JP2008309000A - 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 compatibly establishing reduction of exhaust pressure of an internal combustion engine, and acceleration of diffusion and atomization of reducer at a high level, and capable of reducing exhaust pressure of the internal combustion engine and achieving good exhaust emission control performance by evenly supplying reducer to each section of a catalyst device. <P>SOLUTION: This exhaust emission control device has a casing 22 comprising an expansion part 22a expanding diameter toward a downstream side, a large diameter part 22b continuing from the expansion part 22a with a same diameter, and a contraction part 22c contracting diameter toward a downstream side from the large diameter part 22b arranged at an upstream side of an SCR (selective reduction type NOx catalyst) in an exhaust gas passage, a fin device 26 forming swirl arranged at the large diameter part 22b, and an injection nozzle 34 injecting urea water solution arranged at a downstream of the fin device 26. Increase of pressure loss is suppressed by forming swirl in the large diameter part 22b of which passage cross section is large, and swirl is accelerated in the contraction part 22c after that to diffuse and atomize urea water solution by good agitation action. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus that injects a reducing agent from an injection nozzle into exhaust gas flowing through an exhaust passage and supplies the reducing agent to a downstream purification apparatus.

As an exhaust gas purification device that injects a reducing agent into this type of exhaust gas and supplies it to a downstream purification device, for example, there is one equipped with an SCR catalyst (selective reduction type NOx catalyst). As is well known, since the SCR catalyst requires NH ₃ (ammonia) to reduce NOx in the exhaust gas, an aqueous urea solution is injected as a reducing agent from an injection nozzle disposed upstream of the SCR catalyst in the exhaust passage. In addition, the NOx reduction action by the SCR catalyst is obtained by utilizing NH ₃ (ammonia) generated by hydrolysis of the urea aqueous solution by exhaust heat and water vapor in the exhaust gas.

The NOx reduction action of the SCR catalyst is strongly influenced by the supply state of the urea aqueous solution, and in order to obtain a good reduction action, the urea aqueous solution is sufficiently diffused and atomized in the exhaust gas and the urea on the wall of the exhaust passage and the like It is necessary to supply NH ₃ evenly to each part of the SCR catalyst while preventing adhesion of the aqueous solution. In order to achieve such a demand, various countermeasures have been proposed in which means for stirring exhaust gas is provided in the exhaust passage (see, for example, Patent Document 1).

The technique disclosed in Patent Document 1 is directed to a NOx reduction converter provided in an exhaust passage of an internal combustion engine instead of an SCR catalyst, and a reducing agent (unburned fuel) is injected from an injection nozzle disposed upstream of the converter. However, it is common in that it is desired to supply the reducing agent evenly to each part of the converter. For this purpose, in the second embodiment shown in FIG. 2 of Patent Document 1, as a stirring means for stirring the exhaust gas, a rod-shaped member is arranged on the downstream side of the injection nozzle in a direction crossing the exhaust flow, Is made to collide with the rod-shaped member and stirred to promote diffusion and atomization of the reducing agent into the exhaust gas.
Japanese Patent Laid-Open No. 2002-213233 (FIG. 2)

  By the way, this kind of agitation means can promote the diffusion and atomization of the reducing agent by the agitation action of the exhaust gas, but it causes pressure loss due to the installation in the exhaust passage, so the exhaust pressure of the internal combustion engine is increased and the running performance is lowered. Can be a factor. Both conditions are basically in a trade-off relationship. However, in the technique of the above-mentioned Patent Document 1, for example, a rod-shaped member for the purpose of improving the stirring action because of the principle of obtaining a stirring action by colliding exhaust gas with the rod-shaped member. When the number of the cylinders is increased, the exhaust pressure of the internal combustion engine increases rapidly with the pressure loss, and as a result, both conditions can only be achieved at a low level.

