JP5032409B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device provided with urea water supply means for supplying urea water into exhaust gas in order to supply ammonia to a selective ammonia selective reduction catalyst using ammonia as a reducing agent.

Exhaust gas discharged from an engine such as a diesel engine contains particulates, NOx (nitrogen oxides), and the like, which are air pollutants.
Therefore, with regard to particulates, a technology has been conventionally known in which a particulate filter is provided in the exhaust passage of the engine, and the particulates contained in the exhaust gas are collected by the particulate filter so that the particulates are not released into the atmosphere. ing.

  For NOx, an ammonia selective reduction type NOx catalyst is disposed in the exhaust passage of the engine, and ammonia is supplied to the ammonia selective reduction type NOx catalyst as a reducing agent so that NOx is selectively reduced to purify the exhaust gas. An exhaust emission control device is known. In the ammonia selective reduction type NOx catalyst used here, urea water is supplied into the exhaust on the upstream side, and ammonia generated by hydrolysis of the urea water by the heat of the exhaust is supplied. Then, the NOx reduction between the supplied ammonia and NOx in the exhaust gas is promoted by the ammonia selective reduction type NOx catalyst, whereby NOx is reduced and the exhaust gas is purified.

  As described above, in order to make the exhaust purification device perform a desired exhaust purification function, it is common to employ a plurality of exhaust purification means, and the casing for housing the exhaust purification means employs the exhaust purification means. Depending on the situation, it may be divided into multiple parts. For example, as described above, in order to efficiently collect particulates and reduce NOx, a combination of a particulate filter and an ammonia selective reduction type NOx catalyst is used as an exhaust purification device. Has been proposed by.

The exhaust emission control device of Patent Document 1 includes an upstream casing and a downstream casing that is disposed on the downstream side of the upstream casing and communicates with the upstream casing through a communication path. A upstream oxidation catalyst is accommodated in the upstream casing, and a particulate filter is accommodated downstream of the upstream oxidation catalyst. The pre-oxidation catalyst is used to oxidize NO (nitrogen monoxide) in the exhaust gas to generate NO ₂ (nitrogen dioxide), and to perform continuous regeneration of the particulate filter with this NO ₂ .

On the other hand, the ammonia selective reduction type NOx catalyst is accommodated in the downstream casing, and the downstream oxidation catalyst for detoxifying the ammonia flowing out from the ammonia selective reduction type NOx catalyst downstream of the ammonia selective reduction type NOx catalyst. Is housed.
The communication passage that connects the upstream casing and the downstream casing is provided with a urea water injector that injects and supplies urea water into the exhaust gas in the communication passage. The urea water injected from the urea water injector is hydrolyzed by the heat of the exhaust to become ammonia, and is supplied as a reducing agent to the ammonia selective reduction type NOx catalyst.

In this way, when the casing is divided into two parts to accommodate a plurality of exhaust gas purification means, a communication path for communicating both the casings is provided. For example, in the case of an exhaust emission control device used for an engine mounted on a vehicle, the upstream casing and the downstream casing are not necessarily arranged linearly for the convenience of the layout of the on-vehicle equipment. The passage may be provided with a bent portion corresponding to the arrangement of both casings.
JP 2007-162487 A

  However, in the exhaust gas purification apparatus in which such a communication path having a bent portion is used, when urea water is supplied into the exhaust gas flowing in the communication path, the urea water atomized in the exhaust gas communicates in the bent portion. It becomes easy to collide with the inner wall surface of the passage. The temperature of the inner wall surface of the communication path is lower than the temperature of the exhaust gas flowing inside because the outer wall portion of the communication path is in contact with the outside air. For this reason, when urea water atomized in the exhaust gas collides with the inner wall surface of the communication path, it is liquefied on the wall surface, and solid matter such as solid urea is generated by evaporation of water, and is deposited on the inner wall surface of the communication path. There is a problem of end up. If such solid matter accumulates in the communication passage, the flow resistance of the exhaust gas in the communication passage increases and the engine operating efficiency decreases, and the amount of ammonia supplied to the ammonia selective reduction type NOx catalyst is insufficient. Thus, there arises a problem that the exhaust gas purification efficiency by the ammonia selective reduction type NOx catalyst is lowered.

  In order to avoid such a problem, the lower limit value of the exhaust temperature permitting the supply of urea water is increased, and the urea water is supplied only at a relatively high exhaust temperature, thereby atomizing the inner wall surface of the communication passage. It is necessary to make it difficult to liquefy even when the urea water collides, and to make the deposited solid matter gasify again and easily disappear. However, if the lower limit value of the exhaust temperature that permits the supply of urea water is increased in this way, the operating range of the engine that can supply urea water is narrowed, so that sufficient ammonia is supplied to the ammonia selective reduction type NOx catalyst. There is a problem that the exhaust gas purification efficiency of the ammonia selective reduction type NOx catalyst is lowered.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an exhaust purification device capable of suppressing solid accumulation generated from urea water and ensuring good exhaust purification efficiency. It is to provide.

In order to achieve the above object, an exhaust emission control device according to the present invention includes a first casing that is disposed in an exhaust passage of an engine and contains exhaust purification means for purifying the exhaust of the engine, and a downstream side of the first casing. The second casing interposed in the exhaust passage, and the first casing and the second casing are communicated with each other with a bent portion, and the exhaust discharged from the first casing is guided to the second casing. A communication passage, an ammonia selective reduction type NOx catalyst housed in the second casing and selectively reducing NOx in the exhaust gas using ammonia as a reducing agent, and the first casing to the second casing via the communication passage. a urea water supply means for supplying urea water into the exhaust gas flowing with, a position on the downstream side of the urea water supply means, the flow direction is changed by the bending portion At least a part of the previous exhaust is provided at a position where it collides before reaching the inner wall surface of the communication path in the bent portion, and changes the flow direction of the collided exhaust toward the downstream side of the bent portion. A collision plate, and the collision plate includes a plurality of communication holes that allow the flow of exhaust gas between one surface side and the other surface side, and the communication holes are arranged in the flow direction of the exhaust gas. The collision plate is provided only in a predetermined upstream end region and a predetermined downstream end region (Claim 1).

