Method and apparatus for processing exhaust gas

Abstract: An exhaust gas filter has a filter main body (20), a container, a first counter room (210), and a second counter room (212). Counter flow air is introduced into the first counter room through the counter air discharge valve (304), and fine particles trapped in the filter main body are removed and transported to the second counter room. Then, the removed fine particles are further transported to a process portion (6) isolated from an exhaust gas passage, and the fine particles are fired in the process portion. Since the process portion is isolated from the exhaust gas passage, the fine particles in the process portion is not returned to the filter main body. Moreover, since the fine particles are transported by the counter air only to the second counter room, it is possible to reduce the amount of the counter air flow.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method and an apparatus for processing an exhaust gas discharged from an internal combustion engine such as a diesel engine, in which fine particles i.e. soots trapped in a filter are removed outside of the filter so as to regenerate the filter and the removed fine particles are transported outside of an exhaust system and processed. Related Art Statement An exhaust gas discharged from a diesel engine includes a large number of fine particles mainly made of carbon, and thus this is a cause of a public nuisance generation. Therefore, various methods for trapping or eliminating such a fine particles in an exhaust gas are disclosed. For example, Japanese Patent Laid-Open Publication No. 1-159408 (JP-A-1-159408) discloses a method of removing fine particles trapped in a filter by using an intermittent counter flow and firing the removed fine particles in a re-trapping portion arranged in an exhaust gas passage near the filter. Moreover, Japanese Patent Application No. 5-198409 discloses a method of removing fine particles by using two kinds of counter flows, transporting the removed fine particles to a place remote from the filter and outside of the exhaust gas passage by the counter flow mentioned above, and firing the removed and transported fine particles. However, in the method disclosed in JP-A-1-159408, since the re-trapping portion is arranged under the filter or in the exhaust gas passage near the filter, there is a possibility that the fine particles once removed by using the counter flow are returned to the filter by an exhaust gas. Moreover, in the method disclosed in Japanese Patent Application No. 5-198409, since it is necessary to use two kinds of the counter flows, the apparatus for performing the method mentioned above is complicated. Further, since it is necessary to transport the removed fine particles to the place remote from the filter by using the counter flow, a large amount of the counter flow must be used. If the method mentioned above is used for an apparatus of processing an exhaust gas from an engine, it is preferred that an air supply source used for an exhaust brake system and so on of vehicles is also used for a counter air supply source from the vies points of cost, dimensions and so on. In this case, if a large amount of the counter air is used, it is necessary to make an actuator of the exhaust brake system large, and this causes a bad operation of the actuator. US-5253476 describes an exhaust gas particulate control system in which a particulate trap is regenerated by at least one high-pressure, low-velocity pulse of air. The regenerating air pulse enters a casing member containing the trap at an identical port from which the exhaust gas leaves the casing member. The direction of flow of the regenerating air pulse and exhaust gas at the port is parallel to the flow passages of the trap. EP-A-0308972 describes an apparatus for treating the exhaust gas from a diesel engine. A filter unit is provided in a casing having exhaust gas inlet and outlet conduits. A nozzle is provided in the exhaust gas outlet conduit from which a pulse of gas can be ejected for back washing the filter unit. The ejected gas and the exhaust gas have a flow direction, where the exhaust gas outlet conduit joins the casing, which is perpendicular to the flow passages of the filter unit. Summary of the Invention It is an object of the present invention to eliminate the drawbacks mentioned above and to provide a method and an apparatus for processing an exhaust gas, in which, if fine particles are removed from a filter, transported by a counter flow and processed, the removed fine particles are not returned to the filter. It is an another object of the present invention to provide a method and an apparatus for processing an exhaust gas, in which the fine particles can be removed, transported and processed effectively even by a small amount of the counter air. It is an another object of the present invention to provide a method and an apparatus for processing an exhaust gas, in which the fine particles can be removed, transported and processed effectively by an apparatus having a simple constitution. According to the invention, a method for processing an exhaust gas discharged from an internal combustion engine is provided in claim 1. Moreover, according to the invention, an apparatus for processing an exhaust gas discharged from an internal combustion engine is provided in claim 7. Brief Description of the Drawings Fig. 1 is a schematic view showing a first embodiment of an exhaust gas processing apparatus according to a present invention; Fig. 2 is a schematic view illustrating a main portion of the first embodiment in