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EP2059665B1 - Vorrichtung zur steuerung des kraftstoff-luft-verhältnisses und verfahren zur steuerung des kraftstoff-luft-verhältnisses in einem verbrennungsmotor - Google Patents

Vorrichtung zur steuerung des kraftstoff-luft-verhältnisses und verfahren zur steuerung des kraftstoff-luft-verhältnisses in einem verbrennungsmotor Download PDF

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Publication number
EP2059665B1
EP2059665B1 EP07825062A EP07825062A EP2059665B1 EP 2059665 B1 EP2059665 B1 EP 2059665B1 EP 07825062 A EP07825062 A EP 07825062A EP 07825062 A EP07825062 A EP 07825062A EP 2059665 B1 EP2059665 B1 EP 2059665B1
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EP
European Patent Office
Prior art keywords
fuel ratio
air
catalyst
fuel
combustion engine
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
EP07825062A
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English (en)
French (fr)
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EP2059665A2 (de
Inventor
Takahiko Fujiwara
Norihisa Nakagawa
Naoto Kato
Shuntaro Okazaki
Koji Ide
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Toyota Motor Corp
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Toyota Motor Corp
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Publication of EP2059665A2 publication Critical patent/EP2059665A2/de
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Publication of EP2059665B1 publication Critical patent/EP2059665B1/de
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Classifications

    • 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
    • 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
    • F02D41/0295—Control according to the amount of oxygen that is stored on 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
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/16—Oxygen
    • 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
    • F02D2200/0814—Oxygen storage amount

Definitions

  • the invention relates to an air-fuel ratio control apparatus.
  • JP-A-5-321721 describes an example of an air-fuel ratio control apparatus that includes a linear air-fuel ratio sensor disposed upstream of a catalyst, and an oxygen sensor disposed downstream of the catalyst.
  • the air-fuel ratio control apparatus controls an air-fuel ratio based on signals output from the two sensors.
  • the linear air-fuel ratio sensor has a linear output characteristic in which an output linearly changes in proportion to the air-fuel ratio.
  • the oxygen sensor outputs a signal according to the concentration of oxygen in gas.
  • the oxygen sensor has an output characteristic in which the output signal from the oxygen sensor is inverted when the air-fuel ratio changes from a value leaner than a stoichiometric ratio to a value richer than the stoichiometric ratio, or from a value richer than the stoichiometric ratio to a value leaner than the stoichiometric ratio.
  • the air-fuel ratio control apparatus feedback control on a fuel injection amount is executed so that the air-fuel ratio of exhaust gas flowing into the catalyst is equal to the stoichiometric air-fuel ratio, based on the output signal from the linear air-fuel ratio sensor.
  • this feedback control In addition to the feedback control based on the output signal from the linear air-fuel ratio sensor (hereinafter, this feedback control will be referred to as “main feedback control”), another feedback control is executed to correct the fuel injection amount based on the output signal from the oxygen sensor (hereinafter, the feedback control will be referred to as “sub feedback control”).
  • the feedback control In the sub feedback control, a correction value is calculated based on a difference between the output signal from the oxygen sensor and a reference signal corresponding to the stoichiometric air-fuel ratio, and the output signal from the linear air-fuel ratio sensor is corrected using the correction value.
  • the correction value indicates whether the air-fuel ratio of the exhaust gas flowing into the catalyst is leaner or richer than the stoichiometric air-fuel ratio.
  • the catalyst When the air-fuel ratio of the ambient atmosphere around the catalyst is near the stoichiometric air-fuel ratio, the catalyst purifies exhaust gas most efficiently.
  • the catalyst has oxygen storage capacity (OSC) for storing oxygen therein.
  • OSC oxygen storage capacity
  • the air-fuel ratio of the exhaust gas flowing into the catalyst is leaner than stoichiometric air-fuel ratio, the oxygen in the gaseous phase is taken and stored in the catalyst.
  • the air-fuel ratio of the exhaust gas flowing into the catalyst is richer than stoichiometric air-fuel ratio, the oxygen, which has been stored in the catalyst, is released from the catalyst into the gaseous phase.
