DE102014003956A1 - Electric machine. especially for aircraft - Google Patents

Abstract

The invention relates to an electric machine (20) comprising a stator (30) as a first assembly (24) and a rotor (2) rotatable about a rotation axis (28) relative to the stator (30) as a second assembly (26 ), wherein an air gap (32) between the modules (24, 26) is formed. In order to be able to produce a machine with increased force density and increased torque density in a simple manner, it is proposed that at least one of the assemblies (24, 26) has a plurality of segments (36) delimiting the air gap (32) and a gap width maintaining device (34 ) is provided for maintaining a gap width of the air gap (32) having a bearing means (38) for radially movably supporting at least one of the segments (36).

Description

The invention relates to an electric machine comprising a stator and a rotor rotatable relative to the stator about a rotation axis. The stator and the rotor form assemblies of the electrical machine; between the modules, an air gap is formed.

Such an electric machine is for example from the WO 2013/087056 A2 known.

An electric machine is a machine used in electric power engineering. The term "electrical machine" is understood as a generic term for energy converters which convert between electrical energy and mechanical energy. The electric machines include in particular electric motors or generators.

The invention is in the field of rotary electric machines with a stator (also referred to as a stator) and a rotatable about a rotational axis arranged rotor (also referred to as a rotor). Such rotary electric machines include in particular electric motors and electric generators.

In the course of discussing the reduction of greenhouse gases, alternative drives and energy concepts are becoming increasingly important. There is intensive research on new electrical machines for different applications. The invention is particularly directed to electric machines to be used in or on aircraft.

An interesting concept of a permanent magnet-excited flux-switching machine is in the WO 2013/087053 A2 described and illustrated. It is for closer explanations to this type electrical machines in particular on the WO 2013/087056 A2 which is incorporated by reference and forms part of the disclosure herein.

The present invention addresses the problem of the manufacturability of such new drive concepts for practical applications, in particular the industrial mass production of such electrical machines, more particularly for use in or on aircraft.

Although the volumetric torque and power densities of current electric machine technologies would be well suited as aircraft propulsion direct drive, manufacturability for this purpose of most promising electrical machine architectures is an obstacle to these machines in such applications, particularly as a direct drive to propulsion or as a propulsion in aircraft such as airplanes or helicopters or the like.

Two examples of such novel architectures, which are particularly promising for applications in aircraft technology, are the permanent magnet excited transverse flux machines (TFPM for "trans-flux permanent magnet machines" and the permanent magnet excited flux-switching machines (FSPM) for "flux-switching permanent magnet machines ").

A problem with many novel architectures of electric machines characterized by a very high air-gap power density is that the air gap between the assemblies should be kept to extremely tight dimensions to achieve very high air-gap power densities. One desire is to maintain the width of an air gap between the rotor and stator electromagnetic structures on the order of microns. In the known technologies, therefore, the manufacturing tolerances must be kept very low, so that a very high quality production of the modules is necessary.

This problem is exacerbated by the desired increase in the diameter of the assemblies in order to obtain a higher torque solely by increasing the diameter of the assemblies. It would be desirable to have diameters greater than 50 cm and more particularly more than 1 m and above.

For example, electric drives for helicopters represent an alternative to the conventional drive with internal combustion engines. In present-day combustion engines, such as e.g. B. turbomachinery, a mechanical intermediate gear is required to reduce the speed of the output shaft, which also includes weight and manufacturing costs. This transmission and the prime mover or the prime movers can be replaced by a direct drive. Such a direct drive comprises a slow-speed electric motor, in particular a high-torque slow-speed electric motor.

The prior art with respect to such drives for rotor shafts of aircraft and in particular of helicopters is on the DE 10 2010 021 024 A1 , the DE 10 2010 021 025 A1 , the DE 10 2010 021 026 A1 , the WO 2011/144692 A2 , the DE 10 2011 121 174 A1 as well as the above already mentioned WO 2013/087056 A2 directed.

Particularly interesting is the use of electrical machine architectures with very high air gap power densities, to achieve a high performance the smallest possible air gap should be achieved.

