Internal combustion engine and cylinder block
An internal combustion engine to reduce abrasion with a piston while retaining oil film on an upper portion of a cylinder includes: a cylinder block that includes a cylinder, and a piston that is stored in the cylinder in a manner capable of reciprocating along an axis line of the cylinder, in which the cylinder includes a multi-bulging inner circumference portion in which a diameter in a thrust-anti thrust direction is a minimal diameter.
1. An internal combustion engine, comprising:
a cylinder block that includes a cylinder; and
a piston that is stored in the cylinder in a manner capable of reciprocating along an axis line of the cylinder,
wherein
the cylinder includes a multi-bulging inner circumference portion in which a diameter in a thrust-anti thrust direction is a minimal diameter, the multi-bulging inner circumference portion including multiple bulging portions that bulge outward relative to an outer diameter of a virtual cylinder having a perfect circular shape through which the piston passes;
the multi-bulging inner circumference portion is positioned below a position at which a maximal side thrust is received in the cylinder during combustion and expansion strokes; and
the bulging portions are parts having major diameters longer than the minimal diameter and gradually increase downward from the position.
2. The internal combustion engine according to claim 1 , wherein the cylinder includes a perfect-circular inner circumference portion on a side of a top dead center of the piston relative to the multi-bulging inner circumference portion.
3. The internal combustion engine according to claim 1 , wherein the multi-bulging inner circumference portion is positioned below a lower edge position of a skirt portion of the piston that is in a top dead center.
4. A cylinder block, comprising a cylinder that stores therein a piston such that the piston is capable of reciprocating therein,
wherein the cylinder includes a multi-bulging inner circumference portion in which a diameter in a thrust-anti thrust direction is a minimal diameter, the multi-bulging inner circumference portion including multiple bulging portions that bulge outward relative to an outer diameter of a virtual cylinder having a perfect circular shape through which the piston passes;
the multi-bulging inner circumference portion is positioned below a position at which a maximal side thrust is received in the cylinder during combustion and expansion strokes; and
the bulging portions are parts having major diameters longer than the minimal diameter and gradually increase downward from the position.