JP2015110929A - Exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in supply of a reducing agent added from an addition valve to a reduction catalyst in an exhaust emission control system in which the reduction catalyst is arranged in an exhaust passage of an internal combustion engine and a part of an upstream exhaust passage of the reduction catalyst serves as a swirl flow type passage.SOLUTION: In an exhaust passage 3 of a diesel engine 2 as an internal combustion engine, an SCRF 5 as a reduction catalyst and an oxidation catalyst 4 located upstream of the SCRF 5 are arranged. An exhaust passage 31 between the oxidation catalyst 4 and the SCRF 5 serves as a spiral mixer (swirl flow type passage) through which an exhaust gas passes with a swirl flow. An external cylinder 311 of the spiral mixer 31 is provided with an addition valve 6 for adding urea water as a reducing agent into the spiral mixer 31. In the addition valve 6, two injection holes are formed of which injection angels are different. At positions corresponding to the injection angles of the injection holes in the spiral mixer 31, two collision plates 314a and 314b are provided with which urea water added from the injection holes collides.

Description

  The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device that reduces and purifies harmful components in exhaust gas using a reduction catalyst disposed in an exhaust passage of an internal combustion engine.

  A urea SCR system is known as one of exhaust gas purification systems for internal combustion engines. In the urea SCR system, a reduction catalyst (SCR catalyst, NOx selective reduction catalyst, SCRF) for selectively reducing and purifying NOx in the exhaust gas is provided in the exhaust passage. An injection valve (addition valve) for injecting urea water as a reducing agent into the exhaust gas into the exhaust passage is provided upstream of the reduction catalyst. In the reduction catalyst, a reduction reaction is performed in which NOx is decomposed into nitrogen and water with ammonia generated from the urea water.

  In order to effectively reduce and purify NOx with the reduction catalyst, it is necessary to atomize the liquid reducing agent injected from the injection valve and disperse it in a wide range in the exhaust gas. Therefore, conventionally, in order to efficiently disperse (atomize and evaporate) urea water, there is a proposal of a technique in which the exhaust passage upstream (upstream) of the reduction catalyst is a swirling flow passage (see Patent Document 1). In the technique disclosed in Patent Document 1, urea water is injected into the swirling flow type passage, and the injected urea water and exhaust gas pass through the swirling flow type passage in a swirling flow, so that the urea water and the exhaust gas reach the reduction catalyst. It is possible to earn a distance until the end, that is, a dispersion distance of urea water.

US Patent Application Publication No. 2012/0216513

  By the way, in this type of exhaust purification system, if the injection amount of the reducing agent increases, the reducing agent stays on the passage wall of the swirling flow passage without evaporating. When the reducing agent stays on the passage wall, the wall temperature decreases, and the evaporation of the reducing agent is further delayed. As a result, the accuracy of the amount of the reducing agent to be supplied according to the amount of emission reaching the reduction catalyst is greatly deteriorated by the amount of the reducing agent staying on the passage wall. In addition, the reducing agent staying on the passage wall may evaporate over time and reach the reduction catalyst. In this case, more reducing agent than the expected amount is supplied to the reduction catalyst, contributing to reduction purification. A phenomenon called slip is generated in which the reducing agent that is not released is released downstream from the reduction catalyst.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the exhaust-gas purification apparatus which can improve the supply precision to the reduction catalyst of the reducing agent injected from the injection valve.

In order to solve the above problems, an exhaust gas purification apparatus of the present invention includes a reduction catalyst disposed in an exhaust passage of an internal combustion engine,
A swirl flow path on the upstream side of the reduction catalyst and configured to allow exhaust gas to pass in a swirl flow;
An injection valve that injects a reducing agent for causing a reduction reaction with the reduction catalyst into the swirling flow passage through an injection hole;
The injection valve has a plurality of injection holes with different injection angles,
The swirling flow type passage has a collision plate that is installed at a position corresponding to the injection angle of each injection hole of the injection valve and forms a plurality of collision surfaces that collide with each reducing agent injected from each injection hole. It is characterized by that.