The object of the invention is to improve such machines such that a small air gap can be achieved even with lower demands on the tolerances in the production of the electrical machine.

This object is achieved by an electric machine according to claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

Advantageous uses of the electrical machine are specified in the additional claims.

According to a first aspect, the invention provides an electrical machine having a stator as a first assembly and a rotor rotatable relative to the stator about a rotation axis as a second assembly, wherein an air gap is formed between the assemblies, wherein at least one of the assemblies a plurality of segments defining the air gap, and that a gap width maintaining device for maintaining a gap width of the air gap is provided, which has a bearing means for radially movably supporting at least one of the segments.

It is preferred that the gap width maintaining device comprises a force storage and / or generating means for applying the at least one radially movably mounted segment with a counterforce acting against a magnetic force acting radially on the segment.

It is preferred that the one energy storage and / or generating means comprises at least one elastic element for generating a counter-elastic force on the at least one radially movable segment for maintaining a balanced gap width of the air gap.

It is preferred that the energy storage and / or generating means comprises at least one gas bearing between the radially movably mounted segment and the other assembly.

It is preferred that the bearing device has at least one linear bearing and / or slide bearing acting in the radial direction.

It is preferred that at least the region of the stator bounding the air gap is divided into a plurality of stator segments mounted so as to be radially movable relative to the rotor by means of the bearing device.

It is preferred that the stator segments by means of the bearing means are radially displaceable, but are mounted tangentially immovable.

It is preferred that the bearing device has a plurality of radially acting linear bearings and / or plain bearings for the stator segments.

It is preferred that the stator segments each have a stator electromagnetics section and the rotor at least one rotor electromagnetics section such that magnetic attraction forces act across the air gap between each stator segment and the rotor, and that each stator segment in the radial direction by at least one energy storage and / or generating element can be acted upon by an opposing force acting against the magnetic attraction forces.

It is preferred that the at least one energy storage and / or generating element is an elastic element, by means of which an elastic force can be generated as a counterforce.

It is preferred that to form the elastic elements between each stator segment and the rotor one or more pressurized with pressurized gas (s) gas bearing is provided.

Preferably, the electric machine is designed as a permanent magnet-excited transverse flux machine and / or permanent magnet-excited flux-switching machine.

According to a further aspect, the invention relates to an aircraft comprising an electric machine according to the first aspect or its advantageous embodiments.

The electric machine is preferably used in an aircraft as a generator for generating electrical energy and / or as an electric motor.

According to a further aspect, the invention relates to a hybrid drive for an aircraft, comprising such an electric machine according to the first aspect or its advantageous embodiments.

According to yet another aspect, the invention relates to a helicopter comprising such a hybrid drive.

But also for the propulsion of other aircraft, such. As propeller aircraft or the like, is the electric machine as a direct drive very interesting. In particular, the invention relates to an air gap control mechanism or air gap control mechanism for electric machines, with which the width of a gap between rotor and stator can be controlled or controlled. In particular, the width of an air gap should be kept constant - and if possible at a low level.

Particularly preferred is an air gap control or control mechanism for electric machines using gas bearings, such as. B. air bearings provided.

The gas bearings, such as air bearings, are preferred embodiments of elastic members that provide elastic forces for maintaining or maintaining a gap width. The gas bearings are also preferred embodiments of power storage and / or generation devices that provide radial forces between the rotor and stator to maintain desired airgap widths.

Particularly preferably, such radial forces act as counter forces to magnetic forces acting between the rotor and the stator. For example, in particularly narrow air gaps, in at least some architectures of electrical machines, magnetic attraction acts in the air gap between the stator and the rotor. The energy storage and / or generating device is preferably used to generate counter forces for such magnetic attraction forces, so that acts between the rotor and the stator in the air gap, a balance of power.

In order to achieve an excellent adaptation of the radial relative dimensions between rotor and stator even with thermal expansions and / or pulsating forces, at least one of the assemblies rotor and stator has a plurality of segments, which are mounted correspondingly movable in the radial direction and by means of the gap width maintaining device for balancing Such deviations are movable.

Preferably, for this purpose, the above already briefly explained balance of power between force to be generated and magnetic attraction is used.

