Applicants claim priority under 35 U.S.C. §119 of German Application No. 10 2011 106 559.1 filed Jul. 5, 2011, the disclosure of which is incorporated by reference.
1. Field of the Invention
The invention relates to a piston for an internal combustion engine, having an upper piston part and a lower piston part, which form an outer circumferential cooling channel. There are pin boss connections that lie opposite one another, at which pin bosses are provided. The pin bosses have pin bores that define a center axis and the upper piston part and the lower piston part are connected with one another by way of outer joining surfaces and inner joining surfaces.
2. The Prior Art
Pistons of this type are widely known. However, sufficient cooling of the piston during engine operation is a problem. With modern internal combustion engines, thermal stress is very high in the region of the upper piston part, so that sufficient cooling of the underside of the piston crown, in particular, must be guaranteed.
It is therefore an object of the present invention to provide a piston in which cooling of the underside of the piston crown is guaranteed, without disproportionately increasing the weight of the piston.
This object is accomplished according to the invention by a piston having a bridge that runs essentially parallel to the center axis (M) in the region of the pin boss connections. The bridge has two longitudinal sides that delimit an upper bridge surface.
The bridge provided according to the invention forms a partially open additional cooling cavity below the piston crown. The upper bridge surface collects the cooling oil that is present below the piston crown and passes it back in the direction of the underside of the piston crown, on the basis of the Shaker effect. In this manner, additional cooling of the underside of the piston crown is achieved. The partially open cooling cavity formed by the bridge provided according to the invention does not disproportionately increase the weight of the piston, as would be the case with a closed cooling cavity. Furthermore, heated cooling oil can run off in the direction of the pin bosses and be replaced by fresh cooling oil.
In one embodiment of the invention, the bridge is configured in one piece with the lower piston part. In this way, a particularly simple production method, for example forging, is possible.
Preferably, at least the upper bridge surface is disposed above the inner joining surface, in order to allow particularly effective return of the cooling oil in the direction of the underside of the piston crown.
If a depression is configured in the upper bridge surface, a greater amount of cooling oil can be collected in it and cooling of the underside of the piston crown can be further improved.
The two longitudinal sides of the bridge can extend essentially parallel to one another, but they can also run essentially convex or concave relative to one another. In this way, the piston structure can be adapted particularly well to the requirements of an individual case.
Preferably, the two longitudinal sides of the bridge run divergently with reference to the center axis. In the case of this embodiment, in particular, it is particularly advantageous if the lower edges of the longitudinal sides are configured as edges that narrow at an acute angle. In this case, the longitudinal sides can act as cooling oil run-off surfaces and/or the lower edges can act as cooling oil drip edges. In this way, the piston pin can be additionally lubricated, in a particularly effective manner.
If the lower edges of the longitudinal sides are disposed below the inner joining surfaces, an almost closed inner cooling cavity is formed, in which a particularly large amount of cooling oil can be collected, so that cooling of the underside of the piston crown is further improved.
Preferably, at least the lower piston part is configured as a forged part. In the case of this embodiment, in particular, the bridge can be forged in one piece with the lower piston part and can be machined using a chip-producing method. This production method can be implemented easily and cost-advantageously.
Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.
In the drawings, wherein similar reference characters denote similar elements throughout the several views:
Referring now in detail to the drawings and, in particular,
According to the invention, lower piston part 12 has a bridge 24 in the region of pin boss connections 18. Bridge 24 forms a partly open inner cooling cavity 26 with underside 25 of combustion bowl 13, i.e. with underside 25 of the piston crown. In the exemplary embodiment, bridge 26 is connected with lower piston part 12 in one piece. If lower piston part 12 is a forged part, bridge 24 can also be forged, and subsequently machined using a chip-producing method. Bridge 24 has two longitudinal sides 27 that extend essentially parallel in the exemplary embodiment, and delimit an upper bridge surface 28. In the exemplary embodiment, an approximately bowl-shaped depression 29 is formed into upper bridge surface 28. The two longitudinal sides 27 run divergently with reference to the center axis M defined by pin bores 19. In the exemplary embodiment, lower edges 31 of longitudinal sides 27 are configured as edges that narrow at an acute angle. This configuration can take place within the course of the chip-producing machining of bridge 24. Longitudinal sides 27 serve as cooling oil run-off surfaces for the cooling oil collected in the depression and flowing out of it, while lower edges 31 act as drip edges for this cooling oil. Additional lubrication of the piston pin is achieved in this manner.
In the embodiment according to
The significant difference in this embodiment consists in that bridge 124 of piston 110 has longitudinal sides 127, the lower edges 131 of which are disposed below inner joining seam 23 between upper piston part 111 and lower piston part 112. In this way, an almost closed inner cooling cavity 126 is formed, so that particularly effective cooling of underside 25 of the combustion bowl 13, i.e. underside 25 of the piston crown, is guaranteed.
Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
---|---|---|---|
10 2011 106 559 | Jul 2011 | DE | national |
Number | Name | Date | Kind |
---|---|---|---|
4180027 | Taylor | Dec 1979 | A |
4377967 | Pelizzoni | Mar 1983 | A |
4530312 | Kanda et al. | Jul 1985 | A |
6477941 | Zhu et al. | Nov 2002 | B1 |
20080121204 | Scharp | May 2008 | A1 |
20090159037 | Messmer | Jun 2009 | A1 |
20100101527 | Gniesmer | Apr 2010 | A1 |
20100108016 | Scharp et al. | May 2010 | A1 |
20100108017 | Bing et al. | May 2010 | A1 |
20100122681 | Issler | May 2010 | A1 |
20100139480 | Ohmori et al. | Jun 2010 | A1 |
20100307446 | Nodl | Dec 2010 | A1 |
20110119914 | Janssen et al. | May 2011 | A1 |
20120000439 | Scharp et al. | Jan 2012 | A1 |
20120222305 | Scharp et al. | Sep 2012 | A1 |
Number | Date | Country |
---|---|---|
40 07 992 | Sep 1990 | DE |
199 27 931 | Jan 2001 | DE |
10 2007 018 932 | Oct 2008 | DE |
10 2007 058 789 | Jun 2009 | DE |
10 2008 011 922 | Sep 2009 | DE |
10 2009 058 176 | Jan 2011 | DE |
786 985 | Nov 1957 | GB |
Entry |
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German Search Report dated May 22, 2012 in German Patent Application No. 10 2011 106 559.1 with English translation of relevant parts. |
International Search Report of PCT/DE2012/000673, mailed Dec. 11, 2012. |
Number | Date | Country | |
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20130008404 A1 | Jan 2013 | US |