Engine piston having an insulating air gap

• US 20080041333A1
• Filed: 08/18/2006
• Published: 02/21/2008
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Jarrett, Mark Wayne, Hunold, Brent Michael
• Granted Patent: US 7,654,240 B2
• Time in Patent Office: Days
• US Class Current: 123/254
• CPC Class Codes: F02F 2003/0061 by welding
• CPC Class Codes: F02F 3/0023 the parts being bolted or screwed together
• CPC Class Codes: F02F 3/003 the parts being connected by casting, brazing, welding or clamping
• CPC Class Codes: F02F 3/26 having combustion chamber in piston head the surface thereof being covered F02F3/14
• CPC Class Codes: F16J 1/006 of different materials

Abstract

A piston for an internal combustion engine has an upper crown with a top and a bottom surface, and a lower crown with a top and a bottom surface. The upper crown and the lower crown are fixedly attached to each other using welds, with the bottom surface of the upper crown and the top surface of the lower crown forming a mating surface. The piston also has at least one centrally located air gap formed on the mating surface. The air gap is sealed to prevent substantial airflow into or out of the air gap.

Claims

1. A piston for an internal combustion engine, comprising;

an upper crown having a top surface and a bottom surface; and

a lower crown having a top surface and a bottom surface, wherein;

the upper crown and the lower crown are fixedly attached to each other using welds;

the bottom surface of the upper crown and the top surface of the lower crown form a mating surface;

at least one centrally located air gap is formed on the mating surface; and

the air gap is sealed to prevent substantial airflow into or out of the air gap.

2. The piston of claim 1, wherein the area of the air gap exceeds about 60% of the mating surface area.

3. The piston of claim 2, wherein the area of the air gap exceeds about 80% of the mating surface area.

4. The piston of claim 2, wherein the thickness of the air gap varies from about 0.5 mm to about 30 mm.

5. The piston of claim 1, wherein the air gap is filled with a thermal insulating medium.

6. The piston of claim 1, wherein the air gap is radially symmetric about a longitudinal axis of the piston and further includes:

a central air gap between a base of the upper crown and a base of the lower crown; and

an annular air gap between a side wall of the upper crown and a side wall of the lower crown.

7. The piston of claim 6, wherein an annular welded region substantially separates the central air gap from the annular air gap.

8. The piston of claim 1, wherein the welds are formed by at least one of laser welding, induction welding and friction welding.

9. The piston of claim 1 further including:

a protrusion on the bottom surface of the upper crown; and

a cavity on the lower crown, wherein;

the protrusion extends into the cavity, and

the welds are formed along a periphery of the protrusion.

10. The piston of claim 9, wherein the air gap further includes:

an annular central air gap under the base of the upper crown, the annular central air gap being formed around the protrusion;

an annular air gap between a side wall of the upper crown and a side wall of the lower crown; and

an annular protrusion separating the central air gap from the annular air gap.

11. An internal combustion engine comprising;

an engine block forming at least one cylinder;

a crankshaft rotatably disposed within the engine block;

the piston of claim 1 disposed within the cylinder to form a combustion chamber; and

a connecting rod mechanically coupling the piston to the crankshaft.

12. A piston for an internal combustion engine, comprising;

an upper crown having a base and a side wall; and

a lower crown having a base and a side wall, wherein;

the upper crown and the lower crown are removably attached to each other with at least one threaded fastener;

a central air gap is formed between the base of the upper crown and the base of the lower crown; and

an annular air gap is formed between the side wall of the upper crown and a side wall of the lower crown.

13. The piston of claim 12, wherein at least one air gap is filled with a thermal insulating medium.

14. The piston of claim 12, wherein an annular protrusion substantially separates the central air gap from the annular air gap, and the at least one threaded fastener includes multiple threaded fasteners passing through the annular protrusion.

15. The piston of claim 12, wherein:

the ratio of air gap area to an area of physical contact between the upper crown and the lower crown exceeds 3.

16. The piston of claim 12, wherein:

the upper crown is made of at least one of Inconel®

, or Ni-Resist; and

the lower crown is made of at least one of cast iron, steel and an aluminum alloy.

17. The piston of claim 12, further including:

a protrusion on the base of the upper crown, the protrusion having a first threaded cavity;

a second cavity on the base of the lower crown to receive the protrusion; and

a fastener passing through the second cavity into the first threaded cavity to attach the upper and lower crowns.

18. The piston of claim 17 further including a third cavity, substantially concentric with the first threaded cavity, extending from a bottom surface of the second cavity to a bottom surface of the lower crown, wherein the fastener passes through the first threaded cavity, second cavity, and third cavity.

19. An internal combustion engine comprising;

an engine block forming at least one cylinder;

a crankshaft rotatably disposed within the engine block;

the piston of claim 12 disposed within the cylinder to form a combustion chamber; and

a connecting rod mechanically coupling the piston to the crankshaft.

20. A piston for an internal combustion engine, comprising;

an upper crown having a base, a side wall, and a bottom surface; and

a lower crown having a base, a side wall, and a top surface;

wherein;

the upper crown and the lower crown are rigidly attached to each other with the top surface and bottom surface forming a mating surface;

a central air gap is formed between the base of the upper crown and the base of the lower crown;

an annular air gap is formed between the side wall of the upper crown and a side wall of the lower crown;

an annular protrusion substantially separates the central air gap from the annular air gap;

the air gaps are sealed to prevent substantial airflow into or out of the air gaps, and

the area of the air gaps exceed about 75% of the mating surface area.