Such rotors, which are assembled from a multiplicity of individual rotor disks, forming one or more rotor-disk groups, are known in the prior art in a wide variety of embodiments. The rotor disks of each rotor disk unit are pressed flat against each other via the tie rod, wherein the pressure force is normally created by screw-nuts which are screwed onto the tie rod at the end. In most cases, directly adjacently arranged rotor disks are additionally interconnected and centered via a form fit. Such a form fit can for example be formed via a so-called Hirth toothing.
During operation, the rotor is exposed to mechanical vibrations, the frequency of which is dependent inter alia on the freely vibrating length of the tie rod. With increasing overall length of a rotor, the freely vibrating length of the tie rod also increases, which leads to its natural frequency shifting to a lower level close to the rotational frequency of the rotor. Such a frequency shift can involve unacceptably high vibration amplitudes which can impair the function of the rotor and lead to damage.
For reducing the freely vibrating length of the tie rod, it is already known to attach at least one support ring on the outside diameter of the tie rod and to connect it to one of the rotor disks. Via such a support ring, the tie rod can be supported on the corresponding rotor disk. Therefore, for example DE 2 643 886 proposes a support ring in the form of a push-on ring with a widening inside diameter, wherein the push-on ring by its free end of larger inside diameter engages in an annular slot which is provided on the associated rotor disk and by the smallest inside diameter is supported on the tie rod. During operation, the end of the push-on ring which is connected to the rotor disk is widened on account of a centrifugal force stretching of the rotor disk in such a way that the inside diameter of the push-on ring which butts against the outer circumference of the tie rod presses against the tie rod at the end, as a result of which a fixed clamping between the rotor disk and the tie rod is achieved, and therefore the desired support effect.
In order to prevent the effect of a support ring being able to be displaced axially along the outer circumference of the tie rod, it is also known to axially secure the support ring by means of an additional locking ring. Therefore, DE 2 643 886 proposes for example the use of a sleeve-like locking ring which is inserted between the support ring and a further rotor disk and together with the rotor disks is clamped via the tie rod. If a further rotor disk is not available, then a dummy rotor disk has to be used in order to be able to press the locking sleeve axially next to the support ring. The use of such a dummy rotor disk, however, is accompanied by high costs, which is not desirable.