Device provided with a bearing-in-bearing

Abstract

A device includes a bearing-in-bearing with an inner ring, an intermediate ring and an outer ring. Between the inner ring and the intermediate ring and between the intermediate ring and the outer ring, inner roller elements, and outer roller elements, are attached, respectively. The bearing-in-bearing is attached between two components that can rotate in relation to each other, a shaft and a housing, of which one component is or can be connected to a drive. A transmission is provided between the intermediate ring and the driven component in order to drive the intermediate ring. The transmission is a contactless transmission.

Claims

1. A device provided with a bearing-in-bearing comprising: an inner ring, an intermediate ring and an outer ring, wherein between the inner ring and the intermediate ring and between the intermediate ring and the outer ring, inner roller elements and outer roller elements are respectively provided, wherein the bearing-in-bearing with the inner ring and the outer ring is provided between two components in the device that are rotatable in relation to each other, said two components being a shaft and a housing, of which one component is connected to a drive, wherein the device is provided with a transmission between the intermediate ring and the component connected to the drive in order to drive the intermediate ring, wherein the transmission is a contactless transmission, and either the inner ring or the outer ring is a driven bearing ring, which is driven via said component connected to the drive, wherein the transmission comprises one or more permanent magnets which rotate along with the driven bearing ring and a braking ring which is connected with the intermediate ring, the braking ring containing a ring of non-magnetic yet electrically conductive material, in such a way that there is a gap between the one or more permanent magnets and the braking ring.

2. The device according to claim 1, wherein the thickness of said gap is smaller than one and a half millimetres.

3. The device according to claim 1, wherein the braking ring around the ring of non-magnetic yet electrically conductive material contains a ring of magnetically conductive material.

4. The device according to claim 1, wherein a fluid film is applied in the gap in the transmission.

5. The device according to claim 4, wherein both the driven bearing ring and the intermediate ring are provided with a ring, with a gap between both rings, wherein the gap is filled with a fluid.

6. The device according to claim 5, wherein the thickness of said gap is one hundred micrometres or smaller.

7. The device according to claim 1, wherein the transmission to drive the intermediate ring is a magnetic gear transmission between the two components able to rotate in relation to each other.

8. The device according to claim 1, wherein the device is provided with a magnetic brake in order to slow the intermediate ring in a contactless manner.

9. The device according to claim 1, wherein, if the driven bearing ring is the inner ring, the intermediate ring is constructed of two concentric rings comprising an inner concentric ring and an outer concentric ring, attached to each other using a press fitting to form a whole, wherein the inner concentric ring joins the inner ring and the inner roller elements in forming a first bearing and wherein the outer concentric ring joins the outer ring and the outer roller elements in forming a second bearing that is attached concentrically around the first bearing.

10. The device according to claim 1, wherein the inner ring, the intermediate ring and the inner roller elements and/or the intermediate ring, the outer ring and the outer roller elements is a single or double-row ball bearing, a single or double-row angular contact ball bearing, four-point bearing, single or double-row cylinder bearing, tapered roller bearing, swivel-joint roller bearing, needle bearing, thrust ball bearing or cylindrical roller thrust bearing.

11. The device according to claim 10, wherein the bearing-in-bearing is usable for speeds greater than 1.5×10.sup.6 ‘n.dm’ [revolutions per minute.millimetre].

12. The device according to claim 11, wherein the bearing-in-bearing is usable for speeds greater than 1×10.sup.6 ‘n.dm’ [revolutions per minute.millimetre].

13. The device according to claim 1, wherein the bearing-in-bearing is oil-lubricated.

14. The device according to claim 1, wherein if the driven bearing ring is the inner ring, the bearing-in-bearing is grease-lubricated.

15. The turbo machine, wherein it contains a device according to claim 1 for the bearing of at least one shaft with an impeller.

16. The screw compressor, wherein it contains a device according to claim 1 for the bearing of at least one shaft with a rotor.

17. A device provided with a bearing-in-bearing comprising: an inner ring, an intermediate ring and an outer ring, wherein between the inner ring and the intermediate ring and between the intermediate ring and the outer ring, inner roller elements and outer roller elements are respectively provided, wherein the bearing-in-bearing with the inner ring and the outer ring is provided between two components in the device that are rotatable in relation to each other, said two components being a shaft and a housing, of which one component is connected to a drive, wherein the device is provided with a transmission between the intermediate ring and the component connected to the drive in order to drive the intermediate ring, wherein the transmission is a contactless transmission, and either the inner ring or the outer ring is a driven bearing ring, which is driven via said component connected to the drive, wherein the transmission comprises one or more permanent magnets which rotate along with the driven bearing ring, wherein the driven bearing ring is connected with a concentric first ring with permanent magnets, the intermediate ring is connected with a concentric ring with pole pieces and the non-driven bearing ring is connected with a concentric second ring with permanent magnets.