  • the catatyst maintains the air-fuel ratio of the ambient atmosphere at a value near the stoichiometric air-fuel ratio, by storing or releasing the oxygen according to the air-fuel ratio of the exhaust gas flowing into the catalyst.
  • the level of the oxygen storage capacity of the catalyst greatly influences the efficiency of purifying the exhaust gas. That is, even if the air-fuel ratio of the exhaust gas greatly deviates from the stoichiometric air-fuel ratio, or even if the air-fuel ratio oscillates with a large amplitude, the oxygen may be stored in, or released from the catalyst, and the catalyst may maintain the air-fuel ratio of the ambient atmosphere at a value near the stoichiometric air-fuel ratio to purify the exhaust gas if the level of the oxygen storage capacity of the catalyst is high. It is known that the level of the oxygen storage capacity of the catalyst is maintained at a high level when noble metal of the catalyst is activated by repeating the storage and release of oxygen in the catalyst. By executing the above-described feedback control on the fuel injection amount, the air-fuel ratio of the exhaust gas oscillates around the stoichiometric air-fuel ratio, and thus, the storage and release of oxygen may be repeated in the catalyst.
  • the air-fuel ratio of the exhaust gas flowing into the catalyst influences the decrease in the level of the oxygen storage capacity of the catalyst. More specifically, even when the air-fuel ratio of the exhaust gas oscillates around the stoichiometric air-fuel ratio, the level of the oxygen storage capacity of the catalyst may be decreased if the amplitude of the oscillation of the air-fuel ratio is small.
  • FIG. 1 is a graph showing the relation between the air-fuel ratio of the exhaust gas flowing into the catalyst, and the amount of oxygen that may be stored in the catalyst or the amount of oxygen that may be released from the catalyst.
  • the air-fuel ratio becomes richer, i.e., as the air-fuel ratio decreases from the stoichiometric air-fuel ratio, the amount of oxygen that may be stored in the catalyst increases.
  • the air-fuel ratio becomes leaner, i.e., as the air-fuel ratio increases from the stoichiometric air-fuel ratio, the amount of oxygen that may be released from the catalyst increases.
  • the amount of oxygen that may be stored in the catalyst and the amount of oxygen that may be released from the catalyst decreases. Therefore, if the amplitude of the oscillation of the air-fuel ratio around the stoichiometric air-fuel ratio remains small, only a small amount of oxygen is repeatedly stored in, and released from the catalyst. As a result, the level of the oxygen storage capacity of the catalyst remains low and the catalyst is stabilized.
  • the level of the oxygen storage capacity is temporarily decreased.
  • the level of the oxygen storage capacity of the catalyst is recovered.
  • the air-fuel ratio of the exhaust gas is maintained at a value near the stoichiometric air-fuel ratio.
  • emissions may be discharged from the catalyst due to the decrease in the level of the oxygen storage capacity of the catalyst when the air-fuel ratio fluctuates to some extent.
  • Document JP 09222010 A discloses an air-fuel ratio control apparatus for an internal combustion engine that includes a catalyst.
  • the air-fuel ratio is controlled according to this document by an air-fuel ratio control means, so that an air-fuel ratio of exhaust gas is oscillated alternately to the rich sidle and the lean side before the first catalyst is activated.
  • the magnetite of the amplitude of an exhaust air-fuel ratio oscillated alternately to the rich side and the lean side is set by a set means according to the oxygen storage capacity of the catalyst.
  • the reverse frequency of the upper and lower sensor outputs is lager than a reference value, it is decided that the amplitude air-fuel ratio exceeds the oxygen storage capacity of the catalyst and thus, the amplitude is reduced.
  • the amplitude of a lower stream side sensor may serve as a value of a limit of the oxygen storage capacity of the catalyst.
  • an air-fuel ratio control apparatus for an internal combustion engine includes a catalyst, disposed in an exhaust passage, which has oxygen storage capacity.
