JP2011047293A - Exhaust emission purifying apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission purifying apparatus that prevents fixing or crystallization of an additive on the perimeter of an injection hole of an additive injection valve or inside an introduction pipe, facilitates to cause the entire spray of the additive to directly come into collision with a mixer, while reducing thermal damage to the additive injection valve, and evenly supplies the additive to an exhaust emission purifying catalyst. <P>SOLUTION: In an exhaust emission purifying apparatus, an exhaust emission purifying catalyst is disposed within an exhaust passage 11 of an internal combustion engine, an additive injection valve 21 is attached via an introduction pipe 19 to an exhaust passage on an upstream side of the exhaust emission purifying catalyst, and a mixer 18 is provided at a position at which a spray of the additive injected from the additive injection valve 21 comes into collision. Enlarged taper portions 16, 17 in an enlarging shape in a downstream direction of an exhaust gas flow are formed in an exhaust passage 11 on the upstream side of the exhaust emission purifying catalyst, and the introduction pipe 19 is connected to the enlarged taper portions 16, 17. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust purification device for purifying exhaust gas of an internal combustion engine using an exhaust purification catalyst and an additive. In particular, the present invention relates to an exhaust emission control device in which an additive injection valve is attached to an exhaust passage through an introduction pipe, and a mixer of additive and exhaust gas injected from the additive injection valve is provided in the exhaust passage. Is.

Conventionally, exhaust gas of an internal combustion engine mounted on an automobile or the like contains NO _x (nitrogen oxide), PM (particulate matter), and the like. As one of the exhaust purification devices for purifying NO _x , an SCR catalyst (NO _x selective reduction catalyst) which is a kind of exhaust purification catalyst is disposed in the exhaust passage of the internal combustion engine, and from the upstream side of the SCR catalyst. by adding urea water (urea aqueous solution) as an additive, there is a urea SCR system for purifying NO _X. There is also an NSC system in which an NSC catalyst (NO _x storage reduction catalyst) is disposed in an exhaust passage and NO _x is purified using fuel as an additive.

  As an exhaust gas purification device for purifying PM, there is an exhaust gas purification device in which a particulate filter provided with an oxidation catalyst is disposed in an exhaust passage of an internal combustion engine. In this exhaust purification device, after PM is once captured by a particulate filter, fuel is added to the oxidation catalyst, and the PM is burned and purified by the oxidation heat generated in the oxidation catalyst. In some cases, an oxidation catalyst is disposed in the exhaust passage on the upstream side of the particulate filter, and the oxidation heat generated by the oxidation catalyst is used to purify PM trapped in the particulate filter. Even in this case, fuel is added to the oxidation catalyst.

  In each exhaust purification system as described above, in order to prevent additives such as urea water and fuel added on the upstream side of each catalyst from passing through the catalyst without being used for exhaust gas purification. In addition, a mixer may be provided in the exhaust passage upstream of the exhaust purification catalyst. The additive and the exhaust gas are mixed and dispersed widely and uniformly over the entire front surface of the exhaust passage by the mixer.

  In addition, the additive injection valve for injecting the additive is provided with an electromagnetic solenoid, a resin cover, a nozzle plate, and the like, and these have lower heat resistance than other components, so the additive injection valve is exhausted to the additive injection valve. In order to reduce the direct transfer of much of the heat, the additive injection valve may be attached to the exhaust passage via an inlet tube. Further, by reducing the intersecting angle between the central axis of the spray of the injected additive and the central axis of the exhaust gas flow as much as possible, the exhaust gas is prevented from adhering to the wall surface of the exhaust passage. In some cases, an additive injection valve is attached to the exhaust passage through the introduction pipe (see, for example, Patent Documents 1 and 2).

JP 2009-41370 A (FIG. 2 etc.) JP 2009-138598 A (FIG. 1 etc.)