18. The device according to claim 17, wherein there is a gap between the first ring and the ring with pole pieces, and between the ring with pole pieces and the second ring with a maximum thickness of two millimetres.

19. The device according to claim 17, wherein the number of permanent magnets in said first ring and second ring with permanent magnets and the number of pole pieces in the ring with pole pieces is determined in such a way that the intermediate ring rotates at a speed that is lower than the speed of the driven bearing ring.

20. The device according to claim 17, wherein there is a gap between the first ring and the ring with pole pieces, and between the ring with pole pieces and the second ring with a maximum thickness of half a millimetre.

21. The device according to claim 17, wherein the number of permanent magnets in said first ring and second ring with permanent magnets and the number of pole pieces in the ring with pole pieces is determined in such a way that the intermediate ring rotates at a speed that is lower than the speed equal to approximately half the speed of the driven bearing ring.

22. A device provided with a bearing-in-bearing comprising: an inner ring, an intermediate ring and an outer ring, wherein between the inner ring and the intermediate ring and between the intermediate ring and the outer ring, inner roller elements and outer roller elements are respectively provided, wherein the bearing-in-bearing with the inner ring and the outer ring is provided between two components in the device that are rotatable in relation to each other, said two components being a shaft and a housing, of which one component is connected to a drive, wherein the device is provided with a transmission between the intermediate ring and the component connected to the drive in order to drive the intermediate ring, wherein the transmission is a contactless transmission, and either the inner ring or the outer ring is a driven bearing ring, which is driven via said component connected to the drive, wherein the intermediate ring is slowed down in a contactless manner by an electromagnetic force, wherein the intermediate ring is connected with a ring made of non-magnetic yet electrically conductive material and wherein the device with the bearing-in-bearing is provided with a stationary electromagnet in such a way that between the ring and the electromagnet a gap is present across which the electromagnet can create an electromagnetic field in the ring.

23. The device according to claim 22, wherein the device is provided with a sensor to measure the speed of the intermediate ring.

24. The device according to claim 22, wherein the device is provided with a controller configured to regulate the excitation of the windings in the electromagnet based on the speed of the intermediate ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With the intention of better showing the characteristics of the invention, some preferred embodiments of a bearing-in-bearing according to the invention are described hereinafter, by way of an example without any limiting nature, with reference to the accompanying drawings, wherein:

(2) FIGS. 1 and 2 schematically show the front and the back respectively of a bearing-in-bearing according to the invention;

(3) FIG. 3 shows a cross-section according to the line III-III in FIG. 1;

(4) FIGS. 4 and 5 show alternative embodiments of FIG. 3;

(5) FIG. 6 schematically shows a perspective view of the bearing-in-bearing from FIG. 5;

(6) FIG. 7 shows another alternative embodiment of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

(7) The bearing-in-bearing 1 shown in FIGS. 1 to 3 is constructed of an inner ring 2, intermediate ring 3 and an outer ring 4.

(8) Inner roller elements 5 are provided between the inner ring 2 and the intermediate ring 3, while outer roller elements are provided between the outer ring 4 and the intermediate ring 3.

(9) In this case the bearing-in-bearing 1 is constructed of two standard ball bearings, namely an outer ball bearing 9 and an inner ball bearing 10, which are concentric and the intermediate ring 3 is built of two concentric bearing rings, namely the inner ring 7 of the outer ball bearing 9 and the outer ring 8 of the inner ball bearing 10, and possibly even extra components such as rings.

(10) The inner ring 7 of the outer ball bearing 9 is attached using a press fitting or suchlike to the outer ring 8 of the inner ball bearing 10 to form the intermediate ring 3 of the bearing-in-bearing 1.

(11) As clearly shown in FIG. 3, the bearing-in-bearing 1 is provided around a rotating shaft 11, whereby the inner ring 2 of the bearing-in-bearing 1 is the driven bearing ring, driven by the torque from the rotating shaft 11.

(12) The outer ring 4 of the bearing-in-bearing 1 is mounted in a housing 12.

(13) Said rotating shaft 11 can for example be a shaft of a screw rotor of a compressor element and said housing 12 for example a compressor housing.

(14) However, the bearing-in-bearing 1 can also be used in many other machines, such as for example turbo compressors, expanders, vacuum pumps, turbo molecular pumps, spindles, motors, turbines, jet engines, etc.

