JP2007138719A - Nox purification system and method of verifying clogging of nox purification system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an NOx purification system capable of accurately verifying whether clogging is present or not and a method of verifying the clogging of the NOx purification system. <P>SOLUTION: This NOx purification system comprises at least one of a first determination means and a second determination means. The first determination means determines whether a reducer adding part is clogged or not by feeding a high-pressure air from a high-pressure air generating means into a reducer passage and comparing the pressure values measured by second and third pressure sensors with each other with the reducer jetting part closed. The second determination means determines whether the reducer jetting part or the reducer passage is clogged or not by measuring the pressure in the second reducer passage for a predetermined time and verifying the variation of the measured pressure values while feeding a high-pressure air from the high-pressure air generating means into the first reducer passage with the reducer jetting part closed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a NO _x purification system and a clogging verification method for a NO _x purification system. In particular, the present invention relates to a NO _x purification system capable of verifying the presence or absence of clogging of the reducing agent injection unit, the reducing agent passage, and the reducing agent supply unit, and a clogging verification method for the NO _x purification system.

Conventionally, in exhaust gas discharged from an internal combustion engine such as a diesel engine black smoke particles to promote environmental pollution (hereinafter, referred to as PM) and nitrogen oxides (hereinafter, referred to as NO _X), etc. are included . Among them, purifying apparatus used to purify NO _X, NO with absorbs NO _X in the _X catalyst, NO _X which reduces and purifies NO _X by supplying a reducing agent such as urea or raw gas (HC) Purification systems are known.

An SCR (Selective Catalytic Reduction) system as a NO _x purification system absorbs NO _x (NO and NO ₂ ) in exhaust gas into a catalyst and injects a reducing agent mainly composed of urea and HC. the NO _X by reduction, is to discharge decomposed into nitrogen and water. As a supply method of the reducing agent in the SCR system, the liquid reducing agent stored in the tank is pumped by the liquid reducing agent supply pump, and NO _X is absorbed through the injection nozzle arranged in the exhaust pipe. It is common to supply to the catalyst.

Here, the liquid reducing agent used in the SCR system using urea as a reducing agent is, for example, an aqueous solution such as an aqueous urea solution or an aqueous ammonia solution, and this liquid reducing agent is crystallized in the middle of the supply path. Thus, it becomes impossible to efficiently supply the catalyst.
In addition, in a SCR system using urea or HC as a reducing agent, even if foreign matter such as PM in the exhaust passage enters the reducing agent supply system and becomes clogged, the reducing agent is used as a catalyst. On the other hand, it cannot supply efficiently.

In view of this, a NO _x purification device for an internal combustion engine has been proposed that can prevent the stop frequency of the NO _x purification device from increasing excessively due to the urea plugging phenomenon in the NO _x purification device (see Patent Document 1). More specifically, as shown in FIG. 15, the supply passage rn communicating the NO _X catalyst 417, NO _X catalyst upstream of the exhaust system 402 for selectively reducing the NO _X provided in the exhaust system 402 of the engine 401, the supply passage rn A urea water supply device (reducing agent supply means) 429 for supplying urea water to the exhaust system via a high pressure air tank (air supply means) for supplying pressurized air to the exhaust system 402 from the upstream portion of the urea water supply portion g 432, control means for controlling the operation of the urea water supply device 429, an air pressure sensor (air supply state detection means) 424 for detecting the pressure pa in the supply passage rn, pressurized air after adding urea water by the control means And an NO _x purification device for an internal combustion engine provided with determination means for determining whether or not the supply passage is clogged according to the pressure pa detected by the air pressure sensor 424.
JP 2003-269145 A (Claims Fig. 1)

However, although the NO _x purification device for an internal combustion engine disclosed in Patent Document 1 can detect clogging in the reducing agent supply passage, an addition nozzle or reducing agent (urea water) disposed in the exhaust pipe It has been impossible to detect clogging of the reducing agent in the injection section, and also in the passage connecting the reducing agent storage tank and the reducing agent injection section.
That is, the crystallization of the reducing agent is often caused by evaporation of moisture in the reducing agent at a location where the reducing agent is easily stored and easily exposed to the outside air, and a mist-like reducing agent is added. In many cases, it occurs in an addition nozzle, an injection valve for injecting a liquid reducing agent, or a passage connecting the storage tank and the injection valve. Further, in addition to the reducing agent supply passage, foreign substances in the exhaust passage may enter and cause clogging also in the addition nozzle, the injection valve, and the like. Therefore, it is desired that clogging at such locations can be accurately measured.

Therefore, the inventors of the present invention have made diligent efforts to arrange pressure sensors at predetermined locations in the NO _x purification system, and measure the pressure value after blocking valves and passages other than the locations where clogging is to be measured. Thus, the inventors have found that the above-described problems can be solved, and have completed the present invention.
That is, it is an object of the present invention to be able to accurately verify clogging in the reducing agent injection unit, the predetermined reducing agent supply passage, or the reducing agent addition unit of the NO _X purification system with a relatively simple configuration. It is to provide a method for verifying clogging of an _X purification system and an NO _X purification system.

According to the present invention, a catalyst that is provided in an exhaust passage of an internal combustion engine and absorbs NO _{x in} exhaust gas and reduces using a reducing agent;
A reducing agent addition section for adding a reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection section for injecting a reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A pressure sensor disposed in the second reducing agent passage and measuring a pressure in the second reducing agent passage;
A storage tank storing a reducing agent that is transferred to the reducing agent injection unit via the second reducing agent passage;
An air passage connected in the middle of the first reducing agent passage;
High-pressure air generating means for generating high-pressure air supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In a state where no reducing agent is supplied, high-pressure air is supplied from the high-pressure air generating means to the first reducing agent passage, the reducing agent injection section is opened, and the pressure in the second reducing agent passage is measured for a predetermined time. Determining means for determining whether or not the reducing agent injection section or the second reducing agent passage is clogged by verifying the variation of the measured pressure value;
An NO _X purification system (hereinafter referred to as a first NO _X purification system) is provided, which can solve the above-described problems.

Another NO _x purification system of the present invention is provided in the exhaust passage of the internal combustion engine, and absorbs NO _x in the exhaust gas and reduces using a reducing agent,
A reducing agent addition section for adding a reducing agent into the exhaust passage upstream of the catalyst;
A reducing agent passage connected to the reducing agent addition section;
A reducing agent injection section for injecting a reducing agent to the reducing agent passage;
A storage tank storing a reducing agent to be transferred to the reducing agent injection unit;
An air passage provided with an orifice therein and connected in the middle of the reducing agent passage;
Two pressure sensors arranged upstream and downstream of the orifice in the air passage;
High-pressure air generating means for generating high-pressure air supplied to the reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
With the reducing agent injection part closed, high pressure air is supplied from the high pressure air generating means to the reducing agent passage, and the pressure value measured by the two pressure sensors is compared to check whether the reducing agent addition part is clogged. Determining means for determining
Is a NO _X purification system (hereinafter referred to as a second NO _X purification system).

Further, another NO _x purification system of the present invention is provided in an exhaust passage of an internal combustion engine, and absorbs NO _{x in} exhaust gas and reduces using a reducing agent,
A reducing agent addition section for adding a reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection section for injecting a reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A first pressure sensor disposed in the second reducing agent passage and measuring a pressure in the second reducing agent passage;
A storage tank storing a reducing agent that is transferred to the reducing agent injection unit via the second reducing agent passage;
An air passage provided with an orifice therein and connected in the middle of the first reducing agent passage;
Second and third pressure sensors disposed upstream and downstream of the orifice in the air passage;
High-pressure air generating means for generating high-pressure air that is supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In a state where the reducing agent injection unit is closed, high pressure air is supplied from the high pressure air generating means to the first reducing agent passage, and the pressure values measured by the second and third pressure sensors are compared, thereby reducing the reducing agent. First determining means for determining whether or not the adding portion is clogged;
The high pressure air is supplied from the high pressure air generating means to the first reducing agent passage, the reducing agent injection portion is opened, the pressure in the second reducing agent passage is measured for a predetermined time, and the measured pressure value varies. A second determination unit that determines whether or not the reducing agent injection section or the second reducing agent passage is clogged by verifying
Is a NO _X purification system (hereinafter referred to as a third NO _X purification system).

