JP2006220127A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of selecting and sorting large diameter fine particles and small diameter fine particles in an exhaust passage and treating them securely. <P>SOLUTION: This exhaust emission control device for the internal combustion engine catches fine particles included in exhaust gas in the internal combustion engine to catch large diameter fine particles by a first filter and catch small diameter fine particles by a second filter. Separate filters are used as the first filter and the second filter, but the filter used as the first filter is the same as the filter used as the second filter or has rougher mesh than mesh of the second filter to catch only large diameter fine particles. Here, an exhaust passage for leading exhaust gas into a second particulate matter means is branched like side branches for the exhaust passage for leading exhaust gas into the first filter. Consequently, fine particles in exhaust gas can be selected and sorted into large diameter fine particles and small diameter fine particles by inertia force. As a result, large diameter fine particles and small diameter fine particles can be securely treated by the filters corresponding to each of them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine that is disposed in an exhaust passage of the internal combustion engine and collects particulate matter of exhaust gas.

  Particulate matter is contained in exhaust gas discharged from an internal combustion engine such as a diesel engine. For this reason, it is necessary to attach a particulate matter removing device for removing the particulate matter from the exhaust gas to the exhaust passage of the internal combustion engine. For removing the particulate matter, a collection filter is provided, and the particulate matter is collected by the collection filter. In the collection filter, the collected particulate matter is subjected to a treatment such as an oxidation treatment.

  The particulate material is composed of fine particles of various sizes, and there are also large fine particles exceeding 100 nm (hereinafter simply referred to as “large diameter fine particles”). The large-sized fine particles are generated due to the ash of an abrasion material of an internal combustion engine, rust of oxides such as calcium and phosphorus in the oil, Zn, Fe, and the like. Generally, the collection filter of the particulate matter removing device is designed to have a small trap diameter in order to collect fine particles (fine particles smaller than large-sized fine particles, hereinafter simply referred to as “small-sized fine particles”). Therefore, clogging due to insufficient oxidation may occur due to the large-sized fine particles. In addition, since the large-sized fine particles require time for the oxidation treatment, the treatment with the filter cannot be performed in time, and the fine particles are deposited, so that the function as the filter cannot be performed sufficiently. Further, since the large-sized fine particles require an oxidation time, there is a problem that fuel consumption is deteriorated by the removal treatment of the particulate matter.

  In Patent Document 1, a filter for collecting large-sized fine particles and a filter for collecting fine particles smaller than the large-sized fine particles (hereinafter simply referred to as “small-sized fine particles”) are separately provided. A filter for collecting fine particles is connected in series to the upstream side of the filter for collecting small-diameter fine particles.

  However, in the case of Patent Document 1, small-sized fine particles cannot be treated unless the large-sized fine particles are treated, even though the large-sized fine particles take a long time to process. It was insufficient as a solution to this problem.

JP 2001-295627 A

  The present invention has been made in view of the above points, and provides an exhaust emission control device for an internal combustion engine that can selectively process large-sized fine particles and small-sized fine particles in an exhaust passage and reliably process them.

  In one aspect of the present invention, an exhaust emission control device for an internal combustion engine includes a first filter that collects large-diameter particles contained in the exhaust gas of the internal combustion engine, and a second filter that collects small-diameter particles contained in the exhaust gas. A first exhaust passage in which the first filter is disposed, and a second exhaust passage in which the second filter is disposed, branched from the first exhaust passage in a side branch shape. The roughness of the first filter is equal to or greater than the roughness of the second filter.

  The exhaust gas purification apparatus for an internal combustion engine collects particulates contained in the exhaust gas of the internal combustion engine, collects large-diameter particulates with a first filter, and collects small-diameter particulates with a second filter. To do. As the first filter and the second filter, separate filters are used. The filter used for the first filter is a filter used for the second filter in order to collect only large-diameter particles. Similar or coarser filters than the second filter are used. Here, the second exhaust passage for guiding the exhaust gas to the second particulate matter means is branched into a side branch with respect to the first exhaust passage for guiding the exhaust gas to the first filter. Therefore, the fine particles in the exhaust gas can be classified into large-sized fine particles and small-sized fine particles by the inertial force. Thereby, it is possible to reliably process the large-sized fine particles and the small-sized fine particles with the corresponding filters. In a preferred embodiment, in the exhaust gas purification apparatus for an internal combustion engine, the second exhaust passage is directed in a direction shifted by a predetermined angle or more with respect to the axial direction of the first exhaust passage. Here, the predetermined angle or more is preferably 5 ° or more.

