WO2015132646A1 - Control system for internal combustion engine - Google Patents

Control system for internal combustion engine Download PDF

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Publication number
WO2015132646A1
WO2015132646A1 PCT/IB2015/000254 IB2015000254W WO2015132646A1 WO 2015132646 A1 WO2015132646 A1 WO 2015132646A1 IB 2015000254 W IB2015000254 W IB 2015000254W WO 2015132646 A1 WO2015132646 A1 WO 2015132646A1
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WO
WIPO (PCT)
Prior art keywords
temperature
control apparatus
exhaust gas
gas control
fuel
Prior art date
Application number
PCT/IB2015/000254
Other languages
French (fr)
Inventor
Takanori Ueda
Original Assignee
Toyota Jidosha Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Jidosha Kabushiki Kaisha filed Critical Toyota Jidosha Kabushiki Kaisha
Publication of WO2015132646A1 publication Critical patent/WO2015132646A1/en

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Classifications

    • 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
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0408—Methods of control or diagnosing using a feed-back loop
    • 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
    • F01N2900/1404—Exhaust gas temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1602—Temperature of exhaust gas apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/029—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a particulate filter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the invention relates to a control system for an internal combustion engine.
  • JP 2013-029038 A discloses a technique for controlling a temperature of an exhaust gas control apparatus within a temperature range where a sulfur compound can be released and turning of the sulfur compound into white smoke in the atmosphere can be suppressed.
  • techniques relating to exhaust gas control apparatus regeneration are disclosed in Japanese Patent Application Publication No. 2010-229916 (JP 2010-229916 A), Japanese Patent Application Publication No. 2005-090274 (JP 2005-090274 A), Japanese Patent Application Publication No.
  • JP 2005-106047 JP 2005-106047 A
  • JP 2002-320863 JP 2002-320863 A
  • Japanese Patent Application Publication No. 2010-163885 JP 2010-163885 A
  • Japanese Patent Application Publication No. 2012-246842 JP 2012-246842 A
  • Japanese Patent Application Publication No. 2013-142377 JP 2013-142377 A
  • Japanese Patent Application Publication No. 2005-076505 JP 2005-076505 A.
  • prolongation of regeneration control may degrade fuel efficiency in a case where the temperature of the exhaust gas control apparatus drops, affected by an operation state of an internal combustion engine or the like, during the regeneration control for the exhaust gas control apparatus.
  • An object of the invention is to provide a control system for an internal combustion engine that suppresses white smoke generation and suppresses fuel efficiency degradation.
  • a control system for an internal combustion engine and the internal combustion engine includes an exhaust gas control apparatus and a fuel supply apparatus.
  • the exhaust gas control apparatus is disposed in an exhaust gas passage of the internal combustion engine.
  • the fuel supply apparatus is configured to supply a fuel to the exhaust gas control apparatus.
  • the control system includes an electronic control unit.
  • the electronic control unit is configured to: (a) supply the fuel to the exhaust gas control apparatus by using the fuel supply apparatus so that a temperature of the exhaust gas control apparatus is raised and a particulate matter deposited in the exhaust gas control apparatus is burned; (b) when the temperature of the exhaust gas control apparatus is within a first temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a first target temperature rise rate; (c) when the temperature of the exhaust gas control apparatus is within a second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a second target temperature rise rate, the second temperature range being higher than the first temperature range, the second target temperature rise rate being lower than the first target temperature rise rate; (d) when the temperature of the exhaust gas control apparatus is within a third temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is maintained within the third temperature range, the third temperature range being higher than the second temperature range; (e) when a temperature drop of the
  • the electronic control unit may be configured to, when the temperature of the exhaust gas control apparatus is within the second temperature range, execute a feedback control for a supply amount of the fuel to the exhaust gas control apparatus based on a difference between a target temperature of the exhaust gas control apparatus and an actual temperature of the exhaust gas control apparatus.
  • the target temperature of the exhaust gas control apparatus may be a temperature at which the second target temperature rise rate is satisfied.
  • the electronic control unit may be configured to decrease the second target temperature rise rate as sulfur concentration in the fuel supplied to the internal combustion engine increases.
  • FIG. 1 is an explanatory drawing of an engine system according to this embodiment
  • FIG. 2A is a graph illustrating a change in control apparatus temperature during regeneration control
  • FIG. 2B is a graph illustrating a concentration change in S0 3 in an exhaust gas during the regeneration control
  • FIG. 3 is a flowchart illustrating an example of the regeneration control
  • FIG. 4 is a flowchart illustrating an example of slow regeneration control
  • FIG. 5 is a map defining a second target temperature rise rate corresponding to sulfur concentration in a fuel
  • FIG. 6 is a graph illustrating an example of a change in control apparatus temperature that is controlled by feedback control
  • FIG. 7A is a map defining a reference fuel addition amount corresponding to a target control apparatus temperature
  • FIG. 7B is a map defining a correction amount for a fuel addition amount
  • FIG. 7C is a map defining an upper limit value for the fuel addition amount for the feedback control.
  • FIG. 8 is a graph illustrating an example of a change in control apparatus temperature in a case where the control apparatus temperature drops.
  • FIG. 1 is an explanatory drawing of an engine system 10 according to an embodiment.
  • a diesel engine (hereinafter, referred to as an engine) 11 is provided with an intake manifold 12 and an exhaust manifold 13.
  • the intake manifold 12 is connected to an outlet of a compressor 16 of a turbocharger 15 via an intake passage 14.
  • An intercooler IC that cools intake air is disposed in the intake passage 14, and a throttle valve V that adjusts an intake amount to the engine 11 is arranged in the intake passage 14.
  • the exhaust manifold 13 is connected to an inlet of an exhaust turbine 18 of the turbocharger 15 via an exhaust gas passage 17.
  • a variable nozzle vane 18a is disposed at the inlet of the exhaust turbine 18.
  • a flow rate of an exhaust gas that passes through the exhaust turbine 18 can be adjusted to the degree of opening of the variable nozzle vane 18a.
  • An outlet of the exhaust turbine 18 is connected to an exhaust gas passage 19.
  • the exhaust gas from the engine 11 is discharged to the exhaust gas passage 19 through the exhaust turbine 18.
  • the engine 11 is provided with four cylinders C and four fuel injection valves F that inject a fuel directly into the four respective cylinders C, but is not limited thereto.
  • An exhaust gas recirculation (EGR) passage 14a is connected between the intake passage 14 and the exhaust gas passage 17.
  • An EGR valve Va is disposed in the EGR passage 14a.
  • a crank angle sensor CS that detects an engine speed is disposed in the engine 11.
  • An exhaust gas control apparatus E that purifies the exhaust gas is disposed in the exhaust gas passage 19.
  • a diesel oxidation catalyst (DOC) 20 and a diesel particulate filter (DPF) 21 are disposed, in order from an upstream side to a downstream side, in the exhaust gas control apparatus E.
  • the DOC 20 is an oxidation catalyst that oxidizes and converts HC, NO, and CO contained in the exhaust gas to H 2 0, C0 2 , and N0 2 .
  • the DPF 21 collects a particulate matter contained in the exhaust gas.
  • the exhaust gas control apparatus E is an example of an exhaust gas control apparatus.
