US20100050610A1 - Exhaust gas purification system of internal combustion engine - Google Patents

Exhaust gas purification system of internal combustion engine Download PDF

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Publication number
US20100050610A1
US20100050610A1 US12/312,598 US31259808A US2010050610A1 US 20100050610 A1 US20100050610 A1 US 20100050610A1 US 31259808 A US31259808 A US 31259808A US 2010050610 A1 US2010050610 A1 US 2010050610A1
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catalyst
ammonia
upper limit
temperature
allowable upper
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Shunsuke Toshioka
Tomihisa Oda
Kazuhiro Itoh
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Toyota Motor Corp
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Toyota Motor Corp
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Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA reassignment TOYOTA JIDOSHA KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ITOH, KAZUHIRO, ODA, TOMIHISA, TOSHIOKA, SHUNSUKE
Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA reassignment TOYOTA JIDOSHA KABUSHIKI KAISHA CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE ADDRESS, PREVIOUSLY RECORDED ON REEL 022733 FRAME 0030. Assignors: ITOH, KAZUHIRO, ODA, TOMIHISA, TOSHIOKA, SHUNSUKE
Publication of US20100050610A1 publication Critical patent/US20100050610A1/en
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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
    • F01N3/10—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
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • 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
    • B01D53/9495—Controlling the catalytic process
    • 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
    • F01N13/009—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 separate purifying devices arranged in series
    • 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
    • F01N13/009—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 separate purifying devices arranged in series
    • F01N13/0097—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 separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • 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
    • 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
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/2073—Selective catalytic reduction [SCR] with means for generating a reducing substance from the exhaust gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—Urea
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/014—Stoichiometric gasoline engines
    • 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
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146—Control thereof, e.g. control of injectors or injection valves
    • 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
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1402—Exhaust gas composition
    • 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
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1622—Catalyst reducing agent absorption capacity or consumption amount
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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 of an internal combustion engine.
  • part of the urea fed to the catalyst is stored once in the catalyst. From this stored urea, the urea-derived substance such as ammonia is produced. Part of the urea-derived substances is used for reducing the NOx, while the remainder is discharged from the catalyst without being used for reducing the NOx. In this case, the amount of the urea-derived substances released from the catalyst becomes greater the greater the amount of urea stored in the catalyst. Therefore, when the catalyst stores a large amount of urea, a large amount of urea-derived substances is liable to be undesirably discharged from the catalyst.
  • an object of the present invention is to provide an exhaust purification system of an internal combustion engine able to block a large amount of ammonia generating compound from being discharged from a catalyst.
  • an exhaust purification system of an internal combustion engine arranging a catalyst suitable for reducing NOx in the exhaust gas by ammonia under an excess of oxygen in an engine exhaust passage
  • the system comprising: a feeding means for feeding an ammonia generating compound to the catalyst; and a feed controlling means for controlling the amount of feed of the ammonia generating compound, the catalyst having a function of storing at least part of the ammonia generating compound fed to the catalyst in the catalyst and generating ammonia from the ammonia generating compound stored in the catalyst and using the generated ammonia to reduce the NOx in the exhaust gas
  • the system further comprising a judging means for judging if a storage capacity of the catalyst is larger than a preset allowable upper limit capacity, wherein the feed controlling means prohibits the feed of the ammonia generating compound when the storage capacity of the catalyst is larger than the allowable upper limit capacity.
  • FIG. 1 is an overview of an internal combustion engine
  • FIG. 2 is a graph showing a storage capacity of a catalyst
  • FIG. 3 is a graph showing an example of the relationship between an amount of urea stored in the catalyst and a concentration of ammonia later discharged from the catalyst,
  • FIG. 4 is a graph showing an NOx purification rate
  • FIG. 5 is a time chart for explaining an embodiment according to the present invention.
  • FIG. 6 is a flowchart showing a control routine for feed of an aqueous urea solution
  • FIG. 7 is a graph showing an example of a relationship of an amount of urea stored in the catalyst and a concentration of hydrogen cyanide later discharged from the catalyst, and
  • FIG. 8 is a graph showing a relationship between an amount of urea stored in a catalyst and a concentration of isocyanic acid later discharged from the catalyst.
  • FIG. 1 shows the case of application of the present invention to a compression ignition type internal combustion engine. Note that the present invention can also be applied to a gasoline engine.
  • 1 is an engine body
  • 2 is a combustion chamber of each cylinder
  • 3 is an electronic control type fuel injector for injecting fuel into each combustion chamber 2
