JP5791489B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine. More specifically, the present invention relates to an exhaust gas purification apparatus for an internal combustion engine that includes a mixer used for stirring liquid and exhaust gas.

Conventionally, a mixer composed of a plurality of swirl blades used for an exhaust gas purification apparatus for an internal combustion engine is known.
Some mixers of this type have a blocked central part of the mixer.
Some mixers have a hole (center hole) in the center (see Patent Document 1).

JP 2011-111927 A

  In the conventional mixer of the type in which the central portion is closed, the shapes of the plurality of swirl vanes are uniformly curved in the swirl direction. Therefore, the gas flow exiting from the rear end side (downstream side) of the mixer is roughly a uniform swirl flow, but the central portion immediately after the mixer is in a negative pressure state, and stagnation occurs.

Therefore, for example, a reducing agent droplet tends to stay in the central portion immediately after the mixer, and precipitation tends to occur in the central portion on the rear end side of the mixer.
If deposits accumulate at the central part on the rear end side of the mixer, the reducing agent cannot be normally supplied to the catalyst disposed downstream of the mixer, and the purification rate of NOx deteriorates.
In addition, the pressure loss increases because the cross-sectional area of the flow path decreases due to the accumulation of precipitates.

On the other hand, since the center hole type mixer has no partition in the central portion of the mixer, a gas flow is also generated in the central portion immediately after the mixer.
Therefore, the reducing agent and the exhaust gas can be homogeneously introduced into the catalyst, and the NOx purification rate is improved as compared with the conventional mixer of the type in which the central portion is closed.
Further, since the gas escapes through the center hole, the pressure loss is reduced as compared with the conventional mixer of the type in which the central portion is closed.

However, the center hole type mixer improves the gas homogeneity, but the injection range of the reducing agent is limited.
That is, in the case of a center hole type mixer, some of the droplets of the reducing agent injected by the injector slip through the center hole without colliding with the mixer, and the homogeneous supply of reducing agent and exhaust gas to the center of the catalyst is achieved. Getting worse.

As a countermeasure, in the center hole type mixer, the spray of the injector is made into a hollow type or a multi-hole type, and the injection range of the injector is limited to the area of the mixer other than the center hole.
However, even with this measure, the reducing agent droplet is actually sheared by the influence of the gas flow, and the jet trajectory changes. For this reason, it is difficult to manage the droplets of the reducing agent so as to surely collide with the region of the mixer other than the center hole.

  The present invention has been made in view of the above-described problems, and purifies an exhaust gas of an internal combustion engine (such as a mixture of a reducing agent and exhaust gas in an exhaust passage) as a gas stream that is homogeneously stirred while reducing pressure loss. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can be supplied for the purpose.

An exhaust gas purification apparatus for an internal combustion engine (for example, an exhaust gas purification apparatus 5 described later) of the present invention is provided in an exhaust passage (for example, an exhaust pipe 2 described later) of an internal combustion engine (for example, an internal combustion engine 1 described later) to emit exhaust gas. A mixer for stirring (for example, a mixer 20 described later) is provided, and the mixer generates a swirling flow in the exhaust gas from the center of the mixer (for example, the center shaft 22 described later) of the exhaust passage. A plurality of swirl vanes (for example, swirl blades 30 described later) extending toward an inner peripheral portion (for example, a ring frame 21 described later),
The swirl vane has a cross-sectional shape perpendicular to the axial direction at a predetermined position downstream from the front end of the mixer, and an end on the central side of the mixer, and an end on the inner peripheral side of the exhaust passage of the mixer An intermediate portion between the both end portions is configured to protrude in a swirling direction of the swirling flow with respect to a straight line connecting the two .

According to the present invention, exhaust gas (a mixture of a reducing agent and exhaust gas in an exhaust passage) of an internal combustion engine can be supplied for purification as a homogeneously stirred gas stream while reducing pressure loss.
Further, the exhaust gas flowing between two adjacent swirl vanes on the inner peripheral side of the exhaust passage of the mixer is bent in one direction by one swirl blade and then swirled by changing the direction by the other swirl blade. .
Thereby, the exhaust gas flowing into the exhaust passage inner peripheral side of the mixer can be appropriately and effectively stirred.

  In this case, it is preferable that the swirl vane includes a plurality of through holes.

  According to this invention, a part of the silencing function by the silencer provided in the vicinity of the exhaust passage end of the internal combustion engine can be provided to the swirl blades of the mixer.