  According to the present invention, since the collision plate is installed in the swirl flow type passage, most of the reducing agent injected from the injection hole of the injection valve collides with the collision plate, and a part of the colliding reducing agent is repelled. Then, it atomizes and rides on the gas flow to reach the downstream reduction catalyst, and most of the remaining part receives heat on the collision plate and evaporates and vaporizes to reach the downstream reduction catalyst. In the present invention, the injection valve is formed with a plurality of injection holes having different injection angles, and a collision surface for colliding the reducing agent is formed at each position corresponding to each injection hole. The amount of reducing agent injected from the hole can be reduced, and as a result, the amount of heat required for evaporation of the reducing agent to be handled on one collision surface can be reduced. For this reason, it is possible to suppress the temperature drop of each collision surface, and it is possible to suppress the reductant from staying in the swirling flow path. Therefore, the supply accuracy of the reducing agent to the reduction catalyst can be improved.

It is the figure which showed the exhaust gas purification system. It is sectional drawing when an exhaust passage is cut along the II-II line of FIG. It is an enlarged view of the nozzle of an addition valve. It is a figure explaining the view of the area of a collision board, and is a figure showing an addition valve, a collision board, and urea water spray. It is the figure which showed the relationship between k in Formula 9, and urea water temperature TM. 6 is a cross-sectional view of a spiral mixer according to Modification 1. FIG. 10 is a cross-sectional view of a spiral mixer according to Modification 2. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an exhaust purification system 1 mounted on a vehicle. First, the configuration of the exhaust purification system 1 will be described. The exhaust purification system 1 corresponds to the “exhaust gas purification device” of the present invention, and is a system that purifies exhaust gas discharged from a diesel engine 2 (hereinafter simply referred to as an engine) as an internal combustion engine. Specifically, the exhaust purification system 1 is configured to include a urea SCR system that purifies NOx in the exhaust gas. In the exhaust purification system 1, a cylindrical exhaust passage 3 is connected to the engine 2, and exhaust gas discharged from the engine 2 flows through the exhaust passage 3 and is discharged outside the vehicle.

  An oxidation catalyst 4 (DOC: Diesel Oxidation Catalyst) that oxidizes and purifies HC and CO, which are one of harmful components in the exhaust gas, is disposed in the exhaust passage 3. The oxidation catalyst 4 is arranged with no gap between the exhaust catalyst 3 and the passage wall of the exhaust passage 3. The oxidation catalyst 4 carries, for example, a catalyst component (for example, Pt (platinum) or Pd (palladium)) that promotes the oxidation reaction of HC and CO on a wall-through type ceramic honeycomb or metal mesh. It has a structure.

  The activity of the oxidation catalyst 4 is highly dependent on temperature, and has little oxidizing action at low temperatures. Therefore, in order to warm the oxidation catalyst 4 early after the engine 2 is started and promote the oxidation purification of HC and CO, the oxidation catalyst 4 is arranged upstream of the SCRF 5 described later (side closer to the engine 2). The oxidation catalyst 4 also has a role of raising the temperature of the exhaust gas by an oxidation reaction and burning and removing particulate matter (PM, soot) deposited on the SCRF 5 by the heated exhaust gas.

  Although not shown in FIG. 1, between the engine 2 and the oxidation catalyst 4, for example, a turbocharger turbine (variable nozzle turbo (VNT)) (not shown) that recovers energy from exhaust gas is disposed. ing.

  An SCRF (Selective Catalytic Reduction Filter) 5 that selectively reduces and purifies NOx in the exhaust gas is disposed in the exhaust passage 3 downstream of the oxidation catalyst 4. The SCRF 5 is arranged in a state where there is no gap with the passage wall of the exhaust passage 3. SCRF5 contains a catalyst component (SCR catalyst) that promotes SCR (selective catalytic reduction) of NOx, and also has a function of capturing particulate matter in exhaust gas. The SCRF 5 has a structure in which, for example, a catalyst component is supported on a wall-through type ceramic honeycomb. The exhaust gas flows downstream while passing through the porous partition walls of SCRF 5, and particulate matter in the exhaust gas is collected by SCRF 5 during that time.

