SE535378C2 - Electrodynamic actuator, rotating machine and method - Google Patents

Description

25 30 35 535 378 2 but not a dampening effect. In one embodiment, additional shorted conductive loops are provided on the stator. In the rotom. at an adjacent radial position from the additional shorted conductive loops, magnets are provided. If a laterally directed movement takes place, eddy currents are produced in the additional short-circuiting conductive loops in such a way that they want to counteract the movement, which gives a small damping effect. A disadvantage of this arrangement, however, is that the available attenuation is very small, since the speed of the lateral movement is usually very small, and thus also the time derivative of the magnetic fl passing the additional short-circuiting conductive loops.

International patent application WO01 / 84693, describes a bearing system which combines an axial bearing based on electromagnetic control of the axial position with a passive radial magnetic bearing. The passive radial magnetic bearing comprises multiple concentric and radially spaced axially magnetized ring magnets on a stator, and corresponding aligned linear poles on the rotor.

A return force occurs when the rotor is displaced from alignment. Axial forces between the magnets and the annular poles are balanced by the actively controlled axial bearing. A disadvantage of such a bearing system is that the radially acting restoring forces are undamped, which can cause oscillation ions.

SUMMARY A general problem with prior art magnetic bearings is that sufficient attenuation in the radial direction is difficult to provide. Additional separate arrangements are often provided in order to provide bearing stiffness and bearing damping functionality, respectively. Nevertheless, if the vibration levels are too high, the amplitudes must be reduced with the help of extreme landing bearings to avoid damage.

A general object of the present invention is thus to improve the damping in a rotating bearing arrangement in an energy efficient manner. A further object of preferred embodiments is to provide possibilities to actively control the damping properties, and when necessary preferably also to integrate landing bearing functionality. The above objects are achieved with actuator arrangements, rotating machines and methods according to the appended claims. Generally, in a first aspect, the electrodynamic actuator comprises a stator actuator part having a stator magnetic circuit element comprising magnetic material, and a rotor actuator part having a rotor magnetic circuit element containing magnetic material.

The stator actuator part and the rotor actuator part have an intended axis of rotation relative to each other. The electrodynamic actuator further comprises at least one magnet which induces a magnetic beam through a magnetic circuit comprising the stator magnet circuit element and the rotor magnet circuit element. The rotor magnet circuit element is substantially rotationally symmetrical with respect to the axis. A first side of the slator magnet circuit element has at least one of a variable reluctance and a variable magnetization in a radial direction with respect to the axis. A first side of the rotor magnet circuit element facing the first side of the stator magnet circuit element has at least one of a variable reluctance and a variable magnetization in a radial direction with respect to the axis. The stator actuator part further comprises at least one electrically conductive loop which encloses a respective segment of the stator magnet circuit element. This segment of the stator magnetic circuit element comprises magnetic material and is arranged to conduct a magnetic fate having a component, non-zero, through the electrically conductive loop or loops. The segment of the staton magnet circuit element is so arranged as to cause the component, other than zero, to change when the stator actuator part and the rotor actuator part are moved relative to each other in a radial direction. In a second aspect, a rotating machine comprises a stator, a rotor and at least one electrodynamic actuator according to the first aspect. The rotor actuator part is then attached to the rotor and the stator actuator part is attached to the stator. In a third aspect, a method of operating an electrodynamic actuator according to the first aspect comprises rotating the stator actuator part and the rotor actuator part relative to each other about the axis, whereby any deviation from alignment between the stator actuator part and the rotor actuator part gives eddy currents in the electrically conductive loop vibration dampers.

An advantage of the present invention is that improved damping is provided in rotary bearing systems in a simple and energy efficient manner. The damping can be used as a passive damping, but it also allows various active damping solutions. Additional advantages are discussed in connection with various embodiments which are further described below.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with further objects and advantages thereof, is best understood by reference to the following description taken in conjunction with the accompanying drawings, in which: FIG. 1A is a sectional view of an embodiment of an electrodynamic actuator according to the present invention; FlG. 1B is another sectional view of an embodiment of Fig. 1A; FlG. 1C is yet another sectional view of an embodiment of Fig. 1A; FlG. 1D is a sectional view of an embodiment of Fig. 1A, when a rotor actuator part and a stator actuator part are displaced from alignment; 10 15 20 25 30 535 378 4 FIG. 2 is a sectional view of an embodiment of a rotary machine comprising an electrodynamic actuator according to the present invention; FIG. 3 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having electrically conductive loops oriented along the axis; FIG. 4 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having permanent magnets on a first side of the rotor actuator part; FIG. 5 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having permanent magnets on a first side of the stator actuator part; FIG. 6 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having gradually altered magnetic reluctance in a radial direction; FIG. 7 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention in which a stator actuator part faces a rotor actuator part from two hobs; FIG. 8A is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having a symmetrical arrangement in the axial direction; FIG. Fig. 8B is another sectional view of the embodiment 1 of Fig. 8A; FIG. 9A is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having an aligned position with a deliberate displacement between the stator actuator portion and the rotor actuator portion; FIG. 9B is another sectional view of the embodiment of Fig. 9A; FIG. 10 is a sectional view of still another embodiment of an electrodynamic actuator according to the present invention having a symmetrical arrangement in the axial direction; FIG. 11 is a diagram illustrating induced and controlled currents through electrically conductive loops; FIG. 12 is a schematic diagram illustrating a rotating machine with a control unit for controlling currents through electrically conductive loops; FIG. 13 is a flow chart of steps in an embodiment of a method according to the present invention; FIG. 14 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having dual rotor actuator parts; FIG. 15 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention which provides additional restoring forces in a radial direction; FIG. 16 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having the axis of the rotor as part of the magnetic circuit; FIG. 17 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention having a three-part rotor actuator part; 10 15 20 25 30 35 535 378 5 FIG. 18 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention with repulsive permanent magnets; and FIG. 19 is a sectional view of another embodiment of an electrodynamic actuator according to the present invention with air gaps directed in the radial direction.

