WO2019124185A1 - Exhaust gas purification device for internal combustion engine - Google Patents
Exhaust gas purification device for internal combustion engine Download PDFInfo
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- WO2019124185A1 WO2019124185A1 PCT/JP2018/045645 JP2018045645W WO2019124185A1 WO 2019124185 A1 WO2019124185 A1 WO 2019124185A1 JP 2018045645 W JP2018045645 W JP 2018045645W WO 2019124185 A1 WO2019124185 A1 WO 2019124185A1
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- catalyst
- exhaust gas
- upstream
- downstream
- nox
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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
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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
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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
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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
- F01N3/24—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 constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
Definitions
- the present invention relates to an exhaust purification system of an internal combustion engine.
- exhaust gas purification for treating exhaust gas emitted from an engine which is often operated in a state with a large air-fuel ratio (a lean state in which the fuel concentration is lean) such as a lean burn gasoline engine or diesel engine
- a lean state in which the fuel concentration is lean such as a lean burn gasoline engine or diesel engine
- an NOx trap catalyst containing at least an alkali metal and / or an alkaline earth metal and substantially containing no noble metal is disposed upstream of the exhaust flow path, and contains a noble metal catalyst downstream.
- a three-way catalyst having no oxygen storage capacity (OSC), a PM filter, and a three-way catalyst having oxygen storage capacity (OSC) are sequentially arranged from the upstream side to the downstream side of the exhaust flow path.
- the three-way catalyst when the downstream side three-way catalyst does not have oxygen storage capacity (OSC), the three-way catalyst can start NOx purification promptly when transitioning to the rich state, but at the lean state Since the storage function does not have a storage function, the stoichiometric state can not be maintained when changing to the lean state, and there is a possibility that the purification of NOx by the three-way catalytic function can not be performed.
- Patent Document 2 although the exhaust gas can be purified by the three-way catalyst in the stoichiometric state, there is a possibility that the purification of NOx can not be sufficiently performed in the lean state because the NOx storage reduction catalyst is not provided.
- the present invention has been made to solve the above-described problems, and provides an exhaust gas purification apparatus for purifying exhaust gas discharged from an engine having a long lean state, which provides a technique for improving the exhaust gas purification capacity. With the goal.
- the present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following modes.
- an exhaust gas purification apparatus for an internal combustion engine includes an upstream catalyst disposed relatively upstream of an exhaust flow passage through which exhaust gas discharged from the internal combustion engine flows, and a downstream side of the exhaust flow passage with respect to the upstream catalyst.
- a downstream catalyst having an oxygen storage capacity, and the oxygen storage capacity of the upstream catalyst is lower than the oxygen storage capacity of the downstream catalyst, the upstream catalyst and the downstream catalyst At least one of these has a NOx storage reduction function.
- the oxygen storage capacity of the upstream side catalyst is lower than the oxygen storage capacity of the downstream side catalyst, it is possible to promptly start the NOx purification when changing to the rich state.
- the downstream side catalyst since the downstream side catalyst has an oxygen storage capacity, the stoichiometric state can be maintained even if fluctuations occur between the rich state and the lean state at the transition to the stoichiometric state, and the exhaust gas is stabilized. Can be purified.
- at least one of the upstream side catalyst and the downstream side catalyst has the NOx storage and reduction function, and therefore, even when the engine is lean, NOx can be sufficiently purified by the NOx storage and reduction catalyst. Therefore, according to this configuration, the exhaust gas purification capacity can be improved.
- At least the upstream side catalyst may have a NOx storage and reduction function. According to this configuration, the temperature of the NOx storage reduction catalyst can be raised promptly because the engine is close to the engine after the start of the engine, and the exhaust gas purification capacity can be further improved.
- both the upstream side catalyst and the downstream side catalyst may have a NOx storage and reduction function. According to this configuration, it is possible to further improve the NOx purification performance at the time of lean by the NOx storage reduction catalyst of both the upstream side catalyst and the downstream side catalyst.
- the exhaust gas control apparatus further includes a catalyst having a three-way catalyst function provided downstream of the upstream catalyst and upstream of the downstream catalyst in the exhaust passage. May be provided. According to this configuration, it is possible to further improve the exhaust gas purification capacity at the time of high load and high rotation where the flow rate of the exhaust gas increases.
- both the upstream catalyst and the downstream catalyst may have a three-way catalyst function.
- the exhaust gas purification capacity can be further improved by the three-way catalyst of both the upstream side catalyst and the downstream side catalyst.
- the exhaust gas purification apparatus can be miniaturized without providing a separate three-way catalyst.
- the catalyst having the three-way catalyst function is disposed on the upstream side of the three-way catalyst located relatively upstream and the downstream side of the three-way catalyst on the upstream side
- the oxygen storage capacity of the upstream three-way catalyst may be lower than the oxygen storage capacity of the downstream three-way catalyst. According to this configuration, it is possible to further improve the NOx purification performance when transitioning to the rich state. Further, the purification performance of the exhaust gas at the time of fluctuation between the rich state and the lean state can be further improved.
- the present invention can be realized in various modes, for example, a vehicle equipped with an exhaust gas purification catalyst, an exhaust gas purification device, an exhaust gas purification method, a device for manufacturing an exhaust gas purification device, a method for manufacturing an exhaust gas purification device, etc. It can be realized in a form.
- FIG. 1 is a view for explaining an exhaust gas purification device 30 for an internal combustion engine in the first embodiment.
- FIG. 1 illustrates the configuration of a vehicle 10 provided with the exhaust gas purification device 30 of the present embodiment.
- the vehicle 10 includes an engine 11, an intake passage 21, an exhaust passage 22, an exhaust return passage 23, a supercharging device 24, an exhaust purification device 30, a combustion switching control device 40, and an addition control device 60. And have.
- the engine 11 is an internal combustion engine such as a diesel engine or a gasoline engine, and an example diesel engine is shown here.
- Fuel (light oil) supplied from the fuel injection device 13 is injected to each cylinder 12 of the engine 11 at a predetermined timing under the control of the injection control device 41. Further, air is supplied to each cylinder 12 of the engine 11 from the intake passage 21 via an intake valve (not shown). The fuel may be injected to the air supplied from the intake passage 21 to the engine 11. Exhaust gas in the cylinder 12 of the engine 11 is discharged to the exhaust passage 22 via an exhaust valve (not shown). The rotational speed of the engine 11 is detected by the rotational speed sensor 51 and output to the combustion switching control device 40.
- the intake flow passage 21 is configured to include one or more intake pipes, and the downstream end is connected to the engine 11 and the upstream end is connected to an air filter (not shown).
- the air flowing into the intake passage 21 through the air filter is compressed by the intake compressor 25 of the supercharger 24 and then supplied to the engine 11.
- An intake throttle valve 28 is provided in the intake flow passage 21 between the supercharging device 24 and the engine 11, and the flow rate of air is controlled by the control of the intake and exhaust control device 42, and the intake amount to the engine 11 is Adjusted.
- the exhaust flow path 22 is configured to include one or more exhaust pipes, and the upstream end is connected to the engine 11 and the downstream end is open to the outside of the vehicle 10.
- the exhaust gas discharged from the engine 11 drives (rotates) the exhaust turbine 26 of the supercharging device 24 and then is discharged to the outside of the vehicle 10 via the exhaust gas purification device 30.
- a first NOx sensor 52 and a reducing agent addition device 61 are provided in the exhaust passage 22 on the upstream side of the exhaust purification device 30, and a second NOx sensor is provided in the exhaust passage 22 on the downstream side of the exhaust purification device 30.
- An exhaust temperature sensor 54 is provided.
- the first NOx sensor 52 measures the NOx concentration of the exhaust gas flowing into the exhaust purification device 30.
- the second NOx sensor 53 measures the NOx concentration of the exhaust gas discharged from the exhaust gas purification device 30.
- the exhaust temperature sensor 54 measures the temperature of the exhaust gas discharged from the exhaust purification device 30. Information detected by the first NOx sensor 52, the second NOx sensor 53, and the exhaust temperature sensor 54 is output to the combustion switching control device 40.
- the reducing agent addition device 61 injects the reducing agent into the exhaust flow path 22 on the upstream side of the exhaust gas purification device 30 at a predetermined timing under the control of the addition control device 60.
- light oil is injected as a reducing agent.
- the exhaust gas recirculation flow passage 23 is configured to include one or more exhaust gas recirculation pipes, and the upstream end thereof is connected to the upstream side of the supercharger 24 in the exhaust gas flow passage 22, and is downstream An end portion is connected to the downstream side of the intake throttle valve 28 in the intake passage 21.
- An exhaust gas recirculation amount adjustment valve (EGR valve) 29 is provided in the exhaust gas recirculation flow passage 23, and flows through the exhaust gas passage 22 on the upstream side of the supercharger 24 when the exhaust gas recirculation amount adjustment valve 29 is opened. A portion of the exhaust gas is discharged to the intake passage 21 downstream of the intake throttle valve 28.
- the flow rate of the exhaust gas returned from the exhaust flow passage 22 to the intake flow passage 21 is controlled by the intake and exhaust control device 42.
- the supercharging device 24 is a so-called turbocharger that includes an intake compressor 25, an exhaust turbine 26, and a shaft 27, and compresses air supplied to the engine 11 using kinetic energy of exhaust gas.
- the intake compressor 25 and the exhaust turbine 26 are connected by a shaft 27, and the power (rotational force) obtained by the exhaust turbine 26 is transmitted to the intake compressor 25.
- the exhaust gas purification device 30 is a device for purifying the exhaust gas flowing in the exhaust flow passage 22 and includes an upstream catalyst 31 and a downstream catalyst 32.
- the upstream side catalyst 31 is a NOx storage reduction catalyst disposed relatively upstream of the exhaust flow path 22, and has a three-way catalyst function, while substantially having an oxygen storage capacity (OSC: Oxygen Storage Capacity) Do not have).
- the downstream side catalyst 32 is a NOx storage reduction catalyst disposed relatively downstream of the exhaust flow path 22, and has both a three-way catalyst function and an oxygen storage capacity.
- the upstream catalyst 31 contains at least one of an alkali metal and an alkaline earth metal as a NOx storage reduction catalyst, and further contains one or both of a magnetic substrate and K 2 Ti 2 O 5 .
- alkali metals or alkaline earth metals which are main components for storing nitrogen oxides NOx include Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba and Ra.
- the function of the catalyst capable of storing and reducing NOx is also referred to as the NOx storage and reduction function.
- the presence or absence of the NOx storage reduction function in the catalyst means whether the catalyst has a component capable of storing and reducing NOx.
- the upstream catalyst 31 further contains a noble metal for exhibiting a three-way catalytic function.
- the noble metal is a metal having higher electronegativity than copper and is Rh, Pt, Pd, Ir, Au.
- the upstream side catalyst 31 substantially does not contain an oxygen storage / release material (OSC material) such as ceria, and does not substantially have an oxygen storage capacity (OSC).
- OSC material oxygen storage / release material
- the upstream side catalyst 31 has a configuration in which a NOx storage reduction catalyst having a three-way catalytic function and having substantially no oxygen storage capacity is formed on the surface of the porous substrate.
- the NOx storage reduction catalyst may be directly attached to the surface of the porous substrate, but is preferably supported on the porous substrate together with the metal oxide or via the metal oxide.
- metal oxides that can be used as a support include metal oxides such as Al 2 O 3 , SiO 2 , TiO 2 , Si 2 O-Al 2 O 3 , oxides of rare earths, and zeolites. be able to.
- the downstream catalyst 32 contains at least an alkali metal or an alkaline earth metal as a NOx storage reduction catalyst, and contains one or both of magnetic substrate and K 2 Ti 2 O 5 . Further, the downstream side catalyst 32 includes a precious metal for exhibiting a three-way catalytic function, as the upstream side catalyst 31 does. On the other hand, unlike the upstream catalyst 31, the downstream catalyst 32 contains an oxygen storage / release material (OSC material) such as ceria and has an oxygen storage capacity.
- OSC material oxygen storage / release material
- the downstream side catalyst 32 has a configuration in which a NOx storage reduction catalyst having both a three-way catalyst function and an oxygen storage capacity is formed on the surface of a porous substrate.
- the NOx storage reduction catalyst may be directly attached to the surface of the porous substrate, or may be supported on the porous substrate together with the metal oxide or via the metal oxide.
- the combustion switching control device 40 is a device for switching the combustion state (operating state) of the engine 11 and includes the injection control device 41, the intake and exhaust control device 42, the rotation speed sensor 51, the first NOx sensor 52, 2 are electrically connected to the NOx sensor 53, the exhaust temperature sensor 54, and the addition control device 60.
- the combustion switching control device 40 determines the combustion state of the engine 11 based on the information obtained from each sensor in a state where the air-fuel ratio (A / F) is larger than the theoretical air-fuel ratio (a lean state in which the fuel concentration is lean).
- a combustion mode control process is performed to switch to either a stoichiometric air-fuel ratio state (stoichiometric state) or a state where the air-fuel ratio is smaller than the theoretical air-fuel ratio (rich state in which the fuel concentration is high).
- FIG. 2 is a flowchart showing the combustion mode control process of the combustion switching control device 40.
- the combustion mode control process is started by turning on the ignition of the engine 11 and is repeatedly executed in a predetermined cycle.
- the combustion switching control device 40 acquires the engine rotational speed Ne, the exhaust temperature T, and the NOx concentration on the upstream side and the downstream side of the exhaust gas purification device 30 (step S11).
- the combustion switching control device 40 acquires the engine rotational speed Ne from the detection value of the rotational speed sensor 51, acquires the exhaust gas temperature T from the detection value of the exhaust gas temperature sensor 54, and detects the detection value of the first NOx sensor 52.
- the NOx concentration on the upstream side of the exhaust gas purification device 30 is acquired from the above, and the NOx concentration on the downstream side of the exhaust gas purification device 30 is acquired from the detection value of the second NOx sensor 53.
- the combustion switching control device 40 acquires the opening degree of the intake throttle valve 28, the opening degree of the exhaust gas recirculation amount adjustment valve (EGR valve) 29, and the injection amount Q of the fuel (step S12). Specifically, the combustion switching control device 40 obtains information on the opening degree of the intake throttle valve 28 and the opening degree of the exhaust gas recirculation amount adjustment valve (EGR valve) 29 from the intake and exhaust control device 42, and Information on the fuel injection amount Q is acquired. Next, the combustion switching control device 40 acquires the current combustion state (operating state) (step S13). That is, the combustion switching control device 40 acquires information on whether the current combustion state (combustion mode) is lean, stoichiometric or rich. The current combustion state (combustion mode) may be read from, for example, a storage device within the combustion switching control device 40, or may be identified using a predetermined map.
- the combustion switching control device 40 calculates the amount of NOx (NOx storage amount Nq) stored in the NOx storage reduction catalyst of the exhaust gas purification device 30 (step S14).
- the NOx storage amount Nq can be calculated from the NOx concentration on the upstream side and the downstream side of the exhaust gas purification device 30 acquired in step S11.
- the combustion switching control device 40 determines the selectable combustion state (operating state) at the current engine rotational speed Ne and the injection amount Q (step S15).
- the combustion switching control device 40 is provided with a map in which the engine speed Ne, the injection amount Q, and the selectable combustion state (operating state) are associated with each other, and in steps S11 and S12.
- the selectable combustion state (combustion mode) is specified from the acquired engine rotational speed Ne and the injection amount Q.
- the combustion switching control device 40 switches the combustion mode in accordance with the exhaust gas temperature T in the following steps S16 to S23.
- the combustion switching control device 40 determines whether the exhaust gas temperature T acquired in step S11 is higher than a threshold Tht (step S16).
