Permanent magnet rotor for an electric machine

A permanent magnet having end surfaces and an envelope curve shaped as a biconvex lens having first and second convex portions, magnetization running in an arcuate manner along the first convex portion between a north pole and a south poles. The permanent magnet runs along the second convex portion in an arcuate manner, and at least one of the magnet's end surfaces within the envelope curve has a connection surface adapted for connecting with a connection device by fusing or by positive engagement. The rotor is preferably pressed onto the shaft of the rotor after the connection device is formed around a connection surface of the permanent magnets by injection molding.

BACKGROUND OF THE INVENTION

The present invention relates to permanent magnets. More particularly, the invention relates to a permanent magnet used in a rotor of an electric machine, and to a use of permanent magnets in the rotor of the electric machine.

A permanent magnet described in CH 549 307 A has the shape of a horseshoe wherein its yoke is innermost and its limbs are directed outwards. This permanent magnet does not necessarily have the external shape of a horseshoe, since the cited publication discloses that the magnet may be formed in the shape of a hexagonal or segment-type block. In addition to creating the U or V shape of the permanent magnet using individual rectangular permanent magnets, magnets having the shape of a U or V in a single piece are also described. The limbs of the magnet extend radially outwards, such that the two magnetic poles of the permanent magnet are located at circumferentially separate points on the outermost radial surface of the magnet. The magnets in that publication are made of a material having a high coercive force and may be a ceramic or metallic mass or a mixture of Iron powder that is bonded by rubber or resin. Permanent magnets are usually magnetized before assembly, but a stator winding may also be used for magnetizing them or setting a magnetization level.

In that publication, the permanent magnets are used in a permanent magnet rotor for alternating current machines, in particular synchronous motors or synchronous generators. The rotor preferably includes a squirrel-cage winding, which is already known, in order to provide the breakaway moment in a manner similar to the way in which it is provided in squirrel-cage motors. The permanent magnets and the rods can both be held in place by a cast aluminum body, if the rotor end ring of the squirrel-cage winding is an aluminum casting. An adhesive may be used to hold the magnets in place during the casting process. If the squirrel-cage rotor Is made of copper rods, the magnets can be held by the copper rods or a combination of the copper rods and an adhesive that attaches the magnets to the coil, e.g. epoxy resin.

It would be desirable and advantageous to address prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a permanent magnet includes a north pole and a south pole, with a magnetization running from the south pole to the north pole in a cross section of the magnet, an envelope curve on the cross section of the permanent magnet having a bi-convex lens shape, the envelope curve having a first convex portion and a second convex portion, the magnetization in the permanent magnet running in an arcuate manner along the first convex portion of the envelope curve, and the permanent magnet also running in an arcuate manner along the second convex portion of the envelope curve, and end surfaces at a first end and a second end of the permanent magnet within the envelope curve, at least one of the end surfaces having a connection surface adapted for connecting a connection device to the permanent magnet.

In accordance with the present invention, a permanent magnet is constructed to connect to a connection device of the rotor of an electric in an inexpensive and high-quality manner, thereby providing inexpensive, high quality electric machines. The invention provides a method whereby the rotor of an electric machine can be connected to a permanent magnet in an Inexpensive, high-quality manner.

A permanent magnet according to the invention has a north and a south magnetic pole, and a magnetization that can run from the south pole to the north pole in a cross section of the permanent magnet, the cross section having an envelope curve that is shaped as a bi-convex lens. The permanent magnet comprises the first convex portion and a second convex portion, the magnetization of the permanent magnet running in an arcuate manner along the first convex portion, the permanent magnet running in an arcuate manner along the second convex portion, and having end surfaces at a first end and a second end of the permanent magnet, at least one of the end surfaces within the envelope curve has a surface used in connecting a connection device to the permanent magnet.

According to another aspect of he present invention, a rotor for an electric machine includes a permanent magnet extending from a first end to a second end of the permanent magnet parallel to an axis of rotation, a first convex portion of the permanent magnet being disposed along an envelope curve of the rotor, and having respective end surfaces at a first end and a second end of the permanent magnet within the envelope curve, at least one of the end surfaces having a connection surface adapted for connecting a connection device to the permanent magnet, and a connection device having a connection with the connection surface of the permanent magnet.

