Rotor core for a rotating electric machine

Abstract

Rotor core for a rotating electrical machine, the rotor core comprising: a laminated body (22) having a plurality of annular flat metal plates (22A) stacked, the laminated body (22) having a plurality of insertion holes (23) extending through the laminated body (22) in a rotation axis direction parallel to a rotation axis (L1) of the rotor core, the insertion holes (23) being arranged at intervals in a circumferential direction of the metal plates (22A); a permanent magnet (24) housed within each of the insertion holes (23) and fixed to the laminated body (22); and an annular flat end plate (26, 46), wherein a peripheral edge of the end plate (26, 46) is welded and fixed to peripheral edges of the metal plates (22A) so that the end plate (26, 46) is arranged at one end of the laminated body (22) in the rotation axis direction to close openings of the insertion holes (23), the rotor core being characterized in that the annular flat end plate (26, 46) is made of a metal material different from the metal plates (22A), a through hole (30) extends through an outer edge portion of at least one of an outermost metal plate (22A) of the laminated body (22) or the end plate (26, 46) adjacent to the outermost metal plate (22A), and the through hole (30) is located between the rotation axis (L1) and a welding portion (27) which is welded and fixed.

Description

Technical field

[0001] The present invention relates to a rotor core for a rotating electrical machine. Description of the state of the art

[0002] A known rotor core for a rotating electrical machine is of the magnet-embedded type (see Japanese Patent Application Laid-Open No. JP 2007-236019 A). This rotor core has a laminated body formed by stacking annular flat metal plates. The laminated body has insertion holes spaced at intervals in the circumferential direction of the rotor core. Permanent magnets are inserted into the insertion holes and fixed to the laminated body.

[0003] The rotor core also includes two end plates formed by annular flat metal plates. The end plates are arranged at opposite ends of the laminated body in the stacking direction, closing the openings of the insertion holes of the laminated body. In the rotor core described in the aforementioned publication, the peripheral edges of the metal plates of the laminated body and the peripheral edges of the end plates are connected (fixed) by welding.

[0004] In a rotor core described in Japanese Patent Application Laid-Open No. JP 2008 - 199 698 A, metal plates (for example, magnetic steel plates) of a laminated body and end plates (for example, aluminum plates) are made of materials having different coefficients of linear expansion.

[0005] A rotor core in which the metal plates of a laminated body and the end plates are made of materials with different coefficients of linear expansion may have the disadvantages described below if the laminated body and the end plates are connected by welding. More specifically, an increase in the temperature of the rotor core during operation of the rotating electrical machine causes a difference between the amount of thermal expansion of the laminated body and the amount of thermal expansion of the end plates. This difference leads to internal stresses that are generated at a section where the laminated body and the end plates are welded. These internal stresses can reduce the weld strength of the weld section.

[0006] DE 100 60 121 A1 discloses a rotor having the features in the preamble of claim 1. DE 10 2013 218 490 A1, US 2016 / 0 380 493 A1, JP 2004 - 254 466 A and DE 603 ​​312 A disclose further prior art. Summary

[0007] It is an object of the present invention to provide a rotor core for a rotating electrical machine that restrains a reduction in welding strength between a laminated body and end plates.

[0008] This summary is provided to introduce, in a simplified form, a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0009] The above object is achieved by a rotor core according to claim 1. Further advantageous embodiments are disclosed in the dependent claims.

[0010] Other features and aspects will become apparent from the following detailed description, drawings and claims. Brief description of the drawings Fig. 1 is a side view of a rotor to which a rotor core for a rotating electric machine according to an embodiment is applied. Fig. 2 is a sectional view of the rotor along the line II-II in Fig. 1. Fig. 3 is a side view of the rotor core. Fig. 4 is a side view of an end plate. Fig. 5 is an enlarged side view of a welding portion of a rotor core and its surroundings. Fig. 6 is an enlarged side view of a welding portion of a rotor core and its vicinity according to another embodiment.

[0011] Throughout the drawings and detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and representations of elements in the drawings may be exaggerated for clarity, illustration, and convenience. Detailed description

[0012] This description provides a thorough understanding of the described methods, devices, and / or systems. Modifications and equivalents of the described methods, devices, and / or systems will be apparent to those skilled in the art. Orders of acts are exemplary and may be changed as apparent to those skilled in the art, except for those acts that necessarily occur in a particular order. Descriptions of functions and structures that would be familiar to those skilled in the art may be omitted.