  According to the exhaust emission control device configured as described above, the exhaust gas that has passed through the first casing flows into the second casing through the communication path. At this time, the urea water supply means supplies urea water into the exhaust gas flowing from the first casing to the second casing through the communication path. The urea water supplied into the exhaust gas is hydrolyzed by the heat of the exhaust gas, and ammonia is generated. The ammonia thus generated flows into the ammonia selective reduction type NOx catalyst in the downstream casing. In the ammonia selective reduction type NOx catalyst, the NOx in the exhaust gas is selectively reduced using ammonia in the exhaust gas as a reducing agent. Is purified.

  At least a part of the exhaust gas containing the urea water atomized by the urea water supply means collides with a collision plate provided at the bent portion before reaching the inner wall surface of the communication path in the bent portion, and is bent by the collision plate. The flow direction is changed toward the downstream side of the section. At this time, the temperature of the inner wall surface of the communication path is lower than the exhaust temperature due to contact between the outer wall surface and the outside air, etc., but at least a part of the exhaust gas that passes through the bent portion is such a collision plate. The fluid flows toward the second casing without contacting the inner wall surface of the bent portion having a low temperature. Therefore, when passing through the bent portion, precipitation of solid substances such as urea accompanying the collision of urea water contained in the exhaust with the inner wall surface of the communication path is suppressed. In addition, since the collision plate is exposed to the exhaust flowing in the communication path, the temperature of the collision plate becomes almost equal to the exhaust temperature, and even if the urea water in the exhaust collides with the collision plate, the collision plate becomes the urea water in the exhaust. There is no significant temperature drop. As a result, when exhaust gas containing urea water passes through the bent portion, it is possible to reliably suppress the deposition of solid substances such as urea in the bent portion.

Further, in the above exhaust gas purifying device, the collision plate is Runode comprise a plurality of communication holes to allow circulation of the exhaust between the one side and the other surface side, the flow direction of the exhaust by the collision plate Is changed, a part of the exhaust gas flows between one surface side and the other surface side of the collision plate through a plurality of communication holes provided in the collision plate. Therefore, in such a collision plate, the amount of exhaust in contact with the surface opposite to the surface on which the exhaust collides is increased as compared to a collision plate having no communication hole. Will be effectively exposed to the exhaust. Therefore, when starting the engine, the temperature of the collision plate can be quickly raised to near the exhaust temperature, and thereafter, it can be well maintained at a temperature substantially equal to the exhaust temperature.

Furthermore, in the exhaust purification apparatus, the communication hole is provided only on the predetermined upstream end region and a predetermined downstream end region of the impingement plate in the flow direction of the exhaust, the flow direction of the exhaust by the collision plate Is changed, a part thereof flows into a surface opposite to the surface on which the exhaust of the collision plate collides, through a communication hole provided in a predetermined upstream end region of the collision plate. In addition, at least a part of the exhaust gas flowing into the surface opposite to the surface on which the exhaust of the collision plate collides is exhausted through the communication hole provided in a predetermined downstream end region of the collision plate. It flows into the colliding surface side. Due to the exhaust flow through the communication hole, both surfaces of the collision plate are effectively exposed to the exhaust. Therefore, when starting the engine, the temperature of the collision plate can be quickly raised to near the exhaust temperature, and thereafter, it can be well maintained at a temperature substantially equal to the exhaust temperature. Furthermore, since the communication hole is not provided in the middle part of the collision plate, the flow direction of the exhaust gas can be effectively changed toward the downstream side of the bent portion by the collision plate.

Further, in the exhaust purification apparatus, when the communication passage has a plurality of bent portions, the collision plate may be provided on the bent portion of the most upstream side of the bent portion of the communication passage (claim 2) .
When the collision plate is not provided at the bent portion, as described above, the urea water atomized in the exhaust gas collides with the inner wall surface of the communication path at the bent portion and becomes a solid material by depriving heat. Solids are likely to be generated in the first collision part. Therefore, when the communication passage has a plurality of bent portions, by providing a collision plate at the most upstream bent portion, the solid matter from the urea water accompanying the collision with the communication passage of urea water contained in the exhaust gas can be obtained. Formation and deposition are well controlled.

In the exhaust emission control device, the first casing has a cylindrical shape, the second casing has a cylindrical shape, and is disposed laterally with respect to the central axis of the first casing. One end may be connected to the side wall of the first casing, and the other end may be connected to the side wall of the second casing, and the urea water supply means may be directed into the communication path connected to the first casing. Then, urea water may be injected (claim 3 ).

  In the case of the exhaust gas purification apparatus configured as described above, the communication path whose one end is connected to the side wall of the first casing is arranged laterally with respect to the central axis of the first casing by being bent by the bent portion. The other end is connected to the side wall of the second casing.