  • a fuel addition valve 24, a SOx sensor 25, and a temperature sensor 26 are disposed in the exhaust gas passage 19 between the exhaust turbine 18 and the DOC 20.
  • the SOx sensor 25 detects sulfur concentration in the exhaust gas that flows to the DOC 20.
  • the fuel addition valve 24 adds a fuel to the exhaust gas so as to combust the particulate matter deposited in the DPF 21.
  • the temperature sensor 26 detects a temperature of the exhaust gas that flows into the DOC 20.
  • a temperature sensor 27 is disposed in the exhaust gas passage 19 between the DOC 20 and the DPF 21. The temperature sensor 27 detects the temperature of the exhaust gas that flows into the DPF 21 through the DOC 20.
  • a temperature sensor 28 and an air-fuel ratio sensor 29 are disposed, on a downstream side from the DPF 21, in the exhaust gas passage 19.
  • the temperature sensor 28 detects the temperature of the exhaust gas that passes through the DPF 21.
  • the air-fuel ratio sensor 29 detects an air-fuel ratio of the exhaust gas that passes through the DPF 21.
  • An electronic control unit (ECU) 30 performs overall control on the engine system 10.
  • the ECU 30 is a computer and a read only memory (ROM, not illustrated), a random access memory (RAM, not illustrated), a central processing unit (CPU, not illustrated), and the like constitute this computer.
  • the throttle valve V, the EGR valve Va, the above-described sensors, and the like are electrically connected to the ECU 30.
  • the ECU 30 estimates the sulfur concentration in the fuel based on output values from the SOx sensor 25 and the like, but is not limited thereto.
  • a fuel property sensor may be disposed in a fuel tank so that the sulfur concentration in the fuel is directly detected.
  • the sulfur concentration in the fuel that is used in a region where this engine system 10 is used may be stored in advance in the ECU 30.
  • the ECU 30 detects the temperature (hereinafter, referred to as a control apparatus temperature) of the exhaust gas control apparatus E based on values measured by the temperature sensors 26, 27, 28. Temperature sensors may be directly disposed in the DOC 20 and the DPF 21 so that temperatures thereof are detected. The temperature sensors 26, 27, 28 are examples of detection devices that detect the temperature of the exhaust gas control apparatus. The control apparatus temperature may also be estimated from an operation state of the engine 11.
  • the ECU 30 estimates the amount of the particulate matter that flows into the DPF 21 based on the operation state of the engine 11 and estimates the amount of the particulate matter deposited in the DPF 21 through integration.
  • the particulate matter deposition amount in the DPF 21 may also be estimated by the ECU 30 based on a value measured by a sensor that is disposed on the DPF 21 side to detect the particulate matter.
  • the ECU 30 executes regeneration control to regenerate the DPF 21 by combusting the particulate matter deposited in the DPF 21.
  • the ECU 30 controls the amount of the fuel that is supplied from the fuel addition valve 24 to the exhaust gas control apparatus E, raises the control apparatus temperature at a predetermined temperature rise rate, and combusts the particulate matter.
  • the fuel addition valve 24 is an example of a fuel supply apparatus that supplies the fuel to the exhaust gas control apparatus E. A method for supplying the fuel to the exhaust gas control apparatus E and combusting the particulate matter is not limited thereto.
  • the particulate matter deposited in the DPF 21 may be combusted by performing post-injection after main injection by the fuel injection valve F to supply an unburnt fuel to the exhaust gas control apparatus E.
  • the fuel injection valve F is an example of the fuel supply apparatus.
  • the ECU 30 can selectively execute normal regeneration control and slow regeneration control.
  • the normal regeneration control is control for combusting the particulate matter by raising the control apparatus temperature over a short period of time with priority given to suppression of fuel efficiency degradation.
  • the slow regeneration control is control for combusting the particulate matter by slowly raising the control apparatus temperature with priority given to suppression of white smoke generation.
  • FIG. 2A is a graph illustrating a change in control apparatus temperature during the regeneration control.
  • FIG. 2B is a graph illustrating a concentration change in S0 3 in the exhaust gas during the regeneration control.
  • the dotted lines in FIGS. 2A and 2B represent the change in control apparatus temperature and the S0 3 concentration caused by the normal regeneration control and the solid lines in FIGS. 2A and 2B represent the change in control apparatus temperature and the S0 3 concentration caused by the slow regeneration control.
  • the one-dot chain line in FIG. 2B represents the S0 3 concentration at which the exhaust gas begins to be visible as white smoke.
  • a case where the regeneration control is executed in a case where a certain amount of a sulfur compound is deposited in the DOC 20 and the DPF 21 and the sulfur concentration in the fuel is not low is assumed.
  • the range of a temperature Tl to a temperature T2 that is illustrated in FIG. 2A is a temperature range where the amount of sulfur compound desorption from the DOC 20 and the DPF 21 is larger than in other temperature ranges.
  • the temperature Tl is a temperature at which the sulfur compound desorption amount starts to increase.
  • the particulate matter deposited in the DPF 21 is combusted at or above the temperature T2.
  • a temperature below the temperature Tl will be referred to as a first temperature range Dl
  • a temperature that is equal to or above the temperature Tl and below the temperature T2 will be referred to as a second temperature range D2
  • a temperature that is equal to or above the temperature T2 will be referred to as a third temperature range D3 (hereinafter, simply referred to as temperature ranges).
  • the temperature Tl is 450 degrees and the temperature T2 is 650 degrees, but the temperature Tl and the temperature T2 are not limited thereto.
  • the control apparatus temperature is raised in an early stage, at a substantially constant temperature rise rate, until the control apparatus temperature reaches the temperature T2 at which the particulate matter starts to be combusted. After the control apparatus temperature reaches the temperature T2, the control apparatus temperature within a predetermined period is maintained within the temperature range D3 and the particulate matter is combusted. Within the temperature range D3, the control apparatus temperature is maintained at a temperature within the temperature range D3 for a certain period of time. Then, the control apparatus temperature is further raised to be maintained at a certain temperature. Then, the control apparatus temperature is raised to be maintained at a certain temperature. The particulate matter is combusted by raising the control apparatus temperature phase by phase as described above.
  • the temperature range D2 is a temperature range where the amount of sulfur compound desorption from the DOC 20 and the DPF 21 increases. Accordingly, the white smoke is generated in a case where the control apparatus temperature is within the temperature range D2 and the temperature rise rate is high. It is considered that the white smoke is generated because the amount of the sulfur compound (SOx) desorbed from the DOC 20 and the DPF 21 increases and the S0 3 in the exhaust gas is bound to H 2 0 to become H 2 S0 4 mist and discharged as the white smoke when the control apparatus temperature becomes equal to or higher than a predetermined value.
  • SOx sulfur compound
  • the temperature rise rate of the control apparatus temperature is high in a case where the control apparatus temperature is within the temperature range D2 as in the normal regeneration control, the sulfur compound desorption amount per short time period increases and the S0 3 concentration in the exhaust gas increases, and thus the exhaust gas is visible as the white smoke.
  • the control apparatus temperature is raised at a temperature rise rate that is lower than the temperature rise rate for the normal regeneration control in a case where the control apparatus temperature is within the temperature range D2.
