JP4224983B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device that purifies exhaust gas of an internal twisting engine in an exhaust system, and more particularly to an exhaust gas purification device of an internal combustion engine that purifies exhaust gas using a catalyst provided in the exhaust system.
[0002]
[Prior art]
The internal twisting engine installed on the vehicle is steam H₂Zero or carbon dioxide CO₂In this exhaust gas, unburned gas HC, carbon monoxide CO, and nitrogen oxides NOx are mixed. Therefore, the exhaust gas containing HC, CO, and NOx is purified by a three-way catalyst or NOx catalyst provided in the exhaust system, and then discharged to the atmosphere.
For example, many diesel vehicles are equipped with a reduction catalyst that purifies NOx in the exhaust region of the exhaust system, and gasoline vehicles have a three-way catalyst that purifies HC, CO, and NOx under a stoichiometric atmosphere. In many cases, a reductive catalyst is used in addition to a three-way catalyst in addition to a three-way catalyst.
[0003]
As described above, the NOx catalyst and the three-way catalyst provided in the exhaust system of each vehicle are generally arranged as a catalytic converter having a shape bulging in the middle of the exhaust pipe. This catalytic converter is formed in a state where a porous catalyst carrier is disposed inside the main body casing and a NOx catalyst or a three-way catalyst is supported on the catalyst carrier. Exhaust gas from the internal combustion engine flows into such a catalytic converter, and HC, CO, NOx in the exhaust gas is reduced by the catalyst on the catalyst carrier or promoted by the oxidation reaction, rendered harmless, and discharged to the outside. ing.
Usually, the purification rate of the catalyst is lower than the activation temperature of the catalyst temperature as before the completion of the warm-up, and the desired purification rate can be maintained above the activation temperature as after the completion of the warm-up operation. Moreover, the NOx catalyst can maintain a high purification rate when the air-fuel ratio is operated in an oxygen-rich atmosphere, and the three-way catalyst can be operated when the air-fuel ratio is operated with stoichiometry. In many cases, the catalyst temperature and the air-fuel ratio control are performed.
[0004]
[Problems to be solved by the invention]
By the way, when the internal combustion engine is operated at a temperature where the catalyst temperature exceeds the activation temperature, for example, at 300 to 500 ° C., and the high output operation is further continued, the catalyst temperature is excessively increased, for example, It may be higher than 650 ° C. If this state continues, the NOx catalyst supported on the catalyst carrier or the catalyst metal of the three-way catalyst is likely to be scattered, and this catalyst metal may be discharged to the atmosphere.
For example, a NOx purification device used in a diesel engine places an SCR catalyst (NOx catalyst) in its exhaust system, and a catalyst metal for functioning as an SCR catalyst, such as vanadium (V), is supported on the carrier, upstream of it. More urea water is supplied, and ammonia generated by hydrolysis is supplied as a reducing agent to the catalyst so that NOx can be purified under an oxygen-excess atmosphere. In such a diesel engine, when the high output operation is continued, the temperature of the exhaust gas passing through the SCR catalyst excessively rises. For example, if the catalyst temperature exceeds the overheated temperature of about 650 ° C. Then, vaporization of vanadium occurs, and vanadium may be scattered to the environment.
[0005]
As described above, when the state in which the catalyst temperature of the NOx catalyst excessively rises continues, the catalyst is deteriorated early, and the exhaust gas itself is deteriorated. Such scattering of the catalytic metal occurs similarly in the three-way catalyst. Therefore, there is a demand for an exhaust gas purification device that can suppress an excessive increase in the catalyst temperature and prevent the catalyst from being scattered from the catalyst carrier regardless of the operating state.
An object of the present invention is to provide an exhaust gas purifying device for an internal combustion engine that can suppress an excessive increase in the catalyst temperature and prevent the catalyst from scattering, based on the above problems.
[0006]
[Means for Solving the Problems]
  According to claim 1, the catalyst provided in the exhaust system of the internal twisting engineA cooling means for solidification provided in the exhaust system on the downstream side of the catalyst to solidify the metal scattered from the catalyst by reducing the exhaust gas temperature, and the catalyst provided in the exhaust system on the downstream side of the cooling means. And a filter for collecting the metal scattered from the water.
According to claim 1, even if the metal supported on the catalyst carrier is scattered, the metal scattered by the solidification cooling means provided on the downstream side of the catalyst is solidified and then provided on the downstream side of the solidification cooling means. Therefore, it is possible to prevent the metal scattered from the catalyst carrier from being discharged into the exhaust gas.
