摘要：
A steel piston with a bushing applied to pin bore surfaces by laser cladding or laser additive manufacturing is provided. The bushing is formed of metal, such as bronze, and metallurgically bonded to the steel of the piston. Thus, the bushing cannot fail by rotating relative to pin bore surfaces. The bushing has a porosity ranging from 0.05% to 5%, based on the total volume of the bushing, and a thickness ranging from 0.07mm to 6mm. Since the metal is applied directly to the steel by laser cladding or laser additive manufacturing, the overall size of the piston is reduced, compared to typical pistons with a separate steel backed bushing, and the possibility of bushing rotation is avoided. The bushing also provides scuffing resistance and increased unit load capacity of the pin bore.
权利要求：
CLAIMS
1. A method of manufacturing a piston, comprising the steps of:
providing a body portion including a crown and pin bosses depending from the crown, the pin bosses presenting pin bore surfaces;
applying a bushing to at least one of the pin bore surfaces; and
the step of applying including laser cladding or laser additive manufacturing.
2. The method of claim 1, wherein the body portion is formed of steel, and the bushing includes a mixture of copper and tin.
3. The method of claim 1, wherein the applying step includes metallurgically bonding the bushing to the body portion.
4. The method of claim 1, wherein the bushing has a porosity ranging from 0.05% to 5%, based on the total volume of the bushing.
5. The method of claim 1, wherein the bushing has a thickness ranging from 0.07mm to 6mm.
6. The method of claim 1, wherein the applying step includes the laser cladding, and the laser cladding includes applying a stream of a metal in the form of powder to the at least one pin bore surface by feeding the metal into a laser beam as the laser beam is scanned across the at least one pin bore surface.
7. The method of claim 1, wherein the step of applying the bushing to the body portion includes laser additive manufacturing.
8. The method of claim 1, wherein the applying step includes applying multiple layers of metal to each pin bore surface.
9. The method of claim 1 , wherein the body portion is formed of steel, the step of providing the body portion includes forming the crown with an upper crown portion and a lower crown portion separate from one another by casting or forging; the upper crown portion including an upper inner rib, an upper outer rib, and an upper combustion wall, and the lower crown portion including a lower inner rib, a lower outer rib, and an outer gallery floor; j oining the upper crown portion and the lower crown portion by friction welding or hybrid induction welding; the joining step including forming a central cooling gallery between the lower inner rib, the upper inner rib, the upper combustion wall; the j oining step including forming an outer cooling gallery between the lower inner rib, the lower outer rib, the upper inner rib, the upper outer rib, the upper combustion wall, and the outer gallery floor;
the applying step includes applying a metal including copper and tin directly to the steel of the at least one pin bore surface so that the metal metallurgically bonds to the steel; the laser cladding including applying a stream of the metal including the copper and tin in the form of powder to the at least one pin bore surface by feeding the metal into a laser beam as the laser beam is scanned across the at least one pin bore surface;
the applying step includes applying multiple layers of the metal; and
the thickness of the at least one bushing ranges from 0.07mm to 6mm and the porosity of the at least one bushing ranges from 0.05% to 5%.
10. A piston for an internal combustion engine, comprising:
a body portion including a crown,
said body portion including pin bosses depending from said crown, said pin bosses each presenting a pin bore surface,
a bushing metallurgically bonded to at least one of said pin bore surfaces, and said bushing having a porosity ranging from 0.05% to 5%, based on the total volume of said bushing.
1 1. The piston of claim 10, wherein said body portion is formed of steel and said bushing is formed of copper and tin.
12. The piston of claim 10, wherein said at least one bushing has a thickness ranging from 0.07mm to 6mm.
13. The piston of claim 10, wherein said bushing is applied to said body portion by laser cladding or laser additive manufacturing.
14. The piston of claim 9, wherein said body portion is galleryless and thus formed without any cooling galleries, such that an undercrown surface of said crown is exposed.
15. The piston of claim 10, wherein each pin bore surface presents a circumference extending completely around a pin bore axis.
16. The piston of claim 15, wherein said bushing is disposed only on an upper half of said pin bore surface.
17. The piston of claim 10, wherein said bushing cannot rotate relative to said pin bore surfaces, and said body portion is free of a conventional bushing capable of rotating relative to said pin bore surfaces.
18. The piston of claim 10, wherein said bushing is formed of multiple layers of a bronze material, said bronze material including copper and tin.
19. The piston of claim 10, wherein said body portion is formed of steel,
said bushing includes copper and tin,
said bushing has a porosity ranging from 0.05% to 5%,
said crown includes an upper crown portion including an upper inner rib and an upper outer rib each extending annularly around a central axis and depending from an upper combustion wall of said upper crown portion to respective ends,
said crown includes a lower crown portion having a lower inner rib and a lower outer rib each extending to respective ends arranged in alignment and in fixed abutment with the respective free ends of said upper inner and outer ribs, and
said body portion includes an outer cooling gallery presenting an oil passage extending circumferentially around said upper crown portion, and
said lower inner rib, said lower outer rib, said upper inner rib, said upper outer rib, said upper combustion wall, and said outer gallery floor define said outer cooling gallery.
20. The piston of claim 10, wherein said bushing is applied to said body portion by laser cladding or laser additive manufacturing,
said body portion extends along a central axis,
said crown includes an upper crown portion presenting an upper combustion wall, said upper combustion wall includes an uppermost surface presenting a recessed combustion bowl,
said upper crown portion includes an upper inner rib and upper outer rib each extending annularly around said central axis and depending from said upper combustion wall to respective ends,
said crown includes a lower crown portion having a lower inner rib and a lower outer rib each extending to respective ends arranged in alignment and in fixed abutment with the respective free ends of said upper inner and outer ribs,
said body portion includes an outer cooling gallery presenting an oil passage extending circumferentially around said upper crown portion,
said outer cooling gallery surrounds a central cooling gallery located at and around said central axis,
said outer ribs include a plurality of ring grooves,
said lower crown portion includes an outer gallery floor extending laterally between said lower inner rib and said lower outer rib,
said lower inner rib, said lower outer rib, said upper inner rib, said upper outer rib, said upper combustion wall, and said outer gallery floor define said outer cooling gallery, said outer oil gallery is sealed except for an optional passage for conveying of cooling oil,
said pin bosses depend from said outer floor of said crown and are spaced from one another,
each pin boss includes one of said pin bore surfaces defining a pin bore for receipt of a wrist pin,
each pin bore surface has a circular shape,
said bushing cannot rotate relative to said pin bore surfaces,
said bushing is formed of multiple layers of a bronze material, said bronze material including said copper and tin, and
said bushing has a thickness ranging from 0.07mm to 6mm.