Another aspect of the present invention is a catalyst provided in an exhaust passage of an internal combustion engine, which absorbs NO _{x in} exhaust gas and reduces using a reducing agent,
A reducing agent addition section for adding a reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection section for injecting a reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A storage tank storing a reducing agent that is transferred to the reducing agent injection unit via the second reducing agent passage;
An air passage connected in the middle of the first reducing agent passage;
High-pressure air generating means for generating high-pressure air supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In the NO _x purification system comprising the NO _x purification system, the clogging verification method of the NO _x purification system for verifying the presence or absence of clogging in the reducing agent injection section or the second reducing agent passage,
In a state where no reducing agent is supplied, high-pressure air is supplied from the high-pressure air generating means to the first reducing agent passage, the reducing agent injection unit is opened, and the pressure in the second reducing agent passage is measured for a predetermined time. The method for verifying clogging of the NO _X purification system (hereinafter referred to as the first capping method) is characterized by verifying clogging of the reducing agent injection section or the second reducing agent passage by verifying fluctuations in the measured pressure value. This is called a clogging verification method.

  In carrying out the first clogging verification method of the present invention, it is preferable to start supplying high-pressure air when the pressure in the second reducing agent passage is equal to or lower than a predetermined value.

  In carrying out the first clogging verification method of the present invention, when the pressure in the second reducing agent passage exceeds a predetermined value in the state before the supply of high-pressure air, the second reducing agent It is preferable to open a discharge valve provided in the passage so that the pressure in the second reducing agent passage is a predetermined value or less.

  In carrying out the first clogging verification method of the present invention, when the pressure in the second reducing agent passage does not exceed a predetermined pressure value within a predetermined time, the reducing agent injection unit and the second reduction agent It is preferable to determine that the agent passage is clogged.

  Further, in carrying out the first clogging verification method of the present invention, when the pressure of the high pressure air in the high pressure air generating means exceeds a predetermined value, measurement of the pressure in the second reducing agent passage is started. Is preferred.

In carrying out the first clogging verification method of the present invention, it is preferable to open the reducing agent injection section when the pressure in the second reducing agent passage is substantially equal to the atmospheric pressure.
The pressure “substantially equal to the atmospheric pressure” means not only a case where the pressure completely matches the atmospheric pressure but also a pressure value close to the atmospheric pressure.

  In carrying out the first clogging verification method of the present invention, it is preferable to perform clogging verification at the start of the internal combustion engine.

Further, another clogging verification method of the present invention is provided in an exhaust passage of an internal combustion engine, and absorbs NO _{x in} exhaust gas and reduces using a reducing agent,
A reducing agent addition section for adding a reducing agent into the exhaust passage upstream of the catalyst;
A reducing agent passage connected to the reducing agent addition section;
A reducing agent injection section for injecting a reducing agent to the reducing agent passage;
A storage tank storing a reducing agent to be transferred to the reducing agent injection unit;
An air passage provided with an orifice therein and connected in the middle of the reducing agent passage;
High-pressure air generating means for generating high-pressure air supplied to the reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In the NO _x purification system provided with the NO _x purification system for verifying the clogging of the NO _x purification system for verifying the presence or absence of clogging in the reducing agent injection unit,
The reductant injection unit is closed and high-pressure air is supplied from the high-pressure air generating means to the reducing agent passage, and the pressure is reduced by comparing the pressure value difference between the upstream side and the downstream side of the orifice arranged in the air passage. A clogging verification method for an NO _x purification system (hereinafter referred to as a second clogging verification method), characterized by verifying clogging in the agent addition section.

Further, another clogging verification method of the present invention is provided in an exhaust passage of an internal combustion engine, and absorbs NO _{x in} exhaust gas and reduces using a reducing agent,
A reducing agent addition section for adding a reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection section for injecting a reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A storage tank storing a reducing agent that is transferred to the reducing agent injection unit via the second reducing agent passage;
An air passage provided with an orifice therein and connected in the middle of the first reducing agent passage;
High-pressure air generating means for generating high-pressure air that is supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In NO _X purification system with a reducing agent addition unit, the reducing agent injection unit, or the presence or absence of clogging in the second reducing agent passage a clogging verification method of the NO _X purification system for verifying,
The reducing agent injection unit is closed, and high pressure air is supplied from the high pressure air generating means to the first reducing agent passage, and the pressure values on the upstream side and the downstream side of the orifice arranged in the air passage are compared. By verifying the clogging of the reducing agent addition part,
The reducing agent injection part is opened, high pressure air is supplied from the high pressure air generating means to the first reducing agent passage, the pressure in the second reducing agent passage is measured for a predetermined time, and the measured pressure value Verifying the clogging of the reducing agent injection part or the second reducing agent passage by verifying the variation; and
Is a clogging verification method for a NO _x purification system (hereinafter referred to as a third clogging verification method).

  Further, in carrying out the third clogging verification method of the present invention, it is preferable to change the verification condition of the fluctuation of the pressure value in the second reducing agent passage according to the clogging state of the reducing agent addition part. .

According to the first NO _x purification system and the first clogging verification method of the present invention, the reducing agent addition unit disposed in the exhaust passage is closed and the reducing agent injection unit is opened to supply high-pressure air. As a result, when the reducing agent injection unit is clogged, the pressure in the reducing agent passage connecting the reducing agent injection unit and the storage tank is unlikely to increase. Can be easily discovered.
Also, when verifying clogging, the pressure of the high pressure air is set to a predetermined pressure or higher, and the pressure in the reducing agent passage connecting the reducing agent injection part and the storage tank is set to a predetermined pressure or lower. By performing the verification, it becomes possible to easily verify the pressure fluctuation in the reducing agent passage.
Furthermore, since members other than the predetermined determination means can be used as they are in the conventional NO _X purification system, the number of constituent members of the NO _X purification system is not increased, and the configuration is relatively simple. The presence or absence of clogging at a predetermined location can be verified.

In addition, according to the second NO _x purification system and the second clogging verification method of the present invention, the reducing agent addition unit is clogged by supplying high-pressure air with the reducing agent injection unit closed. In this case, the pressure difference between the upstream side and the downstream side of the orifice in the air passage becomes small, so that the clogging of the reducing agent addition portion can be easily found.
Further, other than the predetermined judging means or orifice, to the members that are included in the conventional of the NO _X purification system can be directly used, without increasing the components of the NO _X purification system, relatively simple structure Thus, the presence or absence of clogging at a predetermined location can be verified.

According to the third NO _x purification system and the third clogging verification method of the present invention, after the clogging in the reducing agent addition unit is verified in the first stage, the clogging in the reducing agent injection unit is performed in the second stage. By verifying the clogging, the pressure reference for determining the clogging of the reducing agent injection unit can be corrected according to the degree of clogging of the reducing agent addition unit. Therefore, both the clogged state of the reducing agent addition unit and the clogged state of the reducing agent injection unit can be verified with high accuracy.

Hereinafter, embodiments of the NO _X purification system and clogging verification method of the NO _X purification system according to the present invention will be described in detail. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.

[First Embodiment]
In the first embodiment of the present invention, a first SCR system using urea as a reducing agent and a first eye performed using the first SCR system as the first NO _X purification system described above. This is a clogging verification method.

1. The internal combustion engine for discharging exhaust gas purifying by the first SCR system (1) an internal combustion engine and the exhaust passage a first SCR systems, diesel engines and gasoline engines are typical, purifying of the NO _X in the state It is suitable to target the diesel engine considered as a subject.
In addition, an internal combustion engine operating state detection means for detecting the rotational speed of the internal combustion engine, the combustion temperature, and the like is provided, and the NO _x concentration and the reducing agent injection amount corresponding thereto can be controlled in consideration of the detection result. It is preferable that it is comprised.
The exhaust passage is connected to the outlet of exhaust gas from an internal combustion engine, in the way, NO _X catalyst to absorb NO _X is arranged. The cross-sectional shape of the exhaust passage is not particularly limited, such as a circular, elliptical, or prismatic exhaust passage.

