0062]
That is, the lower the required load L, the smaller the amount of heat generated by combustion. Therefore, low temperature combustion can be performed even if the EGR rate is reduced as the required load L is reduced. When the EGR rate is lowered, the air-fuel ratio increases, so as shown in FIG. 14, the air-fuel ratio A / F increases as the required load L decreases. As the air-fuel ratio A / F increases, the fuel consumption rate improves. Therefore, in order to make the air-fuel ratio as lean as possible, in this embodiment, the air-fuel ratio A / F increases as the required load L decreases.
[0063]
Note that the target opening ST of the throttle valve 16 required to set the air-fuel ratio to the target air-fuel ratio shown in FIG. 14 is a function of the required load L and the engine speed N as shown in FIG. The target opening degree SE of the EGR control valve 23 necessary for setting the air-fuel ratio to the target air-fuel ratio shown in FIG. 14 is stored in the ROM 32 in advance as shown in FIG. And is stored in advance in the ROM 32 in the form of a map as a function of the engine speed N.
[0064]
FIG. 16 shows the target air-fuel ratio when the second combustion, that is, the normal combustion by the conventional combustion method is performed. In FIG. 16, the curves indicated by A / F = 24, A / F = 35, A / F = 45, and A / F = 60 indicate the target air-fuel ratios 24, 35, 45, and 60, respectively. The target opening ST of the throttle valve 16 necessary for setting the air-fuel ratio to the target air-fuel ratio is previously stored in the ROM 32 in the form of a map as a function of the required load L and the engine speed N as shown in FIG. The target opening degree SE of the EGR control valve 23 necessary for setting the air-fuel ratio to the target air-fuel ratio is stored as a function of the required load L and the engine speed N as shown in FIG. It is stored in the ROM 32 in advance in the form of a map.
[0065]
Thus, in the diesel engine of the present embodiment, the first combustion, that is, low-temperature combustion, and the second combustion, that is, normal combustion are switched based on the depression amount L of the accelerator pedal 40 and the engine speed N. In each combustion, based on the depression amount L of the accelerator pedal 40 and the engine speed N, the opening control of the throttle valve 16 and the EGR valve is performed by the map shown in FIG.
[0066]
FIG. 18 is an overall configuration diagram of a diesel engine equipped with an exhaust purification device according to the present invention. Configurations other than those described above will be described. The diesel engine includes a turbocharger 35, and a compressor 36 of the turbocharger 35 is disposed in the intake duct 13. An exhaust duct 18 is connected to the downstream side of the exhaust manifold 17, and a turbine 37 of a turbocharger 35 connected to the compressor 36 is disposed in the exhaust duct 18. Reference numeral 38 denotes an air flow meter disposed on the upstream side of the compressor 36 in the intake duct 13. Reference numeral 39 denotes electric heaters of the same number as the number of cylinders arranged between each exhaust port and the exhaust manifold 17.
[0067]
During low temperature combustion, as described above, a relatively large amount of soot precursor or hydrocarbons in the previous state is discharged. In the low-temperature combustion, since the combustion temperature is low, the exhaust gas temperature is also relatively low. When the exhaust gas is further cooled in the exhaust manifold 17 or the exhaust duct 18, the above-mentioned hydrocarbons are easily liquefied and atomized. Become. In this diesel engine, the turbine 37 is disposed in the exhaust duct 18, and if liquefied hydrocarbons adhere to the rotating shaft or the like of the turbine 37, the turbine rotation is adversely affected. Further, the turbine 37 has a variable nozzle, and can achieve a desired rotation of the turbine with respect to the exhaust gas pressure that changes depending on the engine operating state. If the liquefied hydrocarbon adheres to the movable part of the variable nozzle, the variable nozzle is adversely affected, and in the worst case, the variable nozzle is fixed.
[0068]
In order to prevent such hydrocarbon liquefaction that adversely affects the turbine, during low temperature combustion, the electric heater 39 is operated by the control device 30 to increase the exhaust gas temperature. Further, even during low-temperature combustion, the electric heater 39 may be operated only in the low-rotation low-load side region where the exhaust gas has a low temperature, so that power consumption may be minimized. Of course, the electric heater 39 may be operated only when the actual exhaust gas temperature is detected and it is determined that the hydrocarbon is liquefied. The position of the electric heater 39 is between each exhaust port and the exhaust manifold 17. However, a single electric heater may be arranged on the upstream side of the turbine 37 and on the downstream side of the exhaust merging portion in the exhaust manifold 17. good. Further, in addition to or instead of heating the exhaust gas as required by an electric heater, a heat insulating material is disposed on all or a part of the exhaust manifold 17 and the exhaust duct 18 on the upstream side of the turbine 37, and is supplied to the turbine 37. The inflowing exhaust gas may be kept warm. The heat insulating material may be disposed outside or inside the exhaust manifold 17 and the exhaust duct 18 or both.
[0069]
FIG. 19 is a plan view showing the exhaust purification apparatus of this embodiment, and FIG. 20 is a side view thereof. This exhaust purification device connects the switching unit 71 connected to the downstream side of the turbine 37 of the turbocharger 35 in the exhaust duct 18, the particulate filter 70, and the switching unit 71 on one side of the particulate filter 70. One connection part 72 a, a second connection part 72 b that connects the other side of the particulate filter 70 and the switching part 71, and an exhaust passage 73 on the downstream side of the switching part 71 are provided. The switching unit 71 includes a valve body 71 a that can block the exhaust flow in the switching unit 71. The valve body 71 is driven by a negative pressure actuator or a step motor. At the first cutoff position of the valve body 71a, the upstream side in the switching part 71 is communicated with the first connection part 72a and the downstream side in the switching part 71 is communicated with the second connection part 72b. As indicated by the arrow, the particulate filter 70 flows from one side to the other side.
[0070]
Moreover, FIG. 21 has shown the 2nd interruption | blocking position of the valve body 71a. At this blocking position, the upstream side in the switching unit 71 communicates with the second connection portion 72b and the downstream side in the switching unit 71 communicates with the first connection portion 72a, and the exhaust gas is as shown by arrows in FIG. The particulate filter 70 flows from the other side to the one side. Thus, by switching the valve body 71a from one of the first cutoff position and the second cutoff position to the other, the direction of the exhaust gas flowing into the particulate filter 70 can be reversed, that is, the exhaust of the particulate filter 70. It is possible to reverse the upstream side and the exhaust downstream side.
