Applicant claims priority under 35 U.S.C. §119 of German Application No. 100 46 420.3 filed Sep. 20, 2000. Applicant also claims priority under 35 U.S.C. §365 of PCT/DE01/02773 filed Jul. 18, 2001. The international application under PCT article 21 (2) was not published in English.
1. Field of the Invention
The invention relates to a method for rounding off the edge of a recess on a piston for direct-injection diesel engines.
2. The Prior Art
Such rounded-off recess edges are produced by means of lathe machining of the recess edge at the time the recess is machined by lathe, and serve to prevent tension concentrations. Valve recesses having a base surface that lies at a slant in relation to the piston floor, which intersect with the combustion recess, result in insufficient rounding of the recess edge in the area of the valve recesses. As a solution for the problem of insufficient rounding of the recess edge, it is already known to carry out the recess edge rounding as a so-called S-stroke rounding, see, for example, in DE 4326978, FIGS. 1 and 2. This solution, which is simple in terms of machining, has the disadvantage that the particle emissions increase because of the increased dead volume.
The invention is therefore occupied with the problem of producing a sufficiently rounded edge, using a method of the type indicated in the preamble, even in the case of valve recesses that lie at a slant in relation to the piston floor, without significantly increasing the dead volume.
This problem is solved by means a method for rounding off the edges of a recess on a piston for direct-injection diesel engines, which piston has valve recesses having a base surface inclined at a specific angle to the plane of the piston floor and wherein the recess edge regions beside the valve recesses have a rounded off recess edge produced by cutting machining, wherein inside the valve recesses, a second rounding off of the recess edges is carried out, which lies deeper in the recess as compared to the first rounding off, and wherein during rounding off the recess edge inside the valve recess by means of a concave cutting tool, the axis of the cutting tool lies perpendicular to the inclined base surface of the valve recess.
By guiding the cutting edge of the cutting tool parallel to the plane of the valve recess, sufficient and uniform rounding is achieved there.
The invention will be explained in greater detail below, using an exemplary embodiment. The drawing shows:
As is evident from
Therefore, sharp-edged, non-rounded recess edge regions remain inside the area of the valve recesses, as is evident in
According to
In this connection, either the piston or the machining tool is set at a slant, so that the axis B of the rounding tool C lies perpendicular or at least approximately perpendicular to the plane that forms the base surface k of the valve recess D. The angle between the longitudinal piston axis A and the axis B of the machining tool, i.e., the perpendicular G to the valve recess (
Independent of whether the piston or the tool is set at a slant, the axis B of the cutting tool C lies perpendicular to the inclined base surface k of the valve recess D.
Number | Date | Country | Kind |
---|---|---|---|
100 46 420 | Sep 2000 | GB | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/DE01/02773 | 7/18/2001 | WO | 00 | 7/17/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/27174 | 4/4/2002 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4345138 | Zammert | Aug 1982 | A |
5337714 | Tracy | Aug 1994 | A |
5642706 | Wirth et al. | Jul 1997 | A |
Number | Date | Country |
---|---|---|
20 18 174 | Feb 1972 | DE |
2 124 595 | Apr 1973 | DE |
37 41 218 | Jul 1988 | DE |
37 09 969 | Oct 1988 | DE |
43 26 978 | Feb 1995 | DE |
197 03 121 | May 1998 | DE |
199 52 868 | May 2001 | DE |
0316703 | Jun 1991 | JP |
Number | Date | Country | |
---|---|---|---|
20040031462 A1 | Feb 2004 | US |