- the threshold Tht is a preset fixed value. If the exhaust gas temperature T is higher than the threshold Tht (step S16: YES), the combustion switching control device 40 sets stoichiometric combustion as a switching destination of the combustion state (combustion mode) (step S17).
- the valve opening degree at the stoichiometry of the switching destination can be specified from a predetermined map.
- step S16 NO
- the combustion switching control device 40 determines whether the NOx storage amount Nq calculated in step S14 is higher than the threshold Thn (step S18).
- the threshold Thn is a preset fixed value.
- step S18 If the NOx storage amount Nq is higher than the threshold Thn (step S18: YES), the combustion switching control device 40 sets rich combustion as a switching destination of the combustion state (step S19). The valve opening degree at the time of rich at the switching destination can be specified from the above-mentioned predetermined map. On the other hand, when the NOx storage amount Nq is lower than the threshold Thn (step S18: NO), the combustion switching control device 40 sets lean combustion as a switching destination of the combustion state (step S20). The valve opening degree at the time of switching to the lean can be specified from the above-described predetermined map.
- the combustion switching control device 40 determines whether the combustion state of the switching destination set in steps S17, S19 and S20 is the combustion state (combustion mode) selectable in step S15 (step S21). If the combustion state is selectable (step S21: YES), the combustion state is switched (step S22). If the combustion state is not selectable, the current combustion state is continued (maintained) (Step S23). The above is the flow of the combustion mode control process.
- the exhaust gas purification device 30 can purify the exhaust gas at a high purification rate even if any one of stoichiometric combustion, rich combustion, and lean combustion is selectively executed as described below.
- the exhaust gas purification device 30 when the switching to the stoichiometric combustion is performed in the above steps S17 and S22, the exhaust gas purification device 30 generates NOx, HC, and so on by the three-way catalytic function that each of the upstream side catalyst 31 and the downstream side catalyst 32 has. It is possible to purify CO.
- the exhaust gas purification device 30 purifies NOx by the three-way catalytic function possessed by each of the upstream catalyst 31 and the downstream catalyst 32.
- the exhaust gas purification device 30 performs HC and CO by the three-way catalytic function that each of the upstream side catalyst 31 and the downstream side catalyst 32 has.
- the exhaust gas can be purified by storing the NOx by each of the upstream side catalyst 31 and the downstream side catalyst 32.
- FIG. 3 is a view for explaining the exhaust behavior of the outlet of the upstream side catalyst 31 at the time of switching from lean to stoichiometry.
- the combustion state of the engine 11 is shown in FIG. 3 (A), and the change in gas component at the outlet of the engine 11 is shown in FIGS. 3 (B) to 3 (D).
- the change of the gas component at the outlet of the upstream catalyst 31 is shown.
- FIGS. 3E and 3G changes in gas components when the upstream side catalyst has an oxygen storage capacity as a comparative example are indicated by thick broken lines.
- the upstream side catalyst 31 is described as being in a state where NOx is sufficiently stored and can not be stored any more.
- FIG. 3 (A) when the combustion state of the engine 11 is switched from lean to stoichiometric, residual O 2 , unburned CO, and the like from the engine 11 as shown in FIGS. 3 (B) to (D). HC and NOx are discharged and flow into the upstream catalyst 31.
- the upstream side catalyst 31 of the present embodiment has substantially no oxygen storage capacity, and therefore, the gas phase CO and HC discharged from the engine 11 hardly react with O 2 stored in the catalyst. Therefore, a delay in transition to stoichiometry due to a delay in consumption of residual O 2 in the exhaust gas hardly occurs.
- the upstream catalyst 31 of the present embodiment when the combustion state of the engine 11 is switched from lean to stoichiometric, the air-fuel ratio at the outlet of the upstream catalyst 31 (the thick solid line in FIG. A / F) quickly shifts to the stoichiometric state.
- the exhaust gas discharged from the engine 11 gas phase
- the exhaust gas can be purified by reacting CO and HC with the residual O 2 and NOx in the exhaust gas.
- the upstream side catalyst of the comparative example since the upstream side catalyst of the comparative example has an oxygen storage capacity, the gas phase CO and HC discharged from the engine 11 react with the stored O 2, and the residual O 2 in the exhaust gas is immediately Is not consumed. Therefore, the air-fuel ratio (A / F) at the outlet of the upstream side catalyst does not shift to stoichiometry immediately after the switching of the combustion mode, and the storage O 2 is consumed as shown by the thick broken line in FIG. It will gradually shift to stoichiometry as it Thus, in the upstream side catalyst of the comparative example, a delay occurs in the transition to the stoichiometry, so during that time, as shown by the thick broken line in FIG. 3 (G), the NOx purification by the three way catalyst function is not sufficiently performed. Department is discharged. Since the downstream side catalyst can not store NOx sufficiently, part of the catalyst is discharged outside the vehicle.
- FIG. 4 is a view for explaining the exhaust behavior of the outlet of the downstream side catalyst 32 at the time of switching from lean to stoichiometry.
- the combustion state of the engine 11 is shown in FIG. 4 (A), and the change in gas component at the outlet of the engine 11 is shown in FIGS. 4 (B) to 4 (D).
- the air-fuel ratio of the catalyst surface of the upstream side catalyst 31 is shown, and changes in the gas component at the outlet of the downstream side catalyst 32 are shown in FIGS. 4 (F) and 4 (G).
- FIGS. 4E to 4G changes in the air-fuel ratio or the gas component when the downstream side catalyst does not have the oxygen storage capacity as a comparative example are shown by thick broken lines.
- the change of the gas component at the outlet of the downstream side catalyst 32 when there is a fluctuation (fluctuation) of the combustion state between rich and lean after switching of the combustion state from lean to stoichiometry will be described.
- FIG. 4 (A) when there is fluctuation (fluctuation) of the combustion state between rich and lean after switching the combustion state from lean to stoichiometric, as shown in FIGS. 4 (B) to (D) Thus, residual O 2 and unburned CO, HC, and NOx are discharged from the engine 11. Among these, a part not processed by the upstream side catalyst 31 flows into the downstream side catalyst 32. Since the downstream side catalyst 32 of the present embodiment has an oxygen storage capacity, when rich exhaust gas flows in, stored O 2 is released, and when lean exhaust gas flows in. Since the O 2 in the exhaust gas is absorbed, the catalyst surface is maintained in the stoichiometric state.
- the catalyst surface can be maintained in the stoichiometric state as shown by the thick solid line in FIG. 4 (E). it can.
- the three-way catalyst function can purify the exhaust gas at a high purification rate.
- the upstream catalyst 31 is configured as a NOx storage reduction catalyst that does not substantially have oxygen storage capacity (OSC), and the downstream catalyst 32 is oxygen It is configured as a NOx storage reduction catalyst having storage capacity.
- OSC oxygen storage capacity
- the downstream catalyst 32 is oxygen It is configured as a NOx storage reduction catalyst having storage capacity.
- the exhaust gas purification ability can be improved.
- the NOx storage reduction catalyst stores NOx at the time of lean, but can not store NOx at the time of stoichiometry.
- the three-way catalytic function of the NOx storage reduction catalyst has a high purification rate at the time of stoichiometric, but can not purify CO and HC at the rich time, and can not purify the NOx at the lean time.
- the downstream side catalyst 32 having the oxygen storage capacity releases stored O 2 and oxidizes excess CO and HC.
- Stoichiometric state can be maintained on the catalyst surface. Therefore, CO, HC, and NOx can be purified by the three-way catalyst function.
- NOx stored in the upstream side catalyst 31 and the downstream side catalyst 32 can be purified by the excess CO and HC. That is, CO and HC in the exhaust gas are used to reduce stored NOx, and are also purified by the three-way catalytic function of the NOx storage reduction catalyst.
- O 2 is sufficiently stored in a NOx storage reduction catalyst having an oxygen storage capacity provided downstream of an engine having a long lean state such as a diesel engine.
- the rich spike for reducing the NOx stored in the NOx storage reduction catalyst the reduction of NOx is not performed until the CO in the gas, the occluding O 2 by HC is consumed, there is reduction of NOx problem delayed.
- the exhaust gas purification device 30 of the present embodiment since the upstream side catalyst 31 does not have the oxygen storage capacity, CO and HC in the gas are not the storage O 2 at the time of the rich spike, but the residual O 2 in the gas phase It is possible to quickly reduce the stored NOx with the remaining CO and HC. Moreover, since the residual O 2 in the upstream catalyst 31 is consumed, even the downstream side catalyst 32, the remaining CO, O 2, which is occluded by the HC is consumed rapidly, the absorbed NOx can be reduced quickly.
- the exhaust gas at this time is purified by the three-way catalyst.
- the exhaust gas purification apparatus 30 of the present embodiment has the oxygen storage capacity and the three-way catalyst function in the downstream side catalyst 32. Therefore, when the exhaust gas purification apparatus 30 swings lean, residual O 2 is stored and the stoichiometric state is maintained. In addition, when it fluctuates rich, the stored O 2 is released and the stoichiometric state is maintained.
- the exhaust gas can be purified by the three-way catalyst function since the stoichiometric state is maintained against fluctuations to a slight amount of rich or lean.
- FIG. 5 is a view for explaining an exhaust purification system 30A of an internal combustion engine in a second embodiment.
- FIG. 5 illustrates the configuration of a vehicle 10A provided with the exhaust gas purification device 30A of the present embodiment.
- the vehicle 10A of the second embodiment is different from the vehicle 10 (FIG. 1) of the first embodiment only in the configuration of the exhaust gas purification device, and the configuration other than the exhaust gas purification device is the same.
- the exhaust gas control apparatus 30A according to the second embodiment includes the upstream side catalyst 31 and the downstream side catalyst 32 in the same manner as the exhaust gas control apparatus 30 according to the first embodiment, and further includes an upstream side three-way catalyst 33 and a downstream side. A three-way catalyst 34 is provided.
- the upstream side catalyst 31 is the NOx storage reduction catalyst disposed most upstream among the four catalysts 31 to 34 described above, and has a three-way catalytic function as in the first embodiment, It does not have oxygen storage capacity substantially.
- the downstream side catalyst 32 is the NOx storage reduction catalyst arranged most downstream among the four catalysts 31 to 34 described above, and as in the first embodiment, it has both a three-way catalyst function and an oxygen storage capacity.
- the upstream side three-way catalyst 33 and the downstream side three-way catalyst 34 are disposed side by side at a position downstream of the upstream side catalyst 31 and upstream of the downstream side catalyst 32 in the exhaust passage 22. There is. That is, the upstream three-way catalyst 33 and the downstream three-way catalyst 34 are sandwiched by the upstream catalyst 31 and the downstream catalyst 32.
- the upstream three-way catalyst 33 is a three-way catalyst disposed on the upstream side of the downstream three-way catalyst 34 and has no oxygen storage capacity.
- the upstream three-way catalyst 33 contains a noble metal for exhibiting a three-way catalytic function, and a catalyst substantially free of an oxygen storage / release material (OSC material) such as ceria is formed on the surface of the porous substrate It has the following configuration.
- the downstream side three-way catalyst 34 is a three-way catalyst disposed on the downstream side of the upstream side three-way catalyst 33, and has an oxygen storage capacity.
- the downstream side three-way catalyst 34 has a configuration in which a catalyst containing a noble metal and an oxygen storage and release material is formed on the surface of a porous substrate.
- the combustion switching control device 40 of the second embodiment performs the combustion mode control process (FIG. 2) as in the first embodiment.
- the exhaust gas purification apparatus 30A according to the second embodiment purifies exhaust gas at a high purification rate even if any one of stoichiometric combustion, rich combustion and lean combustion is selectively executed as described below. it can.
- the exhaust gas purification device 30A is configured to perform NOx, HC, and CO by the three-way catalytic function possessed by each of the four catalysts 31 to 34 described above. Can be purified.
- the oxygen storage capacity (OSC) possessed by the two downstream catalysts causes these catalysts to The surface is maintained in stoichiometry. Thereby, NOx, HC, and CO can be purified by the three-way catalyst function.
- OSC oxygen storage capacity
- the exhaust purification device 30A can purify NOx by the three-way catalytic function possessed by each of the four catalysts 31 to 34 described above.
- the NOx stored in each of the upstream side catalyst 31 and the downstream side catalyst 32 can be reduced by CO and HC discharged from the engine 11 to purify them.
- the two upstream catalysts do not have the oxygen storage capacity (OSC). Therefore, when the engine is rich, the NOx stored in the upstream catalyst 31 is promptly reduced.
- OSC oxygen storage capacity
- HC and CO remaining in the exhaust gas react with O 2 in the exhaust gas to be purified.
- the remaining HC and CO are purified by O 2 stored in the downstream side three-way catalyst 34.
- the exhaust gas purification device 30A purifies HC and CO by the three-way catalytic function possessed by each of the four catalysts 31 to 34 described above.
- the exhaust gas can be purified by storing NOx in each of the upstream side catalyst 31 and the downstream side catalyst 32.
- a three-way catalyst (upstream three-way catalyst 33 and downstream three-way catalyst 34) is disposed between two NOx storage reduction catalysts (upstream side catalyst 31 and downstream side catalyst 32)
- NOx can be more efficiently purified.
- the upstream side three-way catalyst 33 can quickly purify CO, HC, and NOx.
- FIG. 6 is a view for explaining the exhaust behavior of the outlets of the upstream side catalyst 31 and the upstream side three-way catalyst 33 at the time of switching from lean to stoichiometry.
- the combustion state of the engine 11 is shown in FIG. 6 (A)
- the change in gas component at the outlet of the upstream catalyst 31 is shown in FIGS. 6 (B) and 6 (D).
- FIGS. 6 (B) and 6 (D) the change of the gas component at the outlet of the upstream side three-way catalyst 33 is shown.
- 6 (B) to (E) show the change of the gas component at the time of low load and low rotation where the flow rate of the exhaust gas is small by a thick solid line, and the change of the gas component at the time of high load and high rotation. Is indicated by a thick broken line.
- FIG. 6A when the combustion state of the engine 11 is switched from lean to stoichiometric, as shown in the first embodiment (FIG. 3), residual O 2 , unburned CO, HC from the engine 11 , NOx are emitted.
- the flow rates of these exhaust gases change depending on the load state and rotation state of the engine 11.
- the upstream catalyst 31 can sufficiently purify CO and HC in the exhaust gas as shown by a thick solid line in FIG. 6 (B).
- the thick broken line in FIG. 6B when the flow rate of the exhaust gas increases during high load and high rotation, part of CO and HC can not be purified.
- the exhaust gas control apparatus 30A of the second embodiment includes the upstream side three-way catalyst 33 downstream of the upstream side catalyst 31. Therefore, as shown in FIG.
- the three-way catalyst 33 can sufficiently purify CO and HC.
- NOx as shown by the thick broken line in FIG. 6 (D)
- purification of NOx can not be sufficiently performed by the upstream side catalyst 31.
- the upstream three-way catalyst 33 is disposed on the downstream side of the upstream catalyst 31, as shown in FIG. 6E, the upstream three-way catalyst 33 sufficiently removes NOx. can do.
- FIG. 7 is a diagram for explaining the state of the air-fuel ratio of each of the downstream side three-way catalyst 34 and the downstream side catalyst 32 at the time of switching from lean to stoichiometry.
- 7 (A) shows the combustion state of the engine 11
- FIG. 7 (B) shows the air-fuel ratio of the catalyst surface of the downstream side three-way catalyst 34
- FIG. 7 (C) shows the downstream.
- the air fuel ratio of the catalyst surface of the side catalyst 32 is shown, and the change of the gas component discharged
- the exhaust gas purification apparatus 30A of the second embodiment includes the downstream side three-way catalyst 34 upstream of the downstream side catalyst 32, the fluctuation range of the air-fuel ratio of the exhaust gas due to the oxygen storage capacity of the downstream side three-way catalyst 34 Can be reduced.
