JP2016186298A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the nitrogen oxide occluding efficiency of a NOx occlusion reduction catalyst by efficiently cooling exhaust gas.SOLUTION: An exhaust emission control device includes: the NOx occlusion reduction catalyst provided in an exhaust pipe 140 into which exhaust gas exhausted from a combustion chamber of an engine is guided, for occluding nitrogen oxide in a predetermined temperature range; an outside air pipe 220 which encircles the exhaust pipe at least at the upstream side of the NOx occlusion reduction catalyst and into which outside air is introduced through an outside air introduction port 222; a communication port 240 provided in the exhaust pipe at its position encircled by the outside air pipe for communicating the exhaust pipe and the outside air pipe with each other; and an outside air introduction part for introducing the outside air through the outside air introduction port into the outside air pipe.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an exhaust gas purification device that purifies exhaust gas discharged from a combustion chamber of an engine.

  In order to improve fuel efficiency, an engine capable of performing lean combustion in which fuel is burned at an air-fuel ratio leaner than the stoichiometric air-fuel ratio (stoichiometric) has been developed. When lean combustion is performed, nitrogen oxides (NOx) are more likely to be generated than when combustion is performed at a stoichiometric air-fuel ratio. For this reason, a NOx occlusion reduction catalyst (LNT: Lean NOx Trap) that removes nitrogen oxides from the exhaust gas may be provided in the exhaust pipe of the engine capable of performing the lean combustion.

  Since the NOx occlusion reduction catalyst occludes nitrogen oxides in a predetermined temperature range (hereinafter referred to as “occlusion temperature range”), it is necessary to maintain the exhaust gas within the occlusion temperature range. In view of this, techniques for introducing the outside air into the exhaust pipe and cooling the exhaust gas (for example, Patent Documents 1 and 2) are disclosed.

JP-A-4-365918 JP-A-10-8943

  In the technology for introducing outside air into the exhaust pipe as described in Patent Documents 1 and 2, development of a technology for cooling the exhaust gas more efficiently is desired.

  Accordingly, an object of the present invention is to provide an exhaust gas purifying apparatus that can efficiently cool exhaust gas and improve the storage efficiency of nitrogen oxides by a NOx storage reduction catalyst.

  In order to solve the above problems, an exhaust gas purification apparatus of the present invention is provided in an exhaust pipe through which exhaust gas discharged from an engine combustion chamber is guided, and stores NOx in a predetermined temperature range. The catalyst and at least the upstream side of the NOx occlusion reduction catalyst in the exhaust pipe are surrounded by the outside air pipe through which the outside air is introduced through the outside air inlet, and the exhaust pipe and the outside air. A communication port that communicates with the inside of the pipe and an outside air introduction unit that introduces outside air into the outside air pipe through the outside air introduction port are provided.

  Further, a plurality of communication ports may be provided apart from each other in the circumferential direction of the exhaust pipe.

  Further, the communication port may be formed so that the opening area becomes larger as it is arranged on the downstream side in the flow direction of the outside air in the circumferential direction of the exhaust pipe.

  Further, it may be provided with a plurality of fins that protrude into the outer air pipe so as to extend from the respective downstream edges in the flow direction of the outside air flowing through the outer air pipe at the plurality of communication ports so as to extend upstream in the flow direction of the outside air. Good.

  Further, the separation distance between the upstream end of the fin and the communication port may be adjusted so that the amount of outside air introduced from all the communication ports is within a predetermined range.

  In addition, the fins may be provided in the plurality of communication ports so that the separation distance between the upstream end of the fin and the communication port increases as the fins are arranged on the downstream side.

  According to the present invention, the exhaust gas can be efficiently cooled, and the nitrogen oxide storage efficiency by the NOx storage reduction catalyst can be improved.

