JP2002106324A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of preventing clogging of a particulate filter by reversing the exhaust upstream and the exhaust downstream of the particulate filter by a simple structure, and restraining emission of particulate into the atmosphere in reversing. SOLUTION: The exhaust upstream and the exhaust downstream of the particulate filter 70 where the scavenged particulates are oxidized are reversed by a reversing means 71, a first scavenging surface and a second scavenging surface of a particulate filter scavenging wall are alternately used for scavenging the particulate. During switching a valve element 71a of a switching means between one and the other of two positions for reversing, some of exhaust gas by-passes the particulate filter, so that when the particulate discharge quantity from an engine combustion chamber becomes lower than a preset discharge quantity, the valve element is switched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine, particularly a diesel engine, contains particulates containing soot as a main component. Since particulates are harmful substances, it has been proposed to arrange a filter in the engine exhaust system for trapping the particulates before releasing them to the atmosphere. In such a filter, it is necessary to burn out the collected particulates in order to prevent an increase in exhaust resistance due to clogging.

[0003] In such filter regeneration, ignition occurs when the particulates reach about 600 ° C. However, the exhaust gas temperature of a diesel engine is normally 6 ° C.
It is much lower than 00 ° C, and usually requires some means such as heating the filter itself.

Japanese Patent Publication No. 7-106290 discloses that if a platinum group metal and an alkaline earth metal oxide are supported on a filter, the particulates on the filter will be at about the normal exhaust gas temperature of a diesel engine. Continuous burning at 400 ° C. is disclosed.

[0005]

However, even if this filter is used, the exhaust gas temperature is not always about 400 ° C., and depending on the operating conditions, a large amount of particulates may be generated from the diesel engine. May be released, and the particulates that could not be burned off at each time may gradually accumulate on the filter.

In this filter, if a certain amount of particulates accumulates, the ability to burn out the particulates is extremely reduced, so that the filter can no longer be regenerated by itself. Thus, simply arranging this type of filter in the engine exhaust system may cause clogging relatively early, resulting in a significant decrease in engine output.

Therefore, an object of the present invention is to prevent the particulate filter from being clogged by reversing the exhaust gas upstream and the exhaust downstream of the particulate filter with a simple structure, and to prevent the particulate filter from being caught in the atmosphere at the time of reverse rotation. An object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine that can suppress the release of curate.

[0008]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, comprising: a particulate filter disposed in an engine exhaust system; and an exhaust upstream side and an exhaust downstream side of the particulate filter. And a reversing means for reversing the above, wherein the collected particulates are oxidized in the particulate filter,
The particulate filter has a collecting wall for collecting particulates, the collecting wall has a first collecting surface and a second collecting surface, and The first collecting surface and the second collecting surface of the collecting wall are used alternately to collect particulates by reversing the exhaust upstream side and the exhaust downstream side, and the reversing means Is provided with a valve body, by switching the valve body from one of the two positions to the other, by reversing the exhaust upstream side and the exhaust downstream side of the particulate filter, the valve body is one of the two positions At least part of the exhaust gas bypasses the particulate filter during the switching from the other to the other. Characterized by reversing the exhaust upstream side of the particulate filter when it becomes less than the constant discharge amount and the exhaust downstream side.

According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the first aspect, wherein the trapping wall carries an active oxygen releasing agent. The active oxygen released from the active oxygen releasing agent oxidizes particulates.

According to a third aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the second aspect of the present invention. It is characterized by taking in oxygen, retaining oxygen, and releasing the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases.

According to a fourth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the second aspect, wherein the active oxygen releasing agent has an excess oxygen in its surroundings. the NO _X is combined with oxygen retains and oxygen concentration surrounding, characterized in that release by decomposing NO _X and oxygen coupled with decreases in the NO _X and the active oxygen.

According to a fifth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects, wherein when it is determined that the engine is being decelerated, Assuming that the particulate discharge amount becomes equal to or less than the set discharge amount, the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed.

According to a sixth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the fifth aspect of the present invention, wherein the engine is operated by detecting that an exhaust brake is operated. It is characterized by judging the time of deceleration.

According to a seventh aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the fifth aspect of the present invention, wherein the exhaust gas purifying apparatus detects the depression of a brake pedal. It is characterized by judging when decelerating.

According to the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the present invention, wherein the exhaust gas purifying apparatus for an internal combustion engine according to the fifth aspect of the present invention detects that the depression amount of an accelerator pedal is reduced. It is characterized in that the time of the engine deceleration is determined.

According to a ninth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects, wherein the reversing means comprises the particulate filter. After the reverse of the exhaust upstream side and the exhaust downstream side, when the set time has not elapsed or when the vehicle has not traveled the set traveling distance, even if the particulate discharge amount becomes equal to or less than the set discharge amount, the particulate matter is reduced. It is characterized in that the exhaust upstream side and the exhaust downstream side of the filter are not reversed.

According to a tenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects. When it is determined that the engine is accelerating during switching, the switching speed of the valve body is increased.

According to a further aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects, wherein a fuel injection amount is equal to or less than a set injection amount. When it is determined that there is, the particulate emission amount becomes equal to or less than the set emission amount, and the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed.

According to a twelfth aspect of the present invention, there is provided an exhaust purification system for an internal combustion engine according to any one of the first to fourth aspects, wherein the depression amount of the accelerator pedal is set to the set depression amount. It is characterized in that when it is determined to be less than or equal to the above, it is determined that the particulate discharge amount is equal to or less than the set discharge amount, and the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed.

According to a thirteenth aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects, it is determined that the clutch pedal is depressed. It is characterized in that at times the particulate matter discharge amount becomes equal to or less than the set discharge amount, the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed.

Further, according to a fourteenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein a particulate filter disposed in an engine exhaust system and an exhaust upstream side and an exhaust downstream side of the particulate filter are reversed. Reversing means for the particulate filter, the collected particulates are oxidized in the particulate filter, the particulate filter has a collecting wall for collecting particulates, the collecting wall is A first collection surface and a second collection surface, wherein the reversing means reversely rotates the exhaust upstream side and the exhaust downstream side of the particulate filter to collect particulates; The first collection surface and the second collection surface of a wall are used alternately, and the reversing means includes a valve body, and the valve body is moved from one of two positions to the other. By switching, the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed, and at least a part of the exhaust gas bypasses the particulate filter while the valve body switches from one of the two positions to the other. The reversing means reverses the upstream side and the downstream side of the exhaust of the particulate filter with a switching speed of the valve according to an engine operating state.

According to a fifteenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the fourteenth aspect, wherein the trapping wall carries an active oxygen releasing agent. The active oxygen released from the active oxygen releasing agent oxidizes particulates.

According to the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the present invention, wherein the active oxygen releasing agent is characterized in that excess oxygen exists around the active oxygen releasing agent. It is characterized by taking in oxygen, retaining oxygen, and releasing the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases.

According to a seventeenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the fifteenth aspect, wherein the active oxygen releasing agent has an excess oxygen in its surroundings. the NO _X is combined with oxygen retains and oxygen concentration surrounding, characterized in that release by decomposing NO _X and oxygen coupled with decreases in the NO _X and the active oxygen.

[0025]

FIG. 1 is a schematic longitudinal sectional view of a four-stroke diesel engine provided with an exhaust emission control device according to the present invention, and FIG. 2 is an enlarged longitudinal sectional view of a combustion chamber in the diesel engine of FIG. FIG. 3 is a bottom view of the cylinder head in the diesel engine of FIG. 1 to 3, reference numeral 1 denotes an engine body, 2 denotes a cylinder block, 3 denotes a cylinder head, 4 denotes a piston,
5a is a cavity formed on the top surface of the piston 4;
Is a combustion chamber formed in the cavity 5a, 6 is an electrically controlled fuel injection valve, 7 is a pair of intake valves, 8 is an intake port, 9
Denotes a pair of exhaust valves, and 10 denotes an exhaust port. The intake port 8 is connected to the surge tank 1 via the corresponding intake branch 11.
2, 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 provided in the intake duct 13.
Is arranged. On the other hand, the exhaust port 10 is connected to the exhaust manifold 17.

As shown in FIG. 1, the exhaust manifold 17
Inside, an air-fuel ratio sensor 21 is arranged. The exhaust manifold 17 and the surge tank 12 are connected to each other via an EGR passage 22, and an electrically controlled EGR is provided in the EGR passage 22.
A control valve 23 is arranged. A cooling device 24 for cooling the EGR gas flowing in the EGR passage 22 is provided 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 engine cooling water cools the EGR gas.

On the other hand, each fuel injection valve 6 is connected via a fuel supply pipe 25 to a fuel reservoir, a so-called common rail 26. Fuel is supplied into the common rail 26 from an electric control type variable discharge fuel pump 27, 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. Is controlled.

An electronic control unit 30 receives an output signal of the air-fuel ratio sensor 21 and an output signal of the fuel pressure sensor 28. A load sensor 41 that generates an output voltage proportional to the amount of depression 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 the crank angle sensor 42 that generates an output pulse every time the motor rotates by, for example, 30 ° is also input. Thus, the electronic control unit 30 controls the fuel injection valve 6, the electric motor 15, the EGR control valve 2 based on various signals.
3, and the fuel pump 27 is operated.