  • the air-fuel ratio control apparatus includes: fuel injection amount control means for controlling an amount of fuel injected to the internal combustion engine so that an air-fuel ratio of exhaust gas flowing into the catalyst oscillates around a stoichiometric air-fuel ratio; oxygen storage capacity estimation means for estimating a level of the oxygen storage capacity of the catalyst; and amplitude reduction means for reducing an amplitude of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio when it is estimated that the level of the oxygen storage capacity of the catalyst is lower than a predetermined reference capacity.
  • the air-fuel ratio control apparatus for the internal combustion engine may include an air-fuel ratio sensor that outputs a signal according to the air-fuel ratio of the exhaust gas flowing into the catalyst.
  • the oxygen storage capacity estimation means may estimate that the level of the oxygen storage capacity of the catalyst is lower than the predetermined reference capacity when the amplitude of the signal output from the air-fuel ratio sensor remains smaller than a predetermined value more than a prescribed period.
  • the fuel injection amount control means may control the amount of fuel injected to the internal combustion engine by executing a feedback control on the air-fuel ratio based on a difference between the signal output from the air-fuel ratio sensor and a reference value corresponding to the stoichiometric air-fuel ratio.
  • the amplitude reduction means may reduce the amplitude of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio on the feedback control by reducing a gain used to correct the amount of fuel injected to the internal combustion engine or by limiting a correction amount based on the difference between the signal output from the air-fuel ratio sensor and the reference value corresponding to the stoichiometric air-fuel ratio.
  • the fuel injection amount control means may control the amount of fuel injected to the internal combustion engine by executing a feedback control on the air-fuel ratio based on a difference between the signal output from the air-fuel ratio sensor and a reference value corresponding to the stoichiometric air-fuel ratio while the fuel injection amount control means corrects the amount of fuel injected to the internal combustion engine based on a difference between the output signal from the oxygen sensor and the reference value corresponding to the stoichiometric air-fuel ratio.
  • the amplitude reduction means may reduce the amplitude of the oscillation of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio by reducing a gain used to correct the amount of fuel injected to the internal combustion engine or by limiting a correction amount based on the difference between the signal output from the oxygen sensor and the reference value corresponding to the stoichiometric air-fuel ratio.
  • the air-fuel ratio control apparatus for the internal combustion engine may further include amplitude reduction stop means for stopping reducing the amplitude of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio when one of fuel supply cutoff control and fuel injection amount increase control is executed.
  • the air-fuel ratio control apparatus for the internal combustion engine may further include execution frequency increase means for increasing at least one of an execution frequency of the fuel supply cutoff control and an execution frequency of the fuel injection amount increase control when the amplitude of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio remains reduced more than a prescribed period.
  • the execution frequency increase means may increase at least one of an execution frequency of the fuel supply cutoff control and an execution frequency of the fuel injection amount increase control when an accumulated amount of air taken into the internal combustion engine exceeds a prescribed amount after the amplitude of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio is reduced.
  • FIG. 2 is a schematic diagram showing an internal combustion engine system that includes an air-fuel ratio control apparatus according to the embodiment of the invention.
  • an internal combustion engine 2 is connected to an exhaust passage 4.
  • At least the catalyst 6 on an upstream side has oxygen storage capacity.
  • “storage” used herein means retention of a substance (solid, liquid, gas molecules) in the form of at least one of adsorption, adhesion, absorption, trapping, occlusion, and others.
  • the catalyst 6 on the upstream side is disposed close to an exhaust manifold (not shown).
  • the catalyst 8 on a downstream side is disposed under the floor of a vehicle.
  • a linear air-fuel ratio sensor 12 is installed upstream of the catalyst 6.
  • An oxygen sensor 14 is installed downstream of the catalyst 6.
  • the linear air-fuel ratio sensor 12 has a linear output characteristic in which an output linearly changes in proportion to an air-fuel ratio.
  • the oxygen sensor 14 outputs a signal according to the concentration of oxygen in the exhaust gas.
  • the oxygen sensor 14 has an output characteristic in which the output signal from the oxygen sensor is inverted when the air-fuel ratio changes from a value leaner than the stoichiometric ratio to a value richer than the stoichiometric ratio, or from a value richer than the stoichiometric ratio to a value leaner than the stoichiometric ratio.
