JP4706686B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus that uses ammonia as a reducing agent.

An SCR (Selective Catalytic Reduction) system is known as an exhaust purification device that reduces NOx discharged from an internal combustion engine, particularly a diesel engine. An exhaust gas purification apparatus using an SCR system generates nitrogen and water from NOx contained in exhaust gas by, for example, injecting urea, ammonia, or the like as a reducing agent (refer to Patent Document 1 for an exhaust gas purification apparatus).
Japanese Patent No. 3917816

  However, when an exhaust purification device using urea is applied to a vehicle equipped with an internal combustion engine, compressed air for injecting liquid urea water is required. Further, when ammonia that is easier to vaporize than urea water is used as the reducing agent, ammonia can be added to the exhaust gas without using compressed air from the injection valve. However, the injection valve has an electromagnetic drive unit composed of a coil or the like. For this reason, if an injection valve is disposed in the vicinity of the exhaust passage through which the exhaust flows, the heat of the exhaust causes destruction of the coil and changes in dimensions. As a result, there is a problem that the durability of the drive part including the electromagnetic drive part is lowered.

  Accordingly, an object of the present invention is to provide an exhaust purification device that reduces the heat received by the ammonia injection valve from the exhaust gas and increases the durability of the ammonia injection valve.

  In the first aspect of the present invention, a heat receiving portion is provided between the exhaust passage and the ammonia injection valve together with a part of the supply passage. Therefore, the heat received by the heat receiving portion from the exhaust flowing through the exhaust passage is transferred to ammonia flowing through the supply passage. Ammonia is heated by the heat receiving portion that receives heat from the exhaust, and liquid ammonia is vaporized. At this time, the ammonia to be vaporized takes the ambient temperature by the heat of vaporization and cools the heat receiving portion. That is, the heat of the exhaust vaporizes ammonia flowing through the supply passage, and the heat receiving portion is cooled by the vaporization of ammonia. The heat receiving part including a part of the supply passage is provided between the exhaust passage and the ammonia injection valve. Thereby, the transfer of heat from the exhaust passage to the ammonia injection valve is reduced. Therefore, the heat received by the ammonia injection valve from the exhaust due to vaporization of ammonia flowing through the supply passage portion can be reduced. Further, by reducing the heat received by the ammonia injection valve from the exhaust, the malfunction of the ammonia injection valve drive unit is reduced, and the durability can be enhanced.

  In the first aspect of the present invention, the liquid ammonia stored in the tank part is vaporized by the heat of the exhaust gas in the supply passage part via the heat receiving part. Therefore, even when liquid ammonia is used as the reducing agent, gaseous ammonia is injected from the ammonia injection valve. Therefore, the diffusion and mixing of ammonia to the exhaust gas is promoted, and the conversion efficiency from NOx to nitrogen and water can be increased.

In the first aspect of the present invention, the heat receiving portion is provided on the holding member in contact with the exhaust pipe portion. The heat receiving part constituting a part of the supply passage is provided at the end of the ammonia injection valve on the exhaust passage side. Therefore, the heat of the exhaust is blocked from being transmitted to the ammonia injection valve side by vaporization of ammonia flowing through the heat receiving portion. Therefore, the heat received by the ammonia injection valve can be reduced. In the first aspect of the present invention, the heat receiving portion is provided at the end of the ammonia injection valve on the exhaust passage side. Therefore, the ammonia flowing through the heat receiving part passes near the exhaust passage. Therefore, the heat that ammonia receives from the exhaust gas increases, and vaporization of ammonia can be promoted.

According to the second aspect of the present invention, a cooling section is provided which forms a circulation passage separately from the supply passage. That is, the holding member is provided with not only a supply passage for supplying ammonia from the tank portion to the ammonia injection valve, but also a circulation passage for circulating ammonia between the tank portion. Thereby, when the temperature of the exhaust gas flowing through the exhaust passage is high, or when the heat receiving part receives a large amount of heat from the exhaust, the ammonia supplied from the tank part to the ammonia injection valve via the heat receiving part is insufficiently cooled. Sometimes, the holding member is cooled by the ammonia flowing through the circulation passage. Therefore, the heat received by the ammonia injection valve can be reduced.

