JP2014109239A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine that can suppress a rise in exhaust pressure by a deflection member when an exhaust flow rate increases while allowing exhaust to flow in an exhaust emission control device substantially equally when the exhaust flow rate is small.SOLUTION: An exhaust emission control device 4 includes an oxidation catalyst 7, a DPF 8, an SCR catalyst 9, and an ammonia oxidation catalyst 10 in this order from the upstream side. An exhaust passage 3 is formed in a channel shape right before the oxidation catalyst 7 and SCR catalyst 9, and exhaust changes its course by 180 degrees and flows in the oxidation catalyst 7 and SCR catalyst 9. Here, deflection members 21, 21 made of a temperature-sensing deformation material are arranged in a projection region on an inner wall of the exhaust passage 3 (channel-shaped part 31) when the oxidation catalyst 7 and SCR catalyst 9 are projected upstream. The deflection members 21, 21 deflect exhaust deviating outward and flowing in the curvature of the exhaust passage 3 toward the center and deform so as to make the deflection (exhaust resistance) of the flow of the exhaust less when the exhaust temperature is high than when the exhaust temperature is low.

Description

  The present invention relates to an exhaust emission control device interposed in an exhaust passage of an internal combustion engine.

  In Patent Document 1, a flow path change plate is welded to an opening end of an inlet pipe connected to a catalyst casing, and the flow path of the exhaust gas is changed by the flow path change plate, thereby supplying exhaust gas to each part of the catalyst. An exhaust emission control device is disclosed which reduces the quantity difference.

JP 2011-099415 A

  By the way, if the deflection characteristics such as the angle of the deflection member are set so that the deviation of the exhaust flow in the exhaust purification device such as a catalyst or a filter can be reduced when the exhaust flow rate is small, the exhaust flow rate increases In addition, the exhaust resistance by the deflecting member is increased to increase the back pressure of the internal combustion engine, which causes a reduction in fuel efficiency of the internal combustion engine.

  In view of the above-described problems of the prior art, the present invention reduces the deviation of the exhaust flow in the exhaust purification device when the exhaust flow rate is small, and reduces the back pressure of the engine due to the deflection member when the exhaust flow rate increases. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can suppress the increase.

  For this reason, the exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a deflection member that deflects the flow of exhaust gas so as to disperse the flow of exhaust gas in a cross section of the exhaust gas purification apparatus. The deflecting member is formed of a temperature-sensitive deformable material that deforms according to the exhaust temperature, and is deformed so that the deflection of the exhaust flow is weakened when the exhaust temperature is high compared to when the exhaust temperature is low.

  According to the present invention, when the exhaust gas flow rate is low and the exhaust gas temperature is low, the deflection member disperses the flow of the exhaust gas in the cross section of the exhaust gas purification device, while the exhaust gas flow rate increases and the exhaust gas temperature increases. Since the deflection member is deformed and the deflection of the exhaust is weakened, the exhaust resistance due to the deflection member is weakened, and an increase in exhaust pressure (back pressure of the internal combustion engine) can be suppressed.

The figure which shows the exhaust system of the diesel engine in embodiment of this invention The figure which shows the flow of exhaust when not providing a deflection | deviation member in embodiment of this invention The perspective view which shows the deflection | deviation member in embodiment of this invention The figure which shows the deformation | transformation characteristic by the exhaust temperature of the deflection | deviation member in embodiment of this invention, and the deflection | deviation characteristic of exhaust_gas | exhaustion The perspective view which shows the deflection | deviation member which has a through-hole in embodiment of this invention The perspective view which shows the deflection | deviation member made into two sets in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a diagram showing an exhaust system of an engine including an exhaust purification device.
The diesel engine (internal combustion engine) 1 includes an exhaust purification device 4 in an exhaust passage (exhaust pipe) 3 on the downstream side of the exhaust manifold 2.

Since the diesel engine 1 is equipped with the exhaust emission control device 4, the diesel engine 1 includes an upstream first casing 5a, a downstream second casing 5b, and a communication path 6 between the casings 5a and 5b.
In the first casing 5a, a diesel oxidation catalyst (DOC; Diesel Oxidation Catalyst) 7 is accommodated in the front stage (upstream side), and a diesel particulate filter (hereinafter referred to as “DPF”) 8 is accommodated in the rear stage (downstream side). ing.

The DPF 8 is a filter that collects PM (Particulate Matter) that is particulate matter in the exhaust gas. The DPF 8 is made of, for example, a porous ceramic honeycomb structure, and has a large number of passages communicating with the upstream side and the downstream side, and the upstream side and the downstream side are alternately sealed between adjacent passages. This is a wall flow type filter.
In this wall flow type DPF 8, the exhaust flows from a passage whose upstream end is open and whose downstream end is sealed, passes through a passage wall (a pore in the partition wall), the upstream end is sealed, and the downstream end opens. It flows out to the passage, and at this time, PM in the exhaust is collected on the passage wall.