According to still another aspect of the present invention, an electric machine includes a rotor rotatably supported for rotation about an axis of rotation, a permanent magnet extending from a first end to a second end of the permanent magnet parallel to the axis of rotation, a first convex portion of the permanent magnet being disposed along an envelope curve of the rotor, and having respective end surfaces at a first end and a second end of the permanent magnet within the envelope curve, at least one of the end surfaces having a connection surface adapted for connecting a connection device to the permanent magnet; and a connection device having a connection with the connection surface of the permanent magnet, and a stator located to magnetically interact with the rotor across an air gap during the operation of the electric machine.

In accordance with the invention, a permanent magnet in a rotor of an electric machine includes a connection between a connection device and at least one surface of one of the end surfaces of the permanent magnet, and a cross section of the permanent magnet has an envelope curve that has the shape of a biconvex lens. Because the envelope curve of the cross section of the permanent magnet has a biconvex-lens shape in accordance with the invention, the surface of at least one end surface of the permanent magnet can be used to connect to the permanent magnet in an advantageously inexpensive and high-quality manner; also, the magnetization of the permanent magnet runs from the south pole to the north pole in an arcuate manner so that lateral magnetization can advantageously be provided using a modest amount of magnetic material.

Because of lateral magnetization in accordance with the invention, the north pole and the south pole are provided along the first convex portion of the biconvex envelope curve in an advantageously space-saving manner, that is, on one side of the permanent magnet. Because the first convex portion and the second convex portion are arranged reciprocally in a biconvex-lens shape, the end surfaces of the permanent magnet provide advantageously large surfaces for the connection of a connection device to the permanent magnet, a connection device in an electric machine, in particular.

The permanent magnet extends in a first direction from its first end to its second end. The cross section of the permanent magnet extends in a plane defined by a second direction and a third direction. The second direction and the third direction are perpendicular to the first direction. In a particular embodiment, at least one of the end surfaces of the permanent magnet of may be included in an envelope curve of the cross section. Thus, since the end surface does not project beyond the envelope curve, the end surface can be used in an electric machine and produced in an advantageously inexpensive and high-quality manner.

A rotor in accordance with the invention has the further advantage that a rotor having advantageously small dimensions can be provided in an advantageously inexpensive and high-quality manner. In accordance with the invention, the permanent magnets can advantageously have a modest height, said height being measured as the greatest distance between the first and the second convex portions.

A rotor in accordance with the invention can have at least two permanent magnets extending parallel to an axis of rotation from their first end to their second end. The first convex portions of the permanent magnets are disposed on a circular profile curve of the rotor that is concentric with the axis of rotation of the rotor. The rotor has at least one connection device and includes connections between the connection device and a surface of the permanent magnets. Thereby an advantageously smoother rotational movement of the rotor about the axis of rotation can be achieved.

According to another advantageous feature of the present invention, the north pole of one permanent magnet can be located next to the north pole of the closest permanent magnet along the circular profile curve of the rotor. Each magnetic pole of a rotor in this embodiment therefore can therefore include the same pole of each of the two closest permanent magnets along the envelope curve of the rotor in an advantageously inexpensive and high-quality manner. The distance between one permanent magnet and the next closest permanent magnet, thus, need not correspond to the distance between the north pole and the south pole of the same permanent magnet so that an electric machine having advantageously small dimensions can be provided in an advantageously inexpensive and high-quality manner.

Permanent magnets that are attached to a rotor in accordance with the invention in an advantageously space-saving manner using the connection surface of the permanent magnets that is described above can have an advantageously high level of air-gap induction, because of the space-saving provided using that connection surface, in accordance with the invention. In particular, bandaging the entire rotor can be dispensed with because of that connection surface. Thus the magnetic poles of the permanent magnets are not completely covered by a connection device in the air gap, e.g. a bandage. Advantageously, they are not covered at all. It is therefore advantageously possible to further increase the air-gap Induction, or to reduce the dimensions of the electric machine in accordance with the invention.