In known architectures of electrical machines, in particular the TFPM machines or FSPM machines, very high quality demands are to be placed on the tolerances during production. In particular, if the air gap is to be kept very small, for example below 1.0 mm, more particularly below 0.5 mm and more especially 0.1 mm or below, such tolerances can be achieved only with very high production costs.

Also, it is difficult to attach control or regulating mechanisms to the correspondingly narrow air gaps.

The inventive design makes it possible in particular to be able to compensate for physical phenomena such as thermal or mechanical expansion and deflections due to pulsating normal and tangential forces.

An advantage of particularly preferred embodiments of the invention is to be able to produce electrical machines with very high demands on low air gap widths with reasonable effort, while at the same time by the thermal expansion of the rotor structure and the stator structures and the problem of vibration in such close together arranged assemblies and the mechanical Expansion of the rotor due to centrifugal forces is avoided or at least reduced.

This provides a greater variety of different design options for novel architectures of electrical machines that are suitable for many applications, including aircraft propulsion.

It is known from the prior art mentioned at the outset that electric motors are used for generating electricity or for driving purposes in various types of applications in the aviation industry. The electric motors, in particular due to the use of iron materials in their core, can potentially produce a high force density in the air gap up to the extent permitted by magnetic saturation and cooling. Air gap width is an important parameter in electric machines because the air gap width directly affects the amount of air gap force density that can be achieved before saturation occurs and before line losses become too high. The application rule for this aspect is simple: the smaller the air gap width, the higher the air gap power density can be achieved with a given phase current.

While some types of machines are less sensitive to the requirement of air gap width than others, this air gap condition is nevertheless applicable to all types of electrical machines. Those architectures of electrical machines that achieve the maximum air gap force densities are among those that are most sensitive to the air gap width. This is especially the case with TFPM machines and FSPM machines.

• – Eine sehr kleine Luftspaltbreite ist bei vielen Maschinentypen erforderlich, um eine verbesserte Performance oder Leistung gegenüber dem bisher nach dem Stand der Technik Möglichen zu erreichen.
• – Wärmeausdehnung und pulsierende Kräfte in der Normalrichtung machen es sehr schwierig, einen schmalen Luftspalt zu erreichen, selbst wenn die erforderliche Herstellungstoleranz erzielt werden kann. Dieses Problem vergrößert sich, je größer der Durchmesser der Maschine ist.

Disadvantages of previous electrical machines with regard to the air gap width requirements are:

• - A very small air gap width is required for many types of machines to achieve improved performance or performance over what has been possible in the prior art.
• - Thermal expansion and pulsating forces in the normal direction make it very difficult to achieve a narrow air gap, even if the required manufacturing tolerance can be achieved. This problem increases as the diameter of the machine increases.

An embodiment of the invention will be explained in more detail with reference to the accompanying drawings. It shows:

1 a plan view of an electric machine with a rotor, a stator, an air gap between rotor and stator and a gap width maintaining device for maintaining a gap width of the air gap;

2 a partially sectioned side view through a half of the electric machine of 1 ,

In the figures is an electric machine 20 shown schematically, the z. B. as an electric motor 22 or as an electric generator in an aircraft, such as a helicopter (not shown), is usable. The electric motor 22 is particularly suitable as a propulsion engine or direct engine for driving a main engine shaft of a propulsion and / or buoyancy engine of the aircraft.

The electric motor 22 has a stationary first assembly 24 in the form of a stand 30 and a movable second assembly 26 in the form of a runner 2 on, around a rotation axis 28 relative to the stand 30 is rotatably arranged.

Between the runner 2 and the stand 30 is an annular air gap 32 educated. The "air gap" is the annular gap between the electromagnetically effective sections 5 . 8th from runner 2 and stand 30 designated. The air gap 32 does not necessarily and always have to be filled with air; This is a free space between the corresponding electromagnetic sections 5 . 8th of the runner 2 and stand 30 that according to the atmosphere in which the electric machine 20 can be operated, can also be filled with other gases or can also be evacuated. According to the general designation in the field of electrical machines, the term "air gap" is used for this annular space. 32 used.