- the oxygen storage capacity of the downstream side catalyst 32 can maintain the stoichiometric state of the catalyst surface, and the exhaust gas can be sufficiently purified.
- the purification rate of the exhaust gas can be further enhanced than the exhaust gas purification apparatus 30 of the first embodiment.
- NOx, HC, and CO can be more reliably purified even at high load and high rotation where the flow rate increases.
- the exhaust gas can be purified more reliably even when the fluctuation of the combustion state between rich and lean becomes large.
- both the upstream side catalyst 31 and the downstream side catalyst 32 have the NOx storage reduction function, but only one of them may have. Even in this case, the exhaust gas purification capacity can be improved.
- the downstream side catalyst 32 is constituted by a three-way catalyst having an oxygen storage capacity and not having a NOx storage reduction function
- the NOx storage reduction function of the upstream side catalyst 31 when lean.
- the exhaust gas can be purified by storing NOx.
- the three-way catalytic function of the upstream side catalyst 31 can purify the exhaust gas.
- the exhaust gas can be promptly purified by the three-way catalytic function after the exhaust gas changes to the stoichiometric state.
- the exhaust gas can be purified by the reduction of NOx stored in the upstream side catalyst 31, and the exhaust gas can also be purified by the three-way catalytic function of the downstream side catalyst 32.
- downstream catalyst 32 which has an oxygen storage capacity, maintaining the catalyst surface in stoichiometric state by the release of occluded O 2 in rich time, it can purify exhaust gas by the three-way catalyst.
- the upstream catalyst 31 is preferable.
- both the upstream side catalyst 31 and the downstream side catalyst 32 have the NOx storage and reduction function.
- both the upstream side catalyst 31 and the downstream side catalyst 32 have the three-way catalyst function, but only one of them may have. Even in this case, for example, as in the exhaust gas purification apparatus 30A of the second embodiment, if a catalyst having a three-way catalytic function is separately provided, improvement of the exhaust gas purification capacity is achieved as the entire configuration. Can. However, it is preferable that at least one of the upstream side catalyst 31 and the downstream side catalyst 32 have a three-way catalyst function, and it is more preferable that both have it.
- the upstream catalyst 31 has been described as having substantially no oxygen storage capacity, but if the capacity is lower than the oxygen storage capacity of the downstream catalyst 32, the oxygen storage is possible. It may have a function.
- the ability of the oxygen storage capacity is low means that the amount of oxygen that can be stored in the entire catalyst is small.
- the upstream side catalyst 31 and the downstream side catalyst 32 are described as being separate bodies, but may be configured as one catalyst. That is, the configuration may be different between the upstream side and the downstream side of one catalyst. Also in the second embodiment, in the upstream side catalyst 31, the upstream side three-way catalyst 33, the downstream side three-way catalyst 34, and the downstream side catalyst 32, two to four continuous catalysts are configured as one catalyst. May be
- Exhaust purification device 30A Exhaust purification device 31: Upstream side catalyst 32: Downstream side catalyst 33: Upstream side three-way catalyst 34: Downstream side three-way catalyst 40: Combustion switching control device DESCRIPTION OF SYMBOLS 41 ... Injection control apparatus 42 ... Intake / exhaust control apparatus 51 ... Rotation speed sensor 52 ... 1st NOx sensor 53 ... 2nd NOx sensor 54 ... Exhaust temperature sensor 60 ... Addition control apparatus 61 ... Reductant addition apparatus
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Abstract
This exhaust gas purification device for an internal combustion engine is provided with: an upstream-side catalyst disposed on the relatively upstream side of an exhaust flow path through which exhaust gas discharged from the internal combustion engine flows; and a downstream-side catalyst provided on the downstream side of the upstream-side catalyst in the exhaust flow path, and having an oxygen storage capacity; wherein the oxygen storage capacity of the upstream-side catalyst is lower than the oxygen storage capacity of the downstream-side catalyst, and the upstream-side catalyst and/or the downstream-side catalyst has an NOx storage-reduction function.
Description
本発明は、内燃機関の排気浄化装置に関する。
The present invention relates to an exhaust purification system of an internal combustion engine.
従来から、リーンバーンガソリンエンジンやディーゼルエンジンのように、空気燃料比が大きい状態(燃料濃度が希薄なリーン状態)で運転されることが多いエンジンから排出される排気ガスを処理するための排気浄化装置が知られている。例えば、引用文献1には、排気流路の上流側に、少なくともアルカリ金属および/またはアルカリ土類金属を含み、貴金属を実質的に含有しないNOxトラップ触媒が配置され、下流側に貴金属触媒を含有する三元触媒が配置された排気浄化装置が開示されている。また、引用文献2には、排気流路の上流側から下流側に向かって順に、酸素吸蔵能(OSC)を有さない三元触媒、PMフィルタ、酸素吸蔵能(OSC)を有する三元触媒が配置された排気浄化装置が開示されている。
2. Description of the Related Art Conventionally, exhaust gas purification for treating exhaust gas emitted from an engine which is often operated in a state with a large air-fuel ratio (a lean state in which the fuel concentration is lean) such as a lean burn gasoline engine or diesel engine The device is known. For example, in the cited reference 1, an NOx trap catalyst containing at least an alkali metal and / or an alkaline earth metal and substantially containing no noble metal is disposed upstream of the exhaust flow path, and contains a noble metal catalyst downstream. Discloses an exhaust purification system in which a three-way catalyst is disposed. Further, in the cited reference 2, a three-way catalyst having no oxygen storage capacity (OSC), a PM filter, and a three-way catalyst having oxygen storage capacity (OSC) are sequentially arranged from the upstream side to the downstream side of the exhaust flow path. An exhaust purification system is disclosed in which the
しかしながら、特許文献1、2の技術においても、リーン状態が長いエンジンから排出される排気ガスの浄化能力に関しては、なお、改善の余地があった。例えば、引用文献1の排気浄化装置では、下流側の三元触媒が酸素吸蔵能(OSC)を有している場合、エンジン側で空気燃料比が小さい状態(燃料濃度が高いリッチ状態)に推移しても、下流側の三元触媒の表面付近において酸素濃度が速やかに低下せず、NOxの浄化開始タイミングが遅れることがあった。これは、リッチ状態に推移した後の排気ガスが下流側の三元触媒に到達しても、到達した当初は触媒に吸蔵された酸素O2が、流入してきた排気ガス中の一酸化炭素COや炭化水素HCとの反応に利用され、排気ガス中の酸素濃度が低下せず、三元触媒が機能するストイキ状態になるまでにタイムラグが生じるためである。一方、下流側の三元触媒が酸素吸蔵能(OSC)を有していない場合、リッチ状態に推移したときに三元触媒は速やかにNOx浄化を開始することができるが、リーン状態時に酸素を吸蔵する機能を持っていないため、リーン状態に推移したときにストイキ状態を維持することができず、三元触媒機能によるNOxの浄化ができなくなるおそれがあった。引用文献2では、ストイキ状態では三元触媒によって排気ガスを浄化できるが、NOx吸蔵還元触媒を備えていないため、リーン状態時にNOxの浄化が十分におこなえないおそれがあった。
However, even with the techniques of Patent Documents 1 and 2, there is still room for improvement with regard to the purification capability of exhaust gas discharged from an engine with a long lean state. For example, in the exhaust gas control apparatus of Patent Document 1, when the three-way catalyst on the downstream side has the oxygen storage capacity (OSC), the air fuel ratio is small on the engine side (a rich state with high fuel concentration) Even in this case, the oxygen concentration does not rapidly decrease near the surface of the three-way catalyst on the downstream side, and the timing for starting the purification of NOx may be delayed. This is because even if the exhaust gas after transition to the rich state reaches the downstream three-way catalyst, the oxygen O 2 stored in the catalyst initially reaches the carbon monoxide CO in the inflowing exhaust gas It is because it is used for the reaction with hydrocarbon HC, the oxygen concentration in the exhaust gas does not decrease, and a time lag occurs until the stoichiometric state in which the three-way catalyst functions. On the other hand, when the downstream side three-way catalyst does not have oxygen storage capacity (OSC), the three-way catalyst can start NOx purification promptly when transitioning to the rich state, but at the lean state Since the storage function does not have a storage function, the stoichiometric state can not be maintained when changing to the lean state, and there is a possibility that the purification of NOx by the three-way catalytic function can not be performed. According to Patent Document 2, although the exhaust gas can be purified by the three-way catalyst in the stoichiometric state, there is a possibility that the purification of NOx can not be sufficiently performed in the lean state because the NOx storage reduction catalyst is not provided.
本発明は、上述した課題を解決するためになされたものであり、リーン状態が長いエンジンから排出される排気ガスを浄化する排気浄化装置において、排気ガス浄化能力の向上を図る技術を提供することを目的とする。
The present invention has been made to solve the above-described problems, and provides an exhaust gas purification apparatus for purifying exhaust gas discharged from an engine having a long lean state, which provides a technique for improving the exhaust gas purification capacity. With the goal.
本発明は、上述の課題の少なくとも一部を解決するためになされたものであり、以下の形態として実現することが可能である。
The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following modes.
(1)本発明の一形態によれば、内燃機関の排気浄化装置が提供される。この排気浄化装置は、前記内燃機関から排出される排気ガスが流通する排気流路の相対的に上流側に配置される上流側触媒と、前記排気流路において、前記上流側触媒よりも下流側に設けられ、酸素吸蔵能を有する下流側触媒と、を備え、前記上流側触媒の酸素吸蔵能は、前記下流側触媒の酸素吸蔵能よりも能力が低く、前記上流側触媒と前記下流側触媒の少なくとも一方は、NOx吸蔵還元機能を有している。
(1) According to one aspect of the present invention, an exhaust gas purification apparatus for an internal combustion engine is provided. The exhaust gas control apparatus includes an upstream catalyst disposed relatively upstream of an exhaust flow passage through which exhaust gas discharged from the internal combustion engine flows, and a downstream side of the exhaust flow passage with respect to the upstream catalyst. A downstream catalyst having an oxygen storage capacity, and the oxygen storage capacity of the upstream catalyst is lower than the oxygen storage capacity of the downstream catalyst, the upstream catalyst and the downstream catalyst At least one of these has a NOx storage reduction function.
この構成によれば、上流側触媒の酸素吸蔵能は、下流側触媒の酸素吸蔵能よりも能力が低くいため、リッチ状態に推移したときに速やかにNOx浄化を開始することができる。一方、下流側触媒は酸素吸蔵能を有しているため、ストイキ状態への推移時にリッチ状態とリーン状態の間の変動が生じても、ストイキ状態を維持することができ、安定して排気ガスを浄化することができる。また、上流側触媒と下流側触媒の少なくとも一方は、NOx吸蔵還元機能を有しているため、リーン時においてもNOx吸蔵還元触媒によって十分にNOxの浄化をおこなうことができる。よって、この構成によれば、排気ガス浄化能力の向上を図ることができる。
According to this configuration, since the oxygen storage capacity of the upstream side catalyst is lower than the oxygen storage capacity of the downstream side catalyst, it is possible to promptly start the NOx purification when changing to the rich state. On the other hand, since the downstream side catalyst has an oxygen storage capacity, the stoichiometric state can be maintained even if fluctuations occur between the rich state and the lean state at the transition to the stoichiometric state, and the exhaust gas is stabilized. Can be purified. Further, at least one of the upstream side catalyst and the downstream side catalyst has the NOx storage and reduction function, and therefore, even when the engine is lean, NOx can be sufficiently purified by the NOx storage and reduction catalyst. Therefore, according to this configuration, the exhaust gas purification capacity can be improved.
(2)上記形態の排気浄化装置において、少なくとも前記上流側触媒は、NOx吸蔵還元機能を有していてもよい。この構成によれば、エンジンの始動後、エンジンに近いため速やかにNOx吸蔵還元触媒を昇温させることができ、さらに排気ガス浄化能力の向上を図ることができる。
(2) In the exhaust gas purification apparatus of the above aspect, at least the upstream side catalyst may have a NOx storage and reduction function. According to this configuration, the temperature of the NOx storage reduction catalyst can be raised promptly because the engine is close to the engine after the start of the engine, and the exhaust gas purification capacity can be further improved.
(3)上記形態の排気浄化装置において、前記上流側触媒と前記下流側触媒は、いずれもNOx吸蔵還元機能を有していてもよい。この構成によれば、上流側触媒と下流側触媒の両方のNOx吸蔵還元触媒によって、リーン時におけるNOxの浄化性能をさらに向上させることができる。
(3) In the exhaust gas purification apparatus of the above aspect, both the upstream side catalyst and the downstream side catalyst may have a NOx storage and reduction function. According to this configuration, it is possible to further improve the NOx purification performance at the time of lean by the NOx storage reduction catalyst of both the upstream side catalyst and the downstream side catalyst.
(4)上記形態の排気浄化装置は、さらに、前記排気流路において、前記上流側触媒よりも下流側であって、前記下流側触媒よりも上流側に設けられる三元触媒機能を有した触媒を備えていてもよい。この構成によれば、排気ガスの流量が増加する高負荷・高回転時において、さらに、排気ガス浄化能力の向上を図ることができる。
(4) The exhaust gas control apparatus according to the above aspect further includes a catalyst having a three-way catalyst function provided downstream of the upstream catalyst and upstream of the downstream catalyst in the exhaust passage. May be provided. According to this configuration, it is possible to further improve the exhaust gas purification capacity at the time of high load and high rotation where the flow rate of the exhaust gas increases.
(5)上記形態の排気浄化装置において、前記上流側触媒と前記下流側触媒は、いずれも三元触媒機能を有していてもよい。この構成によれば、上流側触媒と下流側触媒の両方の三元触媒によって、さらに排気ガス浄化能力の向上を図ることができる。また、上流側触媒と下流側触媒が三元触媒機能を備えることにより、別体の三元触媒を設けずに排気浄化装置の小型化を図ることができる。
(5) In the exhaust gas purification apparatus of the above aspect, both the upstream catalyst and the downstream catalyst may have a three-way catalyst function. According to this configuration, the exhaust gas purification capacity can be further improved by the three-way catalyst of both the upstream side catalyst and the downstream side catalyst. Further, by providing the upstream catalyst and the downstream catalyst with the three-way catalyst function, the exhaust gas purification apparatus can be miniaturized without providing a separate three-way catalyst.
(6)上記形態の排気浄化装置において、前記三元触媒機能を有した触媒は、相対的に上流側に配置される上流側三元触媒と、前記上流側三元触媒の下流側に配置される下流側三元触媒とを含んでおり、前記上流側三元触媒の酸素吸蔵能は、前記下流側三元触媒の酸素吸蔵能よりも能力が低くてもよい。この構成によれば、リッチ状態に推移したときのNOx浄化性能をさらに向上させることができる。また、リッチ状態とリーン状態の間の変動時の排気ガスの浄化性能をさらに向上させることができる。
(6) In the exhaust gas purification apparatus of the above aspect, the catalyst having the three-way catalyst function is disposed on the upstream side of the three-way catalyst located relatively upstream and the downstream side of the three-way catalyst on the upstream side The oxygen storage capacity of the upstream three-way catalyst may be lower than the oxygen storage capacity of the downstream three-way catalyst. According to this configuration, it is possible to further improve the NOx purification performance when transitioning to the rich state. Further, the purification performance of the exhaust gas at the time of fluctuation between the rich state and the lean state can be further improved.
なお、本発明は、種々の態様で実現することが可能であり、例えば、排気浄化触媒、排気浄化装置を備える車両、排気浄化方法、排気浄化装置の製造装置、排気浄化装置の製造方法などの形態で実現することができる。
The present invention can be realized in various modes, for example, a vehicle equipped with an exhaust gas purification catalyst, an exhaust gas purification device, an exhaust gas purification method, a device for manufacturing an exhaust gas purification device, a method for manufacturing an exhaust gas purification device, etc. It can be realized in a form.