It is the schematic which shows the structure of an engine system. It is the schematic which shows the structure of an exhaust-gas purification | cleaning unit. It is a figure for demonstrating an external air pipe, a communicating port, and a fin. (A) is a figure for demonstrating the flow of the external air through a communicating port, (b) is the IV-IV sectional view taken on the line of FIG. It is a flowchart for demonstrating the flow of an external air introduction process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a schematic diagram illustrating a configuration of an engine system 100 according to the present embodiment. In FIG. 1, the signal flow is indicated by broken arrows. As shown in FIG. 1, the engine system 100 is provided with an ECU (Engine Control Unit) 110 formed of a microcomputer including a central processing unit (CPU), a ROM storing programs and the like, a RAM as a work area, and the like. The ECU 110 performs overall control of the engine 120. However, the configuration and processing related to the present embodiment will be described in detail below, and the description of the configuration and processing unrelated to the present embodiment will be omitted.

  The engine 120 is a multi-cylinder engine having a plurality of cylinders 122a, and an intake manifold 126 is communicated with an intake port 124 of each cylinder 122a formed in the cylinder block 122. An intake pipe 130 is communicated with a collective portion of the intake manifold 126 via an air chamber 128, an air cleaner 132 is provided on the upstream side of the intake pipe 130, and a throttle valve 134 is provided on the downstream side of the air cleaner 132.

  An exhaust manifold 138 communicates with the exhaust port 136 of each cylinder 122 a formed in the cylinder block 122 of the engine 120. A muffler 142 is communicated with a collective portion of the exhaust manifold 138 through an exhaust pipe 140, and an exhaust gas purification unit 200 described later is provided in the exhaust pipe 140.

  The engine 120 is provided with a spark plug 148 for each of the cylinders 122a so that the tip thereof is located in the combustion chamber 146. An injector 150 is provided in the combustion chamber 146 of each cylinder 122a.

  In the engine system 100, an intake air amount sensor 160 that detects the amount of intake air flowing into the engine 120 between the air cleaner 132 and the throttle valve 134 in the intake pipe 130, and the temperature of the air flowing into the engine 120 are detected. An intake air temperature sensor 162 is provided. The engine system 100 is also provided with a throttle opening sensor 164 that detects the opening of the throttle valve 134 and a crank angle sensor 166 that detects the crank angle of the crankshaft.

  Further, in the engine system 100, an intake valve (not shown) that can open and close the combustion chamber 146 and the intake port 124, and an exhaust valve (not shown) that can open and close the combustion chamber 146 and the exhaust port 136 are opened and closed. A VVT actuator 152 that drives a cam (not shown) and a cam sensor 168 that detects the rotation angle of the cam are provided. The engine system 100 is provided with an accelerator opening sensor 170 that detects the opening of an accelerator (not shown).

  Each of these sensors 160 to 170 is connected to ECU 110 and outputs a signal indicating the detected value to ECU 110.

  ECU 110 acquires signals output from sensors 160 to 170 to control engine 120. When the ECU 110 controls the engine 120, the signal acquisition unit 180, the target value derivation unit 182, the air amount determination unit 184, the injection amount determination unit 186, the throttle opening determination unit 188, the ignition timing determination unit 190, and the drive control unit 192. It functions as the outside air introduction control unit 194.

  The signal acquisition unit 180 acquires signals indicating values detected by the sensors 160 to 170. The target value deriving unit 182 derives the current engine speed based on the signal indicating the crank angle acquired from the crank angle sensor 166. Further, the target value deriving unit 182 refers to a pre-stored map based on the derived engine speed and a signal indicating the accelerator opening acquired from the accelerator opening sensor 170, and the target torque and the target engine speed. Is derived.

  The air amount determination unit 184 determines a target air amount to be supplied to each cylinder 122a based on the target engine speed and the target torque derived by the target value deriving unit 182. The throttle opening determination unit 188 derives the total target air amount of each cylinder 122a determined by the air amount determination unit 184, and determines the target throttle opening for intake of the total amount of air from the outside.

  The injection amount determination unit 186, based on the target air amount of each cylinder 122a determined by the air amount determination unit 184, for example, the fuel supplied to each cylinder 122a so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. A target injection amount is determined. In addition, the injection amount determination unit 186 performs each injection based on a signal indicating the crank angle detected by the crank angle sensor 166 in order to inject the determined target injection amount from the injector 150 in the intake stroke or compression stroke of the engine 120. The target injection timing and target injection period of the injector 150 are determined.