  In this case, it is preferable that the plurality of through holes are provided on a rear end side of the swirl vane.

  According to the present invention, since no through hole is formed on the front end side of the swirl vane, hydrolysis of the reducing agent droplet (urea water) is not affected. A part of the silencing function by the silencer can be achieved by the through hole formed on the rear end side of the swirl vane.

  In this case, the urea supply means (for example, urea water injection device 10 described later), the mixer, and the SCR catalyst (for example, NOx purification catalyst 50 described later) are arranged in this order from the upstream side to the downstream side of the exhaust passage. It is preferable that

According to this invention, the flow after the mixer is a linear flow in the same direction as the flow of the exhaust gas at the center, and the swirling flow at the outer peripheral portion. Therefore, the flow diffuses in all directions at the conical portion in front of the SCR catalyst, and urea can be supplied uniformly.
Moreover, since a gas flow is ensured in the central part after the mixer, precipitation of the reducing agent can be suppressed.
Since the swirler blades are packed in the mixer inlet as seen from the injector injection direction, the injected reducing agent can be splashed reliably and atomization of the reducing agent can be promoted.

The method for producing a mixer of the present invention is a method for producing a mixer for stirring exhaust gas provided in an exhaust passage of an internal combustion engine,
In order to generate a swirling flow in the exhaust gas, the shape of a plurality of swirling blades extending from the central portion of the mixer toward the inner peripheral portion of the exhaust passage is orthogonal to the axial direction at a predetermined position downstream from the front end portion of the mixer. In the cross-sectional shape, the intermediate portion between the both ends of the straight line connecting the end portion on the central portion side of the mixer and the end portion on the inner peripheral portion side of the exhaust passage of the mixer is the swirling flow. Formed in a shape that protrudes in the turning direction ,
The plurality of swirl blades formed are arranged in an annular frame of the mixer,
The outer end of each swirl wing is fixed to the annular frame.

According to this invention, the shape of the swirl vane of the mixer is a cross-sectional shape orthogonal to the axial direction at a predetermined position downstream from the front end portion of the mixer, and the end portion on the central portion side of the mixer and the inner peripheral portion of the mixer exhaust passage An intermediate portion between both end portions is formed in a shape protruding in the swirling direction of the swirling flow with respect to a straight line connecting the end portions on the side .
As a result, the exhaust gas flowing in between the two swirl blades adjacent on the inner peripheral side of the exhaust passage of the mixer is bent in one direction by one swirl blade, and then swirled by switching the direction by the other swirl blade. The
Therefore, the exhaust gas flowing into the inner peripheral side of the exhaust passage of the mixer can be appropriately and effectively stirred.

According to the present invention, exhaust gas of an internal combustion engine (a mixture of a reducing agent and exhaust gas in an exhaust passage) can be supplied for purification as a homogeneously stirred gas stream while reducing pressure loss.
Further, the exhaust gas flowing between two adjacent swirl vanes on the inner peripheral side of the exhaust passage of the mixer is bent in one direction by one swirl blade and then swirled by changing the direction by the other swirl blade. .
Thereby, the exhaust gas flowing into the exhaust passage inner peripheral side of the mixer can be appropriately and effectively stirred.

1 is a schematic configuration diagram showing an embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention. It is the end elevation seen from the front of a 1st embodiment of a mixer used for an exhaust gas purification device shown in Drawing 1. It is the perspective view seen from the front side which abbreviate | omits and shows the annular frame of the mixer shown in FIG. FIG. 4 is a side view of the mixer shown in FIG. 3. FIG. 5 is a longitudinal front view taken along line VV in FIG. 4. It is the perspective view seen from the rear surface side of the mixer shown in FIG. FIG. 4 is a front view of one swirl blade of the mixer shown in FIG. 3. It is a top view of the swirl | wing blade shown in FIG. It is a right view of the swirl | wing blade shown in FIG. It is a left view of the swirl | wing blade shown in FIG. It is a schematic plan view which shows the swirl | vortex flow which a swirl | wing blade produces | generates in the position of 43a-43d of FIG. FIG. 10 shows a second embodiment of the mixer used in the exhaust emission control device shown in FIG. 1 and is a view of a swirl blade viewed from the same direction as in FIG. 9. It is the perspective view seen from the front side which abbreviate | omits an annular frame and shows an example of the conventional mixer. It is a side view of the mixer shown in FIG. It is the longitudinal cross-sectional front view taken along the XV-XV line | wire of FIG. It is the figure of the swirl | wing blade of the mixer shown in FIG. 13 seen from the same direction as FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of an exhaust purification device 5 for an internal combustion engine 1 according to the present invention.