  • the sulfur compound desorption amount per unit time can be suppressed to below a certain level, the S0 3 concentration in the exhaust gas can be suppressed, and the exhaust gas being visible as the white smoke can be suppressed.
  • the control apparatus temperature is raised at a first temperature rise rate during the slow regeneration control in a case where the control apparatus temperature is within the temperature range Dl. In this manner, the control apparatus temperature is allowed to reach the temperature Tl in an early stage and fuel efficiency degradation is suppressed.
  • the control apparatus temperature is raised at a second temperature rise rate that is lower than the first temperature rise rate. In this manner, S0 3 concentration in the exhaust gas can be suppressed and white smoke generation can be suppressed.
  • the control apparatus temperature is maintained within the temperature range D3 for a predetermined period. In this manner, the particulate matter deposited in the DPF 21 is combusted.
  • the second temperature rise rate is, for example, 0.7°C/sec but is not limited thereto.
  • the control apparatus temperature is raised at the first temperature rise rate described above in a case where the control apparatus temperature is within the temperature range Dl or the temperature range D2.
  • FIG. 3 is a flowchart illustrating an example of the regeneration control.
  • the regeneration control is initiated in a case, for example, where the ECU 30 determines that the amount of particulate matter deposition to the DPF 21 exceeds a predetermined value. For example, the ECU 30 estimates the amount of particulate matter deposition to the DPF 21 based on a traveling distance or the like.
  • the ECU 30 determines whether or not the sulfur concentration in the fuel is equal to or above a predetermined value (Step SI).
  • the predetermined value means a reference value for determining whether or not the white smoke is generated by the execution of the normal regeneration control.
  • Step S2 the ECU 30 executes the normal regeneration control (Step S2). This is because it is considered that the amount of sulfur compound deposition to the DOC 20 and the DPF 21 is small in a case where the sulfur concentration in the fuel is low, below the predetermined value for example, and the white smoke is unlikely to be generated despite the execution of the normal regeneration control.
  • This regeneration control is terminated when the normal regeneration control is terminated.
  • Step S3 the ECU 30 executes the slow regeneration control. This is because the white smoke may be generated when the normal regeneration control is executed in a case where the sulfur concentration in the fuel is at or above a predetermined value. This regeneration control is terminated when the slow regeneration control is terminated.
  • FIG. 4 is a flowchart illustrating an example of slow regeneration control.
  • the ECU 30 determines whether or not the control apparatus temperature is within the temperature range Dl (Step Sll). In the case of a positive determination, the ECU 30 controls a fuel addition amount of the fuel addition valve 24 and raises the control apparatus temperature at the first temperature rise rate (Step S12). Specifically, the ECU 30 sets a first target temperature rise rate for the control apparatus temperature to be raised at the first temperature rise rate and controls the fuel addition amount of the fuel addition valve 24 to correspond to the first target temperature rise rate.
  • Step S13 the ECU 30 raises the control apparatus temperature at the second temperature rise rate (Step S13).
  • the ECU 30 sets a second target temperature rise rate to correspond to the sulfur concentration in the fuel.
  • the second target temperature rise rate is a target value for raising the control apparatus temperature at the second temperature rise rate.
  • FIG. 5 is a map defining the second target temperature rise rate corresponding to the sulfur concentration in the fuel. This map is stored in advance in the ECU 30. This map is defined for the second target temperature rise rate to become lower as the sulfur concentration in the fuel increases.
  • the ECU 30 feedback-controls the fuel addition amount of the fuel addition valve 24 based on the actual control apparatus temperature so that the control apparatus temperature is raised at the second temperature rise rate.
  • FIG. 6 is a graph illustrating an example of a change in control apparatus temperature that is controlled by the feedback control.
  • the dotted line in FIG. 6 represents a target control apparatus temperature corresponding to the second target temperature rise rate.
  • the target control apparatus temperature rises with time.
  • the ECU 30 calculates a reference fuel addition amount based on the target control apparatus temperature that corresponds to the second target temperature rise rate which is set based on the sulfur concentration in the fuel.
  • FIG. 7A is a map defining the reference fuel addition amount corresponding to the target control apparatus temperature. This map differs by intake air amount and is stored in advance in the ECU 30.
  • the reference fuel addition amount is a fuel addition amount that is calculated in advance in an experiment for the control apparatus temperature to be raised at the second target temperature rise rate in a normal operation state other than transient operation conditions.
  • the ECU 30 adds a correction amount to the reference fuel addition amount and feedback-controls the fuel addition amount.
  • FIG. 7B is a map defining the correction amount for the fuel addition amount.
  • the correction amount is set based on a temperature difference that is obtained by subtracting the actual control apparatus temperature from the target control apparatus temperature.
  • the temperature difference is a positive value
  • the correction amount is added to the reference fuel addition amount, and the fuel addition amount increases.
  • the correction amount is set to increase as the temperature difference increases and the fuel addition amount increases as the temperature difference increases.
  • the correction amount is a negative value
  • the correction amount that is the negative value is added to the reference fuel addition amount, and the fuel addition amount decreases.
  • the absolute value of the correction amount that is the negative value is set to increase as the temperature difference increases and the fuel addition amount decreases as the temperature difference increases.
  • the control apparatus temperature is controlled to be raised at the second temperature rise rate by using the fuel addition amount that is set as described above. Calculation of the fuel addition amount that is controlled by the feedback control is not limited to the maps described above. For example, the calculation may also be based on a formula or the like.
  • FIG. 7C is a map defining the upper limit value for the fuel addition amount for the feedback control.
  • the upper limit value for the fuel addition amount is set to increase as the actual control apparatus temperature increases. In a case where the fuel addition amount that is set based on the maps in FIGS. 7A and 7B exceeds the upper limit value in FIG. 7C, the upper limit value in FIG. 7C is preferentially applied in performing actual fuel addition.
  • the upper limit value for the fuel addition amount may be lower than a fuel addition amount corresponding to the first temperature rise rate.
  • the maps that are illustrated in FIGS. 7 A to 7C are recorded in advance in the ECU 30 through calculation in an experiment or the like.
  • the ECU 30 determines whether or not temperature drop of the control apparatus temperature drops (Step S14). In the case of a negative determination, the ECU 30 records and updates the current control apparatus temperature in a case where the control apparatus temperature is within the temperature range D2 as a maximum temperature (Step S15). Then, the ECU 30 determines whether or not the control apparatus temperature is within the temperature range D2 (Step S16). In the case of a positive determination, the ECU 30 executes the processing of Step S13 and the subsequent processing again, continues raising the control apparatus temperature at the second temperature rise rate, and records and updates the maximum temperature of the control apparatus temperature.
  • Step S14 In the case of a positive determination in Step S14, that is, in a case where the control apparatus temperature drops, the ECU 30 raises the control apparatus temperature at the first temperature rise rate (Step S17). Then, the ECU 30 determines whether or not the actual control apparatus temperature exceeds the maximum temperature that is recorded or updated in Step S15 (Step S18). In the case of a negative determination, the ECU 30 continues with the processing of Step S17 again. In other words, the ECU 30 raises the control apparatus temperature at the third temperature rise rate until the control apparatus temperature reaches the maximum temperature. In the case of a positive determination in Step S18, the ECU 30 executes the processing of Step S13 and the subsequent processing again. In other words, the control apparatus temperature is raised at the second temperature rise rate in a case where the control apparatus temperature exceeds the maximum temperature.