the case of a fine particle trapping operation according to the invention; Fig. 3 is a schematic view depicting a main portion of the first embodiment in the case of a filter regenerating operation according to the invention; Fig. 4 is a perspective view showing one embodiment of a filter main body according to the first embodiment of the invention; Fig. 5 is a cross sectional view illustrating one embodiment of the filter main body shown in Fig. 4; Fig. 6 is a cross sectional view depicting one embodiment of the filter main body in the case of the filter regenerating operation according to the invention; Fig. 7 is a schematic view showing a filter of the first embodiment according to the invention; Fig. 8 is a graph illustrating a relation in a first counter space between pressure variation and time according to the first embodiment of the invention; Fig. 9 is a timing chart depicting operations of exhaust gas supply valves and a counter air discharge valve according to the first embodiment of the invention; Fig. 10 is a cross sectional view showing one embodiment of a process portion according to the first embodiment of the invention; Fig. 11 is a schematic view illustrating another embodiment of the exhaust gas processing apparatus according to the invention in which one filter is used; Fig. 12 is a cross sectional view depicting a filter according to a second embodiment of the invention; Fig. 13 is a timing chart showing a relation between a pressure difference defined by pressures at an inlet portion and an outlet portion of the filter main body according to the second embodiment of the invention; Fig. 14 is a schematic view illustrating a third embodiment of the exhaust gas processing apparatus according to the invention; Fig. 15 is a schematic view depicting a main portion of the third embodiment in the case of the fine particle trapping operation according to the invention; Fig. 16 is a schematic view showing a main portion of the third embodiment in the case of the filter regenerating operation according to the invention; Fig. 17 is a schematic view illustrating a fourth embodiment of the exhaust gas processing apparatus according to the invention; Fig. 18 is a schematic view depicting a main portion of the fourth embodiment in the case of the fine particle trapping operation according to the invention; and Fig. 19 is a schematic view showing a main portion of the fourth embodiment in the case of the filter regenerating operation according to the invention. Description of the Preferred Embodiment Hereinafter, the present invention will be explained in detail with reference to the drawings. (First Embodiment) Figs. 1 to 10 are schematic views respectively showing the first embodiment of the invention. As shown in Fig. 1, an apparatus for processing an exhaust gas according to the first embodiment of the invention comprises (1) filters 2, 4, (2) counter air supply portion 3, (3) exhaust gas supply pipe 7, (4) exhaust gas discharge pipe 8, (5) transport pipe 5, (6) process portion 6. (1) Filter As shown in Fig. 1, an exhaust gas discharged from a diesel engine can be flowed through one of or both of a first filter 2 and a second filter 4. In this embodiment, if the first filter 2 and the second filter 4 are alternately regenerated, an exhaust gas processing operation can be continuously performed. Fig. 7 is a schematic view showing a construction of the filter 2 or 4. As shown in Fig. 7, a filter main body 20 is accommodated in a container 201 having a cylindrical shape. A first counter space 210 is formed at a downstream position of the filter main body 20, and a second counter space 212 is formed at an upstream position of the filter main body 20. The filter main body 20 is made of a porous honeycomb structural body having a cylindrical shape, which is formed integrally by extruding a cordierite batch. As shown in Figs. 4 and 5, a number of through holes 30 arranged parallel to an axis of the filter main body 20 are formed. The through holes 30 have such a construction that partition walls 34 extended in x direction and partition walls 36 extended in y direction are crossed with each other and the crossed partition walls 34 and 36 are extended in z direction, as shown in Fig. 4. One end of the through hole 30 is sealed by a plug member 38, and the other end of the adjacent through hole 30 is sealed by a plug member 39. In this case, as shown in Fig. 4, the through holes 30 arranged at both ends of the filter main body 20 are sealed by the plug members 38 and 39 like a checker flag pattern. Therefore, as shown in Fig. 5, an exhaust gas is supplied from the through holes 30, at which the plug members 39 are arranged, into the filter main body 20. Then, the supplied exhaust gas is passed through the partition walls 36 as shown by an arrow in Fig. 5. Then, the passed through exhaust gas is discharged from the adjacent through holes 30. In this case, fine particles in the exhaust gas are trapped by the partition walls 36 at its exhaust gas supply side. The trapped fine particles are piled up gradually corresponding to a lapse of time. As shown in Fig. 7, the filter main body 20 is secured to an inner wall 201a of the cylindrical container 201 by seal rings 202, 203 and support rings 204,205. A space 206 is formed between the filter main body 20 and the inner wall 201a of the container 201. A filter support member 207 is arranged in the space 206. As for the filter support member 207, use is made of a ceramic mat used for supporting a catalyst carrier of an exhaust gas purifying converter assembled in a gasoline engine vehicle. The filter