The catalyst component contained in SCRF5 promotes the reduction reaction of, for example, the following formula 1, formula 2, and formula 3 as a reduction reaction between ammonia (NH3) generated from urea water and NOx, such as vanadium, Base metal oxides such as molybdenum and tungsten. Thus, while the exhaust gas passes through the SCRF 5, NOx is decomposed (purified) into water and nitrogen by, for example, the following formula 1, formula 2, and formula 3. Instead of SCRF5, a normal SCR catalyst, that is, a catalyst that does not have a particulate matter collecting function and performs only NOx reduction purification may be employed.
4NO + 4NH3 + O2 → 4N2 + 6H2O (Formula 1)
6NO2 + 8NH3 → 7N2 + 3H2O (Formula 2)
NO + NO2 + 2NH3 → 2N2 + 3H2O (Formula 3)

  In addition, SCRF5 cannot store ammonia inexhaustably, and the maximum amount of ammonia that can be stored in SCRF5 varies depending on the temperature (catalyst temperature) of SCRF5. When the catalyst temperature rapidly decreases or when ammonia (urea water) is excessively supplied to the SCRF 5, a phenomenon called ammonia slip in which ammonia is released from the SCRF 5 occurs. For this reason, an oxidation catalyst for purifying ammonia released from SCRF 5 may be provided in the exhaust passage downstream of SCRF 5.

  The exhaust passage 31 between the oxidation catalyst 4 and the SCRF 5 is configured as a swirling flow passage that allows the exhaust gas to pass in a swirling flow, that is, generates a swirling flow. Hereinafter, the swirl flow path is referred to as a spiral mixer. The length of the spiral mixer 31, that is, the length between the oxidation catalyst 4 and the SCRF 5, is about 50 mm to 100 mm, for example. The spiral mixer 31 is a passage for dispersing urea water (urea water spray) added from an addition valve 6 described later in the exhaust gas so as to improve the mixing of the urea water and the exhaust gas. The spiral mixer 31 includes a cylindrical outer cylinder 311 constituting the outer peripheral wall of the spiral mixer 31, and a rod-shaped boss 312 arranged on the central axis L1 of the outer cylinder 311 and extending in the direction of the central axis L1. And a swirl flow plate 313 which is welded to the outer cylinder 311 and the boss 312 and formed in a spiral shape (spiral shape) along the outer periphery of the boss 312.

  FIG. 2 is a cross-sectional view of the spiral mixer 31 taken along the line II-II in FIG. 1 (a line perpendicular to the axis L1 in the inlet region of the spiral mixer 31). As shown in FIGS. 1 and 2, the spiral mixer 31 is provided with a collision plate 314 that causes the urea water added from the addition valve 6 to collide. As will be described later, the addition valve 6 is formed with a plurality of injection holes having different injection angles of urea water, but a plurality of collision plates 314 are provided at positions corresponding to the injection angles of the addition valve 6. Specifically, in this embodiment, two collision plates 314a and 314b (two collision surfaces) are provided.

  Each of the collision plates 314a and 314b is connected to the swirl flow plate 313 by welding or the like. Each of the collision plates 314a and 314b has a shape in which the plate surfaces (collision surfaces) of the collision plates 314a and 314b face toward the addition valve 6 in the inlet region of the spiral mixer 31 where the addition valve 6 adds urea water. And connected to the swirling flow plate 313. Specifically, the peripheral edge of the first collision plate 314a is connected to the plate surface of the swirl flow plate 313a arranged on the most upstream side in the spiral mixer 31. Further, the first collision plate 314a is arranged at a position on the inner side in the radial direction of the spiral mixer 31 (closer to the boss 312) than the second collision plate 314b. That is, the first collision plate 314a is arranged in a form standing from the plate surface of the most upstream swirl flow plate 313a at a position inside the second collision plate 314b.

  Moreover, as shown in FIG. 1, the periphery of the 2nd collision board 314b is connected to the board surface of the swirl flow board 313b arrange | positioned downstream from the most swirl flow board 313a. The second collision plate 314b is disposed at a position radially outward (closer to the outer cylinder 311) than the first collision plate 314a. In other words, the second collision plate 314b is disposed so as to stand up from the plate surface of the downstream swirl flow plate 313b at a position outside the first collision plate 314a. Although the second collision plate 314b is connected to the downstream swirl flow plate 313b, a part of the second collision plate 314b enters the inlet region (urea water addition region) of the spiral mixer 31. .

  Moreover, each collision board 314a, 314b is formed in the circular arc shape (arc shape seeing from the direction of FIG. 2) of curvature according to the curvature of the cross-sectional shape (circular shape) of the outer cylinder 311 or the curvature of the swirling flow plate 313, for example. Has been. The collision plates 314a and 314b do not have to be arcuate as long as the urea water added from the addition valve 6 collides, and may be connected anywhere. For example, the collision plates 314a and 314b may be connected to the outer cylinder 311 via other members.

