WO2011092223A2

WO2011092223A2 - Electromagnetic generator

Info

Publication number: WO2011092223A2
Application number: PCT/EP2011/051093
Authority: WO
Inventors: Thomas Becker; Jürgen Heinz; Martin Kluge; Gerhard KRÖTZ; Sebastian MÖST; Tommy Umbreit
Original assignee: Hochschule Kempten; Eads Deutschland Gmbh
Priority date: 2010-01-26
Filing date: 2011-01-26
Publication date: 2011-08-04
Also published as: WO2011092223A3

Abstract

An electromagnetic generator (1) comprising a magnetic oscillator (3) and a magnetic stator (5) as well as a conductor arrangement (17) in which a current is induced by the motion of the magnetic oscillator (3). The magnetic oscillator (3) has two degrees of freedom for its pivoting motion (4).

Description

Description :

Electromagnetic Generator The invention relates to an electromagnetic generator comprising :

- a magnetic oscillator, which is provided with at least one oscillator magnet and which is arranged for performing a pivoting motion, if the electromagnetic generator is vibrat- ing;

- a magnetic stator, provided with at least one stator magnet, which interacts with the at least one oscillator magnet and creates a repulsive force on the oscillator driving the oscillator, if displaced from the rest position, back to the rest position;

- a conductor arrangement, in which a current is induced by the change of a magnetic flux through the conductor arrangement caused by the relative motion of the magnetic oscillator with respect to the conductor arrangement.

Such an electromagnetic generator is known from WO

2008/138278 A2. In the known electromagnetic generator, the magnetic oscillator is formed by a moveable member mounted in a case. The moveable member is further provided with perma- nent magnets, which interact with fixed magnets disposed on an opposite side besides the moveable member. The moveable member is further connected to a magnetic excitation circuit, which creates a magnetic flux through a stationary coil located within the magnetic excitation circuit. In a further embodiment, the coil extends along a tangential direction of the pivoting motion and the magnetic flux is created by permanent magnets creating a magnetic field, which extends in a radial direction with respect to the pivoting motion through the coil.

One disadvantage of the known electromagnetical generator is that the generator can only be used for vibrations with frequency components in the low frequency range. In addition the mechanical energy of the vibrations is only transformed into electrical energy if the mechanical forces act in the direction of a possible motion of the moveable member.

Proceeding from this related art, the present invention seeks to provide an electromagnetic generator, which converts mechanical energy of vibrations more efficiently into electrical energy.

This object is achieved by a method having the features of the independent claim. Advantageous embodiments and refinements are specified in claims dependent thereon. The electromagnetic generator comprises a magnetic oscillator provided with at least one oscillator magnet and a magnetic stator provided with at least one stator magnet. The polarity of the at least one oscillator magnet and the at least one stator magnet vary in a radial direction with respect to the pivoting motion. The radial direction of the pivoting motion should be understood as being a radial direction with respect to the center of the pivoting motion. The electromagnetic generator is further arranged such that the magnetic oscillator has more than one degree of freedom for its pivoting motion. Generally there will be two degrees of freedom for the pivoting motion. By the arrangement and orientation of the at least one oscillator magnet and stator magnet the repulsive force can be adjusted to a large frequency range and the magnetic oscillator can have more than one degree of freedom for its pivoting motion. Thus mechanical forces from various directions can cause the pivoting motion of the oscillator resulting in a higher efficiency for converting mechanical energy into electrical energy. In one embodiment, the magnetic oscillator comprises a series of oscillator magnets along a radial direction from the pivot point, wherein the polarities of the magnets are aligned along a radial direction with respect to the pivoting motion. By providing a series of magnets the strength of the repulsive force acting in a tangential direction and driving the oscillator back in its rest position can be increased.

The oscillator magnets can be each associated with a stationary stator magnet having an inner opening through, which the magnetic oscillator extends. Such an arrangement of oscillator magnets and stator magnets ensures the presence of a repulsive force independent from the direction of the pivoting motion of the magnetic oscillator.

Such an arrangement of oscillator magnets and stator magnets further allow to adjust the magnetic force acting in a radial direction with respect to the pivoting motion. If an oscillator magnet is located near enough to its associated stator magnet, an attractive magnetic force between a stator magnet and oscillator magnet acts in a radial direction of the pivoting motion.