support member 207 functions to not only support but also cushion the filter main body 20. In this embodiment, as for the filter support member use may be made of a combination of the ceramic mat and a stainless wire mesh mat. The seal rings 202, 203 have a circular shape. In order to airtightly seal a boundary between a circumferential peripheral portion of an exhaust gas inlet end or an exhaust gas outlet end of the filter main body 20 and the inner wall 201a of the container 201, a gasket not shown is arranged between the seal ring 202 or 203 and the filter main body 20. The support rings 204, 205 have also a circular shape. The support rings 204, 205 are secured to the inner wall 201a of the container 201 by a bolt not shown in such a manner that the filter main body 20 is compressed in a through hole direction by the support rings 204 and 205. The first counter space 210 is formed in the container 201 at an exhaust gas downstream position of the filter main body 20. A counter air supply inlet 211 is communicated to an inner wall 210a of the first counter room 210. The second counter space 212 is formed in the container 201 at an upstream position of the filter main body 20. An exhaust gas supply inlet 213 and a transport inlet 214 are communicated to an inner wall 212a of the second counter space 212. The transport inlet 214 is arranged downward from the exhaust gas supply inlet 213. In the embodiment mentioned above, since the filter main body 20 is secured to the inner wall 201a of the container 201 with the space, the filter main body 20 is not moved gradually if a vibration due to the engine or a vibration during a movement of the vehicle is applied thereto, and thus it is possible to prevent a crack generation and a breakage of the filter main body 20. Moreover, the filter main body 20 is made of the honeycomb structural body, and thus it endures a relatively high compression strength in a through hole direction. Therefore, if the support rings 204, 205 are secured to the inner wall 201a of the container 201 by a bolt and so on in such a manner that the filter main body 20 is compressed in a through hole direction by the support rings 204 and 205, it is also possible to support the filter main body 20 without generating a crack and a breakage. Further, since a boundary between a circumferential peripheral portion of an exhaust gas inlet end or an exhaust gas outlet end of the filter main body 20 and the inner wall 201a of the container 201 is sealed, all the exhaust gas can be passed through the filter main body 20. Moreover, in this case, since the exhaust gas is not directly supplied to the filter support member 207, it is possible to prevent a deterioration of the filter support member 207. Furthermore, since the filter main body 20 is partly supported by a pressure applied to the above sealed portion, it is possible to decrease a support pressure of the filter main body 20, and thus it is possible to prevent a breakage of the filter main body 20. It should be noted that a cross section of the filter is generally circular, but it is possible to use the filter having a square, a rectangular, an ellipse, or the other cross section. Moreover, a shape of the through hole is generally square, but it is possible to use the through hole having a circular, a triangular, or a hexagonal shape. As the materials for the filter, it is preferred to use a porous cordierite from the view point of a thermal shock resistivity, an endurability, a gas seal performance and a fine particle trapping performance, and to form the filter by an integral extrusion. However, it is possible to use a porous ceramic material such as cordierite, alumina, mullite, silicon carbide, silicon nitride, zirconia, or a three-dimensional net structural body made of a fired porous metal, a ceramic fiber or a fiber material such as a metal fiber and so on. Moreover, since the filter is porous, it functions to be a muffler. Therefore, it is possible to further decrease an exhaust noise if used together with a usual muffler. As a comparison, the exhaust noises in the case that only the usual muffler was used and in the case that the filter was used together with the usual muffler were detected by a noise meter set beyond a tail pipe. As a result, if use is made of the filter together with the usual muffler, it is possible to decrease the exhaust noise by about 5 dB. (2) Counter air supply portion As shown in Fig. 1, the counter air supply portion 3 is arranged at an exhaust gas downstream position of the filter 2 or 4 i.e. at a side of the plug member 38 of the filter 2 or 4. The counter air portion 3 comprises counter air supply portions 3 and counter air discharge valves 304 and 305. For example, as the counter air discharge valves 304 and 305, use is made of a magnetic valve which can perform an open or an close operation in a short time. As shown in Fig. 7, one end of the counter air supply pipe 303 is communicated with the first counter space 210 of the filter 2 or 4 at the counter air supply inlet 211. The counter air supply inlet 211 has no valve, and thus it has a sufficient open area. In Fig. 7, an axis (a) of a counter air flowing direction in the counter air supply pipe 303 is not parallel to an axis (b) of the through hole in the filter main body 20. The axis (a) is crossed orthogonally with respect to the axis (b). Moreover, the other end of the counter air supply pipe 303 is communicated with a counter air tank, and the counter air tank is communicated with a counter air supply source. As the counter air supply source, it is preferred to use a compressor