WO2006041223A1 - 内燃機関の排気浄化システム - Google Patents
内燃機関の排気浄化システム Download PDFInfo
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- WO2006041223A1 WO2006041223A1 PCT/JP2005/019357 JP2005019357W WO2006041223A1 WO 2006041223 A1 WO2006041223 A1 WO 2006041223A1 JP 2005019357 W JP2005019357 W JP 2005019357W WO 2006041223 A1 WO2006041223 A1 WO 2006041223A1
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- Prior art keywords
- fuel ratio
- air
- reducing agent
- catalyst
- nox
- Prior art date
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
- B01D53/9431—Processes characterised by a specific device
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/011—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more purifying devices arranged in parallel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/20—Reductants
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Definitions
- the present invention relates to an exhaust gas purification system for an internal combustion engine.
- the exhaust gas of an internal combustion engine usually contains ⁇ ⁇ , which is bright and harmful. For this reason, in order to purify ⁇ in the exhaust, a ⁇ ⁇ ⁇ catalyst is provided in the exhaust system of the internal combustion engine.
- a ⁇ ⁇ ⁇ catalyst is provided in the exhaust system of the internal combustion engine.
- fuel as a reducing agent is supplied to the NOx storage reduction catalyst so that NOx stored in the catalyst is reduced and released (hereinafter referred to as “NOx reduction treatment”).
- NOx reduction treatment fuel as a reducing agent is supplied to the NOx storage reduction catalyst so that NOx stored in the catalyst is reduced and released
- S Ox poisoning that degrades the purification performance occurs.
- SOx poisoning recovery process fuel as a reducing agent is supplied to the NOx storage reduction catalyst (hereinafter referred to as “SOx poisoning recovery process”).
- the amount of NOx accumulated in the NOx catalyst should be reduced, the amount of exhaust gas flowing through the NOx catalyst is reduced and a reducing agent is supplied when a predetermined elapsed time has passed.
- Techniques to do this have been proposed.
- the oxygen concentration in the exhaust gas discharged from the NOx catalyst when the reducing agent is supplied and detected is detected by an oxygen concentration sensor, and the peak value generated in the oxygen concentration matches the target value.
- a technique for obtaining a high purification rate by correcting the elapsed time has been proposed (see, for example, Japanese Patent Application Laid-Open No. 20 04- 5 26 03).
- An object of the present invention is to reduce the amount of exhaust gas flowing into the NOx storage reduction catalyst and reduce the NOx stored in the NOx catalyst by supplying a reducing agent to the NOx catalyst.
- a technique capable of performing the NOx reduction treatment more reliably is provided.
- the present invention provides air-fuel ratio detection means upstream and downstream of the Ox storage reduction catalyst to reduce the amount of exhaust gas flowing into the NOx catalyst and reduce the exhaust gas into the exhaust gas. Between the air-fuel ratio detected by the air-fuel ratio detecting means arranged upstream of the NOx catalyst and the air-fuel ratio detected by the air-fuel ratio detecting means arranged downstream in the predetermined period after the addition of the agent.
- the greatest feature is to change the addition time of the reducing agent so that the difference becomes a predetermined target value.
- an NOx storage reduction catalyst that is disposed in the exhaust passage of the internal combustion engine and purifies NOx in the exhaust
- a reducing agent adding means that is disposed upstream of the NOx storage reduction catalyst in the exhaust passage and adds a reducing agent into the exhaust;
- An exhaust amount reducing means for reducing the amount of exhaust flowing into the NOx storage reduction catalyst
- the reducing agent adding means adds the reducing agent into the exhaust gas while reducing the exhaust amount flowing into the NOx storage reduction catalyst at least by the exhaust amount reducing means.
- a downstream air-fuel ratio detecting means that is disposed downstream of the NOx catalyst and detects the air-fuel ratio of the exhaust and further comprising:
- the reducing agent addition time by the reducing agent adding means is changed so that the difference between the two values becomes a predetermined target value. .
- the air-fuel ratio detecting means are arranged upstream and downstream of the NOx storage reduction catalyst, and the amount of exhaust gas flowing into the NOx catalyst is reduced by the exhaust amount reducing means.
- the reducing agent is added to the exhaust gas to perform the NOx reduction treatment of the NOx catalyst, the amount of exhaust gas flowing into the NOx catalyst is reduced with the operation of the exhaust amount reducing means.
- the reducing agent added by the reducing agent addition means is dispersed in the NOx catalyst, and NOx near the dispersion position is reduced.
- the reducing agent added from the reducing agent-added calorie means is biased toward the upstream portion or the downstream portion of the NOx catalyst.
- the difference in the air-fuel ratio between the upstream and downstream of the NOx catalyst increases while the amount of exhaust gas entering the NOx catalyst is reduced.
- the reducing agent ' is dispersed in the upstream portion of the NOx catalyst, the air / fuel ratio upstream of the NOx catalyst becomes low and the air / fuel ratio downstream becomes high.
- the reducing agent is unevenly distributed in the downstream portion of the N Ox catalyst, the air-fuel ratio downstream of the N Ox catalyst becomes low, and the air-fuel ratio upstream becomes high.
- the amount of exhaust flowing into the NOx storage reduction catalyst is reduced, and a reducing agent is added to the exhaust by the reducing agent adding means to perform NOx reduction treatment of the NOx catalyst.
- the upstream air-fuel ratio detection means disposed upstream of the NOx catalyst and downstream of the reducing agent addition means, and the exhaust passage.
- a downstream air-fuel ratio detecting means disposed downstream of the NOx catalyst, and the upstream air-fuel ratio detecting means in a predetermined period after adding the reducing agent by the reducing agent adding means. Addition of the reducing agent by the reducing agent adding means so that the difference between the detected value of the air-fuel ratio and the value of the air-fuel ratio detected by the downstream air-fuel ratio detecting means becomes a predetermined target value. We decided to change the time.
- the dispersion method of the reducing agent added from the reducing agent addition means is appropriately changed. can do.
- the reducing agent can be dispersed so that the NOx in the NOx catalyst can be more efficiently reduced, and the NOx reduction treatment in the NOx catalyst can be more reliably performed.
- the reducing agent is made substantially uniform around the center of the N Ox catalyst during the period in which the amount of exhaust gas flowing into the N Ox catalyst is reduced. Can be dispersed. By doing so, the NOx reduction treatment can be more reliably performed on the entire NOx catalyst.