  In addition, the area (size) of each of the collision plates 314a and 314b aims to achieve both the suppression of retention of urea water in the spiral mixer 31 and the inhibition of the flow of exhaust gas. It is set so that you can. Details of the concept of the area will be described later. Each member of the spiral mixer 31 including the collision plates 314a and 314b is made of a corrosion-resistant metal (for example, stainless steel) in order to prevent corrosion due to exhaust gas or urea water.

  An addition valve 6 as an “injection valve” of the present invention for adding urea water (reducing agent) into the spiral mixer 31 is disposed on the outer peripheral wall of the spiral mixer 31, that is, the outer cylinder 311. Specifically, in other words, the addition valve 6 is disposed in the inlet region of the spiral mixer 31 so as to inject urea water in a direction orthogonal to the direction in which the outer cylinder 311 extends. It arrange | positions so that urea water may be injected toward each collision board 314a, 314b. An opening is formed in a portion of the outer cylinder 311 in which the addition valve 6 is disposed, and a cylindrical portion 62 (see FIG. 2) for mounting the addition valve 6 is attached to the opening. The addition valve 6 is attached to the cylindrical portion 62.

  The addition valve 6 has the same structure as a fuel injection valve (injector) that injects fuel into a cylinder or an intake port of a gasoline engine. That is, the addition valve 6 includes a drive unit composed of an electromagnetic solenoid and the like, and a valve main unit having a urea water passage through which urea water flows and a needle for opening and closing a nozzle 61 (front end outlet, see FIG. 3). It is configured as an electromagnetic on-off valve. When the electromagnetic solenoid is energized, the needle moves in the valve opening direction along with the energization, and urea water is injected from the nozzle 61 as the needle moves.

  FIG. 3 is an enlarged view of the nozzle 61. As shown in FIG. 3, a first injection hole 611 for injecting urea water 71 at a first injection angle as a nozzle hole serving as an injection hole for urea water, and a first injection on the tip surface of the nozzle 61. A second injection hole 612 for injecting the urea water 72 at a second injection angle different from the angle is formed. In FIG. 3, the first nozzle holes 611 and 612 are illustrated as a single nozzle hole, but the first nozzle hole 611 is configured by a plurality of nozzle holes set at the first injection angle. It's okay. Similarly, the second nozzle hole 612 may be configured from a plurality of nozzle holes set at the second injection angle.

  The injection angle (first injection angle) of the first injection hole 611 and the first collision plate 314a so that the urea water 71 injected from the first injection hole 611 collides with the first collision plate 314a. The installation position has been adjusted. The injection angle (second injection angle) of the second injection hole 612 and the second collision plate 314b are adjusted so that the urea water 72 injected from the second injection hole 612 collides with the second collision plate 314b. The installation position has been adjusted. That is, the urea water 71 is jetted from the first nozzle hole 611 toward the first collision plate 314a, and the urea water 72 is jetted from the second nozzle hole 612 toward the second collision plate 314b. Is injected. Here, the respective collision plates 314 a and 314 b are installed at positions corresponding to the respective injection holes 611 and 612 of the addition valve 6, but the positions corresponding to the respective injection holes 611 and 612 are the respective injection holes 611. , 612 means that the collision plates 314a, 314b are positioned in the direction of the urea water injected from the nozzle holes 611, 612 so that the urea water injected from the nozzles 612, 314b collides with the collision plates 314a, 314b. To do.

  The exhaust purification system 1 includes a urea water tank (not shown) for storing urea water, a pipe (not shown) connecting the urea water tank and the addition valve 6, and pumping urea water from the urea water tank through the pipe. A pump (not shown) that discharges to the addition valve 6 side, a regulator (not shown) that adjusts the pressure of urea water in the pipe to a predetermined pressure, a control circuit (not shown) that controls the addition valve 6, Is provided. The control circuit intermittently drives the addition valve 6 and causes the addition valve 6 to inject a urea water amount corresponding to the operating state of the engine 2, in other words, a urea water amount corresponding to the NOx amount discharged from the engine 2.

