Rotating electric machine

Abstract

Rotating electric machine (1) with: a rotor (3); a stator (2) comprising a stator core (22) and a stator coil (21) attached to the stator core (22), the stator core (22) having a plurality of slots (22a) formed therein, the stator coil (21) being partially received in the slots (22a) of the stator core (22) to form a pair of coil end parts projecting from the slots (22a) on opposite axial sides of the stator core (22), the stator coil (21) being formed from a plurality of segments (23) of an electrical wire connected to one another, each segment (23) of an electrical wire comprising an electrical conductor (24) and an insulating sheath (25; 25a, 25b; 25a, 25b, 25c) covering an outer surface of the electrical conductor (24); and an insulating resin (27) applied to the coil end parts of the stator coil (21) to cover outer surfaces of the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c) of the segments (23) of an electrical wire forming the stator coil (21), where a tensile strength of the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c) of the segments (23) of an electrical wire is higher than an adhesive strength between the insulating resin (27) and the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c).

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application is based on Japanese patent applications No. 2012-286330, filed on December 27, 2012, and No. 2013-264361, filed on December 20, 2013, the contents of which are hereby incorporated in their entirety by reference into this application, and claims their priority. BACKGROUND 1. Technical field

[0002] The present invention relates to rotating electrical machines, which are used, for example, in motor vehicles as electric motors and electric generators. 2. Description of the related technology

[0003] Rotating electrical machines are known that are used in motor vehicles as electric motors and electric generators. These rotating electrical machines generally have a rotor and a stator. The stator has a stator core arranged radially to the rotor and a stator coil attached to the stator core. The stator coil is formed by connecting a plurality of electrical wires in a predetermined pattern; each of the electrical wires has an insulating sheath formed on its surface. The stator coil also has a slot-internal or slot-running portion that is received in the slots of the stator core, and first and second coil end portions that project from the slots on opposite axial end faces of the stator core.Furthermore, to ensure resistance to vibration, the stator coil is fixed to the first and second coil end parts by applying an insulating resin, such as a varnish.

[0004] Japanese patent JP 3 144 157 B2 also discloses a stator for an electric permanent magnet generator. The stator comprises an armature core, a plurality of armature wires attached to the armature core, and a plurality of bridging wires connecting the armature wires. The stator further comprises first, second, and third insulating layers. The first insulating layer is formed to cover an outer surface of a yoke section of the armature core. The bridging wires are also arranged on the first insulating layer. The second insulating layer is formed on the first insulating layer to cover the bridging wires. The third insulating layer is formed to cover both the second and first insulating layers.The second insulating layer is formed either from a resin that does not adhere to either the first or the third insulating layer, or from a resin that exhibits weak adhesion to both the first and third insulating layers. Consequently, the bond strength between the first and second insulating layers, as well as between the second and third insulating layers, is low. If cracks develop in the first or third insulating layer as a result, it is possible to prevent the application of significant mechanical stress to the bridging wires, thus preventing their breakage.

[0005] The inventors of the present invention have further discovered the following problems with the known rotating electrical machines described above.

[0006] When a lacquer is applied to the first and second coil ends of the stator coil, the lacquer fills the gaps formed between the electrical wires, causing it to adhere to them. Furthermore, the lacquer has a lower coefficient of linear expansion than the insulating sheaths of the electrical wires that make up the stator coil. Consequently, when the rotating electric machine is stopped, and thus the ambient temperature of the stator changes from a high temperature to a low temperature, tensile stress is induced in the lacquer. This tensile stress increases with a decrease in the lacquer temperature, as is the case in Fig. Figure 36 shows that when the tensile stress increases to exceed an allowable mechanical stress, cracks are formed in the varnish. Furthermore, in cases where the bond strength between the varnish and the insulating sheaths of the electrical wires is higher than the tensile strength of the insulating sheaths, if the cracks have progressed to the boundaries between the varnish and the insulating sheaths, the cracks will cause the insulating sheaths to crack along with the varnish, resulting in a breakdown or failure of the insulating sheaths. In particular, in cases where the rotating electrical machine is configured to cool the stator coil with a coolant, the temperature of the varnish will decrease more rapidly after a stoppage of operation of the rotating electrical machine, making it easier for a breakdown of the insulating sheaths to occur.

[0007] Further relevant prior art is disclosed in JP S57 - 36 815 A, US 6 333 573 B1, JP 2005 - 304 223 A, US 5 965 263 A and US 2005 / 0 012 424 A1. SUMMARY

[0008] According to an exemplary embodiment, a first rotating electric machine is provided, comprising a rotor, a stator, and an insulating resin. The stator has a stator core and a stator coil attached to the stator core. The stator core has a plurality of slots formed within it. The stator coil is partially received in the slots of the stator core to form a pair of coil end sections, each projecting from the slots on opposite axial sides of the stator core. The stator coil is formed from a plurality of segments of an electrical wire connected to one another. Each segment of the electrical wire has an electrical conductor and an insulating sheath covering an outer surface of the electrical conductor.The insulating resin is applied to the coil ends of the stator coil to cover the outer surfaces of the insulating sheaths of the electrical wire segments that make up the stator coil. The tensile strength of the insulating sheaths of the electrical wire segments is higher than the bond strength between the insulating resin and the insulating sheaths.

[0009] With the preceding configuration, if the ambient temperature of the stator changes due to a change in the operation of the first rotating electrical machine, and cracks are generated in the insulating resin as a result of the ambient temperature change, the tearing mechanical stress acts in such a way as to separate the insulating resin from the insulating sheaths of the electrical wire segments. Consequently, it prevents the cracks generated in the insulating resin from propagating to the insulating sheaths of the electrical wire segments. That is, it prevents the insulating sheaths from tearing along the insulating resin; thus, it prevents the cracks generated in the insulating resin from reaching the electrical conductors of the electrical wire segments. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths.