The oxidation catalyst 7, and NO in the exhaust is oxidized to generate NO _2, is supplied to the DPF8 the NO ₂ as oxidizing agent, the temperature is raised to DPF8 downstream by generating oxidation heat.
By arranging the oxidation catalyst 7 in the upstream (upstream side) of the DPF 8 in this way, the PM collected by the DPF 8 reacts with the NO ₂ supplied from the oxidation catalyst 7 to be oxidized, and the continuous regeneration of the DPF 8 is performed. Done.

In the second casing 5b, an SCR catalyst 9 having a function of reducing NOx using ammonia as a reducing agent is housed in the front stage (upstream side), and the ammonia flowing out from the SCR catalyst 9 is oxidized in the rear stage (downstream side). An ammonia oxidation catalyst 10 having a function as an oxidation catalyst of N ₂ is accommodated. “SCR” is an abbreviation for Selective Catalytic Reduction.

A urea water injection nozzle 11 that injects a urea aqueous solution (hereinafter referred to as “urea water”) as a reducing agent (ammonia) precursor toward the SCR catalyst 9 in the communication passage 6 upstream of the second casing 5 b. Is provided.
The urea water is supplied from a urea water tank (not shown) to the nozzle 11 via the control module 12 for controlling the injection amount. The control module 12 is controlled by an electronic control unit (ECU) 50 incorporating a microcomputer.

The urea water injected from the urea water injection nozzle 11 is hydrolyzed by the heat of the exhaust to become ammonia, and the ammonia is adsorbed by the SCR catalyst 9. In the SCR catalyst 9, NOx and ammonia (NH ₃ ) are selectively reduced using the adsorbed ammonia as a reducing agent, and NOx is converted into water (H ₂ O) and nitrogen (N ₂ ) for purification. .
The SCR catalyst 9 and the urea water injection nozzle 11 constitute a NOx reduction device.

In addition, the exhaust flow is deflected in the exhaust passage 3 upstream of the oxidation catalyst 7 and upstream of the SCR catalyst 9, so that the cross section of the oxidation catalyst 7 and the SCR catalyst 9 (cross section orthogonal to the exhaust flow direction). Deflection members 21 and 21 are arranged to reduce the deviation of the exhaust flow.
The deflection member 21 can be provided on either the upstream side of the oxidation catalyst 7 or the upstream side of the SCR catalyst 9.

  In the exhaust purification device 4 of the present embodiment, the oxidation catalyst 7 and the DPF 8 are arranged on the same straight line, the SCR catalyst 9 and the ammonia oxidation catalyst 10 are arranged on the same straight line, and the oxidation catalyst 7 and the DPF 8 are made up of the SCR catalyst. 9 and the ammonia oxidation catalyst 10 are arranged substantially in parallel, and the exhaust flow direction in the oxidation catalyst 7 and the DPF 8 and the exhaust flow direction in the SCR catalyst 9 and the ammonia oxidation catalyst 10 are set to be the same. The exhaust passage 3 is provided so that the exhaust gas that has passed through the DPF 8 travels by changing the course by 180 degrees and then flows again into the SCR catalyst 9 by changing the course by 180 degrees.

Further, at the outlet of the exhaust manifold 2, the exhaust passage 3 is arranged such that after the exhaust gas flows in a direction opposite to the flow direction of the exhaust gas in the oxidation catalyst 7 and the DPF 8, the course is changed by 180 degrees and flows into the oxidation catalyst 7. Is provided.
That is, immediately before the oxidation catalyst 7 and the SCR catalyst 9, the exhaust passage 3 is bent to form a U shape, and the exhaust gas is configured to flow into the oxidation catalyst 7 and the SCR catalyst 9 by changing the course by 180 degrees. Yes.

Here, when the flow rate of the exhaust gas is small, as shown in FIG. 2, the exhaust gas flows unevenly toward the outer side 31 a of the U-shaped portion (bending portion) 31 that changes the course of the exhaust gas by 180 degrees. The exhaust flow rate flowing through the curved outer side 31a tends to be larger than the exhaust flow rate flowing through the inner side 31b, and the exhaust gas flowing through the oxidation catalyst 7 and the SCR catalyst 9 is biased. There will be a bias in the flow of exhaust.
Therefore, the exhaust gas flowing toward the outer side 31 a of the U-shaped portion 31 is guided and deflected inward by the deflecting members 21, 21 to disperse the exhaust flow in the exhaust passage 3, thereby oxidizing the catalyst. 7 and the SCR catalyst 9 in the cross section (cross section orthogonal to the exhaust flow direction) is reduced.

