JP4599759B2 - Exhaust gas purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device.
[0002]
[Prior art]
Conventionally, in a diesel engine, in order to remove particulates contained in the exhaust gas, a particulate filter is disposed in the engine exhaust passage, and particulates in the exhaust gas are once collected by this particulate filter, and the particulate filter The particulate filter is regenerated by igniting and burning the fine particles collected above. However, the fine particles collected on the particulate filter are not ignited unless the temperature is about 600 ° C. or higher. On the other hand, the exhaust gas temperature of a diesel engine is usually much lower than 600 ° C. Therefore, it is difficult to ignite the particulates collected on the particulate filter with the exhaust gas heat. In order to ignite the particulates collected on the particulate filter with the exhaust gas heat, the ignition temperature of the particulates is required. Must be lowered.
[0003]
By the way, it has been conventionally known that if the catalyst is supported on the particulate filter, the ignition temperature of the fine particles can be lowered. Therefore, various particulate filters supporting the catalyst are conventionally known in order to lower the ignition temperature of the fine particles. is there.
For example, Japanese Patent Publication No. 7-106290 discloses a particulate filter in which a mixture of a platinum group metal and an alkaline earth metal oxide is supported on a particulate filter. In this particulate filter, fine particles are ignited at a relatively low temperature of about 350 ° C. to 400 ° C., and then burned continuously.
[0004]
[Problems to be solved by the invention]
When the catalyst is thus supported on the particulate filter, the fine particles can be continuously burned at a relatively low temperature of 350 ° C. to 400 ° C. However, in an actual diesel engine, the temperature of the particulate filter may continue to be 350 ° C. or lower, and in this case, particulates continue to accumulate on the particulate filter, and eventually the particulate filter is clogged. Will occur. Even if the temperature of the particulate filter is maintained at 350 ° C. to 400 ° C., if a large amount of fine particles are continuously 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. Therefore, no consideration is given to the countermeasure when the particulate filter is clogged. Absent.
[0005]
On the other hand, in most conventional particulate filters, fine particles deposited on the surface of the particulate filter are burned 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 particulates accumulated in the particulate filter inside the particulate filter, and the particulate filter currently being developed has particulates in the particulate filter. In order to make it easy to enter the inside, the size of the exhaust gas circulation pores in the particulate filter is formed large.
[0006]
In this way, if the size of the exhaust gas flow pores in the particulate filter is increased, the particulate filter may clog depending on how the particulates are deposited, but normally it will not clog, and even if particulates accumulate. The pressure loss in the particulate filter hardly increases. That is, if 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 due to the operating state of the engine as will be described in detail later. If the amount of deposited fine particles on the particulate filter is not increased, the pressure loss in the particulate filter is increased.
[0007]
By the way, 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 deposited 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 sets the set value. When it exceeds, the particulate filter is played back.
[0008]
However, as described above, when the size of the exhaust gas circulation pores is increased, there is a case where the pressure loss in the particulate filter hardly increases even if the deposited fine particles on the particulate filter increase. In this case, if the pressure loss in the particulate filter is hardly increased, it will cause a big problem if it is left as it is. That is, for example, when acceleration operation is performed, the amount of heat generated in the combustion chamber increases and the amount of exhaust gas increases, resulting in a rapid rise in the temperature of the particulate filter. Next, when the operation shifts to a low load operation, the space velocity of the exhaust gas in the particulate filter decreases while the temperature of the particulate filter is high, and the oxygen concentration in the exhaust gas increases. Burned rapidly. At this time, if a large amount of fine particles are accumulated on the particulate filter, the temperature of the particulate filter rises considerably due to the combustion of the fine particles. As a result, the particulate filter melts down, 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.
[0009]
The purpose of the present invention is that when the pressure loss in the particulate filter exceeds the set value, the particulate filter is maintained at a considerably low value with respect to the set value, as well as reusing the particulate filter. It is another object of the present invention to provide an exhaust gas purifying apparatus in which a particulate filter is regenerated as necessary to prevent the particulate filter from being damaged.
[0010]
[Means for Solving the Problems]
  BookIn the invention, in order to achieve the above object, a particulate filter for collecting particulates in the exhaust gas is disposed in the engine exhaust passage,A noble metal catalyst is supported on the particulate filter,In an internal combustion engine that can continuously oxidize and remove particulate deposits on a particulate filter without generating a bright flame when combustion is continuously performed under a lean air-fuel ratio, As a filter, the pressure loss in the particulate filter increases when the amount of deposited particulate on the particulate filter hardly increases even when the amount of particulate deposited on the particulate filter increases due to the operating state of the engine and when the amount of particulate deposited on the particulate filter increases Use a particulate filter that may beThere is a demand for a relationship between the amount of particulates that can be oxidized and removed without emitting a luminous flame per unit time and the temperature of the particulate filter, and the amount of particulates that can be removed by oxidation determined from the temperature of the particulate filter and discharged from the engine. A calculating means for calculating the amount of deposited fine particles on the particulate filter based on the amount of fine particles;Detection means for detecting pressure loss in the particulate filter, and main regeneration means for raising the temperature of the particulate filter to regenerate the particulate filter when the pressure loss detected by the detection means exceeds a set value;Calculated by calculation meansWhen the amount of deposited particulate on the particulate filter increases and the particulate filter may be damaged by the heat of oxidation of the deposited particulate, the pressure loss in the particulate filter hardly increases and does not exceed the set value. In order to regenerate the particulate filter, intermediate regeneration means for raising the temperature of the particulate filter under a lean air-fuel ratio is provided.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
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 Is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to 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, and a cooling device 18 for cooling intake air flowing through the intake duct 13 is disposed around the intake duct 13. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18 and the intake air is cooled by the engine cooling water. On the other hand, the exhaust port 10 is connected to an exhaust turbine 21 of an 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 containing a particulate filter 22.
[0020]
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. A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the EGR passage 24. 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, so-called common rail 27, through a fuel supply pipe 6a. Fuel is supplied into the common rail 27 from an electrically controlled fuel pump 28 with variable discharge amount, and the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 via 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, and a fuel pump 28 is set so that the fuel pressure in the common rail 27 becomes a target fuel pressure based on an output signal of the fuel pressure sensor 29. The discharge amount is controlled.
[0021]
The electronic control unit 30 is composed of a digital computer and includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36 connected to each other by a bidirectional bus 31. It comprises. The output signal of the fuel pressure sensor 29 is input to the input port 35 via the corresponding AD converter 37. 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 is input to the input port 35 via the corresponding AD converter 37. . The particulate filter 22 is provided with 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. The output signal of the sensor 43 is input to the input port 35 via the corresponding AD converter 37.
[0022]
On the other hand, a load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Is done. Further, a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 35. 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 corresponding drive circuits 38.
[0023]
FIG. 2A shows the relationship between the required torque TQ, the amount of depression 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 are TQ = a, TQ = b, The required torque gradually increases in the order of TQ = c and TQ = d. The required torque TQ shown in FIG. 2 (A) is stored in advance in the ROM 32 in the form of a map as a function of the depression amount L of the accelerator pedal 40 and the engine speed N as shown in FIG. 2 (B). In the embodiment according to the present invention, the required torque TQ corresponding to the depression amount L of the accelerator pedal 40 and the engine speed N is first calculated from the map shown in FIG. 2B, and the fuel injection amount is calculated based on the required torque TQ. Etc. are calculated.
[0024]
3A and 3B show the structure of the particulate filter 22 shown in FIG. 3A shows a front view of the particulate filter 22, and FIG. 3B shows a side sectional view of the particulate filter 22. As shown in FIG. As shown in FIGS. 3A and 3B, the particulate filter 22 has a honeycomb structure and includes a plurality of exhaust flow passages 50 and 51 extending in parallel with each other. These exhaust flow passages include an exhaust gas inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust gas outflow passage 51 whose upstream end is closed by a plug 53. In addition, the hatched part in FIG. Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via the thin partition walls 54. 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. Arranged so that.
[0025]
The particulate filter 22 is made of, for example, a porous material such as cordierite. Therefore, the exhaust gas flowing into the exhaust gas inflow passage 50 is surrounded by the partition wall 54 as indicated by an arrow in FIG. Through the exhaust gas outflow passage 51 adjacent thereto.
In the embodiment according to the present invention, the peripheral wall surfaces of the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51, that is, the both side surfaces of the partition walls 54 and the exhaust gas flow pore inner wall surfaces of the partition walls 54 are made of alumina, for example. A support layer is formed, and when noble metal catalyst is present on the support and excess oxygen is present in the surrounding area, oxygen is taken in and retained, and when the surrounding oxygen concentration is lowered, the retained oxygen is in the form of active oxygen. The active oxygen releasing agent to be released is supported.