[0010] In the first rotating electric machine, each of the insulating sheaths of the segments of an electric wire can be configured to have a plurality of layers, each possessing a specific tensile strength. In this case, at least one of the tensile strengths of the layers is higher than the bond strength between the insulating resin and the insulating sheaths. Furthermore, in this case, it is preferable that, in each adjacent pair of insulating sheath layers of the segments of an electric wire, the tensile strength of one of the two layers of the pair formed within the other layer is higher than the bond strength between the two layers of the pair.

[0011] In the first rotating electric machine, each of the segments of an electric wire forming the stator coil can have an essentially rectangular cross-sectional shape.

[0012] In the first rotating electric machine, the stator coil can be attached to the stator core in a distributed winding manner.

[0013] According to another exemplary embodiment, a second rotating electric machine is provided, comprising a rotor, a stator, and an insulating resin. The stator has a stator core and a stator coil attached to the stator core. The stator core has a plurality of slots formed within it. The stator coil is partially received in the slots of the stator core to form a pair of coil end sections, each projecting from the slots on opposite axial sides of the stator core. The stator coil is formed from a plurality of segments of an electrical wire connected to one another. Each segment of the electrical wire has an electrical conductor and an insulating sheath covering an outer surface of the electrical conductor.The insulating resin is applied to the coil ends of the stator coil to cover the outer surfaces of the insulating sheaths of the electrical wire segments that form the stator coil. Each of the insulating sheaths of the electrical wire segments is further configured to have an inner sheath and an outer sheath formed outside the inner sheath. The tensile strength of the inner sheath is higher than the bond strength between the inner and outer sheaths.

[0014] With the preceding configuration, even if cracks induced in the insulating resin reach the boundaries between the inner and outer sheaths of the segments of an electrical wire, it is possible to prevent the cracks from propagating beyond these boundaries to the inner sheaths. This also prevents the cracks from reaching the electrical conductors of the segments of the electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths of the segments of an electrical wire.

[0015] In the second rotating electric machine, the inner and outer casings can be made of different insulating materials.

[0016] In the second rotating electric machine, each of the segments of an electric wire that form the stator coil can have an essentially rectangular cross-sectional shape.

[0017] In the second rotating electric machine, the stator coil can be attached to the stator core in a distributed winding manner.

[0018] In the second rotating electric machine, at least one of the inner and outer shells can be configured to have a plurality of layers. In this case, it is further preferable that, for each adjacent pair of the plurality of layers, the tensile strength of one of the two layers of the pair formed within the other layer is higher than the bond strength between the two layers of the pair.

[0019] Fig. 11 additionally presents the relationship between the tensile strengths of the insulating sheaths of the segments of an electrical wire and the bond strengths between the insulating resin and the insulating sheaths, between the inner and outer sheaths of the insulating sheaths and between different layers of the insulating sheaths in the first and the second rotating electrical machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention can be more fully understood from the detailed description given below and from the accompanying drawings of the exemplary embodiments, which, however, should not be interpreted as limiting the invention to the specific embodiments, but merely serve the purpose of explanation and understanding.

[0021] They show: Fig. 1 a partial cross-sectional view of a rotating electrical machine according to the first embodiment; Fig. 2 a perspective view of a stator of the rotating electric machine; Fig. 3 a side view of part of the stator; Fig. 4 a schematic view showing the occurrence of cracks in a varnish applied to the first and second coil end parts of a stator coil of the stator; Fig. 5 a partial cross-sectional view of part of the stator; Fig. 6 a schematic perspective view showing the configuration of segments of an electrical wire to form the stator coil; Fig. 7 a schematic perspective view showing a method of inserting the segments of an electrical wire into slots formed in a stator core of the stator; Fig. 8 a perspective view showing part of the second coil end section of the stator coil; Fig. 9 a schematic cross-sectional view showing the arrangement of the segments of an electrical wire in the slots of the stator core; Fig. 10 a schematic view showing the configuration of the segments of an electrical wire according to the first embodiment and the varnish applied between the segments of an electrical wire; Fig. 11 a graphic representation showing a comparison between the tensile strengths of insulating sheaths of the segments of an electrical wire and the adhesion strength between the varnish and the insulating sheaths, the adhesion strength between the inner and outer sheaths of the insulating sheaths and the adhesion strength between different layers of the insulating sheaths according to the first to seventh embodiments; Fig. 12 a schematic view showing the configuration of the segments of an electrical wire according to a first comparative example and the varnish applied between the segments of an electrical wire; Fig. 13 a schematic view showing the configuration of the segments of an electrical wire according to the second embodiment and the varnish applied between the segments of an electrical wire; Fig. 14 a schematic view showing the configuration of the segments of an electrical wire according to a second comparative example and the varnish applied between the segments of an electrical wire; Fig. 15 a schematic view showing the configuration of the segments of an electrical wire according to the third comparative example and the varnish applied between the segments of an electrical wire; Fig. 16 a schematic view showing the configuration of the segments of an electrical wire according to a third comparative example and the varnish applied between the segments of an electrical wire; Fig. 17 a schematic view showing the configuration of the segments of an electrical wire according to the fourth embodiment and the varnish applied between the segments of an electrical wire; Fig. 18 a schematic view showing the configuration of the segments of an electrical wire according to a fourth comparative example and the varnish applied between the segments of an electrical wire; Fig. 19 a schematic view showing the configuration of the segments of an electrical wire according to the fifth embodiment and the varnish applied between the segments of an electrical wire; Fig. 20 a schematic view showing the configuration of the segments of an electrical wire according to a fifth comparative example and the varnish applied between the segments of an electrical wire; Fig. 21 a schematic view showing the configuration of the segments of an electrical wire according to the sixth embodiment and the varnish applied between the segments of an electrical wire; Fig. 22 a schematic view showing the configuration of the segments of an electrical wire according to a sixth comparative example and the varnish applied between the segments of an electrical wire; Fig. 23 a schematic view showing the configuration of the segments of an electrical wire according to the seventh embodiment and the varnish applied between the segments of an electrical wire; Fig. 24 a schematic view showing the configuration of the segments of an electrical wire according to a seventh comparative example and the varnish applied between the segments of an electrical wire; Fig. 25 a schematic view showing the configuration of the segments of an electrical wire according to the eighth embodiment and the varnish applied between the segments of an electrical wire; Fig. 26 a schematic view showing the configuration of the segments of an electrical wire according to an eighth comparative example and the varnish applied between the segments of an electrical wire; Fig. 27 a schematic view showing the configuration of the segments of an electrical wire according to the ninth embodiment and the varnish applied between the segments of an electrical wire; Fig. 28 a schematic view showing the configuration of the segments of an electrical wire according to a ninth comparative example and the varnish applied between the segments of an electrical wire; Fig. 29 a schematic view showing the configuration of the segments of an electrical wire according to the tenth embodiment and the varnish applied between the segments of an electrical wire; Fig. 30 a schematic view showing the configuration of the segments of an electrical wire according to a tenth comparative example and the varnish applied between the segments of an electrical wire; Fig. 31 a schematic view showing the configuration of the segments of an electrical wire according to the eleventh embodiment and the varnish applied between the segments of an electrical wire; Fig. 32 a schematic view showing the configuration of the segments of an electrical wire according to an eleventh comparative example and the varnish applied between the segments of an electrical wire; Fig. 33 a schematic view showing the configuration of the segments of an electrical wire according to a first modification and the varnish applied between the segments of an electrical wire; Fig. 34 an enlarged view of part of Fig. 33; Fig. 35 a schematic view showing the configuration of the segments of an electrical wire according to a second modification and the varnish applied between the segments of an electrical wire; and Fig. 36 a graphic representation showing the relationship between the temperature of a varnish applied to the first and second coil end parts of a stator coil of a rotating electrical machine and the tensile stress induced in the varnish. DESCRIPTION OF THE EXAMPLES OF EXECUTION

