| 摘要 |
PURPOSE:To enable low vibration even in a low-speed rotating region by providing a pair of balance shafts driven by a motor and driving the motor only when the rotational frequency of a crankshaft is under a preset value. CONSTITUTION:A pair of balance shafts 12, 13 are disposed symmetrically about a crankshaft 9 outside an engine body 8. A control device 18 controls a motor 17 according to signals input from detecting portions 24, 25 for detecting an angular velocity and a crank angle of the crankshaft 9. The motor 17 is driven only when the rotational frequency of the crankshaft 9 is a preset value or less. Accordingly, vibromotive moment in a low-speed rotating region can be remarkably reduced. |