  • FIG. 8 is a graph illustrating an example of a change in control apparatus temperature in a case where the control apparatus temperature drops.
  • the ECU 30 raises the control apparatus temperature at the first temperature rise rate until the control apparatus temperature reaches the maximum temperature again with the control apparatus temperature at the initiation of the drop recorded and updated as the maximum temperature in the ECU 30. This is because it is considered that the sulfur compound desorbed at or below the maximum temperature is already desorbed and the white smoke is not visible, even if the control apparatus temperature is raised at the first temperature rise rate, at or below the maximum temperature.
  • the ECU 30 calculates a new target temperature based on the second target temperature rise rate by using the maximum temperature as a reference. The maximum temperature that is recorded and updated in the ECU 30 is reset whenever the slow regeneration control is terminated.
  • Step S19 the ECU 30 maintains the control apparatus temperature within the temperature range D3 for a predetermined period (Step S19).
  • the predetermined period means a period that is required for combusting the particulate matter deposited in the DPF 21.
  • the temperature rise rate of the control apparatus temperature is controlled during the slow regeneration control so that white smoke generation can be suppressed.
  • the rise in control apparatus temperature can be accurately controlled at the second temperature rise rate by feedback-controlling the fuel addition amount based on the actual control apparatus temperature.
  • the control apparatus temperature drops to a temperature within the temperature range D2
  • the control apparatus temperature is raised, at the first temperature rise rate, in an early stage until the control apparatus temperature exceeds the temperature at the initiation of the drop so that fuel efficiency degradation can be suppressed.
  • the second target temperature rise rate is set based on the sulfur concentration in the fuel, prolongation of the slow regeneration control can be suppressed in a case where the sulfur concentration is low and the amount of sulfur deposition to the DOC 20 and the DPF 21 is small. Accordingly, fuel efficiency degradation can be suppressed.
  • a third temperature rise rate at which the control apparatus temperature is raised until the control apparatus temperature exceeds the maximum temperature after the control apparatus temperature drops to a temperature within the temperature range D2 is not limited to the first temperature rise rate but may be higher than the second temperature rise rate.
  • a forth temperature rise rate within the temperature range D2 after the control apparatus temperature drops to a temperature within the temperature range D2 and the control apparatus temperature exceeds the maximum temperature is not limited to the second temperature rise rate but may be a temperature rise rate that is lower than the first temperature rise rate.
  • a case where the actual temperature rise rate is lower than the second target temperature rise rate may occur even when the control apparatus temperature is within the temperature range D2 and the fuel addition amount is set to the upper limit value, examples of which include vehicle deceleration and low-speed traveling.
  • the ECU 30 may release a regulation of the upper limit value for the fuel addition amount and raise the control apparatus temperature at a fuel addition amount above the upper limit value. In this manner, prolongation of the regeneration control can be suppressed and fuel efficiency degradation can be suppressed.
  • the fuel addition amount may be limited again to an amount below the upper limit value.
  • the actual temperature rise rate may increase to become higher than the second target temperature rise rate in a case where the control apparatus temperature is within the temperature range D2, examples of which include a case where vehicle idles after sudden acceleration and a case where a clutch is OFF. Accordingly, the ECU 30 may set the fuel addition amount to zero for a predetermined period, for seconds for example, after the idling or the clutch OFF is detected in a case where the control apparatus temperature is within the temperature range D2 during the slow regeneration control. In this manner, sudden control apparatus temperature rise and white smoke generation can be suppressed.
  • the control apparatus temperature may be considered to drop when the fuel addition amount is set to zero, and thus the ECU 30 may raise the control apparatus temperature at a temperature rise rate that is higher than the second temperature rise rate, in a case where the idling is released or the clutch OFF is released, until the maximum temperature of the control apparatus temperature within the temperature range D2 is exceeded.
  • the normal regeneration control and the slow regeneration control are selectively executed as the regeneration control. However, only the slow regeneration control may be executed.
  • the normal regeneration control is executed in a case where the sulfur concentration in the fuel is below a predetermined and the slow regeneration control is executed in a case where the sulfur concentration in the fuel is at or above the predetermined value.
  • the invention is not limited thereto.
  • the normal regeneration control may be executed in a case where the estimated amount of sulfur compound deposition to the exhaust gas control apparatus E is below a predetermined value and the slow regeneration control may be executed in a case where the estimated amount of sulfur compound deposition to the exhaust gas control apparatus E is at or above the predetermined.
  • the normal regeneration control may be executed only in a case where the sulfur concentration in the fuel is below a predetermined value and the estimated sulfur compound deposition amount is below a predetermined and the slow regeneration control may be executed otherwise.

Abstract

A control system for an internal combustion engine includes an electronic control unit. The electronic control unit is configured to: (a) when a temperature of the exhaust gas control apparatus is within a second temperature range, supply a fuel to an exhaust gas control apparatus by using a fuel supply apparatus so that the temperature of the exhaust gas control apparatus is raised at a second target temperature rise rate; (b) when a temperature drop of the exhaust gas control apparatus is occurred within the second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a third target temperature rise rate until the temperature of the exhaust gas control apparatus, reaches a temperature of the exhaust gas control apparatus at occurrence of the temperature drop. The third target temperature rise rate is higher than the second target temperature rise rate.

Description

CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates to a control system for an internal combustion engine.
2. Description of Related Art
[0002] Techniques for regenerating an exhaust gas control apparatus by supplying a fuel to the exhaust gas control apparatus and combusting a deposited particulate matter are known. For example, Japanese Patent Application Publication No. 2013-029038 (JP 2013-029038 A) discloses a technique for controlling a temperature of an exhaust gas control apparatus within a temperature range where a sulfur compound can be released and turning of the sulfur compound into white smoke in the atmosphere can be suppressed. In addition, techniques relating to exhaust gas control apparatus regeneration are disclosed in Japanese Patent Application Publication No. 2010-229916 (JP 2010-229916 A), Japanese Patent Application Publication No. 2005-090274 (JP 2005-090274 A), Japanese Patent Application Publication No. 2005-106047 (JP 2005-106047 A), Japanese Patent Application Publication No. 2002-320863 (JP 2002-320863 A), Japanese Patent Application Publication No. 2010-163885 (JP 2010-163885 A), Japanese Patent Application Publication No. 2012-246842 (JP 2012-246842 A), Japanese Patent Application Publication No. 2013-142377 (JP 2013-142377 A), and Japanese Patent Application Publication No. 2005-076505 (JP 2005-076505 A).
SUMMARY OF THE INVENTION
[0003] In the technique disclosed in JP 2013-029038 A, prolongation of regeneration control may degrade fuel efficiency in a case where the temperature of the exhaust gas control apparatus drops, affected by an operation state of an internal combustion engine or the like, during the regeneration control for the exhaust gas control apparatus.
[0004] An object of the invention is to provide a control system for an internal combustion engine that suppresses white smoke generation and suppresses fuel efficiency degradation.
