US20080034732A1 - Exhaust Emission Control Device - Google Patents
Exhaust Emission Control Device Download PDFInfo
- Publication number
- US20080034732A1 US20080034732A1 US11/569,688 US56968805A US2008034732A1 US 20080034732 A1 US20080034732 A1 US 20080034732A1 US 56968805 A US56968805 A US 56968805A US 2008034732 A1 US2008034732 A1 US 2008034732A1
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- US
- United States
- Prior art keywords
- control device
- selective reduction
- reduction catalyst
- urea water
- reducing agent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/146—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration
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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
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/007—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
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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]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/22—Safety or indicating devices for abnormal conditions
- F02D41/221—Safety or indicating devices for abnormal conditions relating to the failure of actuators or electrically driven elements
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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
- F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
- F01N2550/05—Systems for adding substances into exhaust
-
- 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
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
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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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
- F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
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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
-
- 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
- Y02T10/40—Engine management systems
Definitions
- the present invention relates to an exhaust emission control device wherein NO x in exhaust gas is depurated through reduction.
- some diesel engines have been provided with selective reduction catalyst incorporated in an exhaust pipe through which exhaust gas flows, said catalyst having a characteristic of selectively reacting NO x with a reducing agent even in the presence of oxygen.
- a required amount of reducing agent is added upstream of the selective reduction catalyst to reduce NO x (nitrogen oxides) in the exhaust gas with the reducing agent on the catalyst to thereby reduce a concentration of discharged NO x .
- urea water when added to the exhaust gas upstream of the selective reduction catalyst, the urea water is decomposed into ammonia and carbon dioxide gas with the temperature condition of about 170-180° C. or more to thereby depurate well NO x in the exhaust gas through reduction by ammonia on the catalyst.
- the invention was made in view of the above and has its object to minimize the increase of NO x emission even if the NO x deputation system has malfunction.
- the invention is directed to an exhaust emission control device wherein selective reduction catalyst is incorporated in an exhaust pipe, a reducing agent being added upstream of said catalyst by reducing-agent adding means to depurate NO x through reduction, comprising NO x sensors arranged respectively on entry and exit sides of the selective reduction catalyst for detecting NO x concentrations, and a control device for judging abnormality on the basis of detection signals from both of the NO x sensors by non-attainment of a predetermined NO x reduction ratio and for commanding restriction of an amount of fuel to be injected when said abnormality is judged.
- No x concentrations on the entry and exit sides of the selective reduction catalyst are monitored by the control device on the basis of the detection signals from both of the NO x sensors, and abnormality of not attaining the predetermined NO x reduction ratio is judged when no remarkable difference is ascertained between the NO x concentrations on the entry and exit sides of the selective reduction catalyst; when such abnormality is judged, the amount of fuel to be injected is restricted by the command from the control device, so that an amount of NO x to be generated in the engine is reduced to suppress the increase of NO x emission.
- the reducing agent may be urea water and the selective reduction catalyst may have a characteristic of capable of selectively reacting NO x with ammonia even in the presence of oxygen.
- an excellent effect or advantage is obtained: even when an NO x deputation system has malfunction, the amount of fuel to be injected can be restricted to reduce an amount of NO x to be generated in the engine, whereby increase of NO x emission can be minimized.
- FIG. 1 A schematic view showing an embodiment of the invention.
- FIG. 2 A perspective view showing partly in cutout the selective reduction catalyst of FIG. 1 .
- FIG. 3 A flow chart showing control steps of the NO x depuration control device shown in FIG. 1 .
- FIGS. 1-3 shows the embodiment of the invention.
- reference numeral 1 denotes diesel engine.
- the engine 1 shown has a turbocharger 2 with a compressor 2 a to which air 4 from an air cleaner 3 is fed via an intake pipe 5 .
- the air 4 thus pressurized in the compressor 2 a is fed further through the intake pipe to an intercooler 6 for cooling.
