Source: http://www.google.com/patents/US4620752?dq=6,460,050
Timestamp: 2017-04-28 09:29:42
Document Index: 362876917

Matched Legal Cases: ['arts 3', 'arts 3', 'arts 3', 'arts 3', 'art 1', 'art 1', 'art 8', 'art 8', 'arts 3', 'art 8', 'arts 3', 'art 8', 'arts 3', 'art 3', 'art 3', 'art 8', 'art 8', 'art 8', 'art 8', 'art 8', 'art 8', 'art 8', 'arts 3', 'art 8', 'arts 3', 'art 8', 'art 8', 'art 8', 'art 8', 'arts 3', 'arts 3', 'art 8', 'art 8', 'arts 3', 'art 8']

Patent US4620752 - Magnetic bearing having triaxial position stabilization - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA magnetic bearing having contactless position stabilization of a supported body which includes a damping and aligning arrangement. This arrangement includes two spaced rotating annular permanent magnets which form a gap therebetween and which are attached to a rotor supported by the bearing. A stationary...http://www.google.com/patents/US4620752?utm_source=gb-gplus-sharePatent US4620752 - Magnetic bearing having triaxial position stabilizationAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS4620752 APublication typeGrantApplication numberUS 06/711,239Publication dateNov 4, 1986Filing dateMar 13, 1985Priority dateMar 13, 1984Fee statusPaidAlso published asCA1243066A, CA1243066A1, DE3409047A1, DE3409047C2, DE3567073D1, EP0155624A1, EP0155624B1Publication number06711239, 711239, US 4620752 A, US 4620752A, US-A-4620752, US4620752 A, US4620752AInventorsJohan K. Fremerey, Albrecht WellerOriginal AssigneeKernforschungsanlage Julich Gesellschaft Mit Beschrankter HaftungExport CitationBiBTeX, EndNote, RefManPatent Citations (11), Non-Patent Citations (9), Referenced by (83), Classifications (14), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetMagnetic bearing having triaxial position stabilization
US 4620752 AAbstract
A magnetic bearing having contactless position stabilization of a supported body which includes a damping and aligning arrangement. This arrangement includes two spaced rotating annular permanent magnets which form a gap therebetween and which are attached to a rotor supported by the bearing. A stationary plate having good electrical conductivity and extending into the gap between the permanent magnets, is cut by their rotating magnetic flux. Mechanical disturbances of the rotor generate eddy-currents in the conductive plate which currents damp out these disturbances. A portion of the plate outside the gap is much thicker than the portion in the gap and provides a very low resistance path for the eddy-currents.
1. A magnetic bearing which has a movable means and means for supporting and maintaining said movable means in a bearing relationship with said means for supporting and maintaining, said magnetic bearing having an arrangement comprising:flux means for producing substantially constant, invariant flux, said flux means having means for attachment thereof to said movable means of said bearing; said flux means comprising at least two parts disposed along said movable means and being displaced one from the other; means, being electrically conductive and being non-ferromagnetic and non-magnetizable, for conducting currents generated therein by said flux of said flux means, said electrically conductive means comprising at least one rigid, substantially homogeneous, unitary element, only a sole element of said conductive means being disposed between any two of said at least two parts of said flux means, such that, a substantial portion of said flux of said flux means passes through at least a portion of said electrically conductive means and said at least two parts of said flux producing means; said electrically conductive means being disposed to be displaced from and in a non-contacting relationship with said movable means and said flux means; said electrically conductive means being disposed with respect to said movable means and said flux means, such as not to be movable with said movable means and said flux means; said flux means and said electrically conductive means being disposed so that said flux, produced by said flux means, forms a flux path, at least a portion of said flux path passing through and between said two of said at least two parts of said flux means, said portion of said flux path having substantially one substantially straight component disposed along solely one substantially single continuous direction and further having a substantially constant total flux along said portion of said flux path; each element having a component being disposed perpendicular to said one straight component of said portion of said flux path passing through and between said at least two parts of said flux means; electric control coils for controlling movement of said movable means substantially parallel to said portion of said one straight component to said portion of said flux path passing through and between said at least two parts of said flux means; sensor means for sensing positions of said movable part; electronic amplifier means for amplifying signals from said sensor means; said sensor means having means for connection thereof to said electronic amplifier means; and said electronic amplifier means having means for being connected to said electric control coils for control thereof. 2. A magnetic bearing according to claim 1, wherein said electrically conductive means comprises a stationary plate affixed to a stationary part of said magnetic bearing.
3. A magnetic bearing according to claim 1, wherein each of said at least two parts of said flux means has a permanent magnet disposed therein for producing said flux.
4. A magnetic bearing according to claim 2, wherein each of said at least two parts of said flux means has a permanent magnet disposed therein for producing said flux.
5. A magnetic bearing according to claim 1, including ferromagnetic means disposed to form a low reluctance path for said flux of said flux means whereby stray flux fields are minimized.
6. A magnetic bearing according to claim 2, including ferromagnetic means disposed to form a low reluctance path for said flux of said flux means whereby stray flux fields are minimized.
7. A magnetic bearing according to claim 3, including ferromagnetic means disposed to form a low reluctance path for said flux of said flux means whereby stray flux fields are minimized.
8. A magnetic bearing according to claim 4, including ferromagnetic means disposed to form a low reluctance path for said flux of said flux means whereby stray flux fields are minimized.
9. A magnetic bearing according to claim 2, wherein said movable means comprises a rotationally symmetrical rotor having opposing faces and a longitudinal axis for rotation thereabout and wherein said substantially straight path of said flux is substantially parallel to said longitudinal axis of said rotor, and wherein said stationary plate has a portion being substantially annular and substantially flat with substantially parallel opposing flat surfaces, said opposing surfaces being substantially perpendicular to said substantially straight path of said flux where said flux extends through said at least two parts and said stationary plate, and said bearing having rotationally symmetrical stator means, said rotor being supported in use by said stator means.