- the exhaust gas further includes a bypass passage for bypassing the NOx storage reduction catalyst to the exhaust gas, and the exhaust amount reducing means controls the amount of exhaust gas passing through the bypass passage.
- the valve reduces the storage reduction type NOx catalyst to the storage reduction type NOx catalyst. Even if it is possible to make it the flow stop period when the amount of exhaust flowing in is substantially minimized.
- the exhaust gas further includes a bypass passage for bypassing the NOx storage reduction catalyst to the exhaust gas, and the exhaust gas flowing into the NOx catalyst by controlling the amount of exhaust gas passing through the bypass passage by the exhaust gas reduction means.
- the valve reduces the chapter, the amount of exhaust gas flowing into the NOx catalyst can be reduced by simple control of opening and closing the valve. Then, by the pulp, the NOx catalyst is bypassed to almost all of the exhaust gas of the internal combustion engine, and the exhaust gas flows into the NOx catalyst by passing through the bypass passage. be able to. In this way, when the amount of exhaust gas flowing into the NOx catalyst is reduced, the distribution of the reducing agent added by the reducing agent adding means in the NOx catalyst can be controlled more easily.
- the reducing agent added by the reducing agent addition means can be made substantially stationary in the N Ox catalyst.
- the amount of exhaust gas flowing into the NOx catalyst may be substantially minimized within the valve performance range.
- “substantially minimum” is synonymous with “zero”.
- the reducing agent is set so that a difference between the air-fuel ratio value detected by the upstream air-fuel ratio detection means and the air-fuel ratio value detected by the downstream air-fuel ratio detection means becomes a predetermined target value.
- the air-fuel ratio value detected by the upstream air-fuel ratio detecting means and the air-fuel ratio value detected by the downstream air-fuel ratio detecting means are detected.
- the predetermined period as a flow stop period in which the amount of exhaust gas flowing into the NOx storage reduction catalyst by the pulp is substantially minimized.
- the moving speed of the reducing agent added from the reducing agent addition means is substantially minimized, so that the air-fuel ratio in the period that most affects the NOx reduction treatment can be detected.
- NOx It is possible to control the dispersion of the reducing agent during the period that most affects the reduction treatment.
- the amount of exhaust gas flowing into the NOx catalyst is substantially minimized (substantially zero except for leakage from the valve) by fully closing the pulp. It may be a period of time.
- the bypass passage may be an exhaust pipe that simply connects the N Ox catalyst in the exhaust passage between the upstream side and the downstream side, and in the middle of the exhaust passage, a storage reduction type NOx catalyst or the like may be used.
- a second NOx catalyst may be provided.
- the amount of exhaust gas passing through the bypass passage is increased and the NOx in the exhaust gas is purified by the second NOx catalyst
- the amount of exhaust gas passing through the bypass passage is reduced and the NOx catalyst in the exhaust gas is purified by the NOx catalyst. Good.
- the exhaust gas detected by the upstream air-fuel ratio detection means may be determined that the flow is stopped when the change in the air-fuel ratio is equal to or less than a predetermined change amount.
- the reducing agent added from the reducing agent addition means is the upstream air-fuel ratio detection means. Pass through the neighborhood. After that, when the reducing agent moves further downstream and reaches the vicinity of the NOx catalyst, the amount of exhaust gas flowing into the NOx catalyst becomes substantially zero, and the reducing agent is substantially stationary at that position. To do.
- the valve operation is performed so that the amount of exhaust gas flowing into the NOx catalyst becomes substantially zero when the reducing agent added from the reducing agent addition means reaches the NOx catalyst.
- the relationship between the speed and the addition timing of the reducing agent from the reducing agent adding means is preset. .
- the air-fuel ratio detected by the upstream air-fuel ratio detection means once suddenly decreases when the reducing agent passes in the vicinity of the upstream air-fuel ratio detection means, When the reducing agent reaches the NOx catalyst, it becomes higher again. After that, the amount of gas flowing into the N0x catalyst is stabilized by being substantially zero. That is, there is a high relationship between the change in the air-fuel ratio detected by the upstream air-fuel ratio detection means and the amount of exhaust flowing into the NOx catalyst.
- the amount of the exhaust reducing agent flowing into the NOx catalyst becomes substantially zero, that is, the flow You may judge that it is a stop time. Then, it is not necessary to provide a means for directly detecting the amount of exhaust gas flowing into the NOx catalyst, and the start of the flow stop timing can be detected by a simple method.
- the value of the change in the air-fuel ratio of the exhaust gas detected by the upstream air-fuel ratio detection means is equal to or less than a predetermined change amount
- the air-fuel ratio detected by the upstream air-fuel ratio detection means is The flow stop period may be determined when the value of the fuel ratio is equal to or lower than the predetermined air-fuel ratio. That is, when the flow stop timing is determined only when the value of the change in the air-fuel ratio of the exhaust gas detected by the upstream air-fuel ratio detection means is less than or equal to a predetermined change amount, it is added from the reducing agent addition means. There is a risk that the flow of the reducing agent will be determined as the flow stop timing with the time before passing the vicinity of the upstream air-fuel ratio detection means. On the other hand, before and after the reducing agent is added from the reducing agent adding means, the upstream air-fuel ratio detecting means Therefore, it is known that the detected air-fuel ratio value is completely different.
- the flow stop period is determined more accurately. Judgment can be made.
- the time from the start of the operation of the exhaust gas reduction means until the amount of exhaust gas flowing into the NOx catalyst becomes substantially zero is experimentally obtained in advance.
- the flow stop period may be determined when the experimentally determined time has elapsed since the start of the operation of the exhaust amount reducing means.
- the value of the air-fuel ratio detected by the upstream air-fuel ratio detection means and the downstream air-fuel ratio detection means in the 0 predetermined period after adding the reducing agent by the reducing agent addition means The air-fuel ratio value detected by the upstream air-fuel ratio detecting means and the downstream air-fuel ratio detecting means when the difference from the air-fuel ratio value detected by the above becomes substantially the target value.
- the amount of reducing agent added by the reducing agent adding means may be changed so that the value of the air / fuel ratio becomes a predetermined target air / fuel ratio.
