US20090188236A1 - Exhaust gas purifying device - Google Patents
Exhaust gas purifying device Download PDFInfo
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- US20090188236A1 US20090188236A1 US11/664,735 US66473505A US2009188236A1 US 20090188236 A1 US20090188236 A1 US 20090188236A1 US 66473505 A US66473505 A US 66473505A US 2009188236 A1 US2009188236 A1 US 2009188236A1
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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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- 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
- B01D53/9413—Processes characterised by a specific catalyst
- B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
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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
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
- F02D41/402—Multiple injections
- F02D41/405—Multiple injections with post injections
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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
- B01D2251/202—Hydrogen
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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
- B01D2251/204—Carbon monoxide
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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
- B01D2251/208—Hydrocarbons
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1021—Platinum
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1023—Palladium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1025—Rhodium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/20—Metals or compounds thereof
- B01D2255/204—Alkaline earth metals
- B01D2255/2042—Barium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/90—Physical characteristics of catalysts
- B01D2255/91—NOx-storage component incorporated in the catalyst
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/90—Physical characteristics of catalysts
- B01D2255/915—Catalyst supported on particulate filters
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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
- F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
- F01N2430/08—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing
- F01N2430/085—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing at least a part of the injection taking place during expansion or exhaust stroke
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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
- F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
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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
- F02D2250/00—Engine control related to specific problems or objectives
- F02D2250/11—Oil dilution, i.e. prevention thereof or special controls according thereto
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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
- F02D41/1446—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 exhaust temperatures
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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
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
- F02D41/402—Multiple injections
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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
- Y02T10/40—Engine management systems
Definitions
- the present invention relates to a device that purifies exhaust gas by occluding NOx contained in the exhaust gas of an engine with a NOx occluding reduction catalyst, and also regenerates the catalyst.
- an exhaust gas purifying device for engine in which a filter for collecting particulate is provided in an exhaust passage and the filter is regenerated at the time of filter regeneration (for example, refer to Patent Document 1).
- a regenerating means is provided which carries out per one cycle of engine two times of post-injections and oxygen concentration control of exhaust gas so as to obtain a certain target regeneration speed during the filter regeneration.
- the post-injection is carried out by using a common rail type fuel injecting device.
- the regeneration period using the regenerating means for filter is made up of an early period, a middle period, and a later period.
- the early period consists of an early stage at which temperature elevating control for controlling the temperature to the catalyst activating temperature is carried out and a later stage at which temperature elevating control for controlling the bed temperature of filter to a first target bed temperature, which is a temperature at which the particulate ignites by itself, is carried out.
- a first target bed temperature which is a temperature at which the particulate ignites by itself.
- the first post-injection timing is set in the range from the top dead center position of a piston close to main injection to 60 degrees after the top dead center, and the configuration is made so that the fuel injected by this post-injection burns in a cylinder to directly increase the exhaust gas temperature.
- the second post-injection timing is set 60 degrees or later after the top dead center of the piston, and the configuration is made so that the fuel injected by this post-injection scarcely burns in the cylinder, and is supplied as HC to the oxidation catalyst carried by the filter.
- the bed temperature of filter is rapidly increased to the first target bed temperature.
- first oxygen concentration control is carried out in such a manner that the bed temperature of filter does not exceed the allowable highest temperature. Thereby, a decrease in the durability of filter can be prevented.
- sufficient oxygen is supplied to the filter by increasing the target oxygen concentration as compared with the concentration at the time of first oxygen concentration control. Thereby, the particulate remaining in the filter at the time close to the finish of regeneration can be burnt off rapidly and surely. As a result, the filter regeneration period can be shortened, and the filter can be regenerated almost completely.
- Patent Document 1 Japanese Unexamined Patent Application Publication No. 2004-183525 (claims 1 to 7, paragraphs [0014] to [0019], paragraph [0023], paragraph [0032])
- An object of the present invention is to provide an exhaust gas purifying device capable of efficiently regenerating a NOx occluding reduction catalyst that occludes NOx by post-injecting a necessary and sufficient quantity of fuel without diluting engine oil on the inner wall surface of a cylinder.
- An invention of claim 1 provides an improvement of an exhaust gas purifying device including a NOx occluding reduction catalyst 16 that is provided in an exhaust gas passage 14 of an engine 11 and carries a NOx absorbing agent and an active metal; and a fuel adding means 17 that adds a fuel 15 to the exhaust gas in the exhaust gas passage 14 and thereby supplies the fuel 15 to the NOx occluding reduction catalyst 16 .
- the characteristic configuration is that the fuel adding means 17 is an accumulator fuel injector that carries out post-injection, following main injection into a cylinder 22 of the engine 11 , at timing such that the fuel 15 does not ignite in the cylinder 22 , and the post-injection is carried out at the later period of the expansion stroke of the engine 11 in divided 3 to 20 times.
- the NOx absorbing agent in the catalyst 16 occludes NOx in the exhaust gas as nitrate, and hydrocarbon in the exhaust gas is oxidized by the oxidation action of the active metal carried on the catalyst 16 .
- the accumulator fuel injector 17 carries out post-injection in divided 3 to 20 times at timing such that the fuel 15 does not ignite in the engine 11 . This configuration prevents engine oil on the inner wall surface of the cylinder 22 from being diluted by the fuel, thereby increasing the concentration of hydrocarbon in the exhaust gas at the inlet of the catalyst 16 .
- hydrocarbon reacts with oxygen in the exhaust gas at the inlet of the catalyst 16 , by which oxygen is consumed.
- the air excess ratio of the exhaust gas on the exhaust gas downstream side of the inlet of the catalyst 16 decreases, and HC, CO or H 2 increase as a reducing agent. Therefore, NOx occluded by the catalyst 16 reacts with the HC etc. to yield N 2 , CO 2 and H 2 O, which are released from the catalyst 16 . Since the HC in the exhaust gas has the optimal concentration, most of the HC can be caused to function as a reducing agent in the catalyst 16 .