10. A magnetic bearing according to claim 3, wherein said electrically conductive means comprises a stationary plate affixed to a stationary part of said magnetic bearing, and wherein said movable means comprises a rotationally symmetrical rotor having opposing faces and a longitudinal axis for rotation thereabout and wherein said substantially straight path of said flux is substantially parallel to said longitudinal axis of said rotor, and wherein said stationary plate has a portion being substantially annular and substantially flat with substantially parallel opposing flat surfaces, said opposing surfaces being substantially perpendicular to said substantially straight path of said flux where said flux extends through said at least two parts and said stationary plate, and said bearing having rotationally symmetrical stator means, said rotor being supported in use by said stator means.
11. A magnetic bearing according to claim 4, wherein said movable means comprises a rotationally symmetrical rotor having opposing faces and a longitudinal axis for rotation thereabout and wherein said substantially straight path of said flux is substantially parallel to said longitudinal axis of said rotor, and wherein said stationary plate has a portion being substantially annular and substantially flat with substantially parallel opposing flat surfaces, said opposing surfaces being substantially perpendicular to said substantially straight path of said flux where said flux extends through said at least two parts and said stationary plate, and said bearing having rotationally symmetrical stator means, said rotor being supported in use by said stator means.
12. A magnetic bearing according to claim 5, wherein said electrically conductive means comprises a stationary plate affixed to a stationary part of said magnetic bearing, and wherein said movable means comprises a rotationally symmetrical rotor having opposing faces and a longitudinal axis for rotation thereabout and wherein said substantially straight path of said flux is substantially parallel to said longitudinal axis of said rotor, and wherein said stationary plate has a portion being substantially annular and substantially flat with substantially parallel opposing flat surfaces, said opposing surfaces being substantially perpendicular to said substantially straight path of said flux where said flux extends through said at least two parts and said stationary plate, and said bearing having rotationally symmetrical stator means, said rotor being supported in use by said stator means.
13. A magnetic bearing according to claim 6, wherein said movable means comprises a rotationally symmetrical rotor having opposing faces and a longitudinal axis for rotation thereabout and wherein said substantially straight path of said flux is substantially parallel to said longitudinal axis of said rotor, and wherein said stationary plate has a portion being substantially annular and substantially flat with substantially parallel opposing flat surfaces, said opposing surfaces being substantially perpendicular to said substantially straight path of said flux where said flux extends through said at least two parts and said stationary plate, and said bearing having rotationally symmetrical stator means, said rotor being supported in use by said stator means.
14. A magnetic bearing according to claim 8, wherein said movable means comprises a rotationally symmetrical rotor having opposing faces and a longitudinal axis for rotation thereabout and wherein said substantially straight path of said flux is substantially parallel to said longitudinal axis of said rotor, and wherein said stationary plate has a portion being substantially annular and substantially flat with substantially parallel opposing flat surfaces, said opposing surfaces being substantially perpendicular to said substantially straight path of said flux where said flux extends through said at least two parts and said stationary plate, and said bearing having rotationally symmetrical stator means, said rotor being supported in use by said stator means.
15. A magnetic bearing according to claim 9 wherein said stationary plate has an outer periphery, and wherein said stationary plate includes an electrically conductive part along said periphery, said electrically conductive part being of the same material as the plate and having opposing surfaces being substantially further from one another than said opposing flat surfaces of said stationary plate.
16. A magnetic bearing according to claim 10 wherein said stationary plate has an outer periphery, and wherein said stationary plate includes an electrically conductive part along said periphery, said electrically conductive part being of the same material as the plate and having opposing surfaces being substantially further from one another than said opposing flat surfaces of said stationary plate.
17. A magnetic bearing according to claim 1, wherein said magnetic bearing comprises a passive permanent magnetic bearing system.
18. A magnetic bearing according to claim 2, wherein said magnetic bearing comprises a passive permanent magnetic bearing system.
19. A magnetic bearing according to claim 3, wherein said magnetic bearing comprises a passive permanent magnetic bearing system.
20. A magnetic bearing according to claim 16, wherein said magnetic bearing comprises a passive permanent magnetic bearing system.
The invention relates to magnetic bearings, and more particularly, to magnetic bearings for the triaxial position stabilization of bodies.
Magnetic bearings on opposite ends of a movable bearing part, typically have fixed bearing parts. Between the fixed bearing parts, a magnetic flux is maintained penetrating the movable bearing part in one direction. For the production of retaining forces parallel to the magnetic flux direction, electric coils are installed on the fixed bearing parts, which are controlled by a sensor system which measures the position of the movable bearing part in a contact-less manner to generate an error signal which then is fed to a servomechanism feedback circuit which adjusts the position of the movable bearing part.
Magnetic bearings of this type are known, for example U.S. Pat. No. 3,860,300 and German Patent No. DT-PS 24 44 099. Such bearings are used particularly for the axial stabilization of rotors in magnetic bearings. Refer, for example. to Voss-Cohen, "UHV compatible chopper system" in J. Vac. Sci. Technol., 1980, Vol. 17, No. 1, page 303 ff., and Fremerey/Boden "Active permanent magnet suspensions for scientific instruments" in J. Phys. E.: Sci. Instrum., 1978, Vol. 11, page 106 ff. The advantage of these known permanent magnetic rotor bearings resides in the fact that, for purposes of operating a contact-less bearing manner on all sides of the rotor, they required only a stabilization in the direction of the rotor axis. This advantage, however, is attained only at the expense of the disadvantage, also known, that such bearings exhibit practically no damping in the radial directions. The problems which result when critical rotor speeds are passed through can be countered, to a limited extent, with an increased expenditure, by careful balancing of the rotor system, as described by Voss/Cohen in their above-referenced publication. It is also known that additional electronic or mechanical damping devices can be used, to reduce the disruptive effect of vibrations on the rotor bearing. See Fremerey "Spinning rotor vacuum gauges" in Vacuum, 1982, Vol. 32, No. 10/11, page 685 ff. All the above-cited patents and publications are incorporated herein by reference.
For the stabilization of magnetic bearings, eddy-current damping devices are also used. Thus, in U.S. Pat. No. 3,929,390, the attachment of fixed copper discs to the end surfaces of permanent magnets fastened to rotating parts therein is proposed, to stabilize a bearing system. Such a damping apparatus has a low degree of efficiency in relation to the amount of permanent magnetic material used, because at the free ends of the permanent magnets, the magnetic field produced by the permanent magnets diverges strongly, and thus the magnetic field components, required for the desired radial eddy-current damping, have only a small penetration into the copper discs in the axial direction.
