PURPOSE: To adequately perform the necessary control at the switching time of the actual compression ratio by judging the switching of compression ratios of cylinders in response to the quantity or the operating oil pressure based on the signal from an oil pressure sensor provided on the operating oil passage of a compression ratio-variable mechanism.
CONSTITUTION: The oil pressure of an oil pump 22 feeding the oil of an oil pan 21 to various sections of an engine is utilized to change the relative position of a piston 3 with respect to a connecting rod 23, thereby the compression ratio of the engine is changed. Therefore, a hydraulic solenoid valve 25 is provided as a compression ratio changing means controlled by a controller 27 on an oil line 24 for changing the compression ratio. In this case, an oil pressure sensor 26 is provided on the oil line 24. The controller 27 judges the switching of compression ratios of cylinders in response to the quantity of the operating oil pressure based on the signal from the oil pressure sensor 26. Accordingly, the necessary control is performed with a good timing at the switching time of the actual compression ratio.
TANAKA HIDEKI
HATSUHIRA TSUGIO
YAMAMOTO HIROYUKI