The deflecting members 21 and 21 are formed in a shape in which a rectangular plate is bent near the center in the longitudinal direction, and one is fixed to the inner wall of the exhaust passage 3 with the bent portion 21a as a boundary as shown in FIG. The base portion 21b is formed, and the other is a deflection portion (fin portion) 21c protruding into the exhaust passage 3.
The deflecting members 21 and 21 are projected areas on the inner wall of the exhaust passage 3 (U-shaped portion 31) when the oxidation catalyst 7 and the SCR catalyst 9 are projected toward the upstream side, that is, the U-shaped portion 31 of the U-shaped portion 31. The base portion 21b is on the upstream side of the exhaust flow, and the deflecting portion 21c is on the downstream side at the outer side 31a of the bend, where the exhaust gas changes its course toward the entrance of the oxidation catalyst 7 and the SCR catalyst 9. The base portion 21 b is fixed so as to overlap the inner wall of the exhaust passage 3.
Thereby, the deflection | deviation part 21c has the inclination which leaves | separates from the inner wall of the exhaust passage 3 gradually toward the downstream of the flow of exhaust.

The deflecting portion 21c protrudes into the space in the exhaust passage 3 through which the exhaust flows at the outer side 31a of the U-shaped portion 31 and directs the exhaust flowing along the outer side 31a of the curved U-shaped portion 31 to the inside. Guide and deflect.
As a result, as shown in FIG. 4, when the exhaust gas flows unevenly toward the outer side 31 a of the U-shaped portion 31, the exhaust gas flow can be dispersed, and thus the oxidation catalyst 7 and the SCR catalyst 9. It is possible to reduce the deviation of the exhaust flow in the cross section.

Here, when the exhaust gas flow rate is large (the exhaust gas temperature is high), the deviation of the exhaust gas flow in the cross section of the oxidation catalyst 7 and the SCR catalyst 9 is sufficiently small without performing deflection by the deflection members 21 and 21. Become. Therefore, when the exhaust gas flow rate is large, the effect of deflection by the deflecting members 21 and 21 is reduced, and conversely, the disadvantage of increasing the exhaust resistance is increased.
On the other hand, when the flow rate of the exhaust gas is small (the exhaust gas temperature is low), the exhaust gas tends to flow toward the outer side 31a of the bend of the U-shaped portion 31, so the flow of the exhaust gas is dispersed by the deflecting members 21 and 21. In addition, the exhaust resistance can be suppressed sufficiently small.

Therefore, the deflection members 21 and 21 are formed of a temperature-sensitive deformation material that deforms according to the temperature, and as shown in FIG. 4, the deflection portion 21c and the inner wall (base portion 21b) of the exhaust passage 3 according to the exhaust temperature. Angle θ (ie, the included angle) θ, that is, the inclination of the deflecting portion 21c changes, and when the exhaust gas flow rate is high and the exhaust gas temperature is high, the angle θ is smaller than when the exhaust gas flow rate is low and the exhaust gas temperature is low. The exhaust gas deflection, in other words, the exhaust resistance is weakened.
As a result, when the exhaust gas flow rate is small (when the exhaust temperature is low in the low load and low rotation range of the diesel engine 1), the deviation of the exhaust flow is reduced, and the oxidation catalyst 7, DPF 8, SCR catalyst 9 and ammonia The deviation of the exhaust flow in the cross section of the oxidation catalyst 10 can be reduced, and the exhaust purification device 4 can purify the exhaust with high efficiency.
Further, when the exhaust flow rate is large (when the exhaust temperature is high in a high load and high rotation range of the diesel engine 1), an increase in exhaust resistance due to the deflection members 21 and 21 is suppressed, and the back pressure of the diesel engine 1 is increased. It is possible to suppress a decrease in fuel consumption performance due to fuel.

As the temperature-sensitive deformation material that is a material of the deflecting members 21 and 21, a known temperature-sensitive deformation material such as a bimetal or a shape memory alloy can be used as appropriate, and the correlation between the temperature and the deformation amount (angle θ change amount) is It is adapted so that an increase in exhaust resistance can be suppressed in a high temperature range while reducing an uneven exhaust flow in a low temperature range.
Here, when the deflection members 21 and 21 are formed of a shape memory alloy, a high temperature shape memory alloy that functions in a high temperature range of 100 ° C. or higher is used. As an example of such a high-temperature shape memory alloy, titanium Ti—nickel Ni—zirconium Zr—niobium Nb alloy, titanium Ti—tantalum Ta alloy, or the like can be used.