<第1実施形態>
図1は、第1実施形態における内燃機関の排気浄化装置30を説明するための図である。図1には、本実施形態の排気浄化装置30を備える車両10の構成が例示されている。車両10は、エンジン11と、吸気流路21と、排気流路22と、排気還流流路23と、過給装置24と、排気浄化装置30と、燃焼切替制御装置40と、添加制御装置60と、を備えている。 First Embodiment
FIG. 1 is a view for explaining an exhaustgas purification device 30 for an internal combustion engine in the first embodiment. FIG. 1 illustrates the configuration of a vehicle 10 provided with the exhaust gas purification device 30 of the present embodiment. The vehicle 10 includes an engine 11, an intake passage 21, an exhaust passage 22, an exhaust return passage 23, a supercharging device 24, an exhaust purification device 30, a combustion switching control device 40, and an addition control device 60. And have.
図1は、第1実施形態における内燃機関の排気浄化装置30を説明するための図である。図1には、本実施形態の排気浄化装置30を備える車両10の構成が例示されている。車両10は、エンジン11と、吸気流路21と、排気流路22と、排気還流流路23と、過給装置24と、排気浄化装置30と、燃焼切替制御装置40と、添加制御装置60と、を備えている。 First Embodiment
FIG. 1 is a view for explaining an exhaust
エンジン11は、ディーゼルエンジンやガソリンエンジンなどの内燃機関であり、ここでは、一例としてのディーゼルエンジンが示されている。エンジン11の各気筒12には、燃料噴射装置13から供給される燃料(軽油)が噴射制御装置41の制御によって所定のタイミングで噴射される。また、エンジン11の各気筒12には、図示しない吸気弁を介して吸気流路21から空気が供給される。なお、燃料は、吸気流路21からエンジン11に供給される空気に対して噴射されてもよい。エンジン11の気筒12内の排気ガスは、図示しない排気弁を介して排気流路22に排出される。エンジン11の回転数は、回転数センサ51によって検出され、燃焼切替制御装置40に出力される。
The engine 11 is an internal combustion engine such as a diesel engine or a gasoline engine, and an example diesel engine is shown here. Fuel (light oil) supplied from the fuel injection device 13 is injected to each cylinder 12 of the engine 11 at a predetermined timing under the control of the injection control device 41. Further, air is supplied to each cylinder 12 of the engine 11 from the intake passage 21 via an intake valve (not shown). The fuel may be injected to the air supplied from the intake passage 21 to the engine 11. Exhaust gas in the cylinder 12 of the engine 11 is discharged to the exhaust passage 22 via an exhaust valve (not shown). The rotational speed of the engine 11 is detected by the rotational speed sensor 51 and output to the combustion switching control device 40.
吸気流路21は、1つまたは複数の吸気管を含んで構成されており、下流側の端部がエンジン11に接続され、上流側の端部が図示しないエアフィルターに接続されている。エアフィルターを介して吸気流路21に流入してきた空気は、過給装置24の吸気コンプレッサー25によって圧縮された後、エンジン11に供給される。過給装置24とエンジン11との間の吸気流路21には、吸気絞り弁28が設けられており、吸排気制御装置42の制御によって空気の流量が制御され、エンジン11への吸気量が調整される。
The intake flow passage 21 is configured to include one or more intake pipes, and the downstream end is connected to the engine 11 and the upstream end is connected to an air filter (not shown). The air flowing into the intake passage 21 through the air filter is compressed by the intake compressor 25 of the supercharger 24 and then supplied to the engine 11. An intake throttle valve 28 is provided in the intake flow passage 21 between the supercharging device 24 and the engine 11, and the flow rate of air is controlled by the control of the intake and exhaust control device 42, and the intake amount to the engine 11 is Adjusted.
排気流路22は、1つまたは複数の排気管を含んで構成されており、上流側の端部がエンジン11に接続され、下流側の端部が車両10の外部に開放されている。エンジン11から排出された排気ガスは、過給装置24の排気タービン26を駆動(回転)させた後、排気浄化装置30を経由して車両10の外部に排出される。排気浄化装置30の上流側の排気流路22には、第1NOxセンサ52と、還元剤添加装置61が設けられており、排気浄化装置30の下流側の排気流路22には、第2NOxセンサ53と、排気温センサ54が設けられている。
The exhaust flow path 22 is configured to include one or more exhaust pipes, and the upstream end is connected to the engine 11 and the downstream end is open to the outside of the vehicle 10. The exhaust gas discharged from the engine 11 drives (rotates) the exhaust turbine 26 of the supercharging device 24 and then is discharged to the outside of the vehicle 10 via the exhaust gas purification device 30. A first NOx sensor 52 and a reducing agent addition device 61 are provided in the exhaust passage 22 on the upstream side of the exhaust purification device 30, and a second NOx sensor is provided in the exhaust passage 22 on the downstream side of the exhaust purification device 30. An exhaust temperature sensor 54 is provided.
第1NOxセンサ52は、排気浄化装置30に流入する排気ガスのNOx濃度を測定する。第2NOxセンサ53は、排気浄化装置30から排出される排気ガスのNOx濃度を測定する。排気温センサ54は、排気浄化装置30から排出される排気ガスの温度を測定する。第1NOxセンサ52、第2NOxセンサ53、および、排気温センサ54によって検出された情報は、燃焼切替制御装置40に出力される。還元剤添加装置61は、添加制御装置60の制御によって所定のタイミングにおいて排気浄化装置30の上流側の排気流路22に還元剤を噴射する。ここでは、還元剤として軽油が噴射される。
The first NOx sensor 52 measures the NOx concentration of the exhaust gas flowing into the exhaust purification device 30. The second NOx sensor 53 measures the NOx concentration of the exhaust gas discharged from the exhaust gas purification device 30. The exhaust temperature sensor 54 measures the temperature of the exhaust gas discharged from the exhaust purification device 30. Information detected by the first NOx sensor 52, the second NOx sensor 53, and the exhaust temperature sensor 54 is output to the combustion switching control device 40. The reducing agent addition device 61 injects the reducing agent into the exhaust flow path 22 on the upstream side of the exhaust gas purification device 30 at a predetermined timing under the control of the addition control device 60. Here, light oil is injected as a reducing agent.
排気還流流路23は、1つまたは複数の排気還流管を含んで構成されており、上流側の端部が排気流路22のうちの過給装置24の上流側に接続され、下流側の端部が吸気流路21のうちの吸気絞り弁28の下流側に接続されている。排気還流流路23には、排気還流量調整弁(EGR弁)29が設けられており、排気還流量調整弁29の開弁時には、過給装置24の上流側の排気流路22を流通する排気ガスの一部が吸気絞り弁28の下流側の吸気流路21に排出される。排気流路22から吸気流路21に還流される排気ガスの流量は、吸排気制御装置42によって制御される。
The exhaust gas recirculation flow passage 23 is configured to include one or more exhaust gas recirculation pipes, and the upstream end thereof is connected to the upstream side of the supercharger 24 in the exhaust gas flow passage 22, and is downstream An end portion is connected to the downstream side of the intake throttle valve 28 in the intake passage 21. An exhaust gas recirculation amount adjustment valve (EGR valve) 29 is provided in the exhaust gas recirculation flow passage 23, and flows through the exhaust gas passage 22 on the upstream side of the supercharger 24 when the exhaust gas recirculation amount adjustment valve 29 is opened. A portion of the exhaust gas is discharged to the intake passage 21 downstream of the intake throttle valve 28. The flow rate of the exhaust gas returned from the exhaust flow passage 22 to the intake flow passage 21 is controlled by the intake and exhaust control device 42.
過給装置24は、吸気コンプレッサー25と、排気タービン26と、シャフト27とを備えており、排気ガスの運動エネルギーを用いてエンジン11に供給される空気を圧縮するいわゆるターボチャージャーである。吸気コンプレッサー25と排気タービン26は、シャフト27によって接続されており、排気タービン26によって得られた動力(回転力)が吸気コンプレッサー25に伝達される。
The supercharging device 24 is a so-called turbocharger that includes an intake compressor 25, an exhaust turbine 26, and a shaft 27, and compresses air supplied to the engine 11 using kinetic energy of exhaust gas. The intake compressor 25 and the exhaust turbine 26 are connected by a shaft 27, and the power (rotational force) obtained by the exhaust turbine 26 is transmitted to the intake compressor 25.
排気浄化装置30は、排気流路22を流通する排気ガスを浄化するための装置であり、上流側触媒31と、下流側触媒32と、を備えている。上流側触媒31は、排気流路22の相対的に上流側に配置されるNOx吸蔵還元触媒であり、三元触媒機能を有している一方、実質的に酸素吸蔵能(OSC:Oxygen Storage Capacity)を有していない。下流側触媒32は、排気流路22の相対的に下流側に配置されるNOx吸蔵還元触媒であり、三元触媒機能と酸素吸蔵能の両方を有している。
The exhaust gas purification device 30 is a device for purifying the exhaust gas flowing in the exhaust flow passage 22 and includes an upstream catalyst 31 and a downstream catalyst 32. The upstream side catalyst 31 is a NOx storage reduction catalyst disposed relatively upstream of the exhaust flow path 22, and has a three-way catalyst function, while substantially having an oxygen storage capacity (OSC: Oxygen Storage Capacity) Do not have). The downstream side catalyst 32 is a NOx storage reduction catalyst disposed relatively downstream of the exhaust flow path 22, and has both a three-way catalyst function and an oxygen storage capacity.
上流側触媒31は、NOx吸蔵還元触媒として少なくともアルカリ金属とアルカリ土類金属の一方を含み、さらに、マグネットブランバイトとK2Ti2O5の一方または両方を含んでいる。窒素酸化物NOxを吸蔵するための主要成分であるアルカリ金属あるいはアルカリ土類金属としては、Li、Na、K、Rb、Cs、Be、Mg、Ca、Sr、Ba、Raを例示することができる。本実施形態では、NOxを吸蔵還元できる触媒の機能をNOx吸蔵還元機能とも呼ぶ。触媒においてNOx吸蔵還元機能の有無は、NOxを吸蔵還元可能な成分を有しているか否かを意味する。
The upstream catalyst 31 contains at least one of an alkali metal and an alkaline earth metal as a NOx storage reduction catalyst, and further contains one or both of a magnetic substrate and K 2 Ti 2 O 5 . Examples of alkali metals or alkaline earth metals which are main components for storing nitrogen oxides NOx include Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba and Ra. . In the present embodiment, the function of the catalyst capable of storing and reducing NOx is also referred to as the NOx storage and reduction function. The presence or absence of the NOx storage reduction function in the catalyst means whether the catalyst has a component capable of storing and reducing NOx.
上流側触媒31は、さらに、三元触媒機能を発揮するための貴金属を含んでいる。ここでの貴金属とは、銅よりも電気陰性度の高い金属であり、Rh,Pt、Pd、Ir、Auである。一方、上流側触媒31は、セリアなどの酸素吸蔵放出材(OSC材)を実質的に含んでおらず、酸素吸蔵能(OSC)を実質的に備えていない。
The upstream catalyst 31 further contains a noble metal for exhibiting a three-way catalytic function. Here, the noble metal is a metal having higher electronegativity than copper and is Rh, Pt, Pd, Ir, Au. On the other hand, the upstream side catalyst 31 substantially does not contain an oxygen storage / release material (OSC material) such as ceria, and does not substantially have an oxygen storage capacity (OSC).
上流側触媒31は、三元触媒機能を有し実質的に酸素吸蔵能を有していないNOx吸蔵還元触媒が多孔質基材の表面に形成された構成を有している。このNOx吸蔵還元触媒は、多孔質基材の表面に直接付着していてもよいが、金属酸化物とともに、あるいは、金属酸化物を介して多孔質基材に担持されている方が好ましい。担体として使用可能な金属酸化物としては、例えば、Al2O3、SiO2、TiO2、Si2O-Al2O3等の金属酸化物、希土類の酸化物、および、ゼオライトなどを例示することができる。
The upstream side catalyst 31 has a configuration in which a NOx storage reduction catalyst having a three-way catalytic function and having substantially no oxygen storage capacity is formed on the surface of the porous substrate. The NOx storage reduction catalyst may be directly attached to the surface of the porous substrate, but is preferably supported on the porous substrate together with the metal oxide or via the metal oxide. Examples of metal oxides that can be used as a support include metal oxides such as Al 2 O 3 , SiO 2 , TiO 2 , Si 2 O-Al 2 O 3 , oxides of rare earths, and zeolites. be able to.
下流側触媒32は、上流側触媒31と同様に、NOx吸蔵還元触媒として、少なくともアルカリ金属またはアルカリ土類金属を含み、マグネットブランバイトとK2Ti2O5の一方または両方を含んでいる。また、下流側触媒32は、上流側触媒31と同様に、三元触媒機能を発揮するための貴金属を含んでいる。一方、下流側触媒32は、上流側触媒31と異なり、セリアなどの酸素吸蔵放出材(OSC材)を含んでおり、酸素吸蔵能を備えている。下流側触媒32は、三元触媒機能と酸素吸蔵能の両方を有しているNOx吸蔵還元触媒が多孔質基材の表面に形成された構成を有している。このNOx吸蔵還元触媒は、多孔質基材の表面に直接付着していてもよいし、金属酸化物とともに、あるいは、金属酸化物を介して多孔質基材に担持されていてもよい。
Similar to the upstream catalyst 31, the downstream catalyst 32 contains at least an alkali metal or an alkaline earth metal as a NOx storage reduction catalyst, and contains one or both of magnetic substrate and K 2 Ti 2 O 5 . Further, the downstream side catalyst 32 includes a precious metal for exhibiting a three-way catalytic function, as the upstream side catalyst 31 does. On the other hand, unlike the upstream catalyst 31, the downstream catalyst 32 contains an oxygen storage / release material (OSC material) such as ceria and has an oxygen storage capacity. The downstream side catalyst 32 has a configuration in which a NOx storage reduction catalyst having both a three-way catalyst function and an oxygen storage capacity is formed on the surface of a porous substrate. The NOx storage reduction catalyst may be directly attached to the surface of the porous substrate, or may be supported on the porous substrate together with the metal oxide or via the metal oxide.
燃焼切替制御装置40は、エンジン11の燃焼状態(運転状態)を切り替えるための装置であり、噴射制御装置41と、吸排気制御装置42と、回転数センサ51と、第1NOxセンサ52と、第2NOxセンサ53と、排気温センサ54と、添加制御装置60に電気的に接続されている。燃焼切替制御装置40は、各センサから得られた情報に基づいて、エンジン11の燃焼状態を、空燃比(A/F)が理論空燃比よりも大きい状態(燃料濃度が希薄なリーン状態)、理論空燃比状態(ストイキ状態)、空燃比が理論空燃比よりも小さい状態(燃料濃度が高いリッチ状態)のいずれかに切り替える燃焼モード制御処理をおこなう。
The combustion switching control device 40 is a device for switching the combustion state (operating state) of the engine 11 and includes the injection control device 41, the intake and exhaust control device 42, the rotation speed sensor 51, the first NOx sensor 52, 2 are electrically connected to the NOx sensor 53, the exhaust temperature sensor 54, and the addition control device 60. The combustion switching control device 40 determines the combustion state of the engine 11 based on the information obtained from each sensor in a state where the air-fuel ratio (A / F) is larger than the theoretical air-fuel ratio (a lean state in which the fuel concentration is lean). A combustion mode control process is performed to switch to either a stoichiometric air-fuel ratio state (stoichiometric state) or a state where the air-fuel ratio is smaller than the theoretical air-fuel ratio (rich state in which the fuel concentration is high).