[0005] According to an aspect of the invention, there is provided a control system for an internal combustion engine and the internal combustion engine includes an exhaust gas control apparatus and a fuel supply apparatus. The exhaust gas control apparatus is disposed in an exhaust gas passage of the internal combustion engine. The fuel supply apparatus is configured to supply a fuel to the exhaust gas control apparatus. The control system includes an electronic control unit. The electronic control unit is configured to: (a) supply the fuel to the exhaust gas control apparatus by using the fuel supply apparatus so that a temperature of the exhaust gas control apparatus is raised and a particulate matter deposited in the exhaust gas control apparatus is burned; (b) when the temperature of the exhaust gas control apparatus is within a first temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a first target temperature rise rate; (c) when the temperature of the exhaust gas control apparatus is within a second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a second target temperature rise rate, the second temperature range being higher than the first temperature range, the second target temperature rise rate being lower than the first target temperature rise rate; (d) when the temperature of the exhaust gas control apparatus is within a third temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is maintained within the third temperature range, the third temperature range being higher than the second temperature range; (e) when a temperature drop of the exhaust gas control apparatus is occurred within the second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a third target temperature rise rate until the temperature of the exhaust gas control apparatus reaches a temperature of the exhaust gas control apparatus at occurrence of the temperature drop, the third target temperature rise rate being higher than the second target temperature rise rate; and (f) when the temperature of the exhaust gas control apparatus exceeds the temperature of the exhaust gas control apparatus at the occurrence of the temperature drop within the second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a forth target temperature rise rate, the forth target temperature rise rate being lower than the first target temperature rise rate.
[0006] In the control system according to the aspect described above, the electronic control unit may be configured to, when the temperature of the exhaust gas control apparatus is within the second temperature range, execute a feedback control for a supply amount of the fuel to the exhaust gas control apparatus based on a difference between a target temperature of the exhaust gas control apparatus and an actual temperature of the exhaust gas control apparatus. The target temperature of the exhaust gas control apparatus may be a temperature at which the second target temperature rise rate is satisfied.
[0007] In the control system according to the aspect described above, the electronic control unit may be configured to decrease the second target temperature rise rate as sulfur concentration in the fuel supplied to the internal combustion engine increases.
[0008] According to the control system relating to the aspect described above, white smoke generation can be suppressed and fuel efficiency degradation can be suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is an explanatory drawing of an engine system according to this embodiment;
FIG. 2A is a graph illustrating a change in control apparatus temperature during regeneration control;
FIG. 2B is a graph illustrating a concentration change in S03 in an exhaust gas during the regeneration control;
FIG. 3 is a flowchart illustrating an example of the regeneration control;
FIG. 4 is a flowchart illustrating an example of slow regeneration control;
FIG. 5 is a map defining a second target temperature rise rate corresponding to sulfur concentration in a fuel;
FIG. 6 is a graph illustrating an example of a change in control apparatus temperature that is controlled by feedback control;
FIG. 7A is a map defining a reference fuel addition amount corresponding to a target control apparatus temperature;
FIG. 7B is a map defining a correction amount for a fuel addition amount;
FIG. 7C is a map defining an upper limit value for the fuel addition amount for the feedback control; and
FIG. 8 is a graph illustrating an example of a change in control apparatus temperature in a case where the control apparatus temperature drops.
DETAILED DESCRIPTION OF EMBODIMENTS
[0010] FIG. 1 is an explanatory drawing of an engine system 10 according to an embodiment. A diesel engine (hereinafter, referred to as an engine) 11 is provided with an intake manifold 12 and an exhaust manifold 13. The intake manifold 12 is connected to an outlet of a compressor 16 of a turbocharger 15 via an intake passage 14. An intercooler IC that cools intake air is disposed in the intake passage 14, and a throttle valve V that adjusts an intake amount to the engine 11 is arranged in the intake passage 14. The exhaust manifold 13 is connected to an inlet of an exhaust turbine 18 of the turbocharger 15 via an exhaust gas passage 17. A variable nozzle vane 18a is disposed at the inlet of the exhaust turbine 18. A flow rate of an exhaust gas that passes through the exhaust turbine 18 can be adjusted to the degree of opening of the variable nozzle vane 18a. An outlet of the exhaust turbine 18 is connected to an exhaust gas passage 19. The exhaust gas from the engine 11 is discharged to the exhaust gas passage 19 through the exhaust turbine 18. The engine 11 is provided with four cylinders C and four fuel injection valves F that inject a fuel directly into the four respective cylinders C, but is not limited thereto. An exhaust gas recirculation (EGR) passage 14a is connected between the intake passage 14 and the exhaust gas passage 17. An EGR valve Va is disposed in the EGR passage 14a. A crank angle sensor CS that detects an engine speed is disposed in the engine 11.
[0011] An exhaust gas control apparatus E that purifies the exhaust gas is disposed in the exhaust gas passage 19. A diesel oxidation catalyst (DOC) 20 and a diesel particulate filter (DPF) 21 are disposed, in order from an upstream side to a downstream side, in the exhaust gas control apparatus E. The DOC 20 is an oxidation catalyst that oxidizes and converts HC, NO, and CO contained in the exhaust gas to H20, C02, and N02. The DPF 21 collects a particulate matter contained in the exhaust gas. The exhaust gas control apparatus E is an example of an exhaust gas control apparatus.
[0012] A fuel addition valve 24, a SOx sensor 25, and a temperature sensor 26 are disposed in the exhaust gas passage 19 between the exhaust turbine 18 and the DOC 20. The SOx sensor 25 detects sulfur concentration in the exhaust gas that flows to the DOC 20. The fuel addition valve 24 adds a fuel to the exhaust gas so as to combust the particulate matter deposited in the DPF 21. The temperature sensor 26 detects a temperature of the exhaust gas that flows into the DOC 20. [0013] A temperature sensor 27 is disposed in the exhaust gas passage 19 between the DOC 20 and the DPF 21. The temperature sensor 27 detects the temperature of the exhaust gas that flows into the DPF 21 through the DOC 20. A temperature sensor 28 and an air-fuel ratio sensor 29 are disposed, on a downstream side from the DPF 21, in the exhaust gas passage 19. The temperature sensor 28 detects the temperature of the exhaust gas that passes through the DPF 21. The air-fuel ratio sensor 29 detects an air-fuel ratio of the exhaust gas that passes through the DPF 21.
[0014] An electronic control unit (ECU) 30 performs overall control on the engine system 10. The ECU 30 is a computer and a read only memory (ROM, not illustrated), a random access memory (RAM, not illustrated), a central processing unit (CPU, not illustrated), and the like constitute this computer. The throttle valve V, the EGR valve Va, the above-described sensors, and the like are electrically connected to the ECU 30.
[0015] The ECU 30 estimates the sulfur concentration in the fuel based on output values from the SOx sensor 25 and the like, but is not limited thereto. A fuel property sensor may be disposed in a fuel tank so that the sulfur concentration in the fuel is directly detected. The sulfur concentration in the fuel that is used in a region where this engine system 10 is used may be stored in advance in the ECU 30.
