US20020062640A1 - Device and method for controlling air-fuel ratio of internal combustion engine - Google Patents
Device and method for controlling air-fuel ratio of internal combustion engine Download PDFInfo
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- US20020062640A1 US20020062640A1 US09/987,641 US98764101A US2002062640A1 US 20020062640 A1 US20020062640 A1 US 20020062640A1 US 98764101 A US98764101 A US 98764101A US 2002062640 A1 US2002062640 A1 US 2002062640A1
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- fuel ratio
- air
- exhaust gas
- oxygen
- intake air
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- 239000000446 fuel Substances 0.000 title claims abstract description 100
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 87
- 239000001301 oxygen Substances 0.000 claims abstract description 87
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 87
- 239000007789 gas Substances 0.000 claims abstract description 69
- 230000003197 catalytic effect Effects 0.000 claims abstract description 31
- 238000002347 injection Methods 0.000 claims abstract description 28
- 239000007924 injection Substances 0.000 claims abstract description 28
- 238000001514 detection method Methods 0.000 claims abstract description 17
- 238000011144 upstream manufacturing Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 description 7
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000001603 reducing effect Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
Images
Classifications
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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
- F02D41/02—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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of 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
- 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
-
- 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
- F02D2250/36—Control for minimising NOx emissions
-
- 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
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/0065—Specific aspects of external EGR control
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Definitions
- the present invention relates to a device and method for controlling an air-fuel ratio of an internal combustion engine, in which an air-fuel ratio of the combustion mixture is controlled based on an oxygen quantity stored in a catalytic converter.
- an air-fuel ratio control device that estimates an oxygen quantity stored in a catalytic converter based on an air-fuel ratio to be detected by an oxygen sensor disposed upstream of a catalytic converter and an exhaust gas quantity, to control an air fuel ratio of the combustion mixture so that the stored oxygen quantity reaches a target value (refer to Japanese Unexamined Patent Publication Nos. 6-249028,10-184425).
- the present invention aims at enabling at a high accuracy the estimation of oxygen quantity stored in a catalytic converter even in a state where the exhaust gas recirculation is performed and thereby enabling to maintain the control accuracy of air-fuel ratio.
- a detected amount of new intake air quantity is corrected in accordance with a recirculation rate of exhaust gas, to estimate, based on the corrected result, an oxygen quantity stored in a catalytic converter.
- FIG. 1 shows the system structure of an internal combustion engine
- FIG. 2 is a block diagram showing the details of air-fuel ratio control according to the present invention.
- FIG. 1 is a diagram showing the system structure of an internal combustion engine according to an embodiment.
- FIG. 1 air is sucked into a combustion chamber of each cylinder in an internal combustion engine 1 mounted on a vehicle via an air cleaner 2 , an intake passage 3 , and an electronic controlled throttle valve 4 driven to open/close by a motor.
- An electromagnetic fuel injection valve 5 is further disposed to inject fuel directly into the combustion chamber of each cylinder, and an air-fuel mixture is formed within the combustion chamber by the fuel injected by fuel injection valve 5 and the air sucked into the combustion chamber.
- Fuel injection valve 5 is supplied with the power to a solenoid thereof by an injection pulse signal output from a control unit 20 , to inject fuel adjusted to a predetermined pressure.
- the air-fuel mixture formed within the combustion chamber is ignited by an ignition plug 6 to be combusted.
- internal combustion engine 1 is not limited to the aforementioned direct injection type gasoline engine, but may be an internal combustion engine where fuel is injected into an intake port.
- the exhaust gas of engine 1 is discharged through an exhaust passage 7 that is disposed with a catalytic converter 8 for purifying the exhaust gas.
- Catalytic converter 8 is a three-way catalytic converter having the oxygen storing ability, to oxidize carbon monoxide CO, hydrocarbon HC and to reduce nitric oxide NOx, being the three harmful components included in the exhaust gas, thereby converting them into harmless carbon dioxide, water vapor and nitrogen.