- An invention of to claim 2 is based on claim 1 and further characterized in that, as shown in FIGS. 2 and 3 , when the top dead center position of a piston 26 , which is the start time of the expansion stroke of the engine 11 , is a crank angle of 0 degree, among the post-injections carried in divided 3 to 20 times at the later period of the expansion stroke, the first post-injection is started in the range of 90 to 120 degrees of the crank angle.
- the fuel 15 injected by the post-injection does not ignite in the engine 11 , and can be supplied surely to the catalyst as it remains an unburned fuel 15 .
- An invention of claim 3 is based on claim 1 and further characterized in that, as shown in FIG. 1 , the NOx occlusion quantity of the NOx occluding reduction catalyst 16 is calculated from a prediction map based on an engine load and an engine rotational speed.
- the NOx occlusion quantity of the catalyst 16 can be predicted relatively exactly without the use of a sensor for detecting the concentration of NOx.
- the injection quantities of post-injections carried out in divided 3 to 20 times are equal to each other or decrease gradually after the first post-injection.
- the fuel adding means is an accumulator fuel injector that carries out post-injection, following the main injection into the engine, at timing such that the fuel does not ignite in the engine, and the configuration is made such that the post-injection is carried out in divided 3 to 20 times at the later period of the expansion stroke of the engine. Therefore, NOx in the exhaust gas is occluded as nitrate by the NOx occluding reduction catalyst, and hydrocarbon in the exhaust gas is oxidized. When the NOx occlusion quantity of the catalyst approaches the saturated state, the accumulator fuel injector carries out post-injection in divided 3 to 20 times at timing such that the fuel does not ignite in the engine.
- This configuration prevents engine oil on the inner wall surface of the cylinder from being diluted by the fuel, thereby increasing the concentration of HC in the exhaust gas at the outlet of catalyst.
- HC reacts with oxygen in the exhaust gas, by which oxygen is consumed, and HC etc. increase as a reducing agent in the state in which oxygen is scarcely present. Therefore, NOx occluded by the catalyst reacts with the HC etc. to yield N 2 etc., which are released from the catalyst, so that the catalyst can be regenerated efficiently. Since HC in the exhaust gas has the optimal concentration, most of HC can be caused to function as a reducing agent in the NOx occluding reduction catalyst.
- the first post-injection is started in the range of 90 to 120 degrees of the crank angle, the fuel injected by the post-injection does not ignite in the engine, and can be supplied surely to the catalyst as it remains an unburned fuel.
- the NOx occlusion quantity of the NOx occluding reduction catalyst is calculated from the prediction map based on the engine load and the engine rotational speed, the NOx occlusion quantity of the catalyst can be predicted relatively exactly without the use of the sensor for detecting the concentration of NOx.
- FIG. 1 is a configuration view showing an exhaust gas purifying device including an engine in accordance with a first embodiment of the present invention
- FIG. 2 is a sectional view of an essential portion, showing an expansion stroke of an engine
- FIG. 3 is a graph showing the timing and quantity of main injection and post-injection
- FIG. 4 is a sectional view corresponding to FIG. 3 , showing a second embodiment of the present invention.
- FIG. 5 is a sectional view corresponding to FIG. 3 , showing a third embodiment of the present invention.
- FIG. 6 is a sectional view corresponding to FIG. 3 , showing a fourth embodiment of the present invention.
- an intake port 12 a of a diesel engine 11 is communicatingly connected with an intake pipe 13 b through an intake manifold 13 a, and an exhaust port 12 b is communicatingly connected with an exhaust pipe 14 b through an exhaust manifold 14 a.
- a NOx occluding reduction catalyst 16 is provided in an intermediate portion of the exhaust pipe 14 b.
- the NOx occluding reduction catalyst 16 is a platinum-barium-alumina catalyst that occludes NOx in exhaust gas flowing into the exhaust pipe 14 b and is regenerated by the release of the occluded NOx when the concentration of hydrocarbon (HC) in the exhaust gas increases.
- this catalyst 16 has a cordierite-made monolithic carrier in which a lattice-shaped or honeycomb-shaped passage is formed in the direction of the exhaust gas flowing and a coat layer that is formed on the monolithic carrier and carries a NOx occluding agent and a noble metal (active metal).
- the active metal is exemplified by platinum (Pt), palladium (Pd), rhodium (Rh), and the like.
- a particulate filter with an oxidation catalyst namely, a particulate filter that carries an active metal functioning as an oxidation catalyst.
- the active metal is exemplified by platinum (Pt), palladium (Pd), rhodium (Rh), and the like can be cited.
- a fuel adding means 17 is provided to add a fuel 15 to the exhaust gas in the exhaust pipe 14 b and thereby supply the fuel 15 to the catalyst 16 ( FIGS. 1 and 2 ).
- the fuel adding means 17 is an accumulator fuel injector that regulates the injection timing and injection quantity of the fuel 15 injected into the engine 11 .
- This accumulator fuel injector 17 has electronically controlled injectors 18 each mounted on a cylinder head 12 , a common rail 20 connected to these injectors 18 via fuel transfer pipes 19 , and a fuel supply pump (not shown) connected to the common rail 20 via a fuel supply pipe 21 ( FIGS. 1 and 2 ).
- the injector 18 consists of an injection nozzle 18 a inserted into the cylinder head 12 so as to face to a cylinder 22 , a needle valve (not illustrated) that can open and close the injection hole of the injection nozzle 18 a, and an electromagnetic valve 18 b for injector, which vertically moves the needle valve provided at the proximal end of the injection nozzle 18 a via a compound piston and a unidirectional orifice plate.
- the configuration is made such that when the electromagnetic valve 18 b for injector is in an off state, the injection hole of the injection nozzle 18 a is closed, and when the electromagnetic valve 18 b for injector is turned on, the injection hole is opened and hence the fuel 15 is injected into the cylinder 22 .
- the intake port 12 a and the exhaust port 12 b are formed on the cylinder head 12 so as to face to the cylinder 22 .
- the intake port 12 a is openably closed by an intake valve 23
- the exhaust port 12 b is openably closed by an exhaust valve 24 ( FIG. 2 ).
- a piston 26 is housed so as to be movable up and down.
