WO2012161631A1

WO2012161631A1 - A rotary electric machine, a rotor for a such and a vehicle/craft with such a machine

Info

Publication number: WO2012161631A1
Application number: PCT/SE2011/050658
Authority: WO
Inventors: Mats Leijon; Boel EKERGÅRD
Original assignee: Electric Line Uppland Ab
Priority date: 2011-05-26
Filing date: 2011-05-26
Publication date: 2012-11-29
Also published as: EP2715916A1; EP2715916A4

Abstract

The invention relates to a rotary electric machine having a stator with winding and a rotor. According to the invention, the rotor (1) consists of an even number of separate units (6-11) of magnetisable material. The units (6-11) are joined together such that each unit (6-11) forms a part of the circumferential of the rotor (1) and with an interspace (12) between each adjacent pairs of units (6-11). At least one permanent magnet (13) is arranged in each interspace (12). The invention also relates to a correspondingly constructed rotor 1) for a rotary electric machine and to a vehicle/craft provided with the invented machine.

Description

A ROTARY ELECTRIC MACHINE, A ROTOR FOR A SUCH AND A

VEHICLE/CRAFT WITH SUCH A MACHINE Field of invention

The present invention relates to a rotary electric machine having a stator with winding and a rotor.

The invention also relates to a rotor for a rotary electric machine.

Further, the invention also relates to a vehicle or a craft provided with such a machine.

Background of invention Electric machines, i.e. motors or generators conventionally has a rotor that consists of a substantially cylindrical body having magnets distributed on the circumferential thereof, which magnets form the poles of the rotor. For the production of such machines in large series, for example when used as drive source in vehicles it is important to find a rational way of manufacturing the machines in order to achieve low manufacturing costs.

The object of the present invention is to achieve a machine that meets this demand and thus is cost effective regarding its manufacturing. In particular the object is to improve the rotor in this respect. Summary of invention

This object is achieved in that a rotary electric machine of the kind specified in the preamble of claim 1 includes the specific features that the rotor has an even number of separate units arranged after each other in the circumferential direction and joined together such that each unit forms a part of the circumferential of the rotor and with an interspace between each two adjacent units, and at least one permanent magnet arranged in each said interspace, and which units are made of magnetisable material .

The rotor thereby can be manufactured in a much more rational way. For a conventional rotor it is necessary to provide the cylindrical body with recesses adapted to receive the permanent magnets, fit these into the recesses and secure them therein. This can be quite circumstantial. A rotor according to the present invention eliminates a large part of the manufacturing steps involved in this procedure. The rotor can be built up by units that are uncomplicated in shape and thus easy to produce. The permanent magnets may also be of very simple kind, and the units making up the rotor can easily be joined together. Since the units are made of magnetisable material, they will be magnetised by the permanent magnets and form the poles of the rotor. It is within the scope of the invention that there is only one single permanent magnet in each interspace.

According to a preferred embodiment, the units are identical in shape.

This contributes to an optimized pole distribution and to harmonized and well controlled magnetic fields. The identical shape of the units also rationalises the manufacturing.

According to a further preferred embodiment the number of units is two, and each unit in a cross section perpendicular to the rotor axis has the general shape of a circular segment, having a height that is in the range of 0,5 to 0,97 times the radius of the circular segment and such that the sum of the heights and the distance between the units equals twice said radius.

Forming the rotor of only two units results in a very simple design and assembly of the rotor and is suitable in cases where a two-pole arrangement is appropriate. The defined dimensions result in a generally cylindrical shape of the rotor. The lower and upper limits for the height of each segment define

corresponding upper and lower limits for the distance between the units implying maximum and minimum thickness respectively for the magnets that are arranged in the interspace. In most cases a suitable thickness of the magnets is such that the defined range is more narrow, preferably in the range of 0, 75 to 0, 95.

According to a further preferred embodiment for a two-pole rotor there is a plurality of permanent magnets arranged in the interspace between the two units, which magnets all have their north poles directed in the same direction.

Providing a plurality of magnets offers a flexibility to optimize the magnetic properties of the rotor in correspondence with demands. Building up the magnet arrangement by a plurality of magnets also represents a module concept such that similar magnets can be used for rotors of different size, simply by varying the number of magnets provided in the interspace. A plurality of magnets may be arranged side by side along the diameter of the rotor. Alternatively or

complementary a plurality of magnets may be provided in the axial direction of the rotor. When there are a plurality of magnets they may be arranged in contact with each other or at a distance from each other. The magnets may completely fill the interspace in the lateral directions. A plurality of magnets can also or alternatively, be arranged in the third direction, i. e. in the direction of the width of the

interspace.

According to a further preferred embodiment for a two-pole rotor there is arranged only one single magnet in the interspace between the units.

This represent a very simple embodiment that is easy to manufacture and assembly. Such a rotor will be very reliable and has distinct predictable magnetic behaviour.