  In one aspect of the exhaust gas purification apparatus for an internal combustion engine, the first exhaust passage is connected to the second exhaust passage on the downstream side of the first filter. Thereby, the flow of the exhaust gas can be generated in the first exhaust passage provided with the first filter, and the collection of the large-sized fine particles by the first filter can be performed more effectively. it can. Further, the small-diameter fine particles that have passed through the first filter can be guided to the second filter. Therefore, the small-diameter fine particles that have passed through the first filter can be processed by the second filter.

  In another aspect of the exhaust gas purification apparatus for an internal combustion engine, a throttle is provided in the first exhaust passage, and a cross-sectional area of the first exhaust passage in a portion where the throttle is provided is the second exhaust passage. Smaller than the cross-sectional area of the exhaust passage. Thereby, only large-diameter fine particles can be effectively guided to the exhaust passage 12.

  In another aspect of the exhaust gas purification apparatus for an internal combustion engine, the first filter has a heating means for heating the collected large-diameter fine particles. By burning the large-sized fine particles by a heating means such as an electric heater or a burner, the oxidation treatment of the large-sized fine particles that are easily deposited can be effectively performed. In addition, assuming that the first filter is configured to be replaceable, the entire filter on which large-diameter particles are deposited can be replaced.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
First, an exhaust emission control device according to a first embodiment of the present invention will be described.

  FIG. 1 shows a schematic configuration of a first embodiment in which an exhaust gas purification apparatus according to the present invention is applied to an internal combustion engine. The internal combustion engine 1 is an in-line four-cylinder diesel engine in which four cylinders 2 are arranged in a line, and an intake passage 3, an exhaust passage 4, and a turbocharger 5 that supercharges the internal combustion engine 1. I have. The intake passage 3 is compressed by an air filter 13, an air flow meter 14 for measuring the intake flow rate, a throttle valve (not shown) capable of adjusting the intake flow rate, a compressor 5a of the turbocharger 5, and a compressor 5a. And an intercooler 7 for cooling the intake air. The exhaust passage 4 is provided with a turbine 5b of the turbocharger 5 and an exhaust purification device 20 for reducing harmful substances in the exhaust gas. The intake passage 3 and the exhaust passage 4 are connected by an EGR passage 6 so that a part of the exhaust gas is recirculated from the exhaust passage 4 to the intake passage 3. The EGR passage 6 is provided with an EGR cooler 7 for cooling the exhaust gas to be recirculated to the intake passage 3 and an EGR valve 8 for adjusting the recirculation amount of the exhaust gas. The internal combustion engine 1 is provided with four injectors 9 corresponding to the respective cylinders 2. The four injectors 9 are connected to the common rail 10. The common rail 10 is connected to a supply pump 11 that pumps fuel from a fuel tank (not shown) and pumps the fuel to the common rail 10.

  The exhaust emission control device 20 includes filters 21 a and 21 b that have a function of collecting and reducing NOx in the exhaust gas of the internal combustion engine 1, and an oxidation catalyst 23. As fine particles in the exhaust gas, large-sized fine particles having a size of 100 nm or more generated due to ash of the abrasion material of the internal combustion engine 1, calcium and phosphorus in the oil, rust, and the like, and small-sized fine particles having a smaller size than that. And can be classified. The filter 21 a is for collecting large-diameter particles in the exhaust gas, and is provided on the exhaust passage 12 branched from the exhaust passage 4. On the other hand, the filter 21 b is for collecting small-diameter fine particles in the exhaust gas, and is provided on the exhaust passage 4. The oxidation catalyst 23 is provided on the downstream side of the filter 21b, and oxidizes the fine particles that have passed without being processed in the filter 21b. Here, the filter 21a functions as a first filter, and the filter 21b functions as a second filter.

