WO2020208390A1 - Control method and control device for internal combustion engine - Google Patents

Control method and control device for internal combustion engine Download PDF

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Publication number
WO2020208390A1
WO2020208390A1 PCT/IB2019/000414 IB2019000414W WO2020208390A1 WO 2020208390 A1 WO2020208390 A1 WO 2020208390A1 IB 2019000414 W IB2019000414 W IB 2019000414W WO 2020208390 A1 WO2020208390 A1 WO 2020208390A1
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WIPO (PCT)
Prior art keywords
internal combustion
combustion engine
air
fuel ratio
exhaust
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PCT/IB2019/000414
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French (fr)
Japanese (ja)
Inventor
木村容康
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日産自動車株式会社
ルノー エス． ア． エス．
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Application filed by 日産自動車株式会社, ルノー エス． ア． エス． filed Critical 日産自動車株式会社
Priority to PCT/IB2019/000414 priority Critical patent/WO2020208390A1/en
Priority to JP2021513013A priority patent/JP7115632B2/en
Publication of WO2020208390A1 publication Critical patent/WO2020208390A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K6/00—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00
    • B60K6/20—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs
    • B60K6/42—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs characterised by the architecture of the hybrid electric vehicle
    • B60K6/46—Series type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/04—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units
    • B60W10/06—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units including control of combustion engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/08—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing for rendering engine inoperative or idling
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D45/00—Electrical control not provided for in groups F02D41/00 - F02D43/00

Definitions

  • the present invention relates to a control method and a control device for an internal combustion engine having an air-fuel ratio sensor provided in an exhaust passage in a hybrid vehicle.
  • the internal combustion engine is motorized by an electric motor to a predetermined target speed at which fuel cut occurs after the vehicle is determined to stop, and after the fuel cut is performed, the air-fuel ratio sensor passes through the exhaust passage. I am learning about new energy.
  • Patent Document 1 since fresh air containing a small amount of unburned fuel after fuel cut flows to the air-fuel ratio sensor and is learned, the detected air-fuel ratio detects fresh air containing no unburned fuel. It is learned as a value on the rich side compared to the case of doing. Further, in such learning of the air-fuel ratio, the amount of unburned fuel is usually different at each learning, and there is a possibility that the air-fuel ratio detected at each learning may vary.
  • the present invention has been made in view of such problems, and provides a control method and a control device for an internal combustion engine capable of improving exhaust performance while ensuring combustion stability of the internal combustion engine. is there.
  • the present invention relates to a method for controlling an internal combustion engine that is operated with an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a hybrid vehicle.
  • the internal combustion engine is operated by a power generation motor generator. Motoring is performed, and the state of fresh air passing through the exhaust passage during motoring is learned by the air-fuel ratio sensor.
  • the exhaust performance can be improved while ensuring the combustion stability of the internal combustion engine.
  • FIG. 1 schematically shows the configuration of the series hybrid vehicle 1 of one embodiment.
  • the series hybrid vehicle 1 includes a power generation motor generator 2 that mainly operates as a generator, an internal combustion engine 3 that is used as a power generation internal combustion engine that drives the power generation motor generator 2 in response to a power generation request, and mainly a motor.
  • a traveling motor generator 5 that operates as a motor to drive the drive wheels 4 and 4, a battery 6 that temporarily stores the generated electric power, and an inverter device that performs power conversion between the battery 6 and the motor generators 2 and 5. 7 and are configured.
  • the power generation motor generator 2 is connected to the internal combustion engine 3 via a speed reducer 8 having various gears and the like.
  • the electric power obtained by driving the power generation motor generator 2 by the internal combustion engine 3 is stored in the battery 6 via the inverter device 7.
  • the traveling motor generator 5 is connected to the drive shaft 10 for the drive wheels 4 and 4 via a speed reducer 9 composed of various gears and the like.
  • the traveling motor generator 5 is driven and controlled via the inverter device 7 using the electric power of the battery 6.
  • the electric power at the time of regeneration of the traveling motor generator 5 is also stored in the battery 6 via the inverter device 7.
  • the inverter device 7 includes an inverter for the power generation motor generator 2 and an inverter for the traveling motor generator 5.
  • the inverter device 7 is controlled by a vehicle-side controller 11 that controls the running of the vehicle. That is, the operations of the motor generators 2 and 5 are controlled through the control of the inverter device 7 by the vehicle side controller 11. Signals such as the accelerator opening degree, the vehicle speed, and the amount of brake operation of the vehicle are input to the vehicle side controller 11, and signals indicating the charging state (so-called SOC) of the battery 6 are input.
  • SOC charging state
  • the charging state (SOC) is detected based on the terminal voltage of the battery 6 and the like.
  • the internal combustion engine 3 is controlled by the engine controller 12.
  • the engine controller 12 and the vehicle side controller 11 are connected to each other via the in-vehicle network 13 and exchange signals with each other.
  • the internal combustion engine 3 that drives the power generation motor generator 2 is operated via the engine controller 12 in response to a power generation request from the vehicle side including the state of charge (SOC) of the battery 6. That is, when the engine controller 12 receives a power generation request from the vehicle side controller 11 according to the accelerator pedal opening degree, the vehicle speed, or the like of the vehicle, the internal combustion engine 3 is controlled according to the power generation request.
  • the vehicle-side controller 11 and the engine controller 12 may be integrated as one controller.
  • FIG. 2 is a configuration explanatory diagram showing the system configuration of the internal combustion engine 3.
  • the internal combustion engine 3 is an in-cylinder direct injection type internal combustion engine having four cylinders 14, and is basically operated at a target air-fuel ratio in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio. That is, the internal combustion engine 3 basically performs lean burn that is leaner than the stoichiometric air-fuel ratio.
  • the target air-fuel ratio is set to, for example, 33.
  • the internal combustion engine 3 is provided with a fuel injection valve (not shown) and a spark plug 15 for injecting fuel into the cylinder 14 for each cylinder 14.
  • the injection amount and injection timing of the fuel injection valve and the ignition timing of the spark plug 15 are controlled by a control signal from the engine controller 12.
  • Each cylinder 14 has an intake port 16 that is opened and closed by a pair of intake valves (not shown) and an exhaust port 17 that is opened and closed by a pair of exhaust valves (not shown).
  • the opening / closing timing of the intake valve and the exhaust valve is controlled by a variable valve timing mechanism (VTC) provided on the intake side and the exhaust side, respectively, which are not shown.
  • VTC variable valve timing mechanism
  • the internal combustion engine 3 includes a turbocharger 18 as a supercharger.
  • the internal combustion engine 3 is connected to an intake passage 19 that communicates with the intake port 16 and an exhaust passage 20 that communicates with the exhaust port 17.
  • the intake passage 19 is provided with a throttle valve 21 that controls the amount of intake air.