[0013] Exemplary embodiments may take various forms and are not limited to the described examples. However, the described examples are thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0014] A rotor core 11 for a rotating electrical machine according to an embodiment will now be described with reference to Fig. 1 to 5. In the present embodiment, the rotating electrical machine is an electric motor.

[0015] First, the overall structure of a rotor 10 to which the rotor core 11 according to the present embodiment is applied will be described.

[0016] As in Fig. 1 and Fig. 2, the rotor 10 has the cylindrical rotor core 11 and a rotor shaft 12 which is inserted into a center hole 21 ( Fig. 2) of the rotor core 11 and is fixed to the rotor core 11.

[0017] The rotor core 11 has a laminated body 22 configured by stacking ring-shaped flat metal plates 22A. The metal plates 22A are each formed of an electromagnetic steel plate made of a magnetic material. In the laminated body 22, insertion holes 23 are arranged at intervals in the circumferential direction of the laminated body 22. The insertion holes 23 extend in an axis of rotation direction (right - left direction in Fig. 2), which is parallel to an axis of rotation L1 of the rotor core 11, through the laminated body 22. More specifically, the laminated body 22 has a total of ten pairs of insertion holes 23 that are adjacent to each other in the circumferential direction. The insertion holes 23 each have an elongated cross section. The two insertion holes 23 of each pair extend outward as they approach each other.

[0018] A permanent magnet 24 is inserted and received in each insertion hole 23. The permanent magnet 24 has a long rectangular cross section in the longitudinal direction of the cross section of the insertion hole 23. The permanent magnet 24 is fixed to the laminated body 22 (i.e., the inner surface of the insertion hole 23) with a filler material 25 made of thermosetting epoxy resin. Generally, the magnetic poles of an electric motor are each formed by two permanent magnets 24 inserted and fixed in two insertion holes 23 indicated by the two-dot chain line in Fig. 1 are circled, more precisely two insertion holes 23, which extend inwards as you approach.

[0019] The rotor core 11 has two annular flat end plates 26. The end plates 26 are made of a different metal material than the metal plates 22A. More specifically, the end plates 26 are made of stainless steel, which is a non-magnetic material. The end plates 26 are arranged at the opposite ends of the layered body 22 in the rotation axis direction, so that openings of the insertion holes 23 are closed. The rotor core 11 is configured by stacking the metal plates 22A and the two end plates 26. The two end plates 26 form the outermost layers in the stacking direction.

[0020] In the rotor core 11, the peripheral edges of the end plates 26 and the peripheral edges of the metal plates 22A are welded together, so that the end plates 26 are fixed to the laminated body 22. A welding portion 27 for welding and fixing is set at a location between the two permanent magnets 24 constituting the magnetic pole. The rotor core 11 has welding portions 27 thus set at ten locations for the respective magnetic poles.

[0021] As in Fig. 2, the rotor shaft 12 has an annular flange 13 protruding from its periphery. An external thread 14 is provided at a portion on the outer surface of the rotor shaft 12 that is spaced from the flange 13. A nut 15 is screwed onto the external thread 14. When the rotor core 11 is connected to the rotor shaft 12, the rotor shaft 12 is inserted into the center hole 21 of the rotor core 11. Then, with the rotor core 11 held between the flange 13 of the rotor shaft 12 and the nut 15 (washer 16), the nut 15 is screwed onto the external thread 14 of the rotor shaft 12. The rotor core 11 is thus fixed to the rotor shaft 12.

[0022] In the rotor core 11 according to the present embodiment, the metal plates 22A formed by electromagnetic steel plates in the laminated body 22 and the end plates 26 formed by stainless steel plates are made of materials having different coefficients of linear expansion and are joined by welding. Therefore, when the temperature of the rotor core 11 rises during operation of the electric motor, a difference between the amount of thermal expansion of the laminated body 22 and the amount of thermal expansion of the end plates 26 may generate internal stress at the weld portion 27. This may reduce the weld strength of the weld portions 27.

[0023] In view of this, the rotor core 11 according to the present embodiment has through-holes 30 extending through the end plates 26 to restrict a reduction in the welding strength at the welding portions 27. The through-holes 30 will now be described.