[0016] The ECU 30 detects the temperature (hereinafter, referred to as a control apparatus temperature) of the exhaust gas control apparatus E based on values measured by the temperature sensors 26, 27, 28. Temperature sensors may be directly disposed in the DOC 20 and the DPF 21 so that temperatures thereof are detected. The temperature sensors 26, 27, 28 are examples of detection devices that detect the temperature of the exhaust gas control apparatus. The control apparatus temperature may also be estimated from an operation state of the engine 11.
[0017] The ECU 30 estimates the amount of the particulate matter that flows into the DPF 21 based on the operation state of the engine 11 and estimates the amount of the particulate matter deposited in the DPF 21 through integration. The particulate matter deposition amount in the DPF 21 may also be estimated by the ECU 30 based on a value measured by a sensor that is disposed on the DPF 21 side to detect the particulate matter.
[0018] The ECU 30 executes regeneration control to regenerate the DPF 21 by combusting the particulate matter deposited in the DPF 21. During the regeneration control, the ECU 30 controls the amount of the fuel that is supplied from the fuel addition valve 24 to the exhaust gas control apparatus E, raises the control apparatus temperature at a predetermined temperature rise rate, and combusts the particulate matter. The fuel addition valve 24 is an example of a fuel supply apparatus that supplies the fuel to the exhaust gas control apparatus E. A method for supplying the fuel to the exhaust gas control apparatus E and combusting the particulate matter is not limited thereto. For example, the particulate matter deposited in the DPF 21 may be combusted by performing post-injection after main injection by the fuel injection valve F to supply an unburnt fuel to the exhaust gas control apparatus E. In this case, the fuel injection valve F is an example of the fuel supply apparatus.
[0019] Regarding the regeneration control, the ECU 30 can selectively execute normal regeneration control and slow regeneration control. The normal regeneration control is control for combusting the particulate matter by raising the control apparatus temperature over a short period of time with priority given to suppression of fuel efficiency degradation. The slow regeneration control is control for combusting the particulate matter by slowly raising the control apparatus temperature with priority given to suppression of white smoke generation.
[0020] Next, the regeneration control will be described in detail. FIG. 2A is a graph illustrating a change in control apparatus temperature during the regeneration control. FIG. 2B is a graph illustrating a concentration change in S03 in the exhaust gas during the regeneration control. The dotted lines in FIGS. 2A and 2B represent the change in control apparatus temperature and the S03 concentration caused by the normal regeneration control and the solid lines in FIGS. 2A and 2B represent the change in control apparatus temperature and the S03 concentration caused by the slow regeneration control. The one-dot chain line in FIG. 2B represents the S03 concentration at which the exhaust gas begins to be visible as white smoke.
[0021] A case where the regeneration control is executed in a case where a certain amount of a sulfur compound is deposited in the DOC 20 and the DPF 21 and the sulfur concentration in the fuel is not low is assumed. Herein, the range of a temperature Tl to a temperature T2 that is illustrated in FIG. 2A is a temperature range where the amount of sulfur compound desorption from the DOC 20 and the DPF 21 is larger than in other temperature ranges. In other words, the temperature Tl is a temperature at which the sulfur compound desorption amount starts to increase. The particulate matter deposited in the DPF 21 is combusted at or above the temperature T2. A temperature below the temperature Tl will be referred to as a first temperature range Dl, a temperature that is equal to or above the temperature Tl and below the temperature T2 will be referred to as a second temperature range D2, and a temperature that is equal to or above the temperature T2 will be referred to as a third temperature range D3 (hereinafter, simply referred to as temperature ranges). For example, the temperature Tl is 450 degrees and the temperature T2 is 650 degrees, but the temperature Tl and the temperature T2 are not limited thereto.
[0022] During the normal regeneration control, the control apparatus temperature is raised in an early stage, at a substantially constant temperature rise rate, until the control apparatus temperature reaches the temperature T2 at which the particulate matter starts to be combusted. After the control apparatus temperature reaches the temperature T2, the control apparatus temperature within a predetermined period is maintained within the temperature range D3 and the particulate matter is combusted. Within the temperature range D3, the control apparatus temperature is maintained at a temperature within the temperature range D3 for a certain period of time. Then, the control apparatus temperature is further raised to be maintained at a certain temperature. Then, the control apparatus temperature is raised to be maintained at a certain temperature. The particulate matter is combusted by raising the control apparatus temperature phase by phase as described above. The temperature range D2 is a temperature range where the amount of sulfur compound desorption from the DOC 20 and the DPF 21 increases. Accordingly, the white smoke is generated in a case where the control apparatus temperature is within the temperature range D2 and the temperature rise rate is high. It is considered that the white smoke is generated because the amount of the sulfur compound (SOx) desorbed from the DOC 20 and the DPF 21 increases and the S03 in the exhaust gas is bound to H20 to become H2S04 mist and discharged as the white smoke when the control apparatus temperature becomes equal to or higher than a predetermined value. If the temperature rise rate of the control apparatus temperature is high in a case where the control apparatus temperature is within the temperature range D2 as in the normal regeneration control, the sulfur compound desorption amount per short time period increases and the S03 concentration in the exhaust gas increases, and thus the exhaust gas is visible as the white smoke.
[0023] During the slow regeneration control, the control apparatus temperature is raised at a temperature rise rate that is lower than the temperature rise rate for the normal regeneration control in a case where the control apparatus temperature is within the temperature range D2. In this manner, the sulfur compound desorption amount per unit time can be suppressed to below a certain level, the S03 concentration in the exhaust gas can be suppressed, and the exhaust gas being visible as the white smoke can be suppressed. Specifically, the control apparatus temperature is raised at a first temperature rise rate during the slow regeneration control in a case where the control apparatus temperature is within the temperature range Dl. In this manner, the control apparatus temperature is allowed to reach the temperature Tl in an early stage and fuel efficiency degradation is suppressed. In a case where the control apparatus temperature is within the temperature range D2, the control apparatus temperature is raised at a second temperature rise rate that is lower than the first temperature rise rate. In this manner, S03 concentration in the exhaust gas can be suppressed and white smoke generation can be suppressed. In a case where the control apparatus temperature is within the temperature range D3, the control apparatus temperature is maintained within the temperature range D3 for a predetermined period. In this manner, the particulate matter deposited in the DPF 21 is combusted. The second temperature rise rate is, for example, 0.7°C/sec but is not limited thereto. During the normal regeneration control, the control apparatus temperature is raised at the first temperature rise rate described above in a case where the control apparatus temperature is within the temperature range Dl or the temperature range D2.
[0024] FIG. 3 is a flowchart illustrating an example of the regeneration control. The regeneration control is initiated in a case, for example, where the ECU 30 determines that the amount of particulate matter deposition to the DPF 21 exceeds a predetermined value. For example, the ECU 30 estimates the amount of particulate matter deposition to the DPF 21 based on a traveling distance or the like. After the initiation of the regeneration control, the ECU 30 determines whether or not the sulfur concentration in the fuel is equal to or above a predetermined value (Step SI). The predetermined value means a reference value for determining whether or not the white smoke is generated by the execution of the normal regeneration control. In the case of a negative determination in Step SI, the ECU 30 executes the normal regeneration control (Step S2). This is because it is considered that the amount of sulfur compound deposition to the DOC 20 and the DPF 21 is small in a case where the sulfur concentration in the fuel is low, below the predetermined value for example, and the white smoke is unlikely to be generated despite the execution of the normal regeneration control. This regeneration control is terminated when the normal regeneration control is terminated.
