DRIVE ARRANGEMENT

Abstract

A drive arrangement for a rotational body device comprising a shaft which is held rotatably with respect to a rotational axis, a first bearing module and a second bearing module, each with at least one elastic support element for supporting the shaft, an electric motor, an electrically actuable stabilisation device, and a housing. At least the first bearing module provides a mass body which is held in a non-rotatable fashion with respect to rotational axis by means of the at least one elastic support element. The shaft is supported in a rotatable fashion on the mass body by a bearing of the first bearing module.

Claims

1. A drive arrangement for a rotational body device including a shaft (1) provided rotatable with respect to a rotational axis (15), a first bearing module (5) and a second bearing module (6) each having at least one resilient support member (8) for supporting the shaft, an electric motor with a stator (3) and a rotor (2) which is provided so as to be rotatable relative to the stator (3) and is connected rotationally fixedly to the shaft (1), an electrically controllable stabilizing means, which acts on the rotor (2) in such a manner, that interference forces acting on the shaft (1) and the rotor (2) during rotation are counteracted, a housing (4) at least partially encompassing the stator (3) and a sensor unit for detecting a rotation or twist of the shaft (1) relative to the stator (3), wherein at least the first bearing module (5) is provided with a mass body (7) held non-rotatable with respect to the rotation axis (15) by means of the at least one elastic support element (8) and wherein the shaft (1) is rotatably supported on the mass body (7) via a bearing (10) of the first bearing module (5).

2. The drive arrangement according to claim 1, wherein a vertical measured distance (24) from a center of gravity (25) of the mass body (7) to an effective center plane (23) of the bearing (10) associated with the first bearing module (5) is smaller than an effective bearing diameter (31) of the bearing (10) associated with the first bearing module (5).

3. The drive arrangement according to claim 1, wherein the bearing (10) associated with the first bearing module (5) is provided in a recess of the mass body (7).

4. The drive arrangement according to claim 1, wherein a weight of the mass body (7) corresponds to at least 10% of a weight of the rotating components of the rotational body device.

5. The drive arrangement according to claim 1, wherein at least three support elements (8) are provided arranged circumferentially distributed.

6. The drive arrangement according to claim 1, wherein the sensor unit is adapted for detecting a tilt of the shaft (1) around the axis of rotation (15) and at least one tilt axis oriented perpendicular to the rotational axis (15).

7. The drive arrangement according to claim 1, wherein the sensor unit comprises a speed sensor (16) and/or a rotational angle transmitter and/or a position sensor (17, 18) for the shaft (1).

8. The drive arrangement according to claim 1, wherein a first position sensor (17) of the sensor unit is provided adjacent to the first bearing module (5) and a second position sensor (18) for the shaft (1) is provided adjacent to the second bearing module (6).

9. The drive arrangement according to claim 8, wherein the first position sensor (17) and the second position sensor (18) in each case provides at least one displacement and/or speed and/or acceleration sensor and so cooperates with the sensor unit that a displacement of the shaft (1) perpendicular to the axis of rotation (15) is detected by means of the position transmitters (17, 18) and/or deviation from the tilt axis in terms of magnitude and/or directionally is determined.

10. The drive arrangement according to claim 1, wherein stops (20) are provided for limiting a displacement of the elastically mounted mass body (7) associated with the first bearing module (5), and/or wherein a maximum displacement path (19) for the mass body (7) is smaller than the air gap (21) formed in the electric motor between the stator (3) and the rotor (2).

11. The drive arrangement according to claim 1, wherein the rotor (2) of the electric motor held fixed against rotation on the shaft (1) and the at least one position sensor (17, 18) of the sensor unit associated with the shaft (1) are provided between the two bearing modules (5, 6) and/or wherein the position sensors (17, 18) are on surfaces opposite the rotor (2).

12. The drive arrangement according to claim 1, wherein the first bearing module (5) and/or the second bearing module (6) provide a roller bearing and/or a slide bearing for supporting the shaft (1).

13. The drive arrangement according to claim 1, wherein an elastomer ring (14) is provided as the elastic support element for the first bearing module (5) and/or for the second bearing module (6).

14. The drive arrangement according to claim 1, wherein the stabilizing means includes magnetic support members arranged circumferentially distributed about the axis of rotation (15), and wherein the magnetic support members are constructed as current-carrying windings and individually are electrically controllable such that a radial balancing force counteracting disturbing forces is produced.