DETAILED DESCRIPTION For the drawings, the same reference number is used throughout for similar or corresponding elements.

In the present invention, a bearing arrangement is defined as a bearing arrangement, typically axial, which provides at least one of bearing rigidity and bearing damping in a radial and / or axial direction. A portion of such a bearing arrangement that provides at least a portion of any such functionality based on any electrodynamic interaction in the present invention is called an electrodynamic actuator.

Fig. 1A schematically illustrates an embodiment of an electrodynamic actuator 1 according to the present invention. The electrodynamic actuator is preferably used as or together with a rotating bearing in a rotating machine, and is preferably integrated as part of the rotating bearing. The electrodynamic actuator is arranged so as to provide a damping effect on movements in radial directions. The actuator 1 is partly attached to a rotor 10 and partly to a stator 20.

A rotor actuator part 11 is then attached to the rotor 10 so that it follows the rotor 10 when it rotates. A stator actuator member 21 is likewise attached to the stator 20 so that it remains stationary regardless of whether the rotor 10 rotates. The stator actuator part 21 and the rotor actuator part 11 then have an axis 4 for intended rotation relative to each other. A direction along the axis, which is illustrated by an arrow, is in the present representation referred to as an axial direction 2. Likewise, a direction perpendicular to the axial direction 2 in the same plane as the axial direction 2 is referred to herein as a radial direction 3.

The actuator 1 consists of a magnetic circuit 30, comprising a stator magnetic circuit element 22 and a rotor magnetic circuit element 12. The stator magnetic circuit element 22 is included in the stator actuator part 21 and the rotor magnetic circuit element 12 is included in the rotor actuator part 11. Both the stator magnetic circuit element 22 väg path of destiny. Preferably, the magnetic material has a relative magnetic permeability of at least 100. Since the magnetic circuit 30 has elements in both the stator 20 and the rotor 10, a magnetic beam 32 will pass both the stator actuator part 21 and the rotor actuator part 11.

The magnetic circuit 30 also includes at least two gaps 33 between the stator actuator portion 21 and the rotor actuator portion 11. The magnetic circuit 30 includes at least one magnet 31 which induces the magnetic beam 32 through the stator magnet circuit member 22 and the rotor magnet circuit member 12. In the present embodiment. For example, the magnet 31 is a permanent magnet 34 included in the stator magnet circuit element 22. In alternative embodiments, the magnet 31 may be placed at other positions along the magnetic circuit 30. Multiple magnets 31 may also be used. in an alternative embodiment, the magnetic beam 32 may instead be induced by an electromagnetic arrangement.

The rotor magnet circuit element 12 is substantially rotationally symmetrical with respect to the axis 4 for the intended rotation. A first side 15 of the rotor magnetic circuit element 12 has a variation in magnetic properties in the radial direction 3 with respect to axis 4. In the present embodiment, this variation in magnetic properties is realized by a variable reluctance in the radial direction 3. The first side 15 of the rotor magnetic circuit element 12 is here provided with elevations 16 and depressions 17 in the axial direction 2. These geometric structures give a variable reluctance for a magnetic flux in the axial direction 2.

Similarly, in the present embodiment, a first side 25 of the stator magnetic circuit element 22 has a variation in magnetic properties in the radial direction 3 with respect to axis 4. Again, this variation in magnetic properties is realized by a variable reluctance by means of geometric structures comprising elevations 26 and depressions 27 in the axial direction 2.

The first side 15 of the rotor magnet circuit element 12 faces the first side 25 of the stator magnet circuit element 22. The first side 25 of the staton magnet circuit element 22 and the first side 15 of the rotor magnet circuit element 12 thereby interact magnetically across the gap 33. In the present embodiment, the elevations 16, 26 positioned facing each other, and the depressions 17, 27 are positioned facing each other, giving rise to areas with a narrow gap and areas with a wide gap. The variation in the magnetic properties in the radial direction 3 has the effect that the magnetic field is concentrated in areas of low magnetic reluctance in the axial direction 2. In the present embodiment, almost all the current 32 in the magnetic circuit 30 will pass through the areas with narrow gaps. . When the rotor 10 rotates without any radial displacements, the magnetic pass passing between the stator magnet circuit element 22 and the rotor magnet circuit element 21 is constant due to the rotational symmetry of the rotor magnet circuit element 12.

The stator actuator part 21 further comprises at least one electrically conductive loop 40 enclosing a respective segment 28 of the stator magnet circuit element 22. In this specific embodiment, the electrically conductive loops 40 are located substantially in a plane having a normal direction in the axial direction 2, i.e. the electrically conductive loops 40 extend substantially in radial and / or tangential directions. The electrically conductive loop 40 comprises electrically conductive material, preferably having an electrical conductivity in excess of 10 MS / m and more preferably in excess of 30 MS / m. The segment 28 of the stator magnetic circuit element 22 comprises magnetic material 23. This segment 28 is further arranged so as to conduct a magnetic flux 32 having a non-zero component through the corresponding electrically conductive loop 40. In the manner described in more detail below, the segment 28 of the staton magnet circuit element 22 arranged so as to cause a change of the component, non-zero, when the stator actuator part 21 and the rotor actuator part 11 are displaced relative to each other in the radial direction 3.

