VARIABLE VALVE TIMING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a variable valve timing system using an electric motor as an actuator, capable of appropriately detecting the overheated state of the electric motor and a drive unit so as to protect the system and improve the controlling performance. SOLUTION: An actuator operation quantity setting portion 6000 generates a rotational speed command value Nmref for the electric motor 2060 so that the phase of an intake valve is changed to match a target phase. An electric-motor EDU 4100 controls electric power PWm supplied to the electric motor so that the electric motor 2060 operates in accordance with the rotational speed command value Nmref. An overheat judgment portion 6200 judges whether it is necessary to restrict heat generation or not based on comparison between information showing the electric power PWm supplied to the motor and a criterion of judgment DTYj. A command value restricting portion 6300 restricts the rotational speed command value Nmref fed to the electric-motor EDU 4100 within a predetermined range when it is judged that the restriction of heat generation is required. A judgment criterion setting portion 6100 sets the judgment criterion DTYj to be variable according to the rotational speed of the electric motor 2060. COPYRIGHT: (C)2008,JPO&INPIT