  According to the exhaust emission control device of the present invention, at least a part of the exhaust gas containing the atomized urea water and passing through the bent portion collides with the collision plate, thereby contacting the inner wall surface of the bent portion having a temperature lower than the exhaust temperature. Since the fluid flows toward the second casing without any collision, the collision of the urea water contained in the exhaust gas with the inner wall surface of the communication passage is suppressed when passing through the bent portion. Further, since the temperature of the collision plate is almost equal to the exhaust temperature when the collision plate is exposed to the exhaust, even if the urea water in the exhaust collides with the collision plate, the temperature does not drop greatly. As a result, when exhaust gas containing urea water passes through the bent portion, it is possible to reliably suppress the deposition of solid substances such as urea in the bent portion.

  Therefore, it is not necessary to increase the lower limit of the exhaust temperature that permits the supply of urea water to prevent the solid matter produced from urea water from accumulating, and without reducing the operating range of the engine that can supply urea water. I'm sorry. In addition, it is possible to prevent an insufficient supply amount of ammonia to the ammonia selective reduction-type NOx catalyst accompanying the production of solids such as urea from urea water. As a result, it is possible to secure the ammonia supply amount required for the ammonia selective reduction type NOx catalyst, and it is possible to maintain the exhaust purification efficiency of the ammonia selective reduction type NOx catalyst favorably.

Further, since a plurality of communication holes in opposition veneer, in such impingement plate, the amount of exhaust to the surface where the exhaust collides in contact with the opposite side of the Do that plane, the flow of exhaust gas via a communicating hole Therefore, the collision plate is effectively exposed to the exhaust gas. Therefore, when starting the engine, the temperature of the collision plate can be quickly raised to near the exhaust temperature, and thereafter, it can be well maintained at a temperature substantially equal to the exhaust temperature.

Further, since the provided communication holes only in a predetermined upstream end region of the shock veneer with a predetermined downstream end region, it is possible to expose effectively evacuate the impact plate by the exhaust flowing through the communicating hole When the engine is started, the temperature of the collision plate can be quickly raised to near the exhaust temperature, and thereafter, it can be well maintained at a temperature substantially equal to the exhaust temperature. Furthermore, since the communication hole is not provided in the middle part of the collision plate, the flow direction of the exhaust gas can be effectively changed toward the downstream side of the bent portion by the collision plate.

According to the exhaust gas purification apparatus of the second aspect , when the communication passage has a plurality of bent portions, the collision plate is formed on the most upstream bent portion where solid matter is easily generated from the urea water atomized in the exhaust gas. Therefore, it is possible to satisfactorily suppress the generation and deposition of solid matter from urea water accompanying the collision of the urea water contained in the exhaust gas with the inner wall surface of the communication path.
According to the exhaust purification device of claim 3 , the second casing is disposed laterally with respect to the central axis of the first casing, one end of the communication passage is connected to the side wall of the first casing, and the other end Is connected to the side wall of the second casing, the communication path has a bent portion having a relatively high degree of bending. The greater the degree of bending, the greater the possibility of generation of solid matter due to the collision of urea water with the inner wall surface of the communication path. Therefore, the present invention is particularly effective for an exhaust purification device having such a communication path. is there.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which an exhaust emission control device according to an embodiment of the present invention is applied. Based on FIG. The structure of will be described.
The engine 1 is mounted on a vehicle (not shown) as a power source for driving the vehicle. The engine 1 includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder. In the engine 1, high-pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is supplied to a fuel injection valve 4 provided in each cylinder, and fuel is supplied from each fuel injection valve 4 into each cylinder. Is injected.

  The intake passage 6 is equipped with a turbocharger 8. The intake air drawn from an air cleaner (not shown) flows into the compressor 8a of the turbocharger 8 from the intake passage 6, and the intake air supercharged by the compressor 8a is intercooler. 10 and the intake control valve 12 are introduced into the intake manifold 14. An intake air amount sensor 16 for detecting an intake air flow rate to the engine 1 is provided upstream of the compressor 8a in the intake passage 6.

On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe 20 via an exhaust manifold 18. An EGR passage 24 that communicates the exhaust manifold 18 and the intake manifold 14 via the EGR valve 22 is provided between the exhaust manifold 18 and the intake manifold 14.
The exhaust pipe 20 is connected to the exhaust aftertreatment device 28 via the turbine 8 b of the turbocharger 8 and the exhaust throttle valve 26. The rotating shaft of the turbine 8b is mechanically connected to the rotating shaft of the compressor 8a, and the turbine 8b receives the exhaust flowing in the exhaust pipe 20 and drives the compressor 8a.

  The exhaust after-treatment device 28 includes a cylindrical upstream casing (first casing) 30 and a downstream casing (second casing) 34 that is communicated with the downstream side of the upstream casing 30 through a communication passage 32 to form a cylinder. It consists of. A pre-stage oxidation catalyst 36 is accommodated in the upstream casing 30, and a particulate filter (hereinafter referred to as a filter) 38 is accommodated on the downstream side of the pre-stage oxidation catalyst 36. These pre-stage oxidation catalyst 36 and filter 38 correspond to the exhaust purification means of the present invention.

  The filter 38 is provided for collecting particulates in the exhaust gas and purifying the exhaust gas of the engine 1. The filter 38 is made of a honeycomb-type ceramic body, and a large number of passages communicating with the upstream side and the downstream side are arranged side by side, and the upstream side opening and the downstream side opening of the passage are alternately closed. Particulates in the exhaust are collected as the exhaust flows inside.

Since the pre-stage oxidation catalyst 36 oxidizes NO (nitrogen monoxide) in the exhaust gas to generate NO ₂ (nitrogen dioxide), the pre-stage oxidation catalyst 36 and the filter 38 are arranged in this manner, so that the filter 38 captures them. The collected particulates react with NO ₂ supplied from the pre-stage oxidation catalyst 36 to be oxidized, whereby the filter 38 is continuously regenerated.

