JP2002349237A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage of a particulate filter. SOLUTION: The particulate filter 22 is arranged inside an engine exhaust passage. When pressure loss in the particulate filter 22 exceeds a set value, the particulate filter 22 is regenerated. When a deposited particulate amount on the particulate filter 22 increases and there is a probability of damage to the particulate filter 22, the particulate filter 22 is regenerated even when there is almost no increase of the pressure loss in the particulate filter 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an exhaust gas purifying apparatus.

[0002]

2. Description of the Related Art Conventionally, in a diesel engine, a particulate filter is disposed in an engine exhaust passage in order to remove fine particles contained in exhaust gas, and the fine particles in the exhaust gas are once collected by the particulate filter. In addition, the particulate filter is regenerated by igniting and burning the fine particles collected on the particulate filter. However, the fine particles trapped on the particulate filter do not ignite unless the temperature becomes higher than about 600 ° C., whereas the exhaust gas temperature of a diesel engine is usually much lower than 600 ° C. Therefore, it is difficult to ignite the fine particles collected on the particulate filter with the heat of the exhaust gas. Must be lowered.

By the way, it has been known that if a catalyst is supported on a particulate filter, the ignition temperature of the fine particles can be reduced. Is known. For example, Japanese Patent Publication 7-1062
No. 90 discloses a particulate filter in which a mixture of a platinum group metal and an alkaline earth metal oxide is supported on the particulate filter. In this particulate filter, the fine particles are ignited at a relatively low temperature of approximately 350 ° C. to 400 ° C., and then continuously burned.

[0004]

As described above, when the catalyst is supported on the particulate filter, the temperature is reduced from 350 ° C. to 40 ° C.
Fine particles can be continuously burned at a relatively low temperature of 0 ° C. However, in an actual diesel engine, the temperature of the particulate filter may be continuously reduced to 350 ° C. or less. Will occur. Also,
Particulate filter temperature from 350 ° C to 400 ° C
Even if the temperature is maintained at ° C., if a large amount of fine particles continue to be discharged from the engine, the particulate filter will be clogged in this case as well. However, in the diesel engine described in the above-mentioned publication, it is not assumed that the particulate filter is clogged in this way, and therefore, no consideration is given to measures to be taken when the particulate filter is clogged. Absent.

On the other hand, most of the conventional particulate filters burn fine particles deposited on the surface of the particulate filter on the surface of the particulate filter. On the other hand, the present inventor has been working on the development of a particulate filter capable of oxidizing and removing fine particles accumulated inside the particulate filter inside the particulate filter. The size of the exhaust gas flow pores in the particulate filter is made large in order to make it easy to enter the inside.

As described above, if the size of the exhaust gas flow pores in the particulate filter is increased, the particulate filter may be clogged depending on how the fine particles are deposited. Even though, the pressure loss in the particulate filter hardly increases. That is, when the size of the exhaust gas flow pores in the particulate filter is increased, the pressure loss in the particulate filter almost increases even if the amount of particulates deposited on the particulate filter increases depending on the operation state of the engine, as will be described in detail later. When not performed, and when the amount of deposited fine particles on the particulate filter increases, a field where the pressure loss in the particulate filter increases may occur.

When the pressure loss in the particulate filter increases, that is, when the particulate filter is clogged, it is necessary to burn and remove the accumulated fine particles as soon as possible. In other words, it is necessary to regenerate the particulate filter. . In this case, whether or not the pressure loss in the particulate filter has increased can be easily detected by using a pressure sensor or the like.Therefore, also in the present invention, the pressure loss detected by detecting the pressure loss in the particulate filter becomes the set value. When it exceeds, the particulate filter is regenerated.

[0008] However, as described above, when the size of the exhaust gas flow pores is increased, the pressure loss in the particulate filter hardly increases even if the accumulated fine particles on the particulate filter increase. in this case,
If the particulate filter is left as it is because the pressure loss in the particulate filter hardly increases, a serious problem occurs. That is, for example, when the acceleration operation is performed, the amount of heat generated in the combustion chamber increases and the amount of exhaust gas increases,
As a result, the temperature of the particulate filter rises rapidly. Next, when the operation shifts to the low-load operation, the space velocity of the exhaust gas in the particulate filter decreases in a state where the temperature of the particulate filter is high, and the accumulated particulates on the particulate filter are reduced because the oxygen concentration in the exhaust gas increases. Burns rapidly. At this time, when a large amount of fine particles are deposited on the particulate filter, the temperature of the particulate filter rises considerably due to the burning of the fine particles, and as a result, the particulate filter is melted or the temperature difference on the particulate filter becomes severe. This causes a problem that cracks occur, that is, a problem that the particulate filter is damaged.

An object of the present invention is not only to recycle the particulate filter when the pressure loss in the particulate filter exceeds a set value, but also to maintain the pressure loss in the particulate filter at a value considerably lower than the set value. An object of the present invention is to provide an exhaust gas purifying apparatus that regenerates a particulate filter as needed in order to prevent the particulate filter from being damaged even if it is used.

[0010]

According to a first aspect of the invention, in order to achieve the above object, a particulate filter for collecting particulates in exhaust gas is disposed in an engine exhaust passage, and a lean air-fuel ratio is reduced. In an internal combustion engine that can continuously oxidize and remove accumulated particulates on a particulate filter without generating a bright flame when combustion is continuously performed, the engine is used as a particulate filter. Depending on the operating conditions, the pressure loss in the particulate filter hardly increases even if the amount of particulates deposited on the particulate filter increases, or the pressure loss in the particulate filter increases when the particulates deposited on the particulate filter increase. Detect pressure loss in particulate filter using a curated filter Output means, main regeneration means for increasing the temperature of the particulate filter in order to regenerate the particulate filter when the pressure loss detected by the detection means exceeds a set value, and the amount of particulates deposited on the particulate filter increases. When there is a possibility that the particulate filter may be damaged by the heat of oxidation reaction of the deposited fine particles, the lean filter is used to regenerate the particulate filter even if the pressure loss in the particulate filter hardly increases and does not exceed the set value. An intermediate regeneration means for increasing the temperature of the particulate filter under the air-fuel ratio.

In the second invention, in the first invention,
Estimating means for estimating whether or not the amount of the deposited fine particles on the particulate filter has exceeded a limit value that may cause damage to the particulate filter due to heat of oxidation reaction of the deposited fine particles. When it is estimated that the amount of particulates deposited on the particulate filter has exceeded the limit value, even if the pressure loss in the particulate filter hardly increases and does not exceed the set value, the lean air-fuel ratio must be reduced to regenerate the particulate filter. This raises the temperature of the particulate filter.

In a third invention, in the second invention,
Calculating means for calculating the amount of deposited fine particles on the particulate filter; the estimating means using the amount of deposited fine particles calculated by the calculating means to determine whether or not the amount of deposited fine particles on the particulate filter has exceeded a limit value; Is to be estimated. In a fourth aspect based on the third aspect, the calculating means calculates the amount of particulates deposited on the particulate filter based on the amount of particulates discharged from the engine and the temperature of the particulate filter.

In a fifth aspect, in the first aspect,
When the engine is started, or when the operating time of the engine, the cumulative value of the engine speed, or the vehicle traveling distance exceeds a predetermined value, the amount of the particulate matter deposited on the particulate filter is limited. It is assumed that the value has been exceeded. In a sixth aspect based on the first aspect, the intermediate playback means sets a target playback time required for playback when playback control of the particulate filter is started, and sets the target playback time when playback control is interrupted and then resumed. The time required to raise the temperature of the particulate filter to the regeneration start temperature is added to the remaining time of the target regeneration time at the time of interruption, and the added time is set as a new target regeneration time.

In a seventh aspect, in the first aspect,
A noble metal catalyst is supported on the particulate filter. In an eighth aspect based on the seventh aspect, the active oxygen releasing agent according to the seventh aspect, which takes in oxygen when surrounding oxygen is present, retains oxygen, and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases. Is carried on a particulate filter, and the fine particles adhering to the particulate filter are oxidized by the released active oxygen.

In a ninth invention, in the eighth invention,
The active oxygen releasing agent comprises an alkali metal or an alkaline earth metal or a rare earth or transition metal. In the tenth invention, 1
In th invention, a noble metal catalyst on the particulate filter, the air-fuel ratio of the exhaust gas air-fuel ratio of the exhaust gas flowing into the particulate filter when lean flowing into the particulate filter to absorb NO _x in the exhaust gas NO _x absorbed to be a stoichiometric air-fuel ratio or rich
It carries the _the NO _x absorbent to release the.

[0016] In the tenth invention is a 11th invention, NO _x absorbent is made of a metal alkali metals or alkaline earth or rare earth or transition metal. In 10 th invention is a 12th invention, rich temporarily the air-fuel ratio of the exhaust gas flowing into the particulate filter from lean to when releasing the NO _x absorbed in _the NO _x absorbent from _the NO _x absorbent are provided with _the NO _x releasing control means for switching the.

[0017] In the tenth invention the 13th invention, Patty with the time to release the SO _x that is absorbed in the NO _x absorbent from _the NO _x absorbent to increase the temperature of the particulate filter to release SO _x Temperature are provided with a release of SO _x control means for switching to a rich air-fuel ratio of the exhaust gas flowing into the particulate filter from lean.

[0018] In 13 th invention is a 14 th invention, release SO _x control means sets a target release of SO _x time required to release of the SO _x when the controlled release of the SO _x is started, SO _x the goal SO _x the temperature of the particulate filter to the remaining time of the release time and this sum by adding the time required to raise to release SO _x temperature time at interrupted when the release control is resumed after interruption The new target SO _x release time is set.

[0019]

FIG. 1 shows a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine. Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Denotes an exhaust valve, and 10 denotes an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13.
A throttle valve 17 driven by a step motor 16 is disposed in the intake duct 13.
A cooling device 18 for cooling the intake air flowing through the intake duct 13 is disposed around the cooling device 18. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18, and the engine cooling water cools the intake air. On the other hand, the exhaust port 10 is connected to an exhaust turbine 21 of the exhaust turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20, and an outlet of the exhaust turbine 21 is connected to a casing 23 having a built-in particulate filter 22.