  • the throttle valve 21 has an actuator such as an electric motor, and its opening degree is controlled by a control signal from the engine controller 12.
  • a compressor 18a of the turbocharger 18 is interposed on the upstream side of the throttle valve 21 of the intake passage 19. Further, an intercooler 22 for cooling the intake air compressed by the compressor 18a is provided on the downstream side of the throttle valve 21 of the intake passage 19.
  • the exhaust passage 20 is provided with an exhaust catalyst 23 made of a three-way catalyst.
  • a turbine 18b of the turbocharger 18 is provided on the upstream side of the exhaust passage 20 with respect to the exhaust catalyst 23.
  • the exhaust passage 20 is provided with an exhaust bypass passage 24 that bypasses the turbine 18b and connects the upstream side and the downstream side of the turbine 18b. The downstream end of the exhaust bypass passage 24 is connected to the exhaust passage 20 at a position upstream of the exhaust catalyst 23.
  • the exhaust bypass passage 24 is provided with an electric wastegate valve 25 that adjusts the amount of exhaust gas guided to the turbine 18b.
  • the opening degree of the wastegate valve 25 is controlled by a control signal from the engine controller 12.
  • An air-fuel ratio sensor 26 for detecting the air-fuel ratio of exhaust gas is provided on the downstream side of the exhaust passage 20 from the turbine 18b and on the upstream side of the exhaust catalyst 23. The value of the air-fuel ratio detected by the air-fuel ratio sensor 26 is input to the engine controller 12.
  • an exhaust pressure sensor 27 for detecting the exhaust pressure P of the internal combustion engine 3 is provided on the downstream side of the exhaust passage 20 from the turbine 18b and on the upstream side of the air-fuel ratio sensor 26. The value of the exhaust pressure P detected by the exhaust pressure sensor 27 is input to the engine controller 12.
  • the internal combustion engine 3 is provided with a vibration sensor (not shown) that detects the vibration of the internal combustion engine 3.
  • the value of vibration detected by the vibration sensor is input to the engine controller 12.
  • the air-fuel ratio sensor 26 is performed when the internal combustion engine 3 is motorized to a predetermined target rotation speed Na by the power generation motor generator 2 when the internal combustion engine 3 is started.
  • step S1 it is determined whether or not the engine controller 12 that controls the internal combustion engine 3 has a power generation request (restart request for the internal combustion engine 3) due to, for example, a decrease in the charging state (SOC). If there is a power generation request in step S1, the start in step S2, the power generating motor-generator 2, the motoring of the internal combustion engine 3 toward a predetermined target rotational speed N a corresponding to the power generation point as a best fuel consumption point To do. Thus, the engine speed N is increasing from zero to the predetermined target rotational speed N a, fresh air flowing into the exhaust passage 20 from the intake passage 19.
  • step S3 the air-fuel ratio sensor 26 causes the air-fuel ratio sensor 26 to flow to the air-fuel ratio sensor 26 during the motoring of the internal combustion engine 3, that is, fresh fresh air containing no fuel.
  • Anmospheric learning value I p of the air-fuel ratio sensor 26 is learned. This makes it possible to control the air-fuel ratio using the atmospheric learning value Ip of the air-fuel ratio sensor 26 as a reference for calculating the air-fuel ratio. For example, the state of the atmosphere around the vehicle changes depending on the altitude, atmospheric pressure, temperature, etc., but the accuracy of air-fuel ratio control is improved by learning the actual state of fresh air.
  • step S4 the atmospheric learning value Ip of the air-fuel ratio sensor 26 is corrected based on the exhaust pressure P detected by the exhaust pressure sensor 27.
  • the correction of the atmospheric learning value I p is made by referring to the map shown in FIG. 4 that represents the correlation between the exhaust gas pressure P and the atmospheric learning value I p. As shown in the map of FIG. 4, as the exhaust pressure P increases, the atmospheric learning value I p increases in proportion to the exhaust pressure P.
  • the atmospheric learning value I p By correcting the atmospheric learning value I p based on the exhaust pressure P so as to offset the proportional relationship between such an exhaust pressure P and atmospheric learning value I p, exhaust pressure during fresh air learning of the air-fuel ratio sensor 26 The influence of P can be reduced.
  • the atmospheric learning value Ip may be corrected by using the value of the exhaust pressure determined by the operating state of the internal combustion engine 3.
  • the pressure in the exhaust passage 20 is adjusted by appropriately adjusting the closing timing of the intake valve and the exhaust valve using the variable valve timing mechanism (VTC). Is maintained at a constant pressure (for example, the lowest pressure at which unburned fuel in the exhaust passage 20 can be scavenged), and then the air-fuel ratio sensor 26 learns the atmospheric learning value Ip. Is also good.
  • the constant pressure may be maintained by controlling the flow rate of fresh air using the throttle valve 21 or controlling the flow rate of fresh air using the turbocharger 18 instead of using the variable valve timing mechanism. ..
  • step S5 After learning the atmospheric learning value Ip , in step S5, it is determined whether or not the engine rotation speed N has reached a predetermined target rotation speed Na. This determination is the engine speed N is repeated until it reaches the predetermined target rotational speed N a.
  • step S6 the fuel is injected into each cylinder 14, by igniting a mixture of air and fuel, the engine 3 To start. At this time, the power generation motor generator 2 that has been motorizing the internal combustion engine 3 starts power generation.
  • step S11 it is determined whether or not a predetermined time T1 has elapsed since the start of the internal combustion engine 3. Until the predetermined time T1 elapses in step S11, in the air-fuel ratio control after the start of the internal combustion engine 3 in step S12, the air-fuel ratio on the rich side slightly from the final target air-fuel ratio (for example, 33) (after start).
  • the internal combustion engine 3 is operated at the air-fuel ratio).
  • This air-fuel ratio control is so-called open loop control.
  • the air-fuel ratio after starting is set in consideration of a margin for variation in air-fuel ratio control.
  • the target air-fuel ratio is set to a very lean air-fuel ratio such as 33 as in this embodiment, the exhaust composition is good, but in general, the combustion stability of the internal combustion engine 3 is ensured. Is difficult. Therefore, instead of operating the internal combustion engine 3 at the target air-fuel ratio immediately after the start of the internal combustion engine 3, the variation in the expected air-fuel ratio in consideration of combustion stability is set to be richer than the target air-fuel ratio. After starting, the internal combustion engine 3 is operated at the air-fuel ratio. As a result, combustion stability is ensured.
  • step S13 the vibration of the internal combustion engine 3 is detected by the vibration sensor provided in the internal combustion engine 3.
  • the combustion variation index COV Coefficient of Variation
  • This variation index COV indicates the variation with respect to the desired combustion state of the internal combustion engine 3, and the smaller the value, the more stable the combustion.
