Abstract
In recent years, circumstance for prime mover of automobile has been severer. Reliability or durability also is requested for more long running time. DOHC mechanism for intake or exhaust system must be refined for these requirements. Particularly, jump phenomena on high speed operation cause noise which give offensive to the ear and fracture this system. However, research on this field has not treated direct visibility. Therefore, this study describes that jump phenomena find out running with soft valve spring. Also, it is reported that comparison between test results using strain gage and laser displacement meter, and calculation results of five mass model which has developed for valve mechanism of direct attack type.