used for an exhaust gas brake system of the vehicle from the view points of a vehicle carrying performance, and a cost. Further, in order to minimize an amount of the counter air to be used, it is necessary to set properly an amount of the counter air tank, a dimension of the pipe from the counter air tank to the counter air discharge valve, an opening diameter of the counter air discharge valve, a flow coefficient, a dimension of the pipe from the counter air discharge valve to the first counter space, an amount of the first counter space or the second counter space, a dimension of the filter, a shape of the filter, and so on. If the counter air discharge valves 304, 305 are opened, the compressed counter air is flowed into the first counter space 210 through the counter air supply pipe 303. Therefore, an air pressure of the first counter room 210 is rapidly increased. Then, as shown in Fig. 6 by arrows, the counter air is supplied from the through hole 30, passed through the partition wall 36, and discharged from the adjacent through hole 30. Thereby, the fine particles filed up in the through hole 30 are discharged into the second counter space 212. Since the counter air supply inlet 211 has a sufficient opening area, a large amount of the counter air can be supplied in the first counter room in a short time. Therefore, a large shock can be applied to the through holes 30 of the filter main body 20. Moreover, since the axis (a) of the counter air flowing direction in the counter air supply pipe 303 is perpendicular to the axis (b) of the through hole in the filter main body 20, a rapid pressure increase due to the counter air supplied in the first counter space 210 can be uniformly applied to a surface at an exhaust gas supply side of the filter main body 20. That is to say, it is possible to prevent a local counter air flow, and thus the fine particles can be uniformly removed from the partition wall of the filter main body 20, and the removed fine particles can be transported into the second counter space 212. In the present invention, it is possible to project one end of the counter air supply pipe in the first counter space. Moreover, it is preferred to decrease a pressure loss in the case that the counter air is supplied into the first counter space by arranging a wider taper portion at the end of the counter air supply pipe in the first counter space. (3) Exhaust gas supply pipe One end of the exhaust gas supply pipe 7 is communicated with a diesel engine so as to introduce an exhaust gas, and the other end of the exhaust gas supply pipe 7 is communicated with the exhaust gas supply inlet 213 arranged at the inner wall 212a of the second counter space 212 in the filter 2 or 4. Exhaust supply valves 71 and 72 are arranged in the exhaust gas supply pipe 7 at a position near the filter 2 or 4. During the filter regenerating operation by the counter air, if the exhaust gas supply valves 71, 72 are closed and the counter air is supplied, the fine particles removed from the filter 2 or 4 are not returned into the exhaust gas supply pipe 7 by the counter air. Moreover, the fine particles in the exhaust gas are not introduced into the filter 2 or 4. (4) Exhaust gas discharge pipe One end of the exhaust gas discharge pipe 8 is communicated with the first counter space 210 of the filter 2 or 4, and the other end of the exhaust gas discharge pipe 8 is communicated with the muffler. Exhaust gas discharge valves 81 and 82 are respectively arranged in the exhaust gas discharge pipes 8 at a position near the filter main body 20. The exhaust gas after the fine particle trapping operation is discharged from the exhaust gas discharge pipe 8 to the muffler. During the filter regenerating operation by the counter air, if the exhaust gas discharge valves 81 and 82 are closed and the counter air is supplied, a pressure in the first counter space is increased rapidly, and thus the fine particles can be removed sufficiently. Moreover, the removed fine particles can be effectively transported into the second counter space 212. (5) Transport pipe One end of the transport pipe 5 is communicated with a transport inlet 214 arranged at the inner wall 212a of the first counter space 212 in the filter 2 or 4, and the other end of the transport pipe 5 is communicated with the process portion 6. The transport inlet 214 is arranged downward with respect to the exhaust gas supply inlet 213. Particle discharge valves 51 and 52 are respectively arranged in the transport valve 5 at a position near the transport inlet 214. If the particle discharge valves 51 and 52 are opened, the removed particles in the second counter space 212 can be transported into the process portion 6 through the transport inlet 214 and the the transport pipe 5 by gravity. (6) Process portion The process portion 6 is arranged under the filter 2 or 4 i.e. at a position outside of the exhaust gas system. In the process portion 6, the fine particles removed from the filter main body 20 and transported through the transport pipe 5 are fired. In this case, if a distance from an exhaust gas supply end of the filter main body 20 to the process portion is long, it is necessary to use a larger counter air supply apparatus, and thus a vehicle carrying performance becomes worse. At the same time, it is necessary to use a large amount of the counter air for transporting the fine particles. It is preferred to set the distance mentioned above to less than 100 cm, preferably to less than 70 cm, more preferably to less than 40 cm. As shown in Fig. 10, the process portion 6 comprises a process container 61, a