[0025] In the case of a positive determination in Step SI, the ECU 30 executes the slow regeneration control (Step S3). This is because the white smoke may be generated when the normal regeneration control is executed in a case where the sulfur concentration in the fuel is at or above a predetermined value. This regeneration control is terminated when the slow regeneration control is terminated.
[0026] FIG. 4 is a flowchart illustrating an example of slow regeneration control. The ECU 30 determines whether or not the control apparatus temperature is within the temperature range Dl (Step Sll). In the case of a positive determination, the ECU 30 controls a fuel addition amount of the fuel addition valve 24 and raises the control apparatus temperature at the first temperature rise rate (Step S12). Specifically, the ECU 30 sets a first target temperature rise rate for the control apparatus temperature to be raised at the first temperature rise rate and controls the fuel addition amount of the fuel addition valve 24 to correspond to the first target temperature rise rate.
[0027] In the case of a negative determination in Step Sll, that is, in a case where the control apparatus temperature is not within the temperature range Dl but within the temperature range D2, the ECU 30 raises the control apparatus temperature at the second temperature rise rate (Step S13). Herein, the ECU 30 sets a second target temperature rise rate to correspond to the sulfur concentration in the fuel. The second target temperature rise rate is a target value for raising the control apparatus temperature at the second temperature rise rate. FIG. 5 is a map defining the second target temperature rise rate corresponding to the sulfur concentration in the fuel. This map is stored in advance in the ECU 30. This map is defined for the second target temperature rise rate to become lower as the sulfur concentration in the fuel increases. This is because the amount of sulfur compound deposition to the DOC 20 and the DPF 21 increases and the desorption amount increases as a result as the sulfur concentration in the fuel increases and white smoke generation can be suppressed by setting the second target temperature rise rate to be low. Accordingly, the second temperature rise rate becomes low as the sulfur concentration in the fuel increases.
[0028] The ECU 30 feedback-controls the fuel addition amount of the fuel addition valve 24 based on the actual control apparatus temperature so that the control apparatus temperature is raised at the second temperature rise rate. FIG. 6 is a graph illustrating an example of a change in control apparatus temperature that is controlled by the feedback control. The dotted line in FIG. 6 represents a target control apparatus temperature corresponding to the second target temperature rise rate. The target control apparatus temperature rises with time. By feedback-controlling the fuel addition amount, the control apparatus temperature can be accurately raised at the second temperature rise rate.
[0029] Specifically, the ECU 30 calculates a reference fuel addition amount based on the target control apparatus temperature that corresponds to the second target temperature rise rate which is set based on the sulfur concentration in the fuel. FIG. 7A is a map defining the reference fuel addition amount corresponding to the target control apparatus temperature. This map differs by intake air amount and is stored in advance in the ECU 30. The reference fuel addition amount is a fuel addition amount that is calculated in advance in an experiment for the control apparatus temperature to be raised at the second target temperature rise rate in a normal operation state other than transient operation conditions. The ECU 30 adds a correction amount to the reference fuel addition amount and feedback-controls the fuel addition amount.
[0030] FIG. 7B is a map defining the correction amount for the fuel addition amount. The correction amount is set based on a temperature difference that is obtained by subtracting the actual control apparatus temperature from the target control apparatus temperature. In a case where the temperature difference is a positive value, that is, in a case where the actual control apparatus temperature is lower than the target control apparatus temperature, the correction amount is a positive value, the correction amount is added to the reference fuel addition amount, and the fuel addition amount increases. In this case, the correction amount is set to increase as the temperature difference increases and the fuel addition amount increases as the temperature difference increases. In a case where the temperature difference is a negative value, that is, in a case where the actual control apparatus temperature is higher than the target control apparatus temperature, the correction amount is a negative value, the correction amount that is the negative value is added to the reference fuel addition amount, and the fuel addition amount decreases. In this case, the absolute value of the correction amount that is the negative value is set to increase as the temperature difference increases and the fuel addition amount decreases as the temperature difference increases. The control apparatus temperature is controlled to be raised at the second temperature rise rate by using the fuel addition amount that is set as described above. Calculation of the fuel addition amount that is controlled by the feedback control is not limited to the maps described above. For example, the calculation may also be based on a formula or the like.
[0031] An upper limit value is defined for the fuel addition amount that is controlled by the feedback control. FIG. 7C is a map defining the upper limit value for the fuel addition amount for the feedback control. The upper limit value for the fuel addition amount is set to increase as the actual control apparatus temperature increases. In a case where the fuel addition amount that is set based on the maps in FIGS. 7A and 7B exceeds the upper limit value in FIG. 7C, the upper limit value in FIG. 7C is preferentially applied in performing actual fuel addition. The upper limit value for the fuel addition amount may be lower than a fuel addition amount corresponding to the first temperature rise rate. The maps that are illustrated in FIGS. 7 A to 7C are recorded in advance in the ECU 30 through calculation in an experiment or the like.
[0032] Next, the ECU 30 determines whether or not temperature drop of the control apparatus temperature drops (Step S14). In the case of a negative determination, the ECU 30 records and updates the current control apparatus temperature in a case where the control apparatus temperature is within the temperature range D2 as a maximum temperature (Step S15). Then, the ECU 30 determines whether or not the control apparatus temperature is within the temperature range D2 (Step S16). In the case of a positive determination, the ECU 30 executes the processing of Step S13 and the subsequent processing again, continues raising the control apparatus temperature at the second temperature rise rate, and records and updates the maximum temperature of the control apparatus temperature.
[0033] In the case of a positive determination in Step S14, that is, in a case where the control apparatus temperature drops, the ECU 30 raises the control apparatus temperature at the first temperature rise rate (Step S17). Then, the ECU 30 determines whether or not the actual control apparatus temperature exceeds the maximum temperature that is recorded or updated in Step S15 (Step S18). In the case of a negative determination, the ECU 30 continues with the processing of Step S17 again. In other words, the ECU 30 raises the control apparatus temperature at the third temperature rise rate until the control apparatus temperature reaches the maximum temperature. In the case of a positive determination in Step S18, the ECU 30 executes the processing of Step S13 and the subsequent processing again. In other words, the control apparatus temperature is raised at the second temperature rise rate in a case where the control apparatus temperature exceeds the maximum temperature.
[0034] FIG. 8 is a graph illustrating an example of a change in control apparatus temperature in a case where the control apparatus temperature drops. In a case where the control apparatus temperature drops to a temperature within the temperature range D2 for any reason, the ECU 30 raises the control apparatus temperature at the first temperature rise rate until the control apparatus temperature reaches the maximum temperature again with the control apparatus temperature at the initiation of the drop recorded and updated as the maximum temperature in the ECU 30. This is because it is considered that the sulfur compound desorbed at or below the maximum temperature is already desorbed and the white smoke is not visible, even if the control apparatus temperature is raised at the first temperature rise rate, at or below the maximum temperature. By raising the control apparatus temperature to the maximum temperature in an early stage, prolongation of the regeneration control can be suppressed and fuel efficiency degradation can be suppressed. In a case where the control apparatus temperature exceeds the maximum temperature, the ECU 30 calculates a new target temperature based on the second target temperature rise rate by using the maximum temperature as a reference. The maximum temperature that is recorded and updated in the ECU 30 is reset whenever the slow regeneration control is terminated.