As shown in FIGS. 2 and 3, in the embodiment according to the present invention, the fuel injection valve 6 comprises a hole nozzle having six nozzle openings, and the nozzle opening of the fuel injection valve 6 is slightly downwardly directed to the horizontal plane. The fuel F is injected at equal angular intervals. As shown in FIG. 3, two of the six fuel sprays F scatter along the lower surface of the valve body of each exhaust valve 9. FIGS. 2 and 3 show a case where 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 burned.

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, a case is shown in which 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 which proceeds in the valve body direction of the exhaust valve 9 is directed between the back surface of the head of the exhaust valve 9 and the exhaust port 10. That is, in other words, two of the six nozzle ports of the fuel injection valve 6 emit the fuel spray F when the additional fuel Qa is injected while the exhaust valve 9 is open. It is formed so as to be directed between the back surface of the head of the valve 9 and the exhaust port 10. In this case, in the embodiment shown in FIG. 4, at this time, the fuel spray F collides with the back of the umbrella of the exhaust valve 9, and the fuel mist F colliding with the back of the umbrella of the exhaust valve 9 is reflected on the back of the umbrella of the exhaust valve 9. Then, it goes into the exhaust port 10.

Normally, no additional fuel Qa is injected,
Only the main injection Qm is performed. FIG. 6 shows a change in the output torque when the air-fuel ratio A / F (horizontal axis in FIG. 6) is changed by changing the opening degree of the throttle valve 16 and the EGR rate during the low load operation of the engine, and smoke, HC. , CO,
9 shows an experimental example showing a change in the amount of emission of NO _X. FIG.
As can be seen from the graph, in this experimental example, the EGR rate increases as the air-fuel ratio A / F decreases, and the stoichiometric air-fuel ratio (# 14.
6) In the following cases, the EGR rate is 65% or more.

As shown in FIG. 6, when the air-fuel ratio A / F is decreased by increasing the EGR ratio, the smoke is generated when the EGR ratio becomes close to 40% and the air-fuel ratio A / F becomes about 30. The volume starts to increase. Then
When the EGR rate is further increased and the air-fuel ratio A / F is reduced, the amount of smoke generated sharply increases and reaches a peak. Next, when the EGR rate is further increased and the air-fuel ratio A / F is reduced, the smoke is sharply reduced. When the EGR rate is increased to 65% or more, and the air-fuel ratio A / F is around 15.0, the smoke becomes almost zero. . That is, almost no soot is generated. At this time, the output torque of the engine slightly decreases, and NO
_X generation is significantly lower. On the other hand, at this time, the generation amounts of HC and CO begin to increase.

FIG. 7A shows a change in the combustion pressure in the combustion chamber 5 when the amount of generated smoke is the largest when the air-fuel ratio A / F is around 21, and FIG. 7B shows the air-fuel ratio A / F. The graph shows a change in the combustion pressure in the combustion chamber 5 when the smoke generation amount is substantially zero when F is around 18. As can be seen by comparing FIG. 7A and FIG. 7B, in the case of FIG. 7B in which the amount of smoke generation is almost zero, FIG.
It can be seen that the combustion pressure is lower than in the case shown in (A).

The following can be said from the experimental results shown in FIGS. That is, first, the air-fuel ratio A / F is 15.
0 generation amount of the NO _X as shown in FIG. 6 when the smoke generation amount approximately zero or less drops significantly. The decrease in the amount of generated NO _X means that the combustion temperature in the combustion chamber 5 has decreased. Therefore, when little soot is generated, the combustion temperature in the combustion chamber 5 is considered to be low. I can say. 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 at this time, the combustion temperature in the combustion chamber 5 is low.

Second, when the amount of generated smoke, that is, the amount of generated soot becomes substantially zero, the amount of HC and CO emissions increases as shown in FIG. This means that hydrocarbons are emitted without growing to soot. That is, linear hydrocarbons and aromatic hydrocarbons contained in the fuel as shown in FIG. 8 are thermally decomposed when the temperature is increased in a state of lack of oxygen, soot precursors are formed, and then mainly, Soot consisting of a solid aggregate of carbon atoms is produced. In this case, the actual soot generation process is complicated, and it is not clear what form the soot precursor takes, but in any case, the hydrocarbon as shown in FIG. It will grow to soot. Therefore, as described above, when the generation amount of soot becomes almost zero, the emission amount of HC and CO increases as shown in FIG. 6, but HC at this time is a precursor of soot or a hydrocarbon in a state before it. .

Summarizing these considerations based on the experimental results shown in FIGS. 6 and 7, when the combustion temperature in the combustion chamber 5 is low, the amount of soot generation becomes almost zero. Is discharged from the combustion chamber 5. As a result of further detailed experimental studies on this, when the temperature of the fuel and the surrounding gas in the combustion chamber 5 is lower than a certain temperature, the growth process of the soot is stopped halfway, that is, the soot is Not generated at all, combustion chamber 5
It was found that soot was formed when the temperature of the fuel and its surroundings fell below a certain temperature.

The temperature of the fuel and its surroundings when the process of producing hydrocarbons is stopped in the state of the soot precursor, ie, the above-mentioned certain temperature, depends on various factors such as the type of fuel, the air-fuel ratio and the compression ratio. Although not say that how many times so changed, this certain temperature has a generation amount and the deep relationship between nO _X, thus to some extent defined from the generation of this certain temperature is nO _X can do. That is, the fuel and the gas temperature surrounding it at the time of combustion and the greater the EGR rate, decreases, the amount of the NO _X is reduced. At this time, when the amount of generated NO _X becomes about 10 p.pm or less, soot is hardly generated. Therefore, the above certain temperature is NO
The temperature almost coincides with the temperature when the amount of generated _X is about 10 p.pm or less.

Once soot has been produced, it cannot be purified by post-treatment simply using a catalyst having an oxidizing function. On the other hand, the soot precursor or the hydrocarbon in the state before the soot can be easily purified by a post-treatment using a catalyst having an oxidation function. Thus, NO _X
It is extremely effective in purifying exhaust gas to reduce the generation amount of methane and discharge hydrocarbons from the combustion chamber 5 in the state of a precursor of soot or before it.

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

That is, if there is only air around the fuel, the evaporated fuel immediately reacts with oxygen in the air and burns. In this case, the temperature of the air separated from the fuel does not rise so much, and only the temperature around the fuel becomes extremely high locally. That is, at this time, the air separated from the fuel hardly absorbs the combustion heat of the fuel. In this case, since the combustion temperature locally becomes extremely high, the unburned hydrocarbons that have received the combustion heat will generate soot.

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

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

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

As shown by the curve A in FIG. 9, when the EGR gas is cooled strongly, the soot generation peaks at a point where the EGR rate is slightly lower than 50%. Above a percentage, soot is hardly generated. On the other hand, as shown by the curve B in FIG. 9, when the EGR gas is slightly cooled, the amount of soot generation reaches a peak at a point where the EGR rate is slightly higher than 50%. In this case, the EGR rate is increased to about 65% or more. If so, almost no soot is generated.

As shown by the curve C in FIG.
When the R gas is not forcibly cooled, the EGR rate becomes 5
The soot generation amount peaks near 5%, and in this case, if the EGR rate is set to about 70% or more, soot is hardly generated. FIG. 9 shows the amount of smoke generated when the engine load is relatively high. When the engine load decreases, the EGR rate at which the amount of soot peaks slightly decreases, and the EGR rate at which soot hardly occurs is reduced. Also lowers slightly. As described above, the lower limit of the EGR rate at which almost no soot is generated varies depending on the degree of cooling of the EGR gas and the engine load.

FIG. 10 shows the mixing of EGR gas and air necessary to reduce the temperature of fuel during combustion and its surrounding gas to a temperature lower than the temperature at which soot is generated when EGR gas is used as the inert gas. It shows a gas amount, a ratio of air in the mixed gas amount, and a ratio of EGR gas in the mixed gas. The vertical axis in FIG.
The dashed line Y indicates the total amount of intake gas that can be sucked into the combustion chamber 5 when supercharging is not performed. The horizontal axis shows the required load,
Z1 indicates a low load operation region.

Referring to FIG. 10, the proportion of air, that is, the amount of air in the mixed gas, indicates the amount of air necessary to completely burn the injected fuel. That is, in the case shown in FIG. 10, the ratio between the amount of air and the amount of injected fuel is the stoichiometric air-fuel ratio. On the other hand, in FIG. 10, the ratio of the EGR gas, that is, the amount of the EGR gas in the mixed gas is necessary to make the temperature of the fuel and the 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 the EGR rate, and is 70% or more in the embodiment shown in FIG. That is, the total intake gas amount sucked into the combustion chamber 5 is represented by a solid line X in FIG. 10, and the ratio between the air amount and the EGR gas amount in the total intake gas amount X is as shown in FIG. The temperature of the fuel and the surrounding gas is lower than the temperature at which soot is produced,
Thus, no soot is generated. At this time, NO
_The amount of _X generated is around 10 p.pm or less, and therefore the amount of generated NO _X is extremely small.

