EP 1 522 736 A2 has disclosed a generic bearing arrangement for a rotor shaft, which in the case of said document is the rotor shaft of an electric motor-driven turbocompressor.

In the case of high-speed turbomachines such as the stated turbocompressor or exhaust-gas turbochargers, electrically driven compressors or expander turbines, intense vibration excitations caused by an imbalance or an instability of the rotor shaft can lead to acoustic problems.

It is therefore an object of the present invention to provide a bearing arrangement of the type indicated in the preamble of claim 1 which makes it possible for the stated acoustic problems of known bearing arrangements to be at least minimized.

This object is achieved by the features of claim 1.

Tests carried out within the context of the invention have shown that the vibration excitations or vibrations discussed in the introduction can be reduced considerably through the provision of a spring arrangement. It is furthermore possible for the bearing loading to be reduced. It can furthermore advantageously be achieved that thermal expansions between the bearing seats can be compensated.

The dependent claims contain advantageous developments of the invention.

If the spring element is provided with a simple, open geometry, it is advantageously possible to realize an additional ventilation function. Furthermore, through the provision of a support ring or support strip (sheet- metal strip), it is possible to prevent excessive wear of the housing surrounding the bearing arrangement. The spring element and the support structure formed for example by the stated support ring may be of multi-part or unipartite form. Preferably, the spring element may have a corrugated structure and, in a further preferred embodiment, may have an additional smooth region; these may for example be installed in rolled-up form. It is furthermore possible for at least one axial abutment to be provided for axially fixing the rolling bearing. Said axial abutment may be arranged on the spring element or, if provided, on the support ring or on the support structure.

The axial abutment may be produced by way of a raised embossment, a retaining lug or a shoulder on the spring element or on the support ring.

Finally, it is possible for a multiplicity of preferably equally spaced axial abutments to be provided. The turbomachine may for example be an electrically driven compressor, an expander turbine or a classic exhaust-gas turbocharger. According to the invention, the embodiment of the turbomachine is however not restricted to these exemplary embodiments. In summary, it can be stated that, through the provision of a spring arrangement, decoupling of the rolling bearing from the surrounding housing is possible even without the provision of oil. Use is preferably made of a soft spring structure which has a damping action, which leads to energy dissipation through friction.

The spring arrangement or spring structure may, according to the invention, be similar to those in radial air bearings. The spring element preferably has a natural frequency that lies outside the operating frequency of the turbomachine or of the rotor shaft.

Further details, advantages and features of the present invention can be found in the following description of exemplary embodiments with reference to the drawing, in which:

Figure 1 is a sectional illustration through a first embodiment of a turbomachine in the form of an electrically driven compressor,

Figure 2 shows a plan view of a rolling bearing element that is equipped with a spring arrangement according to the invention,

Figure 3 shows a perspective view of the rolling bearing element as per Figure 2,

Figure 4 is a sectional illustration through a rolling bearing that is equipped with a spring arrangement according to the invention, Figure 5 is a sectional illustration of the installed state of a rolling bearing equipped with a spring arrangement, and

Figure 6 is a schematically highly simplified illustration of an exhaust- gas turbocharger as a further example of a turbomachine according to the invention.

Figure 1 shows a possible embodiment of the turbomachine 3 according to the invention in the form of an electrically driven compressor. The turbomachine 3 has a rotor shaft 2 on which a compressor wheel 15 is arranged. A bearing arrangement 1 that conforms to the principles of the present invention is arranged in a bearing housing 18, which bearing housing will be described in detail below on the basis of Figures 2 to 5. The electrically driven compressor 3 furthermore has an electric motor 14, which is merely schematically illustrated in Figure 1 because it does not need to be explained in detail for the explanation of the principles of the present invention. Viewing Figures 1 to 4 together, it is clear that the bearing arrangement 1 in the example has two rolling bearings 4 and 5, which are preferably of identical form. The rolling bearings 4, 5 each have an inner ring 6 which engages around a bearing section 7 or 7 of the rotor shaft 2, as can be seen in particular in Figures 1 and 4. The rolling bearing 4, 5 also has an outer ring 8 which, together with the inner ring 6, guides a multiplicity of rolling bodies, of which one rolling body is indicated representatively in Figures 4 and 5 by the reference sign 13.

As is clear in particular from viewing Figures 2 to 4 together, a spring arrangement 9 is also provided which is arranged on the outer ring 8 of the respective rolling bearing 4 or 5 and which has at least one spring element 10.

In the particularly preferred embodiment illustrated in Figure 4, said spring element 10 of the spring arrangement 9 is in the form of a corrugated spring that is open on one side. The embodiment of the spring element 10 is however not restricted to said embodiment.

Furthermore, in the embodiment as per Figures 2 to 4, and also in that as per Figure 5, there is provided, as a further element of the spring arrangement 9, a support ring or a support plate 11 which surrounds the spring element 10 and preferably bears against the outside of the latter, as can be seen from the sectional illustration of Figure 4.

In the embodiment as per Figures 2, 3 and 5, the spring arrangement 9 also has at least one axial abutment 12. In the embodiment as per Figures 2 and 3, a multiplicity of such axial abutments 12, in particular nine such abutments, is/are provided, said abutments being provided so as to be uniformly circumferentially spaced apart. The one or more axial abutments 12 may in this case be arranged either on the spring element 10 or, if provided, on the support ring 11.

In Figure 6, as a further example of a turbomachine according to the invention, an exhaust-gas turbocharger 16 is provided which, as is conventional, has a turbine 17 with a turbine wheel 20, the bearing housing 18 for the mounting of the rotor shaft 2, and a compressor 19 with a compressor wheel 21, wherein the compressor wheel 21 and the turbine wheel 20 are, as is conventional, fixed to the ends of the rotor shaft 2.

Accordingly, the invention also constitutes a turbomachine that is equipped with a bearing arrangement according to the invention as described above.

In addition to the above written description of the invention, reference is hereby explicitly made, for additional disclosure thereof, to the diagrammatic illustration of the invention in Figures 1 to 6.

LIST OF REFERENCE SYMBOLS

1 Bearing arrangement

2 Rotor shaft

3 Turbomachine

4, 5 Rolling bearing

6 Inner ring

7, 7' Bearing section

8 Outer ring

9 Spring arrangement

10 Spring element

11 Support ring

12 Axial abutment

13 Rolling body, in particular ball

14 Electric motor

15 Compressor wheel

16 Exhaust-gas turbocharger

17 Turbine

18 Bearing housing

19 Compressor

20 Turbine wheel

21 Compressor wheel