JP4697473B2 - Control device for internal combustion engine - Google Patents

Control device for internal combustion engine Download PDF

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JP4697473B2
JP4697473B2 JP2007107741A JP2007107741A JP4697473B2 JP 4697473 B2 JP4697473 B2 JP 4697473B2 JP 2007107741 A JP2007107741 A JP 2007107741A JP 2007107741 A JP2007107741 A JP 2007107741A JP 4697473 B2 JP4697473 B2 JP 4697473B2
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exhaust valve
internal combustion
closing control
intake pipe
combustion engine
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JP2008267175A (en
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正臣 井上
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Denso Corp
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    • 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
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    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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    • Y02T10/12—Improving ICE efficiencies

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Description

本発明は、内燃機関の排気バルブの制御方法を改善した内燃機関の制御装置に関する発明である。   The present invention relates to a control device for an internal combustion engine, which is an improved control method for an exhaust valve of the internal combustion engine.

近年、車両に搭載される内燃機関においては、出力向上、燃費節減、排気エミッション低減等を目的として、吸気バルブや排気バルブのバルブタイミング（開閉時期）を変化させる可変バルブタイミング装置を採用したものが増加しつつある。   In recent years, internal combustion engines mounted on vehicles have adopted variable valve timing devices that change the valve timing (open / close timing) of intake valves and exhaust valves for the purpose of improving output, reducing fuel consumption, and reducing exhaust emissions. It is increasing.

このような可変バルブタイミング装置を備えたシステムにおいては、特許文献１（特開２００２−２２１０５３号公報）に記載されているように、内燃機関の始動時に排気バルブタイミング（排気バルブの開閉時期）を遅角位置に保持して排気バルブの閉じ時期を上死点後にセットする（つまり排気バルブを上死点後まで開いておく）ことで、排気行程でシリンダから一旦排出された未燃ＨＣを上死点後のピストンの下降により吸い戻して未燃ＨＣの排出を低減し、内燃機関の始動後（完爆から所定時間が経過した後）に排気バルブタイミングを進角することで、燃焼中のガスを排出して後燃え効果により触媒の暖機を促進するようにしたものがある。
特開２００２−２２１０５３号公報（第４頁、第３図等） In a system equipped with such a variable valve timing device, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2002-221053), an exhaust valve timing (exhaust valve opening / closing timing) is set when the internal combustion engine is started. By holding the retarded position and setting the closing timing of the exhaust valve after top dead center (that is, opening the exhaust valve until after top dead center), the unburned HC once discharged from the cylinder in the exhaust stroke is increased. By sucking back by lowering the piston after the dead point, reducing the emission of unburned HC and advancing the exhaust valve timing after starting the internal combustion engine (after a predetermined time has elapsed since the complete explosion), There is one that exhausts gas and promotes warm-up of the catalyst by the afterburning effect.
Japanese Patent Laid-Open No. 2002-221053 (page 4, FIG. 3 etc.)

一般に、内燃機関の停止中は、吸気管内がほぼ大気圧の空気で満たされているため、吸気管圧力がほぼ大気圧であり、内燃機関の始動に伴ってシリンダ内に空気が吸入され始めると、吸気管圧力が低下して排気圧（ほぼ大気圧）よりも低くなる。また、図２に示すように、排気バルブの閉じ時期を上死点後に制御して、排気行程でシリンダから一旦排出された未燃ＨＣを上死点後のピストンの下降により吸い戻す場合、吸気管圧力が低下して排気圧との圧力差が大きくなるほど、上死点後のピストンの下降による未燃ＨＣの吸い戻し効果が高くなる傾向がある。   In general, when the internal combustion engine is stopped, the intake pipe is filled with almost atmospheric pressure air, so the intake pipe pressure is almost atmospheric pressure, and when the internal combustion engine starts, air begins to be sucked into the cylinder. The intake pipe pressure decreases and becomes lower than the exhaust pressure (approximately atmospheric pressure). In addition, as shown in FIG. 2, when the exhaust valve closing timing is controlled after top dead center and unburned HC once discharged from the cylinder in the exhaust stroke is sucked back by lowering of the piston after top dead center, As the pipe pressure decreases and the pressure difference with the exhaust pressure increases, the effect of sucking back unburned HC due to the lowering of the piston after the top dead center tends to increase.

しかし、上記特許文献１の技術では、内燃機関の始動時で吸気管圧力がまだ高くて排気圧との圧力差が小さいときに（上死点後のピストンの下降による未燃ＨＣの吸い戻し効果が低いときに）、排気バルブの閉じ時期を上死点後に制御するため、上死点後のピストンの下降により未燃ＨＣを十分に吸い戻すことができない。   However, in the technique of Patent Document 1, when the internal combustion engine is started and the intake pipe pressure is still high and the pressure difference from the exhaust pressure is small (the effect of sucking back unburned HC by lowering the piston after top dead center) Since the closing timing of the exhaust valve is controlled after the top dead center, the unburned HC cannot be sufficiently sucked back by the lowering of the piston after the top dead center.

一方、内燃機関の始動後で吸気管圧力が十分に低下して排気圧との圧力差が大きいときに（上死点後のピストンの下降による未燃ＨＣの吸い戻し効果が高いときに）、排気バルブタイミングを進角して排気バルブの閉じ時期を上死点前に制御するため、上死点後のピストンの下降による未燃ＨＣの吸い戻しを行うことができない。これらの理由から、上記特許文献１の技術では、未燃ＨＣの排出量を効果的に低減することができないという欠点がある。   On the other hand, when the intake pipe pressure is sufficiently reduced after the internal combustion engine is started and the pressure difference from the exhaust pressure is large (when the effect of sucking back unburned HC due to the lowering of the piston after the top dead center is high), Since the exhaust valve timing is advanced and the closing timing of the exhaust valve is controlled before top dead center, unburned HC cannot be sucked back by lowering the piston after top dead center. For these reasons, the technique disclosed in Patent Document 1 has a drawback that the amount of unburned HC emitted cannot be reduced effectively.

本発明は、これらの事情を考慮してなされたものであり、従って本発明の目的は、ＨＣ排出量を効果的に低減することができて、低エミッション化の要求を満たすことができる内燃機関の制御装置を提供することにある。   The present invention has been made in consideration of these circumstances. Therefore, an object of the present invention is to effectively reduce the amount of HC emissions and satisfy the demand for low emission. It is to provide a control device.

上記目的を達成するために、請求項１に係る発明は、内燃機関の始動時に排気バルブの閉じ時期を上死点前に制御する排気バルブ早閉じ制御を排気バルブ早閉じ制御手段により実行し、内燃機関の吸気管圧力が所定圧力よりも低下した吸気管圧力低下状態であるか否かを吸気管圧力低下状態判定手段により判定して、吸気管圧力低下状態であると判定されたときに排気バルブの閉じ時期を上死点後に制御する排気バルブ遅閉じ制御を排気バルブ遅閉じ制御手段により実行し、更に、排気バルブの開閉時期を変化させる可変排気バルブタイミング装置を設け、排気バルブの開閉時期を進角させるように可変排気バルブタイミング装置を制御することで排気バルブ早閉じ制御を実行し、排気バルブの開閉時期を遅角させるように可変排気バルブタイミング装置を制御することで排気バルブ遅閉じ制御を実行し、更に、排気バルブ早閉じ制御時に吸気バルブの閉じ時期を下死点に近付ける吸気バルブ早閉じ制御を吸気バルブ早閉じ制御手段により実行するようにしたものである。 In order to achieve the above object, the invention according to claim 1 performs exhaust valve early closing control for controlling the closing timing of the exhaust valve before top dead center at the start of the internal combustion engine by the exhaust valve early closing control means, The intake pipe pressure drop state determining means determines whether or not the intake pipe pressure of the internal combustion engine is lower than a predetermined pressure. The exhaust valve slow closing control for controlling the valve closing timing after top dead center is executed by the exhaust valve slow closing control means , and a variable exhaust valve timing device for changing the exhaust valve opening / closing timing is provided, and the exhaust valve opening / closing timing is provided. By controlling the variable exhaust valve timing device to advance the exhaust valve, the exhaust valve early closing control is executed, and the exhaust valve opening / closing timing is retarded. The intake valve early closing control is executed by the intake valve early closing control means that controls the exhaust valve to close the intake valve close timing at the bottom dead center during the exhaust valve early closing control. It is what I did.