  • an ECU (Electronic Control Unit) 10 is provided in the internal combustion engine system.
  • the ECU 10 totally controls the operation of the entire internal combustion engine system.
  • the above-described linear air-fuel ratio sensor 12 and the oxygen sensor 14 are connected to the ECU 10.
  • the ECU 10 executes a feedback control on a fuel injection amount so that the air-fuel ratio of the exhaust gas flowing into the catalyst 6 is equal to the stoichiometric air-fuel ratio, based on the signals output from the linear air-fuel ratio sensor 12 and the oxygen sensor 14.
  • this feedback control will be referred to as "air-fuel ratio feedback control”.
  • the air-fuel ratio feedback control executed by the ECU 10 includes a main feedback control and a sub feedback control.
  • the fuel injection amount is corrected based on a difference between the output signal from the linear air-fuel ratio sensor 12 and the reference value corresponding to stoichiometric air-fuel ratio.
  • the sub feedback control the fuel injection amount is corrected based on a difference between the output signal from the oxygen sensor 14 and a reference value corresponding to the stoichiometric air-fuel ratio.
  • the air-fuel ratio feedback control using the linear air-fuel ratio sensor 12 and the oxygen sensor 14 is a known method. Therefore, the detailed description thereof will be omitted in this specification.
  • the air-fuel ratio feedback control By executing the air-fuel ratio feedback control, the air-fuel ratio of the exhaust gas is maintained at a value near the stoichiometric air-fuel ratio. However, the amount of oxygen that may be stored in the catalyst 6 and the amount of oxygen that may be released form the catalyst 6 are decreased, and thus, the level of the oxygen storage capacity of the catalyst 6 is decreased. As a result, when the air-fuel ratio fluctuates to some extent, emissions are discharged from the catalyst 6. Accordingly, the ECU 10 executes a control for forcibly reducing the amplitude of the oscillation of the air-fuel ratio (hereinafter, referred to as "amplitude reduction control") under a predetermined condition when the air-fuel ratio feedback control is being executed.
  • amplitude reduction control a control for forcibly reducing the amplitude of the oscillation of the air-fuel ratio
  • the amplitude reduction control forcibly reduces the amplitude of the oscillation of the air-fuel ratio, it is possible to avoid a situation where the air-fuel ratio is so rich that the amount of oxygen that needs to be released from the catalyst 6 exceeds the amount of oxygen that may be released from the catalyst 6, or the air-fuel ratio is so lean that the amount of oxygen that needs to be stored in the catalyst 6 exceeds the amount of oxygen that may be stored in the catalyst 6.
  • the amplitude reduction control is executed in the routine of the air-fuel ratio control shown in a flowchart in FIG. 3 .
  • the routine shown in FIG. 3 in the first step, i.e., in step S2, it is determined whether the air-fuel ratio feedback control is being executed.
  • step S4 it is determined whether the amplitude of the output signal from the oxygen sensor 14 is equal to or below a predetermined reference value.
  • the air-fuel ratio of the exhaust gas flowing into the catalyst 6 approaches the stoichiometric air-fuel ratio due to the air-fuel ratio feedback control, and the amplitude of the oscillation of the air-fuel ratio remains small, the amount of oxygen that may be released from the catalyst 6 and the amount of oxygen that may be stored in the catalyst 6 are decreased. This decreases the change in the concentration of oxygen in the exhaust gas that has passed through the catalyst 6, and accordingly decreases the amplitude of the output signal from the oxygen sensor 14 disposed downstream of the catalyst 6.
  • the level of the oxygen storage capacity of the catalyst 6 is estimated based on the amplitude of the output signal from the oxygen sensor 14. That is, by comparing the amplitude of the output signal from the oxygen sensor1 4 with the reference value, it is accurately determined whether the level of the oxygen storage capacity of the catalyst 6 is decreased.