(2) SCR System (2) -1 Basic Configuration FIG. 1 is a diagram illustrating a configuration example of the SCR system 30 of the present embodiment.
The SCR system 30 of the present embodiment is provided in the exhaust passage 20 of the internal combustion engine, absorbs NO _x in the exhaust gas and reduces using the reducing agent 5, and the exhaust passage on the upstream side of the catalyst 13. The reducing agent adding unit 15 for adding the reducing agent 5 into the first reducing agent passage 15, the first reducing agent passage 17 connected to the reducing agent adding unit 15, and the reducing agent is injected into the first reducing agent passage 17. The reducing agent injection unit 36, the second reducing agent passage 18 connected to the reducing agent injection unit 36, and the second reducing agent passage 18 are arranged, and the pressure in the second reducing agent passage 18 is reduced. The pressure sensor 43a to be measured, the storage tank 31 in which the reducing agent transferred to the reducing agent injection unit 36 through the second reducing agent passage 18 is stored, and the first reducing agent passage 17 are connected in the middle. The air passage 19 and the first return via the air passage 19 The high pressure air generating means 33 for generating high pressure air supplied to the agent passage 17 and mixed with the reducing agent injected from the reducing agent injection section 36, and the high pressure air generating means 33 in a state where no reducing agent is supplied. High-pressure air is supplied to the first reducing agent passage 17 and the reducing agent injection section 36 is opened, and the pressure in the second reducing agent passage 18 is measured for a predetermined time to verify the variation in the measured pressure value. Thus, a determination unit 45 that determines whether the reducing agent injection unit 36 or the second reducing agent passage 18 is clogged is provided.

Such an SCR system 30 is a purification means for causing the catalyst 13 to absorb NO _x contained in exhaust gas and reducing and purify NO _x using a reducing agent such as urea, and is absorbed by the catalyst 13. Further, a reducing agent such as urea is added to NO or NO ₂ to cause a reduction reaction, and it can be decomposed into nitrogen (N ₂ ) and water (H ₂ O) and discharged.
Further, in the SCR catalyst system 30, the reducing agent is sprayed from the storage tank 31 using a pump or the like and mixed with high-pressure air with the liquid reducing agent injected by the reducing agent injection unit 36 to form a mist. Is added to the upstream side of the catalyst 13 via the reducing agent addition section 15.

  In such an SCR system 30, generally, after injection of the reducing agent, it is drawn into the first and second reducing agent passages 17 and 18 by being drawn from the reducing agent storage tank 31 through the discharge valve 38. The reducing agent is refluxed into the tank 31. However, it is difficult to completely return all the reducing agents. In particular, the reducing agent tends to accumulate at the connecting portion between the reducing agent addition unit 15, the reducing agent injection unit 36, the reducing agent injection unit 36 and the second reducing agent passage 18.

In this case, when the exhaust gas temperature is equal to or higher than a predetermined temperature (for example, 135 ° C. or higher), such as when the internal combustion engine is continuously operating, clogging is unlikely to occur without crystallization of the reducing agent. . Conversely, when the temperature of the exhaust gas is lower than a predetermined temperature (for example, 70 ° C. or lower), it is difficult for water in the reducing agent to evaporate. Therefore, the injection hole is clogged unless the reducing agent is frozen. There are few things.
On the other hand, when the temperature of the exhaust gas is within a predetermined range (for example, 70 to 135 ° C.), the moisture in the reducing agent evaporates, while the reducing agent does not dissolve and crystallizes and clogs. It tends to occur. Furthermore, even when the internal combustion engine is stopped for a long time, the water in the reducing agent remaining at the tip of the injection hole may spontaneously evaporate and crystallize.

  In addition to the crystallization of the reducing agent, for example, foreign substances such as PM contained in the exhaust gas enter the reducing agent passage and the like through the reducing agent addition unit and accumulate in the passage and in the reducing agent injection unit and the like. May cause clogging.

When such clogging occurs, the reducing agent cannot be sufficiently supplied into the exhaust passage, and NO _x absorbed by the catalyst cannot be reduced. Therefore, in the SCR system of the present embodiment, the clogging in the reducing agent injection part or the second reducing agent passage is quickly found and the internal combustion engine is stopped or the crystallized reducing agent is dissolved quickly. It is necessary to restore the proper injection state.

  In the case where urea is used as the main component of the reducing agent, the temperature at which the reducing agent can be dissolved is about 135 ° C., and the temperature at which the reducing agent is easily crystallized is about 70 ° C. It is not intended to be limited to those temperatures.

(2) -2 Catalyst and Reducing Agent Here, the type of the catalyst 13 that absorbs NO _x used in the SCR system 30 is not particularly limited, and is known, for example, on a porous carrier In addition, those containing strontium or barium as active ingredients, alkaline earth metals such as magnesium, rare earth metals such as cerium and lanthanum, noble metals such as platinum and rhodium, and the like can be used.
Further, the reducing agent for reducing NO and NO ₂ used in the SCR system 30 is not particularly limited. The SCR system of this embodiment mainly verifies with high accuracy whether there is crystallization when using a liquid reducing agent such as urea water or aqueous ammonia solution, or clogging due to foreign matter. However, the present invention can be similarly verified for the presence or absence of clogging by foreign substances when raw gas (HC) or the like is used as the reducing agent.

(2) -3 Reducing agent addition part Moreover, the reducing agent addition part 15 for adding a reducing agent in the exhaust passage 20 in the SCR system 30 of this embodiment is restricted especially, such as an addition nozzle and an injection valve. is not. That is, it is preferably used as long as it can supply the reducing agent in the form of a mist by mixing high-pressure air to the liquid reducing agent injected from the reducing agent injection unit 36 into the exhaust passage 20. it can.

Moreover, it is preferable to provide a heating means for heating to a temperature at which the main component of the crystallized reducing agent can be dissolved, at least around the injection hole in the reducing agent addition section.
The reason for this is that if the main component of the reducing agent has crystallized in the injection hole of the reducing agent addition section, the reducing agent that has crystallized quickly is dissolved to restore the proper injection state of the reducing agent. It is because it can do.
As such a heating means, for example, as shown in FIG. 2, a heating wire 71 may be arranged around or inside the region where the tip of the reducing agent addition unit 15 is located. However, the heating wire is not limited to this, and any heating wire that can heat the vicinity of the injection hole can be used. In addition, when using urea water or ammonia aqueous solution as a reducing agent, in order to dissolve the main component of the crystallized reducing agent, it is necessary to be a heating means that can be heated to, for example, 135 ° C. or higher.

(2) -4 Reducing agent injection unit Although the reducing agent injection unit 36 that injects the liquid reducing agent in the SCR system 30 of the present embodiment to the reducing agent addition unit 15 side is generally an injection valve. It is not limited to. That is, any configuration that can be injected when the liquid reducing agent stored in the storage tank 31 is pumped by the pump 35 or the like can be suitably used.
For example, when an injection valve is used as the reducing agent injection unit 36, the valve is opened according to the pressure of the liquid reducing agent being pumped, and the reducing agent can be injected to the reducing agent addition unit 15 side.
Further, when the main component of the reducing agent is crystallized at least around the injection hole in the reducing agent injection unit 36 as in the heating means (see FIG. 2) of the reducing agent addition unit 15 described above, this crystallized. It is preferable to provide a heating means for heating to a temperature at which the reducing agent can be dissolved.

(2) -5 First and second reducing agent passages Further, the first reducing agent passage 17 connecting the reducing agent adding unit 15 and the reducing agent injection unit 36, the storage tank 31 and the reducing agent injection unit 36 are provided. The second reducing agent passage 18 to be connected is a tubular member through which a liquid reducing agent or a mist-like reducing agent can pass, and the cross-sectional shape and size thereof are not particularly limited.
Further, an air passage 19 to be described later is connected in the middle of the first reducing agent passage 17, and the high pressure air from the high pressure air generating means 33 is mixed with the reducing agent injected from the reducing agent injection unit 36.
Even in the middle of the first and second reducing agent passages 17 and 18, the above-mentioned heating means (see FIG. 2) is appropriately arranged at a place where the main component of the reducing agent may be crystallized. It is preferable to keep it.

