EP1333171A1 - Procédé et dispositif de détection de la concentration d'oxygène - Google Patents

Procédé et dispositif de détection de la concentration d'oxygène Download PDF

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Publication number
EP1333171A1
EP1333171A1 EP03001529A EP03001529A EP1333171A1 EP 1333171 A1 EP1333171 A1 EP 1333171A1 EP 03001529 A EP03001529 A EP 03001529A EP 03001529 A EP03001529 A EP 03001529A EP 1333171 A1 EP1333171 A1 EP 1333171A1
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EP
European Patent Office
Prior art keywords
oxygen concentration
engine
exhaust gas
fuel
exhaust system
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Application number
EP03001529A
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German (de)
English (en)
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EP1333171B1 (fr
Inventor
Hidenori Moriya
Tatsumasa Sugiyama
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Toyota Motor Corp
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Toyota Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2441—Methods of calibrating or learning characterised by the learning conditions
    • F02D41/2448—Prohibition of learning
    • 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
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/12—Introducing corrections for particular operating conditions for deceleration
    • F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
    • 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
    • F02D41/1455—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 with sensor resistivity varying with oxygen concentration
    • 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
    • F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
    • F02D41/1475—Regulating the air fuel ratio at a value other than stoichiometry
    • F02D41/1476—Biasing of the sensor
    • 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
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2438—Active learning methods
    • 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
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2474—Characteristics of sensors
    • 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
    • F02D41/0002—Controlling intake air
    • F02D2041/0022—Controlling intake air for diesel engines by throttle control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2250/00—Engine control related to specific problems or objectives
    • F02D2250/32—Air-fuel ratio control in a diesel engine
    • 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
    • F02D41/0002—Controlling intake air
    • 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
    • F02D41/1456—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 with sensor output signal being linear or quasi-linear with the concentration of oxygen
    • 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
    • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
    • 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
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2454—Learning of the air-fuel ratio control

Definitions

  • the invention relates to an oxygen concentration detecting device/method for detecting a concentration of oxygen contained in exhaust gas of a diesel engine or a gasoline lean-burn engine.
  • an internal combustion engine that is operated by using a mixture of a high air-fuel ratio (lean atmosphere) for combustion over an extensive operational range as in the case of a diesel engine
  • engines which are equipped with an occlusion-reduction type NOx catalyst, an exhaust gas recirculation (EGR) system, and the like in an attempt to improve exhaust emission properties or stabilize an engine combustion state.
  • the occlusion-reduction type NOx catalyst absorbs NOx when the concentration of oxygen contained in exhaust gas is high (in a lean state).
  • the EGR system recirculates part of exhaust gas to an intake system so as to adjust the amount of inactive gas contained in combustion gas.
  • an oxygen concentration sensor disposed in an exhaust system of the engine so as to successively monitor the concentration of oxygen contained in exhaust gas plays a crucially important role.
  • the oxygen concentration sensor outputs a detection signal corresponding to a concentration of oxygen contained in exhaust gas.
  • a diesel engine disclosed in Japanese Patent Laid-Open Application No. 10-212999 has a system for performing calibration relating to detection of a concentration of oxygen contained in exhaust gas by opening a throttle valve during the implementation of fuel cut, introducing air into an intake system, allowing the air to directly enter an exhaust system via combustion chambers without mixing it with fuel or using it for engine combustion, and storing a detection signal output from an oxygen concentration sensor disposed in the exhaust system as an output value corresponding to the concentration of oxygen contained in the atmosphere (reference gas). If the throttle valve is opened (under a condition that engine combustion not be carried out) during the implementation of fuel cut, gases are replaced in the exhaust system.
  • a detecting element of the oxygen concentration sensor can be directly exposed to intake air (the atmosphere), and the output value of the oxygen concentration sensor which corresponds to the concentration of oxygen contained in the atmosphere (reference gas) can be grasped accurately.
  • An oxygen concentration detecting device in accordance with a first aspect of the invention comprises an oxygen concentration sensor disposed in an exhaust system of an engine so as to output a signal corresponding to a concentration of oxygen contained in exhaust gas, a flow rate adjusting valve for adjusting a flow rate of air sucked into combustion chambers of the engine, fuel cut control means for performing a control of stopping fuel supply under a predetermined condition during operation of the engine, intake air increase control means for increasing a flow rate of the air sucked into the combustion chambers in synchronization with the stop of the fuel supply, integrated intake air amount recognition means for recognizing an integrated amount of the air sucked into the combustion chambers, intake air reduction control means for reducing a flow rate of the air sucked into the combustion chambers as soon as the recognized integrated amount exceeds a predetermined amount, and learning means for learning numerical information regarding a signal output from the oxygen concentration sensor during stop of fuel supply as numerical information corresponding to a reference oxygen concentration as soon as the signal from the oxygen concentration sensor converges to a predetermined value after reduction of
  • the exhaust recirculation amount adjusting means reduce or preferably bring to zero the amount of recirculated exhaust gas in synchronization with the stop of fuel supply or an increase in flow rate of the air sucked into the combustion chambers.
  • the oxygen concentration detecting device comprise an exhaust gas purification catalyst disposed in the exhaust system of the engine so as to purify noxious components contained in exhaust gas and first learning prohibition means for prohibiting the numerical information from being learned if the catalyst is at a temperature below a predetermined temperature when the control of stopping fuel supply is performed.
  • the oxygen concentration detecting device having the aforementioned construction comprise gradual change means for performing a processing of gradually changing an amount of fuel supply if fuel supply has been resumed while the flow rate of intake air increases in synchronization with the stop of fuel supply.
  • the oxygen concentration detecting device having the aforementioned construction comprise second learning prohibition means for prohibiting the numerical information from being learned if reducing components are supplied to the exhaust system when or immediately before the control of stopping fuel supply is started.
  • the oxygen concentration detecting device having the aforementioned construction comprise reducing component supply prohibition means for prohibiting reducing components from being supplied to the exhaust system for a period from the start of the control of stopping fuel supply to the end of the learning of the numerical information.