Next, the electric machine 20 a gap width maintaining device 34 on, the one gap width of the air gap 32 keeps constant in a given frame. For forming the gap width maintaining device 34 has at least one of the modules 24 . 26 the electric machine 20 several segments 36 on. At least one of the segments 36 is by means of a storage facility 38 in relation to the axis of rotation 28 Seen radially direction movable.

In a preferred embodiment, the storage facility 38 in particular one or more linear bearings 40 on, with which the at least one radially movable segment 36 is slidably mounted only in the radial direction, but in the tangential direction 4 (or also called circumferential direction) is immovable.

Further, the gap width maintaining device 34 an energy storage and / or generating device 42 for applying the at least one radially movable segment 36 with a radially acting force to maintain the gap width of the air gap 32 on.

The energy storage and / or generating device 42 has at least one energy storage and / or generating element 44 per radially movable segment 36 on to the associated radially movable segment 36 with a corresponding radially acting force for maintaining a predetermined gap width of the air gap 32 between the segment 36 and the other assembly 26 to act on.

In the illustrated embodiment, this is at least one force storage and / or generating element 44 as an elastic element 46 designed to provide an elastic force.

As an elastic element 46 is in the preferred embodiment, a gas bearing 48 between the assigned segment 36 and the other assembly 26 intended. The gas warehouse 48 is pressurized with pressurized gas, so that between the segment 36 and the other assembly 26 a repulsive pressure 12 adjusts the at least one elastic force on the segment 36 exercises.

As a gas warehouse 48 is preferably an air bearing 6 provided, which is filled with compressed air, filled and / or acted upon.

The in the 1 and 2 illustrated electrical machine 20 has as a gap width maintaining device 34 thus preferably an air gap control or regulating mechanism 50 , the air bearing 6 used on.

The electric machine 20 with the air gap control or regulating mechanism 50 using air bearings 6 is essentially from the stand 30 and the runner 2 constructed in its basic features as in conventional electric machines. Examples of usable rotor and stator structures can be found in the WO 2013/087056 A2 ,

The stand 30 is to make up the segments 36 in several stator segments 1 split that around the runner 2 are arranged around and mechanically independent of each other.

Each stand segment 1 is with the storage facility 38 to a surrounding element, such. As an unillustrated housing, or other base 52 attached. The storage facility 38 has several linear bearings 40 on top of the stand segments 1 radially movable relative to the base 52 to store. In particular, each stator segment 1 to the exterior using plain bearings 3 attached. The plain bearings 3 allow movement of the upright segment 1 in the radial direction, but not in the tangential direction 4 ,

Each stator segment 1 has a stator electromagnetics section 5 and at least part of one or more air bearings 6 on.

In the illustrated example, there is a stator electromagnetics section 5 between two air bearings 6 arranged.

The plain bearings 3 , the stator electromagnetics section 5 and the air bearings 6 are in a stand segment 1 by means of a mechanical connection 7 mechanically interconnected.

The runner 2 has a rotor electromagnetics section 8th and an air bearing support section 9 on.

In the illustrated examples is a rotor electromagnetics section 8th between two air bearing support sections 9 arranged.

The rotor electromagnetics section 8th and the air bearing support sections 9 are by means of a mechanical connection 10 mechanically interconnected.

In the unspecified electromagnetic sections 5 . 8th are the usual electromagnetic components of the stator 30 or runner 2 , Depending on the type of electrical machine 20 here permanent magnets, coils, windings, windings, commutators, brushes, cages, etc. are arranged.

In particular, the electromagnetic sections 5 . 6 designed such that, at least when approaching and / or during operation of the electric machine 20 at least with a directional component in the radial direction acting magnetic forces between the stator segments 1 and the runner 2 form, wherein the energy storage and / or generating device 42 Counter-forces to counteract these magnetic forces generated.