[0010]
    Preferably,Claim 1In the exhaust gas purifying apparatus for an internal combustion engine according to claim 1, the solidification cooling means includes a bypass passage branched from the exhaust system and an outside air introduction portion having a venturi portion having a diameter reduced in a part of the bypass passage. It may be done. In this case, the outside air can be introduced from the outside air introduction portion through the venturi portion on the bypass passage, and the catalyst can be cooled with the outside air to prevent the catalyst from deteriorating.
  Preferably,Claim 1In the exhaust gas purifying apparatus for an internal combustion engine described in (1), the solidification cooling means may be composed of a heat exchange chamber formed around the exhaust system and a cooling medium circulating in the heat exchange chamber. In this case, since the cooling medium is circulated and flowed into the heat exchange chamber, the exhaust gas temperature can be lowered and the catalyst can be cooled to prevent deterioration of the catalyst.
  Preferably,Claim 1In the exhaust gas purifying apparatus for an internal combustion engine described in (1), the solidification cooling means may be constituted by cooling fins formed around the exhaust system. In this case, the cooling fins around the exhaust system cool the exhaust gas, and the catalyst is cooled by the low-temperature exhaust gas, so that deterioration of the catalyst can be prevented.
[0011]
  Claim 2The present invention includes a catalyst provided in an exhaust system of an internal twist engine, catalyst temperature detection means for detecting or estimating a catalyst temperature of the catalyst or a parameter correlated with the catalyst temperature, and an exhaust gas provided in the exhaust system upstream of the catalyst. A cooling means for cooling the gas; a cooling means for solidification provided in the exhaust system downstream of the catalyst to reduce the exhaust gas temperature to solidify the metal scattered from the catalyst; and a downstream of the cooling means for solidification A filter provided in the exhaust system for collecting metal scattered from the catalyst, and when the catalyst temperature or the exhaust gas temperature detected or estimated by the catalyst temperature detecting means is equal to or higher than a predetermined temperature, the exhaust gas temperature should be reduced. Control means for controlling the operation of the cooling means is provided.
  Claim 2According to the invention, the cooling means can be operated to cool the catalyst when the catalyst temperature or the exhaust gas temperature at which the metal supported on the catalyst carrier is considered to scatter is higher than a predetermined temperature, so that the catalyst is supported on the catalyst carrier. Even if the metal carried on the catalyst carrier is scattered, the solidified metal is dispersed by the solidification cooling means provided on the downstream side of the catalyst, and the solidification cooling means Since it can collect with the filter provided in the downstream, the discharge | release to the exhaust_gas | exhaustion of the metal which scattered from the catalyst support | carrier can be prevented reliably.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an exhaust gas purifying apparatus for an internal combustion engine as an embodiment of the present invention will be described with reference to FIG. The exhaust gas purifying device for an internal combustion engine here is mounted on an exhaust system 2 of a multi-cylinder diesel engine (hereinafter simply referred to as an engine) 1 mounted on a vehicle (not shown).
The engine 1 is controlled by an engine control device (hereinafter simply referred to as engine ECU) 3, the exhaust gas purification device is controlled by an exhaust gas control device (hereinafter simply referred to as exhaust system ECU) 4, and the engine ECU 3 and exhaust system ECU 4 are The control system communication line 5 is connected so that mutual communication is possible.
In FIG. 1, an engine ECU 3 outputs an output signal corresponding to the calculated injection timing and fuel injection amount Uf to a fuel injection electromagnetic valve of an injector (not shown) to perform fuel injection control of the injector, and an engine such as an EGR valve (not shown). The main unit is controlled.
[0013]
The exhaust gas purifying device for the internal combustion engine of FIG. 1 includes a NOx purifying device 9 and an exhaust gas cooling device 11 provided in the exhaust system 2 of the engine 1.
[0014]
The NOx purification device 9 includes an SCR catalyst 13 that is a NOx catalyst mounted in the middle of the exhaust pipe 12, a urea water supply device 14 that supplies urea water from the supply position f upstream thereof to the exhaust passage E, and the temperature of the SCR catalyst 13. A catalyst temperature sensor 16 that outputs tg and an exhaust system ECU 4 that constitutes a control unit of the NOx purification device 9 are provided.