On the contrary, if the oscillator magnet is located far enough from its associated stator magnet, a repulsive magnetic force between stator magnet and oscillator magnet acts in a radial direction of the pivoting motion. By adjusting the distance between oscillator magnets and associated stator magnets, the magnetic forces acting in a radial direction of the pivoting motion can be adjusted.

The magnetic force acting in radial direction of the pivoting motion can be compensated by a mechanical force. This mechanical force might be provided by a support, which holds a tip of the magnetic oscillator, wherein the contact point between tip and support functions as a pivot point for the pivoting motion. The support then exerts a pressing force on the magnetic oscillator in equilibrium with the magnetic force between the at least one stator magnet and the at least one oscillator magnet. The magnetic force in radial direction of the pivoting motion can also be compensated by a connecting element exerting a drag force on the magnetic oscillator in equilibrium with the magnetic force between the at least one stator magnet and the at least one oscillator magnet.

The magnetic oscillator can be rotationally symmetric with respect to a longitudinal axis extending in a radial direc- tion of the pivoting motion. Thus, the repulsive force in tangential direction is uniform and independent from the direction of the pivoting motion.

Correspondingly, the stator magnets may have a ring shape ensuring a repulsive magnetic force, which is independent from the direction, in which the magnetic oscillator is displaced from the rest position.

The conductor arrangement can comprise a coil, wherein the magnetic oscillator passes through the inner opening of the coil and the oscillator is provided with magnets generating a magnetic field passing through the coil along the longitudinal axis of the coil. In such an arrangement, the conductors of the coil extends essentially along a tangential direction with respect to the pivoting motion. Thus, the changes of the magnetic flux caused by the motion of the magnetic oscillator can be maximized .

In another embodiment, the electromagnetic generator is provided with a conductor arrangement comprising a coil wound around a yoke, having a stationary part and a moveable part, which is connected to the magnetic oscillator. The yoke is further provided with yoke magnets generating a magnetic flux in the yoke. The yoke is also provided with an air gap between the stationary part and the oscillator part, which is delimited by stationary pole pieces and oscillatory poled pieces. In such an embodiment, even a small displacement of the magnetic oscillator can cause a considerable change of the magnetic flux through the yoke resulting into a high current induced in the conductor arrangement.

In order to maximize the magnetic flux through the coil at the rest position, the air gap has the shape of a spherical segment resulting in a minimized air gap at the rest posi- tion.

The change of the magnetic flux through the poled pieces can further be increased by providing the poled pieces with grooves, which may extend along a circle centered on the longitudinal axis of the magnetic oscillator in the rest position .

In another embodiment, the grooves extend in radial direction from the longitudinal axis of the magnetic oscillator in the rest position.

In yet another embodiment, the stationary pole pieces and the moveable pole pieces taper towards the air gap. In a further embodiment, a central pole piece of the yoke is provided with a central part located opposite to the other central pole piece, and is further provided with a protrusion extending towards an opposite outer pole piece. Thus, the magnetic flux through the yoke can be partially reversed, if the movable part of the inductor is displaced from its rest position .

For further enhancing the reversal of the magnetic flux, the central part and the opposite central pole piece are provided with a central recess. The electromagnetic generator is particularly suitable for providing electric power to a remote sensor, which cannot be connected to a power line and therefore needs its own power source. Such sensors may also be provided with a transmitter for wireless transmission of sensor data to a remote station, where the sensor data a further processed.

Further advantages and properties of the present invention are disclosed in the following description, in which exem- plary embodiments of the present invention are explained in detail based on the drawings:

Figure 1 is a cross sectional view of an electromagnetic

generator arranged for transforming the mechanical energy of vibrations into electric energy;

Figure 2 is a diagram illustrating the distribution of the magnetic field around a stator magnet and an oscillator magnet of the electromagnetic generator of Figure 1;

Figure 3 is a further diagram illustrating the magnetic

field around a stator magnet and an oscillator magnet of the electromagnetic generator of Figure 1, if the oscillator is moved farther away from the stator magnet;

Figure 4 is a perspective view of an inductor of the electromagnetic generator from Figure 1;

Figure 5 is a cross sectional view through a modified embodiment of an inductor;

Figure 6 shows a cross section through an inductor with a spherical shaped air gap between pole pieces; Figure 7 is a view from above on the cross section of the pole pieces on opposite sides of the air gap in a displaced position; Figure 8 shows a cross section through a modified inductor, whose pole pieces are provided with circular grooves ;