  • This construction prevents the reducing components from entering the exhaust system when filling the exhaust system with the atmosphere as the reference gas. Therefore, the precision and reliability in learning the numerical information as described above are further enhanced.
  • a second aspect of the invention provides a method of detecting a concentration of oxygen contained in exhaust gas of an engine on the basis of an output value of an oxygen concentration sensor that is disposed in an exhaust system of the engine so as to output a signal corresponding to a concentration of oxygen contained in exhaust gas.
  • This method comprises the steps of increasing an amount of air sucked into combustion chambers of the engine in response to the stop of fuel supply during operation of the engine, reducing the amount of air sucked into the combustion chambers of the engine as soon as an integrated value of the amount of air sucked into the combustion chambers of the engine exceeds a predetermined value during the stop of fuel supply, learning numerical information regarding an output of the oxygen concentration sensor as numerical information corresponding to a reference oxygen concentration as soon as the output converges to a predetermined value, and detecting a concentration of oxygen contained in exhaust gas of the engine on the basis of an output value of the oxygen concentration sensor after referring to a relationship between the learned numerical information and the reference oxygen concentration.
  • an internal combustion engine (hereinafter referred to as an engine) 1 is an in-line four-cylinder diesel engine system that is mainly composed of a fuel supply system 10, combustion chambers 20, an intake system 30, an exhaust system 40, and the like.
  • the fuel supply system 10 is composed of a supply pump 11, a common rail 12, fuel injection valves 13, a shut-off valve 14, a regulator valve 16, a fuel addition valve 17, an engine fuel passage P1, an additional fuel passage P2, and the like.
  • the supply pump 11 increases the pressure of fuel pumped up from a fuel tank (not shown) to a high pressure and supplies the fuel to the common rail 12 via the engine fuel passage P1.
  • the common rail 12 has a function as an accumulator for maintaining high-pressure fuel supplied from the supply pump 11 at a predetermined pressure (i.e., an accumulator for accumulating pressure), and distributes the fuel thus maintained at the predetermined pressure to the fuel injection valves 13.
  • Each of the fuel injection valves 13 is designed as an electromagnetic valve having an electromagnetic solenoid therein, and opens at a suitable timing so as to supply fuel into a corresponding one of the combustion chambers 20 through injection.
  • the supply pump 11 supplies part of the fuel pumped up from the fuel tank to the fuel addition valve 17 via the additional fuel passage P2.
  • the supply pump 11, the shut-off valve 14, the regulator valve 16, and the fuel addition valve 17 are arranged in the additional fuel passage P2 in this order.
  • the shut-off valve 14 shuts off the additional fuel passage P2 in case of emergency, and stops supplying fuel.
  • the regulator valve 16 controls a pressure (fuel pressure) PG of fuel supplied to the fuel addition valve 17.
  • the fuel addition valve 17 is designed as an electromagnetic valve having an electromagnetic solenoid (not shown) therein, and additionally supplies a suitable amount of fuel functioning as a reducing agent to the exhaust system 40 at a location upstream of an NOx catalyst casing 42 at a suitable timing.
  • the intake system 30 forms a passage (intake passage) of intake air supplied to the combustion chambers 20.
  • the exhaust system 40 forms a passage (exhaust passage) of exhaust gas discharged from the combustion chambers 20.
  • the engine 1 is provided with a known supercharger (turbocharger) 50.
  • the turbocharger 50 has rotating bodies 52, 53 that are coupled to each other via a shaft 51.
  • One of the rotating bodies (turbine wheel) 52 is exposed to exhaust gas in the exhaust system 40, and the other rotating body (compressor wheel) 53 is exposed to intake air in the intake system 30.
  • the turbocharger 50 thus constructed rotates the compressor wheel 53 with the aid of exhaust gas flow (exhaust pressure) received by the turbine wheel 52, thus increasing intake pressure.
  • the turbocharger 50 carries out so-called supercharging.
  • an intercooler 31 disposed downstream of the turbocharger 50 forcibly cools intake air that has been heated up by supercharging.
  • a throttle valve 32 disposed further downstream of the intercooler 31 is designed as an electronically controlled open-close valve whose opening can be continuously adjusted.
  • the throttle valve 32 has a function of changing the flow channel area of intake air under a predetermined condition and adjusting the amount of supply (flow rate) of the intake air.
  • An exhaust gas recirculation passage (EGR passage) 60 for communication between the intake system 30 and the exhaust system 40 is formed in the engine 1.
  • the EGR passage 60 has a function of returning part of exhaust gas to the intake system 30 at a suitable timing.
  • An EGR valve 61 and an EGR cooler 62 are disposed in the EGR passage 60.
  • the EGR valve 61 is continuously opened and closed through electronic control, and can freely adjust the flow rate of exhaust gas (EGR gas) flowing through the EGR passage 60.
  • the EGR cooler 62 cools exhaust gas flowing through (returned to) the EGR passage 60.
  • the NOx catalyst casing 42 in which an occlusion-reduction type NOx catalyst and a particulate filter are accommodated is disposed downstream of a portion of communication between the exhaust system 40 and the EGR passage 60.
  • An oxidizing catalyst casing 43 in which an oxidizing catalyst is accommodated is disposed downstream of the NOx catalyst casing of the exhaust system 40.
  • Various sensors are attached to various portions of the engine 1. Each of these sensors outputs a signal regarding an environmental condition of a corresponding one of the portions or an operational state of the engine 1.
  • a rail pressure sensor 70 outputs a detection signal corresponding to a pressure of fuel accumulated in the common rail 12.
  • a fuel pressure sensor 71 outputs a detection signal corresponding to a pressure (fuel pressure) PG of fuel introduced into the fuel addition valve 17 via the regulator valve 16.
  • An airflow meter 72 outputs a detection signal corresponding to a flow rate (amount) GA of intake air at a location upstream of the compressor wheel 53 in the intake system 30.
  • An oxygen concentration sensor 73 outputs a detection signal that continuously changes in accordance with a concentration of oxygen contained in exhaust gas at a location downstream of the NOx catalyst casing 42 (upstream of the oxidizing catalyst casing 43) in the exhaust system 40.