- the load of the engine 11 is detected by a load sensor 27 , and the rotational speed of the engine 11 is detected by a rotation sensor 28 ( FIG. 1 ).
- a temperature sensor 29 In the exhaust pipe 14 b on the exhaust gas upstream side of the catalyst 16 , there is provided a temperature sensor 29 that detects the temperature of exhaust gas flowing in the exhaust pipe 14 b.
- the detection outputs of the load sensor 27 , the rotation sensor 28 , and the temperature sensor 29 are connected to the control input of a controller 31 , and the control output of the controller 31 is connected to the electromagnetic valves 18 b for injector.
- the controller 31 is provided with a memory 32 .
- This memory 32 stores a map for predicting the NOx occlusion quantity of the catalyst 16 based on the engine load detected by the load sensor 27 and the engine rotational speed detected by the rotation sensor 28 .
- the engine 11 is started, and the temperature sensor 29 detects the exhaust gas temperature lower than 220° C.
- the controller 31 calculates the NOx occlusion quantity of the catalyst 16 from the NOx occlusion quantity prediction map stored in the memory 32 based on the engine load detected by the load sensor 27 and the engine rotational speed detected by the rotation sensor 28 . If it is judged that this occlusion quantity is smaller than a predetermined quantity, the controller 31 does not carry out the post-injection of the fuel 15 , and controls the electromagnetic valves 18 b for injector so that the ordinary operation state is established. Therefore, the exhaust gas exhausted from the engine 11 passes through the exhaust pipe 14 b and the catalyst 16 . At this time, NOx contained in the exhaust gas is occluded by the catalyst 16 .
- the NOx discharged from the engine 11 reacts with O 2 in the exhaust gas to yield No 2 in the catalyst 16 . Further, the No 2 reacts with BaO and BaCO 3 in the catalyst 16 to yield [Ba(NO 3 ) 2 ], and is occluded by the catalyst 16 in this state.
- HC contained in the exhaust gas is oxidized by the oxidation action of the noble metal (active metal) carried on the coat layer of the catalyst 16 .
- the controller 31 judges that the NOx occlusion quantity of the catalyst 16 approaches the saturated state, the controller 31 controls the electromagnetic valves 18 b for injector to carry out main-injection of the fuel 15 into the engine 11 , and, following the main injection, carries out post-injection at timing such that the fuel 15 does not ignite in the cylinder 22 in divided 3 to 20 times, preferably 5 to 10 times.
- the first post-injection is started in the range of 90 to 120 degrees, preferably 100 to 110 degrees, of crank angle.
- the post-injection is carried out in divided three times, and the first post-injection is carried out at a crank angle of about 90 degrees.
- the second and third post-injections are carried out at equal intervals within the expansion stroke. In this embodiment, the post-injections are carried out every about 30 degrees of crank angle.
- the injection quantities of post-injections from the first post-injection to the third post-injection are equal to each other.
- the total injection quantity of the first to third post-injections is preferably 20 to 100%.
- the reason why the post-injection is carried out in divided 3 to 20 times is that if the number of post-injections is smaller than 2, the injection speed of fuel increases as the injection quantity becomes larger and the fuel reaches the inner wall surface of cylinder, causing a risk that the engine oil on the inner wall surface of cylinder may be diluted by the fuel, and if the number of post-injections exceeds 20, the response of the needle valve of injector decreases.
- the reason why the first post-injection is started in the range of 90 to 120 degrees of crank angle is that the post-injected fuel is prevented from igniting in the cylinder. Further, the reason why the total injection quantity of post-injections is limited to the range of 20 to 100% at the time when the injection quantity of main injection is 100% is that if the total injection quantity is smaller than 20%, the catalyst 16 does not have a sufficient reduction atmosphere, and if the total injection quantity exceeds 100%, the engine oil is diluted, or the temperature of the catalyst 16 rises excessively.
- the oxygen concentration on the catalyst 16 decreases relatively. That is to say, the air excess ratio of exhaust gas at the inlet of the catalyst 16 decreases, and HC, CO or H 2 increase as a reducing agent. As a result, NOx occluded by the catalyst 16 is released from the catalyst 16 as described below. First, [Ba(NO 3 ) 2 ] occluded by the catalyst 16 reacts with the reducing agent in the exhaust gas and is reduced to NO 2 or N 2 .
- the catalyst 16 functions as a reduction catalyst having high selectivity, and thus the NO 2 reacts with CO and HC in the exhaust gas to yield and discharge harmless N 2 , CO 2 and H 2 O into the atmosphere.
- the catalyst 16 since the catalyst 16 is regenerated, NOx in the exhaust gas can again be occluded by the catalyst 16 , and thus NOx contained in the exhaust gas at the outlet of the catalyst 16 can be reduced.
- HC yielded by the post-injection of the fuel 15 has the optimal concentration, most of HC functions as a reducing agent in the catalyst 16 as described above. However, some of HC does not function as a reducing agent, and passes through the catalyst 16 as it remains unchanged. Therefore the concentration of HC at the outlet of the catalyst 16 increases. But this unburned HC is collected by a particulate filter with a catalyst (not illustrated). The unburned HC collected by this filter is oxidized and burnt by the oxidation action of the noble metal (active metal such as Pt, Pd or Rh) carried on this filter when the exhaust gas that does not contain unburned fuel and is in a lean state in which the air excess ratio is high flows into the filter.
- the noble metal active metal such as Pt, Pd or Rh
- the concentration of HC at the outlet of the filter is kept low, so that the discharge of HC into the atmosphere can be prevented, and the particulate containing soot collected on the filter can be burnt by the heat of reaction. Therefore, the discharge of particulate into the atmosphere can be prevented.
- a natural supply type diesel engine is presented as the engine.
- the exhaust gas purifying device of the present invention may be used for a diesel engine with a turbocharger.
- FIG. 4 shows a second embodiment of the present invention.
- the post-injection is carried out so that the injection quantity is decreased gradually from the first to the third post-injection.
- the injection quantity of the first post-injection is largest, the injection quantity of the second post-injection is made smaller than that of the first post-injection, and the injection quantity of the third post-injection is further decreased.