On the other hand, in the downstream casing 34, an ammonia selective reduction type NOx catalyst (hereinafter referred to as an SCR catalyst) 40 that purifies exhaust by selectively reducing NOx (nitrogen oxide) in exhaust using ammonia in exhaust as a reducing agent. And a downstream oxidation catalyst 42 for removing ammonia flowing out from the SCR catalyst 40 from the exhaust gas. The post-stage oxidation catalyst 42 also has a function of oxidizing CO (carbon monoxide) generated when particulates are incinerated by forced regeneration of the filter 38 and discharging it into the atmosphere as CO ₂ (carbon dioxide). Yes.

  A urea water injector (urea water supply means) 44 is provided on the downstream side of the filter 38 of the upstream casing 30 to inject and supply urea water into the exhaust gas flowing out from the filter 38 and flowing into the communication passage 32. The urea water is supplied to the urea water injector 44 from a urea water tank (not shown). Further, an exhaust gas temperature sensor 46 that detects the temperature of the exhaust gas that flows out of the filter 38 and flows into the communication passage 32 is provided in the vicinity of the urea water injector 44.

  As shown in FIG. 1, the urea water injector 44 and the exhaust temperature sensor 46 are attached to a step portion formed in a direction approaching the central axis from the peripheral surface of the cylindrical upstream casing 30. By mounting the urea water injector 44 and the exhaust temperature sensor 46 at such a position, the exhaust temperature detection point of the exhaust temperature sensor 46 is brought closer to the central portion of the exhaust gas flowing out from the filter 38 to improve the detection accuracy of the exhaust temperature. In addition, the urea water injected from the urea water injector 44 is diffused as evenly as possible into the exhaust gas flowing out from the filter 38.

The urea water injected from the urea water injector 44 is atomized in the exhaust gas, hydrolyzed by the heat of the exhaust gas, converted into ammonia, and supplied to the SCR catalyst 40. The SCR catalyst 40 reduces NOx to harmless N ₂ by promoting a denitration reaction between the supplied ammonia and NOx in the exhaust. At this time, if ammonia flows out of the SCR catalyst 40 without reacting with NOx, the ammonia is removed from the exhaust gas by the post-stage oxidation catalyst 42.

The exhaust aftertreatment device 28 shown in FIG. 1 corresponds to the arrangement of the upstream casing 30 and the downstream casing 34 when viewed from above, and the downstream casing 34 is conveniently mounted on the vehicle. Is arranged laterally with respect to the central axis of the upstream casing 30 having a cylindrical shape.
The upstream end of the communication path 32 is connected to the side wall of the upstream casing 30 via an outflow portion 30 a provided on the side wall of the upstream casing 30 at a position downstream of the filter 38. On the other hand, the downstream end of the communication path 32 is connected to the side wall of the downstream casing 34 via an inflow portion 34 a provided on the side wall of the downstream casing 34 at a position upstream of the SCR catalyst 40. . And in order to enable such a connection, the communicating part 32 has two bent parts, a first bent part 32a and a second bent part 32b downstream of the first bent part 32a.

  On the side wall of the downstream casing 34 at a position downstream of the rear-stage oxidation catalyst 42, an outflow portion 34b extending in the opposite direction in plan view to the extending direction of the inflow portion 34a is provided, A tail pipe 48 for releasing the exhaust gas that has passed through the downstream casing 34 into the atmosphere is connected to the side wall of the downstream casing 34 via the outflow portion 34b. Therefore, the exhaust pipe 20 and the tail pipe 48 correspond to the exhaust passage in the present invention.

  The urea water injector 44 is mounted at a position facing the outflow portion 30 a of the upstream casing 30, and the urea water injection direction is directed to the communication path 32 as indicated by a one-dot chain line in FIG. 1. Since the outer wall surface of the communication path 32 is exposed to the outside air, the inner wall surface of the communication path 32 is at a temperature lower than the temperature of the exhaust flowing inside, and the urea water atomized in the exhaust is When it collides with the inner wall surface of the communication path 32, urea water may be liquefied again due to a decrease in temperature and may adhere to the inner wall surface of the communication path 32. From the urea water adhering to the inner wall surface, the water of the urea water evaporates due to the heat of the exhaust, so that solids such as urea (hereinafter collectively referred to as urea) are deposited and deposited on the inner wall surface of the communication path 32. To do.

  Therefore, in the present embodiment, the exhaust gas that flows out from the filter 38 and then flows into the communication path 32 and flows toward the downstream casing 34, as described above, from the urea water injector 44 toward the communication path 32. By injecting the urea water, it is possible to prevent the injected urea water from colliding with the inner wall surface of the communication path 32 as much as possible, and to suppress the deposition of urea solid matter on the inner wall surface of the communication path 32. Yes.

  The communication passage 32 has two bent portions, a first bent portion 32a and a second bent portion 32b. When the exhaust gas passes through the first and second bent portions 32a and 32b, the exhaust gas is As the flow direction is changed by the first and second bent portions 32a and 32b, urea water atomized in the exhaust gas may collide with the inner wall surfaces of the first and second bent portions 32a and 32b. When such a collision occurs, the urea water atomized in the exhaust gas is liquefied on the inner wall surface of the colliding communication passage 32, and as described above, urea solid matter is deposited and deposited on the inner wall surface. It will be. In particular, since the first bent portion 32a is located on the most upstream side among the plurality of bent portions of the communication passage 32, most of the urea water contained in the exhaust gas is first inside the communication passage 32 in the first bent portion 32a. There is a possibility of colliding with the wall. Accordingly, the first bent portion 32 a can be a portion where urea is easily deposited in the communication path 32.