- the purification performance of three-way catalytic converter 8 is the greatest when an air-fuel ratio is a stoichiometric air-fuel ratio.
- an air-fuel ratio is lean and the oxygen quantity is excessive
- the oxidizing action becomes active but the reducing action becomes inactive
- the oxidizing action becomes inactive but the reducing action becomes active.
- control unit 20 mentioned above estimates the stored oxygen quantity in three-way catalytic converter 8 within an operation region where a target air-fuel ratio is the stoichiometric air-fuel ratio, and feedback controls a fuel injection quantity of fuel injection valve 5 so that when the estimated stored oxygen quantity is smaller than a target quantity, the air-fuel ratio is shifted to lean so as to increase the stored oxygen quantity, whereas when the estimated stored oxygen quantity is greater than the target quantity, the air-fuel ratio is shifted to rich so as to eliminate the excessive oxygen thereby reducing the stored oxygen quantity.
- engine 1 is provided with an exhaust gas recirculation (EGR) device where a portion of the exhaust gas is recirculated to the intake side.
- EGR exhaust gas recirculation
- the exhaust gas recirculation device mentioned above comprises an exhaust gas recirculation passage 18 connecting an exhaust manifold 16 and an intake collector 17 , and an EGR control valve 19 disposed in exhaust gas recirculation passage 18 .
- EGR control valve 19 When EGR control valve 19 is controlled to open, due to a differential pressure generated between the front and back of EGR control valve 19 , a portion of the exhaust gas is recirculated to intake collector 17 .
- Control unit 20 incorporates therein a microcomputer including CPU, ROM, RAM, A/D converter, input/output interface and the like. When receiving output signals from various sensors, control unit 20 performs an operation process based on these signals, to control the opening of electronic controlled throttle valve 4 , the injection quantity and injection timing of fuel injection valve 5 , the ignition timing of ignition plug 6 , and also to control an exhaust gas recirculation rate through the control of EGR control valve 19 .
- control unit 20 sets a target exhaust gas recirculation rate based on operating conditions such as an engine load and an engine rotation speed, to output a control signal corresponding to the target exhaust gas recirculation rate, to an actuator driving EGR control valve 19 such as a step motor or an electromagnetic coil.
- crank angle sensor 21 that detects a crank angle of engine 1 and a cam sensor 22 that takes out cylinder discrimination signals from a camshaft, and based on a signal from crank angle sensor 21 , the engine rotation speed Ne is computed.
- an airflow meter 23 that detects a new intake air quantity Q at the upstream of throttle valve 4 in intake passage 3 , an accelerator sensor 24 that detects a depression quantity APS of an accelerator pedal, a throttle sensor 25 that detects the opening TVO of throttle valve 4 , a water temperature sensor 26 that detects the cooling water temperature Tw of engine 1 , an oxygen sensor 27 that detects in wide range an oxygen concentration within the exhaust gas, and a vehicle speed sensor 28 that detects the vehicle speed VSP.
- control unit 20 based on the stored oxygen quantity is explained with reference to a block diagram of FIG. 2.
- a correction coefficient for correcting the new intake air quantity Q detected by airflow meter 23 is set based on the exhaust gas recirculation rate at that time.
- the correction coefficient is set to 1.0 when the exhaust gas recirculation rate is 0, in other words when the exhaust gas recirculation is stopped, and further set to a greater value as the exhaust gas recirculation rate increases.
- the correction coefficient is set by either searching for a table storing in advance the correction coefficient corresponding to the exhaust gas recirculation rate, or through an operation using the exhaust gas recirculation rate as a variable.
- Airflow meter 23 detects the new intake air quantity of the engine. However, when the exhaust gas recirculation is performed, the recirculated exhaust gas is flown with the new air flowing into the engine, and an exhaust gas quantity will correspond to the total amount of the new intake air quantity and a recirculated exhaust gas quantity.
