Monolithic, galleryless piston and method of construction thereof
A galleryless piston for an internal combustion engine and method of construction thereof are provided. The piston has a monolithic piston body extending along a central longitudinal axis. The piston body has an upper wall forming an upper combustion surface with first and second portions, with the first portion extending annularly along an outer periphery of the upper wall and the second portion forming a combustion bowl. The upper wall has an undercrown surface on an underside of the combustion bowl directly opposite the second portion of the upper combustion surface. The undercrown surface has an openly exposed 2-dimensional surface area, as viewed looking along the central longitudinal axis, between about 35-60 percent of an area defined by a maximum outer diameter of the piston body, thereby providing an expansive area against which oil being splashed or sprayed can freely contact to cool the piston.
1. A galleryless piston for an internal combustion engine, comprising:
a monolithic piston body extending along a central longitudinal axis along which said piston reciprocates in a cylinder bore of an internal combustion engine, said piston body having an upper wall forming an upper combustion surface with an annular ring belt region depending from said upper combustion surface for receipt of at least one piston ring; a pair of skirt portions depending from said ring belt region to facilitate guiding the piston within a cylinder bore and having a pair of pin bosses providing a pair of laterally spaced pin bores aligned along a pin bore axis for receipt of a wrist pin; 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 of said combustion bowl directly opposite said second portion of said upper combustion surface, said undercrown surface having an openly exposed projected 2-dimensional surface area, as viewed looking along said central longitudinal axis, between about 35-60 percent of an area defined by a maximum outer diameter of said piston body.
2. The galleryless piston of claim 1 wherein said undercrown surface has a total 3-dimensional surface area that is greater than 40 percent of said area defined by the maximum outer diameter of said piston body.
3. The galleryless piston of claim 2 wherein said undercrown surface has a total 3-dimensional surface area greater than 50 percent of said area of said piston body.
4. The galleryless piston of claim 2 wherein said undercrown surface has a total 3-dimensional surface area greater than 60 percent of said area of said piston body.
5. The galleryless piston of claim 2 wherein said undercrown surface has a total 3-dimensional surface area greater than 70 percent of said area of said piston body.
6. The galleryless piston of claim 1 wherein said undercrown surface has a diameter between about 75-90 percent of said maximum outer diameter of said piston body.
7. The galleryless piston of claim 1 wherein said combustion bowl has a maximum combustion bowl diameter and said undercrown surface has a diameter that is at least 85 percent of said maximum combustion bowl diameter.
8. The galleryless piston of claim 7 wherein said undercrown surface has a diameter that is between 100-140 percent of said maximum combustion bowl diameter.
9. The galleryless piston of claim 1 wherein a pair of pockets extend radially outwardly from said pin bosses along said pin bore axis to said ring belt region, said pockets defining at least a portion of said undercrown surface, a portion of an underside of said first portion and a portion of an inner surface of said annular ring belt region, said pockets having a total 3-dimensional surface area between about 45-85 percent of said 2-dimensional surface area.
10. The galleryless piston of claim 9 wherein said pockets have a total 3-dimensional surface area greater than 60 percent of said maximum 2-dimensional area of said piston body.
11. The galleryless piston of claim 10 wherein said pockets have a total 3-dimensional surface area greater than 70 percent of said maximum 2-dimensional area of said piston body.
12. The galleryless piston of claim 1 wherein said pin bosses have radially outermost surfaces spaced from one another along said pin bore axis at a first distance that is less than 60 percent of said maximum outer diameter of said piston body.
13. A method of constructing a galleryless piston for an internal combustion engine, comprising:
forming a monolithic piston body in one of a machining, forging or casting process having an upper wall with an upper combustion surface and an annular ring belt region depending from the upper combustion surface, the upper combustion surface having first and second portions, with 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 of the combustion bowl directly opposite the second portion, the piston body having a pair of skirt portions depending from the annular ring belt region and a pair of laterally spaced pin bores aligned along a pin bore axis for receipt of a wrist pin, the undercrown surface having an openly viewable projected 2-dimensional surface area, as viewed looking along the central longitudinal axis, between about 35-60 percent of an area defined by a maximum outer diameter of the piston body.
14. The method of claim 13 wherein said undercrown surface is formed having a total 3-dimensional surface area greater than 40 percent of the area defined by the maximum outer diameter of the piston body.
15. The method of claim 13 wherein said undercrown surface is formed having a total 3-dimensional surface area greater than 50 percent of said area defined by the maximum outer diameter of said piston body.
16. The method of claim 13 wherein the undercrown surface is formed having a diameter between about 75-90 percent of the maximum outer diameter of the piston body.
17. The method of claim 13 wherein the undercrown surface is formed having a diameter that is at least 85 percent of a maximum diameter of the combustion bowl.
18. The method of claim 17 wherein said undercrown surface is formed having a diameter that is between 100-140 percent of the maximum combustion bowl diameter.
19. The method of claim 13 further including forming a pair of pockets in the machining, forging or casting process, with the pockets extending radially outwardly from the pin bosses along the pin bore axis to the ring belt region, the pockets defining at least a portion of the undercrown surface, a portion of an underside of the first portion and a portion of an inner surface of the annular ring belt region, with the pockets having a total 3-dimensional surface area between about 45-85 percent of the maximum 2-dimensional area of the piston body.
20. The method of claim 13 further including forming the pin bosses having radially outermost surfaces spaced from one another along the pin bore axis a first distance that is less than 60 percent of the maximum outer diameter of the piston body.