plate 62 arranged at a bottom of the process container 61, and a discharge outlet 60. The fine particles transported to the process portion 6 through the transport pipe 5 are fallen down to the plate 62 by gravity. The plate 62 is a stainless plate having a thickness of 0.5-2 mm. An electric heater 50 is arranged under the plate 62. As the heater 50, use is made of a resistance heating wire of 200 W, which is wound like a spiral under the plate 62. The plate 62 is heated by the heater 50, and the fine particles piled up on the plate 62 are fired. After that, a residual ash component is discharged from the discharge outlet 60. In the first embodiment mentioned above, as shown in Fig. 1, the one process portion is used for both of the first filter and the second filter, but it is possible to arrange the process portions for the first filter and the second filter respectively. In the present invention, the electric heater is arranged under the plate, but it is possible to arrange the electric heater in the plate. Moreover, as a fine particle firing means, use is made of a sheath heater or a glow plug in which the fine particles are fired around it, or a burner for firing the fine particle directly. Further, it is possible to improve a firing performance of the fine particles by using an oxidizing catalyst or a microwave generator together with the firing means mentioned above. In this case, the firing improvement means is arranged at a position near the second counter room as compared with the firing means. Moreover, a filter through which an air is transmitted may be arranged at a part of the process container. In this case, an oxygen component necessary for firing can be introduced through the filter. Moreover, as the plate, use may be made of a ceramic plate. In this case, it is possible to use a far infrared effect of the ceramic plate. Hereinafter, valve changeover operations in a trapping mode and in a counter air processing mode and an ON/OFF operation of the counter air will be explained with reference to Figs. 1, 2, 3, 8, and 9. In the trapping mode, as shown in Fig. 1, the exhaust gas discharge valves 81 and 82 and the exhaust gas supply valves 71 and 72 are opened, and the particle discharge valves 51 and 52 are closed. In this case, the fine particles in the exhaust gas from the diesel engine are trapped by the filter 2 or 4. Then, in the counter air processing mode, the filter main body 20 is processed by the counter air periodically. This counter air processing process comprises (A) regenerating process, (B) transporting process, and (C) processing process. (A) Regenerating process In the regenerating process, as shown in Fig. 9, the exhaust gas discharge valve 81 and the exhaust gas supply valve 71 are changed to a close state , and just after this change the particle discharge valve 51 is changed to an open state. This state is maintained for e.g. 1 second. After e.g. 0.7 second from the particle discharge valve 51 being changed to the open state, the counter air discharge valve 304 is opened for e.g. 0.1 second. Thereby, the counter air is introduced into the first counter space 210. In this case, it is preferred to set a relation between a valve opening duration (t) of the counter air discharge valves 304, 305 and a duration (T) to T/t≦5, where the duration (T) is a time duration required for recovering a pressure in the first counter space 210 to a normal level before applying the counter air. Thereby, it is possible to perform a rapid pressure increase due to the counter air supply and a rapid pressure decrease after that in the first counter space 210. Therefore, it is possible to remove the fine particles from the filter main body 20 and transport the removed fine particle to the second counter space 212 referred below as (B) effectively by the counter air. After finishing the regenerating process of the first filter 2, a regenerating process of the second filter 4 is performed continuously. As is the same as the filter 2, the exhaust gas discharge valve 82 and the exhaust gas supply valve 72 are changed to a close state, and just after this change the particle discharge valve 52 is changed to an open state. This state is maintained for e.g. 1 second. After e.g. 0.7 second from the particle discharge vale 51 being changed to the open state, the counter air discharge valve 305 is opened for e.g. 0.1 second. Thereby, the regenerating processes of the first filter 2 and the second filter 4 are finished. After that, the first filter 2 and the second filter 4 perform a fine particle trapping operation of the exhaust gas. (B) Transporting process In the transporting process, the fine particles removed by the counter air are transported to the process container 61. In this embodiment, the removed fine particles are transported to the second counter space 212 by a pressure of the counter air, but after that the removed fine particles are transported to the process container 61 through the transport pipe 5 by their gravity not by the counter air. Therefore, it is possible to transport the fine particles by a small amount of the counter air which is not affected to a performance of a valve of e.g. the exhaust brake. (C) Processing process The fine particles transported to the process container 61 in the process portion 6 are fired on the plate 62 arranged at a bottom of the process container 61 by using the electric heater 50 and discharged. Thereby, the counter air processing process of the fine particles are finished. In the first embodiment mentioned above, the exhaust gas discharge valves 81 and 82 are arranged respectively, but