[0024] As in Fig. 1, Fig. 4 and Fig. 5, a plurality of through-holes 30 (ten in the present embodiment) extend through an outer peripheral portion of the end plate 26. The through-holes 30 are each arranged between the welded portions 27 and the rotation axis L1. More specifically, the through-holes 30 are each formed at a location between an arrangement portion where the two permanent magnets 24 constituting a magnetic pole are arranged and the corresponding welded portion 27, which is arranged outward from the arrangement portion in the radial direction of the rotor core 11. The outer peripheral end of the through-hole 30 (lower side in Fig. 5) is arcuate and extends along the peripheral edge of the end plate 26. Furthermore, the inner peripheral end of the through hole 30 (upper side in Fig. 5) parallel to the outer surfaces of the two permanent magnets 24, and is curved so that it has a projection that projects inward.

[0025] The through-hole 30 is arranged in this way to form a bridge 31 at a location adjacent to the welding portion 27 in the end plate 26. The bridge 31 is strip-shaped between the peripheral edge of the end plate 26 and the outer peripheral end of the through-hole 30. The bridge 31 forms the end of the outer peripheral portion of the end plate 26. The bridge 31 is arc-shaped and extends in the outer peripheral portion. In the bridge 31, the width (indicated by W1 in Fig. 5) a portion close to the welding portion 27 is larger than the width (indicated by W2 in Fig. 5) a portion located remote from the welding portion 27.

[0026] The rotor core 11 according to the present embodiment achieves the following advantages.

[0027] (1) The rotor core 11 according to the present embodiment has the through-holes 30 at locations near the welded portions 27 in the outer peripheral portion of the end plates 26. This forms the strip-shaped bridges 31 with low rigidity at locations adjacent to the welded portions 27 in the end plates 26. Therefore, when an increase in the temperature of the rotor core 11 during operation of the electric motor causes a difference between the amount of thermal expansion of the laminated body 22 and the amount of thermal expansion of the end plates 26, the bridges 31 are warped in the radial direction, and therefore generates a force that displaces the peripheral edges of the end plates 26 and the peripheral edge of the laminated body 22 in the radial direction.

[0028] The bridges 31 of the end plates 26 are deformed to offset part of the force acting on the welded portions 27, so that the force acting on the welded portions 27 is reduced compared to a structure in which the through holes 30 are not included. This reduces internal stresses generated at the welded portions 27 of the laminated body 22 and the end plates 26 and limits a reduction in the weld strength between the laminated body 22 and the end plates 26.

[0029] (2) The rotor core 11 has the through holes 30 at locations between the welded portions 27 in the end plates 26 and the rotation axis L1. This reduces the rigidity of the area around the welded portions 27 in the end plates 26, so that the area around the welded portions 27 is easily deformed.

[0030] (3) The rotor core 11 has the strip-shaped bridges 31 at locations adjacent to the welded portions 27 in the end plates 26. The bridges 31 are slightly deformed. The bridges 31 are deformed to reduce internal stresses generated at the welded portions 27.

[0031] (4) The bridge 31 forms the end of the outer edge portion of the end plate 26 and extends in the outer edge portion. In the bridge 31, the width of a portion near the weld portion 27 is larger than the width of a portion far from the weld portion 27. This reduces the width of the portion far from the weld portion 27 in the bridge 31 for easy deformation. The portion far from the weld portion 27 is deformed, so that the total amount of deformation of the bridge 31 is ensured. In addition, the width of the portion near the weld portion 27 in the bridge 31 is increased, so that the portion is comparatively less likely to be deformed.This limits the distortion deformation and torsional deformation at the portion near the weld portion 27, and therefore reduces internal stresses at the weld portion 27 that may result from the distortion deformation and torsional deformation. This preferably limits a reduction in the weld strength between the laminated body 22 and the end plates 26.

[0032] The embodiments explained above can be modified as follows.

[0033] The metal plates 22A of the laminated body 22 may be metal plates other than electromagnetic steel plates, for example, metal plates made of iron or an iron alloy. The metal plates of the end plates 26 may be metal plates other than stainless steel plates, for example, metal plates made of an aluminum alloy.

[0034] Through holes may be arranged at the portion near the welding portion 27 in an end plate 46. Fig. 6 shows an example of such a rotor core. In the Fig. 6, a strip-shaped auxiliary bridge 41 extending in a straight line connecting the welding portion 27 and the rotation axis L1 is arranged between the inner peripheral end and the outer peripheral end of the through hole 30 (see Fig. 5). This divides the opening of the through-hole 30, so that the through-hole 30 is divided into two through-holes 43, 44 arranged in the circumferential direction. With this structure, the auxiliary bridge 41 can be used as a deformation portion deformed by a force resulting from a difference between the amount of thermal expansion of the end plate 46 and the amount of thermal expansion of the metal plate 22A, or a reinforcing portion that restricts the deformation of the bridge 31 caused by the force. Thus, the rigidity of the portion near the weld portion 27 in the end plate 46 is freely determined. In the Fig. In the example shown in Figure 6, one of the two through holes 43, 44 may be omitted.