  Based on the target engine speed derived by the target value deriving unit 182 and a signal indicating the crank angle detected by the crank angle sensor 166, the ignition timing determining unit 190 is a target of the spark plug 148 in each cylinder 122a. Determine the ignition timing.

  The drive control unit 192 drives a throttle valve actuator (not shown) so that the throttle valve 134 opens at the target throttle opening determined by the throttle opening determination unit 188. Further, the drive control unit 192 drives the injector 150 at the target injection timing and the target injection period determined by the injection amount determination unit 186, thereby causing the injector 150 to inject fuel of the target injection amount. Further, the drive control unit 192 ignites the spark plug 148 at the target ignition timing determined by the ignition timing determination unit 190.

  Thus, the exhaust gas generated by the combustion of the fuel in the combustion chamber 146 is discharged to the outside through the exhaust pipe 140. The exhaust gas includes hydrocarbon (HC: HydroCarbon), one Since carbon oxide (CO) and nitrogen oxide (NOx) are contained, it is necessary to remove them. Therefore, an exhaust gas purification unit 200 is provided in the exhaust pipe 140, and hydrocarbons, carbon monoxide, and nitrogen oxides are removed in the exhaust gas purification unit 200.

  The ECU 110 functions as the outside air introduction control unit 194 when controlling the exhaust gas purification unit 200. The processing of the outside air introduction control unit 194 will be described in detail later.

  FIG. 2 is a schematic diagram showing the configuration of the exhaust gas purification unit 200. In FIG. 2, the signal flow is indicated by broken arrows. As shown in FIG. 2, the exhaust gas purification unit 200 includes a three-way catalyst 210, a NOx occlusion reduction catalyst 212, an outside air pipe 220, an outside air introduction unit 230, a communication port 240, fins, and the like. 250 and temperature sensors 260 and 262.

  The three-way catalyst 210 is provided in the exhaust pipe 140. The three-way catalyst 210 includes, for example, platinum (Pt), palladium (Pd), and rhodium (Rh). The three-way catalyst 210 removes hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas discharged from the exhaust port 136. Remove.

  The NOx occlusion reduction catalyst 212 is provided on the downstream side of the three-way catalyst 210 in the exhaust pipe 140, temporarily occludes nitrogen oxides that could not be removed by the three-way catalyst 210, and the occluded nitrogen oxides have a predetermined timing. Reduce (purify).

  Specifically, the NOx occlusion reduction catalyst 212 occludes nitrogen oxides in a predetermined occlusion temperature range (for example, a temperature range of 300 ° C. to 500 ° C.), and the reduction is higher than the upper limit value of the occlusion temperature range. It has a characteristic of reducing nitrogen oxides at a temperature (for example, 550 ° C.) or higher. On the other hand, in the state where the air-fuel ratio is lean in the engine 120, that is, in the state where lean combustion (lean burn) is being performed, the state where the stoichiometric air-fuel ratio is set, or the state where the air-fuel ratio is rich, that is, rich combustion (rich rich) The amount of nitrogen oxide emission is larger than that in the state where the burn is performed, and the temperature of the exhaust gas is lower.

  Therefore, it is desirable that the NOx occlusion reduction catalyst 212 occludes nitrogen oxides in a state where lean combustion is performed, and reduces nitrogen oxides in a state where rich combustion is being performed. That is, it is preferable that the temperature of the exhaust gas is within the storage temperature range in the state where the lean combustion is being performed, and the temperature of the exhaust gas is equal to or higher than the reduction temperature in the state where the rich combustion is being performed. The engine 120 of the present embodiment normally performs lean combustion and intermittently performs rich combustion for a short period (for example, several seconds), so that the NOx storage reduction catalyst 212 performs nitrogen oxide during lean combustion. And nitrogen oxides are reduced during rich combustion.