(2) -6 Storage Tank The storage tank 31 is not particularly limited as long as it is a tank that can store a liquid reducing agent. In addition, for example, by providing the pump 35 and the like, it is possible to pump the reducing agent at a flow rate necessary for the reducing agent injection unit 36.

(2) -7 Discharge Valve It is preferable that a discharge valve 38 for returning the excess reducing agent to the storage tank 31 after the injection of the reducing agent is provided in the middle of the second reducing agent passage 18. The reason for this is to prevent surplus reducing agent from remaining and causing crystallization.
Further, the exhaust valve 38 uses the second reducing agent in advance when verifying the presence or absence of clogging in the reducing agent injection unit 36 or the second reducing agent passage 18 using the first SCR system of the present embodiment. It can also be used to reduce the pressure in the passage 18. This is to facilitate detection of pressure fluctuations due to high-pressure air.

(2) -8 High Pressure Air Generating Unit The high pressure air generating unit 33 converts the liquid reducing agent injected from the reducing agent injection unit 36 into a reducing agent addition unit 15 in the form of a mist reducing agent. For example, an air pump or a compressor can be used.

(2) -9 Air passage The air passage 19 is a tubular member for transferring the high-pressure air generated by the high-pressure air generating means 33 to the first reducing agent passage 17, and its cross-sectional shape, diameter, etc. Is not particularly limited.
In addition, an orifice 41 is preferably provided in the middle of the air passage. This is because the pressure of the high-pressure air generated by the high-pressure air generating means 33 can be adjusted and transferred to the first reducing agent passage 17.

(2) -10 Pressure Sensor The second reducing agent passage 18 in the SCR system 30 of the present embodiment is provided with a pressure sensor 43 a for measuring the pressure in the second reducing agent passage 18. That is, when clogging occurs in the reducing agent injection section 36 or the second reducing agent passage 18, the high-pressure air is less likely to flow into the second reducing agent passage 18, and the second reducing agent passage 18 Therefore, it is possible to easily verify the presence or absence of clogging by detecting this pressure fluctuation.
Such a pressure sensor 43a is not particularly limited, and a known sensor can be used as appropriate.

  Further, the arrangement of the pressure sensor 43a is not particularly limited as long as it is in the middle of the second reducing agent passage 18, but since the verification range of clogging in the second reducing agent passage 18 can be widened, the second It is preferable that the reducing agent passage 18 be disposed as close to the storage tank 31 as possible. That is, by disposing the pressure sensor 43a as close as possible to the storage tank 31, it is possible to ensure a long distance between the pressure sensor 43a and the reducing agent injection unit 36, and therefore, in the second reducing agent passage 18. It is possible to secure a wide area where the presence or absence of clogging can be verified. In other words, if the pressure sensor 43a is disposed between the reducing agent injection unit 36 and the clogged portion, the pressure rises regardless of clogging. Abnormality of change cannot be detected.

(2) -11 Determination Unit The SCR system 30 of the present embodiment supplies high-pressure air from the high-pressure air generation unit 33 to the first reducing agent passage 17 and supplies a reducing agent injection unit in a state where no reducing agent is supplied. 36 is opened, the pressure in the second reducing agent passage 18 is measured for a predetermined time, and the fluctuation of the measured pressure value is verified, whereby the reducing agent injection unit 36 or the second reducing agent passage 18 is It is characterized by comprising determination means 45 for determining the presence or absence of clogging.
That is, when high-pressure air is supplied to the first reducing agent passage 17, if the reducing agent injection unit 36 is clogged, the high-pressure air travels to the second reducing agent passage 18. Since the pressure in the second reducing agent passage 18 becomes difficult to rise, clogging in the reducing agent injection unit 36 or the second reducing agent passage 18 can be easily performed by verifying the pressure fluctuation. Can be detected.
A more specific verification method will be described later.

(2) -12 Control means Although not shown, in the SCR system, when it is determined by the above-mentioned determination means that the reducing agent injection section or the second reducing agent passage is clogged, the heating means It is preferable to provide a control means for controlling to dissolve the reducing agent crystallized by the above.
The reason is that the main component of the crystallized reducing agent can be rapidly dissolved by operating the heating means in response to the clogging of the reducing agent injection part or the second reducing agent passage. This is because it can. Therefore, the proper injection state of the reducing agent can be quickly recovered.

2. Clogging Verification Method of First SCR System Hereinafter, a clogging verification method using the first SCR system having the configuration described so far will be described with reference to the flow of FIG. 3 and FIGS. 4 to 5.

First, as step 1, it is preferable to set the pressure in the second reducing agent passage to a predetermined value or less in advance. For example, when the initial value of the pressure in the second reducing agent passage exceeds a predetermined value, as shown in FIG. 4A, the discharge valve 38 disposed in the second reducing agent passage 18 is opened. The internal pressure is preferably set to a predetermined value or less.
The reason for this is to make it easier to detect a pressure change in the second reducing agent passage when the high-pressure air has entered the second reducing agent passage. In addition, since a discharge valve for returning excess reducing agent into the storage tank is usually provided after injection of the reducing agent, the existing valve can be used without increasing the number of components by using the discharge valve. By using this valve, the pressure in the second reducing agent passage can be reduced.

In this case, it is preferable that the pressure value in the second reducing agent passage is substantially equal to the atmospheric pressure. This is because the initial value of the pressure is set to a value that is sufficiently lower than the pressure when the supplied high-pressure air enters the second reducing agent passage. This is to make it possible to easily detect a change in pressure.
Here, the pressure “substantially equal to the atmospheric pressure” means not only a case where the pressure completely coincides with the atmospheric pressure but also a pressure value close to the atmospheric pressure. However, needless to say, although it is not essential to set the pressure in the second reducing agent passage to a pressure value substantially equal to the atmospheric pressure, high-pressure air may enter the second reducing agent passage in a later step. In such a case, it is necessary to reduce the pressure change to such an extent that it can be detected.
Note that when the discharge valve 38 is opened and the pressure in the second reducing agent passage 18 is reduced, the discharge valve 38 is closed again.

  Next, as step 2, as shown in FIG. 4B, high-pressure air 21 is supplied from the high-pressure air generating means 33 to the first reducing agent passage 17 in a state where no reducing agent is supplied. At this stage, the reducing agent injection unit 36 is closed, and a part of the supplied high-pressure air 21 is released from the reducing agent addition unit 15, while the pressure in the first reducing agent passage 17 gradually increases. To do.

Next, as step 3, as shown in FIG. 4C, the reducing agent injection unit 36 is opened. That is, the high-pressure air 21 supplied to the first reducing agent passage 17 is in a state where it can flow into the second reducing agent passage 18.
Here, when the reducing agent injection unit 36 is opened, after confirming that the pressure of the high-pressure air 21 supplied from the high-pressure air generating means 33 exceeds a predetermined value, the reducing agent injection unit 36 is opened. Is preferred. The reason for this is that if the pressure of the high-pressure air is not sufficiently high, a pressure change in the second reducing agent passage is detected even if the high-pressure air has entered the second reducing agent passage. This is because it may be difficult to do.

Next, as step 4, as shown in FIG. 5A, the pressure variation in the pressure sensor 43 a disposed in the second reducing agent passage 18 is verified, thereby reducing the reducing agent injection unit 36 or the second reducing agent. The presence or absence of clogging in the agent passage 18 is determined.
Thus, when the reducing agent injection unit or the second reducing agent injection unit is clogged, the high-pressure air does not enter the second reducing agent passage, or even if it enters, there is a small amount. For this reason, the pressure in the second reducing agent passage does not rise or rises at a significantly slow speed. Therefore, for example, when the pressure does not rise to a predetermined pressure value within a predetermined time, it can be determined that there is clogging in the reducing agent injection unit or the second reducing agent passage.
On the other hand, when the reducing agent injection unit and the second reducing agent passage are not clogged, the high-pressure air also enters the second reducing agent passage, and the pressure in the second reducing agent passage quickly increases. Therefore, it is possible to easily detect the pressure change and determine that no clogging has occurred.

  After determining the presence or absence of clogging, as shown in FIG. 5B, as shown in FIG. 5B, the supply of high-pressure air is stopped and the discharge valve 38 provided in the second reducing agent passage 18 is opened again. Then, the internal pressures of the first and second reducing agent passages 17 and 18 are reduced, and the clogging verification is finished.