Significantly higher efficiencies are achieved by the installation of fixed copper discs in the field between two permanent magnets connected in series behind one another (See Report ESA-CR (P)-696, MU/EX No. 47.055/75, page 12, which is incorporated herein by reference. In this apparatus, the magnetic fields run inside the copper essentially in the axial direction, so that there is an optimal utilization of the field for the eddy-current damping of radial rotor movements. The effort and expense involved, however, are considerable. A total of 6 annular permanent magnets are required, 2 of which must also exhibit the radial magnetization direction, which is difficult to achieve from a manufacturing point of view. Considerably simpler, in the design configuration of its magnetic circuit regarding the efficiency achieved, is the radial eddy-current damping of a magnet system suspended on threads, described by Fremerey in "High vacuum gas friction manometer" in J. Vac. Sci. Technol., 1972, Vol. 9, No. 1, pp 108 ff which is incorporated herein by reference. Here, a fixed copper disc is penetrated by a magnetic field running axially between the end surface of a permanent magnet and a flat iron disc. On this apparatus, however, the coupling of the eddy-current damping apparatus to the body supported in a contact-less manner is very difficult and expensive. For this purpose, electronic amplifiers with multi-element sensor coils and electromagnetic deflection coils are necessary which are disposed in two directions independent of one another.
The last two devices described above, in addition to the indicated expense and complexity, have the disadvantage that they can only be used for radial damping. Further, they do not represent magnetic bearings.
In Sabnis, Dendy and Schmitt, "A Magnetically Suspended Large Momentum Wheel," J. Spacecraft, July 1975, Vol. 12, No. 7, pp. 420 ff., which is incorporated herein by reference, a three-loop magnetic bearing is shown where bias flux is provided by a stationary ring magnet. This flux is lead by the structure of the bearing across four axial gaps. Passive radial stiffness is provided through the action (minimum reluctance) of opposed concentric rings at their air gaps, the total stiffness being proportional to the number of rings. Radial damping is provided at least in part by conducting material, such as copper wire, placed in the inter-ring grooves at the air gaps. This bearing requires a complex, intricate and heavy ferromagnetic structure attached to the bearing shaft which is expense to manufacture. As the bearing gaps are formed between iron pole pieces, the bearing structure suffers a considerable unbalance stiffness along the axial direction. Further, the efficiency of the damping is rather low because of the limited amount of conducting material which can be placed in the relatively small inter-ring grooves.
The eddy-current damping apparatus described above according to U.S. patent application Ser. No. 3,929,390 uses, for damping, the permanent magnets of the radial bearing, but for the reasons mentioned above it has only a low degree of efficiency. The required magnetic bearing's axial bearing is located elsewhere.
An object according to the invention is to create a magnetic bearing, of the simplest possible design, for the triaxial contact-less stabilization of the position of bodies with effective eddy-current damping, in which the flux of a single permanent magnetic circuit is used for the axial stabilization and simultaneously for the radial centering and damping.
The invention resides broadly in a magnetic bearing which has a movable part and means for supporting and maintaining said movable part in a bearing relationship with said means for supporting and maintaining, said magnetic bearing having an arrangement comprising: flux means for producing substantially constant, invariant flux, said flux means having means for attachment thereof to said movable means of said bearing; said flux means comprising at least two parts disposed along said movable means and being displaced one from the other; means, being electrically conductive and being non-ferromagnetic and non-magnetizable, for conducting currents generated therein by said flux of said flux means, said electrically conductive means comprising at least one rigid, substantially homogeneous, unitary element, only a sole element of said conductive means being disposed between any two of said at least two parts of said flux means, such that, a substantial portion of said flux of said flux means passes through at least a portion of said electrically conductive means; said electrically conductive means being disposed to be displaced from and in a non-contacting relationship with said movable means and said flux means; said electrically conductive means being disposed with respect to said movable means and said flux means, such as not to be movable with said movable means and said flux means; said flux means and said electrically conductive means being disposed so that said flux, produced by said flux means, forms a flux path, at least a portion of said flux path passing through and between said two of said at least two parts of said flux means, said portion of said flux path having substantially one substantially straight component disposed along solely one substantially single continuous direction and further having a substantially constant total flux along said portion of said flux path; and each element of said at least one element having a component being disposed perpendicular to said at least portion of said flux path passing through and between said at least two parts of said flux means.
Another aspect of the invention resides in a magnetic bearing of the type described above according to the invention having a movable bearing part which has at least two permanent magnetic regions in association therewith, which regions are separated from one another by a gap. The flux produced by and interlinking the two permanent magnetic regions extends through the gaps therebetween. The gap is preferably flat and extends in radial directions. The flux direction is preferably perpendicular to the radial directions. Projecting into the gap preferably in its radial directions is a plate of non-ferromagnetic and non-magnetizable material having a high electrical conductivity. The plate is fixed in place and does not come into contact with the movable bearing part.
A high magnetic flux with low stray flux fields is produced in the gap parallel to the axis of the rotating body of the permanent magnetic regions located abutting the gap.
The magnetic flux exiting through the pole surfaces penetrates the plate of non-magnetic material having high electrical conductivity located in the gap. Copper is preferably used as the plate material. If the movable bearing part is now moved parallel to the plate with its pole surfaces oriented parallel to the plate surface, then electrical voltages are induced in the plate with an orientation perpendicular to the direction of movement of the movable bearing part. The part of the plate which is inside the gap therefore becomes a voltage source, whereby the level of the induced voltage is proportional to the velocity of movement of the moving part of the bearing. The internal resistance of this voltage source is related to the cross-section and the thickness portion of the plate material penetrated by the permanent magnetic flux, and is also proportional to its electrical conductivity.
The damping of the movable bearing part is obtained as a result of the fact that the area, of the plate material of the electrical highly-conductive plate not penetrated by the magnetism, short-circuits the voltage source produced in the gap region, thus permitting a short-circuit current to flow. The loss energy thereby consumed is obtained from the movement energy of the moving bearing part. The plate thereby heats up, and the movement of the movable bearing part is damped.
To reudce the electrical resistance of the plate outside the area of the plate material penetrated by the magnetic flux, in another embodiment of the invention the plate material can be thicker outside the gap.