According to a third aspect of the present invention, a cooling water supply unit that supplies cooling water of the internal combustion engine to the heat receiving unit is provided separately from the supply passage. That is, the holding member is supplied not only with ammonia from the tank portion via the supply passage, but also with cooling water of the internal combustion engine. Thereby, when the temperature of the exhaust gas flowing through the exhaust passage is high, or when the heat receiving part receives a large amount of heat from the exhaust, the ammonia supplied from the tank part to the ammonia injection valve via the heat receiving part is insufficiently cooled. Sometimes, the heat receiving part is cooled by the cooling water of the internal combustion engine. Therefore, the heat received by the ammonia injection valve can be reduced.

In invention of Claim 4 , the surrounding channel | path part is provided. The circulation passage portion circulates around the outer peripheral side of the exhaust pipe portion. As a result, the area of the ammonia supplied from the tank part to the ammonia injection valve receives heat from the exhaust pipe part in the circulation passage part. Therefore, ammonia receives more heat from the exhaust flowing through the exhaust pipe. Therefore, vaporization of ammonia can be promoted.

Hereinafter, a plurality of embodiments of an exhaust emission control device according to the present invention will be described with reference to the drawings. In addition, in each embodiment, the same code | symbol is attached | subjected to the substantially same component, and description is abbreviate | omitted.
(First embodiment)
FIG. 1 shows an exhaust emission control device according to a first embodiment of the present invention. The exhaust purification device 10 is provided in an exhaust system 12 of a diesel engine 11 as an internal combustion engine. Exhaust gas discharged from the diesel engine 11 flows through an exhaust passage 14 formed by the exhaust pipe portion 13. The exhaust system 12 is provided with an oxidation catalyst 15 and an exhaust purification device 10. Exhaust gas discharged from the diesel engine 11 flows into the oxidation catalyst 15 via the exhaust passage 14. In the oxidation catalyst 15, hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust are oxidized to produce water (H ₂ O) or carbon dioxide (CO ₂ ). Exhaust gas that has passed through the oxidation catalyst 15 flows into the exhaust gas purification device 10. A DPF (Diesel Particulate Filter) may be provided in the exhaust system 12 such as between the diesel engine 11 and the oxidation catalyst 15 or between the oxidation catalyst 15 and the exhaust purification device 10.

  The exhaust purification device 10 includes an injector 21 as an ammonia injection valve, a tank unit 22, a supply unit 23, a control unit 24, an SCR catalyst 25, a NOx sensor 26, an ammonia oxidation catalyst 27, and a holding member 28. Further, the exhaust pipe portion 13 forming the exhaust passage 14 of the exhaust system 12 also constitutes the exhaust purification device 10. The injector 21 has a movable part that reciprocates in the axial direction inside the body (not shown). The movable part is driven by the electromagnetic drive part 31. The injector 21 is provided with an injection hole 32 for injecting ammonia to the tip of the body, that is, the exhaust passage 14 side. By reciprocating the movable part by the electromagnetic drive part 31, the injection hole 32 is opened and closed, and the injection of ammonia is interrupted.

  The tank unit 22 stores ammonia. Ammonia is pressurized and stored in the tank unit 22 as a liquid. The supply unit 23 includes a supply pipe part 41, a vaporization pipe part 42, and a pump 43. The supply pipe part 41 connects the tank part 22 and the holding member 28. The vaporizing pipe portion 42 connects the holding member 28 and the injector 21. The pump 43 pressurizes ammonia supplied from the tank unit 22 to the injector 21.

The control unit 24 is an ECU (Electronic Control Unit) that controls the injection of ammonia by the injector 21. The control unit 24 is composed of a microcomputer having a CPU, ROM and RAM (not shown). The control unit 24 is connected to another control device (not shown) of the diesel engine 11 via an in-vehicle LAN (not shown). In the SCR catalyst 25, NOx contained in the exhaust is selectively reduced. Specifically, NOx contained in the exhaust is converted into nitrogen (N ₂ ) and water (H ₂ O) by ammonia injected from the injector 21 in the SCR catalyst 25.