[0071]
As described above, the exhaust purification apparatus can reverse the exhaust upstream side and the exhaust downstream side of the particulate filter with a very simple configuration. In addition, in the particulate filter, a large opening area is required to facilitate the inflow of exhaust gas. However, in the present exhaust purification device, vehicle mountability is deteriorated as shown in FIGS. 19 and 20. In addition, a particulate filter having a large opening area can be used.
[0072]
On the other hand, this exhaust purification device is configured to rotate the valve body 71a from one of the first cutoff position and the second cutoff position to the other in order to reverse the exhaust upstream side and the exhaust downstream side of the particulate filter. In FIG. 22, the exhaust gas bypasses the particulate filter as shown in FIG.
[0073]
FIG. 23 shows the structure of the particulate filter 70. 23A is a front view of the particulate filter 70, and FIG. 23B is a side sectional view. As shown in these drawings, the particulate filter 70 has an oblong front shape, and is, for example, a wall flow type having a honeycomb structure formed of a porous material such as cordierite, and has a large number of axes. It has a number of axial spaces subdivided by partition walls 54 extending in the direction. In the two adjacent axial spaces, one is closed on the exhaust downstream side by the plug 53 and the other is closed on the exhaust upstream side. In this way, one of the two adjacent axial spaces becomes the exhaust gas inflow passage 50 and the other becomes the outflow passage 51, and the exhaust gas always passes through the partition wall 54 as shown by an arrow in FIG. Particulates in the exhaust gas are very small compared to the size of the pores of the partition wall 54, but collide with the exhaust upstream surface of the partition wall 54 and the surface of the pores in the partition wall 54 and are collected. Is done. Thus, each partition wall 54 functions as a collecting wall for collecting particulates. In the present particulate filter 70, in order to oxidize and remove the collected particulates, alumina or the like is used on both side surfaces of the partition wall 54, and preferably on the pore surface in the partition wall 54, as described below. An active oxygen release agent and a noble metal catalyst are supported.
[0074]
The active oxygen release agent is an agent that promotes oxidation of particulates by releasing active oxygen. Preferably, oxygen is taken in and retained when excess oxygen is present in the surroundings, and the oxygen concentration in the surroundings is increased. When lowered, the retained oxygen is released in the form of active oxygen.
[0075]
As the noble metal catalyst, platinum Pt is usually used, and as the active oxygen release agent, alkali metals such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb, barium Ba, calcium Ca, and strontium Sr are used. At least one selected from alkaline earth metals, lanthanum La, rare earths such as yttrium Y, and transition metals is used.
[0076]
In this case, as the active oxygen release agent, alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr are used. preferable.
[0077]
Next, how the collected particulates are oxidized and removed by such a particulate filter carrying an active oxygen release agent will be described by taking platinum Pt and potassium K as an example. The same particulate removal action can be performed using other noble metals, alkali metals, alkaline earth metals, rare earths, and transition metals.
[0078]
In a diesel engine, combustion is usually performed under excess air, and therefore the exhaust gas contains a large amount of excess air. That is, when the ratio of air and fuel supplied to the intake passage and the combustion chamber is called the air-fuel ratio of the exhaust gas, the air-fuel ratio is lean. Further, since NO is generated in the combustion chamber, the exhaust gas contains NO. The fuel also contains sulfur S, which reacts with oxygen in the combustion chamber to react with SO.₂It becomes. Therefore, in the exhaust gas, SO₂It is included. Therefore excess oxygen, NO and SO₂The exhaust gas containing the gas flows into the exhaust upstream side of the particulate filter 70.
[0079]
24A and 24B schematically show enlarged views of the exhaust gas contact surface in the particulate filter 70. FIG. In FIGS. 24A and 24B, 60 indicates platinum Pt particles, and 61 indicates an active oxygen releasing agent containing potassium K.
[0080]
As described above, since a large amount of excess oxygen is contained in the exhaust gas, when the exhaust gas comes into contact with the exhaust gas contact surface of the particulate filter, as shown in FIG.₂Is O₂ ^-Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the exhaust gas is O on the surface of platinum Pt.₂ ^-Or O^2-Reacts with NO₂(2NO + O₂→ 2NO₂). Then the generated NO₂A part of N is oxidized on platinum Pt and absorbed in the active oxygen release agent 61 and combined with potassium K, as shown in FIG._Three ^-Diffused into the active oxygen release agent 61 in the form of potassium nitrate KNO_ThreeIs generated. Thus, in this embodiment, NO contained in the exhaust gas._xCan be absorbed by the particulate filter 70, and the amount released into the atmosphere can be greatly reduced.
[0081]
On the other hand, as described above, the exhaust gas contains SO.₂Is also included, this SO₂Is absorbed into the active oxygen release agent 61 by the same mechanism as NO. That is, as described above, oxygen O₂Is O₂ ^-Or O^2-Is attached to the surface of platinum Pt in the form of SO₂Is O on the surface of platinum Pt.₂ ^-Or O^2-Reacts with SO_ThreeIt becomes. The generated SO_ThreeIs partly oxidized on the platinum Pt while being absorbed into the active oxygen release agent 61 and combined with potassium K._Four ^2-Diffused into the active oxygen release agent 61 in the form of potassium sulfate K₂SO_FourIs generated. In this way, potassium nitrate KNO is contained in the active oxygen release catalyst 61._ThreeAnd potassium sulfate K₂SO_FourIs generated.
[0082]
Particulates in the exhaust gas adhere to the surface of the active oxygen release agent 61 carried by the particulate filter, as indicated by 62 in FIG. At this time, the oxygen concentration at the contact surface between the particulate 62 and the active oxygen release agent 61 decreases. When the oxygen concentration is lowered, a difference in concentration occurs between the active oxygen release agent 61 having a high oxygen concentration. Try to move towards. As a result, potassium nitrate KNO formed in the active oxygen release agent 61_ThreeIs decomposed into potassium K, oxygen O, and NO, oxygen O is directed to the contact surface between the particulate 62 and the active oxygen release agent 61, and NO is released from the active oxygen release agent 61 to the outside. NO released to the outside is oxidized on the platinum Pt on the downstream side, and is again absorbed in the active oxygen release agent 61.