According to a further preferred embodiment the number of units is at least four, and each unit in a cross section perpendicular to the rotor axis has a shape that is limited by an outer circular arc and two side profiles that extend inwardly from a respective end of the arc and meet each other at a meeting point, such that a radius through the meeting point symmetrically intersects the cross section and such that the distance between the meeting point and the arc is shorter than the radius, and which circular arcs have a common centre point.

In many cases a multi-pole rotor is required, and this embodiment in an advantageous way applies the principle of the invention to that. The number of units thereby determines the number of poles of the rotor and can be any even number; four, six, eight etc. The shape defined above is generally that of a circular sector, however with some deviation from the strict mathematical definition of a sector since the units do not reach all the way into the centre point. It is also to be understood that, although the side profiles may be just straight lines, they may deviate from straight lines.

According to a further preferred embodiment for a multi-pole rotor there is a plurality of magnets arranged in the interspace between each pair of adjacent units.

This embodiment has advantages corresponding to those described above for a two-pole rotor, and the plurality of magnets may be arranged in similar patterns as in the two-pole rotor. According to a further embodiment for a multi-pole rotor all magnets in one interspace have the north poles directed in the same rotational direction and the rotational direction is opposite to each other for two adjacent interspaces.

Thereby the magnets in each pair of adjacent interspaces will have their north poles directed to the intermediate unit to effectively form this unit as a north pole. The adjacent units will correspondingly be formed as south poles.

According to a further preferred embodiment for a multi-pole rotor there is one single magnet arrange in the interspace between each pair of adjacent units.

This embodiment has advantages corresponding to those described above for a two-pole rotor having only one magnet.

According to a further preferred embodiment, the rotor at at least one axial end thereof has a radial bearing which journals the rotor at a radius that is at least as large as the radius of the rotor.

Thereby disturbance from a central shaft and the bearing arrangements on the magnetic field of the rotor is eliminated or at least reduced. This arrangement also eliminates the need for a central rotor shaft, which have particular advantages in connection with a rotor that is built up by units according to the present invention since such a rotor otherwise would require certain specific measures for providing drive connection between the shaft and the units. Preferably the rotor is journaled on both sides with this kind of outer bearings.

According to a further preferred embodiment, the rotor on at least one axial side of the stator has a tubular extension, the outer surface of which is journalled in said bearing.

The tubular extension is a simple and reliable way of adapting the rotor for journaling it in bearings at a radius that is at least as large as the radius of the rotor.

The invention also relates to a rotor for a rotary electric machine, which rotor has the same features as the rotor in the machine according to the present invention, in particular to any of the preferred embodiments of the machine.

The invented rotor has advantages of the same kind as those of the rotary electric machine according to the present invention and the preferred

embodiments thereof, which advantages have been described above. Further, the invention also relates to a vehicle or a craft provided with a rotary electric motor according to the present invention, in particular to any of the preferred embodiments thereof.

Due to its simplicity and its low manufacturing costs, the machine is particularly useful in applications at large series and for consumer products which normally are very price sensitive, which is the case for cars and the like. For vehicles or crafts that at least partly are electrically powered it is therefore very advantageous to have a machine according to the present invention.

According to a preferred embodiment of the invented vehicle/craft, the machine is arranged to operate alternating as a generator or a motor.

According to a further preferred embodiment, the machine has a power in the range of 30 kW to 3 MW.

According to a further preferred embodiment, the vehicle/craft is arranged to operate at a voltage in the range of 1 kV to 12 kV.

According to a further preferred embodiment, the vehicle/craft has a hybride driving system or an entirely electrical driving system.

According to a further preferred embodiment, the machine includes a flywheel connected to the rotor.

The preferred embodiments of the vehicle/craft are important for a achieving a drive system that meets the increasing demand on improved power utilization and increased environmental concern. In EP 1565337 describes a driving system for a vehicle, which to a large extent is similar to the those of the preferred

embodiments of the vehicle/car mentioned above. This document is hereby incorporated by reference into the present application. The advantages of these systems are explained in that disclosure. The vehicle/craft according to the present invention may be provided with the specific kind of stator winding disclosed in that reference. Thereby the stator comprises a first winding arranged to operate at low voltage and a second winding arranged to operate at high voltage, which first and second windings are arranged to operate independently of each other. Also as in the system of the reference at least one of the stator winding may comprise a conductor surrounded by a first semiconducting layer, surrounded by a layer of solid insulation and with a second semiconducting layer surrounding the insulation layer. The above described preferred embodiments of the invention are specified in the dependent claims. It is to be understood that further preferred embodiments of course can be constituted by any possible combination of the preferred

embodiments above and by any possible combination of these and features mentioned in the description of examples below.

The invention will be further explained through the following detailed description of examples thereof and with reference to the accompanying drawings.