A partial sectional view of the embodiment illustrated in Fig. 1A taken along the line A-A is shown in Fig. 1B.

The elevations 26 and the depressions 27 are clearly visible. The elevations 26 in this embodiment are interrupted by slots 29 at different tangential positions, and the electrically conductive loops 40 are located through these slots 29. In the present embodiment, each electrically conductive loop 40 is a separate loop enclosing a respective segment 28 of the elevations 26. In alternative embodiments, the electrically conductive loop 40 may enclose more than one segment 28 and they may overlap. The electrically conductive loops 40 may also be electrically connected to each other in different configurations. Fig. 1C illustrates a part of a sectional view of the embodiments illustrated in Fig. 1a taken along the line B-B. Shown here is the rotational symmetry of the elevations 16 and the depressions 17.

Fig. 1D illustrates a part of the actuator 1i in Fig. 1A, in a situation where the rotor actuator part 11 and the stator actuator part 21 are displaced relative to each other by a distance 5 in the radial direction. Due to the displacement by the distance 5, the width of the narrow gap areas in the gap 33 is reduced.

This means that the magnetic reluctance of the entire magnetic circuit 30 increases and the magnetic som across the gap 33 decreases. A magnetic force is then created between the rotor actuator part 11 and the stator actuator part 21. An axial component of this magnetic force 6 tries to close the gap between the rotor actuator part 11 and the stator actuator part 21. At small distances 5 this force 6 will be relatively unchanged compared to what is in it. aligned the state. A radial component of the magnetic force tries to reduce the distance 5. This magnetic force then acts in a similar way as shown in WO 01/84693.

If the situation in Fig. 1D is stationary, i.e. the magnetic forces are compensated in some sense, the fate through the gap 33 and the segments 28 enclosed by the electrically conductive loops 40 will be constant due to the rotational symmetry of the rotor magnetic circuit element 12. Thereby no currents are induced in the electrically conductive loops 40. However, during the transition between the situations in Fig. 1A and Fig. 1D, respectively, the fate will change, i.e. fl fate has a time derivative that is not zero. The same applies if the magnetic forces are allowed to reduce the distance 5. During such events, eddy currents will be induced in the electrically conductive loops 40. This current will, according to the general principle of eddy currents, counteract the flow change which gives rise to the eddy current, i.e. counteract the displacement change, regardless of the direction in which the displacement has changed. In this way a damping effect is obtained.

The returning magnetic force in the radial direction depends only on the instantaneous magnitude of the displacement, ie. the distance 5. Such a dependence thus acts as a spring which tries to move the rotor actuator part 11 and the stator actuator part 21 relative to each other towards a common equilibrium point.

However, since only the displacement itself is important, it means that no dam is present. Conversely, the counteracting forces created by the eddy currents in the electrically conductive loops 40, on the other hand, depend on the speed of the displacement change. If the displacement does not change, then the force produced by the electrically conductive loops 40 is zero. Furthermore, even if the offset is directed straight towards the position where the rotor actuator part 11 and the stator actuator part 21 are perfectly aligned with each other, the force created by the electrically conductive loop 40 will also counteract such changes. In other words, all forms of movement are counteracted, which means that damping is provided.

By utilizing variations in the magnetic properties in the radial direction 3, changes in the magnetic beam through the electrically conductive loops 40 can be amplified, whereby a strong damping effect can be obtained, compared with solutions according to the prior art. The segment 28 of the stator magnet circuit element 22 is thereby arranged so as to cause a non-zero component to change when the stator actuator part 21 and the rotor actuator part 11 are moved relative to each other in radial direction 3.

Fig. 2 schematically illustrates a rotating machine 9 comprising a stator 20 and a rotor 10. The rotating machine 9 comprises at least one electrodynamic actuator 1 in accordance with the principles shown in the present representation. The rotor actuator part 11 is attached to the rotor 10 and the stator actuator part 21 is attached to the stator 20.

There are many variations in the detailed configuration of the stator actuator part 21 and the rotor actuator part 11, all of which give a technical effect relative to the prior art as above. Fig. 3 shows another embodiment of an electrodynamic actuator 1. In this embodiment, an electrically conductive loop 40 encloses the stator magnetic circuit element 22 at a segment connecting two groups of elevations 26, between which a magnetic field flows. In this embodiment, the magnetic field through the electrically conductive loop 40 deserts in a radial direction 3. However, any change in the geometric relationship between the elevations 26 at the stator actuator portion 21 and the depressions 16 at the rotor actuator portion 11 also gives rise to to a change in the magnetic flux passing through the electrically conductive loop 40. An advantage of this embodiment is that there is typically more space for an electrically conductive loop 40 in such a position. In Fig. 4, another embodiment of an electrodynamic actuator 1 is shown. In this embodiment, the first side 15 of the rotor magnetic circuit element 12 also has a variation of the magnetic properties in radial direction 3 with respect to shaft 4. to provide a variable magnetization in radial direction 3. Permanent magnets 34 are provided on the surface of the rotor actuator part 11 facing the first side of the stator actuator part 21. Permanent magnets 34 are brittle and are therefore preferably mechanically supported in radial direction with solid non-magnetic material 39. A advantage of such an embodiment is that the rotor actuator part 11 and the stator actuator part 21 can be made smaller, since both the magnetization and the variation in radial direction are provided by one and the same structure.

