Rotor for axial flux machines, method for manufacturing a rotor for axial flux machines, and axial flux machine

Abstract

The invention relates to a rotor (1) for an axial flux electric machine (2) operable as a motor and / or generator, the rotor comprising a support (3), a plurality of magnet elements (4) arranged against, on or in the support (3) and extending radially outwards from the inside, the magnet elements (4) being magnetized in a circumferential direction and arranged in series in alternating opposite magnetization directions individually or in groups around the circumference, and a plurality of flux conducting elements (5) conducting magnetic flux and arranged against, on or in the support (3) and between the magnet elements (4) around the circumference. According to the invention, between at least one of the magnet elements (4) and a flux conducting element (5) arranged adjacent to the magnet element in the circumferential direction, a flux distributing element (6) is arranged distributing the magnetic flux.

Description

TECHNICAL FIELD

[0001] The invention relates to a rotor for an axial flux electric machine which can be operated as a motor and / or as a generator. The axial flux machine comprises a support, a plurality of magnet elements arranged against, on or in the support and extending radially from the inside to the outside, and a plurality of flux conducting elements conducting the magnetic flux and arranged against, on or in the support and around the circumference between the magnet elements. The magnet elements of the axial flux machine are magnetized in the circumferential direction and arranged in series in alternating opposite magnetization directions around the circumference, individually or in groups. BACKGROUND

[0002] A rotor for an axial flux machine is known from DE 10 2013 218 829 A1. For this rotor, a frame is formed from rotor laminations in which an insert is incorporated. The rotor laminations have separate punching for both the magnets and the insert.

[0003] Further configurations of the rotor for an axial flux machine or further configurations of the axial flux machine itself are described by DE 10 2017 204 434 A1, DE 10 2005 053 119 A1, DE 10 2004 038 884 A1, DE 10 2015 208 281 A1, DE 10 2017 127 157 A1 or WO 2018 / 015293 A1, among others.

[0004] The magnetic flux in an electric motor designed as an axial flux motor is oriented axially in the air gap between the stator and the rotor. For high speeds and high frequencies, the laminated rotor is designed in layers in the axial direction. For axial magnetic flux, soft magnetic composite material, also known as SMC material (soft magnetic component, soft magnetic compound / soft magnetic powder), is generally used as the material for the flux conducting elements, since in this case the three-dimensional propagation of the magnetic flux can not have significant eddy currents. For smaller rotors, a homogeneous SMC rotor is possible as long as the mechanical load does not exceed the low strength of the SMC. The SMC material is generally made of high-purity iron powder with a special surface coating on each particle. The electrically insulating surface thus achieved ensures a high electrical resistance, which can be maintained even after pressing and heat treatment. The eddy current losses can thus be practically negligible. SUMMARY

[0005] It is an object of the invention to provide a rotor for an axial flux electric machine, a method for manufacturing a rotor for an axial flux electric machine, and an axial flux electric machine, with which the amount of soft magnetic composite material required can be reduced.

[0006] This object is achieved by a rotor having the features of claim 1, by a method for manufacturing a rotor having the features of claim 11, and by an axial flux machine having the features of claim 12.

[0007] The rotor for an axial flux machine which can be operated as a motor and / or as a generator according to the invention comprises a support, a plurality of magnet elements arranged against, on or in the support and extending approximately radially from the inside to the outside, and a plurality of flux conducting elements which conduct magnetic flux and are arranged against, on or in the support and around the circumference between the magnet elements. The magnet elements of the axial flux machine are magnetized in the circumferential direction and arranged in series around the circumference, individually or in groups, with alternating opposite magnetization directions. According to the invention, a flux distribution element which distributes the magnetic flux, preferably spatially, is arranged between at least one of the magnet elements and the flux conducting elements which are arranged adjacent to the magnet elements in the circumferential direction. This offers the advantage that a low-cost material for the flux conducting elements can be used to form the rotor magnets for the axial flux machine, and a higher-quality and more expensive material for the transition area between the magnet elements and the flux conducting elements is introduced only at selected points on the rotor. The design of the rotor according to the invention ensures a three-dimensional distribution of the magnetic flux from the magnet elements to the air gap and reduces the amount of soft-magnetic composite material required.