  • 4 is an intake manifold
  • 5 is an exhaust manifold.
  • the intake manifold 4 is connected through an intake duct 6 to an outlet of a compressor 7 a of an exhaust turbocharger 7 .
  • An inlet of the compressor 7 a is connected through an air flow meter 8 to an air cleaner 9 .
  • an electrical control type throttle valve 10 is arranged inside the intake duct 6 .
  • a cooling device 11 is arranged to cool the intake air flowing inside the intake duct 6 .
  • the engine cooling water is guided into the cooling device 11 where the engine cooling water is used to cool the intake air.
  • the exhaust manifold 5 is connected to an inlet of an exhaust turbine 7 b of the exhaust turbocharger 7 .
  • the outlet of the exhaust turbine 7 b is connected to an exhaust post-treatment device 20 .
  • the exhaust manifold 5 and the intake manifold 4 are connected with each other through an exhaust gas recirculation (hereinafter referred to as an “EGR”) passage 12 .
  • EGR exhaust gas recirculation
  • an electrical control type EGR control valve 13 is arranged inside the EGR passage 12 .
  • a cooling device 14 is arranged for cooling the EGR gas flowing through the EGR passage.
  • engine cooling water is guided into the cooling device 14 where the engine cooling water is used to cool the EGR gas.
  • each fuel injector 3 is connected through a fuel feed tube 15 to a common rail 16 .
  • This common rail 16 is connected through an electronic control type variable discharge fuel pump 17 to a fuel tank 18 .
  • the fuel in the fuel tank 18 is fed by the fuel pump 17 inside the common rail 16 .
  • the fuel fed into the common rail 16 is fed through each fuel feed tube 15 to each fuel injector 3 .
  • the exhaust post-treatment device 20 is provided with an upstream side catalytic converter 22 connected through an exhaust pipe 21 to an outlet of the exhaust turbine 7 b and a downstream side catalytic converter 24 connected through an exhaust pipe 23 to the upstream side catalytic converter 22 .
  • a catalyst 25 and catalyst 26 are arranged in that order from the upstream side.
  • a catalyst 27 and catalyst 28 are arranged in that order from the upstream side.
  • the catalysts 25 , 26 , and 28 are comprised of catalysts having oxidation functions, for example, oxidation catalysts or three-way catalysts.
  • the catalyst 27 is comprised of an NOx selective reduction catalyst suitable for reducing the NOx in the exhaust gas by ammonia under an excess of oxygen. Further, the catalysts 25 , 27 , and 28 are carried on honeycomb carriers. The catalyst 26 is carried on a particulate filter for trapping particulate in the exhaust gas. In the exhaust pipe 23 , a temperature sensor 29 for detecting the exhaust gas flowing into the downstream side catalytic converter 24 is arranged. The temperature of the exhaust gas flowing into the downstream side catalytic converter 24 expresses the temperature of the catalyst 27 .
  • a liquid containing an ammonia generating compound which generates ammonia is stored in a tank 30 .
  • the liquid containing the ammonia generating compound stored in the tank 30 is fed into the exhaust pipe 23 through a feed pump 31 and an electromagnetically controlled addition control valve 32 .
  • the electronic control unit 40 is comprised of a digital computer which is provided with components connected to each other by a bidirectional bus 41 such as a ROM (read only memory) 42 , RAM (random access memory) 43 , CPU (microprocessor) 44 , input port 45 , and output port 46 .
  • the air flow meter 8 generates an output voltage proportional to the intake air amount. This output voltage is input through a corresponding AD converter 47 to the input port 45 . On the other hand, the output signal of the temperature sensor 29 is input through a corresponding AD converter 47 to the input port 45 .
  • An accelerator pedal 49 has a load sensor 50 connected to it for generating an output voltage proportional to the amount of depression of the accelerator pedal 49 .
  • the output voltage of the load sensor 50 is input through a corresponding AD converter 47 to the input port 45 .
  • the input port 45 has a crank angle sensor 51 connected to it for generating an output pulse each time the crankshaft rotates by for example 30°.
  • the output port 46 is connected through a corresponding drive circuit 48 to the fuel injector 3 , throttle valve 10 drive device, EGR control valve 13 , fuel pump 17 , feed pump 31 , and addition control valve 32 .
  • the exhaust pipe 23 upstream of the catalyst 27 is fed a liquid containing an ammonia generating compound.
  • the ammonia generating compound able to generate ammonia there are various compounds. Therefore, various compounds can be used as the ammonia generating compound.
  • urea is used as the ammonia generating compound.
  • an aqueous urea solution is used as the liquid containing the ammonia generating compound. Therefore, below, the present invention will be explained taking as an example the case of feeding an aqueous urea solution into the exhaust pipe 23 upstream of the catalyst 27 .
  • the catalyst 27 is comprised of a NOx selective reduction catalyst.
  • a catalyst V 2 O 5 /TiO 2 using titania as the carrier and carrying vanadium oxide on this carrier hereinafter referred to as a “vanadium titania catalyst”
  • a catalyst Cu/ZSM5 using zeolite as the carrier and carrying copper on this carrier hereinafter referred to as a “copper zeolite catalyst”.
  • the NO contained in the exhaust gas is reduced by the ammonia NH 3 generated from the urea CO(NH 2 ) 2 on the catalyst 27 (for example, 2NH 3 +2NO+1/2O 2 ⁇ 2N 2 +3H 2 O).
  • the urea in the fed aqueous urea solution first deposits on the catalyst 27 .
  • the temperature of the catalyst 27 is high, for example, substantially 350° C. or more, the urea thermally decomposes all at once and generates ammonia.
  • the urea when the temperature of the catalyst 27 is from about 132° C. to about 350° C., the urea is stored once inside the catalyst 27 , then ammonia is generated and released a little bit at a time from the urea stored inside the catalyst 27 .
  • the ammonia is generated in this case probably because the urea morphologically changes in the catalyst 27 .
  • the urea changes to biuret at about 132° C.
  • the biuret changes to cyanuric acid at about 190° C.