The exhaust purification device 5 includes a urea water injection device 10, a mixer 20, and a NOx purification catalyst 50 that are arranged in order from the upstream side to the downstream side in the exhaust passage (exhaust pipe) 2 of the internal combustion engine 1.
The urea water injection device 10 disposed on the most upstream side injects and supplies urea water as a reducing agent into the exhaust pipe 2 upstream of the NOx purification catalyst 50 disposed on the most downstream side.
The mixer 20 disposed between the urea water injection device 10 in the exhaust pipe 2 and the NOx purification catalyst 50 stirs and mixes the urea water injected by the urea water injection device 10 and the exhaust gas.

The urea water injection device 10 includes a urea water tank 11, a urea water supply pipe 12 extending from the urea water tank 11, a urea water injection nozzle 13 attached to the tip of the urea water supply pipe 12, and a urea water pump (not shown). . The urea water injection nozzle 13 includes an injection valve (not shown).
The urea water injection nozzle 13 is disposed inside the exhaust pipe 2 and is positioned at a position where the urea water injected from the nozzle tip collides with a swirl blade 30 described later.

The NOx purification catalyst 50 is a conventionally known so-called SCR (selective reduction type) catalyst, and is prepared by a conventionally known preparation method.
The NOx purification catalyst 50 captures NH ₃ produced by hydrolysis of the urea water supplied by the urea water injection device 10.
The NOx purification catalyst 50 has at least a NOx purification function, and reduces and purifies NOx in the exhaust gas by using the captured or supplied NH ₃ .

  FIG. 2 is an end view of the mixer 20 according to the first embodiment disposed in the exhaust pipe 2 as viewed from the front (upstream side). That is, since FIG. 2 is an end view, the internal structure of the mixer 20 (for example, the internal shape of the swirl blade 30) is not shown.

The mixer 20 includes an annular frame 21 fitted to the inner peripheral surface of the exhaust pipe 2, a central shaft 22 positioned at the center of the annular frame 21, and a plurality of swirl vanes 30 that connect the annular frame 21 and the central shaft 22. .
Exhaust gas flowing from the internal combustion engine 1 through the exhaust pipe 2 and urea water droplets injected from the urea water injection nozzle 13 of the urea water injection device 10 are introduced into the mixer 20. The introduced urea water droplets pass through a flow path formed between the plurality of swirl vanes 30 together with the exhaust gas while being finer by hitting a plurality of swirl vanes 30 described later. At this time, the mixer 20 adjusts the flow direction of the swirl vanes 30 to stir and mix the exhaust gas and the urea water droplets, and supply them to the NOx purification catalyst 50.

  FIG. 3 is a perspective view seen from the front side (upstream side) of the mixer 20 with the annular frame 21 omitted. 4 is a side view of the mixer 20, FIG. 5 is a longitudinal front view taken along the line VV in FIG. 4, and FIG. 6 is a perspective view seen from the back side (downstream side) of the mixer 20. is there.

The swirl vane 30 of the mixer 20 generates a linear flow or a weak swirl flow in the same direction as the flow of the exhaust gas in the exhaust gas flowing into the central portion side of the mixer 20 (that is, the central shaft 22 side of the mixer 20).
The swirl vanes 30 of the mixer 20 generate a strong swirl flow in the exhaust gas flowing into the inner peripheral side of the exhaust pipe 2 of the mixer 20 (that is, the annular frame 21 side of the mixer 20).

  Specifically, as shown in FIG. 5, the swirl vane 30 has a cross-sectional shape orthogonal to the axial direction at a predetermined position downstream from the front end of the mixer 20, and an end on the central axis 22 side of the mixer 20, and the mixer An intermediate portion (protrusion portion 40) between both end portions protrudes in a swirling direction of a strong swirling flow with respect to a straight line R connecting the end portion of the 20 annular frame 21 side. This will be described later.