  If the precipitation and deposition of urea solids in the communication path 32 continues, the exhaust flow resistance in the communication path 32 increases, the exhaust pressure of the engine 1 increases, and the operating efficiency of the engine 1 decreases. There is a possibility that the amount of ammonia supplied to the SCR catalyst 40 is reduced from the required amount, and the selective reduction of NOx by the SCR catalyst 40 is not sufficiently performed. Therefore, in the present embodiment, among the two bent portions of the first bent portion 32a and the second bent portion 32b, the first bent portion 32a in which urea solids are most likely to precipitate as described above is formed in the communication path 32. A collision plate 50, the details of which will be described later, is provided so as to suppress the collision of urea water to the inner wall surface of the communication path 32 in the first bent portion 32a.

  The engine 1 supplies fuel supply control for supplying an amount of fuel required for operation of the engine 1 from the fuel injection valve 4 to each cylinder, and an amount of urea water required for the SCR catalyst 40 is urea water. An ECU 52 is provided that performs overall control for maintaining good operation performance and exhaust purification performance of the engine 1, such as urea water supply control for supplying from the injector 44. In order to perform these controls, on the input side of the ECU 52, in addition to the intake air amount sensor 16 and the exhaust gas temperature sensor 46, a rotational speed sensor 54 that detects the rotational speed of the engine 1, and the depression amount of an accelerator pedal (not shown) Various sensors such as an accelerator opening sensor 56 for detecting the above are connected. On the other hand, various devices such as the fuel injection valve 4, the intake control valve 12, the EGR valve 22, the exhaust throttle valve 26, and the urea water injector 44 are connected to the output side of the ECU 52 as the above-described various control targets.

  Since the urea water supply control performed by the ECU 52 is already widely known, detailed description thereof is omitted here, but the ECU 52 supplies urea water into the exhaust based on the detection value of the exhaust temperature sensor 46. When it is determined that the exhaust temperature can be supplied without hindrance, the required amount of urea water is supplied to the SCR catalyst 40 based on the NOx emission amount from the engine 1 obtained from the detection values of various sensors. The urea water injector 44 is controlled.

Next, the collision plate 50 provided in the first bent portion 32a of the communication path 32 will be described in detail based on FIG. 2 and FIG. 2 is a schematic sectional view showing the first bent portion 32a of the communication passage 32 provided with the collision plate 50 and its peripheral portion, and FIG. 3 is a schematic sectional view taken along the line III-III in FIG. is there.
The communication path 32 is configured by a double pipe including an inner pipe 32c through which exhaust gas flows and an outer pipe 32d provided outside the inner pipe 32c and having an outer wall surface touching the outside air. An air layer is formed between the inner tube 32c and the outer tube 32d, and the heat of the exhaust gas flowing in the inner tube 32c is difficult to escape into the outside air. As shown in FIG. 2, the flat collision plate 50 is provided at a position where the exhaust gas flowing in the communication path 32 can collide before reaching the inner wall surface of the inner tube 32 c in the first bent portion 32 a. As shown in FIG. 3, the collision plate 50 is provided so as to be spanned across two locations on the inner wall surface forming the circular shape of the inner tube 32 c when viewed in the radial cross section of the inner tube 32 c. A space is formed on both sides. Further, the upstream end 50a and the downstream end 50b of the collision plate 50 each have a gap with the inner wall surface of the inner tube 32c.

  Most of the exhaust gas that includes the atomized urea water supplied from the urea water injector 44 and flows into the first bent portion 32a with the overall flow direction as indicated by the arrow A in FIG. By colliding with the first surface 50c, the overall flow direction is changed in the direction of arrow B, which is the downstream direction of the first bent portion 32a, and flows out of the first bent portion 32a. At this time, the remaining exhaust gas flowing into the first bent portion 32a passes through the gap between the upstream end 50a of the collision plate 50 and the inner wall surface of the inner tube 32c, and the inside of the second surface 50d of the collision plate 50 and the inner tube 32c. It flows into the space between the wall surfaces, and flows out toward the downstream side of the first bent portion 32a through the gap between the downstream end 50b of the collision plate 50 and the inner wall surface of the inner tube 32c.

  In the first bent portion 32a, as described above, the inner tube 32c is not in direct contact with the outside air by the double tube structure of the inner tube 32c and the outer tube 32d, but the outer wall surface of the outer tube 32d is in contact with the outside air. Therefore, the temperature of the inner wall surface of the inner pipe 32c is lower than the exhaust temperature. However, as described above, most of the exhaust gas flowing into the first bent portion 32a is changed in the flow direction by colliding with the first surface 50c of the collision plate 50 and flows out from the first bent portion 32a. The collision between the urea water in the exhaust when passing through the first bent portion 32a and the inner wall surface of the first bent portion 32a having a temperature lower than the exhaust temperature is greatly suppressed.

  Further, the collision plate 50 has a space between the second surface 50d and the inner wall surface of the inner tube 32c in the first bent portion 32a, and as described above, the first surface 50c and the second surface 50d. Therefore, the collision plate 50 is heated up to near the exhaust temperature immediately after the engine 1 is started, and is maintained well at a temperature substantially equal to the exhaust temperature. For this reason, even if urea water contained in the exhaust gas collides with the collision plate 50, a large temperature drop does not occur.

