Stator and electric machine including the same

Abstract

The invention relates to an electric machine with a stator. The stator includes a stator core at least partially formed of an anisotropic material.

Description

Technical Field

[0001] The invention relates to an electric motor. Background Art

[0002] An electric vehicle (EV) is a vehicle powered by an electric motor. In recent years, electric vehicles have received a lot of attention for their environmental friendliness. As the electric vehicle market develops, people are also actively developing efficient and high-output motors.

[0003] The electric machine can generally be an axial flux electric machine or a radial flux electric machine. The magnetic flux of the radial flux electric machine is formed along the radial direction of the electric machine, while the magnetic flux of the axial flux electric machine is formed parallel to the rotation axis of the electric machine.

[0004] Radial flux motors are mainly used in electric vehicles. In recent years, axial flux motors have been vigorously developed from the perspective of improving the torque density and efficiency of axial flux motors.

[0005] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention. Therefore, this Background section may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0006] The present invention is directed to solving the above-mentioned problems associated with the prior art.An object of the present invention is to provide an axial flux electric machine with improved efficiency.

[0007] The purpose of the present invention is not limited to the above-mentioned purpose. A person skilled in the art in the field to which the present invention relates may clearly understand other technical purposes not mentioned herein through the detailed description of the embodiments.

[0008] In one aspect, the present invention provides a stator for an electric machine. The stator includes a stator core formed at least in part from an anisotropic material.

[0009] In another aspect, the present invention provides an axial flux motor including a rotor. The rotor includes a plurality of permanent magnets. The axial flux motor also includes a stator disposed in an axial direction of the rotor and the axial flux motor. The stator includes a stator core on which a coil is mounted. The stator core is at least partially formed of an anisotropic material.

[0010] The above-described aspects and other aspects and embodiments of the present invention are discussed below.

[0011] It should be understood that the terms "vehicle," "vehicle-like," or other similar terms as used herein generally include motor vehicles. Such motor vehicles may include passenger cars, including sports utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including various boats and ships, aircraft, etc. Such motor vehicles may also include hybrid vehicles, electric vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from non-petroleum resources). As described herein, a hybrid vehicle is a vehicle having two or more power sources, for example, a vehicle powered by gasoline and electricity.

[0012] The above and other features of the present invention are discussed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other characteristics of the present invention are described in detail below with reference to certain embodiments shown in the accompanying drawings, which are given by way of illustration only and therefore do not limit the present invention, in which:

[0014] Figure 1 is a partial cross-sectional view of an axial flux motor according to an embodiment of the present invention;

[0015] Figure 2 is a view showing a stator of an axial flux motor according to an embodiment of the present invention;

[0016] Figure 3 is a view showing a stator core of an axial flux motor according to an embodiment of the present invention;

[0017] Figure 4-6 is a plan view showing a stator core of an axial flux motor according to some embodiments of the present invention; and

[0018] Figure 7 is a view showing iron loss based on magnetic flux of a non-oriented electrical steel sheet and a grain-oriented electrical steel sheet according to an embodiment of the present invention.

[0019] It should be understood that the drawings are not necessarily drawn to scale and represent only slightly simplified representations of various features illustrative of the basic principles of the invention. Specific design features of embodiments of the present invention, including, for example, specific dimensions, orientations, locations, and shapes, are determined in part by the specific intended application and use environment.

[0020] In the drawings, like reference numerals refer to the same or equivalent parts of the present invention throughout the various figures of the drawing. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific structural or functional descriptions are carried out in conjunction with embodiments of the present invention, and the description is illustrative only for the purpose of describing embodiments of the present invention. Embodiments according to the present invention can be implemented in various forms. In addition, it should be understood that this description is not intended to limit the present invention to the described embodiments. On the contrary, the present invention is intended to cover not only the described embodiments, but also various alternatives, modifications, equivalents and other embodiments that can be included in the spirit and scope of the present invention defined in the appended claims.