  • step S4 When it is determined that the amplitude of the output signal from the oxygen sensor 14 is equal to or below the reference value in step S4, it is determined that the level of the oxygen storage capacity of the catalyst 6 is decreased. In this case, the amplitude reduction control is executed in step S6.
  • the determination processes in steps S2 and S4 are repeatedly executed until the condition in step S2 (i.e., the condition that the air-fuel ratio feedback control is being executed) is not satisfied, or the condition in step S4 (i.e., the condition that the amplitude of the output signal from the oxygen sensor 14 is equal to or below the reference value) is satisfied.
  • a gain used to correct the fuel injection amount based on the difference between the output signal from the linear air-fuel ratio sensor 12 and the reference value corresponding to the stoichiometric air-fuel ratio in the main feedback (hereinafter, this gain will be referred to as "main feedback correction gain") is reduced.
  • the main feedback correction gain is a fixed value.
  • the main feedback correction gain is multiplied by a correction coefficient that is smaller than 1.
  • step S8 it is determined whether the air-fuel ratio feedback control is still being executed.
  • the processes in steps S10, S12, and S14 are skipped, and a process in step S16 is executed.
  • step S16 the amplitude reduction control on the air-fuel ratio is stopped, and the main feedback correction gain, which is reduced in step S6, is returned to a normal value.
  • step S16 When the air-fuel ratio feedback control is still being executed, the process in step S16 is executed on the condition that fuel supply is cut off.
  • the exhaust gas that contains a large amount of oxygen i.e., the exhaust gas at a lean air-fuel ratio flows into the catalyst 6, and thus the level of the oxygen storage capacity of the catalyst 6 is recovered.
  • the oxygen may be stored in, and released from the catalyst 6 even when the air-fuel ratio fluctuates to some extent. Accordingly, in this case, the amplitude reduction control is stopped, and therefore the main feedback correction gain is returned to the normal value to use the oxygen storage capacity of the catalyst 6 to the fullest extent.
  • step S14 it is determined whether the fuel supply is cut off.
  • step S14 the fuel supply continues to be cut off during a prescribed period.
  • the prescribed period is a sufficient time period during which the level of the oxygen storage capacity of the catalyst 6 is recovered by the inflow of the exhaust gas at a lean air-fuel ratio.
  • step S10 When the air-fuel ratio feedback control is still being executed, a determination process in step S10 is executed before a determination process in step S14 is executed. In step S10, an elapsed time after the main feedback correction gain is reduced by the amplitude reduction control is measured. Then, it is determined whether a predetermined time has elapsed after the main feedback correction gain is reduced.
  • step S12 When the predetermined time has elapsed after the main feedback correction gain is reduced, a process in step S12 is executed.
  • step S12 the frequency of execution of a fuel supply cutoff control, and a period during which the fuel supply cutoff control is executed are increased by relaxing a condition for executing the fuel supply cutoff control, and tightening a condition for ending the fuel supply cutoff control (i.e., a condition for restarting the fuel supply).
  • step S14 i.e., the condition that the fuel supply is cut off
  • the air-fuel ratio feedback control is quickly returned to the normal air-fuel ratio feedback control to use the oxygen storage capacity of the catalyst 6 to the fullest extent.
  • the air-fuel ratio control is executed according to the above-described routine, along with the air-fuel ratio feedback control.
  • the air-fuel ratio control according to the above-described routine when the level of the oxygen storage capacity of the catalyst 6 is decreased, it is possible to forcibly reduce the amplitude of the oscillation of the air-fuel ratio that oscillates around the stoichiometric air-fuel ratio.
  • the air-fuel ratio is so rich that the amount of oxygen that needs to be released from the catalyst 6 exceeds the amount of oxygen that may be released from the catalyst 6, or the air-fuel ratio is so lean that the amount of oxygen that needs to be stored in the catalyst 6 exceeds the amount of oxygen that may be stored in the catalyst 6. Accordingly, the discharge of emissions from the catalyst 6 is suppressed when the air-fuel ratio feedback control is executed.
  • the fuel injection amount control means according to the invention is implemented.
  • the oxygen storage capacity estimation means according to the invention is implemented.