The SCR catalyst 13 is accommodated in a NOx catalytic converter 18 in the middle of the exhaust pipe 12 forming the exhaust path E. The NOx catalytic converter 18 includes a substantially cylindrical casing 181, and the casing 181 includes a honeycomb-shaped ceramic catalyst carrier (overlapping the block display of the SCR catalyst 13), and the catalyst carrier is bundled with a metal network. It supports without deviation through the sealing material 182, and a catalyst metal for functioning as the SCR catalyst 13, for example, vanadium (V) is supported on the carrier.
[0015]
The SCR catalyst 13 can selectively reduce NOx in the exhaust gas using ammonia (NH3) as a reducing agent. Here, urea water (urea water) is supplied to the exhaust passage E by the urea water supply device 14, the urea water is hydrolyzed as in the following formula (1), and ammonia can be added to the SCR catalyst 13. Yes.
(NH₂) 2CO + H₂O → 2NH₃+ CO₂(1)
Here, in the ammonia adsorption state, the SCR catalyst 13 mainly performs the reaction of the following formula (2) at the high temperature and the following formula (3) at the low temperature in accordance with the atmospheric temperature of the NOx in the exhaust gas, It is known to promote the denitration reaction between NH3 and nitrogen oxides.
[0016]
4NH₃+ 4NO + O₂→ 4N₂+ 6H₂O ... (2)
2NH₃+ NO + NO₂→ 2N₂+ 3H₂O (3)
Next, the exhaust gas cooling device 11 as a cooling means of the exhaust system 2 of FIG. 1 will be described. The exhaust gas cooling device 11 flows outside air as a cooling medium into the air supply position g between the urea water supply device 14 and the SCR catalyst 13 in the middle of the exhaust pipe 12, and the temperature of the exhaust gas and the catalyst temperature of the SCR catalyst 13. Reduce tg.
[0017]
An outside air introduction part 121 having a venturi part b that is reduced in diameter from other parts is formed in a part of the exhaust pipe 12, an air supply position g is set in the outside air introduction part 121, and the air pipe 27 is connected to the part g. The air inlet 271 is connected so as to open. As a result, the exhaust gas flow rate in the venturi part b is increased, and the air on the air pipe 27 side communicating with the outside air introduction part 121 is formed to be able to flow into the upstream side of the SCR catalyst 13 in the exhaust path E.
The air pipe 27 forms an outside air introduction passage ra, and is fitted with an outside air introduction valve 28 that controls the opening and closing of the outside air introduction passage ra. The outside air introduction valve 28 is a normally closed electromagnetic valve, and is connected to the exhaust system ECU 4.
[0018]
The exhaust system ECU 4 takes in the catalyst temperature tg from the catalyst temperature sensor 16 and introduces the outside air to the cooling means to reduce the exhaust gas temperature when the catalyst temperature tg is equal to or higher than a predetermined temperature, that is, an overheating temperature (for example, 650 ° C.) thα. The valve 28 is opened, air as a cooling medium flows into the air supply position g, and the exhaust gas temperature and the catalyst temperature tg of the SCR catalyst 13 are lowered.
Next, each control process of the engine ECU 3 and the exhaust system ECU 4 in FIG. 1 will be described along the control routines in FIGS. 2 and 3.
When the engine 1 is driven, the engine ECU 3 operates the fuel pressure control unit n1, the fuel discharge amount adjustment unit (not shown), and the fuel control unit n2, the fuel adjustment unit (not shown) according to the input value of each sensor. Each sensor output obtained at that time is also transmitted to the exhaust system ECU 4.
[0019]
On the other hand, the exhaust system ECU 4 repeats the main routine of FIG. 2 every predetermined control cycle simultaneously with turning on of the engine key. Here, the key-on is confirmed at step sa, the outside air introduction valve is initially set to be closed (off) at step sb, and the process proceeds to step sc.
In step sc, a catalyst temperature tg and other data are taken in, and it is determined whether or not it is an appropriate value. If it is not normal, a failure indicator lamp (not shown) is driven. If normal, the process proceeds to step sd. In step sd, a NOx purification process is performed. Thereafter, in step se, a catalyst cooling process is executed, and in step sf, other known control processes are executed, and the process returns.
Next, when the catalyst cooling process of step se is reached in the middle of the main routine of the exhaust system ECU 4, the catalyst cooling process routine of FIG. 3 is executed here.