  In the exhaust gas purification apparatus in which the additive injection valve is attached to the exhaust passage through the introduction pipe as in Patent Document 1 and Patent Document 2, the exhaust gas in the introduction pipe is exhausted when the additive is injected. A large eddy current is generated in the introduction pipe and the exhaust passage. Part of the spray of the injected additive is caught in this vortex and stays in the introduction pipe, and adheres to the wall surface of the introduction pipe and the periphery of the injection hole of the additive injection valve. The adhering additive is fixed or crystallized to block the nozzle hole of the additive injection valve, or to narrow the passage of the additive in the introduction pipe, thereby inhibiting normal spray formation of the additive. As a result, the supply of the additive to the exhaust purification catalyst is not normally performed, and the exhaust gas may not be sufficiently purified.

  In addition, the additive injection valve is provided with a cooling device for reducing heat damage, etc., while avoiding contact between the cooling device and the exhaust passage, the spray axis of the injected additive and the exhaust gas flow If the crossing angle with the central axis is made smaller, the introduction tube becomes longer, and the spray of the additive tends to adhere to the wall surface of the introduction tube. The additive adheres to the wall of the introduction pipe and does not reach the mixer, or the additive is not sufficiently mixed and diffused with the exhaust gas, and the additive is not uniformly supplied to the entire exhaust purification catalyst. As a result, the exhaust gas may not be sufficiently purified in the exhaust purification catalyst in the portion where the additive has not been sufficiently supplied.

  If the introduction pipe is simply shortened to prevent the generation of large eddy currents in the introduction pipe or the adhesion of the additive to the wall of the introduction pipe, the distance between the additive injection valve and the exhaust passage or the exhaust gas flow will be reduced. Since exhaust heat is easily transmitted to the injection valve, the possibility of damage to the additive injection valve due to heat increases.

  In the exhaust emission control device as described above, the present invention reduces the generation of a large vortex accompanying the injection of the additive from the additive injection valve, so that the addition around the nozzle hole of the additive injection valve and inside the introduction pipe It is possible to prevent sticking and crystallization of the agent, and it is possible to easily make the entire spray of the additive collide directly with the mixer while reducing heat damage to the additive injection valve. It is an object of the present invention to provide an exhaust purification device capable of evenly supplying an additive to a purification catalyst.

  According to the present invention, the exhaust purification catalyst is disposed in the exhaust passage of the internal combustion engine, and the additive injection valve is attached to the exhaust passage upstream of the exhaust purification catalyst via the introduction pipe. In the exhaust purification apparatus in which the mixer is provided at a position where the spray of additive injected from the agent injection valve collides, the enlarged taper portion having a shape that expands in the downstream direction of the exhaust gas flow is located upstream of the exhaust purification catalyst. An exhaust purification device is provided which is formed in the exhaust passage and has an introduction pipe connected to the enlarged taper portion, and can solve the above-described problem (claim 1).

  Further, in configuring the exhaust emission control device of the present invention, in the cross section including the central axis of the exhaust passage and the apex of the tip portion of the additive injection valve, the upstream contact among the contacts of the introduction pipe and the enlarged taper portion Is A and B is the downstream contact, it is preferable that the central axis of the spray of the additive injected from the additive injection valve and the straight line AB passing through the contacts A and B are orthogonal to each other. ).

  Further, in configuring the exhaust emission control device of the present invention, it is preferable that a reduction taper portion that is reduced in the downstream direction of the exhaust gas flow is formed in the exhaust passage between the exhaust purification catalyst and the mixer (claim). Item 3).

  Further, in configuring the exhaust emission control device of the present invention, in the cross section including the central axis of the exhaust passage and the apex of the tip of the additive injection valve, the central axis of the spray of the additive injected from the additive injection valve is Preferably, γ = α ± 30 °, where α is an angle formed with respect to the central axis of the exhaust passage and γ is an inclination angle of the reduced taper portion with respect to the central axis of the exhaust gas flow. 4).

  In configuring the exhaust emission control device of the present invention, it is preferable that a second expansion taper having a shape expanding in the downstream direction of the exhaust gas flow is formed in the exhaust passage on the downstream side of the mixer. ).

  In configuring the exhaust emission control device of the present invention, a mixer is disposed in the exhaust passage downstream of the enlarged taper portion, and the cross-sectional area of the exhaust gas passage portion of the mixer is upstream of the enlarged taper portion. Preferably, it is formed larger than the cross-sectional area of the exhaust passage.