According to another advantageous feature of the present invention, the rotor can be attached to a shaft that is rotatably supported for rotation about its axis of rotation by first and second bearing devices. When the electric machine is operated as a generator, the rotor of an electric machine is set into motion about the axis of rotation by mechanical energy. The mechanical energy can be converted into electrical energy by the magnetic Interaction between magnetic poles of the rotor and the stator across the advantageous air gap provided in accordance with the invention. The electrical energy thus produced in the stator contributes to forming the electromagnetic poles of the stator and is drawn off from at least one winding of the stator by connecting an electric load to the winding. When the electric machine is operated as a motor, electrical energy can then be supplied to the stator using at least one winding, and the electrical energy can be converted into mechanical energy as a result of the magnetic interaction across the advantageous air gap between the magnetic poles of the stator and of the rotor provided in accordance with the invention. This produces a rotational moment that initiates rotation of the rotor about its axis of rotation and the mechanical energy is then delivered to a mechanical load by this rotational movement of the shaft of the rotor.

Use of the permanent magnet in accordance with the invention, has the further advantage that a permanent magnet having advantageously small dimensions can be supplied in an inexpensive, high-quality manner. It is therefore possible to economize on the space needed to transport the permanent magnets and the associated safety precautions that transport requires.

According to another advantageous feature of the present invention, the connection surface on the end surface of the first end can be connected to the connection device by fusing. In particular the permanent magnet can advantageously be fused to the connection device along a plane, which has the advantage that fusing along a plane can be produced using simple instruments and simple motion sequences.

According to another advantageous feature of the present invention, the connection surface on the permanent magnet advantageously can be un-machined. Because the connection surface is un-machined, a high-quality, inexpensive connection can be achieved without a coating. The un-machined surface of the permanent magnet allows the transfer of strong forces to the connection device, since the fused layer between them adheres better to the surface of permanent magnet because of its roughness. Any finishing of the connection surface after sintering the permanent magnet may be dispensed with.

According to another advantageous feature of the present invention, the surface of the permanent magnet may have a coating. It is then advantageously possible to inexpensively achieve a high-quality connection that achieves that transfer of strong forces by fusing the connection device, the coating and a permanent magnet together, according to the invention. In this context, the surface may be machined or un-machined before the coating is applied to the permanent magnet.

According to another advantageous feature of a permanent magnet according to the invention, the end surface on the first end can have a contour that includes the connection surface. In this way, the connection device can be connected to the permanent magnet by positive engagement. The contour may advantageously be produced at the end surface, which can be advantageously large surface because of the biconvex lens shape of envelope curve and the arcuate course of the magnetization in the permanent magnet.

According to another advantageous feature of a permanent magnet according to the invention, the contour can include a recess in the end surface of the first end. Because of the advantageously large connection surface, despite the recess, it is possible for the recess to have a boundary that avoids the recess's damaging the permanent magnet. The recess may advantageously comprise a groove. A groove has the advantage of being able to absorb force components that act on the permanent magnet parallel to the cross section, which are distributed over the connection surface in accordance with the particular course of the groove.

According to another advantageous feature of a permanent magnet according to the invention, the contour can include a ridge that protrudes from the end surface. A ridge has the advantage that it can be easily embedded in the connection device to provide positive engagement with the connection device.

According to another advantageous feature of a permanent magnet according to the invention, the contour can have a circular boundary. The circular boundary provides an advantageously large connection surface.

According to another advantageous feature of the present invention, the boundary of the contour on the connection surface can extend in an arcuate manner from a first point on the second convex portion to a second point on the second convex portion. Therefore force components acting on the connection device parallel to the cross section of the permanent magnet can advantageously be absorbed by the boundary of the contour. This is particularly advantageous in the case of a rotor in which forces act in a radial direction.

According to another advantageous feature of the present invention, the connection device can have a connection part having a circumferential lip that provides positive engagement with the boundary of the contour. Thus, the positive engagement of the connection device to the permanent magnet includes a positive engagement with the circumferential lip. In this way, strong forces from the boundary can advantageously be absorbed by the circumferential lip, particularly in the case of a rotor according to the invention, since the circumferential lip has no beginning or end and therefore when the forces act on the lip they are distributed over the whole circumferential lip.

