WO2021148069A1 - Rotor and axial flux machine - Google Patents

Abstract

The invention relates to a rotor (1) for an electrical axial flux machine (2) that can be operated as a motor and/or generator, said rotor comprising a support (3), a plurality of magnet elements (4) arranged against, on, or in the support (3) and running radially outwards, the magnet elements (4) being magnetized in a circumferential direction and being arranged individually or in groups in series around the circumference with alternating opposing magnetization directions, and a plurality of flux conduction elements (5) which conduct the magnetic flux and are arranged against, on, or in the support (3) and around the circumference, between the magnet elements (4). According to the invention, the rotor (1) or the support (3) has, on its axial rear face, a shielding element (6) consisting of a magnetically permeable material.

Description

Rotor and axial flux machine

The present invention relates to a rotor for an electric, motor-driven and / or generator-driven axial flux machine, comprising a carrier, a plurality of magnet elements arranged on, on or in the carrier, extending radially from the inside to the outside, and a plurality of circumferentially between the magnet elements arranged, the magnetic flux conducting flux guide elements. The magnetic elements are designed to be magnetized in the circumferential direction and are arranged alternately one behind the other individually or in groups circumferentially with the opposite direction of magnetization. The invention also relates to an axial flow machine.

A rotor for an axial flux machine is already known from DE 102013218829 A1. In this rotor, the rotor laminations form a type of frame into which inlays are integrated. The rotor laminations have individual cutouts for both the magnets and the inlays.

Further structures of rotors for axial flux machines or of axial flux machines themselves are described, inter alia, by DE 102017 204434 A1, DE 102005053 119 A1, DE 102004038884 A1, DE 10 2015208 281 A1, DE 102017127 157 A1 or WO 2018 / 015293 A1.

The magnetic flux in an axial flux motor (electric motor) is axially directed in the air gap between the stator and rotor. A laminated rotor for high speeds and frequencies is layered in the axial direction. The axial magnetic flux has to overcome the adhesive layers, as a result of which the magnetic circuit experiences a shear (additional air gap) and loses its efficiency. This in turn causes the engine to lose power. For the axial magnetic flow, SMC (soft magnetic components / soft magnetic powder) is often used, since a 3D flow without significant eddy currents is possible here. A homogeneous SMC rotor is possible for smaller rotors as long as the mechanical load does not exceed the low strength of the SMC. The invention is based on the object of providing a rotor for an axial flux machine as well as an axial flux machine, which are optimized to the effect that the running behavior of the rotor in the axial flux machine or the running behavior of the axial flux machine itself is improved. A rotor or an axial flux machine should advantageously be created, the power losses occurring within an electrical axial flux machine being minimized.

This object is achieved in each case by the entirety of the features of the individual independent claims 1 and 9. Preferred developments of the invention are each defined in the subclaims.

A rotor designed according to the invention for an electrical, motorized and / or generator operated axial flux machine comprises a carrier, a plurality of radially outwardly extending magnet elements arranged on, on or in the carrier and a plurality of arranged on, on or in the carrier, Flux guide elements which are arranged circumferentially between the magnetic elements and conduct the magnetic flux. The magnetic elements are designed to be magnetized in the circumferential direction and are arranged alternately one behind the other individually or in groups circumferentially with the opposite direction of magnetization. According to the invention, the carrier or the rotor has a shielding element made of magnetically conductive material on its axial rear side (or the axial side facing away from the air gap). This has the advantage that the magnetic flux exiting on the rear side of the rotor in the form of lines of magnetic flux and forming a stray field is short-circuited and the strength of the exiting magnetic field is minimized. This in turn improves the running behavior of the electrical machine, since eddy currents generated by the stray field and the rotating rotor and the braking effects caused by them can be largely avoided. The heat loss is reduced accordingly.

Among the different alternatives of "on", "on" or "in" the carrier mentioned above, the following statements are meant as examples: • "On": The carrier consists, for example, of an internal hub body, with the magnets and flux guide elements being attached to the hub body radially on the outside and, for example, held radially on the hub body by means of a ring.

