Flywheel device for position stabilization of a spacecraft

Abstract

The invention relates to a flywheel device for position stabilization of a spacecraft, comprising a carrier (1), a rotor (2), a magnetic drive (4) for the rotatingly driving the rotor (2) relative to the carrier (1), and a roller bearing (3) arranged between the rotor (2) and the carrier (1). A magnetic force can be generated between the rotor (2) and the carrier (1) by means of the magnetic drive (4) in order to pre-stress the rolling bearing (3). The outer diameter (A) of the rotor (2) can have, for example, only a maximum of 2.5 times of the rolling bearing diameter (W).

Claims

1. A flywheel device for position stabilization of a spacecraft, the flywheel device comprising: a carrier; a rotor; a magnetic drive configured to drive the rotor rotatingly relative to the carrier; and a roller bearing arranged between the rotor and the carrier, wherein the magnetic drive is configured to generate a magnetic force between the rotor and the carrier for pre-stressing the roller bearing, wherein an outer diameter of the rotor is at most 2.5 times a diameter of the roller bearing.

2. The flywheel device of claim 1, wherein the outer diameter of the rotor is at most 2 times the diameter of the roller bearing.

3. The flywheel device of claim 1, wherein the outer diameter of the rotor is at most 1.5 times the diameter of the roller bearing.

4. The flywheel device of claim 1, wherein the outer diameter of the rotor is at most 1.3 times the diameter of the roller bearing.

5. The flywheel device of claim 1, wherein the outer diameter of the rotor is at most 1.2 times the diameter of the roller bearing.

6. The flywheel device of claim 1, wherein the outer diameter of the rotor is at most 1.0 times the diameter of the roller bearing.

7. The flywheel device of claim 1, wherein the magnetic drive comprises: a magnetic ring arranged at the rotor and comprising magnetic poles; a magnetic circuit closing means arranged at the carrier opposite to the magnetic ring; and magnetic coils arranged at the carrier between the magnetic ring and the magnetic circuit closing means.

8. The flywheel device of claim 7, wherein during operation of the flywheel device the magnetic drive is configured to generate the magnetic force between the magnetic ring and the magnetic circuit closing means.

9. The flywheel device of claim 1, wherein precisely one roller bearing is arranged between the rotor and the carrier.

10. The flywheel device of claim 1, wherein the roller bearing is configured to carry radial forces and axial forces.

11. The flywheel device of claim 1, wherein the roller bearing comprises: a lower bearing ring arranged at the carrier; and an upper bearing ring arranged at the rotor.

12. The flywheel device of claim 11, wherein the upper bearing ring is formed integrally at the rotor.

13. The flywheel device of claim 1, further comprising an additional mass provided at the rotor.

14. The flywheel device of claim 13, wherein the additional mass is an additional mass ring arranged on the rotor.

15. The flywheel device of claim 1, further comprising a holding magnet arranged at the rotor or on the carrier and configured to act between the rotor and the carrier to generate a magnetic holding force between the rotor and the carrier.

16. The flywheel device of claim 1, further comprising a greasing device configured to grease the roller bearing.

Description

(1) These and further advantages and features will be explained in what follows with regard to an example by reference to the accompanying FIGURE. It shows

(2) FIG. 1 a section through a flywheel device.

(3) FIG. 1 shows a sectional view of a flywheel device for position stabilization of a spacecraft as for example a satellite.

(4) The flywheel device comprises a carrier 1 that carries a rotor 2 rotatably.

(5) The carrier 1 should have sufficient stability and in particular torsional stiffness in order to be able to carry the rotor 2 reliably also for the forces acting during operation.

(6) The rotor 2 is supported via a roller bearing 3 on the carrier 1. The rotor 2 constitutes the actual flywheel or balance wheel that rotates during operation with a high rotational frequency and generates due to this the desired gyroscopic forces for stabilization of the spacecraft.

(7) The rotor 2 has an appropriate diameter, for example of up to 200 mm or even more. Due to the fact that the entire mass of the rotor 2 is arranged outwards, i.e. far from the middle axis X, the desired gyroscopic forces can be generated with high effectivity.

(8) For a rotational drive of the rotor 2 relative to the carrier 1 a magnetic drive 4 is provided. The magnetic drive 4 comprises a magnetic ring 5 that is carried by the rotor 2 and that comprises an appropriate number of magnetic poles.

(9) Further, the magnetic drive 4 comprises several magnetic coils 6 that are arranged in appropriate manner in or at the carrier 1 and that can be controlled by a control that is not illustrated.

(10) Further, at the back of the carrier 1 magnetic circuit closing means 7 are provided also as part of the magnetic drive 4.