In addition, in the technique of Patent Document 1, since the reducing agent is injected from the injection nozzle into a very narrow exhaust passage, the reducing agent tends to adhere to the opposing wall of the injection nozzle. And since the reducing agent once adhered is difficult to diffuse and atomize in the exhaust gas, this phenomenon also contributes to the above-mentioned problems related to the trade-off.
The present invention has been made in order to solve such problems. The object of the present invention is to reduce the exhaust pressure of the internal combustion engine and promote the diffusion and atomization of the reducing agent at a high level. An exhaust purification device for an internal combustion engine that can achieve good running performance by reducing exhaust pressure of the internal combustion engine, and can achieve good purification performance by uniformly supplying a reducing agent to each part of the catalyst device It is to provide.

  In order to achieve the above object, a first aspect of the present invention comprises a purification device disposed in an exhaust passage of an internal combustion engine, and a part of an exhaust passage on the upstream side of the purification device, from the exhaust passage toward the downstream side. An enlarged part that expands in diameter, a large-diameter part that keeps the same diameter from the enlarged part and continues downstream, and a reduced part that shrinks from the large-diameter part toward the downstream side and is connected to the purification device side And a swirl flow generating means for generating a swirl flow in the exhaust gas flowing through the large diameter portion, and disposed in the large diameter portion of the casing and flowing through the large diameter portion. And a reducing agent injection means for injecting a reducing agent required for the operation of the purification catalyst into the exhaust gas.

  Therefore, the exhaust gas of the internal combustion engine flows through the casing through the exhaust passage and reaches the downstream purification device, and after the harmful components are purified by the purification device, it is discharged into the atmosphere. In the process of circulating in the casing, first, the exhaust gas is transferred from the enlarged portion to the large diameter portion to reduce the flow velocity, and in this large diameter portion, the swirling flow is generated by the swirling flow generating means, and the reducing agent injection means A reducing agent is injected. Note that any one of the swirl flow generation means and the reducing agent injection means may be upstream.

  In the large-diameter portion having a large passage cross-sectional area, it is possible to set the injection distance of the reducing agent from the reducing agent injection means to the opposing wall, so that the injected reducing agent is prevented from adhering to the opposing wall. Further, a large-diameter swirling flow generating means can be installed in the large-diameter portion having a large passage cross-sectional area, and the large-diameter swirling flow generating means reduces the pressure loss of the exhaust gas when generating the swirling flow, And since the exhaust gas flow velocity when circulating in the large diameter portion is low, the pressure loss accompanying the occurrence of the swirling flow is further reduced. Therefore, at this time, a swirling flow is generated in the exhaust gas due to the minimum pressure loss of the exhaust gas.

  Thereafter, the exhaust gas is introduced into the reduced portion through the large diameter portion while diffusing and atomizing the reducing agent by the stirring action of the swirling flow. Since the passage cross-sectional area gradually decreases in the reduction portion, the swirling flow of the exhaust gas is gradually increased according to the so-called angular momentum conservation law of the swirling flow, and the stirring of the exhaust gas is further promoted. Accordingly, in combination with the suppression of the wall surface of the reducing agent on the large-diameter portion, the reducing agent is diffused and atomized well in the exhaust gas, and is evenly supplied to each part of the downstream purification device.

According to a second aspect of the present invention, in the first aspect, the swirling flow generating means is provided with a plurality of fins for generating a swirling flow in the exhaust gas on the outer peripheral side centered on the axis in the large diameter portion, and the axis of the large diameter portion. A nose cone for guiding the exhaust gas to the outer peripheral side is provided on the upstream side in the vicinity.
Accordingly, since the fin of the swirl flow generating means is located on the outer peripheral side centering on the axis of the large diameter portion, it is necessary to change the transfer direction of the exhaust gas along the axis to the outer peripheral side. Since the exhaust gas is smoothly guided to the outer peripheral side by the nose cone located in the vicinity, the pressure loss of the exhaust gas when flowing through this portion is suppressed to the minimum.

