JP2009299572A - Exhaust emission control device for compression self-ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration in fuel economy by reducing fuel used for increasing a temperature of a filter and a SO<SB>X</SB>trap catalyst, in an exhaust emission control device for a compression self-ignition type internal combustion engine. <P>SOLUTION: The SO<SB>X</SB>trap catalyst 13 has properties in which SO<SB>X</SB>contained in exhaust gas is trapped when an air-fuel ratio of exhaust gas flowing into the SO<SB>X</SB>trap catalyst is lean, and the trapped SO<SB>X</SB>is diffused in the SO<SB>X</SB>trap catalyst to recover the SO<SB>X</SB>trap ability of the SO<SB>X</SB>trap catalyst when the temperature of the SO<SB>X</SB>trap catalyst is increased to a recovery start temperature or higher during a lean air-fuel ratio of exhaust gas. A SO<SB>X</SB>trap recovery process increasing the temperature of the SO<SB>X</SB>trap catalyst to recover the SO<SB>X</SB>trap ability of the SO<SB>X</SB>trap catalyst, and a filter regeneration process raising the temperature of a particulate filter to recover particulate matter trapping ability of a particulate filter 17 can be executed. The SO<SB>X</SB>recovery process is performed when the filter regeneration process is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for a compression self-ignition internal combustion engine.

_The NO _X storage catalyst with _the NO _X storage ability, the inclusion of SO _X in the exhaust gas flowing occludes the SO _{X, the} NO _X storage ability of the NO _X storage catalyst is reduced along with this It is known. Therefore, in order to prevent the SO _X flows into the NO _X storing catalyst, an internal combustion engine arranged to _the SO _X trap catalyst is known in the NO _X storage catalyst in the engine exhaust passage upstream of (e.g., I see Patent Document 1) .

In particular, the SO _X trap catalyst captures SO _X contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the SO _X trap catalyst is lean, and the SO _X trap catalyst has a lean exhaust air-fuel ratio. As the temperature rises, the trapped SO _X gradually diffuses into the SO _X trap catalyst. Internal Thus, _the SO _X trap also SO _X on the surface of the catalyst is trapped is SO _X trap ability of _the SO _X trap catalyst decreases, _the SO _X trap the temperature of the catalyst is raised SO _X and _the SO _X trap catalyst by diffusing to, it is possible to recover the SO _X trap ability of _the SO _X trap catalyst.

JP 2005-133610 A JP 2003-328727 A JP 2006-188985 A

Meanwhile, the exhaust gas discharged from the compression ignition type internal combustion engine includes particulate matter in addition of the NO _X or SO _X. In order to collect the particulate matter, a particulate filter (hereinafter simply referred to as “filter”) is provided in the engine exhaust passage of the compression ignition type internal combustion engine. However, in the filter, when the amount of accumulated particulate matter increases, the filter becomes clogged and resistance to the flow of exhaust gas increases. For this reason, generally, when the amount of particulate matter deposited on the filter increases, the temperature of the filter is increased. Thereby, the particulate matter deposited on the filter is oxidized and removed, and the resistance to the flow of the exhaust gas is kept low.

Here, whether the temperature of the filter is raised to oxidize and remove particulate matter deposited on the filter, or the temperature of the SO _X trap catalyst is raised to restore the SO _X trap catalyst's SO _X trapping ability, Fuel will be consumed directly or indirectly due to temperature. Therefore, if the temperature rise of the filter and the temperature rise of the SO _X trap catalyst are executed at different timings, the fuel consumption is deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress the deterioration of fuel consumption by reducing the fuel used for raising the temperature of the filter and the SO _X trap catalyst in an exhaust purification device of a compression self-ignition internal combustion engine.

In order to solve the above problems, in the first invention, an SO _X trap catalyst that is disposed in the engine exhaust passage and captures SO _X contained in the exhaust gas, and an exhaust downstream side of the SO _X trap catalyst are provided. And a particulate filter that collects particulate matter contained in the exhaust gas, and the SO _X trap catalyst is an exhaust gas when the air-fuel ratio of the exhaust gas flowing into the SO _X trap catalyst is lean the SO _X captured contained in the diffusion temperature air-fuel ratio is lean under _the SO _X trap catalyst in the exhaust gas is raised above recovery start temperature, captured SO _X is inside the _the SO _X trap catalyst to _the SO _X trap has a property of _the SO _X trap ability is restored catalyst, _the SO _X trap _the SO _X trap ability temperature recovery initiation temperature than the _the SO _X trap catalyst in order to recover the catalyst And _the SO _X trap recovery process is raised to above, filter regeneration to oxidize and remove the particulate matter deposited on the particulate filter by raising the temperature of the particulate filter in order to recover the particulate matter trapping ability of the particulate filter is capable of executing a process, sO _X recovery process was performed during execution of the filter regeneration process, the exhaust purification device of compression ignition type internal combustion engine is provided.
According to the first invention, the SO _X recovery process is performed simultaneously with the filter regeneration process. As a result, the heat used to raise the temperature of the SO _X trap catalyst in the SO _X recovery process also flows into the particulate filter. For this reason, the amount of fuel used to raise the temperature of the particulate filter to perform the filter regeneration process is reduced.

In the second invention, in the first invention, to estimate the particulate matter deposit amount estimation means for estimating the deposition amount of the particulate material into the particulate filter, the SO _X trapped amount of the _the SO _X trap catalyst SO _X trap amount estimation means, and the filter regeneration process is executed when the amount of particulate matter deposited on the particulate filter exceeds an allowable amount, and the SO _X trap recovery process is performed by the SO _X trap catalyst SO. be more than the amount _{that X} trapped amount reaches a predetermined done when the filter regeneration process is being executed, also the filter regeneration SO _X trapped amount of _the SO _X trap catalyst is not more predetermined amount or more It is not performed when processing is not being executed.

In the third invention, in the first or second invention, when the SO _X trap recovery process and the filter regeneration process are simultaneously performed and then the SO _X trap recovery process ends first, the SO _X trap catalyst The temperature increase is stopped and fuel is added only from the downstream fuel addition device.

