JP4129628B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

【００３７】
ｆ10(WT)は、エンジン１の始動時において冷却水温度ＷＴの関数として設定される直送係数αの初期値である（直送割合初期値）。実際にはｆ10(WT)についても冷却水温度ＷＴの関数として表２のようにマップ化されており、当該マップより読み取られる（直送割合初期値設定手段）。
【００３８】
【表２】

【００３９】
即ち、直送係数αは、エンジン１の始動時における初期値ｆ10(WT)と始動後において冷却水温度ＷＴの上昇に応じて時々刻々と変化するｆ1(WT)との荷重平均値として求められる（直送割合加重平均手段）。
そして、γは、初期値ｆ10(WT)とｆ1(WT)との荷重平均を求めるための重み係数、即ち初期値ｆ10(WT)とｆ1(WT)間の補間割合である。
【００４０】
このように、重み係数γとする初期値ｆ10(WT)とｆ1(WT)との荷重平均から直送係数αを求めるようにするのは、直送係数α、即ち燃料の直送割合が吸気弁１１の温度に依存するとともに、この吸気弁１１の温度が燃焼ガスで加熱されて一次遅れ応答で上昇することに起因している。
即ち、吸気弁１１は、冷態始動直後においては低温であるために吸気弁１１に燃料が付着し易く、燃焼室５内への燃料の直送割合は低い一方、吸気弁１１が燃焼ガスで急速に昇温すると、吸気弁１１に付着した燃料が蒸発し易くなり、直送割合も増大することになるのであるが、この直送割合の増大の仕方が上記一次遅れ応答を示す吸気弁１１の温度上昇に略一致しているのである。
【００４１】
また、ここでは、重み係数γは、初期値０からエンジン１の燃焼回数Ｎ（経過期間）に応じて増大し、燃焼回数Ｎが例えば所定回数Ｎx（例えば、６０００回）に達したところで上限値１．０となるように設定されている。これは、エンジン１の始動後の吸気弁１１の温度上昇が、定常時温度（約２００℃程度）に達するまでの期間、他の運転条件（エンジン回転速度Ｎeやエンジン負荷）に拘わらず、略エンジン１の燃焼回数Ｎだけをパラメータとして増大していることに基づいている。
【００４２】
つまり、図４を参照すると、エンジン回転速度Ｎeを高速（実線）、中速（破線）、低速（一点鎖線）とし、さらにエンジン負荷を大（○印）、小（△印）とした場合のエンジン１の始動後燃焼回数Ｎと吸気弁１１の温度上昇度合い（（現在温度−始動時温度）／（定常時温度−始動時温度））との関係が実験結果として示されているが、同図に示すように、エンジン１の始動後、吸気弁１１の温度が定常時温度に達するまでの期間は、吸気弁１１の温度上昇はエンジン回転速度Ｎeやエンジン負荷に依らず略エンジン１の燃焼回数Ｎにのみ依存しているのである。
【００４３】
そして、重み係数γは、エンジン１の燃焼回数Ｎに応じ、吸気弁１１の温度上昇度合い（所定傾向）に一致して変化するように設定されている。つまり、図４において燃焼回数Ｎと吸気弁１１の温度上昇度合いとの近似曲線が例えば所定回数Ｎxを上限として求まり（図示せず）、吸気弁１１の温度上昇度合い（縦軸）をそのまま重み係数γに置き換えることで、当該近似曲線から重み係数γが設定される。実際には、燃焼回数Ｎと重み係数γとが表３のように予めマップ化されており、当該マップより読み取られる。
【００４４】
【表３】

【００４５】
なお、ここでは、エンジン１の燃焼回数Ｎに応じて重み係数γを設定するようにしたが、燃焼回数Ｎと相関のある始動後経過時間（経過期間）に応じて重み係数γを設定するようにしてもよい。
また、ｆ2(Ne)は、エンジン回転速度Ｎeが速くなると燃料噴射タイミングが吸気行程とオーバラップし、気筒内への直接飛び込みが増加する現象を考慮して設けられた項であり、エンジン回転速度Ｎeの関数で与えられる。
【００４６】
これにより、冷態始動直後から、直送係数α、即ち燃料の直送割合の適正化が図られる。
次に、配分係数β、即ち噴射された燃料のうち吸気ポート９の内壁に付着する燃料量と吸気弁１１に付着する燃料量との配分比率、つまり吸気弁１１の配分比率を次式(3)から算出する。
β＝ｆ3(WT) …(3)
【００４７】
配分係数βは、燃料噴霧の付着面積の比率を基準に設定されるが、付着面積の比率が冷却水温度ＷＴに対応して変化するため、冷却水温度ＷＴの関数として設定される。
そして、弁部蒸発係数Ｘ、即ち吸気弁１１に付着した燃料のうち吸気弁１１から蒸発して燃焼室５内に輸送される燃料の割合を次式(4)から設定する。
Ｘ＝γ・ｆ4(WT)＋（１−γ）・ｆ40(WT) …(4)
【００４８】
即ち、吸気弁１１に付着した燃料の一部は蒸発して燃焼室５へ輸送されるため、実際に燃焼室５内に輸送される吸気弁１１からの蒸発燃料の割合を弁部蒸発係数Ｘとして設定する。
直送係数αと同様、弁部蒸発係数Ｘは、実験結果に基づき設定されるが、エンジン温度との相関が高いため、基本的には冷却水温度ＷＴの関数としてｆ4(WT)で示される（弁部蒸発割合）。つまり、エンジン温度が高くなるほど吸気弁１１から蒸発する燃料量が増大し、弁部蒸発係数Ｘは増加する。実際にはｆ4(WT)は冷却水温度ＷＴの関数として表４のように予めマップ化されており、当該マップより読み取られる（弁部蒸発割合設定手段）。
【００４９】
【表４】

【００５０】
ｆ40(WT)は、エンジン１の始動時において冷却水温度ＷＴの関数として設定される弁部蒸発係数Ｘの初期値である（弁部蒸発割合初期値）。実際にはｆ40(WT)についても冷却水温度ＷＴの関数として表５のようにマップ化されており、当該マップより読み取られる（弁部蒸発割合初期値設定手段）。
【００５１】
【表５】

【００５２】
即ち、弁部蒸発係数Ｘは、エンジン１の始動時における初期値ｆ40(WT)と始動後において冷却水温度ＷＴの上昇に応じて時々刻々と変化するｆ4(WT)との荷重平均値として求められる（弁部蒸発割合加重平均手段）。
そして、γは、初期値ｆ40(WT)とｆ4(WT)との荷重平均を求めるための重み係数、即ち初期値ｆ40(WT)とｆ4(WT)間の補間割合である。
【００５３】
このように、重み係数γとする初期値ｆ40(WT)とｆ4(WT)との荷重平均から弁部蒸発係数Ｘを求めるようにするのは、上記直送係数αの場合と同様に、弁部蒸発係数Ｘ、即ち弁部蒸発割合が吸気弁１１の温度に大きく依存するとともに、この吸気弁１１の温度が燃焼ガスで加熱されて一次遅れ応答で上昇することに起因している。
【００５４】
つまり、吸気弁１１は、冷態始動直後においては低温であるために吸気弁１１に付着した燃料が蒸発し難く、弁部蒸発割合は低い一方、吸気弁１１が燃焼ガスで急速に昇温すると、吸気弁１１に付着した燃料は蒸発し易くなり、弁部蒸発割合も増大することになるのであるが、この弁部蒸発割合の増大の仕方が、上記直送割合と同様、上記一次遅れ応答を示す吸気弁１１の温度上昇に略一致しているのである。
【００５５】
重み係数γは、上記直送割合の設定に使用した値と同一値であり、上記同様に、初期値０からエンジン１の燃焼回数Ｎに応じて増大し、燃焼回数Ｎが例えば所定回数Ｎxで上限値１．０となるように設定されており、実際には表３のマップから読み出される。重み係数γの設定手法については上述した通りであり、ここでは説明を省略する。
【００５６】
これにより、冷態始動直後から、弁部蒸発係数Ｘ、即ち弁部蒸発割合の適正化が図られる。
さらに、ポート壁部蒸発係数Ｙ、即ち吸気ポート９の内壁に付着した燃料のうち蒸発して燃焼室５内に輸送される燃料の割合を次式(5)から設定する（ポート壁部蒸発割合設定手段）。
Ｙ＝ｆ5(WT) …(5)
【００５７】
つまり、吸気ポート９の内壁に付着した燃料の一部は蒸発して燃焼室５へ輸送されるため、実際に燃焼室５内に輸送される吸気ポート９の内壁からの蒸発燃料の割合をポート壁部蒸発係数Ｙとして設定する。
ポート壁部蒸発係数Ｙは、実験結果に基づき設定されるが、エンジン温度との相関が高いため、冷却水温度ＷＴの関数としてｆ5(WT)で示される（ポート壁部蒸発割合）。つまり、エンジン温度が高くなるほど吸気ポート９の内壁から蒸発する燃料量が増大し、ポート壁部蒸発係数Ｙは増加する。実際にはｆ5(WT)は冷却水温度ＷＴの関数として表６のように予めマップ化されており、当該マップより読み取られる。
【００５８】
【表６】