  Next, details of the concept of the area of the collision plate 314 will be described. FIG. 4 is a diagram for explaining the concept of the area of the collision plate 314, showing the addition valve 6, the collision plate 314, and urea water spray. In FIG. 4, urea water spray injected from one nozzle hole (first nozzle hole 611 or second nozzle hole 612) is indicated by reference numeral “7” as urea water spray, and the urea water spray is shown in FIG. 4. 7, the urea water spray that reaches the collision plate 314 is indicated by a symbol “73”, and the urea water spray that does not reach the collision plate 314 is indicated by a symbol “74”. Further, of the urea water spray 73 that has reached the collision plate 314, the spray repelled (reflected) by the collision plate 314 is indicated by reference numeral 75, and the urea water that stays in the collision plate 314 (retained urea water) is indicated by reference numeral "76". ing. Further, when the staying urea water 76 evaporates by receiving heat from the collision plate 314, the evaporated spray is indicated by reference numeral “77”.

From one nozzle hole (first nozzle hole 611 or second nozzle hole 612), m (g) urea water spray 7 is jetted, and the staying urea water 76 in the m (g) urea water spray 7 is injected. The amount of heat Q required to evaporate all the retained urea water 76 is expressed by the following equation (4) where ξ is 0 (0 <ξ <1). In Equation 4, qv is the heat of vaporization of the urea water, c is the specific heat of the urea water, and ΔT is the temperature increase required to evaporate the staying urea water 76. Further, k = (qv + cΔT) × ξ.
Q = (qv + cΔT) × ξ × m = k × m (Formula 4)

The amount of heat Q is covered by the amount of heat transfer Qg from the exhaust gas to the staying urea water 76 and the amount of heat transfer Qf from the collision plate 314 to the staying urea water 76 as shown in Equation 5 below.
Q = Qg + Qf (Formula 5)

The heat transfer amount Qg is expressed by the following formula 6. In Equation 6, hg is a heat transfer coefficient from the exhaust gas to the staying urea water 76, and β × S (0 <β <1, S is the total area of the collision plate 314) is a collision plate wetted with urea water. 314, that is, the area of the staying urea water 76. Tg is the temperature of the exhaust gas, and Tm is the temperature of the retained urea water 76.
Qg = hg × β × S × (Tg−Tm) (Formula 6)

In the equilibrium state, the heat transfer amount Qf is equal to the heat amount transferred from the exhaust gas to the collision plate 314. Therefore, the heat transfer amount Qf is expressed by the following formula 7. In Equation 7, hf is a heat transfer coefficient from the exhaust gas to the collision plate 314, 2 × S is an area of both surfaces of the collision plate 314, and Tf is a temperature of the collision plate 314. Note that β × S and Tg in Equation 7 are the same as β × S and Tg in Equation 6.
Qf = hf × (2-β) S × (Tg−Tf) (Expression 7)

Tg in Equations 6 and 7 is the minimum allowable addition gas temperature TG determined from the exhaust purification characteristics, the addition amount m (injection amount) is the maximum addition amount M, and the collision is performed to maintain the evaporation rate of urea water on the collision plate 314. Assuming that the temperature Tf of the plate 314 is kept at the lowest collision plate temperature TF, the following equation 8 can be derived from the above equations 4 to 7 and TG, M, and TF. In Equation 8, the temperature TM of the addition valve 6 (the temperature of the urea water at the addition valve 6) is used as the urea water temperature Tm (see Equation 6).
k * M = hg * [beta] * S * (TG-TM) + hf * (2- [beta]) S * (TG-TF) (Equation 8)

  When the expression of the area S of the collision plate 314 is obtained from Expression 8, the following Expression 9 is obtained. In Expression 9, α is a correction coefficient corresponding to the volume of the spiral mixer 31, the vehicle type on which the exhaust purification system 1 is mounted, and takes a value of 0.8 to 1.2, for example. Further, k is k = (qv + cΔT) × ξ as described above. However, when ΔT = the boiling point of urea water−the urea water temperature TM, k changes as shown in FIG. 5 with respect to the urea water temperature TM. That is, the higher the urea water temperature TM, the smaller the value.