As a result, when exhaust gas containing urea water supplied from the urea water injector 44 and atomized passes through the first bent portion 32a, solid deposition of urea in the first bent portion 32a and the collision plate 50 is ensured. And it can suppress well.
Therefore, in the urea water supply control from the urea water injector 44 performed by the ECU 52, the lower limit of the exhaust temperature that permits the supply of urea water for the purpose of preventing accumulation of solid matter generated from the urea water in the first bent portion 32a. It is not necessary to increase the value, and the operating range of the engine 1 that enables the supply of urea water can be expanded as compared with the conventional urea water supply control. In addition, it is possible to prevent an insufficient supply amount of ammonia to the SCR catalyst 40 due to the generation of solids such as urea from urea water. As a result, it is possible to appropriately secure the ammonia supply amount necessary for the SCR catalyst 40, and it is possible to maintain the exhaust purification efficiency of the SCR catalyst 40 favorably.

Although the description of the exhaust emission control device according to one embodiment of the present invention has been completed above, the present invention is not limited to the above embodiment. For example, the collision plate is not limited to the collision plate 50 used in the above embodiment. Various collision plates can also be used.
An example in which the collision plate is variously modified will be described below with reference to the drawings. First, a first modification of the above embodiment will be described with reference to FIGS. In addition, about the member substantially the same as the member used in the said embodiment, detailed description shall be abbreviate | omitted using the same code | symbol as the corresponding member of the said embodiment, and the part which is different from the said embodiment is centered. Will be described in detail.

FIG. 4 is a schematic cross-sectional view showing the first bent portion 32a of the communication path 32 provided with the collision plate 150 and the peripheral portion thereof in the first modification. 5 is a schematic sectional view taken along the line VV in FIG. 4, and FIG. 6 is a plan view of the collision plate 150. As shown in FIG.
The collision plate 150 used in the first modified example is the same as the collision plate 50 used in the above embodiment with respect to the outer shape and the position provided in the first bent portion 32a. In the above-described embodiment, the collision plate 50 is a simple flat plate member. However, in the first modification, the first surface 150c, which is a surface on which the exhaust gas collides, and the second surface, which is the opposite surface. It differs from the collision plate 50 of the said embodiment by the point by which the some communication hole 152 which enables the flow of exhaust_gas | exhaustion between the surfaces 150d side is provided in the collision plate 150. FIG. As shown in FIG. 6, the communication holes 152 are provided at equal intervals over almost the entire surface excluding the peripheral portion of the collision plate 150.

  Exhaust gas containing the urea water atomized by being supplied from the urea water injector 44 flows into the first bent portion 32a with the overall flow direction as the direction of arrow A in FIG. The first surface 150c is reached. A portion of the exhaust gas that has reached the first surface 150c collides with the first surface 150c of the collision plate 150, as in the above-described embodiment, so that the overall flow direction is downstream of the first bent portion 32a. It changes to the direction of the arrow B which is the direction of the side, and flows out from the 1st bending part 32a. Further, the remaining exhaust gas that has reached the first surface 150c flows to the second surface 150d side through the communication hole 152, and through the gap between the upstream end 150a of the collision plate 150 and the inner wall surface of the inner tube 32c. The exhaust gas flowing into the space between the second surface 150d of the collision plate 150 and the inner wall surface of the inner tube 32c merges. Further, a part of the exhaust gas flowing in the space between the second surface 150 d of the collision plate 150 and the inner wall surface of the inner tube 32 c is directed to the first surface 150 c side of the collision plate 150 through the communication hole 152. To flow.

  Accordingly, since the amount of exhaust in contact with the second surface 150d in the collision plate 150 increases as compared with the case where the communication hole 152 is not provided, the collision plate 150 is quickly raised to near the exhaust temperature after the engine 1 is started. In addition, the temperature can be maintained at a temperature substantially equal to the exhaust temperature. Even when the collision plate 150 is configured in this way, the exhaust gas collides with the collision plate 150 when the collision plate 150 passes through the first bent portion 32a, and the flow direction is changed. Collision with the inner wall surface of the first bent portion 32a having a temperature lower than the temperature is suppressed.

As a result, also in the first modified example, when the exhaust gas containing urea water supplied from the urea water injector 44 passes through the first bent portion 32a, the solid substance of urea in the first bent portion 32a and the collision plate 150 Can be reliably and satisfactorily suppressed.
Therefore, in the urea water supply control from the urea water injector 44 performed by the ECU 52, the lower limit of the exhaust temperature that permits the supply of urea water for the purpose of preventing accumulation of solid matter generated from the urea water in the first bent portion 32a. It is not necessary to increase the value, and the operating range of the engine 1 that enables the supply of urea water can be expanded as compared with the conventional urea water supply control. In addition, it is possible to prevent an insufficient supply amount of ammonia to the SCR catalyst 40 due to the generation of solids such as urea from urea water. As a result, it is possible to appropriately secure the ammonia supply amount necessary for the SCR catalyst 40, and it is possible to maintain the exhaust purification efficiency of the SCR catalyst 40 favorably.

In the first modified example, the plurality of communication holes 152 are arranged at almost equal intervals over the substantially entire surface of the collision plate 150. However, the arrangement of the communication holes 152 is not limited to this, and the intervals are not limited, for example. It may be uniform. The communication hole 152 may have a shape other than a circle.
Below, the 2nd modification using the collision board from which the arrangement | positioning of a communicating hole differs from the said 1st modification is demonstrated using FIG.7 and FIG.8. In addition, about the member substantially the same as the member used by the above-mentioned embodiment, detailed description shall be abbreviate | omitted using the same code | symbol as the corresponding member of the said embodiment, and the above-mentioned embodiment and said 1st deformation | transformation shall be abbreviate | omitted. This will be described in detail with a focus on differences from the example.