- the value of the air-fuel ratio detected by the upstream air-fuel ratio detection means and the downstream air-fuel ratio in a predetermined period after the reducing agent is added by the reducing agent addition means
- the reducing agent addition time by the reducing agent adding means so that the difference from the air-fuel ratio value detected by the detecting means becomes a predetermined target value
- the dispersion of the reducing agent in the NOx catalyst is reduced.
- the air-fuel ratio value detected by the upstream air-fuel ratio detection means and the air-fuel ratio value detected by the downstream air-fuel ratio detection means are the target values in the NOx reduction process. It may be out of the air-fuel ratio value.
- the value of the air-fuel ratio detected by the upstream air-fuel ratio detection means in a predetermined period of 0 after adding the reducing agent by the reducing agent addition means The value of the air-fuel ratio detected by the upstream air-fuel ratio detecting means when the difference from the value of the air-fuel ratio detected by the downstream air-fuel ratio detecting means becomes substantially the predetermined target value, and the The amount of reducing agent added by the reducing agent adding means is changed so that the value of the air fuel ratio detected by the downstream air fuel ratio detecting means becomes a predetermined target air fuel ratio.
- the air-fuel ratio value detected by the upstream air-fuel ratio detection means and the air-fuel ratio value detected by the downstream air-fuel ratio detection means are the target air-fuel ratio in the NOx reduction process.
- the amount of the reducing agent added from the reducing agent adding means is appropriate, the reducing agent added from the reducing agent adding means is There may be cases of excessive concentration in the central part. In such a case, the number of reducing agents added from the reducing agent addition means is increased without increasing the amount of reducing agent added from the reducing agent addition means, or You may make it add a reducing agent by reducing the addition rate of the reducing agent added from a reducing agent addition means.
- the reducing agent can be more uniformly dispersed throughout the NOx catalyst.
- the NOx reduction treatment can be satisfactorily performed on the entire NOx catalyst.
- a plurality of the storage reduction type NOx catalysts are arranged in series in the exhaust passage, and the upstream air-fuel ratio detection means is arranged upstream of the plurality of storage reduction type NOx catalysts.
- the downstream air-fuel ratio detection means is disposed downstream of the plurality of storage reduction type NOx catalysts, and during the NOx reduction treatment, the reduction required for each catalyst among the plurality of storage reduction type NOX catalysts.
- the predetermined target value may be set according to the dosage.
- the air-fuel ratio upstream of the NOx catalyst becomes low, and The air-fuel ratio becomes high.
- the air-fuel ratio downstream of the NOx catalyst is low.
- the upstream air-fuel ratio becomes higher.
- the value of the air-fuel ratio detected by the upstream air-fuel ratio detection means and the downstream air-fuel ratio detection means is changed by changing the addition timing of the reducing agent added from the reducing agent addition means so that the difference from the value of the air-fuel ratio detected by the above becomes a desired value. Can be changed.
- the plurality of storage reduction type NOx catalysts when NOx reduction treatment is performed on a plurality of storage reduction type NOx catalysts arranged in the exhaust passage, the plurality of storage reduction type NOx catalysts
- the predetermined target value was changed according to the amount of reducing agent required for each catalyst. For example, when the amount of reducing agent required in the upstream NOx catalyst is larger than the amount of reducing agent required in the downstream NOx catalyst, the center of dispersion of the reducing agent during the flow stop period Change the target value so that is on the upstream side.
- the dispersion of the reducing agent during the flow stop period is changed so that the center of is on the downstream side.
- the entire NOx catalyst can be satisfactorily reduced. Processing can be performed. Further, by performing the same control, when one long N Ox catalyst is provided in the exhaust passage, the amount of reducing agent required by each part of the N Ox catalyst in the N Ox reduction process is different. However, the NOx reduction treatment can be performed satisfactorily for the entire NOx catalyst.
- FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its exhaust system and control system in Embodiment 1 of the present invention.
- FIG. 2 is a time chart showing opening / closing of the first valve, ON / OFF of the first reducing agent addition valve, and the amount of exhaust gas flowing into the first NOx catalyst in Example 1 of the present invention. is there.
- FIG. 3A shows the air-fuel ratio upstream of the first NOx catalyst when the fuel added from the first reducing agent addition valve is unevenly distributed in the upstream part of the INOx catalyst. It is the graph which showed change of.
- FIG. 3B is a graph showing the change in the air-fuel ratio downstream of the first NOx catalyst in the same case.
- FIG. 4A shows the air-fuel ratio upstream of the first NOx catalyst when the fuel added from the first reducing agent addition valve is unevenly distributed in the downstream part of the INOx catalyst. It is the graph which showed change of.
- FIG. 4B is a graph showing the change in the air-fuel ratio downstream of the first NOx catalyst in the same case.
- FIG. 5 is a flowchart showing the NOx reduction processing routine in the first embodiment of the present invention.
- FIG. 6 is a flowchart showing an exhaust amount reduction period correction routine in Embodiment 1 of the present invention. .
- FIG. 7 is a flow chart showing the NOx reduction processing routine in Embodiment 2 of the present invention.
- FIG. 8 is a time chart regarding the opening and closing of the first valve, the ON / OFF of the first reducing agent addition valve, and the amount of exhaust gas flowing into the first NOx catalyst in Example 2 of the present invention.
- FIG. 9 is a diagram showing a schematic configuration of the internal combustion engine and its exhaust system and control system in Embodiment 3 of the present invention.
- FIG. 10 is a flow chart showing a NOx reduction processing routine in Embodiment 3 of the present invention.
- FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine according to this embodiment and its exhaust system and control system.
- the inside of the internal combustion engine 1 and its intake system are omitted.
- an internal combustion engine 1 includes an exhaust pipe 5 through which exhaust from the internal combustion engine 1 flows.
- This exhaust pipe 5 is connected downstream to a muffler (not shown).
- the exhaust pipe 5 is branched into a first branch passage 10a and a second branch passage 10b on the way, and the first branch passage 10a and the second branch passage 1Ob merge downstream.
- the first branch passage 10a is provided with a first NOx catalyst 1 1a for storing and reducing NOx in the exhaust
- the second branch passage 10b is also provided with the second NOx catalyst 1 1b. Is provided.
- a first valve 12a for controlling the amount of exhaust gas passing through the first branch passage 10a is provided upstream of the first and NOx catalysts 11a in the first branch passage 10a.
- a second valve 12b is provided upstream of the second NOx catalyst 11b in the second branch passage 1Ob.