It is also possible to use permanent magnets 34 to provide the variation in the magnetic properties of the stator actuator part 21, as shown by an embodiment in Fig. 5. This is usually an advantage if the rotating machine to which the described actuator 1 is connected operates at high speed, since no centrifugal forces occur on any permanent magnets in the stator actuator part 21. In a further alternative, an embodiment of magnets which induces the magnetic in most applications, however, electromagnets can also be used.

Fig. 6 further illustrates a principle for how a variation of the magnetic properties can be arranged in radial direction 3. Here the first surface 15, 25 of the rotor actuator part 11 and the stator actuator part 21, respectively, are flat. instead, the composition of material varies in the radial direction so that a variable magnetic reluctance is obtained. This has been indicated by different shading on the surface region. This embodiment has the advantage that the surfaces rotating close to each other are smooth, which entails a reduced risk of damage if the bearing 'function in the axial direction temporarily fails.

So far, the illustrated embodiments have shown gaps in a single plane in the radial direction. However, as mentioned before, the pure magnetic forces between the rotor actuator part 11 and the stator actuator part 10 tend to attract each other. A strong force in the axial direction then arises. This can be used as an advantage in applications where the rotor is relatively heavy and the axis of rotation is vertical. The magnetic forces in the axial direction can then assist in lifting the rotor. A change in the distance between the rotor actuator part and the stator actuator part also affects the magnitude of the magnetic flux passing through the gap, which means that this type of movement is also damped by the electrically conductive loops.

However, these forces are not repulsive forces, but only damping, so an axial bearing is still needed. nevertheless, in many applications, e.g. where the rotor is very light or where the shaft is horizontal, the axially directed forces are a disadvantage.

Fig. 7 illustrates another embodiment of an electrodynamic actuator 1, which shows a reduced contribution to the axial forces when the rotor actuator part 11 and the stator actuator part 21 are perfectly centered relative to each other. Here too, however, an axial bearing is needed which provides restorative forces when the position of the shaft becomes offset. nevertheless, the magnetic bias force from the electrodynamic actuator 1 is significantly reduced. In this embodiment the stator actuator part 21 comprises two segments 47, 48, placed on opposite sides in axial direction 2, to the rotor actuator part 11. In this embodiment the two segments 47, 48 are magnetically connected to each other by a stator actuator bridge 49. Two magnetic gaps 33, 35 at each side of the rotor actuator part 11, where both gaps 33, 35 form parts of the magnetic circuit 30. The magnetic forces try to close the gaps and therefore act against each other, so that the total influence of the magnetic axial forces is reduced.

The segment 48 is located with a narrow gap 35 to the rotor actuator part 11. This can be used further in applications that work with a pressure difference along the axis of the rotor. Examples of such applications are e.g. vacuum pumps. In the present embodiment, a surface of segment 48 facing the rotor actuator part is provided with a grooved structure 71. The grooves have a helical shape and actuate gas present in the gap 35 to move towards the shaft 4 when the rotor flat rotor actuator part 11 rotates rapidly relative to the stator actuator part 21. A pumping effect thereby arises in accordance with principles known as such according to the state of the art. However, this type of pump is preferably combined with narrow flat gaps that create advantageous synergy functions. In order not to affect too much the magnetic properties of the actuator as a whole, the grooved surface 71 may be made of a non-magnetic material, e.g. a polymer. In alternative embodiments, the grooved surface 71 may instead sit on the rotor actuator portion 11 and interact with a flat actuator surface on the stator instead. In Fig. 8A, these ideas have been further developed. In this embodiment, both segments 47, 48 are provided with variable reluctance in radial direction facing matching structures on the rotor. In other words, the rotor magnet circuit element 12 has a second side 19, directed in the opposite direction in the axial direction to the first side 15. A second side 46 of the stator magnet circuit element 22 faces the second side 19 of the rotor magnet circuit element. 12, separated by the gap 35. The second side 46 of the stator magnetic circuit element 22 is in magnetic contact with the first side 15 of the stator magnetic circuit element 22.

In addition, the other side 46 of the stator magnet circuit element has at least one of a variable reluctance and a variable magnetization in a radial direction 3 with respect to axis 4, and the other side 19 of the rotor magnet circuit element 12 has at least one of a variable reluctance and a variable magnetization in a radial direction 3 with respect to axis 4.

Electrically conductive loops 40 are also provided on the other side 46 of the stator magnetic circuit element 22, for the purpose of capturing changes in the magnetic field 32 also on this part of the magnetic circuit 30.

In addition, a further electrically conductive loop 41 is provided around the rotor magnet circuit element 12, in radial direction 3. This electrically conductive loop 41 is positioned inside the actuator bridge 49 of the stator and thereby captures all fate changes in the gaps 33, 35.

In this way, electrically conductive loops 40, 41 for effectively detecting and counteracting all relative movements between the rotor actuator part 11 and the stator actuator part 21 in radial direction 3 are provided. , since a decrease in the gap distance on one side of the rotor actuator part 11 is compensated by a corresponding increase in the gap distance on the other side.

This is the result of the same magnetic flux passing through both gaps 33, 35. In the same way, the magnetic forces in the axial direction are also mutually compensated. A movement in the axial direction will admittedly reduce one of the gaps 33.35, but will instead increase the other gap by the same amount. The resulting magnetic forces in the axial direction are therefore mainly compensated. Also in this embodiment, grooved structures 71 can be used to achieve a pumping effect.

For this purpose, the volume between the elevations in the rotor actuator part 11 is filled with non-magnetic material and the grooved structure 71 is provided on top of these, utilizing the stator actuator part 21 as the opposite planar pumping structure. Note that the grooves at gaps 33 and 35, respectively, are helical in the opposite direction to obtain a combined pumping action. Here too, in some cases it may be useful to change places on the grooved structure 71 and the flat surfaces between rotor and stator.