[0022] It should be understood that although the terms "first", "second", etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another component. For example, the first component discussed below may be referred to as the second component without departing from the teachings of the present invention. Similarly, the second component may also be referred to as the first component.

[0023] When a component is referred to as being "connected" or "engaged" to another component, it may be directly connected or engaged to the other component, or one or more other components may exist between them. In addition, it should be understood that when a component is referred to as being "directly connected" or "directly in contact with" another component, there are no other components between them. Other expressions describing the relationship between components, such as "between", "directly between", "adjacent" or "directly adjacent", should also be understood in the same manner.

[0024] Throughout the specification, the same reference numerals represent the same components. In addition, the terms in the specification are only used to describe the embodiments and are not intended to limit the present invention. Unless otherwise clearly specified in the context, in this specification, the expression in the singular also includes the plural form. As used herein, expressions such as "comprising / comprise" do not exclude the existence or addition of one or more components, steps, operations and / or elements outside those components, steps, operations and / or elements described. When the components, devices, elements, etc. of the present invention are described as having a purpose or performing an operation, function, etc., the components, devices or elements should be considered to be "configured to" meet the purpose or perform the operation or function.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the axial flux motor 1 includes a stator 100 and a rotor 200. The stator 100 and the rotor 200 are arranged along the axial direction A of the axial flux motor 1. A gap 300 is arranged between the stator 100 and the rotor 200. The gap 300 is arranged between the stator 100 and the rotor 200 along the axial direction A of the axial flux motor 1.

[0027] The rotor 200 may be rotated by electromagnetic interaction generated between the stator 100 and the rotor 200. To this end, in some embodiments, the stator 100 includes an electromagnet 110, for example, a coil, and the rotor 200 includes a plurality of permanent magnets 220. In another embodiment, each of the stator 100 and the rotor 200 may include an electromagnet.

[0028] refer to Figure 2 , the stator 100 includes a stator core 120. The stator core 120 may be formed by arranging divided unit cores in a circumferential direction C of the stator 100. The stator core 120 is wrapped and supported by a reinforcing bobbin 130. The reinforcing bobbin 130 has an electromagnet 110 mounted thereon.

[0029] The electromagnet 110 may include a coil wound around the stator core 120 or the reinforcing bobbin 130. Current may be applied from an external power source to the electromagnet 110. The shaft 400 of the axial flux motor 1 may be rotated by an attractive force or a repulsive force between magnetic flux generated by the applied current of the stator 100 and magnetic flux generated by the electromagnet or magnet of the rotor 200.

[0030] The axial flux motor 1 further includes an inner housing 140 and an outer housing 150. The inner housing 140 and the outer housing 150 may be coupled to the inner side and the outer side of the reinforcing bobbin 130, respectively, so that the stator 100 may be assembled.

[0031] like Figure 3 As shown, by stacking a plurality of thin plates in a stacking direction L, a stator core 120 having a predetermined shape can be formed. In some embodiments, the stator core 120 of the axial flux motor 1 is formed of an isotropic material. Isotropy refers to the uniformity property of a material in a direction so that the physical properties do not change in different directions. As a non-limiting example, the isotropic material forming the stator core 120 may be a non-oriented electrical steel sheet or a soft magnetic composite (SMC). The stator core 120 of the axial flux motor 1 may be made of a single material to prevent efficiency degradation in the portion where the direction of the magnetic flux toward the yoke 160 changes.

[0032] refer to Figure 4 When the stator core 120 is made of a single material non-oriented electrical steel sheet, the characteristic of the isotropic material has the function of preventing efficiency degradation generated in the curved flux section S2 having the curved flux FX therein. However, there is a disadvantage that efficiency degradation is generated in the straight flux section S1 in which the magnetic flux FX is formed in a straight line in the stator 100. Therefore, an object of the present invention is to provide a stator 100 of an axial flux motor 1 capable of preventing efficiency degradation.

