US20200173328A1 - Controller for exhaust gas purification system - Google Patents

Controller for exhaust gas purification system Download PDF

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Publication number
US20200173328A1
US20200173328A1 US16/783,251 US202016783251A US2020173328A1 US 20200173328 A1 US20200173328 A1 US 20200173328A1 US 202016783251 A US202016783251 A US 202016783251A US 2020173328 A1 US2020173328 A1 US 2020173328A1
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Prior art keywords
nox
amount
ozone
exhaust gas
ozone supply
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US16/783,251
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English (en)
Inventor
Yusuke MAJIMA
Kazuhiro Higuchi
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Denso Corp
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Denso Corp
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Assigned to DENSO CORPORATION reassignment DENSO CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HIGUCHI, KAZUHIRO, MAJIMA, YUSUKE
Publication of US20200173328A1 publication Critical patent/US20200173328A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion
    • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/10—Preparation of ozone
    • C01B13/11—Preparation of ozone by electric discharge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • 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
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • 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
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/38—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an ozone (O3) generator, e.g. for adding ozone after generation of ozone from air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/06—Adding substances to exhaust gases the substance being in the gaseous form
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1402—Exhaust gas composition
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present disclosure relates to a controller for an exhaust gas purification system that includes a NOx storage reduction type catalyst to purify NOx (nitrogen oxides).
  • a known technique to purify NOx uses a NOx storage reduction type catalyst in an exhaust gas purification system of an internal combustion engine.
  • a controller, according to an aspect of the present disclosure, for the exhaust gas purification system includes a NOx amount acquisition unit, a calculation unit, and a control unit.
  • FIG. 1 is a diagram showing an exhaust gas purification system of an engine.
  • FIG. 2 is a graph showing a relationship between a ratio of ozone to NO in exhaust gas and a storage efficiency.
  • FIG. 3 is a flow chart showing a control procedure of an ozone supply.
  • FIGS. 4A to 4F are views showing relationships between various parameters and estimated NOx amounts (NOx_est), respectively.
  • FIGS. 5A and 5B are views showing relationships between changes ⁇ Y and correction amounts, respectively.
  • a NOx storage reduction type catalyst is used to purify NOx in an exhaust gas purification system of an internal combustion engine.
  • the NOx storage reduction type catalyst exhibits a storage efficiency for NO (nitric oxide) that is different from a storage efficiency for NO2 (nitrogen dioxide).
  • NO2 nitrogen dioxide
  • the storage efficiency of NO is decreased in a low temperature, for example. Therefore, an ozone supply device supplies ozone to an upstream of the NOx storage reduction type catalyst in an exhaust passage of the internal combustion engine, and the ozone oxidizes NO in exhaust gas to NO2.
  • the exhaust gas purification system supplies ozone to an upstream of a NOx storage reduction type catalyst.
  • the NOx storage reduction type catalyst may not exhibit a desired performance of NOx purification.
  • the present disclosure is provided with a controller for an exhaust gas purification system configured to properly supply ozone and to properly purify NOx.
  • a controller is applicable to an exhaust gas purification system.
  • the exhaust gas purification system includes a NOx storage reduction type catalyst equipped in an exhaust passage of an internal combustion engine and configured to purify NOx in exhaust gas, an ozone supply device configured to supply ozone to an upstream of the catalyst in the exhaust passage, and a NOx sensor provided at a downstream of the catalyst and configured to detect a NOx amount in exhaust gas.
  • the controller for the exhaust gas purification system includes a NOx amount acquisition unit, a calculation unit, and a control unit.
  • the NOx amount acquisition unit is configured to acquire a detected NOx amount detected by the NOx sensor in a state where the internal combustion engine operates and where the ozone supply device supplies the ozone.
  • the calculation unit is configured to calculate an amount of NOx discharged to a downstream of the catalyst as an estimated NOx amount based on at least one of exhaust gas information about exhaust gas discharged from the internal combustion engine and catalyst information about the catalyst.
  • the control unit is configured to implement comparison of the detected NOx amount acquired by the NOx amount acquisition unit with the estimated NOx amount calculated by the calculation unit and to perform at least one of an ozone supply amount control by the ozone supply device and an abnormality diagnosis of the ozone supply device based on a result of the comparison.