The exhaust manifold 19 and the surge tank 12 are connected to each other via an exhaust gas recirculation (hereinafter, referred to as EGR) passage 24, and an electrically controlled EGR control valve 25 is disposed in the EGR passage 24. Also, the EGR passage 24
A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the cooling device 26. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 26, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 6 is connected to a fuel reservoir, a so-called common rail 27, via a fuel supply pipe 6a. Fuel is supplied into the common rail 27 from a fuel pump 28 of an electrically controlled variable discharge amount, and the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 through each fuel supply pipe 6a. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27. The fuel pump 28 is controlled so that the fuel pressure in the common rail 27 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 29. Is controlled.

The electronic control unit 30 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, An output port 36 is provided. The output signal of the fuel pressure sensor 29 is input to the input port 35 via the corresponding AD converter 37. Further, a temperature sensor 39 for detecting the temperature of the particulate filter 22 is attached to the particulate filter 22, and an output signal of the temperature sensor 39 corresponds to an analog signal.
The signal is input to the input port 35 via the converter 37. Further, a pressure sensor 43 for detecting a pressure difference between the upstream exhaust gas pressure and the downstream exhaust gas pressure of the particulate filter 22, that is, a pressure loss in the particulate filter 22, is attached to the particulate filter 22,
The output signal of the pressure sensor 43 is output to the corresponding AD converter 3
7 to the input port 35.

On the other hand, a load sensor 41 for generating an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is supplied to an input port via a corresponding AD converter 37. 35 is input. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, by 30 °. On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, and the fuel pump 28 via the corresponding drive circuit 38.

FIG. 2A shows the relationship between the required torque TQ, the depression amount L of the accelerator pedal 40, and the engine speed N. In FIG. 2A, each curve represents an equal torque curve, a curve indicated by TQ = 0 indicates that the torque is zero, and the remaining curves include TQ = a, TQ
The required torque gradually increases in the order of Q = b, TQ = c, and TQ = d. The required torque TQ shown in FIG.
As shown in (B), the ROM is previously stored in the form of a map as a function of the depression amount L of the accelerator pedal 40 and the engine speed N.
32. In the embodiment according to the present invention, FIG.
A required torque TQ corresponding to the depression amount L of the accelerator pedal 40 and the engine speed N is calculated first from the map shown in FIG.

FIGS. 3A and 3B show the structure of the particulate filter 22 shown in FIG. FIG. 3A is a front view of the particulate filter 22, and FIG.
FIG. As shown in FIGS. 3A and 3B, the particulate filter 22 has a honeycomb structure and includes a plurality of exhaust passages 50 and 51 extending parallel to each other. These exhaust gas passages have an exhaust gas inflow passage 5 whose downstream end is closed by a plug 52.
0 and an exhaust gas outflow passage 51 whose upstream end is closed by a stopper 53. In FIG. 3A, hatched portions indicate plugs 53. Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged with the thin partition walls 54 interposed therebetween. In other words, the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51 are each surrounded by the four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by the four exhaust gas inflow passages 50. It is arranged so that.

The particulate filter 22 is formed of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust gas inflow passage 50 is
As shown by an arrow in (B), it flows into the adjacent exhaust gas outflow passage 51 through the partition wall 54 around the periphery.
In the embodiment according to the present invention, for example, alumina is formed on the peripheral wall surface of each exhaust gas inflow passage 50 and each exhaust gas outflow passage 51, that is, on both side surfaces of each partition wall 54 and on the inner wall surface of the exhaust gas flow pore in the partition wall 54. A layer of a carrier is formed, and on the carrier, a noble metal catalyst and, when excess oxygen is present in the surroundings, take in oxygen to retain oxygen and, when the surrounding oxygen concentration decreases, retain the oxygen in the form of active oxygen. An active oxygen releasing agent to be released is supported.

In this case, in the embodiment according to the present invention, platinum Pt is used as a noble metal catalyst, and an alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, rubidium Rb, or barium Ba is used as an active oxygen releasing agent. , Calcium Ca, alkaline earth metals such as strontium Sr, lanthanum La, rare earths such as yttrium Y, cerium Ce, and tin Sn, iron F
At least one selected from transition metals such as e is used.

In this case, as the active oxygen releasing agent, an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li,
It is preferable to use cesium Cs, rubidium Rb, barium Ba, strontium Sr, or cerium Ce. Next, the action of removing particulates in the exhaust gas by the particulate filter 22 will be described by taking as an example a case where platinum Pt and potassium K are carried on a carrier, but other noble metals, alkali metals, alkaline earth metals, rare earths, transition metals The same effect of removing fine particles can be obtained by using.

In a compression ignition type internal combustion engine as shown in FIG. 1, combustion takes place under excess air, so that the exhaust gas contains a large amount of excess air. That is, when the ratio of air and fuel supplied to the intake passage, the combustion chamber 5 and the exhaust passage is referred to as the air-fuel ratio of the exhaust gas, the air-fuel ratio of the exhaust gas in the compression ignition type internal combustion engine as shown in FIG. It is lean. Further, since NO is generated in the combustion chamber 5, the exhaust gas contains NO. The fuel contains sulfur S
This sulfur S reacts with oxygen in the combustion chamber 5 to become SO ₂ . Therefore, SO ₂ is contained in the exhaust gas. Therefore, exhaust gas containing excess oxygen, NO, and SO ₂ flows into the exhaust gas inflow passage 50 of the particulate filter 22.

FIGS. 4A and 4B schematically show enlarged views of the inner peripheral surface of the exhaust gas inflow passage 50 and the surface of the carrier layer formed on the inner wall surface of the pores in the partition wall 54. FIG. .
4A and 4B, reference numeral 60 denotes platinum Pt.
And 61 denotes an active oxygen releasing agent containing potassium K. When the exhaust gas because the exhaust gas as described above contains a large amount of excess oxygen flows into the exhaust gas inflow passages 50 of the particulate filter 22 4 These oxygen O ₂ as shown in (A)
There 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 becomes O ₂ ^- or O ₂ on the surface of platinum Pt.
Reacts with ^2- to form 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 2 as shown in FIG.
₃ ^- of diffuse in the active oxygen release agent 61 in the form, some of the nitrate ions NO ₃ ^- produces potassium nitrate KNO _3.

On the other hand, as described above, SO is contained in the exhaust gas.
₂ is also included, this SO ₂ is absorbed in the active oxygen release agent 61 by a NO similar mechanisms. That is,
Oxygen O ₂ as described above O ₂ ^- or platinum O ^2- in the form Pt
Are attached on the surface, SO ₂ in the exhaust gas is platinum Pt
Or O ^2- reacts with the SO ₃ ^- O ₂ at the surface of the. Next, a part of the generated SO ₃ is absorbed into the active oxygen releasing agent 61 while being further oxidized on the platinum Pt, and is combined with potassium K to form the active oxygen releasing agent 61 in the form of sulfate ion SO ₄ ^2−.
To form potassium sulfate K ₂ SO ₄ . Thus, potassium nitrate K is contained in the active oxygen releasing catalyst 61.
NO ₃ and potassium sulfate K ₂ SO ₄ are produced.

On the other hand, fine particles mainly composed of carbon C are generated in the combustion chamber 5, and therefore, these fine particles are contained in the exhaust gas. These fine particles contained in the exhaust gas are used as the particulate filter 2 in the exhaust gas.
2B, when flowing in the exhaust gas inflow passage 50 or when going from the exhaust gas inflow passage 50 to the exhaust gas outflow passage 51, as shown by 62 in FIG. It contacts and adheres to the surface of the oxygen releasing agent 61.

As described above, the fine particles 62 serve as the active oxygen releasing agent 6
1 and the fine particles 62 and the active oxygen releasing agent 6
At the contact surface with No. 1, the oxygen concentration decreases. 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. As a result, the potassium nitrate KNO ₃ formed in the active oxygen releasing agent 61 becomes potassium K and oxygen O
Is decomposed into NO and the oxygen O is directed to the contact surface between the fine particles 62 and the active oxygen releasing agent 61, and NO is
1 to the outside. The NO released to the outside is oxidized on platinum Pt on the downstream side, and is absorbed again in the active oxygen releasing agent 61.

On the other hand, at this time, the particulate filter
If the temperature of 22 is high, it is formed in the active oxygen releasing agent 61.
Potassium sulfate K_Two SO_Four Also potassium K and oxygen O
SO _Two And oxygen O is released to the fine particles 62 and active oxygen.
Toward the contact surface with the powder 61, SO_Two Is an active oxygen release agent
It is released from 61 to the outside. SO released to the outside_TwoIs
It is oxidized on platinum Pt on the downstream side and releases active oxygen again.
It is absorbed into the dispensing agent 61.

On the other hand, the oxygen O heading toward the contact surface between the fine particles 62 and the active oxygen releasing agent 61 is oxygen decomposed from a compound such as potassium nitrate KNO ₃ or potassium sulfate K ₂ SO ₄ . Oxygen O decomposed from the compound has high energy and extremely high activity. Therefore, the fine particles 6
Oxygen toward the contact surface between 2 and the active oxygen releasing agent 61 is active oxygen O. When the active oxygen O comes into contact with the fine particles 62, the oxidizing action of the fine particles 62 is promoted, and the fine particles 6
2 can be removed by oxidation in a few minutes to several tens of minutes without emitting a bright flame. On the other hand, as shown in FIG.
While the particles are being oxidized, other fine particles adhere to the particulate filter 22 one after another. Therefore, in practice, a certain amount of fine particles is constantly deposited on the particulate filter 22, and some of the deposited fine particles are oxidized and removed. In this way, the fine particles 62 adhering to the particulate filter 22 are continuously burned without emitting a bright flame.

It is considered that NO ₂ diffuses 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 fine particles 62 are also oxidized by this active oxygen. Further, the fine particles 62 thus adhered on the particulate filter 22 are oxidized by the active oxygen O, but the fine particles 62 are also oxidized by the oxygen in the exhaust gas.

