Rotary electrical machine and rotary electrical machine system

Abstract

This rotary electrical machine comprises a rotor and a stator. The rotor has a rotor core and a field coil wound around the rotor core. The rotor core has a plurality of magnetic pole protrusions which protrude radially outward and around which the field coil is wound. The rotor core is provided with a holding part for holding the axial end of the field coil from the inner diameter side. The circumferential width of the holding part is smaller than the circumferential width of a portion where the field coil is wound in each of the magnetic pole protrusions.

Description

Various cooling systems are available for rotary electrical machines. For example, there is an axial-flow open-type cooling system that is of a simple structure and has a high cooling capability. An axial-flow open-type cooling system that is included in a rotary electrical machine provides a direct fluidal connection between the interior and exterior of the rotary electrical machine. A refrigerant for cooling the rotary electrical machine can be obtained from a fan disposed on a rotational shaft in the rotary electrical machine or an electric air blower separate from the rotary electrical machine. In particular, when the rotary electrical machine needs to be cooled also during shutdown, forced draft system is employed to cause the electric air blower to force the refrigerant to flow in the rotary electrical machine.

[0005] The kinds of rotary electrical machines that are available include an induction machine and a synchronous machine, and rotary electrical machines are required to employ cooling structures matching their kinds. A salientpole-type rotary electrical machine (salient-pole-type synchronous machine) has field coils wound on a rotor core. The field coils have more turns than stator coils wound in a 2024255741   12 Oct 2026 stator core and tend to have a thick coil layer. Therefore, the heat inside the field coils is less liable to radiate, and the field coils are more liable to have higher temperatures. Accordingly, there is required a structure for effectively cooling the field coils. Further, the field coils rotate in unison with the rotor core. Therefore, the field coils are subject to centrifugal forces, vibrations, etc. It is thus necessary for the rotary electrical machine to have structures by which the field coils are appropriately fixed to the rotor core.

[0006] Patent Document 1 discloses a salient-pole-type rotary electrical machine including coil supports that are provided between the poles of a rotor core to support field coils. Each of the coil supports includes a coil support body made of an insulating material and a bolt having a proximal end fixed to the rotor core and a distal end attached to the coil support body. The coil support body is formed into a tapered shape so as to support the field coil. Patent Document

[0007] Patent Document 1: JP-2018-152937-A

[0008] However, with the structure disclosed in Patent Document 1, the flow of a refrigerant (cooling air) between the poles is obstructed by the coil supports disposed 2024255741   12 Oct 2026 therebetween. Consequently, the disclosed rotary electrical machine remains to be improved in terms of cooling capability.

[0009] It is desired to address or alleviate one or more disadvantages or limitations of the prior art, or to at least provide a useful alternative, for example a rotary electrical machine that is capable of effectively cooling field coils while appropriately holding the field coils in position. Summary

[0010] A rotary electrical machine according to an aspect of the present invention includes a rotor and a stator, in which the rotor has a rotor core and field coils wound on the rotor core, the rotor core has a plurality of salient poles around which the field coils are wound, the salient poles protruding radially outwardly, a holder for holding an axial end of each of the field coils from a radially inner side is provided on the rotor core, and a circumferential width of the holder is smaller than a circumferential width of a portion of each of the salient poles where the field coil is wound.

[0011] According to at least some embodiments of the present invention, it is possible to provide a rotary electrical machine that is capable of effectively cooling field coils 2024255741   12 Oct 2026 while appropriately holding the field coils in position. Brief Description of the Drawings

[0012] One or more embodiments of the present invention are hereinafter described, by way of example only, with reference to the accompanying drawings in which: [Fig. 1] Fig. 1 is a sectional side elevational view of a rotary electrical machine according to a first embodiment, schematically illustrating a cross section taken along a rotational central axis of the rotary electrical machine. [Fig. 2] Fig. 2 is an enlarged sectional plan view of the rotary electrical machine, schematically illustrating a cross section taken along line II-II of Fig. 1. [Fig. 3] Fig. 3 is an enlarged sectional plan view of a rotor, illustrating an inter-pole portion of the rotor. [Fig. 4A] Fig. 4A is a plan view of a pole assembly of the rotary electrical machine according to the first embodiment. [Fig. 4B] Fig. 4B is a side elevational view of the pole assembly of the rotary electrical machine according to the first embodiment. [Fig. 5A] Fig. 5A is a plan view of the pole assembly with a 2024255741   12 Oct 2026 field coil omitted from illustration. [Fig. 5B] Fig. 5B is a side elevational view of the pole assembly with the field coil omitted from illustration. [Fig. 6A] Fig. 6A is a plan view of a pole assembly of a rotary electrical machine according to a second embodiment. [Fig. 6B] Fig. 6B is a side elevational view of the pole assembly of the rotary electrical machine according to the second embodiment. [Fig. 7A] Fig. 7A is a plan view of a pole assembly of a rotary electrical machine according to a third embodiment. [Fig. 7B] Fig. 7B is a side elevational view of the pole assembly of the rotary electrical machine according to the third embodiment. [Fig. 8] Fig. 8 is a side elevational view of a holder of the rotary electrical machine according to the third embodiment, illustrating its state before being attached to a rotor core. [Fig. 9] Fig. 9 is a diagram illustrating the relation between a width ratio Wr (= W1 / W2) of a circumferential width W1 of the holder to a circumferential width W2 of a salient pole and each of a temperature T of a field coil and a 2024255741   12 Oct 2026 concentrated stress o. [Fig. 10] Fig. 10 is a plan view of a pole assembly of a rotary electrical machine according to a fourth embodiment. [Fig. 11] Fig. 11 is a view illustrating the configuration of a rotary electrical machine system according to a fifth embodiment. Detailed Description