Fig. 8B illustrates a sectional view of the same embodiment as in Fig. 8A, but perpendicular to the axis of rotation, along line C-C. Here it can be noted that also the electrically conductive loops 40, 41 which enclose the segment 28 of the stator magnetic circuit element 22 also enclose the axis of rotation. The electrically conductive loops 40, 41 are therefore in the present embodiment preferably realized as solid copper rings soldered in the depressions in the stator actuator part 21.

An advantage of the design in Fig. 8B is that the losses are minimized due to the rotationally symmetrical magnetic field. Another advantage is that the embodiment is relatively easy to manufacture.

Referring again to Fig. 8A, it is worth noting that since the geometric structures of the rotor actuator part 11 and the stator actuator part 21 in the present embodiment are in phase with each other, a maximum magnet fl gap 32 is obtained through the magnetic circuit 30 when the rotor actuator part 11 and the stator actuator part 21 are perfectly aligned in the radial direction. Any deviation from this relationship will reduce the magnetic flux 32. With such a design, any radial movement of the rotor actuator portion 11 and the stator actuator portion 21 will result in either increased or constant reluctance in the gaps in all portions of the magnetic circuit or decreased or constant reluctance in the gaps. in all parts of the magnetic circuit. In other words, there is no possible radial movement with the configuration in the present embodiment which causes the magnetic reluctance to increase in one part of the magnetic circuit and to decrease in other parts. This is the reason why the electrically conductive loops 40, 41 are allowed to enclose the axis of rotation 4.

The magnetic return forces in the radial direction are quite strong in the above embodiment. In yet another embodiment, illustrated in Fig. 9A, the magnetically repulsive forces in the radial direction are reduced at the same time as the damping function is substantially the same or better. Delta is accomplished by deliberately introducing a deviation between the geometric structures of the rotor actuator part 11 and the stator actuator part 21. Note that Fig. 9A is drawn in the intentionally aligned position between the rotor actuator part 11 and the stator actuator part 21. When the rotor 10 and the stator 20 rotate in an aligned relationship the elevations 26 on the stator actuator part 21 placed at a smaller radius than the elevations 16 on the rotor actuator part 11. The magnetic forces at a point along the actuator 1 will try to displace the stator outwards. However, such a movement will result in a larger deviation on the opposite side of the actuator 1. The magnetic forces strive in the opposite direction and will thus compensate each other, at least to some extent.

At the same time, a dampening effect is maintained. If a movement in one direction occurs, a change in the magnetic fate will occur on both sides of the rotor. On the one hand, the magnetic ökar fate increases as the reluctance decreases as the elevations 16 and 26 come closer to a matching position. On the opposite side, however, the fate will decrease as the reluctance increases as the elevations 16 and 26 are displaced apart. However, if each electrically conductive loop 40, 41 covers only a portion of the stator actuator portion 21 along a longitudinal direction, then both of these changes can be detected and used to create attenuating eddy currents. In Fig. 98, a sectional view D-D perpendicular to the axis 4 of an embodiment arm is shown. The electrically conductive sieves 40 are provided here by a solid copper plate provided with holes for the segments 28. In other words, the electrically conductive sieves 40 comprise solid non-magnetic electrically conductive metal pieces. In this embodiment, four transverse connections 55 are provided in the radial direction, which allow four substantially independent eddy currents to pass through the copper plate. The currents in two opposite sides of the copper plate will typically circulate in opposite directions compared to each other. But the currents in the different parts will in any case always strive to counteract all movement.

The interruptions in the elevations 26 have the advantage that they prevent the magnetic field from taking a path along the elevations 26 instead of passing the gaps, when there is a difference between different sides of the stator actuator part 21. The attenuation thereby becomes more effective. However, the interruptions in the rotationally symmetrical magnetic field cause some losses. This effect can be reduced by inserting a narrow pole bridge on the surface of the stator actuator part 21 on top of the electrically conductive sieves 40, 41. Another way of obtaining a cross connection is to provide the elevations 26 with heels instead. The size of these holes is determined by a compromise between the desire to have rotationally symmetrical magnetic properties and the desire to prevent magnetic fields propagating along the ridges. and finally by having a sufficient cross-coupling area for the electrically conductive screens 40.

Alternatively, the cross-couplings can consist of the magnetic material itself, ie. through the elevations. If the width of the elevations 26 is small enough, then the electrical resistance in the radial direction becomes small enough to enable electrically conductive loop 40 to include a portion of the elevations 26. In other words, the electrically conductive loops 40 comprise in part a portion of the stator magnetic circuit element.

Based on Fig. 9A, in a further alternative embodiment, wire is used for the electrically conductive sieves. Since the design itself results in currents with different directions in opposite sides of the stator actuator part, the wires are connected to the electrically conductive sieves on the opposite side, and yet in the opposite direction. In other words, the wires lie in coils wound clockwise around one sector of the stator actuator part and counterclockwise around an opposite sector, in order to obtain the radial damping effects, in particular the fundamental tone of each oscillation.

Preferably, an electrically conductive loop 41 is also used which encloses all the gaps between the rotor actuator part 11 and the stator actuator part 21. Such an electrically conductive loop 41 will have a limited effect on the fundamental tone of each oscillation, but can effectively attenuate a first harmonic of each oscillation.