When the fuel injection amount increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the surrounding gas at a temperature lower than the temperature at which the soot is generated, the heat generated by the EGR gas is required. Must be increased. Therefore, as shown in FIG. 10, the EGR gas amount must be increased as the injected fuel amount increases. That is, the EGR gas amount needs to increase as the required load increases.

On the other hand, in the load region Z2 in FIG. 10, the total intake gas amount X required to prevent 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 required to prevent the generation of soot into the combustion chamber 5, both the EGR gas and the intake air, or EG
It is necessary to supercharge or pressurize the R gas. When the EGR gas or the like is not supercharged or pressurized, the total intake gas amount X matches the total intake gas amount Y that can be taken in the load region Z2. Therefore, in this case, in order to prevent the generation of soot, the amount of air is slightly reduced to increase the amount of EGR gas, and the fuel is burned under a rich air-fuel ratio.

As described above, FIG.
FIG. 10 shows a case where combustion is performed under
FIG. 10 shows the air amount in the low load operation region Z1.
Even if it is less than the amount of air
NO while preventing soot generation _X10p.p.m before
Later or less, and as shown in FIG.
In the low load region Z1, the amount of air
Even if it is larger than the air volume, that is, the average value of the air-fuel ratio is increased from 17
Even with a lean of 18, NO while preventing the generation of soot_XDeparture
The production amount can be around 10p.p.m or less
You.

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

As described above, in the engine low load operation region Z1, soot is generated regardless of the air-fuel ratio, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio is lean. However, the amount of generated NO _X 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 at this time lean.

By the way, the temperature of the fuel and its surrounding gas during combustion in the combustion chamber can be suppressed to a temperature below the temperature at which the growth of hydrocarbons stops halfway, only when the calorific value due to combustion is small and the engine load is relatively low. Can be Therefore, in the embodiment according to the present invention, when the engine load is relatively low, the first combustion, that is, the low-temperature combustion is performed by suppressing the temperature of the fuel during combustion and the gas around it to a temperature below the temperature at which the growth of hydrocarbons stops halfway. When the engine load is relatively high, the second combustion,
That is, the combustion that is conventionally performed is performed. Here, the first combustion, that is, low-temperature combustion, as is clear from the description so far, the amount of inert gas in the combustion chamber is larger than the worst inert gas amount at which the amount of soot is maximized, and soot is almost generated. The second combustion, that is, the combustion that is usually performed in the past, is the combustion in which the amount of inert gas in the combustion chamber is smaller than the worst inert gas amount that maximizes soot generation. Say

FIG. 11 shows a first operation region I in which first combustion, that is, low-temperature combustion is performed, and a second combustion region II in which second combustion, that is, combustion by a conventional combustion method, is performed. The vertical axis L in FIG.
, 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 operating region I and the second operating region II, and Y (N) indicates the first operating region I and the second operating region. The second boundary with the area II is shown. First operating region I
Is determined on the basis of the first boundary X (N), and the change determination of the operating region from the second operating region II to the first operating region I is performed based on the first boundary X (N). The determination is performed based on the second boundary Y (N).

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

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, with reference to FIG.
The operation control in the operation region II will be schematically described.

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 operating region I where the required load L is low, the opening of the throttle valve 16 is gradually increased from almost fully closed to about half-open as the required load L increases, and the EGR control valve 23 is opened. Is gradually increased from near fully closed to fully open as the required load L increases. FIG.
In the example shown in (1), in the first operating region I, the EGR rate is approximately 70%, and the air-fuel ratio is a slightly lean air-fuel ratio.

In other words, in the first operating region I, the EGR
The opening of the throttle valve 16 and the opening of the EGR control valve 23 are controlled so that the rate becomes approximately 70% and the air-fuel ratio becomes a slightly lean air-fuel ratio. In addition,
The air-fuel ratio at this time is controlled to the target lean air-fuel ratio by correcting the opening 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 delayed as the injection start timing θS is delayed.

During the idling operation, the throttle valve 16 is closed until the valve is almost fully closed. At this time, the EGR control valve 23 is also closed almost completely. When the throttle valve 16 is closed close to the fully closed position, the pressure in the combustion chamber 5 at the start of compression decreases, and the compression pressure decreases. When the compression pressure decreases, the compression work by the piston 4 decreases, so that the vibration of the engine body 1 decreases. That is, at the time of idling operation, the throttle valve 16 is closed to almost fully closed in order to suppress the vibration of the engine body 1.

On the other hand, the operating region of the engine is the first operating region I.
From the second operation 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.
The air-fuel ratio is reduced in steps from 40 percent to less than 40 percent, and the air-fuel ratio is increased in steps. That is, since the EGR rate jumps over the EGR rate range (FIG. 9) in which a large amount of smoke is generated, a large amount of smoke is generated when the operation region of the engine changes from the first operation region I to the second operation region II. There is no.

In the second operation region II, the conventional combustion is performed. Soot and NO _X is slightly higher for although thermal efficiency as compared with low temperature combustion occurs, thus operating region of the engine is the first second from operating region I of the operation area II in the combustion process
The injection amount is reduced stepwise as shown in FIG.

In the second operating region II, the throttle valve 16 is kept fully open except for a part, and the opening of the EGR control valve 23 is gradually reduced as the required load L increases. In this operating region II, the EGR rate decreases as the required load L increases, and the air-fuel ratio decreases as the required load L increases. However, the air-fuel ratio is a lean air-fuel ratio even when the required load L increases. In the second operation region II, the injection start timing θS is set near the compression top dead center TDC.

FIG. 14 shows the air-fuel ratio A / F in the first operating region I. In FIG. 14, A / F = 15.
5, the curves indicated by A / F = 16, A / F = 17, and A / F = 18 have air-fuel ratios of 15.5, 16, 17, and 18, respectively.
And the air-fuel ratio between the curves is determined by proportional distribution. As shown in FIG. 14, the air-fuel ratio is lean in the first operating region I, and in the first operating region I, the air-fuel ratio A / F becomes leaner as the required load L decreases.

That is, the lower the required load L, the smaller the amount of heat generated by combustion. Therefore, low-temperature combustion can be performed even if the EGR rate is reduced as the required load L decreases. When the EGR rate is reduced, the air-fuel ratio increases. Therefore, as shown in FIG. 14, as the required load L decreases, the air-fuel ratio A / F increases. As the air-fuel ratio A / F increases, the fuel consumption rate increases. Therefore, in order to make the air-fuel ratio as lean as possible, in this embodiment, the air-fuel ratio A / F is increased as the required load L decreases.

The target opening degree ST of the throttle valve 16 required for setting the air-fuel ratio to the target air-fuel ratio shown in FIG.
5 (A), the required load L and the engine speed N
The target opening SE of the EGR control valve 23 required for setting the air-fuel ratio to the target air-fuel ratio shown in FIG. 14 is shown in FIG. As described above, a map is stored in advance in the ROM 32 as a function of the required load L and the engine speed N.

FIG. 16 shows the target air-fuel ratio when the second combustion, that is, the normal combustion by the conventional combustion method is performed. In FIG. 16, A / F = 24 and A / F = 3.
Curves indicated by 5, A / F = 45, and A / F = 60 indicate target air-fuel ratios 24, 35, 45, and 60, respectively. Throttle valve 1 required to set air-fuel ratio to this target air-fuel ratio
The target opening degree ST of No. 6 is stored in the ROM 32 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 17B, the target opening SE of the EGR control valve 23 necessary for this is stored in the ROM 32 in advance in the form of a map as a function of the required load L and the engine speed N.

Thus, in the diesel engine of this embodiment, the first combustion, that is, the low temperature combustion, and the second combustion, that is, the normal combustion, are performed based on the depression amount L of the accelerator pedal 40 and the engine speed N. The switching is performed, and in each combustion, the opening control of the throttle valve 16 and the EGR valve is performed based on the depression amount L of the accelerator pedal 40 and the engine speed N according to the map shown in FIG. 15 or FIG.

FIG. 18 is a plan view showing an exhaust gas purifying apparatus, and FIG. 19 is a side view thereof. The exhaust gas purification device includes a switching unit 71 connected to the downstream side of the exhaust manifold 17 via an exhaust pipe 18, a particulate filter 70,
A first connecting portion 72a connecting one side of the particulate filter 70 to the switching portion 71; a second connecting portion 72b connecting the other side of the particulate filter 70 to the switching portion 71; Exhaust passage 73. The switching unit 71 includes a valve body 71a that can shut off the exhaust flow in the switching unit 71. The valve body 71a is driven by a negative pressure actuator, a step motor, or the like. At one of the shutoff positions of the valve body 71a, the upstream side in the switching section 71 is communicated with the first connection section 72a, and the downstream side in the switching section 71 is connected to the second connection section 72b.
And the exhaust gas, as indicated by the arrow in FIG.
It flows from one side of the particulate filter 70 to the other side.

FIG. 20 shows the other blocking position of the valve body 71a. In this cutoff position, the switching unit 71
The upstream side is communicated with the second connection portion 72b, and the downstream side inside the switching portion 71 is communicated with the first connection portion 72a. From one side. Thus,
By switching the valve body 71a, it is possible to reverse the direction of the exhaust gas flowing into the particulate filter 70, that is, to reverse the exhaust upstream side and the exhaust downstream side of the particulate filter 70.