[0013] <First Embodiment> A rotary electrical machine 100 according to a first embodiment of the present invention will be described below with reference to Figs. 1 through 5B. In the following description, an “axial direction,” a “circumferential direction,” a “radial direction” are defined as follows. The “axial direction” refers to a direction along a rotational central axis of the rotary electrical machine 100 (rotor 2). The rotational central axis is aligned with a central axis of a stator 3 having a hollow cylindrical shape. The “circumferential direction” refers to a direction along the direction in which the rotary electrical machine 100 rotates (the direction in which the rotor 2 rotates), i.e., a circumferential direction perpendicular to the rotational central axis and around the rotational central axis. The “radial direction” refers to a radiating direction, i.e., a radius direction, perpendicular to the 2024255741   12 Oct 2026 rotational central axis of the rotary electrical machine 100 and around the rotational central axis. Moreover, an “inner circumferential side” refers to the inside in the radial direction (radially inner side), and an “outer circumferential side” refers to a side opposite to the inner circumferential side, i.e., the outside in the radial direction (radially outer side).

[0014] Fig. 1 is a sectional side elevational view of the rotary electrical machine 100 according to the first embodiment, schematically illustrating a cross section taken along the rotational central axis of the rotary electrical machine 100. Fig. 2 is an enlarged sectional plan view of the rotary electrical machine 100, schematically illustrating a cross section taken along line II-II of Fig. 1. Fig. 2 illustrates a cross section of one pole of each of the rotor 2 and the stator 3. The rotary electrical machine 100 is mainly used while being connected to an internal combustion engine such as a diesel engine.  The rotary electrical machine 100 includes, for example, an electric generator having an output power of approximately several hundred [kVA], a voltage of approximately several hundred [V], and a rotational speed of approximately several thousand [rpm], and is used as a power supply for vehicles such as large-size dump trucks or railroad vehicles.

[0015] As illustrated in Figs. 1 and 2, the rotary electrical machine 100 includes the rotor 2 provided 2024255741   12 Oct 2026 rotatably, the stator 3 disposed radially outwardly of the rotor 2 with a gap 14 interposed between itself and the rotor 2, and a frame (housing) 1 that houses the rotor 2 and the stator 3. The rotary electrical machine 100 is a salient-pole three-phase synchronous generator. When the rotary electrical machine 100 is driven by the internal combustion engine, it operates as an electric generator to output the generated three-phase alternating-current electric power.

[0016] The frame 1 is provided on an outer circumferential side of the stator 3 and fixes the stator 3 in place. The frame 1 has a refrigerant inlet for introducing cooling air into itself and a refrigerant outlet for releasing cooling air out of itself. According to the present embodiment, the refrigerant inlet and the refrigerant outlet are provided in one and other axial ends of the rotary electrical machine 100. In other words, the rotary electrical machine 100 according to the present embodiment employs an axial-flow open-type cooling structure.

[0017] The frame 1 has a plurality of fixing parts for fixing the stator 3 in place at predetermined intervals along the circumferential direction of the stator 3. Rear ducts 16 for delivering a refrigerant (air) 17 in the axial direction are formed between the fixing parts arrayed in the circumferential direction.

[0018] 2024255741   12 Oct 2026 As illustrated in Fig. 1, the rotor 2 is rotatably supported in the frame 1 by a bearing 4 provided in the frame 1.  Although not depicted, a bearing by which the output shaft of the internal combustion engine is rotatably supported is provided on the right side, as illustrated, of the rotary electrical machine 100. The rotor 2 has a shaft 5 that is of a cylindrical or hollow cylindrical shape. The shaft 5 is supported by the bearing 4 provided in the frame 1 and the bearing (not depicted) provided in the internal combustion engine, so that the rotor 2 is rotatably held in the stator 3. In Fig. 1, only one bearing 4 is illustrated that supports the rotor 2 in the frame 1. However, a pair of bearings 4 that support axially opposite ends of the rotor 2 may be provided in the frame 1.

[0019] The stator 3 has a hollow cylindrical stator core 9 and stator coils 13 wound in the stator core 9. As illustrated in Fig. 2, the stator core 9 has a plurality of slots (60 slots in the present embodiment) formed in an inner circumferential portion thereof to extend parallel to its central axis.  The stator coils 13 are mounted in the respective slots.  Stator wedges 15 for fixing the stator coils 13 in the slots are provided in inner circumferential sides of the slots. As illustrated in Fig. 1, core clamps 11 are provided on axially opposite ends of the stator core 9 to sandwich axially opposite sides of the stator core 9 and fix the stator core 9 in position. The core clamps 11 apply a surface pressure axially to axially opposite 2024255741   12 Oct 2026 surfaces of the stator core 9.

[0020] The rotor 2 has a rotor core 7, the shaft 5 fixed to the rotor core 7, and field coils 12 wound on the rotor core 7. As illustrated in Fig. 2, the rotor core 7 has a hollow cylindrical shaft-fixed portion 71 fixed to the shaft 5 and a plurality of salient poles 72 protruding radially outwardly from the shaft-fixed portion 71. The salient poles 72 are formed at equal intervals along the circumferential direction of the rotor core 7.