[0083]
On the other hand, potassium sulfate K formed in the active oxygen release agent 61 at this time₂SO_FourAlso potassium K, oxygen O and SO₂The oxygen O is directed to the contact surface between the particulate 62 and the active oxygen release agent 61, and SO₂Is released from the active oxygen release agent 61 to the outside. SO released to the outside₂Is oxidized on the platinum Pt on the downstream side and absorbed again into the active oxygen release agent 61. However, potassium sulfate K₂SO_FourIs stabilized, potassium nitrate KNO_ThreeIt is difficult to release active oxygen compared to.
[0084]
On the other hand, the oxygen O toward the contact surface between the particulate 62 and the active oxygen release agent 61 is potassium nitrate KNO._ThreeAnd potassium sulfate K₂SO_FourIt is oxygen decomposed from a compound such as Oxygen O decomposed from the compound has high energy and has extremely high activity. Therefore, the oxygen directed toward the contact surface between the particulate 62 and the active oxygen release agent 61 is active oxygen O. When these active oxygen O comes into contact with the particulate 62, the particulate 62 is oxidized in a short time of several minutes to several tens of minutes without emitting a luminous flame. Further, the active oxygen O that oxidizes the particulate 62 is transferred to the active oxygen release agent 61 by NO and SO.₂Is also released when is absorbed. That is, NO_XNitrate ions NO in the active oxygen release agent 61 while repeatedly binding and separating oxygen atoms_Three ^-The active oxygen is generated during this period. The particulate 62 is also oxidized by this active oxygen. Further, the particulates 62 adhering to the particulate filter 70 in this manner are oxidized by the active oxygen O, but these particulates 62 are also oxidized by oxygen in the exhaust gas.
[0085]
By the way, since platinum Pt and the active oxygen release agent 61 are activated as the temperature of the particulate filter increases, the amount of active oxygen O released from the active oxygen release agent 61 per unit time increases as the temperature of the particulate filter increases. To do. As a matter of course, the higher the temperature of the particulate itself, the easier it is to be removed by oxidation. Therefore, the amount of fine particles that can be removed by oxidation without emitting a luminous flame per unit time on the particulate filter increases as the temperature of the particulate filter increases.
[0086]
The solid line in FIG. 25 shows the amount G of fine particles that can be removed by oxidation without emitting a bright flame per unit time. In FIG. 25, the horizontal axis shows the temperature TF of the particulate filter. FIG. 25 shows the amount G of fine particles that can be removed by oxidation when the unit time is 1 second, that is, the amount G of fine particles that can be removed by oxidation per second. be able to. For example, when 10 minutes is used as the unit time, the oxidizable and removable fine particle amount G per unit time represents the oxidizable and removable fine particle amount G per 10 minutes. Even in this case, the unit on the particulate filter 70 As shown in FIG. 25, the amount G of fine particles that can be removed by oxidation without emitting a bright flame per hour increases as the temperature of the particulate filter 70 increases.
[0087]
Now, when the amount of particulate discharged from the combustion chamber per unit time is referred to as discharged particulate amount M, when this discharged particulate amount M is smaller than the oxidizable and removable particulate amount G, for example, the amount of particulate discharged per second. When M is less than the amount G of fine particles that can be removed by oxidation per second, or when the amount M of fine particles discharged per 10 minutes is less than the amount of fine particles G that can be removed by oxidation per 10 minutes, that is, in the region I in FIG. All the particulates discharged from the chamber are sequentially oxidized and removed within the short time without emitting a bright flame on the particulate filter 70. On the other hand, when the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation, that is, in the region II in FIG. 25, the amount of active oxygen is insufficient to sequentially oxidize all the particulates. FIGS. 26A to 26C show the state of particulate oxidation in such a case.
[0088]
That is, when the amount of active oxygen is insufficient to oxidize all the particulates, if the particulates 62 adhere on the active oxygen release agent 61 as shown in FIG. Particulates that are only oxidized and not fully oxidized remain on the exhaust upstream side of the particulate filter. Next, when the state where the amount of active oxygen is insufficient continues, the particulate portion that has not been oxidized from one to the next remains on the exhaust upstream surface. As a result, as shown in FIG. The exhaust upstream surface is covered with the residual particulate portion 63.
[0089]
Such residual particulate portion 63 gradually changes to a carbonaceous material that is difficult to oxidize, and when the exhaust upstream surface is covered with the residual particulate portion 63, NO and SO by platinum Pt.₂The active oxygen release action by the active oxygen release agent 61 is suppressed. Accordingly, the residual particulate portion 63 can be gradually oxidized over time, but another particulate 64 is formed on the residual particulate portion 63 from the next to the next as shown in FIG. And deposit. That is, when the particulates are deposited in a laminated form, these particulates are separated from platinum Pt and the active oxygen release agent, so that even if the particulates are easily oxidized, they are not oxidized by active oxygen. Absent. Therefore, further particulates are deposited on the particulate 64 one after another. In other words, if the state in which the amount M of discharged particulates is larger than the amount G of particulates that can be removed by oxidation continues, the particulates are deposited on the particulate filter in a stacked manner.
[0090]
In this way, in the region I in FIG. 25, the particulates are oxidized on the particulate filter in a short time without emitting a bright flame, and in the region II in FIG. 25, the particulates are deposited on the particulate filter in a stacked manner. To do. Therefore, if the relationship between the discharged fine particle amount M and the oxidizable and removable fine particle amount G is in the region I, the accumulation of particulates on the particulate filter can be prevented. As a result, the pressure loss of the exhaust gas flow in the particulate filter 70 is maintained at a substantially constant minimum pressure loss value without changing at all. Thus, a reduction in engine output can be kept to a minimum. However, this is not always realized, and if nothing is done, particulates may accumulate on the particulate filter.
[0091]
In this embodiment, the electronic control unit 30 controls the operation of the valve body 71a, so that the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed, and the particulates are reliably deposited on the particulate filter. It is preventing. The switching timing for switching the valve body 71a from one of the two blocking positions to the other is, for example, for each set time or set travel distance.
