Electric motor

Abstract

This document discloses an example of an electric motor that takes into account the fact that "non-uniformity of current density within a slot" has a significant impact on the generation of eddy current losses. [Solution] In each part of the coil located within slot 3B (hereinafter referred to as the conductor portion 41), the electrical resistivity of the second conductor portion 4B and the third conductor portion 4C, located radially inward and radially outward, is greater than that of the first conductor portion 4A, which is located in the center. Therefore, in the stator 3, the flow of current through the second conductor portion 4B and the third conductor portion 4C is suppressed, and the suppressed current flows through the first conductor portion 4A, thus mitigating the unevenness of current density. In each conductor portion 41, the cross-sectional area of ​​the second conductor portion 4B is larger than that of the third conductor portion 4C, so an increase in current density in the second conductor portion 4B can be suppressed.

Description

Technical Field

[0001] The present disclosure relates to an electric motor including a rotor and a stator.

Background Art

[0002] For example, in the stator described in Patent Document 1, the electric resistance of the coil portion located radially inside is larger than the electric resistance of the coil portion located radially outside. Thus, in the invention described in Patent Document 1, the generation of eddy current loss occurring on the radially inner side where eddy currents are likely to occur is suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor has discovered, through detailed analysis, that "non-uniformity of current density in the slots" has a great influence on the generation of eddy current loss. The present disclosure discloses an example of an electric motor in view of this discovery.

Means for Solving the Problems

[0005] An electric motor including a rotor (2) and a stator (3) preferably includes at least one of the following constituent elements. In other words, the configuration requirements are as follows: The stator (3) comprises a stator core (3A) and coils (4) arranged in slots (3B) of the stator core (3A), and at least one of the multiple conductor portions (41) of the coil (4) located within the slots (3B) is composed of a first conductor portion (4A), a second conductor portion (4B), and a third conductor portion (4C), the second conductor portion (4B) is located closer to the rotor (2) than the first conductor portion (4A) and is made of a material with a higher electrical resistivity than the first conductor portion (4A), the third conductor portion (4C) is located on the opposite side of the rotor (2) from the first conductor portion (4A) and is made of a material with a higher electrical resistivity than the first conductor portion (4A), and furthermore, the cross-sectional area of ​​the second conductor portion (4B) is greater than the cross-sectional area of ​​the third conductor portion (4C).

[0006] Furthermore, if the electric motor is, for example, an inner rotor type electric motor, then the "rotor (2) side" of the electric motor corresponds to the "radially inward side," and the "side opposite the rotor (2) across the first conductor (4A)" corresponds to the "radially outward side."

[0007] Furthermore, if the electric motor is, for example, an outer rotor type electric motor, then the "rotor (2) side" of the electric motor corresponds to the "radially outer side," and the "side opposite the rotor (2) across the first conductor (4A)" corresponds to the "radially inner side."

[0008] Furthermore, one of the causes of non-uniform current density is the influence of magnetic fields induced by adjacent sections of the conductor. In other words, the magnetic fields induced by adjacent sections of the conductor cause the strength of the magnetic field to become non-uniform within the conductor section (41). As a result, the current density within the conductor section (41) becomes non-uniform, with the current density on the radially outer and radially inner sides being greater than the current density in the central part.

[0009] In contrast, for example, in the case of an inner rotor type electric motor, in the conductor portion (41) related to the stator, the electrical resistivity of the second conductor portion (4B) and the third conductor portion (4C), which are located radially inward and radially outward relative to the first conductor portion (4A) located in the center, is greater than the electrical resistivity of the first conductor portion (4A).

[0010] Therefore, if the stator is the stator of an inner rotor type electric motor, the flow of current through the second conductor section (4B) and the third conductor section (4C) is suppressed, and the suppressed current flows through the first conductor section (4A), thus mitigating the unevenness of current density.

[0011] Furthermore, the second conductor section (4B), located radially inward, tends to have a higher current density than the third conductor section (4C), located radially outward. In contrast, in the stator-related conductor section (41), the cross-sectional area of ​​the second conductor section (4B) is larger than that of the third conductor section (4C), thus suppressing an increase in current density in the second conductor section (4B).