  According to the exhaust emission control device of the first aspect of the invention, the additive injection valve and the mixer are connected while reducing the influence of heat on the additive injection valve by connecting the introduction pipe to the enlarged taper portion of the exhaust passage. The volume of the introduction tube can be reduced in the case where the distance to is constant. As a result, the amount of exhaust gas pushed out from the introduction pipe to the exhaust passage along with the injection of the additive from the additive injection valve is reduced, so that the generation of a large vortex is suppressed. As a result, the spray of the additive is caught in the vortex and stays in the introduction pipe, and is prevented from adhering to the wall surface of the introduction pipe or the vicinity of the injection hole of the additive injection valve and being fixed or crystallized.

  Further, according to the exhaust purification device of the second aspect of the present invention, the additive injection valve and the enlarged taper portion are configured to have a predetermined arrangement configuration, so that no extra space is generated in the exhaust passage. In addition, the volume of the introduction pipe can be reduced when the distance between the additive injection valve and the mixer is constant without making the exhaust passage complicated.

  According to the exhaust purification device of the third aspect of the present invention, the reduction taper portion having a shape that decreases in the downstream direction of the exhaust gas flow is provided in the exhaust passage between the exhaust purification catalyst and the mixer, thereby mixing the exhaust gas flow. Mixing of the exhaust gas and the additive can be further promoted while rectifying the turbulent flow generated by the vessel.

  According to the exhaust purification device of the fourth aspect of the present invention, the additive injection valve and the reduced taper portion are configured to have a predetermined arrangement configuration, so that the entire length of the exhaust purification device is not excessively extended. The mixing of the exhaust gas and the additive can be further promoted while rectifying the turbulent flow generated by the mixer.

  According to the exhaust purification device of the fifth aspect of the invention, the second enlarged taper portion having a shape expanding in the downstream direction of the exhaust gas flow is provided in the exhaust passage on the downstream side of the mixer, thereby Since the generated turbulent flow can be guided to the exhaust purification catalyst while expanding along the wall surface of the exhaust passage, the additive can be uniformly supplied to the entire inlet surface of the exhaust purification catalyst.

  According to the exhaust purification device of the sixth aspect of the invention, the cross-sectional area of the exhaust gas passage portion of the mixer is configured to be larger than the cross-sectional area of the exhaust passage upstream of the enlarged taper portion. Thus, it is possible to reduce the exhaust resistance and pressure loss increase.

It is a figure for demonstrating the basic composition of the exhaust gas purification device in embodiment of this invention. It is a figure for demonstrating the additive injection valve attachment part periphery in embodiment of this invention. It is a figure which shows the velocity distribution simulation result of the exhaust gas flow around the additive injection valve attachment part in embodiment of this invention. It is a figure which shows the speed distribution simulation result of the exhaust gas flow around the additive injection valve attachment part in a prior art. It is a figure for demonstrating the modification 1 of the additive injection valve attachment part in embodiment of this invention. It is a figure for demonstrating the modification 2 of the additive injection valve attachment part in embodiment of this invention. It is a figure for demonstrating the modification 3 of the additive injection valve attachment part in embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment embodying an exhaust emission control device according to the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same members, and the description thereof is omitted as appropriate. However, the exhaust emission control device of this embodiment shows one aspect of the present invention, and does not limit the present invention. For example, each configuration of the embodiment can be arbitrarily changed within the scope of the present invention, such as replacing the SCR catalyst with an NSC catalyst or an oxidation catalyst, or using fuel or the like as an additive instead of urea water. is there.

1. Configuration of Exhaust Purification Device FIG. 1 shows the configuration of the exhaust purification device 10 in the present embodiment. The exhaust purification device 10 is a device for purifying NO _{x in} exhaust gas discharged from an internal combustion engine 5 such as a diesel engine mounted on a vehicle, and is configured as a urea SCR system.

  The exhaust purification device 10 is constructed from various sensors arranged in the exhaust system of the internal combustion engine 5, an SCR catalyst 13, a mixer 18, a urea water injection device 20, a control device 25, and the like. Various sensors, the urea water injection device 20, the control device 25, and the like are connected to a CAN (Controller Area Network) 28, and can acquire information existing on the CAN 28 and output information to the CAN 28. Yes. The CAN 28 can communicate with a device (not shown, hereinafter referred to as “ECU: Engine Control Unit”) for controlling the operation state of the internal combustion engine 5, and can perform fuel injection amount and injection. Information relating to the operating state of the internal combustion engine 5 such as timing and internal combustion engine speed can be read.

