JP2003293734A - NOx CLEANING DEVICE FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the stay of urea water by straightening the flow of pressurized air in a supply passage and to prevent the solid form of the urea water in the supply passage and the clogging due to the solid form. <P>SOLUTION: To a NOx catalyst 17 provided in an exhaust pipe 28 in an engine 1 for selectively reducing NOx in exhaust gas, the urea water 40 supplied via the supply passage 31 communicating with the exhaust pipe on the upstream side of the catalyst with reducer supply means 30 is supplied while being mixed with the pressurized air supplied from a supply passage 31A located upstream beyond a supply region 41 for the urea water supplied from the reducer supply means 30 with air supply means 7. A straightening member 4 is provided in the supply passage 31A downstream beyond a supply region for the pressurized air and upstream beyond the supply region 41 for the urea water for straightening the pressurized air upstream beyond the supply region 41. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an NOx purification device for an internal combustion engine equipped with an NOx catalyst that has an NOx purification action when exhaust gas is in an oxygen excess atmosphere.

[0002]

2. Description of the Related Art There is known a NOx purifying device which uses ammonia generated by hydrolysis by adding urea water to exhaust gas or ammonia by direct addition as a reducing agent of a selective reduction catalyst. When such a NOx purification device is mounted on a vehicle equipped with an internal combustion engine, a selective reduction catalyst capable of purifying NOx in an exhaust system of the internal combustion engine in an oxygen excess atmosphere, a so-called urea SCR catalyst (hereinafter referred to as “NOx catalyst”). "
(Referred to as “NO”) and urea water or ammonia is added to the exhaust gas as a reducing agent from the upstream side of the catalyst to generate NO.
It is configured to supply to the x catalyst. Particularly in a system in which urea water is added as a reducing agent, urea water is supplied from the reducing agent supply means via a supply passage communicating with the exhaust system upstream of the NOx catalyst, but it can be quickly added to the exhaust gas flowing through the exhaust system. As described above, pressurized air is supplied from the air supply means to the supply passage upstream of the urea water supply portion supplied from the reducing agent supply means, and the pressurized air flowing through the supply passage and the urea water are mixed and added. It is atomized with a nozzle and added to the exhaust gas.

[0003]

In the NOx purifying apparatus in which the urea water is added as the reducing agent, the urea water is added to the supply passage through which the pressurized air flows and mixed with the pressurized air. Urea mist, which is a mixture of water and pressurized air, is likely to accumulate in a portion having a low flow velocity distribution (pressure distribution) flowing through the supply passage. The pressurized air supplied into the supply passage generally has a flow velocity distribution characteristic that the side near the inner wall surface is slower than the center side of the supply passage. Therefore, the flow velocity decreases in the supply passage.
The urea mist tends to accumulate near the inner wall surface (where the pressure drops). Further, the flow velocity of the pressurized air flowing through the supply passage is
Since the shape deformation portion of the supply passage is also different, a turbulent flow is generated around the shape deformation portion, and urea mist tends to accumulate. If urea mist accumulates in a poor flow area in the supply passage, urea water is a solution of powdered urea in a liquid such as water. The water component evaporates and the urea component is solidified on the inner wall surface, and if the amount of solidified urea attached increases, the supply passage becomes clogged. The present invention provides a NOx purification device capable of suppressing accumulation of urea water by rectifying the flow of pressurized air in the supply passage, and preventing solidification of urea water in the supply passage and clogging due to solidification. The purpose is to do.

[0004]

NO of the internal combustion engine of the present invention
The x purification device includes an NOx catalyst provided in an exhaust system of an internal combustion engine for selectively reducing NOx in exhaust gas, and a reducing agent supply means for supplying urea water through a supply passage communicating with an exhaust system upstream of the NOx catalyst. An air supply means for supplying compressed air from a supply passage upstream of a supply portion of the urea water supplied from the reducing agent supply means, and a supply portion of the urea water downstream of the supply portion of the compressed air in the supply passage It is characterized in that it is provided with a rectifying member provided on the more upstream side. According to the present invention, the flow regulating member provided on the upstream side of the urea water supply site suppresses the decrease in the flow velocity of the pressurized air in the inner wall portion of the supply passage and the occurrence of the turbulent flow around the urea water supply portion. Examples of the rectifying member include a honeycomb structure and a mode in which the rectifying member is formed in a lattice shape in section.