When the particulates deposited on the particulate filter 22 are burned, the particulate filter 22 becomes red hot and burns with a flame. Such combustion with a flame cannot be sustained unless it is at a high temperature, so that the temperature of the particulate filter 22 must be maintained at a high temperature in order to maintain the combustion with such a flame.

On the other hand, in the present invention, the fine particles 62 are oxidized without emitting a bright flame as described above,
At this time, the surface of the particulate filter 22 does not glow. That is, in other words, in the present invention, the fine particles 62 are usually oxidized and removed at a considerably low temperature. Therefore, in the present invention, the action of removing fine particles 62 by oxidation of the fine particles 62 that do not emit a bright flame is completely different from the action of removing fine particles by combustion accompanied by a flame.

Meanwhile, platinum Pt and active oxygen releasing agent 6
1 is activated as the temperature of the particulate filter 22 increases, so that the amount of active oxygen O that the active oxygen releasing agent 61 can release per unit time increases as the temperature of the particulate filter 22 increases. Naturally, the fine particles are more easily oxidized and removed as the temperature of the fine particles themselves is higher. Accordingly, the amount of fine particles that can be oxidized and removed on the particulate filter 22 without emitting a bright flame per unit time increases as the temperature of the particulate filter 22 increases.

The solid line in FIG. 5 shows the oxidation rate of the fine particles on the particulate filter 22, that is, the amount G (g / min) of the fine particles which can be oxidized and removed without emitting a luminous flame per minute and the temperature of the particulate filter 22, for example. T
The relationship with F is shown. That is, the balance point at which the amount of the fine particles flowing into the curved particulate filter 22 shown in FIG. On this curve, since the amount of the inflowing fine particles is equal to the amount of the fine particles to be oxidized and removed, the amount of the fine particles deposited on the particulate filter 22 is kept constant. On the other hand, in the region I of FIG. 5, the amount of the inflowing fine particles is smaller than the amount of the fine particles that can be oxidized and removed. Therefore, if the state of the region I continues, the amount of the deposited fine particles gradually decreases. On the other hand, in the region II of FIG. 5, the amount of the inflowing fine particles is larger than the amount of the fine particles that can be oxidized and removed, so that all the inflowing fine particles cannot be oxidized. In this case, the deposited fine particles are gradually changed to carbon which is hardly oxidized as time elapses after the deposition, and thus, if the state of the region II is continued, the deposited fine particles gradually become hard to oxidize.

As described above, when the particulate filter 22 according to the present invention is used, when the amount of the inflowing fine particles is equal to the amount of the fine particles that can be removed by oxidation (on the curve in FIG. 5), the amount of the flowing fine particles is smaller than the amount of the fine particles that can be removed by oxidation. Time (Fig. 5
In the region I), the fine particles deposited on the particulate filter 22 are sequentially oxidized and removed. That is, the deposited fine particles are continuously oxidized. On the other hand, when the amount of inflowing fine particles is larger than the amount of oxidizable fine particles (region I in FIG. 5).
Even in I), some of the deposited fine particles are continuously oxidized, but some of the deposited fine particles are deposited without being oxidized. Therefore, the amount of the deposited fine particles gradually increases as the inflowing fine particles continue to be larger than the oxidized fine particles. .

As described above, in the embodiment according to the present invention, a layer of a carrier made of, for example, alumina is formed on both side surfaces of each partition wall 54 of the particulate filter 22 and on the inner wall surface of the exhaust gas flow pore in the partition wall 54. The noble metal catalyst and the active oxygen releasing agent are supported on the carrier. Further, in the embodiment according to the present invention flows the carrier onto the noble metal catalyst, and when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is lean absorbs NO _x contained in the exhaust gas to the particulate filter 22 exhaust _the NO _x absorbent to release the NO _x when the air-fuel ratio of the gas is absorbed and becomes the stoichiometric air-fuel ratio or rich is carried.

The in the embodiment according to the present invention, platinum Pt is used as the precious metal catalyst, potassium as _the NO _x absorbent K, sodium Na, lithium Li, cesium C
s, alkali metal such as rubidium Rb, barium B
a, calcium Ca, alkaline earth such as strontium Sr, lanthanum La, yttrium Y, cerium C
At least one selected from rare earths such as e is used. Note that largely match the metal constituting the metal forming the NO _x absorbent as can be seen by comparison with the metal comprising the active oxygen release agent described above, the active oxygen release agent.

In this case, different metals can be used as the NO _x absorbent and the active oxygen releasing agent, or the same metal can be used. When the same metal is used as the NO _x absorbent and the active oxygen release agent, NO _x
Both functions as an absorbent and a function as an active oxygen releasing agent are simultaneously performed. Then using platinum Pt as the precious metal catalyst, the described absorption and release action of the NO _x taking as an example the case of using potassium K as _the NO _x absorbent.

First, when the NO _x absorbing action is examined, NO _x is absorbed by the NO _x absorbent by the same mechanism as shown in FIG. 4 (A). However, in this case, reference numeral 61 in FIG. 4A indicates a NO _x absorbent. That is, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is lean, a large amount of excess oxygen is contained in the exhaust gas, so that the exhaust gas flows into the exhaust gas inflow passage 50 of the particulate filter 22. As shown in FIG. 4 (A), these oxygens O ₂ adhere to the surface of platinum Pt in the form of O ₂ ⁻ or O ²⁻ . On the other hand, NO in the exhaust gas on the surface of the platinum Pt O ₂ ^- reacting or O ^2- as,
NO ₂ (2NO + O ₂ → 2NO ₂ ). Next, a part of the generated NO ₂ is absorbed in the NO _x absorbent 61 while being oxidized on the platinum Pt, and is combined with potassium K in FIG.
Nitrate ions NO as shown in (A) ₃ ^- in the form of the NO _x
The nitrate ion NO ₃ ⁻ diffuses into the absorbent 61 to generate potassium nitrate KNO ₃ . In this way, NO becomes N
It is absorbed in the O _x absorbent 61.

On the other hand, the exhaust gas flowing into the particulate filter 22 is nitrate ion NO ₃ becomes rich ^- is decomposed into oxygen and O and NO, the next to the next _the NO _x absorbent 6
1 releases NO. Therefore, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 becomes rich, NO is released from the NO _x absorbent 61 in a short time, and since the released NO is reduced, NO is released into the atmosphere. Is not emitted.

In this case, NO is released from the NO _x absorbent 61 even if the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is set to the stoichiometric air-fuel ratio. However it takes some long time to release all NO _x absorbed in _the NO _x absorbent 61 to the NO from _the NO _x absorbent 61 are not only released gradually in this case. Incidentally, as described above, different metals can be used as the NO _x absorbent and the active oxygen release agent. However, in the embodiment according to the present invention, the same metal is used as the NO _x absorbent and the active oxygen releasing agent. In this case will be performing the functions of both the function of the function and the active oxygen release agent as _the NO _x absorbent as described above at the same time, the following ones to fulfill this manner both functions simultaneously, active oxygen referred to as release · NO _x absorbent. Therefore, in the embodiment according to the present invention, reference numeral 61 in FIG. 4A indicates an active oxygen releasing / NO _x absorbent.

Such an active oxygen releasing / NO _x absorbent 6
When using 1, fine air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is NO, which at the time of lean contained in the exhaust gas is absorbed in the active oxygen release · NO _x absorbent 61, contained in the exhaust gas Is active oxygen release ・ N
O _x absorbent when attached to 61 the particulate active oxygen contained in the exhaust gas and the active oxygen release · NO _x absorbent 6
It is oxidized and removed by active oxygen or the like released from 1. Therefore, at this time, the particulates and NO _x in the exhaust gas
Can be prevented from being discharged into the atmosphere.

On the other hand, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 becomes rich, NO is released from the active oxygen release / NO _x absorbent 61. This NO is reduced by the unburned HC and CO, and thus NO is not discharged to the atmosphere at this time. Further, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is switched from lean to rich, that is, when the oxygen concentration in the exhaust gas sharply decreases, active oxygen is released from the active oxygen release / NO _x absorbent 61 at once. Is done. Therefore, at this time, the oxidizing action of the deposited fine particles on the particulate filter 22 is rapidly promoted by the active oxygen released from the active oxygen release / NO _x absorbent 61.

As described above, when the state where the amount of the inflowing fine particles is larger than the amount of the oxidized fine particles continues, the amount of the deposited fine particles gradually increases. In this case, in the particulate filter 22 used in the present invention, the pressure loss in the particulate filter 22 hardly increases even if the amount of particulates deposited on the particulate filter 22 increases depending on the operation state of the engine.
When the amount of the deposited fine particles on the second filter 2 increases, the pressure loss in the particulate filter 22 may increase. Next, this will be described with reference to FIGS. 6 (A) and 6 (B).

FIGS. 6A and 6B are enlarged sectional views of the partition wall 54 of the particulate filter 22.
Exhaust gas flows inside the partition wall 54 as shown by arrows. 6A and 6B, a hatched portion 70 indicates a base material of the particulate filter 22, and a space formed between the base materials 70 is a fine hole 71 through which exhaust gas flows. Is shown. A black circle 72 indicates the deposited fine particles.

In the particulate filter 22 used in the present invention, the size of the exhaust gas flow holes 71 is made larger than before. Further, the entire surface of the substrate 70 facing the exhaust gas flow pores 71 is also covered with a layer of a carrier made of, for example, alumina in order to perform the oxidizing and removing action of the fine particles inside the partition wall 54 of the particulate filter 22. The active oxygen release / N
O _x absorbent 61 is carried. Incidentally, the fine particles even lower temperature TF of 200 ° C. or less as can be seen from Figure 5 the use of the active oxygen release · NO _x absorbent 61 becomes possible oxide removal.

