| 摘要 |
PURPOSE:To reduce not only operational force but also exciting force given to a tappet valve system at the time of changing over a cam by forming a lift control cam for a valve through arranging the plural number of plane surfaces so as to be changed monotonously and operating said cam througth an elastic member. CONSTITUTION:A lift control cam 20 is formed through joining the plural number of plane cam faces C1-C5 by a smooth curved line, and the cam 20 is connected to a cam control shaft, which operates the cam 20, through an elastic member. By means of driving torque reserved in the elastic body during lift of an air intake/exhaust valve, the control cam 20 can be rotated during closure of the valve, and operation can be performed by small driving force. Further, since distances from the center of rotation to C1-C5 cam faces are such that said faces show monotonous changes in the same direction of rotation, exciting force given to the tappet valve system at the time of changing over the cam faces is reduced and generation of impact sound is suppressed. |