For bearing rotating bodies, a preferred embodiment of the magnetic bearing is described having the fixed bearing parts which are fastened to a hollow cylinder of material which has low reluctance and then is a good magnetic conductor. The hollow cylinder is used to carry the flux and also works as a magnetic shield for the magnetic bearing. The hollow cylinder shields the magnetic bearing on one hand against external interference fields, so that correct operation of the magnetic bearing is assured even in the vicinity of other electromagnetic equipment, for example, drive motors. Still further, the shielding also blocks magnetic interference from the magnet bearing itself upon neighboring equipment. In addition, the magnetic bearing with the hollow cylinder forms a quasi-closed unit, which is mechanically rugged and strong and also easy to handle.
The properties of the magnetic bearing can be applied to special advantage if the bearing is used for the stabilization of passive permanent magnet bearing systems. Such bearings, with rotationally-symmetric geometry exhibit in the direction of the bearing axis, properties resulting in a significant instability of forces. These unstable properties generate forces which push the supported rotating body to one side or the other out of its magnetic neutral position to the nearest axial mechanical stop. This instability is eliminated by the installation of the magnetic bearing arrangement described by the invention. The radially passive permanent magnetic bearing system can thus also be operated in the range of critical speeds, without the occurrence of interfering dynamic instabilities, for example, nutations. The farther the magnetic bearing is installed from the center of gravity of the rotating body, the better the damping action of the magnetic bearing, as far as rotational oscillations of the rotating shaft of the supported body around a quadrature axis are concerned. The magnetic bearing is preferably suited for the stabilization of bearing systems for flywheels. Moreover, a special advantage of its use as a suspension or support bearing for ultracentrifuges with a vertical axis of rotation and for turbomolecular pumps.
The invention is explained in greater detail below the means of embodiments, which are schematically illustrated in the drawing.
FIG. 1 shows a magnetic bearing for rotating bodies.
FIG. 2 shows a bearing system with a passive permanent magnetic radial bearing, which is stabilized by a magnetic bearing according to FIG. 1.
FIG. 3 shows a block diagram of a bridge circuit configuration for use with the magnetic bearings of FIGS. 1 and 2.
FIG. 1 shows a rotationally-symmetric magnetic bearing. The magnetic bearing serves as a suspension or support bearing for a shaft 1 of a body rotating around a vertical axis 2. The magnetic bearing exhibits fixed bearing parts 3a, 3b, which are components of a hollow cylinder 4 manufactured of a material which has a low reluctivity which is a good magnetic conductor, preferably iron. The fixed bearing parts 3a, 3b comprise a rotationally symmetrical stator. The ring shaped fixed bearing parts 3a, 3b are connected by the hollow cylinder 4. The rings are located in the embodiment at both ends of the hollow cylinder 4. Between the annular fixed bearing parts 3a, 3b and the hollow cylinder 4, there are electric coils 5a, 5b for the control of the magnetic bearing, whose current throughout is controlled by a sensor system 6 and an electronic regulator 7. The electrical connection lines are shown in the drawing in dotted lines. The sensor system 6 senses the position of the shaft 1 of the rotating body. A shaft part 1' penetrates the hollow cylinder 4 axially. On the shaft part 1' there is a movable bearing part 8, which rotates with the shaft 1 and thus forms the movable bearing part of the magnetic bearing. The movable bearing part 8 is located between the fixed bearing parts 3a, 3b whereby the opposite sides 8', 8" of the movable bearing part 8 are closely juxtaposed with the fixed bearing parts 3a, 3b forming a small gap 11A. Between the movable and fixed bearing parts, the magnetic flux runs parallel to the axis 2. The magnetic flux which toroidally surrounds the axis 2 is represented in FIG. 1 by a solid line penetrating the bearing parts shown in section.
The movable bearing part 8 exhibits two permanent magnetic regions 9a, 9b which are located at an axial distance from one another, and between which there is a gap 11 oriented perpendicular to the magnetic flux produced with the flux direction 10, which separates the permanent magnetic regions 9a, 9b from one another. An annular plate 12 projects into the gap 11, which is fixed in place and, in the embodiment, is fastened to the hollow cylinder 4. The plate 12 projects far enough into the gap 11 so that it is exposed to the magnetic field. The plate 12 comprises a non-magnetizable, non-ferromagnetic material of high electrical conductivity, preferably copper.
For the configuration of the permanent magnetic regions 9a, 9b, a rare earth cobalt alloy is preferably used as the permanent magnetic material on their pole surfaces 13a, 13b at the gap 11. This highly coercive material is magnetized parallel to the axis 2 and arranged so that the regions 9a, 9b are permanent magnets connected in series in a magnetically aiding relationship one behind the other to reinforce the action of their magnetic fields.
Together with the fixed bearing parts 3a, 3b which have opposite magnetic polarization, the result is thus a permanent magnetic flux in a specified direction through the low reluctance, magnetically high-conducting hollow cylinder 4. In FIG. 1, the flux direction 10 resulting in the embodiment is indicated by arrows. The fixed bearing part 3a thus represents a magnetic north pole, and the fixed bearing part 3b a magnetic south pole.
The magnetic fields produced by current flow and the annular electric coils 5a, 5b when there is a current flow in the coils, produce an axial force which, depending on the current direction in the coils, acts in one or the other direction axially on the movable bearing part 8 and thus on the shaft 1. The sensor system 6 produces electrical signals, which are proportional to the deviations of the shaft 1 from its specified axial position. The signals from the sensor system 6 are amplified by the electronic regulator 7 and determine the current direction and current magnitude in the coils 5a, 5b. The axial force thereby produced by means of the coils on the movable bearing part 8 counteracts the axial deviation of the shaft 1 from the specified position as measured by the sensor system 6. When the specified position is reached, no more current flows.
Between the pole surfaces 13, 13b of the permanent magnetic regions 9a, 9b, a large magnetic flux is produced. The magnetic flux, exiting through the pole surfaces 13a, 13b, penetrates in the flux direction 10 the plate 12 projecting into the gap 11, so that when there are radial movements of the shaft 1, a voltage is induced in the plate 12. The region of the plate 12 in the gap 11 therefore represents a voltage source, whereby the level of voltage induced is proportional to the radial movement velocity of the movable bearing part 8.