Hereinafter, the shape of the swirl blade 30 and the state of the swirl flow will be described with reference to FIGS.
7 is a front view of one swirl blade 30 of the mixer 20, FIG. 8 is a plan view, FIG. 9 is a view of a rear edge 35 to be described later from the right side, and FIG. 10 is a left side view. . FIG. 11 is a schematic plan view showing a swirl flow generated by the swirl vane 30 at positions 43a to 43d in FIG.

As shown in FIGS. 7-10, each swirl | wing blade 30 is formed by bending one board | plate material. The shape of the plate 30s before bending is shown by a two-dot chain line in FIG.
Each swirl vane 30 is located on the front edge 31 located on the front end side (upstream side) of the mixer 20, the inner edge 33 located on the center axis 22 side of the mixer 20, and the rear end side (downstream side) of the mixer 20. A rear edge 35 and an outer edge 37 located on the annular frame 21 side of the mixer 20 are provided.

The front edge 31 of the swirl vane 30 extends linearly along the radial direction from the central axis 22 of the mixer 20 to the annular frame 21.
An inner edge 33 of the swirl vane 30 extends linearly along the central axis 22 of the mixer 20.
The rear edge 35 of the swirl vane 30 extends linearly along the radial direction from the central axis 22 of the mixer 20 to the annular frame 21.
The outer edge 37 of the swirl vane 30 extends in a curved shape along the inner peripheral surface of the annular frame 21 of the mixer 20.

The inner end of the front edge 31 and the front end of the inner edge 33 intersect each other at an intersection point 32 at an angle of approximately 90 °.
The rear end of the inner edge 33 and the inner end of the rear edge 35 intersect each other at an intersection point 34 at an angle of approximately 90 °.
The outer end of the rear edge 35 and the rear end of the outer edge 37 intersect each other at an intersection point 36 at an angle of approximately 90 °.
The front end of the outer edge 37 and the outer end of the front edge 31 intersect at an intersection point 38 at an angle of approximately 90 °.

  In FIG. 7, the front edge 31 is arranged in parallel to the paper surface. The front edge 31 is arranged perpendicular to the paper surface in FIG. In FIG. 9, the front edge 31 is disposed to be inclined with respect to the paper surface. That is, the intersection point 32 that is the inner end of the front edge 31 contacts the paper surface, and the intersection point 38 that is the outer end of the front edge 31 floats forward from the paper surface. In FIG. 10, the front edge 31 is arranged in parallel to the paper surface.

  In FIG. 7, the inner edge 33 is arranged perpendicular to the paper surface. In FIG. 8, the inner edge 33 is arranged in parallel to the paper surface. In FIG. 9, the inner edge 33 is arranged in parallel to the paper surface. In FIG. 10, the inner edge 33 is arranged in parallel to the paper surface.

  In FIG. 7, the rear edge 35 is arranged in parallel to the paper surface. In FIG. 8, the rear edge 35 is disposed to be inclined with respect to the paper surface. That is, the intersection point 34 that is the inner end of the rear edge 35 is in contact with the paper surface, and the intersection point 36 that is the outer end of the rear edge 35 floats up from the paper surface. In FIG. 9, the rear edge 35 is arranged in parallel to the paper surface. In FIG. 10, the rear edge 35 is inclined with respect to the paper surface. That is, the intersection point 34 that is the inner end of the rear edge 35 is in contact with the paper surface, and the intersection point 36 that is the outer end of the rear edge 35 floats up from the paper surface.

As shown in FIGS. 7 and 8, a predetermined angle is formed between the front edge 31 and the rear edge 35 along the circumferential direction of the mixer 20.
As shown in FIG. 8, the outer edge 37 has a large curve from the intersection point 38 with the front edge 31 toward the intersection point 36 with the rear edge 35 along the inner peripheral surface of the annular frame 21 of the mixer 20. It is formed to draw.

As described above with reference to FIG. 5, the swirl vane 30 is intermediate between both ends with respect to a straight line connecting the inner edge 33 and the outer edge 37 in the middle between the front edge 31 and the rear edge 35. The part protrudes in the swirl direction of the strong swirl flow.
Since this protrusion 40 is formed by the curvature of the surface which comprises the swirl | wing blade 30, it does not appear as a line in FIGS.
However, the protrusion 40 is a very important element for the swirl vane 30 and hence the mixer 20. Therefore, in FIG. 9 and FIG. 10, the protruding portion 40 is expressed as a band drawn with dots.

