Piston and internal combustion engine

Abstract

A piston includes a cooling portion formed in an annular cavity inside a piston head and through which lubricating oil flows, a discharge port that communicates with the cooling portion and discharges lubricating oil from the cooling portion to a lower side the piston head, and a skirt portion extending downward from a lower end portion of an outer periphery of the piston head. The skirt portion includes a groove portion that is formed in an inner peripheral surface and through which the lubricating oil discharged from the discharge port flows along the inner peripheral surface.

What is claimed is: 
     
         1 . A piston that reciprocates within a cylinder, the piston comprising:
 a piston head having a combustion chamber formed on a top surface;   a cooling portion formed in an annular cavity inside the piston head and through which lubricating oil flows;   a discharge port that communicates with the cooling portion and discharges lubricating oil from the cooling portion to a lower side of the piston head; and   a skirt portion extending downward from a lower end portion of an outer periphery of the piston head, wherein the skirt portion includes a flow path portion that is formed in an inner peripheral surface opposite to an outer peripheral surface facing the cylinder, and through which lubricating oil discharged from the discharge port flows along the inner peripheral surface.   
     
     
         2 . The piston according to  claim 1 , wherein the flow path portion is formed in the inner peripheral surface up to a lower end of the skirt portion. 
     
     
         3 . The piston according to  claim 1 , wherein the flow path portion is a groove portion in which the inner peripheral surface of the skirt portion is recessed along an axial direction of the piston. 
     
     
         4 . The piston according to  claim 3 , wherein a distance between a bottom surface of the groove portion and the outer peripheral surface of the skirt portion decreases toward a lower end of the skirt portion. 
     
     
         5 . The piston according to  claim 3 , wherein a width of the groove portion in a direction perpendicular to a vertical direction is larger than a diameter of the discharge port. 
     
     
         6 . The piston according to  claim 3 , wherein a width of the groove portion in a direction perpendicular to a vertical direction increases toward a lower end of the skirt portion. 
     
     
         7 . The piston according to  claim 1 , wherein the flow path portion is formed in the inner peripheral surface to extend from an upper end to a lower end of the skirt portion. 
     
     
         8 . The piston according to  claim 7 , wherein a thickness of the skirt portion decreases from the upper end toward the lower end. 
     
     
         9 . The piston according to  claim 1 , wherein the flow path portion is connected to a discharge path having the discharge port formed at a distal end. 
     
     
         10 . An internal combustion engine comprising:
 a cylinder; and   a piston that reciprocates within the cylinder, wherein the piston includes:   a piston head having a combustion chamber formed on a top surface;   a cooling portion formed in an annular cavity inside the piston head and through which lubricating oil flows;   a discharge port that communicates with the cooling portion and discharges lubricating oil from the cooling portion to a lower side of the piston head; and   a skirt portion extending downward from a lower end portion of an outer periphery of the piston head, among which the skirt portion includes a flow path portion that is formed in the inner peripheral surface opposite to an outer peripheral surface facing the cylinder, and through which lubricating oil discharged from the discharge port flows along the inner peripheral surface.