[0008] In the context of the invention, the directional indication "approximately radially" is understood to mean that the magnet elements and / or the flux conducting elements and / or the flux distribution elements arranged in, against or on the support can extend exactly radially from the inside to the outside, wherein the central axis of the respective longitudinal extent of the magnet elements and / or the flux conducting elements and / or the flux distribution elements would also be formed to extend through the central rotor rotation axis. However, arrangements are also included in the context of the invention in which the central axis of the magnet elements, flux conducting elements or flux distribution elements arranged in, against or on the support is arranged to extend at an angle, so that the central axis of the magnet elements, flux conducting elements or flux distribution elements no longer intersects the central rotor rotation axis, but is aligned slightly obliquely and extends slightly closer to the central rotor rotation axis.

[0009] In the context of the invention, a group of magnet elements comprises at least two magnet elements arranged adjacent around the circumference, each with the same circumferential magnetization direction.

[0010] In the context of the present invention, magnetization in circumferential direction means that the magnet elements or groups of magnet elements are formed and distributed around the circumference in such a way that the orientation of the magnetic field of the magnet elements or groups of magnet elements is not in axial direction or radial direction, but in circumferential direction. These directional indications are to be understood as rough directions (as opposed to axial direction and radial direction, axial direction as a direction in or parallel to the rotor rotation axis, radial direction as a direction approximately perpendicular to the rotor rotation axis). The magnetic field emitted by a magnet element is determined by a magnetic field vector, which is tangentially oriented in circumferential direction or deviates from circumferential direction by a scattering range. The scattering range is preferably given as approximately plus / minus 20 angular degrees - particularly preferably estimated as approximately plus / minus 15 angular degrees.

[0011] In the different alternatives of the above-mentioned "against" support or located "on" or "in" the support, the following embodiments mean by way of example:

[0012] • "Against" support: the support comprises an inner hub body, for example, on which the magnet elements and flux conducting elements are mounted radially outwardly and / or are held radially on the hub body, for example, by means of a ring.

[0013] • Located "on" the support: the support has a disc-shaped shape area or radially protruding struts or other support elements protruding radially from the inside to the outside, on or between which the magnetically effective components are attached, for example, by bonding and / or by a circumferential ring band.

[0014] • Located "in" the support: the support and the magnetically permeable element are arranged similarly to the figures with regard to the exemplary embodiments of the present invention.

[0015] The axial flux machine in the context of the present invention is characterized in that the magnetic flux generated in the air gap between the rotor and the stator extends in axial direction parallel to the rotor rotation axis of the electric machine. In other words, the air gap is enlarged in a plane formed perpendicular to the rotation axis of the rotor or the plane of the air gap extends in a plane formed perpendicular to the rotation axis of the rotor.

[0016] The magnetic flux conducting material is preferably formed from iron powder or a mixture with iron powder. The above-mentioned SMC material is particularly preferred.

[0017] In a particularly preferred embodiment of the support, the support has an inner ring designed as a support hub via which the rotor can be connected to the shaft in a rotationally fixed manner, and a support outer ring which limits the rotor in the radial direction. Between the support hub and the support outer ring, the support can have a support disk in the form of a base portion, by means of which the support hub and the support outer ring are connected to one another, and which, together with the radially outer ring surface of the support hub and the radially inner ring surface of the support outer ring, forms an accommodation space which opens in the direction of the air gap for accommodating the magnet elements and the flux conducting elements of the rotor.

[0018] The support can also be designed as a hub structure which extends to the inner radius of the magnetic circuit and is equipped with attached permanent magnets and flux conducting elements. An annular band then holds the attached magnet elements and flux conducting elements in place.