[0020]
In step a1, it is determined whether or not the catalyst temperature tg is equal to or higher than a preset overheated temperature (for example, 550 ° C.) thα. When the temperature is lower than the overheating temperature th, the process proceeds to step a2, and the process proceeds to step a6. If Fc = 1 is not true, the process returns to the main routine.
[0021]
If the process proceeds to step a2 assuming that the overheated temperature thα has not been reached, it is determined whether or not the execution flag Fc = 1, that is, whether or not the catalyst cooling process is being executed. If the in-execution flag Fc = 1, the process returns to step a3. If the in-execution flag Fc = 1 is not satisfied, the process returns to the main routine. In step a3, it is determined whether or not the catalyst temperature tg is lower than a predetermined temperature (for example, 500 ° C.) taβ lower than a preset overheating temperature thα. Since the catalyst temperature has fallen, the outside air introduction valve is controlled to the closed side, and in step a5, the catalyst cooling process execution flag Fc is set to 0, and the process returns. If the catalyst is equal to or higher than the determination temperature taβ, the current routine is maintained and the process returns to the main routine.
[0022]
  Step a1 determines that the catalyst temperature tg is equal to or higher than the overheating temperature thα.a6Here, the outside air introduction valve is opened (ON), and the catalyst cooling process execution flag Fc is set to 1 in step a7, and the process returns. At this point, the catalyst metal on the catalyst carrier of the SCR catalyst 13 is at or above the overheating temperature thα, and if this state continues, there is a possibility that the catalyst metal will eventually begin to scatter.
  However, immediately after step a1, in step a6, the process for opening the outside air introduction valve 28 is started. For this reason, outside air is introduced from the venturi part b of the outside air introduction part 121 via the outside air introduction passage ra of the air pipe, and the outside air flowing into the exhaust passage E cools the catalyst and lowers the catalyst temperature tg. If the state where the outside air introduction valve 28 is opened continues, the catalyst temperature tg will eventually fall below the excessive temperature thα.
[0023]
At this time, the process proceeds from step a1 to step a3 via step a2. When the catalyst temperature tg is equal to or higher than the determination temperature taβ, the state in which the outside air flows into the exhaust path E from the air pipe is continued, and the process returns to the main routine. Become.
As described above, when the catalyst temperature tg is equal to or higher than a predetermined overheating temperature thα that is considered to be scattered by the metal supported on the catalyst carrier, the outside air introduction valve 28 is opened and the venturi portion b of the exhaust passage E is opened. Outside air can be easily introduced, the SCR catalyst 13 can be cooled, and deterioration of the catalyst can be prevented.
[0024]
The exhaust gas cooling device 11 of FIG. 1 includes an outside air introduction part 121 having a venturi part b as a cooling means, and an outside air introduction valve (on / off valve) 28 for controlling opening and closing of the outside air introduction passage ra. By opening 121, outside air is easily introduced into the venturi portion b of the exhaust passage E. Therefore, for example, even when the vehicle continues high-output operation and the exhaust gas temperature is excessively high, the catalyst can be cooled regardless of the operation state, and the catalyst carrier Scattering of the catalyst metal supported on the catalyst can be avoided in advance, and deterioration of the SCR catalyst 13 can be prevented.
[0025]
In the exhaust gas cooling device 11 of FIG. 1, the outside air introduction portion 121 that constitutes a main part of the cooling means is directly formed in the exhaust pipe 12, but instead of this, as shown in FIG. May be adopted.
The exhaust gas cooling device 11a shown in FIG. 4 forms a bypass passage EB in a part of the exhaust passage E, forms an outside air introduction portion 121a on the bypass passage EB, and an air pipe 27a at an air supply position g of the outside air introduction portion 121a. The air inlet 271a is connected so as to open. A shutter valve 29, which is an electromagnetic valve, is mounted between the branching portion d and the merging portion e of the exhaust passage E facing the bypass passage EB. The shutter valve 29 is a normally open valve and is connected to the exhaust system ECU 4a. The exhaust gas cooling device 11a is different from the exhaust gas cooling device 11 of FIG. 1 in that a bypass passage EB having an outside air introduction portion 121a is formed in the exhaust passage E, and a shutter valve 29 is provided in the exhaust passage E. Except for the difference in a part of a later-described catalyst cooling processing routine, the same configuration as that of the exhaust gas cooling device 11 of FIG.
