Piston of internal combustion engine

Abstract

A piston of an internal combustion engine includes a crown surface, a first cavity, and a second cavity. The crown surface forms an internal wall surface of a combustion chamber. The first cavity is a depression provided in the crown surface. The second cavity is a depression provided inside the first cavity. The first cavity includes an upstream portion located upstream of the second cavity in a flow direction of a tumble flow flowing along the crown surface and a downstream portion located downstream of the second cavity in the flow direction. The upstream portion extends further in the flow direction than the downstream portion.

The invention claimed is: 
     
       1. A piston of an internal combustion engine, comprising:
 a crown surface configured to both form an internal wall surface of a combustion chamber and to receive a tumble flow along the crown surface; 
 a first cavity that is a depression provided in the crown surface; and 
 a second cavity that is a depression provided inside the first cavity, wherein 
 the first cavity includes an upstream portion located upstream of the second cavity in a flow direction of the tumble flow flowing along the crown surface and a downstream portion located downstream of the second cavity in the flow direction, the upstream portion extending farther in the flow direction than the downstream portion, and 
 wherein the second cavity has a curved wall surface extending between a more centralized region of the second cavity and up to a border region with the first cavity 
 wherein the crown surface has a radial outer surface extending radially inward from an outer periphery of the crown surface to a border location with the first cavity, and the first cavity has a curved surface extending between a more centralized region of the first cavity and up to a border region with the radial outer surface of the crown surface, and 
 said piston further comprising a plurality of recesses spaced circumferentially about the crown surface, with at least one recess extending through the radial outer surface and to the first cavity, and at least one other recess extending through the radial outer surface, within the first cavity, and to the second cavity. 
 
     
     
       2. The piston according to  claim 1 , wherein the second cavity has an elliptical shape whose short axis lies in the flow direction. 
     
     
       3. A piston of an internal combustion engine, comprising:
 a crown surface configured to both form an internal wall surface of a combustion chamber extending along a first axis and to receive a tumble flow along the crown surface; 
 a first cavity that is a depression provided in the crown surface; and 
 a second cavity that is a depression provided inside the first cavity, wherein 
 the first cavity includes an upstream portion located upstream of the second cavity in a flow direction of the tumble flow flowing along the crown surface and a downstream portion located downstream of the second cavity in the flow direction, the upstream portion extending farther in the flow direction than the downstream portion, and 
 wherein the crown surface has a radial outer surface extending radially inward from an outer periphery of the crown surface to a border location with the first cavity, and wherein the first cavity has a curved wall surface extending between a more centralized region of the first cavity and up to a border region with the radial outer surface, and 
 said piston further comprising a plurality of recesses spaced circumferentially about the crown surface, with at least one recess extending through the radial outer surface and to the first cavity, with at least one other recess extending through the radial outer surface, within the first cavity, to the second cavity. 
 
     
     
       4. The piston according to  claim 3 , wherein the second cavity has an elliptical shape whose short axis lies in the flow direction.