Short description of the drawings

Fig. 1 is a section perpendicular to the rotor axis through a rotor of a machine according to a first example of the invention.

Fig. 2 is a section similar to that of fig. 1 according to a second example of the invention.

Fig. 3 is a section similar to that of fig. 1 according to a third example of the invention.

Fig. 4 is a transparent view in perspective of the rotor in fig. 3.

Fig. 5 is a side view of the rotor according to fig. 1 .

Fig. 6 is a detail of the rotor in fig. 1 but somewhat modified.

Fig. 7 is a schematic side view if a vehicle according to the invention.

Description of examples

Fig. 1 illustrates one example of a rotor 1 in an electric machine according to the invention. The rotor 1 has six separate units 6-1 1 assembled together to form a substantially cylindrical rotor body. Between each pair of adjacent units there is an interspace 12. In each interspace 12 a permanent magnet 13 is squeezed between the two adjacent units 6-1 1 . Each unit 6-1 1 has a cross sectional shape consisting of an outer circular arc A and two side profiles L1 , L2, in this example being straight lines, that extend inwardly from a respective end of the arc A and intersect at a meeting point P not far from the centre point O of the arc A. A radius R from the centre point O through the meeting point P

symmetrically divides the cross section of the unit 6-1 1 . The distance I from the meeting point P to the arc A is smaller than the radius R. The angle between the side lines is 60°. The magnet 13 in each interspace has its poles directed in the rotational direction. In every second interspace 13 the north pole N of the magnet is facing in the clockwise direction and the south pole S in the counter-clockwise direction. In the intermediate interspaces each magnet is oppositely oriented. Each unit 6-1 1 is of magnetisable material such as iron. The magnets 13 in the interspaces 12 thus will make the units 6-1 1 magnetized.

Due to the orientation of the magnets 13 described above each unit 6-1 1 will face a magnet pole of the same kind and thus will be magnetised either as a north pole N or a south pole S. Thereby every second unit 6, 8, 10 will be a south pole S and each intermediate unit 7, 9, 1 1 will be a north pole N. The units 6-1 1 thus will form the magnetic poles of the rotor 1 and induce current in the stator winding when the rotor rotates.

In the example according to the figure there is one magnet 13 in each interspace. Alternatively there can be a plurality of magnets in each interspace. In that case all the magnets in one interspace have to have the same direction with regards to its poles.

The units may be kept together as an assembled rotor by any suitable means, for example by bolt flanges joining adjacent units to each other or by circumferential bands around the complete rotor.

In the example above the number of units is six, but a rotor can consist of a much larger even number of units than that. The rotor may also have f ewer number of units. In the example of fig. 2 the rotor has only two units 106, 107. Each unit 106, 107 has a cross section with the general shape of a circular sector, having a height h, which in this example is about 90% of the radius but might be chosen to be larger or smaller than that.

In the interspace 1 12 between the units 106, 107 there are three permanent magnets 1 13a - 1 13c having their poles facing in the same direction. The upper unit 106 will thereby be magnetised to be a north pole N and the lower unit 107 a south pole S. This rotor thus has only two poles.

Fig. 3 illustrates another example of the invention related two a machine with a two-pole rotor 201 . In this example there is only one single magnet 212 in the interspace 212 between the two units 206, 207. The rotor 201 is shown inside its stator 202. The stator 202 in this example has 48 winding grooves 217. In fig. 4 the rotor 201 of the machine in fig. 3 is shown in a transparent view in perspective. It can be seen that the magnet 213 has the shape of an orthogonal box with a length a little shorter than the diameter of the rotor 201 , a bradth corresponding to the axial extension of the rotor 201 and a width that is about 10 % of the diameter.

Fig. 5 illustrates the rotor 1 of fig. 1 in a side view and located within the stator. In this example the rotor 1 has a peripheral extension 3a, 3b on each side of the rotor body. The rotor is journalled in bearings 4a, 4b on each of the extensions 3a, 3b.

Fig. 6 illustrates a modification of a detail in the rotor 1 of fig 1 . In the rotor of fig 1 the cross section of each unit 6-1 1 has profile sides L1 , L2 that are straight lines. However the side profiles L1 , L2 may have shapes that deviate from that. In the example of fig. 4 each side profile L1 , L2 has a recess 14 for receiving the magnet 13. A plurality of recesses may be provided if there is a plurality of magnets.

Further, the inner end of the unit 6 may be rounded by a circular portion 15. In some alternatives, in particular if the rotor is provided with a central shaft the circular portion 15 in stead may be a concave circular portion. Also the connection between the arc and the side profile may be rounded by a circular portion 16.

The angle between the profile sides L1 , L2 in the units according to fig. 1 is 60°. This angle may however deviate from that, e.g. be somewhat larger, with the result that the interspace will slightly converge in the outward direction.