[0026]
In this case, platinum Pt is used as a noble metal catalyst in the examples according to the present invention, and alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb, barium Ba, calcium Ca as active oxygen release agents. At least one selected from alkaline earth metals such as strontium Sr, rare earths such as lanthanum La, yttrium Y and cerium Ce, and transition metals such as tin Sn and iron Fe is used.
[0027]
In this case, as the active oxygen release agent, an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, strontium Sr, or cerium is used. It is preferable to use Ce.
Next, the action of removing particulates in the exhaust gas by the particulate filter 22 will be described by taking as an example the case where platinum Pt and potassium K are supported on the carrier, but other noble metals, alkali metals, alkaline earth metals, rare earths, transition metals. The same fine particle removing action is performed even when using.
[0028]
In a compression ignition type internal combustion engine as shown in FIG. 1, combustion is performed under an excess of air, and therefore the exhaust gas contains a large amount of excess air. That is, when the ratio of air and fuel supplied into the intake passage, the combustion chamber 5 and the exhaust passage is referred to as 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 also contains sulfur S, which reacts with oxygen in the combustion chamber 5 to react with SO.₂ It becomes. Therefore, in the exhaust gas, SO₂ It is included. Therefore excess oxygen, NO and SO₂ The exhaust gas containing the gas flows into the exhaust gas inflow passage 50 of the particulate filter 22.
[0029]
4A and 4B schematically show enlarged views of the surface of the carrier layer formed on the inner peripheral surface of the exhaust gas inflow passage 50 and the inner wall surface of the pores in the partition wall 54. FIG. In FIGS. 4A and 4B, reference numeral 60 indicates platinum Pt particles, and reference numeral 61 indicates an active oxygen release agent containing potassium K.
As described above, since a large amount of excess oxygen is contained in the exhaust gas, when the exhaust gas flows into the exhaust gas inflow passage 50 of the particulate filter 22, as shown in FIG.₂ Is O₂ ^-Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the exhaust gas is O on the surface of platinum Pt.₂ ^-Or O^2-Reacts with NO₂ (2NO + O₂ → 2NO₂). Then the generated NO₂ A part of the catalyst is oxidized on the platinum Pt and absorbed in the active oxygen release agent 61 and combined with potassium K, as shown in FIG._Three ^-And diffused into the active oxygen release agent 61 in the form of some nitrate ions NO_Three ^-Is potassium nitrate KNO_Three Is generated.
[0030]
On the other hand, as described above, the exhaust gas contains SO.₂ Is also included, this SO₂ Is absorbed into the active oxygen release agent 61 by the same mechanism as NO. That is, as described above, oxygen O₂ Is O₂ ^-Or O^2-Is attached to the surface of platinum Pt in the form of SO₂ Is O on the surface of platinum Pt.₂ ^-Or O^2-Reacts with SO_Three It becomes. The generated SO_Three Is partly oxidized on platinum Pt while being absorbed in the active oxygen release agent 61 and combined with potassium K, sulfate ions SO._Four ^2- Diffused into the active oxygen release agent 61 in the form of potassium sulfate K₂ SO_Four Is generated. In this way, potassium nitrate KNO is contained in the active oxygen release catalyst 61._Three And potassium sulfate K₂ SO_Four Is generated.
[0031]
On the other hand, fine particles mainly made 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 shown in FIG. 4 when the exhaust gas flows through the exhaust gas inflow passage 50 of the particulate filter 22 or when the exhaust gas flows from the exhaust gas inflow passage 50 toward the exhaust gas outflow passage 51. As shown at 62 in (B), it contacts and adheres to the surface of the carrier layer, for example, the surface of the active oxygen release agent 61.
[0032]
When the fine particles 62 adhere to the surface of the active oxygen release agent 61 as described above, the oxygen concentration at the contact surface between the fine particles 62 and the active oxygen release agent 61 decreases. When the oxygen concentration is lowered, a concentration difference is generated between the active oxygen release agent 61 having a high oxygen concentration, and thus oxygen in the active oxygen release agent 61 is directed toward the contact surface between the fine particles 62 and the active oxygen release agent 61. Try to move. As a result, potassium nitrate KNO formed in the active oxygen release agent 61_Three Is decomposed into potassium K, oxygen O, and NO, oxygen O is directed to the contact surface between the fine particles 62 and the active oxygen release agent 61, and NO is released from the active oxygen release agent 61 to the outside. NO released to the outside is oxidized on the platinum Pt on the downstream side, and is again absorbed in the active oxygen release agent 61.
[0033]
On the other hand, if the temperature of the particulate filter 22 is high at this time, potassium sulfate K formed in the active oxygen release agent 61 will be described.₂ SO_Four Also potassium K, oxygen O and SO₂ The oxygen O is directed to the contact surface between the fine particles 62 and the active oxygen release agent 61, and the SO₂ Is released from the active oxygen release agent 61 to the outside. SO released to the outside₂ Is oxidized on the platinum Pt on the downstream side and is absorbed again into the active oxygen release agent 61.
[0034]
On the other hand, the oxygen O toward the contact surface between the fine particles 62 and the active oxygen release agent 61 is potassium nitrate KNO._Three And potassium sulfate K₂ SO_Four It is oxygen decomposed from a compound such as Oxygen O decomposed from the compound has high energy and has extremely high activity. Therefore, oxygen toward the contact surface between the fine particles 62 and the active oxygen release agent 61 is active oxygen O. When the active oxygen O comes into contact with the fine particles 62, the oxidation action of the fine particles 62 is promoted, and the fine particles 62 can be oxidized and removed without emitting a luminous flame in several minutes to several tens of minutes. On the other hand, while the fine particles 62 are oxidized in this way, other fine particles adhere to the particulate filter 22 from one to the next. Therefore, in practice, a certain amount of fine particles are always 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.
[0035]
NO₂ Is a nitrate ion NO in the active oxygen release agent 61 while repeating the binding and separation of oxygen atoms._Three ^-The active oxygen is generated during this period. The fine particles 62 are also oxidized by this active oxygen. Further, the fine particles 62 adhering to the particulate filter 22 in this manner are oxidized by the active oxygen O, but the fine particles 62 are also oxidized by oxygen in the exhaust gas.
[0036]
When the particulates deposited in a laminated form on the particulate filter 22 are burned, the particulate filter 22 is red hot and burns with a flame. The combustion with such a flame cannot be continued unless the temperature is high. Therefore, in order to continue the combustion with such a flame, the temperature of the particulate filter 22 must be maintained at a high temperature.
[0037]
On the other hand, in the present invention, the fine particles 62 are usually oxidized without emitting a bright flame as described above, and at this time, the surface of the particulate filter 22 is not red hot. That is, in other words, in the present invention, the fine particles 62 are usually removed by oxidation at a considerably low temperature. Therefore, the particulate removal action by oxidation of the particulate 62 that does not emit a luminous flame in the present invention is completely different from the particulate removal action by combustion accompanied by a flame.
[0038]
By the way, platinum Pt and the active oxygen release agent 61 are activated as the temperature of the particulate filter 22 increases. Therefore, the amount of the active oxygen O that can be released by the active oxygen release agent 61 per unit time is high at the temperature of the particulate filter 22. It increases. As a matter of course, fine particles are more easily removed by oxidation as the temperature of the fine particles themselves increases. Therefore, the amount of fine particles that can be removed by oxidation without emitting a bright flame per unit time on the particulate filter 22 increases as the temperature of the particulate filter 22 increases.
[0039]
The solid line in FIG. 5 indicates the oxidation rate of the fine particles on the particulate filter 22, that is, the amount G (g / min) of fine particles that can be oxidized and removed without emitting a luminous flame per minute and the temperature TF of the particulate filter 22. Showing the relationship. That is, a balance point is shown in which the amount of fine particles flowing into the curved particulate filter 22 shown in FIG. On this curve, since the amount of inflowing particulates is equal to the amount of particulates removed by oxidation, the amount of particulates deposited on the particulate filter 22 is kept constant. On the other hand, in the region I of FIG. 5, the amount of inflowing particulates is smaller than the amount of particulates that can be removed by oxidation. On the other hand, in region II of FIG. 5, the amount of inflowing particulates is larger than the amount of particulates that can be oxidized and removed, and therefore all inflowing particulates cannot be oxidized. In this case, the deposited fine particles gradually change to a carbonaceous material that is hardly oxidized as time passes after deposition, and therefore, the deposited fine particles gradually become difficult to oxidize as the state of the region II continues.