15. The use of a drive arrangement according to claim 1 in a laboratory centrifuge, wherein a sample receiving body is provided rotationally fixed on the shaft (1), which has sample recesses for laboratory samples arranged distributed circumferentially.

16. The drive arrangement according to claim 1, wherein a vertical measured distance (24) from a center of gravity (25) of the mass body (7) to an effective center plane (23) of the bearing (10) associated with the first bearing module (5) is less than one thirtieth of the effective bearing diameter (31) of the bearing (10) associated with the first bearing module (5).

17. The drive arrangement according to claim 1, wherein the center of gravity (25) of the mass body (7) is in the effective center plane (23) of the bearing (10) associated with the first bearing module (5).

18. The drive arrangement according to claim 1, wherein a weight of the mass body (7) corresponds to at least 20% of the weight of the rotating components of the rotational body device.

Description

[0013] Further advantages, features and details of the invention can be taken from the further subclaims and the following description. Characteristics mentioned there can relevant to the invention either individually or in any desired combination. The drawings are merely illustrative of the for clarification of the invention and are not limiting.

[0014] There is shown in:

[0015] FIG. 1 a schematic diagram of a drive arrangement of the invention for a rotational body device having a resiliently supported shaft and a mass body according to the section AA,

[0016] FIG. 2 a plan view of the drive arrangement according to FIG. 1,

[0017] FIG. 3 a visualization of the physical operating principle of the drive arrangement according to the invention,

[0018] FIG. 4 an arrangement of a bearing of the drive arrangement to the elastically held mass body,

[0019] FIG. 5 a second embodiment of the drive arrangement of the invention in a sectional illustration,

[0020] FIG. 6 a perspective view of a third embodiment of the drive arrangement according to the invention, and

[0021] FIG. 7 a sectional view of the drive arrangement according to FIG. 6.

[0022] A drive assembly according to the invention according to FIGS. 1 and 2 comprises, in the illustrated rest position, a substantially vertically oriented shaft 1, an electric motor with a rotor 2 fixed rotationally on the shaft 1, a stator 3 surrounding the rotor 2, which is set in a bell-shaped housing 4, as well as a first bearing module 5 and a second bearing module 6 for supporting the shaft 1. The first bearing module 5 provides a mass body 7, which surrounds the shaft 1 on the housing side, and three resilient support elements 8 distributed circumferentially disposed non-rotatable with respect to the shaft 1. A recess 9 is formed in the mass body 7 which serves to receive a bearing 10 assigned to the first bearing module 5. The bearing 10 is formed by way of example in the manner of a ball bearing, a stationary outer ring 11 of the bearing 10 being supported on the mass body 7 and the bearing 10 being connected to the shaft 1 by an inner ring 12. In the region of the first bearing module 5, the shaft 1 is resiliently mounted. In this case, the elasticity is provided by the elastic support elements 8. Similarly, in the area of the second bearing module 6 the shaft 1 is elastically supported by a bearing 13 assigned to the second bearing module 6. The bearing 13 is likewise designed in the manner of a ball bearing and is supported in the housing 4 via an elastomer ring 14.

[0023] The shaft 1, resiliently supported by the bearing modules 5, 6, is rotatably supported with respect to a rotation axis 15. At the free end of the rotation axis 15 opposite the first bearing module 5, which extends out from the housing 4, a rotating body, for example a sample-receiving body, is mounted fixed against rotation. The drive assembly according to the invention is particularly part of a rotational body means which is designed for example in the manner of a laboratory centrifuge.

