Internal combustion engine

1. An internal combustion engine, comprising:

a cylinder block;

a crankshaft rotatably supported in the cylinder block;

an oil pan fastened to a lower end portion of the cylinder block;

a chain case fastened to one end wall of the cylinder block in an axial direction of the crankshaft;

a belt wound around a crank pulley provided on an end portion of the crankshaft protruding from the chain case and an accessory pulley provided on an engine accessory; and

a tensioner contacting a back surface of the belt and applying a tension to the belt,

wherein the tensioner includes multiple fastening portions, such that one of the multiple fastening portions is fastened to at least one of the cylinder block and the chain case, and another one of the multiple fastening portions is fastened to the oil pan, and

wherein the oil pan protrudes more outward than the end wall of the cylinder block in the axial direction of the crankshaft, and

the chain case has a lower end fastened to an upper end of an end portion of the oil pan in a vertical direction.

2. The internal combustion engine according to claim 1 , wherein the oil pan is fastened to the chain case by a bolt extending vertically, and

the multiple fastening portions of the tensioner are fastened to the chain case and the oil pan by bolts extending in the axial direction of the crankshaft.

3. The internal combustion engine according to claim 1 , wherein the tensioner includes a base member provided with the multiple fastening portions, an arm member having a base end rotatably supported by the base member and a tip end provided with a roller, and an urging member urging the arm member relative to the base member in a direction in which the tip end of the arm member approaches the belt, and

the arm member extends upward from the base end to the tip end in a state where the roller is in contact with the belt.

4. The internal combustion engine according to claim 3 , wherein the base end of the arm member is located lower than a rotation center of the crank pulley, and the tip end of the arm member is located higher than the rotation center of the crank pulley.

5. The internal combustion engine according to claim 1 , wherein the oil pan includes a flange fastened to the lower end portion of the cylinder block, a ridge extending downward from the flange, and a fastening seat provided on the ridge and fastened to the other one of the fastening portions of the tensioner.