- the total injection quantity of post-injection is equal to that of the post-injection of the first embodiment.
- the other configurations are the same as those of the first embodiment.
- the exhaust gas purifying device configured as described above, even if the injection quantity of the first post-injection is large, the injected fuel evaporates before reaching the inner wall surface of cylinder because the temperature in the cylinder is extremely high, and the quantity of post-injection decreases as the temperature in the cylinder decreases. As a result, the adhesion of fuel onto the inner wall surface of cylinder due to post-injection can be prevented more surely than in the case of the first embodiment.
- the other operations are almost the same as those of the first embodiment, so that the repeated explanation is omitted.
- FIG. 5 shows a third embodiment of the present invention.
- the post-injection is carried out in divided five times, and the first post-injection is carried out at a crank angle of about 90 degrees.
- the second to fifth post-injections are carried out at equal intervals in the expansion stroke.
- the post-injections are carried out every about 15 degrees of crank angle.
- the total injection quantity of the first to fifth post-injections is equal to the total injection quantity of the first to third post-injections in the first embodiment.
- the other configurations are the same as those of the first embodiment.
- the injection quantity of each post-injection is smaller than the injection quantity of each post-injection in the first embodiment, so that the adhesion of fuel onto the inner wall surface of cylinder due to post-injection can be prevented more surely than in the case of the first embodiment.
- the other operations are almost the same as those of the first embodiment, and thus the repeated explanation is omitted.
- FIG. 6 shows a fourth embodiment of the present invention.
- the post-injection is carried out in such a manner that the injection quantity is decreased gradually from the first time to the fifth time.
- the injection quantity of the first post-injection is largest, and the injection quantity of the second and subsequent post-injections is decreased gradually.
- the total injection quantity of post-injection is equal to that of the post-injection of the third embodiment.
- the other configurations are the same as those of the third embodiment.
- the exhaust gas purifying device configured as described above, even if the injection quantity of the first post-injection is large, the injected fuel evaporates before reaching the inner wall surface of cylinder because the temperature in the cylinder is extremely high, and the quantity of post-injection decreases as the temperature in the cylinder decreases. As a result, the adhesion of fuel onto the inner wall surface of cylinder due to post-injection can be prevented more surely than in the case of the third embodiment.
- the other operations are almost the same as those of the third embodiment, and thus the repeated explanation is omitted.
- the NOx occluding reduction catalyst that occludes NOx can be regenerated efficiently by carrying out post-injection of a necessary and sufficient quantity of fuel without diluting engine oil on the inner wall surface of cylinder. Therefore, the present invention can be applied to not only an onboard engine but also an engine for industrial machinery or the like.
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- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Biomedical Technology (AREA)
- Health & Medical Sciences (AREA)
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Fuel-Injection Apparatus (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
A NOx occluding reduction catalyst that occludes NOx is efficiently regenerated by carrying our post-injection of a necessary and sufficient quantity of fuel without diluting engine oil on the inner wall surface of a cylinder. A NOx absorbing agent and an active metal are carried on the NOx occluding reduction catalyst (16) provided in an exhaust gas passage (14) of an engine (11), and the fuel is supplied to the NOx occluding reduction catalyst (16) by adding the fuel to the exhaust gas in the exhaust gas passage (14) with a fuel adding means (17). The fuel adding means (17) is an accumulator fuel injector that carries out post-injection, following main injection into a cylinder (22) of the engine (11), at timing such that the fuel does not ignite in the cylinder (22). The post-injection with the accumulator fuel injector (17) is carried out in divided 3 to 20 times at the later period of the expansion stroke of the engine (11).
Description
- The present invention relates to a device that purifies exhaust gas by occluding NOx contained in the exhaust gas of an engine with a NOx occluding reduction catalyst, and also regenerates the catalyst.
- Conventionally, there has been disclosed an exhaust gas purifying device for engine in which a filter for collecting particulate is provided in an exhaust passage and the filter is regenerated at the time of filter regeneration (for example, refer to Patent Document 1). In this exhaust gas purifying device for engine, a regenerating means is provided which carries out per one cycle of engine two times of post-injections and oxygen concentration control of exhaust gas so as to obtain a certain target regeneration speed during the filter regeneration. The post-injection is carried out by using a common rail type fuel injecting device. The regeneration period using the regenerating means for filter is made up of an early period, a middle period, and a later period. In the case where the filter carries an oxidation catalyst, the early period consists of an early stage at which temperature elevating control for controlling the temperature to the catalyst activating temperature is carried out and a later stage at which temperature elevating control for controlling the bed temperature of filter to a first target bed temperature, which is a temperature at which the particulate ignites by itself, is carried out. At the early stage of the early period, one time of post-injection for increasing the exhaust gas temperature is carried out per one cycle of engine, and at the later stage of the early period, two times of post-injections for increasing the exhaust gas temperature and for supplying HC are carried out per one cycle of engine. Further, in the middle period, one time of post-injection for increasing the exhaust gas temperature is carried out per one cycle of engine, and in the later period, two times of post-injections for increasing the exhaust gas temperature and for supplying HC are carried out per one cycle of engine. Out of two times of post-injections, the first post-injection timing is set in the range from the top dead center position of a piston close to main injection to 60 degrees after the top dead center, and the configuration is made so that the fuel injected by this post-injection burns in a cylinder to directly increase the exhaust gas temperature. Out of the two times of post-injections, the second post-injection timing is set 60 degrees or later after the top dead center of the piston, and the configuration is made so that the fuel injected by this post-injection scarcely burns in the cylinder, and is supplied as HC to the oxidation catalyst carried by the filter.