As shown in FIGS. 9 and 10, the protruding portion 40 of the swirl vane 30 has an outer end (intersection point 38) of the front edge 31 and an outer end (intersection point 36) of the rear edge 35. It is substantially formed so as to be curved and tie through inward in the radial direction from (intersection points 38, 26).
The protrusion 40 protrudes toward the back side in FIG. The protrusion 40 protrudes toward the near side in FIG.

A swirl flow ( a linear flow 43a and a weak swirl flow 43b in the same direction as the exhaust gas flow described later) and the annular frame 21 of the mixer 20 on the central axis 22 side of the mixer 20 with the protrusion 40 of the swirl blade 30 interposed therebetween. It is very different from the swirl flow on the side (strong swirl flows 43c and 43d described later) and draws a completely different locus. This will be described below.

The curved shape of the swirl vane 30 in the innermost region (inner side region 41) of the projecting portion 40 in the innermost region is formed as follows.
The curved shape of the swirl vane 30 is formed in a region near the inner edge 33 of the swirl vane 30 in the inner side region 41 so that the gas flow flowing from the front end of the mixer 20 flows in a substantially straight line. The

Specifically, as indicated by reference numeral 43a in FIG. 10, the gas flow flowing in a region close to the inner edge 33 of the swirl blade 30 in the inner side area 41 is substantially as indicated by reference numeral 43a in FIG. 11. In particular, it passes through the swirl vane 30 (mixer 20) as a linear flow 43a in the same direction as the flow of the exhaust gas .
More specifically, the linear flow 43a in the same direction as the exhaust gas flow moves slightly left in FIG. 11 and flows linearly. The movement to the left is negligible.

  In the region far from the inner edge 33 of the swirl vane 30 in the inner side region 41, the gas flow flowing in from the front end portion of the mixer 20 once changes its direction slightly and then flows back to its original direction. The curved shape of the swirl vane 30 is formed.

Specifically, as indicated by reference numeral 43 b in FIG. 10, the gas flow flowing in a region far from the inner edge 33 of the swirl blade 30 in the inner side area 41 is weak as indicated by reference numeral 43 b in FIG. 11. The swirl flow 43b passes through the swirl vane 30 (mixer 20).
More specifically, the weak swirl flow 43b once changes its direction slightly to the left in FIG. 11, and then returns to its original direction. That is, the weak swirl flow 43b basically has a linear flow in the same direction as the exhaust gas flow that shifts to the left.

The curved shape of the swirl wing 30 in the outermost region (outer side region 42) than the innermost part of the protrusion 40 is formed as follows.
Of the outer side region 42, in the region far from the outer edge 37 of the swirl blade 30, the gas flow that flows in from the front end of the mixer 20 bends in one direction, and then bends greatly in the opposite direction. The curved shape of the swirl vane 30 is formed.

Specifically, as indicated by reference numeral 43 c in FIG. 10, the gas flow flowing in a region far from the outer edge 37 of the swirler 30 in the outer side region 42 is strong as indicated by reference numeral 43 c in FIG. 11. The swirl flow 43c passes through the swirl vane 30 (mixer 20).
More specifically, in FIG. 11, the strong swirl flow 43 c first turns to the right, then turns to the left and returns to the original state, and further turns to the left and flows toward the left.

  Of the outer side region 42, in the region near the outer edge 37 of the swirl vane 30, the gas flow flowing in from the front end of the mixer 20 bends greatly in one direction and then flows in a larger direction in the opposite direction. In addition, the curved shape of the swirl vane 30 is formed.

Specifically, as indicated by reference numeral 43d in FIG. 10, the gas flow flowing in the region near the outer edge 37 of the swirl blade 30 in the outer side region 42 is further increased as indicated by reference numeral 43d in FIG. The strong swirl flow 43d (one aspect of the strong swirl flow) passes through the swirl blade 30 (mixer 20).
More specifically, in FIG. 11, the stronger swirling flow 43d first turns to the right, then turns to the left, and flows toward the left.

The expression “weak” or “strong” in the above-mentioned swirling flow represents not only the degree of swirling strength (swirl R) of the swirling flow but also the swirling flows that are essentially different from each other.
First, the bending direction is different between the weak swirl flow 43b and the strong swirl flows 43c and 43d. The weak swirl flow 43b returns to the original direction after turning to the left. On the other hand, the strong swirl flows 43c and 43d turn to the right and then turn to the left.