  • the ozone supply device supplies the ozone to the upstream of the NOx storage reduction type catalyst in the exhaust passage of the internal combustion engine, and NO in the exhaust gas is oxidized to NO2. Therefore, a NOx storage capacity of the NOx storage reduction type catalyst can be raised. In this case, when an amount of the ozone supplied by the ozone supply device is decreased unintentionally, the NOx storage capacity of the NOx storage reduction type catalyst is decreased, and a performance of a NOx purification may be decreased.
  • the detected NOx amount detected by the NOx sensor is acquired. Based on the detected NOx amount, at least one of the ozone supply amount control by the ozone supply device and the abnormality diagnosis of the ozone supply device is performed. Accordingly, the ozone supply amount control or the abnormality diagnosis can be performed appropriately while observing a reduction of an actual NOx purification efficiency. Therefore, the ozone can be properly supplied, and a proper NOx purification can be performed.
  • An exhaust gas purification system which purifies exhaust gas discharged from a diesel engine on a vehicle, adds ozone from an ozone supply device especially to an upstream of a catalyst in the present embodiment.
  • the same reference numerals are given to the same structures in the embodiments which will be described below, and the explanations for the structures with the same reference numerals are incorporated in the embodiments.
  • An engine 10 in FIG. 1 is a multiple-cylinder diesel engine and uses light oil as a fuel.
  • Each of the cylinders of the diesel engine is connected to an air intake pipe 11 and an exhaust pipe 12 .
  • a supercharger 13 is equipped in the engine 10 .
  • An intake compressor 14 arranged at the air intake pipe 11 , an exhaust turbine 15 arranged at the exhaust pipe 12 , and a rotation shaft 16 which connects the intake compressor 14 to the exhaust turbine 15 are equipped in the supercharger 13 .
  • An intercooler may be provided as a heat exchanger on the air intake pipe 11 at a downstream of the intake compressor 14 .
  • An air flow sensor 18 is provided to the air intake pipe 11 at an upstream of the intake compressor 14 and configured to detect an amount of air which passes through the air intake pipe 11 .
  • a rotation speed sensor 19 is provided to an output shaft of the engine 10 and configured to detect a rotation speed of the engine.
  • a NOx storage reduction type catalyst is provided to the exhaust pipe 12 as a NOx purification device to purify NOx in the exhaust gas flowing in an exhaust passage provided in the exhaust pipe 12 .
  • the NOx storage reduction type catalyst is referred to as NOx catalyst 21 hereinafter.
  • the NOx catalyst 21 is, as generally known, configured to store the NOx included in the exhaust gas during a lean-burn combustion and to reduce and remove the NOx, which has been stored, with a reducing component such as HC or CO included in the exhaust gas during a rich-burn combustion.
  • a silver as a reduction catalyst is carried on alumina coated on a surface of a carrier.
  • a NOx sensor 22 configured to detect an amount of the NOx in the exhaust gas discharged from the engine 10 and an exhaust gas temperature sensor 23 configured to detect an exhaust gas temperature are provided to the exhaust pipe 12 at an upstream of the NOx catalyst 21 .
  • the sensors 22 , 23 are provided at an upstream of a supply pipe 31 which will be described below.
  • a NOx sensor 24 is provided at a downstream of the NOx catalyst 21 and configured to detect the NOx amount at the downstream of the catalyst.
  • the NOx catalyst 21 includes a catalyst temperature sensor 25 configured to detect a catalyst temperature.
  • the NOx sensors 22 , 24 are each limiting current type gas sensors which are configured with a solid electrolyte, for example.
  • the NOx sensor 22 at the upstream of the catalyst is also referred to as upstream NOx sensor 22
  • the NOx sensor 24 at the downstream of the catalyst is referred to as downstream NOx sensor 24 , hereinafter.
  • the catalyst temperature sensor 25 may be provided at the downstream of the NOx catalyst 21 .
  • the ozone is supplied to the exhaust pipe 12 at the upstream of the NOx catalyst 21 and oxidizes NO in the exhaust gas to NO2. Because of this, a NOx storage capacity of the NOx catalyst 21 is raised.
  • the structures of the exhaust gas purification system will be described below.
  • the supply pipe 31 is connected to the exhaust pipe 12 at the upstream of the NOx catalyst 21 .
  • An air pump 32 is a motor pump, for example, and configured to pressurize atmospheric air inhaled from the exterior and to send the air to the ozone generator 33 .
  • the structure of the ozone generator 33 is generally known, and a detailed description with reference to a drawing is omitted.
  • the ozone generator 33 includes multiple electrodes in a container in which a flow passage is formed. The ozone is generated by a high voltage application between the multiple electrodes.
