Torsional vibration damper and manufacturing method thereof

A manufacturing method of a torsional vibration damper comprising:

• a planetary gear unit including
• a sun gear,
• a ring gear arranged concentrically around the sun gear,
• a plurality of planetary pinion gears interposed between the sun gear and the ring gear to transmit a torque to at least one of the sun gear and the ring gear, and
• a carrier supporting the pinion gears 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 rotates relatively to the input element and the output element,
• the input element and the output element are rotated relatively to each other while deforming an elastic member interposed therebetween by a pulsation of the torque of the engine,
• the inertia element is oscillated by the pulsation of the torque of the engine,
• the manufacturing method comprising:
• forming at least one of the sun gear, the ring gear, and the planetary pinion gears by a press forming method in which a forming tool is moved in a direction of face width;
• forming the remaining gear(s) such that each tooth is thinned toward one side of the gear(s);
• and
• thereafter engaging the gear formed by the press forming method with the remaining gear(s) such that a thinner portion of each tooth is individually contacted to a thicker portion of the adjacent teeth of the remaining gear(s).