【００５９】
吸気ポート９は吸気弁１１よりも上流側であることから、ポート壁部蒸発係数Ｙ、即ちポート壁部蒸発割合は、吸気弁１１の温度には依存しない。従って、ポート壁部蒸発係数Ｙについては、特にエンジン温度との相関が高く、上記直送係数αや弁部蒸発係数Ｘのように初期値を設定したり荷重平均を求めたりしなくても、エンジン１の冷却水温度ＷＴのみに基づいて良好に設定される。
【００６０】
これにより、ポート壁部蒸発係数Ｙ、即ちポート壁部蒸発割合についても、冷態始動直後から適正化が図られる。
ステップＳ１４２では、上記のように設定した基本噴射量ＴB(n)で燃料噴射をする場合に、実際に燃焼室５内に輸送される燃料、即ち予測輸送量ＴTRNS(n)を次式(6)から算出する（予測輸送量算出手段）。
ＴTRNS(n)＝ＴB(n)・α＋ＴTRNSX(n-4)＋ＴTRNSY(n-4) …(6)
【００６１】
ここに、ＴB(n)・αは、基本噴射量ＴB(n)に対し直送係数αに基づき求められる直接輸送量であり、ＴTRNSX(n-4)、ＴTRNSY(n-4)は、それぞれ弁部蒸発輸送量、ポート壁部蒸発輸送量であって、４サイクル前（ｎ−４）、即ち４サイクル４気筒からなるエンジン１では同一気筒での前回の燃料噴射時に、後述のステップＳ１４６においてそれぞれ弁部蒸発係数Ｘ、ポート壁部蒸発係数Ｙに基づき求められる弁部蒸発輸送量、ポート壁部蒸発輸送量である。このように弁部蒸発輸送量、ポート壁部蒸発輸送量について前回値を用いるのは、吸気ポート９や吸気弁１１から蒸発する燃料は主として前回噴射された燃料に依るものだからである。
【００６２】
このようにして、予測輸送量ＴTRNS(n)は、直接輸送量ＴB(n)・αと前回の噴射に基づく弁部蒸発輸送量ＴTRNSX(n-4)とポート壁部蒸発輸送量ＴTRNSY(n-4)とから良好に算出される。
エンジン１の始動直後においては、ＴTRNSX(n-4)やＴTRNSY(n-4)は算出されていないので、この場合には、ＴTRNSX(n-4)及びＴTRNSY(n-4)は例えば値０であり、予測輸送量ＴTRNS(n)はＴB(n)・αである。
【００６３】
ステップＳ１４４では、基本噴射量ＴB(n)と上記予測輸送量ＴTRNS(n)とに基づき実燃料噴射量ＴINJ(n)を決定する。
ここでは、先ず、基本噴射量ＴB(n)と予測輸送量ＴTRNS(n)とに基づき次式(7)から偏差△Ｔ(n)を求める。
△Ｔ(n)＝ＴB(n)−ＴTRNS(n) …(7)
つまり、燃焼室５内において基本噴射量ＴB(n)を確保しようとしたときに不足する燃料量を算出する。
【００６４】
そして、当該偏差△Ｔ(n)に基づき次式(8)から実際に噴射すべき実燃料噴射量ＴINJ(n)を求める（実噴射量算出手段）。
ＴINJ(n)＝ＴB(n)＋１／α・△Ｔ(n) …(8)
つまり、基本噴射量ＴB(n)に対し不足する燃料分を補正量として加えるようにする。
【００６５】
ここで、補正量として偏差△Ｔ(n)に直送係数αの逆数１／αを乗算した値を用いるようにしているのは、補正量として噴射する燃料についても直送係数αに対応する量のみが気筒内に供給されることを考慮したためである。つまり、直送係数αを乗じた場合に筒内において不足する偏差△Ｔ(n)の量となるよう補正量を設定する。
【００６６】
ステップＳ１４６では、上述したように弁部蒸発輸送量ＴTRNSX(n)及びポート壁部蒸発輸送量ＴTRNSY(n)を次式(9)、(10)から算出する。詳しくは、今回の燃料噴射によって付着する燃料の蒸発量、即ち同一気筒での次回の燃料噴射時に使用される弁部蒸発輸送量及びポート壁部蒸発輸送量を算出する。
ＴTRNSX(n)＝(１−Ｘ)・ＴTRNSX(n-4)＋Ｘ・(１−α)・β・ＴINJ(n)…(9)
ＴTRNSY(n)＝(１−Ｙ)・ＴTRNSY (n-4)＋Ｙ・(１−α)・(１−β)・ＴINJ(n)…(10)
【００６７】
即ち、弁部蒸発輸送量ＴTRNSX(n)及びポート壁部蒸発輸送量ＴTRNSY(n)は、それぞれ弁部蒸発係数Ｘ、ポート壁部蒸発係数Ｙを重み係数として、前回値であるＴTRNSX(n-4)、ＴTRNSY (n-4)と今回の燃料噴射により吸気ポート９や吸気弁１１にそれぞれ付着する燃料量(１−α)・β・ＴINJ(n)、(１−α)・(１−β)・ＴINJ(n)との荷重平均値として求められる。なお、βは上記配分係数、即ち吸気弁１１の配分比率であり、１−βは吸気ポート９の配分比率である。
【００６８】
つまり、弁部蒸発係数Ｘやポート壁部蒸発係数Ｙは、上述したように冷却水温度ＷＴの関数であってエンジン温度が高くなるほど増加するため、弁部蒸発輸送量ＴTRNSX(n)及びポート壁部蒸発輸送量ＴTRNSY(n)は、エンジン温度の上昇に伴って徐々に増大することになる。
このように弁部蒸発輸送量ＴTRNSX(n)及びポート壁部蒸発輸送量ＴTRNSY(n)について荷重平均を用いるのは、定常運転時において吸気ポート９や吸気弁１１からの燃料の蒸発分がそれぞれ一次遅れ応答による輸送遅れを伴って供給されるためである。なお、この手法については上記特許文献１（特開平７−１５８４８０号公報）等において公知であり、詳細についてはここでは説明を省略する。
【００６９】
このように弁部蒸発輸送量ＴTRNSX(n)及びポート壁部蒸発輸送量ＴTRNSY(n)が算出されると、これらＴTRNSX(n)及びＴTRNSY(n)は、次回の噴射に対する上記ステップＳ１４２での演算時において、上式(6)中のＴTRNSX(n-4)、ＴTRNSY(n-4)として用いられる。
以上のようにして燃料の噴射量補正が行われると、当該噴射量補正制御のサブルーチンを抜け、ステップＳ１６において、実燃料噴射量ＴINJ(n)に基づいて燃料噴射指令を出力することとなる。
【００７０】
これにより、燃焼室５内には基本噴射量ＴB(n)に相当する燃料が良好に供給され、エンジン１の始動直後、加減速時においても空燃比変動を抑えて筒内の空燃比が目標空燃比に維持されることになり、エンジン１の運転状態の安定化が図られる。
特に、本発明の燃料噴射制御装置では、吸気弁１１の温度に依存しないポート壁部蒸発係数Ｙについては、冷却水温度ＷＴのみの関数とし、一方、吸気弁１１の温度に依存する直送係数αと弁部蒸発係数Ｘについては、エンジン１の始動後、吸気弁１１の温度が定常時温度に達するまでの間、吸気弁１１の温度上昇に略一致して変化する重み係数γを用い、エンジン１の始動時の直送割合初期値ｆ10(WT)、弁部蒸発割合初期値ｆ40(WT)と冷却水温度ＷＴの上昇に応じて時々刻々と変化する直送割合ｆ1(WT)、弁部蒸発割合ｆ4(WT)との荷重平均値として求めるようにしている。
【００７１】
従って、冷却水温度ＷＴの低いエンジン１の冷態始動直後であっても、ポート壁部蒸発係数Ｙとともに直送係数α及び弁部蒸発係数Ｘの適正化を図ることができ、ポート壁部蒸発輸送量ＴTRNSY(n)のみならず直接輸送量ＴB(n)・α及び弁部蒸発輸送量ＴTRNSX(n)を現実に即して適切に求め、燃料噴射量の補正を常に正確に実施することが可能である。
【００７２】
これにより、エンジン温度の低い冷態始動直後から、目標空燃比に対応した基本噴射量ＴB(n)分の適正量の燃料を燃焼室５内に良好に供給することが可能となり、燃料噴射制御の制御精度を向上させることができ、冷態始動直後におけるエンジン１の出力性能の悪化や排ガス性能の悪化等を確実に防止することができる。
【００７３】
以上で本発明に係る燃料噴射制御装置の実施形態についての説明を終えるが、上記実施形態に限られるものではない。
例えば、上記実施形態では、直送係数αと弁部蒸発係数Ｘの双方について重み係数γを用いた荷重平均値を適用するようにしたが、他の実施形態として、吸気弁１１の温度に特に大きく依存する弁部蒸発係数Ｘについてのみ重み係数γを用いた荷重平均値を適用するようにしてもよいし、また、直送係数αについてのみ重み係数γを用いた荷重平均値を適用するようにしてもよい。
これにより、燃料噴射量の補正を良好に行うことができ、やはり燃料噴射制御の制御精度を向上させることができる。
【００７５】
【発明の効果】
以上詳細に説明したように、本発明の請求項１の内燃機関の燃料噴射制御装置によれば、吸気弁に付着した弁部付着燃料量のうち内燃機関の始動直後に内燃機関の温度に応じて設定される蒸発燃料の弁部蒸発割合初期値と内燃機関の温度変化に応じて逐次設定される弁部蒸発割合との加重平均値を求め、この弁部蒸発割合の加重平均値に基づいて弁部蒸発輸送量を求め、一方、基本噴射量のうち内燃機関の温度変化に応じて逐次設定される直送割合及び吸気ポートの内壁に付着したポート壁部付着燃料量のうち内燃機関の温度変化に応じて逐次設定されるポート壁部蒸発割合に基づいて直接輸送量及びポート壁部蒸発輸送量を求め、基本噴射量と、これら直接輸送量、弁部蒸発輸送量、ポート壁部蒸発輸送量の和である予測輸送量との偏差から基本噴射量の燃焼室への輸送を実現すべき補正量を算出し実噴射量を算出するようにしたので、ポート壁部蒸発割合、弁部蒸発割合の適正化を図り、直接輸送量とともにポート壁部蒸発輸送量及び弁部蒸発輸送量を現実に即して適切に求めることができ、燃料噴射量の補正を正確に行うことができる。
【００７６】
これにより、冷態始動直後においても目標空燃比に対応した基本噴射量分の燃料を良好に燃焼室内に供給することができ、燃焼室内の実際の空燃比を目標空燃比通りに制御することができる。
また、請求項２の燃料噴射制御装置によれば、基本噴射量のうち内燃機関の始動直後に内燃機関の温度に応じて設定される燃料の直送割合初期値と内燃機関の温度変化に応じて逐次設定される直送割合とから加重平均値を求め、さらに、吸気弁に付着した弁部付着燃料量のうち内燃機関の始動直後に内燃機関の温度に応じて設定される蒸発燃料の弁部蒸発割合初期値と内燃機関の温度変化に応じて逐次設定される弁部蒸発割合との加重平均値を求め、これら直送割合の加重平均値及び弁部蒸発割合の加重平均値に基づいて直接輸送量及び弁部蒸発輸送量をそれぞれ求め、一方、吸気ポートの内壁に付着したポート壁部付着燃料量のうち内燃機関の温度変化に応じて逐次設定されるポート壁部蒸発割合に基づいてポート壁部蒸発輸送量を求め、基本噴射量と、これら直接輸送量、弁部蒸発輸送量、ポート壁部蒸発輸送量の和である予測輸送量との偏差から基本噴射量の燃焼室への輸送を実現すべき補正量を算出し実噴射量を算出するようにしたので、直送割合とともにポート壁部蒸発割合及び弁部蒸発割合の適正化を図り、直接輸送量とともにポート壁部蒸発輸送量及び弁部蒸発輸送量を現実に即して適切に求めることができ、燃料噴射量の補正を正確に行うことができる。
【００７７】
これにより、冷態始動直後においても目標空燃比に対応した基本噴射量分の燃料を良好に燃焼室内に供給することができ、燃焼室内の実際の空燃比を目標空燃比通りに正確に制御することができる。
また、請求項３の燃料噴射制御装置によれば、内燃機関の始動後の経過期間に応じて所定傾向（例えば、吸気弁の温度上昇カーブ）で増加する重み付けを施して直送割合の加重平均値を求めることにより、直送割合初期値とその後の内燃機関の温度変化に応じた直送割合との加重平均値をより一層適正なものとし、直送割合の最適化を図ることができる。
【００７８】
また、請求項４の燃料噴射制御装置によれば、内燃機関の始動後の経過期間に応じて所定傾向（例えば、吸気弁の温度上昇カーブ）で増加する重み付けを施して弁部蒸発割合の加重平均値を求めることにより、弁部蒸発割合初期値とその後の内燃機関の温度変化に応じた弁部蒸発割合との加重平均値をより一層適正なものとし、弁部蒸発割合の最適化を図ることができる。
【００７９】
また、請求項５の燃料噴射制御装置によれば、内燃機関の始動後の燃焼回数に応じて所定傾向（例えば、吸気弁の温度上昇カーブ）で増加する重み付けを施して直送割合、弁部蒸発割合の加重平均値を求めることにより、加重平均値を極めて適正なものとし、弁部蒸発割合のさらなる最適化を図ることができる。
【図面の簡単な説明】
【図１】本発明に係る内燃機関の燃料噴射制御装置の概略構成図である。
【図２】本発明に係る燃料噴射制御装置の燃料噴射制御の制御ルーチンを示すフローチャートである。
【図３】噴射量補正制御のサブルーチンを示すフローチャートである。
【図４】エンジンの始動後燃焼回数Ｎと吸気弁の温度上昇度合い（（現在温度−始動時温度）／（定常時温度−始動時温度））との関係を示す図である。
【符号の説明】
１ エンジン
５ 燃焼室
６ 燃料噴射弁
９ 吸気ポート
１０ 吸気マニホールド
１１ 吸気弁
４０ ＥＣＵ（電子コントロールユニット）
４４ 水温センサ
４６ イグニションスイッチ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine that is suitable for use in an internal combustion engine that injects fuel into an intake pipe.
[0002]
[Related background]
2. Description of the Related Art In recent years, intake pipe injection type fuel injection control devices that are easy to perform highly accurate fuel supply amount control and easily cope with maintaining an appropriate air-fuel ratio and increasing the output of an internal combustion engine (engine) have been widely used.
However, an internal combustion engine equipped with such a fuel injection control device has a problem of transient air-fuel ratio fluctuations due to the presence of fuel adhering to the intake pipe and the intake valve. That is, in the fuel injection control device of the intake pipe injection method, fuel is not injected directly into the cylinder, but the fuel is injected into the intake pipe, so that a part of the injected fuel adheres to the inner wall of the intake pipe and the intake valve. The evaporated part from the adhering fuel is transported into the cylinder. For this reason, even if the fuel amount corresponding to the intake air amount is injected, during a transition such as acceleration or deceleration, the fuel transported into the cylinder is insufficient or excessive, and misfires, air-fuel ratio fluctuations, exhaust gas There is a possibility of degrading performance.
[0003]
Therefore, the amount of fuel directly entering the combustion chamber out of the basic injection amount of fuel corresponding to the target air-fuel ratio is obtained, and the amount of fuel evaporated from the fuel adhering to the inner wall of the intake pipe and the intake valve is calculated, thereby calculating the fuel injection amount. In particular, a technique for performing fuel injection control with correction of the amount of fuel has been developed, and in particular, based on the high correlation between the amount of evaporated fuel and the temperature of the internal combustion engine, the amount of direct input fuel and the inner wall of the intake pipe A technique has been developed for obtaining the amount of fuel evaporated from the intake valve and correcting the fuel injection amount (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP-A-7-158480
[0005]
[Problems to be solved by the invention]
By the way, in an internal combustion engine, although the temperature of the intake valve rises to about 200 ° C. during steady operation, the temperature is low at the time of cold start. Therefore, fuel is likely to adhere to the intake valve immediately after the cold start. For this reason, there is a tendency that the fuel directing rate into the combustion chamber is low and the fuel evaporation rate of the intake valve is very low due to the slow evaporation rate of the adhering fuel from the intake valve.
[0006]
Therefore, as disclosed in the above-mentioned Patent Document 1, in the method in which the direct injection fuel amount and the evaporated fuel amount from the intake valve are uniformly obtained according to the temperature of the internal combustion engine and the fuel injection amount is corrected, the internal combustion engine operates in a steady state. Although correct correction is possible when the engine is in a state, immediately after the cold start, there is no problem with the amount of evaporated fuel from the inner wall of the intake pipe, while the amount of fuel directly injected or the amount of evaporated fuel from the intake valve matches the actual value. However, there is a problem that the basic fuel injection amount and thus the target air-fuel ratio is deviated, and appropriate fuel injection control cannot be performed.
[0007]
The present invention has been made to solve such problems, and an object of the present invention is to provide a fuel for an internal combustion engine that can perform good fuel injection amount control even immediately after the cold start of the internal combustion engine. To provide an injection control device.
[0011]
[Means for Solving the Problems]
  To achieve the above objectives,Claim1In the internal combustion engine fuel injection control device,Fuel injection of an internal combustion engine comprising basic injection amount setting means for setting a basic injection amount of fuel so as to achieve a target air-fuel ratio with respect to an intake air amount to the internal combustion engine, and injection amount correction means for correcting the basic injection amount In the control device,The injection amount correcting means includes a direct feed ratio initial value setting means for setting a direct feed ratio initial value, which is directly transported to the combustion chamber immediately after starting the internal combustion engine, in accordance with the temperature of the internal combustion engine. A direct feed rate setting means for sequentially setting a direct feed rate directly transported to the combustion chamber in accordance with a temperature change of the internal combustion engine, and a weighted average value of the direct feed rate initial value and the sequentially set direct feed rate Direct feed rate weighted averaging means and valve part evaporation rate setting means for sequentially setting the valve part evaporation rate that is evaporated and transported to the combustion chamber out of the amount of fuel adhering to the intake valve according to the temperature change of the internal combustion engine Of the fuel adhering to the wall of the port wall adhering to the inner wall of the intake portWithout setting an initial value, without obtaining a weighted average value with the initial value,A port wall evaporation rate setting means that is sequentially set according to a temperature change of the internal combustion engine, and a direct transport amount of fuel is obtained based on the basic injection amount and a weighted average value of the direct feed rate, and based on the valve portion evaporation rate Find the valve evaporation transport amount,It is sequentially set according to the temperature change of the internal combustion enginePort wall evaporation rateonlyThe port wall evaporative transport amount is calculated based on the above, and the predicted transport amount that is expected to be realized by the injection of the basic injection amount is calculated based on the sum of the direct transport amount, the valve portion evaporative transport amount, and the port wall evaporative transport amount An estimated transport amount calculating means for calculating a correction amount to realize transport of the basic injection amount to the combustion chamber from a deviation between the basic injection amount and the predicted transport amount, and an actual injection amount including the correction amount And an actual injection amount calculating means for calculating.
[0012]
That is, of the amount of fuel adhering to the intake valve adhering to the intake valve, it is sequentially set according to the initial value of the evaporation portion of the evaporated fuel that is set according to the temperature of the internal combustion engine immediately after starting the internal combustion engine and the temperature change of the internal combustion engine The weighted average value of the valve portion evaporation rate is obtained, and the valve portion evaporation transport amount is obtained based on the weighted average value of the valve portion evaporation rate. On the other hand, the basic injection amount is sequentially changed according to the temperature change of the internal combustion engine. Direct transport amount and port wall evaporative transport based on the set direct feed rate and the port wall evaporating rate sequentially set according to the temperature change of the internal combustion engine out of the port wall adhering fuel amount adhering to the inner wall of the intake port Find the amount. And the correction amount that should realize the transport of the basic injection amount to the combustion chamber from the deviation between the basic injection amount and the predicted transport amount that is the sum of the direct transport amount, the valve portion evaporative transport amount, and the port wall portion evaporative transport amount And finally the actual injection amount including the correction amount is calculated.
[0013]
  Therefore, immediately after the cold start, since the intake valve is at a low temperature and the evaporation rate of the attached fuel from the intake valve is slow, the fuel evaporation rate of the intake valve tends to be very low. By setting an initial value and obtaining the valve portion evaporation transport amount based on the weighted average value of the valve portion evaporation rate initial value and the subsequent valve portion evaporation rate according to the temperature change of the internal combustion engine, the valve portion evaporation rate Of optimizationCan.In addition, it has been confirmed through experiments that the port wall portion evaporation rate has a higher correlation with the temperature of the internal combustion engine (for example, the cooling water temperature) than the intake valve temperature. By calculating the port wall evaporating transport amount based only on the port wall evaporating rate sequentially set according to the temperature change of the internal combustion engine, the port wall evaporating rate can be optimized. Therefore, it is possible to appropriately determine the evaporative transport amount of the valve portion and the evaporative transport amount of the port wall portion together with the direct transport amount, and it becomes possible to accurately correct the fuel injection amount.
[0014]
  As a result, even after the cold start, fuel for the basic injection amount corresponding to the target air-fuel ratio can be satisfactorily supplied into the combustion chamber, and the actual air-fuel ratio in the combustion chamber can be controlled according to the target air-fuel ratio. Become.