The damping effect depends on several parameters, e.g. the width of the gap and the rate of change of the magnetic properties in the radial direction. In cases where geometric shapes are used, the width of the elevations is also of great importance. In general, the change in the magnetic flux across the gap is greater in designs that have many narrow elevations compared to designs with fewer but wider ones. The effect also increases with decreasing size of the gap. Small geometric structures will be more sensitive to relative movements. In this way, the actuator can be designed so that it provides almost any desired damping effect.

Fig. 10 illustrates another embodiment of an electrodynamic actuator 1, showing another solution to a double-sided concept. In this case, the stator actuator part 21 has segments 47, 48 on opposite sides of the rotor actuator part 11. But instead of having an actuator bridge on the stator, the magnetic circuit is closed by two magnetic circuits through the rotor actuator part 11. Such an embodiment can be made thinner in radial direction and still have the same number of gaps. Magnets can be provided on one segment as well as both segments on the stator actuator part 21 and / or in the rotor actuator part 1 1.

One way to control the damping of the actuator is to provide a custom design regarding the width of the elevations, gaps, etc. etc. In other applications, on the other hand, the damping requirement may not be sufficient or it may need to change over time. The damping function depends on the generation of eddy currents in the electrically conductive loops. Since the electrically conductive loops are located on the stator side, the eddy currents are a quantity that can be easily measured. By connecting one or more conductive loops 40 to a control unit 90, as illustrated in Fig. 12, the eddy currents can be monitored as a function of time. Fig. 11 is a graph showing the time course of such an eddy current 101.

Such monitoring also opens up to actively control the damping force.

If the damping force spontaneously provided by the eddy currents in an actuator system is considered to be too small, then the time course across the eddy currents in which case provides information on when and how currents through the electrically conductive loops provide a damping effect. Such time information can be difficult to obtain in other ways. But not only monitoring the eddy currents, but also controlling them provides an opportunity to control the damping effect and / or the rigidity of the bearing. The control unit 90 (Fig. 12) is thereby arranged to control currents through the electrically conductive loops. If the control unit increases a current through the electrically conductive loops so that a total current 102 having the same phase as the pure eddy current 101, but higher amplitude, is fed to the electrically conductive loops, the attenuation effect is increased. Shifting the phase of the applied current, as in curve 4, can also play an important role, especially if the inductance of the coil is high.

Similarly, if the attenuation generated by a pure eddy current is too large, the attenuation can be counteracted by applying a current in the opposite direction to the eddy current. The total current can look like in curve 103. In extreme cases, the attenuation can also be controlled to become negative, i.e. a total current flowing through the electrically conductive loop flows in the opposite direction to what an uncontrolled eddy current would do. A vibration in such a machine can be intentionally increased in this way.

Those skilled in the art will readily appreciate that the methods of controlling the damping effect can be varied in many ways. Since an electrical connection to the electrically conductive loops already exists, it is advantageous to use the electrically conductive loops themselves also for the controlled currents. However, it is quite possible to add separate conductive loops, preferably parallel to the original electrically conductive loops, in which a correction current is conducted. The total power on the rotating machine will be essentially the same, but if the controlled current is opposite to the eddy current, the total heat generated in the loops will increase.

If the electrically conductive loops 41 are connected in the opposite direction on opposite sides of the stator, as discussed earlier in connection with Fig. 9A, then an adequate control of the current can give rise to a resulting force in the radial direction. This possibility is most pronounced if non-aligned stator and rotor geometries are used.

Fig. 13 illustrates a fate diagram showing the steps in an embodiment of a method in accordance with the present invention. The method of operating an electrodynamic actuator according to the principles presented in the present invention starts in step 200. In step 210, the stator actuator part and the rotor actuator part are rotated relative to each other about an axis. In step 220, the vibrations are damped by inducing eddy currents in the electrically conductive loops. This occurs spontaneously as a result of the amplitude changing on a deviation from alignment between the stator actuator part and the rotor actuator part. In step 230, currents are controlled through the electrically conductive loops to control at least one of the damping efficiency and rigidity properties. The method ends in step 299.

The steps in Fig. 13 should not be interpreted as a strict fl fate diagram, but rather to create an awareness of the existence of the various steps. Steps 210-230 should therefore be considered possible to perform continuously and / or simultaneously.

The eddy currents provide information about the relative movement in the radial direction between the stator and the rotor.

By integrating this signal, and by using the equilibrium position as a fixed position, one can obtain information about an absolute position. It is thereby possible to control the movement laterally.

The same possibility can also be provided with a position sensor.

Fig. 14 illustrates another embodiment of an electrodynamic actuator 1. In this case, the rotor actuator part 11 comprises two segments 61, 62, magnetically coupled through the rotor 10. The stator actuator part 21 has four segments 63, 64, 65, 66, facing each rotor actuator part 61. , 62 parvis. The two pairs are magnetically coupled to a permanent magnet 34. An electrically conductive loop 70 per segment 61, 62 in the rotor actuator part is provided, which encloses the respective segments 61, 62 in the radial direction. The magnetic circuit thus involves both segment pairs 63, 64, 65, 66 in the stator actuator part, both segments 61, 62 in the rotor actuator part, a part of the rotor 10 and the permanent magnet. The magnetic circuit also has two branches at each of segments 61, 62 of the rotor actuator part, one from above (shown in the figure) and one from below. These two flow paths open into the region within the electrically conductive loops 70 in opposite directions. The flow also enters one of the segments 61 in the rotor actuator part and leaves through the other 62.

The electrically conductive loop 70, on the other hand, has no damping effect, since the net change in magnetic solder through the electrically conductive loop 70 is zero, regardless of the radial movement.

The electrically conductive loops 70 are controllable according to similar ideas presented above.