[0012] As described above, if the stator is an inner rotor type electric motor stator, the non-uniformity of the current density can be mitigated, and thus the generation of large eddy current losses can be suppressed. Furthermore, even if the stator is an outer rotor type electric motor stator, the non-uniformity of current density can be mitigated in the same way as if the stator were an inner rotor type electric motor stator.

[0013] Incidentally, the symbols in each of the parentheses above are just examples showing the correspondence with the specific configurations etc. described in the embodiments described later, and this disclosure is not limited to the specific configurations etc. indicated by the symbols in the parentheses above. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram showing an electric motor according to the first embodiment. [Figure 2] This is an enlarged view of the coil (wire portion) according to the first embodiment. [Figure 3] It is a diagram showing the connection structure of the conductor part. [Figure 4] It is an enlarged view of the coil (conductive wire part) according to the second embodiment. [Figure 5] It is an enlarged view of the conductive wire part according to the third embodiment. [Figure 6] It is a diagram showing the electric motor according to the fourth embodiment. [Figure 7] It is an enlarged view of the coil (conductive wire part) according to the fourth embodiment. [Figure 8] It is an enlarged view of the coil (conductive wire part) according to the fourth embodiment. [Figure 9] It is an enlarged view of the conductive wire part according to the fourth embodiment.

Embodiments for Carrying Out the Invention

[0015] The following "Embodiments of the Invention" show an example of embodiments belonging to the technical scope of the present disclosure. That is, the specific matters of the invention described in the claims are not limited to the specific configurations and structures shown in the following embodiments.

[0016] The arrows, slashes, etc. indicating the directions attached to each figure are described to facilitate understanding of the relationships between the figures and the shapes of each member or part. Therefore, the invention shown in the present disclosure is not limited to the directions attached to each figure. The figure with slashes does not always show a cross-sectional view.

[0017] At least the members or parts described with reference numerals are provided with at least one, unless otherwise stated such as "one". That is, when there is no statement such as "one", two or more of such members may be provided. The electric motor shown in the present disclosure includes at least one of the components such as the members or parts described with reference numerals and the structural parts shown in the drawings.

[0018] (First Embodiment) <1. Overview of the Electric Motor> This embodiment is one in which an example of the electric motor according to the present disclosure is applied to the inner rotor type electric motor shown in FIG. 1. That is, the electric motor 1 includes at least a rotor 2 and a stator 3 and the like.

[0019] In the inner rotor type electric motor 1, the rotor 2 is rotatably disposed within the annular (cylindrical) stator 3. The stator 3 is fixed to a housing (not shown). The rotor 2 is rotatably supported by the housing via a rotor shaft 2A.

[0020] <2. Configuration of the stator> <2.1 Outline of the stator> The stator 3 is configured to include at least a stator core 3A and a coil 4 and the like. The stator core 3A is a member made of a metal with low iron loss such as an electromagnetic steel sheet. The coil 4 is a winding disposed in a slot 3B of the stator core 3A.

[0021] The slot 3B has an opening on the side of the rotor 2 and is a groove extending in a direction parallel to the rotor shaft 2A. A number of such slots 3B forming the groove are provided along the inner peripheral surface of the stator core 3A.

[0022] <2.2 Configuration of the conductor portion> The conductor portion 41 refers to the portion of the coil 4 located within the slot 3B, that is, the portion of the coil 4 extending substantially parallel to the rotor shaft 2A. The direction parallel to the rotor shaft 2A corresponds to the direction parallel to the central axis of the electric motor.

[0023] And at least one of the plurality of conductor portions 41 (in this embodiment, at least three including the conductor portion 41 closest to the rotor 2) is configured to have a first conductor portion 4A, a second conductor portion 4B, and a third conductor portion 4C as shown in FIG. 2.

[0024] In Figure 2, three wire portions 41A to 41C are shown in one slot 3B. However, this disclosure is not limited to this. That is, it is sufficient for at least one wire portion 41 to be present in one slot 3B.

[0025] The second conductor portion 4B of each conductor portion 41A to 41C is located on the rotor 2 side (radially inward in this embodiment) than the corresponding first conductor portion 4A, and is made of a material with a higher electrical resistivity than the first conductor portion 4A.