  • the cyanuric acid changes to cyanic acid or isocyanic acid at about 360° C.
  • the urea changes to biuret.
  • the biuret changes to cyanuric acid, and the cyanuric acid changes to cyanic acid or isocyanic acid. It is thought that ammonia is generated a little bit at a time in the process of this kind of morphological change.
  • the temperature of the catalyst 27 is equal to or lower than about 132° C. which is the thermal decomposition temperature of urea, if feeding the aqueous urea solution to the catalyst 27 , the urea in the aqueous urea solution will be stored in the catalyst 27 . At this time, almost no ammonia is generated from the stored urea.
  • the amount of the urea-derived substances discharged from the catalyst 27 becomes greater the greater the amount of urea stored in the catalyst 27 . Therefore, if the catalyst 27 stores a large amount of urea, a large amount of urea-derived substances is liable to be undesirably discharged from the catalyst 27 .
  • the catalyst 27 can only store the urea up to its storage capacity.
  • This storage capacity varies in accordance with the atmosphere of the catalyst 27 , for example, the temperature of the catalyst 27 , therefore when the storage capacity of the catalyst 27 is large, the catalyst 27 can store a large amount of urea, while when the storage capacity of the catalyst 27 is small, the catalyst 27 can only store a small amount of urea.
  • the storage capacity SC of the catalyst 27 becomes larger when the temperature TC of the catalyst 27 is high compared to when it is low.
  • the storage capacity SC of the catalyst 27 becomes the upper limit amount SCU.
  • the temperature TC where the storage capacity SC of the catalyst 27 becomes the allowable upper limit capacity SCU is set as a preset temperature TCX.
  • TCX the temperature TC of the catalyst 27 is lower than this preset temperature TCX, it is judged that the storage capacity SC of the catalyst 27 is greater than the allowable upper limit capacity SCU. At this time, the feed of the aqueous urea solution is prohibited.
  • the temperature of the catalyst 27 is higher than the preset temperature TCX, it is judged that the storage capacity SC of the catalyst 27 is smaller than the allowable upper limit capacity SCU. At this time, the feed of the aqueous urea solution is allowed.
  • aqueous urea solution is fed to the catalyst 27 by an amount corresponding to the amount of NOx discharged from the engine.
  • the amount of urea stored in the catalyst 27 will never exceed the allowable upper limit capacity SCU. Therefore, even without finding the amount of urea actually stored in the catalyst 27 , it is possible to block a large amount of urea from being stored in the catalyst 27 .
  • the allowable upper limit capacity SCU may be set in any way.
  • the allowable upper limit capacity SCU is set as follows.
  • FIG. 3 shows an example of the relationship between the amount Q of urea stored in the catalyst 27 and the concentration CA of ammonia discharged from the catalyst 27 for example at the time of engine acceleration.
  • the allowable upper limit capacity SCU is set to the upper limit amount QAU for ammonia. As a result, the concentration of ammonia discharged later from the catalyst 27 is blocked from exceeding the allowable upper limit value CAU.
  • the NOx purification rate EFF of the catalyst 27 becomes lower than the allowable lower limit rate EFFL if the temperature TC of the catalyst 27 is lower than the lower limit temperature TCEL or higher than the upper limit temperature TCEH, and becomes higher than the allowable lower limit rate EEFL if the temperature TC of the catalyst 27 is from the lower limit temperature TCEL to the upper limit temperature TCEH.
  • the above-mentioned preset temperature TCX is higher than this lower limit temperature TCEL.
  • aqueous urea solution feed start timing after the engine has started.
  • X in FIG. 5 when the engine is started, the temperature TC of the catalyst 27 gradually rises. At this time, the feed of the aqueous urea solution is stopped.
  • Y in FIG. 5 even if the temperature TC of the catalyst 27 reaches the lower limit temperature TCEL, the feed of the aqueous urea solution is not started.
  • Z in FIG. 5 if the temperature TC of the catalyst 27 reaches the preset temperature TCX, the feed of the aqueous urea solution is started.
  • the feed of the aqueous urea solution is not started. Only when the temperature TC of the catalyst 27 rises to the temperature able to block the discharge of a large amount of urea-derived substances is the feed of the aqueous urea solution finally started.
  • FIG. 6 shows the routine for controlling the feed of the aqueous urea solution in an embodiment according to the present invention. This routine is executed by interruption every fixed time interval.
  • step 100 it is judged if the temperature TC of the catalyst 27 is lower than the preset temperature TCX.
  • TC ⁇ TCX next the routine proceeds to step 101 where the feed of the aqueous urea solution is allowed.
  • step 102 next the routine proceeds to step 102 where the feed of the aqueous urea solution is prohibited.
  • the allowable upper limit capacity SCU can be set as follows:
  • FIG. 7 shows an example of the relationship between the amount of urea Q stored in the catalyst 27 and the concentration of hydrogen cyanide CC discharged from the catalyst 27 later, for example, at the time of engine acceleration
  • FIG. 8 shows an example of the relationship between the amount of urea Q stored in the catalyst 27 and the concentration of isocyanic acid CI discharged from the catalyst 27 later, for example, at the time of engine acceleration.
  • the allowable upper limit capacity SCU it is also possible to set the allowable upper limit capacity SCU to the smallest of the upper limit amounts QAU, QCU, and QIU for the ammonia, hydrogen cyanide, and isocyanic acid. By doing this, it is possible to block the ammonia, hydrogen cyanide, and isocyanic acid from exceeding the allowable upper limit values CAU, CCU, and CIU, respectively.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Toxicology (AREA)
  • Materials Engineering (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
US12/312,598 2007-04-06 2008-04-03 Exhaust gas purification system of internal combustion engine Abandoned US20100050610A1 (en)