The portion of the plate 12 projecting out of the gap 11 is not affected by the magnetic flux. In this area, free of magnetic fields, no electrical voltage is induced. The voltage source produced within the gap 11 in the region of the plate 12 is short-circuited by this outer region of the plate 12. The energy loss dissipated in the short circuit is produced by the short-circuit current which flows due to the movement of the rotating body and thereby damps the latter, whereupon the plate 12 heats up. To create the least possible electrical resistance in the outside region of the plate 12 in the area free of a magnetic field, the plate 12 exhibits, in its area outside the gap 11, a thickening of the material 14, which is configured in the embodiment as annular collars extending above and below the plate 12, which are symmetrically disposed about the plane of the gap 11 and which thickening is wider than the gap 11. As a result of this thickening of the material 14, high short-circuit currents can flow in the plate 12, which in comparison to unthickened plates lead to significantly greater damping capacity at the same level of induced voltage.
The movable bearing part 8 can also have several permanent magnetic regions located at some distance from one another, with a plate projecting into each of the gaps being formed between the magnetic regions. The gaps alway run perpendicular to the magnetic flux, and are therefore arranged behind one another in the direction of axis 2 and parallel to one another. Such a configuration of the magnetic bearing increases the damping capacity.
In the embodiment, the permanent magnetic regions 9a, 9b of the movable bearing part 8 from annular permanent magnets, whereby a very high weight-specific magnetic moment is achieved for the movable bearing part 8. The weight load of the body rotating with the shaft 1 or of the rotor system is therefore light. The rotor system comprises a rotationally symmetrical rotor system. The arrangement, of the annular permanent magnets in the series connection, leads to an optimal efficiency for the coils 5a, 5b which correct the axial deviations of the shaft 1. The magnetic moment of the high-coercivity permanent magnetic material is such that it is not adversely affected by the magnetic fields of the coils 5a, 5b or by a magnetic field penetrating from outside into the bearing element. At the same time, the low magnetic conductivity, which characterizes the highly-coercive magnetic materials, guarantees in the direction of axis 2 of the rotating body a relatively low magnetic background instability of the movable bearing part 8 in the axial direction with respect to the fixed bearing parts 3a, 3b.
The hollow cylinder 4, made of a material which is a good magnetic conductor, forms a magnetic shield for the bearing element, which offers protection against external magnetic interference fields. In addition, the cylinder 4 also eliminates magnetic interference effects on neighboring equipment in the vicinity of the magnetic bearing as a result of the strong magnetic fields produced by the magnetic bearing itself.
A special application of the magnetic bearing according to FIG. 1 is illustrated in FIG. 2. FIG. 2 shows a passive, permanent magnetic bearing system for a flywheel 15 with two passive, permanent magnetic radial bearings 16a, 16b which include, in a manner well known to the product, permanent magnets 17a, 17b with a radially repelling action as shown by the configuration of radial bearing 16a, or an axially attracting action as shown by the configuration of radial bearing 16b. In the embodiment, the permanent magnets 17a are fixed in position, and the permanent magnets 17b form movable bearing parts with the shaft 18 and the flywheel 15 as the rotor system. Such a magnetic bearing, when the rotor system is in its neutral position, exhibits a significant axial force instability, which pushes the rotor system out of the neutral position to one side or the other, for example, when the movable permanent magnets 17b in the axial direction of the shaft 18 assume a symmetrical position in relation to the fixed permanent magnets 17a. This instability is eliminated by a magnetic bearing 19, which is of the design illustrated in FIG. 1. The magnetic bearing 19 is controlled by a position sensor system 20 with amplifier 21 in the same manner as the magnetic bearing illustrated in FIG. 1. With the magnetic bearing 19, the rotor system with shaft 18 and flywheel 15 can now also be operated in the range of critical speeds, without dynamic instabilities such as nutations which occur and cause disturbances. The farther the magnetic bearing element 19 is installed from the center of gravity of the rotor system, the better the damping action of the magnetic bearing, as far as rotational oscillations of the shaft 18 around a quadrature axis are concerned. Of course, several magnetic bearings 19 can be used to increase the damping action.
The magnetic bearing described by the invention is therefore characterized by the following features:
The magnetic bearing contains a single, toroidally-closed permanent magnet circuit. The flux is shown in FIG. 1 by the solid lines with arrows indicating the direction 10 of the flux.
The axial contactless stabilization of the movable bearing part 8 between the fixed bearing parts 3a, 3b is achieved by means of coils 5a, 5b which are fed by the sensor system 6 and electronic regulator 7 with currents in opposite directions of rotation, as described in DE-PS No. 2 444 099, which is incorporated herein by reference. The direction and magnitude of these currents are determined by the output signal of the sensor system, which measures the axial position of the shaft 1 and therefore the position of the movable bearing part 8 in a contactless manner. The regulator 7 produces currents which are converted by means of the coils 5a, 5b in connection with the permanent magnetic regions 9a, 9b into retaining forces which act parallel to the flux direction 10, as soon as the movable bearing part 8 is moved from that axial position in which the output current of the regulator disappears. The regulator simultaneously produces damping forces, which independent of the current axial position, counteract all axial movements, especially axial oscillations of the movable bearing part 8.
The radial centering of the movable bearing part 8 in relation to the fixed bearing parts 3a, 3b is produced by a juxtaposition of pole surfaces 13a, 13b with the same shape as the permanent magnetic regions 9a, 9b and of magnetizable annular fixed bearing parts 3a, 3b which preferably comprise iron.
The radial damping is finally effected by the action of the plate 12 made of non-magnetizable and non-ferromagnetic material with high electrical conductivity, preferably copper, installed in a fixed manner between the permanent magnetic regions 9a, 9b of the movable bearing part 8. When there are radial movements of the bearing part 8, electrical voltages are induced in the areas of the plate 12 penetrated by the magnetic flux.
The magnetic bearing described by the invention therefore provides contact-free retaining, centering and damping forces in three axial directions independent of one another (one axial, two radial). It comprises, in the preferred embodiment, of two iron rings which form the fixed bearing parts 3a, 3b, of two annular permanent magnetic regions 9a, 9b for the movable bearing part 8, and of two electric coils 5a, 5b and an annular plate 12 of copper. All parts can be manufactured in a simple manner and can be installed easily.