it is possible to use the valve of the exhaust brake as the exhaust gas discharge valves 81,82. That is to say, in the vehicles such as bus, track, and so on, in which the diesel engine is assembled, a valve for closing an opening area in an exhaust gas passage is arranged so as to decrease a revolution speed of the diesel engine. The valve mentioned above is used as the exhaust gas discharge valves arranged in the exhaust gas discharge pipe. In this case, it is possible to decrease the number of the valves to be used . (Second embodiment) A second embodiment of the present invention is shown in Figs. 12 and 13. In the first embodiment mentioned above, the counter air processing process is performed alternately and periodically to the first filter 2 and the second filter 4. However, in the second embodiment, the counter air processing process is performed when a pressure difference of the filter main body at between the inlet portion and the outlet portion becomes more than a predetermined value. If the exhaust gas from the diesel engine is passed through a filter 400, a pressure difference P 0 is generated at between an inlet portion 402 and an outlet portion 403 of a filter main body 401, since the filter main body 401 has a resistivity for transmitting the exhaust gas. In this case, if the counter air processing process is continued, a pressure at the inlet portion 402 is increased corresponding to an amount of the fine particles piled up in the filter main body 401. Therefore, a pressure difference P 1 at between the inlet portion 402 and the outlet portion 403 is detected, and the counter air processing process is performed when the detected pressure difference P 1 is beyond a predetermined pressure difference P 2 . After the counter air processing process is finished, the pressure difference P 1 is gradually decreased to a level equal to the initial pressure difference P 0 ideally or less. In this case, the pressure difference P 2 is determined by an amount of the fine particles to be trapped and a trapping performance of the filter main body, and it is less than 3 kPa preferably less than 2 kPa. Since the fine particles trapped by the filter main body is light and gathered, it is effective to perform the counter air processing process when the fine particles are piled up to some extent. However, if the fine particles are piled up in excess, a pressure loss of the filter main body is larger and thus an effect of the counter air processing process is decreased. Therefore, it is necessary to perform the counter air processing process when the pressure difference i.e. pressure loss is more than a predetermined value. In the second embodiment according to the invention, since the counter air processing process is controlled by the pressure difference P 1 at between the inlet portion 402 and the outlet portion 403 of the filter main body 401, it is possible to perform the counter air processing process effectively at a minimizing frequency. (Third embodiment) A third embodiment of the present invention is shown in figs. 14 to 16. In the third embodiment, a partition is arranged instead of the particle discharge valve arranged at a position in the transport pipe near the transport inlet. A partition 502 inclined toward the process portion 6 from the second counter space 212 is arranged along a peripheral portion 501a of a transport inlet 501. The partition 502 has an opening 502a at its center portion. The fine particles removed from the filter main body 20 and transported to the second counter space 212 are fallen down in the process container 61 by their gravity through the opening 502a. Since the partition 502 is inclined toward the process container 61, the fine particles fallen down in the process container 61 are not returned to the second counter space 212. In the third embodiment according to the invention, since it is not necessary to use the particle discharge valve arranged near the transport inlet of the transport pipe, it is possible to reduce the number of the parts to be used. Moreover, since the number of the valves is reduced, a noise due to an operation of the valve can be deduced. In the present invention, a position of the partition is not limited to the position near the inlet portion, but it is arranged at any inner wall of the transport pipe between the second counter space and the process container. In order to completely prevent a return of the fine particles into the second counter space 212, it is possible to use the particle discharge valve arranged near the inlet of the transport pipe together with the partition mentioned above. (Fourth embodiment) A fourth embodiment of the present invention is shown in Figs. 17 to 19. In the fourth embodiment, the process portion is arranged under the filter at a position remote from the second counter space so as not to return the fine particles into the second counter space. The process portion 6 is arranged under the filter 2 through a transport pipe 510. That is to say, the process portion 6 is arranged at a position remote from an inlet 511 formed to the second counter space 212 toward an exhaust gas flowing direction. A length of the transport pipe 510 is set to a length in which the fine particles are not returned to the second counter space 212 even if the particle discharge valve or the partition is not used. In the fourth embodiment, since it is not necessary to use the particle discharge valve and the partition, the number of the parts to be used can be reduced. Moreover, since the number of the valves to be operated can be reduced, it is possible to reduce an amount