FIG. 7 is a schematic cross-sectional view showing the first bent portion 32a of the communication path 32 provided with the collision plate 250 and its peripheral portion in the second modification, and FIG. 8 is a plan view of the collision plate 250.
The collision plate 250 used in the second modified example is the same as the collision plate 50 used in the above-described embodiment and the collision plate 150 used in the first modified example with respect to the outer shape and the position provided in the first bent portion 32a. It is. In the second modification, the arrangement of the plurality of communication holes 252 is different from the collision plate 150 of the first modification. That is, as shown in FIG. 8, the communication hole 252 has an upstream end region 250 e that is a predetermined region on the upstream end 250 a side of the collision plate 250 and a downstream end side that is a predetermined region on the downstream end 250 b side of the collision plate 250. The collision plate 150 is different from the collision plate 150 of the first modification in that the communication hole 252 is not provided in the intermediate region 250g provided only in the region 250f and between the upstream end region 250e and the downstream end region 250f.

  In the second modified example in which such a collision plate 250 is provided, the exhaust gas is communicated between the first surface 250c and the second surface 250d via the communication hole 252 as in the first modified example described above. In the intermediate region 250g in which the flow is generated but the communication hole 252 is not provided, all the exhaust gas that has reached the first surface 250c of the collision plate 250 collides with the collision plate 250, so that it flows toward the downstream side of the first bent portion 32a. Is deflected.

  Due to the flow of exhaust toward the second surface 250d through the communication hole 252 as described above, the collision plate 250 can be heated up to near the exhaust temperature immediately after the engine 1 is started, and thereafter, the exhaust temperature It can be well maintained at approximately the same temperature. Furthermore, by providing the intermediate region 250g where the communication hole 252 is not provided in the collision plate 250, the flow direction of the exhaust gas can be effectively changed toward the downstream side of the first bent portion 32a.

As a result, also in the second modified example, when the exhaust gas containing urea water supplied from the urea water injector 44 passes through the first bent portion 32a, urea solids in the first bent portion 32a and the collision plate 250 are obtained. Can be reliably and satisfactorily suppressed.
Therefore, in the urea water supply control from the urea water injector 44 performed by the ECU 52, the lower limit of the exhaust temperature that permits the supply of urea water for the purpose of preventing accumulation of solid matter generated from the urea water in the first bent portion 32a. It is not necessary to increase the value, and the operating range of the engine 1 that enables the supply of urea water can be expanded as compared with the conventional urea water supply control. In addition, it is possible to prevent an insufficient supply amount of ammonia to the SCR catalyst 40 due to the generation of solids such as urea from urea water. As a result, it is possible to appropriately secure the ammonia supply amount necessary for the SCR catalyst 40, and it is possible to maintain the exhaust purification efficiency of the SCR catalyst 40 favorably.

  In the first modification, the communication holes 152 are provided on almost the entire surface of the collision plate 150, while in the second modification, the communication holes 252 are provided only in the upstream end region 250e and the downstream end region 250f. The amount of exhaust deflected by the collision plate depending on the number and position of the communication holes, and the amount of exhaust flowing to the surface (second surface) opposite to the surface (first surface) on which the exhaust collides It is possible to adjust. Therefore, it is possible to grasp the flow characteristics of the exhaust gas in the communication passage 32 and the generation state of solid matter from the urea water, and to set the number and positions of the communication holes appropriately through experiments and the like.

  In the first and second modified examples, the plurality of communication holes 152 are provided in the collision plate 150. However, the flow of exhaust gas between the first surface side and the second surface side is other than the communication holes. An example of this may be described below as a third modification. In addition, about the member substantially the same as the member used by the above-mentioned embodiment, detailed description shall be abbreviate | omitted using the same code | symbol as the corresponding member of the said embodiment, and said embodiment and said 1st And it demonstrates in detail centering on the part which is different from a 2nd modification.

  FIG. 9 is a plan view of a collision plate 350 used in the third modification. The collision plate 350 is used in the collision plate 50 used in the above-described embodiment, the collision plate 150 used in the first modification example, and the second modification example with respect to the outer shape and the position provided in the first bent portion 32a. This is the same as the collision plate 250. The collision plate 350 is provided with a mesh-like mesh portion (mesh member) 352 as shown in FIG. 9 instead of the plurality of communication holes provided in the first and second modifications.

  Even when the collision plate 350 is configured as described above, when the flow direction of the exhaust gas is changed by the collision plate 350, a part of the collision plate 350 passes through the mesh-shaped mesh portion 352 constituting the collision plate 350. It flows between one surface side and the other surface side. Therefore, both surfaces of the collision plate 350 are effectively exposed to the exhaust, and the collision plate 350 can be raised to the exhaust temperature immediately after the engine 1 is started, and thereafter, the temperature is improved to a temperature substantially equal to the exhaust temperature. Can be maintained. Further, when the exhaust gas collides with the collision plate 350 when passing through the first bent portion 32a and the flow direction is changed, the urea solution in the exhaust gas and the first bent portion 32a having a temperature lower than the exhaust temperature are changed. Collision with the wall surface is suppressed.

As a result, also in the third modified example, when the exhaust gas containing urea water supplied from the urea water injector 44 passes through the first bent portion 32a, solid urea in the first bent portion 32a and the collision plate 350 is obtained. Can be reliably and satisfactorily suppressed.
Therefore, in the urea water supply control from the urea water injector 44 performed by the ECU 52, the lower limit of the exhaust temperature that permits the supply of urea water for the purpose of preventing accumulation of solid matter generated from the urea water in the first bent portion 32a. It is not necessary to increase the value, and the operating range of the engine 1 that enables the supply of urea water can be expanded as compared with the conventional urea water supply control. In addition, it is possible to prevent an insufficient supply amount of ammonia to the SCR catalyst 40 due to the generation of solids such as urea from urea water. As a result, it is possible to appropriately secure the ammonia supply amount necessary for the SCR catalyst 40, and it is possible to maintain the exhaust purification efficiency of the SCR catalyst 40 favorably.