In addition, since it is difficult to finely adjust the deflection characteristics in the deformation using the temperature-sensitive deformable material, for example, as shown in FIGS. 5A and 5B, a plurality of through holes are formed in the deflection portion 21c (deflection fin portion). 21d can be drilled, and the deflection characteristics can be adjusted by setting the arrangement region, diameter, density (interval), axial direction, and the like of the through-hole 21d. For example, near the base portion 21b of the deflecting portion 21c, if the diameter of the through hole 21d and / or the number of holes per unit area are made smaller than the tip side, the exhaust flowing along the inner wall of the exhaust passage 3 is closer to the center. While deflecting, it is possible to suppress the exhaust gas flowing near the center of the exhaust passage 3 from being excessively deflected.
In addition, a plurality of deflection members 21 can be arranged side by side at the same location. For example, in the example shown in FIGS. 6A and 6B, two deflection members 211 and 212 are arranged in the circumferential direction of the exhaust passage 3. It is arranged. FIG. 6A is an example in which the two deflection members 211 and 212 do not include the through hole 21d, and FIG. 6B is an example in which the two deflection members 211 and 212 both have the through hole 21d. .

Although the contents of the present invention have been specifically described with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.
For example, a plurality of deflecting members can be provided adjacent to each other in the exhaust flow direction.
Further, the deflection member can be used for suppressing the bias of the inflowing exhaust gas with respect to the catalyst (exhaust purification device), and can be used for suppressing the bias of the inflowing exhaust gas with respect to the filter (exhaust gas purification device).

  Further, as shown in the embodiment, the deflection member is provided upstream of the exhaust purification device such as a catalyst or a filter, so that the bias of the exhaust gas in the downstream exhaust purification device can be suppressed, and the downstream side of the exhaust purification device. It is possible to suppress the deviation of the exhaust gas in the upstream side exhaust purification device. That is, by providing the deflecting member on the downstream side of the exhaust purification device and on the side where the exhaust is biased, the exhaust resistance in the path on the side where the exhaust is biased increases, and the bias of the exhaust flow can be suppressed.

Further, the exhaust system to which the deflection member is applied is not limited to an exhaust system in which the exhaust passage 3 is bent on the upstream side of the exhaust purification device. For example, the exhaust passage 3 is straight on the upstream side of the exhaust purification device. The present invention can also be applied to an extended exhaust system.
In the case of an exhaust system in which the exhaust passage extends straight on the upstream side of the exhaust purification device, for example, when the exhaust gas flows unevenly near the axis of the exhaust purification device (catalyst or filter), the periphery of the exhaust purification device A deflecting member that deflects exhaust toward the part is provided, and when the exhaust temperature becomes high, the deflecting member is deformed so that the deflection (exhaust resistance) is weakened.

Further, a deflection member that deforms according to the exhaust temperature and a deflection member that does not deform can be used in combination, or a plurality of deflection members having different deformation (angle changes) characteristics with respect to the exhaust temperature can be used in combination.
Further, the internal combustion engine to which the deflecting member is applied is not limited to the diesel engine 1, but can be applied to a gasoline engine or the like, and in the case of the gasoline engine, the exhaust bias in the exhaust purification device such as a three-way catalyst is improved. However, an increase in exhaust resistance can be suppressed.

1 Diesel engine (internal combustion engine)
2 Exhaust manifold 3 Exhaust passage (exhaust pipe)
4 Exhaust purification device 5a 1st casing 5b 2nd casing 6 Communication path 7 Oxidation catalyst (DOC)
8 Diesel particulate filter (DPF)
9 SCR catalyst 10 Ammonia oxidation catalyst 21 Deflection member 21d Through hole 31 U-shaped part (bent part)

Claims (7)

A deflection member for deflecting the exhaust flow so as to disperse the exhaust flow in the cross section of the exhaust purification device is disposed in the exhaust passage of the internal combustion engine;
The deflection member is formed of a temperature-sensitive deformable material that deforms according to the exhaust temperature, and is deformed so as to weaken the deflection of the exhaust flow when the exhaust temperature is high compared to when the exhaust temperature is low. .   The exhaust purification device for an internal combustion engine according to claim 1, wherein the deflection member is formed in a plate shape, and is deformed according to an exhaust temperature to change an angle with respect to the exhaust passage.   The internal combustion engine according to claim 1, wherein a bent portion of the exhaust passage is disposed in front of the exhaust purification device, and the deflecting member deflects exhaust flowing along the outside of the bent portion of the bent portion inward. Engine exhaust purification system.   4. The device according to claim 1, wherein the deflecting member is formed in a plate shape, and a sandwich angle formed by the plate-shaped deflecting member and the inner wall of the exhaust passage is deformed so as to decrease as the exhaust gas temperature increases. An exhaust purification device for an internal combustion engine according to claim 1.   The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein a plurality of through holes are formed in the plate-shaped deflection member.   The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the temperature-sensitive deformation material forming the deflection member is a shape memory alloy.   The exhaust gas purification apparatus for an internal combustion engine according to claim 6, wherein the shape memory alloy is a titanium-nickel-zirconium-niobium alloy or a titanium-tantalum alloy.