Fig. 7 schematically depicts a car 20 being provided with a rotary electric machine 21 according to the invention. The machine 21 is arranged to be able to operate either as a motor or a generator. A flywheel 22 for storing kinetic energy is connected to the machine 21 . The machine may be included in a drive system of the kind disclosed in the above mentioned EP 1565337.

Claims

1 . A rotary electric machine having a stator (2, 202) with winding and a rotor (1 ), characterized in that the rotor (1 , 101 , 201 ) has an even number of separate units (6 -1 1 , 106, 107, 206, 207) arranged after each other in the circumferential direction and joined together such that each unit (6-1 1 , 106, 107, 206, 207) forms a part of the circumferential of the rotor (1 , 101 , 201 ) and with an interspace (12, 1 12, 212) between each two adjacent units (6- 1 1 , 106, 107, 206, 207) , in that at least one permanent magnet (13, 1 13a- 1 13c, 213) is arranged in each said interspace (12, 1 12, 212), and in that each unit (6-1 1 , 106, 107, 206, 207) is made of magnetisable material.

2. A rotary electric machine according to claim 1 , characterized I that said units (6-1 1 , 106, 107, 206, 207) are identical to each other in shape.

3. A rotary electric machine according to claim 1 or 2, characterized in that the number of units (106, 107, 206, 207) is two and that each unit (106, 107, 206, 207) in a cross section perpendicular to the rotor axis has the general shape of a circular segment, having a height (h) that is in the range of 0,5 to 0,97 times the radius of the circular segment, and in that the sum of the heights (h) and the distance (d) between the units (106, 107, 206, 207) equals twice said radius.

4. A rotary electric machine according to claim 3, characterized in that a plurality of permanent magnets (1 13a-1 13c) are arranged in the interspace (1 12) between the units (106, 107), which magnets (1 13a-1 13c) all have their north poles (N) directed in the same direction.

5. A rotary electric machine according to claim 3, characterized in that only one single magnet (213) is arranged in the interspace (212) between the units (206, 207).

6. A rotary electric machine according to claim 2, characterized in that the number of units (6-1 1 ) is at least four, that each unit (6-1 1 ) in a cross section perpendicular to the rotor axis has a shape that is limited by an outer circular arc (A) and two side profiles (L1 , L2) that extend inwardly from a respective end of the arc (A) and meet each other at a meeting point (P), such that a radius (R) through the meeting point (P) symmetrically intersects the cross section and such that the distance (I) between the meeting point (P) and the arc (A) is shorter than the radius (R), and which circular arcs (A) have a common centre point (O).

7. A rotary electric machine according to claim 6, characterized in that a

plurality of magnets (13) are arranged in the interspace (12) between each pair of adjacent units (6-1 1 ).

8. A rotary electric machine according to claim 6 or 7, characterized in that all magnets (13) in one interspace (12) have the north poles (N) directed in the same rotational direction and in that said rotational direction is opposite to each other for two adjacent interspaces (12).

9. A rotary electric machine according to claim 6, characterized in that only one single magnet (13) is arranged in the interspace (12) between each pair of adjacent units (6-1 1 )

10. A rotary electric machine according to any of claims 1 -9, characterized in that the rotor (1 , 101 , 201 ) at least at one axial side of the stator (2, 202) has a radial bearing (4a, 4b) that journals the rotor (1 , 101 , 201 ) at a radius that is as least as large as the radius of the rotor (1 , 101 , 201 ).

1 1 .A rotary electric machine according to claim 10, characterized in that the rotor (1 , 101 , 201 ) on at least one axial side of the stator (2, 202) has a tubular axial extension (3a, 3b), the outer surface of which is journalled in said bearing (4a, 4b).

12. A rotor (1 , 101 , 201 ) for a rotary electric machine, characterized in that the rotor (1 , 101 , 201 ) has the features specified for the rotor (1 , 101 , 201 ) of the rotary electric machine according to any of claims 1 -9.

13. A vehicle (20) or a craft, characterized in that the vehicle (20) or the craft is provided with a rotary electric machine (21 ) according to any of claims 1 - 1 1 .

14. A vehicle or a craft according to claim 13, characterized in that the

machine (21 ) is arranged to operate alternating as a generator or a motor.

15. A vehicle (20) or a craft according to claim 13, characterized in that the machine (21 ) has a power in the range of 30 kW to 3 MW.

16. A vehicle (20) or a craft according to claim 13, characterized in that the vehicle (20) or the craft is arranged to operate at a voltage in the range of 1 kV to 12 kV.

17. A vehicle (20) or a craft according to any of claims 13-16 , characterized in that the vehicle (20) or craft has a hybrid driving system or an entirely electrical driving system.

18 A vehicle (20) or a craft according to any of claims 13-17, characterized in that the machine (21 ) includes a flywheel (22) connected to the rotor.