Stator core and stator for axial flux rotating electrical machine

Abstract

The present disclosure relates to a stator core (2) for an axial flux rotating electrical machine, the stator core (2) may comprise two preferably identical single piece core portions (X1, X2, X3, X4) juxtaposed to form the core (2), and at least the central body (7, 70, 700) is a discontinuous body comprising at least one discontinuity (7A, 70A, 600A ').

Description

Technical Field

[0001] The present disclosure relates to cores of stators of rotating electrical machines, and more particularly to axial flux rotating electrical machines. Background Art

[0002] In the case of electric motors, electric machines are devices used to convert electrical energy into mechanical energy, and vice versa in the case of generators. They are generally composed of four basic structures: the rotor, which is the rotating part that carries the current; the static element called the stator, which is also powered; the bearings, which are responsible for connecting the static and rotating parts; and finally, the casing, which acts as a housing and facilitates integration with other auxiliary systems.

[0003] Electric machines can be classified based on various characteristics, one of which is the direction of the magnetic flux. The main categories are radial flux machines and axial flux machines.

[0004] In an axial flux machine, the magnetic flux travels in an axial direction, parallel to the machine's mechanical axis. This is due to the machine's construction, which typically consists of at least one stator, consisting of multiple axially arranged coils, and at least one rotor, typically flat or disc-shaped, containing permanent magnets. Consequently, the magnetic fields generated by the rotor and stator are aligned in the same axial direction, generating torque and causing the machine to rotate.

[0005] Axial flux motors include arrangements where the stator may or may not have a yoke. The latter, referred to as "yokeless," enables greater torque density with reduced space and power losses. The absence of a yoke also results in overall weight savings due to the reduced mass of the motor.

[0006] However, the difficulties found in all electric machines are generally related to energy losses, which directly affect the performance of the machine and can be divided into four parts: iron losses, mechanical losses, Joule effect losses and replenishment losses.

[0007] Iron losses can be divided into hysteresis losses and eddy current losses. Hysteresis losses depend on the microstructural characteristics of the core material, such as impurity bonds, mechanical stress, grain size, and bonding. Eddy current losses primarily result from the circulation of currents induced in the motor's ferromagnetic core.

[0008] The need to control eddy currents is particularly relevant in axial flux machines, as demand for this type of machine has been increasing in the automotive market and industrial applications, with increased losses in high-speed applications.

[0009] In the prior art, SMC (Soft Magnetic Composite) is known for use in axial flux electrical machines, since said material enables the formation of a stator core by means of non-laminated solid components.

[0010] The concept of SMC composite materials is based on applying an electrically insulating nanoscale surface layer to magnetic particles, which are then connected into a three-dimensional matrix. Thus, thanks to the isotropy of this material, 3D magnetic properties are obtained, providing freedom to create project concepts for unique and innovative applications.

[0011] The disadvantage of this type of material is that a large number of eddy currents can occur, mainly in large cores and at high frequencies.

[0012] Therefore, there is a constant search for technical solutions which facilitate the optimization of the structural characteristics of the core of the stator of an axial flux electric machine and which make it possible to reduce the formation of eddy currents.

[0013] For example, document KR102458545B1 describes a known solution. This document describes an electric motor capable of improving performance by reducing eddy currents. The motor includes: a stator rear disc forming a magnetic circuit; a plurality of stator teeth radially formed on the top surface of the stator rear disc and manufactured using soft magnetic powder; and a first recessed slot located in at least one of the top surface of the stator rear disc and the top surface of the stator teeth in an axial motor, wherein a magnetic field is formed in the axial direction.

[0014] Document EP1536542B1 describes a motor that limits the generation of eddy currents caused by leakage magnetic flux and reduces iron loss due to eddy currents. A gear is mounted on a stator disk with at least a portion (the portion inserted into the disk) inserted into an insertion hole formed in a surface opposing the stator disk. When a drum is energized, the cross-sectional area of the gear portion of the insert disk, taken perpendicularly to the magnetic flux generated on the gear, is larger than the cross-sectional area of the portion of the gear disposed within the drum, taken perpendicularly to the magnetic flux. Summary of the Invention

[0015] Purpose of this disclosure

[0016] One of the objects of the present disclosure is to provide a stator core for an axial flux rotating electric machine having a construction and geometry that reduces eddy currents.