[0019] In another embodiment of the support, the support is provided without an outer ring and / or without a base portion. The magnet elements and the flux conducting elements can be held radially inwards by bonding the magnet elements and the flux conducting elements to the support. As an alternative to or in addition to the bonding, the magnet elements and the flux conducting elements can also be mechanically fixed using claw elements which are then supported on the inner hub-like support body by means of struts.

[0020] According to an advantageous embodiment of the application, it can be provided that the or each flux distribution element has a triangular cross section as viewed in a cross-sectional plane perpendicular to the rotor rotation axis, wherein the flux distribution element in each case rests with its triangular base edge against an adjacent magnet element, and wherein the flux distribution element is arranged in such a way that its two remaining side edges are in magnetically conductive contact with adjacently arranged flux conducting elements. The advantage of this design is that this easily realisable geometry in terms of manufacture ensures an approximately optimum flux distribution between the magnet elements and the flux conducting elements.

[0021] According to a further preferred further development of the application, it can also be provided that the or each flux distribution element has a cross section which is an acute-angled triangle (for example, wedge-shaped) as viewed in a cross-sectional plane perpendicular to the rotor rotation axis, wherein the flux distribution element rests with its short triangular base edge g against the inner surface of the support outer ring, and the flux distribution element rests with one of its remaining triangular side edges in each case against an adjacent magnet element and with its other triangular side edge against a flux conducting element. The flux distribution element ensures a largely uniformly distributed magnetic flux density in the air gap by guiding or distributing a portion of the magnetic flux of the radially more inward magnet elements to radially more outward regions of the air gap.

[0022] As an alternative to the triangular shape, the flux conducting element can also be designed in the form of a parabola as observed in a cross section. Although this will be slightly more expensive in terms of the manufacturing process, this can additionally save expensive soft magnetic composites compared to the triangular shape.

[0023] Furthermore, according to a further advantageous embodiment of the application, it can be provided that the or each flux distribution element has a rectangular cross section as observed in a cross-sectional plane perpendicular to the rotor rotation axis, which can further simplify the manufacturing and assembly of the rotor.

[0024] According to a further particularly preferred embodiment of the application, it can be provided that the or each flux distribution element has the same axial depth over the entire radial extent. This design further supports the possibility of using common parts and further simplifies the assembly of the rotor.

[0025] Furthermore, the application can also be further developed in that at least one of the flux distribution elements is formed substantially entirely of soft magnetic composite material or ferrite material, thereby optimizing the flux conducting properties of the flux distribution element.

[0026] In a further preferred embodiment of the application, it can also be provided that at least one of the flux conducting elements is designed in the form of a stack of laminated sheets, in particular formed of electrical sheets. Preferably, these sheets are designed such that the flux conducting element has the same axial depth over its entire radial extent. This ensures an optimized design of the flux conducting element in terms of material costs and manufacturing.

[0027] It can also be advantageous to further develop the application such that the magnet element is designed as a permanent magnet and is advantageously formed of a plurality of individual magnets which are electrically insulated from one another and in particular have the same axial depth over the entire radial extent. This design of the magnet element allows the use of standardized common parts and ensures simple assembly.

[0028] In a particularly preferred embodiment, the support has a support hub designed in the form of a ring, a support disc designed in the form of a ring and a support outer ring radially outwardly delimiting the support. In this case, an annular pot-shaped receiving region for receiving the magnet element, the flux conducting element and the flux distribution element is formed between the support hub and the support outer ring, which has a pot-shaped base formed by the support disc. This ensures the provision of an easily equipped rotor support with high mechanical strength.

[0029] Finally, the application can also advantageously be embodied such that the support hub has a polygonal cross-sectional shape on its radially outer ring surface (cross-sectional plane perpendicular to the rotor rotation axis) and / or the support outer ring has a polygonal cross-sectional shape on its radially inner ring surface. On the one hand, this provides assembly assistance when equipping the rotor support, and on the other hand, ensures high strength of the entire rotor in terms of the acting torque.