  Claims2In the fuel injection control device, the injection amount correction means sets the initial value of the direct feed rate, which is directly transported to the combustion chamber immediately after the start of the internal combustion engine, in the basic injection amount according to the temperature of the internal combustion engine. Setting means, direct feed ratio setting means for sequentially setting a direct feed ratio directly transported to the combustion chamber in the basic injection amount in accordance with a temperature change of the internal combustion engine, the direct feed ratio initial value and the direct feed ratio being sequentially set A direct feed ratio weighted average means for obtaining a weighted average value and an initial value of the valve portion evaporation ratio that is evaporated immediately after starting the internal combustion engine and transported to the combustion chamber out of the amount of fuel adhering to the intake valve The valve portion evaporation rate initial value setting means that is set according to the temperature of the valve and the valve portion evaporation rate that is evaporated and transported to the combustion chamber out of the amount of fuel attached to the valve portion are sequentially set according to the temperature change of the internal combustion engine. Valve portion evaporation rate setting means; A valve portion evaporation rate weighted average means for obtaining a weighted average value of the valve portion evaporation rate initial value and the sequentially set valve portion evaporation rate; The evaporation rate of the port wall transported to the combustion chamberWithout setting an initial value, without obtaining a weighted average value with the initial value,Port wall evaporation rate setting means for sequentially setting according to temperature change of the internal combustion engine, and determining the direct transport amount of fuel based on the basic injection amount and the weighted average value of the direct delivery rate, and weighting the valve portion evaporation rate Based on the average value, find the valve evaporation transport amount,It is sequentially set according to the temperature change of the internal combustion enginePort wall evaporation rateonlyThe port wall evaporative transport amount is calculated based on the above, and the predicted transport amount that is expected to be realized by the injection of the basic injection amount is calculated based on the sum of the direct transport amount, the valve portion evaporative transport amount, and the port wall evaporative transport amount An estimated transport amount calculating means for calculating a correction amount to realize transport of the basic injection amount to the combustion chamber from a deviation between the basic injection amount and the predicted transport amount, and an actual injection amount including the correction amount And an actual injection amount calculating means for calculating.
[0015]
That is, a weighted average value is calculated from the initial value of the direct fuel delivery ratio set according to the temperature of the internal combustion engine immediately after the start of the internal combustion engine and the direct feed ratio sequentially set according to the temperature change of the internal combustion engine. Further, of the amount of fuel adhering to the intake valve and the amount of fuel adhering to the intake valve, depending on the initial value of the evaporation portion of the evaporated fuel set according to the temperature of the internal combustion engine immediately after the start of the internal combustion engine and the temperature change of the internal combustion engine Obtaining a weighted average value with the valve part evaporation rate sequentially set, and determining the direct transport amount and the valve part evaporation transport amount based on the weighted average value of these direct feed ratios and the weighted average value of the valve part evaporation rate, respectively, The port wall evaporative transport amount is obtained based on the port wall portion evaporation ratio sequentially set according to the temperature change of the internal combustion engine in the port wall portion adhering fuel amount adhering to the inner wall of the intake port. And the correction amount that should realize the transport of the basic injection amount to the combustion chamber from the deviation between the basic injection amount and the predicted transport amount that is the sum of the direct transport amount, the valve portion evaporative transport amount, and the port wall portion evaporative transport amount And finally the actual injection amount including the correction amount is calculated.
[0016]
  Therefore, immediately after the cold start, since the intake valve is low in temperature, the rate of direct delivery of fuel into the combustion chamber is low, and the rate of fuel evaporation from the intake valve is slow, so the rate of fuel evaporation in the intake valve is extremely low. First, the direct feed rate initial value and the valve portion evaporation rate initial value are set, and the direct feed rate initial value, the valve portion evaporation rate initial value and the direct feed rate according to the temperature change of the internal combustion engine thereafter, the valve Part evaporation rateeachBy determining the direct transport amount and valve part evaporation transport amount based on the weighted average value, the direct feed rate and valve part evaporation rate are optimized.Can.In addition, as described above, it has been confirmed that the port wall portion evaporation ratio is higher in correlation with the temperature of the internal combustion engine (for example, the cooling water temperature) than the intake valve temperature. By calculating the port wall evaporating transport amount based only on the port wall evaporating rate sequentially set according to the temperature change of the internal combustion engine, the port wall evaporating rate can be optimized. Therefore, it is possible to appropriately determine the evaporative transport amount of the valve portion and the evaporative transport amount of the port wall portion together with the direct transport amount, and it becomes possible to accurately correct the fuel injection amount.
[0017]
  As a result, even after the cold start, it is possible to satisfactorily supply the fuel for the basic injection amount corresponding to the target air-fuel ratio into the combustion chamber, and accurately control the actual air-fuel ratio in the combustion chamber according to the target air-fuel ratio. It becomes possible.
  Claims3In the fuel injection control apparatus, the direct feed ratio weighted average means weights the direct feed ratio by applying a weight that increases with a predetermined tendency according to an elapsed period after the start of the internal combustion engine with respect to the sequentially set direct feed ratio. It is characterized by obtaining a value.
[0018]
That is, it has been confirmed through experiments that the temperature increase of the intake valve is not affected by the engine rotational speed Ne or the engine load, but is influenced only by the elapsed period after the start of the internal combustion engine. By applying a weight that increases with a predetermined tendency (for example, the temperature rise curve of the intake valve) according to the elapsed period and obtaining a weighted average value of the direct feed ratio, the direct feed ratio initial value and the subsequent temperature change of the internal combustion engine It is possible to optimize the direct sending ratio by making the weighted average value with the direct sending ratio even more appropriate.
[0019]
  Claims4In the fuel injection control apparatus, the valve portion evaporation rate weighted average means weights the valve portion evaporation rate that is sequentially set according to an elapsed period after the start of the internal combustion engine in accordance with a predetermined tendency. It is characterized in that a weighted average value of the partial evaporation rate is obtained.
  That is, similarly to the above, by applying a weight that increases with a predetermined tendency (for example, the temperature rise curve of the intake valve) according to the elapsed period after starting, the weighted average value of the valve portion evaporation rate is obtained, thereby obtaining the valve portion evaporation rate. The weighted average value of the initial value and the subsequent valve portion evaporation rate corresponding to the temperature change of the internal combustion engine can be made more appropriate, and the valve portion evaporation rate can be optimized.
[0020]
  Claims5In this fuel injection control device, the elapsed period after the start of the internal combustion engine is the number of combustions after the start of the internal combustion engine.
  That is, it has been confirmed through experiments that the temperature rise of the intake valve is highly correlated with the number of combustions of the internal combustion engine, and a predetermined tendency (for example, the temperature rise curve of the intake valve) according to the number of combustions after the start of the internal combustion engine. ) To obtain the weighted average value of the direct feed rate and the valve portion evaporation rate, and the direct feed rate initial value, the initial value of the valve portion evaporation rate, and the direct feed rate according to the temperature change of the internal combustion engine thereafter, the valve It is possible to further optimize the valve portion evaporation rate by making the weighted average value with the portion evaporation rate extremely appropriate.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of a fuel injection control device for an internal combustion engine according to the present invention mounted on a vehicle, and the configuration of the exhaust gas purification device will be described below.
As shown in the figure, as an engine body (hereinafter simply referred to as an engine) 1 that is an internal combustion engine, for example, an intake pipe injection type (Multi Point Injection: MPI) gasoline engine having four cycles and four cylinders is employed.
[0023]
An ignition plug 4 is attached to each cylinder of the cylinder head 2 of the engine 1, and an ignition coil 8 that outputs a high voltage is connected to the ignition plug 4.
The cylinder head 2 is provided with an intake port 9 for each cylinder. The intake port 9 is opened and closed on the combustion chamber 5 side in accordance with the cam of the camshaft 12 that rotates in accordance with the engine rotation. An intake valve 11 for communicating and blocking each intake port 9 and the combustion chamber 5 is provided. Each intake port 9 is connected to one end of an intake manifold 10. An electromagnetic fuel injection valve 6 is attached to the intake manifold 10, and a fuel supply device (not shown) having a fuel tank is connected to the fuel injection valve 6 via a fuel pipe 7. .
[0024]
An electromagnetic throttle valve 17 that adjusts the amount of intake air is provided upstream of the fuel injection valve 6 of the intake manifold 10, and a throttle position sensor (TPS) that detects the opening of the throttle valve 17. ) 18 is provided. Further, an air flow sensor 19 for detecting the intake air amount Qa is provided upstream of the throttle valve 17.
[0025]
Further, the cylinder head 2 has an exhaust port 13 formed in a substantially horizontal direction for each cylinder, and a cam of a camshaft 16 that rotates in accordance with engine rotation is provided on the combustion chamber 5 side of each exhaust port 13. An exhaust valve 15 that opens and closes and performs communication between each exhaust port 13 and the combustion chamber 5 and shut off is provided. One end of an exhaust manifold 14 is connected to each exhaust port 13.
[0026]
Since the MPI engine is a known one, the detailed description of its configuration is omitted.
An exhaust pipe 20 is connected to the other end of the exhaust manifold 14, and a three-way catalytic converter 30 is interposed in the exhaust pipe 20 as an exhaust purification catalyst device. Further, on the upstream side of the three-way catalytic converter 30 in the exhaust pipe 20, an oxygen concentration is detected.₂A sensor 22 is provided.
[0027]
The ECU (electronic control unit) 40 includes an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer counter, and the like. Overall control of the fuel injection control device is performed.
On the input side of the ECU 40, the above-described TPS 18, air flow sensor 19, O₂In addition to the sensor 22, a crank angle sensor 42 for detecting the crank angle of the engine 1, a water temperature sensor 44 for detecting the coolant temperature WT of the engine 1, an ignition switch (key switch) 46 for starting the engine 1, a combustion cylinder (fuel injection) Various sensors such as a cylinder discriminating sensor 48 for discriminating an accelerator opening degree θacc and an accelerator opening degree sensor (APS) 50 for detecting an accelerator opening degree θacc are connected, and detection information from these sensors is inputted. The engine speed Ne is detected based on the crank angle information from the crank angle sensor 52.
[0028]
On the other hand, various output devices such as the fuel injection valve 6, the ignition coil 8, and the throttle valve 17 are connected to the output side of the ECU 40, and these various output devices are operated based on detection information from various sensors. The fuel injection amount, the fuel injection timing, the ignition timing, etc., are output, respectively, whereby the air-fuel ratio is controlled to an appropriate target air-fuel ratio, and an appropriate amount of fuel is injected from the fuel injection valve 6 at an appropriate timing, Spark ignition is performed at an appropriate timing by the spark plug 4.
[0029]
Specifically, the engine 1 is an MPI engine and injects fuel into the intake pipe. Therefore, a part of the injected fuel adheres to the inner wall of the intake port 9 and the intake valve 11, and the amount of evaporation from the attached fuel Therefore, the fuel injection control device corrects the fuel injection amount in consideration of the amount of fuel adhering to the inner wall of the intake port 9 and the intake valve 11 and the amount of evaporated fuel. Like to do.
[0030]
Hereinafter, the fuel injection control content of the fuel injection control device according to the present invention configured as described above will be described.
Referring to FIG. 2, a control routine for fuel injection control of the fuel injection control device according to the present invention executed by the ECU 40 is shown in a flowchart, and will be described along the flowchart. The control routine is set so that the calculation is executed for each cycle after the engine 1 is started in accordance with the fuel injection of each cylinder.
[0031]
First, in step S10, the intake air amount Qa (n) is detected by the air flow sensor 19. Here, the subscript n indicates that the current routine is being executed, and so on. Therefore, at the previous execution, that is, one cycle before is indicated by n-1, two cycles before is indicated by n-2, three cycles before is indicated by n-3, and four cycles before is indicated by n-4.
[0032]
In step S12, in order to achieve the target air-fuel ratio set based on the accelerator opening θacc information from the APS 50 and the engine speed Ne information, the following equation (1) is obtained based on the detected intake air amount Qa (n). Thus, the basic fuel injection amount TB (n) is set (basic injection amount setting means).
TB (n) = KINJ · Qa (n) (1)
Here, KINJ is a fuel amount conversion coefficient for converting the intake air amount Qa into a fuel amount in accordance with the target air-fuel ratio.
[0033]
In step S14, correction control is performed on the basic injection amount TB (n) obtained as described above (injection amount correcting means).
Referring to FIG. 3, the injection amount correction control subroutine is shown in a flowchart. Hereinafter, the injection amount correction control according to the present invention will be described with reference to the flowchart.
[0034]
In step S140, various coefficients for correcting the injection amount are set.
First, the direct feed coefficient α, that is, the ratio of the fuel directly transported to the combustion chamber 5 in the basic injection amount TB (n) is set from the following equation (2).
α = {γ · f1 (WT) + (1−γ) · f10 (WT)} · f2 (Ne) (2)
That is, a part of the fuel injection amount adheres to the inner wall of the intake port 9 and the intake valve 11, so that the amount of fuel adhering to the inner wall of the intake port 9 and the intake valve 11 is taken into consideration and the fuel that is actually sent directly into the combustion chamber 5. Is set as the direct feed coefficient α.
[0035]
Although the direct feed coefficient α is set based on the experimental result, it has a high correlation with the engine temperature, and is basically represented by f1 (WT) as a function of the coolant temperature WT (direct feed rate). That is, as the engine temperature increases, the amount of fuel adhering to the inner wall of the intake port 9 and the intake valve 11 decreases, and the direct feed coefficient α increases. Actually, f1 (WT) is previously mapped as a function of the coolant temperature WT as shown in Table 1, and is read from the map (direct feed ratio setting means).
[0036]
[Table 1]