- the cooled air 4 from the intercooler 6 is fed to an intake manifold (not shown) where the air 4 is introduced to each cylinder of the engine 1 .
- the exhaust gas 7 discharged from each cylinder of the engine 1 is fed via an exhaust manifold 8 to a turbine 2 b of the turbocharger 2 , the exhaust gas 7 after having driven the turbine 2 b being discharged outside via an exhaust pipe 9 .
- Selective reduction catalyst 10 encased in a casing 11 is incorporated in the exhaust pipe 9 through which exhaust gas 7 flows.
- the selective reduction catalyst 10 is formed as flow-through type honeycomb structure as shown in FIG. 2 , and has a characteristic of capable of selectively reacting NO x with ammonia even in the presence of oxygen.
- urea-water injection valve 13 with an injection nozzle 12 , the injection valve 13 being connected to an urea water tank 14 arranged at an appropriate site via an urea-water supply line 15 , so that the urea water (reducing agent) 17 in the tank 14 can be added upstream of the selective reduction catalyst 10 via the injection valve 13 by driving a supply pump 16 incorporated in the supply line 15 .
- urea-water adding means (reducing-agent adding means) 18 is constituted by the urea-water injection valve 13 , urea water tank 14 , urea-water supply line 15 and supply pump 16 .
- the engine 1 is provided with a revolution sensor 19 for detecting revolution of the engine.
- a revolution signal 19 a from the revolution sensor 19 and a load signal 20 a from an accelerator sensor 20 (sensor for detecting treadled angle of an accelerator pedal) are inputted into an engine control unit or electric control unit 21 (ECU).
- a fuel injection signal 22 a for commanding fuel injection timing and amount to be injected is outputted to a fuel injection device 22 for injecting fuel to each cylinder of the engine 1 , so that appropriate fuel injection control is carried out on the basis of current operation status judged from the above-mentioned revolution and load signals 19 a and 20 a from the sensors 19 and 20 .
- the fuel injection device 22 comprises a plurality of injectors (not shown) each for each cylinder, an electromagnetic valve in each of the injectors being controlled in its opening by the fuel injection signal 22 a so as to appropriately control the fuel injection timing and amount to be injected.
- An NO x deputation control device 23 (control device) arranged separately from the ECU 21 outputs a valve-opening command signal 13 a to the urea-water injection valve 13 , and further outputs a drive command signal 16 a to the supply pump 16 .
- a valve-opening command signal 13 a to the urea-water injection valve 13
- a drive command signal 16 a to the supply pump 16 .
- the NO x depuration control device 23 receives from the ECU 21 the revolution and load signals 19 a and 20 a from the sensors 19 and 20 and, on the basis of current operation status judged from these signals, NO x generation amount is estimated; an amount of urea water 17 to be added commensurate with the estimated NO x generation amount is calculated and addition of such required amount of urea water 17 is carried out.
- Inputted to the NO x deputation control device 23 are detection signals 24 a and 25 a from NO x sensors 24 and 25 arranged respectively on the entry and exit sides of the selective reduction catalyst 10 for detecting NO x concentrations as well as a detection signal 26 a from a temperature sensor 26 arranged on the entry side of the catalyst 10 ; on the basis of these detection signals 24 a , 25 a and 26 a , abnormality where a predetermined temperature or more is attained and a predetermined No x reduction ratio is not attained is judged and, when such abnormality is judged, the control device outputs a control signal 21 a to the ECU 21 so as to command restriction of an amount of fuel to be injected.
- the revolution signal 19 a from the revolution sensor 19 is ascertained in step S 1 ; the detection signal 26 a from the temperature sensor 26 is ascertained in step S 2 ; and the detections signals 24 a and 25 a from both of the NO x sensors 24 and 25 , respectively, are ascetained in step S 3 .
