Kinematic design and analysis of a four-bar linkage-type continuously variable valve actuation mechanism

Abstract

This paper proposes a simple mechanical CVVA system using a four-bar linkage, a rotating first cam, and oscillating second cams. The relationship between the cam profiles and valve motion is analyzed using planar-cam theory. The theory is applied to analyze the second cams that have oscillatory motion with variable angular speed. The kinematic behavior of the CVVA system was tested with a computer model. In order to verify the accuracy of the analysis method, calculated valve motions are compared with those from commercial CAD software. Analysis results are used to determine the feasibility of the CVVA mechanism for application to automotive engines. A prototype CVVA system was designed and manufactured. The newly designed CVVA system is successfully operated on a test bench up to 7000 engine rpm, which is the range of the overrun speed of most production spark ignition engines. The CVVA system sustains proper valve timing and event control across the whole speed range.