WO2017194352A1

WO2017194352A1 - Electrical machine having a double rotor arrangement

Info

Publication number: WO2017194352A1
Application number: PCT/EP2017/060404
Authority: WO
Inventors: Mykhaylo Filipenko
Original assignee: Siemens Aktiengesellschaft
Priority date: 2016-05-13
Filing date: 2017-05-02
Publication date: 2017-11-16
Also published as: DE102016208259A1

Abstract

An electrical machine having a double rotor arrangement. The invention relates to an electrical machine having a radial double rotor arrangement comprising an internal rotor and an external rotor, wherein a stator is arranged between the two rotors. Permanent magnets are located on the rotors, while the stator bears a multiplicity of coils which interact electromagnetically with the permanent magnets during mutual rotation of rotor and stator. The external rotor and optionally also the internal rotor are mounted rotatably on the stator with the aid of respective pairs of ball bearings, and therefore possibly occurring bending torques are absorbed by the rolling bearings. Accordingly, the rotors, in particular the external rotor, can be realized in less robust form and therefore with a lighter weight.

Description

description

The invention relates to an electric machine with a double-rotor arrangement, in particular a machine having an inner rotor and an outer rotor, between which a stator is arranged. For the classification of an electrical machine, among other things, the so-called power density can be used, wel ^¬ Che sets the achievable by the machine power in relation to their weight and is usually given in kW / kg. While up to 2 kW / kg are sufficient for many industrial applications, power densities in orders of magnitude, Need Beer ^¬ you Untitled eg. For the electrification of aviation electrical machines with power densities of at least 20 kW / kg.

The power density of an electrical machine scales directly with the magnetic flux density, which can be generated by the electric or permanent magnets used in the electric machine and which can be used with the example of the

Stator of the machine arranged coils interacts electromagnetically. This relationship between the flux density and the power density allows a significant increase in the power density of the machine in that a Doppel ^¬ runner configuration is used, in which the stator or arranged on the stator coils between two magnetic flux density-causing magnets equipped runners is arranged. In this case, for example, in the case of a radial double-rotor configuration, the stator is arranged in the radial direction between an external rotor and an internal rotor.

Such double-armature configurations are electromagnetically advantageous, since they allow both very high magnetic flux densities in the air gaps and best map the magnetic circuit, since the runners on both sides of the stator for the generation and for the guidance of the magnetic flux. can be used. These and other measures can be reflected in increased power density.

One approach to increasing the power density is thus to use a Doppelrotorkonfigu ^¬ ration in the electrical machine. Usually radial double ^¬ runner configurations are realized with at least one so-called bell runner. This is shown in FIG 1, where ^¬ in the radially outer outer rotor has a bell shape and this surrounds the inner rotor and the stator.

The bell shape is open at one end as viewed in the axial direction and closed at one end, wherein the bell or the rotor at the closed end with a shaft of the electric machine is connected such that a torque from the rotor to the shaft or vice versa can be transmitted , The main disadvantage of this construction is that high bending moments occur on ^¬ due to the magnetic attraction forces in the radial direction, the effect, in particular, at the open end of the bell and the intercepted by a relatively heavy mechanical design of the rotor ^¬ the need. The above-mentioned advantages of the electromagnetic ^¬ tischen design can be partially overcompensated by these mechanical disadvantages. It is therefore an object of the present invention to provide an alternative way to increase the power weight of an electric machine.

This object is achieved by the electrical machine described in claim 1. The subclaims describe advantageous embodiments.

An electrical machine according to the invention has an inner ^¬ runner and an outer rotor which together form a double-pelläuferanordnung, and a stator. The inner rotor and the outer rotor are arranged concentrically with each other such that the inner rotor is located radially inside the outer rotor. The stator is in the radial direction disposed between the inner rotor and the outer rotor and concentric with the inner rotor and the outer rotor. The external rotor is rotatably mounted on the stator with the aid of a pair of roller bearings, wherein the two roller bearings of the pair are arranged in the axial direction spaced from each other.

Furthermore, the inner rotor with the aid of another pair of rolling bearings can be rotatably mounted on the stator, wherein the two rolling bearings of the other pair of rolling bearings are also arranged spaced apart in the axial direction.

Here, "rotatably mounted on the stator" means that the per ^¬ stays awhile rotor is rotatable relative to the stator and that the respective pair of roller bearings on the respective rotor

Stator supports, so that represents the respective pair of bearings a rotary connection between the respective rotor and the stator. The advantage of this configuration with rolling bearings is that the structure of the double-rotor arrangement can be easier, since the structure does not have to bear a one-sided, strong bending moment. The advantage therefore lies in the complete elimination of the external bending moments, which lead to a streamlining of the mechanical structure of the double-rotor arrangement and thus of the electrical machine as a whole. As a result, the double-rotor arrangement can exploit its electromagnetic advantages without being disadvantaged by the mechanical design.

