Magneto generator

A magneto generator comprising:

• a magnet rotor having a cup-shaped rotor yoke with a peripheral wall and a bottom wall and a permanent magnet mounted to an inner periphery of the peripheral wall of the rotor yoke;
• and an armature placed inside the magnet rotor,
• wherein the bottom wall of said rotor yoke is drilled at a portion closer to an outer periphery to circumferentially provide a plurality of air vents in said peripheral wall,
• an annular plate having a plurality of through holes corresponding to the plurality of air vents in the bottom wall of said rotor yoke, and a plurality of cooling air introducing portions each provided to protrude in an opposite direction to said rotor yoke and cover at least a part of each of said plurality of through holes from outside is placed with said through holes communicating with corresponding air vents and fastened by screws to the bottom wall of said rotor yoke,
• a cooling air introducing passage is formed inside each of said cooling air introducing portions, and an end of the cooling air introducing passage communicates with a corresponding through hole,
• the other end of the cooling air introducing passage inside said cooling air introducing portion opens forward in the rotational direction of said magnet rotor through an opening end of said cooling air introducing portion,
• said cooling air introducing portion has an outer side wall provided to extend in a sloping direction from near a corresponding through hole toward the outer peripheral portion of said rotor yoke and reach said opening end, and
• the opening end of said cooling air introducing portion is directed in a sloping direction toward an inner diameter of said rotor yoke with respect to the direction orthogonal to a reference plane including both a straight line between the center of the bottom wall of said rotor yoke and the center of a corresponding through hole, and a central axis of said rotor yoke.