WO2010136325A2

WO2010136325A2 - Bearing arrangement for a touch-free magnetic axial bearing and x-ray tubes with said bearing

Info

Publication number: WO2010136325A2
Application number: PCT/EP2010/056364
Authority: WO
Inventors: Sven Fritzler; Jan Matschulla; Peter-Klaus Budig; Nils HÜBNER; Marcus Paditz
Original assignee: Siemens Aktiengesellschaft
Priority date: 2009-05-29
Filing date: 2010-05-10
Publication date: 2010-12-02
Also published as: CN102449335A; WO2010136325A3

Abstract

The invention relates to a bearing arrangement for a touch-free magnetic axial bearing (1), comprising a rotor/stator pair (2, 3) which can be rotated relative to each other on a common rotational axis (6), wherein magnets are provided both on the rotor side and on the stator side, which create a magnetic field bearing acting towards the axial direction, and a definite gap is present between the rotor (2) and stator (3), so that the rotor (2) and stator (3) do not touch each other, wherein on the side of the rotor (2) and on the side of the stator (3) permanent magnets (4) which are opposite to each other are arranged, the stator-side polarity is directed contrary to the rotor-side polarity, and on the side of the stator (3) at least one control and/or adjustable electromagnet having a coil (5) is arranged, which is opposite to a metal surface on the side of the rotor (2), which serves as a magnet yolk. Further, the invention relates to an X-ray tube (8) having a vacuum housing (9) and a rotary anode localized in the vacuum housing (9), which has at least one magnetic axial bearing (1) of the above-mentioned embodiment for the rotary anode.

Description

description

Bearing arrangement for a non-contact magnetic thrust bearing and X-ray tube with this bearing

The invention relates to a bearing assembly for a contactless magnetic thrust bearing, comprising a rotatable on a common axis relative to each other rotor / stator pair, wherein both rotor side and stator side magnets are provided which generate a magnetic field bearing acting in the axial direction, and between the rotor and stator there is a finite gap, so that rotor and stator do not touch during operation.

Furthermore, the invention also relates to an X-ray tube with a vacuum housing and in the vacuum housing located rotary anode, which has at least one magnetic thrust bearing for the rotary anode.

Basically, such bearings are well known and used in conjunction with vacuum environment applications such as the storage of rotors of turbomolecular pumps or rotating anode plates in high dose rate X-ray tubes. By way of example, reference is made here to the German publication DE 26 01 529 C2, the document US Pat. No. 6,327,340 or the document US Pat. No. 6,198,803.

A disadvantage of such bearings is that these previously known versions each claim relatively large axial lengths, whereby the natural vibration frequencies of such relatively long rotary components decrease and accordingly the resonance speeds due to mechanical deformations are smaller and thus can be close to the operating frequency of the magnetically mounted rotor , If these components are to be operated in a subcritical frequency range, considerable difficulties arise with regard to the executability of these axial bearings. It is therefore an object of the invention to find a thrust bearing, which is associated with the smallest possible overall length. Accordingly, an X-ray tube to be proposed, which allows a compact design of the rotary anode with storage.

This object is solved by the features of the independent claims. Advantageous further developments of the invention are the subject of the subordinate claims.

The inventors have recognized that a bearing arrangement of a magnetic thrust bearing for a rotor / stator pair is possible, which on the side of the rotor exclusively permanent magnets, the permanent magnets on the rotor side are arranged opposite and facing each other, to a permanent repulsion between the rotor and to effect stator. At the same time this repulsive force counteracting electromagnets can be arranged on the stator side, which use a part of the rotor as Magnetj och and tighten the rotor controlled and thus allow accurate positioning of the rotor relative to the stator via known control and regulating mechanisms.

In accordance with this basic idea, the inventors propose the improvement of a bearing arrangement for a non-contact magnetic thrust bearing which has a rotor / stator pair rotatable relative to one another on a common axis, wherein both rotor side and stator side magnets are provided, which magnetic field bearing acting in the axial direction and there is a finite gap between the rotor and the stator so that the rotor and the stator do not touch each other. The improvement is brought about by the fact that on the side of the rotor and on the side of the stator, in each case opposite permanent magnets are arranged, the stator-side polarity of which is oriented opposite to the rotor-side polarity, and furthermore on the side of the stator. At least one control and / or controllable electromagnet is arranged, which faces a metallic surface on the side of the rotor, which acts as Magnetj och.