[0021] Each of the salient poles 72 has a pole body 73 extending radially outwardly from the shaft-fixed portion 71 and a pole head (pole shoe) 74 attached to the proximal end of the pole body 73.  The field coil 12 is wound around the pole body 73. The salient pole 72 and the field coil 12 form a pole assembly 180. The rotary electrical machine 100 according to the present embodiment has eight poles.

[0022] As illustrated in Fig. 1, coil ends (hereinafter referred to as “field coil ends”) 6 of each of the field coils 12 are formed on axial ends of the rotor core 7. The field coil ends 6 refer to portions of the field coil 12 that protrude axially from the rotor core 7. In other words, the field coil ends 6 constitute axial end portions of the field coil 12 wound around the salient pole 72. Similarly, coil ends (hereinafter referred to as “stator coil ends”) 10 of each of the stator coils 13 are formed on 2024255741   12 Oct 2026 axially opposite ends of the stator core 9.

[0023] Next, the flow of the refrigerant 17 will be described below. In Fig. 1, arrows represented by thick solid lines schematically indicate the flow of the refrigerant 17.  The refrigerant 17 flows from the left side of Fig. 1 into the frame 1 (the rotary electrical machine 100). After flowing into the rotary electrical machine 100, the refrigerant 17 branches into and flows through the rear ducts 16, the gap 14, and inter-pole portions 18 (see Fig. 3).

[0024] The refrigerant 17 that has flowed into the rear ducts 16 flows axially through the rear ducts 16 and absorbs heat mainly from the stator 3, thereby reducing an iron loss caused by the stator core 9 and a temperature rise due to a copper loss caused by the stator coils 13.

[0025] The refrigerant 17 that has flowed into the gap 14 flows axially through the gap 14 and absorbs heat from the stator 3 and the rotor 2, thereby reducing the iron loss caused by the stator core 9, the copper loss caused by the stator coils 13, and a temperature rise due to a copper loss caused by the field coils 12.

[0026] The refrigerant 17 that has flowed into the interpole portions 18 (see Fig. 3) flows axially through the inter-pole portions 18 and absorbs heat from the field coils 2024255741   12 Oct 2026 12, thereby reducing a temperature rise due to the copper loss caused by the field coils 12. After leaving the rear ducts 16, the gap 14, and the inter-pole portions 18, the refrigerant 17 flows out of the frame 1 (the rotary electrical machine 100) from the right side, as illustrated in Fig. 1, of the frame 1 and is vented into the atmosphere.

[0027] Fig. 3 is an enlarged sectional plan view of the rotor 2, illustrating the inter-pole portion 18 of the rotor 2. In Fig. 3, two poles of the rotor 2 are depicted in cross section. The inter-pole portion 18 refers to a space between a plurality of pole assemblies 180 spaced along the circumferential direction. As illustrated in Fig. 3, the inter-pole portion 18 represents a space where there is nothing to obstruct the flow of the refrigerant 17. Therefore, the refrigerant 17 that has flowed into the rotary electrical machine 100 smoothly moves axially through the inter-pole portion 18.

[0028] A protruding length L1 of the pole body 73 that protrudes from the shaft-fixed portion 71, i.e., a radial length from the proximal end of the pole body 73 to the proximal end of the pole head 74, is larger than a radial width L2 of a wound portion 12a of the field coil 12 (L1>L2). The wound portion 12a refers to a portion of the field coil 12 that is wound around the pole body 73. The wound portion 12a of the field coil 12 has a radial end held in abutment against the pole head 74. Therefore, a space 2024255741   12 Oct 2026 18a that is shaped as a triangular prism and that is free of any obstacle to cooling air from one axial end face to the other axial end face of the rotor core 7 is formed radially inwardly of the wound portion 12a of the field coil 12. The protruding length L1 of the pole body 73 may be referred to as the depth of a groove 75 between a pair of pole bodies 73 positioned next to each other. In other words, the groove 75 between the salient poles 72 arrayed circumferentially around the rotor 2 is formed deeply such that a bottom 75a of the groove 75 is positioned radially inwardly from the wound portion 12a of the field coil 12.

[0029] As illustrated in Fig. 1, the refrigerant 17 that has flowed into the rotary electrical machine 100 cools the field coil ends 6 and the stator coil ends 10. The winding type of the stator coils 13 is a distributed winding type. That is, each of the stator coils 13 is wound in the stator core 9 over a certain interval. Therefore, spaces are formed between the coils of the stator coil ends 10. Since the refrigerant 17 flows through the spaces between the coils of the stator coil ends 10, it effectively cools the stator coil ends 10. On the other hand, the winding type of the field coils 12 is a concentrated winding type. That is, each of the field coils 12 is wound around one salient pole 72 in a concentrated manner. Therefore, no space is formed between the coils of the field coil ends 6. In other words, the field coil ends 6 have a smaller area (heat transfer area) for contacting the refrigerant 17 than the stator coil 2024255741   12 Oct 2026 ends 10 where spaces are formed between their coils.

[0030] Since the field coils 12 are wound on the rotor core 7 that is a rotating body, the field coils 12 need to be held appropriately in position on the rotor core 7. If a holder is provided for holding an entire radially inner face of the wound portion 12a of the field coil 12, then, though the field coil 12 can be held appropriately in position on the rotor core 7, the field coil 12 has a heat transfer area reduced by its area contacted by the holder.