図2は、燃焼切替制御装置40の燃焼モード制御処理を示すフローチャートである。この燃焼モード制御処理は、エンジン11のイグニッションONにより開始され、所定の周期で繰り返し実行される。燃焼モード制御処理では、まず、燃焼切替制御装置40は、エンジン回転数Ne、排気温度T、および、排気浄化装置30の上流側と下流側のNOx濃度を取得する(ステップS11)。具体的には、燃焼切替制御装置40は、回転数センサ51の検出値からエンジン回転数Neを取得し、排気温センサ54の検出値から排気温度Tを取得し、第1NOxセンサ52の検出値から排気浄化装置30の上流側のNOx濃度を取得し、第2NOxセンサ53の検出値から排気浄化装置30の下流側のNOx濃度を取得する。
FIG. 2 is a flowchart showing the combustion mode control process of the combustion switching control device 40. The combustion mode control process is started by turning on the ignition of the engine 11 and is repeatedly executed in a predetermined cycle. In the combustion mode control process, first, the combustion switching control device 40 acquires the engine rotational speed Ne, the exhaust temperature T, and the NOx concentration on the upstream side and the downstream side of the exhaust gas purification device 30 (step S11). Specifically, the combustion switching control device 40 acquires the engine rotational speed Ne from the detection value of the rotational speed sensor 51, acquires the exhaust gas temperature T from the detection value of the exhaust gas temperature sensor 54, and detects the detection value of the first NOx sensor 52. The NOx concentration on the upstream side of the exhaust gas purification device 30 is acquired from the above, and the NOx concentration on the downstream side of the exhaust gas purification device 30 is acquired from the detection value of the second NOx sensor 53.
次に、燃焼切替制御装置40は、吸気絞り弁28の開度、排気還流量調整弁(EGR弁)29の開度、および、燃料の噴射量Qを取得する(ステップS12)。具体的には、燃焼切替制御装置40は、吸排気制御装置42から吸気絞り弁28の開度と排気還流量調整弁(EGR弁)29の開度に関する情報を取得し、噴射制御装置41から燃料の噴射量Qに関する情報を取得する。次に、燃焼切替制御装置40は、現在の燃焼状態(運転状態)を取得する(ステップS13)。すなわち、燃焼切替制御装置40は、現在の燃焼状態(燃焼モード)が、リーンか、ストイキか、リッチかについての情報を取得する。現在の燃焼状態(燃焼モード)は、例えば、燃焼切替制御装置40内部の記憶装置から読み出されてもよいし、所定のマップを用いて特定されてもよい。
Next, the combustion switching control device 40 acquires the opening degree of the intake throttle valve 28, the opening degree of the exhaust gas recirculation amount adjustment valve (EGR valve) 29, and the injection amount Q of the fuel (step S12). Specifically, the combustion switching control device 40 obtains information on the opening degree of the intake throttle valve 28 and the opening degree of the exhaust gas recirculation amount adjustment valve (EGR valve) 29 from the intake and exhaust control device 42, and Information on the fuel injection amount Q is acquired. Next, the combustion switching control device 40 acquires the current combustion state (operating state) (step S13). That is, the combustion switching control device 40 acquires information on whether the current combustion state (combustion mode) is lean, stoichiometric or rich. The current combustion state (combustion mode) may be read from, for example, a storage device within the combustion switching control device 40, or may be identified using a predetermined map.
次に、燃焼切替制御装置40は、排気浄化装置30のNOx吸蔵還元触媒に吸蔵されているNOxの量(NOx吸蔵量Nq)を算出する(ステップS14)。NOx吸蔵量Nqは、ステップS11において取得された、排気浄化装置30の上流側と下流側のNOx濃度から算出することができる。次に、燃焼切替制御装置40は、現在のエンジン回転数Ne、噴射量Qにおいて選択可能な燃焼状態(運転状態)を判定する(ステップS15)。具体的には、燃焼切替制御装置40は、エンジン回転数Neと、噴射量Qと、選択可能な燃焼状態(運転状態)と、が対応づけられたマップを備えており、ステップS11、S12において取得したエンジン回転数Neと噴射量Qから選択可能な燃焼状態(燃焼モード)を特定する。
Next, the combustion switching control device 40 calculates the amount of NOx (NOx storage amount Nq) stored in the NOx storage reduction catalyst of the exhaust gas purification device 30 (step S14). The NOx storage amount Nq can be calculated from the NOx concentration on the upstream side and the downstream side of the exhaust gas purification device 30 acquired in step S11. Next, the combustion switching control device 40 determines the selectable combustion state (operating state) at the current engine rotational speed Ne and the injection amount Q (step S15). Specifically, the combustion switching control device 40 is provided with a map in which the engine speed Ne, the injection amount Q, and the selectable combustion state (operating state) are associated with each other, and in steps S11 and S12. The selectable combustion state (combustion mode) is specified from the acquired engine rotational speed Ne and the injection amount Q.
続いて、燃焼切替制御装置40は、以下のステップS16~S23で排気温度Tに応じて燃焼モードの切り替えをおこなう。まず、燃焼切替制御装置40は、ステップS11において取得した排気温度Tが閾値Thtより高いか否かの判定をおこなう(ステップS16)。閾値Thtは予め設定された固定値である。排気温度Tが閾値Thtよりも高い場合(ステップS16:YES)、燃焼切替制御装置40は、燃焼状態(燃焼モード)の切り替え先としてストイキ燃焼を設定する(ステップS17)。切り替え先のストイキ時のバルブ開度は所定のマップから特定できる。一方、排気温度Tが閾値Thtよりも低い場合(ステップS16:NO)、燃焼切替制御装置40は、ステップS14において算出したNOx吸蔵量Nqが閾値Thnよりも高いか否かの判定をおこなう(ステップS18)。閾値Thnは予め設定された固定値である。
Subsequently, the combustion switching control device 40 switches the combustion mode in accordance with the exhaust gas temperature T in the following steps S16 to S23. First, the combustion switching control device 40 determines whether the exhaust gas temperature T acquired in step S11 is higher than a threshold Tht (step S16). The threshold Tht is a preset fixed value. If the exhaust gas temperature T is higher than the threshold Tht (step S16: YES), the combustion switching control device 40 sets stoichiometric combustion as a switching destination of the combustion state (combustion mode) (step S17). The valve opening degree at the stoichiometry of the switching destination can be specified from a predetermined map. On the other hand, when the exhaust temperature T is lower than the threshold Tht (step S16: NO), the combustion switching control device 40 determines whether the NOx storage amount Nq calculated in step S14 is higher than the threshold Thn (step S18). The threshold Thn is a preset fixed value.
NOx吸蔵量Nqが閾値Thnよりも高い場合(ステップS18:YES)、燃焼切替制御装置40は、燃焼状態の切り替え先としてリッチ燃焼を設定する(ステップS19)。切り替え先のリッチ時のバルブ開度は上述の所定のマップから特定できる。一方、NOx吸蔵量Nqが閾値Thnよりも低い場合(ステップS18:NO)、燃焼切替制御装置40は、燃焼状態の切り替え先としてリーン燃焼を設定する(ステップS20)。切り替え先のリーン時のバルブ開度は上述の所定のマップから特定できる。
If the NOx storage amount Nq is higher than the threshold Thn (step S18: YES), the combustion switching control device 40 sets rich combustion as a switching destination of the combustion state (step S19). The valve opening degree at the time of rich at the switching destination can be specified from the above-mentioned predetermined map. On the other hand, when the NOx storage amount Nq is lower than the threshold Thn (step S18: NO), the combustion switching control device 40 sets lean combustion as a switching destination of the combustion state (step S20). The valve opening degree at the time of switching to the lean can be specified from the above-described predetermined map.
次に、燃焼切替制御装置40は、ステップS17、S19、S20で設定された切り替え先の燃焼状態が、ステップS15において選択可能な燃焼状態(燃焼モード)か否かの判定をおこなう(ステップS21)そして、選択可能な燃焼状態である場合には(ステップS21:YES)、燃焼状態の切り替えをおこない(ステップS22)、選択可能な燃焼状態ではない場合には、現在の燃焼状態を継続(維持)する(ステップS23)。以上が燃焼モード制御処理の流れである。
Next, the combustion switching control device 40 determines whether the combustion state of the switching destination set in steps S17, S19 and S20 is the combustion state (combustion mode) selectable in step S15 (step S21). If the combustion state is selectable (step S21: YES), the combustion state is switched (step S22). If the combustion state is not selectable, the current combustion state is continued (maintained) (Step S23). The above is the flow of the combustion mode control process.
排気浄化装置30は、以下に説明するように、ストイキ燃焼、リッチ燃焼、リーン燃焼のいずれが選択実行された場合であっても、高い浄化率で排気ガスを浄化することができる。まず、上記のステップS17、S22によってストイキ燃焼への切り替えが実行された場合には、排気浄化装置30は、上流側触媒31と下流側触媒32のそれぞれが持つ三元触媒機能によってNOx、HC、COを浄化することができる。また、上記のステップS19、S22によってリッチ燃焼への切り替えが実行された場合には、排気浄化装置30は、上流側触媒31と下流側触媒32のそれぞれが持つ三元触媒機能によってNOxを浄化することができ、上流側触媒31と下流側触媒32のそれぞれに吸蔵されているNOxを排気ガス中のCO、HCによって還元させることによってこれらを浄化することができる。また、上記のステップS20、S22によってリーン燃焼への切り替えが実行された場合には、排気浄化装置30は、上流側触媒31と下流側触媒32のそれぞれが持つ三元触媒機能によってHC、COを浄化することができ、上流側触媒31と下流側触媒32のそれぞれがNOxを吸蔵することによって排気ガスを浄化することができる。
The exhaust gas purification device 30 can purify the exhaust gas at a high purification rate even if any one of stoichiometric combustion, rich combustion, and lean combustion is selectively executed as described below. First, when the switching to the stoichiometric combustion is performed in the above steps S17 and S22, the exhaust gas purification device 30 generates NOx, HC, and so on by the three-way catalytic function that each of the upstream side catalyst 31 and the downstream side catalyst 32 has. It is possible to purify CO. Further, when switching to rich combustion is performed in the above-described steps S19 and S22, the exhaust gas purification device 30 purifies NOx by the three-way catalytic function possessed by each of the upstream catalyst 31 and the downstream catalyst 32. These can be purified by reducing NOx stored in each of the upstream side catalyst 31 and the downstream side catalyst 32 with CO and HC in the exhaust gas. Further, when the switching to lean combustion is executed in the above steps S20 and S22, the exhaust gas purification device 30 performs HC and CO by the three-way catalytic function that each of the upstream side catalyst 31 and the downstream side catalyst 32 has. The exhaust gas can be purified by storing the NOx by each of the upstream side catalyst 31 and the downstream side catalyst 32.
図3は、リーンからストイキへの切替時における上流側触媒31の出口の排気挙動を説明するための図である。図3(A)には、エンジン11の燃焼状態が示され、図3(B)~(D)には、エンジン11の出口におけるガス成分の変化が示され、図3(E)~(G)には、上流側触媒31の出口におけるガス成分の変化が示されている。図3(E)、(G)には、比較例として上流側触媒が酸素吸蔵能を有している場合のガス成分の変化が太破線で示されている。ここでは、上流側触媒31にはNOxが十分に吸蔵されており、これ以上の吸蔵ができない状態であるものとして説明する。
FIG. 3 is a view for explaining the exhaust behavior of the outlet of the upstream side catalyst 31 at the time of switching from lean to stoichiometry. The combustion state of the engine 11 is shown in FIG. 3 (A), and the change in gas component at the outlet of the engine 11 is shown in FIGS. 3 (B) to 3 (D). In, the change of the gas component at the outlet of the upstream catalyst 31 is shown. In FIGS. 3E and 3G, changes in gas components when the upstream side catalyst has an oxygen storage capacity as a comparative example are indicated by thick broken lines. Here, the upstream side catalyst 31 is described as being in a state where NOx is sufficiently stored and can not be stored any more.
図3(A)に示すように、エンジン11の燃焼状態がリーンからストイキに切り替わると、図3(B)~(D)に示すように、エンジン11からは残存O2、未燃のCO、HC、NOx、が排出され上流側触媒31に流入する。本実施形態の上流側触媒31は、酸素吸蔵能を実質的に備えていないため、エンジン11から排出された気相のCO、HCが触媒に吸蔵されたO2と反応することがほぼない。そのため、排気ガス中の残存O2の消費が遅れることによるストイキへの推移の遅れが生じにくい。よって、本実施形態の上流側触媒31によれば、エンジン11の燃焼状態がリーンからストイキに切り替わると、図3(E)の太実線に示すように、上流側触媒31の出口の空燃比(A/F)は速やかにストイキ状態に推移する。これにより、図3(F)、(G)の太実線に示すように、ストイキへの燃焼モードの切り替え後、速やかに三元触媒機能によって、エンジン11から排出された排気ガス中(気相)のCO、HCと、排気ガス中の残存O2、NOxを反応させて排気ガスを浄化することができる。
As shown in FIG. 3 (A), when the combustion state of the engine 11 is switched from lean to stoichiometric, residual O 2 , unburned CO, and the like from the engine 11 as shown in FIGS. 3 (B) to (D). HC and NOx are discharged and flow into the upstream catalyst 31. The upstream side catalyst 31 of the present embodiment has substantially no oxygen storage capacity, and therefore, the gas phase CO and HC discharged from the engine 11 hardly react with O 2 stored in the catalyst. Therefore, a delay in transition to stoichiometry due to a delay in consumption of residual O 2 in the exhaust gas hardly occurs. Therefore, according to the upstream catalyst 31 of the present embodiment, when the combustion state of the engine 11 is switched from lean to stoichiometric, the air-fuel ratio at the outlet of the upstream catalyst 31 (the thick solid line in FIG. A / F) quickly shifts to the stoichiometric state. Thereby, as shown by thick solid lines in FIGS. 3F and 3G, after switching the combustion mode to the stoichiometry, in the exhaust gas discharged from the engine 11 (gas phase) promptly by the three-way catalyst function The exhaust gas can be purified by reacting CO and HC with the residual O 2 and NOx in the exhaust gas.
一方、比較例の上流側触媒は、酸素吸蔵能を有しているため、エンジン11から排出された気相のCO、HCは吸蔵O2と反応し、排気ガス中の残存O2がすぐには消費されない。そのため、上流側触媒の出口の空燃比(A/F)は、燃焼モードの切り替え後すぐにはストイキに推移せず、図3(E)の太破線に示すように、吸蔵O2が消費されるに従って徐々にストイキに推移する。このように、比較例の上流側触媒ではストイキへの推移に遅れが生じるため、その間、図3(G)の太破線に示すように、三元触媒機能によるNOxの浄化が十分におこなわれず一部が排出される。なお、下流側触媒においてもNOxが十分に吸蔵できないため一部が車外に排出される。
On the other hand, since the upstream side catalyst of the comparative example has an oxygen storage capacity, the gas phase CO and HC discharged from the engine 11 react with the stored O 2, and the residual O 2 in the exhaust gas is immediately Is not consumed. Therefore, the air-fuel ratio (A / F) at the outlet of the upstream side catalyst does not shift to stoichiometry immediately after the switching of the combustion mode, and the storage O 2 is consumed as shown by the thick broken line in FIG. It will gradually shift to stoichiometry as it Thus, in the upstream side catalyst of the comparative example, a delay occurs in the transition to the stoichiometry, so during that time, as shown by the thick broken line in FIG. 3 (G), the NOx purification by the three way catalyst function is not sufficiently performed. Department is discharged. Since the downstream side catalyst can not store NOx sufficiently, part of the catalyst is discharged outside the vehicle.
