This application is related to EP 02 025 788.7 filed Nov. 16, 2002, the entire disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The invention concerns a connecting rod and a method for producing a connecting rod in accordance with the independent claims.
The book “Jahrbuch Schleifen, Honen, Läppen und Polieren” (annual grinding, honing, lapping and polishing) by H.-W. Hoffmeister and H.-K. Tönshoff (publisher), Vulkan-Verlag Essen, 2002, pages 396 to 408 discloses a holding groove on a connecting rod eye into which a nose, formed on the bearing shell, projects. The surface of the connecting rod eye is conventionally honed to improve the tight fit of the bearing shell.
It is the underlying purpose of the invention to produce a connecting rod of this type, which provides sufficient fixation of the bearing shell in the connecting rod eye even under high loads, and to propose a method for producing a connecting rod having a long service life.
SUMMARY OF THE INVENTION
This object is achieved with a connecting rod having the features of the independent claims.
Good fixation of a bearing shell in a connecting rod eye is ensured by providing a surface structure in a connecting rod eye with depressions whose outer periphery is delimited by elevations. The elevations on the structured edges of the structure anchor the bearing shell in the connecting rod eye. The structure may be a uniform pattern which can be adapted to the loads which occur and which can be reproduced during manufacture. The structure can be adapted to working loads in a simple manner by changing the depth of the depressions and the height of the elevations.
The depressions with sideward elevations are suitably designed as furrows. The furrows may advantageously be straight or cross each other. The furrows may also be wavy. The depressions may advantageously be formed as closed pockets. As viewed from above, the pockets may advantageously have an elongated or round shape. The inner surface of a bearing shell and/or the surface of a component disposed in the bearing shell advantageously has/have a structure which is formed from depressions only. The depressions act as micro-pressure chambers which facilitate hydraulic lubrication to reduce friction between the sliding partners.
The production of the connecting rod can be facilitated by structuring the surface of a connecting rod eye using a laser. The laser structuring simultaneously permits good adaptation of the structure to the working loads. The elevations are formed by displaced melt produced during processing at the structure edges, which is generated through thermal processing. The height of the elevations can be adjusted via the displaced melt volume. The melt volume can be varied by the processing parameters, i.e., for example, via the advance speed or via the laser parameters, i.e., for example, through adjustment of the power or the pulse duration. Laser processing facilitates changes to the design of the structure, such as the surface portion of pocket structures or the angles of intersection of crossing structures. The height and the width of the elevations influence the adhesion of the bearing shell in the connecting rod eye and can also be easily varied during laser processing.
Embodiments of the invention are explained below with reference to the drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a schematic perspective view of a connecting rod;
FIG. 2 shows a section through a large connecting rod eye with bearing shell disposed therein, and a crankshaft;
FIG. 3 shows the profile of a surface of a connecting rod eye along the line III-III in FIG. 4;
FIG. 4 shows a top view onto a section of a surface of a connecting rod eye;
FIG. 5 shows the profile of the surface of a connecting rod eye along the line V-V in FIG. 6;
FIG. 6 shows a section of a top view onto the surface of a connecting rod eye;
FIGS. 7 shows a schematic view from above of first surface structures;
FIGS. 8 shows a schematic view from above of second surface structures;
FIGS. 9 shows a schematic view from above of third surface structures;
FIGS. 10 shows a schematic view from above of fourth surface structures;
FIGS. 11 shows a schematic view from above of fifth surface structures; and
FIGS. 12 shows a schematic view from above of sixth surface structures.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The connecting rod 1, schematically shown in FIG. 1, has a small connecting rod eye 2 and a large connecting rod eye 3. For use in a combustion engine, a piston pin is conventionally disposed in the small connecting rod eye 2 and the crankshaft is disposed in the large connecting rod eye 3. A bearing shell 4 is disposed in the small connecting rod eye 2, and a bearing shell 5 is disposed in the large connecting rod eye 3. To rigidly fix the bearing shells 4, 5 in the connecting rod eyes 2, 3, the bore surfaces 12 and 13 of the connecting rod eyes 2 and 3 have structures 6 and 7. The structures 6 and 7 increase the adhesion of the bearing shells 4 and 5. Instead of or in addition to the structures 6, 7 of the bore surfaces 12, 13, the outer surfaces of the bearing shells 4, 5 which are in contact with the bore surfaces 12, 13 may have corresponding structures. The friction between the inner side of the bearing shells 4 and 5 and the piston pin or the crankshaft should be minimized. To reduce friction, the inner surface 21 of the bearing shell 4 has a structure 22 and the inner surface 18 of the bearing shell 5 has a structure 20.
To fix a bearing shell 4, 5 in a connecting rod eye 2, 3, a nose 15 may be disposed on the outer periphery of a bearing shell, in addition to the structure 6, 7, as exemplarily shown in the bearing shell 5 of FIG. 2. The nose 15 extends radially outwardly at the outer periphery of the bearing shell 5. In the region of the nose 15, the connecting rod eye 3 of the connecting rod 1 has a holding groove 14 into which the nose 15 projects. The surface 13 of the connecting rod eye 3 additionally has a structure (not shown in FIG. 2). The crankshaft 16 is disposed in the bearing shell 5 and rotates in the direction of the arrow 17. While the friction between bearing shell 5 and connecting rod eye 3 should be as large as possible to rigidly hold the bearing shell 5 in the connecting rod eye 3, the friction between the bearing shell 5 and the crankshaft 16 should be as small as possible. Towards this end, the inner surface 18 of the bearing shell 5 has a structure 20 (shown in FIG. 1). A structure corresponding to the structure 20 may be provided on the outer surface 19 of the crankshaft 16 rather than on the inner surface 18.