- the first valve 12a and the second valve 12b described above correspond to the exhaust amount reducing means in this embodiment.
- the first fuel addition valve 13a for adding the fuel to the exhaust and the first upstream air-fuel ratio sensor 14a for detecting the air-fuel ratio of the exhaust upstream of the first NOx catalyst 11a are provided in parallel from the upstream side. It has been.
- the second fuel addition valve 13b and the second upstream air-fuel ratio sensor 14a are upstream between the second valves 1 and 2b and the second NOx catalyst 1 1.b in the second branch passage 10b. It is provided side by side.
- a first downstream air-fuel ratio sensor 15 a for detecting an air-fuel ratio of exhaust gas downstream of the first NOx catalyst 1 1 a is located downstream of the first NOx catalyst 1 1 a in the first branch passage 10 a. Is provided.
- a second downstream air-fuel ratio sensor 15 b that detects the air-fuel ratio of the exhaust downstream of the second NOx catalyst 11 b is located downstream of the second NOx catalyst 11 b in the second branch passage 10 b. Is provided.
- the first upstream air-fuel ratio sensor 14a and the second upstream air-fuel ratio sensor 14b constitute upstream air-fuel ratio detection means in the present embodiment.
- first downstream air-fuel ratio sensor 15 a and the second downstream air-fuel ratio sensor 15 b constitute downstream air-fuel ratio detection means in this embodiment.
- first reducing agent addition valve 13a and the second reducing agent addition valve 13 constitute the reducing agent addition means in this embodiment.
- the internal combustion engine 1 configured as described above and its exhaust system include an electronic control unit (ECU) for controlling the internal combustion engine 1 and the exhaust system.
- Unit) 35 is attached.
- the ECU 35 controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request, as well as the first NOx catalyst 1 1a and the second N Ox catalyst 1 of the internal combustion engine 1. This unit performs control related to NOx reduction treatment for 1b.
- the ECU 35 includes a sensor for controlling the operating state of the internal combustion engine 1 such as a crank position sensor and an accelerator position sensor (not shown), a first upstream air-fuel ratio sensor 14 a, and a second upstream air-fuel ratio sensor 14 b.
- the first downstream air-fuel ratio sensor 15 a and the first downstream air-fuel ratio sensor 15 b are connected via electrical wiring, and their output signals are input to the ECU 35.
- a fuel injection valve (not shown) in the internal combustion engine 1 is connected to the ECU 35 via an electrical wiring, and the first valve 12a, the second valve 12b, and the first The reducing agent addition valve 13 a and the second reducing agent addition valve 13 b are connected via electric wiring and are controlled by the ECU 35.
- the ECU 35 includes a CPU, a ROM, a RAM, and the like.
- the ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data.
- NOx reduction processing routine for reducing and releasing NOx occluded in 1 lb of the 1st NOx catalyst 1 1a and 2nd NOx catalyst 1 Is one of the programs stored in. ,
- FIG. 2 is used to explain the operation of the first reducing agent addition valve 13 a and the change in the amount of exhaust gas flowing into the first NOx catalyst 11 a.
- FIG. 2 is a time chart showing the opening / closing of the first valve 12a, the ON-OF F of the first reducing agent addition valve 13a, and the amount of exhaust gas flowing into the first NOx catalyst 11a. The axis is time.
- the ECU 35 issues a fully closed operation command to the first valve 12a, and a fully open operation command to the second valve 12b. It is. As a result, substantially the entire amount of the exhaust gas passing through the exhaust pipe 5 passes through the second branch passage 10b. Therefore, as shown in FIG. 2, after the first valve is fully closed, the amount of exhaust gas flowing into the first NOx catalyst 11a decreases, and the first valve 12a Except for leakage, it becomes almost zero.
- the ECU 35 issues a fully open operation command to the first valve 12a, and releases the fully open operation command of the second valve 12b.
- the amount of exhaust gas flowing into the first INOx catalyst 11a begins to increase, and becomes the same value as before the NOx reduction treatment.
- the first valve 12 a After the first valve 12 a is fully closed and the amount of exhaust gas flowing into the first INOx catalyst 1 1 a becomes substantially zero, the first valve 12 a starts to fully open, and the first INOx catalyst 1 1 The period until the amount of exhaust flowing into a begins to increase is called the “flow stop period”.
- the valve closing speed of the first valve 12a, or the delay time ⁇ varies, the fuel added from the first reducing agent addition valve 13 3a
- the upstream portion of the first INOx catalyst 1 1 a is not dispersed uniformly in the first INOx catalyst 1 1 a. Or, it may be distributed in a state of being biased to the downstream part.
- the delay time ⁇ is too short, the first reducing agent addition valve 1 3 a force and the added fuel will move longer before the flow stop period, so the fuel will be in the flow stop period At that time, it will disperse in the downstream part of the first INOx catalyst 11a.
- the delay time ⁇ is too long, the travel distance before the stop period of the flow of the fuel added from the first reducing agent addition valve 1 3 a becomes shorter, so the fuel is contained in the first INOx catalyst 1 1 a. It will be disperse in the upstream part. As a result, the NOx occluded over the entire INOx catalyst 11a may not be sufficiently reduced.
- the fuel added from the first reducing agent addition valve 13a is unevenly distributed in the upstream portion in the first NOx catalyst 11 1d. It is known that the air-fuel ratio upstream of the first INOx catalyst 11a is lower than the air-fuel ratio downstream. Similarly, when the fuel added from the first reducing agent addition valve 13a is unevenly distributed in the downstream portion in the first INOx catalyst 11a, the fuel of the first INOx catalyst 11a It has been found that the downstream air-fuel ratio is lower than the upstream air-fuel ratio.
- FIG. 3A shows the case where the fuel added from the first reducing agent addition valve 1 3 a is dispersed upstream in the upstream portion of the first INOx catalyst 1 1 a and upstream of the first INOx catalyst 11 a.
- 3 is a graph showing changes in air-fuel ratio.
- FIG. 3B is a graph showing the change in the air-fuel ratio in the downstream of the INOx catalyst 11a in the same case.
- the vertical axis indicates the air-fuel ratio
- the horizontal axis indicates the time from the start to the end of the approximate NOx reduction process.
- the value of the air-fuel ratio required for the N0x reduction process is indicated by a broken line as the target air-fuel ratio.