In the particulate filter 22 of the present invention, regardless of whether the amount of fine particles flowing into the particulate filter 22 is larger or smaller than the amount of fine particles that can be removed by oxidation, normal fine particles are separated from the partition walls as shown in FIG. It is dispersed and deposited on the surface of the substrate 54 and the surface of the substrate 70 in the partition wall 54. In this case, when the amount of the inflowing fine particles is equal to or smaller than the amount of the fine particles that can be oxidized and removed, all the accumulated fine particles 72 are sequentially oxidized and removed. On the other hand, when the amount of the inflowing fine particles is larger than the amount of the fine particles that can be oxidized and removed, some of the fine particles 72 are removed by oxidation, but some of the fine particles 72 continue to be deposited without being oxidized and removed. Will gradually increase. However, even if the amount of deposited fine particles gradually increases in this manner, the particulate filter
Since the size of the exhaust gas flow pores 71 is large and fine particles are dispersed and deposited, the pressure loss in the particulate filter 22 hardly increases.

On the other hand, as shown in FIG. 5 (B), if particulates are intensively deposited at the inlet of the exhaust gas passage pore 71 for some reason, the particulate filter 22 is clogged, and thus the particulate filter 22 is clogged. Filter 2
2, the pressure loss increases. The increase in the pressure loss of the particulate filter 22 occurs even when the amount of the deposited fine particles is smaller than the amount of the deposited fine particles in the case where the deposited fine particles are dispersed and deposited as shown in FIG. That is, whether or not the pressure loss of the particulate filter 22 increases has no direct relation to the amount of deposited particles, but depends on the method of depositing the particles.

It can be roughly predicted from experience based on what operating state the particulate filter 22 becomes clogged as shown in FIG. 6 (B). However, since the actual operating state of the engine changes in a complicated manner, it is difficult to determine whether or not the particulate filter 22 has clogged from the operating state of the engine. It is necessary to detect whether or not the pressure loss in the particulate filter 22 has increased.

On the other hand, when fine particles are dispersed and deposited as shown in FIG. 6A, even if the fine particles deposited on the particulate filter 22 increase as described above, almost no pressure loss occurs in the particulate filter 22. Does not increase. In this case, if the pressure drop in the particulate filter 22 hardly increases because it hardly increases, a serious problem occurs as described at the beginning.
That is, for example, when an acceleration operation is performed, the amount of heat generated in the combustion chamber 5 increases, and the amount of exhaust gas increases. As a result, the temperature of the particulate filter 22 rapidly increases. Next, when the operation shifts to the low load operation, the space velocity of the exhaust gas in the particulate filter 22 decreases in a state where the temperature of the particulate filter 22 is high,
Since the oxygen concentration in the exhaust gas increases, the deposited fine particles on the particulate filter 22 are rapidly burned. At this time, if a large amount of fine particles 72 are deposited on the particulate filter 22, the temperature of the particulate filter 22 rises considerably due to the burning of the fine particles 72,
As a result, the particulate filter 22 is melted,
Alternatively, there is a problem that the temperature difference on the particulate filter 22 becomes so large that a crack is generated, that is, a problem that the particulate filter 22 is damaged.

Therefore, according to the present invention, when the amount of the particulates deposited on the particulate filter 22 increases and the particulate filter 22 may be damaged by the heat of oxidation reaction of the particulates, the pressure loss in the particulate filter 22 is reduced. The temperature of the particulate filter 22 is increased under a lean air-fuel ratio in order to regenerate the particulate filter 22 even when the temperature does not substantially increase.

That is, in the embodiment according to the present invention, as shown in FIG. 7, when the pressure loss PD in the particulate filter 22 exceeds the preset value MAX predetermined according to the operating state of the engine, the air-fuel ratio A / F The regeneration process is performed in a lean state, and even when the pressure loss PD in the particulate filter 22 is lower than the set value MAX, the amount of particulates deposited on the particulate filter 22 is reduced by the oxidation reaction heat of the particulate filter. 22
When it is estimated that the air-fuel ratio A / F has exceeded the limit value that may cause damage, the regeneration process is performed.

In practice, the amount of particulates deposited on the particulate filter 22 is smaller than the frequency at which the particulate filter 22 is clogged.
2 is much higher than the limit value that may cause damage to the second filter 2, and therefore, as shown in FIG.
Compared to the frequency of the playback process performed when the value exceeds AX,
The frequency of the regenerating process performed when it is estimated that the amount of particulates deposited on the particulate filter 22 has exceeded a limit value that may cause damage to the particulate filter 22 is much higher.

In the regeneration process shown in FIG. 7, the particulate filter 2 is heated from 500.degree. C. to 600.degree. C. at which the deposited fine particles on the particulate filter 22 ignite and start burning.
2 and then increase the temperature of the particulate filter 22 by 5 until most of the deposited particulates have burned.
This is a process of maintaining the temperature from 00 ° C to 600 ° C or more. In this case, there are various methods for raising the temperature of the particulate filter 22. For example, a method of arranging an electric heater at the upstream end of the particulate filter 22 and heating the particulate filter 22 or the exhaust gas flowing into the particulate filter 22 by the electric heater,
A method of heating the particulate filter 22 by injecting fuel into an exhaust passage upstream of the particulate filter 22 and burning the fuel, or a method of increasing the temperature of the particulate filter 22 by increasing the temperature of the exhaust gas. is there.

Here, the last method, that is, a method of increasing the exhaust gas temperature will be briefly described with reference to FIG. One of the effective methods for increasing the exhaust gas temperature is to retard the fuel injection timing until after the compression top dead center. That is, normally the main fuel Q _m is injected near compression top dead center as shown in (I) in FIG. 8. In this case, the main injection timing of fuel Q _m is burning period becomes longer after the is retarded as shown in (II) of FIG. 8, the exhaust gas temperature rises in thus. As the exhaust gas temperature increases, the temperature TF of the particulate filter 22 increases accordingly.

In order to increase the exhaust gas temperature, FIG.
As shown in (III), the main fuel Q _m Plus inspiratory death
Auxiliary fuel Q near the point_v Can also be injected.
Thus, the auxiliary fuel Q_v Additional fuel and auxiliary fuel
Q_V Exhaust gas to increase the amount of fuel
Temperature rises, and thus the particulate filter 22
Temperature TF rises.

On the other hand, in the vicinity of the intake top dead center,
Auxiliary fuel Q_v Is injected during the compression process by the heat of compression.
This auxiliary fuel Q_v From aldehydes, ketones, peroxas
And intermediate products such as carbon monoxide
Main fuel Q by inter-product_mReaction is accelerated. Follow
In this case, as shown in FIG. _m 
It is good without misfire even if the injection timing of
Good combustion is obtained. That is, the main fuel Q_m Jet of
Since the firing time can be greatly delayed, the exhaust gas temperature
Considerably higher, thus the particulate filter 2
The temperature TF of No. 2 can be immediately increased.

[0063] In addition to the main fuel Q _m as shown in (IV) of FIG. 8, the auxiliary fuel Q or during the exhaust stroke during the expansion stroke
_p can also be injected. That is, in this case, the auxiliary fuel Q _p most is discharged into the exhaust passage in the form of unburned HC without being burned. This unburned HC is oxidized by excess oxygen on the particulate filter 22, and the temperature TF of the particulate filter 22 is raised by the participating reaction heat generated at this time.

As described above, when the air-fuel ratio of the exhaust gas is lean, NO _x in the exhaust gas is absorbed by the active oxygen release / NO _x absorbent 61. However, NO _x
There is a limit to the absorption of NO _x capacity of the absorbent 61, is necessary to the active oxygen release · absorption of NO _x agent 61 before absorption of NO _x capacity of the active oxygen release · absorption of NO _x agent 61 is saturated releasing NO _x is there. For this purpose it is necessary to estimate the amount of NO _x absorbed in the active oxygen release · NO _x absorbent 61. Therefore, in the embodiment according to the present invention, NO per unit time
_{The x} absorption amount A is obtained in advance in the form of a map as shown in FIG. 9 as a function of the required torque TQ and the engine speed N,
So that to estimate the amount of NO _x ΣNOX absorbed in the active oxygen release · absorption of NO _x agent 61 by integrating the absorption of NO _x amount A per unit time.

[0065] Moreover, the active oxygen release · NO when this absorption of NO _x amount ΣNOX as shown in FIG. 7 exceeds an allowable maximum value MAXN predetermined in this embodiment of the present invention
The air-fuel ratio A / F of the exhaust gas flowing into the _x absorbent 61 is temporarily made rich, so that the active oxygen release / NO _x absorbent 25 releases NO _x . In this case, there are various methods for temporarily switching the air-fuel ratio A / F from lean to rich. For example, a method of enriching the average air-fuel ratio in the combustion chamber 5, a method of injecting additional fuel into the combustion chamber 5 during the latter half of the expansion stroke or during the exhaust stroke, and a method of adding additional fuel to the exhaust passage upstream of the particulate filter 22 There is a method of injecting fuel.

On the other hand, the exhaust gas contains SO_x Is included
Release active oxygen_x NO in the absorbent 61_x Only
Not SO_x Is also absorbed. This active oxygen release NO_x 
SO to absorbent 61_x NO absorption mechanism is NO_x Absorption of
It is considered to be the same as the mechanism. That is, NO_x of
In the same manner as when the absorption mechanism was explained, platinum P
Explanation of the case where t and potassium K are carried as an example
Then, as described above, the air-fuel ratio of the exhaust gas is lean.
Oxygen O_Two Is O_Two ^-Or O^2-On the surface of platinum Pt
Adhering to SO in exhaust gas_Two Is the surface of platinum Pt
O_Two ^-Or O^2-Reacts with SO_Three Becomes Then generated
SO_Three Some of the active acid is further oxidized on platinum Pt
Elementary release / NO_x Absorbed in the absorbent and combined with potassium K
While sulfate ion SO_Four ^2- Active oxygen release in the form of N
O_x Sulfate K that diffuses into the absorbent and is stable _Two SO_Four Raw
To achieve.

However, the sulfate K ₂ SO ₄ is stable and hard to decompose, and as described above, releases active oxygen.
Even _if the air-fuel ratio of the exhaust gas is made rich to release NO _x from the NO _x absorbent 61, the sulfate K ₂ SO ₄ remains without being decomposed. Therefore, active oxygen release / NO _x absorbent 61
In time, the sulfate K ₂ SO ₄ increases as time elapses, and thus the amount of NO _x that can be absorbed by the active oxygen release / NO _x absorbent 61 decreases as time elapses. Become.