[0017] Another object of the present disclosure is to provide a stator core for an axial flux rotating electric machine having a low manufacturing cost and a compact and lightweight geometry for various applications.

[0018] Brief Description of the Disclosure

[0019] The present disclosure relates to a stator core for an axial flux rotating electric machine comprising a central structure formed from an electrically conductive material, wherein the central structure comprises at least one discontinuity formed from a discontinuity in the electrically conductive material.

[0020] In an embodiment of the present disclosure, the central structure is formed from two, preferably identical, single-piece core sections juxtaposed to form the core, each of the core sections comprising a central body and at least one interruption formed in the central body. In an embodiment of the present disclosure, the at least one interruption has a thickness of from 0.2 mm to 5 mm, more preferably from 2.0 mm to 3.0 mm.

[0021] In an embodiment of the present disclosure, each of the core portions may include a base and a central body protruding from the base, the base forming an edge around the bottom periphery of the central body. The edge of the base may also have at least one discontinuity in the form of a slot, the at least one discontinuity preferably having a thickness of from 0.2 mm to 5 mm, more preferably from 2.0 mm to 3.0 mm.

[0022] In an embodiment of the present disclosure, at least one discontinuity has the form of a slot extending between the lower periphery of the central body and the outer periphery of the rim. Thus, in an embodiment of the present disclosure, the thickness of the slot is preferably from 0.2 mm to 5 mm, more preferably from 2.0 mm to 3.0 mm.

[0023] In another embodiment, each of the core sections comprises four interruptions in the form of four slots extending from the bottom periphery of the central body to the outer periphery of the rim and positioned symmetrically with respect to the geometrical centre of the core section.

[0024] In embodiments of the present disclosure, the central body is a segmented body having two lowered blocks and two raised blocks, the lowered blocks being arranged diagonally relative to a transverse plane passing through the longitudinal geometric axis of the core portion, and the raised blocks being arranged diagonally in a mirror-image manner relative to the same transverse plane. In these embodiments, at least one discontinuity is formed between the two raised blocks, and the lowered blocks have the same height, the raised blocks have the same height, and the raised blocks have a height greater than the lowered blocks.

[0025] Preferably, the top surface of one of the lowered blocks is the same size and a mirror image of the top surface of one of the raised blocks; and the top surface of the other of the lowered blocks is the same size and a mirror image of the top surface of the other of the raised blocks.

[0026] In an embodiment of the present disclosure, the at least one discontinuity of the edge of the base and the at least one discontinuity of the central body are continuous and take the shape of a slot extending from the outer periphery of the edge to the inner region of the central body.

[0027] The core portion may comprise three interruptions at the edge of the base and three interruptions at the central body, each interruption at the edge of the base and each interruption at the central body being continuous.

[0028] In an embodiment of the present disclosure, the at least one discontinuity of the central body is a straight slot extending along a portion of the central longitudinal geometric axis of the core portion.

[0029] In an embodiment of the present disclosure, the outer surface of the base of each core section has at least one groove. Preferably, the outer surface has a plurality of grooves forming parallel channels transverse to the central longitudinal geometric axis of the core section.

[0030] The present disclosure also relates to a stator for an axial flux rotating electrical machine, the stator comprising a plurality of cores according to the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present disclosure will now be described in more detail with reference to the accompanying drawings, in which:

[0032] Figure 1 is a perspective view of an axial flux electric machine having a yokeless stator according to the present disclosure, the yokeless stator including a stator core;

[0033] Figure 2 is an exploded view of the main components of an axial flux electric machine having a yokeless stator including a stator core according to the present disclosure;

[0034] Figure 3 is a perspective view of a stator core portion according to a first embodiment of the present disclosure;

[0035] Figure 4 is a perspective view of a stator core portion according to a second embodiment of the present disclosure;

[0036] Figure 5 is another perspective view of a stator core portion according to a second embodiment of the present disclosure;

[0037] Figure 6 is a schematic assembly diagram of a stator core of a core portion according to a second embodiment of the present disclosure;

[0038] Figure 7 is a top perspective view of a stator core portion according to a third embodiment of the present disclosure;

[0039] Figure 8 is a top perspective view of a stator core portion according to a fourth embodiment of the present disclosure; and

[0040] Figure 9 is a bottom view of a core portion according to the present disclosure. DETAILED DESCRIPTION

[0041] Figure 1 A perspective view of an axial flux electric machine 1 including a stator core 2 according to the present disclosure is shown. Figure 2 The motor is presented in an exploded view in an arrangement comprising a stator 2 and two rotors 3. Figure 1 and Figure 2 Only one stator and two rotors are shown, but the present disclosure can be implemented with any axial flux machine arrangement, such as a stator and rotor, a stator between two rotors, a rotor between two stators, or various levels, including various rotors and stators on the same shaft.