つまり、内燃機関の始動開始時（クランキング開始時）やその直後で、まだ吸気管圧力低下状態になっていないときには、吸気管圧力と排気圧との差が小さく、上死点後のピストンの下降による未燃ＨＣの吸い戻し効果が低いため、排気バルブの閉じ時期を上死点前に制御する排気バルブ早閉じ制御を実行することで、未燃ＨＣをシリンダ内に閉じ込めてＨＣ排出量を低減する。   In other words, at the start of the internal combustion engine (at the start of cranking) or immediately after that, when the intake pipe pressure is not yet lowered, the difference between the intake pipe pressure and the exhaust pressure is small, and the piston after the top dead center Since the effect of sucking back unburned HC by lowering is low, by executing exhaust valve early closing control that controls the closing timing of the exhaust valve before top dead center, the unburned HC is confined in the cylinder and the HC emission amount is reduced. To reduce.

その後、吸気管圧力低下状態になったときには、吸気管圧力と排気圧との差が大きくなって、上死点後のピストンの下降による未燃ＨＣの吸い戻し効果が高くなるため、排気バルブの閉じ時期を上死点後に制御する排気バルブ遅閉じ制御を実行することで、シリンダから一旦排出された未燃ＨＣを上死点後のピストンの下降により効果的に吸い戻す。   After that, when the intake pipe pressure is reduced, the difference between the intake pipe pressure and the exhaust pressure becomes large, and the effect of sucking back unburned HC by the lowering of the piston after the top dead center is increased. By executing exhaust valve slow closing control for controlling the closing timing after top dead center, unburned HC once discharged from the cylinder is effectively sucked back by lowering of the piston after top dead center.

これらの排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果と排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果により、ＨＣ排出量を効果的に低減することができて、低エミッション化の要求を満たすことができる。   The effect of confining unburned HC by the exhaust valve early closing control and the effect of sucking back unburned HC by the exhaust valve slow closing control can effectively reduce the amount of HC emissions and meet the demand for low emissions. Can be satisfied.

この場合、請求項１のように、排気バルブの開閉時期を変化させる可変排気バルブタイミング装置を設け、排気バルブの開閉時期を進角させるように可変排気バルブタイミング装置を制御することで排気バルブ早閉じ制御を実行し、排気バルブの開閉時期を遅角させるように可変排気バルブタイミング装置を制御することで排気バルブ遅閉じ制御を実行するようにすれば、排気バルブ早閉じ制御と排気バルブ遅閉じ制御を簡単に実行することができる。 In this case, as in claim 1 , a variable exhaust valve timing device for changing the opening / closing timing of the exhaust valve is provided, and the variable exhaust valve timing device is controlled so as to advance the opening / closing timing of the exhaust valve. close running control, to lever to perform the exhaust valve closing retardation control by controlling the variable exhaust valve timing device so as to retard the closing timing of the exhaust valve, the exhaust valve early closing control and the exhaust valve late The closing control can be easily executed.

このように可変排気バルブタイミング装置で排気バルブの開閉時期を進角させて排気バルブ早閉じ制御を実行すると、排気バルブの開き時期も進角されるため、燃焼ガスの排気開始時期が早くなって燃焼状態が不安定になる可能性がある。   When the variable exhaust valve timing device is used to advance the opening / closing timing of the exhaust valve and execute the early closing control of the exhaust valve, the opening timing of the exhaust valve is also advanced, so that the combustion gas exhaust start timing is advanced. The combustion state may become unstable.

そこで、請求項１に係る発明では、排気バルブ早閉じ制御時に吸気バルブの閉じ時期を下死点に近付ける吸気バルブ早閉じ制御を吸気バルブ早閉じ制御手段により実行するようにしたものである。このようにすれば、混合気の圧縮開始時期が下死点付近に進角されるため、混合気の実圧縮比を高くして燃焼状態を安定化させることができる。 Therefore, in the invention according to claim 1, the intake valve early closing control is executed by the intake valve early closing control means for bringing the closing timing of the intake valve close to the bottom dead center during the exhaust valve early closing control . In this way, the compression start timing of the air-fuel mixture is advanced to near the bottom dead center, so that the actual compression ratio of the air-fuel mixture can be increased and the combustion state can be stabilized.

この場合、請求項２のように、吸気バルブの開閉時期を変化させる可変吸気バルブタイミング装置を設け、吸気バルブの開閉時期を進角させるように可変吸気バルブタイミング装置を制御することで吸気バルブ早閉じ制御を実行するようにすると良い。このようにすれば、吸気バルブ早閉じ制御を簡単に実行することができる。 In this case, a variable intake valve timing device for changing the opening / closing timing of the intake valve is provided as in claim 2 , and the variable intake valve timing device is controlled so as to advance the opening / closing timing of the intake valve. It is preferable to execute the closing control. In this way, the intake valve early closing control can be easily executed.

また、請求項３のように、内燃機関の運転状態（例えば機関回転速度や吸入空気量等）に基づいて推定した吸気管圧力を用いて吸気管圧力低下状態であるか否かを判定するようにしても良い。このようにすれば、吸気管圧力センサを備えていないシステムに本発明を適用する場合でも、吸気管圧力推定値を用いて吸気管圧力低下状態であるか否かを精度良く判定することができる。 Further, as in claim 3 , it is determined whether or not the intake pipe pressure is in a lowered state using the intake pipe pressure estimated based on the operating state of the internal combustion engine (for example, engine speed, intake air amount, etc.). Anyway. In this way, even when the present invention is applied to a system that does not include an intake pipe pressure sensor, it is possible to accurately determine whether or not the intake pipe pressure is reduced using the estimated intake pipe pressure value. .

或は、請求項４のように、内燃機関の始動後の経過時間が所定時間を越えたか否かによって吸気管圧力低下状態であるか否かを判定するようにしても良い。内燃機関の始動後の経過時間に応じて吸気管圧力が低下するため、内燃機関の始動後の経過時間が所定時間を越えたか否かを判定すれば、吸気管圧力が所定圧力よりも低下した吸気管圧力低下状態であるか否かを精度良く判定することができる。 Alternatively, as in claim 4 , it may be determined whether or not the intake pipe pressure is in a lowered state based on whether or not the elapsed time after the start of the internal combustion engine exceeds a predetermined time. Since the intake pipe pressure decreases according to the elapsed time after the start of the internal combustion engine, if it is determined whether the elapsed time after the start of the internal combustion engine has exceeded a predetermined time, the intake pipe pressure has decreased below the predetermined pressure It can be accurately determined whether or not the intake pipe pressure is reduced.