  • the variation index COV may be calculated based on parameters other than the vibration detected by the vibration sensor, for example, the combustion pressure detected by the combustion pressure sensor or the in-cylinder pressure detected by the in-cylinder pressure sensor.
  • step S14 feedback control of the air-fuel ratio is performed so that the variation index COV becomes a predetermined level while controlling the air-fuel ratio detected by the air-fuel ratio sensor 26 so as to be as close as possible to the target air-fuel ratio (for example, 33). ..
  • the air-fuel ratio sensor 26 learns the state of fresh fresh air containing no fuel, that is, the atmospheric learning value Ip of the air-fuel ratio sensor 26. To do.
  • the air-fuel ratio can be controlled using the atmospheric learning value Ip as the reference for calculating the air-fuel ratio, and the error between the target air-fuel ratio of the internal combustion engine 3 and the actual air-fuel ratio becomes small. Therefore, in the air-fuel ratio control of the internal combustion engine 3, the combustion stability of the internal combustion engine 3 can be ensured under a very lean target air-fuel ratio (for example, 33).
  • NOx can be reduced and exhaust performance can be improved.
  • the atmospheric learning value Ip is corrected by referring to the map showing the correlation between the exhaust pressure P and the atmospheric learning value Ip .
  • an error occurs in the atmospheric learning value Ip due to the influence of the exhaust pressure P of the internal combustion engine 3.
  • the atmospheric learning value Ip is corrected based on the proportional relationship between the exhaust pressure P and the atmospheric learning value Ip shown in the map.
  • an internal combustion engine is cranked by a starter motor and then ignited and burned like a general internal combustion engine, it takes a relatively long time for the combustion state of the internal combustion engine to stabilize.
  • the internal combustion engine 3 operates at a target air-fuel ratio that is much leaner than the stoichiometric air-fuel ratio, but the internal combustion engine 3 can also operate at another air-fuel ratio.
  • the catalyst should be activated early, such as when starting an engine cooler, it may be operated on the rich side of the stoichiometric air-fuel ratio, or the stoichiometric air-fuel ratio may be set as the target air-fuel ratio. ..

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Hybrid Electric Vehicles (AREA)
  • Control Of Vehicle Engines Or Engines For Specific Uses (AREA)

Abstract

A hybrid vehicle (1) comprises an internal combustion engine (3) that runs at an air-fuel ratio leaner than a stoichiometric air-fuel ratio. The internal combustion engine (3) comprises an air-fuel ratio sensor (26) that detects the state of fresh air passing through an exhaust path (20). In a control method of this internal combustion engine (3), when there is a restart request, the internal combustion engine (3) is motored by a motor generator (2) for power generation, and the state of fresh air passing through the exhaust path (20) during motoring is learned by the air-fuel ratio sensor (26).

Description

内燃機関の制御方法および制御装置Internal combustion engine control method and control device
　本発明は、ハイブリッド車両において、排気通路に設けられた空燃比センサを有する内燃機関の制御方法および制御装置に関する。 The present invention relates to a control method and a control device for an internal combustion engine having an air-fuel ratio sensor provided in an exhaust passage in a hybrid vehicle.
　特許文献１に記載のハイブリッド車両では、車両の停止判定後に電動機によって内燃機関を燃料カットが生じる所定の目標回転数までモータリングし、燃料カットが行われた後に、空燃比センサによって排気通路を通過する新気の学習を行っている。 In the hybrid vehicle described in Patent Document 1, the internal combustion engine is motorized by an electric motor to a predetermined target speed at which fuel cut occurs after the vehicle is determined to stop, and after the fuel cut is performed, the air-fuel ratio sensor passes through the exhaust passage. I am learning about new energy.
　上記特許文献１では、燃料カット後の未燃の燃料を僅かに含む新気が空燃比センサへ流れて学習されるので、検出された空燃比が、未燃の燃料を含まない新気を検出する場合と比べてリッチ側の値として学習される。さらに、このような空燃比の学習は、各学習時に未燃の燃料の量が異なることが通常であり、各学習時に検出された空燃比に、ばらつきが生じる虞があった。 In Patent Document 1, since fresh air containing a small amount of unburned fuel after fuel cut flows to the air-fuel ratio sensor and is learned, the detected air-fuel ratio detects fresh air containing no unburned fuel. It is learned as a value on the rich side compared to the case of doing. Further, in such learning of the air-fuel ratio, the amount of unburned fuel is usually different at each learning, and there is a possibility that the air-fuel ratio detected at each learning may vary.
　また、近年、ＮＯｘを低減して排気性能を向上させることを目的として、理論空燃比よりも非常にリーンな空燃比、例えば空気過剰率λ２以上のリーンな空燃比で希薄燃焼を行いたいという要求がある。 Further, in recent years, for the purpose of reducing NOx and improving exhaust performance, there is a demand for lean combustion at an air-fuel ratio that is much leaner than the stoichiometric air-fuel ratio, for example, a lean air-fuel ratio of λ2 or more. There is.
　しかし、このような非常にリーンな空燃比で希薄燃焼を行う際には、空燃比がリーンになるほど、内燃機関の燃焼安定性を確保することが困難となるという問題があった。 However, when lean combustion is performed with such a very lean air-fuel ratio, there is a problem that it becomes difficult to secure the combustion stability of the internal combustion engine as the air-fuel ratio becomes leaner.
　本発明はこのような課題に着目してなされたものであり、内燃機関の燃焼安定性を確保しつつ、排気性能を向上させることが可能な内燃機関の制御方法および制御装置を提供するものである。 The present invention has been made in view of such problems, and provides a control method and a control device for an internal combustion engine capable of improving exhaust performance while ensuring combustion stability of the internal combustion engine. is there.
特開２０１３−２０３３２４号公報Japanese Unexamined Patent Publication No. 2013-203324
　本発明は、ハイブリッド車両において、空燃比が理論空燃比よりもリーンな状態で作動される内燃機関の制御方法に関し、内燃機関の再始動要求があったときに、発電用モータジェネレータにより内燃機関をモータリングし、モータリング中に排気通路を通過する新気の状態を空燃比センサによって学習する。 The present invention relates to a method for controlling an internal combustion engine that is operated with an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a hybrid vehicle. When an internal combustion engine is requested to be restarted, the internal combustion engine is operated by a power generation motor generator. Motoring is performed, and the state of fresh air passing through the exhaust passage during motoring is learned by the air-fuel ratio sensor.
　従って、学習した新気の状態を空燃比の算出の基準とした空燃比制御が可能となる。 Therefore, it is possible to control the air-fuel ratio using the learned state of fresh air as a reference for calculating the air-fuel ratio.
　本発明によれば、内燃機関の燃焼安定性を確保しつつ、排気性能を向上させることができる。 According to the present invention, the exhaust performance can be improved while ensuring the combustion stability of the internal combustion engine.