The NOx purifying apparatus for an internal combustion engine according to the present invention comprises a NOx catalyst provided in an exhaust system of the internal combustion engine for selectively reducing NOx in exhaust gas, and a urea passage through a supply passage communicating with the exhaust system upstream of the NOx catalyst. The reducing agent supply means for supplying water, the air supply means for supplying pressurized air from the supply passage upstream of the supply portion of the urea water supplied from the reducing agent supply means, and the shape deforming portion in the supply passage are provided. And a rectifying member. According to the present invention, the rectifying member provided in the shape deforming portion of the supply passage suppresses the pressure drop of the pressurized air on the inner wall surface of the shape deforming portion and the occurrence of turbulent flow around the shape deforming portion. An example of the rectifying member provided in the shape deforming portion is a plate rectifying plate.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A NOx purifying device for an internal combustion engine as a first embodiment of the present invention will be described. In FIG.
Reference numeral 1 denotes a diesel engine (hereinafter referred to as "engine") mounted on a vehicle (not shown). The output control of the engine 1 is performed by the engine control device 5. The engine control unit 5 controls the fuel injection amount obtained from the fuel system,
Information such as accelerator opening and engine speed is controlled by the control means 3
Output to. Control means 3 and engine control device 5
Are mainly composed of a computer and are connected to each other via a control communication line so that they can communicate with each other.

The NOx purifying device of this embodiment is provided in an exhaust pipe 28 which is connected to the exhaust manifold 25 of the engine 1 and constitutes the exhaust system 2, and which selectively reduces NOx in the exhaust gas 24 and upstream of the NOx catalyst 17. Exhaust pipe 2
The reducing agent supply means 30 and the reducing agent supply means 3 for supplying the urea water 40 through the injection pipe 31 which serves as a supply passage communicating with 8.
The air supply means 7 for supplying pressurized air to the injection pipe 31A upstream of the supply site of the urea water 40 supplied from 0, the control means 3 for controlling the stop / operation of the air supply means 7 and the reducing agent supply means 30, and A rectifying member 4 is provided.

The NOx catalyst 17 is formed by adhering catalyst components to a catalyst carrier having a honeycomb structure, and is housed in the casing of the NOx catalytic converter 27 provided in the exhaust pipe 28. The NOx catalyst 17, which is a selective reduction catalyst, includes vanadium-based, platinum-based, zeolite-based, and the like.
The NOx catalyst 17 adsorbs ammonia (NH ₃ ) and selectively reduces NOx in the exhaust gas 24, and promotes the denitration reaction between ammonia and nitrogen oxides in the ammonia adsorbed state. .

In the casings before and after the NOx catalyst 17,
A catalyst temperature sensor 22 is provided as a temperature detecting means for outputting the catalyst temperature Tg. A front NOx sensor 19 for detecting the NOx concentration Snoxf on the upstream side of the NOx catalyst 17 is provided in the exhaust pipe 28 immediately after the exhaust manifold 25.
A rear NOx sensor 26 for detecting the NOx concentration Snoxr on the downstream side of the NOx catalyst 17 is arranged in the exhaust pipe 28 on the downstream side of the catalyst 17, respectively. The catalyst temperature sensor 22 and the front and rear NOx sensors 19 and 26 are respectively connected to the control means 3 by signal lines, and output the catalyst temperature Tg and the NOx concentrations Snoxf and Snoxr to the control means 3, respectively.

The reducing agent supply means 30 is an addition nozzle 18 for spraying and adding the urea water 40 toward the upstream opening side of the NOx catalytic converter 27, an injection pipe 31 connected to the addition nozzle 18, and an injection pipe 31. Urea water supply pipe 34 connected to
And urea water tank 35 containing urea water 40 for addition
And the urea water 40 in the urea water tank 35 to the urea water supply pipe 3
4 and a urea water supply unit 37 for supplying a metered amount to the injection pipe 31. The addition nozzle 18 uses the front NOx sensor 19
Is mounted on the exhaust pipe 28 between the NOx catalyst 17 and the NOx catalyst 17. In the present embodiment, the connecting portion between the urea water supply pipe 34 and the injection pipe 31 constitutes the supply part 41 of the urea water 40. The urea water supply unit 37 is connected to the control means 3 by a signal line.

The air supply means 7 includes an air tank 32 connected to the upstream end of the injection pipe 31A, a pressurized air control valve 33 for controlling the supply of pressurized air to the injection pipe 31, and a compressor driven by the engine 1. And 38. The air compressor 38 and the air tank 32 are connected by an air pipe 38A. The pressurized air control valves 33 are connected to the control means 3 by signal lines, respectively.

