Torsional vibration damper

A torsional vibration damper, comprising:

• a planetary gear unit that performs a differential action among
• a sun gear,
• a ring gear arranged concentrically around the sun gear, and
• a carrier supporting a plurality of pinion gears interposed between the sun gear and the ring gear in a rotatable manner,
• wherein one of the sun gear, the ring gear, and the carrier serves as an input element to which a torque is delivered from an engine,
• another one of the sun gear, the ring gear, and the carrier serves as an output element that outputs the torque,
• still another one of the sun gear, the ring gear, and the carrier serves as an inertia element that is rotated relatively to the input element and the output element by an inertia force,
• an elastic member is interposed between the input element and the output element to be deformed elastically by a torsional torque causing a relative rotation between the input element and the output element, and
• each of the pinion gears is individually moved from an initial position when the relative rotation between the input element and the output element is caused by the torsional torque, and individually oscillated by a pulsation of the torque delivered to the input element from the engine,
• each of the pinion gears is individually oscillated within a first oscillating range when the torsional torque is smaller than a reference torque,
• each of the pinion gears is individually oscillated within a second oscillating range when the torsional torque is greater than the reference torque, and
• each backlash between the pinion gears and at least one of the sun gear and the ring gear within the second oscillating range is individually wider than each backlash between the pinion gears and the sun gear within the first oscillating range, and each backlash between the pinion gears and the ring gear within the first oscillating range.