(15) According to the invention, where the inner ring 2 is directly driven by the torque from the rotating shaft 11, the intermediate ring 3 is driven in a contactless manner by part of this torque.

(16) In the embodiment of FIGS. 1 to 4, this driving is performed by a so-called magnetic gear.

(17) As can be seen in FIG. 3, the inner ring 2 is connected with a first ring 13 with permanent magnets 14 and the intermediate ring 3 is connected with a ring 15 containing pole pieces 18.

(18) Pole pieces 18 are blocks of magnetically conductive material.

(19) The other material the ring 15 consists of holds the pole pieces 18 in place and is preferably a non-magnetic and non-electrically conductive material, such as for example a synthetic or composite material, so that no or little additional electromagnetic loss occurs in that material.

(20) Between the first ring 13 with permanent magnets 14 and the ring 15 of non-magnetic and non-electrically conductive material in which the pole pieces 18 are fixed there is a gap 16a.

(21) This gap 16a is approximately half a mm thick.

(22) According to the invention the thickness of this gap 16a is smaller than one and a half mm, and preferably even smaller than one mm.

(23) Furthermore the outer ring 4 is connected with a second ring 19 with permanent magnets 17.

(24) Also, between the second ring 19 with permanent magnets 17 and the ring 15 with pole pieces 18 there is a gap 16b, whereby the gap 16b is also preferably smaller than one and a half mm, and more preferably even smaller than one mm. In this case the gap 16b is half a mm thick.

(25) The first ring 13 and the second ring 19 with permanent magnets 14 and 17 respectively, and the ring 15 with pole pieces 18 jointly form a magnetic gear transmission 20 or ‘magnetic gear’. Such magnetic gear transmissions 20 are discussed in U.S. Pat. No. 5,633,555 and in “A novel high-performance magnetic gear”, K. Atallah, D. Howe, IEEE Transactions on Magnetics, vol. 37, No. 4, July 2001″.

(26) The permanent magnets 14 and 17 are placed with alternating polarity so that upon rotation of the rings 13 and 19 an alternating magnetic field is induced. The permanent magnets 14 and 17 each form a specific number of pole pairs, equal to half of the number of magnets in such a ring. The number of pole pairs corresponding with the number of permanent magnets 14 in the first ring 13 and the number of pole pairs corresponding with the number of permanent magnets 17 in the second ring 19 and the number of pole pieces 18 in the ring 15 is chosen depending on the speed at which the intermediate ring 3 must rotate in relation to the inner ring 2. These functions are known from literature.

(27) The speed at which the intermediate ring 3 must rotate in relation to the inner ring 2, i.e. the driven bearing ring, depends on the application in which the bearing-in-bearing 1 will be used.

(28) Preferably the number of permanent magnets 14, 17 in said first ring 13 and second ring 19 with permanent magnets 14, 17 and the number of pole pieces 18 in the ring 15 with pole pieces 18 is determined so that the intermediate ring 3 rotates at a slower speed than that of the driven bearing ring, preferably with a speed approximately equal to half the speed of the driven bearing ring.

(29) The operation of the device 1 is very simple and as follows.

(30) During use, the shaft 11 will rotate, whereby the inner ring 2 that is attached to the shaft 11 will rotate at the speed of the shaft 11.

(31) Together with inner ring 2, the first ring 13 with permanent magnets 14 will also rotate.

(32) The permanent magnets 14 generate magnetic fields across the gap 16a which are closed across the pole pieces 18 of magnetic material which are fixed in the ring 15. The ring 15 is connected with the intermediate ring 3.

(33) Similarly the permanent magnets 17 which do not rotate generate magnetic fields across the gap 16b which are closed across the pole pieces 18 of magnetic material which are fixed in the ring 15.

(34) Due to the discrete number of permanent magnets 14 and 17, and the discrete number of pole pieces 18 we obtain modulated magnetics fields in the air gaps 16a and 16b. By choosing the appropriate relationship between the number of permanent magnets 14, the number of pole pieces 18 and the number of permanent magnets 17, based on formulas known from literature as previously mentioned, the modulated fields in the air gaps 16a and 16b interact in a synchronised manner and allow the intermediate ring 3 to rotate in a particular ratio to the speed of the inner ring 2.

(35) In this way the intermediate ring 3 will rotate at a particular speed ratio in relation to the driving shaft 11 without requiring an electrical motor with a high frequency controller.