Here, with reference to FIG. 6, the pressure fluctuation in the second reducing agent passage when the first clogging verification method according to the present embodiment is performed will be described.
In FIG. 6, the horizontal axis indicates the passage of time, and the vertical axis indicates the pressure value. In FIG. 6, the dotted line A indicates the pressure value of the high-pressure air on the downstream side of the orifice of the air passage, and the solid line B indicates the inside of the second reducing agent passage when the reducing agent injection portion is not clogged. The broken line C indicates the pressure value in the second reducing agent passage when the reducing agent injection unit is clogged. A chain line D indicates the open / close state of the high-pressure air supply valve in the high-pressure air generating means, a chain line E indicates the open / close state of the discharge valve provided in the second reducing agent passage, and a chain line F indicates the opening / closing state of the reducing agent injection unit. Indicates the state.

  First, in step 0 before the start of verification, as indicated by chain lines D, E, and F, the high-pressure air supply valve is opened about half, and the discharge valve and the reducing agent injection unit are closed. Further, as shown by the dotted line A, the pressure downstream of the orifice in the air passage at this time is maintained in a high pressure state, and as shown by the solid line B and the broken line C, the pressure in the second reducing agent passage The pressure is maintained at the pressure increased by the supply pump.

  Next, in Step 1, the high pressure air supply valve is closed, while the discharge valve provided in the second reducing agent passage is opened to reduce the pressure in the second reducing agent passage. Accordingly, the pressure of the high-pressure air on the downstream side of the orifice decreases and is maintained at a low pressure, while the pressure in the second reducing agent passage gradually decreases to a pressure close to atmospheric pressure.

  Next, in step 2, the high-pressure air supply valve is opened, and the discharge valve provided in the second reducing agent passage is closed. Accordingly, the pressure downstream of the orifice increases. However, at this time, the reducing agent injection section remains closed, and the pressure in the second reducing agent passage is still maintained at a pressure close to atmospheric pressure.

Next, in steps 3 and 4, the reducing agent injection unit is opened while maintaining the high-pressure air supplied at a predetermined value, and the reducing agent is changed based on the pressure fluctuation in the second reducing agent passage. The presence or absence of clogging in the injection unit or the second reducing agent passage is verified.
When the reducing agent injection unit is not clogged, as indicated by the solid line B, the pressure in the second reducing agent passage is about 3 to 4 seconds after the reducing agent injection unit is opened. It clearly shows an increase due to air pressure. On the other hand, in the case where the reducing agent injection part is clogged, as indicated by the broken line C, even if 30 seconds have elapsed after the reducing agent injection part is opened, The pressure has hardly increased. Therefore, it is possible to easily determine the presence or absence of clogging in the reducing agent injection unit.
Needless to say, such a difference in pressure fluctuation is the same even when clogging occurs in the second reducing agent passage.

  Next, in step 5, the high-pressure air supply valve is closed and the discharge valve provided in the second reducing agent passage is opened. As a result, the pressure of the high-pressure air on the downstream side of the orifice and the pressure in the second reducing agent passage are lowered, and the clogging verification process ends.

As described above, when the clogging of the reducing agent injection unit and the second reducing agent passage has not occurred, the pressure in the second reducing agent passage rises to a predetermined pressure within a predetermined time. By monitoring the pressure fluctuation in the second reducing agent passage, the presence or absence of clogging in the reducing agent injection portion or the second reducing agent passage can be verified.
The required time and the threshold value for the pressure increase are optional, and these values are set in accordance with the degree of clogging that can be tolerated according to the performance of the exhaust purification device and the user's specifications. be able to.

  Moreover, when clogging in the reducing agent injection part or the second reducing agent passage is detected by carrying out the first clogging verification method, the heating means provided around these parts is operated, etc. Thus, it is preferable to dissolve the main component of the crystallized reducing agent. In addition, in the case of clogging due to foreign matter, it is necessary to remove the foreign matter.

Although the timing for performing the first clogging verification method described so far is not particularly limited, for example, it is preferably performed when the internal combustion engine is started. This is because during the operation of the internal combustion engine, NO _x purification may have to be interrupted while clogging is being verified. In addition, when the internal combustion engine is in an operating state, the crystallized reducing agent that causes the clogging can be dissolved by the heat of the exhaust gas, etc., and the clogging may be resolved naturally. Because there is.
Therefore, it is preferable to check the presence or absence of clogging at the start of the internal combustion engine, to quickly eliminate clogging, and to start normal operation.

[Second Embodiment]
In the second embodiment of the present invention, a second SCR system using urea as a reducing agent and a second eye performed using the second SCR system as the second NO _x purification system described above. This is a clogging verification method.
Note that description of points that can be configured in the same manner as in the first embodiment will be omitted as appropriate, and differences from the first embodiment will be mainly described.

1. Second SCR System (1) Internal Combustion Engine and Exhaust Passage The internal combustion engine that exhausts exhaust gas purified by the second SCR system, the operating state detection means provided in the internal combustion engine, and the exhaust passage are the same as those in the first embodiment. Since the configuration can be the same as that in FIG.

(2) SCR System (2) -1 Basic Configuration FIG. 7 is a diagram illustrating a configuration example of the SCR system 80 of the present embodiment.
The SCR system 80 of the present embodiment is provided in the exhaust passage 20 of the internal combustion engine, absorbs NO _x in the exhaust gas and reduces using the reducing agent 5, and the exhaust passage on the upstream side of the catalyst 13. A reducing agent adding unit 15 for adding the reducing agent 5 into the reducing agent, a reducing agent passage 17 connected to the reducing agent adding unit 15, and a reducing agent injection unit 36 for injecting the reducing agent into the reducing agent passage 17. The storage tank 31 in which the reducing agent transferred to the reducing agent injection unit 36 is stored, the orifice 41 inside, the air passage 19 connected in the middle of the reducing agent passage 17, and the air passage 19 Two pressure sensors 43b and 43c arranged on the upstream side and downstream side of the orifice 41 and the reducing agent supplied to the reducing agent passage 17 via the air passage 19 and injected from the reducing agent injection unit 36 In a state where the high-pressure air generating means 33 for generating the high-pressure air to be mixed and the reducing agent injection unit 36 are closed, the high-pressure air is supplied from the high-pressure air generating means 33 to the reducing agent passage 17 and the two pressure sensors 43b, 3c. And determining means 81 for determining whether or not the reducing agent adding section 15 is clogged by comparing the pressure values measured by the above.

Here, the NO _X catalyst 13 used in the SCR system 80, the reducing agent, the reducing agent addition unit 15, the reducing agent injection unit 36, the reducing agent passage (first reducing agent passage) 17, the storage tank 31, the discharge valve 38, the high-pressure air generating means 33, the control means for operating the heating means when the reducing agent is crystallized, and the like can be configured in the same manner as in the first embodiment.

(2) -2 Air Passage On the other hand, the air passage 19 provided in the SCR system of the present embodiment can be basically configured similarly to the first embodiment. However, an orifice 41 is provided in the middle of the air passage 19 in the SCR system 80 of the present embodiment, and pressure sensors 43b and 43c are provided on the upstream side and the downstream side of the orifice 41, respectively. That is, by providing the orifice 41, the pressure of the high-pressure air generated by the high-pressure air generating means 33 is adjusted and transferred to the first reducing agent passage 17, and the upstream and downstream pressures of the orifice 41 are different. Therefore, the presence or absence of clogging of the reducing agent addition unit 15 can be verified by comparing the pressures on the upstream side and the downstream side.
The air passage 19, the orifice 41, and the pressure sensors 43 b and 43 c that are used are not particularly limited, and known ones can be used as in the first embodiment.