- the air-fuel ratio in the downstream of the INOx catalyst 11a is higher than the target air-fuel ratio in substantially the entire flow stop period. After the end of the flow stop period, the air-fuel ratio downstream of the first INOx catalyst 11a once suddenly decreases and is immediately recovered. This is because the fuel added from the first reducing agent addition valve 13a disperses in the upstream part of the first INOx catalyst 11a and is distributed downstream of the first INOx catalyst 11a.
- the first INOx catalyst 1 1 This is because the fuel dispersed in the upstream portion in a passes downstream of the INOx catalyst 11a.
- FIG. 4A shows the upstream of the INOx catalyst 11a when the fuel added from the first reducing agent addition valve 13a is dispersely distributed 5 on the downstream side in the INOx catalyst 11a.
- 6 is a graph showing changes in the air-fuel ratio at.
- FIG. 4B is a graph showing changes in the air-fuel ratio downstream of the first INOx catalyst 11a in the same case.
- the 0th INOx The air-fuel ratio upstream of the catalyst 11a once becomes extremely low before the flow stop period, and then continues to be higher than the target air-fuel ratio for substantially the entire flow stop period. This is because the fuel added from the first reducing agent addition valve 13a passes upstream of the first INOx catalyst 11a before the flow stop period and reaches the downstream side portion in the first INOx catalyst 11a. During the flow stoppage period, the fuel is not distributed much upstream of the first NOx catalyst 11a because it is distributed in the downstream part of the first INOx catalyst 11a. .
- the air-fuel ratio in the downstream of the INOx catalyst 11a is lower than the target air-fuel ratio throughout the flow stop period. This is because the fuel added from the first reducing agent addition valve 13a is zero in the flow stop period! : This is because it is unevenly distributed in the downstream portion of the first INOx catalyst 11a.
- the characteristics of the upstream and downstream air-fuel ratios of the first NOx catalyst 11a as described above are utilized, and the first INOx catalyst is detected by the upstream air-fuel ratio sensor 14a and the downstream air-fuel ratio sensor 15a.
- the first reducing agent is added during the flow stop period.
- the fuel added from the valve 13a was uniformly dispersed in the first INOx catalyst 11a.
- FIG. 5 shows the NOx reduction processing routine in this embodiment.
- This routine is a program stored in the ROM of the ECU 35, and is executed when the NOx reduction process start condition is satisfied.
- This NOx reduction treatment start condition is the same as the previous NOx reduction treatment. It may be specified that the operating time of the internal combustion engine 1 or the mileage of the vehicle after the control exceeds the threshold value, or the NOx concentration detected downstream of the first INOx catalyst 1 la exceeds the threshold value May be defined as satisfying.
- the air-fuel ratio upstream and downstream of the first NOx catalyst 11a is detected. Specifically, the output value AFU of the first upstream air-fuel ratio sensor 14a and the output value AFL of the first downstream air-fuel ratio sensor 15a are detected by taking them into the ECU 35.
- the air-fuel ratio difference value A FS is a value obtained experimentally in advance, and if the absolute value of the difference between the air-fuel ratio upstream and downstream of the NOx catalyst is less than this value, it is added from the reducing agent addition valve. It is the difference value as a threshold value that can be judged that the burned fuel is dispersed around the center of the NOx catalyst during the flow stop period.
- the fuel added from the first reducing agent addition valve 13a is the first NOx catalyst 1 1 Since it can be determined that it is not distributed in the central part in a and is distributed unevenly in the upstream part or the downstream part, the process proceeds to S 105 to correct the delay time ⁇ .
- the fuel added from the first reducing agent addition valve 13a is transferred to the center in the first NOx catalyst 11a. Since it can be determined that the signal is distributed to the part, the process proceeds to S 106 without correcting the delay time ⁇ .
- the difference between AFU and AFL calculated in S104 is a positive value, that is, when AFU is a large value with respect to AFL, the fuel is within the first NOx catalyst 11a. If it is judged that the fuel is distributed to the downstream side and the AFU is smaller than the AFL, the fuel is distributed to the upstream part in the first NOx catalyst 11a. It is judged that
- the correction for changing the delay time ⁇ is performed.
- the value ⁇ is derived.
- the delay time ⁇ T is set to be calculated by adding a correction value ⁇ T ′ to the reference delay time ⁇ TS, and for the difference value between AFU and AFL and the difference value, Map the relationship between the delay time correction value ⁇ 'to make the difference between A FU and AFL zero.
- the value of the correction value ⁇ corresponding to the difference value between AFU and AFL calculated in S104 is derived by reading from the aforementioned map. If the process of S105 is completed, and if it is determined in S104 that the absolute value of the difference between AFU and AFL is not more than AFS, the process proceeds to S106.
- the absolute value of the deviation between the average value of AFU and AFL detected in S103 and the target air-fuel ratio AFT in the NOx reduction process of the first NOx catalyst 11a is less than or equal to the predetermined target air-fuel ratio deviation AFD
- the power is determined.
- the target air-fuel ratio deviation A FD is a value obtained experimentally in advance, and the absolute value of the deviation between the average value of the air-fuel ratio upstream and downstream of the NOx catalyst and the target air-fuel ratio is less than this value.
- the value of the deviation as a threshold with which it can be determined that the NOx reduction process is performed well.
- the fuel added from the first reducing agent addition valve 13a Since the amount of fuel is too small or too large, it can be judged that the NOx reduction treatment at 1 1a in the first NOx catalyst is not performed well, so proceed to S 1 0 7 to correct the fuel addition amount F .
- the process proceeds to S108 without correcting the fuel addition amount F.
- the correction value F for correcting the fuel addition amount F is derived. Specifically, the fuel addition amount F is set to be calculated by adding the correction value F ′ to the reference fuel addition amount FS, and the deviation between the average value of AFU and AFL and the target air-fuel ratio AFT For that deviation, 1; and? The relationship between the average value of 1 ⁇ and the correction value F 'for setting the target air-fuel ratio AFT in advance is mapped. Then, the value of the correction value F corresponding to the deviation between the average value of A FU and A FL calculated in S 106 and the target air-fuel ratio A FT is read out from the aforementioned map.
- the processing of S107 is completed and when it is determined in S106 that the absolute value of the deviation between the average value of AFU and AFL and the target air-fuel ratio AFT is not more than AFD, the process proceeds to S108.