Figure 9 is a view from above on the pole pieces of the

inductor from Figure 8 at a displaced position;

Figure 10 shows a cross section through a further inductor, whose pole pieces are provided with radial grooves;

Figure 11 is a view from above on the pole pieces of the

inductor from Figure 10 at a displaced position;

Figure 12 shows a cross section through an inductor with

tapered pole pieces;

Figure 13 is a view from above of the pole pieces of the

inductor from Figure 12 at a displaced position;

Figure 14 shows a cross section through an inductor with a central crown-shaped pole piece;

Figure 15 is a view from above of the pole pieces of the

inductor from Figure 14 at a displaced position; Figure 16 shows a cross section through a further inductor with a central crown-shaped pole piece;

Figure 17 is a view from above of the pole pieces of the

inductor from Figure 16 at a displaced position;

Figure 18 is a further diagram illustrating the magnetic

field around a stator magnet and an oscillator mag- net of a modified embodiment of the electromagnetic generator;

Figure 19 shows a modified connection between housing and

oscillator; and

Figure 20 shows a further modified connection between housing and oscillator. Figure 1 is a cross sectional view of an electromagnetic generator 1. The generator 1 comprises an outer housing 2, which has a cylindrical shape. Within the housing 2 a magnetic oscillator 3 is disposed. Oscillator 3 can perform a pivoting motion 4 within the housing 2, if the housing 2 is vibrating. The electromagnetic generator 1 is further provided with a magnetic stator 5 which holds the oscillator 3 in a rest position 6. The electromagnetic generator 1 is further provided with the inductor 7 for converting the mechanical energy of the pivoting motion 4 into electric energy.

The oscillator 3 is provided with a needle like tip 8, which rests on a support 9 mounted in a bottom 10 of the housing 2. A contact point 11 between the needle like tip 8 and the support 9 forms the pivot point around which the pivoting motion 4 is performed.

The needle like tip 8 is connected to a conical part 12 of oscillator 3. At a rear face 13 of the conical part 12, a central bore 14 is provided, in which the lower end of a threaded rod 15 is inserted. The rod 15 passes through a central opening 16 of a coil 17 which is attached to the housing 2 and forms part of the inductor 7. The inductor 7 further comprises a front yoke part 18 and a rear yoke part 19. Permanent inductor magnets 20 and 21 are disposed on the side of the front yoke part 18 which is oriented towards the coil 17. Further permanent inductor magnets 22 and 23 are disposed on the side of the rear yoke part 19, which is oriented towards the coil 17. The polarity of the permanent magnets 20 to 23 is chosen such, that a magnetic circuit is formed through the coil 17.

Next to the rear yoke part 19 a cylindrical part 24 is located, which extends through a central opening 25 of a ring shaped stator magnet 26, which is attached to the housing 2. The cylindrical part 24 further abuts to an oscillator magnet 27, which interacts with the stator magnet 26 to form an attractive magnetic force, which presses the magnetic oscillator 3 towards the support 9. The arrangement of cylindrical part 24, stator magnet 26 and oscillator magnet 27 repeats another two times along rod 15. The sequence finally termi- nates with a cylindrical part 28 at the back end of rod 15.

It should be noted, that the front yoke part 18, the rear yoke part 19, the cylindrical part 24 and the oscillator magnets 27 each have a cylindrical shape and are provided with an inner bore through which the rod 15 passes. The inner bore of these components can also be provided with a thread for positioning and fixing these components on the rod 15. Thus the generator 1 and in particular the oscillator 3 is rotationally symmetric around a symmetry axis S.

The oscillator 3 has three degrees of freedom: a pivoting motion around the x-axis and y-axis and a rotation around the z-axis. A translational motion in the direction of the z-axis is unpratical since the magnetic force pressing the oscilla- tor 3 in place is strong enough for holding the oscillator 3 in place.

The conical part 12 and the cylindrical parts 24 are made from a material which is paramagnetic and has a high specific density such as tungsten. The front yoke part 18 and the rear yoke part 19 are preferably made from a ferromagnetic material such as a material based on iron. The center of gravity of the oscillator should be positioned within the inner and outer oscillator magnet 27 in order to avoid that the tip 8 is removed from the support 9 by any external force. The inductor magnets 20 to 23, the stator magnets and the oscillator magnets are preferably made from rare earth metals such as NdFeB.