  • the detection signal output from the oxygen concentration sensor 73 is utilized as a parameter for calculating an air-fuel ratio A/F in a mixture that is used for engine combustion in the engine 1.
  • An exhaust gas temperature sensor 74 is attached to a predetermined portion in the NOx catalyst casing 42 in the exhaust system 40 (between a later-described honeycomb structural body 42a and a later-described particulate filter 42b), and outputs a detection signal corresponding to an exhaust gas temperature (temperature of gas flowing into the filter) at the predetermined portion.
  • An accelerator position sensor 76 is attached to an accelerator pedal (not shown), and outputs a detection signal corresponding to a depression stroke ACC of the accelerator pedal.
  • a crank angle sensor 77 outputs a detection signal (pulse) every time an output shaft of the engine 1 rotates by a certain angle.
  • These sensors 70 to 77 are electrically connected to an electronic control unit (ECU) 90.
  • ECU electronice control unit
  • the ECU 90 has a central processing unit (CPU) 91, a read-only memory (ROM) 92, a random access memory (RAM) 98, a back-up RAM 94, a timer counter 95, and the like.
  • the ECU 90 also has a logical operation circuit, which is constructed by interconnecting those components 91 to 95, an external input unit 96 including an A/D converter, and an external output circuit 97 by means of a bidirectional bus 98.
  • the ECU 90 thus constructed not only performs processings for detection signals from the aforementioned sensors, for example, a calculation processing or the like of calculating an air-fuel ratio A/F in a mixture used for engine combustion on the basis of a detection signal from the oxygen concentration sensor 73 but also performs various controls regarding the operational state of the engine 1 on the basis of detection signals or the like from the sensors, such as a control regarding open-close operation of the fuel injection valves 13, adjustment of the opening of the EGR valve 61, adjustment of the opening of the throttle valve 32, and the like.
  • the ECU 90 constructed as described above, the oxygen concentration sensor 73, the throttle valve 32, and the like constitute the oxygen concentration detecting device in accordance with the first embodiment.
  • the honeycomb structural body 42a and the particulate filter (hereinafter referred to simply as a filter) 42b are arranged in series inside the NOx catalyst casing 42.
  • the honeycomb structural body 42a and the filter 42b serve as exhaust gas purification catalysts and are spaced from each other by a predetermined distance.
  • the honeycomb structural body 42a is of straight flow type and is mainly made of alumina (Al 2 O 3 ).
  • the filter 42b is of wall flow type and is mainly made of a porous material.
  • Carrier layers made of alumina or the like are formed in a plurality of passages forming the honeycomb structural body 42a.
  • An alkaline metal such as potassium (K), sodium (Na), lithium (Li), or cesium (Cs), an alkaline earth such as barium (Ba) or calcium (Ca), a rare earth such as lanthanum (La) or yttrium (Y), and a noble metal such as platinum (Pt) are carried on the surfaces of the carrier layers.
  • the alkaline metal functions as an NOx occluding agent.
  • the noble metal functions as an oxidizing catalyst (noble metal catalyst).
  • the NOx occluding agent has properties of occluding NOx when the concentration of oxygen contained in exhaust gas is high and discharging NOx when the concentration of oxygen contained in exhaust gas is low (when the concentration of reducing components is high).
  • the noble metal catalyst promotes an oxidizing reaction of the HC and CO, whereby an oxidation-reduction reaction occurs with NOx being an oxidizing component and with HC and CO being reducing components. That is, HC and CO are oxidized into CO 2 and H 2 O, whereas NOx are reduced into N 2 .
  • the NOx occluding agent occludes a predetermined limit amount of NOx even when the concentration of oxygen contained in exhaust gas is high, it no longer occludes NOx.
  • reducing components are intermittently supplied to the exhaust passage at a location upstream of the NOx catalyst casing 42 through post injection or the addition of fuel, whereby the concentration of the reducing components contained in exhaust gas is increased. These reducing components periodically discharge and reductively purify the NOx occluded in the NOx catalyst before the amount of NOx occluded in the NOx catalyst (NOx occluding agent) reaches the limit amount. As a result, the NOx occluding capacity of the NOx occluding agent is restored.
  • the porous material of which the filter 42b is made is obtained by wash-coating a ceramic material such as rhodolite with a coating material such as alumina, titania, zirconia, or zeolite, and is pervious to exhaust gas.
  • the filter 42b is of so-called wall flow type in which exhaust gas inflow passages and exhaust gas outflow passages extend in parallel.
  • Each of the exhaust gas inflow passages has an open upstream end and a closed downstream end, and each of the exhaust gas outflow passages has a closed upstream end and an open downstream end.
  • Coat layers (carrier layers) made of alumina or the like are formed in pores that are formed on and inside partitions each located between the exhaust gas inflow and outflow passages.
  • the NOx occluding agent and the noble metal catalyst are carried on the surfaces of the coat layers.
  • the filter 42b thus constructed purifies particulates contained in exhaust gas such as soot and noxious components such as NOx according to a mechanism described below.
  • the NOx occluding agent cooperates with the noble metal catalyst so as to repeatedly occlude, discharge, and purify NOx in accordance with the concentration of oxygen contained in exhaust gas or the amount of reducing components.
  • the NOx occluding agent has a property of secondarily producing active oxygen while thus purifying NOx.
  • the active oxygen produced by the NOx occluding agent has extremely high reactivity (activity) as an oxidizing agent, those of the captured particulates which have been deposited on or close to the surface of the NOx catalyst swiftly react with the active oxygen (without generating luminous flames) and are purified.
  • Reactive heat generated from the honeycomb structural body (the NOx catalyst carried on the structural body) 42a disposed on the upstream side in the NOx catalyst casing 42 efficiently heats up the filter 42b disposed on the downstream side. As a result, the effect achieved by the filter 42b in decomposing particulates is enhanced.