[0068] However temperature the active oxygen release · NO _x in the sulfate K ₂ SO ₄ is the active oxygen release · NO _x absorbent 61
Constant temperature determined by the absorbent 61, for example, approximately 600 ° C.
Decomposes exceeds, SO _x from the active oxygen release · NO _x absorbent 61 when this time the air-fuel ratio of the exhaust gas flowing into the active oxygen release · NO _x absorbent 61 rich is released. However, the active oxygen release / NO _x absorbent 61
_It takes a considerably longer time to release _x than to release NO _x from the active oxygen release / NO _x absorbent 61.

Therefore, in the embodiment according to the present invention, when SO _x is to be released from the active oxygen releasing / NO _x absorbent 61, the active oxygen releasing / NO _x absorbent 6 is kept at a lean air-fuel ratio.
The temperature TF of Step 1 is raised to approximately 600 ° C., and then the air-fuel ratio of the exhaust gas flowing into the active oxygen release / NO _x absorbent 61 is made rich to release SO _x from the active oxygen release / NO _x absorbent 61. I have to. In this case, as the method for raising the temperature TF of the active oxygen release / NO _x absorbent 61 to approximately 600 ° C., the various methods described above can be used.

When the air-fuel ratio is maintained lean, the surface of platinum Pt is covered with oxygen, and so-called platinum Pt
Oxygen poisoning occurs. When such oxygen poisoning occurs, N
Since the oxidizing effect on O _x decreases, the absorption effect of NO _x decreases, and thus the active oxygen release / NO _x absorbent 61
Release of active oxygen from However the air-fuel ratio of oxygen poisoning is eliminated because the Once rich, oxygen on the platinum Pt surface is consumed, therefore the oxidation action on NO _x is strengthened when the air-fuel ratio is switched from rich to lean. Therefore, the NO _x absorption efficiency is increased, and thus the amount of active oxygen released from the active oxygen release / NO _x absorbent 61 is increased.

Accordingly, as shown in FIG. 7, the air-fuel ratio A / F
When the air-fuel ratio A / F is switched from lean to rich occasionally while the air-fuel ratio is maintained lean, the oxygen poisoning of platinum Pt is eliminated each time, so that active oxygen release when the air-fuel ratio A / F is lean The amount is increased, and thus the oxidizing action of the fine particles on the particulate filter 22 can be promoted.

Cerium Ce takes in oxygen when the air-fuel ratio is lean (Ce ₂ O ₃ → ₂ CeO ₂ ), and releases active oxygen when the air-fuel ratio becomes rich ( ₂ CeO ₂ → C).
e ₂ O ₃ ) function. Particles by the released active oxygen etc. Thus the air-fuel ratio when using cerium Ce as the active oxygen release · NO _x absorbent 61 is fine particles are deposited on the particulate filter 22 at the time of lean from the active oxygen release · NO _x absorbent 61 When the air-fuel ratio becomes rich, a large amount of active oxygen is released from the active oxygen release / NO _x absorbent 61, so that the fine particles are oxidized. Therefore, cerium C is used as the active oxygen release / NO _x absorbent 61.
Even when e is used, the oxidation reaction of the fine particles on the particulate filter 22 can be promoted by occasionally switching the air-fuel ratio from lean to rich.

Next, referring to FIG.
The NO _x release flag set when NO _x should be released from the O _x absorbent 61 and the SO set when the active oxygen release / NO _x absorbent 61 should release SO _x
The processing routine of the _x release flag will be described. In addition,
This routine is executed by interruption every predetermined time.

Referring to FIG. 10, first, in step 1
At 00, NO per unit time is obtained from the map shown in FIG.
_{The x} absorption amount A is calculated. Next, at step 101, N
A is added to the O _x absorption amount .SIGMA.NOX. Next, at step 102 NO _x absorption amount ΣNOX allowable maximum value MAXN
Is determined. Becomes a .SIGMA.NOX> MAXN proceeds to step 103, NO _x releasing flag showing that should be released NO _x is set. Next, the routine proceeds to step 104.

In step 104, the product k · Q obtained by multiplying the injection amount Q by the constant k is added to ΣSOX. The fuel contains a substantially constant amount of sulfur S. Therefore, the amount of SO _x absorbed by the active oxygen release / NO _x absorbent 61 can be represented by k · Q. Therefore, ΔSOX obtained by sequentially integrating k · Q represents the SO _x amount estimated to be absorbed by the active oxygen release / NO _x absorbent 61. In step 105, it is determined whether or not the SO _x amount ΣSOX has exceeded the allowable maximum value MAXS.
Willing release SO _x flag to the step 106 becomes to X> MAXS is set.

Next, the operation control according to the present invention will be described with reference to FIG. Referring to FIG. 11, first, at step 200, the particulate filter 2
Intermediate regeneration control for regenerating the particulate filter 22 is performed based on the estimation of whether or not the amount of the deposited fine particles on the second filter 2 exceeds a limit value that may cause damage to the particulate filter 22. Then step 300
In the control, NO _x release control for releasing NO _x from the active oxygen release / NO _x absorbent 61 is executed. Next, at step 400, when the pressure loss in the particulate filter 22 exceeds the set value, the particulate filter 2
2 is performed. Next, at step 500, the active oxygen release / NO _x absorbent 61
release of SO _x control for releasing _x is executed.

Next, the intermediate reproduction control, NO_x Release system
Control, main regeneration control, SO_x The release control will be explained sequentially
You. First, referring to FIG. 12, step 2 of FIG.
First Embodiment of Intermediate Reproduction Control Executed at 00
Will be described. In the first embodiment, a particulate filter is used.
Particulate W on the filter 22_{n + 1} Is calculated, and
Of deposited fine particles W_{n + 1} Exceeds a predetermined limit value WX
The fine particles deposited on the particulate filter 22
Particle size may cause damage to the particulate filter 22.
Is determined to exceed the limit that may cause
The port filter 22 is reproduced.

That is, referring to FIG. 12, first, in step 201, the amount M of inflow particulates flowing into the particulate filter 22 per unit time, that is, the amount M of exhaust particulates discharged from the engine per unit time is calculated. The amount M of discharged particulate varies depending on the model of the engine, but when the model of the engine is determined, it becomes a function of the required torque TQ and the engine speed N. Figure 13 (A) shows the amount M of discharged particulate of the internal combustion engine shown in FIG. 1, the curves M _1, M _2, M _3,
M ₄ and M ₅ are the amounts of fine particles discharged (M ₁ <M ₂ <M ₃ <M ₄ <
M ₅ ). In the example shown in FIG. 13A, the higher the required torque TQ, the greater the amount M of discharged particulates.
It should be noted that the amount M of discharged particulate shown in FIG. 13A is a function of the required torque TQ and the engine speed N as shown in FIG.
Are obtained in the form of a map shown in FIG.

Next, at step 202, the amount W _{n + 1} of deposited fine particles on the particulate filter 22 is calculated based on the following equation.
Is calculated. _{W n + 1 = M + W} n -G wherein M represents a discharged particulate per unit time as described above, W _n is the deposition amount of particulate on the particulate filter 22, which is calculated when the previous processing cycle G indicates the amount of fine particles that can be removed by oxidation per unit time shown in FIG. That is, the amount of particulates to be newly deposited per unit time is M, the final deposited particulate amount W _{n + 1} since the amount of particulate is oxidized and removed per unit time is a G
Is represented by the above equation.

Next, at step 203, the amount W of deposited fine particles
_It is determined whether or not _{n + 1} exceeds the limit value WX. W _{n + 1}
If> WX, the routine proceeds to step 204, where the regeneration process of the particulate filter 22 is performed. In this reproduction processing, a target reproduction time for regenerating the particulate filter 22 is set in advance, and the reproduction control of the particulate filter 22 is performed for the predetermined target reproduction time. W _n proceeds to step 205 when the regeneration process is complete the particulate filter 22 is made zero, then executed at step 300 of FIG. 11 NO _x
Proceed to release control.

When the engine is started, normally, the temperature of the particulate filter 22 is low, so that the amount G of the particulates that can be oxidized and removed in the above equation is kept at zero or close to zero for a while after the start of the engine. Therefore, when the engine is started, the amount Wn _{+ 1 of the} normally deposited fine particles continues to increase and exceeds the limit value. Therefore, when the engine is started, the regeneration process of the normal particulate filter 22 is executed.

Next, a description will be given of a second embodiment of the intermediate reproduction process executed in step 200 of FIG.
It can be estimated to some extent whether or not the amount of fine particles deposited on the particulate filter 22 has exceeded a limit value that may cause damage to the particulate filter 22. For example, when the engine is started, the deposited fine particles usually exceed the limit value as described above. Therefore, when the guidance of the engine is given, it can be estimated that the amount of deposited fine particles on the particulate filter 22 has exceeded the limit value.

When the operating state of the engine continues for a certain period or more, it is considered that the amount of particulates deposited on the particulate filter 22 exceeds the limit value. Therefore, even when the operating time of the engine, the accumulated value of the engine speed, or the vehicle travel distance exceeds a predetermined value, the particulate filter 22 can be used.
It can be estimated that the amount of the deposited fine particles above the limit value.

Therefore, in the second embodiment, when it is estimated that the amount of deposited fine particles on the particulate filter 22 has exceeded the limit value, the particulate filter 22 is regenerated. That is, referring to FIG. 14 for carrying out the second embodiment, first, in step 211, it is determined whether or not it is estimated that the amount of fine particles deposited on the particulate filter 22 has exceeded the limit value. Regeneration process of the particulate filter 22 proceeds to step 212 when the deposition amount of particulate on the particulate filter 22 is estimated to exceed the limit value is performed, then the routine proceeds to _the NO _x releasing control. Also in this reproduction processing, a target reproduction time for reproducing the particulate filter 22 is set in advance, and the reproduction control of the particulate filter 22 is performed for the predetermined target reproduction time.

