Piston for internal combustion engine having congruous combustion bowl and gallery surfaces and method of making the same

A piston for an internal combustion engine comprising:

• a piston body defining a piston center axis extending between a first axial piston body end and a second axial piston body end;
• the first axial piston body end having a bowl surface forming a combustion bowl, a rim surface forming an annular rim extending circumferentially around the combustion bowl, and a gallery surface exposed to a backside cooling gallery of the piston;
• the bowl surface includes an outer bowl surface that is concave to the combustion bowl, and forms a bowl profile that is varied circumferentially around the piston center axis, such that the bowl surface defines, within the combustion bowl, a plurality of bowl peak points and a plurality of bowl valley points;
• the gallery surface is concave to the combustion bowl and convex to the backside cooling gallery, and forms a gallery profile that is varied circumferentially around the piston center axis, such that the gallery surface defines, within the backside cooling gallery, a plurality of gallery peak points and a plurality of gallery valley points circumferentially aligned with the plurality of bowl peak points and the plurality of bowl valley points, respectively;
• a wall thickness is defined between the bowl surface and the gallery surface;
• and
• the bowl profile is varied, circumferentially around the center axis, to a greater relative extent, and the gallery profile is varied, circumferentially around the center axis, to a lesser relative extent, such that the wall thickness is greater at circumferential locations of the plurality of bowl peak points and the plurality of valley peak points than at circumferential locations of the plurality of bowl valley points and the plurality of gallery valley points.

A method of making a piston for an internal combustion engine comprising:

• forming, in a piston body defining a center axis, a combustion bowl and an annular rim extending circumferentially around the combustion bowl;
• forming, in the piston body, a backside cooling gallery;
• profiling the combustion bowl, circumferentially around the center axis, such that a bowl surface concave to the combustion bowl defines a plurality of bowl peak points within a plurality of bowl peaks and a plurality of bowl valley points within a plurality of bowl valleys;
• the plurality of bowl peaks each having a lesser circumferential extent around the center axis and a rounded profile that is convex to the combustion bowl, and the plurality of bowl valleys each having a greater circumferential extent around the center axis and being located at high heat input locations of the piston body;
• varying a bowl profile of the combustion bowl, circumferentially around the center axis, to a greater relative extent based on the profiling of the combustion bowl;
• profiling the backside cooling gallery, circumferentially around the center axis, such that a gallery surface defines a plurality of gallery peak points and a plurality of gallery valley points circumferentially aligned with the plurality of bowl peak points and the plurality of bowl valley points, respectively;
• and
• limiting hot spot formation at the high heat input locations of the piston body at least in part by:
• shaping the gallery surface, in a circumferential aspect, such that a gallery profile formed by the gallery surface is congruous with a bowl profile formed by the bowl surface;
• shaping the gallery surface, in an axial aspect, such that the gallery surface has a curvature that is concave to the combustion bowl and convex to the backside cooling gallery;
• and
• varying a wall thickness defined between the bowl surface and the gallery surface, circumferentially around the center axis, to a lesser relative extent based on the profiling of the backside cooling gallery, such that the wall thickness is greater at circumferential locations of the plurality of bowl peak points and the plurality of valley peak points than at circumferential locations of the plurality of bowl valley points and the plurality of gallery valley points.