  • the ECU 90 performs fuel injection control on the basis of an operational condition that is grasped from detection signals of the sensors. It is to be noted in the first embodiment that fuel injection control relates to the implementation of fuel injection into the combustion chambers 20 through the fuel injection valves 13 and that fuel injection control means a series of processings of setting parameters such as fuel injection amount Q, fuel injection timing, and fuel injection pattern and individually opening or closing the fuel injection valves 13 on the basis of the parameters thus set.
  • the ECU 90 repeatedly performs the series of processings as mentioned above at intervals of a predetermined period while the engine 1 is in operation.
  • the fuel injection amount Q and the fuel injection timing are basically determined by referring to a map (not shown) that is set in advance on the basis of a depression stroke ACC of the accelerator pedal and an engine speed NE (a parameter that can be calculated on the basis of a pulse signal from the crank angle sensor).
  • the ECU 90 not only ensures an engine output by injecting fuel into cylinders in the vicinity of a compression top dead center as main injection but also performs fuel injection preceding main injection (hereinafter referred to as pilot injection) and fuel injection following main injection (hereinafter referred to as post injection) as subsidiary injection during a selected period for a selected one of the cylinders.
  • pilot injection fuel injection preceding main injection
  • post injection fuel injection following main injection
  • the temperature in combustion chambers reaches a temperature for inducing self-ignition in the final stage of a compression stroke.
  • the operational condition of the engine corresponds to an intermediate-to-high load range
  • fuel that is used for combustion is supplied into the combustion chambers through injection at a time
  • the fuel explosively burns while making noise.
  • pilot injection fuel that has been supplied prior to main injection serves as a heat source (or pilot flames), and the heat source is gradually enlarged in the combustion chambers and causes combustion.
  • fuel in the combustion chambers relatively gently burns, and the ignition delay time is shortened.
  • the level of a noise made as a result of the operation of the engine is reduced.
  • the amount of NOx contained in exhaust gas is reduced as well.
  • Fuel supplied into the combustion chambers 20 through post injection is reformed into light HC in combustion gas and is discharged to the exhaust system 40. That is, the light HC functioning as a reducing agent are added to the exhaust system 40 through post injection, and thus increase the concentration of reducing components contained in exhaust gas.
  • the reducing components added to the exhaust system 40 react with NOx discharged from the NOx catalyst or with other oxidizing components contained in exhaust gas via the NOx catalyst in the NOx catalyst casing 42. The reactive heat generated at this moment raises the temperatures of exhaust gas and the NOx catalyst.
  • Post injection requires that fuel be directly supplied into the combustion chambers through injection and that the fuel be irrelevant to engine combustion. Hence, the amount of fuel that can be supplied at a time is limited.
  • SOx poisoning recovery control for heating up the NOx catalyst to such an extent that the SOx and the like can be thermally decomposed is performed at intervals of a predetermined period.
  • SOx poisoning recovery control requires that one or both of the aforementioned post injection and addition of fuel be continuously carried out over a relatively long period.
  • the ECU 90 performs fuel cut under a certain operational condition, for example, during deceleration of a vehicle.
  • Fuel cut is a kind of operational control.
  • the supply (fuel injection) of fuel to the combustion chambers 20 is temporarily suspended, for example, if the engine speed NE has exceeded a prescribed value that is preset in accordance with an operational state of the engine 1.
  • a load imposed on the engine 1 prevention of calefaction of the NOx catalyst and the oxidizing catalyst, an improvement in fuel consumption, or the like is achieved.
  • the engine 1 misfires and engine combustion is suspended.
  • Fig. 2 shows a cross-sectional structure of a main part of the detecting element of the oxygen concentration sensor 73 disposed in the exhaust system 40.
  • the detecting element of the oxygen concentration sensor 73 is formed by laminating porous insulating materials (sheet materials) 73a, 73b, 73c having oxygen-ion conductivity and heat resistance. These materials are, for example, zirconia (Zr 2 O 3 ).
  • An atmosphere introduction space S1 for communication with the atmosphere is formed inside a laminated body composed of the sheet materials 73a, 73b, 73c.
  • An electrode 73d is attached to one surface of the sheet material 73a, namely, on a sheet surface of the detecting element which faces an outer space (a space in the exhaust passage) S2.
  • An electrode 73e is attached to the other surface of the sheet material 73a, namely, on a sheet surface of the detecting element which faces the atmosphere introduction space S1 formed inside.
  • An electrothermal heater (not shown) is built into the sheet material 73c so as to maintain the temperature of the detecting element at a predetermined temperature. If a predetermined voltage is applied between the electrodes 73d, 73e, oxygen molecules in the vicinity of the electrodes 73d, 73e are ionized and penetrate the sheet material 73a along an arrow ⁇ . The current flowing between the electrodes 73d, 73e at this moment is quantitatively related to the difference in oxygen concentration between the spaces S1, S2.
  • the oxygen concentration in the space S1 is known as the oxygen concentration (e.g., 21%) in the atmosphere.
  • the oxygen concentration in the space S2 the concentration of oxygen contained in exhaust gas
  • Fig. 3 is a graph showing a relationship between current and impressed voltage between the electrodes 73d, 73e.
  • Fig. 4 is graph schematically showing a relationship in correspondence between limiting current and oxygen concentration in the space S2.
  • the limiting current increases in proportion to an increase in the oxygen concentration in the space S2 (the concentration of oxygen contained in exhaust gas).
  • the concentration of oxygen contained in exhaust gas can be estimated from a detection signal (limiting current) from the oxygen concentration sensor 73 on the basis of a line (characteristic curve) connecting the two coordinates.
  • the oxygen concentration detecting device in accordance with the first embodiment, modifications described below are adopted in setting an analytical curve for determining a relationship in correspondence between oxygen concentration in exhaust gas and limiting current.
  • the oxygen concentration detecting device is ensured of enhanced precision and reliability.
  • Fig. 5 is a graph showing in detail a relationship in correspondence between oxygen concentration in exhaust gas and limiting current, which are learned and stored by the ECU 90.