  Second, the weak swirl flow 43b and the strong swirl flows 43c and 43d have different flow directions when exiting the mixer 20. The weak swirl flow 43 b flows substantially along the axial direction of the mixer 20. On the other hand, the strong swirl flows 43c and 43d swirl greatly in the circumferential direction of the mixer 20 and flow.

Such a difference between the (weak) swirl flow 43b and the (strong) swirl flows 43c and 43d occurs even when the twist angle is adjusted in the conventional swirl vane 130 as shown in FIGS. It is a difference that cannot be obtained.
In FIGS. 13 to 16, by adding 100 to the reference numerals used in the corresponding diagrams shown in FIGS. 3 to 5 and 9, the correspondence with each part in FIGS. 3 to 5 and 9. Indicates.

According to this embodiment, there are the following effects.
(1) Contrary to the fact that the swirl vanes 30 generate strong swirl flows 43c and 43d in the exhaust gas flowing into the annular frame 21 side of the mixer 20 (the inner peripheral side of the exhaust pipe 2), the mixer 20 A straight flow 43a or a weak swirl flow 43b in the same direction as the flow of the exhaust gas is generated in the exhaust gas flowing into the central shaft 22 side (center side). Therefore, the pressure loss due to the exhaust gas flowing into the central shaft 22 side of the mixer 20 colliding with the swirl blade 30 is clearly reduced, and therefore the pressure loss of the mixer 20 as a whole can be reduced.

(2) Exhaust gas flowing into the central axis 22 side of the mixer 20 flows downstream of the central axis 22 as a linear flow 43a or weak swirl flow 43b in the same direction as the flow of the exhaust gas . Therefore, on the downstream side of the mixer 20, homogeneous exhaust gas can be supplied from the center side to the inner peripheral side of the exhaust pipe 2.

  (3) The swirl blade 30 is swirled in a strong swirl flow in the middle between both ends with respect to a straight line connecting the inner edge 33 and the outer edge 37 in the middle between the front edge 31 and the rear edge 35. Protrudes in the direction. Therefore, the exhaust gas flowing between the two swirl blades 30, 30 adjacent on the annular frame 21 side of the mixer 20 is bent in one direction by one swirl blade 30, and then the direction is switched by the other swirl blade 30. Is turned. Accordingly, the exhaust gas flowing into the annular frame 21 side of the mixer 20 can be appropriately and effectively stirred.

  (4) The urea water injection device 10, the mixer 20, and the NOx purification catalyst 50 are sequentially arranged in the exhaust pipe 2 of the internal combustion engine 1 from the upstream side toward the downstream side. Therefore, the flow velocity distribution after the mixer 20 becomes uniform in the channel cross-sectional area. Therefore, urea can be uniformly supplied to the NOx purification catalyst (SCR catalyst) 50.

  (5) A gas flow is secured in the center after the mixer 20. Therefore, precipitation of a reducing agent can be suppressed.

  (6) When viewed from the injection direction of the urea water injection nozzle (injector) 13, the swirl vane 30 is clogged at the inlet of the mixer 20 without being removed. Therefore, the injected reducing agent can be reliably splashed and atomization of the reducing agent can be promoted.

Next, a second embodiment of the mixer will be described with reference to the swirl vanes shown in FIG.
As shown in FIG. 12, a plurality of through holes 45 are formed in the swirl vane 30A.
Specifically, the plurality of through holes 45 are formed on the rear end side of the swirl vane 30A.
Although not shown, the mixer including a plurality of swirl blades 30A is the same as the mixer 20 according to the first embodiment except that a plurality of through holes 45 are provided.