[0042] Figure 2 Also shown are the core 2 of the yokeless stator and the permanent magnets 4 forming the rotor 3 .

[0043] Naturally, those skilled in the art will readily appreciate that the axial flux machine may include other components not described herein, so that only relevant elements for understanding the present disclosure will be described and presented.

[0044] As indicated in the drawings of the present disclosure, the core of the yokeless stator consists of a one-piece central structure or is divided into two preferably identical single-piece parts X1, X2, X3, X4, which are preferably made of soft magnetic composite material (SMC). For example, the core parts can be manufactured using methods such as 3D printing methods or compacting coated powders in a matrix to form a solid material, which is then heat-treated to solidify the bonds around the particles and oxidize to increase the resistivity of the magnetic core. It is worth noting that although the cores of the present disclosure are preferably made of SMC, they can be made of any other conductive material with electrical, magnetic and / or thermal conductivity.

[0045] In the embodiment of the present disclosure, the parts X1, X2, X3, X4 comprise a base 6, 60, 600 and a central body 7, 70, 700 protruding from said base 6, 6, 600. Thus, the central bodies 7, 70, 700 can be connected in a juxtaposed arrangement to form the structure of the stator core 2. The fastening can be performed, for example, on a support of the stator comprising an outer plate positioned around the core 2.

[0046] In the embodiment shown in the present disclosure, the central body 7, 70, 700 has a preferably elongated trapezoidal cross section with four rounded corners, at least in the region in which it protrudes from the base 6, 60, 600. However, it should be emphasized that the central body may be another shape, such as, for example, oval, circular or rectangular.

[0047] Figure 3A first embodiment of a core portion X1 according to the present disclosure is shown. In this embodiment, the core portion includes a base 6 and a center body 7 protruding from the base 6. The base 6 forms an edge 6A around the area where the center body 7 protrudes. Thus, the edge 6A is formed around the bottom periphery of the center body 7. In a preferred embodiment of the present disclosure, the base 6 and the center body 7 are formed in a single component. However, it should be noted that in an alternative arrangement of the present disclosure, the base 6 and the center body 7 can be formed in different components and then connected to form the core.

[0048] In this embodiment, the central body 7 has an elongated trapezoidal cross section with four rounded corners and at least one discontinuity 7A, which means that the central body 7 is not continuous.

[0049] like Figure 3 As shown, the discontinuity 7A is preferably a straight slot that extends along a portion of the geometric longitudinal axis L without reaching the area of the edge of the trapezoidal shape of the main body 7. Preferably, the straight slot forming the discontinuity 7A extends for a length greater than half of the greater longitudinal length of the trapezoid. Also in this embodiment, the thickness of the straight slot forming the discontinuity 7A is preferably 0.2 mm to 5 mm, more preferably 2.0 mm to 3.0 mm.

[0050] However, it must be emphasized that in alternative embodiments of the present disclosure, the slots may not be on the longitudinal axis. Thus, in such embodiments, the slots may be, for example, diagonal or transverse. Furthermore, in embodiments of the present disclosure, more than one slot, collinear or otherwise, is contemplated. Furthermore, the slots may be penetrating, extending through the body, or non-penetrating, such as grooves.

[0051] In the embodiment shown, the discontinuity / slot 7A is formed on the body 7, but in optional embodiments of the present disclosure, the discontinuity / slot 7A may extend to the area of the edge 6A in, for example, one of the bases of the trapezoidal shape, or even to the area of the outer periphery of the edge 6A.

[0052] Figures 4 to 6 A second embodiment of a core portion X2 according to the present disclosure is shown. In this embodiment, the core portion includes a base 60 and a center body 70 protruding from the base 60. The base 60 forms an edge 60A around the area from which the center body 70 protrudes. Thus, the edge 60A is formed around the bottom periphery of the center body 70.