  • the ECU 10 executes the process in step S6 "the amplitude reduction means” according to the invention is implemented.
  • a gain used to correct the fuel injection amount based on the difference between the output signal from the oxygen sensor 14 and the reference value corresponding to the stoichiometric air-fuel ratio in the sub feedback control (hereinafter, this gain will be referred to as "sub feedback correction gain”) may be reduced.
  • the amplitude reduction means according to the invention may be implemented.
  • both of the main feedback correction gain and the sub feedback correction gain may be reduced.
  • a limit may be imposed on a correction amount by which the fuel injection amount is corrected based on the difference between the output signal from the linear air-fuel ratio sensor 12 and the reference value corresponding to the stoichiometric air-fuel ratio in the main feedback control.
  • a limit may be imposed on a correction amount by which the fuel injection amount is corrected based on the difference between the output signal from the oxygen sensor 14 and the reference value corresponding to the stoichiometric air-fuel ratio in the sub feedback control.
  • the amplitude reduction control may be stopped on the condition that the fuel supply is cut off, or the fuel injection amount is increased during acceleration or the like. That is, when the predetermined time has elapsed after the amplitude reduction control on the air-fuel ratio is started, at least one of the frequency of execution of the fuel supply cutoff control and the frequency of execution of the fuel injection amount increase control may be increased.
  • the execution frequency increase means may be implemented.
  • the level of the oxygen storage capacity of the catalyst 6 may be estimated based on the output signal from the linear air-fuel ratio sensor 12.
  • the output signal from the linear air-fuel ratio sensor 12 indicates the air-fuel ratio of the exhaust gas flowing into the catalyst 6. Accordingly, when the amplitude of the output signal from the linear air-fuel ratio sensor 12 remains small, only a small amount of oxygen is repeatedly stored in, and released from the catalyst 6. Therefore, it is estimated that the level of the oxygen storage capacity of the catalyst 6 is decreased.
  • the oxygen storage capacity estimation means may be implemented.
  • the sensor disposed upstream of the catalyst 6 is not limited to the linear air-fuel ratio sensor. Any air-fuel ratio sensor that outputs a signal according to the air-fuel ratio of the exhaust gas flowing into the catalyst may be employed.
  • the same oxygen sensor as that disposed downstream of the catalyst 6 in the embodiment may be disposed upstream of the catalyst 6 as an air-fuel ratio sensor.
  • the invention may be applied to an internal combustion engine system in which the air-fuel ratio sensor is provided upstream of the catalyst 6, but the oxygen sensor is not provided downstream of the catalyst 6, that is, an internal combustion engine system where the air-fuel ratio feedback control is executed by using only the main feedback control.
  • the level of the oxygen storage capacity of the catalyst 6 may be estimated based on the output signal from the air-fuel ratio sensor disposed upstream of the catalyst 6 as described above.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Claims (9)

  1. Luftkraftstoffverhältnissteuergerät für eine Brennkraftmaschine (2), die einen Katalysator (6), der in einem Abgasdurchgang angeordnet ist, aufweist, welcher eine Sauerstoffspeicherkapazität aufweist, gekennzeichnet durch:
    eine Kraftstoffeinspritzmengensteuereinrichtung zum Steuern einer Menge von Kraftstoff, die in die Brennkraftmaschine (2) eingespritzt ist, so dass ein Luftkraftstoffverhältnis des Abgases, das in den Katalysator (6) strömt, um ein stöchiometrisches Luftkraftstoffverhältnis herum oszilliert;
    eine Sauerstoffspeicherkapazitätschätzeinrichtung (10), die ein Niveau der Sauerstoffspeicherkapazität des Katalysators schätzt,
    eine Amplitudenverringerungseinrichtung zum Verringern einer Amplitude des Luftkraftstoffverhältnisses des Abgases, das um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, wenn bestimmt ist, dass das Niveau der Sauerstoffspeicherkapazität des Katalysators (6) niedriger als eine vorbestimmte Referenzkapazität ist,
    einen Luftkraftstoffverhältnissensor (12), der ein Signal gemäß dem Luftkraftstoffverhältnis des Abgases ausgibt, das in den Katalysator (6) strömt,
    wobei die Sauerstoffspeicherkapazitätschätzeinrichtung (10) schätzt, dass das Niveau der Sauerstoffspeicherkapazität des Katalysators (6) niedriger als die vorbestimmte Referenzkapazität ist, wenn die Amplitude des Signals, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, länger als eine vorgeschriebene Zeitdauer niedriger als ein vorbestimmter Wert bleibt.
