The invention relates to a bearing device having a shaft which is mounted magnetically such that it can rotate about an axis with respect to a stator. A bearing device such as this is disclosed, for example, in DE 10 2005 028 209 A1.
Magnetic bearing devices allow non-contacting and wear-free bearing of moving parts. They do not require any lubricants and can be designed with low friction. Magnetic bearing devices such as these are used, for example, for turbomolecular pumps, ultracentrifuges, high-speed spindles of machine tools and X-ray tubes with rotating anodes. Furthermore, magnetic bearings are used for turbines and compressors, but in particular also for motors and generators.
A magnetic bearing device may allow radial and/or axial bearing of a rotating shaft with respect to a stator. The magnetic-field-producing means which are required for the magnetic bearing of a shaft can be provided by the windings of an electromagnet or else by permanent magnets. The magnetic-field-producing means may be both part of the rotating part of a magnetic bearing device and part of the stator of a device such as this.
Active magnetic bearing devices are generally known from the prior art. In the case of active bearing devices, the magnetic forces which are required for the axial and/or radial magnetic bearing of a shaft are controlled by a regulation device. An active magnetic bearing such as this is disclosed, for example, in DE 38 44 563 A1. Furthermore, magnetic bearing devices are known which are, for example, intrinsically stable in a radial direction with respect to a rotation axis of the magnetically borne shaft. Passive magnetic bearings such as these may comprise a plurality of rotor disk elements which are arranged one behind the other on a shaft in the direction of the rotation axis and are separated from one another, forming an intermediate space. In the case of a bearing such as this, stator disk elements which are connected to the shaft can engage in the intermediate spaces between the rotor disk elements. The rotor disk elements and the stator disk elements can be provided with a toothed structure, on their mutually opposite surfaces, in order to provide radial self-stabilization for the bearing. By way of example, a bearing such as this is disclosed in DE 10 2005 028 209 A1.
Further passive magnetic bearings which are known from the prior art are superconducting magnetic bearings. In the case of a superconducting magnetic bearing, one of the two bearing parts is formed by permanent-magnetic elements, and the other bearing part comprises a superconductor. The permanent-magnetic elements induce field changes at the location of the superconductor, when a position change occurs. Shield currents are induced in the superconductor by the varying fields. The resultant forces which are caused by the shield currents may be both attractive and repulsive. However, they are always directed such that they counteract any deflection from the nominal position. This results in an inherently stable bearing being produced, and there is no need for complex regulation, which may be subject to faults. A superconducting magnetic bearing such as this is disclosed, for example, in DE 101 24 193 A1.
Both conventional and superconducting magnetic bearings have little damping of the bearing shaft with respect to the stator, by virtue of their design. In particular, high-quality superconducting magnetic bearings, for which superconducting material with a high critical current density is used, have particularly light damping, which is virtually negligible.
Magnetic bearing devices can be used for the bearing of motor shafts or generator shafts, or for the bearing of other high-speed machines. High rotation speeds of a bearing such as this, resulting from the field of operation, are frequently in a so-called supercritical range. In this case, the expression a supercritical range means the rotation speed range of a bearing which is above the resonant frequency or the resonant frequencies of the bearing. Starting from a stationary bearing shaft, as the rotation speed of a magnetic bearing such as this rises, it is necessary to pass through the resonant frequency or the resonant frequencies of the bearing. The bearing shaft oscillations which typically occur in the region of the resonant frequencies, as known from the prior art, are suppressed by means of mechanical back-up bearings.
The object of the present invention is to specify a bearing device which is better than the solutions known from the prior art in terms of the damping of a magnetically borne shaft.
This object is achieved by the measures specified in the independent claims 1 and 7.
The invention is in this case based on the idea of using the eddy-current losses produced in a conductive material by a varying magnetic field to damp a shaft in a magnetic bearing.
The invention is also based on the idea of producing a magnetic field which is rotationally symmetrical with respect to a rotation axis of a shaft of a magnetic bearing and is inhomogeneous in a direction radially with respect to the rotation axis of the shaft. A further aim is to subject an electrically highly conductive component to a magnetic field such as this.
The component and the already described magnetic field are also intended to rotate with respect to one another. When the component rotates about a fixed rotation axis, no eddy currents are induced in it. In contrast, if the component moves away from the predetermined rotation axis, then eddy currents are induced in the component since the magnetic field to which the component is subject is inhomogeneous in the radial direction. These eddy currents result in a damping force effect on the component, pointing in a direction at right angles to its rotation axis.
