Galleryless piston with cutout above pin bore
View Patent ↗A galleryless piston having a reduced weight and a reduced operating temperature is provided. The piston includes an undercrown surface exposed from an underside of the piston, a ring belt, pin bosses each presenting a pin bore, and skirt panels depending from the ring belt and coupled to the pin bosses by strut. The piston further includes an inner undercrown region extending along the undercrown surface and surrounded by the skirt panels, the struts, and the pin bosses. The piston also includes outer pockets each extending along the undercrown surface and each surrounded by a portion of the ring belt, one of the pin bosses, and the struts coupling the one pin boss to the skirt panels. Cutouts are located in the pin bosses above the pin bores to increase the area of the undercrown surface and thus allow cooling oil to remove more heat from the undercrown surface.
1. A piston, comprising:
an upper wall including an undercrown surface exposed from an underside of said piston,
a ring belt depending from said upper wall and extending circumferentially around a center axis of said piston,
a pair of pin bosses depending from said upper wall,
each of said pin bosses presenting a pin bore,
a pair of skirt panels depending from said ring belt and coupled to said pin bosses by struts,
an inner undercrown region extending along said undercrown surface and surrounded by said skirt panels and said struts and said pin bosses,
a pair of outer pockets extending along said undercrown surface,
each outer pocket being surrounded by a portion of said ring belt and one of said pin bosses and said struts coupling said one pin boss to said skirt panels, and
at least one cutout in at least one of said pin bosses,
said at least one cutout being located above at least one of said pin bores,
said at least one cutout including two inner cutouts,
each one of said inner cutouts being open to said inner undercrown region,
each one of said inner cutouts extending radially outwardly from said center axis to a location above one of said pin bores,
each one of said inner cutouts including a concave surface located above said pin bore and facing said center axis of said piston,
said undercrown surface extending radially outwardly from said center axis to an uppermost surface of each of said inner cutouts,
each one of said inner cutouts including a base surface facing said undercrown surface and extending from said concave surface toward said center axis,
said concave surface of each one of said inner cutouts being spaced radially from one of said outer pockets by material of said body, and
each one of said inner cutouts being completely spaced radially from one of said outer pockets by said material of said body.
2. The piston of claim 1 including a body, wherein said body includes said upper wall and said ring belt and said pin bosses and said skirt panels and said struts, said upper wall presents an upper combustion surface, and each of said cutouts is spaced from said upper combustion surface and said pin boss by material of said body.
3. The piston of claim 2 , wherein a radial width of material of said body remaining above each pin bore between one of said cutouts and one of said outer pockets is at least 2.5% of a maximum outer diameter of said piston.
4. The piston of claim 1 , wherein said piston includes a body formed of a single piece of steel, said body includes said upper wall, said ring belt, said pin bosses, and said skirt panels.
5. The piston of claim 1 , wherein each one of said inner cutouts further includes a hole extending from said concave surface to one of said outer pockets.
6. The piston of claim 5 , wherein said holes extend at a downward angle from said inner undercrown region to said outer pockets.
7. The piston of claim 5 , wherein said holes extend straight from said inner undercrown region to said outer pockets.
8. The piston of claim 5 , wherein each one of said holes has a cross-sectional area between 10 mm 2 and 150 mm 2 .
9. The piston of claim 1 , wherein said at least one cutout further includes two outer cutouts, each one of said outer cutouts is open to one of said outer pockets and extends radially toward said center axis to a location above one of said pin bores, each one of said outer cutouts includes a concave surface located above said pin bore and facing one of said outer pockets, said undercrown surface along said outer pockets extends inwardly to an uppermost surface of each of said outer cutouts, each one of said outer cutouts includes a base surface facing said undercrown surface and extending from said concave surface away from said center axis, and said concave surface of each one of said outer cutouts is spaced from said inner undercrown region by said material of said body.
10. The piston of claim 9 , wherein each of said pin bosses includes a hole extending from said inner cutout to said outer cutout.
11. The piston of claim 10 , wherein said holes extend at a downward angle or straight from said inner cutout to said outer cutout.
12. The piston of claim 10 , wherein each one of said holes has a cross-sectional area between 10 mm 2 and 150 mm 2 .
13. The piston of claim 10 , wherein each one of said holes further extends through a back wall of one of said ring grooves and into one of said outer pockets.
14. The piston of claim 1 , wherein said piston does not include a cooling gallery floor or other feature bounding or partially bounding a cooling gallery.
15. The piston of claim 1 including a body formed of a single piece of material,
said material of said body is steel,
said body does not have a cooling gallery floor or other features bounding or partially bounding a cooling gallery,
said body includes said upper wall presenting an upper combustion surface,
said upper combustion surface is a non-planar surface around said center axis,
said ring belt includes a plurality of ring grooves spaced from one another by lands extending circumferentially around said center axis and along an outer diameter of said piston,
said pin bosses are disposed inwardly of said ring belt,
said pin bores are laterally spaced from one another and surround a pin bore axis,
said pair of skirt panels are located diametrically opposite one another,
said undercrown surface is disposed radially inwardly of said ring belt,
said undercrown surface is not bounded by an enclosed or partially enclosed cooling gallery or any other feature tending to retain fluid,
a first portion of said undercrown surface is provided by said inner undercrown region and a second portion of said undercrown surface is provided by said outer pockets,
said inner undercrown region is located at said center axis and is surrounded by said pin bosses and said skirt panels and said struts,
said undercrown surface located in said inner undercrown region is concave when viewed from the bottom of said piston,
said outer pockets are located outwardly of said pin bosses,
said at least one cutout includes a plurality of said cutouts each spaced from said combustion surface and from one of said pin bores by said steel of said body, and
a radial width of said steel of said body remaining above each pin bore between said concave surface of one of said inner cutouts and an adjacent one of said outer pockets is at least 2.5% of a maximum outer diameter of said piston.
16. A method of manufacturing a piston, comprising the steps of:
providing a body including an upper wall, the upper wall including an undercrown surface exposed from an underside of the piston, a ring belt depending from the upper wall and extending circumferentially around a center axis of the piston, a pair of pin bosses depending from the upper wall, each of the pin bosses presenting a pin bore, a pair of skirt panels depending from the ring belt and coupled to the pin bosses by struts, an inner undercrown region extending along the undercrown surface and surrounded by the skirt panels and the struts and the pin bosses, a pair of outer pockets extending along the undercrown surface, each outer pocket being surrounded by a portion of the ring belt and one of the pin bosses and the struts coupling the one pin boss to the skirt panels, and
forming at least one cutout in at least one of the pin bosses above at least one of the pin bores, the at least one cutout including two inner cutouts, each one of the inner cutouts being open to the inner undercrown region, each one of the inner cutouts extending radially outwardly from the center axis to a location above one of the pin bores, each one of the inner cutouts including a concave surface located above the pin bore and facing the center axis of the piston, the undercrown surface extending radially outwardly from the center axis to an uppermost surface of each of the inner cutouts, each one of the inner cutouts including a base surface facing the undercrown surface and extending from the concave surface toward the center axis, the concave surface of each one of the inner cutouts being spaced radially from one of the outer pockets by material of the body, and each one of the inner cutouts being completely spaced radially from one of the outer pockets by the material of the body.
17. The method of claim 16 , wherein the body is a single piece of material, the step of providing the body includes forging or casting the body, and the cutouts are formed during the casting or forging step or the cutouts are formed after the casting or forging step by machining or cutting.