  The NOx sensor 26 is provided on the outlet side of the SCR catalyst 25 in the exhaust passage 14 of the exhaust system 12. The NOx sensor 26 detects the concentration of NOx contained in the exhaust flowing through the exhaust passage 14. The NOx sensor 26 outputs the detected concentration of NOx to the control unit 24 as an electrical signal. Based on the NOx concentration detected by the NOx sensor 26 and various data relating to the operating state of the diesel engine 11 acquired via the in-vehicle LAN, the control unit 24 is configured to control the amount of ammonia injected from the injector 21, that is, the injector 21. Control the valve opening time.

The ammonia oxidation catalyst 27 oxidizes ammonia. When NOx contained in the exhaust gas is reduced, unreacted ammonia may be discharged into the atmosphere when ammonia as a reducing agent is excessively supplied or when the reaction in the SCR catalyst 25 is insufficient. Ammonia is a gas with an irritating odor, and if discharged into the atmosphere, it may affect the environment. Therefore, excess or unreacted ammonia is oxidized by the ammonia oxidation catalyst 27 and then discharged into the atmosphere.
The holding member 28 is attached to the exhaust pipe portion 13. The injector 21 is held by the exhaust pipe portion 13 by a holding member 28. The injector 21 is provided downstream of the oxidation catalyst 15 and upstream of the SCR catalyst 25 in the exhaust flow direction. The tip of the injector 21 on the injection hole 32 side is exposed to the exhaust passage 14. Thereby, the ammonia injected from the injector 21 is blown to the exhaust gas flowing through the exhaust passage 14.

  As shown in FIG. 2, the holding member 28 has an insertion hole 51 penetrating in the axial direction on the center side. The injector 21 is inserted into the insertion hole 51. Therefore, the injector 21 is fixed to the exhaust pipe portion 13 while being held on the inner peripheral side of the holding member 28. By inserting the injector 21 into the insertion hole 51 of the holding member 28, the radially outer side of the injector 21 is covered by the holding member 28, and the vicinity of the tip on the exhaust passage 14 side excluding the injection hole 32 is covered by the holding member 28. .

  The holding member 28 has a heat receiving portion 52 inside. The heat receiving portion 52 is provided at the distal end side of the holding member 28, that is, the end portion on the exhaust passage 14 side. As shown in FIG. 3, the heat receiving portion 52 is formed in an annular shape concentric with the holding member 28. The heat receiving portion 52 is located at the tip end side of the injector 21, that is, the end portion on the exhaust passage 14 side, and is provided in an annular shape on the outer peripheral side of the injector 21. The holding member 28 has a hole 53 and a hole 54 extending in the axial direction. The hole 53 and the hole 54 extend from the end 281 of the holding member 28 on the side opposite to the exhaust passage 14 to the heat receiving part 52. That is, the hole 53 and the hole 54 connect the end 281 of the holding member 28 opposite to the exhaust passage 14 and the heat receiving part 52.

  The end of the hole 53 opposite to the heat receiving part 52 is connected to the tank part 22 via the supply pipe part 41. The hole 54 is connected to the inlet 33 of the injector 21 through the vaporization pipe 42 at the end opposite to the heat receiving part 52. Thereby, the supply pipe part 41, the hole part 53, the heat receiving part 52, the hole part 54, and the vaporization pipe part 42 constitute the supply passage part of the claims, and the ammonia supplied from the tank part 22 to the injector 21 Forming a supply passage through which. That is, the ammonia stored in the tank part 22 flows into the injector 21 through a supply passage formed by the supply pipe part 41, the hole part 53, the heat receiving part 52, the hole part 54 and the vaporization pipe part 42.

Next, the operation of the exhaust emission control device 10 having the above configuration will be described.
The pump 43 discharges liquid ammonia stored in the tank portion 22 to the supply pipe portion 41. The liquid ammonia discharged to the supply pipe portion 41 flows into the heat receiving portion 52 via the hole portion 53. The heat receiving portion 52 is heated by the exhaust gas flowing through the exhaust passage 14. Therefore, the liquid ammonia flowing into the heat receiving unit 52 is vaporized in the heat receiving unit 52 by receiving heat. Vaporized ammonia, that is, gaseous ammonia, flows into the injector 21 from the inlet 33 via the hole 54 and the vaporization pipe 42. As a result, the liquid ammonia is vaporized by passing through the heat receiving portion 52 and then flows into the injector 21.

