Reciprocating internal combustion engine

A reciprocating internal combustion engine comprising:

• a planetary gear mechanism including a ring gear that is an internal gear, a carrier that is rotatably supported with respect to the ring gear, and a planetary gear that is rotatably supported with respect to the carrier and meshes with the ring gear;
• a crank member coupled to the planetary gear to rotate integrally with the planetary gear, with a direction along a carrier axis which is a rotation axis of the carrier being defined as an axial direction, a direction orthogonal to the carrier axis being defined as a radial direction, and a direction orthogonal to a planetary axis which is a rotation axis of the planetary gear being defined as a planetary radial direction;
• a piston member coupled to the crank member to be relatively rotatable about an input axis set at a position separately from the planetary axis in the planetary radial direction;
• and
• a transmission mechanism configured to transmit a rotation of the carrier to an output member, wherein
• a radius of the ring gear is twice a radius of the planetary gear,
• a pair of planetary bearings are disposed separately on both sides of the planetary gear in the axial direction to rotatably support the planetary gear with respect to the carrier,
• a pair of carrier bearings are disposed separately on both sides of the ring gear in the axial direction to rotatably support the carrier with respect to the ring gear,
• the crank member includes a first crank portion and a second crank portion which are a pair of crank portions disposed separately on both sides of the carrier in the axial direction,
• the piston member includes a piston body and a pair of coupling portions including a first coupling portion and a second coupling portion that are coupled to the piston body and disposed separately on both sides of the carrier in the axial direction,
• the first crank portion and the second crank portion are disposed to extend in the planetary radial direction,
• the first coupling portion is coupled to the first crank portion to be relatively rotatable about the input axis, and
• the second coupling portion is coupled to the second crank portion to be relatively rotatable about the input axis.