Design of High Speed Engine's Cam Profile Using B-Spline Functions for Controlled Dynamics

摘要

Recent trends towards design of High Performance Diesel engines creating more challenges in the area of design, durability and NVH aspects of components and systems. In particular, Valvetrain system of High Speed application engines is one of the most critical and complicated dynamic system in terms of precise control of events, max. Lift, control over accelerations and vibration related issues. This can be tackled by designing the cam profile for better valve train dynamics. High frequency components and/or excessive jerks in a cam profile are important sources of cam-follower vibrations. There are various techniques of designing cam profile to achieve controlled valve train dynamic behavior at high speed operations. Present paper discuss the impact of various cam profile options designed using Polydyne, N-Harmonic and B-Spline methodologies on a field problem of cam wear for high speed engine application. Conventional Polydyne method for designing the cam profile has certain limitations in controlling the cam accelerations for valve train system operating at high speed. The cam profile designed using N-harmonic algorithm showed better dynamics and improved cam lobe wear. However, this method also has certain limitations in controlling the cam profile curve for the existing pushrod operated valve train system. Cam profile design technique using B-Spline Curves has ability in controlling curve by defining the boundary conditions for higher derivatives. Therefore, B-spline curve algorithm is adopted for cam profile design of High Speed engines in order to control excessive jerks which were the major cause of the vibrations.