On the other hand, when ammonia is vaporized in the heat receiving part 52, it takes away the surrounding heat by the heat of vaporization. Therefore, the holding member 28 forming the heat receiving portion 52 is cooled by the heat of vaporization when ammonia is vaporized. As a result, the heat receiving portion 52 in contact with the exhaust pipe portion 13 forming the exhaust passage 14 receives heat from the exhaust flowing through the exhaust passage 14, but the heat transfer is blocked by the heat receiving portion 52. That is, the heat transmitted from the exhaust pipe part 13 to the holding member 28 is blocked by the heat receiving part 52, and the transfer from the heat receiving part 52 to the side opposite to the exhaust passage 14, that is, to the inlet 33 side of the injector 21 is reduced. .
The injector 21 has an electromagnetic drive unit 31 closer to the inlet 33 than the nozzle hole 32. By providing the heat receiving portion 52 in the vicinity of the nozzle hole 32 that is the tip of the injector 21, the heat transfer from the exhaust passage 14 is blocked by the heat receiving portion 52 in the electromagnetic drive portion 31 that is susceptible to heat. Therefore, the heat received by the electromagnetic drive unit 31 in the injector 21 is reduced.

  As described above, in the first embodiment, the holding member 28 that holds the injector 21 in the exhaust pipe portion 13 has the heat receiving portion 52. The heat receiving part 52 covers the tip of the injector 21. Liquid ammonia stored in the tank unit 22 is supplied to the heat receiving unit 52. Since the holding member 28 is in contact with the exhaust pipe portion 13 that forms the exhaust passage 14, the heat receiving portion 52 is heated by the exhaust gas flowing through the exhaust passage 14. Therefore, the ammonia passing through the heat receiving part 52 is vaporized in the heat receiving part 52. Accordingly, the holding member 28 forming the heat receiving portion 52 is cooled by the heat of vaporization of ammonia, and heat transfer from the exhaust passage 14 to the electromagnetic drive portion 31 side of the injector 21 is blocked by the heat receiving portion 52. Therefore, the heat received by the injector 21 from the exhaust gas flowing through the exhaust passage 14 can be reduced, and the durability of the injector 21 can be improved.

  In the first embodiment, since the heat receiving unit 52 is heated by exhaust gas, ammonia is vaporized by the heat receiving unit 52. In order to efficiently reduce NOx in the SCR catalyst 25, it is necessary to promote diffusion of ammonia as a reducing agent. In order to promote the diffusion of ammonia and mixing with the exhaust, it is desirable that the ammonia be a gas. In the first embodiment, by separately evaporating liquid ammonia in the heat receiving part 52, a configuration for vaporizing ammonia separately is not required. Therefore, it is possible to promote the vaporization of ammonia without increasing the complexity of the structure and increase the NOx reduction efficiency in the SCR catalyst 25. Further, as described above, it is possible to achieve both the improvement of the durability of the injector 21 and the promotion of the vaporization of ammonia.

(Second Embodiment)
An exhaust emission control device according to a second embodiment of the present invention is shown in FIGS.
In the case of the second embodiment, the exhaust purification device 10 includes a cooling unit 61. As shown in FIG. 5, the cooling unit 61 is further provided on the exhaust passage 14 side of the heat receiving unit 52 of the holding member 28. That is, the holding member 28 has a cooling part 61 on the exhaust passage 14 side of the heat receiving part 52.
As shown in FIGS. 5 and 6, the holding member 28 has a cooling hole 62 and a cooling hole 63 that extend in the axial direction substantially parallel to the hole 53 and the hole 54. The cooling hole 62 and the cooling hole 63 extend from the end 281 of the holding member 28 on the side opposite to the exhaust passage 14 to the cooling unit 61. The cooling hole portion 62 is connected to the tank portion 22 via the circulation pipe portion 64 as shown in FIG. Further, the cooling hole portion 63 is connected to the tank portion 22 via the circulation pipe portion 65. The circulation pipe 65 is provided with a pump 66. Thereby, the ammonia discharged from the tank part 22 is returned to the tank part 22 via the circulation pipe part 64, the cooling hole part 62, the cooling part 61, the cooling hole part 63 and the circulation pipe part 65. That is, the circulation pipe part 64, the cooling hole part 62, the cooling part 61, the cooling hole part 63, and the circulation pipe part 65 form a circulation passage through which ammonia circulates between the tank part 22 and the cooling part 61. The circulation passage that connects the tank portion 22 and the cooling portion 61 is a separate system from the supply passage that supplies ammonia from the tank portion 22 to the injector 21.