- In the exhaust gas purifying device for engine configured as described above, first, at the early period of the filter regenerating period, the bed temperature of filter is rapidly increased to the first target bed temperature. Next, at the middle period of the filter regenerating period, in the state in which the bed temperature of filter is maintained at the first target bed temperature, first oxygen concentration control is carried out in such a manner that the bed temperature of filter does not exceed the allowable highest temperature. Thereby, a decrease in the durability of filter can be prevented. Further, at the later period of the filter regenerating period, in the state in which the bed temperature of filter is maintained at the second target bed temperature higher than the first target bed temperature, sufficient oxygen is supplied to the filter by increasing the target oxygen concentration as compared with the concentration at the time of first oxygen concentration control. Thereby, the particulate remaining in the filter at the time close to the finish of regeneration can be burnt off rapidly and surely. As a result, the filter regeneration period can be shortened, and the filter can be regenerated almost completely.
- Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-183525 (claims 1 to 7, paragraphs [0014] to [0019], paragraph [0023], paragraph [0032])
- In the conventional exhaust gas purifying device of engine described in Patent Document 1, the fuel injected by the second post-injection as it remains unburned is supplied to the oxidation catalyst carried by the filter. However, if this unburned fuel is injected by one time of post-injection per one cycle of engine, relatively large quantity of fuel must be injected at one time. Therefore, the injection speed is high, and the injected fuel reaches the inner wall surface of the cylinder. For this reason, the engine oil forming a lubrication film on the inner wall surface of the cylinder is diluted by the injected fuel, so that there occurs a trouble such that the lubrication of engine is hindered, and a sufficient quantity of fuel cannot be supplied to the filter by post-injection.
- An object of the present invention is to provide an exhaust gas purifying device capable of efficiently regenerating a NOx occluding reduction catalyst that occludes NOx by post-injecting a necessary and sufficient quantity of fuel without diluting engine oil on the inner wall surface of a cylinder.
- An invention of claim 1 provides an improvement of an exhaust gas purifying device including a NOx
occluding reduction catalyst 16 that is provided in anexhaust gas passage 14 of anengine 11 and carries a NOx absorbing agent and an active metal; and afuel adding means 17 that adds afuel 15 to the exhaust gas in theexhaust gas passage 14 and thereby supplies thefuel 15 to the NOxoccluding reduction catalyst 16. - The characteristic configuration is that the
fuel adding means 17 is an accumulator fuel injector that carries out post-injection, following main injection into acylinder 22 of theengine 11, at timing such that thefuel 15 does not ignite in thecylinder 22, and the post-injection is carried out at the later period of the expansion stroke of theengine 11 in divided 3 to 20 times. - In the exhaust gas purifying device described in claim 1, when the exhaust gas passes through the NOx
occluding reduction catalyst 16, the NOx absorbing agent in thecatalyst 16 occludes NOx in the exhaust gas as nitrate, and hydrocarbon in the exhaust gas is oxidized by the oxidation action of the active metal carried on thecatalyst 16. When the NOx occlusion quantity of thecatalyst 16 approaches the saturated state, theaccumulator fuel injector 17 carries out post-injection in divided 3 to 20 times at timing such that thefuel 15 does not ignite in theengine 11. This configuration prevents engine oil on the inner wall surface of thecylinder 22 from being diluted by the fuel, thereby increasing the concentration of hydrocarbon in the exhaust gas at the inlet of thecatalyst 16. Therefore, hydrocarbon reacts with oxygen in the exhaust gas at the inlet of thecatalyst 16, by which oxygen is consumed. As a result, the air excess ratio of the exhaust gas on the exhaust gas downstream side of the inlet of thecatalyst 16 decreases, and HC, CO or H2 increase as a reducing agent. Therefore, NOx occluded by thecatalyst 16 reacts with the HC etc. to yield N2, CO2 and H2O, which are released from thecatalyst 16. Since the HC in the exhaust gas has the optimal concentration, most of the HC can be caused to function as a reducing agent in thecatalyst 16. - An invention of to claim 2 is based on claim 1 and further characterized in that, as shown in
FIGS. 2 and 3 , when the top dead center position of apiston 26, which is the start time of the expansion stroke of theengine 11, is a crank angle of 0 degree, among the post-injections carried in divided 3 to 20 times at the later period of the expansion stroke, the first post-injection is started in the range of 90 to 120 degrees of the crank angle. - In the exhaust gas purifying device described in claim 2, the
fuel 15 injected by the post-injection does not ignite in theengine 11, and can be supplied surely to the catalyst as it remains anunburned fuel 15. - An invention of claim 3 is based on claim 1 and further characterized in that, as shown in
FIG. 1 , the NOx occlusion quantity of the NOxoccluding reduction catalyst 16 is calculated from a prediction map based on an engine load and an engine rotational speed. - In the exhaust gas purifying device described in claim 3, the NOx occlusion quantity of the
catalyst 16 can be predicted relatively exactly without the use of a sensor for detecting the concentration of NOx. - It is preferable that the injection quantities of post-injections carried out in divided 3 to 20 times are equal to each other or decrease gradually after the first post-injection.
- As described above, according to the present invention, the fuel adding means is an accumulator fuel injector that carries out post-injection, following the main injection into the engine, at timing such that the fuel does not ignite in the engine, and the configuration is made such that the post-injection is carried out in divided 3 to 20 times at the later period of the expansion stroke of the engine. Therefore, NOx in the exhaust gas is occluded as nitrate by the NOx occluding reduction catalyst, and hydrocarbon in the exhaust gas is oxidized. When the NOx occlusion quantity of the catalyst approaches the saturated state, the accumulator fuel injector carries out post-injection in divided 3 to 20 times at timing such that the fuel does not ignite in the engine. This configuration prevents engine oil on the inner wall surface of the cylinder from being diluted by the fuel, thereby increasing the concentration of HC in the exhaust gas at the outlet of catalyst. As a result, at the inlet of the catalyst, HC reacts with oxygen in the exhaust gas, by which oxygen is consumed, and HC etc. increase as a reducing agent in the state in which oxygen is scarcely present. Therefore, NOx occluded by the catalyst reacts with the HC etc. to yield N2 etc., which are released from the catalyst, so that the catalyst can be regenerated efficiently. Since HC in the exhaust gas has the optimal concentration, most of HC can be caused to function as a reducing agent in the NOx occluding reduction catalyst.