  • the on-off valve 34 is arranged to restrain a reverse flow of the exhaust gas from the exhaust pipe 12 .
  • the ozone is supplied to the exhaust pipe 12 when the on-off valve 34 is opened, and the ozone supply is stopped when the on-off valve 34 is closed.
  • the air pump 32 and the ozone generator 33 correspond to the ozone supply device.
  • the air pump 32 is driven, and the on-off valve 34 is opened, under a state where the ozone generator 33 generates the ozone by a voltage application. Because of this, the ozone flows with air which passes the ozone generator 33 into the exhaust pipe 12 . Subsequently, the NOx catalyst 21 stores the NO and the NO2 and performs reduction and purification, while the oxidization is performed at the upstream of the NOx catalyst 21 to convert the NO2 from the NO.
  • An ECU 40 is a well-known electronic controller and includes mainly a microcomputer which includes CPU, ROM, RAM, and the like.
  • the ECU 40 is configured to perform controls of an exhaust gas purification according to detection signals of the sensors described above, by executions of control programs stored in the ROM, respectively.
  • the ECU 40 is configured to perform an ozone supply amount control which controls an amount of the ozone supplied by the ozone supply device at a desired amount.
  • the ECU 40 controls statuses of the air pump 32 , the ozone generator 33 , and the on-off valve 34 to supply a prescribed amount of the ozone to the exhaust pipe 12 , for example.
  • the ECU 40 performs the ozone supply to the exhaust pipe 12 according to the request.
  • a storage efficiency of the NOx catalyst 21 for the NO in the NOx in the exhaust gas is different from the storage efficiency for the NO2 in the NOx in the exhaust gas.
  • the storage efficiency of the NO becomes extremely lower. Therefore, the ozone is supplied to the exhaust pipe 12 to oxidize NO into NO2 at the low temperature.
  • the ozone amount is insufficient by a deterioration of the performance of the ozone supply device, the oxidation of the NO into NO2 at the upstream of the catalyst may be insufficient. In this state, a ratio of the NO in the NOx is increased, and a NOx storage efficiency of the NOx catalyst 21 may be decreased.
  • FIG. 2 is a graph showing a relationship between a ratio of the ozone to the NO in the exhaust gas and a storage efficiency. As show in FIG. 2 , the storage efficiency of the NOx catalyst 21 decreases as the ratio of the ozone to the NO in the exhaust gas decreases.
  • the ozone supply device In a case where the ozone supply device does not supply the ozone at an appropriate amount due to a malfunction or the like, the NOx catalyst 21 may not exhibit a desired performance of NOx purification. Therefore, in the present embodiment, in a state where the engine 10 operates and where the ozone supply device supplies the ozone, the ozone supply device acquires a detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 . Subsequently, based on the detected NOx amount (NOx_sens), the ozone supply device performs the ozone supply amount control and an abnormality diagnosis of the ozone supply device.
  • NOx_sens a detected NOx amount detected by the downstream NOx sensor 24 .
  • the ECU 40 calculates an amount of the NOx discharged to the downstream of the NOx catalyst 21 as an estimated NOx amount (NOx_est) based on exhaust gas information about the exhaust gas discharged from the engine 10 and based on catalyst information about the NOx catalyst 21 . Subsequently, the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 , is compared with the estimated NOx amount (NOx_est). Based on the result of the comparison, the ozone supply amount control by the ozone supply device and the abnormality diagnosis of the ozone supply device are performed.
  • NOx_est estimated NOx amount
  • FIG. 3 is a flow chart showing a control procedure of an ozone supply, and its processing is performed by the ECU 40 at a prescribed cycle.
  • step S 11 it is determined whether or not an operating state of the engine 10 under the operating state is in a stable state, but not in a transitional state. In this case, it may be determined that the engine operating state is stable in a case where the rotation speed of the engine is not larger than a predetermined value and a load change is not larger than a predetermined value within a predetermined period. The stability of the operating state of the vehicle may be determined based on an accelerator operation amount or the like.
  • step S 11 makes a negative determination, the processing proceeds to step S 12 .
  • step S 11 makes a positive determination, the processing proceeds to step S 13 .
  • step S 12 the operation of the air pump 32 or the ozone generator 33 is started with a predetermined control command value to supply a predetermined amount of the ozone to the exhaust pipe 12 .
  • step S 11 makes a negative determination, the abnormality diagnosis of the ozone supply device is not performed.
