MAGNETIC COUPLING

Abstract

A magnetic coupling includes an inner rotor (11) and an outer rotor (9) which at least partly surrounds the inner rotor (11). These rotors (11, 9) each are formed of magnetic material (18) and are coupled to one another by way of magnetic forces. The inner rotor (11) and/or the outer rotor (9) contain powdery, magnetizable material (18). The powdery, magnetizable material (18) is magnetized at a side lying opposite the other rotor at several locations distributed over the periphery.

Claims

1. A magnetic coupling comprising: an inner rotor; and an outer rotor which at least partly surrounds the inner rotor, said rotors each comprising magnetic material and being coupled to one another by way of magnetic forces, wherein the inner rotor or the outer rotor or both the inner rotor and the outer rotor contain powdery magnetizable material which from a side lying opposite the other rotor, is magnetized at several locations distributed over a periphery thereof.

2. A magnetic coupling according to claim 1, wherein the magnetization at several locations is such that in the coupled condition, a wavy-line distribution of the magnetic flux density exists between the rotors in planes transverse to the longitudinal middle axis and rotation axis of the coupling.

3. A magnetic coupling according to claim 1, wherein the magnetization at several locations is distributed over the periphery of the rotor at a same angular distance with respect to a common longitudinal middle axis and rotation axis of the coupling.

4. A magnetic coupling according to claim 1, wherein at least one of the rotors comprises a hermetically closed receptacle, in which the magnetic material is arranged in a compacted form.

5. A magnetic coupling according to claim 1, wherein at least one of the rotors comprises an annular space which is open at least at one side and in which the magnetic material is arranged, in compacted form, wherein the powdery, magnetic material comprises a protective coating and an adhesive.

6. A magnetic coupling according to claim 4, wherein at least the receptacle of the outer rotor has a hollow-cylindrical shape and a ratio of a distance of adjacent magnetic poles along an inner peripheral surface of the outer rotor to a thickness of the magnetic material in the outer rotor is between 2 and 3.

7. A magnetic coupling according to claim 4, wherein at least the receptacle of the inner rotor has a hollow-cylindrical shape and a ratio of a distance of adjacent magnetic poles along an outer peripheral surface of the inner rotor to a thickness of the magnetic material in the inner rotor is between 2 and 3.

8. A magnetic coupling according to claim 6, wherein the ratio of the distance to the thickness is 2.2 to 2.8.

9. A magnetic coupling according to claim 1, wherein a permeability of the an outer wall of the outer rotor, which surrounds the magnetic material, is between 1 and 2.

10. A magnetic coupling according to claim 1, wherein magnetic poles in the inner and in the outer rotor run obliquely seen in a longitudinal direction at an angle of between 10 and 60.

11. A magnetic coupling according to claim 1, wherein magnetic poles in the inner and in the outer rotor run in a curvilinear manner seen in a longitudinal direction.

12. A magnetic coupling according to claim 1, wherein the powdery, magnetizable material consists of 0 to 50% by volume of soft-magnetic materials and of 50 to 100% by volume of hard-magnetic materials.

13. A magnetic coupling according to claim 1, wherein one of the rotors comprises permanent magnets which are arranged in a Halbach-array configuration.

14. A magnetic coupling according to claim 1, wherein the magnetic material in the rotor is formed by one or more fully or partially annular shaped bodies which are pre-shaped from powdery material.

15. A method for manufacturing a rotor for a magnetic coupling comprising an inner rotor and an outer rotor which at least partly surrounds the inner rotor, said rotors each comprising magnetic material and being coupled to one another by way of magnetic forces, wherein the inner rotor or the outer rotor or both the inner rotor and the outer rotor contain powdery magnetizable material which from a side lying opposite the other rotor, is magnetized at several locations distributed over a periphery thereof, the method comprising th steps of: arranging the powdery, material in or on the rotor, whereupon a magnitization is effected from the coupling-active side of the rotor, and according to a desired pole number, at the several locations distributed over a periphery thereof.

16. A method according to claim 15, wherein the magnetizable material is brought into the rotor and is compacted there, whereupon the rotor space is closed by way of welding and/or forming a rotor wall.

17. A method according to claim 16, wherein the magnetizable material is connected into an annular shaped body which is then arranged in a space within the rotor and which is subsequently hermetically closed.

18. A method according to claim 16, wherein the magnetizable material for a rotor is brought into two or more annular shaped bodies which are subsequently arranged in an annular space of the rotor in a manner lying over one another and filling this space, and compacted, whereupon the annular space is hermetically closed.