According to another advantageous feature of the present invention, the permanent magnet can have a recess in the first convex portion between the north pole and the south pole. In an electric machine according to the invention, the surface of the rotor that faces the air gap advantageously has a recess between the north pole and the south pole of the permanent magnet.

According to another advantageous feature of the present invention, the permanent magnet can run along a first convex portion between the north pole and the south pole. In a machine according to the invention, the surface of the rotor that faces the air gap can advantageously has a continuous surface between the north pole and the south pole of the permanent magnet.

According to another advantageous feature of the present invention, the permanent magnet can be a sintered permanent magnet.

A permanent magnet in accordance with the invention advantageously provides a high level of air-gap induction in a space-saving manner because of the strong magnetic force and reliable connection of the permanent magnet to the rotor in accordance with the invention.

According to another advantageous feature of the present invention, the rotor can have a connection to the connection device on an end surface at a first axial end of the rotor and a second connection to the connection device on an end surface at a second axial end of the permanent magnet. In particular, the permanent magnets connected to the rotor at both of their end surfaces can thereby advantageously be attached within the envelope curve of the rotor.

According to another advantageous feature of the present invention, a third connection can be provided between a pair of permanent magnets between the first and a second axial ends of the rotor. In this way, a plurality of permanent magnets can advantageously be attached to the rotor one behind the other in an axial direction.

According to another advantageous feature of a rotor according to the present invention, an annular connection part can extend annularly in a cross section of the rotor between ends of two permanent magnets, the annular connection part being concentric with the profile curve of the rotor. It is thereby possible to achieve an advantageously uniform distribution of centrifugal forces on the connection device during operation of the electric machine and, in the case of a plurality of permanent magnets located one behind the other in an axial direction, advantageously ensures little or no interruption in the profile of the rotor by the connections between permanent magnets arranged one behind the other in the axial direction.

According to another advantageous feature of the present invention, the permanent magnet can be embedded in the connection device. The requirements relating to the dimensional accuracy of the permanent magnet can then be advantageously modest, since the connection device fills the gaps which are present due to any lack of dimensional accuracy of the permanent magnet. It is therefore advantageously possible e.g. to dispense with mechanical finishing of a permanent magnet after sintering.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawing, and in particular toFIG. 1, there is shown a first exemplary embodiment of a permanent magnet10according to the invention, including a north pole21and a south pole22as magnetic poles, and end surfaces12,32, on a first end11and a second end31. The shape of envelope curve15of the cross section13of the permanent magnet10is a biconvex lens having a first convex portion16and a second convex portion17. All cross sections of the permanent magnet10along that first direction1have identical envelope curves15.

A lateral magnetization14runs along the first convex portion16of the envelope curve15in an arcuate manner, so that the permanent magnet10provides the north pole21and the south pole22on one side of the permanent magnet10, along that first convex portion16. The permanent magnet10extends along the second convex portion17in an arcuate manner. At least one of the end surfaces12has a surface portion18within the envelope curve15that includes a connection surface where the permanent magnet10is fused to a connection device.

A height of the permanent magnet10is measured as the greatest distance between the first convex portion16and the second convex portion17. The cross section13of the permanent magnet10extends in a plane defined by a second axis2and a third axis3. The axes that indicate the second direction2and the third direction3run perpendicular to the axis of the first direction1. InFIG. 1, surface portion18on the end surface12at the first end11of the permanent magnet10is a plane surface. The permanent magnet10is a sintered permanent magnet that extends from the north pole21and the south pole22along the first convex portion16.

FIG. 2is a view of an end surface112of a second exemplary embodiment of a permanent magnet110according to the invention, which has features that are described above with reference toFIG. 1, but has reference numerals that are produced by adding the prefix “1” or “10” to reference numerals appearing inFIG. 1. The features of the permanent magnet110that differ from the permanent magnet10are as follows: The permanent magnet110has a recess119in the second convex portion117between the north pole121and the south pole122of the first convex portion116. The surface118of the permanent magnet110that includes a connection surface where the permanent magnet110is fused to a connection device is un-machined; more specifically, the surface118on the end surface112of the permanent magnet110was not mechanically machined after sintering.