(36) The intermediate ring 3 is driven by a magnetic gear transmission 20, at a particular speed in relation to the inner ring 2, whereby the relationship between the speeds is fixed and determined by the number of permanent magnets 14 in the first ring 13 and the number of permanent magnets 17 in the second ring 19 and the number of pole pieces 18 in the ring 15.

(37) The system as shown in FIGS. 1 to 3 is an entirely passive system, without any active control. It is clear that the embodiment as shown in these figures is simple, relatively cheap and robust.

(38) In FIG. 4 a variant is shown according to FIG. 1, whereby in this case a double bearing-in-bearing 1 is illustrated, whereby a magnetic gear transmission 20 is attached between two adjacent bearing-in-bearings 1.

(39) Or, in other words, a further bearing-in-bearing 1 is attached beside the magnetic gear transmission 20 in FIG. 3.

(40) As shown in FIG. 4, both intermediate rings 3 are connected with the ring 15 with pole pieces 18.

(41) Similarly both inner rings 2 and both outer rings 4 are connected respectively with the first ring 13 with permanent magnets 14 and second ring 19 with permanent magnets 17.

(42) The magnetic gear transmission 20 will in other words control both bearing-in-bearings 1. Otherwise the operation is entirely similar to the previous embodiment.

(43) FIGS. 5 and 6 show an alternative embodiment, whereby in this case the intermediate ring 3 is driven in a contactless manner by “magnetic drag”, whereby the driven inner ring 2 is connected with a first ring 13 with permanent magnets 14 and the intermediate ring 3 is connected with a braking ring 27.

(44) A potential embodiment for this braking ring 27 is shown in FIG. 5. The braking ring in this case consists of a ring 28 of magnetically conductive material, such as for example steel, and two rings 29a and 29b of non-magnetic yet electrically conductive material, such as for example aluminium, which are attached concentrically to the inside, respectively the outside of ring 28.

(45) Between the first ring 13 with permanent magnets 14 and the ring 29a of electrically conductive material there is a gap 16a. This gap is approximately half a mm thick. According to the invention the thickness of this gap 16a is smaller than one and a half mm, and preferably even smaller than one mm.

(46) The permanent magnets 14 are placed with alternating polarity so that, when the first ring 13 rotates, an alternating magnetic field is induced in the air gap 16a and in the ring 29a of non-magnetic yet electrically conductive material, and that is closed in the ring 28 of magnetically conductive material. As the material in the ring 29a is electrically conductive, so-called Eddy currents will be generated in the alternating magnetic field, leading to so-called Eddy current losses. In order to compensate these losses the ring 29a, and therefore also the braking ring 27, will start to rotate. The braking ring 27 is thus driven by “magnetic drag”.

(47) The torque with which this “magnetic drag” drives the braking ring 27, depends on different factors, such as the strength of the induced magnetic field, the speed difference between ring 13 and braking ring 27, and the construction and material properties of braking ring 27.

(48) It shall be ensured that the intermediate ring 3 rotates faster than the desired speed for the specific bearing-in-bearing application, for example by choosing the appropriate thickness of the gap 16a and the number of permanent magnets 14 and their magnetic strength.

(49) Again, in order to slow the intermediate ring 3 and allow it to rotate at the desired speed, use is made of a contactless transmission which also operates on the principle of so-called “eddy currents”.

(50) Use is made of a magnetic brake 21, a so-called ‘Eddy current brake’, which is formed by said ring 28 made of magnetically conductive material, the ring 29b made of non-magnetic yet electrically conductive material and a stationary electromagnet 22, which is provided in such a way that between the ring 29b made of non-magnetic yet electrically conductive material and the electromagnet 22 there is a gap 23 across which the electromagnet 22 can generate an electromagnetic field in the ring 29b and that is closed in the ring 28.

(51) The gap 23 between the ring 29b and the stationary electromagnet 22 is of the same order of magnitude as said gaps 16a and 16b in the embodiment of FIGS. 1 to 3 between the first ring 13 and second ring 19, with respectively permanent magnets 14 and 17, and the ring 15.

(52) By applying a current to the stationary electromagnet 22 when the braking ring 27 is rotating, Eddy currents will be generated in the ring 29b made of electrically conductive material, whereby the intermediate ring 3 will be slowed.

(53) The extent to which braking occurs on the intermediate ring 3 will be determined by the size of the current and/or voltage, the way in which the power is turned on and off and the frequency.

(54) A sensor, not shown on the figures, can be provided to determine the speed of the intermediate ring 3 and a control that sends a current through the electromagnet 22 based on the measured speed in order to be able to slow the intermediate ring 3 to the desired speed.