19. A method according to claim 15, wherein the magnetization of poles of the rotor is effected simultaneously.

20. A magnetic coupling according to claim 5, wherein: the annular space of the outer rotor has a hollow-cylindrical shape and a ratio of a distance of adjacent magnetic poles along an inner peripheral surface of the outer rotor to a thickness of the magnetic material in the outer rotor is between 2 and 3; and the annular space of the inner rotor has a hollow-cylindrical shape and a ratio of the a distance of adjacent magnetic poles along an outer peripheral surface of the inner rotor to a thickness of the magnetic material in the inner rotor is between 2 and 3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the drawings:

[0032] FIG. 1 is a greatly simplified longitudinal section representation showing a multi-stage centrifugal pump with a motor stool and a magnetic coupling located therein;

[0033] FIG. 2 is an enlarged representation showing the detail B from FIG. 1;

[0034] FIG. 3 is a greatly simplified enlarged and perspective longitudinal sectional representation showing an inner and an outer rotor;

[0035] FIG. 4 is a schematic representation of the outer rotor on magnetization;

[0036] FIG. 5 is a diagram showing the magnetization in the inner and the outer rotor as well as the flux density distribution in the gap between the rotors, in a plane transverse to the longitudinal axis;

[0037] FIG. 6 is a diagram showing the magnetic alignment in the outer rotor in a plane transverse to the longitudinal axis;

[0038] FIG. 7 is a diagram showing the magnetic alignment in the inner rotor in a plane transverse to the longitudinal axis;

[0039] FIG. 8 is a diagram showing the magnetic alignment and the magnetic flux in a magnetic coupling with parallelepiped permanent magnets according to the state of the art; and

[0040] FIG. 9 is a diagram showing the magnetic alignment and the magnetic flux in a coupling according to the invention, in a plane transverse to the longitudinal axis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Referring to the drawings, the centrifugal pump represented in FIG. 1 is a multistage centrifugal pump 1 which in some features of the construction corresponds to known centrifugal pumps of the type Grundfos CR. Hereby, it is the case of a pump which is operated with a vertical shaft 2, and is with a foot 3 which stands on the floor and onto which a middle section closed off to the outside by a jacket 4 connects, in which section impellers 5 are seated on the shaft 2. The jacket 4 which on the one hand is received in the foot 3, on the other hand is received in a head part 6, from which the upper end of the shaft 2 is led out. A so-called motor stool 7 is arranged above the head part 6 and is provided for receiving an electric motor for the drive of the pump 1, wherein this electric motor is not represented in FIG. 1.

[0042] A magnetic coupling 8 which comprises an outer rotor 9 which is connected to the motor shaft via a receiver 10, as well as an inner rotor 11 which is connected to the upper end of the shaft 2 in a rotational fixed manner, is provided in the region of the motor stool 7. A can pot 12 which hermetically closes the pump 1 in the region of the head part 6 is arranged between the outer rotor 9 and the inner rotor 11.

[0043] With regard to the represented centrifugal pump 1, it is the case of an inline pump. The fluid which reaches into a suction chamber 13 in the foot 3 via a suction connection is delivered via the pump stages lying over one another, from the impeller to the diffuser and from there to the next stage, and via an annular channel formed within the jacket 4 is led back into the foot 3 and there is led to a pressure connection, as is counted as belonging to the state of the art, to which one refers inasmuch as this is concerned. The drive connection to the motor is effected via the magnetic coupling 8, wherein the outer rotor 9 is connected in a rotationally fixed manner to the motor shaft, and the inner rotor 11 in a rotationally fixed manner to the shaft 2 of the centrifugal pump 1. The moment transmission is effected exclusively magnetically through the can pot 12.

[0044] The outer rotor 9 has an essentially hollow-cylindrical annular shape with a reinforced, supporting outer wall 14 which radially outwardly delimits an annular space 15 open to the top. To the bottom, this annular space 15 is delimited by a wall 16 which forms the base of the annular space 15 and which connects to the outer wall 14 in an aligned or flush manner. An inner wall 17 on the inner side of the wall 16 extends parallel to the outer wall 14 upwards as far as the reinforced part of the outer wall 14 which is clearly visible in FIGS. 2 and 3 reaches. This annular space 15 which is open to the top is filled with magnetizable, powder-like (powdery) material 18 which is filled into the annular space 15 and is compacted from above by way of a pressing tool. Thereby, the powdery material 18 can either be filled into the annular space 15 in a powdered manner and compacted in layers, or consist of shaped bodies of powdery material (not shown) which are formed previously by way of pressing and which are applied into the annular space 15 in a manner lying over one another, and subsequently pressed once again.