The mixer according to the second embodiment has the following effects in addition to the above effects.
(7) A plurality of through holes 45 are formed in the swirl blade 30A of the mixer. Therefore, a part of the silencing function by the silencer provided near the end of the exhaust pipe 2 of the internal combustion engine 1 can be given to the swirl blade 30A of the mixer.
(8) The plurality of through holes 45 are formed on the rear end side of the swirl vane 30A. Therefore, since the through hole 45 is not formed on the front end side of the swirl vane 30A, the hydrolysis of the reducing agent droplet (urea water) is not affected. A part of the silencing function by the silencer can be achieved by the through hole 45 formed on the rear end side of the swirl vane 30A.
(9) The gas flow rate drop due to the pressure loss of the mixer can be compensated by reducing the flow resistance of a silencer or the like. However, there is concern that exhaust noise and exhaust noise will deteriorate. Therefore, by providing a part of the silencing function to the swirl vane 30A of the mixer, an exhaust noise reduction effect by reducing exhaust pulsation (vibration) can be expected.
(10) By punching the plurality of through holes 45, the surface area of the swirl vane 30A can be increased. Therefore, the heat receiving area of the reducing agent droplet (urea water) can be increased to achieve both the silencing function while aiming to improve the hydrolysis performance of the urea water and to maintain and improve the diffusibility.
(11) The volume of the silencer that is originally provided is reduced by using a mixer with a silencing function, in which the swirl vane 30A includes a plurality of through holes 45. Therefore, the output can be maintained by improving the exhaust gas flow rate, and the cost can be reduced by reducing the silencer member.

Next, an embodiment of a method for manufacturing a mixer will be briefly described.
In the case of the mixer 20 according to the first embodiment, the manufacturing method is at least:
While the exhaust gas flowing into the central axis 22 side of the mixer 20 generates a linear flow 43a or a weak swirl flow 43 in the same direction as the exhaust gas flow , the exhaust gas flowing into the annular frame 21 side of the mixer 20 is strongly swirled. A first step of forming the shape of each swirl blade 30 to generate the flow 43c, 43d;
A second step of disposing the plurality of swirl blades 30 formed in the annular frame 21 of the mixer 20;
A third step of fixing the outer edge 37 of each swirl vane 30 to the annular frame 21.

  The inner edge 33 of each swirl blade 30 is preferably fixed to the central shaft 22 of the mixer 20.

  In the case of the mixer 20 according to the second embodiment described above, a plurality of embodiments of the manufacturing method are provided on the rear end side of the swirl blade 30A in the first step of the method of manufacturing the mixer 20 according to the first embodiment. It is only necessary to add the step of forming the through-hole 45 of the above.

  In each of the above embodiments, urea water is used as the reducing agent droplets handled by the exhaust gas purification device 5, but the invention is not limited to this. Other suitable reducing agent droplets can be used and are not limited to droplets.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust pipe (exhaust passage)
5 ... Exhaust gas purification device 10 ... Urea water injection device (urea supply means)
DESCRIPTION OF SYMBOLS 20 ... Mixer 21 ... Ring frame 22 ... Center axis 30, 30A ... Swirling blade 43a ... Linear flow 43b ... weak swirl flow 43c ... Strong swirl flow 43d ... Strong swirl flow 45 ... Through hole 50 ... NOx purification catalyst (SCR catalyst)

Claims (5)

A mixer provided in the exhaust passage of the internal combustion engine for stirring the exhaust gas;
The mixer includes a plurality of swirl vanes extending from a central portion of the mixer toward an inner peripheral portion of the exhaust passage in order to generate a swirl flow in the exhaust gas,
The swirl vane has a cross-sectional shape perpendicular to the axial direction at a predetermined position downstream from the front end of the mixer, and an end on the central side of the mixer, and an end on the inner peripheral side of the exhaust passage of the mixer With respect to the straight line connecting the two ends, the intermediate portion protrudes in the swirling direction of the swirling flow,
An exhaust purification device for an internal combustion engine. The exhaust purification device for an internal combustion engine according to claim 1, wherein the swirl vane includes a plurality of through holes. The exhaust purification device for an internal combustion engine according to claim 2 , wherein the plurality of through holes are provided on a rear end side of the swirl vane. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3 , wherein urea supply means, the mixer, and an SCR catalyst are arranged in this order from the upstream side to the downstream side of the exhaust passage. A method for manufacturing a mixer provided in an exhaust passage of an internal combustion engine for stirring exhaust gas,
In order to generate a swirling flow in the exhaust gas, the shape of a plurality of swirling blades extending from the central portion of the mixer toward the inner peripheral portion of the exhaust passage is orthogonal to the axial direction at a predetermined position downstream from the front end portion of the mixer. In the cross-sectional shape, the intermediate portion between the both ends of the straight line connecting the end portion on the central portion side of the mixer and the end portion on the inner peripheral portion side of the exhaust passage of the mixer is the swirling flow. Formed in a shape that protrudes in the turning direction ,
The plurality of swirl blades formed are arranged in an annular frame of the mixer,
Fixing the outer end of each swirl to the annular frame;
A method for manufacturing a mixer.

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