また、請求項５のように、内燃機関の温度又はこれに関連性のある温度情報（例えば冷却水温や油温等）に応じて吸気管圧力低下状態の判定条件を変更するようにしても良い。このようにすれば、内燃機関の温度に応じて未燃ＨＣの発生状況が変化して、排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果や排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果が変化するのに対応して、吸気管圧力低下状態の判定条件を変更して、排気バルブ早閉じ制御から排気バルブ遅閉じ制御に切り換える時期を適正な時期に設定することができる。 Further, as described in claim 5 , the determination condition of the intake pipe pressure drop state may be changed in accordance with the temperature of the internal combustion engine or temperature information related thereto (for example, cooling water temperature, oil temperature, etc.). . In this way, the unburned HC generation state changes according to the temperature of the internal combustion engine, and the unburned HC trapping effect by the exhaust valve early closing control and the unburned HC sucking back effect by the exhaust valve late closing control are performed. In response to this change, the determination condition of the intake pipe pressure drop state can be changed, and the timing for switching from the exhaust valve early closing control to the exhaust valve late closing control can be set to an appropriate timing.

また、請求項６のように、排気バルブ早閉じ制御時に内燃機関の温度又はこれに関連性のある温度情報が低くなるほど排気バルブの閉じ時期を進角するようにしても良い。このようにすれば、内燃機関の温度が低くなるほど未燃ＨＣの発生量が多くなるのに対応して、排気バルブ早閉じ制御時の排気バルブの閉じ時期を進角して、排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果を大きくすることができる。 Also, as in claim 6, may be advanced the closing timing of the exhaust valve as the temperature or the temperature information that is relevant to the internal combustion engine when the exhaust valve early closing control is lowered. In this way, in response to the increase in the amount of unburned HC as the temperature of the internal combustion engine decreases, the exhaust valve close timing at the time of exhaust valve early closing control is advanced, and the exhaust valve early closing is performed. The confinement effect of unburned HC by control can be increased.

更に、請求項７のように、排気バルブ遅閉じ制御時に内燃機関の温度又はこれに関連性のある温度情報が低くなるほど排気バルブの閉じ時期を遅角するようにすると良い。このようにすれば、内燃機関の温度が低くなるほど未燃ＨＣの発生量が多くなるのに対応して、排気バルブ遅閉じ制御時の排気バルブの閉じ時期を遅角して、排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果を大きくすることができる。 Furthermore, as in claim 7, it may be as retarding the closing timing of the higher exhaust valve temperature or temperature information that is relevant to the exhaust valve closing retardation control when the internal combustion engine becomes lower. In this way, in response to the increase in the amount of unburned HC as the temperature of the internal combustion engine decreases, the exhaust valve closing timing during the exhaust valve delay closing control is delayed to delay the exhaust valve delay. The effect of sucking back unburned HC by the control can be increased.

また、請求項８のように、アクセルペダルが踏み込まれたときに排気バルブ早閉じ制御及び排気バルブ遅閉じ制御を禁止するようにしても良い。このようにすれば、運転者のアクセル操作に応じた排気バルブタイミング制御を排気バルブ早閉じ制御や排気バルブ遅閉じ制御よりも優先的に実行することができ、加速性を向上させることができる。
Further, as in claim 8 , when the accelerator pedal is depressed, the exhaust valve early closing control and the exhaust valve slow closing control may be prohibited. In this way, the exhaust valve timing control according to the driver's accelerator operation can be executed with priority over the exhaust valve early closing control and the exhaust valve late closing control, and the acceleration performance can be improved.

以下、本発明を実施するための最良の形態を具体化した幾つかの実施例を説明する。   Several embodiments embodying the best mode for carrying out the present invention will be described below.

本発明の実施例１を図１乃至図８に基づいて説明する。
まず、図１に基づいてエンジン制御システム全体の概略構成を説明する。内燃機関であるエンジン１１の吸気管１２の最上流部には、エアクリーナ１３が設けられ、このエアクリーナ１３の下流側に、吸入空気量を検出するエアフローメータ１４が設けられている。このエアフローメータ１４の下流側には、モータ１５によって開度調節されるスロットルバルブ１６と、このスロットルバルブ１６の開度（スロットル開度）を検出するスロットル開度センサ１７とが設けられている。 A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

更に、スロットルバルブ１６の下流側には、サージタンク１８が設けられ、このサージタンク１８に、吸気管圧力を検出する吸気管圧力センサ１９が設けられている。また、サージタンク１８には、エンジン１１の各気筒に空気を導入する吸気マニホールド２０が設けられ、各気筒の吸気マニホールド２０の吸気ポート近傍に、それぞれ燃料を噴射する燃料噴射弁２１が取り付けられている。また、エンジン１１のシリンダヘッドには、各気筒毎に点火プラグ２２が取り付けられ、各点火プラグ２２の火花放電によってシリンダ内の混合気に着火される。   Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. Further, a spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22.

また、エンジン１１には、吸気バルブ３０のバルブタイミング（開閉時期）を可変する可変吸気バルブタイミング装置３２と、排気バルブ３１のバルブタイミングを可変する可変排気バルブタイミング装置３３とが設けられている。   Further, the engine 11 is provided with a variable intake valve timing device 32 that varies the valve timing (opening / closing timing) of the intake valve 30 and a variable exhaust valve timing device 33 that varies the valve timing of the exhaust valve 31.

一方、エンジン１１の排気管２３には、排出ガスの空燃比又はリッチ／リーン等を検出する排出ガスセンサ２４（空燃比センサ、酸素センサ等）が設けられ、この排出ガスセンサ２４の下流側に、排出ガスを浄化する三元触媒等の触媒２５が設けられている。   On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

また、エンジン１１のシリンダブロックには、冷却水温を検出する冷却水温センサ２６や、エンジン１１のクランク軸が所定クランク角回転する毎にパルス信号を出力するクランク角センサ２７が取り付けられている。このクランク角センサ２７の出力信号に基づいてクランク角やエンジン回転速度が検出される。更に、アクセルセンサ３４によってアクセル操作量（アクセルペダルの踏込量）が検出される。   A cooling water temperature sensor 26 that detects the cooling water temperature and a crank angle sensor 27 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 27, the crank angle and the engine speed are detected. Further, the accelerator operation amount (depressed amount of the accelerator pedal) is detected by the accelerator sensor 34.

これら各種センサの出力は、制御回路（以下「ＥＣＵ」と表記する）２９に入力される。このＥＣＵ２９は、マイクロコンピュータを主体として構成され、内蔵されたＲＯＭ（記憶媒体）に記憶された各種のエンジン制御プログラムを実行することで、エンジン運転状態に応じて燃料噴射弁２１の燃料噴射量や点火プラグ２２の点火時期を制御する。   Outputs of these various sensors are input to a control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 21 according to the engine operating state. The ignition timing of the spark plug 22 is controlled.

一般に、エンジン１１の停止中は、吸気管１２内がほぼ大気圧の空気で満たされているため、吸気管圧力がほぼ大気圧であり、エンジン１１の始動に伴ってシリンダ内に空気が吸入され始めると、吸気管圧力が低下して排気圧（ほぼ大気圧）よりも低くなる。また、図２に示すように、排気バルブ３１の閉じ時期を上死点後に制御して、排気行程でシリンダから一旦排出された未燃ＨＣを上死点後のピストン３５の下降により吸い戻す場合、吸気管圧力が低下して排気圧との差が大きくなるほど、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が高くなる傾向がある。   In general, when the engine 11 is stopped, the intake pipe 12 is filled with almost atmospheric pressure air, so the intake pipe pressure is almost atmospheric pressure, and air is drawn into the cylinder as the engine 11 starts. When started, the intake pipe pressure decreases and becomes lower than the exhaust pressure (approximately atmospheric pressure). Also, as shown in FIG. 2, when the closing timing of the exhaust valve 31 is controlled after top dead center, unburned HC once discharged from the cylinder in the exhaust stroke is sucked back by the lowering of the piston 35 after top dead center. As the intake pipe pressure decreases and the difference from the exhaust pressure increases, the effect of sucking back unburned HC due to the lowering of the piston 35 after top dead center tends to increase.