[0024] As part of the drive arrangement, there is provided a not fully illustrated sensor device and a likewise not illustrated stabilization device. The stabilization device includes a plurality of magnetic support members arranged circumferentially distributed about the rotation axis 15, associated with the stator 3, which have current-carrying windings and are so individually controllable electrically, that disturbing forces that occur during operation of the drive assembly are counteracted from the stabilization device by balancing forces acting radially via the magnetic support members. With the aid of the stabilizing device, interfering influences occurring during operation can be reduced and the vibration tendency of the drive arrangement can be counteracted. The stabilization device receives measurement or, as the case may be, control signals of a sensor unit. The sensor unit is used to detect a rotation of the shaft 1 about the axis of rotation 15 and additionally a tilt of the shaft 1 about a tilt axis oriented perpendicular to the axis of rotation 15 or as the case may be a parallel displacement of the shaft 1 perpendicular to the rotation axis of 15. For this purpose, the position of the shaft 1 is determined via a speed sensor 16, a first position sensor 17 and a second position sensor 18. The first position sensor 17 which is provided between the first bearing module 5 and the electric motor cooperates with the second position sensor 18 which is provided between the electric motor and the second bearing module 6, for example by means of an absolute measuring arrangement so that a displacement of the shaft 1 perpendicular to the axis of rotation 15 or a pivoting of the shaft 1 about a tilting axis oriented perpendicular to the axis of rotation 15 is determined in terms of magnitude and/or direction. The first position sensor 17 and the second position sensor 18 are formed, for example, in the manner of a displacement, velocity or acceleration sensor. Each of the position sensors 17, 18 has an encoder disc 17.1, 18.1 rotationally fixed connected to the shaft and detectors 17.2. 18.2 associated with the transmitter discs 17.1, 18.1. The detectors 17.2, 18.2 are provided for example distributed in the circumferential direction about the encoder disk of 17.1, 18.1 or are ring shaped. By way of example four detectors 17.2, 18.2 are provided in the illustrated example, which are provided in a measuring plane extending perpendicular to the rotational axis 15 at an angle of 90 to each other. For example, a measurement with only two mutually angularly displaced associated detectors 17.2, 18.2 take place. The detectors are, for example, offset by 90 relative to one another in the measuring plane. The speed sensor 16 is associated with the shaft 1 in the region of the first bearing module 5. It includes, for example, a Hall sensor, which is adapted to detect the rotation speed, the rotation angle or the rotation direction of the shaft 1, and which interacts with an encoder associated with the Hall sensor. For example, the Hall sensor is associated with the shaft in the area of the first bearing module 5 and the incremental encoder is mounted on the mass body 7. Since the mass body 7 is supported on the shaft 1 in a play-free and rotatable manner via the bearing 10, there results an exact positional arrangement of the functional components of the rotational speed sensor 16 when the drive arrangement is excited to oscillation during operation.

[0025] Due to the provision of the circumferentially arranged distributed elastic support elements 8 in the area of the first bearing module 5 and the elastomer ring 14 in the area of the second bearing module 6, the shaft 1 is supported resiliently and mounted displaceably in relation to the rest position of the drive assembly axis of rotation 15. The bearing modules 5, 6 enable in this way a soft or yielding support of the shaft 1. Due to the soft support of the shaft 1 in cooperation with the stabilizing means, the vibration behavior of the drive assembly, in particular during the run-up in the range of a resonant frequency or during continuous operation at the nominal operating speed, are positively influenced.

[0026] In operation, interfering influences will arise, for example, due to an asymmetrical distribution of mass of the rotating body, which will be counteracted, in particular during the run-up operation to the rated speed, by an active intervention by the stabilizing device. Insofar, in particular in the region of the resonance rotating speed, the interference influences or forces are detected by sensors and balancing forces are imparted on the rotor 2 by the magnetic support members, which dampen the vibration of the shaft 1 with the thereon mounted rotor 2 and limit the amplitude of the oscillations. At the nominal operating point, an active vibration damping by means of the stabilization device is also conceivable in principle. However, due to the high rotational speed, the power requirement for the operation of the stabilizing device is very high. For this reason, the tendency to vibration of the drive assembly, particular in the region of the nominal speed, is passively reduced in the soft-supported shaft 1 by the provision of the mass body 7. For this purpose, the mass body 7 is held non-rotatably relative to the elastic support elements 8. The shaft 1, which is rotatably supported relative to the mass body 7 via the bearing 10 assigned to the first bearing module 5, can be vibrated or displaced together with the mass body 7 in a vibration oscillation oriented perpendicular to the axis of rotation 15. A maximum displacement 19 for the mass body 7 and the shaft 1 is in this case defined by stops 20 provided on the housing 4. The maximum displacement path 19 is thereby smaller than an air gap 21 formed in the electric motor between the rotor 2 and the stator 3.

[0027] The elastic support elements 8 are formed, for example, from an elastomer material. The support elements 8 can in particular be made of elastomeric solid material or be formed by layers of elastomer and non-elastomer annular disks which are connected to one another. The non-elastomer annular disks can, for example, be made of a metallic material. The support elements 8 can be realized, for example, in the form of cuboids or cylindrically. In the illustrative case, the resilient support elements 8 are mounted outside the housing 4. The elastic support elements 8 support the mass body 7 via substantially horizontally extending arms 22.