  The exhaust system of the internal combustion engine 5 is configured such that an exhaust passage 11 is connected to the internal combustion engine 5 and an SCR catalyst 13 is disposed in the exhaust passage 11. An additive injection valve mounting portion 14 is provided between the internal combustion engine 5 and the SCR catalyst 13, and an additive injection valve 21 of the urea water injection device 20 is installed. A mixer 18 is disposed in the exhaust passage 11 between the SCR catalyst 13 and the additive injection valve 21. A mixer 18 having a known structure can be used as appropriate, and is disposed at a position where the spray of urea water injected from the additive injection valve 21 directly collides.

SCR catalyst 13 disposed in the exhaust passage 11, reducing the NO _X in the exhaust gas by contacting the NO _X in the exhaust gas with the injected urea water into the exhaust passage 11 to the N ₂ (nitrogen) or the like a _the NO _X selective reducing catalyst to harmless by, it can be used as appropriate known ones. Depending on the SCR catalyst used, an ammonia oxidation catalyst for preventing ammonia slip may be disposed downstream of the SCR catalyst 13.

A NO _x sensor 26 is provided on the downstream side of the SCR catalyst 13, and a temperature sensor 27 is provided on the upstream side. These sensors detect NO _x concentration information and temperature information in the exhaust passage 11 and control the system. Sent to 25, ECU, etc. Although a detailed description of the ECU is omitted here, a control device for a general internal combustion engine used in an automobile or the like may be used.

  The urea water injection device 20 is a device for supplying urea water as an additive stored in the urea water tank 22 to the SCR catalyst 13. The urea water injection device 20 is constructed by an additive injection valve 21, a urea water tank 22, a urea water pump 23, a urea water supply pipe 24, and a control device 25. The additive injection valve 21 is attached to an additive injection valve mounting portion 14 provided in the exhaust passage upstream of the SCR catalyst 13, and urea water in the urea water tank 22 is passed through the urea water supply pipe 24 and the like. It is supplied sequentially. Specifically, the urea water tank 22 is connected to an additive injection valve 21 via a urea water supply pipe 24, and a urea water pump 23 is provided in the middle of the urea water supply pipe 24. For example, an electric pump or the like that is rotationally driven by a drive signal from the control device 25 is used as the urea water pump 23, and its output is fed back so that the pressure value of the urea water in the urea water supply pipe 24 becomes a predetermined value. Be controlled.

When the urea water pump 23 is driven to rotate with the start of the urea water injection device 20, urea water is pumped from the urea water tank 22 and supplied to the additive injection valve 21 through the urea water supply pipe 24. Then, by controlling the opening and closing of the additive injection valve 21 in accordance with the operating state of the internal combustion engine 5 and the temperature state of the SCR catalyst 13, an appropriate amount of urea water is injected into the exhaust passage 11 at an appropriate timing. The Then, the urea water is hydrolyzed in the exhaust passage 11 to generate NH ₃ and is supplied to the SCR catalyst 13 together with the exhaust gas, and the exhaust gas is purified by the NO _x reduction reaction in the SCR catalyst 13. .

  In the present embodiment, the control of each actuator of the urea water injection device 20 is performed by the control device 25, but it is also possible to appropriately perform the control by the ECU as a function in the ECU.

2. Additive Injection Valve Mounting Portion The structure of the additive injection valve mounting portion 14 in the present embodiment is shown in FIGS. FIG. 2B corresponds to a view of the additive injection valve mounting portion 14 of FIG. The additive injection valve mounting portion in the present embodiment is an upstream side enlarged taper portion 16 and a downstream side enlarged taper portion 17 provided in the exhaust passage 11, and between the upstream side enlarged taper portion 16 and the downstream side enlarged taper portion 17. The part that combines the exhaust passages. The enlarged taper portion is a portion formed in the exhaust passage 11 so that the cross-sectional area gradually increases toward the downstream side of the exhaust gas flow, and the cross-sectional shape is appropriately changed to a circular shape or a square shape. Can be formed.