  • the ECU 90 learns and stores a line A-B at a suitable timing. It is to be noted herein that a current IA corresponds to a limiting current under a condition that the concentration of oxygen contained in exhaust gas be 0%, and that a current IB corresponds to a limiting current under a condition that the concentration of oxygen contained in exhaust gas be 21%. In monitoring the concentration of oxygen contained in exhaust gas, reference is made to the line A-B (characteristic curve) connecting the two coordinates A, B.
  • the limiting current is quite negligible (theoretically equal to "0" regardless of the difference among individual sensor elements, aging, or the like.
  • the concentration of oxygen contained in exhaust gas be 21% (in a state where the sensor element is exposed to the atmosphere)
  • the limiting current assumes a relatively large value, which fluctuates (is dispersed) depending on the difference among individual sensor elements, aging, or the like.
  • the ECU 90 measures a limiting current at a suitable timing in a state where the sensor element of the oxygen concentration sensor 73 is exposed to the atmosphere (under a condition equivalent thereto), and makes a correction (hereinafter referred to as atmospheric correction) from an old value (e.g., a current IB') to a new value (e.g., the current IB).
  • atmospheric correction a correction from an old value (e.g., a current IB') to a new value (e.g., the current IB).
  • the limiting current is theoretically equal to "0" under the condition that the concentration of oxygen contained in exhaust gas be 0%. In fact, however, a quite negligible limiting current is detected due to the existence of a circuit or the like which is interposed between the ECU 90 and the oxygen concentration sensor 73.
  • the ECU 90 detects a limiting current IA" under a condition that the sensor element itself of the oxygen concentration sensor 73 output no detection signal (e.g., under a condition that the oxygen concentration sensor 73 be in an inactive state (low-temperature state) immediately after the engine has been started), and recognizes a difference (hereinafter referred to as a circuit offset) OS between the limiting current IA" and a reference current IA ("0" ampere).
  • the circuit offset OS is always taken into account. As a result, the precision in detecting oxygen concentration is further enhanced.
  • Figs. 6A to 6E are time charts showing along a single time axis how various parameters regarding the operational state of the engine 1 change during implementation of atmospheric correction of the oxygen concentration sensor 73. It is to be noted herein that fuel cut is started at a timing t1 in each of these time charts.
  • Fig. 6A shows how the opening of the throttle valve 32 changes.
  • the ECU 90 gradually reduces the opening of the throttle valve 32 to a predetermined opening in response to the start of fuel cut at the timing t1 (from the timing t1 to a timing t2).
  • the ECU 90 then introduces fresh air into the exhaust system 40 by holding the throttle valve 32 substantially open (at an opening sufficient to ensure a predetermined amount of intake air) for a predetermined period (from the timing t2 to a timing t3). Thereafter, the ECU 90 completely closes the throttle valve 32 and holds it completely closed as long as the implementation of fuel cut continues.
  • Fig. 6B shows how the integrated value of the intake air amount GA changes from a specific timing calculated by the ECU 90.
  • the ECU 90 starts integration of the intake air amount GA from the timing (t2) when the throttle valve 32 shifts to a completely open state.
  • the ECU 90 recognizes that fresh air introduced by opening the throttle valve 32 has completely replaced exhaust gas remaining in the exhaust system 40, and then completely closes the throttle valve 32 (see Fig. 6A as well).
  • Fig. 6C shows how the pressure in the exhaust system 40 changes.
  • the pressure in the exhaust system 40 fluctuates as the throttle valve 32 is opened or closed from the timing t1 to the timing t3.
  • the pressure in the exhaust system 40 is stably maintained at a pressure substantially equal to the atmospheric pressure as long as the implementation of fuel cut continues.
  • Fig. 6D shows how the NOx catalyst bed temperature estimated on the basis of a detection signal from the exhaust gas temperature sensor 74 changes.
  • fresh air is introduced into the exhaust system 40 from the timing t1 to the timing t3, whereby the NOx catalyst bed temperature gradually falls.
  • the introduction of fresh air into the exhaust system 40 is stopped upon a shift of the throttle valve 32 to the completely closed state at the timing t3. Therefore, a fall in the NOx catalyst bed temperature is suppressed after the timing t3.
  • the opening of the throttle valve 32 from the timing t1 to the timing t3 be sufficient to realize efficient introduction of fresh air. That is, it is not absolutely required that the throttle valve 32 be completely open from the timing t1 to the timing t3.
  • the intake air amount (the efficiency in introducing fresh air), which increases in proportion to an increase in the opening of the throttle valve 32, has an upper limit.
  • a predetermined opening e.g. 90% of the completely open state
  • the efficiency in introducing fresh air does not change in some cases. It is also appropriate to set a maximum opening of the throttle valve 32 from the timing t1 to the timing t3, for example, from the standpoint of stabilizing engine torque and maintaining good exhaust emission properties while efficiently introducing fresh air.
  • the opening or closing operation of the throttle valve 32 may be subjected to an averaging processing (gradual change processing).
  • Fig. 6E shows how the detection signal from the oxygen concentration sensor 73 changes.
  • the detection signal (limiting current) of the oxygen concentration sensor 73 gradually rises in level in response to the start of fuel cut. However, this signal tends to gradually fall in level while the throttle valve 32 is completely open (from the timing t2 to the timing t3).
  • the output of the oxygen concentration sensor 73 tends to fall from the timing t2 to the timing t3 because the pressure of gas in the exhaust system increases as a result of a shift of the throttle valve 32 to the completely open state. If the throttle valve 32 is completely closed afterwards, fresh air introduced from the intake system 30 completely replaces the gas remaining in the exhaust system 40 and stays within the exhaust system 40.
  • the oxygen concentration sensor 73 stably outputs a detection signal corresponding to the oxygen concentration (21%) in the atmosphere.
  • atmospheric correction of the oxygen concentration sensor 73 is continued until the implementation of fuel cut is terminated.
  • the oxygen concentration detecting device in accordance with the first embodiment first opens the throttle valve 32 completely and replaces exhaust gas remaining in the exhaust system with fresh air in the intake system 30, then stabilizes the pressure and temperature in the exhaust system 40 by closing the throttle valve 32, and makes atmospheric correction.