[0022] Exemplary implementations are described below with reference to Fig. 1-35 described. It should be noted that, for the sake of clarity and understanding, identical components with identical functions are marked throughout the description, where possible, with the same reference numerals in each of the figures, and that, to avoid redundancy, descriptions of identical components are not repeated. [First embodiment]

[0023] Fig. Figure 1 shows the overall configuration of a rotating electric machine according to a first embodiment.

[0024] In the present embodiment, the rotating electric machine is configured as a motor vehicle AC generator 1 for use in a motor vehicle, such as a passenger car or a truck.

[0025] As in Fig. As shown in Figure 1, the AC generator 1 has a stator 2, which functions as an armature, a rotor 3, which functions as a field, a pair of front and rear casings 4a and 4b, which are connected and fixed by a plurality of bolts 4c and together house both the stator 2 and the rotor 3, and a rectifier 5, which rectifies the three-phase AC power output by the stator 2 into DC power.

[0026] Stator 2, as shown in Fig. Figure 2 shows a hollow cylindrical stator core 22, a three-phase stator coil 21 attached to the stator core 22, and insulators 29 that electrically isolate the stator coil 21 from the stator core 22. Referring back to Fig. 1. The stator 2 is held between the front and rear housings 4a and 4b to surround the rotor 3 with a predetermined radial gap formed between the stator 2 and the rotor 3. The detailed configuration of the stator 2 is described later.

[0027] The rotor 3 comprises a rotating shaft 33, a rotor core 32 having a pair of Lundell-type magnetic pole cores 32a and 32b, and a field coil 31. The rotating shaft 33 is rotatably supported by bearings through the front and rear housings 4a and 4b. The rotating shaft 33 has a pulley 20, which is attached to a front end section (i.e., a left end section in Fig. 1) is attached to the same so that it can be driven by an internal combustion engine (not shown) of the vehicle via the pulley 20. Each of the magnetic pole cores 32a and 32b has a plurality of magnetic pole claws 32c. The field coil 31 is, for example, made of insulated copper wire and wound in a hollow cylindrical form. The magnetic pole cores 32a and 32b are tightly fitted to the rotating shaft 33, with the field coil 31 held between the magnetic pole cores 32a and 32b.

[0028] In the present embodiment, the number of magnetic pole claws 32c of each of the magnetic pole cores 32a and 32b is additionally 8. That is, the rotor 3 has a total of sixteen magnetic poles.

[0029] The AC generator 1 also includes a semi-axial cooling fan 35 or a mixed-flow cooling fan 35, a centrifugal or radial cooling fan 36, a pair of slip rings 37 and 38 and a brush assembly 7.

[0030] The semi-axial cooling fan 35, for example, is attached by welding to a front end face of the magnetic pole core 32a, which is located on the front side (i.e., the left side in Fig. 1) is located, fixed. The semi-axial cooling fan 35 draws in cooling air from the front side and discharges it in both the axial and radial directions of the rotating shaft 33. The radial cooling fan 36, on the other hand, is fixed, for example, by welding to a rear end face of the magnetic pole core 32b, which is located on the rear side (that is, the right side in Fig. 1) is located, fixed. The radial cooling fan 36 draws in cooling air from the rear side and discharges it in the radial direction of the rotating shaft 33.

[0031] In a front end wall of the front housing 4a, a plurality of cooling air intake openings 42a are formed, through which cooling air is drawn into the AC generator 1 by the semi-axial cooling fan 35. Conversely, in a rear end wall of the rear housing 4b, a plurality of cooling air intake openings 42b are formed, through which cooling air is drawn into the AC generator 1 by the radial cooling fan 36. In the side walls of the front and rear housings 4a and 4b, a plurality of cooling air discharge openings 41 are also formed, through which cooling air is discharged from the AC generator 1 by the semi-axial and radial cooling fans 35 and 36, respectively. In the present embodiment, the cooling air discharge openings 41 are also formed in the front and rear housings 4a and 4b to face those parts of the stator coil 21 that project from the axial end faces of the stator core 22.