このような特性を考慮して、本実施例１では、後述する図４の排気バルブタイミング制御ルーチンを実行することで、次のような排気バルブタイミング制御を行う。   In consideration of such characteristics, in the first embodiment, the following exhaust valve timing control is performed by executing an exhaust valve timing control routine of FIG. 4 described later.

図８のタイムチャートに示すように、エンジン１１の始動開始時（クランキング開始時）やその直後で、まだ吸気管圧力低下状態（吸気管圧力が所定圧力αよりも低下した状態）になっていないときには、吸気管圧力と排気圧との差が小さく、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が低いため、排気バルブタイミング（排気バルブ３１の開閉時期）を進角させるように可変排気バルブタイミング装置３３を制御して、排気バルブ３１の閉じ時期を上死点前に制御する排気バルブ早閉じ制御［図３（ａ）参照］を実行することで、未燃ＨＣをシリンダ内に閉じ込めてＨＣ排出量を低減する。   As shown in the time chart of FIG. 8, at the start of engine 11 (at the start of cranking) or immediately after that, the intake pipe pressure is still in a lowered state (intake pipe pressure is lower than a predetermined pressure α). When there is not, the difference between the intake pipe pressure and the exhaust pressure is small, and the effect of sucking back unburned HC due to the lowering of the piston 35 after the top dead center is low, so the exhaust valve timing (open / close timing of the exhaust valve 31) is advanced. By controlling the variable exhaust valve timing device 33 so as to cause the exhaust valve 31 to close before the top dead center, the exhaust valve early closing control [see FIG. Is confined in the cylinder to reduce HC emissions.

その後、吸気管圧力が所定圧力αよりも低下して、吸気管圧力低下状態になったときには、吸気管圧力と排気圧との差が大きくなって、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が高くなるため、排気バルブタイミングを遅角させるように可変排気バルブタイミング装置３３を制御して、排気バルブ３１の閉じ時期を上死点後に制御する排気バルブ遅閉じ制御［図３（ｂ）参照］を実行することで、排気行程でシリンダから一旦排出された未燃ＨＣを上死点後のピストン３５の下降により効果的に吸い戻す。   After that, when the intake pipe pressure falls below the predetermined pressure α and the intake pipe pressure is lowered, the difference between the intake pipe pressure and the exhaust pressure becomes large, and the difference between the intake pipe pressure and the exhaust pressure after the top dead center has not increased. Since the effect of sucking back the fuel HC increases, the exhaust valve timing control device 33 is controlled so as to retard the exhaust valve timing, and the exhaust valve slow closing control for controlling the closing timing of the exhaust valve 31 after top dead center [ By executing FIG. 3B, the unburned HC once discharged from the cylinder in the exhaust stroke is effectively sucked back by the lowering of the piston 35 after the top dead center.

これらの排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果と排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果により、ＨＣ排出量を効果的に低減する。
以下、ＥＣＵ２９が実行する図４の排気バルブタイミング制御ルーチンの処理内容を説明する。 The HC emission amount is effectively reduced by the confinement effect of unburned HC by the exhaust valve early closing control and the unburned HC sucking back effect by the exhaust valve slow closing control.
Hereinafter, the processing content of the exhaust valve timing control routine of FIG. 4 executed by the ECU 29 will be described.

［排気バルブタイミング制御ルーチン］
図４に示す排気バルブタイミング制御ルーチンは、ＥＣＵ２９の電源オン中（例えばイグニッションスイッチのオン後）に所定周期で実行される。本ルーチンが起動されると、まず、ステップ１０１で、アクセルセンサ３４の出力に基づいてアクセルＯＮである（アクセルペダルが踏み込まれている）か否かを判定し、アクセルＯＦＦであると判定されれば、ステップ１０２に進み、図５の所定圧力αのマップを参照して、現在の冷却水温に応じた所定圧力αを算出する。ここで、所定圧力αは、大気圧よりも十分に低く、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が高くなる吸気管圧力である。 [Exhaust valve timing control routine]
The exhaust valve timing control routine shown in FIG. 4 is executed at a predetermined cycle while the ECU 29 is powered on (for example, after the ignition switch is turned on). When this routine is started, first, at step 101, it is determined whether the accelerator is ON (accelerator pedal is depressed) based on the output of the accelerator sensor 34, and it is determined that the accelerator is OFF. For example, the process proceeds to step 102, and the predetermined pressure α corresponding to the current cooling water temperature is calculated with reference to the map of the predetermined pressure α in FIG. Here, the predetermined pressure α is an intake pipe pressure that is sufficiently lower than the atmospheric pressure and increases the suction effect of unburned HC due to the lowering of the piston 35 after the top dead center.

エンジン温度に応じて未燃ＨＣの発生状況が変化して、排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果や排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果が変化するため、図５の所定圧力αのマップにより、冷却水温（エンジン温度の代用情報）に応じて所定圧力α（吸気管圧力低下状態の判定条件）を変更して、排気バルブ早閉じ制御から排気バルブ遅閉じ制御に切り換える時期を適正な時期に設定する。   The generation state of unburned HC changes according to the engine temperature, and the effect of confining unburned HC by the exhaust valve early closing control and the sucking back effect of unburned HC by the exhaust valve slow closing control change. Based on the map of the predetermined pressure α, the predetermined pressure α (determination condition for the intake pipe pressure drop state) is changed according to the coolant temperature (substitute information of the engine temperature) to switch from the exhaust valve early closing control to the exhaust valve late closing control. Set the time to an appropriate time.

尚、冷却水温以外のエンジン温度代用情報（例えば油温等）に応じて所定圧力αを算出するようにしても良い。或は、エンジン温度に応じて所定圧力αを算出するようにしても良い。   The predetermined pressure α may be calculated according to engine temperature substitution information (for example, oil temperature) other than the coolant temperature. Alternatively, the predetermined pressure α may be calculated according to the engine temperature.

この後、ステップ１０３に進み、吸気管圧力センサ１９で検出した吸気管圧力が所定圧力αよりも低下したか否かによって吸気管圧力低下状態であるか否かを判定する。これらのステップ１０２，１０３の処理が特許請求の範囲でいう吸気管圧力低下状態判定手段としての役割を果たす。   Thereafter, the routine proceeds to step 103, where it is determined whether or not the intake pipe pressure is in a lowered state based on whether or not the intake pipe pressure detected by the intake pipe pressure sensor 19 has decreased below a predetermined pressure α. The processes of these steps 102 and 103 serve as intake pipe pressure drop state determination means in the claims.

このステップ１０３で、吸気管圧力センサ１９で検出した吸気管圧力が所定圧力α以上であり、まだ吸気管圧力低下状態になっていないと判定された場合には、吸気管圧力と排気圧との差が小さく、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が低いため、排気バルブ遅閉じ制御よりも排気バルブ早閉じ制御を実行した方が良いと判断して、排気バルブ早閉じ制御を次のようにして実行する。   If it is determined in step 103 that the intake pipe pressure detected by the intake pipe pressure sensor 19 is equal to or higher than the predetermined pressure α and the intake pipe pressure is not yet lowered, the intake pipe pressure and the exhaust pressure are Since the difference is small and the effect of sucking back unburned HC due to the lowering of the piston 35 after the top dead center is low, it is determined that it is better to execute the exhaust valve early closing control than the exhaust valve slow closing control. The early closing control is executed as follows.