  Here, in the state where the rich combustion is performed, the temperature of the exhaust gas becomes equal to or higher than the reduction temperature, so that the nitrogen oxide can be reduced. However, in the state where the lean combustion is performed, the temperature of the exhaust gas falls within the storage temperature range. It may exceed the reduction temperature. If it does so, there exists a possibility that the storage efficiency of the NOx storage reduction catalyst 212 may fall, and the removal rate of a nitrogen oxide may reduce.

  Therefore, the exhaust gas purification unit 200 of the present embodiment includes the outside air pipe 220, the outside air introduction unit 230, the communication port 240, the fins 250, and the temperature sensors 260 and 262, and the temperature of the exhaust gas exceeds the storage temperature range (for example, When the temperature of the exhaust gas exceeds 500 ° C.), outside air (air) is introduced to the upstream side of the NOx storage reduction catalyst 212 in the exhaust pipe 140 to cool the exhaust gas to the storage temperature range.

  More specifically, the external air pipe 220 surrounds the three-way catalyst 210 and the NOx storage reduction catalyst 212 in the exhaust pipe 140. The outside air tube 220 is provided with an outside air introduction port 222, and outside air is introduced by the outside air introduction unit 230 through the outside air introduction port 222. That is, the outside air pipe 220 forms a double pipe together with the exhaust pipe 140. The exhaust gas passes through the flow path inside the double pipe (exhaust pipe 140) and the flow path outside the double pipe (outside air pipe 220). ) Outside air will circulate. Further, the outside air introduction pipe 232 is provided orthogonal to the flow direction of the exhaust gas, and when outside air is introduced through the outside air introduction port 222, the outside air flows along the circumferential direction of the outside air introduction pipe 232. The flow direction of the external air in the external air pipe 220 and the flow direction of the exhaust gas in the exhaust pipe 140 are orthogonal to each other.

  The outside air introduction unit 230 includes, for example, an outside air introduction pipe 232 communicated with the outside air introduction port 222 and a pump 234 provided in the outside air introduction pipe 232, and the outside air introduction port is configured by driving the pump 234. Outside air is introduced into the outside air tube 220 through 222. The communication port 240 is provided in a portion of the exhaust pipe 140 that is surrounded by the outside air pipe 220, and communicates the exhaust pipe 140 and the outside air pipe 220. When the outside air is introduced into the outside air pipe 220 by the outside air introduction unit 230, the outside air is introduced into the exhaust pipe 140 through the communication port 240.

  3A and 3B are views for explaining the outer air tube 220, the communication port 240, and the fin 250. FIG. 3A is a perspective view in which the fin 250 is omitted, and FIG. 3B is a perspective view in which the fin 250 is provided. FIG. 3C is an enlarged perspective view of the communication port 240 and the fin 250. In FIG. 3, the communication port 240 is shown in black, the flow of exhaust gas is indicated by a white arrow, and the flow of outside air is indicated by a solid arrow.

  As shown in FIG. 3A, in the present embodiment, a plurality of communication ports 240 are provided in the circumferential direction of the exhaust pipe 140 (here, seven). In the present embodiment, the communication ports 240 are provided at equal intervals in the circumferential direction of the exhaust pipe 140 so that the distances between the adjacent communication ports 240 are equal. The communication port 240 is formed in the exhaust pipe 140 in a substantially triangular shape. Further, the communication port 240 is provided with a check valve (not shown) that allows the outside air to flow into the exhaust pipe 140 from the outside air pipe 220 and restricts the outflow of the exhaust gas from the exhaust pipe 140 to the outside air pipe 220. ing.