As described above, the present exhaust gas purifying apparatus can reverse the exhaust gas upstream side and the exhaust downstream side of the particulate filter with a very simple configuration. Also,
In a particulate filter, a large opening area is required in order to facilitate the inflow of exhaust gas.
In the present exhaust gas purification apparatus, as shown in FIGS. 18 and 19, a particulate filter having a large opening area can be used without deteriorating the vehicle mountability.

On the other hand, in order to reverse the exhaust gas upstream side and the exhaust downstream side of the particulate filter, the present exhaust gas purifying apparatus is configured to rotate the valve body 71a from one of the two shut-off positions to the other. As shown in FIG. 21, the exhaust gas is released to the atmosphere without passing through the particulate filter.

FIG. 22 shows the structure of the particulate filter 70. 22A is a front view of the particulate filter 70, and FIG. 22B is a side sectional view. As shown in these figures, the particulate filter 70 has an elliptical front shape, and is, for example, a wall flow type having a honeycomb structure formed of a porous material such as cordierite. It has a number of axial spaces subdivided by directional partitions 54. In the two adjacent axial spaces, one is closed downstream of the exhaust and the other is closed upstream of the exhaust by the plug 53. Thus, 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 is
As shown by the arrow in (B), it always passes through the partition wall 54.
Although the particulates in the exhaust gas are very small compared to the size of the pores of the partition wall 54, they collide with and collect on the upstream surface of the partition wall 54 and the surface of the pores in the partition wall 54. 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, on both surfaces of the partition wall 54, and
Preferably, an active oxygen releasing agent and a noble metal catalyst described below are supported on the pore surfaces in the partition walls 54 using alumina or the like.

The active oxygen releasing agent promotes the oxidation of particulates by releasing active oxygen. Preferably, when excess oxygen is present in the surroundings, oxygen is taken in to retain oxygen and maintain the surrounding oxygen. When the oxygen concentration decreases, the retained oxygen is released in the form of active oxygen.

As a noble metal catalyst, platinum Pt is usually used, and as an active oxygen releasing agent, alkali metals such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb, barium Ba, calcium Ca, strontium. Alkaline earth metals such as Sr,
At least one selected from lanthanum La, rare earths such as yttrium Y, and transition metals is used.

In this case, as the active oxygen releasing agent, 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,
It is preferable to use strontium Sr.

Next, how the collected particulates are oxidized and removed by the particulate filter carrying such an active oxygen releasing agent will be described.
The case of platinum Pt and potassium K will be described as an example.
The same particulate removal effect can be obtained by using other noble metals, alkali metals, alkaline earth metals, rare earths, and transition metals.

In a diesel engine, combustion is usually performed under excess air, and thus 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 referred to as the air-fuel ratio of the exhaust gas, the air-fuel ratio is lean. NO in the combustion chamber
Therefore, NO is contained in the exhaust gas. The fuel contains sulfur S, and this sulfur S
Reacts with oxygen in the combustion chamber to form SO ₂ . Therefore, SO ₂ is contained in the exhaust gas. Therefore, excess oxygen, N
Exhaust gas containing O and SO ₂ flows into the exhaust gas upstream of the particulate filter 70.

FIGS. 23A and 23B schematically show enlarged views of the exhaust gas contact surface of the particulate filter 70. FIG. 23 (A) and 23 (B), reference numeral 60 denotes platinum Pt particles, and reference numeral 61 denotes an active oxygen releasing agent containing potassium K.

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. ₂ O ₂ ^- it is attached to or O the surface of the platinum Pt in ^2-form. On the other hand, NO in the exhaust gas reacts with O ₂ ⁻ or O ²⁻ on the surface of the platinum Pt to become NO ₂ (2NO + O ₂ → 2NO ₂ ). Next, a part of the generated NO ₂ is absorbed in the active oxygen releasing agent 61 while being oxidized on the platinum Pt, and is combined with potassium K to form nitrate ion NO ₃ ⁻ as shown in FIG. Diffuses into the active oxygen releasing agent 61 to generate potassium nitrate KNO ₃ . Thus, in the present embodiment, the NO contained in the exhaust gas
_X can be absorbed by the particulate filter 70 and the amount of emission into the atmosphere can be significantly reduced.

On the other hand, as described above, the exhaust gas contains SO
_{2 is} also contained, and this SO ₂ is also absorbed into the active oxygen releasing agent 61 by the same mechanism as NO. That is, the oxygen O ₂ as described above O ₂ ^- are attached to or O ^2- form on the surface of the platinum Pt in, SO ₂ in the exhaust gas on the surface of the platinum Pt O ₂ ^- or O ^2- and Reacts to SO ₃ . Next, a part of the generated SO ₃ is absorbed in the active oxygen releasing agent 61 while being further oxidized on the platinum Pt, and is combined with the potassium K in the active oxygen releasing agent 61 in the form of sulfate ion SO ₄ ^2-. Diffuses to produce potassium sulfate K ₂ SO ₄ . Thus, potassium nitrate KNO is contained in the active oxygen releasing catalyst 61.
₃ and potassium sulfate K ₂ SO ₄ are produced.

The particulates in the exhaust gas are shown in FIG.
As shown by 62 in (B), it adheres to the surface of the active oxygen releasing agent 61 carried on the particulate filter. At this time, the oxygen concentration decreases at the contact surface between the particulate 62 and the active oxygen releasing agent 61. When the oxygen concentration decreases, a concentration difference occurs between the active oxygen releasing agent 61 having a high oxygen concentration and the oxygen inside the active oxygen releasing agent 61. Try to move towards. As a result, the potassium nitrate KNO ₃ formed in the active oxygen releasing agent 61 is decomposed into potassium K, oxygen O and NO, and the oxygen O goes to the contact surface between the particulate 62 and the active oxygen releasing agent 61, and NO Is released from the active oxygen releasing agent 61 to the outside.
The NO released to the outside is oxidized on platinum Pt on the downstream side, and is again absorbed in the active oxygen releasing agent 61.

On the other hand, potassium sulfate K ₂ SO ₄ formed in the active oxygen releasing agent 61 at this time is also decomposed into potassium K, oxygen O and SO _2, and oxygen O is
The SO ₂ is released from the active oxygen releasing agent 61 to the outside, toward the contact surface between the active oxygen releasing agent 61 and the active oxygen releasing agent 61. The SO ₂ released to the outside is oxidized on platinum Pt on the downstream side,
It is again absorbed in the active oxygen releasing agent 61. However, since potassium sulfate K ₂ SO ₄ is stabilized, it is difficult to release active oxygen as compared with potassium nitrate KNO ₃ .

On the other hand, the oxygen O heading toward the contact surface between the particulate 62 and the active oxygen releasing agent 61 is potassium nitrate KN
Oxygen decomposed from compounds such as O ₃ and potassium sulfate K ₂ SO ₄ . Oxygen O decomposed from the compound has high energy and extremely high activity. Therefore, the oxygen going to the contact surface between the particulate 62 and the active oxygen releasing agent 61 is active oxygen O. When the 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 bright flame. The active oxygen O that oxidizes the particulate 62 is also released when NO and SO ₂ are absorbed by the active oxygen releasing agent 61. That is, NO _X
Is considered to diffuse in the form of nitrate ion NO ₃ ^{− in} the active oxygen releasing agent 61 while repeating bonding and separation of oxygen atoms, and active oxygen is also generated during this time. The particulate 62 is also oxidized by this active oxygen. Further, the particulates 62 thus adhered on the particulate filter 70 are oxidized by the active oxygen O, but these particulates 62 are also oxidized by the oxygen in the exhaust gas.

By the way, platinum Pt and active oxygen releasing agent 61
Is activated as the temperature of the particulate filter increases, so that the amount of active oxygen O released from the active oxygen releasing agent 61 per unit time increases as the temperature of the particulate filter increases. Also, of course,
The higher the temperature of the particulate itself, the more easily it is oxidized and removed. Accordingly, the amount of oxidizable particles that can oxidize and remove particulates per unit time on the particulate filter without emitting luminous flame per unit time increases as the temperature of the particulate filter increases.

The solid line in FIG. 24 shows the amount G of the oxidizable particles that can be oxidized and removed without emitting a luminous flame per unit time. In FIG. 24, the horizontal axis shows the temperature TF of the particulate filter. FIG. 24 shows the amount of fine particles G that can be oxidized and removed per second when the unit time is 1 second, that is, the unit time is as follows.
Any time such as 1 minute, 10 minutes, etc. can be adopted. For example, if 10 minutes is used as the unit time, the amount G of oxidizable and removable fine particles per unit time indicates the amount G of oxidizable and removable fine particles per 10 minutes. As shown in FIG. 24, the amount G of particulates that can be oxidized and removed without emitting a bright flame per hour increases as the temperature of the particulate filter 70 increases.