- If among the post-injections carried out in divided 3 to 20 times at the later period of the expansion stroke of engine, the first post-injection is started in the range of 90 to 120 degrees of the crank angle, the fuel injected by the post-injection does not ignite in the engine, and can be supplied surely to the catalyst as it remains an unburned fuel.
- Further, if the NOx occlusion quantity of the NOx occluding reduction catalyst is calculated from the prediction map based on the engine load and the engine rotational speed, the NOx occlusion quantity of the catalyst can be predicted relatively exactly without the use of the sensor for detecting the concentration of NOx.
-
FIG. 1 is a configuration view showing an exhaust gas purifying device including an engine in accordance with a first embodiment of the present invention; -
FIG. 2 is a sectional view of an essential portion, showing an expansion stroke of an engine; -
FIG. 3 is a graph showing the timing and quantity of main injection and post-injection; -
FIG. 4 is a sectional view corresponding toFIG. 3 , showing a second embodiment of the present invention; -
FIG. 5 is a sectional view corresponding toFIG. 3 , showing a third embodiment of the present invention; and -
FIG. 6 is a sectional view corresponding toFIG. 3 , showing a fourth embodiment of the present invention. - 11 diesel engine
- 14 exhaust gas passage
- 15 fuel
- 16 NOx occluding reduction catalyst
- 17 accumulator fuel injector (fuel adding means)
- 22 cylinder
- 26 piston
- The best mode for carrying out the present invention will now be described with reference to the accompanying drawings.
- As shown in
FIGS. 1 and 2 , anintake port 12 a of adiesel engine 11 is communicatingly connected with anintake pipe 13 b through anintake manifold 13 a, and anexhaust port 12 b is communicatingly connected with anexhaust pipe 14 b through anexhaust manifold 14 a. In an intermediate portion of theexhaust pipe 14 b, a NOx occludingreduction catalyst 16 is provided. The NOxoccluding reduction catalyst 16 is a platinum-barium-alumina catalyst that occludes NOx in exhaust gas flowing into theexhaust pipe 14 b and is regenerated by the release of the occluded NOx when the concentration of hydrocarbon (HC) in the exhaust gas increases. Although not illustrated, thiscatalyst 16 has a cordierite-made monolithic carrier in which a lattice-shaped or honeycomb-shaped passage is formed in the direction of the exhaust gas flowing and a coat layer that is formed on the monolithic carrier and carries a NOx occluding agent and a noble metal (active metal). The active metal is exemplified by platinum (Pt), palladium (Pd), rhodium (Rh), and the like. In theexhaust pipe 14 b on the exhaust gas downstream side of the NOx occludingreduction catalyst 16, although not illustrated, there is provided a particulate filter with an oxidation catalyst, namely, a particulate filter that carries an active metal functioning as an oxidation catalyst. The active metal is exemplified by platinum (Pt), palladium (Pd), rhodium (Rh), and the like can be cited. - On the other hand, on the
engine 11, a fuel adding means 17 is provided to add afuel 15 to the exhaust gas in theexhaust pipe 14 b and thereby supply thefuel 15 to the catalyst 16 (FIGS. 1 and 2 ). The fuel adding means 17 is an accumulator fuel injector that regulates the injection timing and injection quantity of thefuel 15 injected into theengine 11. Thisaccumulator fuel injector 17 has electronically controlledinjectors 18 each mounted on acylinder head 12, acommon rail 20 connected to theseinjectors 18 viafuel transfer pipes 19, and a fuel supply pump (not shown) connected to thecommon rail 20 via a fuel supply pipe 21 (FIGS. 1 and 2 ). Theinjector 18 consists of aninjection nozzle 18 a inserted into thecylinder head 12 so as to face to acylinder 22, a needle valve (not illustrated) that can open and close the injection hole of theinjection nozzle 18 a, and anelectromagnetic valve 18 b for injector, which vertically moves the needle valve provided at the proximal end of theinjection nozzle 18 a via a compound piston and a unidirectional orifice plate. The configuration is made such that when theelectromagnetic valve 18 b for injector is in an off state, the injection hole of theinjection nozzle 18 a is closed, and when theelectromagnetic valve 18 b for injector is turned on, the injection hole is opened and hence thefuel 15 is injected into thecylinder 22. Theintake port 12 a and theexhaust port 12 b are formed on thecylinder head 12 so as to face to thecylinder 22. Theintake port 12 a is openably closed by anintake valve 23, and theexhaust port 12 b is openably closed by an exhaust valve 24 (FIG. 2 ). Further, in thecylinder 22, apiston 26 is housed so as to be movable up and down. - The load of the
engine 11 is detected by aload sensor 27, and the rotational speed of theengine 11 is detected by a rotation sensor 28 (FIG. 1 ). In theexhaust pipe 14 b on the exhaust gas upstream side of thecatalyst 16, there is provided atemperature sensor 29 that detects the temperature of exhaust gas flowing in theexhaust pipe 14 b. The detection outputs of theload sensor 27, therotation sensor 28, and thetemperature sensor 29 are connected to the control input of acontroller 31, and the control output of thecontroller 31 is connected to theelectromagnetic valves 18 b for injector. Thecontroller 31 is provided with amemory 32. Thismemory 32 stores a map for predicting the NOx occlusion quantity of thecatalyst 16 based on the engine load detected by theload sensor 27 and the engine rotational speed detected by therotation sensor 28. - The operation of the exhaust gas purifying device configured as described above is explained.
