Crank cap assembly and internal combustion engine

A crank cap assembly provided with a crank cap rotatably supporting a crankshaft, the crank cap assembly comprising:

• a mass portion;
• two cap bolts fixing the crank cap to an engine body;
• and
• an elastic supporter disposed between the two cap bolts, the elastic supporter elastically supporting the mass portion with respect to the crank cap in an axial direction of the crankshaft, wherein
• the elastic supporter includes an attachment bolt attaching the mass portion to the crank cap, and a first elastic body disposed between the mass portion and the crank cap,
• the mass portion has a through hole penetrating the mass portion,
• the attachment bolt extends through the through hole and attaches the mass portion to the crank cap such that the first elastic body is sandwiched between the mass portion and the crank cap,
• the first elastic body is rubber, and
• an elastic modulus of a middle portion of the first elastic body is larger than an elastic modulus of both of first end portions of the first elastic body in the axial direction of the crankshaft.