(55) To this end the control can be provided with an algorithm to ensure that the ‘n.dm’ value of the inner bearing 10 is equal to the ‘n.dm’ value of the outer bearing 9, or that the ratio of both values lies within certain margins. In the present example this corresponds with a speed ratio of from 70-30 to 60-40. It is clear that this ratio can vary depending on the application.

(56) In FIG. 6 the electromagnet 22 is clearly visible. This is stationary, which means that, in this case, this is fixed to the housing 12 and therefore will not rotate along with the bearing-in-bearing 1.

(57) The electromagnet 22 is in this case horseshoe-shaped and provided with windings 24. However, this is only an illustrative example and the invention is not limited to this.

(58) Although the embodiment from FIGS. 5 and 6 is not entirely passive and requires an additional control and sensor, this embodiment has the advantage of allowing the speed of the intermediate ring 3 to be freely controlled. In the previous embodiment the speed of the intermediate ring is fixed.

(59) FIG. 7 shows a further variant, whereby in this case the slowing of the intermediate ring 3 will take place in the same way as in the example in FIGS. 5 and 6, i.e. with the magnetic brake 21, yet whereby the contactless driving in this case occurs using a viscous force of resistance or drag.

(60) To do so both the inner ring 2 and the intermediate ring 3 are provided with a ring 25a, 25b, with a gap 26 between both rings 25a, 25b, whereby this gap 26 is filled with a fluid.

(61) The thickness of this gap 26 depends on the fluid concerned. The fluid can for example be a lubricant, such as oil, or water.

(62) In the case of oil, the thickness of the gap 26 is preferably 100 micrometres or smaller.

(63) The operation of the contactless drive is based on the fact that, by rotating the inner ring 2, the intermediate ring 3′ will start to rotate by the viscous force of resistance or drag created by the thin film of the fluid in the gap 26.

(64) The thickness of the gap 26 will determine how much torque is generated and therefore also at what speed the intermediate ring 3 will rotate along.

(65) Again it is ensured that the intermediate ring 3 will rotate too quickly so that this may be slowed to the desired speed with the magnetic brake 21.

(66) An additional advantage of this embodiment is that the oil film in the gap 26 has a damping effect, allowing any vibrations to be accommodated.

(67) All described bearing-in-bearings 1 can also be lubricated with grease. This means that the bearing-in-bearings 1 in FIGS. 1 to 6 and in FIG. 7, to the extent that no oil film is used, are suitable for oil-free applications, such as for example oil-free compressors, such as for example oil-free turbo or screw compressors.

(68) Such grease-lubricated bearing-in-bearings 1 are suited to speeds greater than 1×10.sup.6 ‘n.dm’ [revolutions per minute.millimetre], whereby the speed can even reach more than 1.3×10.sup.6 ‘n.dm’ or 1.6×10{circumflex over ( )}.sup.6 ‘n.dm’.

(69) Alternatively the bearing-in-bearings 1 can also be lubricated with oil.

(70) In this case the oil is preferably injected into the bearing-in-bearing 1 using an oil jet or oil mist.

(71) Such bearing-in-bearings 1 are suited to very high speeds, greater than 1.5×10.sup.6 ‘n.dm’ [revolutions per minute.millimetre], whereby speeds greater than 2.0×10.sup.6 ‘n.dm’ and even greater than 2.6×10.sup.6 ‘n.dm’ are possible.

(72) Preferably, the bearing-in-bearing 1 is as compact as possible in axial terms, so that the shaft 11 on which the bearing-in-bearing 1 is mounted can be kept as short as possible, which is appropriate for use at very high speeds.

(73) For this reason the power, and therefore also the torque, transmitted from the inner ring 2 to the intermediate ring 3 is best limited to a little more than the torque required to compensate the friction torque of the outer bearing so that the intermediate ring 3 rotates as well.

(74) The width in axial terms of said gaps 16a, 16b, 23, 26 is preferably smaller than three times the width of the roller elements 5, 6 of the bearing-in-bearing 1, and even more preferably smaller than twice the width of the roller elements 5, 6.

(75) This is completely different to the known magnetic gear transmissions 20 as documented in literature which in axial terms are not compact, given that these are designed for applications with much lower speeds, but with high torques.

(76) Although, in the examples shown, the inner ring 2 is always driven by said torque, meaning that the inner ring 2 is mounted on a rotating shaft 11, and the outer ring 4 is stationary, and therefore attached in a housing 12, it is not excluded according to the invention that the outer ring 4 is driven by said torque and that the inner ring 2 is stationary.

(77) The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a bearing-in-bearing according to the invention can be realised in all kinds of forms and dimensions without departing from the scope of the invention.