[0026]
Here, the exhaust system ECU 4a of the exhaust gas cooling device 11a in FIG. 4 is compared with the exhaust system ECU 4 of the exhaust gas cooling device in FIG. 1, and the same control is performed in the main routine and the NOx purification processing routine in FIG. Since only a part of the catalyst cooling processing routine of No. 5 is different, the difference will be mainly described here.
In steps a1 to a3 and steps a6 'to a7' of the catalyst cooling processing routine of FIG. 5, the same control as in the catalyst cooling processing routine of FIG. 3 is performed. That is, when the catalyst temperature tg is equal to or higher than the overheated temperature thα, the process proceeds to step a6 ′, and when the catalyst temperature tg has not reached the overheated temperature thα, or has once exceeded the overheated temperature and then becomes less than the overheated temperature th. The process proceeds to step a2 to determine whether or not the execution flag Fc = 1, that is, whether or not the catalyst cooling process is being executed. If the in-execution flag Fc = 1, the process returns to step a3. If the in-execution flag Fc = 1 is not satisfied, the process returns to the main routine.
[0027]
When the catalyst temperature tg reaches the overheated temperature thα and reaches step a6 ′, the outside air introduction valve 28a is opened, the shutter valve 29 is closed, and the catalyst cooling process execution flag Fc is set to 1 in step a7 ′. And return.
The shutter valve 29 is opened at the initial setting of the main routine (step sb) and is closed here. As a result, the outside air rides on the exhaust gas flowing on the bypass passage EB via the outside air introduction passage ra of the air pipe 27a and flows into the SCR catalyst 13, whereby the catalyst temperature tg can be lowered.
[0028]
Note that instead of closing the shutter valve 29 in step a6 ', only a predetermined angle may be driven to the closing side.
[0029]
If the catalyst temperature tg reaches step a3 via step a2 assuming that the catalyst temperature tg has not reached the excessive temperature thα, it is determined here whether or not the catalyst temperature tg is lower than the determination temperature taβ. In step a4 ′, the outside air introduction valve 28a is controlled to the closed side and the shutter valve 29 is controlled to the open side, and the catalyst cooling process execution flag Fc is set to 0 in step a5 ′. To return. If the catalyst temperature tg is equal to or higher than the determination temperature taβ, the process returns to the main routine while maintaining the current state.
In the case of the exhaust gas cooling device 11a of FIG. 4, both the exhaust passage E and the bypass passage EB are opened during normal operation, and the same effect as the exhaust gas cooling device 11 of FIG. 1 can be obtained, in particular, the exhaust resistance can be reduced, Output reduction can be prevented.
[0030]
Although the exhaust gas cooling device 11 in FIG. 1 uses outside air as a cooling medium, an exhaust gas cooling device using cooling water as a cooling medium may be used instead.
In this case, the exhaust gas cooling device includes a heat exchanger that forms cooling means in a part of the exhaust path E, a cooling water control unit that controls the flow of water that is a cooling medium circulating in the heat exchanger, and an exhaust system ECU. Consists of
The exhaust system ECU of the exhaust gas cooling device in this case is different from the exhaust gas cooling device 11 of FIG. 1 except that the control of steps a4 and a5 in the catalyst cooling processing routine of FIG. 3 is different. Since the same control is performed, description of the control system is omitted here.
[0031]
That is, in the exhaust cooling device using the cooling water as a cooling medium, control is performed so that water is circulated in the heat exchanger instead of step a4 in FIG. 3 and water circulation is stopped instead of step a5.
In this exhaust gas cooling device, the same effect as the exhaust gas cooling device 11 of FIG. 1 can be obtained. In particular, since the exhaust gas is cooled by the cooling water, the cooling efficiency can be relatively increased.
FIG. 6 shows an exhaust gas purification apparatus for an internal combustion engine which is another embodiment of the present invention.
Here, the exhaust system 2 of the engine 1 includes a NOx purification device 9, a solidification cooling means 41, and a filter 42. In addition, the same code | symbol is attached | subjected to the member same as the member in FIG. 1 here, and duplication description is abbreviate | omitted.
[0032]
The NOx purification device 9 has the same configuration as that disclosed in FIG. 1, and includes a catalytic converter 18 and a urea water supply device 14 in which an SCR catalyst 13 is accommodated in an exhaust pipe 12, and these are similarly driven and controlled by an exhaust system ECU 4c. ing.