[0092]
FIG. 27 is an enlarged cross-sectional view of the partition wall 54 of the particulate filter. As described above, the exhaust upstream surface of the partition wall 54 where the exhaust gas mainly collides and the exhaust gas flow facing surface in the pores collide and collect the particulates as one of the collection surfaces, and the active oxygen release agent Although the collected particulates are oxidized and removed by the released active oxygen, the operation in the region II of FIG. 25 may be performed while traveling for the set time or the set travel distance, and FIG. As indicated by the lattice, particulate removal may remain due to insufficient oxidation removal. The exhaust resistance of the particulate filter accompanying such accumulation of particulates does not adversely affect the running of the vehicle, but if particulates accumulate further, problems such as a significant decrease in engine output occur. However, if the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed at this point, no further particulates accumulate on the particulate remaining on one of the collecting surfaces of the partition wall 54. Residual particulates are gradually oxidized and removed by the active oxygen released from one of the collecting surfaces. Further, the particulates remaining in the pores of the partition walls are easily destroyed and fragmented by the exhaust gas flow in the reverse direction, as shown in FIG. 27 (B), and move downstream.
[0093]
As a result, many of the finely divided particulates are dispersed in the pores of the partition walls, i.e., the particulates flow and directly with the active oxygen release agent supported on the pore inner surfaces of the partition walls. There are many opportunities for contact and oxidation removal. In this way, by supporting the active oxygen release agent in the pores of the partition walls, the residual particulates can be remarkably easily removed by oxidation. Further, in addition to this oxidation removal, the other collection surface of the partition wall 54 that has become upstream due to the backflow of the exhaust gas, that is, the exhaust upstream surface of the partition wall 54 where the exhaust gas mainly collides and the inside of the pores On the exhaust gas flow facing surface (which is on the side opposite to the one collecting surface), new particulates in the exhaust gas adhere and are oxidized and removed by the active oxygen released from the active oxygen release agent. . A part of the active oxygen released from the active oxygen release agent during the oxidation removal moves to the downstream side together with the exhaust gas, and the remaining particulates are oxidized and removed by the backflow of the exhaust gas.
[0094]
That is, the residual particulates on one collecting surface in the partition wall are not only for the active oxygen released from this collecting surface, but also for the oxidation removal of the particulates on the other collecting surface of the partition wall by the backflow of exhaust gas. The remaining active oxygen used comes from the exhaust gas. As a result, even if particulates are accumulated to some extent on one collecting surface of the partition wall at the time of switching of the valve body, if the exhaust gas flows backward, the particulates accumulated on the residual particulates In addition to the arrival of active oxygen, no further particulates are deposited, so the deposited particulates are gradually oxidized and removed. Oxidation removal is possible. Thus, when the first collection surface and the second collection surface of the particulate filter collection wall are alternately used to collect the particulates by reversing the exhaust upstream side and the exhaust downstream side of the particulate filter, Compared to the case where particulates are always collected on a single collection surface, the amount of particulates collected on each collection surface can be reduced, which is advantageous for the removal of particulates by oxidation. It is possible to reliably prevent the accumulation of the particulates on the particulate filter.
[0095]
The switching of the valve body may be performed irregularly even if it is not performed periodically, such as every set time or set travel distance. Further, the valve body may be switched every time the engine is decelerated. For the determination at the time of engine deceleration, it is possible to detect an operation that the driver intends to decelerate the vehicle, for example, release of an accelerator pedal, depression of a brake pedal, fuel cut, or the like.
[0096]
Further, the valve body may be switched when the amount of particulate accumulation on the particulate filter reaches a set amount. For the estimation of the particulate deposition amount, for example, the differential pressure between the upstream side and the downstream side of the particulate filter 70 that increases with the increase in the particulate deposition amount can be used. The electrical resistance value on the predetermined partition wall of the particulate filter that decreases with an increase in the amount of deposited particulate may be used, and light transmission on the predetermined partition wall of the particulate filter that decreases with an increase in the amount of particulate deposition. Rate or reflectance may be used. Further, based on the graph of FIG. 25, when the amount M of the discharged particulate estimated from the current engine operating state exceeds the amount G of the particulate removable by oxidation considering the temperature of the particulate filter estimated from the current engine operating state. The difference (M−G) may be integrated as the particulate deposition amount.
[0097]
Further, when the air-fuel ratio of the exhaust gas is made rich, that is, when the oxygen concentration in the exhaust gas is lowered, the active oxygen O is released from the active oxygen release agent 61 to the outside at once. With the active oxygen O released at once, the deposited particulates are easily oxidized and easily removed by oxidation. On the other hand, when the air-fuel ratio is maintained lean, the surface of platinum Pt is covered with oxygen, and so-called oxygen poisoning of platinum Pt occurs. When such oxygen poisoning occurs, NO_XNO is reduced due to reduced oxidation_XAs a result, the active oxygen release amount from the active oxygen release agent 61 is reduced. However, when the air-fuel ratio is made rich, oxygen on the platinum Pt surface is consumed, so that oxygen poisoning is eliminated. Therefore, when the air-fuel ratio is switched again from rich to lean, NO._XNO to increase the oxidation effect on_XAs a result, the active oxygen release amount from the active oxygen release agent 61 increases. Accordingly, when the air-fuel ratio is maintained lean, the oxygen poisoning of platinum Pt is eliminated every time the air-fuel ratio is temporarily switched from lean to rich, so that active oxygen release when the air-fuel ratio is lean is performed. The amount increases, and thus the oxidation action of the particulates on the particulate filter 70 can be promoted. Furthermore, the elimination of oxygen poisoning is, so to speak, the combustion of the reducing substance, so that the temperature of the particulate filter is raised with heat generation. As a result, the amount of fine particles that can be removed by oxidation in the particulate filter is improved, and the residual and deposited particulates can be easily removed by oxidation. If the air-fuel ratio of the exhaust gas is made rich immediately after switching between the exhaust upstream side and the exhaust downstream side of the particulate filter by the valve body 71a, the other collection surface in the particulate filter partition wall where no particulates remain is obtained. Since the active oxygen is easily released as compared with the one collecting surface, the remaining particulates on the one collecting surface can be more reliably oxidized and removed by the active oxygen released in a larger amount. Of course, the air-fuel ratio of the exhaust gas may be occasionally enriched regardless of the switching of the valve body 71a, so that it is difficult for the particulates to remain and accumulate on the particulate filter.