[0032] The slip rings 37 and 38 are located on a rear end section (that is, a right end section in Fig. 1) provided for the rotating shaft 33 and each connected to opposite ends of the field coil 31.

[0033] The brush device 7 has a pair of brushes, each arranged on the radially outer peripheries of the slip rings 37 and 38, to supply the field coil 31 with a field current via the slip rings 37 and 38.

[0034] The automotive AC generator 1, which has the configuration described above, operates as follows. When torque is transmitted from the drive motor to the pulley 20 via, for example, a belt (not shown), the rotor 3 is driven by the torque to rotate in a predetermined direction. During the rotation of the rotor 3, the field coil 31 is supplied with field current through the sliding contact between the slip rings 37 and 38 and the brushes of the brush assembly 7, thereby magnetizing the magnetic pole claws 32c of the magnetic pole cores 32a and 32b to generate a rotating magnetic field. The rotating magnetic field induces three-phase AC power in the stator coil 21.The rectifier 5 then converts the three-phase alternating current power output by the stator coil 21 into direct current power and outputs the resulting direct current power via its output terminals.

[0035] After describing the overall configuration and operation of the AC generator 1, the detailed configuration of the stator 2 of the AC generator 1 is described with reference to Fig. 2-10 described.

[0036] The stator core 22 has a plurality of slots 22a for receiving the stator coil 21. As in Fig. As shown in Figure 5, each of the slots 22a has a substantially rectangular cross-section perpendicular to the axial direction of the stator core 22. In the present embodiment, two slots 22a are provided per magnetic pole of the rotor 3, which has sixteen magnetic poles, and per phase of the three-phase stator coil 21. The total number of slots 22a formed in the stator core 22 is therefore 96 (i.e., 2 x 16 x 3). The slots 22a are additionally spaced apart from each other at equal intervals along the circumferential direction of the stator core 22.

[0037] In the present embodiment, the stator coil 21 is attached to the stator core 22 in a manner of a distributed winding.

[0038] In the present embodiment, more precisely, the stator coil 21 is formed by attaching a plurality of essentially U-shaped segments 23 of an electrical wire, as in Fig. 6 and Fig. Figure 7 shows the stator core 22 and then the joining of corresponding pairs of distal end parts 23f of the segments 23 of an electrical wire.

[0039] Each of the segments 23 of an electrical wire is obtained by bending a straight segment of an electrical wire into an essentially U-shape; the straight segment of an electrical wire has an essentially rectangular cross-section perpendicular to its direction of extension.

[0040] In the present embodiment, as it appears in Fig. As shown in Figure 10, each segment 23 of an electrical wire is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 is removed from both distal end parts 23f of the segment 23 of the electrical wire, thus exposing the electrical conductor 24 from the insulating sheath 25 at the distal end parts 23f. Consequently, it is possible to join corresponding pairs of the distal end parts 23f of the segments 23 of the electrical wire by welding.

[0041] In the present embodiment, the insulating sheath 25 is additionally formed by, for example, a polyimide (PI) and has a thickness in the range of, for example, 1 to 10 µm. More precisely, the insulating sheath 25 is formed by (1) immersing the segment 25 of an electrical conductor in a polyimide melt contained in a bath for a predetermined time and then removing it from the bath, (2) passing the segment 25 of an electrical conductor through a hole of a predetermined size to uniformize the thickness of the polyimide adhering to the outer surface of the segment 25 of an electrical conductor, and (3) curing the polyimide adhering to the outer surface of the segment 25 of an electrical conductor in a curing oven for a predetermined time.

[0042] As in Fig. As shown in Figure 7, before being attached to the stator core 22, each segment 23 of an electrical wire has a pair of straight sections 23g extending parallel to each other and a winding or bending section 23h connecting the ends of the straight sections 23g on the same side. When forming the stator coil 21, the straight sections 23g are inserted axially from one axial side of the stator core 22 into corresponding two of the slots 22a of the stator core 22; the corresponding two slots 22a are separated from each other by a predetermined division or distance. Then those parts of the straight sections 23g, which each protrude from the corresponding two slots 22a on the other axial side of the stator core 22, are bent to extend obliquely along the circumferential direction of the stator core 22 at a predetermined angle with respect to the axial end face of the stator core 22.Then corresponding pairs of the distal end parts 23f (see . Fig. 6) the segments 23 of an electrical wire joined by, for example, welding.

[0043] In the resulting stator coil 21, each of the segments 23 of an electrical wire, as shown in Fig. Figure 6 shows a pair of groove-running sections 23a, a first end section 23b, and a pair of second end sections 23c. The groove-running sections 23a are each received in the corresponding two slots 22a of the stator core 22 and extend in the axial direction of the stator core 22. The first end section 23b, which corresponds to the winding section 23h before the segment 23 of an electrical wire is attached to the stator core 22, connects the groove-running sections 23a on one axial side (i.e., the rear side of the AC generator 1 or the right side in Fig. 1) of the stator core 22. The second end sections 23c each extend from the sections 23a running in a groove to the other axial side (that is, the front side of the AC generator 1 or the left side in Fig. 1) of the stator core 22.

[0044] The first end section 23b also has a curved portion 23d at its tip, which is essentially V-shaped. Each of the second end sections 23c, on the other hand, is bent twice to form an inclined portion 23e and a distal end section 23f. The inclined portion 23e extends obliquely along the circumferential direction of the stator core 22 at a predetermined angle to the axial end face of the stator core 22 on the opposite axial side of the stator core 22. As previously described, the insulating sheath 25 is additionally removed from the distal end section 23f to expose the electrical conductor 24.