図4は、リーンからストイキへの切替時における下流側触媒32の出口の排気挙動を説明するための図である。図4(A)には、エンジン11の燃焼状態が示され、図4(B)~(D)には、エンジン11の出口におけるガス成分の変化が示され、図4(E)には、上流側触媒31の触媒表面の空燃比が示され、図4(F)、(G)には、下流側触媒32の出口におけるガス成分の変化が示されている。図4(E)~(G)には、比較例として下流側触媒が酸素吸蔵能を有していない場合の空燃比またはガス成分の変化が太破線で示されている。ここでは、リーンからストイキに燃焼状態の切り替えが実行された後、リッチとリーンの間で燃焼状態の変動(ゆらぎ)があったときの下流側触媒32の出口のガス成分の変化について説明する。
FIG. 4 is a view for explaining the exhaust behavior of the outlet of the downstream side catalyst 32 at the time of switching from lean to stoichiometry. The combustion state of the engine 11 is shown in FIG. 4 (A), and the change in gas component at the outlet of the engine 11 is shown in FIGS. 4 (B) to 4 (D). The air-fuel ratio of the catalyst surface of the upstream side catalyst 31 is shown, and changes in the gas component at the outlet of the downstream side catalyst 32 are shown in FIGS. 4 (F) and 4 (G). In FIGS. 4E to 4G, changes in the air-fuel ratio or the gas component when the downstream side catalyst does not have the oxygen storage capacity as a comparative example are shown by thick broken lines. Here, the change of the gas component at the outlet of the downstream side catalyst 32 when there is a fluctuation (fluctuation) of the combustion state between rich and lean after switching of the combustion state from lean to stoichiometry will be described.
図4(A)に示すように、リーンからストイキへの燃焼状態の切り替え後、リッチとリーンの間で燃焼状態の変動(ゆらぎ)があったとき、図4(B)~(D)に示すように、エンジン11から残存O2、未燃のCO、HC、NOx、が排出される。これらのうち、上流側触媒31によって処理されなかった一部が下流側触媒32に流入する。本実施形態の下流側触媒32は、酸素吸蔵能を有しているため、リッチの排気ガスが流入してきた場合には、吸蔵O2が放出され、リーンの排気ガスが流入してきた場合には、排気ガス中のO2が吸蔵されることで、触媒表面上がストイキ状態に維持される。そのため、エンジン11においてリッチとリーンの間で燃焼状態の変動(ゆらぎ)があった場合であっても、図4(E)の太実線で示すように、触媒表面をストイキ状態に維持することができる。これにより、図4(F)、(G)の太実線に示すように、三元触媒機能によって、排気ガスを高い浄化率で浄化することができる。
As shown in FIG. 4 (A), when there is fluctuation (fluctuation) of the combustion state between rich and lean after switching the combustion state from lean to stoichiometric, as shown in FIGS. 4 (B) to (D) Thus, residual O 2 and unburned CO, HC, and NOx are discharged from the engine 11. Among these, a part not processed by the upstream side catalyst 31 flows into the downstream side catalyst 32. Since the downstream side catalyst 32 of the present embodiment has an oxygen storage capacity, when rich exhaust gas flows in, stored O 2 is released, and when lean exhaust gas flows in. Since the O 2 in the exhaust gas is absorbed, the catalyst surface is maintained in the stoichiometric state. Therefore, even if there is a fluctuation (fluctuation) of the combustion state between rich and lean in the engine 11, the catalyst surface can be maintained in the stoichiometric state as shown by the thick solid line in FIG. 4 (E). it can. As a result, as shown by thick solid lines in FIGS. 4F and 4G, the three-way catalyst function can purify the exhaust gas at a high purification rate.
一方、比較例の下流側触媒は、酸素吸蔵能を有していないため、触媒表面の空燃比は、エンジン11の空燃比と連動する。そのため、図4(A)に示すように、エンジン11においてリッチとリーンの間で燃焼状態の変動(ゆらぎ)があった場合、図4(E)の太破線で示すように、触媒表面の空燃比もリッチとリーンの間で変動する。リッチ時には、三元触媒機能によるCO、HCの浄化が十分におこなわれず、図4(F)の太破線で示すように、CO、HCが排出され、リーン時には三元触媒機能によるNOxの浄化が十分におこなわれず、図4(G)の太破線で示すように、NOxが排出される。
On the other hand, since the downstream side catalyst of the comparative example does not have the oxygen storage capacity, the air fuel ratio of the catalyst surface interlocks with the air fuel ratio of the engine 11. Therefore, as shown in FIG. 4A, when there is fluctuation (fluctuation) in the combustion state between the rich and lean in the engine 11, as shown by the thick broken line in FIG. 4E, the catalyst surface is empty The fuel ratio also fluctuates between rich and lean. When rich, purification of CO and HC by the three-way catalyst function is not sufficiently performed, and as shown by the thick broken line in FIG. 4 (F), CO and HC are discharged, and when lean, purification of NOx by the three-way catalyst function is performed. As shown by the thick broken line in FIG. 4 (G), NOx is emitted, which is not sufficiently performed.
以上説明した、第1実施形態の排気浄化装置30によれば、上流側触媒31は実質的に酸素吸蔵能(OSC)を有していないNOx吸蔵還元触媒として構成され、下流側触媒32は酸素吸蔵能を有するNOx吸蔵還元触媒として構成されている。これにより、排気ガス浄化能力の向上を図ることができる。一般的に、NOx吸蔵還元触媒は、リーン時にNOxを吸蔵するが、ストイキ時にNOxを吸蔵できない。NOx吸蔵還元触媒の三元触媒機能は、ストイキ時には高い浄化率を有するが、リッチ時にはCO、HCの浄化ができず、リーン時にはNOxが浄化できない。一方、本実施形態の排気浄化装置30によれば、ストイキからリッチへ推移した場合には、酸素吸蔵能を有する下流側触媒32では、吸蔵O2が放出されて余剰のCO、HCを酸化し、触媒表面においてストイキ状態を維持することができる。そのため、三元触媒機能によって、CO、HC、NOxを浄化することができる。さらに、リッチ状態では、上流側触媒31および下流側触媒32に吸蔵されているNOxを余剰のCO、HCによって浄化することができる。すなわち、排気ガス中のCO、HCは、収蔵NOxの還元に使われるとともに、NOx吸蔵還元触媒の三元触媒機能によっても浄化される。一方、ストイキからリーンへ推移した場合には、上流側触媒31においてNOxが吸蔵されるとともに、下流側触媒32では余剰のO2が吸蔵され触媒表面においてストイキ状態を維持することができる。この結果、三元触媒機能によってCO、HC、NOxを浄化することができる。
According to the exhaust gas purification device 30 of the first embodiment described above, the upstream catalyst 31 is configured as a NOx storage reduction catalyst that does not substantially have oxygen storage capacity (OSC), and the downstream catalyst 32 is oxygen It is configured as a NOx storage reduction catalyst having storage capacity. Thereby, the exhaust gas purification ability can be improved. Generally, the NOx storage reduction catalyst stores NOx at the time of lean, but can not store NOx at the time of stoichiometry. The three-way catalytic function of the NOx storage reduction catalyst has a high purification rate at the time of stoichiometric, but can not purify CO and HC at the rich time, and can not purify the NOx at the lean time. On the other hand, according to the exhaust gas purification device 30 of the present embodiment, when transitioning from stoichiometric to rich, the downstream side catalyst 32 having the oxygen storage capacity releases stored O 2 and oxidizes excess CO and HC. Stoichiometric state can be maintained on the catalyst surface. Therefore, CO, HC, and NOx can be purified by the three-way catalyst function. Furthermore, in the rich state, NOx stored in the upstream side catalyst 31 and the downstream side catalyst 32 can be purified by the excess CO and HC. That is, CO and HC in the exhaust gas are used to reduce stored NOx, and are also purified by the three-way catalytic function of the NOx storage reduction catalyst. On the other hand, when transitioning from stoichiometric to lean, NOx is stored in the upstream side catalyst 31, and excess O 2 is stored in the downstream side catalyst 32, and the stoichiometric state can be maintained on the catalyst surface. As a result, CO, HC and NOx can be purified by the three-way catalyst function.
一般的に、ディーゼルエンジンのようにリーン状態の期間が長いエンジンの下流に設けられた酸素吸蔵能を有するNOx吸蔵還元触媒にはO2が十分に吸蔵されている。NOx吸蔵還元触媒に吸蔵されているNOxを還元するリッチスパイク時には、ガス中のCO、HCによって吸蔵O2が消費されるまでNOxの還元がおこなわれず、NOxの還元が遅れる問題があった。本実施形態の排気浄化装置30によれば、上流側触媒31は酸素吸蔵能を有していないため、リッチスパイク時にガス中のCO、HCが、吸蔵O2ではなく、気相の残存O2と反応し、残ったCO、HCによって吸蔵NOxを速やかに還元することができる。また、上流側触媒31において残存O2が消費されるため、下流側触媒32においても、残ったCO、HCによって吸蔵されているO2が速やかに消費され、吸蔵NOxを速やかに還元できる。
Generally, O 2 is sufficiently stored in a NOx storage reduction catalyst having an oxygen storage capacity provided downstream of an engine having a long lean state such as a diesel engine. When the rich spike for reducing the NOx stored in the NOx storage reduction catalyst, the reduction of NOx is not performed until the CO in the gas, the occluding O 2 by HC is consumed, there is reduction of NOx problem delayed. According to the exhaust gas purification device 30 of the present embodiment, since the upstream side catalyst 31 does not have the oxygen storage capacity, CO and HC in the gas are not the storage O 2 at the time of the rich spike, but the residual O 2 in the gas phase It is possible to quickly reduce the stored NOx with the remaining CO and HC. Moreover, since the residual O 2 in the upstream catalyst 31 is consumed, even the downstream side catalyst 32, the remaining CO, O 2, which is occluded by the HC is consumed rapidly, the absorbed NOx can be reduced quickly.
ディーゼルエンジンのようにリーン状態の期間が長いエンジンで、出力を上げるときにストイキで運転する場合、このときの排気ガスは三元触媒によって浄化される。しかし、実際には完全にストイキ状態を維持することは困難であり、多少、リッチやリーンに振れることがある。本実施形態の排気浄化装置30は、下流側触媒32に酸素吸蔵能と三元触媒機能を有しているため、リーンに振れたときには、残存O2が吸蔵されてストイキ状態が維持される。また、リッチに振れたときには、吸蔵されているO2が放出されてストイキ状態が維持される。これにより、多少のリッチやリーンへの変動に対しては、ストイキ状態が維持されるため、三元触媒機能によって排気ガスを浄化できる。
When the engine is operated for a long period of time in a lean state such as a diesel engine and operated at a stoichiometric ratio when increasing the output, the exhaust gas at this time is purified by the three-way catalyst. However, in practice it is difficult to maintain the stoichiometry completely, and it may be somewhat rich or lean. The exhaust gas purification apparatus 30 of the present embodiment has the oxygen storage capacity and the three-way catalyst function in the downstream side catalyst 32. Therefore, when the exhaust gas purification apparatus 30 swings lean, residual O 2 is stored and the stoichiometric state is maintained. In addition, when it fluctuates rich, the stored O 2 is released and the stoichiometric state is maintained. Thus, the exhaust gas can be purified by the three-way catalyst function since the stoichiometric state is maintained against fluctuations to a slight amount of rich or lean.
<第2実施形態>
図5は、第2実施形態における内燃機関の排気浄化装置30Aを説明するための図である。図5には、本実施形態の排気浄化装置30Aを備える車両10Aの構成が例示されている。第2実施形態の車両10Aは、第1実施形態の車両10(図1)と比較して、排気浄化装置の構成のみが異なり、排気浄化装置以外の構成については同様であるため説明を省略する。第2実施形態の排気浄化装置30Aは、第1実施形態の排気浄化装置30と同様に、上流側触媒31と、下流側触媒32を備えるほか、さらに、上流側三元触媒33と、下流側三元触媒34を備えている。 Second Embodiment
FIG. 5 is a view for explaining anexhaust purification system 30A of an internal combustion engine in a second embodiment. FIG. 5 illustrates the configuration of a vehicle 10A provided with the exhaust gas purification device 30A of the present embodiment. The vehicle 10A of the second embodiment is different from the vehicle 10 (FIG. 1) of the first embodiment only in the configuration of the exhaust gas purification device, and the configuration other than the exhaust gas purification device is the same. . The exhaust gas control apparatus 30A according to the second embodiment includes the upstream side catalyst 31 and the downstream side catalyst 32 in the same manner as the exhaust gas control apparatus 30 according to the first embodiment, and further includes an upstream side three-way catalyst 33 and a downstream side. A three-way catalyst 34 is provided.
図5は、第2実施形態における内燃機関の排気浄化装置30Aを説明するための図である。図5には、本実施形態の排気浄化装置30Aを備える車両10Aの構成が例示されている。第2実施形態の車両10Aは、第1実施形態の車両10(図1)と比較して、排気浄化装置の構成のみが異なり、排気浄化装置以外の構成については同様であるため説明を省略する。第2実施形態の排気浄化装置30Aは、第1実施形態の排気浄化装置30と同様に、上流側触媒31と、下流側触媒32を備えるほか、さらに、上流側三元触媒33と、下流側三元触媒34を備えている。 Second Embodiment
FIG. 5 is a view for explaining an
上流側触媒31は、上述の4つの触媒31~34のうち、最も上流側に配置されるNOx吸蔵還元触媒であり、第1実施形態と同様に、三元触媒機能を有している一方、実質的に酸素吸蔵能を有していない。下流側触媒32は、上述の4つの触媒31~34のうち、最も下流側に配置されるNOx吸蔵還元触媒であり、第1実施形態と同様に、三元触媒機能と酸素吸蔵能の両方を有している。上流側三元触媒33と下流側三元触媒34は、排気流路22において、上流側触媒31よりも下流側であって、下流側触媒32よりも上流側となる位置に並んで配置されている。すなわち、上流側三元触媒33と下流側三元触媒34は、上流側触媒31と下流側触媒32によって挟まれている。
The upstream side catalyst 31 is the NOx storage reduction catalyst disposed most upstream among the four catalysts 31 to 34 described above, and has a three-way catalytic function as in the first embodiment, It does not have oxygen storage capacity substantially. The downstream side catalyst 32 is the NOx storage reduction catalyst arranged most downstream among the four catalysts 31 to 34 described above, and as in the first embodiment, it has both a three-way catalyst function and an oxygen storage capacity. Have. The upstream side three-way catalyst 33 and the downstream side three-way catalyst 34 are disposed side by side at a position downstream of the upstream side catalyst 31 and upstream of the downstream side catalyst 32 in the exhaust passage 22. There is. That is, the upstream three-way catalyst 33 and the downstream three-way catalyst 34 are sandwiched by the upstream catalyst 31 and the downstream catalyst 32.
上流側三元触媒33は、下流側三元触媒34の上流側に配置される三元触媒であり、酸素吸蔵能を有していない。上流側三元触媒33は、三元触媒機能を発揮するための貴金属を含み、セリアなどの酸素吸蔵放出材(OSC材)を実質的に含んでいない触媒が多孔質基材の表面に形成された構成を有している。下流側三元触媒34は、上流側三元触媒33の下流側に配置される三元触媒であり、酸素吸蔵能を有している。下流側三元触媒34は、貴金属と酸素吸蔵放出材を含んだ触媒が多孔質基材の表面に形成された構成を有している。
The upstream three-way catalyst 33 is a three-way catalyst disposed on the upstream side of the downstream three-way catalyst 34 and has no oxygen storage capacity. The upstream three-way catalyst 33 contains a noble metal for exhibiting a three-way catalytic function, and a catalyst substantially free of an oxygen storage / release material (OSC material) such as ceria is formed on the surface of the porous substrate It has the following configuration. The downstream side three-way catalyst 34 is a three-way catalyst disposed on the downstream side of the upstream side three-way catalyst 33, and has an oxygen storage capacity. The downstream side three-way catalyst 34 has a configuration in which a catalyst containing a noble metal and an oxygen storage and release material is formed on the surface of a porous substrate.