FIG. 3shows a longitudinal section through a first exemplary embodiment of an inventive rotor600wherein the permanent magnets1010of the rotor600extends parallel to the axis of rotation4from its first end1011to its second end1031, and the rotor600includes the connection670between a connection device672and the surface1018of the permanent magnet1010. The permanent magnet1010shown inFIG. 3has features related to features of the permanent magnet10ofFIG. 1, and here the reference numerals are prefixed with a “10”.

However, the permanent magnet1010inFIG. 3has coated surfaces1018,1038. The first connection device672comprises a synthetic material that forms a connection to the permanent magnet1010by fusing with its coating. To provide the connections670,671, between the connection device672and the surfaces1018,1038, of the respective end surfaces at the first end1011and second end1031of the permanent magnet1010, the synthetic material of the connection device673is heated to fuse those connections670,671. The rotor600has a first connection of the connection device to the coated surface1018at a first axial end641of the permanent magnet1010and a second connection671of the connection device672to the coated surface1038at the second end1031of the permanent magnet1010. The rotor600comprises a shaft605that extends along the axis of rotation4. The shaft605has knurling606that extends along the connection device672in a direction parallel to the axis of rotation4. Attachment of the permanent magnets1010to the shaft605via the connection device672is provided by injection molding. In the injection molding process, the shaft605and the permanent magnets1010are positioned accordingly, and the synthetic material of the connection device672is injected by an injection molding instrument between the permanent magnets1010and the shaft605and onto the first and second ends1011,1031of the permanent magnets1010. The Injection molding material forms the first connection1018and second connection1038at the end surfaces of the permanent magnets1010by fusing with them, so that the permanent magnets1010are embedded in the connection device772. Moreover, because of the knurling606on the shaft605, the fused connection there provides a positive connection between the shaft605and the connection device672.

The first and second ends1011,1031, of the permanent magnets1010include respective end surfaces1018,1038, for making connections670,671, between the connection device672and the permanent magnet1010within the envelope curve1015of the cross section of the permanent magnets1010. Because the end surfaces1018,1038, the permanent magnets1010are attached inside the ends670,671, of the connection device672, the outer surfaces673,674, of the connection device672can advantageously provide inexpensive and high-quality limit stops for the bearings of respective first and second bearing devices58on the rotor600in an electric machine61.

FIG. 4shows a cross section of the rotor600ofFIG. 3at the section line IV-IV. The permanent magnets1010on the rotor600provide at least two first convex portions1016on the circular profile curve675of the rotor600that is concentric with the axis of rotation4. The permanent magnets1016extend from a first end1011to a second end1031parallel to the axis of rotation4. InFIG. 4, the circular curve provided by the first convex portions1016cannot be distinguished from the circular profile curve675of the rotor600, since they completely cover the circular envelope curve675, at least in the pictorial illustration, and therefore the circular profile curve675inFIG. 4is shown as being congruent with the first convex portions1016of the permanent magnets1010on the rotor600. Along the circular profile675of the rotor600, the same poles of the adjacent permanent magnets1010are adjacent to each other: a north pole of one permanent magnet1010is adjacent to the north pole of the next permanent magnet1010, and so on.

FIG. 5shows an end surface212of a third exemplary embodiment of a permanent magnet210according to the invention. This embodiment also has features that are related to features described above with reference toFIG. 1, but their reference numerals have the prefix “2”. The end surface212on the first end211of the permanent magnet210has a contour223that includes the recess surface218where the connection device772is connected to the permanent magnet210in a positive engagement. The contour223has a circular boundary225, at which the recess surface218extends into the recess224.

FIG. 6shows a longitudinal section of the permanent magnet210ofFIG. 5along the section line VI-VI. The contour223on the permanent magnet210has a recess224in the end surface212of the first end211of the permanent magnet210. On the surface238at the second end231of the permanent magnet210is a similar contour for a second connection providing positive engagement of the connection device772to the permanent magnet210. In a further exemplary embodiment of a permanent magnet according to the invention (not shown), instead of a recess224, the contour comprises a ridge that protrudes from the end surface, the surfaces providing the positive-engagement connection are located on the protruding ridge, instead of in the recess224.