- a new delay time ⁇ is calculated by adding the correction value ⁇ 'derived in S105 to the reference delay time ATS.
- a new fuel addition amount F is calculated by adding the correction value F ′ derived in S107 to the reference fuel addition amount F S.
- the difference between the output value AFU of the first upstream air-fuel ratio sensor 14 a and the output value AF L of the first downstream air-fuel ratio sensor 15 a Is greater than the air-fuel ratio difference value AFS, the difference between the output value AFU of the first upstream air-fuel ratio sensor 14a and the output value AFL of the first downstream air-fuel ratio sensor 15a is made zero. Therefore, the delay time ⁇ is changed. Therefore, the delay time ⁇ when the fuel is added from the first reducing agent addition valve 13a next time is changed, and the fuel is fed to the center in the first NOx catalyst 11a during the next flow stop period. Can be dispersed.
- the output value AFU of the first upstream air-fuel ratio sensor 14a and the first downstream air-fuel ratio sensor When the absolute value of the deviation between the average value of the output value AFL of the sensor 15 a and the target air-fuel ratio AFT is larger than the target air-fuel ratio deviation AFD, the output value A FU of the first upstream air-fuel ratio sensor 14 a The fuel addition amount F is changed so that the deviation between the average value of the output value A FL of the first downstream side air-fuel ratio sensor 15a and the target air-fuel ratio AFT becomes zero. Therefore, the fuel addition amount F when the fuel is added from the reducing agent addition valve 13a next time is changed, and an appropriate amount of fuel is added to perform the NOx reduction treatment in the first NOx catalyst 1'1a.
- the NOx reduction treatment in the first INOx catalyst 11a can be performed more reliably.
- the INOx catalyst 1 An example of performing NOx reduction treatment for 1a has been described. After the fully open operation command is issued to the first valve 12a and the fully closed operation command is issued to the second valve 12b, the second NOx catalyst 11 Even when NOx reduction treatment is performed on b, the same control is performed by using the second reducing agent addition valve 13 b, the second upstream air-fuel ratio sensor 14 b, and the second downstream air-fuel ratio sensor 15 b.
- the NOx reduction treatment in the second NOx catalyst 1 1 b can be performed more reliably.
- NOx reduction treatment is performed on the first INOx catalyst 11a
- the same control is applied when the NOx reduction treatment is performed on the second NOx catalyst 11b. Is possible.
- the average value of the output value AFU of the first upstream air-fuel ratio sensor 14 a and the output value AFL of the first downstream air-fuel ratio sensor 15 a, the target air-fuel ratio AFT and The control is performed so that the deviation of the first air-fuel ratio sensor 14a is zero, but the output value AFU of the first upstream air-fuel ratio sensor 14a and the output value AFL of the first downstream air-fuel ratio sensor 15a are different from each other. Control may be performed so that the deviation between AFU and AFT 1 and the deviation between AFL and AFT 2 are set to zero by setting the fuel ratio (for example, AFT 1 and AFT 2).
- the flow stop period is a period in which the amount of exhaust gas flowing into the first INOx catalyst 11a is substantially zero.
- the start of this flow stop period is the first valve 12 by the ECU 35. It may be the time when the exhaust amount reduction period TD, which is a constant value obtained experimentally in advance, elapses after the fully closed operation command is issued to a and the second valve 12 b is issued to the fully open operation command.
- the output signal of the first upstream side air-fuel ratio sensor 14a decreases rapidly and then recovers and stabilizes. The start of the flow stop period may be determined.
- the output of the first upstream air-fuel ratio sensor 14a is such that the exhaust gas containing fuel added from the first reducing agent addition valve 13a moves in the first branch passage 10a.
- the amount of exhaust flowing into the first INOx catalyst 11a in other words, the amount of exhaust containing fuel added from the first reducing agent addition valve 13a is not stable. This is because the flow rate is considered to be stable when it becomes nearly zero.
- the time until it recovers and stabilizes is measured, and the exhaust amount reduction period TD is calculated based on the measurement result. You may make it supplement.
- FIG. 6 shows an exhaust amount reduction period correction routine in this embodiment.
- This routine is a routine that is executed at the same time as the NOx reduction treatment routine of the first NOx catalyst 11a shown in FIG. 5, for example.
- this routine it is first determined in S201 whether or not the first valve 12a has been fully closed. Specifically, it is determined whether or not the ECU 35 has issued a command to fully close the first valve 12a. Here, if it is determined that the fully-closed operation of the first valve 12a has not started, this routine is ended as it is. On the other hand, if it is determined that the first valve 12a is fully closed, the process proceeds to S202.
- the value of AFU may be acquired by reading the output signal of the first upstream air-fuel ratio sensor 14a into the ECU 35 again in the processing of this routine, or it may be the latest in S103 in FIG. You may use the detected value detected.
- the difference between the AFU value obtained this time and the AFU value obtained at the previous execution of this routine is divided by the execution interval time of this routine. You may acquire by doing.
- the reference variation is dAFUZdT
- the absolute value is less than this, it can be determined that the output signal of the first upstream air-fuel ratio sensor 14a is stable, in other words, the amount of exhaust flowing into the first INOx catalyst 11a has become substantially zero. This is the value of AF-U change as a threshold.
- the absolute value of dAFUZdT is larger than the reference change amount, it can be determined that the output signal of the first upstream air-fuel ratio sensor 14a is not stable. Going back, the exhaust amount reduction period correction value TD "is incremented again. Then, in S203, the processes of S202 and S203 are repeatedly executed until it is determined that the absolute value of dAFUZdT is equal to or less than the reference change amount.
- the reference air-fuel ratio value is the value before the fuel added by the first reducing agent addition valve 13a passes through the vicinity of the first upstream air-fuel ratio sensor 14a. It is the value of the air-fuel ratio as a threshold that can be determined to be in the state.
- the start of the flow stop period is defined as the point at which the exhaust amount reduction period TD has elapsed since the start of the fully closed operation of the first valve 12a, and the exhaust amount reduction period
- the value of TD is always corrected so as to coincide with the period until the output of the first upstream air-fuel ratio sensor 14a is stabilized after the fuel is added from the first reducing agent addition valve 13a. As a result, it is possible to more accurately determine the start of the flow stop period as a period when the amount of exhaust gas flowing into the first INOx catalyst 11a becomes substantially zero.