In FIG. 3 there is shown a well-known bridge circuit arrangement 30 for establishing a signal corresponding to the relative separation and/or movement between the shaft 1 and the sensor 6 (as shown in FIG. 1) or 20 (as shown in FIG. 2) as determined by changes in the capacitance of the sensor 6 or 20 which functions as a variable capacitor as the distance between the shaft 1 and the sensor 6 or 20 varies.
The sensor 6 (as shown in FIG. 1) or 20 (as shown in FIG. 2) in conjunction with an impedance element 32, preferably a capacitor, forms one-half of the bridge circuit 30. The capacitance magnitude of the capacitance sensor 6 or 20 changes in a relationship to the separation between the sensor 6 or 20 and the shaft 2. The magnitude of the impedance element 32 is selected in accordance with a desired separation therebetween. Adjustment of the impedance element 32 changes the desired position of the shaft 1. Two other impedance elements 33 and 34 form the other half of the bridge circuit 30. A signal source 35, which is preferably alternating current, is connected across the bridge circuit 30. The operation of such a bridge circuit 30 is well known in the electrical prior art. The output signal from the bridge circuit 30 is supplied to an amplifier 37 which outputs a signal in accordance with the separation and movement of the sensor 6 or 20 in reflection to the shaft 1, which output signal is fed back through connecting circuitry to the coils 5a, 5b in an appropriate manner, as indicated by the dotted lines in FIGS. 1 and 2, to correct excursions of the shaft 1 from its desired position.
The bridge circuit 30 through the amplifier 37 provides the signal to the connecting circuitry including a phase sensitive detector 39 which senses the movement of the shaft 1 relative to the sensor 6 or 20. The envelope detector 40 senses the magnitude of its input signal to provide an output signal in accordance with the distance of movement of shaft 1. A phase switch 42 provides an output signal in accordance with the magnitude and the direction of movement of the sensor 6 or 20. The signals from the envelope detector 40 and the phase switch 42 may be combined and/or thresholded and/or compared with reference signals in the referencing and thresholding circuitry 43, which circuitry when connected through to a power amplifier 44 generates output signals for connection to the electrical connections of the coils 5a, 5b. The power amplifier 44 preferably also includes an integrating circuit so that the error in the distance between the shaft 1 and the sensor 6 or 20 can be reduced to substantially zero.
The above circuit as shown in FIG. 3 is just one of many circuits which could be used for the control and regulation of the position of the shaft 1 in a magnetic bearing. Other circuits well known in the prior art could be substituted for this shown circuit.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3698775 *Apr 1, 1970Oct 17, 1972Technical Management ServicesMagnetic support and motor structureUS3860300 *Dec 20, 1972Jan 14, 1975Cambridge Thermionic CorpVirtually zero powered magnetic suspensionUS3877761 *Mar 16, 1973Apr 15, 1975Padana AgElectromagnetic bearing meansUS3890019 *Mar 19, 1973Jun 17, 1975Padana AgMagnetic bearingsUS3929390 *Dec 22, 1971Dec 30, 1975Cambridge Thermionic CorpDamper system for suspension systemsUS3976339 *Jan 14, 1974Aug 24, 1976Sperry Rand CorporationMagnetic suspension apparatusUS4077678 *Jul 30, 1976Mar 7, 1978The United States Of America As Represented By The Administrator Of The National Aeronautics And Space AdministrationEnergy storage apparatusUS4211452 *Mar 14, 1978Jul 8, 1980Societe Nationale Industrielle AerospatialeInertia wheelUS4268095 *Dec 1, 1978May 19, 1981Massachusetts Institute Of TechnologyMagnetic bearingUS4444444 *Oct 19, 1981Apr 24, 1984Societe Nationale Industrielle AerospatialeEquipment for storage of energy under kinetic form and recovery thereof in electric form and method of using such equipmentDE2444099A1 *Sep 14, 1974Apr 1, 1976Kernforschungsanlage JuelichBeruehrungsloses lagerelement fuer mindestens teilweise magnetisierbare koerper* Cited by examinerNon-Patent CitationsReference1"Satellite Flywheels with Magnetic Bearings and Passive Radial Centering," P. C. Poubeau, J. Spacecraft, 1980, vol. 17, No. 2, pp. 93-97.2 *A Magnetically Suspended Large Momentum Wheel, Sabnis, Dendy, and Schmitt J. Spacecraft, Jul. 1975, col. 12, No. 7, pp. 420 ff.3 *Active Permanent Magnet Suspensions for Scientific Instruments, Johan Fremerey & Karl Boden, J. Phys. E: Sci. Instrum., 1978, vol. 11, p. 106 ff.4 *Design and Development of a Momentum Wheel with a Mainly Passive Magnetic Bearing, Report ESA CR (P) 696, MU EX No. 47.055/75, p. 12.5Design and Development of a Momentum Wheel with a Mainly Passive Magnetic Bearing, Report ESA-CR (P)-696, MU-EX No. 47.055/75, p. 12.6 *High Vacuum Gas Friction Manometer, Johan K. Fremerey, J. Vac. Sci. Technol., 1972, vol. 9, No. 1, pp. 108 ff.7 *Spinning Rotor Vacuum Gauges, Johan K. Fremerey, Vacuum, 1982, vol. 32, No 10/11, p. 685 ff.8UHV Compatible Chopper System, Donald E. Voss & Samuel A. Cohen, J. Vac. . Technol., 1980, vol. 17, No. 1, p. 303 ff.9 *UHV Compatible Chopper System, Donald E. Voss & Samuel A. Cohen, J. Vac. Sci. Technol., 1980, vol. 17, No. 1, p. 303 ff.