[0098]
As a method for enriching the air-fuel ratio of the exhaust gas, for example, the low-temperature combustion described above may be performed. Alternatively, the combustion air-fuel ratio may be simply made rich. In addition to normal main fuel injection in the compression stroke, fuel may be injected into the cylinder (post-injection) in the exhaust stroke or expansion stroke by the engine fuel injection valve, or fuel in the cylinder in the intake stroke. May be jetted (bi-rubber jet). Of course, it is not always necessary to provide an interval between the post injection or the big rubber injection and the main fuel injection. It is also possible to supply fuel to the engine exhaust system.
[0099]
Thus, it is necessary to prevent a relatively large amount of particulates from being deposited on the particulate filter in order to prevent a decrease in engine output accompanying an increase in exhaust resistance, and a large amount of accumulated particulates are ignited at once. When burned, the particulate filter can become very hot and melt, which is also necessary to avoid this danger.
[0100]
By the way, calcium Ca in the exhaust gas is SO._ThreeIn the presence of calcium sulfate CaSO_FourIs generated. This calcium sulfate CaSO_FourIs hardly removed by oxidation and remains as ash on the particulate filter. Therefore, in order to prevent the particulate filter from being clogged due to residual calcium sulfate, it is preferable to use an alkali metal or alkaline earth metal, such as potassium K, which has a higher ionization tendency than calcium Ca as the active oxygen release agent 61. , Thereby diffusing into the active oxygen release agent 61_ThreeBinds potassium K and potassium sulfate K₂SO_FourCalcium Ca is SO_ThreeIt passes through the partition wall of the particulate filter without being combined with. Therefore, the particulate filter is not clogged by ash. Thus, as described above, as the active oxygen release agent 61, an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, strontium Sr is used. Is preferred.
[0101]
In addition, even if only a noble metal such as platinum Pt is supported on a particulate filter as an active oxygen release agent, NO retained on the surface of platinum Pt.₂Or SO_ThreeActive oxygen can be released from However, in this case, the solid line indicating the amount G of fine particles that can be removed by oxidation moves slightly to the right as compared with the solid line shown in FIG. It is also possible to use ceria as the active oxygen release agent. Ceria absorbs oxygen when the oxygen concentration in the exhaust gas is high (Ce₂O_Three→ 2CeO₂), Active oxygen is released when the oxygen concentration in the exhaust gas decreases (2CeO)₂→ Ce₂O_ThreeTherefore, it is necessary to enrich the air-fuel ratio in the exhaust gas periodically or irregularly in order to oxidize and remove particulates. Instead of ceria, iron or tin may be used.
[0102]
Moreover, NO in exhaust gas as an active oxygen release agent_xNO used for purification_xIt is also possible to use an occlusion reduction catalyst. In this case, NO_xOr SO_xIn order to release the exhaust gas, it is necessary to at least temporarily enrich the air-fuel ratio of the exhaust gas.
[0103]
In this embodiment, the particulate filter itself carries the active oxygen release agent, and the particulates are oxidized and removed by the active oxygen released by the active oxygen release agent. However, this limits the present invention. It is not a thing. For example, the active oxygen and the particulate oxidation component such as nitrogen dioxide that functions in the same way as the active oxygen may be released from the particulate filter or a substance carried on the particulate filter or may flow into the particulate filter from the outside. . Even when the particulate oxidation component flows from the outside, in order to collect the particulates, by alternately using the first collection surface and the second collection surface of the collection wall, Particulates are not newly deposited on one of the collected surfaces, and the deposited particulates are gradually oxidized and removed by the particulate oxidizing component flowing in from the other collecting surface. Can be sufficiently oxidized and removed in a certain time. In the meantime, the other collecting surface is oxidized by the particulate oxidation component together with the collection of the particulates, and thus the same effect as described above is brought about.
[0104]
Incidentally, the diesel engine includes the turbocharger 35 as described above. The opening control of the variable nozzle of the turbine 37 in the turbocharger 35 is controlled according to the first flowchart shown in FIG. First, at step 101, the current engine speed N is detected by the crank angle sensor 42, and the current engine load L is detected by the load sensor 41. Next, at step 102, the reference opening TH of the variable nozzle that is optimal for the current engine operating state determined by the current engine speed N and the current engine load L is determined using a map (not shown) or the like. The In step 103, similarly, the reference fuel injection amount Q in the current engine operating state is determined using a map (not shown) or the like.
[0105]
Next, at step 104, it is determined whether or not the valve element 71a is being switched in order to reverse the exhaust upstream side and the exhaust downstream side of the particulate filter 70. That is, it is determined whether or not the valve body 71a is a position between the first cutoff position and the second cutoff position. For this determination, the position of the valve body 71a may be detected directly, or the position of the valve body 71a may be detected indirectly based on the operation of the actuator of the valve body 71a. When this determination is negative, that is, when the valve element 71a is in the first cutoff position or the second cutoff position and the exhaust gas passes through the particulate filter, in step 105, the opening of the variable nozzle is It is controlled to the reference opening TH.
[0106]
Thereafter, in step 106, the intake air amount GN is detected by the air flow meter 38, and in step 107, a correction coefficient k of the fuel injection amount is determined using a map (not shown) or the like based on the intake air amount GN. . The reference fuel injection amount Q determined in step 103 does not consider that the intake air amount increases due to supercharging by the turbocharger 35, and the correction coefficient k is actually supplied into the cylinder by supercharging. This is for correcting the reference fuel injection amount Q in accordance with the intake air amount GN.
[0107]
Next, at step 113, the reference fuel injection amount Q is corrected by the correction coefficient k to obtain the actual fuel injection amount Q. At step 114, the fuel injection by the fuel injection valve 6 is controlled to this fuel injection amount Q. . The correction in step 113 is multiplication of a correction coefficient, but of course, it may be added depending on the correction coefficient.