Next, a third embodiment of the intermediate reproduction control executed in step 200 of FIG. 11 will be described.
As described above, in the first embodiment of the intermediate reproduction control shown in FIG. 12 and the second embodiment of the intermediate reproduction control shown in FIG. 14, the target reproduction time is set in advance, and the target reproduction time is particulate. Regeneration control of the filter 22 is performed. However, the particulate filter 22
Is not started until the temperature of the particulate filter 22 reaches a temperature at which the particulates can be ignited and burned. Therefore, in the third embodiment, the reproduction control of the particulate filter 22 is performed for the target reproduction time from when the actual reproduction operation of the particulate filter 22 is started. Next, this will be described with reference to FIG.

FIG. 15A shows a change in the temperature TF at the upstream end of the particulate filter 22 after the regeneration control of the particulate filter 22, that is, the temperature rise control is started. In FIG. 15A, TFX indicates the temperature at which the combustion of the fine particles starts. FIG. 15 (A)
When the regeneration control is started as shown in (2), the temperature TF at the upstream end of the particulate filter 22 starts to rise,
The temperature TF at the upstream end of the particulate filter 22 is 5
When the combustion start temperature TFX from about 00 ° C. to about 600 ° C. is reached, the combustion of the deposited particulates is started at the upstream end of the particulate filter 22. However, at this time, the temperature other than the upstream end of the particulate filter 22 is lower than the combustion start temperature TFX, and
It takes some time for the entire temperature TF of No. 2 to become equal to or higher than the combustion start temperature TFX. This time, that is, the delay time from when TF becomes TFX to when combustion is started in the entire particulate filter 22 is Δt in FIG.
Indicated by

The delay time Δt becomes shorter as the exhaust gas temperature becomes higher, and becomes shorter as the exhaust gas amount becomes larger. That is,
This delay time Δt has a relationship as shown in FIG.
(Δt ₁ <Δt ₂ <Δt ₃ <Δt ₄ <Δt ₅ ). In the third embodiment, the delay time Δt is calculated from the relationship shown in FIG. 15 (B), and the reproduction control of the particulate filter 22 is performed for the target reproduction time after the delay time Δt has elapsed after TF becomes TFX. Like that.

As shown in FIG. 1, in the embodiment according to the present invention, since the temperature at the upstream end of the particulate filter 22 is detected by the temperature sensor 39, it is necessary to consider the delay time Δt as described above. come. Therefore, when the temperature at which the burning of particulates starts in the entire particulate filter 22 can be detected by the temperature sensor, it is not necessary to consider such a delay time.

In the third embodiment, consideration is also given to the case where the regeneration is interrupted during the regeneration control of the particulate filter 22, for example, when the engine stops. That is, in the third embodiment, when the regeneration control is resumed after the interruption, the time required for raising the temperature of the entire particulate filter 22 to the regeneration start temperature is set to the remaining time of the target regeneration time at the time of the interruption. The added time is set as a new target reproduction time.

FIGS. 16 and 17 illustrate the third embodiment.
9 shows an intermediate reproduction control routine for performing the operation. FIG.
Referring to FIG. 6 and FIG.
A playback flag indicating that playback control is being performed in
Is set or not. Play flag is
If not set, go to step 222
From the map shown in Fig. 13 (B), the emitted particulates per unit time
The quantity M is calculated. Next, at step 223, based on the following equation:
Of particulate matter deposited on the particulate filter 22
W_{n + 1} Is calculated.

[0091] _{W n + 1 = M + W} n -G wherein M represents a discharged particulate per unit time as described above, W _n is deposited on the particulate filter 22, which is calculated when the previous processing cycle G represents the amount of fine particles that can be removed by oxidation per unit time shown in FIG.

Next, at step 224, the deposited fine particle amount W
_{n + 1} Causes damage to the particulate filter 22
It is determined whether a possible limit value WX has been exceeded.
W_{n + 1} When ≦ WX, it is determined in step 300 in FIG.
NO executed_x Proceed to release control. On the other hand, W
_{n + 1} > WX, the routine proceeds to step 225, where the reproduction flag is set.
Is set, and then the routine proceeds to step 226, where the target reproduction is performed.
Time t_n Is set. Then go to step 227
Playback control is started. The next time the playback flag is set
Step 221 to Step 227
Jump to

Next, at step 228, it is determined whether or not a reproduction start flag indicating that the reproduction has actually started is set. When the process proceeds to step 228 for the first time after the reproduction flag is set, the reproduction start flag is reset.
Go to 9. In step 229, it is determined whether or not the temperature TF of the particulate filter 22 detected by the temperature sensor 39 has become higher than the combustion start temperature TFX. When the TF ≦ TFX goes to _the NO _x releasing control. On the other hand, if TF> TFX, the routine proceeds to step 230.

In step 230, the delay time Δt is calculated from the relationship shown in FIG. Then step 23
At 1, it is determined whether or not the delay time Δt has elapsed. When the delay time Δt has not elapsed, the process proceeds to the NO _x release control. On the other hand, when the delay time Δt has elapsed, it is determined that the regeneration operation has been started in the entire particulate filter 22, and the routine proceeds to step 232, where the regeneration start flag is set. Next, the routine proceeds to step 233.
When the reproduction start flag is set, the process jumps from step 228 to step 233 in the next processing cycle.

In step 233, a certain time α is added to the elapsed time t from the start of the regenerating operation in the entire particulate filter 22. Then step 2
At 34, it is determined whether or not the reproduction control has been interrupted. The elapsed time t advances to step 235 whether exceeds the target playback time t _n is determined when the regeneration control is not being interrupted. When t ≦ t _n, the process proceeds to NO _x release control. On the other hand, when t> t _n , the process proceeds to step 236 to stop the reproduction control, and then in step 237 the reproduction flag and the reproduction start flag are reset. Then willing deposited particulate weight W _n and the elapsed time t in step 238 is set to zero.

Regenerative action of the particulate filter 22 from the regenerative action in the whole is started to the target playback time t _n has passed the particulate filter 22 is performed when [0096] That is, the playback control in the regeneration control is not interrupted . On the other hand, when it is determined in step 234 that the regeneration control has been interrupted, the routine proceeds to step 239, and until the state in which the regeneration control should be interrupted is canceled, for example, when the regeneration control is interrupted by stopping the operation of the engine, the engine is stopped. The intermediate regeneration control is stopped until the operation of is restarted. Next, at step 240, the reproduction start flag is reset. At this time the elapsed time t represents the remainder of the target playback time t _n, the remainder of the time t is stored as it is.

Now, even if the reproduction control is interrupted, the reproduction flag is kept set. Therefore, when the state in which the reproduction control is to be interrupted is released, steps 221 to 22
7, the reproduction control is started. At this time, since the reproduction start flag has been reset, steps 229 and 2 are executed.
At 30 and 231, it is determined whether or not the delay time Δt has elapsed since TF> TFX. When the delay time Δt elapses after TF> TFX, the process proceeds to step 233 via step 232, and the fixed time α to the elapsed time t
Is started. That is, the remaining time t of the target reproduction time t _n when the reproduction control is interrupted is set as a new target reproduction time, and the reproduction operation is performed for the new target reproduction time unless the reproduction control is interrupted again. If the reproduction control is interrupted again during this reproduction operation, the reproduction operation is performed again for the remaining time of the new target reproduction time when the state in which the reproduction control should be interrupted is released.

Next, FIG. 18 showing the NO _x release control executed in step 300 of FIG. 11 will be described.
_The NO _x releasing flag, first, at step 301 and referring to FIG. 18, whether it is set or not. When _the NO _x releasing flag has not been set, the process proceeds to the regeneration control executed in step 400 of FIG. 11. _The NO _x releasing flag has rich processing for switching temporarily to a rich air-fuel ratio proceed to when set step 302 from the lean air-fuel ratio is made to this. When this rich process is performed, NO _x is released from the active oxygen release / NO _x absorbent 61. At this time, the oxidizing action of the deposited fine particles is promoted by the active oxygen released from the active oxygen release / NO _x absorbent 61. The rich processing is complete is ΣNOX is cleared proceeds to step 303, then _the NO _x releasing flag is reset in step 304. Next, the routine proceeds to the main reproduction control.

Next, FIG. 19 showing the main reproduction control executed in step 400 of FIG. 11 will be described. FIG.
Referring to FIG. 9, first, at step 401, it is determined whether or not a full regeneration flag indicating that the clogged particulate filter 22 should be reproduced is set. Normally, since the main regeneration flag is not set, the routine proceeds to step 402, where the pressure loss P in the particulate filter 22 detected by the pressure sensor 43 is determined.
It is determined whether D has exceeded the set value MAX. PD ≦
When the MAX proceeds to release of SO _x control executed in step 500 of FIG. 11. PD> MA
When X is reached, the routine proceeds to step 403, where the main regeneration flag is set. Then, the routine proceeds to step 404, where the regeneration control of the particulate filter 22 is started. When the main reproduction flag is set, in the next processing cycle, step 401
Jump to step 404.

Next, at step 405, it is determined whether or not the pressure loss PD has become lower than the lower limit value MIN, that is, whether or not the clogging of the particulate filter 22 has been eliminated. When PD ≧ MIN, step 500 in FIG.
To jump release SO _x control executed in EN
Proceeding to D, the regeneration operation for eliminating the clogging of the particulate filter 22 is continued. When PD <MIN, the routine proceeds to step 406, where the reproduction control is stopped, and then, in step 407, the main reproduction flag is reset.

In the embodiment shown in FIG. 1, the pressure loss PD is detected from the pressure difference between the upstream side and the downstream side of the particulate filter 22. However, the particulate filter 2
2 is detected only on the upstream side, and the pressure loss PD
Can also be detected. Further, if the pressure loss PD increases, the EGR gas amount increases if the opening degree of the EGR control valve 25 is the same, and the EGR gas does not change at this time so that the intake air amount does not change.
When the control valve 25 is controlled, the opening degree of the EGR control valve 25 is reduced. That is, the change in the EGR gas amount or the EGR
The pressure loss PD can be detected from the change in the opening degree of the control valve 25. In the present invention, the detection of the pressure loss PD includes the case where the pressure loss PD is detected by these various methods.