  An A / F sensor 26 for detecting the air-fuel ratio of the exhaust gas is provided between the filter 21b and the oxidation catalyst 23, and an output signal of the A / F sensor 26 is input to an engine control unit (ECU) (not shown). Further, the exhaust purification device 20 includes a fuel addition injector 28 for adding a reducing agent (fuel) to the exhaust passage 4 in order to reduce NOx occluded by the filters 21a and 21b. The fuel addition injector 28 is connected to the supply pump 11. The addition of fuel by the injector 28 for addition is controlled by the ECU based on the input signal from the A / F sensor 26 as necessary to reduce the NOx stored in the filters 21a and 21b.

  The exhaust gas flowing into the exhaust purification device 20 is first guided to the branching section 30. FIG. 2 is an enlarged view of the branch portion 30. The exhaust passage 12 and the exhaust passage 4 are branched at the branch portion 30. At this time, the branching direction of the exhaust passage 4 is formed in a direction that bends the traveling direction when the particulates in the exhaust gas are guided to the branching portion 30, while the branching direction of the exhaust passage 12 is that the particulates are It is formed in the same direction as its traveling direction when guided to the branching section 30. That is, in the branch portion 30, the exhaust passage 4 branches in a side branch shape with respect to the exhaust passage 12. When the angle of the branch direction of the exhaust passage 4 with respect to the direction of the exhaust passage 12 at this time is “θ”, the angle θ is preferably 5 ° or more. That is, the direction of the exhaust passage 4 is preferably directed in a direction shifted by 5 ° or more with respect to the axial direction of the exhaust passage 12. The exhaust passage 12 corresponds to the first exhaust passage in the present invention, and the exhaust passage 4 corresponds to the second exhaust passage.

  The fine particles in the exhaust gas are accelerated by the flow of the exhaust gas when guided to the branch part 30. Among the fine particles in the exhaust gas, the large-sized fine particle Pa having a large volume has a larger mass than the small-sized fine particle Pb having a small volume, so that the inertial force generated by acceleration is increased. Since the large-diameter particulate Pa has a large inertia force, the large-diameter particulate Pa cannot be bent by riding on the flow of the exhaust gas along the exhaust passage 4 in the branch portion 30, and goes straight as it is, and the exhaust passage that is in its course direction Enter 12. On the other hand, since the small-diameter fine particles Pb have a small mass, inertial force generated by acceleration is small. Therefore, the small particle Pb can be bent on the flow of the exhaust gas along the exhaust passage 4 at the branch portion 30. In this way, in the branching portion 30, the fine particles in the exhaust gas can be sorted into the large-sized fine particles Pa and the small-sized fine particles Pb by using the inertia force thereof. The large-diameter particulates Pa that have entered the exhaust passage 12 are guided to the filter 21a, and the small-diameter particulates Pb that can be bent along the exhaust passage 4 are guided to the filter 21b. As described above, the large-sized fine particles and the small-sized fine particles can be separated using their inertial forces and processed with separate filters. Therefore, it is possible to prevent clogging of the filter that has occurred by collecting the large-sized fine particles and the small-sized fine particles with the filter on the same exhaust passage, and it is possible to prevent the efficiency of the fine particle treatment from being lowered.

  FIG. 3A shows the shape of the filter 21a viewed from the inlet through which the exhaust gas and large-diameter particles flow, and FIG. 3B shows a cross-sectional view of the filter 21a. The filter 21a is formed in a honeycomb shape having a large number of cells (through holes) 51a. Each of the cells 51a is plugged with a plug 52a at one of both ends. The plug 52a is provided so that the cells 51a plugged at the inlet end 51a_in and the cells 51a plugged at the outlet end 51a_out are alternately arranged. Since the filter 21a has a role of collecting large-diameter particles, the structure of the inlet of the filter 21a shown in FIG. For this reason, the structure of the inlet of the filter 21a is similar to the structure of the inlet of the filter 21b (see FIG. 4A) described later, or is coarser than the structure of the inlet of the filter 21b. A partition wall 53a is provided between the cells 51a adjacent to each other, and a large number of fine holes (not shown) that do not allow large-sized fine particles to pass therethrough are formed. The exhaust gas guided to the inlet end 51_in of the filter 21a passes through the path indicated by the arrow in FIG. 3B, and after the large-diameter particles are removed by the partition wall 53a, is guided to the outlet end 51a_out.