  As shown in FIG. 3B, the fin 250 is provided so as to protrude into the outside air tube 220 for each of the plurality of communication ports 240. More specifically, as shown in FIG. 3C, the fin 250 includes a base 252, an extending part 254, and a connecting part 256. The base 252 is a plate member standing in the outside air pipe 220 from the downstream edge 242 in the outside air flow direction at the communication port 240. The extending portion 254 is a plate member that extends from the base portion 252 to the upstream side in the flow direction of the outside air. The connecting portion 256 is a plate member that stands in the outside air pipe 220 from the downstream edge portion 244 in the exhaust gas flow direction at the communication port 240 and is connected to the extending portion 254. The extending portion 254 is formed so as to cover the communication port 240, and here, the extending portion 254 is formed so that the width in the exhaust gas flow direction gradually decreases from the downstream side to the upstream side in the external air flow direction. Yes. (It is formed in a shape (substantially triangular) similar to the communication port 240).

  4A is a view for explaining the flow of outside air through the communication port 240, and FIG. 4B is a cross-sectional view taken along line IV-IV in FIG. As shown in FIG. 4A, seven fins 250 are provided from the upstream side in the flow direction of the outside air at positions corresponding to the communication ports 240 (indicated by 240A to 240G in order from the upstream side in FIG. 4). (In FIG. 4, 250A to 250G are shown in order from the upstream side). Accordingly, a part of the outside air introduced from the outside air introduction part 230 through the outside air introduction port 222 is first introduced into the exhaust pipe 140 through the communication port 240A provided with the fins 250A. A part of the outside air that has not been introduced into the exhaust pipe 140 through the communication port 240A is introduced through the communication port 240B provided with the fins 250B. Thereafter, similarly, the communication port 240C provided with the fin 250C, the communication port 240D provided with the fin 250D, the communication port 240E provided with the fin 250E, the communication port 240F provided with the fin 250F, and the fin 250G were provided. Outside air is sequentially introduced into the exhaust pipe 140 through the communication port 240G.

  As shown in FIG. 4B, the separation distance L between the upstream end portion 258 of the fin 250 and the communication port 240 increases as the fin 250 is arranged downstream in the flow direction of the outside air. As described above, the communication port 240 is provided. That is, the separation distance L of the fin 250A is smaller than the separation distance L of the fin 250B, the separation distance L of the fin 250B is smaller than the separation distance L of the fin 250C, and the separation distance L of the fin 250C is the separation distance L of the fin 250D. Smaller than. Further, the separation distance L of the fin 250D is smaller than the separation distance L of the fin 250E, the separation distance L of the fin 250E is smaller than the separation distance L of the fin 250F, and the separation distance L of the fin 250F is the separation distance L of the fin 250G. Smaller than. In this way, the separation distance L between the upstream end 258 of the fin 250 and the communication port 240 is adjusted so that the amount of outside air introduced from all the communication ports 240 is within a predetermined range.

  The pressure (flow velocity) of the outside air flowing through the outside air pipe 220 is the largest in the vicinity of the outside air introduction port 222 and decreases as it moves away from the outside air introduction port 222, that is, toward the downstream side. Therefore, when the opening area of the communication port 240 (the cross-sectional area of the outside air at the communication port 240) is the same, the amount of outside air introduced into the exhaust pipe 140 from the communication port 240 disposed on the downstream side in the flow direction of the outside air. Is less than the amount of outside air introduced into the exhaust pipe 140 from the communication port 240 disposed on the upstream side.

  Therefore, the separation distance L is set as described above, and the area (projected area) orthogonal to the flow of the outside air in the flow path defined by the fins 250 increases from the upstream side to the downstream side in the flow direction of the outside air. Then, the amount of outside air introduced from all the communication ports 240 is set within a predetermined range. Thereby, variation in the amount of outside air introduced into the exhaust pipe 140 due to the position of the communication port 240 can be reduced. Therefore, the outside air can be introduced into the exhaust pipe 140 substantially evenly, and the exhaust gas can be uniformly cooled without being biased.

  Returning to FIG. 2, the temperature sensor 260 detects the temperature of the exhaust gas between the three-way catalyst 210 and the communication port 240 in the exhaust pipe 140. The temperature sensor 262 detects the temperature of the outside air introduced into the outside air introduction pipe 232.

  The outside air introduction control unit 194 controls the pump 234 of the outside air introduction unit 230 according to the temperature of the exhaust gas detected by the temperature sensor 260, the temperature of the outside air detected by the temperature sensor 262, and the operating conditions.