(2) -3 Determination Unit The SCR system 80 of the present embodiment supplies high-pressure air from the high-pressure air generation unit 33 to the reducing agent passage 17 in a state where the reducing agent injection unit 36 is closed, and the first and first It is characterized by comprising a determination means 81 for determining whether or not the reducing agent addition unit 15 is clogged by comparing the pressure values measured by the two pressure sensors 43b and 43c.
That is, when high pressure air is supplied to the reducing agent passage 17 with the reducing agent injection unit 36 closed, if the reducing agent addition unit 15 is not clogged, the high pressure air is added to the reducing agent. The pressure on the downstream side of the orifice 41 of the air passage 19 that is discharged from the portion 15 is lower than the pressure on the upstream side. On the other hand, if the reducing agent addition unit 15 is clogged, the high-pressure air is less likely to be discharged to the outside. Therefore, the pressure on the downstream side of the orifice 41 in the air passage 19 is equal to the upstream pressure. The approximate value will be shown. Therefore, the clogging of the reducing agent adding portion 15 can be easily verified by comparing the pressure values on the upstream side and the downstream side of the orifice 41.
A more specific verification method will be described later.

2. Clogging Verification Method of Second SCR System Hereinafter, a clogging verification method using the second SCR system having the above-described configuration will be described with reference to the flow of FIG. 8 and FIG.

First, as step 1, it is preferable to set the pressure in the reducing agent passage and the air passage to a predetermined value or less in advance. The reason for this is to make it easier to detect a pressure change in the air passage when high-pressure air is supplied.
In addition, when using the addition nozzle normally used as a reducing agent addition part, a pressure falls because internal air is discharge | released from the said addition nozzle.

  Next, as step 2, as shown in FIG. 9A, high-pressure air 21 is supplied from the high-pressure air generating means 33 to the reducing agent passage 17 in a state where the reducing agent injection unit 36 is closed. As a result, first, the air passage on the upstream side of the orifice is filled with high-pressure air, and the high-pressure air gradually flows into the downstream side of the orifice.

Next, as step 3, as shown in FIG. 9B, the pressure values on the upstream side and downstream side of the orifice 41 arranged in the air passage 19 are measured using the pressure sensors 43b and 43c, respectively. By comparing the measured pressure values, the presence or absence of clogging in the reducing agent addition unit 15 is determined.
As a result, when the reducing agent addition unit 15 is clogged, the high-pressure air 21 is not released to the outside, or even if it is released, the amount is very small. Along with this, the pressure on the upstream side of the orifice 41 approximates the pressure on the downstream side. Therefore, for example, when the difference between the pressure on the upstream side and the pressure on the downstream side of the orifice 41 falls within a predetermined range within a predetermined time, it can be determined that there is clogging in the reducing agent addition unit 15. .
On the other hand, when the reducing agent addition unit 15 is not clogged, the high-pressure air 21 supplied into the reducing agent passage 17 is released from the reducing agent addition unit 15, so the pressure on the downstream side of the orifice 41 is Since it does not rise above a certain level, it can be determined that no clogging has occurred.

  After determining the presence or absence of clogging, in step 4, the supply of high-pressure air from the high-pressure air generating means 33 is stopped, and the clogging verification is finished.

Here, with reference to FIG. 10, the pressure fluctuation in the downstream side of the orifice in the air passage when the second clogging verification method according to the present embodiment is performed will be described.
In FIG. 10, the horizontal axis indicates the passage of time, and the vertical axis indicates the pressure value. In FIG. 10, a solid line A indicates the pressure value of the high pressure air in the air passage on the upstream side of the orifice, and a dotted line B indicates the pressure value in the air passage on the downstream side of the orifice. A chain line C indicates an open / close state of the high pressure air supply valve in the high pressure air generating means.

As shown in FIG. 10, in step 1, the high-pressure air supply valve is closed as shown by the chain line C, and the pressure values on the upstream side and downstream side of the orifice are almost the same as shown by the dotted line A and the solid line B. It is held at the same pressure.
Next, in Steps 2 to 3, the high pressure air supply valve is opened, and the presence or absence of clogging in the reducing agent addition unit is verified based on the pressure values on the upstream side and downstream side of the orifice. In this data, the pressure on the upstream side of the orifice rises rapidly, and then gradually rises, and is maintained at a predetermined high pressure state after about 7 to 8 seconds after opening the valve. On the other hand, the pressure on the downstream side of the orifice gradually increases after opening the valve, but after about 5 to 6 seconds, the orifice is throttled to a constant value that is clearly lower than the pressure on the upstream side. Is maintained. This data is based on the use of a reducing agent addition section that is not clogged, so even after a predetermined time has elapsed after opening the high-pressure air supply valve, the pressure upstream and downstream of the orifice Results showed that the values never approximated.

As described above, since the pressure in the air passage on the upstream side and the downstream side of the orifice does not approximate when the clogging of the reducing agent addition portion has not occurred, the value of these two pressures. By comparing these, the presence or absence of clogging of the reducing agent addition part can be verified.
However, the time when determining that there is no clogging and the threshold value for the pressure difference are optional, and depending on the performance of the exhaust purification system and the user's specifications, it can be adjusted according to the allowable degree of clogging. , You can set their values.

  Further, when clogging in the reducing agent addition unit is detected by performing the second clogging verification method, the crystallization is performed by operating a heating means provided around the reducing agent addition unit. It is preferable to dissolve the main component of the reducing agent. In addition, in the case of clogging due to foreign matter, it is necessary to remove the foreign matter.

  Note that the timing for performing the second clogging verification method described so far is not particularly limited as in the first clogging verification method, and is preferably performed, for example, when the internal combustion engine is started. Therefore, it is preferable to check the presence or absence of clogging at the start of the internal combustion engine, to quickly eliminate clogging, and to start normal operation.

[Third Embodiment]
In the third embodiment of the present invention, a third SCR system using urea as a reducing agent and a third eye performed using the third SCR system as the third NO _x purification system described above. This is a clogging verification method.
Note that description of points that can be configured in the same manner as in the first or second embodiment will be omitted as appropriate, and differences from the first or second embodiment will be mainly described.

1. Third SCR system (1) Internal combustion engine and exhaust passage The internal combustion engine that discharges exhaust gas to be purified by the third SCR system, the operating state detection means of the internal combustion engine, and the exhaust passage are the same as in the first embodiment. The description here will be omitted.

(2) SCR System (2) -1 Basic Configuration FIG. 11 is a diagram illustrating a configuration example of the SCR system 90 of the present embodiment.
The SCR system 90 of the present embodiment is provided in the exhaust passage 20 of the internal combustion engine, absorbs NO _x in the exhaust gas and reduces using a reducing agent, and the exhaust passage 30 upstream of the catalyst 13. A reducing agent adding unit 15 for adding the reducing agent 5 therein, a first reducing agent passage 17 connected to the reducing agent adding unit 15, and a reduction for injecting the reducing agent into the first reducing agent passage 17. An agent injection unit 36, a second reducing agent passage 18 connected to the reducing agent injection unit 36, and the second reducing agent passage 18 are disposed in the second reducing agent passage 18, and the pressure in the second reducing agent passage 18 is measured. The first pressure sensor 43a, the storage tank 31 storing the reducing agent transferred to the reducing agent injection unit 36 via the second reducing agent passage 18, the orifice 41 inside, and the first tank Air communication connected in the middle of the reducing agent passage 18 19, the second and third pressure sensors 43 b and 43 c disposed on the upstream side and the downstream side of the orifice 41 in the air passage 19, and the first reducing agent passage 17 through the air passage 19. The high-pressure air generating means 33 for generating high-pressure air mixed with the reducing agent injected from the reducing agent injection section 36 and the first reduction from the high-pressure air generating means 33 with the reducing agent injection section 36 closed. First determination for determining whether the reducing agent addition unit 15 is clogged by supplying high-pressure air to the agent passage 17 and comparing the pressure values measured by the second and third pressure sensors 43b and 43c. The high pressure air is supplied from the means 45 and the high pressure air generating means 33 to the first reducing agent passage 17, the reducing agent injection section 36 is opened, and the pressure in the second reducing agent passage 18 is measured for a predetermined time. And a second determination unit 81 that determines whether or not the reducing agent injection unit 36 or the second reducing agent passage 18 is clogged by verifying the variation of the measured pressure value.