FIGS. 3 and 4 show, in an enlarged scale, a structure 37 of a surface 39 which may be the surface 12, 13 of a connecting rod eye 2, 3. The structure 37 may be provided in the small connecting rod eye 2 and/or in the large connecting rod eye 3. The structure 37 is introduced into the surface 39 which has a basic structure 23. The structure 37 is advantageously produced with a laser. The basic structure 23 may e.g. be a cross structure produced through honing. The basic structure 23 may also consist of peripheral furrows produced during spindling of the surface 39. Elongated pockets 11 are introduced into the basic structure 23 at regular intervals which are formed by a depression 8 whose periphery is delimited by a circumferential elevation 9. The depressions 8 have a depth a relative to the surface 39 while the elevations 9 extend beyond the surface 39 by a height b. The elevations 9 have a width c and the depressions 8 have a width d. The depth a and the height b advantageously are approximately up to 50 μm. The width c, d is advantageously selected to be ≦50 μm.
FIGS. 5 and 6 show an embodiment of a structure 38 of the large connecting rod eye 3 which may be introduced into the surface 12, 13 of the connecting rod eye 2, 3 and is formed by round pockets 10. The round pockets 10 are suitably uniformly introduced into the surface 40. The round pockets 10 have a circular depression 8 whose outer periphery is also surrounded by a circular elevation 9. The round pockets 10 are also introduced into a surface 40 having a basic structure 23.
FIGS. 7 through 12 show examples of an arrangement of a structure on a surface. The double arrow 36 thereby designates the peripheral direction of the connecting rod eye or of the bearing shell. In the structure 24 shown in FIG. 7, the pockets 25 are disposed in a regular pattern. The pockets 25 may have a depression 8 and an elevation 9, in correspondence with the round pockets 10 shown in FIGS. 5 and 6. The structure 24 is suitably introduced on the bore surface 12 of the small connecting rod eye 2 or the bore surface 13 of the large connecting rod eye 3. It may also be appropriate to provide pockets 25 without elevations 9. Such pockets reduce the friction between the sliding partners, since they are used as a lubricant reservoir thereby permitting full hydrodynamic lubrication. The pockets simultaneously act as micro-pressure chambers. Pockets 25 of such a design are suitably disposed on the inner surface 21 of the bearing shell 4 and/or on the outer periphery of a piston pin and on the inner surface 18 of the bearing shell 5 and/or the outer surface 19 of the crankshaft 16.
FIG. 8 shows elongated pockets 27 which extend approximately in a peripheral direction. The elongated pockets 27 are disposed at regular intervals and form a structure 26. The structure 28 of FIG. 9 is formed by elongated pockets 29 which extend approximately transversely to the peripheral direction. It may also be suitable to provide elongated pockets which subtend an angle of between 0° and 90° with respect to the peripheral direction. The structures 26 and 28 may be disposed on the inner surface 18 of the bearing shell 5 or the outer surface 19 of the crankshaft 16 and/or the inner surface 21 of the bearing shell 4 or the outer surface of a piston pin. The pockets 27 and 29 are thereby suitably formed only as depressions. The pockets 27 and 29 may each be delimited at their outer periphery by an elevation 9. Pockets 27 and 29 of this design increase friction and are preferably disposed on the surface 12 of the connecting rod eye 2 or the surface 13 of the connecting rod eye 3.
The structure 30 of FIG. 10 is formed by crossing furrows 31 which are each delimited by elevations 9. The furrows 31 have an angle of intersection a. The structure 30 is suitably formed on a surface 12, 13 of a connecting rod eye 2, 3. The adhesion of the structure 30 may be influenced by varying the angle of intersection α. FIG. 11 shows a structure 32 having wavy furrows 33. The outer periphery of the furrows 33 also comprises elevations 9. The furrows 33 are suitably disposed on the surfaces 12 and 13 of the connecting rod eyes 2 and 3. FIG. 12 shows a structure 34 with furrows 35 which extend parallel to each other. The furrows 35 are disposed approximately perpendicularly to the peripheral direction in FIG. 12. The furrows 35 may suitably subtend an angle of less than 90° with respect to the peripheral direction. The furrows 35 may also have elevations 9 at their outer periphery to increase the friction between connecting rod eye 2, 3 and bearing shell 4, 5.
A connecting rod 1 is advantageously produced by structuring the surface 12, 13 of one or both connecting rod eyes 2, 3 using a laser. The surface 12, 13 is advantageously fine machined before laser structuring thereby producing a basic structure 23 into which the structure is introduced. For pocket structures 10, 11, 24, 26, 28, the adhesion of a structure 6, 7 on the surface 12, 13 of a connecting rod eye 2, 3 may be greatly influenced by the surface portion. For cross structures 30, the adhesion can be changed by varying the angle of intersection α. The height b of the elevations 9 and the width of the elevations 9 have an influence on the adhesion of all structures.
Patent Application
20050155451