Applications Claiming Priority (3)

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JP2007100649A JP4710863B2 (ja) 2007-04-06 2007-04-06 内燃機関の排気浄化装置
JP2007-100649 2007-04-06
PCT/JP2008/057040 WO2008126876A1 (ja) 2007-04-06 2008-04-03 内燃機関の排気浄化装置

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US (1) US20100050610A1 (de)
EP (1) EP2146064B1 (de)
JP (1) JP4710863B2 (de)
CN (1) CN101646845B (de)
WO (1) WO2008126876A1 (de)

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US20100031642A1 (en) * 2008-03-04 2010-02-11 Toyota Jidosha Kabushiki Kaisha Exhaust purification device of internal combustion engine
CN106460617A (zh) * 2014-06-12 2017-02-22 大陆汽车有限公司 用于传送液体的泵

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JP4720773B2 (ja) * 2007-04-06 2011-07-13 トヨタ自動車株式会社 内燃機関の排気浄化装置
JP5251596B2 (ja) * 2009-02-26 2013-07-31 マツダ株式会社 排気ガス浄化装置
FR2966870B1 (fr) * 2010-10-27 2016-02-19 Peugeot Citroen Automobiles Sa Dispositif de traitement de gaz d'echappement de moteur essence avec filtre a particules, ligne d'echappement et vehicule correspondant
DE102011002425A1 (de) * 2011-01-04 2012-07-05 Robert Bosch Gmbh Fördervorrichtung zur Versorgung eines Abgasnachbehandlungssytems einer Brennkraftmaschine mit einem Reduktionsmittel sowie Verfahren
JP5716687B2 (ja) 2012-01-27 2015-05-13 トヨタ自動車株式会社 内燃機関の排気浄化装置
GB2500194A (en) * 2012-03-12 2013-09-18 Jaguar Cars Exhaust temperature control during SCR injection events
DK178097B1 (en) * 2013-10-31 2015-05-18 Man Diesel & Turbo Deutschland A combustion engine system
CN105736094A (zh) * 2016-04-12 2016-07-06 苏州水木康桥环境工程技术有限公司 一种用于船用尾气净化装置的气态氨生成系统

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EP2146064A4 (de) 2011-03-16
EP2146064B1 (de) 2012-10-17
CN101646845B (zh) 2012-07-04
CN101646845A (zh) 2010-02-10
JP4710863B2 (ja) 2011-06-29
EP2146064A1 (de) 2010-01-20
JP2008255937A (ja) 2008-10-23

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