まず、ステップ１０４で、図６の所定進角量Ａのマップを参照して、現在の冷却水温に応じた所定進角量Ａを算出する。図６の所定進角量Ａのマップは、冷却水温（エンジン温度の代用情報）が低くなるほど所定進角量Ａが大きくなって排気バルブ早閉じ制御時の排気バルブ３１の閉じ時期を進角するように設定されている。これにより、エンジン温度が低くなるほど未燃ＨＣの発生量が多くなるのに対応して、排気バルブ早閉じ制御時の排気バルブ３１の閉じ時期を進角して、排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果を大きくする。   First, in step 104, the predetermined advance amount A corresponding to the current coolant temperature is calculated with reference to the map of the predetermined advance amount A in FIG. In the map of the predetermined advance amount A in FIG. 6, the predetermined advance amount A increases as the coolant temperature (engine temperature substitute information) decreases, and the closing timing of the exhaust valve 31 during the early exhaust valve closing control is advanced. Is set to As a result, the lower the engine temperature, the greater the amount of unburned HC that is generated, and the timing for closing the exhaust valve 31 during the exhaust valve early closing control is advanced so that unburned by the exhaust valve early closing control. Increase the confinement effect of HC.

尚、冷却水温以外のエンジン温度代用情報（例えば油温等）に応じて所定進角量Ａを算出するようにしても良い。或は、エンジン温度に応じて所定進角量Ａを算出するようにしても良い。   It should be noted that the predetermined advance amount A may be calculated according to engine temperature substitution information other than the coolant temperature (for example, oil temperature or the like). Alternatively, the predetermined advance amount A may be calculated according to the engine temperature.

この後、ステップ１０５に進み、排気バルブタイミングを中間位置（例えば排気バルブ３１の閉じ時期がほぼ上死点となる位置）から所定進角量Ａだけ進角した位置まで進角させるように可変排気バルブタイミング装置３３を制御して、排気バルブ３１の閉じ時期を上死点前に制御する排気バルブ早閉じ制御を実行することで、未燃ＨＣをシリンダ内に閉じ込めてＨＣ排出量を低減する。これらのステップ１０４、１０５の処理が特許請求の範囲でいう排気バルブ早閉じ制御手段としての役割を果たす。   After this, the routine proceeds to step 105, where the variable exhaust is performed so that the exhaust valve timing is advanced from the intermediate position (for example, the position where the closing timing of the exhaust valve 31 is almost top dead center) to a position advanced by a predetermined advance amount A. By controlling the valve timing device 33 and executing the exhaust valve early closing control for controlling the closing timing of the exhaust valve 31 before top dead center, unburned HC is confined in the cylinder and the HC emission amount is reduced. The processing of these steps 104 and 105 serves as exhaust valve early closing control means in the claims.

この後、ステップ１０６に進み、吸気バルブタイミング（吸気バルブ３０の開閉時期）を中間位置（例えば吸気バルブ３０の開き時期がほぼ上死点となる位置）よりも進角させるように可変吸気バルブタイミング装置３２を制御して、吸気バルブ３０の閉じ時期を下死点に近付ける吸気バルブ早閉じ制御を実行する。これにより、混合気の圧縮開始時期を下死点付近に進角して、混合気の実圧縮比を高くして燃焼状態を安定化させる。このステップ１０６の処理が特許請求の範囲でいう吸気バルブ早閉じ制御手段としての役割を果たす。   Thereafter, the routine proceeds to step 106 where the variable intake valve timing is set so that the intake valve timing (opening / closing timing of the intake valve 30) is advanced from an intermediate position (for example, a position where the opening timing of the intake valve 30 is substantially at the top dead center). By controlling the device 32, the intake valve early closing control is executed to bring the closing timing of the intake valve 30 close to the bottom dead center. Thereby, the compression start timing of the air-fuel mixture is advanced to near the bottom dead center, and the actual compression ratio of the air-fuel mixture is increased to stabilize the combustion state. The processing in step 106 serves as the intake valve early closing control means in the claims.

その後、上記ステップ１０３で、吸気管圧力センサ１９で検出した吸気管圧力が所定圧力αよりも低下して、吸気管圧力低下状態であると判定された場合には、吸気管圧力と排気圧との差が大きくなって、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が高くなるため、排気バルブ早閉じ制御よりも排気バルブ遅閉じ制御を実行した方が良いと判断して、排気バルブ遅閉じ制御を次のようにして実行する。   Thereafter, when it is determined in step 103 that the intake pipe pressure detected by the intake pipe pressure sensor 19 is lower than the predetermined pressure α and the intake pipe pressure is in a lowered state, the intake pipe pressure and the exhaust pressure are Since the difference between the two increases and the effect of sucking back unburned HC due to the lowering of the piston 35 after top dead center increases, it is determined that it is better to execute the exhaust valve late closing control than the exhaust valve early closing control. Then, the exhaust valve slow closing control is executed as follows.

まず、ステップ１０７で、図７の所定遅角量Ｂのマップを参照して、現在の冷却水温に応じた所定遅角量Ｂを算出する。図７の所定遅角量Ｂのマップは、冷却水温（エンジン温度の代用情報）が低くなるほど所定遅角量Ｂが大きくなって排気バルブ遅閉じ制御時の排気バルブ３１の閉じ時期を遅角するように設定されている。これにより、エンジン温度が低くなるほど未燃ＨＣの発生量が多くなるのに対応して、排気バルブ遅閉じ制御時の排気バルブ３１の閉じ時期を遅角して、排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果を大きくする。   First, in step 107, the predetermined retardation amount B corresponding to the current coolant temperature is calculated with reference to the map of the predetermined retardation amount B in FIG. In the map of the predetermined delay amount B in FIG. 7, the predetermined delay amount B increases as the coolant temperature (engine temperature substitute information) decreases, and the closing timing of the exhaust valve 31 during the exhaust valve delay closing control is delayed. Is set to As a result, the amount of unburned HC generated increases as the engine temperature decreases, and the closing timing of the exhaust valve 31 during the exhaust valve slow closing control is retarded, so that unburned by the exhaust valve slow closing control occurs Increase the HC absorption effect.

尚、冷却水温以外のエンジン温度代用情報（例えば油温等）に応じて所定遅角量Ｂを算出するようにしても良い。或は、エンジン温度に応じて所定遅角量Ｂを算出するようにしても良い。   It should be noted that the predetermined retardation amount B may be calculated according to engine temperature substitute information (for example, oil temperature) other than the coolant temperature. Alternatively, the predetermined retardation amount B may be calculated according to the engine temperature.

この後、ステップ１０８に進み、排気バルブタイミングを中間位置から所定遅角量Ｂだけ遅角した位置まで遅角させるように可変排気バルブタイミング装置３３を制御して、排気バルブ３１の閉じ時期を上死点後に制御する排気バルブ遅閉じ制御を実行することで、排気行程でシリンダから一旦排出された未燃ＨＣを上死点後のピストン３５の下降により効果的に吸い戻す。これらのステップ１０７、１０８の処理が特許請求の範囲でいう排気バルブ遅閉じ制御手段としての役割を果たす。   Thereafter, the routine proceeds to step 108, where the variable exhaust valve timing device 33 is controlled so as to retard the exhaust valve timing from the intermediate position to a position retarded by a predetermined retardation amount B, thereby increasing the closing timing of the exhaust valve 31. By executing the exhaust valve slow closing control that is controlled after the dead center, the unburned HC once discharged from the cylinder in the exhaust stroke is effectively sucked back by the lowering of the piston 35 after the top dead center. The processing in these steps 107 and 108 serves as exhaust valve slow closing control means in the claims.