[0045] Each of the slots 22a of the stator core 22 contains an even number of electrical conductors (that is, the sections 23a of the segments 23 of an electrical wire running in a slot).

[0046] In the present embodiment, as it appears in Fig. As shown in Figure 5, more precisely, each of the slots 22a of the stator core 22 accommodates four electrical conductors aligned in the radial direction of the stator core 22. These four electrical conductors are referred to sequentially below as an innermost conductor, an inner middle conductor, an outer middle conductor, and an outermost conductor, running from the radial inside to the radial outside of the slot 22a. All four electrical conductors accommodated in the same slot 22a also belong to the same phase of the stator coil 21.

[0047] The electrical conductors which are received in the slots 22a of the stator core 22 are also connected to each other in a predetermined pattern, forming the stator coil 21.

[0048] In the present embodiment, the electrical conductors received in the slots 22a of the stator core 22 are formed from the sections 23a of the segments 23 of an electrical wire running in a slot. On one axial side of the stator core 22, the electrical conductors received in the slots 22a of the stator core 22 are electrically connected to each other via the first end sections 23b of the segments 23 of an electrical wire. On the other axial side of the stator core 22, the electrical conductors received in the slots 22a of the stator core 22 are electrically connected to each other by joining corresponding pairs of the distal end sections 23f of the segments 23 of an electrical wire. Referring again to Fig. 2 All first end sections 23b of the segments 23 of an electrical wire together form a first coil end section of the stator coil 21 on one axial side of the stator core 22. All second end sections 23c of the segments 23 of an electrical wire together form a second coil end section of the stator coil 21 on the other axial side of the stator core 22.

[0049] In the present embodiment, each electrically connected pair of electrical conductors is also accommodated in a pair of slots 22a of the stator core 22, which are separated from each other by a predetermined division.

[0050] Referring to Fig. 6 and Fig. For example, in one of the slots 22a, the innermost conductor 231a in the slot 22a is electrically connected via a connecting conductor 213c to the outermost conductor 231b in another of the slots 22a, which is positioned away from the slot 22a by one magnetic pole division in the clockwise direction; the connecting conductor 231c is located on one axial side of the stator core 22.

[0051] Similarly, for one of the slots 22a, the inner central conductor 232a in slot 22a is connected via a connecting conductor 232c to the outer central conductor 232b in another of the slots 22a, which is positioned away from slot 22a by one magnetic pole division in the clockwise direction; the connecting conductor 23c is also located on one axial side of the stator core 22.

[0052] On one axial side of the stator core 22, each of the connecting conductors 232c, which each connect pairs of the inner middle conductors 232a and the outer middle conductors 232b, is therefore circumscribed by a corresponding connecting conductor 231c, which each connect pairs of the innermost conductors 231a and the outermost conductors 231b. As a result, all connecting conductors 232c together form an axially inner layer of the first coil end section of the stator coil 21; all connecting conductors 231c together form an axially outer layer of the first coil end section of the stator coil 21.

[0053] For one of the slots 22a, the inner middle conductor 232a in slot 22a on the other axial side of the stator core 22 is electrically connected to the innermost conductor 231'a in another of the slots 22a, which is positioned one magnetic pole pitch clockwise away from slot 22a. More precisely, the inner middle conductor 232a is electrically connected to the innermost conductor 231'a by joining a pair of connecting conductors 232d and 231d', which extend from the inner middle conductor 232a and the innermost conductor 231a', respectively.

[0054] Similarly, for one of the slots 22a, the outermost conductor 231b' in slot 22a on the other axial side of the stator core 22 is electrically connected to the outer central conductor 232b in another of the slots 22a, which is positioned one magnetic pole pitch clockwise away from slot 22a. More precisely, the outermost conductor 231b' is electrically connected to the outer central conductor 232b by joining a pair of connecting conductors 231e' and 232e, each extending from the outermost conductor 231b' and the outer central conductor 232b, respectively.

[0055] On the other axial side of the stator core 22, each of the connections between the connecting conductors 232d and the connecting conductors 231d' is therefore positioned away from a corresponding connection between the connecting conductor 231e' and the connecting conductors 232e in both radial and circumferential directions of the stator core 22. As a result, as shown in Fig. As shown in Figure 8, all connections between the connecting conductors 232d and the connecting conductors 231d' fall on the same circle to form a radially inner layer of the second coil end part of the stator coil 21; all connections between the connecting conductor 231e' and the connecting conductors 232e fall on the same circle to form a radially outer layer of the second coil end part of the stator coil 21.

[0056] To electrically isolate the joints between the connecting conductors 232d and the connecting conductors 231d' from the joints between the connecting conductor 231e' and the connecting conductors 232e, all joints are as shown in Fig. 3 is shown, coated with an insulating resin 26.

[0057] In the present embodiment, as it appears in Fig. 6 and Fig. As shown in Figure 7, the segments 23 of an electrical wire also comprise a plurality of pairs of large and small segments 231 and 232 of an electrical wire. Each connected set of an innermost conductor 231a, an outermost conductor 231b, and connecting conductors 231c, 231d, and 231e is formed from a single-piece structure using one of the large segments 231 of an electrical wire. Conversely, each connected set of an inner middle conductor 232a, an outer middle conductor 232b, and connecting conductors 232c, 232d, and 232e is formed from a single-piece structure using one of the small segments 232 of an electrical wire.

[0058] In the present embodiment, the three-phase stator coil 21 has phase windings connected in a star configuration. Each phase winding is formed from a predetermined number of segments 23 of an electrical wire and extends around the stator core 22 in two turns. It should also be noted that segments of an electrical wire, which differ in shape from the segments 23 of an electrical wire described above, are also used to form the stator coil 21. These segments of an electrical wire include, for example, segments of an electrical wire for forming the output and neutral terminals of the phase windings of the stator coil 21 and segments of an electrical wire for connecting different turns of the same phase winding.