• "On": The carrier has a disc-shaped area or radially protruding struts or other protruding support elements on which the magnetically active components are attached (e.g. gluing)

• "in": The carrier and the magnetic guide elements are arranged similar to the figures.

An axial flux machine within the meaning of the invention is characterized in that the magnetic flux generated in the air gap between rotor and stator extends in the axial direction parallel to the axis of rotation of the electrical machine. In other words, the air gap is expanded in a plane that is perpendicular to the axis of rotation of the rotor.

The magnetic flux conducting material is preferably formed from iron powder or from a mixture with iron powder. SMC material is particularly preferably used.

In a particularly preferred embodiment of the carrier, this has an inner ring, via which the rotor can be connected to a shaft in a rotationally fixed manner, and an outer ring which delimits the rotor outward in the radial direction. The carrier can be formed between the inner ring and the outer ring with a bottom part via which the inner ring and the outer ring are connected to one another and which, together with the radial outer ring surface of the inner ring and the radial inner ring surface of the outer ring, provides a receiving space open in the direction of the air gap for receiving the magnetic elements and which forms the flux guide elements of the rotor. It is also possible to design the carrier as a hub construction which extends as far as the inner radius of the magnetic circuit and which is equipped with attached permanent magnets and flux guide pieces. A ring band or some other method (gluing, form fit) then holds the attached permanent magnets and flux guide pieces in position.

In another possible embodiment of a carrier, a carrier is provided without an outer ring and / or without a bottom part (quasi as a central hub part with radially outwardly pointing spokes with radially outwardly pointing free ones End, without a limiting outer ring). The magnet elements and the flux guide elements can be held radially inward by gluing on the carrier. As an alternative or in addition to gluing, the magnetic elements and the flux guide elements can also be fixed mechanically by claw elements, which are then supported by means of struts on the inner hub-like carrier body.

The carrier material used is preferably materials with a high electrical specific resistance, with a high mechanical tensile strength and with a low specific density. Preferred materials for this can be fiber-reinforced plastics or aluminum.

According to an advantageous embodiment of the invention, it can be provided that the shielding element is designed as a sheet metal part in the shape of a circular ring disk, which is preferably formed from electrical steel. The shielding element is advantageously designed in such a way that it covers the axial rear side of the rotor at least over the circular ring surface which is covered within the rotor by the magnetic elements and the flux guide elements. The shielding element particularly preferably covers the entire rear side of the carrier or of the rotor and extends from the edge of the shaft opening, radially outward, to the end of the carrier outer ring. The shielding element is to be designed and dimensioned in its axial thickness in such a way and to be arranged at a defined distance from the magnetic elements and the flux guide elements on the rear of the rotor that it does not become magnetically saturated when the electrical machine is in operation. The advantage of this embodiment is that an effective solution for reducing the stray fields on the back of a rotor of an axial flow machine has been found with structurally simple means.

As an alternative to a design as a sheet metal part, the shielding element can also be designed as a coated film, which in turn can be advantageous with regard to the assembly of the rotor.

According to a preferred further development of the invention, it can also be provided that the carrier has a spacer element on its rear side, which keeps the shielding element at a defined distance from the magnet elements and the flux guide elements. This creates a possibility for different technical interpretations of the electrical machine to ensure a defined distance between the shielding element arranged on the rear of the rotor and the magnetic and flux guide elements arranged in the carrier.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the carrier has an inner carrier ring part and an outer carrier ring part, the inner carrier ring part and the outer carrier ring part being connected to one another via an annular disk-like carrier base part. Furthermore, it can be provided that the spacer element is formed in one piece with the carrier through the carrier base part of the carrier, or is designed as a separate component arranged between the carrier and the shielding element. The advantageous effect of this embodiment is based on the fact that a spacer element for axially spacing the shielding element can be integrated into the carrier through the base part of the carrier. With a separate spacer element, whether in addition to the carrier base or in the case of a base-less carrier, the desired axial distances from the shielding element can be set very flexibly.