[0040]
Thus, when the particulate filter 22 according to the present invention is used, the amount of inflowing particulates is equal to the amount of particulates that can be oxidized and removed (on the curve in FIG. 5) and the amount of inflowing particulates is less than the amount of particulates that can be removed by oxidation (see FIG. 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, even when the inflowing particulate amount is larger than the oxidizable particulate amount (region II in FIG. 5), some of the deposited particulates are continuously oxidized, but some of the deposited particulates are deposited without being oxidized. Therefore, when the amount of inflowing particulates continues to be greater than the amount of oxidized particulates, the amount of deposited particulates gradually increases.
[0041]
As described above, in the embodiment according to the present invention, a carrier layer made of alumina, for example, 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. A noble metal catalyst and an active oxygen release agent are supported on the carrier. Further, in the embodiment according to the present invention, the NOx contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the noble metal catalyst and the particulate filter 22 on the carrier is lean._x Is absorbed when the air-fuel ratio of the exhaust gas that flows into the particulate filter 22 becomes stoichiometric or rich._x NO release_x An absorbent is supported.
[0042]
In the examples according to the present invention, platinum Pt is used as the noble metal catalyst, and NO._x As an absorbent, alkaline metals such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb, alkaline earths such as barium Ba, calcium Ca, and strontium Sr, rare earths such as lanthanum La, yttrium Y, and cerium Ce At least one selected from is used. As can be seen from comparison with the metal constituting the active oxygen release agent described above, NO_x The metal that constitutes the absorbent and the metal that constitutes the active oxygen release agent are mostly the same.
[0043]
In this case, NO_x Different metals can be used as the absorbent and the active oxygen release agent, respectively, or the same metal can be used. NO_x NO when using the same metal as the absorbent and active oxygen release agent_x Both the function as an absorbent and the function as an active oxygen release agent are performed simultaneously.
Next, using platinum Pt as a noble metal catalyst, NO_x NO when taking potassium K as an absorbent_x The absorption / release action will be described.
[0044]
First of all NO_x When the absorption action of NO is examined, NO_x Is NO with the same mechanism as shown in FIG._x Absorbed by absorbent. In this case, however, reference numeral 61 in FIG._x Indicates an 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 4 (A), these oxygen O₂ Is O₂ ^-Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the exhaust gas is O on the surface of platinum Pt.₂ ^-Or O^2-Reacts with NO₂ (2NO + O₂ → 2NO₂). Then the generated NO₂ Part of NO is being oxidized on platinum Pt_x Nitrate ion NO as shown in FIG. 4 (A) while being absorbed in the absorbent 61 and combined with potassium K_Three ^-NO in the form of_x Diffusion into the absorbent 61 and some nitrate ions NO_Three ^-Is potassium nitrate KNO_Three Is generated. In this way NO is NO_x Absorbed in the absorbent 61.
[0045]
On the other hand, when the exhaust gas flowing into the particulate filter 22 becomes rich, nitrate ions NO_Three ^-Is decomposed into oxygen, O and NO, and NO from one to the next_x NO is released from the absorbent 61. Therefore, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 becomes rich, the NO in a short time._x NO is released from the absorbent 61, and since the released NO is reduced, NO is not discharged into the atmosphere.
[0046]
In this case, even if the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is the stoichiometric air-fuel ratio, NO_x NO is released from the absorbent 61. However in this case NO_x NO is released from the absorbent 61 only gradually._x Total NO absorbed by absorbent 61_x It takes a little longer time to release.
By the way, as mentioned above, NO_x Different metals can be used as the absorbent and the active oxygen release agent. However, in embodiments according to the present invention, NO_x The same metal is used as the absorbent and the active oxygen release agent. In this case, as described above, NO_x The function of both the function as an absorbent and the function as an active oxygen release agent will be performed at the same time._x It is called an absorbent. Therefore, in the embodiment according to the present invention, reference numeral 61 in FIG._x The absorbent is shown.
[0047]
Such active oxygen release / NO_x When the absorbent 61 is used, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is lean, NO contained in the exhaust gas releases active oxygen / NO_x Fine particles absorbed in the absorbent 61 and contained in the exhaust gas release active oxygen and NO_x When adhering to the absorbent 61, the fine particles become active oxygen contained in the exhaust gas and release of active oxygen / NO._x It is oxidized and removed by active oxygen released from the absorbent 61. Therefore, at this time, fine particles in the exhaust gas and NO_x Both of them can be prevented from being discharged into the atmosphere.
[0048]
On the other hand, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 becomes rich, the release of active oxygen / NO_x NO is released from the absorbent 61. This NO is reduced by unburned HC and CO, and therefore NO is not discharged into the atmosphere at this time as well. 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 rapidly decreases, the release of active oxygen / NO_x Active oxygen is released at once from the absorbent 61. Therefore, at this time, the deposited fine particles on the particulate filter 22 release active oxygen and NO._x Oxidation is rapidly accelerated by the active oxygen released from the absorbent 61.
[0049]
Now, as described above, when the inflowing particulates continue to be larger than the oxidized particulate amount, the amount of deposited particulates 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 when the amount of accumulated particulates on the particulate filter 22 increases due to the operating state of the engine and on the particulate filter 22. When the deposited fine particles increase, the pressure loss in the particulate filter 22 may increase. Next, this will be described with reference to FIGS. 6 (A) and 6 (B).
[0050]
6A and 6B are enlarged sectional views of the partition wall 54 of the particulate filter 22, and the exhaust gas flows through the partition wall 54 as indicated by arrows. 6A and 6B, the hatched portion 70 indicates the base material of the particulate filter 22, and the space formed between the base materials 70 is a pore in which 71 exhaust gas flows. Is shown. Black circles 72 indicate the deposited fine particles.
[0051]
In the particulate filter 22 used in the present invention, the size of the exhaust gas flow hole 71 is made larger than that of the conventional one. Further, the entire surface of the base material 70 facing the exhaust gas circulation pores 71 is covered with a carrier layer made of alumina, for example, in order to perform the oxidation removal action of the fine particles inside the partition wall 54 of the particulate filter 22. The active oxygen release / NO on this carrier_x An absorbent 61 is supported. This active oxygen release / NO_x When the absorbent 61 is used, as can be seen from FIG. 5, fine particles can be removed by oxidation even at a low temperature TF of 200 ° C. or lower.
[0052]
In the particulate filter 22 according to the present invention, the normal fine particles remain on the surface of the partition wall 54 as shown in FIG. 6A 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 oxidized and removed. And it disperse | distributes and accumulates on the surface of the base | substrate 70 in the partition 54. FIG. In this case, when the amount of inflowing fine particles is equal to the amount of fine particles that can be removed by oxidation or less than the amount of fine particles that can be removed by oxidation, the accumulated fine particles 72 are sequentially removed by oxidation. On the other hand, when the amount of inflowing particulates exceeds the amount of particulates that can be removed by oxidation, some particulates 72 are removed by oxidation, but some particulates 72 continue to be deposited without being removed by oxidation, and as a result, the amount of particulates deposited. Will gradually increase. However, even if the amount of accumulated particulates gradually increases in this way, the size of the exhaust gas flow pores 71 of the particulate filter 22 is large and the particulates are dispersed and deposited, so the pressure loss in the particulate filter 22 hardly increases. .
[0053]
On the other hand, as shown in FIG. 5B, when the fine particles are concentrated on the inlet portion of the exhaust gas circulation pore 71 for some reason, the particulate filter 22 is clogged, and thus the particulate filter 22 Pressure loss increases. As described above, 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 when the particles are dispersed and deposited as shown in FIG. That is, whether or not the pressure loss of the particulate filter 22 is increased is not directly related to the amount of deposited fine particles, and depends on how fine particles are deposited.
[0054]
It can be roughly estimated by experience whether the particulate filter 22 is clogged as shown in FIG. However, since the actual operating state of the engine changes in a complicated manner, it is difficult to determine from the operating state of the engine whether the particulate filter 22 has become clogged. Therefore, whether the particulate filter 22 has become clogged. It is necessary to detect whether or not the pressure loss in the particulate filter 22 has increased.
[0055]
On the other hand, when fine particles are dispersed and deposited as shown in FIG. 6A, the pressure loss in the particulate filter 22 hardly increases even when the fine particulate matter deposited on the particulate filter 22 increases as described above. In this case, if the pressure loss in the particulate filter 22 is hardly increased, leaving it as it is causes a serious problem as described at the beginning. That is, for example, when acceleration operation is performed, the amount of heat generated in the combustion chamber 5 increases and the amount of exhaust gas increases, and as a result, the temperature of the particulate filter 22 rises rapidly. Next, when the operation is shifted to a low load operation, the space velocity of the exhaust gas in the particulate filter 22 is reduced while the temperature of the particulate filter 22 is high, and the oxygen concentration in the exhaust gas is increased. Accumulated particulates are burned rapidly. 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 combustion of the fine particles 72, and as a result, the particulate filter 22 is melted or the particulate filter 22. There arises a problem that the temperature difference in the upper part becomes intense and cracks occur, that is, the particulate filter 22 is damaged.