- The
engine 11 is started, and thetemperature sensor 29 detects the exhaust gas temperature lower than 220° C. Thecontroller 31 calculates the NOx occlusion quantity of thecatalyst 16 from the NOx occlusion quantity prediction map stored in thememory 32 based on the engine load detected by theload sensor 27 and the engine rotational speed detected by therotation sensor 28. If it is judged that this occlusion quantity is smaller than a predetermined quantity, thecontroller 31 does not carry out the post-injection of thefuel 15, and controls theelectromagnetic valves 18 b for injector so that the ordinary operation state is established. Therefore, the exhaust gas exhausted from theengine 11 passes through theexhaust pipe 14 b and thecatalyst 16. At this time, NOx contained in the exhaust gas is occluded by thecatalyst 16. If, for example, barium (Ba) is used as a NOx absorbing agent carried on the coat layer of thecatalyst 16, the NOx discharged from theengine 11 reacts with O2 in the exhaust gas to yield No2 in thecatalyst 16. Further, the No2 reacts with BaO and BaCO3 in thecatalyst 16 to yield [Ba(NO3)2], and is occluded by thecatalyst 16 in this state. HC contained in the exhaust gas is oxidized by the oxidation action of the noble metal (active metal) carried on the coat layer of thecatalyst 16. - In the state in which the
temperature sensor 29 detects the exhaust gas temperature not lower than 220° C., if thecontroller 31 judges that the NOx occlusion quantity of thecatalyst 16 approaches the saturated state, thecontroller 31 controls theelectromagnetic valves 18 b for injector to carry out main-injection of thefuel 15 into theengine 11, and, following the main injection, carries out post-injection at timing such that thefuel 15 does not ignite in thecylinder 22 in divided 3 to 20 times, preferably 5 to 10 times. When the top dead center position of thepiston 26, which is the start time of the expansion stroke of theengine 11, is a crank angle of 0 degree, among the post-injections carried out dividedly at the later period of expansion stroke, the first post-injection is started in the range of 90 to 120 degrees, preferably 100 to 110 degrees, of crank angle. In this embodiment, as shown inFIGS. 2 and 3 , the post-injection is carried out in divided three times, and the first post-injection is carried out at a crank angle of about 90 degrees. The second and third post-injections are carried out at equal intervals within the expansion stroke. In this embodiment, the post-injections are carried out every about 30 degrees of crank angle. Further, the injection quantities of post-injections from the first post-injection to the third post-injection are equal to each other. When the injection quantity of main injection is 100%, the total injection quantity of the first to third post-injections is preferably 20 to 100%. The reason why the post-injection is carried out in divided 3 to 20 times is that if the number of post-injections is smaller than 2, the injection speed of fuel increases as the injection quantity becomes larger and the fuel reaches the inner wall surface of cylinder, causing a risk that the engine oil on the inner wall surface of cylinder may be diluted by the fuel, and if the number of post-injections exceeds 20, the response of the needle valve of injector decreases. The reason why the first post-injection is started in the range of 90 to 120 degrees of crank angle is that the post-injected fuel is prevented from igniting in the cylinder. Further, the reason why the total injection quantity of post-injections is limited to the range of 20 to 100% at the time when the injection quantity of main injection is 100% is that if the total injection quantity is smaller than 20%, thecatalyst 16 does not have a sufficient reduction atmosphere, and if the total injection quantity exceeds 100%, the engine oil is diluted, or the temperature of thecatalyst 16 rises excessively. - By carrying out post-injection of the
fuel 15 at timing such that thefuel 15 does not ignite in thecylinder 22 as described above, the oxygen concentration on thecatalyst 16 decreases relatively. That is to say, the air excess ratio of exhaust gas at the inlet of thecatalyst 16 decreases, and HC, CO or H2 increase as a reducing agent. As a result, NOx occluded by thecatalyst 16 is released from thecatalyst 16 as described below. First, [Ba(NO3)2] occluded by thecatalyst 16 reacts with the reducing agent in the exhaust gas and is reduced to NO2 or N2. Next, thecatalyst 16 functions as a reduction catalyst having high selectivity, and thus the NO2 reacts with CO and HC in the exhaust gas to yield and discharge harmless N2, CO2 and H2O into the atmosphere. As a result, since thecatalyst 16 is regenerated, NOx in the exhaust gas can again be occluded by thecatalyst 16, and thus NOx contained in the exhaust gas at the outlet of thecatalyst 16 can be reduced. - Since HC yielded by the post-injection of the
fuel 15 has the optimal concentration, most of HC functions as a reducing agent in thecatalyst 16 as described above. However, some of HC does not function as a reducing agent, and passes through thecatalyst 16 as it remains unchanged. Therefore the concentration of HC at the outlet of thecatalyst 16 increases. But this unburned HC is collected by a particulate filter with a catalyst (not illustrated). The unburned HC collected by this filter is oxidized and burnt by the oxidation action of the noble metal (active metal such as Pt, Pd or Rh) carried on this filter when the exhaust gas that does not contain unburned fuel and is in a lean state in which the air excess ratio is high flows into the filter. Therefore, the concentration of HC at the outlet of the filter is kept low, so that the discharge of HC into the atmosphere can be prevented, and the particulate containing soot collected on the filter can be burnt by the heat of reaction. Therefore, the discharge of particulate into the atmosphere can be prevented. - In this embodiment, a natural supply type diesel engine is presented as the engine. However, the exhaust gas purifying device of the present invention may be used for a diesel engine with a turbocharger.
-
FIG. 4 shows a second embodiment of the present invention. - In this embodiment, the post-injection is carried out so that the injection quantity is decreased gradually from the first to the third post-injection. In other words, among the three times of post-injections, the injection quantity of the first post-injection is largest, the injection quantity of the second post-injection is made smaller than that of the first post-injection, and the injection quantity of the third post-injection is further decreased. The total injection quantity of post-injection is equal to that of the post-injection of the first embodiment. The other configurations are the same as those of the first embodiment.
- In the exhaust gas purifying device configured as described above, even if the injection quantity of the first post-injection is large, the injected fuel evaporates before reaching the inner wall surface of cylinder because the temperature in the cylinder is extremely high, and the quantity of post-injection decreases as the temperature in the cylinder decreases. As a result, the adhesion of fuel onto the inner wall surface of cylinder due to post-injection can be prevented more surely than in the case of the first embodiment. The other operations are almost the same as those of the first embodiment, so that the repeated explanation is omitted.
-
FIG. 5 shows a third embodiment of the present invention. - In this embodiment, the post-injection is carried out in divided five times, and the first post-injection is carried out at a crank angle of about 90 degrees. The second to fifth post-injections are carried out at equal intervals in the expansion stroke. In this embodiment, the post-injections are carried out every about 15 degrees of crank angle. Further, the total injection quantity of the first to fifth post-injections is equal to the total injection quantity of the first to third post-injections in the first embodiment. The other configurations are the same as those of the first embodiment.