As described above, according to the exhaust gas purification apparatus for an internal combustion engine of the first aspect of the present invention, the reduction of the exhaust pressure of the internal combustion engine and the promotion of diffusion and atomization of the reducing agent can be achieved at a high level. The exhaust pressure can be reduced to realize good running performance, and the reducing agent can be evenly supplied to each part of the catalyst device to achieve good purification performance.
According to the exhaust gas purification apparatus for an internal combustion engine of the second aspect of the present invention, in addition to the first aspect, the exhaust gas is smoothly guided to the fins of the swirling flow generating means to further reduce the pressure loss of the exhaust gas and thus the exhaust pressure of the internal combustion engine. Can be reduced.

Hereinafter, an embodiment in which the present invention is embodied in an exhaust gas purification apparatus for an internal combustion engine equipped with an SCR catalyst will be described.
FIG. 1 is an overall configuration diagram showing a diesel engine to which an exhaust gas purification apparatus for an internal combustion engine of the present embodiment is applied. The internal combustion engine 1 is configured as an in-line 6-cylinder engine. Each cylinder of the internal combustion engine 1 is provided with a fuel injection valve 2. Each fuel injection valve 2 is supplied with pressurized fuel from a common common rail 3, and injects fuel into the cylinder of the corresponding cylinder when the valve is opened. .

  An intake manifold 4 is mounted on the intake side of the internal combustion engine 1, and an intake passage 5 connected to the intake manifold 4 is provided with an air cleaner 6, a compressor 7 a of a turbocharger 7, and an intercooler 8 from the upstream side. An exhaust manifold 10 is mounted on the exhaust side of the internal combustion engine 1, and a turbine 7 b of a turbocharger 7 connected coaxially with the compressor 7 a is connected to the exhaust manifold 10. An exhaust passage 11 is connected to the turbine 7b, and a first converter 12, a urea injection stirring unit 13, and a second converter 14 are disposed in the exhaust passage 11 from the upstream side. A vessel is provided.

  The first converter 12 has a cylindrical shape along the front-rear direction (exhaust gas flow direction), the upstream oxidation catalyst 15 is disposed on the upstream side of the first converter 12, and PM (particulate matter) in the exhaust gas is disposed on the downstream side. A wall flow type DPF (Diesel Particulate Filter) 16 is provided for collecting slag. A fuel injection valve 17 for forced regeneration of the DPF 16 is installed at a position upstream of the first converter 12 in the exhaust passage 11.

Like the first converter 12, the second converter 14 has a cylindrical shape along the front-rear direction, and an SCR catalyst (selective reduction type NOx) that reduces NOx in the exhaust gas by supplying NH ₃ (ammonia) is provided upstream of the second converter 14. Catalyst) 18 is disposed, and a downstream oxidation catalyst 19 is disposed downstream.
In the following description, the exhaust passage 11 connecting the first and second converters 12 and 14 is referred to as an upstream exhaust pipe 21a and a downstream exhaust pipe 21b. These upstream side and downstream side exhaust pipes 21a and 21b are formed in a pipe shape having a circular cross section like the other exhaust passages 11, and the inner diameter of the exhaust pipes 21a and 21b takes into account the specifications such as the displacement of the internal combustion engine 1, It is set to a dimension (for example, 65 mm) that does not greatly increase the exhaust pressure during exhaust gas circulation. The urea injection stirring unit 13 is disposed between the upstream and downstream exhaust pipes 12 and 14 and constitutes a part of the exhaust passage 11.