(Outside air introduction processing)
Subsequently, an outside air introduction process by the outside air introduction control unit 194 will be described. FIG. 5 is a flowchart for explaining the flow of outside air introduction processing. In the present embodiment, the outside air introduction process is repeatedly performed by interruptions generated at predetermined time intervals.

(Step S310)
As shown in FIG. 5, the outside air introduction control unit 194 first has the temperature of the exhaust gas upstream of the NOx storage reduction catalyst 212 detected by the temperature sensor 260 exceeding the upper limit value (for example, 500 ° C.) of the storage temperature range. Determine whether.

  As a result, when it is determined that the temperature of the exhaust gas exceeds the upper limit value of the storage temperature range (YES in step S310), the process proceeds to step S320, and does not exceed the upper limit value of the storage temperature range (storage temperature range). If it is determined that it is equal to or less than the upper limit value (NO in step S310), the outside air introduction process ends.

(Step S320)
First, the outside air introduction control unit 194 estimates the amount of heat to be reduced based on the amount of exhaust gas exhausted from the combustion chamber 146 and the temperature of the exhaust gas detected by the temperature sensor 260. Then, the outside air introduction control unit 194 derives the amount of outside air introduced that can reduce the estimated amount of heat based on the estimated amount of heat and the temperature of the outside air detected by the temperature sensor 262.

(Step S330)
The outside air introduction control unit 194 drives and controls the pump 234 so that the outside air introduction amount derived in step S320 is obtained.

  As described above, according to the exhaust gas purification apparatus of the present embodiment configured by the exhaust gas purification unit 200 and the outside air introduction control unit 194, the outside air can be uniformly introduced into the exhaust pipe 140 in the circumferential direction, It becomes possible to evenly mix outside air with the exhaust gas flowing through the exhaust pipe 140. Therefore, the exhaust gas can be uniformly cooled without unevenness, and the exhaust gas can be efficiently cooled within the storage temperature range. As a result, the storage efficiency of nitrogen oxides by the NOx storage reduction catalyst 212 can be improved.

  Further, as described above, since the outside air pipe 220 surrounds the exhaust pipe 140, the outside air introduced into the outside air pipe 220 flows through the outside air pipe 220 along the outer periphery of the exhaust pipe 140 and then becomes a communication port. 240 is introduced into the exhaust pipe 140. Therefore, heat can be exchanged between the outside air and the exhaust gas through the exhaust pipe 140 while flowing along the outer periphery of the exhaust pipe 140, and the exhaust gas can be indirectly cooled with the outside air.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  In the above embodiment, the configuration in which the ECU 110 functions as the outside air introduction control unit 194 has been described as an example. However, the outside air introduction control unit 194 may be configured separately from the ECU 110.

  Moreover, in the said embodiment, the structure provided with the external air pipe | tube 220 surrounding between the three way catalyst 210 and the NOx storage reduction catalyst 212 in the exhaust pipe 140 was mentioned as an example, and was demonstrated. However, the outside air pipe 220 only needs to surround at least the upstream side of the NOx storage reduction catalyst 212.

  Moreover, in the said embodiment, the exhaust gas purification unit 200 demonstrated and demonstrated the structure provided with the temperature sensor 260 as an example. However, the exhaust gas purification unit 200 may not include the temperature sensor 260. In this case, for example, an exhaust gas temperature map in which the engine speed and the accelerator opening are associated with the exhaust gas temperature is stored in the ECU 110 in advance. The outside air introduction control unit 194 refers to the exhaust gas temperature map based on the engine speed derived by the target value deriving unit 182 and the signal indicating the accelerator opening obtained from the accelerator opening sensor 170. The exhaust gas temperature may be estimated, and the outside air introduction amount may be derived based on the estimated exhaust gas temperature.