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS4948348 *May 4, 1988Aug 14, 1990Robert DollImmersion pump, especially for low-boiling fluidsUS5053662 *Apr 18, 1990Oct 1, 1991General Electric CompanyElectromagnetic damping of a shaftUS5126610 *Oct 25, 1990Jun 30, 1992Kernforschungsanlage Julich Gesellschaft Mit Beschrankter HaftungAxially stabilized magnetic bearing having a permanently magnetized radial bearingUS5204568 *Sep 23, 1991Apr 20, 1993Gwr InstrumentsSuperconducting bearing for borehole and survey gravimetersUS5270601 *Oct 17, 1991Dec 14, 1993Allied-Signal, Inc.Superconducting composite magnetic bearingsUS5355042 *Nov 13, 1990Oct 11, 1994University Of Virginia Patent FoundationMagnetic bearings for pumps, compressors and other rotating machineryUS5396136 *Oct 28, 1992Mar 7, 1995Sri InternationalMagnetic field levitationUS5514924 *Oct 14, 1993May 7, 1996AVCON--Advanced Control Technology, Inc.Magnetic bearing providing radial and axial load support for a shaftUS5543673 *Jul 27, 1993Aug 6, 1996Sundstrand CorporationHigh performance magnetic bearingUS5686772 *Jan 18, 1995Nov 11, 1997Alcatel CitMagnetic bearing and an assembly comprising a stator portion and a rotor portion suspended via such a bearingUS5708312 *Nov 19, 1996Jan 13, 1998Rosen Motors, L.P.Magnetic bearing system including a control system for a flywheel and method for operating sameUS5729065 *Dec 15, 1993Mar 17, 1998Leybold AktiengesellschaftMagnetic bearing cell with rotor and statorUS5731645 *Feb 5, 1996Mar 24, 1998Magnetic Bearing Technologies, Inc.Integrated motor/generator/flywheel utilizing a solid steel rotorUS5736798 *Jul 22, 1996Apr 7, 1998Eastman Kodak CompanyPassive magnetic damperUS5783885 *Aug 7, 1995Jul 21, 1998The Regents Of The University Of CaliforniaSelf-adjusting magnetic bearing systemsUS5820079 *Apr 24, 1997Oct 13, 1998Hughes ElectronicsMechanism for mounting and actuating a momentum wheel with high vibration isolationUS5905321 *Feb 17, 1998May 18, 1999Active Power, Inc.Energy storage flywheel apparatus and methodsUS5920138 *Feb 17, 1998Jul 6, 1999Active Power, Inc.Motor/generator and axial magnetic bearing utilizing common magnetic circuitUS5932935 *Apr 11, 1997Aug 3, 1999Active Power, Inc.Energy storage flywheel emergency power source and methodsUS5955816 *Feb 17, 1998Sep 21, 1999Active Power, Inc.Energy storage flywheel apparatus and methodsUS5969457 *Feb 17, 1998Oct 19, 1999Active Power, Inc.Energy storage flywheel apparatus and methodsUS6166472 *Feb 17, 1998Dec 26, 2000Active Power, Inc.Airgap armature coils and electric machines using sameUS6213737Apr 16, 1998Apr 10, 2001Ebara CorporationDamper device and turbomolecular pump with damper deviceUS6628021 *Dec 15, 2000Sep 30, 2003Aisin Aw Co., Ltd.Hybrid vehicle driving apparatus electrical motor having magnetic flux leakage shielded position sensorUS7301252 *Jul 11, 2001Nov 27, 2007Rolls-Royce PlcMagnetic bearingsUS7307365Mar 28, 2003Dec 11, 2007Forschungszentrum Julich GmbhMagnetic guiding deviceUS7485994Oct 22, 2007Feb 3, 2009Rolls-Royce PlcMagnetic bearingsUS7800275May 9, 2008Sep 21, 2010Motor Excellence, LlcElectrical devices using electronmagnetic rotorsUS7851965Nov 3, 2009Dec 14, 2010Motor Excellence, LlcTransverse and/or commutated flux system stator conceptsUS7863797Jul 30, 2010Jan 4, 2011Motor Excellence, LlcElectrical devices using electromagnetic rotorsUS7868508Nov 3, 2009Jan 11, 2011Motor Excellence, LlcPolyphase transverse and/or commutated flux systemsUS7868511May 9, 2008Jan 11, 2011Motor Excellence, LlcElectrical devices using disk and non-disk shaped rotorsUS7876019May 9, 2008Jan 25, 2011Motor Excellence, LlcElectrical devices with reduced flux leakage using permanent magnet componentsUS7923886Nov 3, 2009Apr 12, 2011Motor Excellence, LlcTransverse and/or commutated flux system rotor conceptsUS7973446May 9, 2008Jul 5, 2011Motor Excellence, LlcElectrical devices having tape wound core laminate rotor or stator elementsUS7989084May 9, 2008Aug 2, 2011Motor Excellence, LlcPowdered metal manufacturing method and devicesUS7994678Nov 18, 2010Aug 9, 2011Motor Excellence, LlcPolyphase transverse and/or commutated flux systemsUS8008821Nov 9, 2010Aug 30, 2011Motor Excellence, LlcTransverse and/or commutated flux system stator conceptsUS8030819Mar 3, 2011Oct 4, 2011Motor Excellence, LlcTransverse and/or commutated flux system rotor conceptsUS8033442Nov 28, 2007Oct 11, 2011Tyco Heathcare Group LpTool assembly for a surgical stapling deviceUS8053944May 3, 2010Nov 8, 2011Motor Excellence, LlcTransverse and/or commutated flux systems configured to provide reduced flux leakage, hysteresis loss reduction, and phase matchingUS8058758Jun 22, 2006Nov 15, 2011Siemens AktiengesellschaftApparatus for magnetic bearing of rotor shaft with radial guidance and axial controlUS8061577Oct 8, 2010Nov 22, 2011Tyco Healthcare Group LpTool assembly for a surgical stapling deviceUS8110955Jun 12, 2006Feb 7, 2012Siemens AktiengesellschaftMagnetic bearing device of a rotor shaft against a stator with rotor disc elements, which engage inside one another, and stator disc elementsUS8193679Jun 30, 2011Jun 5, 2012Motor Excellence LlcPolyphase transverse and/or commutated flux systemsUS8222786May 3, 2010Jul 17, 2012Motor Excellence LlcTransverse and/or commutated flux systems having phase offsetUS8242658Sep 12, 2011Aug 14, 2012Electric Torque Machines Inc.Transverse and/or commutated flux system rotor conceptsUS8395291May 3, 2010Mar 12, 2013Electric