- the oxygen quantity is judged based on a quantity smaller than an actual exhaust gas quantity to estimate the storage oxygen quantity based on the judged oxygen quantity, causing degradation of estimation accuracy of the stored oxygen quantity.
- the detection value of the new air intake quantity is increasingly corrected by an amount of recirculated exhaust gas, so that the corrected new intake air quantity indicates the actual exhaust gas quantity correctly, to be used in the estimating operation of the stored oxygen quantity.
- the value corrected by the correction coefficient corresponds to the exhaust gas quantity including the amount of the recirculated exhaust gas.
- correction coefficient set by correction coefficient setting unit 101 is multiplied on the new intake air quantity Q detected by airflow meter 23 , and data of the new intake air quantity Q after the multiplication correction is further multiplied by a deviation ⁇ between the stoichiometric air-fuel ratio and the air-fuel ratio detected by oxygen sensor 27 .
- an excess air ratio showing the air-fuel ratio based on oxygen sensor 27 is computed, and since the excess air ratio corresponding to the stoichiometric air-fuel ratio is 1 , the deviation ⁇ is computed as:
- the air-fuel ratio deviation ⁇ becomes a positive value, while if it is richer, the deviation ⁇ becomes a negative value, which correspond to the situation where the stored oxygen quantity of catalytic converter 8 is increasingly changed when the air-fuel ratio of the combustion air-fuel mixture is leaner than the stoichiometric air-fuel ratio, while the stored oxygen quantity of catalytic converter 8 is decreasingly changed when the air-fuel ratio of the combustion air-fuel mixture is richer than the stoichiometric air-fuel ratio.
- a constant K is multiplied on the multiplication result of the new intake air quantity Q and the air-fuel ratio deviation ⁇ , and this multiplication result is integrated one after another by an integrator 102 , to thereby obtain the stored oxygen quantity of catalytic converter 8 .
- the new intake air quantity Q utilized in estimating the stored oxygen quantity is corrected to a value including the amount of recirculated exhaust gas during the exhaust gas recirculation state, so the stored oxygen quantity can be obtained based on the actual exhaust gas quantity even the exhaust gas recirculation is performed.
- a feedback correction coefficient setting unit 103 input with data of deviation of the stored oxygen quantity, a feedback correction coefficient of the air-fuel ratio is computed so that the estimated value of the stored oxygen quantity corresponds to the target value.
- the feedback correction coefficient is set so that when the stored oxygen quantity is smaller than the target quantity, the air-fuel ratio is shifted to leaner so as to increase the stored oxygen quantity, and in contrast, when the stored oxygen quantity is greater than the target quantity, the air-fuel ratio is shifted to richer so as to eliminate the excessive oxygen thereby decreasing the stored oxygen quantity.
- an injection quantity computing unit 104 the above feedback correction coefficient is utilized, to correct a basic fuel injection quantity thereby computing a final fuel injection quantity, and an injection pulse signal corresponding to the computed final fuel injection quantity is output to fuel injection valve 5 .
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Exhaust-Gas Circulating Devices (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
In a system for estimating an oxygen quantity stored in a catalytic converter of an internal combustion engine and feedback controlling a fuel injection quantity based on the estimated oxygen quantity, a detection value of the new intake air quantity is corrected according to an exhaust gas recirculation rate, and the oxygen quantity is estimated based on the corrected new intake air quantity.
Description
- The present invention relates to a device and method for controlling an air-fuel ratio of an internal combustion engine, in which an air-fuel ratio of the combustion mixture is controlled based on an oxygen quantity stored in a catalytic converter.
- Heretofore, there is known an air-fuel ratio control device that estimates an oxygen quantity stored in a catalytic converter based on an air-fuel ratio to be detected by an oxygen sensor disposed upstream of a catalytic converter and an exhaust gas quantity, to control an air fuel ratio of the combustion mixture so that the stored oxygen quantity reaches a target value (refer to Japanese Unexamined Patent Publication Nos. 6-249028,10-184425).