  2. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch 1, ferner mit
    einem Sauerstoffsensor (14), der ein Signal gemäß einer Konzentration von Sauerstoff in dem Abgas ausgibt, das durch den Katalysator (6) getreten ist,
    wobei die Sauerstoffspeicherkapazitätschätzeinrichtung (10) schätzt, dass das Niveau der Sauerstoffspeicherkapazität niedriger als die vorbestimmte Referenzkapazität ist, wenn die Amplitude des Signals, das von dem Sauerstoffsensor (14) ausgegeben ist, niedriger als ein vorbestimmter Wert ist.
  3. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch oder 2, ferner mit
    einem Luftkraftstoffverhältnissensor (12), der ein Signal gemäß dem Luftkraftstoffverhältnis des Abgases ausgibt, das in den Katalysator (6) strömt, wobei
    die Kraftstoffeinspritzmengensteuereinrichtung (10) die Menge von Kraftstoff steuert, die in die Brennkraftmaschine (2) eingespritzt ist, durch ein Ausführen einer Regelung auf das Luftkraftstoffverhältnis basierend auf einer Differenz zwischen dem Signal, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, und einem Referenzwert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht, und
    wobei die Amplitudenverringerungseinrichtung (10) die Amplitude des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, an der Regelung durch ein Verringern einer Zunahme verringert, die verwendet ist, um die Menge von Kraftstoff zu korrigieren, die in die Brennkraftmaschine (2) eingespritzt ist, basierend auf der Differenz zwischen dem Signal, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, und dem Referenzwert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht.
  4. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch 1 oder 2, ferner mit
    einem Luftkraftstoffverhältnissensor (12), der ein Signal gemäß dem Luftkraftstoffverhältnis des Abgases ausgibt, das in den Katalysator (6) strömt,
    wobei die Kraftstoffeinspritzmengensteuereinrichtung (10) die Menge von Kraftstoff steuert, die in die Brennkraftmaschine (2) eingespritzt ist, durch ein Ausführen einer Regelung auf das Luftkraftstoffverhältnis basierend auf einer Differenz zwischen dem Signal, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, und einem Referenzwert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht, und
    wobei die Amplitudenverringerungseinrichtung (10) die Amplitude des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, an der Regelung durch ein Begrenzen eines Korrekturbetrags verringert, basierend auf der Differenz zwischen dem Signal, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, und dem Referenzwert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht.
  5. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch 1 oder 2, ferner mit
    einem Luftkraftstoffverhältnissensor (12), der ein Signal gemäß dem Luftkraftstoffverhältnis des Abgases ausgibt, das in den Katalysator (6) strömt; und
    einem Sauerstoffsensor (14), der ein Signal gemäß einer Konzentration von Sauerstoff in dem Abgas ausgibt, das durch den Katalysator (6) getreten ist,
    wobei die Kraftstoffeinspritzmengensteuereinrichtung (10) die Menge von Kraftstoff, die in die Brennkraftmaschine (2) eingespritzt ist, durch ein Ausführen einer Regelung auf das Luftkraftstoffverhältnis steuert, basierend auf einer Differenz zwischen dem Signal, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, und einem Referenzwert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht, während die Kraftstoffeinspritzmengensteuereinrichtung (10) die Menge von Kraftstoff, die in die Brennkraftmaschine (2) eingespritzt ist, basierend auf einer Differenz zwischen dem Ausgabesignal von dem Sauerstoffsensor (12) und dem Referenzwert steuert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht, und
    wobei die Amplitudenverringerungseinrichtung (10) die Amplitude der Oszillation des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, durch ein Verringern einer Zunahme verringert, die verwendet ist, um die Menge von Kraftstoff, die in die Brennkraftmaschine (2) eingespritzt ist, basierend auf der Differenz zwischen dem Signal, das von dem Sauerstoffsensor (12) ausgegeben ist, und dem Referenzwert zu korrigieren, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht.