The air tank 32 is provided with a relief valve (not shown) that opens when the tank internal pressure exceeds a predetermined pressure, and a well-known pressure sensor. The pressure sensor detects the tank internal pressure, and outputs the detected value to the control means 3.

As shown in an enlarged view in FIG. 2, the rectifying member 4 is provided in the injection pipe 31A downstream of the pressurized air control valve 33 and upstream of the supply portion 41 of the urea water 40. The rectifying member 4 has a honeycomb structure in cross section and has a function of rectifying the flow velocity of the pressurized air 32A on the upstream side of the rectifying member 4 so as to be substantially uniform in the cross section of the injection pipe 31A. A lattice-shaped member may be used as the rectifying member 4.

The control means 3 determines the catalyst temperature Tg on the basis of the information from the catalyst temperature sensor 22, and the NOx sensors 19 and 2 respectively.
NOx concentration from No. 6 from Snoxf, Snoxr to actual NO
The x purification rate is derived, and the operating state of the engine 1 is determined based on the engine speed, the accelerator opening, and the like.
The control means 3 controls the urea water 40 to be injected corresponding to the operating state.
Is stored as map data, and the pressurized air control valve 33 and the urea water supply unit 37 are configured so that the addition amount selected according to the operating state can be injected from the addition nozzle 18 into the exhaust pipe 28. Control movements.

In the NOx purification device of this embodiment, the engine 1
When the engine is started, information from various sensors is taken in by the control means 3, and the addition amount of the urea water 40 is determined based on the information, and the pressurized air is supplied so that the determined addition amount can be supplied to the exhaust pipe 28. The operations of the control valve 33, the urea water supply unit 37, and the compressor clutch 39 are controlled.

As shown in FIG. 2, the pressurized air 32A in the air tank 32 is supplied to the injection pipe 31A, and the urea water 40 is adjusted from the tank 35 by the urea water supply unit 37 and injected at the supply portion 41. It is supplied to the pipe 31, and urea mist 41 is generated by mixing the two. Urea mist generated 4
1 is added from the addition nozzle 18 to the exhaust pipe 28 through the injection pipe 31, and is supplied to the NOx catalyst 17.

In the case of this embodiment, the pressurized air 32A reaching the supply portion 41 is rectified to a substantially uniform flow velocity by the rectifying member 4 provided on the upstream side of the supply portion 41, so that the passage inner wall portion of the injection pipe 31A is conditioned. The flow velocity decrease at 310 is extremely small, and rectification can be formed from upstream to downstream of the supply site 41. For this reason, the urea mist 41 is less likely to accumulate in the injection pipe 31A, and the injection pipe 31
It is possible to prevent the urea water droplets from adhering to the inner wall surface 310 of A, etc., and prevent the adhered urea water droplets from solidifying due to water evaporation and clogging due to solidification.

FIG. 3 illustrates a NOx purifying device for an internal combustion engine according to a second embodiment of the present invention. The NOx purification device according to this embodiment is basically the same as the first embodiment except that the structure and arrangement of the rectifying member are different from those of the first embodiment. Therefore, the components having the same functions as those of the first embodiment shown in FIG.
Detailed description is omitted.

In the NOx purifying device of this embodiment, the bent portion 31B of the injection pipe 31A, which is the shape-deformed portion in the supply passage, is
A plurality of plate-shaped rectifying members 50 are arranged. The bent portion 31B is arranged downstream of the pressurized air control valve 33 in the urea water 40.
Is formed in the injection pipe 31A on the upstream side of the supply portion 41 of FIG. Such a bent portion 31B is a portion that is generated from the positions of the reducing agent supply means 30 and the air supply means 7 due to the convenience of piping. In the present embodiment, in order to downsize the device, the length of the injection pipe 31A is made shorter than that of the first embodiment, and as a result, the urea water supply pipe 34 and the injection pipe 31A are obtained.
The supply site 41, which is a joining position with the, is formed at a position close to the bending portion 31B.

As shown in an enlarged view in FIG. 4, the rectifying member 50 has a crescent shape (arc shape) along the shape of the bent portion 31B, and the pressurized air 32A flowing in the injection pipe 31A.
It has a function of rectifying the flow velocities on the inner inner wall surface 311 side and the outer inner wall surface 312 side to be substantially uniform in the cross section of the injection pipe 31A.

