Monolithic, galleryless piston and method of construction thereof

A piston for an internal combustion engine, comprising:

• a monolithic piston body extending along a central longitudinal axis;
• said piston body having an upper wall forming an upper combustion surface with an annular ring belt region depending from said upper combustion surface;
• said upper combustion surface having first and second portions, said first portion extending annularly along an outer periphery of said upper wall and said second portion forming a combustion bowl depending radially inwardly from said first portion;
• said upper wall having an undercrown surface formed on an underside thereof, said undercrown surface being located directly opposite said second portion of said upper combustion surface;
• said piston body including a pair of skirt portions depending from said ring belt region;
• said piston body including a pair of pin bosses spaced from one another by said skirt portions, each of said pin bosses including an inner surface facing toward said central longitudinal axis and an outer surface facing away from said central longitudinal axis, and each of said pin bosses providing a pin bore extending continuously from said inner surface to said outer surface;
• said piston body being free of a cooling gallery along said undercrown surface between said skirt portions and pin bosses;
• said undercrown surface including a concave center portion located between said pin bosses;
• said undercrown surface having an exposed 2-dimensional area when viewed from an underside of said piston, wherein said exposed 2-dimensional area has a length between about 75-90 percent of a maximum outer diameter of said piston body;
• and
• said undercrown surface including undercrown pockets formed between said outer surfaces of said pin bosses and an inner surface of said ring belt region, and said undercrown pockets defining a portion of said undercrown surface.

A method of constructing piston, comprising the steps of:

• forming a monolithic piston body by at least one of a machining, forging and casting process, the piston body extending along a central longitudinal axis and having an upper wall forming an upper combustion surface with an annular ring belt region depending from the upper combustion surface, the upper combustion surface having first and second portions, the first portion extending annularly along an outer periphery of the upper wall and the second portion forming a combustion bowl depending radially inwardly from the first portion, the upper wall having an undercrown surface formed on an underside thereof, the undercrown surface being located directly opposite the second portion of the upper combustion surface, the piston body including a pair of skirt portions depending from the ring belt region, the piston body including a pair of pin bosses spaced from one another by the skirt portions, each of the pin bosses including an inner surface facing toward the central longitudinal axis and an outer surface facing away from the central longitudinal axis, and each of the pin bosses providing a pin bore extending continuously from the inner surface to the outer surface, the piston body being free of a cooling gallery along the undercrown surface between the skirt portions and pin bosses, the undercrown surface including a concave center portion located along the central longitudinal axis, the undercrown surface including undercrown pockets formed between the outer surfaces of the pin bosses and an inner surface of the ring belt region, and the undercrown pockets defining a portion of the undercrown surface.

A method of constructing piston, comprising the steps of:

• forming a monolithic piston body by at least one of a machining, forging and casting process, the piston body extending along a central longitudinal axis and having an upper wall forming an upper combustion surface with an annular ring belt region depending from the upper combustion surface, the upper combustion surface having first and second portions, the first portion extending annularly along an outer periphery of the upper wall and the second portion forming a combustion bowl depending radially inwardly from the first portion, the upper wall having an undercrown surface formed on an underside thereof, the undercrown surface being located directly opposite the second portion of the upper combustion surface, the piston body including a pair of skirt portions depending from the ring belt region, the piston body including a pair of pin bosses spaced from one another by the skirt portions, each of the pin bosses including an inner surface facing toward the central longitudinal axis and an outer surface facing away from the central longitudinal axis, and each of the pin bosses providing a pin bore extending continuously from the inner surface to the outer surface, the piston body being free of a cooling gallery along the undercrown surface between the skirt portions and pin bosses, the undercrown surface including a concave center portion located between the pin bosses, the undercrown surface having an exposed 2-dimensional area when viewed from an underside of the piston, wherein said exposed 2-dimensional area has a length between about 75-90 percent of a maximum outer diameter of the piston body, and the undercrown surface including undercrown pockets formed between the outer surfaces of the pin bosses and an inner surface of the ring belt region, and the undercrown pockets defining a portion of the undercrown surface.