[0053] However, the base 60 is formed so that the edge 60A is discontinuous. Thus, the edge 60A has at least one discontinuity 60A', which means that the edge is not continuous.

[0054] like Figure 4 and Figure 5As shown, discontinuity 60A' is preferably in the form of a straight slot extending between outer periphery 60E of rim 60A and the bottom periphery of center body 70. In this embodiment, discontinuity 60A' has a thickness of 0.2 mm to 5 mm, more preferably 2.0 mm to 3.0 mm.

[0055] Also in Figure 4 and Figure 5 In the embodiment of the core portion of FIG2 , the edge 60A includes four discontinuities 60A′ extending from the lower periphery of the central body 70 to the outer periphery 60E of the edge 60A and positioned symmetrically relative to the geometric center of the core portion X2. However, it must be emphasized that in alternative embodiments, the edge 60A may exhibit another number of discontinuities, symmetrically or otherwise positioned.

[0056] The central body 70 is formed in a discontinuous manner with at least one discontinuity 70A. Figures 4 to 6 In the embodiment shown, the central body 70 is segmented and has two lowered blocks 8A, 8B and two raised blocks 9A, 9B.

[0057] The lowered blocks 8A, 8B are preferably arranged diagonally with respect to a transverse plane passing through the geometric longitudinal axis L2 of the portion X2 and the raised blocks 9A, 9B are arranged diagonally in a mirrored manner with respect to the same transverse plane. A discontinuity 70A is formed between the two raised blocks 9A, 9B.

[0058] In the embodiment shown, blocks 8A and 8B have the same height, and blocks 9A and 9B have the same height. However, the heights may be different provided they can be juxtaposed between two preferably identical core sections. Therefore, there may be an embodiment in which the combined height of blocks 9A and 8B is equal to the combined height of blocks 9B and 8A, but in which the heights of 9A and 9B are different and the heights of 8A and 8B are different. In addition, blocks 8A and 9A have top surfaces of the same size and mirror shape, which also occurs in blocks 8B and 9B. This means that when juxtaposing two preferably single-piece identical core sections X2, the blocks 8A and 8B, 9A and 9B of one section are juxtaposed with the blocks 9A and 9A and 8A and 8B of the other core section, respectively.

[0059] Figure 6 The juxtaposition between two preferably identical core parts is schematically illustrated. Thus, FIG. (a) shows two preferably identical X2 core parts with central bodies facing each other. FIG. (b) shows the two parts X2 during packaging, and FIG. (c) shows the parts X2 after assembly to form the stator core 2.

[0060] It should be noted that in the preferred arrangement of the present disclosure, the two sections having juxtaposed cores are identical. However, in alternative arrangements of the present disclosure, the two core sections may be different from each other, such as, for example, the juxtaposition of X1 and X4.

[0061] Figure 7 A third embodiment of a core portion X3 according to the present disclosure is shown. In this embodiment, the core portion includes a base 600 and a center body 700 protruding from the base 600. The base 600 forms an edge 600A around the area where the center body 700 protrudes. Thus, the edge 600A is formed around the bottom periphery of the center body 700.

[0062] The core portion X3 is formed so that the edge 600A and the center body 700 are discontinuous. Thus, this portion has at least one continuous discontinuity 600A', preferably in the form of a straight slot extending from the outer periphery 600E of the edge 600A to the interior region of the center body 700. In this embodiment, the thickness of the continuous discontinuity 600A' is preferably 0.2 mm to 5 mm, more preferably 2.0 mm to 3.0 mm.

[0063] exist Figure 7 In the embodiment of the present disclosure, the core portion X3 comprises three continuous discontinuities 600A' extending from the outer periphery of the edge 600A to the inner region of the central body 700. However, it should be emphasized that in alternative embodiments, the X3 portion may exhibit another number of straight slots extending on the edge and for the central body portion of the core portion. However, it should be emphasized that in alternative embodiments of the present disclosure, the discontinuities 600A' extend only on the edge 600A and do not enter the main body 700. However, the reduction in losses due to eddy currents will be smaller.

[0064] Figure 8 A fourth embodiment of the core portion X4 is shown, which is constructed similarly to Figure 7 , but its edge 600B also presents a discontinuity 600B' that extends from the outer periphery of the edge 600B to the bottom periphery of the central body 700B.