  FIG. 4A shows the shape of the filter 21b viewed from the inlet through which the exhaust gas and small-diameter particles flow, and FIG. 4B shows a cross-sectional view of the filter 21b. Similarly to the filter 21a, the filter 21b is also formed in a honeycomb shape having a large number of cells (through holes) 51b. Each of the cells 51b is plugged with a plug 52b at one of both ends. The plug 52b is provided so that the cells 51b plugged at the inlet end 51b_in and the cells 51b plugged at the outlet end 51b_out are alternately arranged. A partition wall 53b is provided between the cells 51b adjacent to each other. A number of fine holes (not shown) are also formed in the partition wall 53b, and the size of the holes is such that exhaust gas can pass but small diameter fine particles cannot pass. The exhaust gas guided to the inlet end 51b_in of the filter 21b passes through the path indicated by the arrow in FIG. 4B, and after the small-diameter particles are removed by the partition wall 53b, is guided to the outlet end 51b_out.

  In the above-described filters 21a and 21b, the partition walls 53a and 53b carry an oxidation catalyst material such as platinum (Pt) or cerium oxide (CeO2), and have the function of occluding NOx, such as potassium (K) and barium ( A NOx occlusion material made of one or a combination of alkali metals such as Ba), alkaline earths such as calcium (Ca), rare earths such as lanthanum (La), and the like, is supported. The filters 21a and 21b have a function of accelerating the oxidation of fine particles collected by the action of the oxidation catalyst substance, and occlude and reduce NOx by the action of the NOx occlusion substance. An appropriate material can be used for the outer walls 50a and 50b and the partition walls 53a and 53b of the filters 21a and 21b. For example, ceramic can be used. In addition, alumina, silica-alumina, zeolite, cordierite, and layered oxide can be used.

  In the filter 21a that collects large-sized fine particles, the collected large-sized fine particles are likely to be thickly deposited on the partition wall 53a due to its size, and depending on only the oxidation catalyst substance carried on the partition wall 53a, There is a possibility that fine particles cannot be oxidized. In that case, in this invention, it is good also as installing the electric heater 40 around the filter 21a. The electric heater 40 can raise the temperature of the partition wall 53a by heating the filter 21a. Therefore, the large diameter fine particles collected in the partition wall 53a can be burned and oxidized more efficiently. In addition, it is good also as using a burner instead of the electric heater 40, and burning large diameter microparticles | fine-particles directly and oxidizing. This electric heater or burner functions as a heating means in the present invention.

  Further, instead of providing such a heating means, the filter 21a may be exchangeable, and when the large-diameter particles are deposited thick on the partition wall 53a, the filter 21a may be replaced with a new filter 21a.

[Second Embodiment]
Next, an exhaust purification system according to a second embodiment of the present invention will be described.

  5 and 6 show a schematic configuration of a second embodiment in which the exhaust gas purification apparatus according to the present invention is applied to an internal combustion engine. As shown in FIG. 5, in the exhaust gas purification apparatus 20a according to the second embodiment, the exhaust passage 12 is also provided on the downstream side of the filter 21a that collects large-diameter particulates, and further, the exhaust passage 12a on the downstream side is provided. The merging portion 31 is joined with the exhaust passage 4. By doing in this way, the flow of exhaust gas can be generated also in the exhaust passages 12 and 12a. As a result, the large-diameter particulates separated from the exhaust flow in the exhaust passage 4 by the inertia force can be accelerated along the exhaust passage 12 in the branch portion 30, and the large-diameter particulates are effectively applied to the filter 21a. Can be collected. The exhaust passages 12 and 12a correspond to the first exhaust passage in the present invention.

  Further, as described above, in the filter 21a that collects large-sized fine particles, the partition wall 53a is provided, and a large number of fine holes (not shown) that cannot pass the large-sized fine particles are formed. A small amount of small-diameter particles that have entered the exhaust passage 12 may pass through the partition wall 53a. In the second embodiment, the exhaust passage 12a on the downstream side of the filter 21a is joined again with the exhaust passage 4 at the joining portion 31. Therefore, a small amount of small-diameter particles that have passed through the filter 21a can be sent to the exhaust passage 4 via the merging portion 31 and processed by the filter 21b.