[0026] The third conductor portion 4C of each conductor portion 41A to 41C is located on the opposite side of the rotor 2 from the first conductor portion 4A (radially outward in this embodiment), and is made of a material with a higher electrical resistivity than the first conductor portion 4A.

[0027] Furthermore, the cross-sectional area of ​​the second conductor section 4B is larger than the cross-sectional area of ​​the third conductor section 4C. Note that the cross-sectional area of ​​the second conductor section 4B refers to the area of ​​the second conductor section 4B projected onto a virtual plane perpendicular to the extension direction of the slot 3B.

[0028] The cross-sectional area of ​​the third conductor section 4C refers to the area of ​​the third conductor section 4C projected onto the virtual plane described above. Incidentally, in this embodiment, the first conductor section 4A is made of copper, and the second conductor section 4B and the third conductor section 4C are made of aluminum.

[0029] Furthermore, the electrical resistance of the wire portion 41 located in the slot 3B that is furthest from the rotor 2 in the radial direction (wire portion 41A in Figure 2) is smaller than the electrical resistance of the wire portion 41 located in the slot 3B that is closest to the rotor 2 (wire portion 41C in Figure 2).

[0030] In other words, in this embodiment, the proportions of the first conductor portion 4A, the second conductor portion 4B, and the third conductor portion 4C in each of the conductor portions 41A to 41C are different. In particular, the proportion of the first conductor portion 4A, which has the lowest electrical resistivity, increases as it moves further away from the rotor 2.

[0031] Therefore, in this embodiment, the electrical resistance of the wire portion 41 located furthest from the rotor 2 is smaller than the electrical resistance of the wire portion 41 located closest to the rotor 2.

[0032] The coil 4 is wound in the area between two adjacent slots 3B in the circumferential direction. Therefore, each wire portion 41 located in the two adjacent slots 3B is electrically connected at one end and the other end in the longitudinal direction of the slot 3B, as shown in Figure 3.

[0033] <3. Features of the electric motor (especially the stator) according to this embodiment> One of the causes of non-uniform current density is the influence of magnetic fields induced by other adjacent conductors.

[0034] In other words, the magnetic field induced by adjacent sections of the conductor causes the magnetic field strength to be non-uniform within the conductor section 41. As a result, the current density within the conductor section 41 becomes non-uniform, with the radially outer and radially inner current densities being greater than the current density in the central section.

[0035] In contrast, in each conductor portion 41 according to this embodiment, the electrical resistivity of the second conductor portion 4B and the third conductor portion 4C, which are located radially inward and radially outward, is greater than that of the first conductor portion 4A, which is located in the center.

[0036] Therefore, in the stator 3, the flow of current in the second conductor section 4B and the third conductor section 4C is suppressed, and the suppressed current flows to the first conductor section 4A, thus mitigating the unevenness of current density.

[0037] Furthermore, the second conductor section 4B, located radially inward, tends to have a higher current density than the third conductor section 4C, located radially outward. In contrast, in each conductor portion 41 of the stator 3, the cross-sectional area of ​​the second conductor portion 4B is larger than the cross-sectional area of ​​the third conductor portion 4C, so it is possible to suppress an increase in current density in the second conductor portion 4B.

[0038] Furthermore, the electrical resistance of the wire portion 41A located in the slot 3B that is furthest from the rotor 2 in the radial direction is smaller than the electrical resistance of the wire portion 41C located in the slot 3B that is closest to the rotor 2.

[0039] This can suppress the increase in current density in the conductor portion 41C located radially inward of slot 3B. As a result, in the stator 3 according to this embodiment, the non-uniformity of current density can be mitigated, and the generation of large eddy current losses can be suppressed.

[0040] (Second Embodiment) This embodiment is a modified example of the stator 3 according to the first embodiment. The following description concerns the differences from the electric motor according to the above embodiment. Components identical to those in the above embodiment are denoted by the same reference numerals. Therefore, redundant descriptions are omitted in this embodiment.