The magnetic forces between one of the stator magnets 26 and an associated oscillator magnet 27 depends strongly on the relative position of the oscillator magnet 27 with respect to the stator magnet 26.

In the following, a radial direction 29 is a direction point- ing away from the contact point 11 between the needle like tip 8 and the support 9. A tangential direction 30 is the direction at right angle to the radial direction 29.

Figure 2 is a diagram, in which magnetic field lines 31 illustrate the direction and the strength of the magnetic field. Figure 2 is a cross section along the radial direction

29 and the tangential direction 30. The radial direction 29 is represented by an z-axis, while the tangential direction

30 is represented by an x-axis. Figure 2 further contains the contours of one of the stator magnets 26 and one of the oscillator magnets 27. As can be recognized from Figure 2, the polarity of the magnetization of the stator magnet 26 and of the oscillator magnet is 27 aligned in the radial direction 29. Thus, the polarity of the stator magnet 26 and the oscillator magnet vary along the radial direction 29.

It should be noted that the direction of the magnetization of the stator magnet 26 must not necessarily be aligned in parallel with the symmetry axis S, but can also be arranged at a angle smaller 90° with respect to symmetry axis S. For instance, the stator magnet 26 may also be composed of several magnets which are arranged in a ring shaped manner around the symmetry axis, wherein the orientation of the magnetization of each of these several magnets may be inclined with respect to the symmetry axis S. Figure 2 and 3 now illustrate two cases:

If the distance h along the z-axis is small enough, as shown in Figure 2, the magnetic force F between the stator magnet 26 and the oscillator magnet 27 is directed towards a tip 8 and pulls the stator magnet 26 and the oscillator magnet 27 together .

If, however, the distance h is large enough, as shown in Fugure 3, the magnetic force F is directed in the opposite direction away from the tip 8 and the stator magnet 26 and the oscillator magnet 27 are driven apart.

For ensuring a sufficient force pressing the tip 8 against the support 9, the distance h between the stator magnet 26 and the oscillator magnet 27 must sufficiently be narrowed down. Thus, the oscillator 3 is safely held in place. On the other hand, the pressing force must not be too high, since the mechanical damping would otherwise become too strong, due to the friction between tip 8 and support 9.

It can also be recognized from the distribution of the magnetic field lines 31 in Figure 2 and 3 that a magnetic repulsive force will be applied to the oscillator magnet 27, if the oscillator magnet 27 is displaced in x-direction out of its rest position 6 depicted in Figure 2 and 3, because a movement in x-direction would entail a higher energy density of the magnetic field in the direction, in which the oscillator magnet 27 is moving and a decreasing energy density of the magnetic field in the space, from which the oscillator magnet 27 is moving away. Thus, any displacement from the symmetry axis S of the stator magnet 26 will cause a repulsive force, which drives the oscillator magnet 27 back into its rest position. Since the strength of the repulsive force depends also on the position of the oscillator magnet 27 with respect to the stator magnet 26 and oscillator magnet 27, the resonance frequency of the electromagnetic generator 1 can be adjusted. The adjustment can be performed by adjusting the height of the support 9. The support 9 can be a screw, whose height within the housing 2 is variable. By adjusting the height of the support, the resonance frequency of the generator 1 can be adapted to the actual frequency spectrum of the vibrations.

If the electromagnetic generator 1 is exposed to vibrations, the oscillator 3 performs an oscillatory pivoting motion around contact point 11. By the motion of the oscillator 3, a current is induced in coil 17, since the magnetic field created by the inductor magnets 20 to 23 creates a changing magnetic flux within coil 17.

Figure 4 shows an enlarged perspective view of the inductor 7 from the electromagnetic generator 1 depicted in Figure 1. The inductor magnets 20 to 23 can be semicircular shaped magnets. The polarity of the magnetization of the inductor magnets 20 to 24 arranged side by side around the rod 15 is just the opposite. For instance, the north pole of inductor magnet 20 is located at the upper side oriented towards the air gap between inductor magnets 20 and 22, whereas the north pole of inductor magnet 21 is located at the lower side of inductor magnet 21. However, the orientation of the magnetization of inductor magnets 20 and 22 as well as 21 and 23, which are aligned above each other in the radial direction 29, is the same. Thus, a magnetic circuit through the coil 17, through the front yoke part 18 and the rear yoke part 19 is formed resulting in a magnetic flux through the coil 17. One disadvantage of the inductor 7 depicted in Figure 4 is that a current is only induced in the coil 17 if the oscillator 3 is moved in a direction 32, which is perpendicular to the separating slot 33 between the inductor magnets 20 to 23, i.e. in a direction parallel to the x-axis.