By changing the current through the electrically conductive loops 70, the magnetic flux to / from the segments 61, 62 in the rotor actuator part can be differentiated between the upper and lower segments 63, 64, 65, 66 in the stator actuator part, respectively. This means that it is possible to intentionally e.g. increase the fate of the lower segments 64, 66 in the stator actuator part and decrease the fate of the segments 63, 65 in the stator actuator part, or vice versa. In such a case, a net force will be directed in the axial direction, ie. a controllable axial force is provided at the same time as damping in the radial direction is provided. This is just an example of how the basic concept of the present invention can be combined in new configurations, with interesting features.

Electrically conductive loops 40 are also provided around portions of each of the stator parts segments 63-66. These electrically conductive loops 40 provide a damping effect. In order to avoid damping also the axial control provided by the electrically conductive loop 70, the electrically conductive loop 40 is preferably wound in the opposite direction on opposite parts of the stator actuator part, as discussed in the alternative embodiment in connection with Fig. 9A. In addition, the electrically conductive loop 40 on the upper and lower stator part segments, respectively, must be provided with different polarity.

Another possibility to expand the field of application of the present invention is to combine the basic ideas with different concepts according to known technology. Since the magnetic flux in the rotor actuator part 11 is already differential in the radial direction, this differentiation can e.g. be used to create radial return forces. Fig. 15 illustrates such an embodiment. The rotor actuator part 11 further comprises at least one electrically conductive rotor loop 69 enclosing a respective segment 68 of the rotor magnet circuit element 12. The segment 68 of the rotor magnet circuit element 12 comprises magnetic material and is arranged to conduct a magnetic flux having a non-zero component through the electrically conductive the rotor loop 69. The segment 68 of the rotor magnet circuit element 12 is arranged so as to receive the component. non-zero, to be changed when the rotor actuator portion 11 and the stator actuator portion are offset from an aligned relationship in the radial direction relative to each other. The stator magnet circuit element 22 is substantially rotationally symmetrical with respect to the shaft 4. In this embodiment, a displacement in the radial direction causes the electrically conductive rotor loop 69 on the rotor actuator part 11 to create a return force. A movement in the radial direction, ie. the time derivative of the motion is non-zero, instead causing the electrically conductive loop 40 on the stator actuator part 21 to create a damping force.

Fig. 16 shows an embodiment of an electrodynamic actuator 1 according to the present invention having the rotor shaft 76 as part of the magnetic circuit 30. The magnetic flux passes from the stator actuator part 21 over to the rotor actuator part 11 via the gaps 33 and 35. The feed 32 is then led out to the rotor shaft 76 , where magnetic conductors 77 separate the current 32 into two parts. Each part fl passes a further gap 78 over to a magnetic conductor 72 on the stator actuator part 21. An electrically conductive loop 70 is provided around substantially the entire magnetic circuit 30 and can also be used to regulate the axial position. By utilizing the rotor shaft 76 to guide the magnetic axis in two directions, the arrangement can be made more compact in the axial dimension.

Fig. 17 shows another embodiment of an electrodynamic actuator 1 according to the present invention which has a three-part rotor actuator part 11. The upper and the lower function as in Fig. 14. In the middle part, on the other hand, the rotor actuator part instead functions as a pure damper, e.g. . similar to that shown in Fig. 8A. The arrangement is extended in the axial direction. This can also be used because it also to some extent prevents gas and others from passing through the arrangement. A so-called labyrinth seal has thereby been formed. This labyrinth structure can also be expanded by providing it with additional sealing rings 74 in available spaces to increase the length of the flow path through the arrangement. The sealing rings 74 protrude from the first side and / or second side 47 of the stator magnetic circuit element 22. The rings 74 are preferably made of the same material as the conductive rings 40. The rings 74 may also be surface treated with a low friction coating so that they Fig. 18 shows another embodiment of an electrodynamic actuator 1 according to the present invention, here with repulsive permanent magnets 75. The magnetic flux 32 in the main magnetic circuit 30 is caused by ring magnets 31 at the rotor 10, fixed with bandage 79. By also adding magnets 75 to the stator actuator part, directed parallel to the magnets 31 at the rotor 10, a repulsive force can be created which acts as a normal magnetic bearing. Introducing the additional magnets 75 will not appreciably alter the damping properties of the arrangement in general.

In the above embodiment, the rotor magnetic circuit element and the stator magnetic circuit element are magnetically interacting over a gap extending in axial direction 2. Fig. 19 shows another embodiment of an electrodynamic actuator according to the present invention with air gaps 33, 36 instead directed in radial direction 3. A movement in radial direction causes a change in magnetic flux through the electrically conductive loop 40 and attenuation occurs. Typically, the damping can be made very effective. However, such a solution tends to be somewhat more unstable.

The embodiments described above are to be understood as a few illustrative examples of the present invention. It will be apparent to those skilled in the art that various modifications, combinations and alterations may be made to the embodiments without departing from the scope of the present invention. In particular, different sub-solutions in different embodiments can be combined in other configurations, where technically possible. In particular, most illustrated embodiments having a geometric structure design on the rotor actuator portion and the stator actuator portion aligned can typically be easily modified to provide non-aligned configurations. Surfaces with a pumping effect or with labyrinth seals can also be combined with most embodiments. However, the scope of the present invention is defined by the appended claims.