- In estimating the above-mentioned stored oxygen quantity being stored, instead of directly measuring the exhaust gas quantity, a detection value of new intake air quantity is used, which is considered to substantially correspond to the exhaust gas quantity.
- However, in an engine equipped with an exhaust gas recirculation system where a portion of exhaust gas is recirculated to an intake system, the recirculated exhaust gas is added to a new intake air quantity detected by an airflow meter to be flown into the intake system when the exhaust gas recirculation is performed.
- Therefore, a difference is caused between the new intake air quantity detected by airflow meter and an actual exhaust gas quantity, and this difference leads to an estimation error in the stored oxygen quantity, deteriorating the control accuracy of the air-fuel ratio as a result.
- Therefore, the present invention aims at enabling at a high accuracy the estimation of oxygen quantity stored in a catalytic converter even in a state where the exhaust gas recirculation is performed and thereby enabling to maintain the control accuracy of air-fuel ratio.
- In order to achieve the above object, according to the present invention, a detected amount of new intake air quantity is corrected in accordance with a recirculation rate of exhaust gas, to estimate, based on the corrected result, an oxygen quantity stored in a catalytic converter.
- These and other objects and features of the present invention will become understood from the following description with reference to the accompanying drawings.
- FIG. 1 shows the system structure of an internal combustion engine; and
- FIG. 2 is a block diagram showing the details of air-fuel ratio control according to the present invention.
- FIG. 1 is a diagram showing the system structure of an internal combustion engine according to an embodiment.
- In FIG. 1, air is sucked into a combustion chamber of each cylinder in an internal combustion engine 1 mounted on a vehicle via an
air cleaner 2, anintake passage 3, and an electronic controlledthrottle valve 4 driven to open/close by a motor. - An electromagnetic
fuel injection valve 5 is further disposed to inject fuel directly into the combustion chamber of each cylinder, and an air-fuel mixture is formed within the combustion chamber by the fuel injected byfuel injection valve 5 and the air sucked into the combustion chamber. -
Fuel injection valve 5 is supplied with the power to a solenoid thereof by an injection pulse signal output from acontrol unit 20, to inject fuel adjusted to a predetermined pressure. - The air-fuel mixture formed within the combustion chamber is ignited by an
ignition plug 6 to be combusted. - However, internal combustion engine 1 is not limited to the aforementioned direct injection type gasoline engine, but may be an internal combustion engine where fuel is injected into an intake port.
- The exhaust gas of engine 1 is discharged through an
exhaust passage 7 that is disposed with acatalytic converter 8 for purifying the exhaust gas. -
Catalytic converter 8 is a three-way catalytic converter having the oxygen storing ability, to oxidize carbon monoxide CO, hydrocarbon HC and to reduce nitric oxide NOx, being the three harmful components included in the exhaust gas, thereby converting them into harmless carbon dioxide, water vapor and nitrogen. - The purification performance of three-way
catalytic converter 8 is the greatest when an air-fuel ratio is a stoichiometric air-fuel ratio. When the air-fuel ratio is lean and the oxygen quantity is excessive, the oxidizing action becomes active but the reducing action becomes inactive, and in reverse, when the air-fuel ratio is rich and the oxygen quantity is low, the oxidizing action becomes inactive but the reducing action becomes active. - However, since three-way
catalytic converter 8 has the oxygen storing ability, when the air-fuel ratio becomes temporarily rich, the oxygen stored incatalytic converter 8 is used, and when the air-fuel ratio becomes temporarily lean, the excessive oxygen is stored incatalytic converter 8 so that the exhaust gas purification performance can be maintained. - Accordingly, in order to be able to reduce nitric oxide NOx when the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio and also to oxidize carbon monoxide CO and hydrocarbon HC when the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, it is required to maintain the oxygen quantity to be stored in three-way
catalytic converter 8 to approximately half the maximum storage amount, so that excessive oxygen can be stored to the catalytic converter when needed and so that oxygen necessary for the oxidation process can be supplied by eliminating from the stored oxygen when needed. - Therefore,
control unit 20 mentioned above estimates the stored oxygen quantity in three-waycatalytic converter 8 within an operation region where a target air-fuel ratio is the stoichiometric air-fuel ratio, and feedback controls a fuel injection quantity offuel injection valve 5 so that when the estimated stored oxygen quantity is smaller than a target quantity, the air-fuel ratio is shifted to lean so as to increase the stored oxygen quantity, whereas when the estimated stored oxygen quantity is greater than the target quantity, the air-fuel ratio is shifted to rich so as to eliminate the excessive oxygen thereby reducing the stored oxygen quantity. - Further, engine 1 is provided with an exhaust gas recirculation (EGR) device where a portion of the exhaust gas is recirculated to the intake side.