In an illustrated example, the stator segments 1 near the runner 2 arranged, causing magnetic attraction 11 between the stator electromagnetics section 5 and the rotor electromagnetics section 8th leads. These magnetic attractions 11 Serve as a magnetic preload or magnetic preload for the air bearings 6 , The air bearings 6 compensate the magnetic attractions 11 between the stator electromagnetics section 5 and the rotor electromagnetics section 8th due to the repulsive pressure 12 passing through the air bearings 6 against the air bearing support section 9 is exercised. In particular, this is the air bearing 6 filled with compressed air or applied.

Because the stator segments 1 Free yourself to the runner 2 or away from the runner 2 in the radial direction - but preferably not in the tangential direction 4 can move - will any size change to the stand segment 1 - z. B. caused by thermal expansion - or the runner 2 - z. B. caused by thermal expansion or by mechanical expansion due to centrifugal forces - by an automatic readjustment of the position of the stator segment 1 compensated. At the same time, the width of the air gap remains 32 between the stand segment 1 and the runner 2 due to the balance between the magnetic forces of attraction 11 Between the stator electromagnetics section 5 and the rotor electromagnetics section 8th - and the repulsive pressure 12 - between the air bearing 6 in the upright segment 1 and the air bearing support portion 9 in the runner 2 - unchanged.

Although plain bearings 3 because of its simple structure for forming the linear bearings 40 are preferred, the linear bearings 40 be constructed differently, for. B. using rolling elements, such as balls or rollers.

The elastic element 46 is preferably as a gas bearing 48 and in particular as an air bearing 6 educated. This has the advantage of easy adjustability by appropriate adjustment of the repulsive pressure 12 , Depending on the design of the gas storage 48 is also a change in the repulsive pressure 12 possible during operation, eg. B. by connecting corresponding gas lines to a gas reservoir (not shown) and by control with Control valves (not shown). The construction as an air bearing 6 or gas storage 48 is preferred, as a result of maintaining a desired gap width by means of the gap width maintaining device 34 is possible without or with only very low friction losses. Of course, but other elastic elements 46 , such as As mechanical springs or the like, between a rotary axis bearing 48 and the individual segments 36 possible. Also, the power storage and / or generating device 42 also for imposing other forces, such. As magnetic forces or the like may be formed. Preferably, elastic elements 46 provided with elastic forces to also dynamic changes in operation, eg. As shocks in the normal direction or the like, easy to compensate.

• – Durch die Spaltbreitenaufrechterhaltungsvorrichtung 34 bzw. den Luftspaltsteuer- oder -regelmechanismus 50 ist eine erhöhte Kraft- oder Leistungsdichte und eine erhöhte Drehmomentdichte, d. h. ein erhöhter Kilowatt-Wert pro Kilogramm und ein erhöhter Newton-Meter-Wert pro Kilogramm, aufgrund einer verbesserten Performance durch die Möglichkeit eines kleineren Luftspaltes ermöglicht.
• – Dies bietet eine effektive Lösung für durch thermische und mechanische Ausdehnung sowie durch Vibrationen und unbalancierte Magnetkräfte verursachte Probleme.

Some advantages of the embodiment of the electric machine shown here are:

• - By the gap width maintaining device 34 or the air gap control or regulating mechanism 50 is an increased power or power density and increased torque density, ie an increased kilowatt value per kilogram and an increased Newton meter per kilogram, due to improved performance by the possibility of a smaller air gap allows.
• This provides an effective solution to problems caused by thermal and mechanical expansion as well as by vibration and unbalanced magnetic forces.

LIST OF REFERENCE NUMBERS

1

stator segments

2

runner

3

bearings

4

tangential

5

Ständerelektromagnetiksektion

6

air bearing

7

mechanical connection (stand)

8th

Läuferelektromagnetiksektion

9

Luftlagerabstützsektion

10

mechanical connection (runner)

11

magnetic attraction

12

repulsive pressure

20

electric machine

22

electric motor

24

first assembly

26

second module

28

axis of rotation

30

stand

32

air gap

34

Gap width maintaining means

36

segment

38

Storage facility

40

linear bearings

42

Power storage and / or generating device

44

Power storage and / or generating element

46

elastic element

48

gas storage

50

Air gap control or regulating mechanism

52

Base

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2013/087056 A2 [0002, 0006, 0013, 0063]
• WO 2013/087053 A2 [0006]
• DE 102010021024 A1 [0013]
• DE 102010021025 A1 [0013]
• DE 102010021026 A1 [0013]
• WO 2011/144692 A2 [0013]
• DE 102011121174 A1 [0013]