[0031] According to the present embodiment, there are provided holders 110 capable of holding the field coil 12 appropriately in position on the rotor core 7 while restraining a reduction in the heat transfer area of the field coil 12. Holding structures for the field coil 12 according to the present embodiment will be described in detail below with reference to Figs. 4A, 4B, 5A, and 5B. Fig. 4A is a view of the pole assembly 180 as viewed from the axial direction, i.e., a plan view of the pole assembly 180. Fig. 4B is a view of the pole assembly 180 as viewed sideways (in the circumferential direction), i.e., a side elevational view of the pole assembly 180. Fig. 5A is a plan view of the pole assembly 180 with the field coil 12 omitted from illustration. Fig. 5B is a side elevational view of the pole assembly 180 with the field coil 12 omitted from illustration. In Figs. 4A through 5B, the shapes of one pole of the rotor 2 are depicted. 2024255741   12 Oct 2026

[0032] The pole head 74 is removably attached to the pole body 73. As illustrated in Fig. 2, the pole head 74 is a component for passing field fluxes to the gap 14 and has a radially outward curved face (arcuate face) along an inner circumferential surface of the stator core 9. As illustrated in Figs. 4A through 5B, the pole head 74 is larger in circumferential width than the pole body 73. Further, the pole head 74 is larger in axial length than the pole body 73. For example, after the field coil 12 has been mounted on the pole body 73, the pole head 74 is fastened to the pole body 73 by a bolt inserted from a radially outward direction of the rotor 2. The joint structure between the pole head 74 and the pole body 73 may adopt a dovetail structure instead of the fastening structure using a bolt.

[0033] As illustrated in Figs. 4A and 4B, the pole head 74 protrudes beyond the field coil 12 in the axial direction. Portions of the pole head 74 that protrude beyond the pole body 73 in the axial direction hold the field coil ends 6 on the radially outer side. In other words, the pole head 74 functions as an outer holder for holding axial ends (field coil ends 6) of the field coil 12 from the radially outer side. The pole head 74 holds not only the field coil ends 6 but also an entire radially outer end face of the wound portion 12a of the field coil 12, preventing the field coil 12 from being positionally shifted radially outwardly.

[0034] 2024255741   12 Oct 2026 The field coil ends 6 are held on the radially inner side by the holders 110 that are provided on the axial ends of the rotor core 7.  The holders 110 function as inner holders for holding axial ends (field coil ends 6) of the field coil 12 from the radially inner side such that the field coil 12 will not be dislodged radially inwardly. Therefore, the field coil ends 6 are radially sandwiched by the pole head (outer holder) 74 and the holders (inner holders) 110. The holding structures for the field coil ends 6 are identical to each other on one and other axial ends of the rotor core 7.

[0035] As illustrated in Figs. 5A and 5B, each of the holders 110 is integrally formed with the rotor core 7. The holder 110 includes a protrusive portion protruding axially from an axial end face 7a of the rotor core 7. The axial end face 7a of the rotor core 7 includes an axial end face 7a1 of a distal end portion of the pole body 73 on which the field coil 12 is round, an axial end face 7a2 of a proximal end portion of the pole body 73 that lies flush with the axial end face 7a1 of the distal end portion of the pole body 73, and an axial end face 7a3 of the shaft-fixed portion 71.

[0036] The holder 110 is of a cuboidal shape and extends radially straight from the shaft 5. The holder 110 has an axial length (protruding height) H that is approximately the same as a protruding height Hc (see Fig. 4B) of the field 2024255741   12 Oct 2026 coil end 6. The holder 110 has a radial length that is larger than a width W1 along the circumferential direction (circumferential width) of the holder 110. The circumferential width W1 of the holder 110 is smaller than a width W2 along the circumferential direction (circumferential width) of the pole body 73 (W1 < W2). The circumferential width W1 of the holder 110 is approximately 1 / 2 of the circumferential width W2 of the pole body 73, for example. The larger the circumferential width W1 of the holder 110 is, the larger its holding area is. The smaller the circumferential width W1 of the holder 110 is, the larger the heat transfer area of the field coil end 6 is. Therefore, the circumferential width W1 should preferably be in the range of 2 / 5 to 3 / 5 of the circumferential width W2.

[0037] The holder 110 is provided on a central pole axis Ca of the pole assembly 180. The central pole axis Ca corresponds to an axis that passes through the center in the circumferential direction of the salient pole 72 and that extends radially. The holder 110 has its center in the circumferential direction aligned with the center in the circumferential direction of the salient pole 72. Any one of the holders 110 is thus able to hold the field coil 12 more stably than if the holder 110 is offset from the central pole axis Ca to one side in the circumferential direction.

[0038] A portion of the field coil 12 on the radially inner 2024255741   12 Oct 2026 side affects electric characteristics less than a portion thereof on the radially outer side. Consequently, the holder 110 is not limited to the cuboidal shape, and may be of any of various shapes that are capable of holding the field coil 12 against dislodgement in the radially inward direction. For example, the holder 110 may be of a semicylindrical shape, a triangular prismatic shape, or a trapezoidal shape. However, at least the circumferential width W1 of the portion of the holder 110 that abuts against the field coil end 6 should be smaller than the circumferential width W2 of the portion of the pole body 73 on which the field coil 12 is wound.

[0039] The embodiment described above offers the following advantages.

