Study of a Valve Train Cam Profile with Continuous Jerk

In order to address the problem that the valve cam of internal combustion engine could not maintain the continuity of jerk in the whole working sections, a new segmented low-order combined cam profile model was proposed.Through analyzing the motion law of the cam profile model, a method of calculating the angle and expression of each segment via design parameters was obtained, and the constraint conditions of the relevant design parameters were studied.Based on this model, the intake and exhaust cams of an internal combustion engine were designed and were compared with the existing cam profiles.The findings suggest that the cam profile designed by this model can guarantee the continuity of jerk curve at the ramp section, the basic section and the connection of each section.Under the specified design parameters, this model can quickly obtain a uniquely determined cam profile, the number of segments can be automatically adjusted without optimization and adjustment, ensuring maximum velocity and maximum fullness coefficient.Compared with similar profiles, it is found that the fullness coefficient of this cam profile is 1%～12% larger, the maximum velocity is 1%～13.5% larger, and the maximum derivative of jerk is 20%～70% smaller under the same limits.