A flow rotor of this kind, which is formed in particular as a turbine wheel of an exhaust-gas turbocharger, has a wheel core, on the outside of which there is arranged an outer part with guide vanes. In the case of the turbine wheel of the generic type, the wheel core and the outer part consist of the same material, such that a homogeneous turbine wheel is formed.

By way of contrast, it is an object of the present invention to provide a flow rotor, in particular a turbine wheel, of the type indicated in the preamble of claim 1 which has an improved moment of inertia and a reduced mass.

This object is achieved by the features of claim 1.

By virtue of the fact that the wheel core and the outer part are constructed from different materials, it is possible, by a suitable material selection, to reduce the weight of the wheel core, such that as a whole the moment of inertia of the flow rotor or turbine wheel according to the invention is improved and the mass thereof is reduced.

The dependent claims contain advantageous developments of the inventions.

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 sectional illustration through a first embodiment of a flow rotor according to the invention, which in the example is formed as a turbine wheel;

figure 2 shows an illustration, corresponding to figure 1 , of a second embodiment of the flow rotor, and

figure 3 shows a perspective illustration of an embodiment of a wheel core of the flow rotor according to the invention.

Figure 1 shows a sectional illustration of a flow rotor 1 , which in the example is formed as a turbine wheel. In principle, however, it is also possible that the flow rotor can form a compressor wheel. Flow rotors of this kind are used, for example, in exhaust-gas turbochargers as a turbine or compressor wheel.

The turbine wheel 1 has a wheel core 2 which, in the example, has a bell-like cross section. The outer face 8 of the wheel core 2 is provided with an outer part 3, which is provided with a plurality of guide vanes, of which one guide vane 7 can be seen on account of the sectional illustration. According to the invention, the wheel core 2 is produced from a different material than the outer part 3. To improve the moment of inertia and to reduce the mass, the material of the wheel core 2 has a lower density than the material of the outer part 3. To connect the wheel core 2 and the outer part 3, the outer face 8 of the wheel core 2 may be provided with a suitable coating, in order to make it possible to achieve a better connection between the wheel core 2 and the outer part 3. Furthermore, as is evident from the illustration in figure 3, it is possible to provide the wheel core 2 with a form-fitting connection device 4, which, in the example shown in figure 3, is constructed from a plurality of grooves running in the longitudinal direction of the wheel core 2.

To connect the wheel core 2 and the outer part 3, it is possible, for example, to weld these to one another or to connect them to one another in a composite casting process.

An example of welding is shown in the embodiment according to figure 2. In this case, the wheel core 2 has a continuous longitudinal center recess 5 which extends along the longitudinal axis L and into which a weld pin 6 is inserted. In this case, the weld pin 6 consists of the same material as the outer part 3, with the advantage that a standard welding process (for example a friction welding process or an EB welding process) can be used. In the embodiment shown in figure 2, too, the material of the wheel core 2 has a lower density than the material of the outer part 3 or of the weld pin 6 for reducing the mass and for improving the moment of inertia.

To connect the wheel core 2 and the outer part 3, the weld pin 6 is inserted into the longitudinal center recess 5 and then welded to the outer part 3.

An example of the material of the wheel core 2 is a nickel-based alloy.

The material of the outer part 3 and of the weld pin 6 may be titanium aluminide or ceramic.

In addition to the welding and composite casting connection processes mentioned above, other common connection processes are, of course, also conceivable.

In addition to the written disclosure of the invention above, reference is hereby made explicitly to the diagrammatic illustration thereof in figures 1 to 3. LIST OF REFERENCE SIGNS

1 Flow rotor, in particular turbine wheel

2 Wheel core/boss

3 Outer part/outer skin

4 Form-fitting connection device

5 Longitudinal center recess/longitudinal bore

6 Weld pin

7 Guide vanes

8 Outer face of the wheel core 2

L Longitudinal center axis