When the amount of particulates discharged from the combustion chamber per unit time is referred to as the amount M of discharged fine particles, when the amount M of discharged fine particles is smaller than the amount G of fine particles removable by oxidation, for example, per second, When the amount M of discharged fine particles is smaller than the amount G of oxidizable and removable particles per second, or when the amount M of discharged fine particles per 10 minutes is smaller than the amount of oxidizable and removable fine particles G per 10 minutes, that is, the region of FIG. In I, all the particulates discharged from the combustion chamber are sequentially oxidized and removed within a short period of time on the particulate filter 70 without producing a bright flame.

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. 24, the amount of active oxygen is insufficient to sequentially oxidize all the particulates. FIGS. 25A to 25C show how particulates are oxidized in such a case.

In other words, when the amount of active oxygen is insufficient to oxidize all the particulates, the particulates 62 become active oxygen releasing agents 61 as shown in FIG.
If it adheres to the upper part, only a part of the particulate 62 is oxidized, and the particulate part that has not been sufficiently oxidized remains on the exhaust upstream side surface of the particulate filter. Next, when the state where the amount of active oxygen is insufficient continues, the particulate portion which has not been oxidized from one to the next remains on the exhaust gas upstream surface, and as a result, as shown in FIG. The exhaust upstream surface is covered with the residual particulate portion 63.

The residual particulate portion 63 as described above
Is gradually transformed into a carbon material which is hardly oxidized, and when the exhaust upstream surface is covered with the residual particulate portion 63, the oxidizing action of NO and SO ₂ by platinum Pt and the releasing action of active oxygen by the active oxygen releasing agent 61 are reduced. Is suppressed. As a result, the residual particulate portion 63 can be gradually oxidized over time.
As shown in (C), the residual particulate portion 63
Another particulate 64 is deposited on top of each other. That is, when the particulates are deposited in a layered manner, these particulates are separated from the platinum Pt and the active oxygen releasing agent, so that even if the particulates are easily oxidized, they cannot be oxidized by the active oxygen. Absent. Therefore, further particulates accumulate on this particulate 64 one after another. That is, if the state in which the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation continues, the particulates are deposited on the particulate filter in a layered manner.

As described above, in the region I of FIG. 24, the particulates are oxidized in a short time without emitting a bright flame on the particulate filter. In the region II of FIG. 24, the particulates are laminated on the particulate filter. Deposit in a shape. Therefore, if the relationship between the amount M of discharged fine particles and the amount G of fine particles that can be removed by oxidation is set to the region I, it is possible to prevent the accumulation of particulates on the particulate filter. 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 decrease in engine output can be kept to a minimum. However, this is not always achieved, and if nothing is done, particulates may accumulate on the particulate filter.

In this embodiment, the electronic control unit 3
0, the switching control of the valve body 71a is performed according to the first flowchart shown in FIG. 26, and the accumulation of particulates on the particulate filter is prevented. This flowchart is repeated every predetermined time. First, in step 101, it is determined whether the integrated time t is equal to or longer than the set time ts. The integrated time t is an integrated time after switching the valve element 71a. When the determination in step 101 is denied, the integration time t is integrated in step 105 and the processing is terminated. When the determination is affirmative, the processing proceeds to step 102. In step 102, it is determined whether or not the accelerator pedal is released by a limit switch or the like attached to the accelerator pedal while the vehicle is running. If this determination is denied, the integration time t is integrated in step 105, and the processing ends.

When the determination in step 102 is affirmative, in step 103, the valve body 71a is switched. That is, the exhaust gas upstream and the exhaust downstream of the particulate filter are reversed. Next, in step 104, the integration time t is reset to 0, and in step 105, the integration time t is newly added and the processing ends.

FIG. 27 is an enlarged sectional view of the partition wall 54 of the particulate filter. While the vehicle is running, driving in the region II of FIG. 24 may be performed, and FIG.
As shown by a grid in FIG.
The surface on the exhaust upstream side and the surface facing the exhaust gas flow in the pores collide and collect particulates as one collecting surface, and are oxidized and removed by an active oxygen releasing agent. Particulates may remain. At this time, the exhaust resistance of the particulate filter is not so great as to adversely affect the running of the vehicle, but if the particulates accumulate further, a problem such as a drastic decrease in engine output occurs. If the upstream side and the downstream side of the exhaust of the particulate filter are reversed at such a point where the particulates remain, more particulates accumulate on the particulates remaining on one collection surface of the partition wall 54. However, the residual particulates are gradually oxidized and removed by the active oxygen released from one of the collecting surfaces. Particularly, the particulates remaining in the pores of the partition wall 54 are caused by the exhaust gas flow in the opposite direction.
As shown in (B), it is easily broken and fragmented, and moves downstream.

As a result, many of the finely divided particulates are dispersed in the pores of the partition walls, that is, the particulates flow to form an active oxygen releasing agent supported on the inner surfaces of the pores of the partition walls. The chance of being oxidized and removed by direct contact increases. By carrying the active oxygen releasing agent also in the pores of the partition walls, residual particulates can be remarkably easily oxidized and removed. Furthermore, in addition to this oxidation removal, the other trapping 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 against which the exhaust gas currently mainly collides and the inside of the pores In the exhaust gas flow-facing surface (which is on the opposite side 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 releasing agent. . Part of the active oxygen released from the active oxygen releasing agent during these oxidative removals moves downstream together with the exhaust gas, and oxidizes and removes the particulates still remaining due to the backflow of the exhaust gas.

That is, not only the active oxygen released from this collecting surface but also the particulates on the other collecting surface of the partition due to the backflow of the exhaust gas are included in the residual particulates on one collecting surface of the partition. The remaining active oxygen used for the oxidation removal comes with the exhaust gas. Thereby, even if the particulates are deposited to some extent on the one collecting surface of the partition wall at the time of switching of the valve element, if the exhaust gas is made to flow backward, the particulates are deposited on the residual particulates. In addition to the arrival of active oxygen, no more particulates accumulate, so the accumulated particulates are gradually oxidized and removed, and if there is some time before the next backflow,
During this period, it can be sufficiently removed by oxidation.

In the first flow chart, the switching of the valve body is performed every time the accelerator pedal is released during the running of the vehicle. There are many opportunities to release the pedal, and the period during which the valve body is not switched is not so long. Thereby, even if the operation in the region II of FIG. 24 is performed frequently, a large amount of particulates does not accumulate on the particulate filter at the time of switching of the valve element. There is no possibility that the deposited particulates are left for a long period of time and deteriorate to carbon which is hardly oxidized.
In this way, the residual and accumulated particulates can be reliably oxidized and removed as described above only by the backflow of the exhaust gas. Problems such as melting of the particulate filter due to combustion heat do not occur.

Reversing the exhaust gas upstream and the exhaust downstream of the particulate filter is very effective for oxidizing and removing the residual and accumulated particulates. As described above, part of the exhaust gas bypasses the particulate filter 70 during switching from one of the first shut-off position and the second shut-off position of the valve body 71a to the other, as described above.
Accordingly, at this time, if the amount of particulates discharged from the engine combustion chamber exceeds the set amount of emissions, a relatively large amount of particulates is contained in the exhaust gas, and the particulates are released to the atmosphere. The Rukoto.

However, in the first flowchart, the switching of the valve body is performed when the accelerator pedal is released. At this time, the engine is cut off with the intention of decelerating the vehicle or only a small amount of fuel is injected. The amount of particulates discharged from the combustion chamber is equal to or less than the set amount, and the exhaust gas contains almost no particulates. In the first flowchart, when the integrated time t from the previous accelerator pedal release has not reached the set time when the accelerator pedal is released, the switching of the valve body is not performed.

Although this is not a limitation on the present invention, unnecessary switching of the valve body can be prevented when the accelerator pedal is released frequently, and the valve body and the actuator for driving the valve body can be prevented. Extend the life,
It is possible to reduce the chance of generating noise when driving the valve element. In this flowchart, the release of the accelerator pedal is detected and used to determine when the engine is decelerated.Of course, it is also detected that the reduction amount or reduction ratio in the accelerator pedal depression amount has become larger than the respective set value. Then, this may be used for determining when the engine is decelerated.
In this case, even if the accelerator pedal is not released, the fuel injection amount at this time becomes sufficiently small, and the particulate discharge amount discharged from the engine combustion chamber becomes equal to or less than the set discharge amount. The amount of particulates released to the atmosphere is not so large and does not pose any particular problem.

FIG. 28 is a second flowchart executed in place of the first flowchart. Only the difference between the two will be described below. In this flowchart, when the accumulated traveling distance D is equal to or longer than the set traveling distance Ds,
During traveling of the vehicle, it is determined whether or not the brake pedal is depressed by a limit switch or the like attached to the brake pedal. When the determination is affirmed, the valve body is switched, and the exhaust upstream and downstream of the particulate filter are switched. The side is reversed. This limit switch can be shared with a switch for lighting a brake lamp without newly providing the limit switch. Alternatively, it may be determined that a brake pedal is depressed based on an operation signal of an exhaust brake provided in a large truck or the like.