  FIG. 2 is an enlarged cross-sectional view showing the urea injection stirring unit 13, and FIG. 3 is a cross-sectional view taken along the line III-III of FIG. The casing 22 of the urea injection stirring unit 13 has an enlarged diameter 22a that expands in a cone shape toward the downstream side while continuing from the rear end (downstream side) of the upstream exhaust pipe 21a, and the same diameter from the rear end of the enlarged portion 22a. The large-diameter portion 22b that continues to the downstream side while maintaining the diameter, and the diameter decreases in a cone shape toward the downstream side while continuing from the rear end of the large-diameter portion 22b, and the rear end is the front end (upstream of the downstream exhaust pipe 21b The reduction part 22c connected to the side). Compared to the upstream and downstream exhaust pipes 12 and 14, the large diameter portion 22a of the casing 22 has a larger inner diameter (for example, 98 mm). Exhaust gas from the upstream side exhaust pipe 21a flows through the casing 22 of the urea injection stirring unit 13 and is transferred to the downstream side exhaust pipe 21b. The exhaust gas changes its flow rate according to the change in the cross-sectional area of the passage in the casing 22. The flow rate of the exhaust gas is greatly reduced in the large-diameter portion 22b due to the setting of the inner diameter.

  The front end of the enlarged portion 22a of the casing 22 is welded to the rear end of the upstream side exhaust pipe 21a, and the rear end of the reduced portion 22c of the casing 22 is welded to the front end of the downstream side exhaust pipe 21b. Further, square plate-like flanges 23 are welded to the rear end of the enlarged portion 22a of the casing 22 and the front end of the large-diameter portion 22b, respectively, and these flanges 23 are mutually fastened by bolts 24 and nuts 25 to enlarge. The portion 22a and the large diameter portion 22b are integrated. Between the flange 23 of the enlarged portion 22a and the large diameter portion 22b, the periphery of the base portion 27 of the fin device 26 (swirl flow generating means) having a square plate shape is sandwiched and fastened together. It arrange | positions with the attitude | position orthogonal to the distribution direction of waste gas in the casing 22 of the urea injection stirring part 13. FIG.

  The base part 27 is manufactured by press-molding a steel plate. Hereinafter, the configuration of the fin device 26 including the base part 27 will be described in detail. In the casing 22, a circular through hole 28 (shown in FIG. 3) centering on the axis L of the casing 22 is provided in the base portion 27. 29 and the fin support part 30 are formed. The fins 29 and the fin support portions 30 are alternately arranged in the circumferential direction around the through hole 28, and each fin 29 is set to be significantly longer in the circumferential direction than the fin support portions 30. Each fin 29 is continuous with one of the fin support portions 30 located on both sides (clockwise side in FIG. 3), and the other fin support portion 30 (counterclockwise side in FIG. 3) and the inside of the casing 22 are provided. The peripheral wall is divided by press molding.

  As a result, the fin support portions 30 extend from the four equally divided locations on the inner peripheral side of the casing 22 toward the inner periphery, and the base ends of the fins 29 corresponding to the one side edges of the fin support portions 30 are supported. Has been. Each fin 29 is bent from the boundary with the fin support portion 30 on the proximal end side, whereby each fin 29 is directed in the large diameter portion 22b of the casing 22 with the distal end side downstream in the exhaust gas circulation direction, and The posture is raised from the base portion 27 at an angle α in the same circumferential direction. Further, the fan 27 is bent to form four fan-shaped flow holes 31 corresponding to the fins 29 in the base portion 27, and the enlarged portion 22 a and the large diameter portion 22 b communicate with each other through the flow holes 31. ing.

  A nose cone 32 of a fin device 26 press-molded into a cup shape is disposed in the enlarged portion 22 a of the casing 22, and the nose cone 32 has a distal end directed upstream on an axis L of the casing 22, and a proximal end Is arranged in a posture in which it is brought into contact with the base portion 27. The base end of the nose cone 32 is formed in a cylindrical shape and substantially the same diameter as the through hole 28 of the base portion 27, and is fixed on the base portion 27 by being welded to the inner peripheral edge of each fin support portion 30. ing. A ring-shaped guide path 33 is formed around the nose cone 32 in the enlarged portion 22 a of the casing 22, and the guide path 33 communicates with the inside of the large-diameter portion 22 b through the flow holes 31 of the fin device 26. .