  An introduction pipe 19 for guiding the spray of urea water added from the additive injection valve 21 to the exhaust passage 11 is connected to the upstream side enlarged taper part 16, and the upstream side enlarged taper part 16 and the downstream side enlarged taper part A mixer 18 is disposed in the exhaust passage 11 between 17.

  The introduction pipe 19 is formed in a cylindrical shape, and an additive injection valve 21 is connected to one end thereof, and the other end is connected to the upstream side enlarged taper portion 16 of the exhaust passage 11. In order to prevent the spray of urea water from adhering to the wall surface of the introduction pipe 19, the introduction pipe 19 is formed in a tapered shape that expands from one end to which the additive injection valve 21 is connected toward the other end. The tapered shape, diameter, length, and the like of the introduction pipe 19 are appropriately determined according to the urea water spray shape.

  By connecting the introduction pipe 19 to the upstream side enlarged taper portion 16, the volume of the introduction pipe 19 can be reduced as compared with the case where the introduction pipe 19 is directly connected to the straight tubular exhaust passage. As a result, the amount of exhaust gas pushed out from the introduction pipe 19 to the exhaust passage 11 with the injection of urea water from the additive injection valve 21 is reduced, so that in the introduction pipe 19 and in the vicinity of the outlet of the introduction pipe 19 Generation of large eddy currents is suppressed. Then, the spray of urea water is caught in the vortex and stays in the introduction pipe 19, and is prevented from adhering to the wall surface of the introduction pipe 19 and the periphery of the injection hole of the additive injection valve 21 to be fixed or crystallized.

  Since the contact area between the exhaust passage 11 and the introduction pipe 19 is reduced by connecting the introduction pipe 19 to the upstream side enlarged taper portion 16, the possibility that the additive injection valve 21 is damaged by heat can be reduced. Further, the use of the mixer 18 having a large cross-sectional area of the exhaust gas passage portion reduces the pressure loss in the exhaust passage 11 and improves the straightness of the exhaust gas flow. Therefore, the possibility that the additive injection valve 21 is damaged by heat can be further reduced.

  The upstream side enlarged taper portion 16 in the additive injection valve mounting portion 14 is α, the angle of the angle formed by the central axis of the additive spray injected from the additive injection valve 21 with respect to the central axis of the exhaust passage 11, The upstream contact A between the introduction pipe 19 and the upstream enlarged taper portion 16, the straight line AB passing through the downstream contact B between the introduction pipe 19 and the upstream enlarged taper portion 16, and the central axis of the exhaust passage 11 are formed. When the angle (inclination angle of the upstream enlarged taper portion 16 with respect to the central axis of the exhaust gas flow) is β, β is formed to be 90 ° −α or less. Compared with the case where β is larger than 90 ° −α, the generation of vortex accompanying the injection of urea water without generating an extra space in the exhaust passage 11 and without making the exhaust passage 11 complicated. Can be effectively suppressed.

  In particular, in the cross section including the central axis of the exhaust passage 11 and the apex of the tip of the additive injection valve 21, the upstream contact point A between the introduction pipe 19 and the upstream enlarged taper part 16, the introduction pipe 19 and the upstream enlargement. The straight line AB passing through the contact B on the downstream side with the tapered portion 16 is preferably formed so as to be orthogonal to the central axis of the spray of the additive injected from the additive injection valve 21. Since the central axis of the spray of the additive and the straight line AB are perpendicular to each other, the volume of the introduction pipe 19 is reduced when the distance between the additive injection valve 21 and the mixer 18 is constant. be able to.

  The exhaust passage 11 between the upstream enlarged taper portion 16 and the downstream enlarged taper portion 17 has a larger cross-sectional area than the exhaust passage 11 on the upstream side of the upstream enlarged taper portion 16. Is provided with a mixer 18 for efficiently mixing and diffusing the spray of urea water and the exhaust gas. In order to reduce the exhaust resistance and pressure loss caused by the arrangement of the mixer 18, the cross-sectional area of the exhaust gas passage portion in the mixer 18 is larger than the cross-sectional area of the exhaust passage 11 upstream of the upstream enlarged taper portion 16. Is also formed large.