The filter 42 includes a substantially cylindrical filter casing 421, and a filter main body 422 is provided in the casing 421, and the filter main body 422 is supported without deviation through a seal member 423 in which a metal net is bundled.
[0033]
The filter main body 422 is made of ceramic and has a honeycomb structure in which a large number of passages j are arranged in parallel. The passages j adjacent to each other have different positions of the front and rear end closing plugs k. Thus, when the exhaust gas is moved from one to the other passage k, the catalyst metal solidified by the solidification cooling means 41 after being scattered from the SCR catalyst 13 in the exhaust gas can be collected. It is formed.
The solidification cooling means 41 is attached to the cooling part 121 c of the exhaust pipe 12 between the SCR catalyst 13 and the filter 42.
The cooling part 121c is formed with a venturi part m having a diameter smaller than that of the exhaust pipe 12 at another part, and is connected so that the air inlet 441 of the air pipe 44 is opened there. As a result, the exhaust gas flow velocity of the venturi part m is increased, and the air on the air pipe 44 side communicating with the cooling part 121c is formed to be able to flow into the exhaust path EC side.
[0034]
As described above, according to the exhaust gas purification apparatus of FIG. 6, even when the high load operation is continued and the exhaust gas temperature is excessively high, the outside air is introduced by the solidification cooling means 41. The catalyst metal scattered by cooling the exhaust gas can be solidified, and the catalyst metal solidified by the filter 42 can be collected, so that it is possible to avoid discharge to the atmosphere. The solidification cooling means 41 in FIG. 6 is formed directly on the exhaust pipe 12, but may be configured as shown in FIG. 7 instead.
[0035]
The solidification cooling means 41a shown in FIG. 7 forms a bypass passage EC in a part of the exhaust passage E downstream of the SCR catalyst 13 and upstream of the filter 42, and forms an outside air introduction part 121d on the bypass passage EC to introduce outside air. The air inlet 441 of the air pipe 44 is connected to the portion 121d so as to open. A shutter valve 29a driven by an electromagnetic valve 45 is mounted between the branching portion d and the merging portion e of the exhaust passage E in parallel with the bypass passage EC. The shutter valve 29a is a normally open valve, and the electromagnetic valve 45 is connected to the exhaust system ECU 4c.
Compared with the exhaust system ECU 4 of the exhaust gas cooling device of FIG. 1, the exhaust system ECU 4c controls the main routine and NOx purification processing routine of FIG. 2 in the same way, and instead of the catalyst cooling processing routine of FIG. The catalyst metal solidification processing routine shown is executed.
[0036]
In the main routine of FIG. 2 used here, step se ′, which is a catalyst metal solidification process, is executed instead of step se, and this point is also shown by a two-dot chain line in FIG.
In steps a1 to a3 and steps ah to a7 of the catalyst metal solidification processing routine of FIG. 8, the same control as that of the catalyst cooling processing routine of FIG. 3 is performed. That is, when the catalyst temperature tg is equal to or higher than the overheated temperature thα, the process proceeds to step ah, and when the catalyst temperature tg has not reached the overheated temperature thα, or has once exceeded the overheated temperature and then becomes less than the overheated temperature th. In step a2, it is determined whether or not the execution flag Fc = 1, that is, whether or not the exhaust gas cooling process is being executed. If the in-execution flag Fc = 1, the process returns to step a3. If the in-execution flag Fc = 1 is not satisfied, the process returns to the main routine.
[0037]
If the catalyst temperature tg exceeds the overheating temperature thα and the catalyst metal vaporized and scattered from the SCR catalyst 13 is mixed in the exhaust gas and reaches step ah, the shutter valve 29a is closed. As a result, the exhaust gas flows through the bypass path EC, and outside air is mixed into the exhaust gas on the exhaust path E via the air pipe to lower the exhaust gas temperature. Instead of closing the shutter valve 29a in step ah, it may be driven to the closing side only at a predetermined angle.
As a result, when the catalyst metal scattered from the SCR catalyst 13 is mixed in the exhaust gas, the catalyst metal can be cooled and solidified. When the solidified catalyst metal reaches the filter main body 422, it is collected when moving the ceramic wall portion, and the release of the catalyst metal scattered from the catalyst carrier to the atmosphere can be prevented.