[0037]
f10 (WT) is an initial value of the direct feed coefficient α set as a function of the coolant temperature WT when the engine 1 is started (direct feed rate initial value). Actually, f10 (WT) is also mapped as a function of the coolant temperature WT as shown in Table 2, and is read from the map (direct feed ratio initial value setting means).
[0038]
[Table 2]

[0039]
That is, the direct feed coefficient α is obtained as a load average value between an initial value f10 (WT) at the time of starting the engine 1 and f1 (WT) that changes momentarily as the cooling water temperature WT increases after the start ( Direct delivery rate weighted average means).
Γ is a weighting factor for obtaining a weighted average of the initial values f10 (WT) and f1 (WT), that is, an interpolation ratio between the initial values f10 (WT) and f1 (WT).
[0040]
As described above, the direct feed coefficient α is obtained from the load average of the initial values f10 (WT) and f1 (WT) as the weighting coefficient γ because the direct feed coefficient α, that is, the direct feed ratio of the fuel is the value of the intake valve 11. This depends on the temperature, and the temperature of the intake valve 11 is heated by the combustion gas and rises with a first-order lag response.
That is, since the intake valve 11 is at a low temperature immediately after the cold start, the fuel is likely to adhere to the intake valve 11 and the direct feed rate of the fuel into the combustion chamber 5 is low, while the intake valve 11 is rapidly made of combustion gas. When the temperature is raised to, the fuel adhering to the intake valve 11 is likely to evaporate, and the direct feed rate also increases. However, the way of increasing the direct feed rate is the temperature rise of the intake valve 11 showing the first-order lag response. Is almost the same.
[0041]
Here, the weighting factor γ increases from the initial value 0 in accordance with the number of combustions N (elapsed period) of the engine 1, and the upper limit value when the number of combustions N reaches, for example, a predetermined number Nx (for example, 6000 times). It is set to be 1.0. This is approximately the period until the temperature rise of the intake valve 11 after starting the engine 1 reaches the steady-state temperature (about 200 ° C.) regardless of other operating conditions (engine speed Ne or engine load). This is based on the fact that only the number of combustions N of the engine 1 is increased as a parameter.
[0042]
That is, referring to FIG. 4, the engine speed Ne is high (solid line), medium speed (broken line), low speed (dashed line), and engine load is large (circle) and small (triangle). The relationship between the number of combustions N after starting the engine 1 and the temperature rise degree of the intake valve 11 ((current temperature−starting temperature) / (steady temperature−starting temperature)) is shown as an experimental result. As shown in the figure, after the engine 1 is started, during the period until the temperature of the intake valve 11 reaches the steady-state temperature, the temperature increase of the intake valve 11 does not depend on the engine rotational speed Ne or the engine load, but is almost combusted by the engine 1. It depends only on the number of times N.
[0043]
The weighting factor γ is set so as to change in accordance with the temperature rise degree (predetermined tendency) of the intake valve 11 according to the number of combustions N of the engine 1. That is, in FIG. 4, an approximate curve between the number of combustions N and the temperature rise degree of the intake valve 11 is obtained, for example, with the predetermined number Nx as an upper limit (not shown), and the temperature rise degree (vertical axis) of the intake valve 11 is directly used as a weighting factor. By replacing with γ, the weighting coefficient γ is set from the approximate curve. Actually, the number of combustions N and the weighting coefficient γ are previously mapped as shown in Table 3, and are read from the map.
[0044]
[Table 3]