[0040] (1) The rotary electrical machine 100 includes the rotor 2 and the stator 3. The rotor 2 has the rotor core 7 and the field coils 12 wound on the rotor core 7. The rotor core 7 has the plurality of salient poles 72 around which the field coils 12 are wound, the salient poles 72 protruding radially outwardly. The holder 110 for holding the axial end (field coil end 6) of the field coil 12 from the radially inner side is provided on the rotor core 7 (see Figs. 4A and 4B). The circumferential width W1 of the holder 110 is smaller than the circumferential width W2 of the portion of the salient pole 72 where the field coil 12 is wound (see Figs. 5A and 5B). 2024255741   12 Oct 2026

[0041] With this configuration, as illustrated in Figs. 4A and 4B, portions that are of a radially inner end face of the field coil 12 wound around the salient pole 72 and that do not include a portion held in contact with the holder 110 at the axial end act as heat transfer faces held in contact with the refrigerant 17. Specifically, faces (first end faces) 12b that are included in a radially inner end face of the field coil end 6 and that are not held in contact with the holder 110 and faces (second end faces) 12c of circumferential ends of the wound portion 12a of the field coil 12 that extend axially act as heat transfer faces that directly perform the heat exchange with the refrigerant 17.

[0042] With this configuration, therefore, the heat transfer area of the field coil 12 can be made larger than that with a holding structure for holding the entire radially inner face of the wound portion 12a of the field coil 12. Further, inasmuch as the holder 110 holds the field coil 12 in position, there is no need to provide, between the pole assemblies 180, a holding structure for holding the field coils 12. In other words, it is not necessary to provide a structure that would obstruct the flow of the refrigerant 17 in the space (inter-pole portion 18) between the pole assemblies 180. Consequently, the refrigerant 17 flows smoothly in the inter-pole portions 18 to cool the field coils 12 effectively and prevent the field coils 12 effectively from increasing their temperatures. 2024255741   12 Oct 2026

[0043] According to the present embodiment, as described above, it is possible to provide the rotary electrical machine 100 that is capable of cooling the field coils 12 effectively while holding the field coils 12 appropriately in position. According to the present embodiment, in other words, since the field coils 12 are prevented from being overheated and from being positionally shifted (dislodged), it is possible to provide the rotary electrical machine 100 that is highly reliable in that its insulation and robustness are maintained over a long period of time.

[0044] (2) The groove 75 formed between the salient poles 72 that are arrayed in the circumferential direction of the rotor 2 has the bottom 75a positioned radially inwardly of the field coils 12 wound around the salient poles 72 (see Fig. 3). This configuration allows the flow channel (interpole portion 18) for the refrigerant 17 between the salient poles 72 to have a sufficient cross-sectional area, i.e., area through which air flows.

[0045] (3) The single holder 110 is provided on an axial end of each of the salient poles 72 (see Fig. 4A). The holder 110 is provided at the center in the circumferential direction of the salient pole 72. This configuration makes it possible to hold the field coil 12 stably in position.

[0046] <Second Embodiment> 2024255741   12 Oct 2026 A rotary electrical machine 100 according to a second embodiment of the present invention will be described below with reference to Figs. 6A and 6B. Those parts that are identical or correspond to those described in the first embodiment are denoted by identical reference characters, and the differences will mainly be described below. Fig. 6A is a plan view of a pole assembly 280 of the rotary electrical machine 100 according to the second embodiment, and Fig. 6B is a side elevational view of the pole assembly 280 of the rotary electrical machine 100 according to the second embodiment.

[0047] According to the second embodiment, as illustrated in Figs. 6A and 6B, the field coil 12 and a holder 210 protrude axially outwardly from the axial end face 7a of the rotor core 7, as with the first embodiment. The second embodiment is different from the first embodiment in that the protruding height H of the holder 210 is larger than the protruding height Hc of the field coil 12. In other words, the holder 210 protrudes axially outwardly beyond the field coil 12. With this configuration, when the rotor 2 is rotated, a plurality of holders 210 function as a fan, increasing the flow rate of cooling air in the rotary electrical machine 100. Moreover, the plurality of holders 210 functioning as the fan cause flows of cooling air in the circumferential direction and the radial direction, effectively cooling the axial end faces of the field coil ends 6. According to the second embodiment, therefore, it 2024255741   12 Oct 2026 is possible to further lower the temperature of the field coils 12 than that in the first embodiment.

[0048] <Third Embodiment> A rotary electrical machine 100 according to a third embodiment of the present invention will be described below with reference to Figs. 7A, 7B, 8, and 9. Those parts that are identical or correspond to those described in the first embodiment are denoted by identical reference characters, and the differences will mainly be described below. Fig. 7A is a plan view of a pole assembly 380 of the rotary electrical machine 100 according to the third embodiment, and Fig. 7B is a side elevational view of the pole assembly 380 of the rotary electrical machine 100 according to the third embodiment.

[0049] According to the first embodiment, it has been described by way of example that the holder 110 is integrally formed with the rotor core 7. According to the third embodiment, by contrast, a holder 310 and the rotor core 7 are separate from each other. The holder 310 is fixed to the rotor core 7 by at least one of welding and bolt fastening. Structural details of the holder 310 will be described below.

[0050] Fig. 8 is a side elevational view of the holder 310, illustrating its state before being attached to the rotor core 7. The holder 310 includes a plate-shaped member 2024255741   12 Oct 2026 having a V-shaped cross section. The holder 310 has a fixed portion 311 fixed to the rotor core 7 and a biasing portion 312 extending at a predetermined angle from an end of the fixed portion 311. The angle (hereinafter referred to as a “bend angle”) 0 formed between the biasing portion 312 and the fixed portion 311 is larger than 90 degrees but smaller than 180 degrees. The holder 310 is elastically deformable. With the fixed portion 311 being fixed in position, the holder 310 elastically deforms so as to reduce the bend angle 0 when a pressing force acts on the biasing portion 312 toward the fixed portion 311.