In order to generate electrical energy independent from the direction of the motion 4, a second inductor 7 must be provided, whose slot 33 is turned by 90 degrees. Both inductors 7 cannot be connected in series since due to the superposition principle this would be equivalent to an single inductor, whose magnetic field is restriced to opposing quadrats of the xy-plain, but whose magnetic field has two times the strength of the inductor magnets 20 to 23. Thus, the result would be, that a current is only induced if the direction of the motion 4 lies within these quadrants. Therefore it is necessary to provide each of the inductors with a separate rectifier, wherein the DC exits of same polarity may be interconnected.

Figure 5 shows a modified inductor 34, which creates a cur- rent in a coil 35 independent from the direction of the pivoting motion. The inductor 34 is provided with a yoke 36 which comprises a stationary part 37 and a moveable part 38. The stationary part 37 can be connected to the housing 2, whereas the moveable part 38 can be connected to the rear end of the rod 15, for instance to the cylindrical part 28. As the oscillator 3, the inductor 34 comprises a rotational symmetry around the symmetry axis S and is provided with a rod like central section 39 and a cylindrical outer section 40. The coil 35 is disposed in an intermediate space between central section 39 and outer section 40. The moveable part 38 is further provided with a permanent central inductor magnet 41 and an permanent outer inductor magnet 42. The polarity of the magnetization of the central inductor magnet 41 and the outer inductor magnet 42 is oriented in opposite directions. Thus, a magnetic circuit is formed through the central section 39 and the outer section 40 around the coil 35. The stationary part 37 and the moveable part 38 are only separated by a small air gap 43 which is delimited by stationary pole pieces 44 of the stationary part 37 and moveable pole pieces 45 of the movable part 38.

If the moveable part 38 is displaced from the rest position depicted in Figure 5 in a x- or y-direction, then the magnetic flux through the magnetic circuit will be diminished. In consequence a current will be induced in coil 35.

Figure 6 shows a cross sectional view of a modified embodiment of the inductor 34. In this embodiment of inductor 34, the air gap 43 has the shape of a spherical segment in order to keep the distance between stationary part 37 and moveable part 38 constant during any displacement of the moveable part 38.

Figure 7 is the view from above on the stationary pole pieces 44 and moveable pole pieces 45 during a displacement of the moveable part 38. As can be recognized from Figure 7, the overlapping section of the stationary pole pieces 44 and the movable pole pieces 45 are reduced if the movable part 38 is diplaced from the rest position 6. Figure 8 shows a cross sectional view of a further modified embodiment of the inductor 34. In this embodiment, stationary pole pieces 44 and the moveable pole pieces 45 are provided with a groove 46 along a circle around the symmetry axis S. Figure 9 shows an view from above on the stationary pole piece 44 and the moveable pole piece 45 during a displacement of the moveable part 38. It can be recognized from Figure 9 that the overlapping section of the stationary pole piece 44 and the moveable pole piece 45 is much smaller than in the embodiment shown in Figure 6 and 7. Figure 10 depicts a further embodiment, in which the stationary pole pieces 44 and the moveable pole pieces 45 are provided with radial grooves 47, which have also the effect to reduce the overlapping area of the stationary pole pieces 44 and the moveable pole pieces 45 once the moveable part 38 is displaced from the rest position 6 as can be recognized from Figure 11, which illustrates the lack of overlapping during a displacement of the moveable part 38. Figure 12 shows an embodiment, in which the stationary pole pieces 44 and the moveable pole pieces 45 are tapering towards the air gap 43, so that the overlapping area is also reduced during displacement of the moveable part 38 as can be recognized from Figure 13. In the embodiment shown in Figure 12 and 13, the outer inductor magnet has been omitted so that the magnetic flux through the yoke 36 is created by the central inductor magnet 41 only.