  • Fig. 7 is a flowchart showing "an atmospheric correction routine of the oxygen concentration sensor" which is executed through the ECU 90. This routine is repeatedly executed at intervals of a predetermined period after the engine 1 has been started.
  • step S101 determines first in step S101 whether or not fuel cut is to be started at the moment. If the result of step S101 is positive, the operation proceeds to step S102. If the result of step S101 is negative, the operation temporarily leaves the present routine. That is, only if the present routine has been subjected to a processing at the start of fuel cut, the ECU 90 performs processings in step S102 and the following steps (atmospheric correction of the oxygen concentration sensor 73).
  • step S102 the throttle valve 32 is opened.
  • the throttle valve 32 is closed after having been held open for a predetermined period.
  • the ECU 90 integrates the intake air amount GA after the throttle valve 32 has been opened, thus successively estimating an amount of fresh air introduced from the intake system 30 to the exhaust system 40. If it is determined that a predetermined amount of fresh air has been introduced into the exhaust system 40 and that exhaust gas remaining in the exhaust system 40 has been completely replaced with fresh air, the throttle valve 32 is closed (see Figs. 6A and 6B).
  • the ECU 90 closes the EGR valve 61 as soon as fuel cut is started (as soon as the throttle valve 32 is opened).
  • the EGR valve 61 is held open until fuel cut is terminated (until atmospheric correction is terminated).
  • the ECU 90 waits until the output of the oxygen concentration sensor 73 converges into a predetermined range (a substantially constant value). If it is determined that the output of the oxygen concentration sensor 73 has converged into the predetermined range, the ECU 90 recognizes a limiting current (a value taking the circuit offset OS into account) output from the oxygen concentration sensor 73 (step S103), and learns and stores this limiting current as a detection signal corresponding to the oxygen concentration (21%) in the atmosphere (step S104).
  • a limiting current a value taking the circuit offset OS into account
  • step S104 the ECU 90 temporarily leaves the present routine.
  • the oxygen concentration detecting device in accordance with the first embodiment learns a relationship in correspondence between the detection signal from the oxygen concentration sensor 73 and the concentration of oxygen contained in exhaust gas according to the procedure described above, and acquires a concentration of oxygen contained in exhaust gas (an air-fuel ratio of the mixture used for engine combustion) on the basis of the learned result.
  • Fig. 8 shows a relationship between the precision in estimation of air-fuel ratio that is calculated (estimated) on the basis of a detection signal from the oxygen concentration sensor 73 and the true value of air-fuel ratio.
  • the axis of abscissa represents true value of the air-fuel ratio A/F (hereinafter referred to as base air-fuel ratio), and the axis of ordinate represents a difference ⁇ A/F between base air-fuel ratio and air-fuel ratio that is estimated on the basis of a detection signal from the oxygen concentration sensor 73 (hereinafter referred to as detected air-fuel ratio).
  • the detecting element (zirconia element) constituting the oxygen concentration sensor 73 has the following property. That is, as indicated by a broken line L1 or a broken line M1 for example, the absolute value of the difference ⁇ A/F tends to increase in proportion to an increase in difference between the base air-fuel ratio and the stoichiometric air-fuel ratio. In other words, the base air-fuel ratio tends to become distant from the detected air-fuel ratio in proportion to an increase in difference between the base air-fuel ratio and the stoichiometric air-fuel ratio.
  • the absolute value of the difference ⁇ A/F is held at a sufficiently small value even in the event of fluctuations of the base air-fuel ratio, as indicated by a solid line L2 or a solid line M2. That is, the credibility of the detected air-fuel ratio is enhanced over an extensive oxygen concentration range.
  • the first embodiment is designed such that the intake air amount GA is increased under a condition that fuel cut be carried out during operation of the engine 1, that exhaust gas remaining in the exhaust system 40 is temporarily replaced with fresh air introduced from the intake system 30 into the combustion chambers 20, and that the intake air amount GA is then reduced swiftly.
  • the atmosphere whose oxygen concentration is known is swiftly introduced to fill up the exhaust system.
  • the atmosphere that has thus filled up the exhaust system is defined as a reference gas, and numerical information (e.g., limiting current) regarding a signal output from the oxygen concentration sensor 73 is stored as numerical information corresponding to the concentration of oxygen contained in the reference gas.
  • numerical information e.g., limiting current
  • the oxygen concentration sensor 73 can be ensured of high detecting precision and high reliability over a long period irrespective of the difference (dispersion) among individual detecting elements or detecting circuits or the progressive degree of aging.
  • the temperature in the exhaust system 40 drops extremely slightly as a result of the learning of the numerical information as described above (atmospheric correction).
  • the temperature of the exhaust system 40 can be held high enough to maintain the exhaust gas purification catalyst in an activated state.
  • the intake air amount GA is increased in synchronization with the start of fuel cut, and the introduction of the atmosphere into the exhaust system 40 is promoted.
  • the opportunity to learn the numerical information as described above is enlarged. That is, while the period for implementing fuel cut is limited during operation of the engine 1, it is possible to make the most of this limited period.
  • the operation of opening and closing the throttle valve 32 and the operation of closing the EGR valve 61 are performed together in synchronization with the start of fuel cut.
  • the operation of opening and closing the throttle valve 32 is performed while the EGR valve 61 is held open, it is possible to achieve an effect that is similar to the effect of the first embodiment.
  • the engine system to be employed and the oxygen concentration detecting device are identical in hardware construction (Figs. 1 to 4) to those of the aforementioned first embodiment.
  • members, hardware constructions, and the like which are functionally and structurally identical to those of the first embodiment are denoted by the same reference numerals, and repetition of the same description as in the first embodiment will be avoided hereinafter.
  • the oxygen concentration detecting device in accordance with the second embodiment is identical to the oxygen concentration detecting device in accordance with the first embodiment in that the circuit offset OS of the oxygen concentration sensor 73 is quantitatively recognized during the start of the engine 1 or the like, that fresh air in the intake system 30 replaces exhaust gas remaining in the exhaust system by first opening the throttle valve 32 completely during the implementation of fuel cut, and that atmospheric correction is made while the pressure and temperature in the exhaust system 40 are stabilized by thereafter closing the throttle valve 32.