Thus, rotor and stator oppositely oriented permanent magnets are used, which cause a repulsion between the rotor and stator, wherein the repulsive force extends in the axial direction. As a counteracting force electromagnets are used on the stator side, which act with their flow on a rotor-side metallic surface and depending on the strength of the electrically operated magnetic field, the rotor controlled or used on the stator and thus counteract the repulsive forces of the permanent magnets.

Such an arrangement can be realized very compact, so that this bearing assembly requires only a very short length and thus low natural vibration frequencies can be avoided on the rotor side.

Advantageously, the permanent magnets may consist of coaxial ring pairs or of a plurality of coaxially arranged magnetic rings.

Furthermore, it is proposed that the at least one electromagnet is constructed from at least one coaxial toroid, it being advantageous that the at least one coaxial annular coil has a partial coil for the basic excitation and a partial coil for the control excitation. In this case, the partial coil for the basic excitation and / or the partial coil for the control excitation can be electrically connected to one power converter each.

It is further proposed that, advantageously, the permanent magnets are arranged radially inwardly, while the electromagnets are arranged radially farther outward than the permanent magnets. In addition to the bearing arrangement according to the invention, the inventors also propose an X-ray tube with a vacuum housing and a rotary anode located in the vacuum housing, wherein at least one magnetic thrust bearing is provided for the rotary anode and this is designed at least one thrust bearing in accordance with the invention.

Furthermore, it is proposed that the rotor is arranged within the vacuum housing of the X-ray tube and runs in the gap between the rotor and stator, the magnetic flux little influencing and airtight partition. In this case, it is proposed with respect to the partition wall that this at least partially consists of a material of the following list: ceramic, stainless steel, plastic, fiber-reinforced plastic, glass.

In the following the invention with reference to the preferred embodiments with reference to the figures will be described in more detail, with only the features necessary for understanding the invention features are shown. The following reference numerals are used: 1: magnetic thrust bearing; 2: rotor; 3: stator; 4: permanent magnet; 5: coaxial coil; 6: rotation axis; 7: magnetic flux; 8: X-ray tube; 9: vacuum housing; 10: partition; 11: cathode assembly; 12: radial bearings; 13: exit window; 14: power converter; 15: spindle housing.

They show in detail:

1 shows a longitudinal section through an inventive contactless magnetic thrust bearing; 2 shows embodiment of the magnetic thrust bearing according to

1 with schematically illustrated magnetic flux lines; 3 shows an example of an inventively designed X-ray tube in a schematic representation. FIG. 1 shows a magnetic axial bearing 1 according to the invention, which consists of magnets arranged on the rotor side and on the stator side. On the side of the rotor 2 there are two permanent magnets 4, wherein their orientation is designed so that the magnetic south pole is directed in the direction of the stator. The rotor 2 coaxial with the axis of rotation 6 opposite a stator 3 is arranged, which also has Ü permanent magnets 4, which, however, are arranged opposite to the permanent magnet 4 on the rotor side. Radially further away from the axis of rotation 6 is located on the stator side of a coaxial coil 5, which can be traversed by a time-varying current. The polarity of the permanent magnet 4, which is of annular design here, is directed counter to the permanent magnet 4, which is likewise designed as a ring magnet, on the rotor side, so that a repelling force arises between the two permanent magnets 4. The coaxial coil 5 generates a magnetic field which is aligned so that in the case of a current flow in the coaxial coil 5, a magnetic field is created, which draws the rotor to the stator. By appropriate control of the

Current flow can be generated with the aid of distance sensors, not shown here, a direction which keeps the rotor 2 at a predetermined distance to the stator 3.

It is also advantageous if two coils are used instead of a single coaxial coil, so that a first coaxial coil can be charged with a base excitation current and a second coaxial coil can be fed with a control excitation current, which is ultimately responsible for the Ab- regulation. Alternatively, it is also possible to use a single coil with two different windings instead of two separate coils, wherein the one winding is supplied with the ground excitation current and the other winding with the control excitation current.

To illustrate the basic principle, the same bearing arrangement as shown in FIG. 1 is again shown in FIG. Here, the magnetic fluxes 7, which arise through the permanent magnets and the coaxial coil, are shown here in a schematic way.

The arrangement of the magnetic thrust bearing shown here now makes it possible to reduce the rotor by the length of a coaxial arrangement, so that due to the smaller overall length and the natural vibration of the rotor increases and thus the resonance frequencies are also shifted to a higher frequency range.

It should be noted that the inventive type of axial bearing course with various designs of radial bearings, preferably magnetic radial bearings, can be combined. For example, heteropolargers, homopolar bearings and unipolar bearings can be used for this purpose.

