Torsional vibration damping device

A torsional vibration damping device, comprising:

• a rotary member;
• a plurality of rolling masses that are oscillated relatively to the rotary member by torque pulse;
• a bore formed on an outer circumferential portion of the rotary members to penetrate through the rotary member in a direction parallel to a rotational center axis;
• a cover as a hollow annular member having a rectangular cross-section, that covers the outer circumferential portion of the rotary member to hold the rolling masses and bores liquid-tightly;
• and
• a deformation-preventing member that prevents a deformation of the cover in a direction toward the rolling mass, the deformation-preventing member including a plurality of ribs extending from an inner lateral face of the cover perpendicular to the rotational center axis at positions in a circumferential direction of the rotary member between the bores,
• wherein the bores are formed on the rotary member in a circular manner,
• wherein the deformation-preventing member is arranged between the bores, and prevents the rolling masses from contacting the cover, and
• wherein each of the ribs are formed respectively between the bores at a position not to cause an interference with an oscillating motion of the rolling masses.