| 摘要 |
PROBLEM TO BE SOLVED: To suppress subsequent progress of oil deterioration when the oil deterioration reaches replacement time and thus avoid lubrication failure.SOLUTION: An oil deterioration level Or calculated based on a detection signal from an oil deterioration sensor is compared with an oil deterioration determination threshold value Orth corresponding to oil replacement time (Step 3). When the oil deterioration level Or is less than the threshold value Orth, a reference target compression ratio &egr;0 corresponding to an operating condition is set as a target compression ratio t&egr; (Steps 2, 4). When the oil deterioration level Or is equal to or more than the threshold value Orth, a warning lamp is lit (Step 5) and the reference target compression ratio &egr;0 is corrected to the low compression ratio side by compression ratio reduction correction amount &egr;h corresponding to the oil deterioration level Or (Steps 6, 7, 9). When the corrected compression ratio &egr;1 is a minimum compression ratio &egr;min or lower, fixation to the minimum compression ratio &egr;min is performed (Steps 8, 10). Since decrease in a combustion temperature reduces a NOx concentration in blow-by gas, progress of oil deterioration is suppressed. |