- The exhaust gas recirculation device mentioned above comprises an exhaust
gas recirculation passage 18 connecting anexhaust manifold 16 and anintake collector 17, and anEGR control valve 19 disposed in exhaustgas recirculation passage 18. WhenEGR control valve 19 is controlled to open, due to a differential pressure generated between the front and back ofEGR control valve 19, a portion of the exhaust gas is recirculated tointake collector 17. -
Control unit 20 incorporates therein a microcomputer including CPU, ROM, RAM, A/D converter, input/output interface and the like. When receiving output signals from various sensors,control unit 20 performs an operation process based on these signals, to control the opening of electronic controlledthrottle valve 4, the injection quantity and injection timing offuel injection valve 5, the ignition timing ofignition plug 6, and also to control an exhaust gas recirculation rate through the control ofEGR control valve 19. - In the control of exhaust gas recirculation rate,
control unit 20 sets a target exhaust gas recirculation rate based on operating conditions such as an engine load and an engine rotation speed, to output a control signal corresponding to the target exhaust gas recirculation rate, to an actuator drivingEGR control valve 19 such as a step motor or an electromagnetic coil. - As various sensors, there is provided a
crank angle sensor 21 that detects a crank angle of engine 1 and acam sensor 22 that takes out cylinder discrimination signals from a camshaft, and based on a signal fromcrank angle sensor 21, the engine rotation speed Ne is computed. - Other than the above, there is provided an
airflow meter 23 that detects a new intake air quantity Q at the upstream ofthrottle valve 4 inintake passage 3, anaccelerator sensor 24 that detects a depression quantity APS of an accelerator pedal, athrottle sensor 25 that detects the opening TVO ofthrottle valve 4, awater temperature sensor 26 that detects the cooling water temperature Tw of engine 1, anoxygen sensor 27 that detects in wide range an oxygen concentration within the exhaust gas, and avehicle speed sensor 28 that detects the vehicle speed VSP. - Now, the air-fuel ratio control of
control unit 20 based on the stored oxygen quantity is explained with reference to a block diagram of FIG. 2. - In the block diagram of FIG. 2, at a correction
coefficient setting unit 101, a correction coefficient for correcting the new intake air quantity Q detected byairflow meter 23 is set based on the exhaust gas recirculation rate at that time. - The correction coefficient is set to 1.0 when the exhaust gas recirculation rate is 0, in other words when the exhaust gas recirculation is stopped, and further set to a greater value as the exhaust gas recirculation rate increases.
- The correction coefficient is set by either searching for a table storing in advance the correction coefficient corresponding to the exhaust gas recirculation rate, or through an operation using the exhaust gas recirculation rate as a variable.