[0045]
Here, the weighting factor γ is set according to the number of combustions N of the engine 1, but the weighting factor γ is set according to the elapsed time after start (elapsed period) correlated with the number of combustions N. It may be.
Further, f2 (Ne) is a term provided in consideration of the phenomenon that the fuel injection timing overlaps with the intake stroke and the direct jump into the cylinder increases when the engine rotational speed Ne increases. It is given as a function of Ne.
[0046]
As a result, the direct feed coefficient α, that is, the direct feed rate of the fuel is optimized immediately after the cold start.
Next, the distribution coefficient β, that is, the distribution ratio between the fuel amount adhering to the inner wall of the intake port 9 and the fuel amount adhering to the intake valve 11 in the injected fuel, that is, the distribution ratio of the intake valve 11 is expressed by the following equation (3 ).
β = f3 (WT) (3)
[0047]
The distribution coefficient β is set based on the ratio of the adhesion area of the fuel spray, but is set as a function of the cooling water temperature WT because the ratio of the adhesion area changes corresponding to the cooling water temperature WT.
Then, the valve portion evaporation coefficient X, that is, the ratio of the fuel adhering to the intake valve 11 to be evaporated from the intake valve 11 and transported into the combustion chamber 5 is set from the following equation (4).
X = γ · f 4 (WT) + (1−γ) · f 40 (WT) (4)
[0048]
That is, since a part of the fuel adhering to the intake valve 11 is evaporated and transported to the combustion chamber 5, the ratio of the evaporated fuel from the intake valve 11 actually transported into the combustion chamber 5 is expressed as the valve portion evaporation coefficient X. Set as.
As with the direct feed coefficient α, the valve portion evaporation coefficient X is set based on the experimental results. However, since the correlation with the engine temperature is high, it is basically expressed as f4 (WT) as a function of the coolant temperature WT ( Valve part evaporation rate). That is, as the engine temperature increases, the amount of fuel evaporated from the intake valve 11 increases, and the valve portion evaporation coefficient X increases. Actually, f4 (WT) is previously mapped as a function of the coolant temperature WT as shown in Table 4, and is read from the map (valve portion evaporation rate setting means).
[0049]
[Table 4]

