A piezoelectric driven ratchet actuator mechanism with application to automotive engine valves

Increasing demands on the performance of internal combustion engines, specifically automobile engines, require the production of more mechanical energy for a given amount of chemical fuel with reduced tailpipe emissions. Of particular interest in the development of high performance/low emission engines is the control and timing of individual engine valves. This paper investigates the design of an innovative piezoelectric ceramic (PZT) based actuator mechanism with a novel stepping motion amplifier to deliver force and displacement at higher magnitudes and operating frequencies. The target application is an engine valve train which traditionally uses cam-based lifter driven rocker arms to regulate the cylinders' intake and exhaust valve motion. The proposed PZT-based actuator mechanism introduces a high frequency, lightweight, precise position solution for cylinder-by-cylinder variable valve timing. Numerical results are provided to demonstrate the feasibility of a PZT-based/camless valve train. The new valve train demonstrates similar cam-based performance characteristics while enabling computer controlled individual valve timing opportunities. (C) 2003 Elsevier Science Ltd. All rights reserved.