  In the third modification, the mesh-shaped mesh portion 352 is provided over almost the entire surface of the collision plate 350. However, the region where the mesh portion is provided can be arbitrarily changed as necessary. For example, as in the above-described second modification, mesh portions may be provided only in predetermined areas on the upstream end side and the downstream end side of the collision plate 350. Moreover, you may make it use combining a communicating hole like a 1st and 2nd modification, and a mesh part like a 3rd modification.

Although the description about the modification of a collision board is as above, this invention is not limited to embodiment mentioned above or the said 1st thru | or 3rd modification, Furthermore, it can change variously.
For example, in the above-described embodiment and the first to third modifications, the communication path 32 has a double-pipe structure, but the same effect can be achieved by applying the present invention even when a communication path having a single-pipe structure is employed. It is possible to obtain

  In the above-described embodiment and the first to third modifications, the collision plate is provided only in the first bent portion 32a on the most upstream side of the first bent portion 32a and the second bent portion 32b. A similar collision plate may be provided on the second bent portion 32b. Furthermore, the present invention can also be applied to the case where a communication passage having three or more bent portions is used. Also in this case, the same collision plate may be provided only at the most upstream bent portion, or the same collision plate may be provided at a predetermined number of bent portions or all the bent portions from the upstream side. .

  In the above-described embodiment, the present invention is applied to the exhaust aftertreatment device 28 in which the downstream casing 34 is disposed laterally with respect to the central axis of the upstream casing 30. It is not limited. For example, even in an exhaust aftertreatment device in which a downstream casing is disposed in the direction of the central axis of the upstream casing and both casings communicate with each other through a communication path having a bent portion, The effect of can be obtained.

  Furthermore, in the above embodiment, the upstream oxidation catalyst 36 and the filter 38 are accommodated in the upstream casing 30, and the SCR catalyst 40 and the downstream oxidation catalyst 42 are accommodated in the downstream casing 34. The exhaust purification member housed in the casing is not limited to this. The SCR catalyst is housed in the downstream casing, and the downstream casing is connected to the upstream casing through a communication passage having a bent portion. The same effect can be obtained if the exhaust aftertreatment device is configured to supply urea water into the exhaust gas flowing toward the front.

  In the above embodiment, the engine 1 is a four-cylinder diesel engine. However, the number of cylinders and the type of the engine 1 are not limited thereto, and urea water is supplied and NOx in the exhaust gas is exhausted by the SCR catalyst. Similarly, the present invention can be applied to any engine in which selective reduction is performed.

1 is an overall configuration diagram of an engine system to which an exhaust emission control device according to an embodiment of the present invention is applied. It is a schematic sectional drawing which shows the principal part of the communicating path in the exhaust gas purification apparatus of FIG. It is a schematic sectional drawing which follows the III-III line | wire in FIG. It is a schematic sectional drawing which shows the principal part of a communicating path about a 1st modification. It is a schematic sectional drawing which follows the VV line in FIG. It is a top view of the collision board used for the 1st modification of FIG. It is a schematic sectional drawing which shows the principal part of a communicating path about a 2nd modification. It is a top view of the collision board used for the 2nd modification of FIG. It is a top view of the collision board used for the 3rd modification.

Explanation of symbols

1 Engine 20 Exhaust pipe (exhaust passage)
30 Upper casing (first casing)
32 communication path 32a first bent portion 32b second bent portion 34 downstream casing (second casing)
36 Pre-oxidation catalyst (exhaust gas purification means)
38 Particulate filter (exhaust gas purification means)
40 SCR catalyst (ammonia selective reduction type NOx catalyst)
44 Urea water injector (urea water supply means)
48 Tail pipe (exhaust passage)
50, 150, 250, 350 Colliding plate 152, 252 Communication hole 250e Upstream end region 250f Downstream end region 352 Mesh portion (mesh member)

Claims (3)

A first casing that is disposed in an exhaust passage of the engine and contains exhaust purification means for purifying the exhaust of the engine;
A second casing interposed in the exhaust passage downstream of the first casing;
A communication path that communicates the first casing and the second casing with a bent portion, and guides the exhaust discharged from the first casing to the second casing;
An ammonia selective reduction type NOx catalyst housed in the second casing and selectively reducing NOx in the exhaust gas using ammonia as a reducing agent;
Urea water supply means for supplying urea water into the exhaust gas flowing from the first casing to the second casing via the communication path;
At least a part of the exhaust gas at the downstream side of the urea water supply means and before the flow direction is changed by the bent portion collides before reaching the inner wall surface of the communication path in the bent portion. A collision plate provided at a position for changing the flow direction of the collided exhaust gas toward the downstream side of the bent portion ,
The collision plate includes a plurality of communication holes that allow the exhaust to flow between one surface side and the other surface side,
The exhaust purification device according to claim 1, wherein the communication hole is provided only in a predetermined upstream end region and a predetermined downstream end region of the collision plate in the flow direction of the exhaust gas. The communication path has a plurality of bent portions,
2. The exhaust emission control device according to claim 1, wherein the collision plate is provided at a most upstream bent portion of the bent portions of the communication path. The first casing has a cylindrical shape,
The second casing has a cylindrical shape and is disposed laterally with respect to the central axis of the first casing,
The communication path has one end connected to the side wall of the first casing and the other end connected to the side wall of the second casing.
The exhaust purification device according to claim 1, wherein the urea water supply means injects urea water into the communication path connected to the first casing.

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