[0050]
f40 (WT) is an initial value of the valve portion evaporation coefficient X set as a function of the coolant temperature WT when the engine 1 is started (valve portion evaporation ratio initial value). Actually, f40 (WT) is also mapped as a function of the coolant temperature WT as shown in Table 5, and is read from the map (valve portion evaporation ratio initial value setting means).
[0051]
[Table 5]

[0052]
That is, the valve portion evaporation coefficient X is obtained as a load average value between an initial value f40 (WT) at the time of starting the engine 1 and f4 (WT) that changes every moment according to the increase in the coolant temperature WT after the start. (Valve evaporation rate weighted average means).
Γ is a weighting factor for obtaining a weighted average of the initial values f40 (WT) and f4 (WT), that is, an interpolation ratio between the initial values f40 (WT) and f4 (WT).
[0053]
In this way, the valve portion evaporation coefficient X is obtained from the load average of the initial values f40 (WT) and f4 (WT) as the weighting factor γ, as in the case of the direct feed coefficient α. This is because the evaporation coefficient X, that is, the valve portion evaporation ratio greatly depends on the temperature of the intake valve 11, and the temperature of the intake valve 11 is heated by the combustion gas and rises with a first-order lag response.
[0054]
In other words, since the intake valve 11 is at a low temperature immediately after the cold start, the fuel adhering to the intake valve 11 is difficult to evaporate, and the valve portion evaporation rate is low, while the intake valve 11 rapidly rises in temperature with combustion gas. The fuel adhering to the intake valve 11 is likely to evaporate, and the valve portion evaporation rate also increases. However, the method of increasing the valve portion evaporation rate is similar to the direct feed rate in the first-order lag response. This is substantially coincident with the temperature rise of the intake valve 11 shown.
[0055]
The weighting factor γ is the same value as the value used for setting the direct feed ratio, and, similarly to the above, increases from the initial value 0 according to the number of combustions N of the engine 1, and the number of combustions N is, for example, a predetermined number Nx and the upper limit. The value is set to 1.0, and is actually read from the map of Table 3. The method for setting the weighting factor γ is as described above, and the description thereof is omitted here.
[0056]
As a result, the valve portion evaporation coefficient X, that is, the valve portion evaporation rate is optimized immediately after the cold start.
Further, the port wall evaporation coefficient Y, that is, the ratio of the fuel adhering to the inner wall of the intake port 9 to be evaporated and transported into the combustion chamber 5 is set from the following equation (5) (port wall evaporation ratio) Setting means).
Y = f5 (WT) (5)
[0057]
That is, a part of the fuel adhering to the inner wall of the intake port 9 is evaporated and transported to the combustion chamber 5, so the ratio of the evaporated fuel from the inner wall of the intake port 9 that is actually transported into the combustion chamber 5 Set as wall evaporation coefficient Y.
Although the port wall portion evaporation coefficient Y is set based on the experimental results, it has a high correlation with the engine temperature, and is represented by f5 (WT) as a function of the coolant temperature WT (port wall portion evaporation ratio). That is, as the engine temperature increases, the amount of fuel evaporated from the inner wall of the intake port 9 increases, and the port wall portion evaporation coefficient Y increases. Actually, f5 (WT) is previously mapped as a function of the coolant temperature WT as shown in Table 6, and is read from the map.
[0058]
[Table 6]

[0059]
Since the intake port 9 is upstream of the intake valve 11, the port wall portion evaporation coefficient Y, that is, the port wall portion evaporation rate does not depend on the temperature of the intake valve 11. Therefore, the port wall portion evaporation coefficient Y has a particularly high correlation with the engine temperature, and the engine can be used without setting an initial value or obtaining a load average like the direct feed coefficient α and the valve portion evaporation coefficient X. It is set satisfactorily based on only one coolant temperature WT.
[0060]
As a result, the port wall portion evaporation coefficient Y, that is, the port wall portion evaporation rate, is also optimized immediately after the cold start.
In step S142, when fuel is injected with the basic injection amount TB (n) set as described above, the fuel that is actually transported into the combustion chamber 5, that is, the predicted transport amount TTRNS (n) is expressed by the following equation (6). ) (Predicted transportation amount calculation means).
TTRNS (n) = TB (n) ・ α + TTRNSX (n-4) + TTRNSY (n-4)… (6)
[0061]
Here, TB (n) · α is the direct transport amount obtained based on the direct feed coefficient α with respect to the basic injection amount TB (n), and TTRNSX (n-4) and TTRNSY (n-4) Part evaporative transport amount and port wall part evaporative transport amount, respectively, at the time of the previous fuel injection in the same cylinder in the engine 1 having four cycles before (n-4), that is, four cycles of four cylinders, respectively in step S146 described later. These are the valve portion evaporation transport amount and the port wall portion evaporation transport amount obtained based on the valve portion evaporation coefficient X and the port wall portion evaporation coefficient Y. The reason why the previous values are used for the valve portion evaporative transport amount and the port wall portion evaporative transport amount is that the fuel evaporated from the intake port 9 and the intake valve 11 mainly depends on the previously injected fuel.
[0062]
In this way, the predicted transport amount TTRNS (n) is calculated based on the direct transport amount TB (n) · α, the evaporative transport amount TTRNSX (n-4) based on the previous injection, and the evaporative transport amount TTRNSY (n -4).
Immediately after the engine 1 is started, TTRNSX (n-4) and TTRNSY (n-4) are not calculated. In this case, TTRNSX (n-4) and TTRNSY (n-4) have values of 0, for example. The predicted transport amount TTRNS (n) is TB (n) · α.
[0063]
In step S144, the actual fuel injection amount TINJ (n) is determined based on the basic injection amount TB (n) and the predicted transport amount TTRNS (n).
Here, first, a deviation ΔT (n) is obtained from the following equation (7) based on the basic injection amount TB (n) and the predicted transport amount TTRNS (n).
ΔT (n) = TB (n) −TTRNS (n) (7)
That is, the amount of fuel that is insufficient when trying to secure the basic injection amount TB (n) in the combustion chamber 5 is calculated.
[0064]
Based on the deviation ΔT (n), an actual fuel injection amount TINJ (n) to be actually injected is obtained from the following equation (8) (actual injection amount calculating means).
TINJ (n) = TB (n) + 1 / α · ΔT (n) (8)
That is, an amount of fuel that is insufficient with respect to the basic injection amount TB (n) is added as a correction amount.
[0065]
Here, the value obtained by multiplying the deviation ΔT (n) by the reciprocal 1 / α of the direct feed coefficient α is used as the correction amount, and only the amount corresponding to the direct feed coefficient α is used as the correction amount. This is because it is considered that is supplied into the cylinder. That is, the correction amount is set so as to be the amount of deviation ΔT (n) that is insufficient in the cylinder when multiplied by the direct feed coefficient α.
[0066]
In Step S146, as described above, the valve portion evaporation transport amount TTRNSX (n) and the port wall portion evaporation transport amount TTRNSY (n) are calculated from the following equations (9) and (10). Specifically, the evaporation amount of the fuel attached by the current fuel injection, that is, the valve portion evaporation transport amount and the port wall portion evaporation transport amount used at the next fuel injection in the same cylinder are calculated.
TTRNSX (n) = (1-X) .TTRNSX (n-4) + X. (1-.alpha.) .. beta..TINJ (n) (9)
TTRNSY (n) = (1-Y) .TTRNSY (n-4) + Y. (1-.alpha.). (1-.beta.). TINJ (n) (10)
[0067]
That is, the valve portion evaporation transport amount TTRNSX (n) and the port wall portion evaporation transport amount TTRNSY (n) are the previous values TTRNSX (n− 4), TTRNSY (n-4) and the fuel amount (1-α) · β · TINJ (n), (1-α) · (1- It is obtained as a weighted average value with β) · TINJ (n). Β is the above-described distribution coefficient, that is, the distribution ratio of the intake valve 11, and 1-β is the distribution ratio of the intake port 9.
[0068]
That is, as described above, the valve portion evaporation coefficient X and the port wall portion evaporation coefficient Y are a function of the cooling water temperature WT and increase as the engine temperature increases. Therefore, the valve portion evaporation transport amount TTRNSX (n) and the port wall The partial evaporation transport amount TTRNSY (n) gradually increases as the engine temperature rises.
As described above, the load average is used for the valve portion evaporative transport amount TTRNSX (n) and the port wall portion evaporative transport amount TTRNSY (n) because the fuel evaporated from the intake port 9 and the intake valve 11 during the steady operation is used. This is because it is supplied with a transport delay due to a first-order delay response. This method is known in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 7-158480) and the like, and the details are omitted here.
[0069]
When the valve portion evaporation transport amount TTRNSX (n) and the port wall portion evaporation transport amount TTRNSY (n) are calculated in this way, these TTRNSX (n) and TTRNSY (n) are calculated in the above step S142 for the next injection. At the time of calculation, they are used as TTRNSX (n-4) and TTRNSY (n-4) in the above equation (6).
When the fuel injection amount correction is performed as described above, the injection amount correction control subroutine is exited, and in step S16, a fuel injection command is output based on the actual fuel injection amount TINJ (n).
[0070]
As a result, fuel corresponding to the basic injection amount TB (n) is satisfactorily supplied into the combustion chamber 5, and immediately after the engine 1 is started, the air-fuel ratio in the cylinder is controlled while suppressing fluctuations in the air-fuel ratio even during acceleration / deceleration. The air-fuel ratio is maintained, and the operation state of the engine 1 is stabilized.
In particular, in the fuel injection control device of the present invention, the port wall portion evaporation coefficient Y that does not depend on the temperature of the intake valve 11 is a function of only the coolant temperature WT, while the direct feed coefficient α that depends on the temperature of the intake valve 11. As for the valve portion evaporation coefficient X, after the engine 1 is started, a weighting coefficient γ that changes approximately in line with the temperature rise of the intake valve 11 is used until the temperature of the intake valve 11 reaches the steady-state temperature. 1. Direct feed rate initial value f10 (WT) at start-up, valve portion evaporation rate initial value f40 (WT) and direct feed rate f1 (WT), valve portion evaporation rate that changes momentarily as the coolant temperature WT rises It is calculated as a load average value with f4 (WT).
[0071]
Therefore, even immediately after the cold start of the engine 1 having a low coolant temperature WT, the port wall evaporation coefficient Y and the direct feed coefficient α and the valve evaporation coefficient X can be optimized, and the port wall evaporation transport can be achieved. Not only the amount TTRNSY (n) but also the direct transport amount TB (n) · α and the valve evaporation transport amount TTRNSX (n) should be determined appropriately in accordance with the actual situation, and the fuel injection amount must always be corrected accurately. Is possible.
[0072]
This makes it possible to supply an appropriate amount of fuel corresponding to the basic injection amount TB (n) corresponding to the target air-fuel ratio in the combustion chamber 5 immediately after the cold start when the engine temperature is low. Therefore, it is possible to reliably prevent the deterioration of the output performance of the engine 1 and the deterioration of the exhaust gas performance immediately after the cold start.
[0073]
Although the description of the embodiment of the fuel injection control device according to the present invention has been completed, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the load average value using the weighting coefficient γ is applied to both the direct feed coefficient α and the valve portion evaporation coefficient X. However, as another embodiment, the temperature of the intake valve 11 is particularly large. The load average value using the weight coefficient γ may be applied only to the dependent valve portion evaporation coefficient X, or the load average value using the weight coefficient γ may be applied only to the direct feed coefficient α. Also good.
As a result, the fuel injection amount can be corrected favorably, and the control accuracy of the fuel injection control can be improved.
[0075]
【The invention's effect】
  As described in detail above, the present inventionClaim1According to the fuel injection control device for an internal combustion engine of the present invention, the valve portion evaporation ratio initial value of the evaporated fuel that is set according to the temperature of the internal combustion engine immediately after the start of the internal combustion engine among the amount of fuel adhering to the intake valve A weighted average value with the valve portion evaporation rate sequentially set according to the temperature change of the internal combustion engine is obtained, and a valve portion evaporation transport amount is obtained based on the weighted average value of the valve portion evaporation rate. Of these, based on the direct feed ratio that is sequentially set according to the temperature change of the internal combustion engine and the port wall portion evaporation ratio that is sequentially set according to the temperature change of the internal combustion engine out of the fuel amount attached to the inner wall of the intake port. The direct injection amount and the port wall evaporative transport amount are obtained, and the basic injection amount is calculated from the deviation between the basic injection amount and the predicted transport amount that is the sum of the direct transport amount, the valve part evaporative transport amount, and the port wall evaporative transport amount. To be transported to the combustion chamber Because calculating the amount and to calculate the actual injection quantity,Port wall evaporation rate,Direct transportation volume by optimizing the evaporation rate of the valveWithPort wall evaporative transportas well asThe amount of evaporative transport in the valve section can be determined appropriately in accordance with the actual situation, and the fuel injection amount can be corrected.correctCan be done.
[0076]
  As a result, even after the cold start, the fuel for the basic injection amount corresponding to the target air-fuel ratio can be satisfactorily supplied to the combustion chamber, and the actual air-fuel ratio in the combustion chamber can be controlled according to the target air-fuel ratio. it can.
  Claims2According to this fuel injection control apparatus, the direct injection ratio initial value that is set according to the temperature of the internal combustion engine immediately after the start of the internal combustion engine in the basic injection amount and the direct feed that is sequentially set according to the temperature change of the internal combustion engine. Further, a weighted average value is obtained from the ratio, and further, the initial value of the evaporation portion of the evaporated fuel portion set according to the temperature of the internal combustion engine and the internal combustion amount of the fuel attached to the intake valve immediately after the start of the internal combustion engine Obtain the weighted average value with the valve part evaporation rate sequentially set according to the engine temperature change, and based on the weighted average value of the direct delivery rate and the weighted average value of the valve part evaporation rate, the direct transport amount and the valve part evaporation transport On the other hand, the port wall evaporative transport amount is determined based on the port wall evaporating ratio that is sequentially set according to the temperature change of the internal combustion engine in the port wall adhering fuel amount adhering to the inner wall of the intake port. , Basic injection amount, Calculate the correction amount that should realize the transport of the basic injection amount to the combustion chamber from the deviation from the predicted transport amount, which is the sum of the direct transport amount, the valve portion evaporative transport amount, and the port wall portion evaporative transport amount. The direct delivery rateWith port wall evaporation rateAnd the amount of direct transportation by optimizing the evaporation rate of the valveAlong with port wall evaporative transportIn addition, the amount of evaporative transport of the valve portion can be determined appropriately in accordance with the actual situation, and the fuel injection amount can be corrected accurately.
[0077]
  As a result, the fuel for the basic injection amount corresponding to the target air-fuel ratio can be satisfactorily supplied into the combustion chamber even immediately after the cold start, and the actual air-fuel ratio in the combustion chamber is accurately controlled according to the target air-fuel ratio. be able to.
  Claims3According to the fuel injection control device, the weighted average value of the direct feed ratio is obtained by applying a weight that increases with a predetermined tendency (for example, the temperature rise curve of the intake valve) according to the elapsed period after the start of the internal combustion engine, The weighted average value of the direct feed rate initial value and the subsequent direct feed rate corresponding to the temperature change of the internal combustion engine can be made more appropriate, and the direct feed rate can be optimized.
[0078]
  Claims4According to the fuel injection control apparatus, the weighted average value of the valve portion evaporation ratio is obtained by applying a weight that increases with a predetermined tendency (for example, a temperature rise curve of the intake valve) according to the elapsed period after the start of the internal combustion engine. As a result, the weighted average value of the valve portion evaporation rate initial value and the subsequent valve portion evaporation rate corresponding to the temperature change of the internal combustion engine can be made more appropriate, and the valve portion evaporation rate can be optimized.
[0079]
  Claims5According to the fuel injection control apparatus, the weighted average value of the direct feed ratio and the valve portion evaporation ratio is weighted with a predetermined tendency (for example, the temperature rise curve of the intake valve) according to the number of combustions after starting the internal combustion engine. , The weighted average value can be made extremely appropriate, and the valve portion evaporation rate can be further optimized..
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel injection control device for an internal combustion engine according to the present invention.
FIG. 2 is a flowchart showing a control routine of fuel injection control of the fuel injection control device according to the present invention.
FIG. 3 is a flowchart showing a subroutine of injection amount correction control.
FIG. 4 is a diagram showing the relationship between the number N of engine combustions after starting and the degree of temperature increase of the intake valve ((current temperature−starting temperature) / (steady temperature−starting temperature)).
[Explanation of symbols]
1 engine
5 Combustion chamber
6 Fuel injection valve
9 Intake port
10 Intake manifold
11 Intake valve
40 ECU (Electronic Control Unit)
44 Water temperature sensor
46 Ignition switch

