Patent ID: 7111599

Claim:
A valve-driving system which is applied to an internal combustion engine having a plurality of cylinders for driving an intake or exhaust valve provided in each cylinder, comprising: a plurality of valve-driving apparatuses, each of which is provided for at least each one of the intake valve and the exhaust valve, each valve-driving apparatus comprising an electric motor as a driving source for generating rotation motion and a power transmission mechanism provided with a transmitting section for transmitting the rotation motion generated by the electric motor and a converting section for converting the rotation motion transmitted from the transmitting section into opening and closing motion of the valve to be driven; and a motor control device which controls operations of electric motors of the respective valve-driving apparatuses in accordance with an operation state of the internal combustion engine, wherein: the converting section of the power transmission mechanism converts the rotation motion generated by the electric motor into the opening and closing motion utilizing a cam, the motor control device estimates a variation in a number of revolutions of the internal combustion engine based on a variation in the operation state of the internal combustion engine, and sets a control amount of the electric motor while taking a result of the estimation into account, and the motor control device includes a mode switching device which switches driving modes of the electric motor between a normal rotation mode in which the electric motor is drive only in a normal direction to open and close the valve and a normal-reverse rotation mode in which the electric motor is normally or reversely rotated in accordance with the operation state of the internal combustion engine.