- the first branch passage 10a is provided with the first NOx catalyst 11a
- the second branch passage 10b is provided with the second NOx catalyst 11b.
- the first oxidation catalyst is located between the first INOx catalyst 1 1 a and the first upstream air-fuel ratio sensor 14 a
- a second acid catalyst may be provided between the two.
- the difference between the output value AFU of the first upstream air-fuel ratio sensor 14a and the output value AFL of the first downstream air-fuel ratio sensors 1 and 5a during the flow stop period is detected.
- the deviation of the fuel dispersion in the first INOx catalyst 11a is estimated, which is output from the first upstream air-fuel ratio sensor 14a shown in Figs. 3 and 4. It may be estimated from the difference in the waveform of the graph of the output of the first downstream air-fuel ratio sensor 15a.
- the time when the air-fuel ratio upstream of the first INOx catalyst 11a is equal to or lower than the target air-fuel ratio is longer than the time when the air-fuel ratio downstream of the first INOx catalyst 11a is equal to or lower than the target air-fuel ratio.
- the added fuel is presumed to be unevenly distributed in the upstream portion of the first INOx catalyst 11a, and conversely, the time during which the air-fuel ratio upstream of the first INOx catalyst 11a is equal to or less than the target air-fuel ratio.
- Example 2 in the present invention will be described.
- the value of the fuel addition amount F added from the first fuel addition valve 13a is a predetermined constant value, and the NOx reduction described in Example 1 is performed.
- the absolute value of the deviation between the output AFU of the first upstream air-fuel ratio sensor 14a and the output AFL of the first downstream air-fuel ratio sensor 15 5a and the target air-fuel ratio AFT is When the target air-fuel ratio deviation AFD is larger, the fuel addition amount F from the first fuel addition valve 13a does not deviate from the optimum value, but the fuel added from the first fuel addition valve 1 3a is not.
- the first NOx catalyst 11 1a is excessively concentrated and dispersed in the central portion, and is not dispersed in the upstream portion and the downstream portion in the first N Ox catalyst 11 1a. The control for determining that will be described.
- FIG. 7 shows the NOx reduction processing routine in this embodiment.
- the difference between this routine and the NOx reduction processing routine shown in FIG. 5 is only the processing of S301, S302, and S303, and only these processing will be described.
- the delay time ⁇ 1 passes after the fully closed operation command is issued to the first valve 12 a in S 101 and the fully open command is issued to the second valve 12 b in S 101, as in the first embodiment. Then, fuel addition is started by the first reducing agent addition valve 13a. In this embodiment, the amount F of fuel added at this time is not corrected, and a predetermined amount of fuel is added. Instead, in this embodiment, fuel addition is performed in N times, and the value determined in the subsequent processing of this routine is used for the value of N.
- a new delay time ⁇ is calculated by adding the correction value ⁇ 1 derived in S105 to the reference delay time ATS. Further, a new fuel addition number N is determined by substituting the fuel addition number correction value N ”derived in S302 for the fuel addition number N used in the processing of S301. The new fuel addition number N is determined by substituting the fuel addition number correction value N ′ derived in S302 for the fuel addition number N used in step 3.
- this routine is completed. And it ends.
- the fuel added from the first reducing agent addition valve 13a is excessively concentrated and dispersed in the central portion in the first INOx catalyst 11a, and the upstream portion and the downstream side in the first INOx catalyst 11a It is determined that the fuel is not dispersed evenly, and the same amount of fuel is added in an optimal number of times so that it is uniformly dispersed throughout the entire area of the 1st INOx catalyst. As a result, the NOx reduction treatment can be performed more reliably over the entire first INOx catalyst 11a.
- FIG. 8 is a time chart of the opening and closing of the first valve 12a, the ON-OF F of the first reducing agent addition valve 13a, and the amount of exhaust gas flowing into the first NOx catalyst 11a. An example different from that shown is shown.
- FIG. 8A is a time chart for this embodiment described above. After the delay time ⁇ has elapsed from the start of the fully closed operation of the first valve 12a, the fuel corresponding to the predetermined fuel addition amount F is added in a plurality of times from the first reducing agent addition valve 13a. ing. .
- the first reducing agent is used as in the above-described embodiment.
- the fuel addition rate means the amount of fuel added per unit time. In this case, the same amount of fuel is burned over a long time with a small fuel addition rate. By adding the fuel, the fuel can be more uniformly dispersed in the first NOx catalyst 11a.
- Example 3 is an example in which a plurality of NOx catalysts are provided in series in the first branch passage 10a and the second branch passage 10b, for example, the NOx catalyst provided in the first branch passage 10a.
- the difference between the output signals of the first upstream air-fuel ratio sensor 14a and the first downstream air-fuel ratio sensor 15a depends on the amount of reducing agent required in each NOx catalyst. An example of setting the target value will be described.
- FIG. 9 shows a schematic configuration of the internal combustion engine 1 and its exhaust system and control system in the present embodiment.
- the difference between Fig. 9 and Fig. 1 is that between the first NOx catalyst 11a and the first downstream air-fuel ratio sensor 15a in the first branch passage 10a, the NOx storage reduction type NOx
- the first downstream NOx catalyst 16a which is a catalyst, is similarly provided between the second NOx catalyst 11b and the second downstream air-fuel ratio sensor 15b in the second branch passage 10b.
- the catalyst 16b is provided.
- the fuel added from the first fuel addition valve 13a is upstream in the region between the first upstream air-fuel ratio sensor 14a and the first downstream air-fuel ratio sensor 15a during the flow stop period. It is known that the output AFU of the first upstream side air-fuel ratio sensor 14a becomes lower and the output AFL of the first downstream side air-fuel ratio sensor 15a becomes higher as it is dispersed. On the other hand, it is known that the output AFU of the first upstream air-fuel ratio sensor 14a increases and the output AFL of the first downstream air-fuel ratio sensor 15a decreases as it is dispersed downstream. Conversely, by changing the delay time ⁇ so that the difference between the AFU value and the AFL value becomes the desired value during the flow stop period, the fuel in each NOx catalyst during the flow stop period is changed. The amount of dispersion can be controlled.
- a target value for which the difference between the AFU value and the AFL value is to be controlled is set according to the amount of reducing agent required for each NOx catalyst. It was decided.
- the center of fuel dispersion is located on the first NOx catalyst 11a side.