- step S 4 determines whether the procedure advances to step S 4 where whether the ratio of the exit-side NO x concentration to the entry-side NO x concentration is less than 0.5 or not is judged; if affirmative or “YES”, the procedure proceeds to step S 5 where restriction of an amount of fuel to be injected is commanded as control signal 21 a to the ECU 21 ; and if negative or “NO”, the procedure returns to step S 1 and the same control sequence is repeated.
- ascertainment of temperature at step S 2 may not always be carried out by actual measurement through the temperature sensor 26 arranged on the entry side of the selective reduction catalyst 10 .
- the exhaust temperature may be estimated from the operation status on the basis of the sensed engine revolution and load.
- the ECU 21 When the ECU 21 receives the control signal 21 a from the NO x deputation control device 23 , it selects a map for fuel injection control with the fuel injection amount being reduced than normal, so that on the basis of this map, a reduced amount of fuel to be injected than usaul is outputted as fuel injection signal 22 a to the fuel injection device 22 .
- restriction of the fuel injection amount lower than usual must be accompanied by changes of injection timing and pressure to appropriate values (corresponding to the change of the fuel injection amount). Therefore these are also adapted to be changed accordingly.
- NO x concentrations on the entry and exit sides of the selective reduction catalyst 10 are monitored by NO x deputation control device 23 on the basis of the detection signals 24 a and 25 a from both of the NO x sensors 24 and 25 : when no remarkable difference between those on the entry and exit sides of the selective reduction catalyst 10 is ascertained, abnormality as non-attainment of a predetermined No x reduction ratio is judged, and when such abnormality is judged, the control signal 21 a is outputted from the NO x depuration control device 23 to the ECU 21 so as to restrict the amount of fuel to be injected; as a result, an amount of NO x to be generated in the engine 1 is reduced to suppress the increase of NO x emission.
- an amount of fuel to be injected can be restricted to reduce an amount of NO x to be generated in the engine 1 to thereby minimize increase of NO x emission.
- an exhaust emission control device of the invention is not limited to the above-mentioned embodiment and that various changes and modifications may be effected without leaving the gist of the invention.
- the reducing agent added to the selective reduction catalyst may be diesel oil or the like other than the urea water.
Abstract
Increase of NOx emission is minimized even under a condition that NOx depuration system has malfunction.
An exhaust emission control device is disclosed which has selective reduction catalyst 10 incorporated in an exhaust pipe 9, urea water 17 (reducing agent) being added to exhaust gas upstream of the selective reduction catalyst 10 by urea water adding means 18 (reducing agent adding means) so as to depurate NOx through reduction. The exhaust emission control device has NOx sensors 24 and 25 respectively arranged on entry and exit sides of the selective reduction catalyst 10 for detecting NOx concentrations, and an NOx deputation control device 23 (control device) which judges abnormality, on the basis of detection signals 24a and 25a from the NOx sensors 24 and 25, by non-attainment of a predetermined Nox reduction ratio and, when such abnormality is judged, restriction of an amount of fuel to be injected is commanded.
Description
- The present invention relates to an exhaust emission control device wherein NOx in exhaust gas is depurated through reduction.
- Conventionally, some diesel engines have been provided with selective reduction catalyst incorporated in an exhaust pipe through which exhaust gas flows, said catalyst having a characteristic of selectively reacting NOx with a reducing agent even in the presence of oxygen. A required amount of reducing agent is added upstream of the selective reduction catalyst to reduce NOx (nitrogen oxides) in the exhaust gas with the reducing agent on the catalyst to thereby reduce a concentration of discharged NOx.
- In a field of industrial plant or the like with flue-gas denitration, it has been well known that ammonia (NH3) is effectively used as reducing agent to depurate NOx through reduction. However, for automobiles, safety in carrying ammonia itself during running is difficult to ensure, so that in recent years, use of nontoxic urea water as reducing agent has been researched (see, for example, Reference 1).