[0041] In other words, in this embodiment, as shown in Figure 4, the second conductor portion 4B and the third conductor portion 4C are made of the same material (aluminum in this embodiment), and the second conductor portion 4B and the third conductor portion 4C are integrated to form a rectangular annular (cylindrical) structure that covers the entire circumference of the first conductor portion 4A.

[0042] Hereinafter, in this embodiment, when the second conductor portion 4B and the third conductor portion 4C are referred to collectively, that is, the rectangular tubular portion covering the entire circumference of the first conductor portion 4A will be referred to as the second conductor portion β. Therefore, the electrical resistivity of the second conductor portion β is greater than that of the first conductor portion 4A.

[0043] Furthermore, the cross-sectional area of ​​the portion of the second conductor β located closer to the rotor 2 than the first conductor 4A is larger than the cross-sectional area of ​​the portion of the second conductor 4B located on the opposite side of the rotor 2 from the first conductor 4A.

[0044] Furthermore, the portion of the second conductor portion β that is located closer to the rotor 2 than the first conductor portion 4A corresponds to the portion of the second conductor portion 4B in the first embodiment, that is, the portion of the conductor portion 41 that is located radially inward.

[0045] The portion of the second conductor portion β located on the opposite side of the rotor 2 from the first conductor portion 4A corresponds to the portion of the third conductor portion 4C according to the first embodiment, that is, the portion of the conductor portion 41 located radially outward.

[0046] Furthermore, this embodiment is the same as the first embodiment except that the second conductor portion 4B and the third conductor portion 4C are made of the same material, and the second conductor portion 4B and the third conductor portion 4C are integrated to form a rectangular ring that covers the entire circumference of the first conductor portion 4A.

[0047] Therefore, in this embodiment as well, it is possible to obtain the same effects and benefits as in the first embodiment. In addition, in the stator 3 according to this embodiment, the non-uniformity of the current density is mitigated, so the generation of large eddy current losses can be suppressed.

[0048] (Third embodiment) Figure 5 shows the conductor portion 41 in this embodiment that is closest to the rotor 2. In this embodiment, the first conductor portion 4A is made of copper, the second conductor portion 4B is made of tungsten, and the third conductor portion 4C is made of aluminum. The cross-sectional area of ​​the second conductor portion 4B and the cross-sectional area of ​​the third conductor portion 4C are the same.

[0049] In other words, the third conductor portion 4C according to this embodiment is located on the opposite side of the rotor 2 from the first conductor portion 4A, and is made of a material with a higher electrical resistivity than the first conductor portion 4A, and a material with a lower electrical resistivity than the second conductor portion 4B.

[0050] In this embodiment as well, the electrical resistance of the wire portion 41 located in the slot 3B that is furthest from the rotor 2 in the radial direction is smaller than the electrical resistance of the wire portion 41 located in the slot 3B that is closest to the rotor 2.

[0051] (Fourth Embodiment) In this embodiment, an example of the electric motor according to this disclosure is applied to the outer rotor type electric motor 1A shown in Figure 6.

[0052] The following description concerns the differences from the electric motor according to the above embodiment. Components identical to those in the above embodiment are denoted by the same reference numerals. Therefore, redundant explanations are omitted in this embodiment.

[0053] In other words, in the outer rotor type electric motor 1A, as shown in Figure 6, the stator 3 is housed in a cylindrical rotor 2. The grooves forming the slots 3B open toward the rotor 2 and are provided in large numbers along the outer circumferential surface of the stator core 3A.

[0054] Therefore, in the outer rotor type electric motor 1A, the "rotor 2 side" corresponds to the "radially outward side," and the side opposite the rotor 2, with the first conductor section 4A in between, corresponds to the "radially inward (center) side."

[0055] Figure 7 shows an example in which the conductor portion 41 according to the first embodiment is applied to an outer rotor type electric motor 1A. Figure 8 shows an example in which the conductor portion 41 according to the second embodiment is applied to an outer rotor type electric motor 1A. Figure 9 shows an example in which the conductor portion 41 according to the third embodiment is applied to an outer rotor type electric motor 1A.