3 shows a schematic representation of an inventive X-ray tube 8, consisting of a vacuum housing 9, in which a rotor 2 according to the invention is located, which is equipped at the right end with a ring-shaped permanent magnet 4. The opposite on the stator side, an annular permanent magnet is also arranged, which, however, with respect to its polarity of the polarity of the rotor-side permanent magnet 4 is opposite. Radially further out to the permanent magnet 4 on the stator side is one or more coaxial coil (s) 5, which can counteract the repulsive force caused by the permanent magnets 4, in the case of a current flow / can. In addition, a radial bearing 12 of the turntable bearing rotor 2 is shown. Also, such storage can be configured in a conventional manner as magnetic storage. Between the rotor 2 and the stator 3, in the illustration shown here, there is a partition 10 made of material which is not difficult to magnetize, which ensures that a sufficient vacuum remains in the region of the vacuum housing 9. Will the stator side Housing additionally designed separable from the vacuum housing 9, it is possible to supply the vacuum housing 9 separately Ar ^¬ particulate.

In addition, in the purely schematic representation also shown that the coil 5 of the stator can be powered by a power converter 14. In addition, the vacuum housing 9 of course has an X-ray exit window 13 and a cathode arrangement 11, from which, when a corresponding high voltage is applied, an electron beam strikes the anode surface of the turntable designed as a rotor and generates X-radiation.

Overall, therefore, a bearing assembly of a non-contact magnetic thrust bearing is shown by the invention, which is much shorter than the known prior art bearing assemblies with respect to their length and thus according to the above object makes it possible to produce a rotor, which due to the smaller overall length with respect Natural frequency is shifted upwards relative to the prior art and accordingly also has higher resonance frequencies. This means that it can still be operated at higher speeds in the subcritical speed range.

It is understood that the abovementioned features of the invention can be used not only in the respectively specified combination but also in other combinations or in isolation, without departing from the scope of the invention.

Claims

claims

1. Bearing arrangement for a non-contact magnetic axial bearing (1), comprising a rotatably on a common rotation axis (6) rotatable rotor / stator pair (2, 3), wherein both rotor side and stator side magnets are provided, which produce a magnetic field bearing acting in the axial direction, and there is a finite gap between the rotor (2) and the stator (3) so that the rotor (2) and stator (3) do not touch, thereby indicating that

1.1. on the side of the rotor (2) and on the side of the Sta ^¬ gate (3) each opposite permanent magnets (4) are arranged, whose stator-side polarity is opposite to the rotor-side polarity, and

1.2. on the side of the stator (3) at least one controllable and / or controllable electromagnet with a coil (5) is arranged, which faces a metallic surface on the side of the rotor (2), which acts as a magnet ^¬ yoke.

2. Bearing arrangement according to the preceding Patent Claim 1, characterized in that the permanent magnets (4) consist of coaxial ring pairs.

3. Bearing arrangement according to the preceding patent claim 1, characterized in that the permanent magnets (4) consist of several coaxially arranged Mag- ned rings.

4. Bearing arrangement according to one of the preceding claims 1 to 3, characterized in that the at least one electromagnet has at least one coaxial annular coil (5).

5. Bearing arrangement according to the preceding claim

4, characterized in that the at least one coaxial annular coil (5) has a partial coil for the basic excitation and a partial coil for the Steuerer- movement.

6. Bearing arrangement according to the preceding claim

5, characterized in that the part ^¬ coil for the basic excitation and / or the partial coil for the control excitation, each with a power converter (14) is connected e- lektrisch.

7. X-ray tube (8) with a vacuum housing (9) with a in the vacuum housing (9) as a rotor (2) formed rotational anode, which is supported by at least one magnetic ^¬ thrust bearing (1), as you r ch ge ke nn zei Chne t, the at least one Axi ^¬ allager (1) has the features of one of claims 1 to. 6

8. X-ray tube (8) according to the preceding Patent Claim 7, characterized in that the rotor (2) within the vacuum housing (9) of the X-ray tube (8) is arranged and in the gap between the rotor (2) and stator (3) one, the magnetic flux (7) little influencing and airtight partition (10) ver ^¬ runs.

9. X-ray tube according to the preceding claim 8, characterized in that the partition wall

(10) consists at least in part of a material of the following list: ceramic, stainless steel, plastic, fiber reinforced plastic, glass.

10. X-ray tube according to one of the preceding patent claims ^¬ 8 to 9, characterized in that the rotor-side vacuum housing (9) from the stator term part (15) of the X-ray tube is designed separable.