  An electromagnetic injection nozzle 34 (reducing agent injection means) is disposed at a position slightly downstream of the fin device 26 of the casing 22 so as to penetrate the inside and outside of the casing 22. Is fixed in a posture oriented at a predetermined angle β on the downstream side. The injection nozzle 34 is configured to be able to arbitrarily inject into the casing 22 using a urea aqueous solution fed from a tank (not shown) as a reducing agent.

  Devices such as the fuel injection valve 2 of each cylinder of the internal combustion engine 1, the fuel injection valve 17 for forced regeneration, the urea aqueous solution injection nozzle 34, and other sensors, not shown, are connected to an ECU 41 (electronic control unit). The drive is controlled by the ECU 41 based on detection information from the sensors. For example, the ECU 41 operates the internal combustion engine 1 by controlling the injection amount, injection pressure, and injection timing of the fuel injection valve 2 based on the operating state of the internal combustion engine 1 such as the engine speed and load.

  During operation of the internal combustion engine 1, exhaust gas discharged from the internal combustion engine 1 is introduced into the first converter 12 through the exhaust manifold 10 through the exhaust passage 11, and after passing through the internal pre-stage oxidation catalyst 15 and the DPF 16, the upstream exhaust pipe. It is introduced into the casing 22 of the urea jet stirring unit 13 from 21a. Further, after flowing through the casing 22, the exhaust gas is introduced into the second converter 14 from the downstream exhaust pipe 21b, and after passing through the internal SCR catalyst 18 and the post-stage oxidation catalyst 19, is exhausted to the atmosphere through a silencer.

In the DPF 16, PM containing exhaust gas flowing through the wall of the internal passage is captured, thereby purifying the PM. The amount of PM collected on the DPF 16 gradually increases with the collection of PM, but the collected PM is in a predetermined operation state (for example, an operation state where the exhaust gas temperature is relatively high). The NO ₂ generated from the NO in the exhaust gas by the oxidation reaction on the pre-stage oxidation catalyst 15 is continuously incinerated and removed using as an oxidizing agent.

  Further, if such an operation state in which the continuous regeneration action of the DPF 16 is not obtained is continued, the amount of PM trapped in the DPF 16 gradually increases and exceeds the allowable amount. The ECU 41 performs forced regeneration to forcibly remove PM on the DPF 16 before the amount of collected PM estimated from the operating state of the internal combustion engine 1 exceeds the allowable amount of the DPF 16. For this forced regeneration, a fuel injection valve 17 on the exhaust passage 11 is used, unburned fuel is injected from the fuel injection valve 17 and supplied onto the pre-stage oxidation catalyst 15, and the downstream DPF 16 is supplied by the oxidation reaction heat. The temperature is raised and PM is removed by incineration. Note that unburned fuel may be supplied onto the pre-stage oxidation catalyst 15 by post-injection in the expansion stroke or exhaust stroke after the main injection.

On the other hand, in order to cause the SCR catalyst 18 to exert a NOx purification action, the ECU 41 detects urea from the injection nozzle 34 based on the operating state of the internal combustion engine 1, a detection value of a temperature sensor (not shown) installed in the vicinity of the injection nozzle 34, and the like. Control the amount of aqueous solution sprayed. The injected urea aqueous solution is hydrolyzed by the exhaust heat and water vapor in the exhaust gas in the process of flowing from the urea injection stirring unit 13 to the downstream side exhaust pipe 21b to generate NH ₃ and is transferred onto the SCR catalyst 18 on the downstream side. Then, NOx in the exhaust gas is reduced to harmless N ₂ using NH ₃ on the SCR catalyst 18. Note that CO generated by combustion of PM in the DPF 16 and excess NH ₃ on the SCR catalyst 18 are processed by the post-stage oxidation catalyst 19.