Concerning . the term of the rolling bearing is to be noted that these are bearings, with which a first component mounted ^¬ example, for example, an inner ring, and a second component mounted ^¬ component, for example, an outer ring are rotatable or rotatable relative to each other. Well-known subgroups of the rolling bearings are, for example, ball bearings or roller bearings, whereby combined designs are also possible, as described, for example, in DE102006044802A1. In a radial rolling bearing inner ring and outer ring are ßenring typically concentrically arranged with a lying in the radial direction between the inner ring and outer ring annular gap. In the annular gap are between the radially inner surface of the outer ring and the radial outer surface of the inner ring rolling elements, so that inner ring and outer ring are rotatable relative to each other by rolling on the rolling elements. Depending on the type of rolling bearing, the rolling elements may, for example, be formed as balls or rollers or rollers. The structure and operation of such rolling bearings are well known, are therefore not further explained. A corresponding arrangement results in a Axi ^¬ alwälzlager, wherein the first and the second component in the axial direction are arranged one behind the other. Both components are annular with substantially the same radii. The rolling elements are also here in one

Gap, which is located in the axial direction between the two components.

The runners, i. the inner rotor and the outer rotor each have a plurality of permanent magnets for generating a magnetic flux.

With suitable alignment of the permanent magnets on the runners, a magnetic flux density can be realized with great homogeneity on both sides of the stator, which is why it may be possible to dispense with flux-conducting material in the stator. Allowing designed as an air coil bobbin is attached to the stator then arranged at least that interacts with the induced by the permanent ^¬ magnets of the inner rotor and the outer rotor mag- netic flux electromagnetically, so that operation of the electrical machine as a generator and / or as an electric motor , The term of the air coil should be noted that these are inductive components han ^¬ delt, which are formed in particular without a magnetic core. This includes both the design with a non ^¬ magnetic core and the embodiment, in which a core is completely dispensed with. Abandoning one likes ^¬ genetic core results in a weight saving, so in consequence, for example, instead of the now largely unnecessary flux-conducting iron, more copper can be used for the coil windings and the machine has a higher efficiency due to reduced copper and iron losses. Furthermore, the complete or even partial waiver of magnetic cores, that magnetic opposing fields are largely prevented from the stator.

The permanent magnets of the inner rotor and the outer rotor are designed and arranged such that a torque between the inner rotor and the outer rotor alone and in particular without the use of the below-mentioned mechanical connection between the runners, but only due to magnetic forces between the inner rotor and the outer rotor arranged permanent magnet is transmitted. Also, this arrangement without the mechanical connection leads to a further weight saving. In addition, the two runners can be largely independently treated, which is particularly in the event that the permanent magnets of the inner rotor and the outer rotor depending ^¬ Weil superconducting, is advantageous. In this case, Kings ^¬ NEN necessary to cool the magnet cryostats be performed inde pendent ^¬ or separated. Also, the magnetization of the superconducting magnets necessary before the operation of the electric machine would be simplified.

As mentioned, the permanent magnets can be formed as superconducting permanent magnets, whereby significantly higher flux densities are possible, which has a positive effect on the power density

The inner rotor and / or the outer rotor are mechanically connected to a shaft of the electric machine, so that a torque can be transmitted between the respective rotor and the shaft. The inner rotor can be connected to the external rotor via a mechanical connection to Drehmomentübertra ^¬ supply to guarantee in a simple way that the full torque between double rotor structure and Wave is transmitted. Especially in machines with high torque, the mechanical connection between inner and outer rotor is useful to ensure an effective torque transmission. However, this is relatively easy, since only torques must be transmitted in the circumferential direction, while bending loads, etc. are intercepted by the rolling bearing assembly.

The inner rotor and / or the outer rotor can each have a yoke, for example an iron yoke, for guiding the magnetic flux generated by the permanent magnets. In the event that the permanent magnets of the inner rotor and / or the outer rotor are each formed as a Halbach arrangement, however, can be dispensed with the use of the iron yokes, since the magnetic flux does not have to be guided over yokes. Halbach arrangements are known, for example, from DE102013225093A1. This also results in a more Gewichtsre ^¬ duzierung. Further advantages and embodiments will become apparent from the drawings and the corresponding description.

In the following the invention and exemplary embodiments will be explained in more detail with reference to drawings. There, the same components in different figures are identified by the same reference numerals.