That is, the third SCR system 90 includes both the determination unit (first determination unit) 45 in the first embodiment and the determination unit (second determination unit) 81 in the second embodiment. It is characterized by. About the detail of each determination means, since it can be set as the structure similar to each determination means in 1st Embodiment and 2nd Embodiment, description here is abbreviate | omitted.
Further, the NO _x catalyst 13, the reducing agent 5, the reducing agent addition unit 15, the reducing agent injection unit 36, the first and second reducing agent passages 17 and 18, the storage tank 31, the discharge valve used in the SCR system 90 are used. 38, the high pressure air generating means 33, the air passage 19, the pressure sensors 43a, 43b, 43c, the control means for operating the heating means when the reducing agent is crystallized, etc., also in the first embodiment or the second implementation. It can be set as the structure similar to this form.

2. Clogging Verification Method of Third SCR System Hereinafter, a clogging verification method using the third SCR system having the above-described configuration will be described with reference to the flow of FIG. 12 and FIGS. 13 to 14 as appropriate.

First, as step 1, it is preferable to set the pressures in the first and second reducing agent passages and the air passage to a predetermined value or less in advance. The reason for this is to make it easier to detect pressure changes in the respective passages when high-pressure air is supplied.
For example, as in the first embodiment, as shown in FIG. 13A, by opening the discharge valve 38 provided in the second reducing agent passage 18, the discharge valve 38 and the reducing agent addition unit 15 are opened. The air and the reducing agent in the passages can be removed from the pressure etc., and the pressure in each passage can be reduced.
Note that when the discharge valve 38 is opened and the pressure in the second reducing agent passage 18 is reduced, the discharge valve 38 is closed again.

  Next, as step 2, as shown in FIG. 13B, high-pressure air 21 is supplied from the high-pressure air generating means 33 to the first reducing agent passage 17 in a state where the reducing agent injection unit 36 is closed. As a result, the air passage 19 upstream of the orifice 41 is filled with the high-pressure air 21 and the high-pressure air 21 gradually flows into the downstream side of the orifice 41.

Next, as step 3, as shown in FIG. 13C, the upstream and downstream pressure values of the orifice 41 disposed in the air passage 19 are measured using the pressure sensors 43b and 43c, respectively. By comparing the measured pressure values, the presence or absence of clogging in the reducing agent addition unit 15 is determined.
As a result, when clogging occurs in the reducing agent addition unit 15, the pressure on the upstream side of the orifice 41 and the pressure on the downstream side are approximated. When the difference between the pressure on the upstream side of 41 and the pressure on the downstream side falls within a predetermined range, it can be determined that there is clogging in the reducing agent addition unit 15.
On the other hand, when the reducing agent addition unit 15 is not clogged, the high-pressure air supplied into the reducing agent passage 17 is released from the reducing agent addition unit 15 and the pressure on the downstream side of the orifice 41 rises above a certain level. Therefore, it can be determined that no clogging has occurred.

  Next, in a state where the reducing agent is not supplied continuously, the high pressure air is continuously supplied from the high pressure air generating means to the first reducing agent passage. At this stage, the reducing agent injection unit is closed, and a part of the supplied high-pressure air is released from the reducing agent addition unit, while the pressure in the first reducing agent passage gradually increases.

Next, as step 4, as shown in FIG. 14A, the reducing agent injection unit 36 is opened. That is, the high-pressure air 21 supplied to the first reducing agent passage 17 is in a state where it can flow into the second reducing agent passage 18.
Here, as in the first embodiment, when the reducing agent injection unit 36 is opened, it is confirmed that the pressure of the high-pressure air 21 supplied from the high-pressure air generating means 33 exceeds a predetermined value. In addition, an open state is preferable.

Next, as step 5, as shown in FIG. 14B, the pressure variation in the pressure sensor 43 a disposed in the second reducing agent passage 18 is verified, thereby reducing the reducing agent injection unit 36 or the second reducing agent. The presence or absence of clogging in the agent passage 18 is determined.
Thus, when the reducing agent injection unit or the second reducing agent injection unit is clogged, the reducing agent injection unit or the second reducing agent is not increased to a predetermined pressure value within a predetermined time. It can be determined that there is clogging in the passage.
On the other hand, when the reducing agent injection section and the second reducing agent passage are not clogged, the pressure in the second reducing agent passage rises quickly, so that the pressure change is detected and clogging occurs. It can be easily determined that no occurs.

At this time, when determining that the reducing agent injection unit or the second reducing agent passage is clogged, the threshold of time and pressure is determined according to the degree of clogging of the reducing agent addition unit verified previously. It is preferable to set.
The reason for this is that the speed at which the high-pressure air enters the second reducing agent passage varies depending on the degree of clogging of the reducing agent addition part, for example, whether it is completely clogged, not clogged at all, or clogged about half. It is.
Therefore, for example, when the reducing agent addition unit is completely clogged, the speed at which the high-pressure air flows into the second reducing agent passage side when the reducing agent injection unit is opened increases. It is preferable to set a short time for rising to a predetermined pressure at which it is determined that there is no clogging. On the other hand, for example, as the degree of clogging of the reducing agent addition unit becomes low, the speed at which the high-pressure air flows into the second reducing agent passage side becomes slow when the reducing agent injection unit is opened. It is preferable to set a longer time for rising to a predetermined pressure at which it is determined that there is no clogging.
Accordingly, the clogging in the reducing agent injection unit or the second reducing agent passage can be accurately verified in accordance with the clogged state of the reducing agent addition unit.

  After determining the presence or absence of clogging, as shown in FIG. 14C, the supply of high-pressure air is stopped and the discharge valve 38 provided in the second reducing agent passage 18 is opened again as step 6. Then, the internal pressures of the first and second reducing agent passages 17 and 18 are reduced, and the clogging verification is finished.

The third clogging verification method described above can be performed under the same conditions as those in the first embodiment and the second embodiment, respectively.
Further, the third clogging verification method is also preferably performed when the internal combustion engine is started. Further, when clogging in the reducing agent addition unit, the reducing agent injection unit or the second reducing agent passage is detected, the heating means provided around each of these units is operated to crystallize the reducing agent. It is preferable to dissolve the main component. In addition, in the case of clogging due to foreign matter, it is necessary to remove the foreign matter.

According to the present invention, the NO _x purification system is provided with the predetermined determination means, so that the presence or absence of clogging in the reducing agent addition unit or the reducing agent injection unit and the second reducing agent passage can be accurately verified. became. Further, in performing the verification of the clogging of the NO _x purification system, the reducing agent addition unit or the reducing agent is measured by shutting off valves and passages other than the verification target location and measuring the pressure value at a predetermined location. The presence or absence of clogging in the injection section and the second reducing agent passage can be verified with high accuracy.
Therefore, in the NO _x purification system using urea or HC as a reducing agent, clogging in the supply system due to crystallization of the reducing agent or intrusion of foreign matters can be easily and accurately verified.

It is a figure which shows the structural example of the SCR system of 1st Embodiment. It is a figure which shows the example of the heating means of a reducing agent addition part. It is a figure which shows the flow of the 1st clogging verification method. It is a figure provided in order to demonstrate the 1st clogging verification method (the 1). It is a figure provided in order to demonstrate the 1st clogging verification method (the 2). It is a figure which shows the pressure fluctuation in a 2nd reducing agent channel | path. It is a figure which shows the structural example of the SCR system of 2nd Embodiment. It is a figure which shows the flow of the 2nd clogging verification method. It is a figure provided in order to demonstrate the 2nd clogging verification method. It is a figure which shows the pressure fluctuation in the air passage of an orifice upstream and downstream. It is a figure which shows the structural example of the SCR system of 3rd Embodiment. It is a figure which shows the flow of the 3rd clogging verification method. It is a figure with which it uses for demonstrating the 3rd clogging verification method (the 1). It is a figure with which it uses for demonstrating the 3rd clogging verification method (the 2). It is a view for explaining the structure of a conventional of the NO _X purification device.