  • step S 13 ozone amount information which indicates the amount of the ozone supplied from the ozone generator 33 into the exhaust pipe 12 through the supply pipe 31 is acquired.
  • the amount of the ozone may be estimated from a voltage applied to the electrode of the ozone generator 33 or an electricity consumption.
  • the amount of the ozone may be calculated in consideration of a volume of air blown by the air pump 32 .
  • step S 14 exhaust gas information which is on the exhaust gas discharged from the engine 10 is acquired.
  • the exhaust gas information includes an exhaust gas parameter such as an exhaust NOx amount which indicates an amount of NOx discharged from the engine 10 , a flow rate of the exhaust gas, or a temperature of the exhaust gas or the like.
  • the exhaust NOx amount is calculated from a detection signal of the upstream NOx sensor 22 .
  • the flow rate of the exhaust gas is calculated from a detection signal of the air flow sensor 18 .
  • the temperature of the exhaust gas is calculated from a detection signal of the exhaust gas temperature sensor 23 .
  • the exhaust NOx amount, the flow rate of the exhaust gas, or the temperature of the exhaust gas may be estimated by using a predetermined estimation model, a predetermined expression or the like, based on the rotation speed of the engine or an engine load.
  • the catalyst information about the NOx catalyst 21 is acquired.
  • the catalyst information includes a catalyst parameter such as a temperature of the NOx catalyst 21 or a NOx storage amount which indicates an amount of NOx which has already been stored in the NOx catalyst 21 or the like.
  • the catalyst temperature is calculated from the detection signal of the catalyst temperature sensor 25 .
  • the NOx storage amount is calculated by estimation from an operation history of the engine 10 or the like. For example, the NOx storage amount may be estimated based on a number of a fuel injection or an amount of the fuel reduction after the rich-burn combustion.
  • step S 16 the amount of the NOx discharged to the downstream of the NOx catalyst 21 is calculated as an estimated NOx amount (NOx_est) based on the ozone amount information, the exhaust gas information, and the catalyst information which are acquired in steps S 13 to S 15 described above.
  • NOx_est an estimated NOx amount
  • FIG. 4A shows a relationship between the ozone amount as the ozone amount information and the estimated NOx amount (NOx_est).
  • the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the ozone amount becomes smaller.
  • FIG. 4B shows a relationship between the exhaust NOx amount as the exhaust gas information and the estimated NOx amount (NOx_est).
  • the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the exhaust NOx amount becomes larger.
  • FIG. 4C shows a relationship between the flow rate of the exhaust gas as the exhaust gas information and the estimated NOx amount (NOx_est).
  • the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the flow rate of the exhaust gas becomes larger.
  • An exhaust gas pressure may be used as the exhaust gas information, instead of the flow rate of the exhaust gas. In this case, the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the exhausted gas pressure becomes larger.
  • FIG. 4D shows a relationship between the temperature of the exhaust gas as the exhaust gas information and the estimated NOx amount (NOx_est).
  • the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the temperature of the exhaust gas becomes lower.
  • FIG. 4E shows a relationship between the catalyst temperature as the catalyst information and the estimated NOx amount (NOx_est).
  • the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the catalyst temperature becomes lower.
  • the relationship between the catalyst temperature and the estimated NOx amount (NOx_est) depends on the ozone amount, and a relationship under consideration of the ozone amount may be defined. In this case, as shown in broken lines in FIG. 4E , as the ozone amount becomes smaller, the estimated NOx amount (NOx_est) may be increased, and a gradient of the estimated NOx amount (NOx_est), which is negative gradient, to the catalyst temperature may be increased.
  • FIG. 4F shows a relationship between the NOx storage amount as the catalyst information and the estimated NOx amount (NOx_est).
  • the ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the NOx storage amount becomes larger.
  • the relationships shown in FIGS. 4A to 4F may be specified as maps or formulas in advance.
  • the values of parameters may be substituted into the map or the formula to calculate the estimated NOx amount (NOx_est).
  • the estimated NOx amount (NOx_est) may be calculated with one or two of the exhaust NOx amount, the flow rate of the exhaust gas, and the temperature of the exhaust gas as the exhaust gas information. Further, the estimated NOx amount (NOx_est) may be calculated with one of the catalyst temperature and the NOx storage amount as the catalyst information. Further, the estimated NOx amount (NOx_est) may be calculated with one or two of the ozone amount information, the exhaust gas information, and the catalyst information.
  • step S 17 the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 is acquired.
  • the detected NOx amount (NOx_sens) corresponds to an actual NOx amount at the downstream of the NOx catalyst 21 .