-
Airflow meter 23 detects the new intake air quantity of the engine. However, when the exhaust gas recirculation is performed, the recirculated exhaust gas is flown with the new air flowing into the engine, and an exhaust gas quantity will correspond to the total amount of the new intake air quantity and a recirculated exhaust gas quantity. - Accordingly, in a state where the exhaust gas recirculation is being performed, if the stored oxygen quantity is estimated based on an assumption that the new intake air quantity detected by
airflow meter 23 indicates the exhaust gas quantity, the oxygen quantity is judged based on a quantity smaller than an actual exhaust gas quantity to estimate the storage oxygen quantity based on the judged oxygen quantity, causing degradation of estimation accuracy of the stored oxygen quantity. - Therefore, in the present embodiment, in order to estimate the stored oxygen quantity according to the actual exhaust gas quantity, the detection value of the new air intake quantity is increasingly corrected by an amount of recirculated exhaust gas, so that the corrected new intake air quantity indicates the actual exhaust gas quantity correctly, to be used in the estimating operation of the stored oxygen quantity.
- In other words, the value corrected by the correction coefficient corresponds to the exhaust gas quantity including the amount of the recirculated exhaust gas.
- The correction coefficient set by correction
coefficient setting unit 101 is multiplied on the new intake air quantity Q detected byairflow meter 23, and data of the new intake air quantity Q after the multiplication correction is further multiplied by a deviation Δλ between the stoichiometric air-fuel ratio and the air-fuel ratio detected byoxygen sensor 27. - In the present embodiment, an excess air ratio showing the air-fuel ratio based on
oxygen sensor 27 is computed, and since the excess air ratio corresponding to the stoichiometric air-fuel ratio is 1, the deviation Δλ is computed as: - Δλ=actual excess air ratio −1
- If the air-fuel ratio of the combustion air-fuel mixture is leaner than the stoichiometric air-fuel ratio, the air-fuel ratio deviation Δλ becomes a positive value, while if it is richer, the deviation Δλ becomes a negative value, which correspond to the situation where the stored oxygen quantity of
catalytic converter 8 is increasingly changed when the air-fuel ratio of the combustion air-fuel mixture is leaner than the stoichiometric air-fuel ratio, while the stored oxygen quantity ofcatalytic converter 8 is decreasingly changed when the air-fuel ratio of the combustion air-fuel mixture is richer than the stoichiometric air-fuel ratio. - A constant K is multiplied on the multiplication result of the new intake air quantity Q and the air-fuel ratio deviation Δλ, and this multiplication result is integrated one after another by an
integrator 102, to thereby obtain the stored oxygen quantity ofcatalytic converter 8. - Here, the new intake air quantity Q utilized in estimating the stored oxygen quantity is corrected to a value including the amount of recirculated exhaust gas during the exhaust gas recirculation state, so the stored oxygen quantity can be obtained based on the actual exhaust gas quantity even the exhaust gas recirculation is performed.
- Next, a deviation between the estimated value of the stored oxygen quantity output from
integrator 102 and the target value corresponding to approximately half the maximum storage oxygen quantity is computed. - Then, at a feedback correction
coefficient setting unit 103 input with data of deviation of the stored oxygen quantity, a feedback correction coefficient of the air-fuel ratio is computed so that the estimated value of the stored oxygen quantity corresponds to the target value. - That is, the feedback correction coefficient is set so that when the stored oxygen quantity is smaller than the target quantity, the air-fuel ratio is shifted to leaner so as to increase the stored oxygen quantity, and in contrast, when the stored oxygen quantity is greater than the target quantity, the air-fuel ratio is shifted to richer so as to eliminate the excessive oxygen thereby decreasing the stored oxygen quantity.
