| 摘要 |
PROBLEM TO BE SOLVED: To provide an EGR ratio estimate device for an internal combustion engine, capable of simulating transfer process of mixed gas in a branch in actual condition after considering compression and expansion of the mixed gas, and capable of always accurately estimating an EGR ratio of the mixed gas introduced into a cylinder in spite of operating condition of the internal combustion engine. SOLUTION: When pressure in a surge tank is increased or decreased according to acceleration/deceleration of a car, the mixed gas in the branch is compressed or expanded. For example, at the time of the acceleration, since a part of the mixed gas enters the upstream part of the branch by the compression and a part of the mixed gas in the upstream part of the branch enters the downstream part of the branch, the EGR ratio R<SB>C</SB>(n) of the mixed gas introduced into the cylinder by transfer accompanying the following air intake is changed. Then, the cylinder EGR ratio R<SB>C</SB>(n) is calculated in consideration of variation of the EGR ratios R<SB>U</SB>(n-4), R<SB>L</SB>(n-4) in the branch by the compression or expansion. COPYRIGHT: (C)2004,JPO
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