Figure 14 and Figure 15 show a further embodiment of the inductor 34, in which the pole pieces 44 and 45 are asymmetric with respect to a plane at right angle to the symmetry axis S. In particular a central movable pole piece 48 is provided with a central part 49 tapering towards the air gap 43. The central part is surrounded by a ring-shaped protru- sion 50, so that the central movable pole piece 48 has the shape of a crown.

In the rest position 6, a central stationary pole piece 51 is located next to the central part 49 of the central movable pole piece 48, and an outer movable pole piece 52 is located next to an outer stationary pole piece 53. Thus, the magnetic flux runs through the central part 49 of the movable pole piece 48 and the central stationary pole piece 51 as well through the outer movable pole piece 52 and the outer sta- tionary pole piece 53. If the movable part 38 is displaced from the rest position 6, the distance between the central part 49 of the central movable pole piece 48 and the central stationary pole piece 51 is increasing, whereas the distance between the protrusion 50 of the movable pole piece 48 and the outer stationary pole piece 53 is decreasing in the direction, in which the movable part 38 is displaced. Thus the magnetic flux is not only diminished by the displacement, but partially reversed.

Figure 14 and Figure 15 show a further embodiment of the inductor 34, in which the central part 49 is ring-shaped around a central recess 54. Also the central stationary pole piece 51 is ring-shaped around a central recess 55 for further enhancing the variation of the magnetic flux.

The arrangement of the stator magnet 26 and the oscillator magnet 27 can also be modified. Figure 18 shows an embodiment, in which the magnetization of the stator magnet 26 and the oscillator magnet has the same orientation and in which the oscillator magnet 27 is located within the ring-shaped stator magnet 26. By displacing the oscillator magnet along the z-axis, a pressing force or a drag force can be created similar to the arrangement depicted in Figures 2 and 3, since the oscillator magnet 27 will be pulled back in the neutral position depicted in Figure 18. If the oscillator magnet 27 is displaced from the rest position along the x-axis, the oscillator magnet is driven back to the rest position by a magnetic force acting in the tangential direction of the x- axis .

In the embodiments depicted in Figure 14 to 17, the protru- sion can also be located on the central stationary pole piece 51, if the central inductor magnet 41 is located in the stationary part 37.

Figure 19 shows a modified embodiment of the connection between oscillator 3 and housing 2. According to Figure 19, the oscillator 3 and the housing are connected by a thread 56, on which the oscillator 3 is pulling. Figure 20 shows a further embodiment, in which the conical part 12 is provided with a hook 57, which engages another hook 58, which is attached to the housing 2. Hook 57 is further provided with a pin 59, which contacts hook 58. If the oscillator 3 is pulled away from hook 58, pin 59 presses against the inside of hook 58 and allows the oscillator to pivot around a contact point 60 between pin 59 and hook 58. The electromagnetic generator 1 described herein is particularly suitable for sensor arrangements which cannot be connected to a power line and must be provided with their own energy source. Such a sensor arrangement can also be provided with a transmission unit for wireless transmission of the sensor data to a processing unit, which further processes the sensor data.

The electromagnetic generator 1 may be particular suitable for sensors, which are located in the driving rod for a flap within the wing of an airplane.

In particular a prototype of the electromagnetic generator 1 was constructed whose resonance frequency was set at 35 Hz. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be appli- cable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

Claims :

1. An electromagnetic generator comprising:

- a magnetic oscillator (3), which is provided with at least one oscillator magnet (27) and which is arranged for performing a pivoting motion (4), if the electromagnetic generator is vibrating;

- a magnetic stator (5), provided with at least one stator magnet (26), which interacts with the at least one oscillator magnet (27) and creates a repulsive force acting on the oscillator (3) driving the oscillator (3), if displaced from the rest position (6), back to the rest position (6);

- a conductor arrangement (17, 35), in which a current is induced by the change of a magnetic flux through the conduc- tor arrangement (17, 35) caused by the relative motion of the magnetic oscillator (3) with respect to the conductor arrangement (17, 35),

c h a r a c t e r i z e d i n t h a t

- the polarity of the at least one oscillator magnet (27) and the at least one stator magnet (26) vary along a radial direction (29) with respect to the pivoting motion (4) and that

- the magnetic oscillator (3) has more than one degree of freedom for its pivoting motion (4) .