[0108]
On the other hand, when the valve body 71a is being switched, that is, when the exhaust gas bypasses the particulate filter, it is determined in step 108 whether or not the current engine operating state is a high rotation high load state. The When this determination is negative, in step 109, the opening of the variable nozzle is controlled to an opening obtained by increasing the reference opening TH by a predetermined amount a. Thereafter, the processing after step 106 is performed as described above.
[0109]
When the exhaust gas bypasses the particulate filter 70, no pressure loss occurs in the particulate filter 70. Therefore, the exhaust pressure immediately downstream of the turbine 37 is reduced, and the variable nozzle is moved to the reference opening TH. Then, the turbine 37 rotates more than intended and the supercharging pressure by the compressor 36 becomes excessive. If the fuel injection amount increases as the intake air amount increases, the engine output rapidly increases and torque fluctuations occur. In this flowchart, when the exhaust gas bypasses the particulate filter 70, the desired rotation speed of the turbine 37 is set by opening the variable nozzle larger than the reference opening TH by the amount that there is no pressure loss in the particulate filter 70. This is achieved to prevent excessive supercharging pressure by the compressor 36. As a result, the intake air amount GN detected in step 106 is an appropriate intake air amount for the current engine operating state, and the correction coefficient k determined in step 107 is also an appropriate value. The opening increment a of the variable nozzle is a constant for the sake of simplicity. Of course, in order to accurately realize the desired rotational speed of the turbine in each engine operating state, a reference opening determined by the engine operating state is used. It is preferable to change according to TH.
[0110]
When the exhaust gas bypasses the particulate filter 70, as a matter of course, if the exhaust gas contains particulates, the particulates are released into the atmosphere. If low temperature combustion is performed in the operating region on the low load side, the exhaust gas contains almost no particulates, and if the engine load and engine speed are not so high, normal combustion will not occur. Even if it is implemented, the exhaust gas does not contain so much particulates, and even if the exhaust gas bypasses the particulate filter for a short time while the valve body 71a is switched, there is no particular problem. . However, when the engine speed is high and the load is high, the exhaust gas contains a large amount of particulates, and it is a problem that the exhaust gas bypasses the particulate filter.
[0111]
In this flowchart, when the high speed and high load are being applied during the switching of the valve body, the determination in step 108 is affirmed, and in step 110, the opening degree of the variable nozzle is the reference open even if there is no pressure loss of the particulate filter. In step 111, the intake air amount GN is detected. The intake air amount GN at this time is an intake air amount that is more than necessary in the current engine operating state due to excessive supercharging pressure by the compressor 36, as described above. In step 112, an intake air amount GN ′ that does not have an excess boost pressure is calculated based on the intake air amount GN, and a correction coefficient k of the fuel injection amount is a map (not shown) based on the intake air amount GN ′. Etc. are determined.
[0112]
Next, at step 113, the reference fuel injection amount Q is corrected based on the correction coefficient k, and at step 114, fuel is injected based on the corrected fuel injection amount Q. Thus, since the intake air amount is excessive with respect to the current engine operating state but the fuel injection amount is appropriate, the engine output does not increase rapidly and torque fluctuation does not occur. Further, excessively supplied intake air suppresses the generation of particulates in order to make the combustion air-fuel ratio leaner than usual. Thereby, even if the exhaust gas bypasses the particulate filter for a short time during the switching of the valve body, it does not matter so much.
[0113]
This flowchart presupposes that exhaust gas bypasses the particulate filter when the exhaust gas upstream side and the exhaust downstream side of the particulate filter are reversed. However, even if such a reverse rotation mechanism is not provided in the particulate filter, a bypass passage is provided, for example, to prevent accumulation of a large amount of particulates on the particulate filter, or other For this reason, it is conceivable that the exhaust gas intentionally bypasses the particulate filter. This flowchart is also effective during this bypass. Thus, this flowchart is valid if there is an opportunity for the exhaust gas to bypass the particulate filter regardless of whether the particulate filter is provided with a reverse rotation mechanism.
[0114]
Further, in this flowchart, when the exhaust gas bypasses the particulate filter, preferably, when the engine is not at high rotation and high load, the opening of the variable nozzle is increased to reduce the turbine efficiency, thereby reducing the turbocharger. The increase in supercharging pressure was suppressed. However, if a passage bypassing the turbine of the turbocharger, that is, a wastegate passage, is provided, the opening degree of the wastegate valve provided in the wastegate passage is replaced by controlling the opening degree of the variable nozzle. It is also possible to suppress an increase in turbocharger supercharging pressure by controlling and reducing turbine efficiency. In this way, even if a turbocharger that does not have a variable nozzle is provided with a waste gate passage, it is possible to prevent torque fluctuation when exhaust gas bypasses the particulate filter.
[0115]
Further, as described above, the diesel engine has the throttle valve 16 that can freely set the opening degree. In the first flowchart, the throttle valve 16 has an optimum opening degree according to the engine operating state determined in step 101. This optimum opening degree is mapped to the engine load and the engine speed. For example, when the exhaust gas bypasses the particulate filter, preferably when the engine speed is not high and the load is high, the variable nozzle has a reference opening according to the engine operating state, and the turbocharger supercharging pressure is excessive. However, at this time, by controlling the throttle valve 16 from the optimal opening degree to the closed side, the intake air amount may be suppressed by making it difficult to supply intake air into the cylinder. Even in this case, correction of the fuel injection amount based on the intake air amount becomes appropriate, and torque fluctuation can be prevented.
[0116]
As described above, the EGR passage 22 is provided with the EGR control valve 23. By controlling the EGR control valve 23, the amount of EGR gas recirculated into the cylinder can be controlled. Similarly to the throttle valve 16, the EGR control valve 22 is controlled based on the optimum opening degree mapped to the engine load and the engine speed. If the amount of EGR gas to be recirculated is increased, intake air is less likely to be supplied into the cylinder. Thus, similarly to the control of the throttle valve, when the exhaust gas bypasses the particulate filter, preferably when the exhaust gas is not at a high rotation and high load, the variable nozzle has a reference opening according to the engine operating state, Although the supercharging pressure of the charger is excessive, at this time, by controlling the EGR control valve 23 from the optimal opening degree to the open side, it is difficult to supply intake air into the cylinder, and the intake air amount is suppressed. Anyway.