In the second flowchart, the switching of the valve element is carried out each time the brake pedal is depressed, so that the period during which the valve element is not switched does not become so long. Thus, as in the first flowchart, the residual and accumulated particulates can be reliably oxidized and removed only by the backflow of the exhaust gas. In the second flowchart, the switching of the valve body is performed when the brake pedal is depressed. At this time, since the fuel is cut or only a small amount of fuel is injected with the intention of decelerating the vehicle, the path from the engine combustion chamber is reduced. The amount of curated emissions is less than the set amount of emissions and the exhaust gas contains almost no particulates, and even if the exhaust gas bypasses the particulate filter when switching the valve element, the particulates in the atmosphere are released. There is no.

In the second flowchart, if the integrated travel distance D from the previous depression of the brake pedal has not reached the set travel distance Ds when the brake pedal is depressed, the switching of the valve body is not performed. Has become. Although this is not a limitation of the present invention, unnecessary switching of the valve element can be prevented when the brake pedal is frequently depressed, and the life of the valve element and the actuator for driving the valve element can be extended. Further, it is possible to reduce the chance of generating noise when driving the valve element.
Of course, in the present flowchart, it is also possible to use the accumulated time as in the first flowchart instead of the accumulated traveling distance, and in the first flowchart, it is also possible to use the accumulated traveling distance instead of the accumulated time. .

In the first and second flowcharts, the switching of the valve body is performed by opening the accelerator pedal or depressing the brake pedal while the vehicle is running. The valve body may be switched by depressing the brake pedal. At this time,
Since the engine is idling, the amount of fuel injection is small and the exhaust gas contains almost no particulates, so that no particulates are released into the atmosphere.

Further, at the time of deceleration of the vehicle and at the time of idling, since the fuel injection is not performed or the fuel injection amount is small, the exhaust gas temperature becomes extremely low. When the low-temperature exhaust gas passes through the particulate filter, the temperature of the particulate filter is lowered, and the amount of fine particles that can be removed by oxidation is reduced. Accordingly, according to the first and second flowcharts, the fact that the low-temperature exhaust gas partially bypasses the particulate filter by switching the valve body is advantageous in suppressing a decrease in the temperature of the particulate filter.
Therefore, it is preferable that the switching speed of the valve element be reduced so that most of the low-temperature exhaust gas bypasses the particulate filter.

However, it is not always necessary to always reduce the valve element switching speed, but it is preferable to change the valve element switching speed according to the third flowchart of FIG.
This flowchart is repeated every predetermined time. First, in step 301, it is determined according to the first flowchart or the second flowchart whether switching of the valve element has been started. If this determination is denied, the process ends. However, when the switching of the valve element is started, it is determined in step 302 whether or not the accelerator pedal is depressed. When this determination is denied, the switching speed of the valve body is kept slow, and the switching of the valve body is continued. The slow switching speed of the valve means not only that the valve moves per unit time but the valve body moves continuously, but also that the valve body moves intermittently. .

On the other hand, when the determination in step 302 is affirmative, the switching speed of the valve body is increased. That is, if acceleration is performed during the switching of the valve body, thereafter, the moving amount of the valve body per unit time is increased and the valve body is continuously moved, and the switching of the valve body is completed as quickly as possible. It is supposed to. In this way, the exhaust gas contains a large amount of particulates due to acceleration.However, by ending the switching of the valve element quickly, it is possible to reduce the particulates released to the atmosphere by bypassing the particulate filter. Can be.

If the valve body is switched according to the first flowchart or the second flowchart, accumulation of a large amount of particulates on the particulate filter is substantially prevented. However, if the accelerator pedal is not released for a long time or the brake pedal is not depressed for a long time for some reason, the valve body does not switch even if a certain amount of particulates accumulates on the particulate filter. Sometimes. In order to further prevent the accumulation of particulates, it is preferable to implement the fourth flowchart shown in FIG. 30 together with the first flowchart or the second flowchart. This flowchart is also repeated every predetermined time.

First, in step 401, the exhaust pressure P1 on one side of the particulate filter 70, that is, the exhaust pressure in the first connection portion 72a (see FIG. 18) is
It is detected by a pressure sensor arranged in the first connection part 72a. Next, in step 402, the exhaust pressure P2 on the other side of the particulate filter, that is, the exhaust pressure in the second connection portion 72b (see FIG. 18) is detected by a pressure sensor arranged in the second connection portion 72b.

In step 403, it is determined whether or not the absolute value of the differential pressure of the exhaust pressure detected in steps 401 and 402 is equal to or greater than the set pressure difference Ps. Here, the reason for using the absolute value of the differential pressure is to enable an increase in the differential pressure to be grasped regardless of which of the first connection portion 72a and the second connection portion 72b is on the exhaust upstream side. When the determination in step 403 is denied, the process ends as it is. However, when this determination is affirmed, deceleration is not performed for a long time,
Since a certain amount of particulates is deposited on the particulate filter, step 40
At 4, the switching speed is increased to switch the valve element.

Thus, as described above, the accumulated particulates are oxidized and removed from the particulate filter. At this time, since the valve body is not switched according to the first flowchart or the second flowchart, it is not at the time of deceleration, but a relatively large amount of particulates may be contained in the exhaust gas. It is preferable to minimize the particulates released into the atmosphere by switching the valve body at a high switching speed. In this flowchart, the accumulation of a certain amount of particulates in the particulate filter is indirectly detected using the differential pressure on both sides of the particulate filter. Watch for changes,
When the electric resistance value becomes equal to or less than the set value due to the accumulation of the particulates, it may be determined that a certain amount of the particulates is accumulated on the particulate filter. It is also possible to determine that a certain amount of particulates has been deposited on the particulate filter by utilizing the fact that the transmittance of light is reduced or the reflectance of light is reduced due to the deposition of the curates. .
Strictly speaking, the differential pressure on both sides of the particulate filter is
Since it also changes depending on the exhaust gas pressure discharged from the cylinder in each engine operating state, it is preferable to specify the engine operating state in determining the accumulation of particulates. Also, utilizing the change in exhaust gas pressure for each engine operating state,
It is also possible to constantly monitor the differential pressure on both sides of the particulate filter or the exhaust pressure on the upstream side of the particulate filter, and use the sudden decrease in the differential pressure or exhaust pressure to determine when the engine is decelerated.

In the first and second flow charts, when the engine is decelerated, the amount of particulates discharged from the engine combustion chamber becomes equal to or less than the set amount of discharge. The amount can be suppressed. However, the fact that the particulate emission amount is equal to or less than the set emission amount is not limited to when the engine is decelerated.

FIG. 31 is a fifth flowchart executed in place of the first flowchart. Only the differences from the first flowchart will be described below. In this flowchart, in step 502, it is determined whether or not the clutch pedal is depressed by a limit switch or the like attached to the clutch pedal, and when this determination is affirmed, the valve body is switched in step 503. I have. The driver, for a gear change,
When the clutch pedal is depressed, usually, the accelerator pedal is released or at least the depression amount of the accelerator pedal is greatly reduced. Thereby, even during such a gear change, since the amount of fuel injection is small and the amount of particulate emissions from the engine combustion chamber is equal to or less than the set emission amount, in order to prevent the accumulation of particulates in the particulate filter. No particular problem occurs even if the valve element is switched. At the same time as the clutch pedal is depressed to reduce the amount of particulate emissions to the atmosphere to zero,
The fuel cut may be performed regardless of the amount of depression of the accelerator pedal, and the fuel cut may be continued during the switching of the valve body regardless of the amount of depression of the accelerator pedal.

FIG. 32 is a sixth flowchart executed in place of the first flowchart. Only the differences from the first flowchart will be described below. In this flowchart, in step 602, it is determined whether or not the fuel injection amount TAU is equal to or less than the set injection amount TAU1, and if this determination is affirmed, the valve body is switched in step 603. In any operating state including engine deceleration and gear change, when the fuel injection amount TAU is equal to or less than the set injection amount TAU1, the fuel injection amount is small and the amount of particulate emissions from the engine combustion chamber is equal to or less than the set emission amount. Therefore, there is no particular problem even if the valve element is switched to prevent the accumulation of particulates on the particulate filter.

FIG. 33 is a seventh flowchart executed in place of the first flowchart. Only the differences from the first flowchart will be described below. In this flowchart, it is determined in step 702 whether or not the depression amount A of the accelerator pedal is equal to or less than the set depression amount A1, and when this determination is affirmed, the valve element is switched in step 703. In any operation state including engine deceleration and gear change, when the accelerator pedal depression amount A is equal to or less than the set depression amount A1, the fuel injection amount is small and the particulate emissions from the engine combustion chamber are set emissions. Since the amount is equal to or less than the amount, even if the valve element is switched to prevent the accumulation of particulates on the particulate filter, no particular problem occurs. When implementing the fifth, sixth, and seventh flowcharts, it is preferable to implement the third and fourth flowcharts, similarly to the first and second flowcharts.

As shown in FIG. 18, the particulate filter 70 of this embodiment is connected to the switching section 71 by a first connection section 72a and a second connection section 72b. And the second connection portion 72b have the same heat retention performance due to the same flow path length. Thus, the temperature of the particulate filter is not affected regardless of which connection portion is on the exhaust upstream side. However, for example, by making the heat radiation characteristics per unit length different by providing a different length or providing a heat insulating material, the temperature of the particulate filter is raised by making one of the connection portions upstream of the exhaust gas, and It is possible to lower the temperature of the particulates by setting the connection part of the exhaust gas upstream side.

