Driving force transmission device and rotary mechanism

A rotary assembly comprising:

• a main wheel including a plurality of driven rollers in an annular shape and rotatable around a rotation axis;
• and
• a pair of driving force transmission devices configured to transmit a driving force to the main wheels;
• wherein
• one driving force transmission device of the pair of driving force transmission devices includes:
• a plurality of drive rollers annular in shape and configured to transmit the driving force to the main wheels;
• a plurality of roller support portions annular in shape and rotatably supporting the plurality of drive rollers, respectively;
• and
• a roller arrangement portion in which the plurality of drive rollers and the plurality of roller support portions are located, wherein
• the roller arrangement portion includes:
• a base portion extending radially outward with respect to the rotation axis;
• an outer frame portion located along a circumferential direction around the rotation axis and protruding from the base portion in an axial direction along the rotation axis;
• and
• an inner frame portion located radially inside the outer frame portion and protruding from the base portion in the axial direction;
• and
• the plurality of roller support portions are fitted between an inner circumferential surface of the outer frame portion and an outer circumferential surface of the inner frame portion;
• the one driving force transmission device of the pair of driving force transmission devices transmits a driving force to the main wheel from one side in the axial direction along the rotation axis;
• and
• another driving force transmission device of the pair of driving force transmission devices has a structure symmetrical to the one driving force transmission device with respect to the main wheel, and transmits a driving force to the main wheel from another side in the axial direction along the rotation axis.