一実施例のシリーズハイブリッド車両の構成説明図である。It is a block diagram of the series hybrid vehicle of one Example. 内燃機関の構成説明図である。It is a block diagram of an internal combustion engine. 内燃機関のモータリング中の新気学習を示すフローチャートである。It is a flowchart which shows the freshness learning during the motoring of an internal combustion engine. 排気圧力と大気学習値との相関関係を示すマップである。It is a map showing the correlation between the exhaust pressure and the atmospheric learning value. 内燃機関の始動後における空燃比の制御を示すフローチャートである。It is a flowchart which shows the control of the air-fuel ratio after the start of an internal combustion engine.
　以下、図面を参照しながら本発明の一実施例について説明する。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
　図１は、一実施例のシリーズハイブリッド車両１の構成を概略的に示している。このシリーズハイブリッド車両１は、主に発電機として動作する発電用モータジェネレータ２と、この発電用モータジェネレータ２を発電要求に応じて駆動する発電用内燃機関として用いられる内燃機関３と、主にモータとして動作して駆動輪４，４を駆動する走行用モータジェネレータ５と、発電した電力を一時的に蓄えるバッテリ６と、該バッテリ６とモータジェネレータ２，５との間で電力変換を行うインバータ装置７と、を備えて構成されている。発電用モータジェネレータ２は、種々のギア等を有する減速機８を介して内燃機関３に接続されている。内燃機関３が発電用モータジェネレータ２を駆動することによって得られた電力は、インバータ装置７を介してバッテリ６に蓄えられる。走行用モータジェネレータ５は、種々のギア等から構成される減速機９を介して、駆動輪４，４用の駆動シャフト１０に接続されている。走行用モータジェネレータ５は、バッテリ６の電力を用いてインバータ装置７を介して駆動制御される。走行用モータジェネレータ５の回生時の電力は、やはりインバータ装置７を介してバッテリ６に蓄えられる。なお、インバータ装置７は、発電用モータジェネレータ２用のインバータと走行用モータジェネレータ５用のインバータとを含んで構成されている。 FIG. 1 schematically shows the configuration of the series hybrid vehicle 1 of one embodiment. The series hybrid vehicle 1 includes a power generation motor generator 2 that mainly operates as a generator, an internal combustion engine 3 that is used as a power generation internal combustion engine that drives the power generation motor generator 2 in response to a power generation request, and mainly a motor. A traveling motor generator 5 that operates as a motor to drive the drive wheels 4 and 4, a battery 6 that temporarily stores the generated electric power, and an inverter device that performs power conversion between the battery 6 and the motor generators 2 and 5. 7 and are configured. The power generation motor generator 2 is connected to the internal combustion engine 3 via a speed reducer 8 having various gears and the like. The electric power obtained by driving the power generation motor generator 2 by the internal combustion engine 3 is stored in the battery 6 via the inverter device 7. The traveling motor generator 5 is connected to the drive shaft 10 for the drive wheels 4 and 4 via a speed reducer 9 composed of various gears and the like. The traveling motor generator 5 is driven and controlled via the inverter device 7 using the electric power of the battery 6. The electric power at the time of regeneration of the traveling motor generator 5 is also stored in the battery 6 via the inverter device 7. The inverter device 7 includes an inverter for the power generation motor generator 2 and an inverter for the traveling motor generator 5.
　インバータ装置７は、車両の走行を司る車両側コントローラ１１によって制御される。つまり、車両側コントローラ１１によるインバータ装置７の制御を介してモータジェネレータ２，５の動作が制御される。車両側コントローラ１１には、車両のアクセル開度や車速、ブレーキ操作量等の信号が入力され、かつバッテリ６の充電状態（いわゆるＳＯＣ）を示す信号が入力されている。なお、充電状態（ＳＯＣ）は、バッテリ６の端子電圧等に基づいて検出される。 The inverter device 7 is controlled by a vehicle-side controller 11 that controls the running of the vehicle. That is, the operations of the motor generators 2 and 5 are controlled through the control of the inverter device 7 by the vehicle side controller 11. Signals such as the accelerator opening degree, the vehicle speed, and the amount of brake operation of the vehicle are input to the vehicle side controller 11, and signals indicating the charging state (so-called SOC) of the battery 6 are input. The charging state (SOC) is detected based on the terminal voltage of the battery 6 and the like.
　また、内燃機関３は、エンジンコントローラ１２によって制御される。このエンジンコントローラ１２と車両側コントローラ１１とは車両内ネットワーク１３を介して接続されており、互いの信号の授受を行っている。発電用モータジェネレータ２を駆動する内燃機関３は、エンジンコントローラ１２を介して、バッテリ６の充電状態（ＳＯＣ）等を含む車両側からの発電要求に応じて運転される。つまり、車両のアクセルペダル開度や車速等に応じて車両側コントローラ１１からエンジンコントローラ１２が発電要求を受けると、その発電要求に応じて内燃機関３が制御される。なお、車両側コントローラ１１とエンジンコントローラ１２とが一つのコントローラとして統合された構成であっても良い。 Further, the internal combustion engine 3 is controlled by the engine controller 12. The engine controller 12 and the vehicle side controller 11 are connected to each other via the in-vehicle network 13 and exchange signals with each other. The internal combustion engine 3 that drives the power generation motor generator 2 is operated via the engine controller 12 in response to a power generation request from the vehicle side including the state of charge (SOC) of the battery 6. That is, when the engine controller 12 receives a power generation request from the vehicle side controller 11 according to the accelerator pedal opening degree, the vehicle speed, or the like of the vehicle, the internal combustion engine 3 is controlled according to the power generation request. The vehicle-side controller 11 and the engine controller 12 may be integrated as one controller.
