Diesel piston with sharp-step profile

Patent metadata

Field	Value
Publication number	US-10634089-B2
Application number	US-201715838648-A
Country	US
Kind code	B2
Filing date	Dec 12, 2017
Priority date	Dec 12, 2017
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

A piston for a diesel engine includes a piston body having a skirt and crown. The piston body has portions defining an outer combustion bowl and an inner combustion bowl within the piston body through the crown. The outer combustion bowl has a curved annular side wall extending from the crown surface and an annular flat shelf extending from the curved annular side wall. The new stepped bowl design integrates a bottom profile with smoothly varying curvature and a sharp step at the top. The annular flat shelf is recessed a distance in the range of 2.5-4.5 millimeters from a line coplanar with the crown surface. The piston body defines an outer convex curved surface connecting the curved annular side wall to the crown surface. The outer convex curved surface has a radius of curvature in the range of 0.25-0.75 millimeter.

First claim

What is claimed is:

1. A piston for a diesel engine, comprising:
a piston body having a skirt extending from a proximal end of the piston body; and
a crown disposed at a distal end of the piston body and defining a crown surface, the piston body having portions defining an outer combustion bowl and an inner combustion bowl within the piston body through the crown, the outer combustion bowl having a curved annular side wall extending from the crown surface and an annular flat shelf extending from the curved annular side wall, the annular flat shelf being recessed a distance in the range of 2.5 to 4.5 millimeters from a line coplanar with the crown surface, the annular flat shelf being a continuous annulus that is symmetrically disposed about a central axis of the piston body, the inner combustion bowl being recessed with respect to the annular flat shelf of the outer combustion bowl, the piston body defining an outer convex curved surface connecting the curved annular side wall to the crown surface, the outer convex curved surface having a radius of curvature in the range of 0.25 to 0.75 millimeter.

2. The piston according to claim 1 , the annular flat shelf being recessed a distance of about 3.5 millimeters from the line coplanar with the crown surface, the radius of curvature of the outer convex curved surface being about 0.5 millimeter.

3. The piston according to claim 1 , the piston body defining an annular valley surface forming the inner combustion bowl, the piston body defining an inner convex curved surface connecting the annular flat shelf of the outer combustion bowl to the annular valley surface of the inner combustion bowl.

4. The piston according to claim 3 , the inner convex curved surface having a radius of curvature in the range of 1 to 2 millimeters, the radius of curvature of the inner convex curved surface being about 1.5 millimeters.

5. The piston according to claim 4 , a radial distance between the annular flat surface and the crown surface being in the range of 1.5 to 2 millimeters, the radial distance being measured along a line perpendicular to the central axis of the piston body.

6. The piston according to claim 5 , a radius of curvature between the curved annular side wall and the annular flat surface being in the range of 0.25 to 0.75 millimeter.

7. The piston according to claim 6 , the inner combustion bowl having a lowest point that is 12 to 14 millimeters from the line coplanar with the crown surface, the inner combustion bowl having a radially outermost point that is 24 to 27 millimeters from the central axis.

8. The piston according to claim 7 , a center of the inner combustion bowl being disposed 5 to 7 millimeters from the line coplanar with the crown surface, the center being located along the central axis of the piston body.

9. The piston according to claim 8 , a radially innermost point of the inner convex curved surface being disposed 23 to 25 millimeters from the central axis.

10. The piston according to claim 9 , the radially innermost point of the inner convex curved surface being disposed radially inward of the radially outermost point of the inner combustion bowl by a radial distance of 1 to 2 millimeters, the radial distance being measured along a line perpendicular to the central axis.

11. The piston according to claim 10 , the outer convex curved surface being disposed a distance of 8 to 10 millimeters from an outer edge of the crown.

12. The piston according to claim 11 , the annular flat shelf having a radial length extending from the curved annular side wall to the inner convex curved surface, the radial length being 7 to 8 millimeters.

13. The piston according to claim 12 , the curved annular side wall extending from the crown surface at an angle between 100 and 110 degrees.

14. The piston according to claim 13 , the piston body having a three-dimensional shape defined in an x-y-z coordinate space, the z-axis being disposed along the central axis of the piston body and intersecting the line coplanar with the crown surface at 90 degrees, the inner and outer combustion bowls being defined by a two-dimensional cross-sectional profile line that begins at the central axis and ends along the crown surface to define a half cross-section of the piston body, the half cross-section being rotatable about the z-axis to form the three-dimensional shape of the piston body.

15. The piston according to claim 14 , the two-dimensional cross-sectional profile line connecting a set of coordinate points in the x-y-z coordinate space, the set of coordinate points including coordinate points (x i , y i , z i ) or coordinate points (fx i , fy i , fz i ), f being any positive multiplier, the coordinate points (x i , y i , z i ) including selected points that substantially coincide with a coordinate set S, the Coordinate Set S including the following subset Coordinate Set Sa:

Coordinate Set Sa

i
x i (mm)
y i (mm)
z i (mm)

147
25.217
0
−6.372

154
24.423
0
−5.093

157
24.212
0
−4.494

160
24.403
0
−3.889

165
25.348
0
−3.478

193
31.381
0
−3.478

197
32.163
0
−3.182

202
32.563
0
−2.198

208
32.898
0
−0.949

212
32.9
0
−0.087

213
33.028
0
0.

16. The piston according to claim 15 , the Coordinate Set S further including the following subset Coordinate Set Sb:

Assignees

• Gm Global Tech Operations Llc

Inventors

• Diwakar Ramachandra
• Domenech-Llopis Vicente
• Peterson Richard C
• Vassallo Alberto Lorenzo

Classifications

• F02B23/0687 Primary

  Multiple bowls in the piston, e.g. one bowl per fuel spray jet · CPC title

• F02F3/027 Primary

  the skirt wall having cavities · CPC title

• Y02T10/12

  Improving ICE efficiencies · CPC title