[0045] This annular space 15, after the filling and the compacting with powdery, magnetizable material 18 is closed by an annular cover or lid 19 which closes the annular space 15 to the top and is peripherally welded to the inner wall 17 and the outer wall 14, so that the material is hermetically closed by the surrounding material, which here is stainless steel. The outer wall 14 comprises an upwardly projecting collar-like (collar) section 21 which is provided for receiving a rotation part 20 designed in a corresponding step-like (step) manner and forming part of the receiver 10 for the motor shaft. The rotation part 20 at both sides is peripherally connected to the outer rotor 9 by way of welding.

[0046] The thus formed rotor component which is schematically represented in FIG. 4 is then magnetized from the inner side, thus on the inner wall 17, by way of the insertion of a head 22 of a magnetizing device, and specifically in a manner such that the desired number of poles, here for example eight poles, are produced at the same angular distance in a manner distributed over the periphery. The head 22 for this comprises eight (not shown) magnetizing probes which are magnetically activated via one or more electromagnets and carry out the desired magnetization of the material 18 in a manner such that in combination with the likewise eight-poled inner rotor 11 which is yet described further below in detail, a sinusoidal distribution of the magnetic flux density arises in the gap between the rotors 9 and 11, thus in the region of the can pot 12, in the coupled condition as is schematically represented by way of FIG. 5.

[0047] The inner rotor 11 in the represented embodiment is constructed similarly to the outer rotor 9. It comprises a reinforced inner wall 23 which is designed in a hollow-cylindrical manner and onto which an annular space 24 connects to the outside, said annular space being delimited on its lower side by a base 25 and on its outer side by a peripheral outer wall 26. This annular space 24 is likewise filled with powdery, magnetizable material 18 which is compacted there. Here, in an analogous manner to the outer rotor 9, either the material 18 is filled in a layered manner and compacted, or preferably is applied in pre-pressed shaped parts in the form of rings which as the case may be are yet one again pressed in their entirety within the annular space 24, whereupon these are closed to the top by an annular cover lid 27 which at its outer side is peripherally welded to the outer wall 26, and at the inner periphery is peripherally welded to the inner wall 23, so that the annular space 24 with the material 18 located therein is hermetically closed. The inner wall 23 is connected to the shaft 2 of the centrifugal pump 1 in a rotationally fixed manner. The magnetizable material 18 within the annular space 24 is magnetized on the outer side, thus from the outer wall 26, and specifically likewise in eight poles, which are preferably simultaneously magnetized and have an equal angular distance about the longitudinal middle axis 28 which is 45.

[0048] The magnetization of the material 18 within the annular space 15 or the annular space 24 can be clearly recognized by way of FIGS. 6 and 7. It is also shown in FIGS. 6 and 7 as to which size relationships are to be preferred. FIG. 6, which represents a section through the outer rotor 9 transverse to the longitudinal axis 28, illustrates how the magnetic alignments of the here exemplarily represented eight poles are directed within the magnetic material 18. The inner rotor and the outer rotor have the same pole number.

[0049] The arrangement is particularly effective when the distance X.sub.a, thus the distance of adjacent magnetic poles on the inner diameter, i.e. on the inner wall (inner peripheral surface) 17 of the outer rotor 9 to the thickness T.sub.a of the magnetic material 18 in the outer rotor 9 is between 2 and 3, preferably 2.5. Accordingly, it is the case that the dimensioning of the inner rotor 11 is selected such that the ratio of the distance X of adjacent magnetic poles on the outer diameter (outer peripheral surface) of the outer wall 26 of the inner rotor 11 to the thickness T.sub.i of the magnetic material in the inner rotor 11 is between 2 and 3, preferably between 2.2 and 2.8, ideally 2.5. Thus, the magnet has an unfavorable operating point in the case that the ratio is smaller than 2, since the magnet material is poorly utilized. The magnetization is made significantly more difficult if T is too large. The least magnet powder is consumed and the greatest magnetic flux density is achieved in the ideal case between 2 and 3.

[0050] As FIG. 5 particularly illustrates, the tangential magnetic flux 29 runs within the annular spaces 15 and 24, whereas the radial magnetic flux 30 enters through the annular gap and the can pot 12 and there, according to the pole arrangement, produces a sinusoidal distribution of the flux density B, which is particularly favorable for the torque transmission.

[0051] As is represented by way of FIGS. 8 and 9, in which the magnetic alignment as well as the course of the flux lines with the magnet coupling according to the invention (FIG. 9) and with the state of the art according to EP 2 054 432 A1 (FIG. 8) are represented, it is evident that the magnetic flux is effected almost exclusively within the magnetic material 18, i.e. within the annular spaces 15 and 24, so that one can make do without a backing or yoke as is applied with the state of the art, and this reduces the radial construction size.

[0052] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.