FIG. 7shows a longitudinal section of a third exemplary embodiment of a rotor700in accordance with the invention having permanent magnets210of the type shown inFIG. 5. Features ofFIG. 7related to features described above with reference toFIG. 3andFIG. 4have reference numerals in which the “6” has been replaced by a “7” inFIG. 7. Like the rotor600, the permanent magnets210of the rotor700are embedded in the connection device772by injection molding, using an injection molding instrument. The first convex portion216of each permanent magnet210is on the circular profile curve of the rotor700that is concentric with the axis of rotation4.

Unlike the rotor600, the rotor700has a first connection that provides positive engagement with a surface218on the first end211of the permanent magnet210at the first axial end741of the rotor700, and a second connection that provides positive engagement with a surface238on the second end231of the permanent magnet210at the second axial end742of the rotor700with the connection device772. This means that, unlike the rotor600, the shaft705of the rotor700can be installed separately. The connection device772has an opening743for the shaft705. After the permanent magnets210have been attached and are embedded in the connection device772, the shaft705can be pressed through the opening743in order to attach the connection device772to the shaft705using frictional engagement.

Because the shaft705is pressed through the opening743in the connection device772inFIG. 6, the shaft705is continuously subject to frictional engagement forces acting on it. InFIG. 7, those forces also enhance connections between the connection device772and the permanent magnets210in an inexpensive, high-quality manner. For example, those forces enhance the frictional engagement of the end surface218at the first end211of the permanent magnet210that connects the connection device772to the permanent magnet210in an advantageously inexpensive and high-quality manner.

FIG. 8shows a cross section view of the rotor ofFIG. 7, at the first axial end of the rotor700. InFIG. 8, dashed lines indicate features of the permanent magnets210, the connection device772, and the shaft705, that cannot be seen in this cross section view.

FIG. 9is a longitudinal section view of a fourth exemplary embodiment of an inventive rotor800having pairs of permanent magnets310in accordance with the invention. Features inFIG. 9that are related to features described above with reference toFIG. 7andFIG. 8have similar reference numerals wherein the “7” prefix is replaced by an “8”. The end surface at the first axial end841and the end surface at the second axial end842of the permanent magnet310of the rotor800are connected to the molded connection device872by positive engagement, and the rotor800has an annular connection part876in addition to the connection device872. The two permanent magnets310in the rotor800have a connection331in the rotor area844between two permanent magnets310. Thus a plurality of permanent magnets310are attached to the rotor800, between the first axial end841and the second axial end842of the rotor800, in axially-oriented pairs with one permanent magnet310located behind the other in the axial direction7.

FIG. 10is a cross section view of the rotor800inFIG. 9along the section line X-X. In the cross section845of the rotor800the connection device872adjoins the permanent magnets310and is concentric with the circular profile curve875of the rotor800. The connection device872also includes an annular connection part876as part of that connection. As noted above, the inventive permanent magnets310, and also other features shown inFIG. 9andFIG. 10, have features described above with reference to first exemplary embodiment ofFIG. 1and other embodiments. The reference numerals of features inFIG. 9andFIG. 10related to other embodiments but not Identical with them, have substituted the prefix “8” for their prefixes.

InFIG. 9, the contour323defines a recess324in the end surface of the first end311of the permanent magnet310having a recess surface318. The contour323defines a groove that is formed by the recess324. The contour323has a boundary309, which extends in an arcuate manner from a first point308on the second convex portion317to a second point320on the second convex portion317inFIG. 10. The annular connection part876, i.e. the ring in the molded connection device872, has a circumferential lip877for positive engagement with the boundary309of the contour323of an end surface of the permanent magnet310. The connection part876thus runs in a groove formed by the two permanent magnets310that are disposed one behind the other inFIG. 10, in the axial direction7. Between a permanent magnet310and the closest other permanent magnet310on the envelope curve875of the rotor800, the annular connection part876is connected to a portion878of the molded connection device872.