[0065] Figure 9 A possible embodiment of a base of a core part of the present disclosure is shown, wherein the outer surface S of the base has at least one groove 10 in order to form a surface with discontinuities.

[0066] exist Figure 9 In the embodiment of the present invention, the outer surface S presents a plurality of grooves 10, which form parallel channels transverse to the central longitudinal geometric axis L3 of the core portion. In other embodiments of the present disclosure, the outer surface S may include a different number of grooves arranged in a non-parallel manner relative to the longitudinal axis or in other manners.

[0067] Furthermore, it should be emphasized that Figure 9 The embodiment can be used with Figures 3 to 8 In combination with the embodiment of Figures 2 to 8 The outer surface S of the base is shown provided with grooves 10 .

[0068] The disclosed construction solutions of the core part—discontinuities on the base and body parts, sections of the body part and discontinuities on the base surface—promote a reduction in the overall length of the eddy current paths, which means that the losses caused by this type of current are significantly reduced.

[0069] Having described the preferred exemplary embodiments of the present disclosure, it should be understood that the scope of the present disclosure encompasses other possible variations of the described inventive concepts, being limited only by the content of the appended claims and the potential equivalents therein.

Claims

1. A stator core (2) for an axial flux rotating electrical machine (1), characterized in that It comprises a central structure formed of an electrically conductive material, wherein the central structure comprises at least one discontinuity (7A, 70A, 600A') formed by a discontinuity of the electrically conductive material.

2. The stator core according to claim 1, characterized in that The central structure is formed by two identical single-piece core sections (X1, X2, X3, X4) juxtaposed to form the core (2), each core section comprising a central body (7, 70, 700) and the at least one interruption (7A, 70A, 600A') formed in the central body.

3. The stator core according to claim 2, characterized in that The at least one discontinuity (7A) of the central body (7) is a straight slot extending along a portion of the longitudinal geometrical axis (L) of the core portion (X1).

4. The stator core according to claim 2, characterized in that: The central body (70) is a segmented body having two lowered blocks (8A, 8B) and two raised blocks (9A, 9B), Considering a transverse plane passing through the longitudinal geometric axis (L2) of the core portion (X2), the lowered blocks (8A, 8B) are arranged diagonally, and considering the same transverse plane, the raised blocks (9A, 9B) are arranged diagonally in a mirror-image manner; and The at least one discontinuity (70A) is formed between the two protruding blocks (9A, 9B).

5. The stator core according to claim 4, characterized in that: The height of the protruding blocks (9A, 9B) is greater than the height of the lowered blocks (8A, 8B); A top surface of one of the lowered blocks is the same size and mirror image of a top surface of one of the raised blocks; and The top surface of the other one of the lowered blocks has the same size and a mirror image shape as the top surface of the other one of the raised blocks.

6. The stator core according to any one of claims 2 to 5, characterized in that: Each of the core parts comprises a base (6, 60) and a central body (7, 70) protruding from the base (6, 60), the base (6, 60) forming a rim (6A, 60A) around the bottom periphery of the central body (7, 70).

7. The stator core according to claim 6, characterized in that The edge (60A) of the base (60) has at least one discontinuity (60A') in the shape of a slot extending between the lower periphery of the central body (70) and the outer periphery (60E) of the edge (60A).

8. The stator core according to claim 2, characterized in that: Each of the core parts (X3, X4) includes a base (600) and a central body (700, 700B) protruding from the base (600), the base (600) forming an edge (600A, 600B) around the bottom periphery of the central body (700, 700B), wherein the edge (600A, 600B) of the base (600) has at least one interruption (600A'), the at least one interruption (600A') is continuous with the at least one interruption of the central body, and the continuous interruption (600A') is in the shape of a narrow slot, which extends from the outer periphery (600E) of the edge to the inner area of the central body (700, 700B).

9. The stator core according to any one of claims 1 to 8, characterized in that: The outer surface (S) of the base of the core portion has a plurality of grooves (10) forming parallel channels transverse to a central longitudinal geometric axis (L3) of the core portion.

10. A stator for an axial flux rotating electrical machine, characterized in that Comprising a plurality of cores (2) according to any one of claims 1 to 9.

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