In the fourth invention, in the first or second invention, when the SO _X trap recovery process and the filter regeneration process are simultaneously performed, and the SO _X trap recovery process ends first, the filter regeneration process is performed. maintaining the temperature increase of _the SO _X trap catalyst until the end.

In a fifth aspect, in the first to fourth any one invention of the _the SO _X trap catalyst, when the temperature of _the SO _X trap catalyst is higher than a high SO _X release limit temperature than the recovery start temperature, has the property of releasing the captured SO _X, when performing the above _the SO _X trap recovery process, heating target temperature of _the SO _X trap catalyst is substantially the same upper limit temperature as the SO _X release temperature limit.

According to a sixth aspect, in the fifth aspect, the upper limit temperature is lowered as the SO _X trap amount of the SO _X trap catalyst increases.

In the seventh invention, in any one of the first to fourth inventions, when performing the SO _X trap recovery process, the temperature is raised to a temperature equal to or lower than the transpiration start temperature of the substance constituting the SO _X trap catalyst.

According to the present invention, since the SO _X recovery process is performed simultaneously with the filter regeneration process, the amount of fuel used to raise the temperature of the particulate filter is reduced, so that deterioration of fuel consumption is suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 shows an overall view of a compression self-ignition internal combustion engine. Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, and 5 is an exhaust manifold. Respectively. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 through the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 8. A throttle valve 9 driven by a step motor is arranged in the intake duct 6, and a cooling device 10 for cooling intake air flowing in the intake duct 6 is arranged around the intake duct 6. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 10 and the intake air is cooled by the engine cooling water.

On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the inlet of the upstream catalytic converter 11. In the upstream catalytic converter 11, an oxidation catalyst 12 is disposed on the upstream side, and an SO _X trap catalyst 13 is disposed on the downstream side. The outlet of the upstream catalytic converter 11 is connected to the downstream catalytic converter 15 via the exhaust pipe 14. In the downstream catalytic converter, a NO _x storage catalyst 16 is disposed on the upstream side, and a particulate filter (hereinafter simply referred to as “filter”) 17 is disposed on the downstream side. The exhaust pipe 14 is provided with a fuel supply device 18 for supplying, for example, fuel into the exhaust gas flowing through the exhaust pipe 14.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 20, and an electronically controlled EGR control valve 21 is disposed in the EGR passage 20. A cooling device 22 for cooling the EGR gas flowing in the EGR passage 20 is disposed around the EGR passage 20. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 22, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 3 is connected to a common rail 24 via a fuel supply pipe 23. Fuel is supplied into the common rail 24 from an electronically controlled fuel pump 25 with variable discharge amount, and the fuel supplied into the common rail 24 is supplied to the fuel injection valve 3 through each fuel supply pipe 23.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. 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. It comprises. 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. . Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °.

Temperature sensor 43 for detecting the temperature of _the SO _X trap catalyst 13 is attached to _the SO _X trap catalyst 13, the temperature sensor 44 for detecting the temperature of the filter 17 is attached to the filter 17. The output signals of these temperature sensors 43 and 44 are input to the input port 35 via the corresponding AD converters 37, respectively. Further, a differential pressure sensor 45 for detecting the differential pressure across the filter 17 is attached to the filter 17, and an output signal of the differential pressure sensor 45 is input to the input port 35 via the corresponding AD converter 37. Is done. On the other hand, the output port 36 is connected to the fuel injection valve 3, the step motor for driving the throttle valve 9, the fuel supply device 18, the EGR control valve 21, and the fuel pump 25 through corresponding drive circuits 38.

  FIG. 2 shows another embodiment of a compression self-ignition internal combustion engine. In this embodiment, in addition to a fuel supply device (hereinafter referred to as “downstream fuel supply device”) 18 attached to the exhaust pipe 14, for example, fuel is supplied into the manifold branch pipe 5 a of the first cylinder of the exhaust manifold 5. A fuel supply device (hereinafter referred to as “upstream fuel supply device”) 26 is provided.

In the above-described embodiment, the exhaust purification elements are arranged in the order of the oxidation catalyst 12, the SO _X trap catalyst 13, the NO _X storage catalyst 16, and the filter 17 in the engine exhaust passage. Absent. That is, the exhaust purification elements may be arranged in any order as long as the SO _X trap catalyst, the NO _X storage catalyst, and the filter are arranged in this order or in the order of the SO _X trap catalyst, the filter, and the NO _X storage catalyst. For example, the SO _X trap catalyst, NO _X storage catalyst, oxidation catalyst, and filter may be arranged in this order from the upstream side. Further, as shown in FIG. 3, a filter 17 ′ having NO _X storage capability may be used instead of the filter. In this case, the NO _x storage catalyst may not be provided in the engine exhaust passage.

  First, the filter 17 shown in FIGS. 1 and 2 will be described. 4A and 4B show the structure of the filter 17. 4A shows a front view of the filter 17, and FIG. 4B shows a side cross-sectional view of the filter 17. As shown in FIGS. 4A and 4B, the filter 17 has a honeycomb structure and includes a plurality of exhaust flow passages 60 and 61 extending in parallel with each other. These exhaust flow passages include an exhaust gas inflow passage 60 whose downstream end is closed by a plug 62 and an exhaust gas outflow passage 61 whose upstream end is closed by a plug 63. In addition, the hatched part in FIG. Therefore, the exhaust gas inflow passages 60 and the exhaust gas outflow passages 61 are alternately arranged via the thin partition walls 64. In other words, in the exhaust gas inflow passage 60 and the exhaust gas outflow passage 61, each exhaust gas inflow passage 60 is surrounded by four exhaust gas outflow passages 61, and each exhaust gas outflow passage 61 is surrounded by four exhaust gas inflow passages 60. Arranged so that.