If an electrically highly conductive component which is subjected to an inhomogeneous magnetic field as described above is now selectively connected either to a rotating part or to a static part of a magnetic bearing, and if a corresponding further component which produces an inhomogeneous magnetic field is also selectively connected to a rotating part or to a static part of a magnetic bearing, then a non-contacting damping device can be specified.
According to the invention, a bearing device is specified having a shaft which is mounted magnetically such that it can rotate about an axis with respect to a stator, and having a damping apparatus wherein the damping apparatus is intended to comprise at least one first damper part, which is arranged at right angles to the axis, is in the form of a disk and is part of the shaft, and at least one yoke body as a second damper part, which is part of the stator. The yoke body is furthermore intended to comprise magnetic-field-producing means and two magnetic-flux-guiding side parts, which are separated from one another, forming an annular cylindrical intermediate space, in an axial direction with respect to the axis. The first damper part projects into the annular cylindrical intermediate space between the side parts in the radial direction with respect to the axis. The second damper part completely surrounds the first damper part, which is in the form of a disk, in the circumferential direction. The side parts of the second damper part are intended to have tooth-like projections on their sides facing the first damper part, in order to produce a magnetic field, which is inhomogeneous in the radial direction with respect to the axis, in the annular cylindrical intermediate space.
Furthermore, according to the invention, it is intended to specify a bearing device having a shaft, which is mounted magnetically such that it can rotate about an axis with respect to a stator, and having a damping apparatus, wherein the damping apparatus comprises at least one first damper part, which is arranged at right angles to the axis, is in the form of a perforated disk and is part of the stator, and at least one yoke body as a second damper part, which is mechanically connected to the shaft. The second damper part is furthermore intended to have magnetic-field-producing means and two magnetic-flux-guiding side parts, which are separated from one another, forming an annular cylindrical intermediate space, in an axial direction with respect to the axis. The first damper part is intended to project into the annular cylindrical intermediate space in the radial direction with respect to the axis, and is intended to completely surround the second damper part, by the shape of a yoke body, in the circumferential direction. The side parts of the second damper part are intended to have tooth-like projections on their sides facing the first damper part, in order to produce a magnetic field, which is inhomogeneous in the radial direction with respect to the axis, in the annular cylindrical intermediate space.
The advantages of the bearing device according to the invention are, in particular, that a bearing device is made possible having a damping apparatus according to the invention, allowing non-contacting damping of a magnetically borne shaft. In consequence, a magnetically borne shaft can be damped in such a way that there is no need for any further components which are mechanically connected to the shaft. Thus, according to the invention, a bearing device can be specified which requires little maintenance, is subject to little wear and has a damping apparatus which likewise requires little maintenance and is subject to little wear.
Advantageous refinements of the abovementioned bearing devices are specified in claims 2 to 6, which are dependent on claim 1, and in claims 8 and 9, which are dependent on claim 7, as well as in the dependent claims 10 to 19. In this case, the embodiment as claimed in claim 1 or claim 7 may in particular be combined with the features of one or preferably also those of a plurality of dependent claims. The bearing device according to the invention can accordingly also have the following features:
Further advantageous refinements of the bearing device according to the invention will become evident from the claims which have not been addressed above and in particular from the drawing, which will be explained in the following text, and in which:
The damping apparatus 200 has a first damper part 201, which is in the form of a disk and is connected to the shaft 101. The first damper part 201, which is in the form of a disk, may be a disk composed of highly conductive material, for example composed of copper or aluminum. The first damper part 201, which is in form of a disk, may, for example, be connected to the shaft 101 by means, for example, of a ring clamping element. The first damper part 201, which is in the form of a disk, may also have a virtually circular shape.
The first damper part 201, which is in the form of a disk, is completely surrounded in the circumferential direction by a second damper part 202, which is in the form of a yoke. The second damper part 202 may also be manufactured predominantly from iron or steel. Further materials which are suitable for magnetic flux guidance may likewise be used. The second damper part 202 has one or more permanent magnets 212 as the magnetic-field-producing means. By way of example, the permanent magnets 212 may be permanent magnets which contain neodymium, iron and boron. Furthermore, the permanent magnets 212 may be closed, annular magnets which surround the axis 101. Alternatively, the magnetic-field-producing means may be formed by an arrangement composed of discrete, individual magnets which are separate from one another, with the individual discrete magnets together with the side parts 211 forming a magnetic arrangement which is closed in the circumferential direction of the side parts 211.