[0059] In the present embodiment, as it appears in Fig. 3 and Fig. As shown in Figure 4, to ensure resistance to vibration, a varnish 27, an insulating resin, is applied to both the first and second coil end sections of the stator coil 21, which is attached to the stator core 22. The varnish 27 is implemented, for example, as an epoxy resin and is applied to cover the insulating sheaths 25 formed on the outer surfaces of the first and wide end sections 23b and 23c of the segments 23 of an electrical wire.

[0060] In the present embodiment, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is also higher than the adhesive strength between the varnish 27 and the insulating sheaths 25. In other words, the adhesive strength between the varnish 27 and the insulating sheaths 25 is lower than the tensile strength of the insulating sheaths 25.

[0061] In the present embodiment, more precisely, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is in a range of, for example, 100 to 200 MPa, while the adhesive strength between the varnish 27 and the insulating sheaths 25 is in a range of, for example, 10 to 50 MPa.

[0062] The alternating current generator 1 described above, according to the present embodiment, has the following advantages.

[0063] In the present embodiment, the AC generator 1 comprises the rotor 3, the stator 2, and the lacquer 27. The stator comprises the stator core 22 and the stator coil 21, which is attached to the stator core 22. The stator core 22 has slots 22a formed within it. The stator coil 21 is partially received in the slots 22a of the stator core 22, such that the first and second coil end sections project from the slots 22a on opposite axial sides of the stator core 22. The stator coil 21 is formed from the segments 23 of an electrical wire, which are connected to one another. Each of the segments 22a of an electrical wire comprises the electrical conductor 24 and the insulating sheath 25, which covers the outer surface of the electrical conductor 24.The lacquer 27 is applied to the first and second coil end sections of the stator coil 21 to cover the outer surfaces of the insulating sheaths 25 of the segments 23 of an electrical wire that form the stator coil 21. Furthermore, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is higher than the adhesive strength between the lacquer 27 and the insulating sheaths 25.

[0064] With the preceding configuration, if the ambient temperature of the stator 2 changes with a change in the operation of the AC generator 1, and cracks are generated in the varnish 27 due to the change in ambient temperature, the mechanical stress at the crack acts in such a way as to separate the varnish 27 from the insulating sheaths 25 of the segments 23 of an electrical wire. Consequently, it prevents the cracks generated in the varnish 27 from propagating to the insulating sheaths 25 of the segments 23 of an electrical wire. That is, it prevents the insulating sheaths 25 from cracking along the varnish 27; thus, it prevents the cracks generated in the varnish 27 from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown or failure of the insulating sheaths 25.

[0065] In the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 also has a substantially rectangular cross-sectional shape.

[0066] With its essentially rectangular cross-sectional shape, if cracks are generated in the lacquer 27, the mechanical stress at which the cracks occur can easily concentrate on the corner sections of the segments 23 of an electrical wire, causing the insulating sheaths 25 of the segments 23 of the electrical wire to tear along the lacquer 27. However, in the present embodiment, as described above, the tensile strength of the insulating sheaths 35 of the segments 23 of an electrical wire is higher than the bond strength between the lacquer 27 and the insulating sheaths 25. As a result, even with the essentially rectangular cross-sectional shape of the segments 23 of an electrical wire, it is still possible to prevent the insulating sheaths 25 from tearing along the lacquer 27, thus preventing a breakdown of the insulating sheaths 25.

[0067] In the present embodiment, the stator coil 21 is attached to the stator core 22 in a manner of a distributed winding.

[0068] With the distributed winding configuration, the number of slots 22a formed in the stator core 22 is relatively large; consequently, the number of locations where the varnish 27 is applied is also relatively large. The possibility of cracks occurring in the varnish 27 is therefore relatively high. However, in the present embodiment, as described above, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is higher than the adhesive strength between the varnish 27 and the insulating sheaths 25. As a result, even with the distributed winding configuration, it is still possible to prevent the insulating sheaths 25 from cracking along the varnish 27, thus preventing a breakdown of the insulating sheaths 25. [First comparative example]

[0069] Fig. Figure 12 represents the configuration of the segments 23 of an electrical wire that form the stator coil 21, according to a first comparative example.

[0070] As in Fig. As shown in Figure 12, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the first embodiment, except that, unlike in the first embodiment, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is lower than the adhesion strength between the varnish 27 and the insulating sheaths 25.

[0071] In this comparative example, if cracks are generated in the varnish 27 due to a change in the ambient temperature of the stator 2, the cracks will propagate across the boundaries between the varnish 27 and the insulating sheaths 25 of the segments 23 of an electrical wire to the insulating sheaths 25, causing the insulating sheaths 25 to crack along the varnish 27. In the worst case, the cracks can eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Second embodiment]

[0072] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine (i.e., the motor vehicle AC generator 1) according to the first embodiment; accordingly, only the differences between them are described below.

[0073] As in Fig. As shown in Figure 13, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 is structured in two layers, comprising an inner layer 251 and an outer layer 252 formed outside the inner layer 251. Each of the inner and outer layers 251 and 252 of the insulating sheath 25 is, for example, made of polyimide (PI) and has a thickness in the range of, for example, 1 to 10 µm.

[0074] In the present embodiment, each of the inner and outer layers 251 and 252 of the insulating jackets 25 is formed in the same way as the insulating jackets 25 in the first embodiment. Furthermore, since the inner and outer layers 251 and 252 are formed from the same insulating material, they can be cured in the same curing oven. The bond strength between the inner and outer layers 251 and 252 can also be easily controlled by adjusting the curing times and temperatures of those layers 251 and 252.

[0075] In the present embodiment, as in the first embodiment, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is also higher than the adhesive strength between the varnish 27 and the insulating sheaths 25.