  From Equations 6 and 7, the heat transfer amounts Qg and Qf to the retained urea water 76 (see FIG. 4) increase as the area S increases, so that the retained urea water 76 can be easily evaporated. However, when the area S is increased, the exhaust gas is less likely to flow due to the presence of the collision plate 314, and thus energy loss increases (high pressure loss). On the contrary, if the area S is small, the energy loss of the exhaust gas is small (low pressure loss), but the heat transfer amounts Qg and Qf are small, and the evaporation rate of the retained urea water 76 is lowered. According to Equation 9, even if a large amount of urea water (maximum addition amount M urea water) is added from the addition valve 6, the minimum necessary amount that can maintain the evaporation rate of the retained urea water 76 at a constant level. The area S (the area S that can be maintained at the lowest collision plate temperature TF) can be obtained.

  The area of each of the collision plates 314a and 314b in FIGS. 1 and 2 is set to the area obtained by Expression 9. When obtaining the area of the first collision plate 314a, the maximum addition amount M1 of the urea water 71 (see FIG. 3) added from the first nozzle hole 611 is used as the maximum addition amount M of Equation 9. Similarly, when obtaining the area of the second collision plate 314b, the maximum addition amount M2 of the urea water 72 (see FIG. 3) added from the second nozzle hole 612 is set as the maximum addition amount M of Equation 9. Use.

  Further, the area of the first collision plate 314a and the area of the second collision plate 314b may be the same or different. In the same case, the injection holes 611 and 612 are designed so that the maximum addition amount M1 from the first injection hole 611 and the maximum addition amount M2 from the second injection hole 612 are the same. In the case of different areas, for example, the second collision plate 314b located on the outer cylinder 311 side of the spiral mixer 31 is made larger than the first collision plate 314a. If the second collision plate 314b on the outer cylinder 311 side is enlarged, the space in the spiral mixer 31 can be used more effectively, and the flow of exhaust gas can be prevented from being hindered. In this case, the injection holes 611 and 612 are designed so that the maximum addition amount M2 from the second injection hole 612 is larger than the maximum addition amount M1 from the first injection hole 611.

  The above is the configuration of the exhaust purification system 1. Next, the operation of the exhaust purification system 1 will be described. The control circuit that controls the addition valve 6 causes the urea valve to be added in an amount corresponding to the operating state of the engine 2. When urea water is added from the addition valve 6, most of the urea water 71 (see FIG. 2) added from the first nozzle hole 611 collides with the first collision plate 314a. Since the area of the first collision plate 314a is set to an optimum area by Equation 9, the urea water 71 that collides with the first collision plate 314a quickly receives heat from the exhaust gas or the first collision plate 314a. Evaporate (atomize). Similarly, most of the urea water 72 (see FIG. 2) added from the second nozzle hole 612 collides with the second collision plate 314b. Since the area of the second collision plate 314b is set to an optimum area according to Equation 9, the urea water 72 that has collided with the second collision plate 314b quickly receives heat from the exhaust gas or the second collision plate 314b. Evaporate (atomize).

  The finely atomized urea spray that collides with each of the collision plates 314a and 314b is scattered evenly over a wide range in the spiral mixer 31 and passes through the spiral passage surrounded by the swirl flow plate 313 together with the exhaust gas, And reaches the upstream surface of SCRF5. The urea water is converted into ammonia (NH 3) by hydrolysis inside the SCRF 5 or before reaching the SCRF 5. Then, at SCRF5, ammonia reacts with NOx, and NOx is reduced and purified.

  As described above, according to this embodiment, since the addition direction (injection angle) of urea water by the addition valve is divided into two directions, the addition amount per direction can be reduced, and the urea water is dispersed. It can be made easy. And since the collision plate is provided for each addition direction (injection angle), it is possible to reduce the amount of heat necessary for the evaporation of urea water to be handled by one collision plate, and to make the collision plate larger than necessary. Also, the temperature drop of the collision plate can be suppressed. Therefore, it can suppress that urea water stagnates in a spiral mixer, As a result, the responsiveness of urea water (ammonia) to SCRF can be improved, and ammonia slip can be suppressed. Further, since the collision plates are separated from each other, heat transfer between the collision plates can be suppressed.

(Modification 1)
Hereinafter, modifications of the exhaust purification system of the present embodiment will be described. FIG. 6 is a cross-sectional view of the spiral mixer 32 according to the first modification. In FIG. 6, the same components as those of the spiral mixer 31 of FIG. In the spiral mixer 32 of FIG. 6, as in FIG. 2, urea water is added in two directions from the addition valve, and collision plates 314 c and 314 d (collision surfaces) that collide the urea water are provided in each direction. The collision plates 314c and 314d are connected to each other by a connecting member 315. The connecting member 315 has a plurality of holes 316 through which exhaust gas passes. That is, the connecting member 315 is formed in a punching metal shape.