- FIG. 10 shows the NOx reduction processing routine in this embodiment. Since the difference between the NOx reduction processing routine in this embodiment and that shown in FIG. 5 is only the processing of S401 and S40′2, only this processing will be described.
- the absolute value of the deviation between the difference between AFU and AFL and the target air-fuel ratio difference AFDT is determined. It is determined whether the air-fuel ratio difference value is AFS or less. In other words, in this embodiment, the target value of the difference between AFU and AFL is not zero, but becomes the target air-fuel ratio difference AFDT.
- the target air-fuel ratio difference AFDT is the reducing agent required for both the first INOx catalyst 11a and the first downstream NOx catalyst 16a during the NOx reduction process. This is the difference value in which the fuel is distributed so that the amount can be supplied, and is a value obtained experimentally in advance.
- the fuel dispersion method during the flow stop period is Since it can be determined that the fuel distribution that can optimally reduce both NOx catalyst 16a and the first downstream NOx catalyst 16a, which has been experimentally obtained in advance, is out of the fuel distribution, the process proceeds to S402.
- a correction value for correcting the delay time ⁇ is calculated.
- the delay time ⁇ T is calculated by adding a correction value ⁇ T 'to the reference delay time ⁇ TS, and the deviation of the difference between AFU and AFL from the target air-fuel ratio difference AFDT and its deviation
- the relationship between the difference between AFU and AFL and the correction value ⁇ 'for setting the target air-fuel ratio difference AFDT is mapped in advance.
- the value of the correction value ⁇ 'corresponding to the deviation of the difference between AFU and AFL calculated in S 401 with respect to the target air-fuel ratio difference AFDT is calculated using the above map. From the above, ⁇ ⁇ ⁇ ⁇ ⁇ 'is derived.
- the first branch passage 10a includes a plurality of NOx catalysts including the first NOx catalyst 1 1a and the first downstream NOx catalyst 16-a-, and all the NOx catalysts are provided.
- the target air-fuel ratio difference AFDT is set for the NOX reduction process.
- the delay time ⁇ is changed so that the difference between AFU and AFL becomes the target air-fuel ratio difference AFDT. Therefore, the NOx reduction treatment can always be satisfactorily performed on both the first NOx catalyst 11a and the first lower stream side NOx catalyst 16a.
- the target value of the difference between AFU and AFL which is optimal for dispersing the fuel added from the first reducing agent addition valve 13a only in the first NOx catalyst 11a.
- the first target air-fuel ratio difference AFDT1 and the second target air-fuel ratio difference AFDT 2 which is the target value of the difference between AFU and AFL, which is optimal for dispersion only in the first downstream NOx catalyst 16a, If you want to perform NOx reduction treatment only for the first NOx catalyst 1 1a in advance by experimentation, you can set the target value of the difference between the AFU value and the AFL value as the first target air-fuel ratio difference AF DT 1 If you want to perform NOx reduction only for the first downstream side NOx catalyst 16a, the target value of the difference between the AFU value and the AFL value can be used as the second target air-fuel ratio difference AFDT 2. .
- the 1S first branch passage has been described in which two NOx catalysts, the first NOx catalyst 11a and the first downstream NOx catalyst 16a, are arranged in the first branch passage 10a.
- the number of NOx catalysts placed in 10a is not limited to two. The same effect can be obtained even if the same control as in the present embodiment is performed on three or more NOx catalysts arranged.
- the NOx catalyst is controlled by performing the same control as in this embodiment. It is possible to control the area where NOx reduction treatment should be performed.
- control described in the above embodiment can also be applied to so-called SOx poisoning recovery processing of the NOx storage reduction catalyst and PM regeneration processing in a filter that collects particulate matter in the exhaust gas.
- the amount of exhaust gas flowing into the NOx storage reduction catalyst is reduced and the reducing agent is supplied to the NOx catalyst to reduce the NOx stored in the NOx catalyst.
- the manner in which the reducing agent is dispersed in the NOx catalyst can be controlled, and NOx reduction treatment can be performed more reliably.
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Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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EP05795135.2A EP1801379B1 (en) | 2004-10-15 | 2005-10-14 | Exhaust purification system for internal combustion engine |
US11/631,778 US7832199B2 (en) | 2004-10-15 | 2005-10-14 | Exhaust purification system for internal combustion engine |
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JP2004-301735 | 2004-10-15 | ||
JP2004301735A JP3969417B2 (ja) | 2004-10-15 | 2004-10-15 | 内燃機関の排気浄化システム。 |
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WO2006041223A1 true WO2006041223A1 (ja) | 2006-04-20 |
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US (1) | US7832199B2 (ja) |
EP (1) | EP1801379B1 (ja) |
JP (1) | JP3969417B2 (ja) |
CN (1) | CN100472040C (ja) |
WO (1) | WO2006041223A1 (ja) |
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JP4349423B2 (ja) | 2007-03-01 | 2009-10-21 | トヨタ自動車株式会社 | 内燃機関の排気浄化システム |
US20110289903A1 (en) * | 2009-01-22 | 2011-12-01 | Man Truck & Bus Ag | Device and method for regenerating a particulate filter arranged in the exhaust section of an internal combustion engine |
US11492946B2 (en) * | 2018-11-26 | 2022-11-08 | Volvo Truck Corporation | Aftertreatment system |
DE112020000481T5 (de) | 2019-01-22 | 2021-11-18 | Cummins Emission Solutions Inc. | Systeme und Verfahren zum Implementieren von Korrekturen an einem Reduktionsmittelabgabesystem in einem Abgasnachbehandlungssystem eines Verbrennungsmotors |
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- 2005-10-14 US US11/631,778 patent/US7832199B2/en not_active Expired - Fee Related
- 2005-10-14 CN CNB2005800343250A patent/CN100472040C/zh not_active Expired - Fee Related
- 2005-10-14 EP EP05795135.2A patent/EP1801379B1/en not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
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US7832199B2 (en) | 2010-11-16 |
EP1801379A4 (en) | 2010-06-02 |
CN100472040C (zh) | 2009-03-25 |
JP3969417B2 (ja) | 2007-09-05 |
EP1801379B1 (en) | 2013-07-03 |
EP1801379A1 (en) | 2007-06-27 |
US20080092530A1 (en) | 2008-04-24 |
JP2006112348A (ja) | 2006-04-27 |
CN101035971A (zh) | 2007-09-12 |
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