Furthermore, the invention can also be further developed in such a way that the shielding element is connected to the carrier in a rotationally fixed manner. The advantage of this configuration is that no eddy currents are generated in the shielding element itself due to a relative movement between the shielding element and the carrier, and losses that occur as a result are avoided - in contrast to shielding by a stationary housing, in which system-related eddy currents are generated in the housing and associated therewith Losses arise.

In a likewise preferred embodiment of the invention, it can also be provided that the flux guide elements are made from SMC material. Alternatively, these can also be formed by laminated metal sheets, in particular made of electrical steel sheet.

In another advantageous embodiment, the rotor can be implemented as a hub construction, which exists up to approximately the inner radius of the magnetic circuit and is provided with attached permanent magnets and flux guide pieces. A ring band or some other method (gluing, form fit) then holds the attached permanent magnets and flux guide pieces in position.

The object on which the invention is based is also achieved by an axial flux machine with a rotor designed according to the invention. Such an axial flux machine comprises a rotor with a carrier and with a plurality of magnetic elements and with a plurality of the magnetic flux-conducting flux guide elements, which are arranged on, on or in the carrier, and a stator with a plurality of coil magnets, the stator on a first Axial rotor side is arranged to form a first air gap and generates a magnetic field which extends substantially in the axial direction in the direction of the rotor. Particularly preferably, the axial flux machine is designed in an H-arrangement and has a stator arranged in the center, non-rotatably arranged, and a rotor each to the left and right of the stator, axially spaced by an air gap in each case.

The invention is explained in more detail below with reference to figures without restricting the general inventive concept.

Show it:

Figure 1 shows an axial flow machine according to the prior art in

Perspective view in schematic representation, with a rotor arranged between two stators,

FIG. 2 shows a further axial flow machine according to the prior art in a perspective view in a schematic representation, in an H-arrangement,

FIG. 3 shows a rotor according to the invention in an axial section, in a schematic representation, FIG. 4 shows the rotor according to FIG. 3 in two different perspective views, with a view from the front being shown in the upper view and a view from the rear of the rotor being shown in the lower view,

Figure 5 shows schematically the course of the field lines in the rotor, air gap, stator and on the back of the rotor for the case without a magnetic shield,

FIG. 6 shows the magnetic flux density along an imaginary line of intersection, in the case of a rotor design without magnetic shielding (see FIG. 5),

FIG. 7 schematically shows the course of the field lines in the rotor, air gap, stator and on the rear side of the rotor for the case with magnetic shielding in a rotor designed according to the invention, and FIG

FIG. 8 in analogy to FIG. 6, the magnetic flux density along an imaginary cutting line in an embodiment with a shielding element according to the invention (see FIG. 7).

FIG. 1 shows an axial flux machine 2 according to the prior art in a perspective view in a schematic representation, with a rotor 1 arranged between two stators 11 in its basic structure. The axial flux machine 2 comprises a rotor 1, which is shown here schematically without its carrier parts but with magnet elements 4 and flux guide elements 5 alternating circumferentially. In the upper illustration, a first stator 11 is shown in a top view from the inside, so that the individual stator coils of the stator 11 can be clearly seen here. Advantageously, two adjacent stator coils are connected together, with a total of six adjacent stator coils resulting in three stator coil packs, each controlled offset by 120 angular degrees. The first stator 11, the illustration above, would be 180 degrees downwards folded and held axially spaced apart from the rotor 1 with the formation of a first air gap 13, the uniform, compact axial flow machine 2 would result in the “assembled” state. In the lower illustration, a top view of the remaining stator-rotor core is shown, the second stator 11 being arranged axially below the rotor 1, spaced apart by a second air gap 13.

FIG. 2 shows a further axial flow machine 2 according to the prior art in a perspective view in a schematic representation, in an H-arrangement. A rotor 1 is arranged axially on both sides of a centrally arranged stator 11 with stator coils, each spaced apart by an air gap 13.