[0030] Furthermore, the object of the application is achieved by a method for manufacturing a rotor configured according to the application, comprising the following method steps: providing a support, providing magnet elements and introducing the magnet elements against, on or in the support; providing flux-conducting elements and introducing the flux-conducting elements against, on or in the support; and providing flux-distributing elements and introducing the flux-distributing elements against, on or in the support. In a particularly preferred embodiment, in a further method step, the elements arranged against, on or in the support are fixed by a circumferential annular band.

[0031] Furthermore, the object of the application is achieved by an axial flux machine having a stator and a rotor designed according to the application. BRIEF DESCRIPTION OF DRAWINGS

[0032] In the following, the application will be explained in more detail without limiting the general idea of the application with reference to the drawings.

[0033] In the drawings:

[0034] Figure 1 An axial flux machine according to the prior art is shown in a schematic perspective view,

[0035] Figure 2 A rotor in a possible embodiment according to the application is shown in different views - in a sectional view taken along the sectional line A-A of the perspective view shown on the top right and in a perspective view of the rotor at the bottom - wherein the rotor is only partially equipped with magnet elements, flux-conducting elements and flux-distributing elements,

[0036] Figure 3 A rotor in a second possible embodiment according to the application is shown in different views - in a perspective view at the top and in a perspective view at the bottom - wherein the rotor is only partially equipped with magnet elements, flux-conducting elements and flux-distributing elements, and

[0037] Figure 4A rotor in a third possible embodiment according to the application is shown in different views - in a perspective view at the top and in a perspective view at the bottom - wherein the rotor is only partially equipped with magnet elements, flux conducting elements and flux distribution elements. DETAILED DESCRIPTION

[0038] Figure 1 An axial flux machine 2 according to the prior art is shown in a schematic perspective view. The shown axial flux machine 2 comprises a central stator 10 and two rotors 1 which are spaced apart on both sides by a respective air gap.

[0039] Figure 2 A rotor 1 in a possible embodiment according to the application is shown in different views. In the upper left, the rotor 1 is shown in a sectional view taken along the sectional line A-A of the perspective view of the fully equipped rotor 1 shown in the upper right. At the bottom, the rotor 1 is shown in another perspective view, wherein the rotor is only partially equipped with magnet elements 4, flux conducting elements 5 and flux distribution elements 6.

[0040] In all shown embodiments, the rotor 1 is designed for an axial flux electric machine 2 which can be operated as a motor and / or as a generator and comprises a support 3, a plurality of magnet elements 4 arranged in a pot-like receiving area of the support 3 and extending radially from the inside to the outside, and a plurality of flux conducting elements 5 conducting a magnetic flux and arranged in the receiving area of the support 3 and between the magnet elements 4 in a circumferential direction. Furthermore, a flux distribution element 6 spatially and in particular in a radial direction distributing the magnetic flux is arranged between each of the magnet elements 4 and the flux conducting elements 5 arranged adjacent to the magnet elements in a circumferential direction.

[0041] In Figure 2 The sectional view in the upper left of shows the structure of the support 3 with the pot-like receiving area for the magnet elements 4, the flux conducting elements 5 and the flux distribution elements 6. The support 3 comprises essentially a centrally arranged support hub 7, a support outer ring 9 arranged in a circumferential direction, and a support disc 8 formed between the support hub 7 and the support outer ring 9 and forming the pot-shaped base of the support 3. It is also shown that the flux conducting elements 5 are formed as a lamination stack, wherein the sheets of the lamination stack have the same depth (width in axial direction) over the entire radial extent of the sheets. In the lower view of Figure 2 In the lower view of it can also be clearly observed that each of the magnet elements 4 radially extending from the inside to the outside in an essentially bar shape (as a single bar or consisting of a plurality of similar single magnets) is arranged in a magnetically conductive manner on both sides around the circumferential direction with the flux distribution elements 6.