　図２は、内燃機関３のシステム構成を示した構成説明図である。この内燃機関３は、４つの気筒１４を有した筒内直噴型内燃機関であって、基本的に空燃比が理論空燃比よりも大きい目標空燃比で作動される。つまり、内燃機関３は、基本的に理論空燃比よりもリーンな希薄燃焼を行うものである。ここで、目標空燃比は、例えば３３に設定される。内燃機関３には、気筒１４内に燃料を噴射する図示せぬ燃料噴射弁と点火プラグ１５が気筒１４毎に設けられている。上記燃料噴射弁の噴射量および噴射時期、並びに点火プラグ１５の点火時期は、エンジンコントローラ１２からの制御信号によって制御される。各気筒１４は、図示せぬ一対の吸気弁によって開閉作動される吸気ポート１６と、図示せぬ一対の排気弁によって開閉作動される排気ポート１７とを有している。吸気弁および排気弁の開閉時期は、吸気側および排気側にそれぞれ設けられた図示せぬ可変バルブタイミング機構（ＶＴＣ）によって制御される。また、内燃機関３は、過給機としてターボチャージャ１８を備えている。 FIG. 2 is a configuration explanatory diagram showing the system configuration of the internal combustion engine 3. The internal combustion engine 3 is an in-cylinder direct injection type internal combustion engine having four cylinders 14, and is basically operated at a target air-fuel ratio in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio. That is, the internal combustion engine 3 basically performs lean burn that is leaner than the stoichiometric air-fuel ratio. Here, the target air-fuel ratio is set to, for example, 33. The internal combustion engine 3 is provided with a fuel injection valve (not shown) and a spark plug 15 for injecting fuel into the cylinder 14 for each cylinder 14. The injection amount and injection timing of the fuel injection valve and the ignition timing of the spark plug 15 are controlled by a control signal from the engine controller 12. Each cylinder 14 has an intake port 16 that is opened and closed by a pair of intake valves (not shown) and an exhaust port 17 that is opened and closed by a pair of exhaust valves (not shown). The opening / closing timing of the intake valve and the exhaust valve is controlled by a variable valve timing mechanism (VTC) provided on the intake side and the exhaust side, respectively, which are not shown. Further, the internal combustion engine 3 includes a turbocharger 18 as a supercharger.
　内燃機関３には、吸気ポート１６と連通する吸気通路１９と、排気ポート１７と連通する排気通路２０とが接続されている。 The internal combustion engine 3 is connected to an intake passage 19 that communicates with the intake port 16 and an exhaust passage 20 that communicates with the exhaust port 17.
　吸気通路１９には、吸入空気量を制御するスロットルバルブ２１が設けられている。このスロットルバルブ２１は、例えば電動モータ等のアクチュエータを有しており、エンジンコントローラ１２からの制御信号によって、その開度が制御されている。吸気通路１９のスロットルバルブ２１よりも上流側には、ターボチャージャ１８のコンプレッサ１８ａが介装されている。また、吸気通路１９のスロットルバルブ２１よりも下流側には、コンプレッサ１８ａにより圧縮された吸入空気を冷却するインタークーラ２２が設けられている。 The intake passage 19 is provided with a throttle valve 21 that controls the amount of intake air. The throttle valve 21 has an actuator such as an electric motor, and its opening degree is controlled by a control signal from the engine controller 12. A compressor 18a of the turbocharger 18 is interposed on the upstream side of the throttle valve 21 of the intake passage 19. Further, an intercooler 22 for cooling the intake air compressed by the compressor 18a is provided on the downstream side of the throttle valve 21 of the intake passage 19.
　また、排気通路２０には、三元触媒からなる排気触媒２３が設けられている。排気通路２０の排気触媒２３よりも上流側には、ターボチャージャ１８のタービン１８ｂが設けられている。さらに、排気通路２０には、タービン１８ｂを迂回してタービン１８ｂの上流側と下流側とを接続する排気バイパス通路２４が設けられている。排気バイパス通路２４の下流側端部は、排気触媒２３よりも上流側の位置で排気通路２０に接続されている。 Further, the exhaust passage 20 is provided with an exhaust catalyst 23 made of a three-way catalyst. A turbine 18b of the turbocharger 18 is provided on the upstream side of the exhaust passage 20 with respect to the exhaust catalyst 23. Further, the exhaust passage 20 is provided with an exhaust bypass passage 24 that bypasses the turbine 18b and connects the upstream side and the downstream side of the turbine 18b. The downstream end of the exhaust bypass passage 24 is connected to the exhaust passage 20 at a position upstream of the exhaust catalyst 23.
　排気バイパス通路２４には、タービン１８ｂへ導かれる排気量を調整する電動のウエストゲートバルブ２５が設けられている。ウエストゲートバルブ２５の開度は、エンジンコントローラ１２からの制御信号によって制御される。 The exhaust bypass passage 24 is provided with an electric wastegate valve 25 that adjusts the amount of exhaust gas guided to the turbine 18b. The opening degree of the wastegate valve 25 is controlled by a control signal from the engine controller 12.
　排気通路２０のタービン１８ｂよりも下流側で、かつ排気触媒２３よりも上流側には、排気の空燃比を検出する空燃比センサ２６が設けられている。この空燃比センサ２６によって検出された空燃比の値は、エンジンコントローラ１２へ入力される。 An air-fuel ratio sensor 26 for detecting the air-fuel ratio of exhaust gas is provided on the downstream side of the exhaust passage 20 from the turbine 18b and on the upstream side of the exhaust catalyst 23. The value of the air-fuel ratio detected by the air-fuel ratio sensor 26 is input to the engine controller 12.
　また、排気通路２０のタービン１８ｂよりも下流側で、かつ空燃比センサ２６よりも上流側には、内燃機関３の排気圧力Ｐを検出する排気圧力センサ２７が設けられている。この排気圧力センサ２７によって検出された排気圧力Ｐの値は、エンジンコントローラ１２へ入力される。 Further, an exhaust pressure sensor 27 for detecting the exhaust pressure P of the internal combustion engine 3 is provided on the downstream side of the exhaust passage 20 from the turbine 18b and on the upstream side of the air-fuel ratio sensor 26. The value of the exhaust pressure P detected by the exhaust pressure sensor 27 is input to the engine controller 12.
　また、内燃機関３には、該内燃機関３の振動を検出する図示せぬ振動センサが設けられている。振動センサによって検出された振動の値は、エンジンコントローラ１２へ入力される。 Further, the internal combustion engine 3 is provided with a vibration sensor (not shown) that detects the vibration of the internal combustion engine 3. The value of vibration detected by the vibration sensor is input to the engine controller 12.
　次に、図３のフローチャートを参照して、内燃機関３の始動に際して発電用モータジェネレータ２によって所定の目標回転数Ｎａまで内燃機関３のモータリングを行うときに実施される、空燃比センサ２６の新気学習を説明する。 Next, referring to the flowchart of FIG. 3, the air-fuel ratio sensor 26 is performed when the internal combustion engine 3 is motorized to a predetermined target rotation speed Na by the power generation motor generator 2 when the internal combustion engine 3 is started. Explain the fresh learning of.
　まず、ステップＳ１において、例えば充電状態（ＳＯＣ）が低下したことにより、内燃機関３を制御するエンジンコントローラ１２に発電要求（内燃機関３の再始動要求）があるか否かを判定する。ステップＳ１において発電要求がある場合には、ステップＳ２において、発電用モータジェネレータ２によって、最良燃費点となる発電点に対応した所定の目標回転数Ｎａに向けて内燃機関３のモータリングを開始する。これにより、機関回転数Ｎがゼロから所定の目標回転数Ｎａへ向かって増加し、新気が吸気通路１９から排気通路２０へ通流する。 First, in step S1, it is determined whether or not the engine controller 12 that controls the internal combustion engine 3 has a power generation request (restart request for the internal combustion engine 3) due to, for example, a decrease in the charging state (SOC). If there is a power generation request in step S1, the start in step S2, the power generating motor-generator 2, the motoring of the internal combustion engine 3 toward a predetermined target rotational speed N a corresponding to the power generation point as a best fuel consumption point To do. Thus, the engine speed N is increasing from zero to the predetermined target rotational speed N a, fresh air flowing into the exhaust passage 20 from the intake passage 19.