Figure 3 shows a rotor 1 according to the invention in an axial section, in a schematic representation. The rotor 1 comprises a carrier 3 designed in the manner of an annular disk, a plurality of radially outwardly extending magnetic elements 4 arranged in the carrier 3, and a plurality of magnetic flux-conducting flux guide elements 5 arranged in the carrier 3 circumferentially between the magnetic elements 4, the carrier 3 having a shielding element 6 made of magnetically conductive material on its axial rear side. The carrier 3 has an inner carrier ring 8 via which the rotor 1 can be connected in a rotationally fixed manner to a shaft (not shown), and an outer carrier ring 9 which delimits the rotor 1 outward in the radial direction. The carrier 3 has a carrier base part 10 between the carrier inner ring 8 and the carrier outer ring 9, via which the carrier inner ring 8 and the carrier outer ring 9 are connected to one another and which, together with the radial outer ring surface of the carrier inner ring 8 and the radial inner ring surface of the carrier outer ring 9, has an open air gap 13 in the direction Forms receiving space for receiving the magnetic elements 4 and the flux guide elements 5 of the rotor 1. The shielding element 6 is designed as a sheet metal part in the form of an annular disk and completely covers the rear circular ring surface of the carrier 3. The figure also clearly shows that the shielding element 6 is axially spaced apart from the magnet elements 4 and the flux guide elements 5 via the carrier base part 10 of the carrier 3. In this embodiment, the spacer element 7 is formed by the integrated support base part 10. In the illustrated embodiment, the Flux guide elements 5 formed from SMC material, which is pressed into the receiving spaces between the magnet elements 4 and is secured against falling out of the receiving space via an edge pointing radially inward from the carrier outer ring 8.

FIG. 4 shows the rotor 1 according to FIG. 3 in two different perspective views, the upper view showing a view obliquely from the front and the lower view showing a view obliquely from the rear of the rotor 1. In the upper view, the arrows drawn in the magnetic elements 4 clearly show the circumferentially alternating magnetic direction, while the lower illustration shows that the shielding element 6 is designed in such a way that it extends approximately over the rear circular surface of the carrier 3 extends, on which the magnet elements 4 and flux guide elements 5 are arranged between the inner carrier ring 8 and the outer carrier ring 9 on the inner side of the carrier.

Figure 5 shows schematically the course of the field lines in the rotor 1, air gap 13, stator 11 and on the back of the rotor 1 for the case without a magnetic shield. The field lines shown run without shielding in the area of the stationary housing or other components near the rear of the rotor 1. If these components are made of electrically conductive material, a rotating magnetic field is generated in this material when the rotor 1 rotates, which eddy currents generated. These eddy currents have a braking effect on the rotor and generate heat loss.

In FIG. 6, the magnetic flux density is shown by way of example along an imaginary cutting line. The X-axis shows the distance in the air gap and outside the air gap) in mm in a range from -10 mm to +30 mm, while on the Y-axis the magnetic field strength B in the air gap in Tesla, in a range between 10 ² and 10 ° Tesla is given. It can be seen that the field strength B is still noticeably present at greater distances from the rear surface of the magnets.

In the real case, the flux density on the back of the rotor is also influenced by the induced magnetic fields due to the current-carrying windings in the stator. Depending on the phase position between energization of the winding and rotor position the magnetic field on the back is strengthened. This is not taken into account in the schematic representations of FIGS. 5 and 6.

Figure 7 shows schematically the course of the magnetic field lines in the rotor 1, air gap 13, stator 11 and on the back of the rotor 1 for the case with a magnetic shield with a shielding element 6 in a rotor 1 designed according to the invention Figure 5, but with a magnetic insulation realized by a shielding element 6 on the back of the rotor 1. The field lines on the back of the rotor 1 are short-circuited in the material of the shielding element 6 and there is hardly any in the area behind the shielding element 6 (above the shielding element 6) a magnetic flux density is still present.