Magnetic-flux-guiding side parts 211 are arranged on both sides of the permanent magnet 212 as part of the damping apparatus 200 and have tooth-like projections 213 on their sides which face the first damping part 201, which is in the form of a disk. The magnetic-flux-guiding side parts 211 may be in the form of a perforated disk, which is oriented at right angles to the axis A.
In order to simplify assembly, the first damper part 201, which is in the form of a disk, may likewise be a component which is assembled from a plurality of segments. For example, the first damper part 201, which is in the form of a disk, may be composed of two elements which are in the form of half-disks and are separated along a plane on which the axis A lies. Furthermore, the first damper part 201, which is in the form of a disk, may be composed of a multiplicity of disk segments.
The permanent magnet or permanent magnets 212 produces or produce a magnetic flux in the side parts 211 which is focused by the tooth-like projections 213 and leads to a magnetic field distribution, which is inhomogeneous with respect to the axis A in a radial direction, in the annular cylindrical air gap between the side parts 211. The magnetic flux passes through the first damper part 201, which is connected to the shaft 101, is in the form of a disk and projects into the annular cylindrical intermediate space, and flows back to the magnetic-field-producing permanent magnet 212 via the corresponding side part 211 on the opposite side. The tooth-like projections 213 on the side parts 211 are radially symmetrical with respect to the axis A.
As an alternative to a configuration with a plurality of tooth-like projections which are radially symmetrical and are concentric with respect to the axis A, the magnetic-flux-guiding side parts 211 may have only one tooth-like projection, which is concentric with respect to the axis A. The tooth-like projections 213 may have a trapezoidal shape, when viewed in the form of a cross section.
When the shaft 101 rotates about the axis A, then the inhomogeneous magnetic field which is present in the gap between the side parts 211 in the radial direction with respect to the axis A results, since this is rotationally symmetrical with respect to rotation about the axis A, with no eddy currents being induced in the first damper part 201, which is in the form of a disk. This is the case because no magnetic field changes occur at the location of the first damper part, which is in the form of a disk, at the location of the first damper part 201, which is in the form of a disk, when the first damper part 201 rotates about the axis A.
In contrast, when the shaft 101 moves radially, the first damper part 201, which is in the form of a disk, is moved in a radial direction with respect to the axis A in the inhomogeneous magnetic field. A movement of the first damper part 201, which is in the form of a disk, such as this in the inhomogeneous magnetic field between the side parts 211 results in eddy currents being induced in the first damper part 201, which is in the form of a disk. The eddy-current losses caused by these eddy currents lead to damping of the movement of the shaft 101.
The magnetic bearing 210 is a passive magnetic bearing which is intrinsically stable in the radial direction. The magnetic bearing 210 has a stator 301 with stator disk elements 302 which are arranged at right angles to the axis A and are at a distance from one another in the direction of the axis A, forming the intermediate space. Permanent-magnetic elements 303 are integrated in the stator disk elements 302 and are used to produce a magnetic holding flux M in order to bear the shaft 101. A rotor disk element 304 projects into each of the intermediate spaces between the stator disk elements 302. The stator disk elements 302 and the rotor disk elements 304 are each provided with tooth-like projections on their mutually facing sides. These tooth-like projections lead to an inhomogeneous magnetic field distribution in the bearing gap of the magnetic bearing 210, between the stator disk elements 302 and the rotor disk elements 304. This inhomogeneous magnetic field distribution in the bearing gap of the magnetic bearing 210 leads to the magnetic bearing 210 being intrinsically stable in the radial direction with respect to the axis A. Furthermore, the surfaces of the stator disk elements 302 and of the rotor disk elements 304 can be inclined at an angle a with respect to the axis A.
The damping apparatus 200 has a first damper part 201, which is in the form of a disk and is connected to the shaft 101, which is mounted such that it can rotate, and is surrounded completely along its circumference by a second damper part 302, which is in the form of a yoke. The second damper part 202, which is in the form of a yoke, may also be mechanically connected to the stator 301 of the magnetic bearing 210.
The second damper part 202, which is in the form of a yoke, comprises two side parts 211 which have tooth-like projections 213 on their sides facing the first damper part 201, which is in the form of a disk. Furthermore, the second damper part 202, which is in the form of a yoke, has magnetic-field-producing means in the form of a magnet winding 305. The magnet winding 305 of the damping apparatus 200 may be located on the radially outer edge area of the second damper part 202, which is in the form of a yoke. A magnetic flux can be produced by means of the magnet winding 305, and is forced away via the tooth-like projections 213 and the first damper part 201, which is in the form of a disk and is arranged between the side parts 211. In addition, the magnet winding 305 may be connected to a regulation apparatus 306 for regulation of the field current of the magnet winding 305. In particular, a damping constant of the damping apparatus 200 can be adjusted by means of the regulation apparatus 306, via the field current of the magnet winding 305. This damping constant may also be regulated as a function of the rotation speed of the shaft 101. For example, a higher damping constant can be set for the damping device 200 when the rotation speed of the shaft 101 is higher.