  • step S 18 it is determined whether or not a difference ⁇ Y is larger than a predetermined threshold TH.
  • the difference ⁇ Y is obtained by a subtraction of the estimated NOx amount (NOx_est) from the detected NOx amount (NOx_sens) and defined as follows.
  • step S 18 it is determined whether or not the NOx amount at the downstream of the catalyst is large relative to an ozone amount (primary ozone amount) by which the ozone supply device should supply ozone.
  • the threshold TH may be determined based on an allowable amount of NOx at the downstream of the NOx catalyst 21 , that is, based on an allowable leakage amount of NOx which is determined based on environmental standards or the like.
  • a correction amount which is added to the ozone supply amount (supply command) is increased and corrected is set according to the difference ⁇ Y, and the ozone supply amount is updated by the correction amount. More specifically, as shown in FIG. 5A , the correction amount is set at a larger value as the difference ⁇ Y becomes larger within a range of 0 to the threshold TH, that is, as the detected NOx amount (NOx_sens) becomes larger with respect to the estimated NOx amount (NOx_est). In a case of ⁇ Y ⁇ 0, the correction amount may be 0. An updated ozone supply amount is calculated by addition of the correction amount to the ozone supply amount at this point.
  • the correction amount may be set variably according to the difference ⁇ Y, or may be a constant correction amount to be added.
  • the correction amount may be set by using a relationship shown in FIG. 5B .
  • FIG. 5B when the difference ⁇ Y is a positive number, that is in a case of NOx_sens>NOx_est, the ozone supply amount is corrected and increased by a positive correction amount.
  • the difference ⁇ Y is a negative number, that is in a case of NOx_sens ⁇ NOx_est, the ozone supply amount is corrected and decreased by a negative correction amount.
  • an upper limit guard processing is performed on the ozone supply amount which has been updated. More specifically, it is determined whether or not the updated ozone supply amount reaches a predetermined upper limit value. In a case where the updated ozone supply amount reaches the upper limit value, the ozone supply amount is restricted to the upper limit value. Therefore, the ozone supply amount is restricted in a range to the upper limit value and is controlled by the feedback control according to the difference ⁇ Y at each time.
  • an applied voltage may be raised to increase a generation amount of the ozone by the ozone generator 33 .
  • the volume of air blown by the air pump 32 may be increased. In a case of ⁇ Y ⁇ TH, it is determined that the ozone supply device is in a normal condition.
  • step S 21 the processing proceeds to step S 21 , and the ECU 40 determines that abnormality is caused in the ozone supply device.
  • step S 22 a warning by a malfunction warning lamp or a sound is performed to inform that the ozone supply device is in an abnormal condition.
  • the ozone supply by the ozone supply device is stopped.
  • the ECU 40 acquires the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 and performs the ozone supply amount control and the abnormality diagnosis based on the detected NOx amount (NOx_sens). Accordingly, the ozone supply amount control or the abnormality diagnosis can be performed appropriately while observing a reduction of an actual NOx purification efficiency. Therefore, the ozone can be properly supplied, and a proper NOx purification can be performed.
  • an appropriate measure can be performed by the warning or by a stopping of the ozone supply.
  • the NOx amount at the downstream of the catalyst is calculated as the estimated NOx amount (NOx_est). Subsequently, based on a comparison result between the estimated NOx amount (NOx_est) and the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 , the ozone supply amount control and the abnormality diagnosis of the ozone control device are performed. Therefore, the ozone supply amount control and the abnormality diagnosis can be performed appropriately, even when a state of the exhaust gas and/or a state of the NOx catalyst 21 is changed according to the engine operating state or the like.
  • the ECU 40 is configured to calculate the estimated NOx amount (NOx_est) based on the exhaust NOx amount, the flow rate of the exhaust gas, and the temperature of the exhaust gas discharged from the engine 10 , and issues such as an accuracy deterioration of the ozone supply amount control or of the abnormality diagnosis due to a change of the each parameter can be restrained.
  • the estimated NOx amount (NOx_est) is calculated based on the temperature of the NOx catalyst 21 and on the NOx storage amount of the NOx catalyst 21 . Therefore, issues such as the accuracy deterioration of the ozone supply amount control or of the abnormality diagnosis due to the change of the each parameter can be restrained.