1 shows a lateral sectional view of a side view

Electric machine with double-rotor arrangement according to the prior art,

2 shows a side sectional view of an electric machine with double rotor arrangement according to the invention, FIG. 3 shows a lateral sectional view of an electric machine according to the invention with double rotor arrangement in a first expanded embodiment, 4 shows a side sectional view of an electric machine according to the invention with double rotor arrangement in a second expanded embodiment. Like reference numerals in different figures indicate like components. It is also noted that terms such as Be ^¬ "axial" and "radial" refer to the coming wave in each beschrie ^¬ surrounded example, or in the respective figure is used. In other words, the directions refer axially and radially always to a rotational axis of the Läu ^¬ fers.

1 shows by way of example and simplified an electrical machine 100 according to the prior art in a lateral section, ie in a radial view. The machine 100 has a rotor 110 in the form of a double-rotor arrangement with an inner rotor 111 and an outer rotor 112, the inner rotor 111 having a smaller diameter than the outer rotor 112. The rotors 111, 112 of the double-rotor arrangement 110 are arranged concentrically to one another, such that the inner rotor 111 is located radially inside the outer rotor 112. In the axial direction, the runners 111, 112 are located substantially at the same position. Both the inner rotor 111 and the outer rotor 112 permanent magnets 113, 114 are mounted, which generate magnetic fields or magnetic fluxes. The runners 111, 112 and attached to the runners 111, 112, magnets 113, 114 are dimensioned such that a respective magnet 113 is located on ^¬ In nenläufer 111 and a magnet 114 at the external rotor in the radial direction with respect to. The magnetic flux extends over the air gap between such a pair of magnets consisting of radially opposite magnets on the inner rotor 111 and the outer rotor 112 and closes on the example. As Eisenjoche 115, 116 formed inner and outer rotor 111, 112th

Furthermore, the machine 100 has a stator 120. The stator 120 is concentric with the inner rotor 111 and Außenläu- fer 112 and further arranged in the radial direction between the inner rotor 111 and the outer rotor 112, so located in the above-mentioned air gap between the inner rotor 111 and outer rotor 112. The stator 120 carries a plurality of windings or coils 121 which are wound on cores 122 may be and are arranged such that they are penetrated by the magnetic flux generated by the permanent magnets 113, 114. The stator 120 may have a mechanical ^¬ African connection 123, for example. Oa a screw to be firmly connected to a housing or other components of the electric machine 100 (not shown in detail), so that the stator 120 relative to the engine 100 in itself or . With respect to the housing is ultimately immobile and essentially only the rotor 110 together with a shaft 130 can perform ne movement.

In the operating state of the electric machine 100, the rotor 110 or the double-rotor arrangement 110 rotates relative to the stator 120. Rotor 110 and stator 120 are arranged relative to one another such that the magnetic field of the permanent magnets 113, 114 and the coils 121 interact with one another in such a way that that the electrical machine 100 operates as a generator and / or in a second operating mode as an electric motor due to the interaction ^¬ effect in a first operating mode. The operation of the electrical machine 100 is thus based on the known concept that the two components 110, 120 interact electromagnetically with each other, so that the electric machine 100 can operate in one of the two operating modes.

If the electric machine 100 ^operates as a generator, then the double rotor arrangement 110 and with it the permanent magnets 113, 114 are, for example, set in rotation via the shaft 130 of the electrical machine 100, so that electrical voltages are induced in the coils 121 of the stator 120 , If the electric machine 100 is to operate as an electric motor, the coils 121 are supplied with electric current, so that due to the interaction of the magnetic field generated therewith. net fields with the fields of the permanent magnets 113, 114 a torque on the rotor 110 and thus acts on the shaft 130. In principle, it is also conceivable, but not shown, that the permanent magnets 113, 114 is not ^¬ arranged on the rotor 110 are, but on the stator 120. The coils 121 are induced in the according to the operating voltages and are supplied with a current are arranged in this case on the runner 110 and can be connected, for example via brushes or other suitable transformer with an electrical load or with a power source (not shown). This embodiment is, however, explained in the following non nä ^¬ ago, it does not WE sentliche role for the actual invention to which the two components 110, 120, the permanent magnets 113, 114 and the coils 121 are arranged respectively.

Typically, the external rotor 112 of the known double-rotor arrangement 110 is realized as a bell-type rotor. Such a bell runner 112 has a bell shape which surrounds the inner rotor 111 and the stator 120. As seen in the axial direction, the bell shape is open at one end 117 and completely or partially closed at the other end 118, wherein the bell 112 and the outer rotor 112 are connected at the closed end to the inner rotor 111 and in particular to the shaft 130 of the electric machine 100 is that a torque from the double-rotor assembly 110 on the shaft 130 or vice versa can be transmitted.