(11) The magnetic drive 4 is in principle a magnetic linear motor that is arranged circularly. The control controls the magnetic coils 6 in appropriate manner such that they act together with the magnetic poles in the magnetic ring 5 and that they cause rotation of the rotor 2. The design of such a magnetic drive 4 is known so that a detailed description will be omitted here.

(12) The control electronics and in particular further components (power electronics or the like) may for example be arranged on the carrier 1 in the space that is enclosed by the rotor 2 andas can be seen in FIG. 1open. This allows a very compact design of the flywheel device. In the space also components of a re-greasing system serving as a greasing device may be arranged, which comprises e.g. a piezo element for providing lubricant or the roller bearing 3.

(13) The roller bearing 3 may for example be a grooved ball bearing as illustrated in FIG. 1. However, also other bearing types such as for example cylinder roller bearings, barrel type bearings or the like may be used. The roller bearing 3 comprises an outer bearing ring 8 (also called upper bearing ring) as well as an inner bearing ring 9 (also called lower bearing ring). Between the two bearing rings 8, 9 the rolling bodies are arranged, which are in the example illustrated in FIG. 1 balls 10.

(14) The outer bearing ring 8 is an integral part of the rotor 2. Speaking differently, one could say that the rotor 2 of the example illustrated in FIG. 1 is formed by the bearing ring 8. For other examples not illustrated in FIG. 1 the outer bearing ring 8 may also be formed as a separate element that is fixed at the rotor 2.

(15) For a proper operation of the roller bearing 3 an according and sufficient number of balls 10 has to be arranged equally distributed between the bearing rings 8, 9. In order to ensure an equal distance between the balls 10 around the circumference of the roller bearing, the balls 10 are held in known manner by a bearing cage that is not shown in FIG. 1. The bearing cage may not only be used for holding the balls in their respective positions, but may also be used to provide a lubricant in order to guarantee a long time greasing of the roller bearing 3. In particular for use of the flywheel device in a satellite typically lifetime lubrication is desired.

(16) Greasing may also be realized e.g. due to centrifugal forces and e.g. by a not illustrated greasing device that is arranged on the rotating parts. Also, a greasing device may be provided in the open space in the inner part of the roller bearing 3, which uses e.g. capillary greasing or an active greasing system having lubricant providing means. The lubricant providing means may e.g. be a piezo injection element.

(17) The rotor 2 and the roller bearing 3 are arranged rotationally symmetric around the middle axis X. The outer diameter A of the rotor 2 may here only be slightly larger than the roller bearing diameter W of the roller bearing 3.

(18) The roller bearing diameter W is defined such that it corresponds to the diameter of the circle around which the centers of gravity of the rolling bodies (here: the balls 10) move.

(19) The smaller the ratio between the outer diameter A of the rotor 2 and the roller bearing diameter W, the more efficient and compact the rotor 2 can be designed. For example, a ratio of maximally 1.5 has turned out in particular appropriate. In the exemplary flywheel device illustrated in FIG. 1 the ratio between the outer diameter A and their roller bearing diameter W is approximately 1.2.

(20) As already explained the mechanical support of the rotor 2 on the carrier 1 is provided only by a single roller bearing 3. To prevent that the roller bearing 3 falls apart and to allow a statically determined support, a magnetic force between the rotor 2 and the carrier 1 (attractive force) is generated in addition by the magnetic drive 4. This magnetic force has to be dimensioned sufficiently large in order to prevent falling apart of the roller bearing 3.

(21) In this manner the flywheel device can be operated reliable and stable.

(22) In the example illustrated in FIG. 1 an additional mass having the form of an additional mass ring 11 is provided on the rotor 2. The additional mass ring 11 is arranged on the upper side of the rotor 2 and enhances the overall flywheel mass of the rotor 2.

(23) Since the additional mass ring 11 constitutes a separate part with respect to the rotor 2 or the outer bearing ring 8, during manufacturing of the flywheel device it is possible in a simple manner to provide different additional masses by selecting different additional mass rings 11, in order to achieve different flywheel effects.

(24) If, in particular in the case of a heavy additional mass provided by the additional mass ring 11, the mass of the entire rotor 2 is large, there will be the possibility that the magnetic holding force of the magnetic drive 4 is not sufficient to prevent a separation of the roller bearing 3. In this case it may be advantageous, if additionally a holding magnet, which is not illustrated in FIG. 1, is provided at the rotor 2 or at the carrier 1 in order to generate an additional magnetic holding force between the rotor 2 and the carrier 1. As the holding magnet ring does not comprise additional mechanically movable parts, it does not suffer from wearing.

(25) Moreover, it does not generate additional vibrations that could impair operation of the flywheel device.