- At an injection
quantity computing unit 104, the above feedback correction coefficient is utilized, to correct a basic fuel injection quantity thereby computing a final fuel injection quantity, and an injection pulse signal corresponding to the computed final fuel injection quantity is output tofuel injection valve 5. - The entire contents of japanese patent application no. 2000-365226 filed Nov. 30, 2000 are incorporated herein by reference:
Claims (14)
1. An air-fuel ratio control device of an internal combustion engine comprising:
a fuel injection valve that injects fuel into said engine;
a catalytic converter disposed to an exhaust pipe of said engine;
an intake air quantity sensor that detects a new intake air quantity of said engine;
an oxygen sensor, disposed to said exhaust pipe on the upstream side of said catalytic converter, that detects an oxygen concentration of the exhaust;
an exhaust gas recirculation pipe that recirculates a portion of the exhaust gas of said engine into an intake pipe;
an exhaust gas recirculation rate detecting unit that detects a recirculation rate of the exhaust gas being recirculated via said exhaust gas recirculation pipe;
a new intake air quantity correcting unit that corrects the detection value of said new intake air quantity based on said exhaust gas recirculation rate;
an oxygen quantity estimating unit that estimates an oxygen quantity stored in said catalytic converter based on said oxygen concentration and said detection value of the new intake air quantity corrected based on the exhaust gas recirculation rate; and
a feedback control unit that feedback controls a fuel injection quantity of said fuel injection valve so that said oxygen quantity approximates a target quantity.
2. An air-fuel ratio control device of an internal combustion engine according to claim 1 , wherein
said new intake air quantity correcting unit corrects the detection value of said new intake air quantity to a higher value as the higher the exhaust gas recirculation rate is.
3. An air-fuel ratio control device of an internal combustion engine according to claim 1 , wherein
said new intake air quantity correcting unit comprises:
a correction coefficient setting unit that sets a correction coefficient according to said exhaust gas recirculation rate; and
a correction computing unit that multiplies said correction coefficient on the detection value of said new intake air quantity to output the multiplied result.
4. An air-fuel ratio control device of an internal combustion engine according to claim 1 , wherein
said oxygen quantity estimating unit comprises:
an air-fuel ratio deviation computing unit that computes a deviation between a stoichiometric air-fuel ratio and an air-fuel ratio corresponding to said oxygen concentration; and
an estimating unit that estimates the oxygen quantity stored in said catalytic converter based on said air-fuel ratio deviation and said corrected detection value of the new intake air quantity.
5. An air-fuel ratio control device of an internal combustion engine according to claim 1 , wherein
said oxygen quantity estimating unit comprises:
an air-fuel ratio deviation computing unit that computes a deviation between a stoichiometric air-fuel ratio and an air-fuel ratio corresponding to said oxygen concentration;
a first multiplying unit that multiplies said air-fuel ratio deviation and said corrected detection value of the new intake air quantity;
a second multiplying unit that multiplies the multiplied result of said first multiplying unit by a constant; and
an integrating unit that integrates the multiplied result of said second multiplying unit.
6. An air-fuel ratio control device of an internal combustion engine according to claim 1 , wherein
said feedback control unit comprises;
a target setting unit that sets half the oxygen quantity of the maximum oxygen quantity capable of being stored in said catalytic converter as said target value.
7. An air-fuel ratio control device of an internal combustion engine according to claim 1 , wherein
said feedback control unit comprises:
an oxygen quantity judging unit that judges whether said estimated oxygen quantity is greater than said target value or not;
a decremental correcting unit that decreasingly corrects said fuel injection quantity when the estimated oxygen quantity is smaller than said target value; and
an incremental correcting unit that increasingly corrects said fuel injection quantity when said estimated oxygen quantity is greater than said target value.
8. An air-fuel ratio control device of an internal combustion engine comprising:
a fuel injection valve that injects fuel into said engine;
a catalytic converter disposed to an exhaust pipe of said engine;
an intake air quantity sensor that detects a new intake air quantity of said engine;
an oxygen sensor, disposed to said exhaust pipe on the upstream side of said catalytic converter, that detects an oxygen concentration of the exhaust;
an exhaust gas recirculation pipe that recirculates a portion of the exhaust gas of said engine into an intake pipe;
exhaust gas recirculation rate detecting means for detecting a recirculation rate of the exhaust gas being recirculated via said exhaust gas recirculation pipe;
new intake air quantity correcting means for correcting the detection value of said new intake air quantity based on said exhaust gas recirculation rate;
oxygen quantity estimating means for estimating an oxygen quantity stored in said catalytic converter based on said oxygen concentration and said detection value of the new intake air quantity corrected based on the exhaust gas recirculation rate; and
feedback control means for feedback controlling a fuel injection quantity of said fuel injection valve so that said oxygen quantity approximates a target quantity.