  In FIG. 5, the merging portion 31 of the exhaust passage 12a is formed on the upstream side of the filter 21b, but is not limited to this, and the merging portion 31 is not limited to this, as in the exhaust purification device 20b shown in FIG. Instead of forming on the upstream side of the filter 21b, it may be formed on the downstream side of the filter 21b.

  As shown in FIG. 6, when the merging portion 31 is on the downstream side of the filter 21 b, a small amount of small diameter fine particles that have passed through the filter 21 a are guided to the oxidation catalyst 23 through the merging portion 31. At this time, the small-diameter fine particles can be treated with the oxidation catalyst 23.

[Third embodiment]
Next, an exhaust emission control device according to a third embodiment of the present invention will be described.

  FIG. 7 shows a schematic configuration of a third embodiment in which the exhaust gas purification apparatus according to the present invention is applied to an internal combustion engine. As shown in FIG. 7, in the exhaust purification device 20c according to the third embodiment, a throttle is provided at an arbitrary location on the exhaust passage 12 in the exhaust purification device 20a according to the second embodiment.

  As described in the second embodiment, when the flow of the exhaust gas is also generated in the exhaust passages 12 and 12a, the exhaust gas flowing into the exhaust passage 12 is used to guide only the large-sized fine particles to the exhaust passage 12 at the branch portion 30. The gas flow rate is preferably smaller than the flow rate of the exhaust gas flowing into the exhaust passage 4. If the flow rate of the exhaust gas flowing into the exhaust passage 12 is larger than the flow rate flowing into the exhaust passage 4, not only large-diameter particles but also small-diameter particles flow into the exhaust passage 12 in large quantities. Therefore, a throttle 35 is provided at an arbitrary location on the exhaust passage 12. The area “s1” of the cross section of the flow path where the throttle 35 is provided is configured to be smaller than the area “s2” of the cross section of the exhaust passage 4. If the flow rate of the exhaust gas flowing into the exhaust passage 12 is smaller than the flow rate of the exhaust gas flowing into the exhaust passage 4, the large-diameter particulates have a large inertial force, and thus flow through the throttle 35 and flow into the exhaust passage 12, but the small-diameter particulates. Flows into the exhaust passage 4 because of its low inertial force. Therefore, only large-diameter particles can be guided to the exhaust passage 12 more effectively.

  In the exhaust purification device 20c of FIG. 7, the throttle 35 is installed on the upstream side of the filter 21a. However, the present invention is not limited to this, and it may be installed on the downstream side instead of installing on the upstream side of the filter 21a. Good. A diaphragm 35a indicated by a broken line is an example when the diaphragm 35 is installed on the downstream side of the filter 21a. Further, in the exhaust purification device 20c of FIG. 7, a throttle is provided in the exhaust purification device 20a shown in FIG. 5 of the second embodiment, but also in the exhaust purification device 20b shown in FIG. 6 of the same second embodiment, A throttle similar to that described above can be provided at any location of the exhaust passage 12, specifically, either upstream or downstream of the filter 21a in the exhaust passage 12. Also by this, the flow rate of the exhaust gas flowing into the exhaust passage 12 can be made smaller than the flow rate of the exhaust gas flowing into the exhaust passage 4, and only large-diameter particles can be guided to the exhaust passage 12 more effectively.

  Note that the same effect can be obtained even if an exhaust pipe having an area smaller than that of the cross section of the exhaust passage 4 is originally used as the exhaust path 12 without providing the throttle 35.

[Fourth embodiment]
Next, an exhaust emission control device according to a fourth embodiment of the present invention will be described.

  FIG. 8 shows a schematic configuration of a fourth embodiment in which the exhaust gas purification apparatus according to the present invention is applied to an internal combustion engine. As shown in FIG. 8, in the exhaust purification device 20d according to the fourth embodiment, a valve-driven throttle 35c is provided at an arbitrary location on the exhaust passage 12 in the exhaust purification device 20 according to the first embodiment. Specifically, the throttle 35 c is configured by a valve 39 provided in the exhaust passage 12. The opening degree of the valve 39 is controlled by a drive signal from an ECU (not shown) or the like, and the flow rate of the exhaust gas passing through the throttle 35 c constituted by the valve 39 is controlled. For example, when the vehicle is accelerated, the amount of fuel injection increases, so the amount of particulate matter to be collected increases. At that time, the opening of the valve 39 is reduced by a control signal from the ECU, and the exhaust gas from the throttle 35c is reduced. Increase the amount of aperture. Thereby, the flow rate of the exhaust gas flowing into the exhaust passage 12 can be made smaller than the flow rate of the exhaust gas flowing into the exhaust passage 4. Thus, by making the throttle a valve-driven type, only large-diameter particles can be more effectively guided to the exhaust passage 12 according to the operating state of the internal combustion engine. A similar throttle 35c may be provided for the exhaust purification apparatus according to the second embodiment shown in FIGS.

[Filter variations]
Next, modified examples of the filters 21a and 21b will be described. The shapes of the filters 21a and 21b are not limited to those described above. Hereinafter, examples of other filters that can be used as the filters 21a and 21b are shown in FIGS.

  FIG. 9 shows a filter 21c that can be used instead of the filter 21a and the filter 21b. FIG. 9A shows the shape of the filter 21c viewed from the inlet through which the exhaust gas and fine particles flow, and FIG. 9B shows a cross-sectional view of the filter 21c. The filter 21c forms concentric cells 61 by concentrically forming ceramic foam or metal foam partition walls 63 each having a large number of fine holes and arranging them in a nested manner. Each of the cells 61 is plugged concentrically with a plug 62 at one of both ends. As indicated by the arrows, the exhaust gas flowing in from the inlet of the filter 21 c passes through the fine holes in the partition wall 63. At this time, large-diameter particles or small-diameter particles in the exhaust gas cannot be passed through the fine holes of the partition wall 63 and are collected by the partition wall 63. By differentiating the interval between the partition walls 63 formed concentrically, a filter for collecting large-sized fine particles and a filter for collecting small-sized fine particles can be configured.

  FIG. 10 shows a filter 21d that can be used instead of the filter 21a and the filter 21b. FIG. 10A shows the shape of the filter 21d viewed from the inlet through which exhaust gas and fine particles flow, and FIG. 10B shows a cross-sectional view of the filter 21d. The filter 21d is a foam filter made of ceramic foam or metal foam in which a large number of fine pores 64 are formed in a sponge shape. The size of the pores 64 is such a size that the exhaust gas can pass through but the large-diameter particles or the small-diameter particles cannot pass through. As indicated by the arrows, the exhaust gas flowing in from the inlet of the filter 21d passes through the pores 64. At this time, large-sized fine particles or small-sized fine particles in the exhaust gas are collected without passing through the pores 64. A filter for collecting large-sized fine particles and a filter for collecting small-sized fine particles can be configured by adjusting the pore diameter and the porosity per volume.

  FIG. 11 shows a filter 21e that can be used instead of the filter 21a and the filter 21b. FIG. 11A shows the shape of the filter 21e viewed from the inlet through which the exhaust gas and fine particles flow, and FIG. 11B shows a cross-sectional view of the filter 21e. The filter 21e has a shape in which the nonwoven fabric 65 is spirally wound using a nonwoven fabric 65 formed in a mesh shape using a metal or a heat-resistant material as a material. Adjacent nonwoven fabrics 65 each have a bag-binding structure at one of both ends 65x. As indicated by the arrows, the exhaust gas flowing from the inlet of the filter 21e passes through the nonwoven fabric 65 and is guided to the outlet. At this time, large-sized fine particles or small-sized fine particles in the exhaust gas are collected by the nonwoven fabric 65. By adjusting the interval between the adjacent nonwoven fabrics 65, a filter for collecting large-diameter particles and a filter for collecting small-diameter particles can be configured.

  FIG. 12 shows a filter 21f that can be used instead of the filter 21a and the filter 21b. FIG. 12A shows the shape of the filter 21f viewed from the inlet through which exhaust gas and fine particles flow, and FIG. 12B shows a cross-sectional view of the filter 21f. The filter 21f is a multi-stage arrangement in which two non-woven fabrics 66a and 66b formed of a metal or a heat-resistant material in a mesh shape face each other, and one of them is bound. As indicated by the arrows, the exhaust gas flowing in from the inlet of the filter 21f passes through the nonwoven fabrics 66a and 66b and is guided to the outlet. At this time, large-sized fine particles or small-sized fine particles in the exhaust gas are collected by the nonwoven fabrics 66a and 66b. By adjusting the interval between the nonwoven fabrics 66a and 66b, a filter for collecting large-sized fine particles and a filter for collecting small-sized fine particles can be configured.

  FIG. 13 shows a filter 21g that can be used instead of the filter 21a and the filter 21b. FIG. 13A shows the shape of the filter 21g viewed from the inlet through which exhaust gas and fine particles flow, and FIG. 13B shows a cross-sectional view of the filter 21g. The filter 21g is formed by arranging non-woven fabrics 67 in which a metal or a heat-resistant material is formed in a mesh shape into a cylindrical shape and plugging one side with a plug 68 side by side. As indicated by the arrows, the exhaust gas flowing in from the inlet of the filter flows in from the inside of the cylindrical nonwoven fabric 67, passes through the side surface thereof, and is guided to the outlet. At this time, large-sized fine particles or small-sized fine particles in the exhaust gas are collected by the nonwoven fabric 67. By adjusting the diameter of this cylindrical shape, it is possible to configure a filter for collecting large-sized fine particles and a filter for collecting small-sized fine particles.

  In the filter described above, when a nonwoven fabric in which a metal is formed in a mesh shape is used, a sintered nonwoven fabric can also be used. In the sintered nonwoven fabric, the intersection of the metal yarn knitted in a mesh shape and the metal yarn is integrated by sintering. Thereby, the strength and corrosion resistance of the filter can be improved. In that case, a filter for collecting large-sized fine particles and a filter for collecting small-sized fine particles can be configured by adjusting the distance between the metal yarns.

1 is a diagram showing a first embodiment in which an exhaust emission control device of the present invention is applied to an internal combustion engine. It is an enlarged view of the branch part of an exhaust gas purification apparatus. It is the figure which showed the detail of the structure of the filter which collects large diameter particulates. It is the figure which showed the detail of the structure of the filter which collects small diameter microparticles | fine-particles. It is the figure which showed 2nd Embodiment which applied the exhaust gas purification apparatus of this invention to the internal combustion engine. It is the figure which showed the other example of 2nd Embodiment which applied the exhaust gas purification apparatus of this invention to the internal combustion engine. It is the figure which showed 3rd Embodiment which applied the exhaust gas purification apparatus of this invention to the internal combustion engine. It is the figure which showed 4th Embodiment which applied the exhaust gas purification apparatus of this invention to the internal combustion engine. It is the figure which showed the detail of the modification of a filter. It is the figure which showed the detail of the modification of a filter. It is the figure which showed the detail of the modification of a filter. It is the figure which showed the detail of the modification of a filter. It is the figure which showed the detail of the modification of a filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4, 12 Exhaust passage 20 Exhaust purification device 21a Filter (For large-diameter particulate collection)
21b Filter (for collecting small particles)
23 Oxidation catalyst 30 Branch

Claims (6)

A first filter that collects large-diameter particulates contained in the exhaust gas of the internal combustion engine;
A second filter that collects small-diameter particles contained in the exhaust gas;
A first exhaust passage in which the first filter is disposed;
A second exhaust passage provided by branching from the first exhaust passage in a side branch shape and having the second filter disposed thereon,
An exhaust emission control device for an internal combustion engine, wherein the first filter has a mesh roughness ≧ the second filter has a mesh roughness.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the second exhaust passage is directed in a direction shifted by a predetermined angle or more with respect to an axial direction of the first exhaust passage.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the first exhaust passage is connected to the second exhaust passage on the downstream side of the first filter.   A throttle is provided in the first exhaust passage, and a cross-sectional area of the first exhaust passage at a portion where the throttle is provided is smaller than a cross-sectional area of the second exhaust passage. Item 6. An exhaust emission control device for an internal combustion engine according to Item 1.   5. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the first filter includes a heating unit that heats the collected large-sized fine particles.   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 5, wherein the first filter is configured to be replaceable.

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