  The downstream expansion taper portion 17 is formed on the downstream side of the mixer 18 and is formed in a shape that expands toward the SCR catalyst 13 in the downstream direction of the exhaust gas flow. By introducing the turbulent flow generated in the mixer 18 to the SCR catalyst 13 while being enlarged by the downstream enlarged taper portion 17, the additive can be uniformly supplied to the entire front surface on the upstream side of the SCR catalyst 13.

  Next, the effect of the additive injection valve mounting portion 14 in the present embodiment will be described. FIG. 3 shows the simulation result of the velocity distribution of the exhaust gas flow around the additive injection valve attachment portion 14 when the additive injection valve 21 is attached to the upstream side enlarged taper portion 16 via the introduction pipe 19 as described above. Shown in For comparison with the prior art, FIG. 4 shows a simulation result of the velocity distribution of the exhaust gas flow around the additive injection valve when the introduction pipe is connected to the straight tubular exhaust passage.

  First, paying attention to the flow in the introduction pipe 19 ′ in FIG. 4, after moving from the area P on the downstream side of the opening of the introduction pipe 19 ′ to the area Q in the vicinity of the injection hole of the additive injection valve 21 ′, Existence of a large vortex flowing toward the region R upstream of the opening of the introduction pipe 19 'with respect to the exhaust passage 11' and further from the region R toward the region P can be seen. Part of the spray injected from the additive injection valve 21 'is caught in this vortex, so that it rides on the vortex and reaches the periphery of the injection hole of the additive injection valve 21' and adheres to the additive injection valve 21 '. It is conceivable that the possibility of adhering to the wall surface of the introduction pipe 19 ′ while staying in the introduction pipe 19 ′ becomes very high. The urea water adhering to the wall surface or the like may crystallize due to evaporation of moisture or alteration due to heat, and may block the space in the introduction pipe 19 'and the injection hole.

  On the other hand, paying attention to the flow in the introduction pipe 19 in FIG. 3, it can be seen that the large vortex flow seen in FIG. 4 is reduced. Since the momentum of the vortex flow in the introduction pipe 19 is lower than that in FIG. 4, the possibility that a part of the spray injected from the additive injection valve 21 is caught in the vortex flow is reduced, and the additive injection valve 21. The possibility of adhering to the vicinity of the nozzle hole and the wall surface of the introduction pipe 19 is greatly reduced. As a result, urea water is crystallized around the nozzle hole of the additive injection valve 21 and in the introduction pipe 19, and spray formation of urea water is obstructed, or appropriate supply of the additive to the SCR catalyst 13 is performed. Is prevented from being disturbed.

3. Modification of Additive Injection Valve Mounting Part As a modification of the additive injection valve mounting part, Modification Example 1 in the case where the downstream side enlarged taper part 17 in FIG. It shows to Fig.5 (a)-(b). FIG. 5B corresponds to a view of the additive injection valve mounting portion 14 of FIG.

  In the first modification, the reduction taper portion 17 ′ is formed on the downstream side of the mixer 18, and is formed in a shape that reduces toward the downstream direction of the exhaust gas flow. In the cross section including the central axis of the exhaust passage 11 and the apex of the tip of the additive injection valve 21, the central axis of the urea water spray injected from the additive injection valve 21 forms the central axis of the exhaust passage 11. When the angle of the angle is α, the inclination angle β of the upstream side enlarged taper portion 16 with respect to the central axis of the exhaust passage 11 and the inclination angle γ of the reduction taper portion 17 ′ with respect to the central axis of the exhaust passage 11 are respectively α. ing. As described above, by providing the reduced taper portion 17 ′ on the downstream side of the mixer 18, the mixing of the exhaust gas and the urea water can be further promoted while rectifying the turbulent flow generated in the mixer 18. .

  Further, although the reduction taper portion 17 ′ increases the rectification effect of the exhaust gas flow as the inclination angle is small, the overall length becomes long. Therefore, the reduction taper portion 17 ′ The inclination angle γ is preferably about α ± 30 °. Thereby, the mixing of the exhaust gas and the additive can be promoted without excessively extending the entire length of the exhaust gas purification apparatus 10.