[0056] Specifically, in the conductor portion 41 shown in Figure 7, the third conductor portion 4C of each conductor portion 41A to 41C is located on the opposite side of the rotor 2 from the first conductor portion 4A (radially inward in this embodiment), and is made of a material with a higher electrical resistivity than the first conductor portion 4A.

[0057] Furthermore, the cross-sectional area of ​​the second conductor section 4B is larger than the cross-sectional area of ​​the third conductor section 4C. In addition, the electrical resistance of the conductor section 41 located furthest from the rotor 2 is smaller than the electrical resistance of the conductor section 41 located closest to the rotor 2.

[0058] The conductor portion 41 shown in Figure 8 is composed of a second conductor portion 4B and a third conductor portion 4C made of the same material, and the second conductor portion 4B and the third conductor portion 4C are integrated to form a rectangular annular (cylindrical) structure that covers the entire circumference of the first conductor portion 4A.

[0059] Furthermore, the cross-sectional area of ​​the portion of the second conductor β located closer to the rotor 2 than the first conductor 4A is larger than the cross-sectional area of ​​the portion of the second conductor 4B located on the opposite side of the rotor 2 from the first conductor 4A.

[0060] In the conductor section 41 shown in Figure 9, the first conductor section 4A is made of copper, the second conductor section 4B is made of tungsten, and the third conductor section 4C is made of aluminum. The cross-sectional area of ​​the second conductor section 4B is the same as the cross-sectional area of ​​the third conductor section 4C.

[0061] In other words, the third conductor section 4C shown in Figure 9 is located on the opposite side of the rotor 2 from the first conductor section 4A, and is made of a material with a higher electrical resistivity than the first conductor section 4A, and a lower electrical resistivity than the second conductor section 4B.

[0062] Therefore, in this embodiment as well, it is possible to obtain the same effects and advantages as in the above-described embodiment. In addition, in the stator 3 according to this embodiment, the non-uniformity of the current density is mitigated, so the generation of large eddy current losses can be suppressed.

[0063] (Other embodiments) In the embodiments described above, all of the multiple conductor portions 41 had a three-layer structure, consisting of three conductors in the radial direction. However, the disclosure is not limited to this. That is, the disclosure may be limited to, for example, having at least one of the multiple conductor portions 41 having a three-layer structure.

[0064] Furthermore, if only one of the multiple wire sections 41 has a three-layer structure, it is desirable that the wire section 41 closest to the rotor 2 has a three-layer structure. In other words, the wire sections 41 other than the wire section 41 closest to the rotor 2 may be made of copper only, for example.

[0065] In the embodiments described above (for example, Figures 2 and 3), three wire portions 41 were depicted as being arranged within slot 3B. However, this disclosure is not limited thereto. That is, the disclosure may also include, for example, a configuration in which four or more wire portions 41 are arranged within slot 3B.

[0066] In this configuration, at least the wire portion 41 located furthest from the rotor 2 may be made of copper only, for example. Even in this configuration, the electrical resistance of the wire portion 41 located furthest from the rotor 2 will be smaller than the electrical resistance of the wire portion 41 located closest to the rotor 2.

[0067] In the first embodiment described above, the cross-sectional area of ​​the portion located on the rotor 2 side of the first conductor portion 4A was larger than the cross-sectional area of ​​the portion located on the opposite side of the rotor 2, with the first conductor portion 4A in between. However, the present disclosure is not limited thereto.

[0068] In other words, the disclosure may, for example, be configured such that the cross-sectional area of ​​the portion located on the rotor 2 side of the first conductor portion 4A is the same as the cross-sectional area of ​​the portion located on the opposite side of the rotor 2 with respect to the first conductor portion 4A, or it may be configured such that the cross-sectional area of ​​the portion located on the rotor 2 side of the first conductor portion 4A is smaller than the cross-sectional area of ​​the portion located on the opposite side of the rotor 2 with respect to the first conductor portion 4A.

[0069] Furthermore, as in the third embodiment, if the electrical resistivity of the second conductor portion 4B and the electrical resistivity of the third conductor portion 4C are different, even if the cross-sectional areas of the second conductor portion 4B and the third conductor portion 4C are the same, it is possible to have the same relationship between the third conductor portion 4C and the second conductor portion 4B as in the first embodiment.