Since the NOx reduction action on the SCR catalyst 18 is strongly influenced by the supply state of the urea aqueous solution from the injection nozzle 34, in this embodiment, the urea injection stirring unit 13 promotes diffusion and atomization of the urea aqueous solution. Hereinafter, the operation and effect of the configuration will be described.
As described above, the exhaust gas that has passed through the first converter 12 is introduced into the second converter 14 through the casing 22 of the urea injection stirring unit 13, and in the process of flowing through the casing 22 of the urea injection stirring unit 13, first, an expansion unit 22a is introduced into the large diameter portion 22b through the flow hole 31 of the fin device 26. Since the flow holes 31 of the fin device 26 are located on the outer peripheral side centering on the axis L of the casing 22 corresponding to the fins 29, it is necessary to change the transfer direction of the exhaust gas along the axis L to the outer peripheral side. Since the exhaust gas is smoothly guided to the outer peripheral side through the guide path 33 by the nose cone 32 positioned on the axis L of the casing 22, the pressure loss of the exhaust gas when flowing through this portion is suppressed to the minimum.

  When passing through the flow holes 31 of the fin device 26, the exhaust gas collides with the fins 29 and is guided along the fin angle α, thereby generating a swirling flow in the large-diameter portion 22b. A large-diameter fin device 26 can be installed in the large-diameter portion 22b having a large passage cross-sectional area, and the fin 29 of the large-diameter fin device 26 reduces the pressure loss of exhaust gas when a swirling flow is generated. And since the exhaust gas when distribute | circulating the inside of the large diameter part 22b has low flow velocity, the pressure loss accompanying generation | occurrence | production of a swirl flow is further reduced. Therefore, at this time, a swirling flow is generated in the exhaust gas due to the minimum pressure loss of the exhaust gas.

  Thereafter, immediately after passing through the fin device 26, urea aqueous solution is injected into the exhaust gas from the injection nozzle 34, and the exhaust gas diffuses and atomizes the urea aqueous solution by the swirling agitating action, and then moves inside the large-diameter portion 22b to the downstream side. It is transferred and introduced into the reduction unit 22c. Since the cross-sectional area of the passage is gradually reduced in the reduction part 22c, the swirling flow of the exhaust gas is gradually increased according to the so-called law of conservation of swirling angular momentum. That is, in the large-diameter portion 22b having a large passage cross-sectional area, although the pressure loss of the exhaust gas can be reduced, a strong swirling flow cannot be expected, and the stirring action by the swirling flow has a limit. However, since the stirring of the exhaust gas is promoted by increasing the swirling flow in the process of passing through the reducing portion 22c, the urea aqueous solution is diffused and atomized well in the exhaust gas.

The urea aqueous solution being transferred together with the exhaust gas generates NH ₃ by hydrolysis. However, since the diffusion and atomization of the urea aqueous solution into the exhaust gas is promoted as described above, the resulting NH ₃ is produced together with the exhaust gas. The SCR catalyst 18 in the second converter 14 is equally supplied to each part.
On the other hand, the urea aqueous solution is sprayed from the injection nozzle 34 toward the opposing wall in the casing 22 and is exposed to the swirling flow until reaching the opposing wall to diffuse and atomize, while reaching the opposing wall and adhere to it. Later, good diffusion and atomization cannot be expected. Therefore, it is desirable to set the injection distance of the urea aqueous solution from the injection nozzle 34 to the opposing wall as long as possible. However, in this embodiment, the urea aqueous solution is injected from the injection nozzle 34 at the large diameter portion 22b having a large passage cross-sectional area. Therefore, adhesion of the urea aqueous solution to the casing wall surface is suppressed as much as possible, and better diffusion / atomization is realized.