　ステップＳ２から僅かに時間が経過した後に、ステップＳ３において、空燃比センサ２６によって、内燃機関３のモータリング中に空燃比センサ２６に流れる新気の状態、つまり燃料を含んでいない新鮮な新気の状態（空燃比センサ２６の大気学習値Ｉｐ）を学習する。これにより、空燃比センサ２６の大気学習値Ｉｐを空燃比の算出の基準とした空燃比制御が可能となる。例えば、標高、気圧、温度等によって車両周囲の大気の状態が変化するが、実際の新気の状態を学習することで、空燃比制御の精度が向上する。 After a short time has passed from step S2, in step S3, the air-fuel ratio sensor 26 causes the air-fuel ratio sensor 26 to flow to the air-fuel ratio sensor 26 during the motoring of the internal combustion engine 3, that is, fresh fresh air containing no fuel. (Atmospheric learning value I p of the air-fuel ratio sensor 26) is learned. This makes it possible to control the air-fuel ratio using the atmospheric learning value Ip of the air-fuel ratio sensor 26 as a reference for calculating the air-fuel ratio. For example, the state of the atmosphere around the vehicle changes depending on the altitude, atmospheric pressure, temperature, etc., but the accuracy of air-fuel ratio control is improved by learning the actual state of fresh air.
　次に、ステップＳ４において、排気圧力センサ２７によって検出された排気圧力Ｐに基づいて空燃比センサ２６の大気学習値Ｉｐを補正する。この大気学習値Ｉｐの補正は、排気圧力Ｐと大気学習値Ｉｐとの相関関係を表す図４に示すマップを参照することにより行われる。図４のマップに示すように、排気圧力Ｐが高くなるほど、この排気圧力Ｐに比例して大気学習値Ｉｐが大きくなる。このような排気圧力Ｐと大気学習値Ｉｐとの比例関係を相殺するように排気圧力Ｐに基づいて大気学習値Ｉｐを補正することで、空燃比センサ２６の新気学習時の排気圧力Ｐの影響を少なくすることができる。また、排気圧力Ｐを実際に検出する代わりに、内燃機関３の運転状態によって決定される排気圧力の値を用いて大気学習値Ｉｐを補正しても良い。なお、排気圧力Ｐに基づいて大気学習値Ｉｐを補正する代わりに、可変バルブタイミング機構（ＶＴＣ）を用いて吸気弁や排気弁の閉時期を適宜調整することにより、排気通路２０内の圧力を一定の圧力（例えば、排気通路２０内の未燃の燃料を掃気することが可能な最も低い圧力）に維持したうえで、空燃比センサ２６の大気学習値Ｉｐの学習を行うようにしても良い。なお、上記の一定の圧力の維持は、可変バルブタイミング機構を用いる代わりに、スロットルバルブ２１を用いた新気の流量制御や、ターボチャージャ１８を用いた新気の流量制御によって行われても良い。 Next, in step S4, the atmospheric learning value Ip of the air-fuel ratio sensor 26 is corrected based on the exhaust pressure P detected by the exhaust pressure sensor 27. The correction of the atmospheric learning value I p is made by referring to the map shown in FIG. 4 that represents the correlation between the exhaust gas pressure P and the atmospheric learning value I p. As shown in the map of FIG. 4, as the exhaust pressure P increases, the atmospheric learning value I p increases in proportion to the exhaust pressure P. By correcting the atmospheric learning value I p based on the exhaust pressure P so as to offset the proportional relationship between such an exhaust pressure P and atmospheric learning value I p, exhaust pressure during fresh air learning of the air-fuel ratio sensor 26 The influence of P can be reduced. Further, instead of actually detecting the exhaust pressure P, the atmospheric learning value Ip may be corrected by using the value of the exhaust pressure determined by the operating state of the internal combustion engine 3. Instead of correcting the atmospheric learning value Ip based on the exhaust pressure P, the pressure in the exhaust passage 20 is adjusted by appropriately adjusting the closing timing of the intake valve and the exhaust valve using the variable valve timing mechanism (VTC). Is maintained at a constant pressure (for example, the lowest pressure at which unburned fuel in the exhaust passage 20 can be scavenged), and then the air-fuel ratio sensor 26 learns the atmospheric learning value Ip. Is also good. The constant pressure may be maintained by controlling the flow rate of fresh air using the throttle valve 21 or controlling the flow rate of fresh air using the turbocharger 18 instead of using the variable valve timing mechanism. ..
　大気学習値Ｉｐの学習後には、ステップＳ５において、機関回転数Ｎが所定の目標回転数Ｎａに到達したか否かを判定する。この判定は、機関回転数Ｎが所定の目標回転数Ｎａに到達するまで繰り返し行われる。ステップＳ５において機関回転数Ｎが所定の目標回転数Ｎａに到達したときには、ステップＳ６において、各気筒１４内に燃料を噴射し、空気と燃料との混合気に点火することで、内燃機関３を始動する。このとき、内燃機関３のモータリングを行っていた発電用モータジェネレータ２は発電を開始する。 After learning the atmospheric learning value Ip , in step S5, it is determined whether or not the engine rotation speed N has reached a predetermined target rotation speed Na. This determination is the engine speed N is repeated until it reaches the predetermined target rotational speed N a. When the engine speed N has reached the predetermined target rotational speed N a in step S5, in step S6, the fuel is injected into each cylinder 14, by igniting a mixture of air and fuel, the engine 3 To start. At this time, the power generation motor generator 2 that has been motorizing the internal combustion engine 3 starts power generation.
　次に、図５のフローチャートを参照して、内燃機関３の始動後における空燃比制御を説明する。 Next, the air-fuel ratio control after the start of the internal combustion engine 3 will be described with reference to the flowchart of FIG.