[0033] like Figure 5As shown, the stator core 120 can be divided into a first material region 500 and a second material region 600. The first material region 500 is formed of an anisotropic material, such as a grain-oriented electrical steel sheet. The second material region 600 is formed of an isotropic material, such as a non-oriented electrical steel sheet. Unlike isotropy, anisotropy refers to that the physical properties of a material vary depending on the direction of the material. In some embodiments, the first material region 500 and the second material region 600 can be bonded to each other using an adhesive. In some embodiments, the first material region 500 and the second material region 600 can be connected to each other by a connection structure therebetween.

[0034] The straight flux segment S1 and the curved flux segment S2 can be distinguished by the point at which the angle θ formed by the magnetic flux FX and the axial direction A of the axial flux machine 1 changes from 0°.

[0035] According to some embodiments of the present invention, the first material region 500 and the second material region 600 may be divided by the above-mentioned point, at which the angle θ formed by the magnetic flux FX and the axial direction A of the axial flux motor 1 changes from 0°. The second material region 600 is a region where the angle θ is greater than 0° and may be formed of an isotropic material. The first material region 500 is a region where the angle θ is 0° and may be formed of an anisotropic material.

[0036] refer to Figure 6 According to some embodiments of the present invention, in the stator core 120, the first material region 500 and the second material region 600 may be separated by a point at which the angle θ formed by the magnetic flux FX and the axial direction A is a preset angle. The preset angle may be in the range of 10° to 20°, for example, about ±15° (i.e., -15° counterclockwise and +15° clockwise relative to the axial direction A). The portion where the angle θ formed by the magnetic flux FX and the axial direction A is less than 15° may be formed of an anisotropic material, and the portion where the angle θ is greater than 15° may be formed of an isotropic material.

[0037] Generally, in the stator core 120, the position where the angle θ is formed between the magnetic flux FX and the axial direction A varies depending on the material. However, in the non-oriented electrical steel sheet, the change in magnetic properties with the bending magnetic flux angle is not significant, while in the grain-oriented electrical steel sheet, when the angle θ formed by the magnetic flux FX and the axial direction A is equal to or greater than 15°, the iron loss increases. In addition, when the above-mentioned angle θ exceeds 15°, the iron loss of the grain-oriented electrical steel sheet is greater than that of the non-oriented electrical steel sheet.

[0038] Based on the rolling direction of the material, the magnetic properties of anisotropic materials are better than those of isotropic materials. For example, the magnetic flux density of anisotropic materials can be 25% or more higher than that of isotropic materials, and the iron loss of anisotropic materials can be reduced by 179% or less. In addition, based on the direction perpendicular to the rolling direction of the material, the magnetic properties of anisotropic materials are lower than those of isotropic materials. For example, the magnetic flux density of anisotropic materials tends to decrease by about 8% or less, and its iron loss tends to increase by about 77% or more. Overall, in the straight flux segment S1, grain-oriented electrical steel sheets are about three times more advantageous than non-oriented electrical steel sheets in terms of iron loss. In the curved flux segment S2, non-oriented electrical steel sheets are about twice more advantageous than grain-oriented electrical steel sheets in terms of iron loss.

[0039] In view of these characteristics, the stator core 120 according to the embodiment of the present invention is formed of at least two materials. Specifically, the stator core 120 may include an isotropic material and an anisotropic material. Therefore, according to the embodiment of the present invention, it is possible to minimize efficiency degradation in the curved flux segment S2 and obtain maximum efficiency in the straight flux segment S1.

[0040] [Table 1]

[0041]

[0042] Refer to Table 1 and Figure 7 , the stator 100 was analyzed, and the stator 100 was formed of anisotropic material and isotropic material, until the part where the magnetic flux angle was less than 15° was the anisotropic material, and the part where the magnetic flux angle was equal to or greater than 15° was the isotropic material. JMAG 2D analysis was performed. The materials used were rotor "Somaly_1000_3P" and stator "27PH095+27PNX". In addition, the rotation speed was 2,000 revolutions per minute (RPM), and the current (amperes) were 0, 50, 100, 200, and 300, respectively.