  The collision plates 314c and 314d and the connecting member 315 are formed, for example, by processing a part of one metal flat plate (stainless steel plate) into a punching metal shape and then using the punching metal portion as a boundary as shown in FIG. It can be obtained by processing in steps.

  As described above, in the first modification, since the two collision plates 314c and 314d are connected, the collision plates 314c and 314d can be easily installed in the spiral mixer 32. In other words, the collision plates 314c and 314d can be easily positioned. Further, since the connecting member 315 has a punching metal shape, heat transfer between the collision plates 314c and 314d can be suppressed as much as possible. Further, since the exhaust gas can pass between the collision plates 314c and 314d, that is, through the connecting member 315, an increase in pressure loss can be suppressed.

  Instead of the connecting member 315, the collision plates 314c and 314d may be connected by a bar, for example. This also makes it possible to easily install the collision plates 314c and 314d and suppress an increase in pressure loss.

(Modification 2)
FIG. 7 is a cross-sectional view of a spiral mixer 33 according to the second modification. In FIG. 7, the same components as those of the spiral mixer 31 shown in FIG. In the spiral mixer 33 of FIG. 7, the addition valve 6 is configured to inject the spray of urea water in three directions, that is, three injection holes set at different injection angles are formed. And the three collision plates 314e, 314f, and 314g with which each spray collides are provided. The areas of the collision plates 314e, 314f, and 314g are set according to Equation 9.

  In this way, by dividing the spray into three and providing a collision plate for each spray, the amount of urea water added from one nozzle hole can be further reduced, and the evaporation of urea water to be handled by one collision plate Therefore, it is possible to further reduce the retention of urea water in the spiral mixer. The number of spray divisions and the number of collision plates installed are not limited to two or three, but may be any number.

  In addition, this invention is not limited to the said embodiment, A various change is possible to the limit which does not deviate from description of a claim. For example, in the above-described embodiment, the example in which the boss of the spiral mixer is disposed on the same axis as the central axis of the exhaust passage has been described. However, the boss may be disposed at a position shifted from the central axis. Further, the present invention may be applied to an exhaust purification system in which a DPF (Diesel Particulate Filter) with an oxidation catalyst is disposed upstream of the SCR catalyst. In this case, a DPF with an oxidation catalyst is arranged instead of the oxidation catalyst 4 of FIG. Further, the present invention may be applied to an exhaust purification system in which an oxidation catalyst is not disposed upstream of a reduction catalyst (SCRF, SCR catalyst).

1 Exhaust gas purification system (exhaust gas purification device)
2 Diesel engine (internal combustion engine)
3 Exhaust passage 4 Oxidation catalyst 5 SCRF (reduction catalyst)
31, 32, 33 Spiral mixer (swirl type passage)
314 Collision plate 6 Addition valve (injection valve)
611, 612 injection hole

Claims (4)

A reduction catalyst (5) disposed in the exhaust passage (3) of the internal combustion engine (2);
A swirl flow path (31, 32, 33) that is upstream of the reduction catalyst and is configured to allow exhaust gas to pass in a swirl flow;
An injection valve (6) for injecting a reducing agent for performing a reduction reaction with the reduction catalyst into the swirling flow passage through an injection hole;
The injection valve is formed with a plurality of injection holes (611, 612) having different injection angles,
The swirl flow passage is installed at a position corresponding to the injection angle of each injection hole of the injection valve, and forms a collision plate (314) that forms a plurality of collision surfaces that collide with each reducing agent injected from each injection hole. An exhaust gas purifying device (1).   The exhaust gas purification device according to claim 1, wherein the plurality of collision surfaces are connected to each other by a member (315) through which the exhaust gas can pass between the plurality of collision surfaces. The plurality of collision surfaces have different sizes,
3. The exhaust gas according to claim 1, wherein each injection hole of the injection valve is set such that a larger amount of the reducing agent is injected as the collision surface assigned to each injection hole is larger. Purification equipment. The reducing agent is urea water;
The exhaust gas purification device according to any one of claims 1 to 3, wherein the reduction catalyst is a catalyst that reduces NOx in exhaust gas with ammonia generated from urea water.

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