[0038]
If the catalyst temperature tg has not reached the overheating temperature thα and reaches step a3 via step a2, it is determined whether or not the catalyst temperature tg is lower than the determination temperature taβ. Since the exhaust gas temperature is lowered by the exhaust gas cooling process, the shutter valve 29a is controlled to the valve opening side at step aj, and the execution flag Fc is set to 0 at step a5 and the process returns. If the catalyst temperature tg is equal to or higher than the determination temperature taβ, the current routine is held (shutter valve closed) and the process returns to the main routine.
[0039]
As described above, the solidification cooling means 41a constituting the main part of the exhaust gas purifying apparatus for the internal combustion engine of FIG. 7 includes the outside air introduction part 121d having the venturi part m, and the shutter valve 29a for closing the exhaust path E. By closing the exhaust passage E with 29a, outside air can be easily introduced from the venturi portion m of the exhaust passage E. For this reason, for example, even when the high output operation is continued and the exhaust gas temperature is excessively high, the exhaust gas and the vaporized gas mixed therein are vaporized regardless of the operation state. The catalyst metal that has been cooled can be solidified by cooling, and the solidified catalyst metal can be collected by the filter main body 422 so as to avoid discharge to the atmosphere.
The solidification cooling means 41a constituting the main part of the exhaust gas purifying apparatus for the internal combustion engine of FIG. 7 is the outside air, and solidifies the catalyst metal mixed in the exhaust gas. Solidification cooling means may be used.
[0040]
The solidification cooling means includes a heat exchanger disposed in a part of the exhaust passage E, a cooling water control unit that controls the flow of water, which is a cooling medium circulating in the heat exchanger, using an exhaust system ECU, Consists of
[0041]
In the solidification cooling means here, the other parts except for step ah and step aj in the catalyst metal solidification processing routine of FIG. 8 used in the solidification cooling means 41a of FIG. 7 are used for control in the same manner. Thus, here, only the steps ah and aj will be described while avoiding redundant explanation.
[0042]
  That is, in the exhaust cooling device using the cooling water as a cooling medium, FIG.Step a hInstead of circulating water in the heat exchanger,Step a jInstead of controlling the water circulation.
[0043]
This solidification cooling means can obtain the same effects as the solidification cooling means 41 of FIG. 7, and in particular, the exhaust gas and the vaporized catalytic metal mixed therein are cooled with cooling water, so the cooling efficiency is compared. Can be large.
FIG. 9 shows an exhaust gas purifying device for an internal combustion engine which is another embodiment of the present invention.
The exhaust gas purifying apparatus here includes the NOx purifying apparatus 9 and the exhaust gas cooling apparatus 11 similar to those shown in FIG. 1 in the exhaust system 2, and further, the solidification cooling means 41 a and the filter shown in FIG. 42 is provided. Here, the same members as those in FIG. 1 and FIG. 7 are denoted by the same reference numerals, and redundant description is omitted.
[0044]
Here, the NOx purification device 9, the exhaust gas cooling device 11, and the solidification cooling means 41a of the exhaust gas purification device are controlled by the exhaust system ECU 4e.
The exhaust system ECU 4e in FIG. 9 executes the main routine in FIG.
Here, the exhaust system ECU 4e repeats the main routine of FIG. 10 every predetermined control cycle simultaneously with the turning on of the engine key. In step sc from step sa, as in the main routine of FIG. 2, key-on is confirmed, in step sb the outside air introduction valve 28 is closed (off), and the cooling water pump 48 is initialized to off. If it is not normal, a failure indicator lamp (not shown) is driven, and if normal, the process proceeds to step sd.
In step sd, the same NOx purification process as described above is performed. Thereafter, in step se, the same catalyst cooling process as described in FIG. 3 is performed, and then in step sf, the same solidification cooling means 41a as shown in FIG. , The catalyst metal solidification processing routine of FIG. 8 is executed, other known control processing is executed at step sg, and the process returns.
[0045]
9, the urea gas is added to the SCR catalyst 13 so that ammonia is used as a reducing agent, and the SCR catalyst 13 can purify NOx in the exhaust gas with high efficiency. Moreover, the exhaust gas cooling device 11 However, by opening the outside air introduction part 121 with the outside air introduction valve 28, the catalyst can be cooled regardless of the driving state of the vehicle, the scattering of the catalyst metal can be avoided, and the solidification cooling means 41a closes the shutter valve 29a. In this case, outside air is introduced regardless of the driving state of the vehicle, the exhaust gas and the vaporized catalyst metal mixed therein are cooled and solidified, and the solidified catalyst metal is collected by the filter body 422. Emissions can be avoided in advance.
