Piston having combustion bowl and engine using same

Patent metadata

Field	Value
Publication number	US-9228531-B2
Application number	US-201313892396-A
Country	US
Kind code	B2
Filing date	May 13, 2013
Priority date	May 13, 2013
Publication date	Jan 5, 2016
Grant date	Jan 5, 2016

Abstract

A piston for balancing combustion efficiency and smoke generation with NOx production includes a combustion face forming a combustion bowl having a compound curvature increased in sharpness in a radially outward direction. An outer bowl surface defines a large radius of curvature adjacent an inner bowl surface, and a medium radius of curvature adjacent a cylindrical wall surface. The inner bowl, outer bowl, and wall surfaces together contour the combustion bowl, such that a diameter of the combustion bowl is about 124 mm so as to establish a bowl to bore ratio of about 0.71 in a direct injection compression ignition engine with a compression ratio of about 15:1 to 17:1.

First claim

What is claimed is:

1. A piston for balancing combustion efficiency and smoke generation with NOx production in a direct injection compression ignition internal combustion engine having a cylinder bore of about 175 mm, the piston comprising:
a piston body defining a longitudinal axis extending between a first axial body end and a second axial body end, and including an outer body surface extending between the first and second axial body ends, and a combustion face upon the first axial body end;
the combustion face forming a combustion bowl and including a conical inner bowl surface, and a concave outer bowl surface extending from the inner bowl surface to a cylindrical wall surface and having a compound curvature increased in sharpness in a radially outward direction;
the combustion face further forming an annular piston rim extending circumferentially around the combustion bowl, and including a planar rim surface, and a convex lip surface transitioning between the rim surface and the wall surface and having an intersection with the wall surface that defines a boundary of the combustion bowl; and
the outer bowl surface defining a large radius of curvature adjacent the inner bowl surface, and a medium radius of curvature adjacent the wall surface, and the lip surface defining a small radius of curvature, each in a longitudinal section plane, and the inner bowl, outer bowl, and wall surfaces together contouring the combustion bowl, such that a diameter of the combustion bowl is about 124 mm and a volume of the combustion bowl is about 190 cm 3 so as to establish a bowl to bore ratio of about 0.71 and a compression ratio of 15:1 to 17:1 when the piston is installed for service in the internal combustion engine, wherein the outer bowl surface has a bottom section adjoining the inner bowl surface and defining the large radius of curvature, and a transition section extending from the bottom section to the wall surface and defining the medium radius of curvature and wherein the large radius of curvature is about twice the medium radius of curvature, and the medium radius of curvature is about five times the small radius of curvature.

2. The piston of claim 1 wherein the planar rim surface defines a plane, and the bottom section of the combustion bowl is at a depth from the plane greater than the medium radius of curvature and less than the large radius of curvature.

3. The piston of claim 2 wherein the large radius of curvature is about 24 mm, the medium radius of curvature is about 12 mm, and the depth is about 20 mm.

4. The piston of claim 3 wherein the inner bowl surface defines a cone angle in the longitudinal section plane of about 137°, and the bowl volume is about 194 cm 3 .

5. The piston of claim 4 wherein the depth is about 19.6 mm, and the bowl volume is about 193.5 cm 3 .

6. The piston of claim 4 wherein a height of the cylindrical wall is from about 2 mm to about 3 mm, the lip surface descends an axial distance from the planar rim surface of about 3 mm or less, and the small radius of curvature is about 3 mm or less.

7. The piston of claim 6 wherein a curvature of the lip surface defining the small radius of curvature is uniform, and a diameter of the rim surface between the outer body surface and the lip surface is about 25 mm.

8. The piston of claim 3 wherein the bowl diameter is 124.25 mm such that the bowl diameter to cylinder bore diameter ratio is 0.71.

9. A direct injection compression ignition internal combustion engine comprising:
an engine housing defining a cylinder bore having a cylinder bore diameter of about 175 mm, and including an intake passage and an exhaust passage each being in fluid communication with the cylinder bore;
a cylinder head coupled with the engine housing;
a fuel injector mounted in the cylinder head and configured to directly inject a fuel into the cylinder;
a piston positioned within the cylinder bore and including a piston body defining a longitudinal axis extending between a first axial body end and a second axial body end, and including an outer body surface extending between the first and second axial body ends, and a combustion face upon the first axial body end;
the combustion face forming a combustion bowl and including a conical inner bowl surface, and a concave outer bowl surface extending from the inner bowl surface to a cylindrical wall surface and having a compound curvature increased in sharpness in a radially outward direction;
the combustion face further forming an annular piston rim extending circumferentially around the combustion bowl, and including a planar rim surface, and a convex lip surface transitioning between the planar rim surface and the wall surface and having an intersection with the wall surface that defines a boundary of the combustion bowl; and
the outer bowl surface defining a large radius of curvature adjacent the inner bowl surface, and a medium radius of curvature adjacent the wall surface, and the lip surface defining a small radius of curvature, each in a longitudinal section plane, and the inner bowl, outer bowl, and wall surfaces together contouring the combustion bowl, such that a ratio of a diameter of the combustion bowl to the bore diameter is about 0.71, and a volume of the combustion bowl is about 190 cm 3 to yield a compression ratio in the internal combustion engine of 15:1 to 17:1, wherein the large radius of curvature is about twice the medium radius of curvature, and the medium radius of curvature is about five times the small radius of curvature and wherein the large radius of curvature is about 24 mm, and the medium radius of curvature is about 12 mm.

10. The engine of claim 9 wherein the planar rim surface defines a plane, and the bottom section of the combustion bowl is at a depth from the plane greater than the medium radius of curvature and less than the large radius of curvature.

11. The engine of claim 10 wherein the depth is about 20 mm and the bowl volume is about 194 cm 3 .

12. The engine of claim 9 wherein the inner bowl surface defines a cone angle in the longitudinal section plane and which differs from the spray angle by about 10° or greater.

13. The engine of claim 12 wherein the cone angle is about 137°, and the spray angle is about 150°.

14. The piston of claim 9 wherein the bowl diameter is 124.25 mm such that the bowl diameter to cylinder bore diameter ratio is 0.71.

Assignees

• Caterpillar Inc

Inventors

• Ness Aaron
• Coulier Scott
• Kammerdiener Thomas
• Kilkenny Jonathan

Classifications

• F02F3/28 Primary

  Other pistons with specially-shaped head · CPC title

• F02F3/22

  the fluid being liquid · CPC title

• F02F3/00

  Pistons · CPC title

• F05C2201/021

  Aluminium · CPC title

• F02B23/0624 Primary

  Swirl flow · CPC title