[0076] The rotating electric machine according to the present embodiment therefore has the same advantages as the same machine according to the first embodiment. More precisely, if cracks are generated in the varnish 27 due to a change in the ambient temperature of the stator 2, the insulating sheaths 25 of the segments 23 of an electrical conductor are prevented from cracking along the varnish 27. As a result, it is possible to reliably prevent a breakdown or failure of the insulating sheaths 25. [Second comparative example]

[0077] Fig. Figure 14 represents the configuration of the segments 23 of an electrical wire that form the stator coil 21, according to a second comparative example.

[0078] As in Fig. As shown in Figure 14, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the second embodiment, except that, unlike in the second embodiment, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is lower than the adhesion strength between the varnish 27 and the insulating sheaths 25.

[0079] In this comparative example, if cracks are generated in the varnish due to a change in the ambient temperature of the stator 2, the cracks will propagate across the boundaries between the varnish 27 and the insulating sheaths 25 of the segments 23 of an electrical wire, causing the insulating sheaths 25 to crack along the varnish 27. In the worst case, the cracks can eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Third embodiment]

[0080] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0081] As in Fig. As shown in Figure 15, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is made of, for example, copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 is structured in two layers, comprising an inner layer 251 and an outer layer 252 formed outside the inner layer 251. Each of the inner and outer layers 251 and 252 of the insulating sheath 25 is made of, for example, polyimide (PI) and has a thickness in the range of, for example, 1 to 10 µm.

[0082] In the present embodiment, each of the inner and outer layers 251 and 252 of the insulating jackets 25 is formed in the same way as the insulating jackets 25 in the first embodiment. Furthermore, since the inner and outer layers 251 and 252 are formed from the same insulating material, they can be cured in the same curing oven. The bond strength between the inner and outer layers 251 and 252 can also be easily adjusted to a desired value by adapting the curing times and temperatures of those layers 251 and 252.

[0083] In the present embodiment, the tensile strength of the insulating layers 25 of the segments 23 of an electrical wire is also higher than the adhesive strength between the inner and outer layers 251 and 252 of the insulating sheaths 25.

[0084] Even if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251 and 252 of the insulating sheaths 25, it is possible to prevent the cracks from propagating beyond these boundaries to the inner layers 251. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25. [Third comparative example]

[0085] Fig. Figure 16 represents the configuration of the segments 23 of an electrical wire that form the stator coil 21, according to a third comparative example.

[0086] As in Fig. As shown in Figure 16, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the third embodiment, except that, unlike in the third embodiment, the tensile strength of the insulating sheaths 25 of the segments 23 of an electrical wire is lower than the adhesion strength between the inner and outer layers 251 and 252 of the insulating sheaths 25.

[0087] In this comparative example, if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251 and 252 of the insulating sheaths 25, the cracks will propagate beyond these boundaries to the inner layers 251. In the worst case, the cracks can eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Fourth example]

[0088] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0089] As in Fig. As shown in Figure 17, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is made of, for example, copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. Each of the inner and outer sheaths 25a and 25b has a thickness in the range of, for example, 1 to 10 µm. The inner and outer sheaths 25a and 25b are formed of different insulating materials. More precisely, the inner sheath 25 is formed of, for example, a polyamide imide (Al), while the outer sheath 25b is formed of, for example, a polyimide (Pi).

[0090] In the present embodiment, each of the inner and outer layers 25a and 25b is formed in the same way as the insulating layers 25 in the first embodiment. The bond strength between the inner and outer layers 25a and 25b can also be easily adjusted to a desired value by adapting the curing times and curing temperatures of those layers 25a and 25b.

[0091] In the present embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is higher than the adhesive strength between the inner and outer sheaths 25a and 25b of the segments 23 of an electrical wire.

[0092] Even if cracks induced in the lacquer 27 reach the boundaries between the inner and outer sheaths 25a and 25b of the segments 23 of an electrical wire, it is possible to prevent the cracks from propagating beyond these boundaries to the inner sheaths 25a. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of the electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of the electrical wire. [Fourth comparative example]

[0093] Fig. Figure 18 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21 according to a fourth comparative example.

[0094] As in Fig. As shown in Figure 18, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the fourth embodiment, except that, unlike in the fourth embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is lower than the adhesive strength between the inner and outer sheaths 25a and 25b of the segments 23 of an electrical wire.

[0095] In this comparative example, if cracks induced in the lacquer 27 reach the boundaries between the inner and outer sheaths 25a and 25b of the segments 23 of an electrical wire, the cracks propagate further across these boundaries to the inner sheaths 25a. In the worst case, the cracks can ultimately reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Fifth example]

[0096] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0097] As in Fig. As shown in Figure 19, in the present embodiment each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is made of, for example, copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured as a single layer, while the outer sheath 25b is structured as two layers, comprising an inner layer 251b and an outer layer 252b.

[0098] The inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. Each of the inner and outer layers 251b and 252b of the outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0099] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251b and 252b of the outer sheath 25b are formed from the same insulating material. More precisely, the inner sheath 25a is formed, for example, from a polyamide imide (Al), while both the inner and outer layers 251b and 252b of the outer sheath 25b are formed from, for example, a polyimide (Pi).

[0100] In the present embodiment, the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer sheaths 25a and 25b and the bond strength between the inner and outer layers 251b and 252b of the outer sheath 25b can also be readily adjusted by modifying the curing times and curing temperatures of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b.

[0101] In the present embodiment, the tensile strength of the outer sheaths 25b of the segments 23 of an electrical wire is higher than the adhesive strength between the inner and outer layers 251b and 252b of the outer sheaths 25b.

[0102] Even if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251b and 252b of the outer sheaths 25b, it is consequently possible to prevent cracks from propagating beyond these boundaries to the inner layers 251b. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire.