[0035] The widths of the sections of the bridge 31 can be changed. For example, the width of the section near the welding section 27 and the width of the section far from the welding section 27 in the bridge 31 can be the same.

[0036] In addition to or instead of the through holes provided in the end plates 26 to restrict a reduction in the welding strength between the laminated body 22 and the end plates 26, through holes may be provided in the outermost metal plates 22A adjacent to the end plates 26 below the metal plates 22A of the laminated body 22. In this case, the through holes may extend through the metal plates 22A including the outermost metal plates 22A.

[0037] Preferably, the through-holes are arranged in the end plates 26 instead of the metal plates 22A of the laminated body 22. When the through-holes are arranged in the metal plates 22A of the laminated body 22, if the locations where the through-holes are arranged overlap the locations where the permanent magnets 24 are arranged in the radial direction, this may degrade the performance of the rotor core 11 and thereby degrade the performance of the electric motor. In view of this, as described above, the through-holes are arranged only in the end plates 26 among the metal plates 22A and the end plates 26, so that the locations where the through-holes are arranged do not overlap the locations where the permanent magnets 24 are arranged in the radial direction.This limits the deterioration of the performance of the rotor core 11 caused by the through holes compared with the through holes arranged in the metal plates 22A of the laminated body 22.

[0038] In the rotor core 11, if the ends of the insertion holes 23 in the rotation axis direction parallel to the rotation axis L1 are filled only with the filler material 25 without the permanent magnet 24, through holes may be arranged at the ends to restrict deterioration of the performance of the rotor core 11.

[0039] The rotor core according to the embodiment is not limited to a rotor having ten magnetic poles (five magnetic pole pairs), and can be applied to a rotor having any number of magnetic poles (four, six, eight, or the like).

[0040] Various changes in form and details may be made to the foregoing examples without departing from the spirit and scope of the claims and their equivalents. The examples are for purposes of description only, and not for purposes of limitation. Descriptions of features in each example should be considered applicable to similar features or aspects in other examples. Purposeful results may be achieved if sequences are performed in a different order, and / or if components in a described system, architecture, device, or circuit are combined differently, and / or substituted for or supplemented with other components or their equivalents. The scope of the invention is defined by the claims, not the detailed description. All variations within the scope of the claims are intended to be included within the invention.

Claims

[1] Rotor core for a rotating electrical machine, the rotor core with: a laminated body (22) having a plurality of annular flat metal plates (22A) stacked, the laminated body (22) having a plurality of insertion holes (23) extending through the laminated body (22) in a rotation axis direction parallel to a rotation axis (L1) of the rotor core, the insertion holes (23) being arranged at intervals in a circumferential direction of the metal plates (22A); a permanent magnet (24) housed within each of the insertion holes (23) and fixed to the laminated body (22); and an annular flat end plate (26, 46), wherein a peripheral edge of the end plate (26, 46) is welded and fixed to peripheral edges of the metal plates (22A) so that the end plate (26, 46) is arranged at one end of the laminated body (22) in the rotation axis direction to close openings of the insertion holes (23), wherein the rotor core characterized by is that the annular flat end plate (26, 46) is made of a metal material different from the metal plates (22A), a through hole (30) extends through an outer edge portion of at least one of an outermost metal plate (22A) of the laminated body (22) or the end plate (26, 46) adjacent to the outermost metal plate (22A), and the through hole (30) is located between the rotation axis (L1) and a welding portion (27) which is welded and fixed. [2] A rotor core for a rotating electrical machine according to claim 1, wherein the through-hole (30) is arranged in the plate to form a strip-shaped bridge (31) at a location adjacent to a welding portion (27) which is welded and fixed. [3] The rotor core for a rotating electrical machine according to claim 2, wherein the bridge (31) forms one end of the outer peripheral portion and extends along the outer peripheral portion, and a width of a portion near the welding portion (27) is larger than a width of a portion located far from the welding portion (27). [4] The rotor core for a rotating electrical machine according to any one of claims 1 to 3, wherein the through hole (30) is not arranged in the outermost metal plate (22A), and is arranged in the end plate (26, 46).

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