  • the second embodiment is different from the first embodiment in that the timing for making atmospheric correction is prevented from becoming contiguous to the timing for adding fuel so as to further enhance the precision and reliability of atmospheric correction.
  • Figs. 9A and 9B are time charts schematically showing how the detection signal from the oxygen concentration sensor 73 changes in accordance with the implementation of fuel cut.
  • fuel cut is started at a timing t11.
  • Fig. 9A shows along a single time axis a curve of change (alternate long and short dash line) in the case where no fuel is added and a curve of change (solid line) in the case where fuel is added at the beginning of fuel cut.
  • the detection signal from the oxygen concentration sensor 73 swiftly rises in level in response to the start of fuel cut (makes a shift to the lean side), and is stabilized upon reaching a value corresponding to the oxygen concentration in the atmosphere at a timing (t12).
  • fuel is added at a timing contiguous to the timing for starting fuel cut, fuel stays within the exhaust system 40.
  • the oxygen concentration in the exhaust system 40 rises with delay.
  • a timing (t13) when the detection signal from the oxygen concentration sensor 73 reaches a value corresponding to the oxygen concentration in the atmosphere is delayed as well.
  • the oxygen concentration detecting device in accordance with the second embodiment performs a control of prohibiting fuel from being added within a predetermined period (e.g., from the timing t11 to the timing t12 in Fig. 9B) from the start of fuel cut so that the oxygen concentration in the exhaust system swiftly becomes equal to the oxygen concentration in the atmosphere after the start of fuel cut.
  • a predetermined period e.g., from the timing t11 to the timing t12 in Fig. 9B
  • the oxygen concentration detecting device in accordance with the second embodiment prohibits fuel from being added.
  • the oxygen concentration detecting device estimates an amount of change in the detection signal from the oxygen concentration sensor resulting from the addition of fuel, and continues atmospheric correction while making a correction of abridging the amount of change (e.g., while successively drawing a fictitious line MSK shown in Fig. 9B).
  • Fig. 10 is a flowchart showing "an atmospheric correction routine of the oxygen concentration sensor" which is executed through the ECU 90. This routine is repeatedly executed at intervals of a predetermined period after the start of the engine 1.
  • step S201 determines first in step S201 whether or not fuel cut is to be started at the moment. If the result of step S201 is positive, the operation proceeds to step S202. If the result of step S201 is negative, the operation jumps to step S207.
  • step S202 It is determined in step S202 whether or not fuel has ever been added until now for the past period of a predetermined length. If the result of step S202 is positive, the operation proceeds to step S203. If the result of step S202 is negative, the operation jumps to step S207. That is, the ECU 90 shifts the operation to the present routine as soon as fuel cut is started, and performs processings in step S230 and the following steps (atmospheric correction of the oxygen concentration sensor 73) only on the condition that no fuel be added immediately before fuel cut is started.
  • step S203 the ECU 90 temporarily prohibits fuel from being added.
  • step S204 the ECU 90 opens the throttle valve 32 for a predetermined period, holds it open for a predetermined period, and then closes the throttle valve 32.
  • the ECU 90 successively estimates an amount of fresh air introduced from the intake system 30 into the exhaust system 40 by integrating the intake air amount GA.
  • the throttle valve 32 is closed (see Figs. 6A and 6B).
  • the ECU 90 opens the EGR valve 61 as soon as fuel cut is started (as soon as the throttle valve 32 is opened).
  • the EGR valve 61 is held closed until fuel cut is terminated (until atmospheric correction is terminated).
  • the ECU 90 waits until the output of the oxygen concentration sensor 73 converges into a predetermined range (a substantially constant value). If it is determined that the output of the oxygen concentration sensor 73 has converged into the predetermined range, the ECU 90 recognizes a limiting current (a value taking the circuit offset OS into account) output from the oxygen concentration sensor 73 (step S205), and learns and stores this limiting current as a detection signal corresponding to the oxygen concentration (21%) in the atmosphere (step S206).
  • a limiting current a value taking the circuit offset OS into account
  • step S207 a processing of allowing fuel to be added, namely, a processing of ceasing to prohibit fuel from being added (step S203) is performed.
  • step S207 After the processing in step S207 has been performed, the ECU 90 temporarily leaves the present routine.
  • the progressive speed of replacement of gases in the exhaust system 40 based on the operations of opening and closing the throttle valve 32 and the EGR valve 61 and the magnitudes of pressure fluctuation and temperature fluctuation in the exhaust system differ depending on the hardware construction of the engine to be employed as well. It is thus preferable that maximum and minimum openings (%) of the valves 32, 61 or gradual change (smoothening) rates of the openings of the valves 32, 61 be adjusted in accordance with the hardware characteristics or the operational situation of the engine.
  • the openings of the throttle valve 32 and the EGR valve 61 be adjusted while successively performing feedback of detection signals from the airflow meter 72 and the exhaust gas temperature sensor 74 so that respective parameters in which the operational state of the engine is reflected change, for example, in such a manner as to establish relationships shown in Figs. 6(a) to 6(e).
  • the operations of opening and closing the throttle valve 32 and the EGR valve 61 and the fuel injection amount be modified at a suitable timing from the standpoint of ensuring good driveability during or prior to the implementation of fuel cut as well as enhancing the precision in making atmospheric correction.
  • the throttle valve 32 is held open in response to the start of fuel cut (from the timing t2 to the timing t3 in Fig. 6) or in the case where the driver of a vehicle equipped with the engine 1 has depressed the accelerator pedal, it is preferable that the fuel injection amount be gradually increased instead of immediately supplying fuel through injection in an amount corresponding to a required torque at that moment.
  • the throttle valve 32 is closed (at the timing t3 in Fig.
  • the throttle valve 32 in response to the termination of replacement of gases in the exhaust system 40, it is preferable from the standpoint of suppressing generation of so-called engine brake that the throttle valve 32 be so controlled as to be gradually closed instead of being abruptly changed in opening (e.g., being shifted to the completely closed state).