第2実施形態の燃焼切替制御装置40は、第1実施形態と同様に、燃焼モード制御処理(図2)をおこなう。第2実施形態の排気浄化装置30Aは、以下に説明するように、ストイキ燃焼、リッチ燃焼、リーン燃焼のいずれが選択実行された場合であっても、高い浄化率で排気ガスを浄化することができる。まず、上記のステップS17、S22によってストイキ燃焼への切り替えが実行された場合には、排気浄化装置30Aは、上述の4つの触媒31~34のそれぞれが持つ三元触媒機能によってNOx、HC、COを浄化することができる。ストイキ状態において排気ガスがリッチとリーンの間で変動した場合には、下流側の2つの触媒(下流側三元触媒34および下流側触媒32)が有する酸素吸蔵能(OSC)によって、これらの触媒表面はストイキ状態に維持される。これにより、三元触媒機能によってNOx、HC、COを浄化することができる。本実施形態では、酸素吸蔵能(OSC)を有する触媒が複数存在するため、より大きな変動に対しても十分に排気ガスを浄化することができる。
The combustion switching control device 40 of the second embodiment performs the combustion mode control process (FIG. 2) as in the first embodiment. The exhaust gas purification apparatus 30A according to the second embodiment purifies exhaust gas at a high purification rate even if any one of stoichiometric combustion, rich combustion and lean combustion is selectively executed as described below. it can. First, when the switching to the stoichiometric combustion is performed in the above steps S17 and S22, the exhaust gas purification device 30A is configured to perform NOx, HC, and CO by the three-way catalytic function possessed by each of the four catalysts 31 to 34 described above. Can be purified. If the exhaust gas fluctuates between rich and lean in the stoichiometric state, the oxygen storage capacity (OSC) possessed by the two downstream catalysts (the downstream three-way catalyst 34 and the downstream catalyst 32) causes these catalysts to The surface is maintained in stoichiometry. Thereby, NOx, HC, and CO can be purified by the three-way catalyst function. In the present embodiment, since there are a plurality of catalysts having an oxygen storage capacity (OSC), exhaust gas can be sufficiently purified even with larger fluctuations.
上記のステップS19、S22によってリッチ燃焼への切り替えが実行された場合には、排気浄化装置30Aは、上述の4つの触媒31~34のそれぞれが持つ三元触媒機能によってNOxを浄化することができ、上流側触媒31と下流側触媒32のそれぞれに吸蔵されているNOxを、エンジン11から排出されたCO、HCによって還元させてこれらを浄化することができる。排気浄化装置30Aは、上流側の2つの触媒(上流側触媒31および上流側三元触媒33)が酸素吸蔵能(OSC)を有していない。そのため、リッチ時には上流側触媒31に吸蔵されているNOxが速やかに還元される。また、上流側三元触媒33では、排気ガス中に残存するHC、COが排気ガス中のO2と反応して浄化される。残ったHC、COは、下流側三元触媒34に吸蔵されているO2によって浄化される。または、下流側触媒32の吸蔵NOxの還元によって浄化される。
When switching to rich combustion is performed in the above steps S19 and S22, the exhaust purification device 30A can purify NOx by the three-way catalytic function possessed by each of the four catalysts 31 to 34 described above. The NOx stored in each of the upstream side catalyst 31 and the downstream side catalyst 32 can be reduced by CO and HC discharged from the engine 11 to purify them. In the exhaust purification system 30A, the two upstream catalysts (the upstream catalyst 31 and the upstream three-way catalyst 33) do not have the oxygen storage capacity (OSC). Therefore, when the engine is rich, the NOx stored in the upstream catalyst 31 is promptly reduced. Further, in the upstream side three-way catalyst 33, HC and CO remaining in the exhaust gas react with O 2 in the exhaust gas to be purified. The remaining HC and CO are purified by O 2 stored in the downstream side three-way catalyst 34. Alternatively, it is purified by reduction of the stored NOx of the downstream side catalyst 32.
上記のステップS20、S22によってリーン燃焼への切り替えが実行された場合には、排気浄化装置30Aは、上述の4つの触媒31~34のそれぞれが持つ三元触媒機能によってHC、COを浄化することができ、上流側触媒31と下流側触媒32のそれぞれがNOxを吸蔵することによって排気ガスを浄化することができる。
When the switching to lean combustion is executed in the above steps S20 and S22, the exhaust gas purification device 30A purifies HC and CO by the three-way catalytic function possessed by each of the four catalysts 31 to 34 described above. The exhaust gas can be purified by storing NOx in each of the upstream side catalyst 31 and the downstream side catalyst 32.
排気浄化装置30Aは、2つのNOx吸蔵還元触媒(上流側触媒31および下流側触媒32)の間に三元触媒(上流側三元触媒33および下流側三元触媒34)が配置されているため、排気ガスがストイキ状態もしくはストイキに近いリーンまたはリッチ状態になった場合、より効率よくNOxの浄化をおこなうことができる。具体的には、リーン状態からストイキ状態に推移した直後では、上流側三元触媒33において速やかにCO、HC、NOxの浄化をおこなうことができる。また、リッチ状態に推移した場合には、下流側三元触媒34において吸蔵されているO2を放出することで、触媒表面をストイキ状態にしてCO、HC、NOxを浄化することができる。リーン状態に推移した場合には、上流側触媒31と下流側触媒32のNOx吸蔵による浄化に加えて、下流側三元触媒34においてO2が吸蔵されてストイキ状態が維持され、三元触媒機能によってNOx浄化をおこなうことができる。このように、ストイキ状態からリーンまたはリッチ状態に変動した場合においても、NOx吸蔵還元触媒の間に三元触媒が配置されているため、さらに効率よくNOxを浄化できる。
In the exhaust purification system 30A, a three-way catalyst (upstream three-way catalyst 33 and downstream three-way catalyst 34) is disposed between two NOx storage reduction catalysts (upstream side catalyst 31 and downstream side catalyst 32) When the exhaust gas is in a stoichiometric state or a lean or rich state close to a stoichiometric state, NOx can be more efficiently purified. Specifically, immediately after the lean state changes to the stoichiometric state, the upstream side three-way catalyst 33 can quickly purify CO, HC, and NOx. When the rich state is reached, releasing the O 2 stored in the downstream side three-way catalyst 34 makes it possible to make the catalyst surface stoichiometric and to purify CO, HC, and NOx. In the lean state, in addition to the purification by NOx storage of the upstream side catalyst 31 and the downstream side catalyst 32, O 2 is stored in the downstream side three-way catalyst 34 and the stoichiometric state is maintained, and the three-way catalyst function NOx purification can be performed by the As described above, even when the stoichiometric state changes to the lean or rich state, the three-way catalyst is disposed between the NOx storage reduction catalysts, so that the NOx can be purified more efficiently.
図6は、リーンからストイキへの切替時における上流側触媒31と上流側三元触媒33のそれぞれの出口の排気挙動を説明するための図である。図6(A)には、エンジン11の燃焼状態が示され、図6(B)、(D)には、上流側触媒31の出口におけるガス成分の変化が示され、図6(C)、(E)には、上流側三元触媒33の出口におけるガス成分の変化が示されている。図6(B)~(E)には、排気ガスの流量が小さい低負荷・低回転時におけるガス成分の変化が太実線で示され、流量が大きい高負荷・高回転時におけるガス成分の変化が太破線で示されている。
FIG. 6 is a view for explaining the exhaust behavior of the outlets of the upstream side catalyst 31 and the upstream side three-way catalyst 33 at the time of switching from lean to stoichiometry. The combustion state of the engine 11 is shown in FIG. 6 (A), and the change in gas component at the outlet of the upstream catalyst 31 is shown in FIGS. 6 (B) and 6 (D). In (E), the change of the gas component at the outlet of the upstream side three-way catalyst 33 is shown. 6 (B) to (E) show the change of the gas component at the time of low load and low rotation where the flow rate of the exhaust gas is small by a thick solid line, and the change of the gas component at the time of high load and high rotation. Is indicated by a thick broken line.
図6(A)に示すように、エンジン11の燃焼状態がリーンからストイキに切り替わると、第1実施形態(図3)で示したように、エンジン11から残存O2、未燃のCO、HC、NOx、が排出される。これらの排気ガスの流量は、エンジン11の負荷状態・回転状態によって変化する。上流側触媒31は、排気ガスの流量が比較的小さい場合には、図6(B)の太実線に示すように、排気ガス中のCO、HCを十分に浄化ができる。一方、図6(B)の太破線に示すように、高負荷・高回転時に排気ガスの流量が増加するとCO、HCの一部が浄化できなくなる。この場合であっても、第2実施形態の排気浄化装置30Aは、上流側触媒31の下流側に上流側三元触媒33を備えているため、図6(C)に示すように、上流側三元触媒33においてCO、HCを十分に浄化することができる。NOxについても同様に、図6(D)の太破線に示すように、排気ガスの流量が増加すると上流側触媒31においてNOxの浄化が十分にできなくなる。この場合であっても、上流側触媒31の下流側に上流側三元触媒33が配置されているため、図6(E)に示すように、上流側三元触媒33においてNOxを十分に浄化することができる。
As shown in FIG. 6A, when the combustion state of the engine 11 is switched from lean to stoichiometric, as shown in the first embodiment (FIG. 3), residual O 2 , unburned CO, HC from the engine 11 , NOx are emitted. The flow rates of these exhaust gases change depending on the load state and rotation state of the engine 11. When the flow rate of the exhaust gas is relatively small, the upstream catalyst 31 can sufficiently purify CO and HC in the exhaust gas as shown by a thick solid line in FIG. 6 (B). On the other hand, as shown by the thick broken line in FIG. 6B, when the flow rate of the exhaust gas increases during high load and high rotation, part of CO and HC can not be purified. Even in this case, the exhaust gas control apparatus 30A of the second embodiment includes the upstream side three-way catalyst 33 downstream of the upstream side catalyst 31. Therefore, as shown in FIG. The three-way catalyst 33 can sufficiently purify CO and HC. Similarly for NOx, as shown by the thick broken line in FIG. 6 (D), if the flow rate of the exhaust gas increases, purification of NOx can not be sufficiently performed by the upstream side catalyst 31. Even in this case, since the upstream three-way catalyst 33 is disposed on the downstream side of the upstream catalyst 31, as shown in FIG. 6E, the upstream three-way catalyst 33 sufficiently removes NOx. can do.
図7は、リーンからストイキへの切替時における下流側三元触媒34と下流側触媒32のそれぞれの空燃比の状態を説明するための図である。図7(A)には、エンジン11の燃焼状態が示され、図7(B)には、下流側三元触媒34の触媒表面の空燃比が示され、図7(C)には、下流側触媒32の触媒表面の空燃比が示され、図7(D)、(E)には車外に排出されるガス成分の変化が示されている。
FIG. 7 is a diagram for explaining the state of the air-fuel ratio of each of the downstream side three-way catalyst 34 and the downstream side catalyst 32 at the time of switching from lean to stoichiometry. 7 (A) shows the combustion state of the engine 11, FIG. 7 (B) shows the air-fuel ratio of the catalyst surface of the downstream side three-way catalyst 34, and FIG. 7 (C) shows the downstream. The air fuel ratio of the catalyst surface of the side catalyst 32 is shown, and the change of the gas component discharged | emitted by the vehicle exterior is shown by FIG.7 (D) and (E).
第1実施形態(図4)のように、リーンからストイキへの燃焼状態の切り替え後、リッチとリーンの間の燃焼状態の変動(ゆらぎ)が比較的小さい場合には、下流側触媒32の酸素吸蔵能(OSC)のみによって触媒表面のストイキ状態を維持することができる。一方、図7(A)に示すように、切り替え後のリッチとリーンの間の変動(ゆらぎ)が大きい場合には、下流側触媒32の酸素吸蔵能のみでは触媒表面をストイキ状態に維持することが困難になる。第2実施形態の排気浄化装置30Aは、下流側触媒32の上流に下流側三元触媒34を備えているため、下流側三元触媒34の酸素吸蔵能によって、排気ガスの空燃比の変動幅を低減させることができる。これにより、下流側触媒32の酸素吸蔵能によって、触媒表面のストイキ状態を維持することができ、排気ガスを十分に浄化することができる。
As in the first embodiment (FIG. 4), when the change in the combustion state between rich and lean is relatively small after the change of the combustion state from the lean state to the stoichiometric state, the oxygen of the downstream side catalyst 32 The stoichiometry of the catalyst surface can be maintained only by the storage capacity (OSC). On the other hand, as shown in FIG. 7A, when the fluctuation (fluctuation) between rich and lean after switching is large, the catalyst surface should be maintained in the stoichiometric state only with the oxygen storage capacity of the downstream side catalyst 32. Will be difficult. Since the exhaust gas purification apparatus 30A of the second embodiment includes the downstream side three-way catalyst 34 upstream of the downstream side catalyst 32, the fluctuation range of the air-fuel ratio of the exhaust gas due to the oxygen storage capacity of the downstream side three-way catalyst 34 Can be reduced. Thus, the oxygen storage capacity of the downstream side catalyst 32 can maintain the stoichiometric state of the catalyst surface, and the exhaust gas can be sufficiently purified.
以上説明した、第2実施形態の排気浄化装置30Aによれば、第1実施形態の排気浄化装置30よりも、さらに排気ガスの浄化率を高めることができる。特に流量が増加する高負荷・高回転時においても、NOx、HC、COをより確実に浄化することができる。また、リッチとリーンの間の燃焼状態の変動(ゆらぎ)が大きくなった場合においても、排気ガスをより確実に浄化することができる。
According to the exhaust gas purification apparatus 30A of the second embodiment described above, the purification rate of the exhaust gas can be further enhanced than the exhaust gas purification apparatus 30 of the first embodiment. In particular, NOx, HC, and CO can be more reliably purified even at high load and high rotation where the flow rate increases. In addition, the exhaust gas can be purified more reliably even when the fluctuation of the combustion state between rich and lean becomes large.
<本実施形態の変形例>
本発明は上記の実施形態に限られるものではなく、その要旨を逸脱しない範囲において種々の態様において実施することが可能であり、例えば次のような変形も可能である。 <Modification of this embodiment>
The present invention is not limited to the above embodiment, and can be implemented in various aspects without departing from the scope of the present invention. For example, the following modifications are possible.
本発明は上記の実施形態に限られるものではなく、その要旨を逸脱しない範囲において種々の態様において実施することが可能であり、例えば次のような変形も可能である。 <Modification of this embodiment>
The present invention is not limited to the above embodiment, and can be implemented in various aspects without departing from the scope of the present invention. For example, the following modifications are possible.