2 shows an inventive electrical machine 100, in which the external rotor 112 has no bell shape. The operation of the machine 100 illustrated in FIG 2 as well as in the further Fi ^¬ guren corresponds to that known from the prior art machine, however, the external rotor 112 by means of two roller bearings 141 rotatably mounted on the stator 120 142, so the roller bearing 141, 142 ei ^¬ ne rotary connection to the stator 120 represent. The two rolling Bearings 141, 142 are in the axial direction of each other

arranged spaced apart, so that, for example, due to the magneti ^¬ attraction forces or other effects occurring Bie ^¬ moments are intercepted in the radial direction.

In addition, but not necessarily, a further pair of roller bearings 143, 144 may be provided between the inner rotor 111 and the stator 120, which produces a rotational connection between the inner rotor 111 and the stator 120. This is likewise shown in FIG. The rolling bearing 143, 144 of the other pair are also arranged spaced apart in the axial direction, so that here in particular ^¬ special acting in the radial direction bending moments can be intercepted.

At least one of the rotors 111, 112, for example, the inner rotor 111, must be mechanically connected to the shaft 130 in order to allow a torque transmission between the double rotor assembly 110 and shaft 130. FIG. 3 shows a further development of the electric machine 100, in which, moreover, the inner rotor 111 is connected to the outer rotor 112 via a mechanical connection 119 for transmitting torque, so that the torques generated on both rotors 111, 112 subsequently act on the Wave 130 are transferable.

However, with sufficiently strong permanent magnets 113, 114, for example if these are designed as superconducting magnets, it is also conceivable to dispense with the mechanical connection 119 and to assume that solely due to the magnetic forces between the magnets 113 of the inner rotor 111 and the magnets 114 of the outer rotor 112, a Drehmo ^¬ ment transmission between the outer rotor 112 and inner rotor 111 takes place. Such an embodiment without the mechanical connection 119 is already illustrated by FIG. A waiver of the connection 119 allows a largely independent embodiment of the two runners 111, 112. In particular, in the event that the inner rotor 111 and the outer rotor 112 have superconducting permanent magnets 113, 114, which must reside on ent ^¬ speaking 100 low temperature during operation of the electrical machine, can be used due to the independent execution example. separate cryostats for internal rotor 111 and external rotor 112th This would on the one hand, a magnetization of the magnets 113, 114 and on the other, the maintenance of the machine 100 vereinfa ^¬ chen.

In the embodiments shown in Figures 2, 3 embodiments of the runners 111, 112 each have an iron yoke 115, 116 for guiding the on by the permanent magnets 113, 114 magnetic flux generated ^¬ tables. The 4 shows in the direction indicated in FIG 2 with "IV" view an alternative arrangement wherein the greatest extent on the use of flux conducting materials can be dispensed starting, so that the runners 111, 112 we ^¬ considerably lighter, more that is lighter in weight In this embodiment, the permanent magnets 113, 114 are each configured as so-called Halbach arrays Such a rotor with Halbach arrangements is, for example, in

DE102013225093A1 shown. As explained there, an advantage of the Halbach array is based on the fact that the genetic like ^¬ flux density in the air gap, the radially between the stator 120 and the respective rotor 111, is 112, extends mainly. For example, a Halbach arrangement may be formed by means of a plurality of permanent magnets, so that by a special arrangement of the individual permanent magnets, the magnetic flux density in the radially inward direction, ie within the respective rotor 111, 112, attenuated while in the associated air gap , that is, outside the respective rotor 111, 112 in the area between the respective rotor 111, 112 and the stator 120, itself amplified and / or concentrated. As a result of the weakening of the magnetic flux density within the respective rotor 111, 112, losses due to eddy currents in the respective rotor 111, 112 are reduced. In addition, a higher torque can be ^¬ riding provided and the power density is increased by the increased in the respective air gap and / or concentrated magnetic flux density. Generally speaking even dispense with a common iron yoke, whereby the mass moment of inertia of the rotor 110, 111, 112 is further reduced. Of the ball bearings 141, 143, only a few balls are shown in FIG. 4 for the sake of clarity. ^{Of course} , the balls extend along the entire circumferences of the two air gaps between stator 120 and external rotor 112 as well as stator 120 and internal rotor 111.