As described above, in the exhaust gas purification apparatus for the internal combustion engine 1 according to the present embodiment, the swirl flow is generated by the large-diameter fin device 26 in the large-diameter portion 22b where the exhaust gas flow velocity is low. As a result, an increase in exhaust pressure of the internal combustion engine 1 can be suppressed to a minimum, and on the other hand, since the swirl flow is accelerated in the process in which the exhaust gas circulates through the contracting portion 22c, the urea aqueous solution is sufficiently contained in the exhaust gas by a good stirring action. Can diffuse and atomize. Moreover, since the urea aqueous solution is injected in the large-diameter portion 22b having a large passage cross-sectional area, it is possible to suppress the adhesion of the urea aqueous solution to the wall surface and realize better diffusion and atomization. As a result, it is possible to reduce the exhaust pressure of the internal combustion engine 1 that is generally in a trade-off relationship and promote the diffusion and atomization of the urea aqueous solution at a high level, and suppress the increase of the exhaust pressure when generating a swirling flow to a minimum. Thus, good running performance can be realized, and NH ₃ can be evenly supplied to each part of the SCR catalyst 18 to achieve good NOx purification performance.

  FIG. 4 is a diagram showing test results comparing the relationship between the NOx purification rate of the SCR catalyst 18 and the pressure loss of the exhaust passage 11 between the conventional technology and the exhaust purification device of the present embodiment. As a conventional technique, the exhaust passage 11 is not provided with the fin device 26 (indicated by white squares in the drawing), and the fin device 26 is simply provided without increasing the diameter of the exhaust passage 11 as in the present embodiment. (Shown by black squares in the figure). Further, as the exhaust emission control device of the embodiment, the nose cone 32 is provided in the fin device 26 and the fin angle α with respect to the base portion 27 is set to 30 ° (indicated by a black circle in the drawing), and the nose is also the same. The fin angle α is set to 60 ° with the cone 32 (indicated by white circles in the drawing), and the fin angle α is set to 30 ° without the nose cone 32 (white in the drawing). And is indicated by a triangle symbol).

  In the prior art, when there is a fin device compared with no fin device, the NOx purification rate improves by promoting diffusion and atomization of the urea aqueous solution in exchange for an increase in pressure loss, but both requirements are high-dimensional as shown by the broken line Cannot be achieved. In contrast, in the exhaust purification apparatus of the present embodiment, although the relationship between the NOx purification rate and the pressure loss changes depending on the difference in the fin angle α and the presence or absence of the nose cone 32, both requirements are increased as shown by the solid line. It can be achieved in a dimension, and it can be seen that the operational effects of the present embodiment are supported.

Further, since the enlarged portion 22a guides the exhaust gas to the outer peripheral side by the nose cone 32 and distributes it through the circulation hole 31 of the fin device 26, the pressure loss at that time can be reduced and the exhaust pressure of the internal combustion engine 1 can be further reduced. Can also be obtained.
In addition, the casing 22 of the urea injection stirring unit 13 is larger in diameter than other parts of the exhaust passage 11, for example, the upstream side exhaust pipe 21a and the downstream side exhaust pipe 21b, but the first and second converters 12, Compared to 14 etc., the diameter is much smaller, and the installation location under the floor of the vehicle is not limited. Therefore, even if the urea injection agitation unit 13 is provided, the mountability of the exhaust gas purification device on the vehicle is hardly deteriorated, and there is an advantage that adverse effects due to the installation of the urea injection agitation unit 13 can be prevented.

  This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the exhaust purification device of the diesel engine 1 including the SCR catalyst 18 is embodied, but the application target is not limited to this. For example, a gasoline engine may be provided with the SCR catalyst 18 assuming a lean combustion operation, and may be applied to such a gasoline engine.