この後、ステップ１０９に進み、吸気バルブタイミングを中間位置よりも遅角させるように可変吸気バルブタイミング装置３２を制御する吸気バルブ遅閉じ制御を実行する。或は、吸気バルブタイミングを中間位置付近まで遅角させるように可変吸気バルブタイミング装置３２を制御する吸気バルブ遅閉じ制御を実行するようにしても良い。   Thereafter, the routine proceeds to step 109, where the intake valve delay closing control for controlling the variable intake valve timing device 32 so as to retard the intake valve timing from the intermediate position is executed. Alternatively, the intake valve delay closing control for controlling the variable intake valve timing device 32 so as to retard the intake valve timing to the vicinity of the intermediate position may be executed.

一方、上記ステップ１０１で、アクセルＯＮである（アクセルペダルが踏み込まれている）と判定された場合には、ステップ１０２以降の処理を実行することなく、本ルーチンを終了する。これにより、排気バルブ早閉じ制御及び排気バルブ遅閉じ制御を停止して、運転者のアクセル操作に応じた排気バルブタイミング制御を排気バルブ早閉じ制御や排気バルブ遅閉じ制御よりも優先的に実行する。   On the other hand, if it is determined in step 101 that the accelerator is ON (the accelerator pedal is depressed), this routine is terminated without executing the processing from step 102 onward. As a result, the exhaust valve early closing control and the exhaust valve late closing control are stopped, and the exhaust valve timing control corresponding to the driver's accelerator operation is executed with priority over the exhaust valve early closing control and the exhaust valve late closing control. .

以上説明した本実施例１では、図８のタイムチャートに示すように、エンジン１１の始動開始時やその直後で、まだ吸気管圧力低下状態（吸気管圧力が所定圧力αよりも低下した状態）になっていないときには、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が低いため、排気バルブタイミングを進角して排気バルブ３１の閉じ時期を上死点前に制御する排気バルブ早閉じ制御を実行することで、未燃ＨＣをシリンダ内に閉じ込めてＨＣ排出量を低減する。その後、吸気管圧力低下状態になったときには、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が高くなるため、排気バルブタイミングを遅角して排気バルブ３１の閉じ時期を上死点後に制御する排気バルブ遅閉じ制御を実行することで、排気行程でシリンダから一旦排出された未燃ＨＣを上死点後のピストン３５の下降により効果的に吸い戻す。   In the first embodiment described above, as shown in the time chart of FIG. 8, at the start of the engine 11 or immediately after that, the intake pipe pressure is still lowered (the intake pipe pressure is lower than the predetermined pressure α). When not, since the effect of sucking back unburned HC due to the lowering of the piston 35 after the top dead center is low, the exhaust valve timing is advanced to control the exhaust valve 31 closing timing before the top dead center. By executing the valve early closing control, unburned HC is confined in the cylinder to reduce the HC emission amount. Thereafter, when the intake pipe pressure is lowered, the effect of sucking back unburned HC due to the lowering of the piston 35 after the top dead center is increased. Therefore, the exhaust valve timing is retarded and the closing timing of the exhaust valve 31 is increased. By executing the exhaust valve slow closing control that is controlled after the dead center, the unburned HC once discharged from the cylinder in the exhaust stroke is effectively sucked back by the lowering of the piston 35 after the top dead center.

これらの排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果と排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果とを組み合わせることにより、図８に示す他の制御（排気バルブタイミングを進角固定して排気バルブ３１の閉じ時期を上死点前に固定する制御、排気バルブタイミングを遅角固定して排気バルブ３１の閉じ時期を上死点前に固定する制御、排気バルブタイミングを中間位置で固定して排気バルブ３１の閉じ時期をほぼ上死点で固定する制御）に比べて、ＨＣ排出量を効果的に低減することができ、低エミッション化の要求を満たすことができる。   By combining the effect of unburned HC confinement by the exhaust valve early closing control and the unburned HC sucking back effect by the exhaust valve slow closing control, another control shown in FIG. 8 (the exhaust valve timing is fixed at an advanced angle). Control to fix the closing timing of the exhaust valve 31 before top dead center, control to fix the exhaust valve timing at a retarded angle and fix closing timing of the exhaust valve 31 before top dead center, and fix the exhaust valve timing at an intermediate position As compared with control for fixing the closing timing of the exhaust valve 31 at almost the top dead center), the HC emission amount can be effectively reduced and the demand for low emission can be satisfied.

ところで、可変排気バルブタイミング装置３３で排気バルブ３１の開閉時期を進角させて排気バルブ早閉じ制御を実行すると、排気バルブ３１の開き時期も進角されるため、燃焼ガスの排気開始時期が早くなって燃焼状態が不安定になる可能性がある。   By the way, when the opening / closing timing of the exhaust valve 31 is advanced by the variable exhaust valve timing device 33 and the exhaust valve early closing control is executed, the opening timing of the exhaust valve 31 is also advanced, so that the combustion gas exhaust start timing is earlier. The combustion state may become unstable.

この対策として、本実施例１では、排気バルブ早閉じ制御時に吸気バルブ３０の閉じ時期を下死点に近付ける吸気バルブ早閉じ制御を実行するようにしたので、混合気の圧縮開始時期を下死点付近に進角して、混合気の実圧縮比を高くして燃焼状態を安定化させることができる。   As a countermeasure against this, in the first embodiment, the intake valve early closing control is executed to bring the closing timing of the intake valve 30 close to the bottom dead center during the exhaust valve early closing control. The combustion angle can be stabilized by advancing to the vicinity of the point and increasing the actual compression ratio of the air-fuel mixture.

尚、上記実施例１では、吸気管圧力センサ１９で検出した吸気管圧力が所定圧力αよりも低下したか否かによって吸気管圧力低下状態であるか否かを判定するようにしたが、吸気管圧力モデル等を用いてエンジン運転状態（例えばエンジン回転速度や吸入空気量等）に基づいて吸気管圧力を推定し、この吸気管圧力推定値が所定圧力αよりも低下したか否かによって吸気管圧力低下状態であるか否かを判定するようにしても良い。このようにすれば、吸気管圧力センサを備えていないシステムに本発明を適用する場合でも、吸気管圧力推定値を用いて吸気管圧力低下状態であるか否かを精度良く判定することができる。   In the first embodiment, it is determined whether or not the intake pipe pressure is reduced depending on whether or not the intake pipe pressure detected by the intake pipe pressure sensor 19 is lower than the predetermined pressure α. The intake pipe pressure is estimated based on the engine operating state (for example, engine speed, intake air amount, etc.) using a pipe pressure model or the like, and the intake air is determined depending on whether or not the estimated intake pipe pressure value is lower than a predetermined pressure α. You may make it determine whether it is a pipe pressure fall state. In this way, even when the present invention is applied to a system that does not include an intake pipe pressure sensor, it is possible to accurately determine whether or not the intake pipe pressure is reduced using the estimated intake pipe pressure value. .

次に、図９及び図１０を用いて本発明の実施例２を説明する。
本実施例２では、後述する図９の排気バルブタイミング制御ルーチンを実行することで、エンジン始動後の経過時間が所定時間βを越えたか否かによって吸気管圧力低下状態であるか否かを判定するようにしている。エンジン始動後の経過時間に応じて吸気管圧力が低下するため、エンジン始動後の経過時間が所定時間βを越えたか否かを判定すれば、吸気管圧力が所定圧力αよりも低下した吸気管圧力低下状態であるか否かを精度良く判定することができる。 Next, Embodiment 2 of the present invention will be described with reference to FIGS. 9 and 10.
In the second embodiment, an exhaust valve timing control routine of FIG. 9 to be described later is executed to determine whether or not the intake pipe pressure is in a lowered state based on whether or not the elapsed time after engine start exceeds a predetermined time β. Like to do. Since the intake pipe pressure decreases according to the elapsed time after the engine start, if it is determined whether or not the elapsed time after the engine start exceeds the predetermined time β, the intake pipe whose intake pipe pressure has decreased below the predetermined pressure α. It is possible to accurately determine whether or not the pressure is reduced.

