DESCRIPTION The invention relates to an exhaust-gas turbocharger as per the preamble of claim 1 and to a VTG cartridge as per the preamble of claim 9.

In the case of such an exhaust-gas turbocharger, provision is made of a variable turbine geometry (VTG), in which guide vanes are adjusted by means of an adjusting ring. An actuation pin is in this context guided in a groove of an adjusting lever.

It is an object of the present invention to provide an exhaust-gas turbocharger of the type indicated in the preamble of claim 1 and a VTG cartridge as per the preamble of claim 9 in the case of which the wear at the contact between the adjusting lever and the actuation pin is as small as possible.

This object is achieved by the features of the independent claims.

The dependent claims contain advantageous developments of the invention.

Claims 9 and 10 define a VTG cartridge according to the invention as an object which can be marketed independently.

Within the context of the invention, it has been identified that the wear between the actuation pin and the adjusting lever can be reduced if the actuation pin has a polygonal rather than a round cross section. Owing to the polygonal cross section, the actuation pin can have rounded side faces with a very large radius. This radius of the side faces is considerably greater than the radius of a conventional pin having a round cross section. The enlarged radius reduces the point loading between the actuation pin and the adjusting lever, and therefore the wear is reduced.

Within the context of this invention, a polygonal cross-sectional shape is not necessarily understood to mean a polygon having sharp edges. Within the context of the invention, it is by all means also possible that the corners on the actuation pin are rounded. Furthermore, provision is preferably made that the side faces of the actuation pin too do not have a planar profile, but rather are curved outward and therefore have a rounding.

The adjusting lever preferably has a groove, in which the actuation pin is seated. A width is defined on this groove. As has already been described, the side faces of the polygonal cross section are preferably rounded with a first radius. The first radius preferably measures at least 1.5 times the width of the groove. This ensures that the polygonal cross-sectional shape bears with the greatest possible first radius against the adjusting lever, and therefore little wear or little material removal takes place.

In particular, the shape of what is termed an "orbiform curve" is chosen for the cross section. This can ensure that the play between the actuation pin and the adjusting lever remains as small as possible.

Particularly for use with utility vehicles, it is provided that the actuation pin comprises a sliding block, the polygonal cross section being formed on the sliding block.

Further details, features and advantages of the invention become apparent from the following description of exemplary embodiments with reference to the drawing, in which:

Figure 1 shows a schematically greatly simplified illustration of an exhaust-gas turbocharger according to the invention according to one embodiment,

Figure 2 shows a perspective plan view of an embodiment of a VTG cartridge according to the invention,

Figure 3 shows an enlarged partial view of the VTG cartridge according to Figure 2,

Figure 4 shows a lateral partial illustration of the VTG cartridge according to Figure 2,

Figure 5 shows a plan view of the actuation pin shown in Figure 2, and

Figure 6 shows a comparison between a conventional actuation pin and an actuation pin according to the invention.

Figure 1 shows a schematically greatly simplified basic illustration of an exhaust-gas turbocharger 1 according to the invention, which has a charger axis of rotation L.

The exhaust-gas turbocharger 1 also has a turbine 2, which comprises a turbine wheel 3 surrounded by an inflow duct 4 which is provided with a so-called VTG cartridge 5. This VTG cartridge 5 will be described in detail hereinbelow with reference to Figures 2 to 6.

The exhaust-gas turbocharger 1 also of course has all the other common parts of an exhaust-gas turbocharger, such as a rotor 20, which is mounted rotatably in a bearing housing 21 and which bears the turbine wheel 3 at one end and a compressor wheel 19 of a compressor 18 at the other end. These parts are likewise shown only in schematically greatly simplified form in Figure 1, since they are not of importance for explaining the principles of the present invention.

A VTG cartridge 5 is understood to mean a structural unit which, between a vane bearing ring 7 and a disk 6, delimits an inflow duct 4 for the passage of exhaust gases to the turbine wheel 3. Furthermore, a VTG cartridge 5 of this type has a plurality of vanes 8, which are arranged in the inflow duct 4 and of which Figures 2 and 4 show one vane designated 8 as a representative example of all vanes 8 bearing the corresponding reference numeral. The vanes 8 can be moved rotatably in the vane bearing ring 7 between a closed and an open position. For this purpose, the vanes 8 have vane shafts 9 each having an axis of rotation. The vane shafts 9 in turn are connected to vane levers 10, of which two vane levers 10 are denoted in each case in Figure 2 with the reference numeral 10. As Figure 2 shows, the embodiment shown there has ten such, preferably cranked vane levers 10, in each case of identical design, and correspondingly ten vanes 8.