[0051] As illustrated in Figs. 7A and 7B, before the pole head 74 is attached to the pole body 73, the fixed portion 311 is fixed to the rotor core 7, and the field coil 12 is wound around the pole body 73.  Then, the pole head 74 is attached to the pole body 73, whereupon a radially inward force from the pole head 74 acts on the biasing portion 312 through the wound portion 12a of the field coil 12. The biasing portion 312 is bent by the applied radially inward force, reducing the bend angle 0. Upon completion of the attachment of the pole head 74 to the pole body 73, the bend angle 0 becomes approximately 90 degrees. The holder 310 is now L-shaped in its cross section.

[0052] Consequently, with the pole head 74 attached to the pole body 73, an elastic force (recovery force) is applied from the elastically deformed holder 310 to the wound 2024255741   12 Oct 2026 portion 12a of the field coil 12. The wound portion 12a of the field coil 12 is thus sandwiched by the pole head 74 and the holder 310.

[0053] As described above, the shorter the circumferential width W1 of the holder 310 is, the larger the heat transfer area of the field coil end 6 is, resulting in a higher cooling capability. However, the shorter the circumferential width W1 of the holder 310 is, the smaller the area of contact (i.e., a holding area) between the holder 310 and the field coil end 6 is. If the holding area is too small, then the field coil end 6 suffers a stress concentration due to a concentrated load applied thereto, tending to become damaged.

[0054] Consequently, the holder 310 needs to be of a size that is capable of satisfying both an increase in cooling capability and a stress reduction.  The inventors of the present application performed a numerical analysis on a model according to the present embodiment to study the relation between appropriate circumferential widths of the holder 310 and the salient pole 72. Fig. 9 is a diagram illustrating the relation between a width ratio Wr (= W1 / W2) of the circumferential width W1 of the holder 310 to the circumferential width W2 of the salient pole 72 and each of a temperature T of the field coil 12 and a concentrated stress o. Each of the temperature of the field coil 12 and the concentrated stress has its value standardized to 1.0 2024255741   12 Oct 2026 [p.u.] when the width ratio Wr is 1 (when W1 = W2).

[0055] As illustrated in Fig. 9, there is a trade-off between the temperature T of the field coil 12 and the concentrated stress o. The smaller the width ratio Wr is, the lower the temperature T of the field coil 12 is, but the larger the concentrated stress o is. The larger the width ratio Wr is, the smaller the concentrated stress o is, but the higher the temperature T of the field coil 12 is.

[0056] With regard to the temperature T of the field coil 12, there are some stipulations concerning temperature rises from a standard temperature in a usage environment and a maximum usage temperature, in view of insulation. For example, according to JEC (Japanese Electrotechnical Committee) standards regarding coil insulation, it is stipulated that temperature rises be equal to or smaller than 110 [K] for a F-type. In view of this stipulation, the temperature T of the field coil 12 is required to be equal to or lower than 0.61 [p.u.]. In order to satisfy this temperature condition, the width ratio Wr needs to be equal to or smaller than 0.6. In addition, the concentrated stress o needs to be equal to or smaller than 2.5 [p.u.] in view of a value for not damaging the field coil 12 and a marginal value. In order to satisfy this stress condition, the width ratio Wr needs to be equal to or larger than 0.4.

[0057] According to the third embodiment, the holder 310 2024255741   12 Oct 2026 functions as a spring member for generating a larger retentive force than that in the first embodiment. Therefore, as described above, it is preferable to determine an appropriate width ratio Wr in advance by way of numerical analyzation and experimentation.

[0058] The third embodiment offers, in addition to similar advantages of the first embodiment, the following advantages.

[0059] (1) The holder 310 and the rotor core 7 are separate from each other. Therefore, the time required to machine the rotor core 7 can be shortened. As a result, the cost of the rotor core 7 can be reduced. Moreover, the rotor core 7 can be formed using a laminated steel sheet. As the weight of the rotor core 7 is reduced, the rotor 2 can be reduced in weight. Furthermore, the holder 310 may be made of a different material from the material of the rotor core 7 for a cost reduction.

[0060] (2) The holder 310 has the fixed portion 311 fixed to the axial end face 7a of the rotor core 7 and the biasing portion 312 that is erected from the fixed portion 311 and that biases the field coil 12 under an elastic force.  With this configuration, the holder 310 includes an elastically deformable plate-shaped member (leaf spring) and biases the field coil 12 from the radially inner side under the elastic force. By adjusting the bend angle 0 of the holder 310 2024255741   12 Oct 2026 before the holder 310 is elastically deformed, it is possible to adjust the biasing force applied from the holder 310 to the field coil 12. Consequently, the retentive force of the holder 310 that acts on the field coil 12 can easily be increased. According to the third embodiment, therefore, the field coil 12 can more effectively be prevented from being positionally shifted and damaged due to vibrations and variations in centrifugal forces and can be more reliable than that in the first embodiment.

[0061] (3) The salient pole 72 has the pole body 73 extending radially outwardly from the shaft 5 fixed to the rotor core 7 and the pole head 74 attached to the distal end of the pole body 73. The field coil 12 is radially sandwiched by the pole head 74 and the holder 31. With this configuration, when the pole head 74 is attached to the pole body 73, the holder 310 can apply an appropriate retentive force to the field coil 12 and can hold the field coil 12 in position.

