Patent ID: 7717075
Filing Date: 2010-05-18
Classification: F01L,Y10T

Abstract:
1. A cam mechanism having forced-valve-opening and valve-closing cams for forcibly driving an air intake valve and exhaust valve, said valve-opening and valve-closing cams having respective cam profiles set on the basis of normal valve lift amount curves that are provided by: plotting, in a graph where a vertical axis represents valve lift amounts of the air intake valve and exhaust valve and a horizontal axis represents cam rotation angles, a basic valve lift curve of the valve-opening cam indicative of relationship between the cam rotation angles and valve lift amounts of the valve-opening cam and a basic valve lift curve of the valve-closing cam indicative of relationship between the cam rotation angles and valve lift amounts of the valve-closing cam by offsetting the basic valve lift curve of the valve-opening cam in a valve-lift-amount increasing direction; setting no-load valve lift correction curves of the valve-opening and valve-closing cams by offsetting a no-load curve section of the basic valve lift curve of the valve-opening cam, along which a corresponding one of the followers for actuating the air intake valve and exhaust valve does not slide, away from the basic valve lift curve of the valve-closing cam and by offsetting a no-load curve section of the basic valve lift curve of the valve-closing cam, along which the follower does not slide, away from the basic valve lift curve of the valve-opening cam, or by modifying the offset no-load curve sections into desired shapes; and forming respective normal valve lift curves of the valve-opening and valve-closing cams by connecting the no-load valve lift correction curves with remaining sections of corresponding ones of the basic valve lift curves, the cam profiles of the valve-opening and valve-closing cams being set on the basis of the respective normal valve lift curves.