of air supplied to actuators for operating the valves. In the first to fourth embodiments of the invention, use is made of two filters, but it is possible to use three or more filters. Moreover, as shown in Fig. 11, it is possible to use one filter by forming a by-pass pipe in the filter. In this case, during the counter air processing, since the exhaust gas is flowed in the by-pass pipe, the fine particles in the exhaust gas is not trapped by the filter. However, the counter air processing requires generally a short time, and thus it is no problem in an actual use. Further, if the counter air processing is not performed during a drive on an ascending road in which a large amount of the fine particles are generated but performed during a engine drive mode i.e. a drive on a highway in which a generation of the fine particles is small, it is possible to reduce an amount of the fine particles not trapped by the filter and discharged through the by-pass pipe during the counter air processing. Furthermore, if an oxidizing catalyst is arranged in the by-pass pipe and the fine particles are fired in the oxidizing catalyst, it is possible to reduce an amount of the fine particles discharged from the by-pass pipe. As mentioned above, according to the invention, since the counter air is uniformly and rapidly introduced to respective portions in the filter main body, it is possible to remove the fine particles trapped in the filter main body effectively by a simple apparatus. Moreover, since the removed fine particles are transported to the process portion and fired, it is possible to regenerate the filter. In the apparatus according to the invention, since the exhaust gas supply valve is arranged in the exhaust gas supply pipe, the fine particles are not returned to the exhaust gas supply pipe if the exhaust gas supply valve is closed. In this case, the fine particles are not introduced into the filter through the exhaust gas supply pipe. In the method and the apparatus according to the invention, if the filter is made of a honeycomb structural body having a plurality of through holes arranged parallel which are defined by porous partitions having a filter function, and exhaust inlets and exhaust outlets of the through holes are sealed alternately, it is possible to perform the fine particle trapping operation and the fine particle removing operation effectively. In the method according to the invention, if the filter main body is arranged in such a manner that a passage direction of the through hole of the filter is horizontal or inclined to a horizontal line, a vehicle assembling performance can be improved. In the method according to the invention, if the counter air discharge valve is opened when a pressure difference at between an inlet portion and an outlet portion of the filter main body is more than a predetermined value, the filter regeneration by the counter air can be performed at a proper interval. Therefore, the fine particles can be removed effectively, and an amount of the counter air can be minimized. In the method according to the invention, if a relation between a valve opening duration (t) of the counter air discharge valves and a duration (T) is set to T/t≦5, where the duration (T) is a time duration required for recovering a pressure in the first counter space to a normal level before applying the counter air, a pressure in the first counter space is increased by the counter air, and then the pressure is decreased effectively. Therefore, the fine particle removing and transporting operations can be performed effectively by a small amount of the counter air. In the method according to the invention, if one end of the counter air supply pipe is projected in the first counter space preferably in a tapered shape, a pressure loss when the counter air is introduced into the first counter space can be reduced. In the apparatus according to the invention, if the exhaust gas discharge valve arranged in the exhaust gas pipe is used as a valve for an exhaust brake, the number of the valves to be used can be reduced. In the apparatus according to the invention, if a particle discharge valve or a partition is arranged in the transport pipe, or if the process portion is arranged under the filter and at a position remote from the second counter space in an exhaust gas flowing direction,or if a connection portion between the transport pipe and the second counter space is arranged at a position lower than the exhaust gas supply pipe, the fine particles are not returned to the filter main body by the exhaust gas. In the apparatus according to the invention, if a peripheral portion of at least an exhaust gas inlet end of the filter main body is sealed airtightly in such a manner that the filter main body is compressed in a through hole direction, the filter main body is not moved gradually if a vibration due to the engine or a vibration during a movement of the vehicle is applied thereto, and thus it is possible to prevent a crack generation and a breakage of the filter main body. Moreover, it is possible to prevent an exhaust gas flow without passing through the filter main body. Further, it is possible to decrease a support pressure of the filter main body, and thus it is possible to prevent a breakage of the filter main body. In the apparatus according to the invention, if the fine particles are fired by the firing means such as electric heater, sheath heater, glow plug, and burner, or by using the oxidizing catalyst or the microwave generator together with the firing means, it is possible to fire the fine particles effectively and rapidly.