- More specifically when urea water is added to the exhaust gas upstream of the selective reduction catalyst, the urea water is decomposed into ammonia and carbon dioxide gas with the temperature condition of about 170-180° C. or more to thereby depurate well NOx in the exhaust gas through reduction by ammonia on the catalyst.
- However, in this kind of selective reduction catalyst, there may be a fear that urea water is left unreplenished or that urea water is not replenished in an appropriate concentration. In such a case, there may be a fear that, even if appropriate addition of urea water is commanded by a control system, system malfunction of not attaining targeted Nox reduction ratio may occur, resulting in increase of NOx emission before such system malfunction is resolved.
- The invention was made in view of the above and has its object to minimize the increase of NOx emission even if the NOx deputation system has malfunction.
- The invention is directed to an exhaust emission control device wherein selective reduction catalyst is incorporated in an exhaust pipe, a reducing agent being added upstream of said catalyst by reducing-agent adding means to depurate NOx through reduction, comprising NOx sensors arranged respectively on entry and exit sides of the selective reduction catalyst for detecting NOx concentrations, and a control device for judging abnormality on the basis of detection signals from both of the NOx sensors by non-attainment of a predetermined NOx reduction ratio and for commanding restriction of an amount of fuel to be injected when said abnormality is judged.
- More specifically, Nox concentrations on the entry and exit sides of the selective reduction catalyst are monitored by the control device on the basis of the detection signals from both of the NOx sensors, and abnormality of not attaining the predetermined NOx reduction ratio is judged when no remarkable difference is ascertained between the NOx concentrations on the entry and exit sides of the selective reduction catalyst; when such abnormality is judged, the amount of fuel to be injected is restricted by the command from the control device, so that an amount of NOx to be generated in the engine is reduced to suppress the increase of NOx emission.
- When the invention is worked out more specifically, the reducing agent may be urea water and the selective reduction catalyst may have a characteristic of capable of selectively reacting NOx with ammonia even in the presence of oxygen.
- According to an exhaust emission control device of the invention as mentioned above, an excellent effect or advantage is obtained: even when an NOx deputation system has malfunction, the amount of fuel to be injected can be restricted to reduce an amount of NOx to be generated in the engine, whereby increase of NOx emission can be minimized.
- [
FIG. 1 ] A schematic view showing an embodiment of the invention. - [
FIG. 2 ] A perspective view showing partly in cutout the selective reduction catalyst ofFIG. 1 . - [
FIG. 3 ] A flow chart showing control steps of the NOx depuration control device shown inFIG. 1 . -
- 1 engine
- 7 exhaust gas
- 9 exhaust pipe
- 10 selective reduction catalyst
- 17 urea water (reducing agent)
- 18 urea water adding means (reducing-agent adding means)
- 21 electronic control unit
- 21 a control signal
- 22 fuel injection device
- 23 NOx depuration control device (control device)
- 24 NOx sensor
- 24 a detection signal
- 25 NOx sensor
- 25 a detection signal
- Next, an embodiment of the invention will be described in conjunction with the drawings.