- In the exhaust gas purifying device configured as described above, the injection quantity of each post-injection is smaller than the injection quantity of each post-injection in the first embodiment, so that the adhesion of fuel onto the inner wall surface of cylinder due to post-injection can be prevented more surely than in the case of the first embodiment. The other operations are almost the same as those of the first embodiment, and thus the repeated explanation is omitted.
-
FIG. 6 shows a fourth embodiment of the present invention. - In this embodiment, the post-injection is carried out in such a manner that the injection quantity is decreased gradually from the first time to the fifth time. In other words, among the five times of post-injections, the injection quantity of the first post-injection is largest, and the injection quantity of the second and subsequent post-injections is decreased gradually. The total injection quantity of post-injection is equal to that of the post-injection of the third embodiment. The other configurations are the same as those of the third embodiment.
- In the exhaust gas purifying device configured as described above, even if the injection quantity of the first post-injection is large, the injected fuel evaporates before reaching the inner wall surface of cylinder because the temperature in the cylinder is extremely high, and the quantity of post-injection decreases as the temperature in the cylinder decreases. As a result, the adhesion of fuel onto the inner wall surface of cylinder due to post-injection can be prevented more surely than in the case of the third embodiment. The other operations are almost the same as those of the third embodiment, and thus the repeated explanation is omitted.
- The NOx occluding reduction catalyst that occludes NOx can be regenerated efficiently by carrying out post-injection of a necessary and sufficient quantity of fuel without diluting engine oil on the inner wall surface of cylinder. Therefore, the present invention can be applied to not only an onboard engine but also an engine for industrial machinery or the like.
Claims (4)
1. An exhaust gas purifying device comprising a NOx occluding reduction catalyst (16) that is provided in an exhaust gas passage (14) of an engine (11) and carries a NOx absorbing agent and an active metal; and a fuel adding means (17) that adds a fuel (15) to the exhaust gas in the exhaust gas passage (14) and thereby supplies the fuel (15) to the NOx occluding reduction catalyst (16), wherein
the fuel adding means (17) is an accumulator fuel injector that carries out post-injection, following main injection into a cylinder (22) of the engine (11), at timing such that the fuel (15) does not ignite in the cylinder (22), and
the post-injection is carried out at the later period of the expansion stroke of the engine (11) in divided 3 to 20 times.
2. The exhaust gas purifying device according to claim 1 , wherein when the top dead center position of a piston (26), which is the start time of the expansion stroke of the engine (11), is a crank angle of 0 degree, among the post-injections carried out in divided 3 to 20 times at the later period of the expansion stroke, the first post-injection is started in the range of 90 to 120 degrees of the crank angle.
3. The exhaust gas purifying device according to claim 1 , wherein the NOx occlusion quantity of the NOx occluding reduction catalyst (16) is integrated from a prediction map based on an engine load and an engine rotational speed.
4. The exhaust gas purifying device according to claim 1 , wherein the injection quantities of post-injections carried out in divided 3 to 20 times are equal to each other or decrease gradually after the first post-injection.
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JP2004290854A JP2006104989A (en) | 2004-10-04 | 2004-10-04 | Exhaust emission control device |
PCT/JP2005/017580 WO2006038480A1 (en) | 2004-10-04 | 2005-09-26 | Exhaust emission control device |
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US20090188236A1 true US20090188236A1 (en) | 2009-07-30 |
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EP (1) | EP1826372A1 (en) |
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US20120186236A1 (en) * | 2009-12-25 | 2012-07-26 | Yasumichi Aoki | Exhaust gas purification device for internal combustion engine |
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CN104975973A (en) * | 2014-04-09 | 2015-10-14 | 现代自动车株式会社 | Method For Compensating Post-injection Timing |
US20180313245A1 (en) * | 2017-04-28 | 2018-11-01 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas control apparatus for internal combustion engine |
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JP2008196352A (en) * | 2007-02-09 | 2008-08-28 | Mitsubishi Motors Corp | Fuel injection device for multi-cylinder engine |
DE102010014468B4 (en) * | 2010-04-09 | 2013-10-31 | Umicore Ag & Co. Kg | Process for the reduction of nitrous oxide in the exhaust aftertreatment of lean burn engines |
GB2544788A (en) * | 2015-11-27 | 2017-05-31 | Gm Global Tech Operations Llc | Method of operating a fuel injector of an internal combustion engine of a motor vehicle |
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US7320215B2 (en) * | 2003-11-07 | 2008-01-22 | Peugeot Ciitroen Automobiles Sa | System for providing assistance in regenerating depollution means integrated in a vehicle exhaust line |
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US20060086083A1 (en) * | 2004-10-21 | 2006-04-27 | Yasser Yacoub | In-cylinder method for air/fuel ratio control |
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US8707685B2 (en) * | 2009-12-25 | 2014-04-29 | Mitsubishi Heavy Industries, Ltd. | Exhaust gas purification device for internal combustion engine |
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US8984869B2 (en) * | 2010-10-27 | 2015-03-24 | Mitsubishi Heavy Industries, Ltd. | Exhaust gas emission control system for diesel engine |
US10677184B2 (en) | 2013-09-25 | 2020-06-09 | Hitachi Automotive Systems, Ltd. | Drive device for fuel injection device |
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US20150292431A1 (en) * | 2014-04-09 | 2015-10-15 | Hyundai Motor Company | Method for compensating post-injection timing |
US20180313245A1 (en) * | 2017-04-28 | 2018-11-01 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas control apparatus for internal combustion engine |
US11982244B1 (en) * | 2022-12-16 | 2024-05-14 | Caterpillar Inc. | System and method for in-cylinder dosing (ICD) for an engine |
Also Published As
Publication number | Publication date |
---|---|
EP1826372A1 (en) | 2007-08-29 |
CN101035970A (en) | 2007-09-12 |
WO2006038480A1 (en) | 2006-04-13 |
JP2006104989A (en) | 2006-04-20 |
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