Development of a Two-Step Variable Valve Actuation Mechanism Equipped with an Electronic Switching System to Realize Switching Performance within One Cycle

This paper introduces a two-step variable valve actuation (VVA) mechanism equipped with an electronic switching system, which can be applied to OHC valve trains with end pivot rocker arms. The electronic switching system is driven by a dedicated solenoid and is not affected by the temperature or pressure of the engine oil. Therefore, not only can the dynamic stability be secured at the time of mode switching but the operation delay time can also be kept short enough. Several models of two-step VVA mechanisms were fabricated and the operability of the mechanism and switching system was experimentally confirmed. The two-step VVA mechanism developed in this study can also be used as a cylinder deactivation (CDA) system by assigning the lift of the low-speed cam to be zero. By attaching a roller to the portion of the rocker arm that is in contact with the base cam, the problem of pad wear, which is often present in CDA mechanism, is also fundamentally solved.