9. An air-fuel ratio control method of an internal combustion engine comprising the steps of:
detecting a new intake air quantity of said engine;
detecting an oxygen concentration of the exhaust at the upstream side of a catalytic converter disposed to an exhaust pipe of said engine;
detecting a recirculation rate of the exhaust gas with respect to said engine;
correcting the detection value of said new intake air quantity based on said exhaust gas recirculation rate;
estimating an oxygen quantity stored in said catalytic converter based on said oxygen concentration and said detection value of the new intake air quantity corrected based on the exhaust gas recirculation rate; and
feedback controlling a fuel injection quantity of said fuel injection valve so that said oxygen quantity approximates a target quantity.
10. An air-fuel ratio control method of an internal combustion engine according to claim 9 , wherein
said step of correcting a new intake air quantity comprises the step of;
correcting the detection value of said new intake air quantity to a higher value as the higher the exhaust gas recirculation rate is.
11. An air-fuel ratio control method of an internal combustion engine according to claim 9 , wherein
said step of correcting a new intake air quantity comprises the steps of:
setting a correction coefficient according to said exhaust gas recirculation rate; and
multiplying said correction coefficient on the detection value of said new intake air quantity to output the multiplied result.
12. An air-fuel ratio control method of an internal combustion engine according to claim 9 , wherein
said step of estimating an oxygen quantity comprises the steps of:
computing a deviation between a stoichiometric air-fuel ratio and an air-fuel ratio corresponding to said oxygen concentration; and
estimating the oxygen quantity stored in said catalytic converter based on said air-fuel ratio deviation and said corrected detection value of the new intake air quantity.
13. An air-fuel ratio control method of an internal combustion engine according to claim 9 , wherein
said step of estimating an oxygen quantity comprises the steps of:
computing a deviation between a stoichiometric air-fuel ratio and an air-fuel ratio corresponding to said oxygen concentration;
multiplying said air-fuel ratio deviation and said corrected detection value of the new intake air quantity;
multiplying the multiplied result of said first multiplying unit by a constant; and
integrating the multiplied result of said second multiplying unit.
14. An air-fuel ratio control method of an internal combustion engine according to claim 9 , wherein
said step of feedback controlling a fuel injection quantity comprises the step of;
setting half the oxygen quantity of the maximum oxygen quantity capable of being stored in said catalytic converter as said target value.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000-365226 | 2000-11-30 | ||
| JP2000365226A JP2002161785A (en) | 2000-11-30 | 2000-11-30 | Air/fuel ratio control device for internal combustion engine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US20020062640A1 true US20020062640A1 (en) | 2002-05-30 |
Family
ID=18836038
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US09/987,641 Abandoned US20020062640A1 (en) | 2000-11-30 | 2001-11-15 | Device and method for controlling air-fuel ratio of internal combustion engine |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US20020062640A1 (en) |
| JP (1) | JP2002161785A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11092095B2 (en) * | 2019-07-03 | 2021-08-17 | Subaru Corporation | Engine system |
-
2000
- 2000-11-30 JP JP2000365226A patent/JP2002161785A/en active Pending
-
2001
- 2001-11-15 US US09/987,641 patent/US20020062640A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11092095B2 (en) * | 2019-07-03 | 2021-08-17 | Subaru Corporation | Engine system |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2002161785A (en) | 2002-06-07 |
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| AS | Assignment |
Owner name: UNISIA JECS CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TAKAHASHI, KOJI;OHKUMA, SHIGEO;REEL/FRAME:012310/0108 Effective date: 20011002 |
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| STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |