ENGINE CONTROL METHOD AND ENGINE

PROBLEM TO BE SOLVED: To suppress deterioration of combustion stability in a deceleration state under EGR control.SOLUTION: An engine includes: a turbo supercharger 5; a throttle chamber 4, disposed in an intake air channel 2 on intake-air downstream side than the turbo supercharger 5, capable of changing an intake air amount to be supplied to an engine; and an exhaust recirculation channel 8 communicating between the intake air channel 2 on intake-air upstream side from the turbo supercharger 5 and an exhaust air channel 3 on exhaust-air downstream side than the turbo supercharger 5 returns portion of exhaust air back to the intake air side. A control method includes: detecting or estimating boost pressure inside the intake air channel 2 on the intake-air downstream side than the turbo supercharger 5; detecting or estimating exhaust air pressure inside the exhaust air channel 3 on the exhaust-air downstream side than the turbo supercharger 5; closing the throttle chamber 4 when an accelerator is turned off by a driver operation; and communicating between the intake air channel 2 on intake-air downstream side than the turbo supercharger 5 and the exhaust air channel 3 on exhaust-air downstream side than the turbo supercharger 5 when the throttle chamber 4 is closed, with the boost pressure higher than the exhaust air pressure.SELECTED DRAWING: Figure 1 【課題】ＥＧＲ制御中の減速状態における燃焼安定度の悪化を抑制する。【解決手段】ターボ過給機５と、ターボ過給機５より吸気下流側の吸気通路２にエンジンに供給する吸気量を可変可能なスロットルチャンバ４を備える。また、ターボ過給機５より吸気上流側の吸気通路２と、ターボ過給機５より排気下流側の排気通路３とを連通する排気再循環通路８により排気の一部を吸気側に戻す。そして、ターボ過給機５より吸気下流側の吸気通路２内の過給圧を検出または推定し、ターボ過給機５より排気下流側の排気通路３内の排気圧を検出または推定する。また、ドライバーにより操作されるアクセルのオフ時に、スロットルチャンバ４を閉じ、当該スロットルチャンバ４が閉じていて、且つ、前記過給圧が前記排気圧より大きい時、ターボ過給機５より吸気下流側の吸気通路２と、ターボ過給機５より排気下流側の排気通路３とを連通する。【選択図】図１