[0062] <Fourth Embodiment> A rotary electrical machine 100 according to a fourth embodiment of the present invention will be described below with reference to Fig. 10. Those parts that are identical or correspond to those described in the third embodiment are denoted by identical reference characters, and the differences will mainly be described below. Fig. 10 is a plan view of a pole assembly 480 of the rotary electrical 2024255741   12 Oct 2026 machine 100 according to the fourth embodiment.

[0063] According to the third embodiment, it has been described by way of example that the single holder 310 is provided on the axial end of the single salient pole 72 (see Fig. 7A). According to the fourth embodiment, by contrast, a pair of holders 310A and 310B are provided on the axial end of the single salient pole 72, as illustrated in Fig. 10. The holders 310A and 310B are disposed on circumferentially opposite ends of the pole body 73. The holders 310A and 310B have respective circumferential widths W1A and W1B each of which is one-half of the circumferential width W1 of the holder 310 according to the third embodiment. In other words, the holders 310A and 310B according to the fourth embodiment can be said to be of a structure obtained by circumferentially dividing the holder 310 according to the third embodiment into two pieces.

[0064] The holders 310A and 310B are disposed one on each side of the central pole axis Ca at the center in the circumferential direction of the salient pole 72. With this configuration, the field coil 12 is supported at two points by the pair of holders 310A and 310B. According to the fourth embodiment, therefore, the field coil 12 is held in position more stably than that in the third embodiment.

[0065] <Fifth Embodiment> A rotary electrical machine system 1000 according to 2024255741   12 Oct 2026 a fifth embodiment of the present invention will be described below with reference to Fig. 11. Fig. 11 is a view illustrating the configuration of the rotary electrical machine system 1000 according to the fifth embodiment. The rotary electrical machine system 1000 illustrated in Fig. 11 is incorporated in a dump truck (transport vehicle for construction). As illustrated in Fig. 11, the rotary electrical machine system 1000 includes a rotary electrical machine unit 500, an internal combustion engine 520 connected to a shaft 5 of the rotary electrical machine unit 500, and a blower 542 that is an electric air blower for generating cooling air (a flow of the refrigerant 17) that flows into the rotary electrical machine unit 500. In the rotary electrical machine system 1000, the internal combustion engine 520 is driven to enable the rotary electrical machine unit 500 to generate electric power.

[0066] The rotary electrical machine unit 500 has a main rotary electrical machine 501 and an auxiliary rotary electrical machine 502. The rotary electrical machine 100 according to one of the first through fourth embodiments is used as at least one of the main rotary electrical machine 501 and the auxiliary rotary electrical machine 502. The frame 1 that houses the rotor 2 and the stator 3 of the main rotary electrical machine 501 doubles as the frame 1 that houses the rotor 2 and the stator 3 of the auxiliary rotary electrical machine 502.

[0067] 2024255741   12 Oct 2026 The rotor 2 of the main rotary electrical machine 501 and the rotor 2 of the auxiliary rotary electrical machine 502 are connected to the shaft 5. Further, the shaft 5 is directly coupled to the internal combustion engine 520 by a coupling 521. When the internal combustion engine 520 is driven, the main rotary electrical machine 501 and the auxiliary rotary electrical machine 502 supply electric power to a main electric power converter 531 and an auxiliary electric power converter 532. The main electric power converter 531 supplies electric power to driving electric motors 541 of a dump truck. The driving electric motors 541 rotate drive wheels to propel the dump truck. The auxiliary electric power converter 532 supplies electric power to a blower (air blower) 542 that is one of accessories, rotating the blower 542. Accordingly, the blower 542 generates cooling air (a flow of the refrigerant 17) for cooling the main rotary electrical machine 501 and the auxiliary rotary electrical machine 502. The refrigerant 17 flows along the direction of the rotational shaft of the rotary electrical machine unit 500.

[0068] According to the fifth embodiment, the rotary electrical machine 100 according to one of the first through fourth embodiments is used as at least one of the main rotary electrical machine 501 and the auxiliary rotary electrical machine 502. Therefore, it is possible to provide the rotary electrical machine system 1000 that is highly reliable as it includes the rotary electrical machine 2024255741   12 Oct 2026 100 that is capable of stably outputting electric power for operating various devices incorporated in the dump truck, over a long period of time. Thus, the dump truck (vehicle) including the rotary electrical machine system 1000 can be made lightweight and highly efficient.

[0069] Modifications to be described below also fall within the scope of the present invention. It is possible to combine structural details according to the modifications and the structural details according to the above embodiments, combine structural details according to the different embodiments described above, and combine structural details according to the different modifications to be described below.

[0070] <First Modification> According to the above embodiments, it has been described by way of example that the rotary electrical machine 100 has eight poles and that the stator 3 has 60 slots. However, the number of poles and the number of slots are not limited to those specified.

[0071] <Second Modification> According to the above embodiments, the axial-flow open-type cooling structure has been described by way of example. However, the present invention is not limited to such a cooling structure. For example, the frame 1 may be of a sealed structure. With the closed structure, an air 2024255741   12 Oct 2026 blower is provided in the frame 1, and cooling air generated by the air blower cools the rotor 2 and the stator 3. Alternatively, the cooling structure may be a double-flow structure for individually cooling one axial end side and other axial end side of the rotary electrical machine 100.