　まず、ステップＳ１１において、内燃機関３の始動開始から所定の時間Ｔ１を経過したか否かを判定する。ステップＳ１１において所定の時間Ｔ１を経過するまでは、ステップＳ１２の内燃機関３の始動後の空燃比制御において、最終的な目標空燃比（例えば３３）よりも僅かにリッチ側の空燃比（始動後空燃比）で内燃機関３を作動する。この空燃比制御は、所謂オープンループ制御となる。ここで、始動後空燃比は、空燃比制御のばらつきに対するマージンを考慮して設定されている。本実施例のように目標空燃比が３３のような非常にリーンな空燃比に設定されている場合には、排気組成が良好である反面、一般に、内燃機関３の燃焼安定性を確保することが困難である。従って、内燃機関３の始動直後に内燃機関３を目標空燃比で作動するのではなく、燃焼安定性を考慮して予想される空燃比のばらつき分だけ目標空燃比よりもリッチ側に設定された始動後空燃比で内燃機関３を作動する。これにより、燃焼安定性が確保される。 First, in step S11, it is determined whether or not a predetermined time T1 has elapsed since the start of the internal combustion engine 3. Until the predetermined time T1 elapses in step S11, in the air-fuel ratio control after the start of the internal combustion engine 3 in step S12, the air-fuel ratio on the rich side slightly from the final target air-fuel ratio (for example, 33) (after start). The internal combustion engine 3 is operated at the air-fuel ratio). This air-fuel ratio control is so-called open loop control. Here, the air-fuel ratio after starting is set in consideration of a margin for variation in air-fuel ratio control. When the target air-fuel ratio is set to a very lean air-fuel ratio such as 33 as in this embodiment, the exhaust composition is good, but in general, the combustion stability of the internal combustion engine 3 is ensured. Is difficult. Therefore, instead of operating the internal combustion engine 3 at the target air-fuel ratio immediately after the start of the internal combustion engine 3, the variation in the expected air-fuel ratio in consideration of combustion stability is set to be richer than the target air-fuel ratio. After starting, the internal combustion engine 3 is operated at the air-fuel ratio. As a result, combustion stability is ensured.
　ステップＳ１１において内燃機関３の始動開始から所定の時間Ｔ１を経過した場合には、ステップＳ１３，Ｓ１４により示される、内燃機関３の振動検出ならびに空燃比センサ２６による空燃比検出に基づく空燃比のフィードバック制御を行う。ステップＳ１３では、内燃機関３に設けられた振動センサによって、内燃機関３の振動を検出する。そして、振動センサによって検出された振動に基づいて、燃焼のばらつき指標ＣＯＶ（Ｃｏｅｆｆｉｃｉｅｎｔ　ｏｆ　Ｖａｒｉａｔｉｏｎ）を算出する。このばらつき指標ＣＯＶは、内燃機関３の望ましい燃焼状態に対するばらつきを示すものであり、値が小さいほど燃焼が安定している。なお、ばらつき指標ＣＯＶの算出は、振動センサによって検出された振動以外のパラメータ、例えば燃焼圧センサによって検出された燃焼圧や、筒内圧センサによって検出された筒内圧に基づいて行われても良い。 When a predetermined time T1 has elapsed from the start of the internal combustion engine 3 in step S11, the air-fuel ratio feedback based on the vibration detection of the internal combustion engine 3 and the air-fuel ratio detection by the air-fuel ratio sensor 26 shown in steps S13 and S14. Take control. In step S13, the vibration of the internal combustion engine 3 is detected by the vibration sensor provided in the internal combustion engine 3. Then, the combustion variation index COV (Coefficient of Variation) is calculated based on the vibration detected by the vibration sensor. This variation index COV indicates the variation with respect to the desired combustion state of the internal combustion engine 3, and the smaller the value, the more stable the combustion. The variation index COV may be calculated based on parameters other than the vibration detected by the vibration sensor, for example, the combustion pressure detected by the combustion pressure sensor or the in-cylinder pressure detected by the in-cylinder pressure sensor.
　そして、ステップＳ１４において、空燃比センサ２６により検出される空燃比が目標空燃比（例えば３３）にできるだけ近づくように制御しつつ、ばらつき指標ＣＯＶが所定レベルとなるように空燃比のフィードバック制御を行う。 Then, in step S14, feedback control of the air-fuel ratio is performed so that the variation index COV becomes a predetermined level while controlling the air-fuel ratio detected by the air-fuel ratio sensor 26 so as to be as close as possible to the target air-fuel ratio (for example, 33). ..
　上記のように、本実施例では、内燃機関３のモータリング中に、空燃比センサ２６によって、燃料を含んでいない新鮮な新気の状態、即ち空燃比センサ２６の大気学習値Ｉｐを学習する。これにより、大気学習値Ｉｐを空燃比の算出の基準とした空燃比制御が可能となり、内燃機関３の目標空燃比と実空燃比との誤差が小さくなる。従って、内燃機関３の空燃比制御において、非常にリーンな目標空燃比（例えば３３）の下で内燃機関３の燃焼安定性を確保することができる。本実施例のように理論空燃比と比べて非常にリーンな空燃比で内燃機関３を作動することにより、ＮＯｘを減少し、排気性能を向上させることができる。 As described above, in the present embodiment, during the motoring of the internal combustion engine 3, the air-fuel ratio sensor 26 learns the state of fresh fresh air containing no fuel, that is, the atmospheric learning value Ip of the air-fuel ratio sensor 26. To do. As a result, the air-fuel ratio can be controlled using the atmospheric learning value Ip as the reference for calculating the air-fuel ratio, and the error between the target air-fuel ratio of the internal combustion engine 3 and the actual air-fuel ratio becomes small. Therefore, in the air-fuel ratio control of the internal combustion engine 3, the combustion stability of the internal combustion engine 3 can be ensured under a very lean target air-fuel ratio (for example, 33). By operating the internal combustion engine 3 at an air-fuel ratio that is very lean compared to the stoichiometric air-fuel ratio as in this embodiment, NOx can be reduced and exhaust performance can be improved.
　また、本実施例では、排気圧力Ｐと大気学習値Ｉｐとの相関関係を示すマップを参照することにより大気学習値Ｉｐを補正する。空燃比センサ２６による新気の学習時には、内燃機関３の排気圧力Ｐの影響を受けて大気学習値Ｉｐに誤差が生じる。この誤差を小さくするために、本実施例では、上記マップに示された排気圧力Ｐと大気学習値Ｉｐとの比例関係に基づいて大気学習値Ｉｐを補正している。これにより、内燃機関３の目標空燃比と実空燃比との誤差を小さくし、目標空燃比にさらに近い空燃比で内燃機関３を作動することができる。よって、内燃機関３の燃焼安定性を確保しつつ、排気性能を効率的に向上させることができる。 Further, in this embodiment, the atmospheric learning value Ip is corrected by referring to the map showing the correlation between the exhaust pressure P and the atmospheric learning value Ip . At the time of learning fresh air by the air-fuel ratio sensor 26, an error occurs in the atmospheric learning value Ip due to the influence of the exhaust pressure P of the internal combustion engine 3. In order to reduce this error, in this embodiment, the atmospheric learning value Ip is corrected based on the proportional relationship between the exhaust pressure P and the atmospheric learning value Ip shown in the map. As a result, the error between the target air-fuel ratio and the actual air-fuel ratio of the internal combustion engine 3 can be reduced, and the internal combustion engine 3 can be operated at an air-fuel ratio closer to the target air-fuel ratio. Therefore, the exhaust performance can be efficiently improved while ensuring the combustion stability of the internal combustion engine 3.
