Abstract: A piston for an internal combustion engine includes a piston head portion, a pair of piston skirt portions, and a pair of side-wall portions. Each of the side-wall portions includes a pin boss portion having a piston pin hole, and is located between the pair of piston skirt portions. There are set a first axis corresponding to a center longitudinal axis of the piston, a second axis corresponding to an axis of the piston pin holes, and a reference plane corresponding to a plane that passes through the first axis and is orthogonal to the second axis.

Abstract: The present invention provides a piston of an internal combustion engine capable of reducing a deformation amount of a piston head. A piston of an internal combustion engine includes a piston head, a pair of piston pin boss portions, a pair of skirt portions, and four apron portions connecting each of the pair of piston pin boss portions and each of the pair of skirt portions. Each of the four apron portions includes a bent portion, a boss portion-side portion positioned on one side where the pair of piston pin boss portions is located with respect to the bent portion, and a skirt portion-side portion positioned on an opposite side from the pair of piston pin boss portions with respect to the bent portion. A distance between an axis perpendicular to both an axis of a cylinder of the internal combustion engine and an axis of a piston hole and the boss portion-side portion is increasing according to an increase in a distance from the axis of the piston pin hole.

Abstract: Disclosed is an internal combustion engine's piston with a piston head having first and second thinnest portions that are thinnest in thickness of the piston head. With respect to the center axis of the first and second pin holes for supporting the piston pin, the first and second thinnest portions of the piston head are respectively provided on both sides of a transverse axis that is perpendicular to the center axis of the first and second pin holes. Each of first and second rib portions that are respectively formed on inner surfaces of first and second pin boss portions extends at the piston head in a direction along the transverse axis to overlap each of the first and second thinnest portions of the piston head. This piston is capable of relaxing stress concentration at a position above the piston pin.

Abstract: Pin body has lightening hole having one-end-side and another-end-side large diameter parts formed on both end sides in the longitudinal direction; a central small diameter part; one-end-side and another-end-side first rounded parts each being provided between the large diameter part and the central small diameter part, having an inner diameter decreasing from each large diameter part side toward the central small part side, and having a rate of change of the inner diameter increasing from each large diameter part side toward the central small diameter part side; and one-end-side and another-end-side second rounded parts each being provided between each first rounded part and the central small diameter part, having an inner diameter decreasing from each first rounded part toward the central small diameter part side, and having a rate of change of the inner diameter decreasing from each first rounded part toward the central small diameter part side.

Abstract: Disclosed is an internal combustion engine's piston with a piston head having first and second thinnest portions that are thinnest in thickness of the piston head. With respect to the center axis of the first and second pin holes for supporting the piston pin, the first and second thinnest portions of the piston head are respectively provided on both sides of a transverse axis that is perpendicular to the center axis of the first and second pin holes. Each of first and second rib portions that are respectively formed on inner surfaces of first and second pin boss portions extends at the piston head in a direction along the transverse axis to overlap each of the first and second thinnest portions of the piston head. This piston is capable of relaxing stress concentration at a position above the piston pin.