A magnet bearing typically has one or more resonant frequencies. The magnet winding 305 can now be excited by means of the regulation apparatus 306 such that the damping constant of the damping device 200 is set to a specific value at rotation speeds of the shaft 101 which lie in the region of the resonant frequency or the resonant frequencies of the magnetic bearing 210. This means that it is possible to pass through the resonant frequency or the resonant frequencies of the magnetic bearing 210 when the rotation speed of the shaft 101 is being accelerated from rest such a way that resonant oscillations in the bearing device 210 are reduced.
The damping apparatus 200 has a first damper part 401, which is in the form of a perforated disk, is mounted in a fixed position and can be mechanically connected, for example, to a stator of the magnetic bearing 210. The first damper part 401, which is in the form of a perforated disk, can be oriented at right angles to the axis A. The first damper part 401, which is in the form of a perforated disk, completely surrounds a second damper part 202, which is in the form of a yoke, in the circumferential direction.
The second damper part 202, which is in the form of a yoke, comprises two magnetic-flux-guiding side parts 211 which have tooth-like projections 213 on their sides facing the first damper part 401, which is in the form of a perforated disk. Furthermore, the second damper part 202, which is in the form of a yoke, has one or more permanent-magnetic elements 212 which can be arranged on the radially inner edge of the side parts 211 which are in the form of disks. The permanent-magnetic elements 212 may be a ring magnet which completely surrounds the shaft 101 or else an arrangement composed of discrete permanent magnets 212 which are separated from one another and, together with the side parts 211, form a closed magnetic arrangement.
The permanent-magnetic elements 212 may be magnetically separated from the shaft 101 by means of non-magnetic reinforcement 402. At the same time, the second damper part 202, which is in the form of a yoke, is mechanically connected to the shaft 101 by means of the non-magnetic reinforcement 402.
The method of operation of the damper device 200, of the bearing device 100 which is illustrated in
The permanent magnets 212 may also be an integrated component of the side parts 211. For example, the permanent magnets can likewise be in the form of disks and may be integrated in the side parts 211.
The magnetic bearing 210 has a stator 301 which comprises stator disk elements 302 which are arranged at right angles to the axis A of the shaft 101. Rotor disk elements 304 which are connected to the shaft 101 project into the intermediate spaces between the stator disk elements 302. The stator disk elements 302 and the rotor disk elements 304 are provided with tooth-like projections on their mutually facing sides. Because of these tooth-like projections, the illustrated magnetic bearing 210 is intrinsically stable in the radial direction with respect to the axis A, in a similar manner to the magnetic bearing 210 illustrated in
The damping device 200 has a first damper part 401 which is in the form of a perforated disk and completely surrounds a second damper part 202, which is in the form of a yoke. The first damper part 401, which is in the form of a perforated disk, can be manufactured, for example, from two separate half-disks, for easier assembly. The second damper part 202, which is in the form of a yoke, also has side parts 211 which have tooth-like projections 213 on their sides facing the first damper part 401, which is in the form of a perforated disk. As magnetic-field-producing means, the second damper part 202, which is in the form of a yoke, may have permanent magnets 212 which are arranged on the radially inner edge of the second damper part 202, which is in the form of a yoke. The second damper part 202 is mechanically connected to the shaft 101 and can be magnetically separated from it by reinforcement 402. The non-magnetic reinforcement 402 can be incorporated in the shaft 101. Furthermore, the shaft 101 may be manufactured from a non-magnetic material. The first damper part 401, which is in the form of perforated disk, may also be mechanically connected to a static part of the magnetic bearing 210, and for example the first damper part 401, which is in the form of a perforated disk, may be mechanically connected to the stator 301.
The damping apparatus 200 is duplicated and it therefore has two first damper parts 201, which are in the form of disks, and, in a corresponding manner, two second damper parts 202, which are in the form of yokes. In general, the damping device 200 can be designed, with the first damper parts 210 which are in the form of disks and with the second damper parts 202 which are in the form of yokes, analogously to the exemplary embodiment shown in
Number | Date | Country | Kind |
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10 2007 019 766.9 | Apr 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP08/54677 | 4/17/2008 | WO | 00 | 10/23/2009 |