Claims (5)

Fuel injection of an internal combustion engine comprising basic injection amount setting means for setting a basic injection amount of fuel so as to achieve a target air-fuel ratio with respect to an intake air amount to the internal combustion engine, and injection amount correction means for correcting the basic injection amount In the control device,
The injection amount correcting means includes
Direct feed rate setting means for sequentially setting the direct feed rate directly transported to the combustion chamber of the basic injection amount according to the temperature change of the internal combustion engine;
Setting the initial value of the valve part evaporation rate, which sets the initial value of the valve part evaporation rate that is evaporated immediately after the start of the internal combustion engine and transported to the combustion chamber, in accordance with the temperature of the internal combustion engine. Means,
A valve portion evaporation ratio setting means for sequentially setting a valve portion evaporation ratio that is evaporated and transported to the combustion chamber out of the valve portion attached fuel amount according to a temperature change of the internal combustion engine;
A valve portion evaporation rate weighted average means for obtaining a weighted average value of the valve portion evaporation rate initial value and the sequentially set valve portion evaporation rate;
Of the amount of fuel attached to the inner wall of the intake port, the evaporation rate of the port wall that is evaporated and transported to the combustion chamber is not set as an initial value, but without obtaining a weighted average value with the initial value. , a port wall portion evaporation rate setting means for setting up sequentially in response to temperature changes of the internal combustion engine,
The port wall evaporation rate is determined sequentially according to the temperature change of the internal combustion engine , determining the direct transport amount of the fuel based on the direct feed rate, determining the valve portion evaporation transport amount based on the weighted average value of the valve portion evaporation rate The port wall evaporative transport amount is obtained based on the above, and the predicted transport amount that is expected to be realized by the injection of the basic injection amount is calculated based on the sum of the direct transport amount, the valve portion evaporative transport amount, and the port wall evaporative transport amount. A predicted transportation amount calculating means for calculating;
An actual injection amount calculation means for calculating a correction amount for realizing transport of the basic injection amount to the combustion chamber from a deviation between the basic injection amount and the predicted transport amount, and calculating an actual injection amount including the correction amount. When,
A fuel injection control device for an internal combustion engine, comprising: Fuel injection of an internal combustion engine comprising basic injection amount setting means for setting a basic injection amount of fuel so as to achieve a target air-fuel ratio with respect to an intake air amount to the internal combustion engine, and injection amount correction means for correcting the basic injection amount In the control device,
The injection amount correcting means includes
Direct feed rate initial value setting means for setting a direct feed rate initial value that is directly transported to the combustion chamber immediately after the start of the internal combustion engine in the basic injection amount according to the temperature of the internal combustion engine;
Direct feed rate setting means for sequentially setting the direct feed rate directly transported to the combustion chamber of the basic injection amount according to the temperature change of the internal combustion engine;
Direct sending rate weighted average means for obtaining a weighted average value of the direct sending rate initial value and the sequentially set direct sending rate;
Setting the initial value of the valve part evaporation rate, which sets the initial value of the valve part evaporation rate that is evaporated immediately after the start of the internal combustion engine and transported to the combustion chamber, in accordance with the temperature of the internal combustion engine. Means,
A valve portion evaporation ratio setting means for sequentially setting a valve portion evaporation ratio that is evaporated and transported to the combustion chamber out of the valve portion attached fuel amount according to a temperature change of the internal combustion engine;
A valve portion evaporation rate weighted average means for obtaining a weighted average value of the valve portion evaporation rate initial value and the sequentially set valve portion evaporation rate;
Of the amount of fuel attached to the inner wall of the intake port, the evaporation rate of the port wall that is evaporated and transported to the combustion chamber is not set as an initial value, but without obtaining a weighted average value with the initial value. , a port wall portion evaporation rate setting means for setting up sequentially in response to temperature changes of the internal combustion engine,
A direct transport amount of fuel is obtained based on the basic injection amount and a weighted average value of the direct feed rate, a valve portion evaporative transport amount is obtained based on the weighted average value of the valve portion evaporation rate, and a temperature change of the internal combustion engine is determined. The port wall evaporative transport amount is obtained based only on the port wall evaporative ratio that is sequentially set , and the basic injection amount is injected based on the sum of these direct transport amount, valve portion evaporative transport amount, and port wall evaporative transport amount. Predicted traffic volume calculating means for calculating a predicted traffic volume predicted to be realized by
An actual injection amount calculation means for calculating a correction amount for realizing transport of the basic injection amount to the combustion chamber from a deviation between the basic injection amount and the predicted transport amount, and calculating an actual injection amount including the correction amount. When,
A fuel injection control device for an internal combustion engine, comprising: The direct feed rate weighted average means obtains a weighted average value of the direct feed rate by applying a weight that increases with a predetermined tendency according to an elapsed period after the start of the internal combustion engine with respect to the sequentially set direct feed rate. The fuel injection control device for an internal combustion engine according to claim 2 . The valve portion evaporation rate weighted average means weights the valve portion evaporation rate that is set in a predetermined manner according to an elapsed period after the start of the internal combustion engine with respect to the sequentially set valve portion evaporation rate. The fuel injection control device for an internal combustion engine according to claim 1 or 2 , characterized in that: The fuel injection control device for an internal combustion engine according to claim 3 or 4 , wherein the elapsed period after the start of the internal combustion engine is the number of combustions after the start of the internal combustion engine.

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