[0117]
FIG. 29 is a second flowchart showing the control of the variable nozzle and the fuel injection amount of the turbocharger turbine, which is performed instead of the first flowchart. This will be described below. First, at step 201, the current engine speed N is detected by the crank angle sensor 42, and the current engine load L is detected by the load sensor 41. Next, at step 202, a variable nozzle reference opening TH optimum for the current engine operating state determined by the current engine speed N and the current engine load L is determined using a map (not shown) or the like. The In step 203, similarly, the reference fuel injection amount Q in the current engine operating state is determined using a map (not shown) or the like.
[0118]
Next, at step 204, the opening of the variable nozzle is controlled to the reference opening TH. Thereafter, in step 205, the exhaust gas pressure P on the downstream side of the turbine 37 is detected by a pressure sensor (not shown). In step 206, the exhaust gas pressure P is variable from the exhaust gas pressure on the upstream side of the turbine 37. Abnormally higher than an appropriate pressure P ′ estimated based on the pressure loss in the turbine 37 based on the reference opening TH of the nozzle and the pressure loss of the particulate filter 70 itself when the particulates are not collected. It is determined whether or not. The exhaust gas pressure upstream of the turbine 37 is estimated in consideration of the amount of exhaust gas exhausted from the cylinder estimated based on the current engine operating state and the amount of EGR gas recirculated through the EGR passage 22. Is possible. The EGR gas amount is estimated based on the pressure difference between the current pressure in the exhaust passage that is upstream of the EGR passage 22 and the current pressure in the intake passage that is downstream, and the current opening of the EGR valve 23. Is possible.
[0119]
When particulates start to accumulate on the particulate filter 70, the pressure loss of the particulate filter 70 gradually increases, so that the exhaust gas pressure upstream of the particulate filter, that is, the exhaust gas downstream of the turbocharger turbine 37. The gas pressure gradually increases. Thus, the actually measured exhaust gas pressure P on the downstream side of the turbine 37 gradually increases from an appropriate pressure P ′ estimated along with an increase in the amount of particulates deposited on the particulate filter. When the determination in step 206 is negative, the particulate filter does not accumulate so much particulates, and in step 207, the variable nozzles are determined based on the actually measured exhaust gas pressure P on the downstream side of the turbine 37. Correct the opening TH. If the actually measured exhaust gas pressure P is substantially equal to the estimated appropriate pressure P ′, it is not necessary to correct the opening TH of the variable nozzle, and the intended supercharging pressure is realized by the turbocharger 35. However, when the actually measured exhaust gas pressure P exceeds the estimated appropriate pressure P ′, the intended pressure loss in the turbine 37 is not performed even if the variable nozzle is set to the reference opening TH. That is, the work in the turbine 37 is insufficient and the turbocharger 35 does not realize the intended supercharging pressure. Thereby, the current opening degree TH of the variable nozzle is corrected to the closed side, and the turbocharger 35 realizes the intended supercharging pressure by increasing the turbine efficiency.
[0120]
Further, when the exhaust gas bypasses the particulate filter due to switching of the valve body 71a or the like, the pressure loss of the particulate filter becomes almost zero, so the actually measured exhaust gas pressure P is the estimated appropriate pressure P. 'Below. At this time, as described in the first flowchart, the current opening TH of the variable nozzle is corrected to the open side, the turbine efficiency is lowered, and the intended supercharging pressure is realized by the turbocharger 35.
[0121]
Next, as in the first flowchart, in step 208, the intake air amount GN is detected by the air flow meter 38. In step 209, a correction coefficient k for the fuel injection amount is determined based on the intake air amount GN. The reference fuel injection amount Q is corrected based on the correction coefficient k, and in step 211, fuel injection is performed based on the corrected fuel injection amount.
[0122]
In this way, even if the pressure loss in the particulate filter increases as the particulate collection volume increases, the decrease in turbocharger supercharging pressure is suppressed, and the desired supercharging pressure is reduced in each engine operating state. Can be realized. Further, even if the exhaust gas bypasses the particulate filter and the pressure loss in the particulate filter decreases, an increase in the turbocharger supercharging pressure is suppressed.
[0123]
On the other hand, when the determination in step 206 is affirmative, that is, when the measured exhaust gas pressure P downstream of the turbine is abnormally higher than the estimated appropriate pressure P ′, a large amount of particulates is present in the particulate filter. It is when the pressure loss is abnormally high due to accumulation, and it is difficult to achieve the desired supercharging pressure even when the variable nozzle is closed to the maximum. At this time, in step 211, the opening TH of the variable nozzle is fixed at the predetermined opening TH1 on the closing side, and the fuel injection amount is not corrected, and is determined in step 212 without considering supercharging. The fuel is injected at the reference fuel injection amount Q.
[0124]
When the pressure loss of the particulate filter becomes abnormally high due to the accumulation of particulates, it is no longer in an abnormal state and needs to be promptly brought into a repair shop. At the time of carrying in, by suppressing the fuel injection amount to the reference fuel injection amount in each engine operating state, the particulate discharge amount is suppressed, and a larger amount of particulates is prevented from accumulating on the particulate filter, Ensure vehicle travel during delivery to the repair shop. In order to further reduce the emission particulates in this vehicle travel, even if the driver depresses the accelerator pedal to the maximum, the fuel injection amount can be prevented from exceeding the set injection amount, and the vehicle can be driven for emergency evacuation. is there. This flowchart is effective even if the particulate filter is not provided with a reversing mechanism for reversing the exhaust upstream side and the exhaust downstream side.
[0125]
In this embodiment, the particulate filter is disposed on the turbine downstream side of the turbocharger, but may be disposed on the turbine upstream side. In this case, if the exhaust gas bypasses the particulate filter, the pressure loss in the particulate filter decreases, and the exhaust gas pressure on the upstream side of the turbine increases. Thus, when the variable nozzle is set to the reference opening, the supercharging pressure becomes excessive, resulting in torque fluctuation. Thereby, in this case, the first flowchart is effective. Further, if the amount of particulate collection in the particulate filter increases and the pressure loss in the particulate filter increases, the exhaust gas pressure on the upstream side of the turbine decreases. Thus, when the variable nozzle is set to the reference opening, the supercharging pressure is insufficient. Thereby, in this case, the second flowchart is effective.