[0072] <Third Modification> According to the first through third embodiments, it has been described by way of example that the single holder 110, 210, or 310 is provided on the one axial end of the single salient pole 72. According to the fourth embodiment, the pair of holders 310A and 310B are provided on the one axial end of the single salient pole 72. However, the present invention is not limited to such details. Three or more holders may be provided on the one axial end of the single salient pole 72. When a plurality of holders are provided, the sum of the circumferential widths of the holders should preferably be equal to or larger than 2 / 5 of the circumferential width W2 of the pole body 73 but equal to or smaller than 3 / 5 of the circumferential width W2.

[0073] <Fourth Modification> According to the first and second embodiments, it has been described by way of example that the single holder 110 or 210 is integrally formed with the rotor core 7. However, the present invention is not limited to such a structure. A pair of holders may be provided in the first and second embodiments. According to the present modification, the 2024255741   12 Oct 2026 pair of holders can be formed by machining a radially extending recess in an axial end face of the salient pole 72 at its center in the circumferential direction.

[0074] <Fifth Modification> According to the fifth embodiment, it has been described by way of example that the rotary electrical machine 100 is incorporated in a dump truck (transport vehicle for construction). However, the present invention is not limited to such an application. The rotary electrical machine 100 is not restricted to an application where it is incorporated in a mobile body such as a vehicle.

[0075] <Sixth Modification> According to the above embodiments, it has been described by way of example that the rotary electrical machine 100 is an electric generator. However, the present invention is not limited such a detail. The rotary electrical machine 100 may be used as an electric motor. Alternatively, the rotary electrical machine 100 may be used as both an electric generator and an electric motor.

[0076] While the embodiments of the present invention have been described above, the above embodiments represent only some examples to which the invention is applicable, and should not be interpreted as limiting the technical scope of the invention to the specific structural details according to the above embodiments. The above embodiments have been 2024255741   12 Oct 2026 described in detail for an easier understanding of the present invention, and the present invention should not necessarily be limited to anything that includes all of the structural details described above. Further, some details of the configuration of a certain embodiment can be replaced with some details of the configuration of another embodiment, and some details of the configuration of a certain embodiment can also be added to some details of the configuration of another embodiment. Moreover, some details of the configuration of a certain embodiment can be deleted, added to, and replaced with some details of the configuration of another embodiment. [0076a] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. [0076b] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates 2024255741   12 Oct 2026 Description of Reference

[0077] 1: Frame 2: Rotor 3: Stator 4: Bearing 5: Shaft 6: Field coil end (axial 7: Rotor core 7a: Axial end face 9: Stator core 10: Stator coil end 12: Field coil 12a: Wound portion 12b: First end face 12c: Second end face 13: Stator coil 14: Gap 17: Refrigerant 18: Inter-pole portion 18a: Space 71: Shaft-fixed portion 72: Salient pole 73: Pole body 74: Pole head 75: Groove 75a: Bottom Characters end of a field coil) 2024255741   12 Oct 2026 100: Rotary electrical machine 110, 210, 310, 310A, 310B: Holder 180, 280, 380, 480: Pole assembly 311: Fixed portion 312: Biasing portion 500: Rotary electrical machine unit 501: Main rotary electrical machine (rotary electrical machine) 502: Auxiliary rotary electrical machine (rotary electrical machine) 520: Internal combustion engine 531: Main electric power converter 532: Auxiliary electric power converter 541: Driving electric motor 542: Blower (air blower) 1000: Rotary electrical machine system Ca: Central pole axis W1: Circumferential width of the holder W2: Circumferential width of the salient pole (pole body) (circumferential width of a portion of the salient pole around which the field coil is wound)

Claims

1. A rotary electrical machine comprising:a rotor; anda stator, whereinthe rotor has a rotor core and field coils wound onthe rotor core,the rotor core has a plurality of salient polesaround which the field coils are wound, the salient poles protruding radially outwardly,a holder for holding an axial end of each of the field coils from a radially inner side is provided on the rotor core, anda circumferential width of the holder is smaller than a circumferential width of a portion of each of the salient poles where the field coil is wound.

2. The rotary electrical machine according to claim 1, whereina groove formed between the salient poles that are arrayed in a circumferential direction of the rotor has a bottom positioned radially inwardly of the field coils wound around the salient poles.

3. The rotary electrical machine according to claim 1,whereinthe field coil and the holder protrude axially2024255741   12 Oct 2026outwardly from an axial end face of the rotor core, anda protruding height of the holder is larger than a protruding height of the field coil.

4. The rotary electrical machine according to claim 1,whereinthe holder has a fixed portion fixed to an axial endface of the rotor core and a biasing portion that is erectedfrom the fixed portion and that biases the field coil underan elastic force.

5. The rotary electrical machine according to claim 4,whereinthe salient pole has a pole body extending radiallyoutwardly from a shaft fixed to the rotor core and a polehead attached to a distal end of the pole body, andthe field coil is radially sandwiched by the pole head and the holder.

6. The rotary electrical machine according to claim 5, whereina pair of the holders are provided on an axial end of the salient pole, andthe pair of holders are disposed one on each side ofa center in a circumferential direction of the salient pole.

7. A rotary electrical machine system comprising:the rotary electrical machine according to claim 1;2024255741   12 Oct 2026an internal combustion engine connected to the rotary electrical machine; andan air blower for generating cooling air that flows into the rotary electrical machine, whereinthe internal combustion engine is driven to enablethe rotary electrical machine to generate electric power.

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