Piston having uncoupled skirt

• US 6,588,320 B2
• Filed: 12/27/2000
• Issued: 07/08/2003
• Est. Priority Date: 12/30/1999
• Status: Expired due to Term

• Current Assignee: Federal-Mogul World Wide LLC (Apollo Global Management, Inc.)
• Original Assignee: Federal-Mogul Worldwide Incorporated (Apollo Global Management, Inc.)
• Inventors: Gaiser, Randall R., Zhu, Xiluo
• Primary Examiner(s): LOPEZ, FRANK D
• Application Number:
  US09/749,705
• Publication Number:
  US 20010029840A1
• Time in Patent Office: 923 Days
• Field of Search: 922/31
• US Class Current: 92/231
• CPC Class Codes: B23P 15/10 pistons
• CPC Class Codes: F02F 2200/04 Forging of engine parts
• CPC Class Codes: F02F 3/003 the parts being connected by casting, brazing, welding or clamping
• CPC Class Codes: F02F 3/025 having circumferentially slotted piston skirts, e.g. T-slots
• CPC Class Codes: F05C 2201/0448 Steel

Abstract

A piston (10) particularly suited for heavy duty diesel engine applications includes upper and lower crown sections (28, 30) joined by a friction weld (32) to define an annular ring belt (14) formed with ring groves (22) and having a lower end (20) and an internal piston cooling chamber (34). A pair of pin bosses (40) depend from the ring belt (14) and are formed as one piece with the lower crown section (30). A skirt (46) is also formed as one piece with the pin bosses (40) and has an upper end (48) that is spaced from the lower end (20) of the ring belt (14) to define a space (52) therebetween which effectively uncouples the skirt (46) from the ring belt (14).

Claims

1. A piston for an engine, comprising:

a piston head having an upper crown portion, a lower crown portion, and a ring belt portion formed with a plurality of ring grooves and having a lower end, said upper crown portion being formed separately from said lower crown portion, said upper crown portion and said lower crown portion having mutual mating surfaces, said upper crown portion being joined to said lower crown portion across said mating surfaces;

a piston cooling gallery formed within said piston head between said upper crown portion and said lower crown portion, said piston cooling gallery including a bottom wall portion fabricated as one piece with said lower crown and coupled to said ring belt portion adjacent said lower end thereof and extending radially inwardly of said ring belt portion to provide a floor to said piston cooling gallery;

said lower crown including a pair of pin bosses formed with axially aligned pin bores; and

a piston skirt fixed immovably to said pin bosses as a unitized structure therewith and having a free upper edge of said piston skirt spaced in uncoupled relation to said ring belt portion and said bottom wall of said piston cooling gallery and open to an interior of said piston skirt.

2. The piston of claim 1 wherein said piston skirt includes a pair of skirt portions formed as one piece of the same material as said pin bosses.

3. The piston of claim 2 wherein said skirt portions are fabricated of steel.

4. The piston of claim 1 wherein an upper section of said ring belt portion is formed as part of said upper crown portion, and a lower section of said ring belt portion is formed as part of said lower crown portion, said lower section including at least one of said plurality of said ring grooves.

5. The piston of claim 1 wherein said upper crown portion includes an annular inner wall spaced radially inwardly from said ring belt portion, and said lower crown portion includes an annular inner wall aligned with said annular inner wall of said upper crown portion, said bottom wall extending transversely between said inner wall of said lower crown portion and said ring belt portion and formed as one piece therewith.

6. The piston of claim 5 wherein said ring belt portion includes a weld joint.

7. The piston of claim 6 wherein said upper edge of said piston skirt is spaced from said weld joint of said skirt portion.

8. The piston of claim 7 wherein said annular inner walls of said upper and lower crown portions are joined by a weld joint.

9. The piston of claim 8 wherein said weld joint comprises a friction weld joint.

10. The piston of claim 7 wherein said weld joint of said ring belt is located between an adjacent pair of said plurality of said ring grooves.

11. The piston of claim 6 wherein said weld joint comprises a friction weld joint.

12. The piston of claim 1 wherein said upper edge of said piston skirt extends above said pin bores of said pin bosses.

13. The piston of claim 1 wherein said upper and lower crown portions are joined by at least one weld joint.

14. The piston of claim 13 wherein said weld joint comprises a friction weld joint.

15. A piston for an engine comprising:

upper and lower crown portions separately formed and joined by at least one friction weld joint to define a piston head having a closed piston cooling gallery formed between the upper and lower crown portions, said piston head having an outer annular ring belt formed with a plurality of piston ring grooves and including a lower end;

said lower crown portion including a pair of depending pin bosses fabricated of a metallic material and formed with aligned pin bores; and

a pair of piston skirt portions formed as one unitary piece with said pin bores of the same material as said material of said pin bosses, said skirt portions including upper free edges spaced in uncoupled relation to said lower end of said ring belt and said friction weld joint of said piston head and open to an interior of said skirt portions.

16. A method of forming a piston for an engine, comprising:

forming an upper crown portion;

forming a lower crown portion separately from the upper crown portion;

joining the upper crown portion to the lower crown portion to provide an internal piston cooling gallery between the joined upper and lower crown portions and including a bottom wall of the piston cooling gallery formed as one piece with the lower crown portion, and to provide an outer annular ring belt portion having a lower end coupled to the bottom wall of the piston cooling gallery;

forming the lower crown portion with a pair of pin bosses having aligned pin bores; and

forming a piston skirt which is directly and immovably fixed to the pin bosses as unitized structure therewith and including an upper free edge that is spaced in uncoupled relation to the ring belt portion and bottom wall of the piston cooling gallery and open to an interior of the piston skirt.

17. The method of claim 16 including fabricating the piston skirt as one piece with the pin bosses of the same material.

18. The method of claim 16 wherein the upper and lower crown portions are joined by friction welding to provide at least two friction weld joints, and wherein the upper free edge of the piston skirt is spaced from the weld joints.