Control performance test of an electrically-controlled variable valve timing system using servo motors

Abstract

Recently, technologies related to green cars are gaining attention. A variable valve-Timing system (VVT) is widely used in internal-combustion engines to improve fuel efficiency and engine performance by controlling the valve open-close timing. Since conventional hydraulically controlled VVT has problems, such as slow response and low efficiency, an electrically controlled variable valve timing (ECVVT) system was developed as an alternative the conventional VVT. This paper presents a performance test rig for an ECVVT system using servo motors. The performance test rig consists of an ECVVT module with a cycloid reducer, an engine cylinder block, a driving part, and a motion controller. A small servo motor drives the ECVVT module through the cycloid gear, while a large servo motor drives the camshafts by means of a timing belt. We carried out simulations using a mathematical model of the ECVVT module, cam shaft, valve, and motion control. We then built a performance test rig for the ECVVT system, and did experiment of cam phase variations of the ECVVT system to confirm its performance. Copyright © The Korean Society for Precision Engineering.