Claims (15)

Electric machine ( 20 ), which has a stand ( 30 ) as a first assembly ( 24 ) and one relative to the stand ( 30 ) about a rotation axis ( 28 ) rotatably arranged runners ( 2 ) as a second assembly ( 26 ), wherein an air gap ( 32 ) between the assemblies ( 24 . 26 ), characterized in that at least one of the assemblies ( 24 . 26 ) several segments ( 36 ) having the air gap ( 32 ) and that a gap width maintenance device ( 34 ) for maintaining a gap width of the air gap ( 32 ) is provided which a storage facility ( 38 ) for radially movably supporting at least one of the segments ( 36 ) having. Electric machine ( 20 ) according to claim 1, characterized in that the gap width maintaining device ( 34 ) a force storage and / or generating device ( 42 ) for acting on the at least one radially movably mounted segment ( 36 ) with a counterforce, which against a radial on the segment ( 36 ) acting magnetic force acts has. Electric machine ( 20 ) according to claim 2, characterized in that the one energy storage and / or generating device ( 42 ) at least one elastic element ( 46 ) for generating an elastic counterforce on the at least one radially movable segment ( 36 ) for maintaining a gap width of the air gap ( 32 ) having. Electric machine ( 20 ) according to one of claims 2 or 3, characterized in that the energy storage and / or generating device ( 42 ) at least one gas bearing ( 48 ) between the radially movably mounted segment ( 36 ) and the other assembly ( 24 . 26 ) having. Electric machine ( 20 ) according to one of the preceding claims, characterized in that the storage device ( 38 ) at least one radially acting linear bearing ( 40 ) and / or plain bearings ( 3 ) having. Electric machine ( 20 ) according to one of the preceding claims, characterized in that at least the air gap ( 32 ) limiting area of the stand ( 30 ) into several by means of the storage device ( 38 ) relative to the runner ( 2 ) radially movably mounted stator segments ( 1 ) is divided. Electric machine ( 20 ) according to claim 6, characterized in that the stator segments ( 1 ) by means of the storage device ( 38 ) are radially displaceable, but are mounted tangentially immobile. Electric machine ( 20 ) according to claim 7, characterized in that the storage device ( 38 ) a plurality of radially acting linear bearings ( 40 ) and / or plain bearings ( 3 ) for the stator segments ( 1 ) having. Electric machine ( 20 ) According to one of claims 6 to 8, characterized in that the stator segments ( 1 ) each a stator electromagnetics section ( 5 ) and the runner ( 2 ) at least one rotor electromagnetics section ( 8th ) such that magnetic attraction forces ( 11 ) over the air gap ( 32 ) between each stator segment ( 1 ) and the runner ( 2 ), and that each stator segment ( 1 ) in the radial direction by at least one energy storage and / or generating element ( 44 ) with one against the magnetic forces of attraction ( 11 ) acting counterforce can be acted upon. Electric machine ( 20 ) according to claim 9, characterized in that the at least one energy storage and / or generating element ( 44 ) an elastic element ( 46 ) is, by means of which an elastic force can be generated as a counter force. Electric machine ( 20 ) according to claim 10, characterized in that for forming the elastic elements ( 46 ) between each stator segment ( 1 ) and the runner ( 2 ) one or more acted upon pressurized gas (s) gas bearing ( 48 ) is provided. Electric machine ( 20 ) according to one of the preceding claims, designed as a permanent magnet-excited transverse flux machine and / or permanent magnet-excited flux-switching machine. Aircraft comprising an electric machine ( 20 ) according to one of the preceding claims as a generator for generating electrical energy and / or as an electric motor ( 22 ). Hybrid drive for an aircraft, in particular a helicopter, comprising an electric machine ( 20 ) according to one of claims 1 to 12. A helicopter comprising a hybrid drive according to claim 14.

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