  • the temperature of the NOx catalyst, the particulate filter, or the oxidizing catalyst is estimated to be lower than a predetermined value when fuel cut is started, it is preferable from the standpoint of suitably maintaining activated states of various catalysts disposed in the exhaust system 40 that a processing of withholding (prohibiting) atmospheric correction regarding fuel cut at the moment be performed.
  • the invention is applied to the oxygen concentration sensor for outputting a limiting current that quantitatively corresponds to a concentration of oxygen contained in exhaust gas.
  • the invention is not limited to such an oxygen concentration sensor. It is also possible to achieve an effect that is equivalent or similar to the effects of the aforementioned embodiments by applying the invention to other oxygen concentration sensors for outputting a detection signal that quantitatively corresponds to a concentration of oxygen contained in exhaust gas.
  • the invention can also be equally applied to sensors (e.g., an NOx sensor for detecting nitrides) for detecting other exhaust components that are related to oxygen components contained in exhaust gas.
  • the aforementioned embodiments are designed such that. the exhaust system is swiftly filled with the atmosphere whose oxygen concentration is known while reliably stabilizing the pressure and temperature if the supply of fuel has been stopped during operation of the engine, and that the relationship in correspondence between the detection signal from the oxygen concentration sensor and the concentration of oxygen contained in exhaust gas can be accurately learned with the atmosphere thus filling up the exhaust system being defined as a reference gas. Accordingly, the precision in detecting the concentration of oxygen contained in exhaust gas by means of the oxygen concentration sensor can be enhanced. In this case, the pressure fluctuation or the fall in temperature resulting from the learning of the numerical information as described above is quite negligible. Moreover, since the atmosphere is swiftly introduced into the exhaust system, the opportunity to learn the numerical information as described above is enlarged.
  • An electronic control unit (90) for managing and controlling an operational state of a diesel engine (1) first opens a throttle valve (32) completely during the implementation of fuel cut so as to replace gas remaining in an exhaust system (40) with fresh air in an intake system (30), then closes the throttle valve (32) to stabilize a pressure and a temperature in the exhaust system (40), and makes atmospheric correction.
  • the electronic control unit (90) performs a control of prohibiting fuel from being added within a predetermined period after the start of fuel cut.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
EP20030001529 2002-01-24 2003-01-23 Procédé et dispositif de détection de la concentration d'oxygène Expired - Lifetime EP1333171B1 (fr)

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JP2002015870A JP4428904B2 (ja) 2002-01-24 2002-01-24 酸素濃度検出装置及び酸素濃度の検出方法
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WO2008071500A1 (fr) * 2006-12-13 2008-06-19 Continental Automotive Gmbh Procédé d'étalonnage d'une sonde lambda et moteur à combustion interne
WO2008146127A2 (fr) * 2007-05-25 2008-12-04 Toyota Jidosha Kabushiki Kaisha Procédé et appareil de commande de moteur à combustion interne
US7770565B2 (en) 2008-04-08 2010-08-10 Cummins Inc. System and method for controlling an exhaust gas recirculation system
US7991539B2 (en) 2007-05-21 2011-08-02 Toyota Jidosha Kabushiki Kaisha Engine controller
US9952120B2 (en) 2011-11-17 2018-04-24 Ngk Spark Plug Co., Ltd. Sensor control device and sensor control system
US10746077B2 (en) 2017-09-07 2020-08-18 Toyota Jidosha Kabushiki Kaisha Diagnostic apparatus for exhaust gas sensor

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JP4821112B2 (ja) * 2004-12-22 2011-11-24 日産自動車株式会社 希薄燃焼内燃機関の制御装置
JP4687690B2 (ja) * 2007-06-04 2011-05-25 株式会社デンソー センサ情報検出装置、センサ校正装置、及びセンサ診断装置
JP5088429B2 (ja) * 2011-03-22 2012-12-05 トヨタ自動車株式会社 内燃機関の制御装置
DE102022203170B3 (de) 2022-03-31 2023-03-30 Vitesco Technologies GmbH Verfahren zum Erkennen einer Manipulation eines Sensorwertes eines Abgassensors einer Brennkraftmaschine für ein Fahrzeug

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EP1748173A2 (fr) * 2005-07-28 2007-01-31 Denso Corporation Dispositif de commande pour un moteur à combustion interne
EP1748173A3 (fr) * 2005-07-28 2010-01-27 Denso Corporation Dispositif de commande pour un moteur à combustion interne
WO2008071500A1 (fr) * 2006-12-13 2008-06-19 Continental Automotive Gmbh Procédé d'étalonnage d'une sonde lambda et moteur à combustion interne
US8108130B2 (en) 2006-12-13 2012-01-31 Continental Automotive Gmbh Method for calibrating a lambda sensor and internal combustion engine
US7991539B2 (en) 2007-05-21 2011-08-02 Toyota Jidosha Kabushiki Kaisha Engine controller
WO2008146127A3 (fr) * 2007-05-25 2009-01-29 Toyota Motor Co Ltd Procédé et appareil de commande de moteur à combustion interne
WO2008146127A2 (fr) * 2007-05-25 2008-12-04 Toyota Jidosha Kabushiki Kaisha Procédé et appareil de commande de moteur à combustion interne
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CN102913333B (zh) * 2007-05-25 2015-07-22 丰田自动车株式会社 内燃机控制装置和方法
US7770565B2 (en) 2008-04-08 2010-08-10 Cummins Inc. System and method for controlling an exhaust gas recirculation system
US9952120B2 (en) 2011-11-17 2018-04-24 Ngk Spark Plug Co., Ltd. Sensor control device and sensor control system
US10746077B2 (en) 2017-09-07 2020-08-18 Toyota Jidosha Kabushiki Kaisha Diagnostic apparatus for exhaust gas sensor

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DE60300545T2 (de) 2006-02-16
JP2003214245A (ja) 2003-07-30
JP4428904B2 (ja) 2010-03-10
DE60300545D1 (de) 2005-06-02
ES2240861T3 (es) 2005-10-16
EP1333171B1 (fr) 2005-04-27

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