[0035] In the case of a negative determination in Step S16, that is, in a case where the control apparatus temperature is not within the temperature range D2, the ECU 30 maintains the control apparatus temperature within the temperature range D3 for a predetermined period (Step S19). The predetermined period means a period that is required for combusting the particulate matter deposited in the DPF 21. After the control apparatus temperature is maintained within the temperature range D3 for the predetermined period, the ECU 30 terminates the slow regeneration control and terminates the regeneration control.
[0036] As described above, the temperature rise rate of the control apparatus temperature is controlled during the slow regeneration control so that white smoke generation can be suppressed. In addition, the rise in control apparatus temperature can be accurately controlled at the second temperature rise rate by feedback-controlling the fuel addition amount based on the actual control apparatus temperature. In a case where the control apparatus temperature drops to a temperature within the temperature range D2, the control apparatus temperature is raised, at the first temperature rise rate, in an early stage until the control apparatus temperature exceeds the temperature at the initiation of the drop so that fuel efficiency degradation can be suppressed. Since the second target temperature rise rate is set based on the sulfur concentration in the fuel, prolongation of the slow regeneration control can be suppressed in a case where the sulfur concentration is low and the amount of sulfur deposition to the DOC 20 and the DPF 21 is small. Accordingly, fuel efficiency degradation can be suppressed.
[0037] A third temperature rise rate at which the control apparatus temperature is raised until the control apparatus temperature exceeds the maximum temperature after the control apparatus temperature drops to a temperature within the temperature range D2 is not limited to the first temperature rise rate but may be higher than the second temperature rise rate. In addition, a forth temperature rise rate within the temperature range D2 after the control apparatus temperature drops to a temperature within the temperature range D2 and the control apparatus temperature exceeds the maximum temperature is not limited to the second temperature rise rate but may be a temperature rise rate that is lower than the first temperature rise rate.
[0038] A case where the actual temperature rise rate is lower than the second target temperature rise rate may occur even when the control apparatus temperature is within the temperature range D2 and the fuel addition amount is set to the upper limit value, examples of which include vehicle deceleration and low-speed traveling. In this case, the ECU 30 may release a regulation of the upper limit value for the fuel addition amount and raise the control apparatus temperature at a fuel addition amount above the upper limit value. In this manner, prolongation of the regeneration control can be suppressed and fuel efficiency degradation can be suppressed. In a case where the control apparatus temperature reaches the target temperature corresponding to the second target temperature rise rate in this case, the fuel addition amount may be limited again to an amount below the upper limit value.
[0039] The actual temperature rise rate may increase to become higher than the second target temperature rise rate in a case where the control apparatus temperature is within the temperature range D2, examples of which include a case where vehicle idles after sudden acceleration and a case where a clutch is OFF. Accordingly, the ECU 30 may set the fuel addition amount to zero for a predetermined period, for seconds for example, after the idling or the clutch OFF is detected in a case where the control apparatus temperature is within the temperature range D2 during the slow regeneration control. In this manner, sudden control apparatus temperature rise and white smoke generation can be suppressed. The control apparatus temperature may be considered to drop when the fuel addition amount is set to zero, and thus the ECU 30 may raise the control apparatus temperature at a temperature rise rate that is higher than the second temperature rise rate, in a case where the idling is released or the clutch OFF is released, until the maximum temperature of the control apparatus temperature within the temperature range D2 is exceeded.
[0040] In the embodiment described above, the normal regeneration control and the slow regeneration control are selectively executed as the regeneration control. However, only the slow regeneration control may be executed. In the embodiment described above, the normal regeneration control is executed in a case where the sulfur concentration in the fuel is below a predetermined and the slow regeneration control is executed in a case where the sulfur concentration in the fuel is at or above the predetermined value. However, the invention is not limited thereto. For example, the normal regeneration control may be executed in a case where the estimated amount of sulfur compound deposition to the exhaust gas control apparatus E is below a predetermined value and the slow regeneration control may be executed in a case where the estimated amount of sulfur compound deposition to the exhaust gas control apparatus E is at or above the predetermined. In addition, the normal regeneration control may be executed only in a case where the sulfur concentration in the fuel is below a predetermined value and the estimated sulfur compound deposition amount is below a predetermined and the slow regeneration control may be executed otherwise.
[0041] The embodiment described above is just an example of the invention and the invention is not limited thereto. Various modifications to the embodiment are also within the scope of the invention. In addition, it is apparent that various embodiments are possible within the scope of the invention.

Claims

CLAIMS:
1. A control system for an internal combustion engine, the internal combustion engine including an exhaust gas control apparatus and a fuel supply apparatus, the exhaust gas control apparatus being disposed in an exhaust gas passage of the internal combustion engine and the fuel supply apparatus being configured to supply a fuel to the exhaust gas control apparatus, the control system comprising:
an electronic control unit configured to:
(a) supply the fuel to the exhaust gas control apparatus by using the fuel supply apparatus so that a temperature of the exhaust gas control apparatus is raised and a particulate matter deposited in the exhaust gas control apparatus is burned;
(b) when the temperature of the exhaust gas control apparatus is within a first temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a first target temperature rise rate;
(c) when the temperature of the exhaust gas control apparatus is within a second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a second target temperature rise rate, the second temperature range being higher than the first temperature range, the second target temperature rise rate being lower than the first target temperature rise rate;
(d) when the temperature of the exhaust gas control apparatus is within a third temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is maintained within the third temperature range, the third temperature range being higher than the second temperature range;
(e) when a temperature drop of the exhaust gas control apparatus is occurred within the second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a third target temperature rise rate until the temperature of the exhaust gas control apparatus reaches a temperature of the exhaust gas control apparatus at occurrence of the temperature drop, the third target temperature rise rate being higher than the second target temperature rise rate; and
(f) when the temperature of the exhaust gas control apparatus exceeds the temperature of the exhaust gas control apparatus at the occurrence of the temperature drop within the second temperature range, supply the fuel to the exhaust gas control apparatus so that the temperature of the exhaust gas control apparatus is raised at a forth target temperature rise rate, the forth target temperature rise rate being lower than the first target temperature rise rate.
2. The control system according to claim 1, wherein the electronic control unit is configured to, when the temperature of the exhaust gas control apparatus is within the second temperature range, execute a feedback control for a supply amount of the fuel to the exhaust gas control apparatus based on a difference between a target temperature of the exhaust gas control apparatus and an actual temperature of the exhaust gas control apparatus, the target temperature of the exhaust gas control apparatus is a temperature at which the second target temperature rise rate is satisfied.
3. The control system according to claim 1 or 2, wherein the electronic control unit is configured to decrease the second target temperature rise rate as sulfur concentration in the fuel supplied to the internal combustion engine increases.
PCT/IB2015/000254 2014-03-05 2015-03-02 Control system for internal combustion engine WO2015132646A1 (en)

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