図９に示す排気バルブタイミング制御ルーチンでは、ステップ２０１で、アクセルＯＦＦであると判定されれば、ステップ２０２に進み、エンジン始動後（例えばエンジン１１の初爆後又は完爆判定後）の経過時間をカウントアップした後、ステップ２０３に進み、図１０の所定時間βのマップを参照して、現在の冷却水温に応じた所定時間βを算出する。ここで、所定時間βは、エンジン始動後に吸気管圧力が所定圧力αよりも低下した吸気管圧力低下状態になるのに必要な時間に相当する。   In the exhaust valve timing control routine shown in FIG. 9, if it is determined in step 201 that the accelerator is OFF, the process proceeds to step 202, and the elapsed time after the engine is started (for example, after the first explosion of the engine 11 or after the complete explosion is determined). Is counted up, the process proceeds to step 203, and a predetermined time β corresponding to the current cooling water temperature is calculated with reference to the map of the predetermined time β shown in FIG. Here, the predetermined time β corresponds to a time required for the intake pipe pressure to be reduced after the engine is started and the intake pipe pressure is lower than the predetermined pressure α.

エンジン温度に応じて未燃ＨＣの発生状況が変化して、排気バルブ早閉じ制御による未燃ＨＣの閉じ込め効果や排気バルブ遅閉じ制御による未燃ＨＣの吸い戻し効果が変化するため、図１０の所定時間βのマップにより、冷却水温（エンジン温度の代用情報）に応じて所定時間β（吸気管圧力低下状態の判定条件）を変更して、排気バルブ早閉じ制御から排気バルブ遅閉じ制御に切り換える時期を適正な時期に設定する。   The generation state of unburned HC changes according to the engine temperature, and the effect of confining unburned HC by the exhaust valve early closing control and the sucking back effect of unburned HC by the exhaust valve slow closing control change. The predetermined time β is changed from the exhaust valve early closing control to the exhaust valve late closing control by changing the predetermined time β (determination condition of the intake pipe pressure drop state) according to the coolant temperature (substitute information of the engine temperature) by the predetermined time β map. Set the time to an appropriate time.

尚、冷却水温以外のエンジン温度代用情報（例えば油温等）に応じて所定時間βを算出するようにしても良い。或は、エンジン温度に応じて所定時間βを算出するようにしても良い。   Note that the predetermined time β may be calculated according to engine temperature substitution information other than the coolant temperature (for example, oil temperature). Alternatively, the predetermined time β may be calculated according to the engine temperature.

この後、ステップ２０４に進み、エンジン始動後の経過時間が所定時間βを越えたか否かによって吸気管圧力低下状態であるか否かを判定する。これらのステップ２０３、２０４の処理が特許請求の範囲でいう吸気管圧力低下状態判定手段としての役割を果たす。   Thereafter, the routine proceeds to step 204, where it is determined whether or not the intake pipe pressure is in a lowered state based on whether or not the elapsed time after the engine start exceeds a predetermined time β. The processing in these steps 203 and 204 serves as an intake pipe pressure drop state determination means in the claims.

このステップ２０４で、エンジン始動後の経過時間が所定時間β以下であり、まだ吸気管圧力低下状態になっていないと判定された場合には、吸気管圧力と排気圧との差が小さく、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が低いため、排気バルブ遅閉じ制御よりも排気バルブ早閉じ制御を実行した方が良いと判断して、排気バルブ早閉じ制御と吸気バルブ早閉じ制御を実行する（ステップ２０５〜２０７）。   In this step 204, if it is determined that the elapsed time after engine start is equal to or less than the predetermined time β and the intake pipe pressure has not been lowered, the difference between the intake pipe pressure and the exhaust pressure is small. Since the effect of sucking back unburned HC due to the lowering of the piston 35 after the dead point is low, it is determined that it is better to execute the exhaust valve early closing control than the exhaust valve slow closing control, and the exhaust valve early closing control and the intake air are controlled. The valve early closing control is executed (steps 205 to 207).

その後、上記ステップ２０４で、エンジン始動後の経過時間が所定時間βを越えて、吸気管圧力低下状態であると判定された場合には、吸気管圧力と排気圧との差が大きくなって、上死点後のピストン３５の下降による未燃ＨＣの吸い戻し効果が高くなるため、排気バルブ早閉じ制御よりも排気バルブ遅閉じ制御を実行した方が良いと判断して、排気バルブ遅閉じ制御と吸気バルブ遅閉じ制御を実行する（ステップ２０８〜２１０）を実行する。   Thereafter, in step 204, if it is determined that the elapsed time after engine start exceeds the predetermined time β and the intake pipe pressure is in a reduced state, the difference between the intake pipe pressure and the exhaust pressure increases, Since the effect of sucking back unburned HC due to the lowering of the piston 35 after the top dead center is enhanced, it is determined that it is better to execute the exhaust valve late closing control than the exhaust valve early closing control. Then, the intake valve slow closing control is executed (steps 208 to 210).

以上説明した本実施例２では、エンジン始動後の経過時間が所定時間βを越えたか否かによって吸気管圧力低下状態であるか否かを判定するようにしたので、吸気管圧力センサを備えていないシステムに本発明を適用する場合でも、吸気管圧力推定値を用いて吸気管圧力低下状態であるか否かを精度良く判定することができる。   In the second embodiment described above, the intake pipe pressure sensor is provided because it is determined whether or not the intake pipe pressure is in a lowered state based on whether or not the elapsed time after engine start exceeds the predetermined time β. Even when the present invention is applied to a system that does not include the intake pipe pressure, it is possible to accurately determine whether or not the intake pipe pressure is reduced using the estimated intake pipe pressure.

尚、本発明は、図１に示すような吸気ポート噴射エンジンに限定されず、筒内噴射エンジン等にも適用して実施できる等、種々変更して実施できる。   The present invention is not limited to the intake port injection engine as shown in FIG. 1, but can be implemented with various modifications such as being applicable to a cylinder injection engine.

本発明の実施例１におけるエンジン制御システム全体の概略構成図である。It is a schematic block diagram of the whole engine control system in Example 1 of this invention. 吸気管圧力と未燃ＨＣの吸い戻し効果との関係を説明する図である。It is a figure explaining the relationship between an intake pipe pressure and the sucking-back effect of unburned HC. （ａ）は排気バルブ早閉じ制御を説明する図であり、（ｂ）は排気バルブ遅閉じ制御を説明する図である。(A) is a figure explaining exhaust valve early closing control, (b) is a figure explaining exhaust valve late closing control. 実施例１の排気バルブタイミング制御ルーチンの処理の流れを説明するフローチャートである。4 is a flowchart for explaining a processing flow of an exhaust valve timing control routine according to the first embodiment. 所定圧力αのマップの一例を概念的に示す図である。It is a figure which shows notionally an example of the map of predetermined pressure (alpha). 所定進角量Ａのマップの一例を概念的に示す図である。It is a figure which shows notionally an example of the map of the predetermined advance amount A. FIG. 所定遅角量Ｂのマップの一例を概念的に示す図である。It is a figure which shows notionally an example of the map of the predetermined retardation amount B. FIG. 実施例１の排気バルブタイミング制御の実行例を説明するタイムチャートである。3 is a time chart illustrating an execution example of exhaust valve timing control according to the first embodiment. 実施例２の排気バルブタイミング制御ルーチンの処理の流れを説明するフローチャートである。6 is a flowchart for explaining a processing flow of an exhaust valve timing control routine according to a second embodiment. 所定時間βのマップの一例を概念的に示す図である。It is a figure which shows notionally an example of the map of predetermined time (beta).