The particulate filter of this embodiment is
Higher temperatures are more advantageous for removing particulates by oxidation. On the other hand, if the temperature of the particulate filter is too high, platinum may sinter and the catalytic function may decrease. In order to prevent this, it is preferable to lower the temperature of the particulate filter by using the above-described configuration so that the other connecting portion is on the exhaust upstream side.
When the switching of the valve body is performed, a relatively large amount of particulates is often contained in the exhaust gas, not at the time of engine deceleration, and it is advantageous to increase the switching speed of the valve body.

Further, when the air-fuel ratio of the exhaust gas is made rich, that is, when the oxygen concentration in the exhaust gas is reduced,
Active oxygen O is released from the active oxygen releasing agent 61 to the outside at a stretch. Due to the active oxygen O released at once, the deposited particulates are easily oxidized and easily oxidized and removed.

On the other hand, if 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. If such oxygen poisoning occurs, NO _X
Since the oxidizing effect on the active oxygen is reduced, the NO _x absorption efficiency is reduced, and the amount of active oxygen released from the active oxygen releasing agent 61 is reduced. N, however the air-fuel ratio is eliminated oxygen poisoning to oxygen on the platinum Pt surface is consumed when it is rich, and hence oxidation when the air-fuel ratio is switched again from rich to lean against NO _X becomes stronger
O _X absorption efficiency is increased, thus to the active oxygen release agent 6
1 increases the amount of active oxygen released.

Therefore, when the air-fuel ratio is temporarily switched from lean to rich while the air-fuel ratio is maintained lean, the oxygen poisoning of platinum Pt is eliminated each time, so that the air-fuel ratio when the air-fuel ratio is lean is reduced. The amount of active oxygen released is increased, and thus the oxidizing action of the particulate on the particulate filter 70 can be promoted.

Furthermore, the elimination of this oxygen poisoning is, so to speak,
Since the combustion of the reducing substance occurs, the temperature of the particulate filter is increased with heat generation. Thereby, the amount of fine particles that can be oxidized and removed in the particulate filter is improved, and the oxidization and removal of the residual and deposited particulates is facilitated. If the air-fuel ratio of the exhaust gas is made rich immediately after switching between the exhaust gas upstream side and the exhaust downstream side of the particulate filter by the valve body 71a, the other trapping surface in the particulate filter partition where no particulate remains remains. Since the active oxygen is more easily released than the one collecting surface, the residual particulates on the one collecting surface can be more reliably oxidized and removed by a larger amount of the released active oxygen. Of course, valve 7
The air-fuel ratio of the exhaust gas may be occasionally made rich irrespective of the switching of 1a, so that the particulates hardly remain and accumulate in the particulate filter.

As a method for enriching the air-fuel ratio of the exhaust gas, for example, the above-described low-temperature combustion may be performed. As described above, since the low-temperature combustion is performed on the engine low-load side, the low-temperature combustion is performed immediately after the fuel cut during engine deceleration. Thus, in the control according to the first flowchart or the second flowchart, low-temperature combustion is performed immediately after the switching of the valve body 71a, and the air-fuel ratio of the exhaust gas is often made rich. Further, in order to make the air-fuel ratio of the exhaust gas rich, the combustion air-fuel ratio may simply be made rich. Also,
In addition to the normal main fuel injection in the compression stroke, fuel may be injected into the cylinder (post-injection) in the exhaust stroke or the expansion stroke by the engine fuel injection valve, or the fuel may be injected into the cylinder in the intake stroke. (Bi rubber injection). Of course, the post injection or the rubber injection does not necessarily require an interval between the main injection and the main injection. Also,
It is also possible to supply fuel to the engine exhaust system.

By the way, calcium Ca in the exhaust gas produces calcium sulfate CaSO ₄ when SO ₃ is present. This calcium sulfate CaSO ₄ is hard to be oxidized and removed, and remains as ash on the particulate filter. Therefore, in order to prevent clogging of the particulate filter due to residual calcium sulfate, an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca as the active oxygen releasing agent 61 is used.
For example, it is preferable to use potassium K, whereby SO ₃ diffused into the active oxygen releasing agent 61 combines with potassium K to form potassium sulfate K ₂ SO ₄ , and calcium Ca does not bind with SO ₃ It passes through the partition wall of the particulate filter. Therefore, the particulate filter is not clogged by the ash.
Thus, as described above, as the active oxygen releasing agent 61, an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium L
It is preferable to use i, cesium Cs, rubidium Rb, barium Ba, and strontium Sr.

Further, even if only a noble metal such as platinum Pt is supported on a particulate filter as an active oxygen releasing agent, active oxygen can be released from NO ₂ or SO ₃ held on the surface of platinum Pt. . 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. Ceria can also be used as an active oxygen releasing agent. Ceria absorbs oxygen when the oxygen concentration in the exhaust gas is high (Ce
₂ O ₃ → ₂ CeO ₂ ), and active oxygen is released when the oxygen concentration in the exhaust gas is reduced ( ₂ CeO ₂ → Ce ₂ O ₃ ). The air-fuel ratio needs to be enriched regularly or irregularly. Iron or tin may be used instead of ceria.

It is also possible to use a NO _X storage reduction catalyst used for purifying NO _{X in} exhaust gas as an active oxygen releasing agent. In this case, it is necessary to at least temporarily make the air in order to release the NO _X or SO _X, the enrichment control after reversal of the upstream and downstream sides of the particulate filter It is preferred to carry out. Even when the enrichment control and the switching of the valve element according to the fourth flowchart are performed at the same time, switching the valve element by increasing the switching speed can reduce exhaust gas containing a large amount of CO and HC. This is advantageous in preventing a large amount from being released into the atmosphere.

In the present embodiment, the particulate filter itself carries an active oxygen releasing agent, and the particulates are oxidized and removed by the active oxygen released by the active oxygen releasing agent. Is not limited. For example, active oxygen and a particulate oxidizing substance such as nitrogen dioxide which functions equivalently to 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 oxidizing substance flows in from the outside, in order to collect the particulates, by alternately using the first collecting surface and the second collecting surface of the collecting wall, the exhaust downstream side and On one of the trapping surfaces, no new particulates accumulate, and the accumulated particulates are gradually oxidized and removed by the particulate oxidizing component flowing from the other trapping surface. Can be sufficiently oxidized and removed in a certain period of time. During this time, on the other collecting surface, the particulates are collected and oxidized by the particulate oxidizing component, so that the same effect as described above is obtained. Also in this case, when the temperature of the particulate filter is increased, the temperature of the particulate filter itself is increased to facilitate oxidation and removal.

Although the diesel engine of this embodiment is designed to switch between low-temperature combustion and normal combustion, this is not a limitation of the present invention. Of course, a diesel engine that performs only normal combustion, or The present invention is also applicable to gasoline engines that emit particulates.

[0127]

As described above, according to the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the particulate filter disposed in the engine exhaust system and the exhaust gas upstream and downstream of the particulate filter are reversed. The particulate filter oxidizes the collected particulates, the particulate filter has a collecting wall for collecting the particulates, and the collecting wall is the first collecting means. A collecting surface and a second collecting surface, and the first collecting wall of the collecting wall for collecting particulates by reversing the exhaust upstream side and the exhaust downstream side of the particulate filter by the reversing means. The surface and the second collection surface are used alternately, and the reversing means includes a valve body, and the valve body is switched from one of the two positions to the other so that the particulate filler is removed. The exhaust upstream side and the exhaust downstream side are reversed, and at least a portion of the exhaust gas bypasses the particulate filter while the valve body switches from one of the two positions to the other. When the amount of particulates discharged from the engine combustion chamber becomes equal to or less than the set amount, the upstream side and the downstream side of the exhaust of the particulate filter are reversed. As a result, depending on the operation state, the particulate filter may not be sufficiently oxidized by the particulate filter, and some of the particulate may remain on one collecting surface of the particulate filter collecting wall. Due to the reversal of the particulate filter on the exhaust upstream side and the exhaust downstream side, no new particulates accumulate on this collecting surface of the collecting wall, and the residual particulates can be gradually oxidized and removed. At the same time, collection and oxidation of particulates are started by the other collection surface of the collection wall. Thus, when the first collecting surface and the second collecting surface are alternately used for collecting the particulates, each collecting surface is compared with the case where the particulates are always collected on a single collecting surface. Since the amount of trapped particulates on the collecting surface can be reduced, which is advantageous for removing particulates by oxidation, there is no accumulation of particulates in the particulate filter, preventing clogging of the particulate filter. can do. Further, the switching of the valve element for reversing the exhaust upstream side and the exhaust downstream side of the particulate filter is performed when the particulate emission from the engine combustion chamber is equal to or less than the set emission. Does not contain a large amount of particulates, and the release of particulates into the atmosphere can be suppressed even if some exhaust gas bypasses the particulate filter during switching of the valve element.

