PURPOSE: To minimize the holding time of high oil pressure and reduce a work loss by holding a high oil pressure which is generated when compression ratio is changed until a changeover is confirmed by a compression ratio changeover confirming means.
CONSTITUTION: In a device in which compression ratio is changed by hydraulical ly operating an eccentric bearing which is roatably provided in between a piston pin and a connecting rod, a signal from a compression ratio changeover confirming means 33 is inputted into an electronic control device 30 for control ling a selector valve 24. This confirming means 33 is formed with a gap sensor for detecting piston position. When compression ratio is changed, the selector valve 24 is switched while a solenoid valve 29 is closed to increase the oil pressure in a passage 25 or 26 and, as the changeover is confirmed by the compression ratio changeover confirming means 33, the solenoid valve 29 is opened. Thereby, the holding time of high oil pressure can be made a required minimum, reducing a work loss by a pump 23.
IWASAKI EIJI
NARUOKA TAKAO
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