[0028] By selecting the composition of the support elements 8, a specific bearing can be formed with a desired bearing stiffness or a desired attenuation. For example, the bearing can be radially soft and axially hard relative to the axis of rotation 15.

[0029] The elastomer ring 14 of the second bearing module 5 can be made, for example, from a solid elastomer material. For example, the geometry of the elastomer ring 14 may be chosen such that for the second bearing module 6, a defined stiffness, or a predetermined amount of attenuation, is set. The elastomer ring 14 can, for example, be implemented in a meandering shape.

[0030] The basic idea of the invention is illustrated in the schematic diagram of FIG. 3. It is essential that the elastically mounted mass body 7 is held fixed against rotation with respect to the shaft 1 by the resilient support elements 8. The shaft 1 is supported on the mass body 7 by means of the bearing 10 assigned to the first bearing module 5. In the region of the second bearing module 6, the provision of a mass body 7 is dispensed with. The bearing 13, which is assigned to the second bearing module 6, is directly held resiliently via the elastomer ring 14. In this case, the mass body 7 is not realized as a rotating mass body 7, but rather is held yieldingly by the elastic support elements 8.

[0031] FIG. 4 shows an example of the dimensioning of the mass body 7 and the relationship thereof to the bearing 10 of the first bearing module 5. The bearing 10 defines by its geometry an effective center plane 23. A vertical distance 24 to a center of gravity 25 is shown exaggerated only for illustrative clarity. The vertical distance 24 is in accordance with the invention smaller than an effective bearing diameter 31 of the bearing 10. Preferably, the distance 24 from the center of gravity 25 of the mass body 7 to the effective center plane 23 of the bearing 10 is smaller than half the effective bearing diameter 31 of the bearing 10. It is particularly preferred that the distance 24 from the center of gravity 25 of the mass body 7 of the effective center plane 23 of the bearing 10 is less than one-thirtieth of the effective bearing diameter 31 of the bearing 10. For example, the vertical distance 23 [sic] is less than 10 mm and preferably less than 1 mm. More preferably, the center of gravity 25 is located in the effective center plane 23 of the bearing 10 associated with the first bearing module 5.

[0032] In the present case, the effective bearing diameter 31 is determined by the distance between the centers of the balls of the ball bearing. Depending on the bearing construction, the effective bearing diameter 31 can, for example, stop at a center axis distance of the rolling elements of a roller, barrel or needle bearing or as the case may be a diameter of a plain bearing bush.

[0033] FIG. 5 shows an alternative embodiment of the drive arrangement according to the invention, which is designed differently in particular in the region of the first bearing module 5. As before the mass body 7 surrounds the shaft 1 and defines an opening recess 9 provided for receiving the bearing 10. The resilient support elements 8 are arranged circumferentially distributed in relation to the rotational shaft 15 inserted in pocket-shaped recesses 26 of the mass body 7, so that a particularly slim construction and the arms 22 projecting relative to the housing 4 are dispensed with. The center of gravity 25 of the mass body 7 lies in the effective center plane 23 of the bearing 10.

[0034] The same components and component features are designated by like reference numerals.

[0035] According to a third exemplary embodiment of the invention according to FIGS. 6 and 7, the electric motor is designed housing-less. The stator 3 is fixed between two housing segments 4.1, 4.2 interconnected by tie rods. The housing segments 4.1, 4.2 are supported by means of three circumferentially evenly arranged cantilever arms 27, and elastomer bodies 28 associated with the cantilever arms 27, on a base plate 29 of the drive arrangement. Likewise, the mass body 7 is fixed to the base plate 29 via the arms 22 and the elastic support elements 8. The shaft 1, which extends out of the first housing segment 4.1 via an end-face opening 30, is designed to receive a rotational body (not shown). The rotational body has on an underside facing the drive assembly, for example, a bell-shaped recess which is adapted to the bell shape of the drive assembly and into which in any case the drive assembly protrudes in sections.

[0036] For example, the drive arrangement is supported by the cantilever arms 27 on a stationary support element, for example a laboratory table. The support of the drive arrangement in the region of the cantilever arms 27 then results in that the mass body 7 is provided suspended, in relation to the electric motor or the stator 3, via the elastomer bodies 28, the base plate 29 and the support members 8 is. For example, a recess in the laboratory table can be provided for fixing the drive arrangement, which is determined with regard to its geometry in such a way that the drive arrangement is inserted into the recess and the first bearing module 5 with the mass body 7 is arranged below a workbench defined by the laboratory table.