Claims: A method for processing an exhaust gas discharged from an internal combustion engine, in which fine particles in the exhaust gas are trapped in a honeycomb filter body (20) having a plurality of parallel passages defined by porous partition walls which perform the filter function, and are removed therefrom by intermittently passing counter air through said filter body with a flow direction reversed with respect to that of the exhaust gas flow, and the removed fine particles are transported outside the path of the exhaust and are processed, the particle removal method comprising (i) stopping the exhaust gas flow through the filter body (20) and supplying said counter air through a counter air supply pipe (303) into a first counter space (210) at the downstream end of said filter body; (ii) removing fine particles trapped in said filter body by said counter air flowing though said filter body; (iii) transporting the removed fine particles to a second counter space (212) arranged upstream of said filter body (20) by said counter air flow and from there to a processing zone (6) outside the exhaust gas flow path; and (iv) firing said transported fine particles in said processing zone (6), and the exhaust gas flow path being arranged such that the flow direction of exhaust gas out of said first counter space is in the direction of the parallel passages of said filter body, characterised in that the flow direction of the counter air into said first counter space (210) from said counter air supply pipe (303) is perpendicular to the direction of said parallel passages of the honeycomb filter body (20). A method according to claim 1, wherein said filter body is arranged so that the direction of said passages thereof is horizontal. A method according to claim 1 or claim 2, wherein said counter air discharge valve (304, 305) is opened when the pressure difference between the inlet and the outlet of said filter body (20) is more than a predetermined value. A method according to any one of claims 1 to 3, wherein said filter body (20) acts as a muffler. A method according to any one of claims 1 to 4, wherein the relation between a valve opening duration (t) of said counter air discharge valve (304, 305) and a duration (T) which is a time duration required for recovering pressure in said first counter space (210) to a normal level before applying the counter air is given by T/t≤5. A method according to any one of claims 1 to 5, wherein one end of said counter air supply pipe projects into said first counter space (210). An apparatus for processing an exhaust gas discharged from an internal combustion engine, comprising a filter body (20) having a plurality of parallel passages defined by porous partition walls which perform a filter function to remove fine particles from the exhaust gas, a first counter chamber (210) at the downstream end of said filter body (20) in the exhaust gas flow direction, a second counter chamber (212) upstream of said filter main body (20), an exhaust gas supply pipe (7) for supplying said exhaust gas to said filter, an exhaust gas discharge pipe (8) for flow of exhaust gas from said first counter chamber (210) to outside, arranged such that the flow direction of exhaust gas out of said first counter chamber is in the direction of the parallel passages of said filter body, processing means (6) connected to said second counter chamber (212) and outside the exhaust gas path in which the removed fine particles are fired, a transport pipe (5) connecting said second counter chamber to said processing means, a counter air supply means including a counter air supply pipe (303) opening into said first counter chamber (210) for supplying thereto counter air whose flow direction in said filter body (20) is reverse to that of the exhaust gas, an exhaust gas supply valve (71, 72) arranged in said exhaust gas supply pipe (7), and an exhaust gas discharge valve (81, 82) arranged in said exhaust gas discharge pipe (8), characterised in that the flow direction of the counter air into said first counter chamber (210) from said counter air supply pipe (303) is perpendicular to the direction of said parallel passages of the honeycomb filter body (20). An apparatus according to claim 7, wherein said exhaust gas discharge valve (81, 82) arranged in said exhaust gas discharge pipe is used as a valve for an exhaust brake. An apparatus according to claim 7 or 8, wherein a particle discharge valve (51) is arranged in said transport pipe, between said second counter chamber (212) and said processing means (6). An apparatus according to any one of claims 7 to 9, wherein a partition (502) is arranged in said transport pipe. An apparatus according to any of claims 7 to 10, wherein said processing means (6) is arranged under said filter body (20) and at a position remote from said second counter chamber in the exhaust gas flow direction so as not to return said fine particles into said filter body through said transport pipe (5). An apparatus according to any one of claims 7 to 11, wherein the connection between said transport pipe (5) and said second counter chamber (212) is at a position lower than the connection thereto of said exhaust gas supply pipe. An apparatus according to any one of claims 7 to 12, wherein a peripheral portion of at least an exhaust gas inlet and of said filter main body (20) is sealed airtightly to a casing (201) in such a manner that said filter body is compressed in the passage direction. The apparatus according to any one of claims 7 to 13, wherein, for firing said fine particles, said processing means has one of a firing plate arranged on an electric heater, a firing plate in which an electric heater is embedded, a sheath heater around which the fine particles are fired, a glow plug around which the fine particles are fired, a burner which gives the fine particles, an oxidizing catalyst arranged together with a fine particle firing means, and a microwave generator arranged together with a fine particle firing means.

Inventors: ICHIKAWA YUKIHITO, MACHIDA MINORU, NAITO TAKESHI, YAMADA TOSHIO, ICHIKAWA, YUKIHITO, MACHIDA, MINORU, NAITO, TAKESHI, YAMADA, TOSHIO, NAITO, TAKESHI, SUN HEIGHTS SHIROYAMA PARK E406
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1995
Main classification: F01N3
IPC codes: F01N7, F02B1, F01N3, B01D46