  • the ECU 40 is configured to acquire the amount of the ozone supplied to the exhaust pipe 12 and to calculate the estimated NOx amount (NOx_est) based on the ozone amount. Therefore, issues such as the accuracy deterioration of the ozone supply amount control or of the abnormality diagnosis due to the change of the ozone amount can be restrained.
  • the ozone supply amount control is performed based on the difference ⁇ Y.
  • the difference ⁇ Y is larger than the threshold TH, the abnormality diagnosis of the ozone supply device is performed. Therefore, on the ozone supply device, the ozone supply amount control and the abnormality diagnosis can be performed appropriately, as required. In this case, before the ECU 40 determines that the ozone supply device is abnormal, the ozone supply amount control enables to obtain a stable purification performance at the NOx catalyst 21 .
  • the ozone supply amount is controlled based on the detected NOx amount (NOx_sens) in a range of the ozone supply amount to a predetermined upper limit value, and the abnormality diagnosis of the ozone supply device is performed in a case where the ozone supply amount is the upper limit value.
  • NOx_sens the detected NOx amount
  • the maximum ozone supply is performed in a control range in which the ozone can be supplied, and the abnormality diagnosis of the ozone supply device is performed under a state where the maximum ozone supply is performed. Therefore, the abnormality diagnosis can be performed properly while the ozone is supplied as possible.
  • the ozone supply amount control and the abnormality diagnosis are performed. Therefore, a control accuracy of the ozone supply amount control can be enhanced. In addition, an erroneous diagnosis of the abnormality diagnosis can be suppressed, and a diagnosis accuracy can be enhanced.
  • the ECU 40 performs the ozone supply amount control and the abnormality diagnosis.
  • the ECU 40 may perform only one of them.
  • the ECU 40 may perform the ozone supply amount control based on the difference ⁇ Y between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est).
  • the ECU 40 may perform the abnormality diagnosis of the ozone supply device based on the difference ⁇ Y between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est).
  • the ozone supply amount control and the abnormality diagnosis are performed based on the difference ⁇ Y between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est).
  • the ozone supply amount control and the abnormality diagnosis may be performed based on only the detected NOx amount (NOx_sens) out of the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est).
  • the ozone supply device is configured to supply the ozone at a constant amount.
  • the ECU 40 sets the ozone supply amount based on the detected NOx amount (NOx_sens), and more specifically, the ozone supply amount becomes larger as the detected NOx amount (NOx_sens) becomes larger.
  • the ECU 40 detects that the abnormality of the ozone supply device is caused.
  • the exhaust gas purification system is not limited to the system shown in FIG. 1 and may include an oxide catalysis at the upstream of the NOx catalyst 21 , or may include a DPF or a DPF with a catalyst at the downstream of the NOx catalyst 21 .
  • the exhaust gas purification system in the embodiments described above may be applied not only to the diesel engine, but also to another type of the engine such as a gasoline engine.
  • the exhaust gas purification system may also be applied to an engine not for a vehicle.
  • a wording of at least one of A, and B encompasses a definition of only A, a definition of only B, and a definition of both A and B.
  • This present disclosure also encompasses various combinations and embodiments, and furthermore, encompasses one or more or less of elements and combinations thereof.

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  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Inorganic Chemistry (AREA)
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  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Oxygen, Ozone, And Oxides In General (AREA)
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220356833A1 (en) * 2018-09-21 2022-11-10 Cummins Inc. Systems and methods for diagnosis of nox storage catalyst
US11946401B2 (en) * 2021-10-19 2024-04-02 Volvo Penta Corporation Method for predicting urea crystal build-up in an engine system

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JP2009281290A (ja) * 2008-05-22 2009-12-03 Toyota Motor Corp 内燃機関の排気ガス浄化装置
JP2010031730A (ja) * 2008-07-29 2010-02-12 Toyota Motor Corp 内燃機関の排気浄化装置
JP6515481B2 (ja) * 2014-10-15 2019-05-22 株式会社デンソー オゾン供給装置
JP2017160333A (ja) 2016-03-09 2017-09-14 旭化成株式会社 ポリアセタールコポリマー、コポリマーの製造方法、およびポリアセタール樹脂組成物

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220356833A1 (en) * 2018-09-21 2022-11-10 Cummins Inc. Systems and methods for diagnosis of nox storage catalyst
US11719151B2 (en) * 2018-09-21 2023-08-08 Cummins Inc. Systems and methods for diagnosis of NOx storage catalyst
US11946401B2 (en) * 2021-10-19 2024-04-02 Volvo Penta Corporation Method for predicting urea crystal build-up in an engine system

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