Torque Machines, Inc.Transverse and/or commutated flux systems for electric bicyclesUS8405275Nov 8, 2011Mar 26, 2013Electric Torque Machines, Inc.Transverse and/or commutated flux systems having segmented stator laminationsUS8408442Sep 26, 2011Apr 2, 2013Covidien LpTool assembly for a surgical stapling deviceUS8415848Oct 12, 2011Apr 9, 2013Electric Torque Machines, Inc.Transverse and/or commutated flux systems configured to provide reduced flux leakage, hysteresis loss reduction, and phase matchingUS8760023 *Jul 17, 2012Jun 24, 2014Electric Torque Machines, Inc.Transverse and/or commutated flux systems having phase offsetUS8836196Mar 12, 2013Sep 16, 2014Electric Torque Machines, Inc.Transverse and/or commutated flux systems having segmented stator laminationsUS8854171Nov 8, 2011Oct 7, 2014Electric Torque Machines Inc.Transverse and/or commutated flux system coil conceptsUS8952590Nov 8, 2011Feb 10, 2015Electric Torque Machines IncTransverse and/or commutated flux systems having laminated and powdered metal portionsUS9138226Sep 26, 2011Sep 22, 2015Covidien LpCartridge assembly for a surgical stapling deviceUS9175742 *May 17, 2010Nov 3, 2015Rolls Royce PlcElectromagnetic damper for rotating machinesUS9433411Mar 7, 2013Sep 6, 2016Covidien LpTool assembly for a surgical stapling deviceUS20040021381 *Jul 11, 2001Feb 5, 2004Garvey Seamus DominicMagnetic bearingsUS20050200218 *Mar 28, 2003Sep 15, 2005Fremerey Johan K.Magnetic guiding deviceUS20080100162 *Oct 22, 2007May 1, 2008Rolls-Royce PlcMagnetic BearingsUS20080309188 *May 9, 2008Dec 18, 2008David Gregory CalleyElectrical output generating devices and driven electrical devices with reduced flux leakage using permanent magnet components, and methods of making and using the sameUS20090160288 *May 9, 2008Jun 25, 2009David Gregory CalleyElectrical output generating devices and driven electrical devices using electromagnetic rotors, and methods of making and using the sameUS20090206696 *May 9, 2008Aug 20, 2009David Gregory CalleyElectrical output generating and driven devices using disk and non-disk shaped rotors, and methods of making and using the sameUS20090208771 *May 9, 2008Aug 20, 2009Thomas JanecekPowdered metal manufacturing method and devicesUS20100109452 *Nov 3, 2009May 6, 2010Motor Excellence LlcTransverse and/or commutated flux system rotor conceptsUS20100109453 *Nov 3, 2009May 6, 2010Motor Excellence LlcPolyphase transverse and/or commutated flux systemsUS20100109462 *Nov 3, 2009May 6, 2010Motor Excellence LlcTransverse and/or commutated flux system stator conceptsUS20100295410 *Jul 30, 2010Nov 25, 2010Motor Excellence Llc.Electrical devices using electromagnetic rotorsUS20110050010 *Nov 9, 2010Mar 3, 2011Motor Excellence LlcTransverse and/or commutated flux system stator conceptsUS20110062723 *Nov 18, 2010Mar 17, 2011Motor Excellence, LlcPolyphase transverse and/or commutated flux systemsUS20110140559 *Jun 12, 2006Jun 16, 2011Ries GuenterMagnetic Bearing Device of a Rotor Shaft Against a Stator With Rotor Disc Elements, Which Engage Inside One Another, and Stator Disc ElementsUS20110148225 *Mar 3, 2011Jun 23, 2011Motor Excellence LlcTransverse and/or commutated flux system rotor conceptsUS20110169365 *May 3, 2010Jul 14, 2011Motor Excellence LlcTransverse and/or commutated flux systems configured to provide reduced flux leakage, hysteresis loss reduction, and phase matchingUS20110169366 *May 3, 2010Jul 14, 2011Motor Excellence LlcTransverse and/or commutated systems having phase offsetUS20110169381 *May 3, 2010Jul 14, 2011Motor Excellence LlcTransverse and/or commutated flux systems for electric bicyclesUS20110221298 *May 20, 2011Sep 15, 2011Motor Excellence, LlcElectrical devices having tape wound core laminate rotor or stator elementsUS20120212111 *May 17, 2010Aug 23, 2012Rolls-Royce PlcElectromagnetic damper for rotating machinesCN103591139A *Nov 22, 2013Feb 19, 2014江苏理工学院Passive radial permanent magnetic bearing for high-speed rotorCN103591139B *Nov 22, 2013Aug 12, 2015江苏理工学院用于高速转子的被动径向永磁轴承DE3715216A1 *May 7, 1987Nov 17, 1988Doll RobertTauchpumpe, insbesondere fuer tiefsiedende fluessigkeitenWO2003087581A1 *Mar 8, 2003Oct 23, 2003Forschungszentrum Jülich GmbHExhaust gas turbochargerWO2017036799A1 *Aug 17, 2016Mar 9, 2017Robert Bosch GmbhApparatus for storing energy as rotational energy, system and method for providing electrical energy* Cited by examinerClassifications U.S. Classification310/90.5International ClassificationF16C32/04, F16C39/06Cooperative ClassificationF16C32/0436, F16C2361/55, F16C32/0461, F16C32/0444, F16C32/0476, F16C32/0468European ClassificationF16C32/04M4R1, F16C32/04M2S, F16C32/04M4D4, F16C32/04M4D2, F16C32/04M4CLegal EventsDateCodeEventDescriptionMay 28, 1985ASAssignmentOwner name: KERNFORSCHUNGSANLAGE JULICH GESELLSCHAFT MIT BESCHFree format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:FREMEREY, JOHAN K.;WELLER, ALBRECHT;REEL/FRAME:004405/0520;SIGNING DATES FROM 19850305 TO 19850307Apr 26, 1990FPAYFee paymentYear of fee payment: 4Jul 26, 1990ASAssignmentOwner name: FORSCHUNGSZENTRUM JULICH GMBHFree format text: CHANGE OF NAME;ASSIGNOR:KERNFORSCHUNGSANLAGE JULICH GMBH;REEL/FRAME:005388/0082Effective date: 19900419May 17, 1994SULPSurcharge for late paymentMay 17, 1994FPAYFee paymentYear of fee payment: 8Apr 23, 1998FPAYFee paymentYear of fee payment: 12RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services