  The filter 17 is made of a porous material such as cordierite. Therefore, the exhaust gas flowing into the exhaust gas inflow passage 60 passes through the surrounding partition wall 64 as shown by an arrow in FIG. And flows into the adjacent exhaust gas outflow passage 61. As described above, the particulate matter contained in the exhaust gas is collected by the filter 17 while the exhaust gas flows through the partition wall 64.

Next, the NO _X storage catalyst 16 shown in FIGS. 1 and 2 will be briefly described. In these the NO _X storing catalyst 16, a carrier layer made of monolithic carrier or pellets carrier on, for example, alumina of the three-dimensional network structure is provided, which is supported noble metal catalyst is dispersed on the surface of the the carrier layer, Further, a layer of NO _x storage agent is formed on the surface of the carrier layer.

In this embodiment, platinum Pt is used as a noble metal catalyst, and the constituents of the NO _x storage agent include, for example, alkali metals such as potassium K, sodium Na and cesium Cs, alkaline earths such as barium Ba and calcium Ca, At least one selected from rare earths such as lanthanum La and yttrium Y is used.

Engine intake passage, when referred to as the air-fuel ratio of the ratio of the supplied air and fuel into the combustion chamber 2 and the NO _X storing catalyst 16 upstream of the exhaust passage (hydrocarbon) exhaust gas, the NO _X storing catalyst 16 is the exhaust gas When the air-fuel ratio is lean, NO _x is occluded, and the absorbed NO _x is released when the oxygen concentration in the exhaust gas decreases. In a compression self-ignition internal combustion engine, combustion is performed under a lean air-fuel ratio, and therefore, exhaust gas discharged from the engine body 1 is stored in the NO _X storage catalyst 16. However, occlusion when burned under a lean air-fuel ratio is continued, it would be _the NO _X storage ability of the NO _X storage catalyst 16 is saturated during the NO _X by the NO _X storing catalyst 16 and thus You will not be able to. Therefore, in this embodiment, before the NO _X storage capacity of the NO _X storage catalyst 16 is saturated, the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst 16 is temporarily reduced by supplying fuel from the fuel supply device 18, for example. to the rich, thereby so that to release NO _X from the NO _X storing catalyst 16.

Meanwhile, the exhaust gas contains SO _{X, the} NO _X storage ability of the NO _X storage catalyst 16 when the SO _X flows into the NO _X storing catalyst 16 is reduced. That is, the NO _X storage catalyst 16 can store not only NO _X in the exhaust gas but also SO _X , and the SO _X stored in the NO _X storage catalyst 16 is difficult to be released. In general, in order to release the SO _X occluded in the NO _X storing catalyst 16 is necessary to the temperature of the NO _X storage catalyst 16 to a high temperature with the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst 16 rich There is. Therefore, from the NO _X storing catalyst 16 attempts to release the SO _X, becomes necessary large amount of fuel to the the NO _X storing catalyst 16 to a high temperature. Further, the SO _x released from the NO _x absorption catalyst 16 is discharged into the atmosphere, which is not preferable.

Therefore, in the present invention to trap SO _X contained in the exhaust gas by this _the SO _X trap catalyst 13 by arranging _the SO _X trap catalyst 13 upstream of the NO _X storing catalyst 16, SO _X thereby the NO _X storage catalyst 16 Does not flow in. Next, the SO _X trap catalyst 13 will be described.

The SO _X trap catalyst 13 is made of, for example, a monolith catalyst having a honeycomb structure, and has a large number of exhaust gas flow holes extending straight in the axial direction of the SO _X trap catalyst 13. When the SO _X trap catalyst 13 is formed from a monolith catalyst having a honeycomb structure as described above, a catalyst carrier made of alumina, for example, is supported on the inner peripheral wall surface of each exhaust gas circulation hole. FIG. A cross section of 50 surface portions is shown schematically. As shown in FIG. 5, a coat layer 51 is formed on the surface of the catalyst carrier 50, and a noble metal catalyst 52 is dispersed and supported on the surface of the coat layer 51.

In this embodiment, platinum is used as the noble metal catalyst 52, and the components constituting the coating layer 51 are, for example, alkali metals such as potassium K, sodium Na, and cesium Cs, and alkaline earth metals such as barium Ba and calcium Ca. At least one selected from rare earths such as lanthanum La and yttrium Y is used. That is, the coat layer 51 of the SO _X trap catalyst 13 exhibits strong basicity. Note that the noble metal catalyst 52 does not necessarily have to be supported on the SO _X trap catalyst 13.

Now, SO _x contained in the exhaust gas, that is, SO ₂ is oxidized in the platinum Pt 52 as shown in FIG. That is, SO ₂ diffuses into the coat layer 51 in the form of sulfate ions SO ₄ ²⁻ to form sulfate. As described above, the coat layer 51 has a strong basicity. Therefore, as shown in FIG. 5, a part of SO ₂ contained in the exhaust gas is directly captured in the coat layer 51.

Shading shows the concentration of trapped SO _X in the coat layer 51 in FIG. As can be seen from FIG. 5, the SO _X concentration in the coat layer 51 is highest near the surface of the coat layer 51 and gradually decreases toward the back. When the SO _X concentration in the vicinity of the surface of the coat layer 51 is increased, the basicity of the surface of the coat layer 51 is weakened and the SO _X capturing ability is weakened. Here, if the ratio of SO _X trapped in _the SO _X trap catalyst 13 within the SO _X contained in the exhaust gas is referred to as _the SO _X trap rate, along with it if weakens the basicity of the surface of the coating layer 51 The SO _X trap rate will decrease.

FIG. 6 shows the temporal change in the SO _X trap rate. As shown in FIG. 6, the SO _X trap rate is close to 100% at first, but rapidly decreases with time. Therefore, in the present invention, as shown in FIG. 7, when the SO _X trap rate is lower than a predetermined rate, the temperature increase control for increasing the temperature of the SO _X trap catalyst 13 under the lean air-fuel ratio of the exhaust gas. Thus, the SO _X trap rate is recovered (SO _X trap recovery process).