[変形例1]
第1、2実施形態では、上流側触媒31と下流側触媒32の両方の触媒がNOx吸蔵還元機能を有していると説明したが、一方のみが有していてもよい。この場合であっても排気ガス浄化能力の向上を図ることができる。具体的には、例えば、下流側触媒32が、酸素吸蔵能を有しNOx吸蔵還元機能を有していない三元触媒によって構成されている場合、リーン時には、上流側触媒31のNOx吸蔵還元機能によってNOxを吸蔵することで排気ガスを浄化できる。ストイキ時には、上流側触媒31の三元触媒機能によって排気ガスを浄化できる。上流側触媒31は、酸素吸蔵能を有していないため、排気ガスがストイキに推移後、速やかに三元触媒機能により排気ガスを浄化できる。リッチ時には、上流側触媒31に吸蔵されたNOxの還元により排気ガスを浄化でき、下流側触媒32の三元触媒機能によっても排気ガスを浄化できる。下流側触媒32は酸素吸蔵能を有しているため、リッチ時には吸蔵O2の放出によって触媒表面をストイキ状態に維持し、三元触媒によって排気ガスを浄化できる。なお、NOx吸蔵還元機能を一方の触媒のみに設ける場合には、上流側触媒31が好ましい。上流側触媒31の方がよりエンジン11に近く暖まりやすく、エンジンの始動後より早く触媒機能を発揮できるためである。ただし、上流側触媒31と下流側触媒32の両方がNOx吸蔵還元機能を備えている方がより好ましい。 [Modification 1]
In the first and second embodiments, it has been described that both theupstream side catalyst 31 and the downstream side catalyst 32 have the NOx storage reduction function, but only one of them may have. Even in this case, the exhaust gas purification capacity can be improved. Specifically, for example, when the downstream side catalyst 32 is constituted by a three-way catalyst having an oxygen storage capacity and not having a NOx storage reduction function, the NOx storage reduction function of the upstream side catalyst 31 when lean. The exhaust gas can be purified by storing NOx. At the time of stoichiometry, the three-way catalytic function of the upstream side catalyst 31 can purify the exhaust gas. Since the upstream side catalyst 31 does not have the oxygen storage capacity, the exhaust gas can be promptly purified by the three-way catalytic function after the exhaust gas changes to the stoichiometric state. When the engine is rich, the exhaust gas can be purified by the reduction of NOx stored in the upstream side catalyst 31, and the exhaust gas can also be purified by the three-way catalytic function of the downstream side catalyst 32. Since downstream catalyst 32 which has an oxygen storage capacity, maintaining the catalyst surface in stoichiometric state by the release of occluded O 2 in rich time, it can purify exhaust gas by the three-way catalyst. When the NOx storage and reduction function is provided for only one of the catalysts, the upstream catalyst 31 is preferable. This is because the upstream side catalyst 31 is more likely to be warmed closer to the engine 11, and the catalyst function can be exhibited earlier than after the engine is started. However, it is more preferable that both the upstream side catalyst 31 and the downstream side catalyst 32 have the NOx storage and reduction function.
第1、2実施形態では、上流側触媒31と下流側触媒32の両方の触媒がNOx吸蔵還元機能を有していると説明したが、一方のみが有していてもよい。この場合であっても排気ガス浄化能力の向上を図ることができる。具体的には、例えば、下流側触媒32が、酸素吸蔵能を有しNOx吸蔵還元機能を有していない三元触媒によって構成されている場合、リーン時には、上流側触媒31のNOx吸蔵還元機能によってNOxを吸蔵することで排気ガスを浄化できる。ストイキ時には、上流側触媒31の三元触媒機能によって排気ガスを浄化できる。上流側触媒31は、酸素吸蔵能を有していないため、排気ガスがストイキに推移後、速やかに三元触媒機能により排気ガスを浄化できる。リッチ時には、上流側触媒31に吸蔵されたNOxの還元により排気ガスを浄化でき、下流側触媒32の三元触媒機能によっても排気ガスを浄化できる。下流側触媒32は酸素吸蔵能を有しているため、リッチ時には吸蔵O2の放出によって触媒表面をストイキ状態に維持し、三元触媒によって排気ガスを浄化できる。なお、NOx吸蔵還元機能を一方の触媒のみに設ける場合には、上流側触媒31が好ましい。上流側触媒31の方がよりエンジン11に近く暖まりやすく、エンジンの始動後より早く触媒機能を発揮できるためである。ただし、上流側触媒31と下流側触媒32の両方がNOx吸蔵還元機能を備えている方がより好ましい。 [Modification 1]
In the first and second embodiments, it has been described that both the
[変形例2]
第1、2実施形態では、上流側触媒31と下流側触媒32の両方の触媒が三元触媒機能を有していると説明したが、一方のみが有していてもよい。この場合であっても、例えば、第2実施形態の排気浄化装置30Aのように、三元触媒機能を有する触媒を別に備えていれば、全体の構成として、排気ガス浄化能力の向上を図ることができる。ただし、上流側触媒31と下流側触媒32の少なくとも一方が三元触媒機能を有している方が好ましく、両方が有していることがより好ましい。 [Modification 2]
In the first and second embodiments, it has been described that both theupstream side catalyst 31 and the downstream side catalyst 32 have the three-way catalyst function, but only one of them may have. Even in this case, for example, as in the exhaust gas purification apparatus 30A of the second embodiment, if a catalyst having a three-way catalytic function is separately provided, improvement of the exhaust gas purification capacity is achieved as the entire configuration. Can. However, it is preferable that at least one of the upstream side catalyst 31 and the downstream side catalyst 32 have a three-way catalyst function, and it is more preferable that both have it.
第1、2実施形態では、上流側触媒31と下流側触媒32の両方の触媒が三元触媒機能を有していると説明したが、一方のみが有していてもよい。この場合であっても、例えば、第2実施形態の排気浄化装置30Aのように、三元触媒機能を有する触媒を別に備えていれば、全体の構成として、排気ガス浄化能力の向上を図ることができる。ただし、上流側触媒31と下流側触媒32の少なくとも一方が三元触媒機能を有している方が好ましく、両方が有していることがより好ましい。 [Modification 2]
In the first and second embodiments, it has been described that both the
[変形例3]
第1、2実施形態では、上流側触媒31は、実質的に酸素吸蔵能を有していないものと説明したが、下流側触媒32の酸素吸蔵能よりも能力が低い程度であれば酸素吸蔵能を有していてもよい。ここで、酸素吸蔵能の能力が低いとは、触媒全体で吸蔵可能な酸素の量が小さいことを意味する。 [Modification 3]
In the first and second embodiments, theupstream catalyst 31 has been described as having substantially no oxygen storage capacity, but if the capacity is lower than the oxygen storage capacity of the downstream catalyst 32, the oxygen storage is possible. It may have a function. Here, that the ability of the oxygen storage capacity is low means that the amount of oxygen that can be stored in the entire catalyst is small.
第1、2実施形態では、上流側触媒31は、実質的に酸素吸蔵能を有していないものと説明したが、下流側触媒32の酸素吸蔵能よりも能力が低い程度であれば酸素吸蔵能を有していてもよい。ここで、酸素吸蔵能の能力が低いとは、触媒全体で吸蔵可能な酸素の量が小さいことを意味する。 [Modification 3]
In the first and second embodiments, the
[変形例4]
第2実施形態では、上流側触媒31と下流側触媒32の間に2つの三元触媒(上流側三元触媒33および下流側三元触媒34)が配置されていると説明したが、上流側触媒31と下流側触媒32の間に三元触媒が1つ配置されていてもよい。この場合であっても、無い場合よりも好ましい。また、上流側触媒31と下流側触媒32の間に3つ以上の三元触媒が配置されていてもよい。 [Modification 4]
In the second embodiment, it has been described that two three-way catalysts (the upstream three-way catalyst 33 and the downstream three-way catalyst 34) are disposed between the upstream catalyst 31 and the downstream catalyst 32. One three-way catalyst may be disposed between the catalyst 31 and the downstream catalyst 32. Even in this case, it is preferable to no case. Also, three or more three-way catalysts may be disposed between the upstream catalyst 31 and the downstream catalyst 32.
第2実施形態では、上流側触媒31と下流側触媒32の間に2つの三元触媒(上流側三元触媒33および下流側三元触媒34)が配置されていると説明したが、上流側触媒31と下流側触媒32の間に三元触媒が1つ配置されていてもよい。この場合であっても、無い場合よりも好ましい。また、上流側触媒31と下流側触媒32の間に3つ以上の三元触媒が配置されていてもよい。 [Modification 4]
In the second embodiment, it has been described that two three-way catalysts (the upstream three-
[変形例5]
第1実施形態では、上流側触媒31と下流側触媒32は別体となっていると説明したが、1つの触媒として構成されていてもよい。すなわち、1つの触媒の上流側と下流側で構成が異なっていてもよい。また、第2実施形態においても、上流側触媒31、上流側三元触媒33、下流側三元触媒34、および、下流側触媒32は連続する2~4つの触媒が1つの触媒として構成されていてもよい。 [Modification 5]
In the first embodiment, theupstream side catalyst 31 and the downstream side catalyst 32 are described as being separate bodies, but may be configured as one catalyst. That is, the configuration may be different between the upstream side and the downstream side of one catalyst. Also in the second embodiment, in the upstream side catalyst 31, the upstream side three-way catalyst 33, the downstream side three-way catalyst 34, and the downstream side catalyst 32, two to four continuous catalysts are configured as one catalyst. May be
第1実施形態では、上流側触媒31と下流側触媒32は別体となっていると説明したが、1つの触媒として構成されていてもよい。すなわち、1つの触媒の上流側と下流側で構成が異なっていてもよい。また、第2実施形態においても、上流側触媒31、上流側三元触媒33、下流側三元触媒34、および、下流側触媒32は連続する2~4つの触媒が1つの触媒として構成されていてもよい。 [Modification 5]
In the first embodiment, the
以上、実施形態、変形例に基づき本態様について説明してきたが、上記した態様の実施の形態は、本態様の理解を容易にするためのものであり、本態様を限定するものではない。本態様は、その趣旨並びに特許請求の範囲を逸脱することなく、変更、改良され得ると共に、本態様にはその等価物が含まれる。また、その技術的特徴が本明細書中に必須なものとして説明されていなければ、適宜、削除することができる。
As mentioned above, although this aspect was demonstrated based on embodiment and a modification, embodiment of the above-mentioned aspect is for making an understanding of this aspect easy, and does not limit this aspect. The present embodiment can be modified and improved without departing from the spirit and the scope of the claims, and the present embodiment includes the equivalents thereof. In addition, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.
10、10A…車両
11…エンジン
12…気筒
13…燃料噴射装置
21…吸気流路
22…排気流路
23…排気還流流路
24…過給装置
25…吸気コンプレッサー
26…排気タービン
27…シャフト
28…吸気絞り弁
29…排気還流量調整弁
30…排気浄化装置
30A…排気浄化装置
31…上流側触媒
32…下流側触媒
33…上流側三元触媒
34…下流側三元触媒
40…燃焼切替制御装置
41…噴射制御装置
42…吸排気制御装置
51…回転数センサ
52…第1NOxセンサ
53…第2NOxセンサ
54…排気温センサ
60…添加制御装置
61…還元剤添加装置 10, 10A ...Vehicle 11 ... Engine 12 ... Cylinder 13 ... Fuel injection device 21 ... Intake flow path 22 ... Exhaust flow path 23 ... Exhaust return flow path 24 ... Supercharger 25 ... Intake compressor 26 ... Exhaust turbine 27 ... Shaft 28 ... Intake throttle valve 29: Exhaust return amount adjustment valve 30: Exhaust purification device 30A: Exhaust purification device 31: Upstream side catalyst 32: Downstream side catalyst 33: Upstream side three-way catalyst 34: Downstream side three-way catalyst 40: Combustion switching control device DESCRIPTION OF SYMBOLS 41 ... Injection control apparatus 42 ... Intake / exhaust control apparatus 51 ... Rotation speed sensor 52 ... 1st NOx sensor 53 ... 2nd NOx sensor 54 ... Exhaust temperature sensor 60 ... Addition control apparatus 61 ... Reductant addition apparatus
11…エンジン
12…気筒
13…燃料噴射装置
21…吸気流路
22…排気流路
23…排気還流流路
24…過給装置
25…吸気コンプレッサー
26…排気タービン
27…シャフト
28…吸気絞り弁
29…排気還流量調整弁
30…排気浄化装置
30A…排気浄化装置
31…上流側触媒
32…下流側触媒
33…上流側三元触媒
34…下流側三元触媒
40…燃焼切替制御装置
41…噴射制御装置
42…吸排気制御装置
51…回転数センサ
52…第1NOxセンサ
53…第2NOxセンサ
54…排気温センサ
60…添加制御装置
61…還元剤添加装置 10, 10A ...
Claims (6)
- 内燃機関の排気浄化装置であって、
前記内燃機関から排出される排気ガスが流通する排気流路の相対的に上流側に配置される上流側触媒と、
前記排気流路において、前記上流側触媒よりも下流側に設けられ、酸素吸蔵能を有する下流側触媒と、を備え、
前記上流側触媒の酸素吸蔵能は、前記下流側触媒の酸素吸蔵能よりも能力が低く、
前記上流側触媒と前記下流側触媒の少なくとも一方は、NOx吸蔵還元機能を有している、
排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine
An upstream catalyst disposed relatively upstream of an exhaust passage through which exhaust gas discharged from the internal combustion engine flows;
And a downstream catalyst provided downstream of the upstream catalyst in the exhaust flow path and having an oxygen storage capacity.
The oxygen storage capacity of the upstream catalyst is lower than the oxygen storage capacity of the downstream catalyst,
At least one of the upstream catalyst and the downstream catalyst has a NOx storage reduction function.
Exhaust purification system. - 請求項1に記載の排気浄化装置において、
少なくとも前記上流側触媒は、NOx吸蔵還元機能を有している、
排気浄化装置。 In the exhaust gas purification apparatus according to claim 1,
At least the upstream catalyst has a NOx storage reduction function.
Exhaust purification system. - 請求項1または請求項2に記載の排気浄化装置において、
前記上流側触媒と前記下流側触媒は、いずれもNOx吸蔵還元機能を有している、
排気浄化装置。 In the exhaust gas purification apparatus according to claim 1 or 2,
Both the upstream side catalyst and the downstream side catalyst have the function of storing and reducing NOx.
Exhaust purification system. - 請求項1から請求項3までのいずれか一項に記載の排気浄化装置は、さらに、
前記排気流路において、前記上流側触媒よりも下流側であって、前記下流側触媒よりも上流側に設けられる三元触媒機能を有した触媒を備えている、
排気浄化装置。 The exhaust gas purification apparatus according to any one of claims 1 to 3, further,
The exhaust flow path includes a catalyst having a three-way catalytic function, which is provided downstream of the upstream catalyst and upstream of the downstream catalyst.
Exhaust purification system. - 請求項1から請求項4までのいずれか一項に記載の排気浄化装置において、
前記上流側触媒と前記下流側触媒は、いずれも三元触媒機能を有している、
排気浄化装置。 In the exhaust gas purification device according to any one of claims 1 to 4,
Both the upstream side catalyst and the downstream side catalyst have a three-way catalytic function,
Exhaust purification system. - 請求項4に記載の排気浄化装置において、
前記三元触媒機能を有した触媒は、相対的に上流側に配置される上流側三元触媒と、前記上流側三元触媒の下流側に配置される下流側三元触媒とを含んでおり、前記上流側三元触媒の酸素吸蔵能は、前記下流側三元触媒の酸素吸蔵能よりも能力が低い、
排気浄化装置。 In the exhaust gas purification apparatus according to claim 4,
The catalyst having the three-way catalytic function includes an upstream three-way catalyst disposed relatively upstream, and a downstream three-way catalyst disposed downstream of the upstream three-way catalyst. The oxygen storage capacity of the upstream three-way catalyst is lower than the oxygen storage capacity of the downstream three-way catalyst.
Exhaust purification system.
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JP2000045751A (en) * | 1998-05-29 | 2000-02-15 | Nissan Motor Co Ltd | Exhaust emission control device for internal combustion engine |
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JP2000045751A (en) * | 1998-05-29 | 2000-02-15 | Nissan Motor Co Ltd | Exhaust emission control device for internal combustion engine |
JP2004076681A (en) * | 2002-08-21 | 2004-03-11 | Toyota Motor Corp | Catalyst deterioration determination device |
JP2005120909A (en) * | 2003-10-16 | 2005-05-12 | Toyota Motor Corp | Exhaust emission control device of internal combustion engine |
JP2005214071A (en) * | 2004-01-29 | 2005-08-11 | Mitsubishi Motors Corp | Exhaust gas purification catalyst device |
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