In the present embodiment, the pressurized air 32A reaching the supply portion 41 is upstream of the supply portion 41 and is the bent portion 31.
Since it is rectified to a substantially uniform flow velocity by the plate-shaped flow rectifying member 50 provided in B, the difference in flow velocity between the inner inner wall portion 311 side and the outer inner wall surface 312 side of the injection pipe 31A is extremely small, and around the bent portion 31B. Turbulence is suppressed. Therefore, the rectification can be formed from the upstream side to the downstream side of the supply portion 41, and the urea mist 41 is unlikely to accumulate in the bent portion 31B1 and the supply portion 41 near the bent portion 31B1. Therefore, the urea water droplets do not adhere to the inner wall surface 310 and the like of the injection pipe 31A, and it is possible to prevent solidification of the adhered urea water droplets due to water evaporation and clogging due to solidification.

In the present embodiment, the plate-like member is used as the flow regulating member 50, but the flow regulating member 4 may be used as in the first embodiment. Further, in the present embodiment, an example is shown in which the bending portion 31B serving as the shape deforming portion is formed on the upstream side of the supply site 41 of the urea water 40, but the present invention is not limited to this.
In order to avoid interference with other devices when mounted on a vehicle, it may be formed in the injection pipe 31 on the downstream side of the supply portion 41.

[0023]

According to the present invention, the flow velocity of the pressurized air in the inner wall of the supply passage and the turbulent flow around the urea water supply portion are reduced by the straightening member provided upstream of the urea water supply portion. Since the generation is suppressed, it is possible to form a laminar flow from the upstream side to the downstream side of the urea water supply site, and it is possible to prevent solidification of the urea water and clogging due to solidification in the supply passage. it can. According to the present invention, the flow regulating member provided in the shape deforming portion of the supply passage suppresses a decrease in the flow velocity of the pressurized air on the inner wall surface of the shape deforming portion and the occurrence of turbulent flow around the shape deforming portion. A laminar flow can be formed at the deforming portion, and clogging due to immobilization or solidification of urea water in the supply passage can be prevented in advance.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a NOx purification device showing a first embodiment of the present invention.

FIG. 2 is a partially enlarged view showing the configuration and arrangement of a flow regulating member according to the first embodiment.

FIG. 3 is an overall configuration diagram of a NOx purification device showing a second embodiment of the present invention.

FIG. 4 is a partially enlarged view showing the configuration and arrangement of a rectifying member according to a second embodiment.

[Explanation of symbols]

1 Internal combustion engine 2 exhaust system 4,50 Straightening member 7 Air supply means 17 NOx catalyst 30 Reducing agent supply means 31 Supply passage 31A upstream supply passage 31B Shape deformation part 41 Urea water supply site

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Hiranuma             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. (72) Inventor Kenji Kawai             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. (72) Inventor Shinichi Saito             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. (72) Inventor Kiyoshi Kawatani             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. (72) Inventor Reiko Momomeki             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. (72) Inventor ▲ Takahashi Yoshinori             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. (72) Inventor Shinozaki Ritsuko             5-33, Shiba, Minato-ku, Tokyo, Mitsubishi Motors             Industry Co., Ltd. F term (reference) 3G091 AA02 AA18 AB04 BA14 CA17                       EA18 EA22 EA33 GA06 HA36                       HA37 HA39 HA42                 4D048 AA06 AB02 AC03 BA11X                       BA23X BA30X BB02 CC22                       CD05 DA02 DA13

Claims (2)

[Claims] 1. A NOx catalyst provided in an exhaust system of an internal combustion engine for selectively reducing NOx in exhaust gas, and a reducing agent supply for supplying urea water through a supply passage communicating with the exhaust system upstream of the NOx catalyst. Means, an air supply means for supplying pressurized air from the supply passage upstream of a supply portion of the urea water supplied from the reducing agent supply means, and a downstream portion of the supply passage for pressurized air in the supply passage. An NOx purifying device for an internal combustion engine, comprising: a rectifying member provided on the upstream side of a urea water supply site. 2. A NOx catalyst provided in an exhaust system of an internal combustion engine for selectively reducing NOx in exhaust gas, and a reducing agent supply for supplying urea water through a supply passage communicating with the exhaust system upstream of the NOx catalyst. Means, an air supply means for supplying pressurized air from the supply passage upstream of the supply portion of the urea water supplied from the reducing agent supply means, and a rectifying member provided in the shape deforming portion of the supply passage. An NOx purifying device for an internal combustion engine, which is characterized by being provided.