[0042] Here, the flux distribution element 6 is designed to be substantially triangular in cross section (as viewed in a cross-sectional plane perpendicular to the rotor rotation axis or in a plan view of the side of the rotor 1 facing the stator 10), wherein an acute-angled corner is cut off and has a predetermined thickness. In the exemplary embodiment shown, the triangular shape is an obtuse triangle and is preferably an isosceles triangle. As viewed in the circumferential direction, the flux distribution element 6 has a long base g that is in complete contact with the associated magnet element 4 over its entire radial extent. Since the triangular tip of the flux distribution element is formed by two remaining sides b, c, the flux distribution element 6 projects into the adjacent lamination stacks of the respective adjacent flux conducting elements 5, pointing away in circumferentially opposite directions from the magnet element 4 arranged centrally between the flux conducting elements. In the embodiment shown, the flux distribution element 6 enclosing the flux conducting elements 5 therebetween is designed and arranged such that the sheets of the lamination stacks of the flux conducting elements 5 have equal widths, which extend from the radially inner side tangentially to the circumferential direction to the triangular tip of the flux distribution element 6. The sheets arranged further radially outward from the triangular tip become increasingly wider.

[0043] In a further development of the embodiment not shown, the flux distribution element 6 can be designed such that the triangular side pointing radially outward from the triangular tip is designed to be stepped or replaced by a stepped section having at least one step. This allows the number of sheets having different widths to be further reduced compared to a design without steps.

[0044] Figure 3 The rotor 1 in a second possible embodiment according to the application is shown in different views. In the view at the top, the rotor 1 is shown in perspective view fully equipped. In the view at the bottom, the rotor 1 is also shown in perspective view, wherein the rotor 1 is here only partially equipped with magnet elements, flux conducting elements and flux distribution elements.

[0045] The rotor 1 according to the application is designed and arranged such that the flux conducting elements 5 and the flux distribution elements 6 are arranged in a lamination stack, wherein the lamination stack is arranged between the magnet elements 4. Figure 2In contrast thereto, the flux distribution element 6 arranged between the magnet element 4 and the flux conducting element 5 is designed as a right-angled triangle as viewed in cross-section, wherein the corner formed as a right angle is cut off and has a predetermined thickness. The triangular shape can be the shape of a right-angled triangle, in particular the shape of an isosceles triangle (with a cut-off right-angled triangle tip), wherein the flux distribution element 6 rests against the support outer ring 9 with its short base edge g from the inside, and the flux distribution element extends radially inwards with its right-angled triangle tip formed by the two remaining side edges b, c and rests against the adjacent magnet element 4 or the adjacent flux conducting element 5. According to the illustrated embodiment, the flux conducting element 5 with the lamination stack is designed such that both the width of the flux conducting element in the "circumferential direction" over its entire radial extent (or the width of the flux conducting element extending tangentially to the circumferential direction) and the axial depth of the flux conducting element (or the width in the axial direction) are constant.

[0046] Figure 4 A rotor 1 according to a third possible embodiment of the application is shown in different views in Figure 2 and Figure 3 The rotor 1 is again shown in the top view in perspective with all components, while in the view at the bottom the rotor is only partially equipped with magnet elements 4, flux conducting elements 5 and flux distribution elements 6 in perspective.

[0047] In contrast to the embodiments according to Figure 2 and Figure 3 The flux distribution element 6 arranged between the magnet element 4 and the flux conducting element 5 has a rectangular cross-sectional shape. According to the illustrated embodiment, the sheets of the lamination stack of the flux conducting element 5 have an increasing width in the radial direction from the inside out, while the axial depth of the flux conducting element is constant, or the flux conducting element is formed with the same width in the axial direction.

[0048] Figures 2 to 4 All embodiments of the application also have in common that the support hub 7 has a polygonal cross-sectional shape on its radially outer ring surface and / or the support outer ring 9 has a polygonal cross-sectional shape on its radially inner ring surface.

[0049] The application is not limited to the embodiments shown in the drawings. Thus, the above description should not be regarded as limiting but rather as illustrative. The appended claims are to be understood as meaning that the named features are present in at least one embodiment of the application. This does not exclude the presence of further features. If a patent claim and the above description define a "first" feature and a "second" feature, this designation is used to distinguish between two features of the same type, not to define a preferential order.