Explanation of symbols

5: reducing agent, 13: catalyst, 15: reducing agent addition section, 17: first reducing agent passage, 18: second reducing agent passage, 19: air passage, 20: exhaust passage, 21: high pressure air, 30 : First SCR system, 31: Storage tank, 33: Air compressor, 35: Reductant supply pump, 36: Reductant injection unit, 37: High pressure air supply valve, 38: Discharge valve, 41: Orifice, 43a and 43b 43c: pressure sensor, 45: determination means (first determination means), 71: heating means, 80: second SCR system, 81: determination means (second determination means), 90: third SCR system

Claims (13)

A catalyst that is provided in the exhaust passage of the internal combustion engine, absorbs NO _x in the exhaust gas, and reduces using a reducing agent;
A reducing agent addition section for adding the reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection unit for injecting the reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A pressure sensor disposed in the second reducing agent passage and measuring a pressure in the second reducing agent passage;
A storage tank in which the reducing agent transferred to the reducing agent injection unit via the second reducing agent passage is stored;
An air passage connected in the middle of the first reducing agent passage;
High-pressure air generating means for generating high-pressure air that is supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In a state where the reducing agent is not supplied, high-pressure air is supplied from the high-pressure air generating means to the first reducing agent passage, the reducing agent injection unit is opened, and the pressure in the second reducing agent passage is changed. Determination means for measuring a predetermined time and verifying the variation of the measured pressure value to determine whether the reducing agent injection section or the second reducing agent passage is clogged;
A NO _X purification system comprising: A catalyst that is provided in the exhaust passage of the internal combustion engine, absorbs NO _x in the exhaust gas, and reduces using a reducing agent;
A reducing agent addition section for adding the reducing agent into the exhaust passage upstream of the catalyst;
A reducing agent passage connected to the reducing agent addition section;
A reducing agent injection unit that injects the reducing agent into the reducing agent passage;
A storage tank storing the reducing agent to be transferred to the reducing agent injection unit;
An air passage provided with an orifice therein and connected in the middle of the reducing agent passage;
Two pressure sensors arranged upstream and downstream of the orifice in the air passage;
High-pressure air generating means for generating high-pressure air supplied to the reducing agent passage via the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In a state where the reducing agent injection unit is closed, high pressure air is supplied from the high pressure air generating means to the reducing agent passage, and the pressure value measured by the two pressure sensors is compared, thereby reducing the reducing agent addition unit. Determining means for determining the presence or absence of clogging,
A NO _X purification system comprising: A catalyst that is provided in the exhaust passage of the internal combustion engine, absorbs NO _x in the exhaust gas, and reduces using a reducing agent;
A reducing agent addition section for adding the reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection unit for injecting the reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A first pressure sensor disposed in the second reducing agent passage and measuring a pressure in the second reducing agent passage;
A storage tank in which the reducing agent transferred to the reducing agent injection unit via the second reducing agent passage is stored;
An air passage provided with an orifice therein and connected in the middle of the first reducing agent passage;
Second and third pressure sensors disposed upstream and downstream of the orifice in the air passage;
High-pressure air generating means for generating high-pressure air that is supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
High pressure air is supplied from the high pressure air generating means to the first reducing agent passage in a state where the reducing agent injection unit is closed, and pressure values measured by the second and third pressure sensors are compared. By the first determination means for determining the presence or absence of clogging of the reducing agent addition unit,
High-pressure air is supplied from the high-pressure air generating means to the first reducing agent passage, the reducing agent injection unit is opened, and the pressure in the second reducing agent passage is measured for a predetermined time. A second determination means for determining whether or not the reducing agent injection section or the second reducing agent passage is clogged by verifying the variation of the pressure value;
A NO _X purification system comprising: A catalyst that is provided in the exhaust passage of the internal combustion engine and absorbs NO _x in the exhaust gas and reduces using a reducing agent;
A reducing agent addition section for adding the reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection unit for injecting the reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A storage tank in which the reducing agent transferred to the reducing agent injection unit via the second reducing agent passage is stored;
An air passage connected in the middle of the first reducing agent passage;
High-pressure air generating means for generating high-pressure air that is supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In the NO _x purification system comprising the NO _x purification system for verifying the clogging of the NO _x purification system for verifying the presence or absence of clogging in the reducing agent injection section or the second reducing agent passage,
In a state where the reducing agent is not supplied, high-pressure air is supplied from the high-pressure air generating means to the first reducing agent passage, the reducing agent injection unit is opened, and the pressure in the second reducing agent passage is changed. Clogging verification of the NO _x purification system characterized by verifying clogging of the reducing agent injection section or the second reducing agent passage by measuring a predetermined time and verifying the variation of the measured pressure value. Method. Wherein when the second pressure of the reducing agent passage is not more than the predetermined value, clogging verification method of the NO _X purifying system according to claim 4, characterized in that to start the supply of the high-pressure air. When the pressure in the second reducing agent passage exceeds a predetermined value in the state before the supply of the high-pressure air, a discharge valve provided in the second reducing agent passage is opened and the second reducing agent passage is opened. clogging verification method of the NO _X purifying system according to claim 4 or 5, wherein the pressure of the reducing agent passage to be lower than or equal to the predetermined value. When the pressure in the second reducing agent passage does not exceed a predetermined pressure value within a predetermined time, it is determined that the reducing agent injection section and the second reducing agent passage are clogged. The clogging verification method for the NO _x purification system according to any one of claims 4 to 6. The measurement of the pressure in the second reducing agent passage is started when the pressure of the high-pressure air in the high-pressure air generation means exceeds a predetermined value. The clogging verification method of the described NO _X purification system. 9. The NO according to claim 4, wherein when the pressure in the second reducing agent passage is substantially equal to atmospheric pressure, the reducing agent injection unit is opened. _X purification system clogging verification method. The clogging verification method for an NO _x purification system according to any one of claims 4 to 9, wherein the clogging verification is performed when the internal combustion engine is started. A catalyst that is provided in the exhaust passage of the internal combustion engine and absorbs NO _x in the exhaust gas and reduces using a reducing agent;
A reducing agent addition section for adding the reducing agent into the exhaust passage upstream of the catalyst;
A reducing agent passage connected to the reducing agent addition section;
A reducing agent injection unit that injects the reducing agent into the reducing agent passage;
A storage tank storing the reducing agent to be transferred to the reducing agent injection unit;
An air passage provided with an orifice therein and connected in the middle of the reducing agent passage;
High-pressure air generating means for generating high-pressure air supplied to the reducing agent passage via the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In the NO _x purification system provided with the clogging verification method of the NO _x purification system for verifying the presence or absence of clogging in the reducing agent injection unit,
The reducing agent injection unit is closed and high pressure air is supplied from the high pressure air generating means to the reducing agent passage, and the difference in pressure value between the upstream side and the downstream side of the orifice arranged in the middle of the air passage is compared. Thus, the clogging verification method of the NO _x purification system is characterized by verifying clogging of the reducing agent addition section. A catalyst that is provided in the exhaust passage of the internal combustion engine and absorbs NO _x in the exhaust gas and reduces using a reducing agent;
A reducing agent addition section for adding the reducing agent into the exhaust passage upstream of the catalyst;
A first reducing agent passage connected to the reducing agent addition section;
A reducing agent injection unit for injecting the reducing agent to the first reducing agent passage;
A second reducing agent passage connected to the reducing agent injection unit;
A storage tank in which the reducing agent transferred to the reducing agent injection unit via the second reducing agent passage is stored;
An air passage provided with an orifice therein and connected in the middle of the first reducing agent passage;
High-pressure air generating means for generating high-pressure air that is supplied to the first reducing agent passage through the air passage and mixed with the reducing agent injected from the reducing agent injection section;
In NO _X purification system wherein the reducing agent adding unit, the reducing agent injection unit, or the clogging verification method of the NO _X purification system for verifying the presence or absence of clogging in the second reducing agent passage,
The reducing agent injection section is closed, and high pressure air is supplied from the high pressure air generating means to the first reducing agent passage, and the pressure on the upstream side and the downstream side of the orifice arranged in the middle of the air passage A step of verifying clogging of the reducing agent addition part by comparing the values;
The reducing agent injection section is opened, high pressure air is supplied from the high pressure air generating means to the first reducing agent passage, and the pressure in the second reducing agent passage is measured for a predetermined time. Verifying clogging of the reducing agent injection section or the second reducing agent passage by verifying fluctuations in pressure value,
A method for verifying clogging of an NO _X purification system, comprising: The clogging of the NO _x purification system according to claim 12, wherein the verification condition of the fluctuation of the pressure value in the second reducing agent passage is changed according to the clogging state of the reducing agent addition section. Method of verification.

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