Each vane lever 10 has a lever head 11, which engages into an associated adjusting ring groove 12 in an adjusting ring 13. Figure 2 shows in this respect that the adjusting ring 13 surrounds the vane bearing ring 7 on the outside, i.e. along the outer circumference thereof.

For radially mounting the adjusting ring 13, provision is made of a radial bearing, which is preferably formed by the vane levers 10. For this purpose, the vane levers 10 are formed as rolling levers, the lever heads 11 of which are supported in the adjusting ring grooves 12 in the adjusting ring 13. Figures 2 and 4 show that the adjusting ring grooves 12 are arranged in a plane that is offset with respect to the bearing plane of the vane levers 10 on the vane bearing ring 7, which is the reason for the cranked configuration of the vane levers 10 in this embodiment.

As can be seen when Figures 2 to 4 are viewed in combination, the exhaust-gas turbocharger 1 according to the invention, or the VTG cartridge 5 according to the invention, also has an adjusting lever 14, which is operative ly connected to an adjusting shaft 15 (which can be seen in Figure 3) for transmitting an adjusting torque to the adjusting ring 13. The adjusting shaft 15 can be actuated by means of a suitable actuator which is known per se and is not shown in detail in Figures 2 to 4, since it is not necessary for the purposes of explaining the principles of the present invention. The adjusting lever 14 has a first end region 14 A, which in the assembled state is adjacent to the adjusting ring 13 and which has a groove 16 that engages around an actuation pin 17. The actuation pin 17 is fixed on the adjusting ring 13, preferably is welded onto the adjusting ring 13.

As can also be seen from Figures 2 to 4, the groove 16 is open on one side, which results in a fork- like structure of the first end region 14 A, as can be seen in particular from the illustration presented in Figure 3. The groove 16 on the adjusting lever 14 has a width W.

The adjusting lever 14 also has a second end region 14B, which is arranged adjacent to the vane bearing ring 7, in particular above the vane bearing ring 7, and is provided with a recess 18 in which the adjusting shaft 15 is fixed. In Figure 2, only the recess 18 can be seen, whereas Figure 3 shows a schematically simplified representation of the arrangement of the adjusting shaft 15 in the recess 18. The adjusting shaft 15 may for example be welded in the recess 18.

In particular, Figures 3 and 5 show the exact configuration of the actuation pin

17 with its polygonal cross-sectional shape. The polygonal cross-sectional shape is defined by three side faces 19 and accordingly three edges 20. Both the side faces 19 and the edges 20 are rounded. At the side faces 19, the actuation pin 17 has a first radius Rl . At the edges 20, the actuation pin 17 has a second radius R2. As is shown in Figure 5, the cross section of the actuation pin 17 is in the form of an orbiform curve.

Figure 3, in contrast to the illustration in Figure 2, shows the adjusting ring grooves 12 as closed pockets. This configurational detail has no effect on the invention, however.

As is shown for example in Figure 3, the adjusting lever 14 bears against a side face 19 of the polygonal cross-sectional shape of the actuation pin 17. With the first radius Rl, the side faces 19 have a much greater radius than for example a conventional round cross-sectional shape.

Figure 6 shows in detail a comparison between a conventional round cross- sectional shape and the polygonal cross-sectional shape according to the invention. A material removal or wear 21 is indicated in Figure 6 in both illustrations. Since a large first radius Rl, greater than the circular radius of the conventional variant, is chosen for the polygonal cross-sectional shape, the material removal 21 can be reduced. In addition to the above written disclosure, reference is hereby explicitly made to the illustrative representation of the invention in Figures 1 to 6 to supplement the disclosure of the invention.

LIST OF REFERENCE SIGNS

1 Exhaust-gas turbocharger

2 Turbine

3 Turbine wheel

4 Inflow duct

5 VTG cartridge

6 Disk

7 Vane bearing ring

8 Vanes

9 Vane shafts

10 Vane levers

11 Lever heads

12 Adjusting ring grooves

13 Adjusting ring

14 Adjusting lever

14 A, 14B End regions of the adjusting ring

15 Adjusting shaft

16 Groove

17 Actuation pin

18 Recess

19 Side faces

20 Edges

21 Material removal

L Charger longitudinal axis

Rl First radius

R2 Second radius

W Width