| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that an oil is vainly consumed and maintenance cost is increased due to earlier oil changing since a diesel engine oil changing is carried out every predetermined mileage based on estimation of an amount of soot generated by combustion, depending on the mileage, but the estimation is not accurate. SOLUTION: An oil degradation degree of the diesel engine is determined depending on an injection terminating time point when the injection is carried out such that the injection terminating time point is made earlier than a certain time point (TB). However, it is found that when the fuel injection terminating time point is made later than the certain time point, a phenomenon (correlation) in which the oil degradation degree is determined depending on an injection amount subsequent to the certain time point and the injection terminating time point. By using the phenomenon, the soot generation amount can be accurately found compared with the prior art. Accordingly, it is determined every fuel injection that the injection terminating time point is earlier or later than the certain time point, whereby a degradation value in a present fuel injection is found using a map depending on the respective injection terminating time points. A value of accumulating and adding the degradation value in the present fuel injection is found thereby determining the oil degradation.
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