The coils 121 of the stator 120 are preferably designed as so-called. Air coils, ie in particular without weichmagneti ^¬ 's core. Instead, the coils 121 may, for example, be wound on nonmagnetic cores 122 of a preferably light material or even completely without a core. This has the consequence that also the stator 120, can inter alia be made such that it has a comparatively low weight ^¬. Although the embodiment using air coils and thus the absence of the magnetic cores is reflected in that the magnetic flux of the permanent magnets 113, 114 is less targeted, resulting in an increase of the magnetic leakage flux, but this ^¬ disturbing effect compensated by the use of the double-rotor arrangement and the case radially opposite permanent magnets, since the magnetic flux causes a guide without a magnetic core due to this arrangement.

The rolling bearings 141, 142, 143, 144 may be formed, for example, as a ball bearing. Also suitable are, for example, embodiments as roller or roller bearings.

In particular, for the case mentioned in connection with FIG. 1, that the coils 121 are not mounted on the stator 120 but on the rotor 110, the coils 121 can be induced into the voltages depending on the operation or to be supplied with a current , are connected via the bearings with an electrical load or with a power source (not shown). On brushes or similar compo- Accordingly, it is possible to dispense with the transmission of the electric current from or onto the coils 121 rotating in this case. It should be noted that the aspects and features of the electric machine explained with reference to the various figures can be combined with one another as far as possible. Due to the use of the rolling bearing are as explained in the introduction advantages with respect to the weight of the arrival order, as inner and outer rotors 111, 112 must be carried out less robust itself, since any possible Be ^¬ loads carried by the bearings. A particular respect. the weight of the overall arrangement advantageous embodiment results from the combination of the embodiment with Halbach arrays on the rotor 110 with the embodiment with Luftspu ^¬ len 121 on the stator 120, because in this case due to the white ^¬ testgoing abandonment of relatively heavy components an electric machine with low weight can be realized.

Claims

claims

1. Electrical machine (100) with an inner rotor (111) and an outer rotor (112) and with a stator (120), wherein - the inner rotor (111) and the outer rotor (112) are arranged concentrically with each other so that the Innenläu ^¬ fer (111) is located radially inside the outer rotor (112),

the stator (120) is arranged in the radial direction between the inner rotor (111) and the outer rotor (112) and concentrically with the inner rotor (111) and the outer rotor (112),

and where

- The external rotor (112) by means of a pair of rolling bearings (141, 142) rotatably mounted on the stator (120), wherein the two rolling bearings (141, 142) of the pair of rolling bearings (141, 142) arranged spaced apart in the axial direction are .

2. The electric machine (100) according to claim 1, characterized indicates overall that the internal rotor (111) by means of a direct wei ^¬ pair of rolling bearings (143, 144) is rotatably mounted on the stator (120), said two rolling bearings ( 143, 144) of the further pair of rolling bearings (143, 144) are arranged spaced apart in the axial direction.

3. Electrical machine (100) according to any one of claims 1 to 2, characterized in that the inner rotor (111) and the outer rotor (112) each have a plurality of permanent magnets (113, 114) for generating a magnetic flux sen.

4. Electrical machine (100) according to claim 3, characterized ge ^¬ indicates that on the stator (120) at least one coil formed as an air coil (121) is arranged, with one of the permanent magnets (113, 114) of the inner rotor

(111) and the external rotor (112) caused magnetic flux interacts electromagnetically.

5. Electrical machine (100) according to one of claims 3 to 4, characterized in that the permanent magnets (113, 114) of the inner rotor (111) and the outer rotor (112) are designed and arranged such that a torque between the inner rotor ( 111) and the outer rotor (112) due to magnetic forces between the permanent magnets (113, 114) is transmitted.

6. Electrical machine (100) according to one of claims 3 to 5, characterized in that the permanent magnets

(113, 114) are superconducting permanent magnets.

7. Electrical machine (100) according to one of claims 3 to

6, characterized in that the inner rotor (111)

and / or the outer rotor (112) each having a yoke (115, 116) for guiding the magnetic flux.

8. Electrical machine (100) according to one of claims 1 to

7, characterized in that the permanent magnets (113, 114) of the inner rotor (111) and / or the outer rotor (112) are each formed as a Halbach arrangement.

9. Electrical machine (100) according to one of claims 1 to

8, characterized in that the inner rotor (111) with the outer rotor (112) via a mechanical connection (119) for

Torque transmission is connected.

10. Electrical machine (100) according to one of claims 1 to

9, characterized in that the inner rotor (111)

and / or the outer rotor (112) mechanically with a shaft

(130) of the electric machine (100) is connected, so that between the respective rotor (111, 112) and the shaft (130) a torque is transferable.