  6. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch 1 oder 2, ferner mit:
    einem Luftkraftstoffverhältnissensor (12), der ein Signal gemäß dem Luftkraftstoffverhältnis des Abgases ausgibt, das in den Katalysator (6) strömt; und
    einem Sauerstoffsensor (12), der ein Signal gemäß einer Konzentration von Sauerstoff in dem Abgas ausgibt, das durch den Katalysator (6) getreten ist,
    wobei die Kraftstoffeinspritzmengensteuereinrichtung (10) die Menge von Kraftstoff, die in die Brennkraftmaschine (2) eingespritzt ist, durch ein Ausführen einer Regelung auf das Luftkraftstoffverhältnis basierend auf einer Differenz zwischen dem Signal, das von dem Luftkraftstoffverhältnissensor (12) ausgegeben ist, und einem Referenzwert steuert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht, während die Kraftstoffeinspritzmengensteuereinrichtung (10) die Menge von Kraftstoff, die in die Brennkraftmaschine (2) eingespritzt ist, basierend auf einer Differenz zwischen dem Ausgabesignal von dem Sauerstoffsensor (12) und dem Referenzwert korrigiert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht, und
    wobei die Amplitudenverringerungseinrichtung (10) die Amplitude der Oszillation des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, durch ein Begrenzen eines Korrekturbetrags basierend auf der Differenz zwischen dem Signal, das von dem Sauerstoffsensor (12) ausgegeben ist, und dem Referenzwert verringert, der dem stöchiometrischen Luftkraftstoffverhältnis entspricht.
  7. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach einem der Ansprüche 1 bis 6, ferner mit
    einer Amplitudenverringerungsstoppeinrichtung (10) zum Stoppen eines Verringerns der Amplitude des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, wenn eine von der Kraftstoffzuführabschaltungssteuerung und einer Kraftstoffeinspritzmengenerhöhungssteuerung ausgeführt ist.
  8. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch 7, ferner mit
    einer Ausführungsfrequenzerhöhungseinrichtung (10) zum Erhöhen von wenigstens einer von einer Ausführungsfrequenz der Kraftstoffzuführungsabschaltungssteuerung und einer Ausführungsfrequenz der Kraftstoffeinspritzmengenerhöhungssteuerung, wenn die Amplitude des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, länger als eine vorgeschriebene Zeitdauer verringert bleibt.
  9. Luftkraftstoffverhältnissteuergerät für die Brennkraftmaschine (2) nach Anspruch 7, ferner mit
    einer Ausführungsfrequenzerhöhungseinrichtung (10) zum Erhöhen von wenigstens einer von einer Ausführungsfrequenz der Kraftstoffzuführungsabschaltungssteuerung und einer Ausführungsfrequenz der Kraftstoffeinspritzmengenerhöhungssteuerung, wenn eine akkumulierte Menge von Luft, die in die Brennkraftmaschine (2) aufgenommen ist, eine vorgeschriebene Menge übersteigt, nachdem die Amplitude des Luftkraftstoffverhältnisses des Abgases, die um das stöchiometrische Luftkraftstoffverhältnis herum oszilliert, verringert ist.
EP07825062A 2006-09-06 2007-09-05 Vorrichtung zur steuerung des kraftstoff-luft-verhältnisses und verfahren zur steuerung des kraftstoff-luft-verhältnisses in einem verbrennungsmotor Expired - Fee Related EP2059665B1 (de)

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PCT/IB2007/002558 WO2008029256A2 (en) 2006-09-06 2007-09-05 Air-fuel ratio control apparatus and air-fuel ratio control method for internal combustion engine

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