2. The electromagnetic generator according to Claim 1, wherein the magnetic oscillator (3) comprises a series of oscillator magnets (27) along a radial direction (29) from a pivot point (11), the polarity of the oscillator magnets (27) being aligned along the radial direction (29) with respect to the pivoting motion (4) .

3. The electromagnetic generator according to Claim 1 or 2, wherein the magnetic stator (5) comprises at least one stator magnet (26) having a inner opening, through which the magnetic oscillator (3) extends.

4. The electromagnetic generator according to any one of Claims 1 to 3,

wherein at least one stator magnet (26) is displaced at a radial distance from an associated oscillator magnet (27) causing an attractive magnetic force between stator magnet (26) and oscillator magnet (27) in a radial direction of the pivoting motion (4) .

5. The electromagnetic generator according to any one of Claims 1 to 4,

wherein at least one stator magnet (26) is displaced at a radial distance from an associated oscillator magnet (27) causing a repulsive magnetic force between stator magnet (26) and oscillator magnet (27) in a radial direction of the pivoting motion (4) .

6. The electromagnetic generator according to any one of Claims 1 to 5,

wherein the magnetic oscillator (3) comprises a tip (8) resting on a support (9), the contact point (11) between tip (8) and support (9) functioning as a pivot point for the pivoting motion (4) and the support (9) exerting a pressing force on the magnetic oscillator (3) in equilibrium with the magnetic force between the at least one stator magnet (26) and the at least one oscillator magnet (27) .

7. The electromagnetic generator according to any one of Claims 1 to 5,

wherein the magnetic oscillator (3) is provided with a con- necting element exerting a drag force on the magnetic oscillator (3) in equilibrium with the magnetic force between the at least one stator magnet (26) and the at least one oscillator magnet (27 ) .

8. The electromagnetic generator according to any one of Claims 1 to 7,

wherein the magnetic oscillator (3) is rotationally symmetric with respect to a symmetry axis (S) extending in a radial direction (29) with respect to the pivoting motion (4) .

9. The electromagnetic generator according to any one of Claims 1 to 8,

wherein the at least one stator magnet (26) is a ring.

10. The electromagnetic generator according to any one of Claim 1 to 9,

wherein the conductor arrangement comprises a coil (17, 35) extending in a tangential direction (30) with respect to the pivoting motion (4) .

11. The electromagnetic generator according to any one of Claims 1 to 10,

wherein the conductor arrangement comprises a coil (17), the magnetic oscillator (3) passing through the inner opening (16) of the coil (17) and the oscillator (3) being provided with inductor magnets (20 - 23) generating a magnetic field passing through the coil (17) along a longitudinal axis of the coil (17) .

12. The electromagnetic generator according to any one of Claims 1 to 11,

wherein the conductor arrangement comprises a coil (35) wound around a yoke (36) having a stationary part (37) and a movable part (38) connected to the magnetic oscillator (3) and being provided with yoke magnets (41, 42) generating a magnetic flux in the yoke (36), and wherein the yoke (36) has an air gap (43) between the stationary part (37) and the movable part (38), which is delimited by stationary pole pieces (44) of the stationary part (37) and movable pole pieces (45) of the movable part (38) .

13. The electromagnetic generator according to Claim 12, wherein the air gap (43) has the shape of a spherical segment .

14. The electromagnetic generator according to Claim 12 or 13,

wherein the stationary pole pieces (44) and/or oscillatory pole pieces (45) are provided with at least one groove (46, 47)

15. The electromagnetic generator according to Claim 14, wherein the at least one groove (46) extends along a circle centered on the symmetry axis (S) of the magnetic oscillator (3) in the rest position (6) .

16. The electromagnetic generator according to Claim 14 or 15,

wherein the groove (47) extends in radial directions (29) from the symmetry axis (S) of the magnetic oscillator (3) in the rest position (6) .

17. The electromagnetic generator according to Claim 14 or 15,

wherein a central pole piece (48) of the yoke (36) is provided with a central part (49) located opposite to the other central pole piece (51), and is further provided with a protrusion (50) extending towards an opposite outer pole piece ( 53 ) .

18. The electromagnetic generator according to Claim 17, wherein the central part (49) and the opposite central pole piece (51) are provided with a central recess (54, 55) .

19. A sensor arrangement having a sensor operated by electric power and transmitter for wireless transmission of sensor data, wherein the sensor arrangement comprises a electromagnetic generator (1) according to any one of the Claims 1 to 18.