[0050] Reference signs

[0051] 1 rotor

[0052] 2 axial flux machine

[0053] 3 support

[0054] 4 magnet element

[0055] 5 flux conducting element

[0056] 6 flux distributing element

[0057] 7 support hub

[0058] 8 support disc

[0059] 9 support outer ring

[0060] g base side of triangle (of flux distributing element with triangular cross section)

[0061] a, b side of triangle (of flux distributing element with triangular cross section)

[0062] X rotor rotation axis

Claims

1. A rotor (1) for an axial flux machine (2) which can be operated as a motor and / or as a generator, the rotor comprising: - a support (3), - a plurality of magnet elements (4) arranged against, on or in the support (3) and extending radially outwards from the inside, the magnet elements (4) being magnetized in the circumferential direction and arranged in series in alternating opposite magnetization directions individually or in groups around the circumference, - and a plurality of flux conducting elements (5) which conduct magnetic flux and are arranged against, on or in the support (3) and arranged around the circumference between the magnet elements (4), characterized in that between at least one of the magnet elements (4) and the flux conducting element (5) arranged adjacent to it in the circumferential direction a flux distribution element (6) with a soft magnetic composite material is arranged which distributes the magnetic flux, the flux distribution element (6) or each flux distribution element having a triangular cross section as observed in a cross-sectional plane perpendicular to the rotor rotation axis, wherein the triangle in each case rests with its base edge (g) against an adjacent magnet element (4) and wherein the triangle contacts the adjacent arranged flux conducting element (5) with its two remaining side edges (b, c); or the triangle rests with its short base edge (g) against a support outer ring (9) of the support (3), wherein the triangle rests with one remaining side edge (b) against a magnet element (4) and wherein the triangle rests with the other remaining side edge (c) against the adjacent arranged flux conducting element (5).

2. The rotor (1) according to claim 1, characterized in that The flux distribution element (6) or each flux distribution element has the same axial depth over the entire radial extent.

3. The rotor (1) according to claim 1 or 2, characterized in that At least one of the flux distribution elements (6) is formed from a soft magnetic composite material or a ferrite material.

4. The rotor (1) according to claim 1 or 2, characterized in that At least one of the flux conducting elements (5) is designed in the form of a lamination sheet, in particular from an electrical sheet, and advantageously has the same axial depth over the entire radial extent.

5. The rotor (1) according to claim 1 or 2, characterized in that The magnet elements (4) are designed as permanent magnets and advantageously formed from a plurality of individual magnets which are electrically insulated from one another, and in particular have the same axial depth over the entire radial extent.

6. The rotor (1) according to claim 1 or 2, characterized in that The support (3) has a support hub (7) designed in the shape of a ring, a support disc (8) designed in the shape of a ring and a support outer ring (9) which delimits the support (3) radially outwards, wherein between the support hub (7) and the support outer ring (9) an annular tank-like receiving region is formed for receiving the magnet elements (4), the flux conducting elements (5) and the flux distribution elements (6), the annular tank-like receiving region having a tank-shaped base formed by the support disc (8).

7. The rotor (1) according to claim 6, characterized in that The support hub (7) has a polygonal cross-sectional shape on a radially outer ring surface of the support hub and / or the support ring (9) has a polygonal cross-sectional shape on a radially inner ring surface of the support ring.

8. A method for manufacturing a rotor (1) according to any one of the preceding claims, comprising the following method steps: - providing a support (3), - providing magnet elements (4) and introducing the magnet elements (4) against, on or into the support (3), - providing flux conducting elements (5) and introducing the flux conducting elements (5) against, on or into the support (3), - providing flux distributing elements (6) and introducing the flux distributing elements (6) against, on or into the support (3).

9. An axial flux machine (2) characterised in that, The axial flux machine (2) has a stator (10) and a rotor (1) designed according to any one of the preceding claims 1 to 7.

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