-
FIGS. 1-3 shows the embodiment of the invention. InFIG. 1 ,reference numeral 1 denotes diesel engine. Theengine 1 shown has aturbocharger 2 with a compressor 2 a to which air 4 from anair cleaner 3 is fed via anintake pipe 5. The air 4 thus pressurized in the compressor 2 a is fed further through the intake pipe to anintercooler 6 for cooling. The cooled air 4 from theintercooler 6 is fed to an intake manifold (not shown) where the air 4 is introduced to each cylinder of theengine 1. - The
exhaust gas 7 discharged from each cylinder of theengine 1 is fed via anexhaust manifold 8 to a turbine 2 b of theturbocharger 2, theexhaust gas 7 after having driven the turbine 2 b being discharged outside via an exhaust pipe 9. -
Selective reduction catalyst 10 encased in acasing 11 is incorporated in the exhaust pipe 9 through whichexhaust gas 7 flows. Theselective reduction catalyst 10 is formed as flow-through type honeycomb structure as shown inFIG. 2 , and has a characteristic of capable of selectively reacting NOx with ammonia even in the presence of oxygen. - Further, arranged upstream of the
casing 11 is an urea-water injection valve 13 with aninjection nozzle 12, theinjection valve 13 being connected to anurea water tank 14 arranged at an appropriate site via an urea-water supply line 15, so that the urea water (reducing agent) 17 in thetank 14 can be added upstream of theselective reduction catalyst 10 via theinjection valve 13 by driving asupply pump 16 incorporated in thesupply line 15. Thus, urea-water adding means (reducing-agent adding means) 18 is constituted by the urea-water injection valve 13,urea water tank 14, urea-water supply line 15 andsupply pump 16. - The
engine 1 is provided with arevolution sensor 19 for detecting revolution of the engine. Arevolution signal 19 a from therevolution sensor 19 and aload signal 20 a from an accelerator sensor 20 (sensor for detecting treadled angle of an accelerator pedal) are inputted into an engine control unit or electric control unit 21 (ECU). - In the
ECU 21, a fuel injection signal 22 a for commanding fuel injection timing and amount to be injected is outputted to afuel injection device 22 for injecting fuel to each cylinder of theengine 1, so that appropriate fuel injection control is carried out on the basis of current operation status judged from the above-mentioned revolution andload signals sensors - More specifically, the
fuel injection device 22 comprises a plurality of injectors (not shown) each for each cylinder, an electromagnetic valve in each of the injectors being controlled in its opening by the fuel injection signal 22 a so as to appropriately control the fuel injection timing and amount to be injected. - An NOx deputation control device 23 (control device) arranged separately from the
ECU 21 outputs a valve-opening command signal 13 a to the urea-water injection valve 13, and further outputs adrive command signal 16 a to thesupply pump 16. Thus, by valve-opening actuation of theinjection valve 13, the amount of theurea water 17 to be added is appropriately controlled and, upon such addition of the urea water any required injection pressure is obtained by driving thesupply pump 16. - The NOx
depuration control device 23 receives from theECU 21 the revolution andload signals sensors urea water 17 to be added commensurate with the estimated NOx generation amount is calculated and addition of such required amount ofurea water 17 is carried out. - Inputted to the NOx
deputation control device 23 aredetection signals selective reduction catalyst 10 for detecting NOx concentrations as well as adetection signal 26 a from atemperature sensor 26 arranged on the entry side of thecatalyst 10; on the basis of these detection signals 24 a, 25 a and 26 a, abnormality where a predetermined temperature or more is attained and a predetermined Nox reduction ratio is not attained is judged and, when such abnormality is judged, the control device outputs acontrol signal 21 a to theECU 21 so as to command restriction of an amount of fuel to be injected. - More specifically, as shown in
FIG. 3 which shows specific control sequence in the NOxdeputation control device 23, therevolution signal 19 a from therevolution sensor 19 is ascertained in step S1; thedetection signal 26 a from thetemperature sensor 26 is ascertained in step S2; and the detections signals 24 a and 25 a from both of the NOx sensors 24 and 25, respectively, are ascetained in step S3. Under the operation status that 50% or more of Nox reduction ratio is surely obtained provided that the NOx deputation system has no malfunction, whether the procedure advances to step S4 where whether the ratio of the exit-side NOx concentration to the entry-side NOx concentration is less than 0.5 or not is judged; if affirmative or “YES”, the procedure proceeds to step S5 where restriction of an amount of fuel to be injected is commanded ascontrol signal 21 a to theECU 21; and if negative or “NO”, the procedure returns to step S1 and the same control sequence is repeated. - In this respect, ascertainment of temperature at step S2 may not always be carried out by actual measurement through the
temperature sensor 26 arranged on the entry side of theselective reduction catalyst 10. For example, the exhaust temperature may be estimated from the operation status on the basis of the sensed engine revolution and load. - When the
ECU 21 receives thecontrol signal 21 a from the NOxdeputation control device 23, it selects a map for fuel injection control with the fuel injection amount being reduced than normal, so that on the basis of this map, a reduced amount of fuel to be injected than usaul is outputted as fuel injection signal 22 a to thefuel injection device 22. - In this case, restriction of the fuel injection amount lower than usual must be accompanied by changes of injection timing and pressure to appropriate values (corresponding to the change of the fuel injection amount). Therefore these are also adapted to be changed accordingly.