Because of the strength of that ring876, the centrifugal forces permissible during operation of the rotor800can advantageously have high values without damaging the rotor800. Since the centrifugal forces subject the material of the annular connection part876to tensile loading, the annular connection part876is preferably made of steel, a carbon fiber reinforced material or a fiberglass reinforced material. These materials provide an advantageously inexpensive and high-quality rotor800. Preferably during production of the rotor800, the permanent magnets310and the annular connection part876are positioned so as to be at least partially held in a fixed position by the injection molding instrument when the molded part878is produced by injecting the molding material, which is a synthetic material.

When the annular connection part876of the rotor800is produced from a fiberglass reinforced material or carbon fiber reinforced material, the rotor800can be produced in an advantageously inexpensive and high-quality manner without a shaft805, and the annular connection part876can then be pre-tensioned by pressing the shaft805into an opening843provided for the shaft. Advantageously the fiberglass-reinforced material or carbon fiber-reinforced material can be sufficiently elastic that a frictional connection between the connection device872and the permanent magnet310is also provided in an advantageously inexpensive and high-quality manner when the shaft is pressing the shaft805into the opening843.

FIG. 11is a longitudinal section through a fifth exemplary embodiment of a rotor900having permanent magnets410. Some features inFIG. 11that are similar to but not the same as features described with reference toFIG. 1,FIG. 9andFIG. 10have reference numerals inFIG. 11wherein their former prefix, the first digit, has been replaced with a “9” inFIG. 11. In this embodiment, the permanent magnet410has a contour473with a groove that has a boundary409that extends in an arcuate manner from the first point on the second convex portion to the second point on the second convex portion. In addition to this, the recess424is not as deep as the groove, and extends as far as the second convex portion of the permanent magnet410.

FIG. 12is a cross section of the rotor900ofFIG. 11along the section line XII-XII. The connection device972extends annularly in a cross section945of the rotor900, adjoining the permanent magnets410and concentrically relative to the envelope curve975of the rotor900. Moreover, the connection device972in the cross section945of the rotor900has an annular connection part976having a circumferential lip977that provides positive engagement with the boundary409of the contour423of the permanent magnet410. The annular connection part976extends as far as the opening943for the shaft905.

In the exemplary embodiment shown inFIG. 11andFIG. 12, the annular connection part976is a disc that extends from its circumferential lip977to the opening943. The connection part976is segmented along the opening943for the shaft905by a series of recesses980. Therefore the rotor900can be attached to the shaft905in an advantageously inexpensive and high-quality manner using an interference fit, and centering of the permanent magnets410relative to the axis of rotation4can also be advantageously achieved. As in the fourth exemplary embodiment of a rotor800according to the invention, the connection part976can be fixed in the molded connection part978by injection molding.

FIG. 13shows a basic structure that provides four principal exemplary embodiments of electric machines according to the invention designated by the reference numerals61,62,63,64. These exemplary embodiments have features that are described above with reference toFIGS. 1 to 12. Features that do not have reference numerals inFIG. 13may be referred to using the reference numerals used in describingFIGS. 1 to 12.

The electric machines represent corresponding exemplary embodiments of inventive uses of permanent magnets in a rotor of an electric machine in accordance with the Invention. For example, the description of the first exemplary embodiment of the machine shown inFIG. 13that has the reference numeral61will be described using the first reference numeral in a group of reference numerals relating to relating to a cited the feature of the electric machine61. Likewise, the fourth exemplary embodiment, having the reference numeral64will be described using the last reference numeral in the group of reference numerals relating to relating to a cited the feature of the electric machine64.

The electric machines61,62,63,64comprise respective rotors600,700,800,900attached to respective shafts605,705,805,905, rotatably supported for rotation about the axis of rotation4and a stator53that interacts magnetically with the respective rotor600,700,800,900across an air gap54during operation of the electric machine61,62,63,64. The rotor600,700,800,900is supported by first and second bearing devices58in a housing52of the electric machine61,62,63,64. The stator53is attached in a non-rotatable manner within the housing52and has at least one winding55that extends along the air gap54in an axial direction7relative to the axis of rotation4.

Exemplary embodiments of electric machines61,62,63,64, use the permanent magnets10,110,210,310,410,1010in their respective rotors600,700,800,900, as is, above with reference to the permanent magnets10,110,210,310,410,1010, and the rotors600,700,800,900.