  Further, in the above-described embodiment, a configuration in which the outside air introduction control unit 194 derives the outside air introduction amount based on the temperature of the exhaust gas flowing between the three-way catalyst 210 and the communication port 240 will be described as an example. did. However, the outside air introduction control unit 194 may derive the outside air introduction amount based on the temperature of the exhaust gas upstream of the three-way catalyst 210, for example.

  Further, in the above embodiment, a description will be given by taking as an example a configuration in which a plurality of communication ports 240 are provided apart from each other in the circumferential direction of the exhaust pipe 140 and the distances between adjacent communication ports 240 are substantially equal. did. However, the distance between adjacent communication ports 240 may not be equal, and the communication ports 240 are not necessarily provided in the circumferential direction of the exhaust pipe 140. Moreover, the communication port 240 may be one.

  Moreover, in the said embodiment, the structure where the opening area of the some communicating port 240 was substantially equal was mentioned as an example, and was demonstrated. However, the opening area of the communication port 240 may be different, and the communication port 240 is formed so that the opening area increases as it is arranged downstream in the flow direction of the outside air in the circumferential direction of the exhaust pipe 140. Good. In this case, the opening area of the communication ports 240 may be adjusted so that the amount of outside air introduced from all the communication ports 240 is within a predetermined range. With this configuration, it is possible to further reduce variation in the amount of outside air introduced into the exhaust pipe 140 due to the position of the communication port 240.

  Moreover, in the said embodiment, the structure provided with the fin 250 was mentioned as an example, and was demonstrated. However, the fins 250 may not be provided. Further, in the above-described embodiment, the configuration in which the fins 250 are respectively provided in the plurality of communication ports 240 has been described as an example so that the separation distance L increases from the upstream side toward the downstream side. However, the separation distance L of the fins 250 is not limited.

  Moreover, in the said embodiment, the case where the three-way catalyst 210 and the NOx storage reduction catalyst 212 were comprised separately was demonstrated as an example. However, the three-way catalyst 210 and the NOx storage reduction catalyst 212 may be arranged in one casing.

  INDUSTRIAL APPLICABILITY The present invention can be used for an exhaust gas purification device that purifies exhaust gas discharged from a combustion chamber of an engine.

120 Engine 140 Exhaust pipe 146 Combustion chamber 200 Exhaust gas purification unit (exhaust gas purification device)
212 NOx occlusion reduction catalyst 220 outside air pipe 222 outside air introduction port 230 outside air introduction part 240 communication port 244 edge 250 fin 258 upstream end

Claims (6)

A NOx occlusion reduction catalyst which is provided in an exhaust pipe through which exhaust gas discharged from the combustion chamber of the engine is guided and occludes nitrogen oxides in a predetermined temperature range;
An outside air pipe that surrounds at least the upstream side of the NOx storage reduction catalyst in the exhaust pipe and into which outside air is introduced through an outside air inlet;
A communication port provided at a location surrounded by the outer air pipe in the exhaust pipe, and communicating between the exhaust pipe and the outer air pipe;
An outside air introduction section for introducing outside air into the outside air pipe through the outside air introduction port;
An exhaust gas purifying device comprising:   The exhaust gas purification device according to claim 1, wherein a plurality of the communication ports are provided apart from each other in a circumferential direction of the exhaust pipe.   The exhaust gas purification device according to claim 2, wherein the communication port is formed so that an opening area increases as it is arranged on the downstream side in the flow direction of the outside air in the circumferential direction of the exhaust pipe. .   A plurality of fins projecting into the external air pipe so as to extend from the respective downstream edges in the flow direction of the external air flowing through the external air pipe at the plurality of communication ports so as to extend upstream in the flow direction of the external air. The exhaust gas purifying device according to any one of claims 2 and 3, wherein   5. The separation distance between the upstream end of the fin and the communication port is adjusted so that the amount of outside air introduced from all the communication ports is within a predetermined range. The exhaust gas purifying apparatus according to 1.   The fin is provided in each of the plurality of communication ports such that a separation distance between an upstream end portion of the fin and the communication port increases as the fin is disposed on the downstream side. The exhaust gas purification device according to 4 or 5.

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