符号の説明Explanation of symbols

１１…エンジン（内燃機関）、１２…吸気管、１６…スロットルバルブ、２１…燃料噴射弁、２２…点火プラグ、２３…排気管、２６…冷却水温センサ、２９…ＥＣＵ（排気バルブ早閉じ制御手段，吸気管圧力低下状態判定手段，排気バルブ遅閉じ制御手段，吸気バルブ早閉じ制御手段）、３０…吸気バルブ、３１…排気バルブ、３２…可変吸気バルブタイミング装置、３３…可変排気バルブタイミング装置、３４…アクセルセンサ   DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 26 ... Cooling water temperature sensor, 29 ... ECU (exhaust valve early closing control means) , Intake pipe pressure drop state determining means, exhaust valve slow closing control means, intake valve early closing control means), 30 ... intake valve, 31 ... exhaust valve, 32 ... variable intake valve timing device, 33 ... variable exhaust valve timing device, 34 ... Accelerator sensor

Claims (8)

内燃機関の始動時に排気バルブの閉じ時期を上死点前に制御する排気バルブ早閉じ制御を実行する排気バルブ早閉じ制御手段と、
内燃機関の吸気管圧力が所定圧力よりも低下した吸気管圧力低下状態であるか否かを判定する吸気管圧力低下状態判定手段と、
前記吸気管圧力低下状態判定手段により前記吸気管圧力低下状態であると判定されたときに前記排気バルブの閉じ時期を上死点後に制御する排気バルブ遅閉じ制御を実行する排気バルブ遅閉じ制御手段と、
前記排気バルブの開閉時期を変化させる可変排気バルブタイミング装置とを備えた内燃機関の制御装置において、
前記排気バルブ早閉じ制御手段は、前記排気バルブの開閉時期を進角させるように前記可変排気バルブタイミング装置を制御することで前記排気バルブ早閉じ制御を実行し、
前記排気バルブ遅閉じ制御手段は、前記排気バルブの開閉時期を遅角させるように前記可変排気バルブタイミング装置を制御することで前記排気バルブ遅閉じ制御を実行し、
前記排気バルブ早閉じ制御時に吸気バルブの閉じ時期を下死点に近付ける吸気バルブ早閉じ制御を実行する吸気バルブ早閉じ制御手段を備えていることを特徴とする内燃機関の制御装置。 Exhaust valve early closing control means for executing exhaust valve early closing control for controlling the closing timing of the exhaust valve before top dead center when the internal combustion engine is started,
An intake pipe pressure drop state determining means for determining whether or not the intake pipe pressure of the internal combustion engine is in an intake pipe pressure drop state lower than a predetermined pressure;
Exhaust valve slow closing control means for executing exhaust valve slow closing control for controlling the closing timing of the exhaust valve after top dead center when it is determined by the intake pipe pressure drop state determining means that the intake pipe pressure is in a lowered state. and,
In a control device for an internal combustion engine comprising a variable exhaust valve timing device for changing the opening and closing timing of the exhaust valve,
The exhaust valve early closing control means executes the exhaust valve early closing control by controlling the variable exhaust valve timing device so as to advance the opening / closing timing of the exhaust valve,
The exhaust valve slow closing control means executes the exhaust valve slow closing control by controlling the variable exhaust valve timing device so as to retard the opening / closing timing of the exhaust valve,
A control apparatus for an internal combustion engine, comprising: intake valve early closing control means for performing intake valve early closing control for bringing the closing timing of the intake valve close to bottom dead center during the exhaust valve early closing control . 前記吸気バルブの開閉時期を変化させる可変吸気バルブタイミング装置を備え、
前記吸気バルブ早閉じ制御手段は、前記吸気バルブの開閉時期を進角させるように前記可変吸気バルブタイミング装置を制御することで前記吸気バルブ早閉じ制御を実行することを特徴とする請求項１に記載の内燃機関の制御装置。 A variable intake valve timing device for changing the opening and closing timing of the intake valve;
The intake valve early closing control means to claim 1, characterized in that performing the intake valve earlier closing control by controlling the variable intake valve timing device so as to advance the closing timing of the intake valve The internal combustion engine control device described. 前記吸気管圧力低下状態判定手段は、内燃機関の運転状態に基づいて推定した吸気管圧力を用いて前記吸気管圧力低下状態であるか否かを判定することを特徴とする請求項１又は２に記載の内燃機関の制御装置。 The intake pipe pressure reduction condition determining means according to claim 1 or 2, characterized in that determining whether said is intake pipe pressure drop state by using the intake pipe pressure estimated based on the operating state of the internal combustion engine The control apparatus of the internal combustion engine described in 1. 前記吸気管圧力低下状態判定手段は、内燃機関の始動後の経過時間が所定時間を越えたか否かによって前記吸気管圧力低下状態であるか否かを判定することを特徴とする請求項１又は２に記載の内燃機関の制御装置。 The intake pipe pressure reduction condition determining means according to claim 1 or, characterized in that the time elapsed after the start of the internal combustion engine to determine whether it is the intake pipe pressure reduction state depending on whether exceeds a predetermined time 3. The control device for an internal combustion engine according to 2 . 前記吸気管圧力低下状態判定手段は、内燃機関の温度又はこれに関連性のある温度情報に応じて前記吸気管圧力低下状態の判定条件を変更することを特徴とする請求項１乃至４のいずれかに記載の内燃機関の制御装置。 The intake pipe pressure reduction condition determining means any of claims 1 to 4, characterized in that to change the determination condition of the intake pipe pressure reduction state in response to the temperature or temperature information that is relevant to the internal combustion engine A control device for an internal combustion engine according to claim 1. 前記排気バルブ早閉じ制御手段は、前記排気バルブ早閉じ制御時に内燃機関の温度又はこれに関連性のある温度情報が低くなるほど前記排気バルブの閉じ時期を進角することを特徴とする請求項１乃至５のいずれかに記載の内燃機関の制御装置。 2. The exhaust valve early closing control means advances the closing timing of the exhaust valve as the temperature of the internal combustion engine or temperature information related thereto decreases during the exhaust valve early closing control. The control apparatus for an internal combustion engine according to any one of claims 1 to 5 . 前記排気バルブ遅閉じ制御手段は、前記排気バルブ遅閉じ制御時に内燃機関の温度又はこれに関連性のある温度情報が低くなるほど前記排気バルブの閉じ時期を遅角することを特徴とする請求項１乃至６のいずれかに記載の内燃機関の制御装置。 2. The exhaust valve delay closing control means delays the closing timing of the exhaust valve as the temperature of the internal combustion engine or temperature information related thereto decreases during the exhaust valve delay closing control. The control apparatus of the internal combustion engine in any one of thru | or 6 . アクセルペダルが踏み込まれたときに前記排気バルブ早閉じ制御及び前記排気バルブ遅閉じ制御を禁止する手段を備えていることを特徴とする請求項１乃至７のいずれかに記載の内燃機関の制御装置。 Exhaust valve early closing control and the control apparatus for an internal combustion engine according to any one of claims 1 to 7, characterized in that it comprises a means for inhibiting said exhaust valve closing retardation control when the accelerator pedal is depressed .
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