Further, according to another exhaust gas purifying apparatus for an internal combustion engine according to the present invention, a particulate filter disposed in an engine exhaust system and an exhaust upstream side and an exhaust downstream side of the particulate filter are reversed. Reversing means, and the collected particulates are oxidized in the particulate filter, and the reversing means includes a valve element, and the valve element is switched from one of the two positions to the other, so that the particulate filter The exhaust upstream side and the exhaust downstream side are reversed, and at least a part of the exhaust gas bypasses the particulate filter while the valve body is switched from one of the two positions to the other. Reverse the upstream and downstream sides of the particulate filter with the switching speed of the valve according to the engine operating state It has become way. Thus, similarly to the above, clogging of the particulate filter can be prevented by reverse rotation of the particulate filter on the exhaust upstream side and the exhaust downstream side. Further, the switching of the valve body for reversing the exhaust upstream side and the exhaust downstream side of the particulate filter is performed with the valve body switching speed according to the engine operating state. If the switching speed is reduced when the exhaust gas temperature is low and almost no particulates are contained in the exhaust gas, it is possible to suppress a decrease in the temperature of the particulate filter without releasing the particulates into the atmosphere. If the switching speed is increased when the exhaust gas contains particulates, the release of the particulates into the atmosphere can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a diesel engine provided with an exhaust gas purification device according to the present invention.

FIG. 2 is an enlarged vertical 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 lift and fuel injection of intake and exhaust valves.

FIG. 6 is a diagram showing the amounts of smoke and NO _X generated.

7A is a diagram showing a change in combustion pressure when the amount of generated smoke is the largest when the air-fuel ratio is around 21 and FIG.
FIG. 9 is a diagram showing a change in combustion pressure when the amount of generated smoke is substantially zero near 8;

FIG. 8 is a diagram showing fuel molecules.

FIG. 9 is a diagram showing a relationship between a generation amount of smoke and an EGR rate.

FIG. 10 is a diagram showing a relationship between an injected fuel amount and a mixed gas amount.

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.

FIG. 14 is a diagram showing an air-fuel ratio in a first operation region I.

15A is a diagram showing a map of a target opening of a throttle valve, and FIG. 15B is a diagram showing a map of a target opening of an EGR control valve.

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

17A is a diagram showing a map of a target opening of a throttle valve, and FIG. 17B is a diagram showing a map of a target opening of an EGR control valve.

FIG. 18 is a plan view of the vicinity of a switching unit and a particulate filter in an engine exhaust system.

FIG. 19 is a side view of FIG. 18;

FIG. 20 is a view showing another shut-off position of the valve body in the switching unit different from FIG. 18;

FIG. 21 is a view showing an open position of a valve body in a switching unit.

FIG. 22A is a front view showing a structure of a particulate filter, and FIG. 22B is a side sectional view showing a structure of the particulate filter.

FIG. 23 is a view for explaining the oxidizing action of particulates.

FIG. 24 is a diagram showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of a particulate filter.

FIG. 25 is a view for explaining the accumulation action of particulates.

FIG. 26 is a first flowchart for preventing accumulation of particulates on a particulate filter.

FIG. 27 is an enlarged sectional view of a partition wall of the particulate filter.

FIG. 28 is a second flowchart for preventing accumulation of particulates on the particulate filter.

FIG. 29 is a third flowchart for preventing accumulation of particulates on the particulate filter.

FIG. 30 is a fourth flowchart for preventing accumulation of particulates on the particulate filter.

FIG. 31 is a fifth flowchart for preventing accumulation of particulates on the particulate filter.

FIG. 32 is a sixth flowchart for preventing accumulation of particulates on the particulate filter.

FIG. 33 is a seventh flowchart for preventing accumulation of particulates on the particulate filter.

[Explanation of symbols]

 6 Fuel injection valve 16 Throttle valve 70 Particulate filter 71 Switching part 71a Valve body

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinya Hirota 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kazuhiro Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Takamitsu Asanuma 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Koichiro Nakatani 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G004 AA01 BA06 DA24 EA01 FA02 FA07 3G090 AA02 BA08 CA01 CB23 DB07 3G091 AA02 AA18 AB13 BA11 BA14 EA00 EA07 EA30

Claims (17)

[Claims] 1. A particulate filter disposed in an engine exhaust system, and reversing means for reversing an exhaust upstream side and an exhaust downstream side of the particulate filter, wherein the particulate filter collects air. The particulates are oxidized, the particulate filter has a collecting wall for collecting particulates, the collecting wall has a first collecting surface and a second collecting surface, The first upstream surface and the second upstream surface of the particulate filter are reversed by the reverse rotation means so that the first and second collection surfaces of the collection wall can collect the particulates by being reversed. Used alternately, wherein the reversing means comprises a valve body, and the valve body is switched from one of two positions to the other by exhausting upstream of the particulate filter. And the exhaust downstream side, and at least a portion of the exhaust gas bypasses the particulate filter while the valve body switches from one of the two positions to the other, and the reversing means An exhaust purification device for an internal combustion engine, characterized in that when the amount of particulate emissions from the engine combustion chamber becomes equal to or less than a set amount of emissions, the upstream side and the downstream side of the exhaust of the particulate filter are reversed. 2. The internal combustion engine according to claim 1, wherein an active oxygen releasing agent is carried on the collecting wall, and active oxygen released from the active oxygen releasing agent oxidizes particulates. Exhaust gas purification device. 3. The active oxygen releasing agent is characterized in that when excess oxygen is present in the surroundings, it takes in oxygen to retain oxygen and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein Wherein said active oxygen release agent, a NO _X and oxygen coupled with the oxygen concentration of the to and surrounding retained by bonding the excess oxygen present around the NO _X and oxygen decreases N
3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the exhaust gas is decomposed into _OX and active oxygen and released. 5. The method according to claim 1, wherein when it is determined that the engine is decelerating, it is determined that the particulate emission amount is equal to or less than the set emission amount, and the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed. An exhaust purification device for an internal combustion engine according to any one of claims 1 to 4. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 5, wherein the engine deceleration is determined by detecting that an exhaust brake has been actuated. 7. The exhaust gas purifying apparatus for an internal combustion engine according to claim 5, wherein the engine deceleration is determined by detecting that a brake pedal is depressed. 8. The exhaust gas purifying apparatus for an internal combustion engine according to claim 5, wherein the engine deceleration is determined by detecting that the depression amount of an accelerator pedal is reduced. 9. The reversing means, after reversing an exhaust upstream side and an exhaust downstream side of the particulate filter,
When the set time has not elapsed or the vehicle has not traveled the set traveling distance, the exhaust upstream side and the exhaust downstream side of the particulate filter should not be reversed even if the particulate emission amount becomes equal to or less than the set emission amount. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, characterized in that: 10. The method according to claim 1, wherein the reversing means increases the switching speed of the valve element when it is determined that the engine is accelerating while switching the valve element. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 11. When it is determined that the fuel injection amount is equal to or less than the set injection amount, it is determined that the particulate emission amount is equal to or less than the set emission amount, and an exhaust upstream side and an exhaust downstream side of the particulate filter are determined. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the device is reversely rotated. 12. An exhaust upstream side and an exhaust downstream side of the particulate filter when it is determined that an accelerator pedal depression amount is equal to or less than a set depression amount and the particulate emission amount becomes equal to or less than the set emission amount. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein? 13. The method according to claim 13, wherein when the clutch pedal is determined to be depressed, the particulate matter discharge amount is equal to or less than the set discharge amount, and the exhaust upstream side and the exhaust downstream side of the particulate filter are reversed. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 4, wherein 14. A particulate filter disposed in an engine exhaust system, and reversing means for reversing an exhaust upstream side and an exhaust downstream side of the particulate filter, wherein the particulate filter collects air. The particulates are oxidized, the particulate filter has a collecting wall for collecting particulates, the collecting wall has a first collecting surface and a second collecting surface, The first upstream surface and the second upstream surface of the particulate filter are reversed by the reverse rotation means so that the first and second collection surfaces of the collection wall can collect the particulates by being reversed. Used alternately, wherein the reversing means comprises a valve body, and the valve body is switched from one of two positions to the other by reducing the exhaust of the particulate filter. The flow side and the exhaust downstream side are reversed, and at least a part of the exhaust gas bypasses the particulate filter while the valve body switches from one of the two positions to the other. The exhaust gas purifying apparatus for an internal combustion engine, wherein the means reverses the upstream side and the downstream side of the exhaust of the particulate filter with a switching speed of the valve body according to an engine operating state. 15. An active oxygen releasing agent is carried on the trapping wall, and active oxygen released from the active oxygen releasing agent oxidizes particulates.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 4. 16. The active oxygen releasing agent takes in oxygen when there is excess oxygen in the surroundings and retains oxygen, and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases. The exhaust gas purifying apparatus for an internal combustion engine according to claim 15, wherein 17. The method according to claim 17, wherein the active oxygen releasing agent is surrounded by excess acid.
NO if element exists _XIs held in combination with oxygen and
NO bound when the oxygen concentration in the surroundings drops_XAnd oxygen
NO_XAnd decomposes into active oxygen and releases
An exhaust gas purifying apparatus for an internal combustion engine according to claim 15.