Claims (18)

10 15 20 25 30 535 378 19 PATENT REQUIREMENTS An electrodynamic actuator (1), comprising: a stator actuator member (21) having a stator magnetic circuit element (22), comprising magnetic material (23); and a rotor actuator part (11) having a rotor magnetic circuit element (12), comprising magnetic material (13); which stator actuator part (21) and rotor actuator part (11) have an axis (4) for a intended rotation relative to each other; at least one magnet (31) which induces magnetic fl fate (32) through a magnetic circuit (30) comprising said stator magnet circuit element (22) and said rotor magnet circuit element (12); which rotor magnet circuit element (12) is substantially rotationally symmetrical with respect to said shaft (4); a first side (25) of said stator magnet circuit element (22) has at least one of a variable reluctance and a variable magnetization in a radial direction (3) with respect to said axis (4); a first side (15) of said rotor magnet circuit element (12), which interacts magnetically with said first side (25) of said stator magnet circuit element (22), has at least one of a variable reluctance and a variable magnetization in said radial direction (3); said stator actuator member (21) further comprising at least one electrically conductive loop (40) enclosing a respective segment (28) of said stator magnet circuit element (22); said segment (28) of said stator magnetic circuit element (22) comprising magnetic material (23) and arranged to conduct a magnetic flux (32) having a non-zero component through said at least one electrically conductive coil (40); which segment (28) of said stator magnetic circuit element (22) is arranged to cause said non-zero component to change when said stator actuator part (21) and said rotor actuator part (11) move relative to each other in said radial direction (3). Electrodynamic actuator according to claim 1, characterized in that said first side (25) of said stator magnetic circuit element (22) is provided with elevations (26) and depressions (27) extending in an axial direction (2), which causes at least one part of said variable reluctance. Electrodynamic actuator according to claim 1 or 2, characterized in that said first side (15) of said rotor magnetic circuit element (12) is provided with elevations (16) and depressions (17) extending in said axial direction (2), which causes at least a portion of said variable reluctance. 10 15 20 25 30 535 373 20 Electrodynamic actuator according to any one of claims 1 to 3, characterized in that said first side (15) of said rotor magnet circuit element (12) and said first side (25) of said stator magnet circuit element (22) interact magnetically over a gap in the axial direction. An electrodynamic actuator according to any one of claims 1 to 3, characterized in that said first side (15) of said rotor magnetic circuit element (12) and said first side (25) of said stator magnetic circuit element (22) interact magnetically over a gap in the radial direction. Electrodynamic actuator according to claim 5, characterized by sealing rings (74) projecting from said first side (25) of said stator magnetic circuit element (22), which sealing rings (74) are surface treated with a low friction coating in order to be able to act as radial emergency bearings. Electrodynamic actuator according to any one of claims 1 to 6, characterized in that said first side (25) of said stator magnet circuit element (22) has a variable magnetization in a radial direction (3). Electrodynamic actuator according to any one of claims 1 to 7, characterized in that said first side (15) of said rotary magnet circuit element (12) has a variable magnetization in a radial direction (3). Electrodynamic actuator according to any one of claims 1 to 8, in turn dependent on claim 2, characterized in that said at least one electrically conductive loop (40) is provided in said depressions (27). Electrodynamic actuator according to any one of claims 1 to 9, characterized in that said at least one electrically conductive loop (40) partly comprises part of said stator magnetic circuit element (22). Electrodynamic actuator according to any one of claims 1 to 10, characterized in that said rotor magnet circuit element (12) has a second side (19), directed opposite to said first side (15); and a second side (46) of said stator magnetic circuit element (22), which interacts magnetically with said second side (19) of said rotor magnetic circuit element (12). Electrodynamic actuator according to claim 11, characterized in that said second side (46) of said stator magnetic circuit element (22) is in magnetic contact with said first side (19) of said stator magnetic circuit element (22). Electrodynamic actuator according to claim 11 or 12, characterized in that said second side (46) of said staton magnetic circuit element (22) has at least one of a variable reluctance and a variable magnetization in said radial direction (3) and that said second side (19 ) on said rotor magnet circuit element (15) has at least one of a variable reluctance and a variable magnetization in said radial direction (3). 10 15 20 25 30 535 373 21 Electrodynamic actuator according to any one of claims 1 to 13, characterized in that said rotor actuator part (11) further comprises at least one electrically conductive rotor loop (69) enclosing a respective segment (68) of said rotor magnet circuit element (12); said segment (68) of said rotor magnet circuit element (12) comprising magnetic material (13) and arranged to conduct a magnetic flux (32) having a non-zero component through said at least one electrically conductive rotor loop (69); which segment (68) of said rotor magnet circuit element (12) is arranged to cause said non-zero component to change when said stator actuator part (21) and said rotor actuator part (11) move relative to each other in said radial direction (3) compared to an aligned position; which stator magnetic circuit element (22) is substantially rotationally symmetrical with respect to said axis (4). Electrodynamic actuator according to any one of claims 1 to 14, characterized by an electrical control unit (90) coupled to said electrically conductive loop (40) and arranged to control currents through said electrically conductive loops (40). A rotating machine (9), comprising: a stator (20); a rotor (10); and at least one electrodynamic actuator (1) according to any one of claims 1 to 15; in which said rotor actuator part (11) is attached to said rotor (10) and said stator actuator part (21) is attached to said stator (20). A method of operating an electrodynamic actuator (1) according to any one of claims 1 to 14, which method comprises the steps of: rotating (210) said stator actuator part (21) and said rotor actuator part (11) relative to each other around said axis; and damping (220) vibrations between said stator actuator part (21) and said rotor actuator part (11) using eddy currents in electrically conductive loops (40) caused by some relative movement between said stator actuator part (21) and said rotor actuator part (11). The method of claim 17, characterized by the further step of controlling (230) currents through said electrically conductive loops to control at least one of attenuation efficiency and stiffness.