- With the exhaust emission control device thus constructed, NOx concentrations on the entry and exit sides of the
selective reduction catalyst 10 are monitored by NOxdeputation control device 23 on the basis of the detection signals 24 a and 25 a from both of the NOx sensors 24 and 25: when no remarkable difference between those on the entry and exit sides of theselective reduction catalyst 10 is ascertained, abnormality as non-attainment of a predetermined Nox reduction ratio is judged, and when such abnormality is judged, thecontrol signal 21 a is outputted from the NOxdepuration control device 23 to theECU 21 so as to restrict the amount of fuel to be injected; as a result, an amount of NOx to be generated in theengine 1 is reduced to suppress the increase of NOx emission. - Thus, according to the above-mentioned embodiment, even if the NOx deputation system has malfunction, an amount of fuel to be injected can be restricted to reduce an amount of NOx to be generated in the
engine 1 to thereby minimize increase of NOx emission. - It is to be understood that an exhaust emission control device of the invention is not limited to the above-mentioned embodiment and that various changes and modifications may be effected without leaving the gist of the invention. For example, the reducing agent added to the selective reduction catalyst may be diesel oil or the like other than the urea water.
Claims (2)
1. An exhaust emission control device wherein selective reduction catalyst is incorporated in an exhaust pipe, a reducing agent being added upstream of said catalyst by reducing-agent adding means to depurate NOx through reduction, comprising NOx sensors arranged respectively on entry and exit sides of the selective reduction catalyst for detecting NOx concentrations, and a control device for judging abnormality on the basis of detection signals from both of the NOx sensors by non-attainment of a predetermined NOx reduction ratio and for commanding restriction of an amount of fuel to be injected when said abnormality is judged.
2. An exhaust emission control device as claimed in claim 1 , wherein the reducing agent is urea water, the selective reduction catalyst having a characteristic of capable of selectively reacting NOx with ammonia even in the presence of oxygen.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2004179734A JP2006002663A (en) | 2004-06-17 | 2004-06-17 | Exhaust emission control device |
JP2004-179734 | 2004-06-17 | ||
PCT/JP2005/011022 WO2005124116A1 (en) | 2004-06-17 | 2005-06-16 | Exhaust gas purification apparatus |
Publications (1)
Publication Number | Publication Date |
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US20080034732A1 true US20080034732A1 (en) | 2008-02-14 |
Family
ID=35509736
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/569,688 Abandoned US20080034732A1 (en) | 2004-06-17 | 2005-06-16 | Exhaust Emission Control Device |
Country Status (4)
Country | Link |
---|---|
US (1) | US20080034732A1 (en) |
EP (1) | EP1767754A4 (en) |
JP (1) | JP2006002663A (en) |
WO (1) | WO2005124116A1 (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090013666A1 (en) * | 2007-07-09 | 2009-01-15 | Jae Yoon Jung | Method for determining malfunction of nitrogen oxide sensor and selective catalytic reduction system operating the same |
US20100031641A1 (en) * | 2007-12-27 | 2010-02-11 | Toyota Jidosha Kabushiki Kaisha | Exhaust purification device of an internal combustion engine |
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Also Published As
Publication number | Publication date |
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JP2006002663A (en) | 2006-01-05 |
WO2005124116A1 (en) | 2005-12-29 |
EP1767754A1 (en) | 2007-03-28 |
EP1767754A4 (en) | 2008-09-17 |
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