[0056]
Therefore, in the present invention, when the amount of deposited particulates on the particulate filter 22 increases and the particulate filter 22 may be damaged by the oxidation reaction heat of the deposited particulates, the pressure loss in the particulate filter 22 hardly increases. Even in this case, in order to regenerate the particulate filter 22, the temperature of the particulate filter 22 is raised under a lean air-fuel ratio.
[0057]
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 that is predetermined according to the operating state of the engine, the air-fuel ratio A / F becomes lean. Even when the pressure loss PD in the particulate filter 22 is lower than the set value MAX, the amount of deposited particulate on the particulate filter 22 is damaged by the oxidation reaction heat of the deposited particulate even when the regeneration process is performed in the state. When it is estimated that the limit value that may cause the air-fuel ratio is exceeded, the regeneration process is performed with the air-fuel ratio A / F being lean.
[0058]
In practice, the frequency at which the amount of particulate matter deposited on the particulate filter 22 exceeds a limit value that may cause damage to the particulate filter 22 is much higher than the frequency at which the particulate filter 22 is clogged. Therefore, as shown in FIG. 7, the amount of particulate matter deposited on the particulate filter 22 is larger than the frequency of regeneration processing performed when the pressure loss PD in the particulate filter 22 exceeds the set value MAX. The frequency of the regeneration process performed when it is estimated that a limit value that may cause damage is exceeded is much higher.
[0059]
The regeneration process shown in FIG. 7 raises the temperature of the particulate filter 22 from 500 ° C. to 600 ° C. at which the deposited particulate on the particulate filter 22 ignites and starts combustion, and then most of the deposited particulate finishes burning. In this process, the temperature of the particulate filter 22 is maintained from 500 ° C. to 600 ° C. or higher. In this case, there are various methods for raising the temperature of the particulate filter 22. For example, an electric heater is arranged at the upstream end of the particulate filter 22 and the exhaust gas flowing into the particulate filter 22 or the particulate filter 22 is heated by the electric heater, or fuel is introduced into the exhaust passage upstream of the particulate filter 22. There are a method of heating the particulate filter 22 by injecting and burning this fuel, and a method of raising the temperature of the particulate filter 22 by raising the exhaust gas temperature.
[0060]
Here, the last method, that is, a method of raising the exhaust gas temperature will be briefly described with reference to FIG.
One effective method for raising the exhaust gas temperature is to retard the fuel injection timing until after compression top dead center. That is, the normal main fuel Q_m Is injected in the vicinity of the compression top dead center as shown in FIG. In this case, as shown in FIG. 8 (II), the main fuel Q_m When the injection timing is delayed, the afterburning period becomes longer, and thus the exhaust gas temperature rises. As the exhaust gas temperature increases, the temperature TF of the particulate filter 22 increases accordingly.
[0061]
Further, in order to raise the exhaust gas temperature, as shown in FIG._m In addition to the auxiliary fuel Q near the intake top dead center_v Can also be injected. Thus, auxiliary fuel Q_v When additional fuel is injected, auxiliary fuel Q_V Since the amount of fuel combusted by the amount increases, the exhaust gas temperature rises, and thus the temperature TF of the particulate filter 22 rises.
[0062]
On the other hand, the auxiliary fuel Q in the vicinity of the intake top dead center in this way._v Is injected by the heat of compression during the compression process._v From these, intermediate products such as aldehydes, ketones, peroxides, carbon monoxide and the like are produced, and these intermediate products produce main fuel Q._m The reaction is accelerated. Therefore, in this case, as shown in FIG._m Even if the injection timing is greatly delayed, good combustion can be obtained without causing misfire. That is, the main fuel Q_m Therefore, the exhaust gas temperature becomes considerably high, so that the temperature TF of the particulate filter 22 can be quickly raised.
[0063]
Further, as shown in FIG. 8 (IV), the main fuel Q_m In addition to the auxiliary fuel Q during the expansion stroke or the exhaust stroke_p Can also be injected. That is, in this case, most of the auxiliary fuel Q_p Is discharged into the exhaust passage in the form of unburned HC without burning. The 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.
[0064]
By the way, as described above, when the air-fuel ratio of the exhaust gas is lean, the NO in the exhaust gas_x Is active oxygen release, NO_x Absorbed by the absorbent 61. However NO_x Absorbent 61 NO_x Absorption capacity is limited, active oxygen release, NO_x Absorbent 61 NO_x Release active oxygen and NO before absorption capacity is saturated_x NO from absorbent 61_x Need to be released. For that purpose, active oxygen release and NO_x NO absorbed by the absorbent 61_x The amount needs to be estimated. Therefore, in the embodiment according to the present invention, NO per unit time is obtained._x The 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, and the NO per unit time is obtained._x Active oxygen release / NO by integrating the absorbed amount A_x NO absorbed by the absorbent 61_x The amount ΣNOX is estimated.
[0065]
Further, in the embodiment according to the present invention, as shown in FIG._x When the absorbed amount ΣNOX exceeds a predetermined allowable maximum value MAXN, the release of active oxygen / NO_x The air-fuel ratio A / F of the exhaust gas flowing into the absorbent 61 is temporarily made rich, thereby releasing active oxygen / NO_x NO from absorbent 25_x To be released.
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 making the average air-fuel ratio in the combustion chamber 5 rich, a method of injecting additional fuel into the combustion chamber 5 during the latter half of the expansion stroke or during the exhaust stroke, There is a method of injecting fuel.
[0066]
On the other hand, the exhaust gas contains SO._x Contains active oxygen release and NO_x NO in absorbent 61_x Not only SO_x Is also absorbed. This active oxygen release ・ NO_x SO to absorbent 61_x NO absorption mechanism_x It is considered that the absorption mechanism is the same.
That is, NO_x The case where platinum Pt and potassium K are supported on the carrier as in the case of explaining the absorption mechanism of oxygen will be described as an example. As described above, when the air-fuel ratio of the exhaust gas is lean, oxygen O₂ Is O₂ ^-Or O^2-Is attached to the surface of platinum Pt in the form of SO₂ O on the surface of platinum Pt₂ ^-Or O^2-Reacts with SO_Three It becomes. The generated SO_Three Part of the active oxygen is released while NO is further oxidized on platinum Pt_x It is absorbed into the absorbent and binds to potassium K, while sulfate ion SO_Four ^2- Active oxygen release in the form of NO_x Stable sulfate K that diffuses into the absorbent₂ SO_Four Is generated.
[0067]
However, this sulfate K₂ SO_Four Is stable and difficult to decompose, as described above, release of active oxygen and NO_x NO from absorbent 61_x Even if the exhaust gas air-fuel ratio is made rich to release₂ SO_Four Remains undisassembled. Therefore, release of active oxygen and NO_x In the absorbent 61, as time passes, sulfate K₂ SO_Four Thus, the release of active oxygen and NO over time_x NO that the absorbent 61 can absorb_x The amount will decrease.
[0068]
However, this sulfate K₂ SO_Four Is active oxygen release NO_x The temperature of the absorbent 61 is active oxygen release / NO_x Decomposes when the temperature exceeds a certain temperature determined by the absorbent 61, for example, approximately 600 ° C._x When the air-fuel ratio of the exhaust gas flowing into the absorbent 61 is made rich, the release of active oxygen and NO_x Absorbent 61 to SO_x Is released. However, release of active oxygen / NO_x Absorbent 61 to SO_x To release active oxygen and NO_x NO from absorbent 61_x Takes considerably longer time than the case of releasing.
[0069]
Therefore, in the embodiment according to the present invention, the release of active oxygen and NO_x Absorbent 61 to SO_x Active oxygen release and NO when the air-fuel ratio is lean_x Increase the temperature TF of the absorbent 61 to approximately 600 ° C., then release active oxygen / NO_x Release the active oxygen by making the air-fuel ratio of the exhaust gas flowing into the absorbent 61 rich._x Absorbent 61 to SO_x To be released. In this case, active oxygen release / NO_x As the method for raising the temperature TF of the absorbent 61 to approximately 600 ° C., the various methods described above can be used.
[0070]
By the way, when the air-fuel ratio is maintained lean, the surface of platinum Pt is covered with oxygen, and so-called oxygen poisoning of platinum Pt occurs. When such oxygen poisoning occurs, NO_x NO is reduced due to reduced oxidation_x The absorption effect of NO is reduced, so that active oxygen release and NO_x The amount of active oxygen released from the absorbent 61 is reduced. However, when the air-fuel ratio is made rich, oxygen on the platinum Pt surface is consumed, so that oxygen poisoning is eliminated, and therefore NO is when the air-fuel ratio is switched from rich to lean._x The oxidative effect on is increased. Therefore NO_x The absorption efficiency of NO is increased, thus releasing active oxygen and NO_x The amount of active oxygen released from the absorbent 61 is increased.
[0071]
Therefore, as shown in FIG. 7, when the air-fuel ratio A / F is occasionally changed from lean to rich when the air-fuel ratio A / F is maintained lean, the oxygen poisoning of platinum Pt is eliminated each time, so The amount of active oxygen released when the fuel ratio A / F is lean is increased, and thus the oxidation action of fine particles on the particulate filter 22 can be promoted.
[0072]
Cerium Ce takes in oxygen when the air-fuel ratio is lean (Ce₂ O_Three → 2CeO₂), Active oxygen is released when the air-fuel ratio becomes rich (2CeO₂ → Ce₂ O_Three) Has a function. Therefore, release of active oxygen and NO_x When cerium Ce is used as the absorbent 61, when the air-fuel ratio is lean, if fine particles adhere to the particulate filter 22, the release of active oxygen and NO_x When the fine particles are oxidized by the active oxygen released from the absorbent 61 and the air-fuel ratio becomes rich, the release of active oxygen / NO_x Since a large amount of active oxygen is released from the absorbent 61, the fine particles are oxidized. Therefore, release of active oxygen and NO_x Even when cerium Ce is used as the absorbent 61, the oxidation reaction of fine particles on the particulate filter 22 can be promoted by switching the air-fuel ratio from lean to rich occasionally.
[0073]
Next, referring to FIG. 10, active oxygen release / NO_x NO from absorbent 61_x NO when set to release_x Release flag and active oxygen release / NO_x Absorbent 61 to SO_x Set when should release_x The processing routine for the release flag will be described. This routine is executed by interruption every predetermined time.
[0074]
Referring to FIG. 10, first, at step 100, the NO per unit time is calculated from the map shown in FIG._x Absorption amount A is calculated. Next, in step 101, NO_x A is added to the absorption amount ΣNOX. Next, in step 102, NO_x It is determined whether or not the absorption amount ΣNOX exceeds an allowable maximum value MAXN. If ΣNOX> MAXN, go to step 103, NO_x NO that should be released_x The release flag is set. Next, the routine proceeds to step 104.
[0075]
In step 104, a product k · Q obtained by multiplying the injection amount Q by a constant k is added to ΣSOX. The fuel contains an almost constant amount of sulfur S. Therefore, the release of active oxygen and NO_x SO absorbed in the absorbent 61_x The quantity can be expressed in k · Q. Therefore, ΣSOX obtained by sequentially accumulating k · Q is active oxygen release · NO_x SO estimated to be absorbed by the absorbent 61_x It represents the quantity. In step 105, this SO_x It is determined whether or not the amount ΣSOX has exceeded the allowable maximum value MAXS. If ΣSOX> MAXS, the routine proceeds to step 106, where SO is reached._x The release flag is set.
[0076]
Next, the operation control according to the present invention will be described with reference to FIG.
Referring to FIG. 11, first, in step 200, the particulate filter is based on the estimation of whether or not the amount of accumulated particulates on the particulate filter 22 has exceeded a limit value that may cause damage to the particulate filter 22. Intermediate reproduction control for performing reproduction of 22 is executed. Next, at step 300, the release of active oxygen / NO_x NO from absorbent 61_x NO to release_x Release control is performed. Next, at step 400, main regeneration control is performed to regenerate the particulate filter 22 when the pressure loss in the particulate filter 22 exceeds a set value. Next, at step 500, the release of active oxygen / NO_x Absorbent 61 to SO_x SO to release_x Release control is performed.
[0077]
Next, these intermediate regeneration controls, NO_x Release control, main regeneration control, SO_x The release control will be described sequentially.
First, the first embodiment of the intermediate reproduction control executed in step 200 of FIG. 11 will be described with reference to FIG. In the first embodiment, the deposited fine particles W on the particulate filter 22 are used._{n + 1} Is obtained by calculation, and this amount of deposited fine particles W_{n + 1} When the particle size exceeds a predetermined limit value WX, it is determined that the amount of accumulated particulates on the particulate filter 22 has exceeded a limit value that may cause damage to the particulate filter 22, and the particulate filter 22 is regenerated. Like to do.
[0078]
That is, referring to FIG. 12, first, in step 201, the amount M of inflowing particulates flowing into the particulate filter 22 per unit time, that is, the amount M of discharged particulates discharged from the engine per unit time is calculated. The amount M of discharged particulates varies depending on the engine model, but when the engine model is determined, it becomes a function of the required torque TQ and the engine speed N. FIG. 13A shows the amount M of discharged fine particles of the internal combustion engine shown in FIG.₁ , M₂ , M_Three , M_Four , M_Five Is the amount of fine particles discharged (M₁<M₂ <M_Three <M_Four <M_Five). In the example shown in FIG. 13A, the amount M of discharged particulate increases as the required torque TQ increases. 13A is obtained as a function of the required torque TQ and the engine speed N in the form of a map shown in FIG. 13B and stored in the ROM 32.
[0079]
Next, at step 202, the amount of deposited particulate W on the particulate filter 22 based on the following equation:_{n + 1} Is calculated.
W_{n + 1} = M + W_n -G
Here, M represents the amount of discharged fine particles per unit time as described above, and W_n Indicates the amount of deposited fine particles on the particulate filter 22 calculated during the previous processing cycle, and G indicates the amount of fine particles that can be removed by oxidation per unit time shown in FIG. That is, the amount of fine particles newly deposited per unit time is M, and the amount of fine particles to be oxidized and removed per unit time is G._{n + 1} Is expressed by the above equation.
[0080]
Next, at step 203, the amount of deposited particulate W_{n + 1} It is determined whether or not 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 regeneration process, a target regeneration time for regeneration of the particulate filter 22 is set in advance, and regeneration control of the particulate filter 22 is performed only for the predetermined target regeneration time. When the regeneration process of the particulate filter 22 is completed, the process proceeds to step 205 and W_n Is zeroed and then executed in step 300 of FIG._x Proceed to release control.
[0081]
It should be noted that the temperature of the particulate filter 22 is usually low when the engine is started, and therefore the amount G of oxidizable particles in the above equation continues to be zero or close to zero for a while after the engine is started. Therefore, when the engine is started, the amount of accumulated particulates W_{n + 1} When the engine continues to increase and exceeds the limit value, and the engine is started, the regeneration process of the normal particulate filter 22 is executed.
[0082]
  Next, a second embodiment of the intermediate reproduction process executed in step 200 of FIG. 11 will be described. 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, normally deposited fine particles exceed the limit value as described above. Therefore institutionalStartIs performed, it can be estimated that the amount of deposited fine particles on the particulate filter 22 exceeds the limit value.
[0083]
Further, if the engine operating state continues for a certain period or longer, it is considered that the amount of deposited fine particles on the particulate filter 22 exceeds the limit value. Therefore, it is possible to estimate that the amount of accumulated particulates on the particulate filter 22 has exceeded the limit value even when the engine operating time, the accumulated value of the engine speed, or the vehicle travel distance exceeds a predetermined value.
[0084]
Therefore, in this second embodiment, the particulate filter 22 is regenerated when it is estimated that the amount of deposited fine particles on the particulate filter 22 exceeds the limit value.
That is, referring to FIG. 14 for executing the second embodiment, first, at step 211, it is determined whether or not it is estimated that the amount of accumulated particulates on the particulate filter 22 exceeds the limit value. When it is estimated that the amount of deposited fine particles on the particulate filter 22 exceeds the limit value, the routine proceeds to step 212, where the regeneration processing of the particulate filter 22 is performed, and then NO._x Proceed to release control. In this regeneration process, the target regeneration time for reproducing the particulate filter 22 is set in advance, and regeneration control of the particulate filter 22 is performed only for the predetermined target regeneration time.
[0085]
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 particulates are set for the preset target reproduction time. Regeneration control of the filter 22 is performed. However, the actual regeneration action of the particulate filter 22 is not started unless the temperature of the particulate filter 22 reaches a temperature at which particulates can be ignited and combusted. Therefore, in the third embodiment, regeneration control of the particulate filter 22 is performed only for the target regeneration time from when the actual regeneration operation of the particulate filter 22 is started. Next, this will be described with reference to FIG.
[0086]
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 raising control is started. In FIG. 15A, TFX indicates a temperature at which the combustion of the fine particles is started. As shown in FIG. 15A, when regeneration control is started, the temperature TF at the upstream end of the particulate filter 22 starts to rise, and the temperature TF at the upstream end of the particulate filter 22 is about 500 ° C. to 600 ° C. When the combustion start temperature TFX is reached, 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 shorter than the combustion start temperature TFX, and it takes some time for the entire temperature TF of the particulate filter 22 to be 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 starts in the entire particulate filter 22 is indicated by Δt in FIG.
[0087]
  The delay time Δt is shorter as the exhaust gas temperature is higher, and is shorter as the exhaust gas amount is larger. That is, this delay time Δt is shown in FIG.B) (Δt)₁ >Δt₂ >Δt_Three >Δt_Four >Δt_Five). In the third embodiment, the delay time Δt is calculated from the relationship shown in FIG. 15B, and the regeneration control of the particulate filter 22 is performed for the target regeneration time after the delay time Δt has elapsed after TF becomes TFX. I am doing so.
[0088]
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. Accordingly, when the temperature at which particulate combustion starts in the entire particulate filter 22 can be detected by the temperature sensor, there is no need to consider such a delay time.
[0089]
In the third embodiment, the case where the regeneration is interrupted by stopping the engine during the regeneration control of the particulate filter 22 is also taken into consideration. That is, in this third embodiment, when the regeneration control is resumed after being interrupted, the time required to raise 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 interruption. The added time is set as a new target reproduction time.
[0090]
FIGS. 16 and 17 show an intermediate reproduction control routine for executing the third embodiment.
Referring to FIGS. 16 and 17, first, at step 221, it is judged if a regeneration flag indicating that regeneration control is being performed is set. When the regeneration flag is not set, the routine proceeds to step 222, where the amount M of discharged particulate per unit time is calculated from the map shown in FIG. Next, at step 223, the amount W of deposited particulate on the particulate filter 22 based on the following equation:_{n + 1} Is calculated.
[0091]
W_{n + 1} = M + W_n -G
Here, M represents the amount of discharged fine particles per unit time as described above, and W_n Indicates the amount of deposited fine particles on the particulate filter 22 calculated during the previous processing cycle, and G indicates the amount of fine particles that can be removed by oxidation per unit time shown in FIG.
[0092]
Next, at step 224, the amount of deposited particulate W_{n + 1} It is determined whether or not the value has exceeded a limit value WX that may cause damage to the particulate filter 22. W_{n + 1} When ≦ WX, NO executed in step 300 of FIG._x Proceed to release control. On the other hand, W_{n + 1} If> WX, the routine proceeds to step 225, where the regeneration flag is set, and then proceeds to step 226, where the target regeneration time t_n Is set. Next, the routine proceeds to step 227, where regeneration control is started. When the reproduction flag is set, the process jumps from step 221 to step 227 in the next processing cycle.
[0093]
Next, at step 228, it is judged if a reproduction start flag indicating that reproduction has actually started is set. When the process proceeds to step 228 for the first time after the regeneration flag is set, the regeneration start flag is reset. Therefore, the process proceeds to step 229 at this time. 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. NO when TF ≦ TFX_x Proceed to release control. On the other hand, when TF> TFX, the routine proceeds to step 230.
[0094]
In step 230, the delay time Δt is calculated from the relationship shown in FIG. Next, at step 231, it is determined whether or not the delay time Δt has elapsed. NO when the delay time Δt has not elapsed._x Proceed to release control. On the other hand, when the delay time Δt has elapsed, it is determined that the regeneration operation has 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.
[0095]
In step 233, a fixed time α is added to the elapsed time t from the start of the regeneration operation in the entire particulate filter 22. Next, at step 234, it is judged if the regeneration control is interrupted. When the regeneration control is not interrupted, the routine proceeds to step 235 where the elapsed time t is the target regeneration time t._n It is determined whether or not the value has been exceeded. t ≦ t_n NO_x Proceed to release control. In contrast, t> t_n At step 236, the reproduction control is stopped, and then at step 237, the reproduction flag and the reproduction start flag are reset. Next, the routine proceeds to step 238, where the amount of deposited particulate W_n The elapsed time t is set to zero.
[0096]
That is, when the regeneration control is not interrupted during the regeneration control, the target regeneration time t after the regeneration action is started in the entire particulate filter 22 is started._n The regeneration of the particulate filter 22 is performed until the time elapses.
On the other hand, when it is determined in step 234 that the regeneration control has been interrupted, the process proceeds to step 239, and until the state where the regeneration control should be interrupted is released, for example, when the regeneration control is interrupted by stopping the engine, the engine The intermediate regeneration control is stopped until the operation is restarted. Next, at step 240, the reproduction start flag is reset. At this time, the elapsed time t is the target reproduction time t_n The remaining time t is stored as it is.
[0097]
Now, even if the playback control is interrupted, the playback flag continues to be set. Therefore, when the state where the playback control should be interrupted is released, the routine jumps from step 221 to step 227 to start the playback control. At this time, the playback start flag is reset, so in steps 229, 230 and 231 TF> TFX. It is determined whether or not the delay time Δt has elapsed since the start. When the delay time Δt elapses after TF> TFX, the process proceeds to step 233 through step 232, and the addition of the fixed time α to the elapsed time t is started. That is, the target regeneration time t when the regeneration control is interrupted_n The remaining time t is set as a new target playback time, and the playback operation is performed for the new target playback time unless the playback control is interrupted again. Even during the regeneration operation, if the regeneration control is interrupted again, the regeneration operation is performed again for the remaining time of the new target regeneration time when the state where the regeneration control should be interrupted is cancelled.
[0098]
Next, the NO executed in step 300 of FIG._x FIG. 18 showing the release control will be described.
Referring to FIG. 18, first, in step 301, NO_x It is determined whether or not the release flag is set. NO_x When the release flag is not set, the process proceeds to the main regeneration control executed in step 400 of FIG. In contrast, NO_x When the release flag is set, the routine proceeds to step 302 where rich processing for temporarily switching the air-fuel ratio from the lean air-fuel ratio to the rich air-fuel ratio is performed. When this rich process is performed, the release of active oxygen and NO_x NO from absorbent 61_x Is released. At this time, active oxygen release and NO_x Oxidation of the deposited fine particles is promoted by the active oxygen released from the absorbent 61. When the rich process is completed, the routine proceeds to step 303, where ΣNOX is cleared, and then at step 304, NO_x The release flag is reset. Next, the process proceeds to the main reproduction control.
[0099]
Next, FIG. 19 showing the main reproduction control executed in step 400 of FIG. 11 will be described.
Referring to FIG. 19, first, at step 401, it is judged if the main regeneration flag indicating that the clogged particulate filter 22 should be regenerated is set. Usually, since this regeneration flag is not set, the routine proceeds to step 402, where it is determined whether or not the pressure loss PD in the particulate filter 22 detected by the pressure sensor 43 has exceeded the set value MAX. When PD ≦ MAX, the SO executed in step 500 of FIG._x Proceed to release control. On the other hand, when PD> MAX, the routine proceeds to step 403 where the main regeneration flag is set, and then the routine proceeds to step 404 where regeneration control of the particulate filter 22 is started. When this regeneration flag is set, the process jumps from step 401 to step 404 in the next processing cycle.
[0100]
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 particulate filter 22 has been clogged. When PD ≧ MIN, the SO executed in step 500 of FIG._x The release control is jumped to END, and the regeneration action for eliminating the clogging of the particulate filter 22 is continued. When PD <MIN, the routine proceeds to step 406, where playback control is stopped, and then at step 407, the main playback flag is reset.
[0101]
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, it is also possible to detect the pressure only on the upstream side of the particulate filter 22 and detect the pressure loss PD from this pressure. Further, when the pressure loss PD increases, the EGR gas amount increases if the opening degree of the EGR control valve 25 is the same. When the EGR control valve 25 is controlled so that the intake air amount does not change at this time, the opening degree of the EGR control valve 25 Is reduced. That is, the pressure loss PD can be detected from the change in the EGR gas amount or the change in the opening degree of the EGR control valve 25. In the present invention, detecting the pressure loss PD includes a case where the pressure loss PD is detected by these various methods.
[0102]
  Next, the SO executed in step 500 of FIG._xThe release control will be described.
  As described above, active oxygen release / NO_xAbsorbent 61 to SO_xActive oxygen release and NO when the air-fuel ratio is lean_xIncrease the temperature TF of the absorbent 61 to approximately 600 ° C., then release active oxygen / NO_xThe air-fuel ratio of the exhaust gas flowing into the absorbent 61 is made rich. Also in this case, the temperature TF of the particulate filter 22 is as shown in FIG.SO_xAfter reaching the discharge temperature TFXX, the temperature TF of the entire particulate filter 22 isSO_xA delay time Δt until the discharge temperature TFXX is reached is calculated, and a predetermined target SO from when the delay time Δt has elapsed is calculated._xActive oxygen release / NO by enriching the air-fuel ratio while continuing temperature rise control for the release time_xAbsorbent 61 to SO_xCan be released.
[0103]
  Also thisSO_xSO even in controlled release_xFor example, when the engine is stopped during emission control, SO_xConsideration is given to the case where the release control is interrupted. That is, thisSO_xSO in controlled release_xWhen release control is resumed after being suspended, the target SO at the time of suspension_xThe temperature of the entire particulate filter is SO for the remaining discharge time._xAdd the time required to raise to the discharge temperature and add this added time to the new target SO_xThe release time is set.
[0104]
  20 and 21 show thisSO_xFig. 5 shows a routine for executing release control.
  Referring to FIGS. 20 and 21, first, in step 501,SO_xIt is determined whether or not an execution flag indicating that the discharge control is being executed is set. When the executing flag is not set, the routine proceeds to step 502, where the SO_xIt is determined whether or not the release flag is set. SO_xWhen the release flag is not set, the processing cycle is completed. On the other hand, SO_xWhen the release flag is set, the routine proceeds to step 503, where the execution flag is set, and then proceeds to step 504, where the target SO_xRelease time t_mIs set. Next, the routine proceeds to step 505 where temperature increase control is started. When the executing flag is set, the process jumps from step 501 to step 505 in the next processing cycle.
[0105]
Next, at step 506, the SO_x It is determined whether or not a release start flag indicating that the release of is started is set. When the process proceeds to step 506 for the first time after the execution flag is set, the release start flag is reset. Accordingly, the process proceeds to step 507 at this time. In step 507, the temperature TF of the particulate filter 22 detected by the temperature sensor 39 is calculated as SO._x It is determined whether or not the temperature is higher than the discharge temperature TFXX. When TF ≦ TFXX, the processing cycle is completed. On the other hand, if TF> TFXX, the process proceeds to step 508.
[0106]
In step 508, the delay time Δt is calculated from the relationship shown in FIG. Next, at step 509, it is judged if the delay time Δt has elapsed. When the delay time Δt has not elapsed, the processing cycle is completed. On the other hand, when the delay time Δt has elapsed, the entire particulate filter 22 has SO._x Is determined to have started, and the routine proceeds to step 510, where the release start flag is set. Next, the routine proceeds to step 511. When the discharge start flag is set, the process jumps from step 506 to step 511 in the next processing cycle.
[0107]
  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, the entire particulate filter 22 isSO_xIs added to the elapsed time t from the start of the release action. Then in step 513SO_xIt is determined whether or not the release control is interrupted.SO_xWhen the release control is not interrupted, the routine proceeds to step 514 where the elapsed time t is equal to the target SO_xRelease time t_mIt is determined whether or not the value has been exceeded. t ≦ t_mIn the case of, the processing cycle is completed. In contrast, t> t_mAt step 515, the temperature raising control is stopped, and then at step 516, the rich process is stopped. Next, at step 517, SO_xThe release flag, the running flag, and the release start flag are reset. Next, the routine proceeds to step 518, where SO_xThe absorption amount ΣSOX and the elapsed time t are set to zero.
[0108]
That is, SO_x SO during the release action_x If the emission control is not interrupted, the entire particulate filter 22 is SO._x Target SO after the release action of_x Release time t_m SO until_x A release action takes place.
On the other hand, in step 513, SO_x When it is determined that the release control has been interrupted, the routine proceeds to step 519, where the SO_x Until the state in which the release control should be interrupted is released, SO_x When the emission control is interrupted, the SO is operated until the engine is restarted._x Release control is stopped. Next, at step 520, the release start flag is reset. At this time, the elapsed time t is the target SO._x Release time t_m The remaining time t is stored as it is.
[0109]
  Now, SO_xEven if the release control is interrupted, the running flag continues to be set. ThereforeSO_xWhen the state where the release control should be interrupted is released, the routine jumps from step 501 to step 505 to start the temperature rise control. At this time, the release start flag is reset, so in steps 507, 508 and 509, TF> TFXX. It is determined whether or not the delay time Δt has elapsed since the start. When the delay time Δt has elapsed since TF> TFXX, the routine proceeds to step 511 through step 510, where rich processing is started. Next, the routine proceeds to step 512, where the operation of adding the fixed time α to the elapsed time t is started. That is, SO_xTarget SO when release control is interrupted_xRelease time t_mThe remaining time t is the new target SO_xRelease time, SO_xThis new target SO unless the release control is interrupted again_xSO only for release time_xA release action takes place. This SO_xSO during the release action_xIf release control is interrupted again, SO_xThe new target SO described above when the state where the release control should be interrupted is released._xSO again for the remaining time of release_xA release action takes place.
[0110]
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, as the EGR rate (EGR gas amount / (EGR gas amount + intake air amount)) increases, the amount of smoke generated gradually increases and reaches a peak, and the EGR rate is further increased. This time, the amount of smoke generated decreases rapidly. This will be described with reference to FIG. 22 showing the relationship between the EGR rate and smoke when the degree of cooling of the EGR gas is changed. In FIG. 22, curve A shows the case where the EGR gas is cooled strongly and the EGR gas temperature is maintained at about 90 ° C., and curve B shows the 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.
[0111]
As shown by curve A in FIG. 22, when the EGR gas is cooled strongly, the amount of smoke generated peaks when the EGR rate is slightly lower than 50%. In this case, the EGR rate is increased to about 55% or more. If this is done, smoke will hardly occur. On the other hand, when the EGR gas is slightly cooled as shown by the curve B in FIG. 22, the amount of smoke generated peaks when the EGR rate is slightly higher than 50%. In this case, the EGR rate is approximately 65% or more. If it is made, smoke will hardly occur. Further, as shown by the curve C in FIG. 22, when the EGR gas is not forcibly cooled, the amount of smoke generated reaches a peak when the EGR rate is around 55%. In this case, the EGR rate is approximately 70%. If it is more than a percentage, smoke is hardly generated.
[0112]
As described above, when the EGR gas ratio is 55% or more, smoke is not generated because the endothermic action of the EGR gas does not cause the temperature of the fuel and the surrounding gas to be so high, that is, low-temperature combustion is performed. This is because hydrocarbons do not grow to soot.
This low temperature combustion suppresses generation of smoke, that is, emission of fine particles regardless of the air-fuel ratio, while NO._x It has the characteristic that the generation amount of can be reduced. That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but the combustion temperature is suppressed to a low temperature, so that the excessive fuel does not grow to the soot, and thus almost no smoke is generated. At this time, NO_x However, only a very small amount is generated. On the other hand, even when the average air-fuel ratio is lean, or even when the air-fuel ratio is the stoichiometric air-fuel ratio, a small amount of soot is produced if the combustion temperature is high, but the combustion temperature is suppressed to a low temperature under low-temperature combustion. Smoke hardly occurs, NO_x However, only a very small amount is generated.
[0113]
On the other hand, when this low-temperature combustion is performed, the temperature of the fuel and the surrounding gas decreases, but the exhaust gas temperature increases. This will be described with reference to FIGS. 23 (A) and 23 (B).
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) shows normal combustion. The relationship between the average gas temperature Tg in the combustion chamber 5 and the crank angle is shown. The solid line in FIG. 23B shows the relationship between the fuel and the surrounding gas temperature Tf and the crank angle when low-temperature combustion is performed, and the broken line in FIG. 23B shows normal combustion. The relationship between the fuel and the surrounding gas temperature Tf when broken and the crank angle is shown.
[0114]
When low-temperature combustion is performed, the amount of EGR gas is larger than when normal combustion is performed. Therefore, as shown in FIG. 23A, before compression top dead center, that is, during the compression process, a solid line The average gas temperature Tg at the time of low-temperature combustion indicated by is higher than the average gas temperature Tg at the time of normal combustion indicated by a broken line. At this time, as shown in FIG. 23B, the fuel and the surrounding gas temperature Tf are substantially the same as the average gas temperature Tg.
[0115]
Next, combustion is started near the compression top dead center. In this case, when low-temperature combustion is being performed, as shown by the solid line in FIG. 23B, the fuel and the surrounding gas temperature Tf are absorbed by the endothermic action of the EGR gas. It wo n’t be that expensive. On the other hand, when normal combustion is performed, since a large amount of oxygen exists around the fuel, the fuel and the surrounding gas temperature Tf become extremely high as shown by the broken line in FIG. . In this way, when normal combustion is performed, the temperature of the fuel and the surrounding gas temperature Tf is considerably higher than when low temperature combustion is performed, but the temperature of the other gases which occupy most is low temperature combustion. Therefore, the average gas in the combustion chamber 5 in the vicinity of the compression top dead center as shown in FIG. 23 (A) is lower than in the case where the normal combustion is performed. The temperature Tg is higher when low-temperature combustion is performed than when normal combustion is performed. As a result, as shown in FIG. 23A, the burned gas temperature 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. Therefore, when the low temperature combustion is performed, the exhaust gas temperature becomes high.
[0116]
However, when the required torque TQ of the engine is increased, that is, when the fuel injection amount is increased, the temperature of the fuel and the surrounding gas at the time of combustion is increased, so that it is difficult to perform low temperature combustion. That is, low-temperature combustion can be performed only when the engine is in a low load operation where the amount of heat generated by combustion is relatively small. 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 in which the amount of generated soot reaches a peak, that is, low temperature combustion can be performed. Region II shows an operation region in which only the normal combustion can be performed, ie, the second combustion in which the amount of inert gas in the combustion chamber is smaller than the amount of inert gas in which the amount of generated soot reaches a peak.
[0117]
FIG. 25 shows the target air-fuel ratio A / F when low temperature combustion is performed in the operation region I, and FIG. 26 shows the opening of the throttle valve 17 according to the required torque TQ when low temperature combustion is performed in the operation region I. The opening degree 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 and the like during normal combustion performed in the operation region II. 25 and 26, it is understood that when the low temperature combustion is performed in the operation region I, the EGR rate is 55% or more and the air-fuel ratio A / F is a lean air-fuel ratio of about 15.5 to 18.
[0118]
The particulate oxidation removal capability of the particulate filter 22 is reduced during engine low load operation when the exhaust gas temperature is lowered. However, when low-temperature combustion is performed during low engine load operation, the exhaust gas temperature rises as described above, and the amount of smoke generated, that is, the amount of discharged particulates is extremely reduced, so that the particulate filter 22 even during low engine load operation. Thus, it is possible to continuously oxidize and remove all the deposited fine particles. 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, release of active oxygen and NO occur without generating smoke._x NO from absorbent 61_x And SO_x Can be released. Furthermore, the temperature TF of the particulate filter 22 can be raised by switching from normal combustion to low temperature combustion during engine operation. That is, low temperature combustion can be used to raise the temperature of the particulate filter 22.
[0119]
【The invention's effect】
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 view showing a required torque of the engine.
FIG. 3 is a diagram showing a particulate filter.
FIG. 4 is a diagram for explaining an oxidizing action of fine particles.
FIG. 5 is a graph showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of the particulate filter.
FIG. 6 is an enlarged cross-sectional view of a partition wall of a particulate filter.
FIG. 7 is a time chart for explaining reproduction processing and the like.
FIG. 8 is a diagram for explaining injection control.
FIG. 9 NO_x It is a figure which shows the map of absorption amount A.
FIG. 10: NO_x Release flag and SO_x It is a flowchart for processing a release flag.
FIG. 11 is a flowchart for controlling the 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 intermediate reproduction control;
FIG. 15 is a diagram for explaining playback control.
FIG. 16 is a flowchart for executing a third embodiment of intermediate reproduction control;
FIG. 17 is a flowchart for executing a third embodiment of intermediate reproduction control;
FIG. 18 NO_x It is a flowchart for performing discharge control.
FIG. 19 is a flowchart for executing the reproduction control.
FIG. 20: SO_x It is a flowchart for performing discharge control.
FIG. 21: SO_x It is a flowchart for performing discharge control.
FIG. 22 is a diagram showing the amount of smoke generated.
FIG. 23 is a diagram showing the gas temperature and the like in the 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 changes in the throttle valve opening and the like.
[Explanation of symbols]
5 ... Combustion chamber
6 ... Fuel injection valve
22 ... Particulate filter

Claims (11)

A particulate filter for collecting particulates in the exhaust gas is arranged in the engine exhaust passage, and a noble metal catalyst is supported on the particulate filter , and combustion is continuously performed under a lean air-fuel ratio. In an internal combustion engine that can continuously oxidize and remove particulates deposited on the particulate filter without generating a bright flame during the operation, the particulate filter is used as a particulate filter depending on the operating condition of the engine. If pressure loss is hardly increased and particulate matter when the deposited particulate on the filter increases with particulate filter and a case where the pressure loss in the particulate filter is increased, unit time of deposition the particulate filter even if the amount of fine particles increases Amount of fine particles that can be removed by oxidation without causing a bright flame per contact The relationship with the temperature of the particulate filter is required, and the amount of particulate deposited on the particulate filter is calculated based on the amount of particulate that can be removed by oxidation determined from the temperature of the particulate filter and the amount of particulate discharged from the engine. Calculating means for detecting, pressure detecting means for detecting pressure loss in the particulate filter, and main regeneration for raising the temperature of the particulate filter to regenerate the particulate filter when the pressure loss detected by the detecting means exceeds a set value And the amount of accumulated particulates on the particulate filter calculated by the calculating means increases, and there is a possibility that the particulate filter is damaged by the oxidation reaction heat of the deposited particulates. Without exceeding the set value above Exhaust gas purifying apparatus comprising an intermediate regeneration means for raising the temperature of the particulate filter under a lean air-fuel ratio in order to reproduce the particulate filter even in the absence. An estimation means for estimating whether or not the amount of deposited fine particles on the particulate filter has exceeded a limit value that may cause damage to the particulate filter due to the oxidation reaction heat of the deposited fine particles, and the intermediate regeneration means comprises: When it is estimated that the amount of deposited fine particles on the particulate filter calculated by the calculating means exceeds the limit value, even if the pressure loss in the particulate filter hardly increases and does not exceed the set value, the particulate filter The exhaust gas purification device according to claim 1, wherein the temperature of the particulate filter is raised under a lean air-fuel ratio in order to regenerate the exhaust gas. When the engine is started, or when the engine operating time, the accumulated value of the engine speed, or the vehicle travel distance exceeds a predetermined value, the estimation means is the amount of deposited fine particles on the particulate filter. The exhaust gas purification device according to claim 2 , wherein the exhaust gas purification device estimates that the value exceeds the limit value . The intermediate reproduction means sets a target reproduction time required for reproduction when the particulate filter reproduction control is started, and sets the target reproduction time remaining at the time of interruption when reproduction control is resumed after interruption. 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 and the added time is set as a new target regeneration time . When there is excess oxygen in the surroundings, oxygen is taken in and retained, and when the surrounding oxygen concentration decreases, an active oxygen release agent that releases the retained oxygen in the form of active oxygen is carried on the particulate filter and released. The exhaust gas purifying apparatus according to claim 1 , wherein fine particles adhering to the particulate filter are oxidized by the active oxygen . The exhaust gas purifying apparatus according to claim 5 , wherein the active oxygen release agent is made of an alkali metal, an alkaline earth metal, a rare earth, or a transition metal . In addition to the above precious metal catalyst on the particulate filter, when the air-fuel ratio of the exhaust gas flowing into the particulate filter is lean, the air-fuel ratio of the exhaust gas that absorbs NO _x in the exhaust gas and flows into the particulate filter is the stoichiometric air-fuel ratio. or an exhaust gas purification device according to claim 1 carrying the _the NO _x absorbent to release the absorbed NO _x to become rich. The exhaust gas purification device according to claim 7 , wherein the NO _x absorbent is made of an alkali metal, an alkaline earth metal, a rare earth, or a transition metal . Claims the absorbed by and NO _x when it should be released from _the NO _x absorbent in _the NO _x absorbent equipped with _the NO _x releasing control means rich temporarily switching the air-fuel ratio of the exhaust gas flowing into the particulate filter from lean Item 8. The exhaust gas purifying device according to Item 7 . Rich, SO _x which is absorbed in the NO _x absorbent the air-fuel ratio of the exhaust gas flowing into the particulate filter together with the time to release from _the NO _x absorbent to increase the temperature of the particulate filter to release SO _x temperature from lean exhaust gas purifying apparatus according to claim 7 provided with the release of SO _x control means for switching the. The release of 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, when interrupted when release of SO _x control is resumed after interruption 11. The time required to raise the temperature of the particulate filter to the SO _x release temperature is added to the remaining time of the target SO _x release time in step S10, and the added time is used as a new target SO _x release time. The exhaust gas purification apparatus as described.

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