[0102] Next release of SO _x control executed in step 500 of FIG. 11 will be described. As described above, when SO _x is to be released from the active oxygen release / NO _x absorbent 61, the active oxygen release / N
The temperature TF of the O _x absorbent 61 is raised to approximately 600 ° C, and then the air-fuel ratio of the exhaust gas flowing into the active oxygen release / NO _x absorbent 61 is made rich. Delay time until this temperature TF particulate filter 22 overall temperature TF after reaching _the NO _x releasing temperature TFXX as shown in FIG. 15 (A) also the particulate filter 22 reaches _the NO _x releasing temperature TFXX Δt is calculated, and a predetermined target SO is set after the delay time Δt has elapsed.
_The air-fuel ratio is made rich while the temperature raising control is continued for the _x release time, and the active oxygen release / NO _x absorbent 61 allows SO _{x to be} released.

Also in the NO _x release control, consideration is given to a case where the SO _x release control is interrupted by, for example, stopping the engine during the SO _x release control. That is, in the NO _x release control, when the SO _x release control is restarted after the interruption, the temperature of the entire particulate filter is set to S during the remaining time of the target SO _x release time at the time of the interruption.
O _x release by adding the time required to raise to a temperature so that the resulting sum time a new target release of SO _x time.

FIGS. 20 and 21 show a routine for executing the NO _x release control. Whether the execution flag is set to indicate that _the NO _x releasing control is executed first, at step 501 and referring to FIGS. 20 and 21 is determined. Whether release of SO _x flag proceeds to step 502 when the execution flag is not set is set or not. When the SO _x release flag is not set, the processing cycle is completed. Contrast is set execution flag is proceeds to step 503 when the release of SO _x flag is set, then the target release SO _x time t _m is set the routine proceeds to step 504. Next, the routine proceeds to step 505, where the temperature rise control is started. When the running flag is set, the process jumps from step 501 to step 505 in the next processing cycle.

Next, at step 506, it is determined whether or not the release start flag indicating that the release of SO _x has been started is set. When the process proceeds to step 506 for the first time after the execution flag has been set, the release start flag has been reset. Therefore, the process proceeds to step 507 at this time. In step 507, the temperature T of the particulate filter 22 detected by the temperature sensor 39
F is whether it is higher than the release of SO _x temperature TFXX is determined. When TF ≦ TFXX, the processing cycle is completed. On the other hand, if TF> TFXX, the process proceeds to step 508.

At step 508, the delay time Δt is calculated from the relationship shown in FIG. Then step 50
In step 9, it is determined whether the delay time Δt has elapsed. When the delay time Δt has not elapsed, the processing cycle is completed. It determines that the release of the SO _x is started in the whole of the particulate filter 22 when this delay time Δt has elapsed relative release starting flag is set the routine proceeds to step 510. Next, the routine proceeds to step 511. When the release start flag is set, the process jumps from step 506 to step 511 in the next processing cycle.

In step 511, a rich process for making the air-fuel ratio slightly richer than the stoichiometric air-fuel ratio is started. Next, at step 512, a certain time α is added to the elapsed time t from the start of the NO _x releasing action in the entire particulate filter 22. Then whether or not _the NO _x releasing control at step 513 is interrupted is determined. _The NO _x releasing control is determined whether the elapsed time t advances to step 514 when the uninterrupted exceeds the target release of SO _x time t _m. the processing cycle is completed when the t ≦ t _m. This Atsushi Nobori control proceeds to step 515 becomes a t> t _m respect is stopped, then rich processing at step 516 is stopped. Next, at step 517 NO _x releasing flag, executing flag and release start flag is reset. Then step 5
Proceed to 18 SO _x absorption amount ΣSOX and the elapsed time t is zero.

That is, _{if the} SO _x release control is not interrupted during the SO _x release operation, the target S is set after the SO _x release operation is started in the entire particulate filter 22.
Release SO _x action to O _x release time t _m elapses is performed. On the other hand, when it is determined in step 513 that the SO _x release control has been interrupted, the process proceeds to step 519 until the state in which the SO _x release control should be interrupted is released.
S until the engine operation is resumed when the release of SO _x control has been interrupted by e.g. the operation of the engine is stopped
_Ox release control is stopped. Next, at step 520, the release start flag is reset. At this time, the elapsed time t
It represents the remainder of the target release of SO _x time t _m, the rest of the time t is stored as it is.

[0109] Now, even release SO _x control is interrupted execution flag continues to be set. Therefore, when the state in which the NO _x release control should be interrupted is released, the process jumps from step 501 to step 505 to start the temperature rise control,
At this time, since the release start flag has been reset, it is determined in steps 507, 508, and 509 whether or not the delay time Δt has elapsed since TF> TFXX. If the delay time Δt has elapsed since TF> TFXX, the process proceeds to step 511 via step 510, and the rich process is started. Next, the routine proceeds to step 512, where the action of adding the certain time α to the elapsed time t is started. That, SO _x remaining time t of the target release of SO _x time t _m at which the controlled release is interrupted is a new target release of SO _x time, release of SO _x control unless interrupted again this new target SO _x release of SO _x action is performed only release time.
If during this release of SO _x activity, release of SO _x control again for the remaining time of the new target release SO _x time described above when the condition to be interrupted release of SO _x control is released when interrupted again SO _x release action is performed.

Finally, a low-temperature combustion method particularly suitable when the particulate filter 22 according to the present invention is used will be described with reference to FIGS. In the internal combustion engine shown in FIG. 1, the EGR rate (EGR gas amount / (EGR
As the amount of gas + the amount of intake air) increases, the amount of generated smoke gradually increases and reaches a peak, and when the EGR rate is further increased, the amount of generated smoke rapidly decreases.
This will be described with reference to FIG. 22 showing the relationship between the EGR rate and the smoke when the degree of cooling of the EGR gas is changed. In FIG. 22, a curve A shows a case where the EGR gas is cooled strongly and the EGR gas temperature is maintained at approximately 90 ° C., and a curve B shows a case where the EGR gas is cooled by a small cooling device. , Curve C shows the case where the EGR gas is not forcibly cooled.

As shown by the curve A in FIG. 22, when the EGR gas is cooled strongly, the amount of smoke generation peaks at a position where the EGR rate is slightly lower than 50%. In this case, the EGR rate is reduced to approximately 55%. Above a percentage, there is almost no smoke. On the other hand, FIG.
As shown by the curve B in FIG. 2, when the EGR gas is slightly cooled, the amount of smoke generation reaches a peak at a point where the EGR rate is slightly higher than 50%.
If the GR rate is set to about 65% or more, smoke is hardly generated. Further, as shown by the curve C in FIG. 22, when the EGR gas is not forcibly cooled, the amount of smoke generation reaches a peak near the EGR rate of 55%, and in this case, the EGR rate becomes approximately 70%. Above a percentage, there is almost no smoke.

When the EGR gas rate is set to 55% or more, no smoke is generated because the temperature of the fuel and the surrounding gas during combustion is not so high due to the endothermic effect of the EGR gas, that is, low-temperature combustion is performed. As a result, hydrocarbons do not grow to soot. This low temperature combustion, production of smoke regardless of the air-fuel ratio that is, has a characteristic that it is possible to reduce the generation amount of the NO _x while suppressing the emission of microparticles. That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but since the combustion temperature is suppressed to a low temperature, the excess fuel does not grow to soot, and thus almost no smoke is generated. At this time, NO
_x is generated only in a very small amount. On the other hand, when the average air-fuel ratio is lean, or even when the air-fuel ratio is the stoichiometric air-fuel ratio, a small amount of soot is generated if the combustion temperature increases, but under low-temperature combustion, the combustion temperature is suppressed to a low temperature. smoked hardly occurs, nO _x is also not only an extremely small amount of generated.

On the other hand, when the low-temperature combustion is performed, the temperature of the fuel and the surrounding gas becomes low, but the temperature of the exhaust gas rises. This will be described with reference to FIGS. The solid line in FIG. 23 (A) shows the relationship between the average gas temperature Tg in the combustion chamber 5 and the crank angle when low-temperature combustion is performed, and the broken line in FIG. 23 (A) indicates normal combustion. 2 shows the relationship between the average gas temperature Tg in the combustion chamber 5 and the crank angle at the time of the combustion. The solid line in FIG. 23 (B) shows the relationship between the fuel and surrounding gas temperature Tf and the crank angle when low-temperature combustion is performed, and the broken line in FIG. 23 (B) shows the normal combustion. The relationship between the crank angle and the temperature Tf of the fuel and the surrounding gas at the time of the collision is shown.

When the low-temperature combustion is being performed, the amount of EGR gas is larger than when the normal combustion is being performed. Therefore, as shown in FIG. In the middle, the average gas temperature Tg at the time of low temperature combustion indicated by the solid line is higher than the average gas temperature Tg at the time of normal combustion indicated by the broken line. At this time, FIG.
As shown in (B), the fuel and its surrounding gas temperature T
f is almost the same as the average gas temperature Tg.

Next, combustion starts near the compression top dead center. In this case, when low-temperature combustion is being performed, as shown by the solid line in FIG. The gas temperature Tf does not increase so much. On the other hand, when the normal combustion is performed, a large amount of oxygen exists around the fuel, and therefore, FIG.
As shown by the broken line in (B), the temperature of the fuel and its surrounding gas Tf becomes extremely high. When normal combustion is performed as described above, the temperature of the fuel and the surrounding gas Tf is considerably higher than that in the case where low-temperature combustion is performed, but the temperature of the other gas that occupies most of the temperature is low. 23A is lower than in the case where normal combustion is performed, and therefore, as shown in FIG. 23A, the average gas in the combustion chamber 5 near the compression top dead center is shown in FIG. The temperature Tg is higher when low-temperature combustion is performed than when normal combustion is performed. As a result, FIG.
As shown in (2), the temperature of the burned gas in the combustion chamber 5 after the completion of the combustion is higher when the low-temperature combustion is performed than when the normal combustion is performed. , The exhaust gas temperature increases.

