Dynamic damper

A dynamic damper comprising:

• a cylindrical mass metal element;
• a cylindrical elastic-body member extending radially inward from said mass metal element toward a center axis of said mass metal element and fitted onto a rotary shaft whose vibrations are to be damped so as to elastically support said mass metal element on said rotary shaft;
• and
• an elastic-body covering portion covering an outer circumferential surface of said mass metal element,
• wherein said elastic-body member and said elastic-body covering portion are not bonded to said mass metal element, and a plurality of protrusions are formed and arranged circumferentially on an inner circumferential surface of said mass metal element.

A dynamic damper comprising:

• a cylindrical mass metal element;
• a pair of cylindrical elastic-body attachment portions disposed a predetermined distance outwardly away from corresponding axial opposite ends of said mass metal element while being coaxial with said mass metal element, said elastic-body attachment portions each having an inside diameter smaller than that of said mass metal element and being fitted onto a rotary shaft whose vibrations are to be damped so as to fixedly attach said dynamic damper on said rotary shaft;
• a pair of elastic-body connection portions adapted to connect the axial opposite ends of said mass metal element and corresponding said elastic-body attachment portions along an entire circumference;
• and
• elastic-body covering portions covering inner and outer circumferential surfaces of said mass metal element,
• wherein said elastic-body connection portions and said elastic-body covering portions are not bonded to said mass metal element, and a plurality of protrusions are formed and arranged circumferentially on opposite end faces of said mass metal element.