　また、本実施例では、発電用モータジェネレータ２によって所定の目標回転数Ｎａまで内燃機関３をモータリングした後に、燃料噴射および点火を行い、内燃機関３を始動する。 Further, in this embodiment, after the internal combustion engine 3 motoring by the generator motor generator 2 to a predetermined target rotational speed N a, performs fuel injection and ignition to start the engine 3.
　仮に、一般的な内燃機関のように、例えばスターターモータにより内燃機関をクランキングした後に点火し燃焼を行うようにすると、内燃機関の燃焼状態が安定するまでに比較的長い時間がかかってしまう。 If, for example, an internal combustion engine is cranked by a starter motor and then ignited and burned like a general internal combustion engine, it takes a relatively long time for the combustion state of the internal combustion engine to stabilize.
　しかし、本実施例のように目標回転数Ｎａまでモータリングした状態で内燃機関３を始動することにより、短時間で内燃機関３の燃焼状態を安定させることができる。 However, by starting the internal combustion engine 3 while motoring to the target rotational speed N a as in this embodiment, it is possible in a short time to stabilize the combustion state of the internal combustion engine 3.
　なお、上記実施例では、内燃機関３が理論空燃比よりも非常にリーンな目標空燃比で作動する例を開示したが、内燃機関３は他の空燃比でも作動することができる。例えば、機関冷機始動時などの触媒を早期に活性化すべき触媒暖機運転時には理論空燃比よりもリッチ側で運転されることもあり、また、理論空燃比を目標空燃比とすることもあり得る。 In the above embodiment, the internal combustion engine 3 operates at a target air-fuel ratio that is much leaner than the stoichiometric air-fuel ratio, but the internal combustion engine 3 can also operate at another air-fuel ratio. For example, during catalyst warm-up operation in which the catalyst should be activated early, such as when starting an engine cooler, it may be operated on the rich side of the stoichiometric air-fuel ratio, or the stoichiometric air-fuel ratio may be set as the target air-fuel ratio. ..

Claims (7)

  1. 　排気通路に設けられた空燃比センサを有する内燃機関によって発電用モータジェネレータを発電し、この発電による電力で走行用モータジェネレータを駆動して走行するハイブリッド車両において、空燃比が理論空燃比よりもリーンな状態で作動される内燃機関の制御方法であって、
    　内燃機関の再始動要求があったときに、前記発電用モータジェネレータによって内燃機関をモータリングし、前記モータリング中に前記排気通路を通過する新気の状態を前記空燃比センサによって学習する、内燃機関の制御方法。     In a hybrid vehicle in which a motor generator for power generation is generated by an internal combustion engine having an air-fuel ratio sensor provided in an exhaust passage and the driving motor generator is driven by the power generated by this power generation, the air-fuel ratio is leaner than the theoretical air-fuel ratio. It is a control method of an internal combustion engine that is operated in a normal state.
    When there is a request to restart the internal combustion engine, the internal combustion engine is motorized by the power generation motor generator, and the state of fresh air passing through the exhaust passage during the motoring is learned by the air-fuel ratio sensor. How to control the engine.
  2. 　前記空燃比センサが学習した大気学習値を、前記排気通路を通流する排気の排気圧力に基づいて補正することを含む、請求項１に記載の内燃機関の制御方法。 The control method for an internal combustion engine according to claim 1, wherein the air-fuel ratio learned value learned by the air-fuel ratio sensor is corrected based on the exhaust pressure of the exhaust gas passing through the exhaust passage.
  3. 　内燃機関に設けられた可変バルブタイミング機構によって、前記排気通路を通流する排気の排気圧力を、前記排気通路内の未燃の燃料を掃気することが可能な最も低い圧力に制御することを含む、請求項１に記載の内燃機関の制御方法。 A variable valve timing mechanism provided in the internal combustion engine includes controlling the exhaust pressure of the exhaust flowing through the exhaust passage to the lowest pressure at which the unburned fuel in the exhaust passage can be scavenged. The method for controlling an internal combustion engine according to claim 1.
  4. 　空燃比のばらつき分だけ目標空燃比よりもリッチ側にある始動後空燃比を設定し、該始動後空燃比で内燃機関を作動することを含む、請求項１~３のいずれかに記載の内燃機関の制御方法。 The internal combustion engine according to any one of claims 1 to 3, which includes setting the post-start air-fuel ratio on the rich side of the target air-fuel ratio by the variation in the air-fuel ratio and operating the internal combustion engine at the post-start air-fuel ratio. How to control the engine.
  5. 　内燃機関に設けられた振動センサによって内燃機関の振動を検出し、この振動を所定レベルにしつつ、空燃比を目標空燃比に近づけることを含む、請求項１~４に記載の内燃機関の制御方法。 The method for controlling an internal combustion engine according to any one of claims 1 to 4, wherein the vibration sensor provided in the internal combustion engine detects the vibration of the internal combustion engine, and the air-fuel ratio is brought close to the target air-fuel ratio while keeping the vibration at a predetermined level. ..
  6. 　前記モータリングは、内燃機関の回転数が発電点の回転数に到達もしくは近接するまで実施される、請求項１に記載の内燃機関の制御方法。 The method for controlling an internal combustion engine according to claim 1, wherein the motoring is performed until the rotation speed of the internal combustion engine reaches or approaches the rotation speed of the power generation point.
  7. 　内燃機関によって発電用モータジェネレータを発電し、この発電による電力で走行用モータジェネレータを駆動して走行するハイブリッド車両において、排気の空燃比を検出する空燃比センサが排気通路に設けられる、内燃機関の制御装置であって、
    　内燃機関の再始動要求があったときに、前記発電用モータジェネレータによって内燃機関をモータリングし、前記モータリング中に前記排気通路を通過する新気の状態を前記空燃比センサによって学習し、理論空燃比よりもリーンな目標空燃比で内燃機関を作動する、内燃機関の制御装置。     In a hybrid vehicle in which a motor generator for power generation is generated by an internal combustion engine and the driving motor generator is driven by the power generated by the power generated, an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gas is provided in an exhaust passage of the internal combustion engine. It ’s a control device,
    When there is a request to restart the internal combustion engine, the internal combustion engine is motorized by the power generation motor generator, and the state of fresh air passing through the exhaust passage during the motoring is learned by the air-fuel ratio sensor, and the theory An internal combustion engine control device that operates an internal combustion engine with a target air-fuel ratio that is leaner than the air-fuel ratio.
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