That is, when the temperature of the SO _X trap catalyst 13 is raised to the recovery start temperature (for example, the melting point of the component constituting the coat layer 51) or higher when the air-fuel ratio of the exhaust gas is lean, the vicinity of the surface in the coat layer 51 is reached. The SO _x intensively present in the coating layer diffuses toward the back of the coat layer 51 so that the SO _x concentration in the coat layer 51 becomes uniform. That is, the nitrate produced in the coat layer 51 changes from an unstable state concentrated near the surface of the coat layer 51 to a stable state uniformly dispersed throughout the coat layer 51. When SO _x existing in the vicinity of the surface in the coat layer 51 diffuses toward the inner part of the coat layer 51, the SO _x concentration in the vicinity of the surface of the coat layer 51 decreases, and thus the temperature increase control of the SO _x trap catalyst 13 is performed. When (recovery control) is completed, the SO _X trap rate (SO _X trap capability) is recovered as shown in FIG.

In the present invention, basically, it is considered that the SO _X trap catalyst 13 is used as it is without replacement after the vehicle is purchased until it is scrapped. In recent years, in particular, the amount of sulfur contained in the fuel has been reduced. Therefore, if the capacity of the SO _X trap catalyst 13 is increased to some extent, the SO _X trap catalyst 13 can be used as it is until it is scrapped without being replaced. Can do. For example the capacity of _the SO _X trap catalyst 13 when the useful travel distance of the vehicle to 500,000 km, the running distance with high _the SO _X trap rate without the recovery control of _the SO _X trap catalyst 13 to about 250,000 km SO _X It is said that the capacity can continue to capture. In this case, the first recovery control is performed when the travel distance is about 250,000 km.

Various methods can be used to raise the temperature of the SO _X trap catalyst 13. For example, the injection timing from the fuel injection valve 3 is retarded until after the compression top dead center. Thereby, the afterburn period in the combustion chamber 2 is lengthened, and thus the temperature of the exhaust gas discharged from the engine body 1 is increased. Alternatively, in performing fuel injection from the fuel injection valve 3, in addition to the main injection performed near the compression top dead center, pilot injection is performed before the main injection. As a result, the total amount of fuel injection is increased or additional combustion is caused by additional injection, and the temperature of the exhaust gas rises. Thus, when the temperature of the exhaust gas discharged from the engine body 1 rises, the temperature of the SO _X trap catalyst 13 is raised accordingly.

Furthermore, in performing fuel injection from the fuel injection valve 3, in addition to main injection performed near the compression top dead center, post injection is performed after main injection. In this case, most of the fuel injected by the post injection is discharged into the exhaust passage in the form of unburned HC without burning, and flows into the SO _X trap catalyst 13. Alternatively, in the internal combustion engine shown in FIG. 2, the fuel is supplied from the fuel supply device 26. Also in this case, the fuel supplied from the fuel supply device 26 flows into the SO _X trap catalyst 13 in the form of unburned HC. Unburned HC flowing thus into _the SO _X trap catalyst 13 is oxidized by the excess oxygen in _the SO _X trap catalyst 13, the temperature of _the SO _X trap catalyst 13 is raised by the heat of oxidation reaction generated at this time. In the following description, a case where the temperature rise of the SO _X trap catalyst 13 is performed by supplying fuel from the fuel supply device 26 will be described as an example.

  On the other hand, the particulate matter contained in the exhaust gas is collected by the filter 17 as described above, but the filter 17 cannot collect the particulate matter indefinitely. Particulate matter collected by the filter 17 gradually accumulates on the filter 17, and when the amount of the particulate matter deposited increases, the filter 17 becomes clogged and resistance to the flow of exhaust gas increases. End up. As a result, the engine output is reduced.

  Therefore, when the amount of particulate matter deposited increases, the deposited particulate matter must be removed. In this case, when the temperature of the filter 17 is raised to the particulate matter combustion start temperature (for example, about 600 ° C.) under excess air, the deposited particulate matter is oxidized and removed.

  Therefore, in the present embodiment, when the amount of particulate matter deposited on the filter 17 exceeds the allowable amount, the temperature of the filter 17 is increased to the particulate matter combustion start temperature or higher under the lean air-fuel ratio of the exhaust gas. The particulate matter thus deposited is removed by oxidation (regeneration processing of the filter 17).

  When the temperature of the filter 17 is increased, in this embodiment, fuel is supplied from the fuel supply device 18 into the exhaust gas. The fuel supplied from the fuel supply device 18 flows into the filter 17 in the form of unburned HC. Unburned HC flowing into the filter 17 is oxidized by excess oxygen in the filter 17, and the temperature of the filter 17 is raised by the oxidation reaction heat generated at this time.

By the way, as described above, the recovery process of the SO _X trap catalyst 13 is performed when the SO _X trap rate falls below a predetermined rate, while the regeneration process of the filter 17 is performed in the form of particles deposited on the filter 17. This is done when the amount of the substance exceeds the allowable amount. For this reason, these processes are usually performed at different timings.

However, in any of these processes, it is necessary to increase the temperature of the filter 17 or the SO _X trap catalyst 13, and fuel is consumed when the temperature is increased.

Since the temperature of the exhaust gas in the case of raising the temperature of _the SO _X trap catalyst 13 is discharged from _the SO _X trap catalyst 13 will be caused to rise, disposed on the exhaust downstream side of _the SO _X trap catalyst 13 The temperature of the filtered filter 17 is also raised. In this case, considering that the temperature of the exhaust gas decreases while the exhaust gas flows from the SO _X trap catalyst 13 to the filter 17, the temperature of the filter 17 does not rise to the particulate matter combustion start temperature. If a small amount of fuel is supplied from the supply device 18 into the exhaust gas, the temperature of the filter 17 can be raised to the particulate matter combustion start temperature. That is, by performing the recovery process of the SO _X trap catalyst 13 and the regeneration process of the filter 17 at the same time, the amount of fuel used for raising the temperature can be suppressed as compared with the case where these processes are performed separately.

Further, when the temperature of the filter 17 is increased by supplying fuel from the fuel supply device 18 provided on the exhaust downstream side of the SO _X trap catalyst 13 as in the present embodiment, the sulfur component in the fuel is SO. Without being captured by the _X trap catalyst 13, it directly flows into the NO _X storage catalyst 16 and the filter 17. For this reason, although the amount is small, SO _X is stored in the NO _X storage catalyst 16 every time the temperature of the filter 17 is increased.

In contrast, as described above, the fuel supply is performed to raise the temperature of the filter 17 to the particulate fuel start temperature by simultaneously performing the recovery process of the SO _X trap catalyst 13 and the regeneration process of the filter 17. The fuel to be supplied from the device 18 can be reduced. Therefore, the SO _X stored in the NO _X storage catalyst 16 when the regeneration process of the filter 17 is performed is reduced.

  Next, various controls of the present embodiment will be specifically described with reference to FIGS. First, the regeneration control of the filter 17 will be described. As described above, the regeneration process of the filter 17 is performed when the amount of particulate matter deposited on the filter 17 exceeds an allowable amount. In the present embodiment, the amount of particulate matter deposited on the filter 17 is estimated based on the differential pressure across the filter 17 detected by the differential pressure sensor 45. That is, when the permissible amount of particulate matter deposited on the filter 17 is exceeded, the differential pressure across the filter 17 becomes higher than the permissible value corresponding to this permissible amount. If the value is equal to or smaller than the value, the regeneration process of the filter 17 is not executed, and the regeneration process of the filter 17 is executed when the differential pressure across the filter 17 becomes higher than the allowable value.

On the other hand, the recovery process of _the SO _X trap catalyst 13 is basically performed when the SO _X trap amount of _the SO _X trap catalyst 13 becomes a predetermined trapped amount or more. That is, it is determined that _the SO _X trap rate has fallen below a predetermined rate when it exceeds the amount of SO _X trapped amount reaches a predetermined of _the SO _X trap catalyst 13, to recover _the SO _X trap rate at this time Therefore, the SO _X trap catalyst 13 is recovered by increasing the temperature of the SO _X trap catalyst 13 while the air-fuel ratio of the exhaust gas is lean. Therefore, first, a method for calculating the SO _X trap amount of the SO _X trap catalyst 13 will be described.

The fuel contains sulfur in a certain ratio, thus SO _X amount contained in the exhaust gas, i.e. SO _X amount trapped by the SO _X trap catalyst 13, is proportional to the fuel injection amount. The fuel injection amount is a function of the required torque and the engine speed, and therefore the SO _X amount captured by the SO _X trap catalyst 13 is also a function of the required torque and the engine speed. Advance in the ROM32 in the form of a map as in the embodiment shown in FIG. 8 (A) as a function of the SO _X amount SOXA is required torque TQ and engine speed N trapped per unit time in _the SO _X trap catalyst 13 It is remembered.

Also, the lubricating oil contain sulfur in a proportion, amount of lubrication oil burned in the combustion chamber 2, i.e. SO _X trapped be included in the exhaust gas to _the SO _X trap catalyst 13 The amount is also a function of the required torque and the engine speed. In this embodiment, the SO _X amount SOXB contained in the lubricating oil and captured per unit time by the SO _X trap catalyst 13 is a map as shown in FIG. 8B as a function of the required torque TQ and the engine speed N. It is stored in advance in the ROM32 in the form of, SO _X trapped amount ShigumaSOX of _the SO _X trap catalyst 13 is calculated by integrating the sum of the SO _X amount SOXA and SO _X amount SOXB (ΣSOX = ΣSOXA + ΣSOXB) .

Next, the predetermined capture amount SO (n) will be described. In the present embodiment, as shown in FIG. 8C, the relationship between the SO _X amount ΣSOX and a predetermined SO _X amount SO (n) when the SO _X trap catalyst 13 is to be recovered is stored in advance. When the SO _X amount ΣSOX exceeds a predetermined SO (n) (n = 1, 2, 3,...), The SO _X trap catalyst 13 is recovered. In FIG. 8C, n indicates the number of recovery processes. As can be seen from FIG. 8C, the predetermined amount SO (n) is increased as the number of recovery processes n for recovering the SO _X trap rate increases, and this predetermined amount SO (n) is increased. The increase ratio decreases as the number of times n increases. That is, the increase rate of SO (3) with respect to SO (2) is smaller than the increase rate of SO (2) with respect to SO (1).

As described above, in the present embodiment, the recovery process of _the SO _X trap catalyst 13 is performed when the SO _X trapped amount ΣSOX of _the SO _X trap catalyst 13 becomes a predetermined amount of trapped SO (n) or It is not necessarily performed immediately after the amount of capture SO (n) is greater than or equal to the predetermined amount. That is, after the SO _X trap amount ΣSOX becomes equal to or greater than the predetermined trap amount SO (n), the recovery process of the SO _X trap catalyst 13 is also started when the regeneration process of the filter 17 is started. In other words, even if the SO _X trapping amount ΣSOX is equal to or larger than the predetermined trapping amount SO (n), the recovery processing of the SO _X trap catalyst 13 is waited until the regeneration processing of the filter 17 is started.

Thus, when the regeneration process of the filter 17 and the recovery process of the SO _X trap catalyst 13 are performed at the same time, the amount necessary for making the temperature of the SO _X trap catalyst 13 higher than the recovery temperature from the upstream side fuel supply device 26. From the downstream fuel supply device 18, an amount of fuel necessary to raise the temperature of the filter 17 to the particulate matter oxidation start temperature or higher is supplied. However, the amount of fuel supplied from the downstream fuel supply device 18 is reduced as compared with the case where the regeneration process of the filter 17 and the recovery process of the SO _X trap catalyst 13 are not performed simultaneously.

  The regeneration period of the filter 17, that is, the period during which the temperature of the filter 17 is raised to the particulate matter oxidation start temperature or higher is calculated according to the amount of particulate matter deposited on the filter 17 and the usage period of the filter 17. Is done. For example, as the amount of particulate matter deposited on the filter 17 increases, the time required to completely oxidize and remove the particulate matter becomes longer. Therefore, the regeneration process period becomes longer, and the use period of the filter 17 becomes longer. Since the oxidizing ability of platinum Pt or the like in the filter 17 is reduced and it takes time to oxidize and remove the particulate matter, the regeneration treatment period becomes long.

On the other hand, the recovery processing period of SO _X trap catalyst 13, i.e. SO temperature period that is raised to above the recovery temperature of the _X trap catalyst 13, _the SO _X trap recovery treatment of the catalyst 13 times or SO _X trap catalyst 13 It is calculated according to the SO _X trapping amount, the components constituting the coat layer 51, and the like.

Thus, since the regeneration process period of the filter 17 and the recovery process period of the SO _X trap catalyst 13 change depending on the situation, the recovery process period of the SO _X trap catalyst 13 is longer than the regeneration process period of the filter 17. In some cases, the regeneration process period of the filter 17 may be longer than the recovery process period of the SO _X trap catalyst 13. When the recovery process period of the SO _X trap catalyst 13 is longer than the regeneration process period of the filter 17, as shown in FIG. 9A, after the regeneration process of the filter 17 is completed, the downstream fuel supply device 18. The fuel supply from is stopped, and the fuel supply from the upstream fuel supply device 26 is maintained as it is.

On the other hand, when the regeneration process period of the filter 17 is longer than the recovery process period of the SO _X trap catalyst 13, the fuel supply from the upstream fuel supply device 26 is stopped as shown in FIG. The amount of fuel supplied from the downstream fuel supply device 18 is increased. This, SO by the end of the heating process of the _X trap catalyst 13 (recovery process), decrease the temperature of the exhaust gas flowing out from _the SO _X trap catalyst 13, therefore the temperature of the exhaust gas flowing into the filter 17 decreases The amount of fuel supplied from the downstream fuel supply device 18 is increased by the amount of decrease in the temperature of the exhaust gas.

Incidentally, in the above description, the recovery process of _the SO _X trap catalyst 13 has been described as to raise the temperature of _the SO _X trap catalyst 13 to over recovery temperature, more precisely, _the SO _X trap of _the SO _X trap catalyst 13 In order to recover the rate, it is necessary to raise the temperature of the SO _X trap catalyst 13 to a temperature between the recovery process lower limit temperature and the recovery process upper limit temperature. Here, the recovery process lower limit temperature is the melting point of the component constituting the coat layer 51 of the SO _X trap catalyst 13, and as shown in FIG. 10, the recovery process lower limit temperature increases as the SO _X trap amount of the SO _X trap catalyst 13 increases. Also rises.

On the other hand, the recovery process limit temperature, increasing the temperature of the more _the SO _X trap catalyst 13, regardless of the air-fuel ratio of the exhaust gas flowing through the _the SO _X trap catalyst 13, the SO _X is released from _the SO _X trap catalyst 13 It is a temperature that will end up. As shown in FIG. 10, the recovery process maximum temperature and SO _X trap amount increases in _the SO _X trap catalyst 13 is reduced. Depending on the components constituting the coating layer 51 of _the SO _X trap catalyst 13, the coating layer 51 before the SO _X from Raising the temperature of _the SO _X trap catalyst 13 _the SO _X trap catalyst 13 from being released The component itself may evaporate. In this case, the limit temperature at which such transpiration does not occur is the recovery process upper limit temperature.

As described above, when performing the recovery process of the SO _X trap catalyst 13, the recovery process lower limit temperature and the recovery process upper limit temperature exist, and therefore it is necessary to perform the temperature increase process at a temperature between them. The higher the temperature of the SO _X trap catalyst 13 is, the more quickly the SO _X trap rate can be recovered, and the amount of SO _X that can be captured after the recovery process can be increased. Therefore, in the present embodiment, when the recovery process of the SO _X trap catalyst 13 is performed, the temperature of the SO _X trap catalyst 13 is increased to a temperature near the upper limit temperature of the recovery process. Therefore, in the present embodiment, and changing the temperature of _the SO _X trap catalyst 13 in the recovery process depending on the SO _X trapped amount of _the SO _X trap catalyst 13.

In the above embodiment, when the recovery process of the SO _X trap catalyst 13 is performed, the temperature of the SO _X trap catalyst 13 is raised to the vicinity of the upper limit temperature of the recovery process. For example, the recovery process of _the SO _X trap catalyst 13, may be to maintain the temperature of _the SO _X trap catalyst 13 to an intermediate temperature and recovery upper temperature limit and recovery minimum temperature. In this case, there is no need to change the target temperature of _the SO _X trap catalyst 13 at the time of recovery process in accordance with the SO _X trapped amount.

Next, a recovery / regeneration control control routine for executing the recovery process of the SO _X trap catalyst 13 and the regeneration process of the filter 17 will be described with reference to FIGS. The illustrated control routine is performed by interruption at regular time intervals.

Referring to FIGS. 11 and 12, first, in step S10, it is determined whether or not the recovery / regeneration processing flag X is 1. The recovery / regeneration flag X is a flag that is set to 1 when the recovery process of the SO _X trap catalyst 13 and the regeneration process of the filter 17 are being executed, and is set to 0 otherwise. When it is determined that the recovery / reproduction process has not been executed, the process proceeds to step S11. In step S <b> 11, the differential pressure sensor 45 detects the differential pressure ΔP before and after the filter 17. Next, at step S12, the SO _X trap amount ΣSOX is calculated based on the required torque TQ, the engine speed N, and the like as described above.

Next, in steps S13 and S14, whether or not the regeneration processing execution condition for the filter 17 is satisfied, for example, whether or not the differential pressure ΔP across the filter 17 is larger than the allowable value PX, and the recovery of the SO _X trap catalyst 13 It is determined whether or not the processing execution condition is satisfied, for example, whether or not the SO _X trap amount ΣSOX is equal to or greater than a predetermined trap amount. If it is determined in steps S13 and S14 that the conditions for executing the regeneration process for the filter 17 are not satisfied, the control routine is terminated, and the regeneration process for the filter 17 and the recovery process for the SO _X trap catalyst 13 are not executed.

On the other hand, if it is determined in steps S13 and S14 that the regeneration process execution condition for the filter 17 is satisfied but the recovery process execution condition for the SO _X trap catalyst 13 is not satisfied, the process proceeds to step S15. In step S15, the fuel amount to be supplied from the downstream fuel supply device 18 is calculated, and then in step S16, fuel is supplied from the downstream fuel supply device 18 by the fuel supply amount calculated in step S15. Thereby, the temperature of the filter 17 is raised and the regeneration process of the filter 17 is performed.

In steps S13 and S14, even if the recovery process execution condition for the SO _X trap catalyst 13 is satisfied, the control routine is terminated if the regeneration process execution condition for the filter 17 is not satisfied. The recovery process of the SO _X trap catalyst 13 is made to wait until the regeneration process execution condition of the filter 17 is satisfied. Thereafter, the regeneration process execution condition of the filter 17 is satisfied, and if it is determined that both the regeneration process execution condition of the filter 17 and the recovery process execution condition of the SO _X trap catalyst 13 are satisfied, the process proceeds to step S17. . In step S17, the recovery / reproduction processing flag X is set to 1. Next, in step S18, the target temperature of _the SO _X trap catalyst 13 when performing the recovery process of _the SO _X trap catalyst 13 is calculated. This target temperature is calculated based on, for example, a map as shown in FIG.

Next, in step S19, the amount of fuel to be supplied from the upstream fuel supply device 26 is calculated. The amount of fuel to be supplied from the upstream fuel supply device 26 is calculated based on the target temperature calculated in step S18 and the temperature of the SO _X trap catalyst 13 detected by the temperature sensor 43. Next, in step S20, the amount of fuel to be supplied from the downstream fuel supply device 18 is calculated. The amount of fuel to be supplied from the downstream fuel supply device 26 includes the fuel supply amount from the upstream fuel supply device 26 calculated in step S19 and the target temperature of the filter 17 (for example, the particulate matter oxidation start temperature of the filter 17). ) And the temperature of the filter 17 detected by the temperature sensor 44. Next, in step S21, fuel is supplied from both the fuel supply devices 18, 26 by the fuel supply amount calculated in step S19 and step S20, and the control routine is terminated.

In the next control routine, it is determined in step S10 that the recovery / regeneration processing flag X is 1, and the process proceeds to steps S22, S23, and S24. In step S22 to S24, whether the recovery process end condition of _the SO _X trap catalyst 13 is satisfied, for example, whether or not a predetermined time from the recovery processing start of _the SO _X trap catalyst 13 has passed, and the filter 17 It is determined whether or not the recovery process end condition is satisfied, for example, whether or not the differential pressure across the filter 17 detected by the differential pressure sensor 45 is equal to or less than a predetermined value.

If it is determined in steps S22 to S24 that the recovery process end condition for the SO _X trap catalyst 13 is not satisfied and the regeneration process end condition for the filter 17 is not satisfied, the process proceeds to step S19. Fuel is supplied from the fuel supply devices 18 and 26. On the other hand, when it is determined that the recovery process end condition for the SO _X trap catalyst 13 is not satisfied but the regeneration process end condition for the filter 17 is satisfied, the process proceeds to step S25. In step S25, the fuel supply from the downstream fuel supply device 18 is terminated. Next, in step S26, the fuel to be supplied from the upstream side fuel supply device 26 based on the target temperature calculated in step S18 and the temperature of the SO _X trap catalyst 13 detected by the temperature sensor 43 as in step S19. A quantity is calculated. Next, in step S27, fuel is supplied from the upstream fuel supply device 26 by the fuel supply amount calculated in step S26, and the control routine is ended.

On the other hand, if it is determined in steps S22 to S24 that the recovery process end condition for the SO _X trap catalyst 13 is satisfied, but the regeneration process end condition for the filter 17 is not satisfied, the process proceeds to step S28. move on. In step S28, the fuel supply from the upstream fuel supply device 26 is terminated. Next, in step S29, the amount of fuel to be supplied from the downstream fuel supply device 26 is calculated. In step S29, unlike step S20, the amount of fuel to be supplied from the downstream fuel supply device 26 is calculated based only on the target temperature of the filter 17 and the temperature of the filter 17 detected by the temperature sensor 44. . Next, in step S30, fuel is supplied from the downstream fuel supply device 18 by the fuel supply amount calculated in step S29, and the control routine is ended.

In Steps S22 to S24, when it is determined that the recovery process end condition for the SO _X trap catalyst 13 and the regeneration process end condition for the filter 17 are both satisfied, the process proceeds to Step S31. In step S31, the fuel supply from both the fuel supply devices 18, 26 is terminated. Next, in step S32, the recovery / regeneration processing flag X is set to 0, and the control routine is ended.

Next, a second embodiment of the present invention will be described. In the above embodiment, when the regeneration process period of the filter 17 is longer than the recovery process period of the SO _X trap catalyst 13, as shown in FIG. 9B, the fuel supply from the upstream fuel supply device 26 is performed. The fuel supply amount from the downstream fuel supply device 18 is increased, and the fuel supply amount from the downstream fuel supply device 18 is increased. On the other hand, in the present embodiment, when the regeneration process period of the filter 17 is longer than the recovery process period of the SO _X trap catalyst 13, as shown in FIG. The fuel supply from the fuel is continued without stopping, and the fuel supply amount from the downstream fuel supply device 18 is maintained as it is. As a result, the amount of fuel supplied from the downstream side fuel supply device 18, that is, the amount of fuel flowing into the NO _X storage catalyst 16 without passing through the SO _X trap catalyst 13 is reduced and supplied from the downstream side fuel supply device 18. Sulfur poisoning of the NO _x storage catalyst 16 due to the sulfur component in the fuel is suppressed.

FIGS. 13 and 14 are flowcharts of a recovery / regeneration control control routine for executing the recovery process of the SO _X trap catalyst 13 and the regeneration process of the filter 17 in the second embodiment. Steps S10 to S27, S31, and S32 in FIGS. 13 and 14 are the same as steps S40 to S57, S61, and S62 in FIGS.

In Steps S52 to S54, when it is determined that the recovery process end condition for the SO _X trap catalyst 13 is satisfied, but the regeneration process end condition for the filter 17 is not satisfied, the process proceeds to Step S58. In step S58, the fuel supply from the upstream fuel supply device 26 is terminated in the same manner as in step S49 (step S19). Next, in step S59, as in step S50 (step S20), the amount of fuel to be supplied from the downstream fuel supply device 26 is calculated. Next, in step S60, fuel is supplied from both fuel supply devices 18 and 26 by the fuel supply amount calculated in steps S58 and S59, and the control routine is terminated.

1 is an overall view of a compression self-ignition internal combustion engine. It is a general view which shows another example of a compression self-ignition internal combustion engine. It is a general view which shows another example of a compression self-ignition internal combustion engine. It is a figure which shows the structure of a particulate filter. FIG. 4 is a cross-sectional view of the surface portion of the catalyst carrier of the SO _X trap catalyst. It is a diagram showing _the SO _X trap rate. It is a diagram for explaining a recovery control of _the SO _X trap catalyst. And SO _X trapped amount ShigumaSOX, a diagram showing the relationships of the Atsushi Nobori control should occluding SO _X amount SO (n). It is a figure which shows transition of the fuel supply amount from both fuel supply apparatuses. It is a graph showing the relationship between the temperature of the SO _X trapped amount and recovery possible _the SO _X trap catalyst. It is a part of flowchart of the control routine of recovery | restoration / reproduction | regeneration control in 1st embodiment. It is a part of flowchart of the control routine of recovery | restoration / reproduction | regeneration control in 1st embodiment. It is a part of flowchart of the control routine of recovery | restoration / reproduction | regeneration control in 2nd embodiment. It is a part of flowchart of the control routine of recovery | restoration / reproduction | regeneration control in 2nd embodiment.

Explanation of symbols

4 Intake Manifold 5 Exhaust Manifold 7 Exhaust Turbocharger 12 Oxidation Catalyst 13 SO _X Trap Catalyst 16 NO _X Storage Catalyst 17 Particulate Filter 18 Downstream Fuel Supply Device 26 Upstream Fuel Supply Device 43, 44 Temperature Sensor 45 Differential Pressure Sensor

Claims (7)

And _the SO _X trap catalyst for trapping SO _X contained in the exhaust gas while being disposed in the engine exhaust passage, the particulate matter contained in the exhaust gas while being disposed on the exhaust downstream side of the _the SO _X trap catalyst A particulate filter to collect,
Said _the SO _X trap catalyst, _the SO _X trap when the air-fuel ratio of the inflowing exhaust gas lean in the catalyst to trap SO _X contained in the exhaust gas, the air-fuel ratio under the lean _the SO _X trap catalyst in the exhaust gas When the temperature is raised above recovery start temperature, has a property of _the SO _X trap ability is restored in _the SO _X trap catalyst captured SO _X is diffused inside of _the SO _X trap catalyst,
A SO _X trap recovery process for raising the temperature of the SO _X trap catalyst to a recovery start temperature or higher in order to restore the SO _X trap catalyst's SO _X trap capability;
In order to recover the particulate matter collecting ability of the particulate filter, it is possible to perform a filter regeneration process for raising the temperature of the particulate filter and oxidizing and removing the particulate matter deposited on the particulate filter.
The exhaust purification device for a compression self-ignition internal combustion engine, in which the SO _X recovery process is performed when the filter regeneration process is executed. Comprising a particulate matter deposit amount estimation means for estimating the deposition amount of the particulate material into the particulate filter, and SO _X trapped amount estimation means for estimating a SO _X trapped amount of the _the SO _X trap catalyst, the filter The regeneration process is executed when the amount of particulate matter deposited on the particulate filter exceeds an allowable amount, and the SO _X trap recovery process is performed so that the SO _X trap catalyst has a SO _X trapping amount equal to or greater than a predetermined amount. This is performed when the filter regeneration process is being executed, and is not performed when the filter regeneration process is not being performed even if the SO _X trap amount of the SO _X trap catalyst is greater than or equal to a predetermined amount. Item 2. An exhaust emission control device for a compression ignition type internal combustion engine according to Item 1. When _the SO _X trap recovery treatment after the above _the SO _X trap restoration process and filter regeneration process is performed at the same time is completed earlier, the fuel only from the downstream side fuel addition device to stop the rise in the temperature of _the SO _X trap catalyst The exhaust emission control device of a compression ignition type internal combustion engine according to claim 1 or 2, wherein the addition is performed. When _the SO _X trap recovery treatment after the above _the SO _X trap restoration process and filter regeneration process is performed at the same time is completed earlier, maintains the Atsushi Nobori of _the SO _X trap catalyst to a filter regeneration process is completed, billing Item 3. An exhaust emission control device for a compression ignition type internal combustion engine according to Item 1 or 2. The SO _X trap catalyst has a property of releasing captured SO _X when the temperature of the SO _X trap catalyst becomes higher than the SO _X release limit temperature higher than the recovery start temperature,
The compression according to any one of claims 1 to 4, wherein when performing the SO _X trap recovery process, the target temperature rise of the SO _X trap catalyst is set to an upper limit temperature substantially the same as the SO _X release limit temperature. An exhaust purification system for a self-igniting internal combustion engine. The exhaust purification device of a compression self-ignition internal combustion engine according to claim 5, wherein the upper limit temperature is lowered as the SO _X trap amount of the SO _X trap catalyst increases. The compression auto-ignition internal combustion engine according to any one of claims 1 to 4, wherein when performing the SO _X trap recovery process, the SO _X trap catalyst is raised to a temperature not higher than a transpiration start temperature of a substance constituting the SO _X trap catalyst. Exhaust purification device.

Images