However, when the required torque TQ of the engine increases, that is, when the fuel injection amount increases, the temperature of fuel and surrounding gas during combustion increases, so that it becomes difficult to perform low-temperature combustion. That is, low-temperature combustion can be performed only during low-load operation in the engine, which generates a relatively small amount of heat by combustion.
In FIG. 24, a region I indicates an operation region in which the first combustion in which the amount of inert gas in the combustion chamber 5 is larger than the amount of inert gas at which the generation amount of soot reaches a peak, that is, low-temperature combustion, can be performed. Region II indicates the second combustion in which the amount of inert gas in the combustion chamber is smaller than the amount of inert gas at which the amount of generated soot becomes a peak, that is, an operation region in which only normal combustion can be performed.

FIG. 25 shows the target air-fuel ratio A / F in the case where low-temperature combustion is performed in the operation region I. FIG. The opening, the opening of the EGR control valve 25, the EGR rate, the air-fuel ratio, the injection start timing θS, the injection completion timing θE, and the injection amount are shown. FIG. 26 also shows the opening degree of the throttle valve 17 during normal combustion performed in the operation region II. 25 and 26, when low-temperature combustion is performed in the operation region I, the EGR rate is set to 55% or more, and the air-fuel ratio A
It can be seen that / F is a lean air-fuel ratio of about 15.5 to 18.

The ability of the particulate filter 22 to oxidize and remove particulates decreases during low engine load operation when the exhaust gas temperature decreases. However, when low-temperature combustion is performed during engine low-load operation, the exhaust gas temperature rises as described above,
In addition, since the amount of generated smoke, that is, the amount of discharged fine particles, is extremely small, it is possible to continuously oxidize and remove all the deposited fine particles of the particulate filter 22 even during the low load operation of the engine. Further, as described above, when low-temperature combustion is performed in the operation region I, smoke is hardly generated even if the air-fuel ratio is made rich.
Therefore, when low-temperature combustion is performed, NO _x and S are released from the active oxygen release / NO _x absorbent 61 without generating smoke.
O _x can be released. Further, when the normal combustion is switched to the low-temperature combustion during the operation of the engine, the temperature TF of the particulate filter 22 can be increased. That is, low-temperature combustion can be used to raise the temperature of the particulate filter 22.

[0119]

According to the present invention, it is possible to prevent the particulate filter from being damaged.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a diagram showing a required torque of an engine.

FIG. 3 is a diagram showing a particulate filter.

FIG. 4 is a view for explaining an oxidizing action of fine particles.

FIG. 5 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. 6 is an enlarged sectional view of a partition wall of the particulate filter.

FIG. 7 is a time chart for explaining a reproduction process and the like.

FIG. 8 is a diagram for explaining injection control.

FIG. 9 is a view showing a map of an NO _x absorption amount A;

FIG. 10 is a flowchart for processing a NO _x release flag and a SO _x release flag.

FIG. 11 is a flowchart for controlling operation of the engine.

FIG. 12 is a flowchart for executing a first embodiment of intermediate reproduction control.

FIG. 13 is a diagram showing the amount of discharged fine particles.

FIG. 14 is a flowchart for executing a second embodiment of the intermediate reproduction control.

FIG. 15 is a diagram for describing playback control.

FIG. 16 is a flowchart for executing a third embodiment of the intermediate reproduction control.

FIG. 17 is a flowchart for executing a third embodiment of the intermediate reproduction control.

FIG. 18 is a flowchart for executing NO _x release control.

FIG. 19 is a flowchart for executing the main reproduction control.

FIG. 20 is a flow chart for executing the release of SO _x control.

FIG. 21 is a flow chart for executing the release of SO _x control.

FIG. 22 is a diagram showing the amount of smoke generated.

FIG. 23 is a diagram showing a gas temperature and the like in a combustion chamber.

FIG. 24 is a diagram showing operation regions I and II.

FIG. 25 is a diagram showing an air-fuel ratio A / F.

FIG. 26 is a diagram showing a change in a throttle valve opening and the like.

[Explanation of symbols]

 5: Combustion chamber 6: Fuel injection valve 22: Particulate filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/02 F01N 3/02 321E 321H 321K 3/08 3/08 A 3/24 3/24 E 3 / 28 301 3/28 301C F02D 41/04 355 F02D 41/04 355 380 380M (72) Inventor Kazuhiro Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Takamitsu Asanuma Toyota City, Aichi Prefecture 1 Toyota Town, Toyota Motor Corporation (72) Inventor Koichi Kimura 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Shunsuke 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Akira Mikami 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term ( Consideration) 3G090 AA03 BA01 BA04 CA01 CB02 CB03 CB12 CB13 DA03 DA04 DA12 DA13 DA18 3G091 AA10 AA11 AA18 AB06 AB09 AB11 AB13 BA04 BA07 BA14 BA23 BA33 CA01 CA04 CA16 CA23 CA26 CB02 CB03 DB06 EA01 EA03 FB04 GB01W GB02W GB03W GB04W GB06W GB10X HA36 HA37 HA39 3G301 HA02 HA11 HA13 JA24 JA25 JA33 KA05 KA21 LB11 LB13 MA01 MA03 MA11 MA19 MA23 NA04 NE01 NE13 NE23 PA17Z PD12Z PD14Z PE01Z PE03Z PF03Z

Claims (14)

[Claims] 1. A particulate filter for collecting particulates in exhaust gas is disposed in an engine exhaust passage, and a particulate filter is disposed on the particulate filter when combustion is continuously performed under a lean air-fuel ratio. In an internal combustion engine that is capable of continuously oxidizing and removing accumulated particulates without generating a bright flame, the particulate filter is used as a particulate filter even if the amount of accumulated particulates on the particulate filter increases due to the operating state of the engine. Detecting means for detecting a pressure loss in the particulate filter, using a particulate filter in which the pressure loss in the particulate filter hardly increases and the pressure loss in the particulate filter increases when the accumulated particulates on the particulate filter increase, The pressure loss detected by the detecting means has exceeded a set value. Occasionally, the main regeneration means for raising the temperature of the particulate filter in order to regenerate the particulate filter, and the amount of deposited particulate on the particulate filter increases, which may cause damage to the particulate filter due to the heat of oxidation of the deposited particulate. Intermediate regeneration in which the temperature of the particulate filter is raised under a lean air-fuel ratio in order to regenerate the particulate filter even if the pressure loss in the particulate filter hardly increases and does not exceed the above set value Exhaust gas purification apparatus comprising: And estimating means for estimating whether or not the amount of deposited fine particles on the particulate filter has exceeded a limit value which may cause damage to the particulate filter due to heat of oxidation reaction of the deposited fine particles. The intermediate regenerating means regenerates the particulate filter even when the pressure loss in the particulate filter hardly increases and does not exceed the set value when it is estimated that the amount of deposited fine particles on the particulate filter exceeds the limit value. 2. The exhaust gas purifying apparatus according to claim 1, wherein the temperature of the particulate filter is increased under a lean air-fuel ratio in order to perform the operation. 3. A calculating means for calculating the amount of particulates deposited on the particulate filter, wherein the estimating means calculates the amount of particulates deposited on the particulate filter using the amount of particulates calculated by the calculating means. 3. The exhaust gas purifying apparatus according to claim 2, wherein whether or not the limit value is exceeded is estimated. 4. The exhaust gas purifying apparatus according to claim 3, wherein said calculating means calculates the amount of particulates deposited on the particulate filter based on the amount of particulates discharged from the engine and the temperature of the particulate filter. 5. The particulate filter according to claim 1, wherein when the engine is started, or when the operating time of the engine, the cumulative value of the engine speed, or the vehicle travel distance exceeds a predetermined value. 3. The exhaust gas purifying apparatus according to claim 2, wherein the amount of the deposited fine particles is estimated to have exceeded the limit value. 6. The intermediate reproduction means sets a target reproduction time required for reproduction when reproduction control of the particulate filter is started, and sets a target reproduction time at the time of interruption when reproduction control is resumed after interruption. 2. The exhaust gas purifying apparatus according to claim 1, wherein a time required for raising the temperature of the particulate filter to the regeneration start temperature is added to the remaining time, and the added time is set as a new target regeneration time. 7. The exhaust gas purifying apparatus according to claim 1, wherein a noble metal catalyst is supported on the particulate filter. 8. An active oxygen-releasing agent which takes in oxygen to retain oxygen when surrounding oxygen is present and releases the retained oxygen in the form of active oxygen when the concentration of oxygen in the surroundings decreases is placed on the particulate filter. The exhaust gas purifying apparatus according to claim 7, wherein the fine particles adhered on the particulate filter are oxidized by the active oxygen released and carried. 9. The exhaust gas purifying apparatus according to claim 8, wherein the active oxygen releasing agent comprises an alkali metal, an alkaline earth metal, a rare earth, or a transition metal. 10. A noble metal on the particulate filter catalyst, the air-fuel ratio of the exhaust gas air-fuel ratio of the exhaust gas flowing into the particulate filter when lean flowing into the particulate filter to absorb NO _x in the exhaust gas exhaust gas purifying apparatus according to claim 1 carrying a _the NO _x absorbent to release the NO _x absorbed and becomes the stoichiometric air-fuel ratio or rich. 11. The exhaust gas purifying apparatus according to claim 10, wherein the NO _x absorbent comprises an alkali metal, an alkaline earth metal, a rare earth, or a transition metal. 12. NO absorbed in the NO _x absorbent _x
The exhaust gas purifying apparatus according to claim 10 provided with the _the NO _x releasing control means rich temporarily switching the air-fuel ratio of the exhaust gas flowing into the particulate filter from lean to when releasing from _the NO _x absorbent. 13. SO is absorbed in _the NO _x absorbent _x
Request provided with the release of SO _x control means for switching to a rich air-fuel ratio of the exhaust gas flowing into the particulate filter from lean with the time to release from _the NO _x absorbent to increase the temperature of the particulate filter to release SO _x Temperature Item 11. An exhaust gas purifying apparatus according to Item 10. 14. The release of SO _x control means sets a target release of SO _x time required to release of the SO _x, release SO _x control is resumed after interruption when controlled release of the SO _x is started target release SO _x temperature SO _x to the discharge temperature by adding the time required to elevate the target new this addition the time release of SO _x time of the particulate filter to the remaining time of the time and at the time of interruption when a Claim 1
4. The exhaust gas purification device according to 3.