This can also be seen in FIG. The X-axis shows the distance in the air gap and outside the air gap) in mm, analogous to the resolution in Figure 6, in a range from -10 mm to +30 mm, while on the Y-axis, in a much finer one Resolution than in Figure 6, the magnetic field strength B in the air gap in Tesla, is given in a range between 10 ⁵ and 10 ° Tesla. At a distance of approximately 9 mm to 10 mm, there is an increased flux density due to the collecting and short-circuiting effect of the shielding element 6. From an area above approximately 11 mm, the flux density is approximately a factor of 100 less than in FIG the shielding element 6 rotates with the rotor 1, no eddy currents arise in this due to a relative movement to the magnetic field, as is the case for e.g. a standing housing wall made of electrically conductive material would be. So that the requirements regarding the avoidance of eddy currents in the magnetic shield are significantly lower than in the case of a possible relative movement (as would be the case, for example, with a motor housing without magnetic shield).

The invention is not limited to the embodiments shown in the figures. The above description is therefore not to be regarded as restrictive, but rather as explanatory. The following patent claims are to be understood in such a way that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of other features the end. If the patent claims and the above description define “first” and “second” features, this designation serves to distinguish between two features of the same type without defining a ranking.

Reference list

1 rotor

2 axial flow machine 3 carriers

4 magnetic element

5 flux guide element

6 shielding element

7 spacer element 8 inner carrier ring part

9 outer carrier ring part

10 carrier base part

11 stator

12 coil magnet 13 air gap

Claims

Claims 1. Rotor (1) for an electric, motor-driven and / or generator-driven axial flux machine (2), comprising - a carrier (3), - A plurality of magnet elements (4) arranged on or in the carrier (3) and extending radially from the inside to the outside, the magnet elements (4) being magnetized in the circumferential direction and being arranged individually or in groups circumferentially alternately with opposite magnetization directions are, - and a plurality of flux guiding elements (5) which conduct the magnetic flux and are arranged on or in the carrier (3), circumferentially between the magnetic elements (4), characterized in that the carrier (3) or the rotor (1) has has a shielding element (6) made of magnetically conductive material on its axial rear side. 2. rotor (1) according to claim 1, characterized in that Shielding element (6) is designed as an annular disk-shaped sheet metal part. 3. rotor (1) according to any one of the preceding claims, characterized in that the carrier (3) or the rotor (1) has a spacer element (7) on its rear side, which the shielding element (6) to a defined axial distance keeps the magnetic elements (4) and the flux guide elements (5) spaced apart. 4. rotor (1) according to any one of the preceding claims, characterized in that the carrier (3) has an inner carrier ring part (8) and an outer carrier ring part (9), wherein the inner carrier ring part (8) and the outer carrier ring part (9) are connected to one another via a carrier base part (10) designed in the manner of an annular disk. 5. rotor (1) according to one of the preceding claims 3 or 4, characterized in that the spacer element (7) formed by the carrier base part (10) of the carrier (3) and formed in one piece with the carrier (3), or as a separate between the carrier (3) and the shielding element (6) arranged component is executed. 6. Rotor (1) according to one of the preceding claims, characterized in that the shielding element (6) is connected to the carrier (3) in a rotationally test. 7. rotor (1) according to any one of the preceding claims, characterized in that the flux guide elements (5) are made of SMC material or are formed by laminated metal sheets, in particular from electrical sheet metal. 8. rotor (1) according to any one of the preceding claims, characterized in that the carrier (3) is designed as a hub, wherein the magnetic elements (4) and the flux guide elements (5) are held together by a circumferentially extending Faßringband on the hub and with these are positively connected. 9. Motor-driven and / or generator-driven axial flux machine (2), characterized in that the axial flux machine (2) has a rotor (1) according to one of the preceding claims. 10. Axial flux machine (2) according to claim 9, comprising - A rotor (1) with a carrier (3) and with a plurality of magnetic elements (4) and with a plurality of the magnetic flux-conducting flux guide elements (5) which are arranged on, on or in the carrier (3), and - A stator (11) with a plurality of coil magnets (12), which is arranged on a first axial rotor side with the formation of a first air gap (13), and which generates a magnetic field which extends essentially in the axial direction towards the rotor (1 ) extends. 11. Axial flux machine (2) according to claim 9 or 10, characterized in that the axial flux machine (2) is designed in an H-arrangement and a stator (11) arranged in the center and arranged in a rotationally fixed manner and to the left and right of the stator (11), axially each having an air gap (13) spaced apart, each having a rotor (1).