[0126]
The diesel engine of the present embodiment is switched between low-temperature combustion and normal combustion, but this does not limit the present invention. Of course, a diesel engine or particulate that performs only normal combustion is used. The present invention is also applicable to a gasoline engine that discharges.
[0127]
【The invention's effect】
  An internal combustion engine exhaust gas purification apparatus according to the present invention includes a particulate filter that is disposed in an engine exhaust system and collects particulates. The internal combustion engine includes a turbocharger and intake air amount suppression means. When bypassing the particulate filter, the pressure loss in the particulate filter decreases, and the supercharging pressure by the turbocharger rises as it is, so the intake air amount suppression means suppresses the increase in the intake air amount. ing. As a result, torque fluctuations caused by an increase in engine output accompanying an increase in the intake air amount are prevented.Further, at the time of high rotation and high load, the increase in the intake air amount is not suppressed by the intake air amount suppression means, and the increase in the fuel injection amount accompanying the increase in the intake air amount is suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a diesel engine equipped with an exhaust emission control device according to the present invention.
FIG. 2 is an enlarged longitudinal sectional view of the combustion chamber of FIG.
FIG. 3 is a bottom view of the cylinder head of FIG. 1;
FIG. 4 is a side sectional view of a combustion chamber.
FIG. 5 is a diagram showing intake / exhaust valve lift and fuel injection.
FIG. 6 Smoke and NO_xIt is a figure which shows the generation amount of etc.
FIG. 7 is a diagram showing combustion pressure.
FIG. 8 is a diagram showing fuel molecules.
FIG. 9 is a diagram showing the relationship between the amount of smoke generated and the EGR rate.
FIG. 10 is a diagram showing the relationship between the amount of injected fuel and the amount of mixed gas.
FIG. 11 is a diagram showing a first operation region I and a second operation region II.
FIG. 12 is a diagram showing an output of an air-fuel ratio sensor.
FIG. 13 is a diagram showing an opening degree of a throttle valve and the like.
14 is a diagram showing an air-fuel ratio in a first operating region I. FIG.
FIG. 15 is a view showing a map of a target opening degree of a throttle valve or the like.
FIG. 16 is a diagram showing an air-fuel ratio in the second combustion.
FIG. 17 is a diagram showing a target opening degree of a throttle valve or the like.
FIG. 18 is an overall configuration diagram of a diesel engine equipped with an exhaust emission control device according to the present invention.
FIG. 19 is a cross-sectional view showing an exhaust emission control device.
20 is a side view of FIG. 19. FIG.
FIG. 21 is a view showing another blocking position of the valve body.
FIG. 22 is a view showing an intermediate position of the valve body.
FIG. 23 is a diagram illustrating a structure of a particulate filter.
FIG. 24 is a diagram for explaining the oxidizing action of particulates.
FIG. 25 is a diagram showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of the particulate filter.
FIG. 26 is a diagram for explaining the particulate deposition action.
FIG. 27 is an enlarged cross-sectional view of a partition wall of a particulate filter.
FIG. 28 is a first flowchart showing opening control and fuel injection amount control of a variable nozzle of a turbocharger turbine.
FIG. 29 is a second flowchart showing opening control and fuel injection amount control of a variable nozzle of a turbocharger turbine.
[Explanation of symbols]
6 ... Fuel injection valve
16 ... Throttle valve
35 ... Turbocharger
36 ... Compressor
37 ... Turbine
70 ... Particulate filter
71 ... switching part
71a ... Valve

Claims (10)

A particulate filter disposed in the engine exhaust system for collecting particulates; the internal combustion engine comprises a turbocharger and intake air amount suppression means; and when the exhaust gas bypasses the particulate filter, the intake The increase in the intake air amount is suppressed by the air amount suppression means, and the increase in the intake air amount is not suppressed by the intake air amount suppression means at the time of high rotation and high load. An exhaust emission control device for an internal combustion engine characterized by suppressing an increase .   The exhaust purification device for an internal combustion engine according to claim 1, wherein the intake air amount suppression means suppresses an increase in supercharging pressure of the turbocharger.   2. The intake air amount suppression unit suppresses an increase in the intake air amount by making it difficult for intake air to be supplied into a cylinder with respect to an increase in supercharging pressure of the turbocharger. An exhaust purification device for an internal combustion engine. A supercharging pressure reduction suppression means for suppressing a reduction in supercharging pressure of the turbocharger with respect to an increase in pressure loss in the particulate filter accompanying an increase in the amount of particulates collected in the particulate filter. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas purification apparatus is an internal combustion engine. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4 , wherein when the particulate collection amount is predicted or detected to be equal to or greater than a set collection amount, the fuel injection amount is suppressed to be equal to or less than the set injection amount. . The internal combustion engine according to claim 1 , wherein a heat retaining means is provided upstream of the turbine of the turbocharger in the engine exhaust system in order to suppress liquefaction of hydrocarbons discharged from the cylinder. Exhaust purification equipment. 2. The internal combustion engine according to claim 1, wherein heating means is provided upstream of the turbine of the turbocharger in the engine exhaust system in order to suppress liquefaction of hydrocarbons discharged from the cylinder. Exhaust purification equipment. A reversing means for reversing the exhaust upstream side and the exhaust downstream side of the particulate filter by switching the valve body from one of the two shut-off positions to the other, and the particulate filter collected in the particulate filter; The particulate filter has a collection wall for collecting particulates, the collection wall has a first collection surface and a second collection surface, and the reverse means In order to collect the particulates by reversing the exhaust upstream side and the exhaust downstream side of the particulate filter, the first collection surface and the second collection surface of the collection wall alternately The exhaust gas bypasses the particulate filter while being used and the valve body switches from one of the two shut-off positions to the other. An exhaust purification system of an internal combustion engine according to any one of 1 to 7. 9. The exhaust gas purification apparatus for an internal combustion engine according to claim 8, wherein an active oxygen release agent is supported on the collection wall, and the active oxygen released from the active oxygen release agent oxidizes the particulates . The active oxygen release agent takes in oxygen and retains oxygen when excess oxygen is present in the surrounding area, and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1.

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