  Next, in order to make the introduction pipe 19 shorter, a second modification in the case where the inclination angle of the upstream side enlarged taper portion 16 '' is set large is shown in FIGS. FIG. 6B corresponds to a view of the additive injection valve mounting portion 14 of FIG. By setting the inclination angle β of the upstream side enlarged taper portion 16 ″ with respect to the central axis of the exhaust passage 11 to 90 ° −α, it is possible to attach the urea injection valve 21 to the exhaust passage 11 with the introduction pipe 19 ″ having the shortest shape. it can. If the inclination angle β is larger than 90 ° −α, an excessive space is formed in the exhaust passage 11 and the shape of the exhaust pipe becomes complicated, which is not preferable.

  Further, in the second modification, as described above, in the cross section including the central axis of the exhaust passage 11 and the apex of the distal end portion of the additive injection valve 21, the upstream side of the introduction pipe 19 and the upstream side enlarged taper portion 16 is provided. A straight line AB passing through a contact B on the downstream side, the contact B on the downstream side of the introduction pipe 19 and the upstream enlarged taper portion 16 is formed so as to be orthogonal to the central axis of the spray of the additive injected from the additive injection valve 21. Has been. Therefore, when the distance between the additive injection valve 21 and the mixer 18 is constant, the volume of the introduction pipe 19 is made smaller.

  In the second modification, the diameter of the exhaust passage 11 between the upstream side enlarged taper portion 16 '' and the reduced taper portion 17 'becomes very large, as shown in FIGS. 7 (a) to 7 (b). The size can be reduced by using one-side taper as in Modification 3.

5: Internal combustion engine, 10: Exhaust gas purification device, 11: Exhaust passage, 13: SCR catalyst, 14: Additive injection valve mounting part, 16: Upstream side expansion taper part, 17: Downstream side expansion taper part, 18: Mixer , 19: introduction pipe, 20: urea water injection device, 21: additive injection valve, 22: urea water tank, 23: urea water supply pump, 24: urea water supply pipe, 25: control device, 26: NO _X sensor , 27: Temperature sensor, 28: CAN

Claims (6)

An exhaust purification catalyst is disposed in an exhaust passage of the internal combustion engine, and an additive injection valve is attached to the exhaust passage upstream of the exhaust purification catalyst via an introduction pipe, and the additive injection valve In the exhaust emission control device in which the mixer is provided at a position where the spray of the additive injected from
An enlarged taper portion having a shape that expands in the downstream direction of the exhaust gas flow is formed in the exhaust passage on the upstream side of the exhaust purification catalyst, and the introduction pipe is connected to the enlarged taper portion. Exhaust purification device. In a cross section including the central axis of the exhaust passage and the apex of the tip of the additive injection valve,
Of the contacts between the introduction pipe and the enlarged taper portion, when the upstream contact is A and the downstream contact is B, the central axis of the spray of the additive injected from the additive injection valve The exhaust emission control device according to claim 1, wherein a straight line AB passing through the contact points A and B is orthogonal to the straight line AB.   3. The exhaust according to claim 1, wherein a reduced taper portion having a shape that decreases in a downstream direction of the exhaust gas flow is formed in the exhaust passage between the exhaust purification catalyst and the mixer. Purification equipment. In a cross section including the central axis of the exhaust passage and the apex of the tip of the additive injection valve,
The angle of the angle formed by the central axis of the additive spray injected from the additive injection valve with respect to the central axis of the exhaust passage is α, and the inclination angle of the reduced taper portion with respect to the central axis of the exhaust gas flow is 4. The exhaust emission control device according to claim 3, wherein γ = α ± 30 ° when γ.   3. The exhaust emission control device according to claim 1, wherein a second expansion taper having a shape expanding in a downstream direction of the exhaust gas flow is formed in the exhaust passage on the downstream side of the mixer.   The mixer is disposed in the exhaust passage on the downstream side of the enlarged tapered portion, and the sectional area of the exhaust gas passage portion of the mixer is larger than the sectional area of the exhaust passage on the upstream side of the enlarged tapered portion. The exhaust purification device according to any one of claims 1 to 5, wherein the exhaust purification device is also formed to be large.