  In the second embodiment, by providing the cooling unit 61, the holding member 28 is cooled by the cooling unit 61 on the tip side of the heat receiving unit 52, that is, the exhaust passage 14 side. Therefore, the heat transmitted from the exhaust passage 14 to the heat receiving part 52 is reduced. Thereby, the heat transmitted from the exhaust gas flowing through the exhaust passage 14 to the electromagnetic drive unit 31 side of the injector 21 is further reduced. Therefore, the heat received by the injector 21 from the exhaust can be further reduced, and the durability of the injector 21 can be further improved.

In the second embodiment, the configuration in which the ammonia supplied to the cooling unit 61 is returned to the tank unit 22 has been described. However, since the cooling unit 61 is provided closer to the exhaust passage 14 than the heat receiving unit 52, the cooling unit 61 promotes vaporization of ammonia more than the heat receiving unit 52. Therefore, a gas-liquid separation unit may be provided in the middle of the circulation pipe unit 65 in which ammonia is returned from the cooling unit 61 to the tank unit 22 to recover the vaporized ammonia. The recovered gaseous ammonia may be supplied to the inlet 33 of the injector 21. Thereby, the vaporized ammonia can be supplied to the injector 21 more efficiently.
In the second embodiment, the configuration in which the cooling unit 61 is provided on the exhaust passage 14 side of the heat receiving unit 52 has been described. However, the positional relationship between the cooling unit 61 and the heat receiving unit 52 is not limited to the above example, and the heat receiving unit 52 may be provided closer to the exhaust passage 14 than the cooling unit 61.

(Third embodiment)
An exhaust emission control device according to a third embodiment of the present invention is shown in FIGS.
In the case of the third embodiment, the exhaust gas purification device 10 includes a cooling water supply unit 70 in addition to the configuration of the second embodiment. The cooling water supply unit 70 supplies the cooling water of the diesel engine 11 to the holding member 28. As shown in FIGS. 8 and 9, the holding member 28 has a cooling water passage 72 in addition to the heat receiving portion 52 and the cooling portion 61. The cooling water passage 72 is connected to the radiator 73 through the holding member 28. Cooling water is supplied to the cooling water passage 72 from the radiator 73. Thereby, the holding member 28 is cooled by the cooling water. In the case of the third embodiment, the cooling water passage 72 is provided further on the exhaust passage 14 side than the cooling portion 61.

  In the third embodiment, the holding member 28 is cooled not only by the ammonia flowing through the heat receiving unit 52 and the cooling unit 61 but also by the cooling water flowing through the cooling water passage 72. Therefore, even when the temperature of the exhaust is high and the amount of heat transferred from the exhaust passage 14 to the heat receiving portion 52 is large, the heat transferred from the exhaust passage 14 to the heat receiving portion 52 by the cooling water flowing through the cooling water passage 72 is reduced. . Thereby, the heat transmitted to the electromagnetic drive part 31 side of the injector 21 is further reduced. Therefore, the heat received by the injector 21 from the exhaust can be further reduced, and the durability of the injector 21 can be further improved.

(Fourth embodiment)
An exhaust emission control device according to a fourth embodiment of the present invention is shown in FIG.
In the case of the fourth embodiment, a circulation passage portion 80 is provided between the tank portion 22 and the injector 21. The circulation passage portion 80 is optional between the tank portion 22 and the injector 21, such as between the tank portion 22 and the heat receiving portion 52, between the heat receiving portion 52 and the inlet 33 of the injector 21, or both. It can be provided in the position. The circulation passage portion 80 circulates on the outer peripheral side of the exhaust pipe portion 13. As a result, the contact area between the circulation passage portion 80 and the exhaust pipe portion 13 is increased, and the ammonia flowing through the circulation passage portion 80 receives more heat from the exhaust gas flowing through the exhaust passage 14. Therefore, vaporization of ammonia can be promoted.