[0046]
The exhaust gas may be cooled using a heat exchanger using cooling water as a cooling medium instead of the solidification cooling means 41a for introducing outside air in the above embodiment. Furthermore, instead of the solidification cooling means 41a, the solidification cooling means 41 shown in FIG. 6 that does not have the bypass EC and the shutter valve 29a may be used.
In the above description, the case where the NOx purification device 9 is provided in the exhaust system 2 has been described. However, the present invention is not limited to this, and the exhaust system is replaced with the NOx purification device 9 and stores NOx containing alkali metal. Even when a catalyst or a three-way catalyst is provided, the present invention can be similarly applied, and similar effects can be obtained.
[0047]
【The invention's effect】
  As described above, according to the present invention, the metal supported on the catalyst carrier is scattered.However, the metal scattered by the solidification cooling means provided on the downstream side of the catalyst can be solidified and then collected by the filter provided on the downstream side of the solidification cooling means. It is possible to prevent the released metal from being discharged into the exhaust.
[0049]
  Claim 2Since the cooling means operates to cool the catalyst when the catalyst temperature or the exhaust gas temperature at which the metal supported on the catalyst carrier is considered to scatter is higher than a predetermined temperature, the metal supported on the catalyst carrier Even if the metal carried on the catalyst carrier is scattered, the metal scattered by the solidification cooling means provided on the downstream side of the catalyst is solidified and then the downstream side of the cooling means for solidification. Therefore, it is possible to reliably prevent the metal scattered from the catalyst carrier from being discharged into the exhaust gas.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a NOx purification device and an engine equipped with the NOx purification device as one embodiment of the present invention.
FIG. 2 is a flowchart of a main routine used by the exhaust system ECU of FIG.
FIG. 3 is a flowchart of a catalyst cooling processing routine used by the exhaust system ECU of FIG.
4 is a schematic configuration diagram of another exhaust gas cooling device as a modification of the exhaust gas cooling device of the NOx purification device of FIG. 1. FIG.
5 is a flowchart of a catalyst cooling process routine performed by an exhaust system ECU in the exhaust gas cooling device of FIG. 4;
FIG. 6 is a schematic configuration diagram of a NOx purification device and an engine equipped with the NOx purification device as another embodiment of the present invention.
7 is a schematic configuration diagram of another exhaust gas cooling device as a modified example of the exhaust gas cooling device of the NOx purification device of FIG. 6. FIG.
8 is a flowchart of a catalyst metal solidification processing routine performed by an exhaust system ECU in the exhaust gas cooling device of FIG.
FIG. 9 is a schematic configuration diagram of a NOx purification device and an engine equipped with the NOx purification device as another embodiment of the present invention.
FIG. 10 is a flowchart of a main routine used by the exhaust system ECU of FIG.
[Explanation of symbols]
1 engine
2 Exhaust system
4-4e Exhaust system ECU
11-11b Exhaust gas cooling device
13 SCR catalyst (NOx catalyst)
14 Urea water supply device
16 Catalyst temperature sensor
tg catalyst temperature
thα Overtemperature (predetermined temperature)

Claims (2)

A catalyst provided in the exhaust system of the internal twisting engine,
A cooling means for solidification that is provided in the exhaust system downstream of the catalyst and solidifies the metal scattered from the catalyst by reducing the exhaust gas temperature;
A filter that is provided in the exhaust system downstream of the cooling means and collects metal scattered from the catalyst;
An exhaust gas purification device for an internal combustion engine, comprising: A catalyst provided in the exhaust system of the internal twisting engine,
A catalyst temperature detecting means for detecting or estimating a catalyst temperature of the catalyst or a parameter correlated with the catalyst temperature;
A cooling means for cooling the exhaust gas provided in the exhaust system upstream of the catalyst;
A cooling means for solidification that is provided in the exhaust system downstream of the catalyst and solidifies the metal scattered from the catalyst by reducing the exhaust gas temperature;
A filter that is provided in the exhaust system downstream of the solidification cooling means and collects metal scattered from the catalyst;
Control means for controlling the operation of the cooling means to reduce the exhaust gas temperature when the catalyst temperature or the exhaust gas temperature detected or estimated by the catalyst temperature detection means is equal to or higher than a predetermined temperature;
An exhaust gas purification device for an internal combustion engine, comprising:

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