One-piece piston featuring additive machining produced combustion bowl rim and cooling gallery
A piston capable of withstanding high temperatures and extreme conditions of a combustion chamber of an internal combustion engine and manufactured with reduced costs is provided. The method of manufacturing the piston includes casting or forging the bulk of the piston as a single-piece with an open cooling gallery from an economical first material, such as steel, cast iron, or aluminum. The method further includes forming a portion of a combustion bowl surface, which is a small area of the piston directly exposed to the combustion chamber, from a second material by additive machining. The second material has a higher thermal conductivity and higher resistance to oxidation, erosion, and oil coking, compared to the first material. The additive machining process is efficient and creates little waste, which further reduces production costs.
1. A method for manufacturing a piston for use in an internal combustion engine, comprises the steps of:
forming a crown portion and a skirt portion from a first material; and
forming at least a portion of a combustion surface along the crown portion from a second material by an additive machining process, including melting the first material along an area of the crown portion after forming the crown portion; and wherein the additive machining process includes melting the second material, and applying the melted second material to the melted first material, and wherein the additive machining process includes applying a plurality of layers of the melted second material to the melted first material.
2. The method of claim 1 , wherein the additive machining process includes applying the second material to the first material by a plasma transfer arc.
3. The method of claim 1 , wherein the additive machining process includes applying the second material to the first material by a high velocity oxygen fuel spray.
4. The method of claim 1 , wherein the additive machining process includes applying the second material to the first material by laser cladding or selective laser sintering.
5. The method of claim 1 , wherein the additive machining process includes applying the second material to the first material by arc welding or additive welding.
6. The method of claim 1 , wherein the second material has at least one of a higher thermal conductivity, higher erosion resistance, higher resistance to coking adhesion, higher strength, and a higher oxidation resistance than the first material.
7. The method of claim 6 , wherein the second material is selected from stainless steel, a nickel-based alloy, and a nickel-chromium-based alloy; and the first material is selected from steel, cast iron, a cast iron alloy, aluminum, and an aluminum alloy.
8. The method of claim 1 , wherein the step of forming the crown portion and skirt portion includes forming the crown portion and skirt portion as a single piece by casting or forging.
9. The method of claim 8 , wherein the casting or forging step includes forming the crown portion to include a combustion bowl extending outwardly from a center axis to an upper end, a cooling gallery base wall extending outwardly from a base of the combustion bowl, and an outer rib extending upwardly from the cooling gallery base wall to present an open cooling gallery surrounding the center axis; and the casting or forging step includes forming the skirt portion to extend from the outer rib to a lower end and to surround the center axis.
10. The method of claim 8 , wherein the additive machining process includes forming the combustion surface between the upper end of the combustion bowl and the outer rib to close the open cooling gallery.
11. The method of claim 10 , wherein the step of forming the combustion surface from the second material by the additive machining process includes forming a rim of the combustion bowl on the upper end of the combustion bowl.
12. The method of claim 11 , wherein the upper end of the combustion bowl is a rim of the combustion bowl formed from the first material.
13. The method of claim 1 , wherein the crown portion formed from the first material and the combustion surface formed from the second material together form a closed cooling gallery.
14. The method of claim 1 , wherein the step of forming the crown portion includes forming an outer rib spaced from a combustion bowl, and the step of forming the combustion surface includes disposing a core material between the outer rib and combustion bowl and applying the second material to the core material.
15. A method of manufacturing a piston for an internal combustion engine, comprising the steps of:
casting or forging a crown portion and a skirt portion as a single piece from a first material, the first material being selected from steel, cast iron, a cast iron alloy, aluminum, and an aluminum alloy;
the casting or forging step including forming the crown portion to include a combustion bowl extending outwardly from a center axis to an upper end, a cooling gallery base wall extending outwardly from a base of the combustion bowl, and an outer rib with ring grooves extending upwardly from the cooling gallery base wall to present an open cooling gallery surrounding the center axis;
the casting or forging step including forming the skirt portion from the first material to extend from the outer rib to a lower end and to surround the center axis, and forming the skirt portion to include a pair of pin bosses disposed opposite one another and each presenting a pin bore for receiving a wrist pin;
forming a combustion surface between the upper end of the combustion bowl and the outer rib to close the open cooling gallery, wherein the combustion surface is formed from a second material having at least one of a higher thermal conductivity, higher erosion resistance, higher resistance to coking adhesion, and a higher oxidation resistance than the first material, and the second material is selected from stainless steel, a nickel-based alloy, and a nickel-chromium-based alloy;
the step of forming the combustion bowl surface from the second material including an additive machining process, the additive machining processes including melting the first material along the upper end of the combustion bowl or along the outer rib, melting the second material, and depositing a plurality of layers of the melted second material on the melted first material; and
the additive machining process including at least one of plasma transfer arc, high velocity oxygen fuel spraying, laser cladding, laser sintering, arc welding, and additive welding.
16. A method for manufacturing a piston for use in an internal combustion engine, comprises the steps of:
forming a crown portion and a skirt portion from a first material,
forming at least a portion of a combustion surface along the crown portion from a second material by an additive machining process; and
wherein the step of forming the crown portion includes forming an outer rib spaced form a combustion bowl, and the step of forming the combustion surface includes disposing a core material between the outer rib and combustion bowl and applying the second material to the core material.
17. The method of claim 16 , wherein the additive machining process includes applying the second material to the first material by a plasma transfer arc.
18. The method of claim 16 , wherein the additive machining process includes applying the second material to the first material by a high velocity oxygen fuel spray.
19. The method of claim 16 , wherein the additive machining process includes applying the second material to the first material by laser cladding or selective laser sintering.
20. The method of claim 16 , wherein the additive machining process includes applying the second material to the first material by arc welding or additive welding.