(Other embodiments)
In the plurality of embodiments described above, the example in which each embodiment is individually applied to the exhaust gas purification apparatus 10 has been described. However, a plurality of embodiments may be combined and applied to the exhaust purification device 10. For example, the cooling unit 61 described in the second embodiment may be removed from the holding member 28 and the cooling water passage 72 described in the third embodiment may be provided in the holding member 28. Moreover, it is good also as a structure where the circulation channel | path part 80 of 4th Embodiment branches from the exhaust gas purification apparatus 10 of 2nd Embodiment or 3rd Embodiment.
As described above, the present invention described above is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the scope of the invention.

1 is a schematic view showing an exhaust emission control device according to a first embodiment of the present invention. The fragmentary sectional view which expanded the principal part of the exhaust gas purification device by 1st Embodiment of this invention. Sectional view cut along line III-III in FIG. Schematic which shows the exhaust gas purification apparatus by 2nd Embodiment of this invention. The fragmentary sectional view which expanded the principal part of the exhaust gas purification device by 2nd Embodiment of this invention. 5A is a cross-sectional view taken along line AA in FIG. 5, and FIG. 5B is a cross-sectional view taken along line BB in FIG. Schematic which shows the exhaust gas purification apparatus by 3rd Embodiment of this invention. The fragmentary sectional view which expanded the principal part of the exhaust gas purification device by 3rd Embodiment of this invention. Sectional drawing cut | disconnected by the IX-IX line of FIG. Schematic which shows the exhaust gas purification device by 4th Embodiment of this invention. (A) is a cross-sectional view taken along line XI-XI in FIG. 10, and (B) is a cross-sectional view taken along line BB in (A).

Explanation of symbols

  In the drawings, 10 is an exhaust purification device, 11 is a diesel engine (internal combustion engine), 13 is an exhaust pipe section, 14 is an exhaust passage, 21 is an injector (ammonia injection valve), 22 is a tank section, 28 is a holding member, 41 is Supply pipe section (supply path section), 42 is a vaporization pipe section (supply path section), 52 is a heat receiving section (supply path section), 53 and 54 are holes (supply path sections), 61 is a cooling section, 62 and 63 Is a cooling hole (circulation passage), 64 and 65 are circulation pipe portions (circulation passage) 70 is a cooling water supply portion, and 80 is a circulation passage portion.

Claims (4)

An exhaust pipe part forming an exhaust passage through which exhaust gas from the internal combustion engine flows;
An ammonia injection valve that is provided in the exhaust pipe portion and injects ammonia into the exhaust gas flowing through the exhaust passage;
A tank part for storing ammonia supplied to the ammonia injection valve as a liquid;
A supply passage portion that forms a supply passage connecting the tank portion and the ammonia injection valve;
The ammonia is provided between the exhaust passage and the ammonia injection valve, constitutes a part of the supply passage, vaporizes ammonia flowing through the supply passage by heat received from exhaust flowing through the exhaust passage, and vaporizes ammonia to be vaporized . A heat receiving portion that is cooled by heat of vaporization and blocks heat transfer from the exhaust pipe member to the ammonia injection valve ;
A holding member in contact with the exhaust pipe part and holding the ammonia injection valve in the exhaust pipe part;
Equipped with a,
The holding member is an exhaust purification system wherein the covering the outer peripheral side of the ammonia injection valve, characterized Rukoto that having a said heat receiving portion in the vicinity of the end portion of the exhaust passage side of the ammonia injection valve. A circulation path that communicates from the tank section to the tank section via the holding member is formed, and a cooling section that cools the holding member by circulating the ammonia in the circulation path is further provided. The exhaust emission control device according to claim 1. The exhaust emission control device according to claim 1, further comprising a cooling water supply unit that supplies cooling water of the internal combustion engine to the holding member and cools the holding member. The exhaust emission control device according to any one of claims 1 to 3, further comprising a circulation passage section that circulates around an outer peripheral side of the exhaust pipe section between the tank section and the ammonia injection valve.

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