[0070] In the above-described embodiment, the electrical resistance of the wire portion 41 located at the part of the slot 3B that is furthest from the rotor 2 in the radial direction was smaller than the electrical resistance of the wire portion 41 located at the part of the slot 3B that is closest to the rotor 2.

[0071] However, the disclosure is not limited thereto. That is, the disclosure may, for example, have a configuration in which all wire portions 41 have the same electrical resistance, or a configuration in which the electrical resistance of the wire portion 41 located furthest from the rotor 2 is greater than the electrical resistance of the wire portion 41 located closest to the rotor 2.

[0072] In the embodiments described above, each of the multiple wire portions 41A to 41C arranged within the same slot 3B had a different configuration. However, the disclosure is not limited thereto. That is, in this disclosure, for example, all of the multiple wire portions 41 may have the same configuration.

[0073] The conductor portion 41 in the above-described embodiment was configured with a rectangular cross-sectional shape. However, this disclosure is not limited thereto. That is, the disclosure may also include, for example, a configuration in which the conductor portion 41 is configured with a circular cross-sectional shape.

[0074] In the above-described embodiment, the first conductor portion 4A, the second conductor portion 4B, and the third conductor portion 4C, or the first conductor portion 4A and the second conductor portion β, which constitute a single conductor portion 41, were joined together to form an integrated structure. However, the present disclosure is not limited thereto.

[0075] Furthermore, this disclosure is not limited to the embodiments described above, but is sufficient to be consistent with the intent of the disclosures described in the embodiments described above. Therefore, it may be a configuration in which at least two of the embodiments described above are combined, or a configuration in which any of the illustrated components or components described with reference numerals in the embodiments described above are omitted. [Explanation of symbols]

[0076] 1. 1A… Electric motor 2… Rotor 3…Stata 3A… Stator core 3B... Slot 4… Coil 4A… First conductor section 4B… Second conductor section 4C… Third conductor section 41… Conductor part

Claims

1. In an electric motor comprising a rotor and a stator, The stator comprises a stator core and coils arranged in slots of the stator core. At least one of the multiple conductor portions located within the slot of the coil is configured to have a first conductor portion, a second conductor portion, and a third conductor portion. The second conductor portion is located on the rotor side of the first conductor portion and is made of a material with a higher electrical resistivity than the first conductor portion. The third conductor portion is located on the opposite side of the rotor from the first conductor portion and is made of a material with a higher electrical resistivity than the first conductor portion. Furthermore, the cross-sectional area of ​​the second conductor portion is larger than the cross-sectional area of ​​the third conductor portion of the electric motor.

2. In an electric motor comprising a rotor and a stator, The stator comprises a stator core and coils arranged in slots of the stator core. Of the coil, at least one of the multiple conductor portions located within the slot is configured to have a first conductor portion and a second conductor portion that covers the entire circumference of the first conductor portion. The second conductor portion is made of a material with a higher electrical resistivity than the first conductor portion. Furthermore, the cross-sectional area of ​​the portion of the second conductor located closer to the rotor than the first conductor is greater than the cross-sectional area of ​​the portion of the second conductor located on the opposite side of the rotor from the first conductor, in an electric motor.

3. In an electric motor comprising a rotor and a stator, The stator comprises a stator core and coils arranged in slots of the stator core. At least one of the multiple conductor portions located within the slot of the coil is configured to have a first conductor portion, a second conductor portion, and a third conductor portion. The second conductor portion is located on the rotor side of the first conductor portion and is made of a material with a higher electrical resistivity than the first conductor portion. The third conductor portion is located on the opposite side of the rotor from the first conductor portion, and is made of a material with a higher electrical resistivity than the first conductor portion, and a material with a lower electrical resistivity than the second conductor portion, in this electric motor.

4. The conductor portion of the slot located closest to the rotor is configured to have at least the first conductor portion and the second conductor portion. Furthermore, the electric motor according to any one of claims 1 to 3, wherein the electrical resistance value of the wire portion located at the part of the slot that is furthest from the rotor in the radial direction is smaller than the electrical resistance value of the wire portion located at the part of the slot that is closest to the rotor.

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