[0043] The results of the analysis indicate that the stator core including at least two materials shown in Table 2 is confirmed to have an iron loss reduced by about 23% or more at the same torque level, compared with a stator core including a single material.

[0044] [Table 2]

[0045]

[0046] According to the embodiments of the present invention, by significantly improving the efficiency of the straight flux section of the stator core, the iron loss of the axial flux motor is greatly reduced, thereby improving the efficiency of the axial flux motor.

[0047] Although the stator according to the embodiment of the present invention is described herein as being used for an axial flux motor, the stator according to the embodiment of the present invention may be applied not only to an axial flux motor but also to a radial flux motor.

[0048] As is apparent from the foregoing description, the present invention provides an axial flux electric machine having improved efficiency.

[0049] The effects of the present invention are not limited to the above effects. A person skilled in the art will understand other effects not mentioned herein through the detailed description of the embodiments.

[0050] The present invention is not limited by the above-mentioned embodiments and drawings. It is obvious to a person skilled in the art that various substitutions, modifications and changes can be made within the technical scope of the present invention.

Claims

1. A stator for an electric machine, the stator comprising a stator core formed at least in part from an anisotropic material.

2. The stator according to claim 1, wherein: The stator core comprises: a straight flux segment having a magnetic flux formed parallel to an axial direction of the stator core; and a curved flux segment having an angle formed by the flux and an axial direction of the stator core; The straight flux segments are formed of the anisotropic material, and the curved flux segments are formed of the isotropic material.

3. The stator according to claim 1, wherein: The stator core comprises: a first material region formed of the anisotropic material; and A second material region is formed of an isotropic material.

4. The stator according to claim 3, wherein: The first material region and the second material region are divided based on a direction of a magnetic flux formed in the stator core.

5. The stator according to claim 4, wherein: The second material region has an angle between the magnetic flux and an axial direction of the stator core.

6. The stator according to claim 5, wherein: The angle is in the range of 10° to 20°.

7. The stator according to claim 6, wherein: The angle is 15°.

8. The stator according to claim 2, wherein: The isotropic material is a non-oriented electrical steel sheet or a soft magnetic composite material (SMC); and The anisotropic material is a grain-oriented electrical steel sheet.

9. The stator according to claim 1, wherein: The stator core has a coil wound thereon.

10. An axial flux motor, comprising: a rotor including a plurality of permanent magnets; and A stator is disposed in an axial direction of the rotor and the axial flux motor, the stator comprising a stator core having a coil mounted thereon, wherein the stator core is at least partially formed of an anisotropic material.

11. The axial flux electric machine according to claim 10, wherein: The stator core comprises: a first material region formed of the anisotropic material; and A second material region is formed of an isotropic material.

12. The axial flux electric machine according to claim 11, wherein: The first material region and the second material region are divided based on a direction of a magnetic flux formed in the stator core.

13. The axial flux electric machine according to claim 12, wherein: In the second material region, the magnetic flux has an angle relative to an axial direction of the axial flux machine.

14. The axial flux electric machine according to claim 13, wherein: The angle is in the range of 10° to 20°.

15. The axial flux electric machine according to claim 10, wherein: The stator core comprises: a straight flux section in which a magnetic flux parallel to an axial direction of the axial flux motor is formed; and a curved flux segment in which the magnetic flux forms an angle with the axial direction of the axial flux machine; The straight flux segments are formed of the anisotropic material, and the curved flux segments are formed of the isotropic material.

16. The axial flux electric machine of claim 15, wherein: The isotropic material is a non-oriented electrical steel sheet or a soft magnetic composite material (SMC); and The anisotropic material is a grain-oriented electrical steel sheet.

17. The axial flux electric machine according to claim 10, wherein: The stator comprises: a bobbin disposed around the stator core, wherein a coil is wound around the bobbin; and The first shell and the second shell are mounted on the first side and the second side of the bobbin, respectively. 18 . The axial flux motor of claim 10 , further comprising a shaft configured to rotate together with the rotor and formed to pass through the stator.

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