  Moreover, in the said embodiment, although the urea injection stirring part 13 was provided in the upstream of the SCR catalyst 18 for spreading | diffusion and atomization of the urea aqueous solution supplied to the SCR catalyst 18, the utilization aspect is not restricted to this. . For example, as is clear from the description of the DPF 16 in the above embodiment, in the forced regeneration in which the unburned fuel supplied from the fuel injection valve 17 is oxidized on the front-stage oxidation catalyst 15 to raise the temperature of the DPF 16, the front-stage oxidation catalyst 15 In order to maximize the oxidation reaction caused by the above, it is desirable to supply unburned fuel evenly to each part of the pre-stage oxidation catalyst 15. Therefore, a casing 22 similar to the urea injection stirring unit 13 of the above embodiment is provided upstream of the upstream oxidation catalyst 15 and the fuel injection valve 17 is installed, and into the exhaust gas of unburned fuel injected from the fuel injection valve 17. You may make it accelerate | stimulate the spreading | diffusion and atomization of. In this case, the DPF 16 corresponds to the purification device of the present invention.

  Although not provided in the exhaust purification device of the present embodiment, if a storage type NOx catalyst is provided for NOx purification instead of the SCR catalyst 18, NOx purge for releasing and reducing the stored NOx is required. As a countermeasure against sulfur poisoning when SOx (sulfur oxide) is occluded instead of NOx, unburned fuel is supplied to the pre-stage oxidation catalyst arranged upstream of the NOx catalyst, and the NOx catalyst is raised by the heat of oxidation reaction. Requires SOx purge to warm and remove SOx. Therefore, for this NOx purge and SOx purge, a casing 22 similar to the urea injection agitation unit 13 of the above embodiment is provided upstream of the storage type NOx catalyst and the pre-stage oxidation catalyst, and the fuel injection valve 17 is installed. The diffusion and atomization of unburned fuel injected from the injection valve 17 may be promoted. In this case, the storage-type NOx catalyst and the pre-stage oxidation catalyst correspond to the purification device of the present invention.

  Moreover, in the said embodiment, while providing the nose cone 32 in the fin apparatus 26 and arrange | positioning the injection nozzle 34 in the downstream of the fin apparatus 26, it does not restrict to this. For example, the nose cone 32 may be omitted and the exhaust gas may be circulated through the central through hole 28 of the base portion 27, or the through hole 28 may be closed. Further, the positions of the fin device 26 and the injection nozzle 34 may be reversed.

1 is an overall configuration diagram showing a diesel engine to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment is applied. It is an expanded sectional view which shows a urea injection stirring part. It is the III-III sectional view taken on the line of FIG. 2 which shows a fin apparatus. It is a figure which shows the test result which compared the relationship between the NOx purification rate of an SCR catalyst, and the pressure loss of an exhaust passage with the prior art and the exhaust purification apparatus of this embodiment.

Explanation of symbols

1 Internal combustion engine 16 DPF (Purification device)
18 SCR catalyst (Purification device)
22 Casing 22a Enlargement part 22b Large diameter part 22c Reduction part 26 Fin device 29 Fin 34 Injection nozzle (reducing agent injection means)

Claims (2)

A purification device disposed in an exhaust passage of the internal combustion engine;
A part of the exhaust passage on the upstream side of the purification device, an enlarged portion that expands from the exhaust passage toward the downstream side, a large diameter portion that keeps the same diameter from the enlarged portion and continues to the downstream side, And a casing constituted by a reduced portion that is reduced in diameter from the large diameter portion toward the downstream side and connected to the purification device side,
A swirl flow generating means disposed in the large diameter portion of the casing and generating a swirl flow in the exhaust gas flowing through the large diameter portion;
An exhaust gas for an internal combustion engine, comprising: a reducing agent injection means disposed in the large diameter portion of the casing and for injecting a reducing agent required for the operation of the purification catalyst into the exhaust gas flowing through the large diameter portion. Purification equipment.   The swirling flow generating means is provided with a plurality of fins for generating a swirling flow in the exhaust gas on an outer peripheral side centering on an axis in the large diameter portion, and the exhaust gas is disposed on the upstream side in the vicinity of the axis of the large diameter portion. 2. An exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising a nose cone for guiding the outer periphery.