[0103] In cases where each of the insulating sheaths 25 of the segments 23 of an electrical wire has a plurality of layers (or sheaths) as in the present embodiment, the bond strengths between the layers may also differ. In such cases, it is preferable to arrange the plurality of layers in each of the insulating sheaths 25 in such a way that the bond strengths between the layers decrease from the inside to the outside of the insulating sheath 25. As a result, it is possible to stop the propagation of cracks that are generated in the lacquer 27 in the outermost layers of the insulating sheaths 25. [Fifth comparative example]

[0104] Fig. Figure 20 represents the configuration of the segments 23 of an electrical wire that form the stator coil 21, according to a fifth comparative example.

[0105] As in Fig. As shown in Figure 20, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the fifth embodiment, except that, unlike in the fifth embodiment, the tensile strength of the outer sheaths 25b of the segments 23 of an electrical wire is lower than the bond strength between the inner and outer layers 251b and 252b of the outer sheaths 25b.

[0106] In this comparative example, if cracks that are generated in the lacquer 28 reach the boundaries between the inner and outer layers 251 and 252b of the outer sheaths 25b, the cracks will propagate beyond these boundaries to the inner layers 251b. In the worst case, the cracks can thus eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Sixth embodiment]

[0107] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0108] As in Fig. As shown in Figure 21, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured as a single layer, while the outer sheath 25b is structured as two layers, comprising an inner layer 251b and an outer layer 252b.

[0109] The inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. Each of the inner and outer layers 251b and 252b of the outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0110] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251b and 252b of the outer sheath 25b are formed from the same insulating material. More precisely, the inner sheath 25a is formed from, for example, a polyimide (PI), while both the inner and outer layers 251b and 252b of the outer sheath 25b are formed from, for example, a polyamide-imide (AI).

[0111] In the present embodiment, the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer sheaths 25a and 25b and the bond strength between the inner and outer layers 251 and 252b of the outer sheath 25b can also be easily adjusted by modifying the curing times and curing temperatures of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b.

[0112] In the present embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is higher than the adhesive strength between the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b of the segments 23 of an electrical wire.

[0113] Even if cracks induced in the lacquer 27 reach the boundaries between the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b, it is consequently possible to prevent the cracks from propagating beyond these boundaries to the inner sheaths 25a. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire. [Sixth comparative example]

[0114] Fig. Figure 22 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21, according to a sixth comparative example.

[0115] As in Fig. As shown in Figure 22, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the sixth embodiment, except that, unlike in the sixth embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is lower than the bond strength between the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b.

[0116] In this comparative example, if cracks induced in the lacquer 28 reach the boundaries between the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b, the cracks will propagate beyond these boundaries to the inner sheaths 25a. In the worst case, the cracks can thus eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Seventh embodiment]

[0117] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0118] As in Fig. As shown in Figure 23, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured in two layers, comprising an inner layer 251a and an outer layer 252a, while the outer sheath 25b is structured in a single layer.

[0119] Each of the inner and outer layers 251a and 252a of the inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. The outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0120] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251a and 252a of the inner sheath 25a are formed from the same insulating material. More precisely, both the inner and outer layers 251a and 252a of the inner sheath 25a are formed from, for example, a polyimide (PI), while the outer sheath 25b is formed from, for example, a polyamide-imide (AI).

[0121] In the present embodiment, the inner and outer layers 251a and 252a of the inner sheath 25a and the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer sheaths 25a and 25b and the bond strength between the inner and outer layers 251a and 252a of the inner sheath 25a can also be easily adjusted by modifying the curing times and curing temperatures of the inner and outer layers 251a and 252a of the inner sheath 25a and the outer sheath 25b.

[0122] In the present embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is higher than the adhesive strength between the outer layers 252a of the inner sheaths 25a and the outer sheaths 25b of the segments 23 of an electrical wire.

[0123] Even if cracks induced in the lacquer 27 reach the boundaries between the outer layers 252a of the inner sheaths 25a and the outer sheaths 25b, it is consequently possible to prevent the cracks from propagating beyond these boundaries to the outer layers 252a of the inner sheaths 25a. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire. [Seventh comparative example]

[0124] Fig. Figure 24 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21 according to a seventh comparative example.

[0125] As in Fig. As shown in Figure 24, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the seventh embodiment, except that, unlike in the seventh embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is lower than the adhesive strength between the outer layers 252a of the inner sheaths 25a and the outer sheaths 25b.

[0126] In this comparative example, if cracks induced in the lacquer 27 reach the boundaries between the outer layers 252a of the inner sheaths 25a and the outer sheaths 25b, the cracks will consequently propagate beyond these boundaries to the outer layers 252a of the inner sheaths 25a. In the worst case, the cracks can thus eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Eighth example]

[0127] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0128] As in Fig. As shown in Figure 25, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured in two layers, comprising an inner layer 251a and an outer layer 252a, while the outer sheath 25b is structured in a single layer.

[0129] Each of the inner and outer layers 251a and 252a of the inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. The outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0130] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251a and 252a of the inner sheath 25a are formed from the same insulating material. More precisely, both the inner and outer layers 251a and 252a of the inner sheath 25a are formed from, for example, polyimide (PI), while the outer sheath 25b is formed from, for example, a polyamide imide (AI).

[0131] In the present embodiment, the inner and outer layers 251a and 252a of the inner sheath 25a and the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer sheaths 25a and 25b and the bond strength between the inner and outer layers 251a and 252a of the inner sheath 25a can also be easily adjusted to the desired values ​​by adapting the curing times and curing temperatures of the inner and outer layers 251a and 252a of the inner sheath 25a and the outer sheath 25b.

[0132] In the present embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is higher than the adhesive strength between the inner and outer layers 251a and 252a of the inner sheaths 25a.

[0133] Even if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251a and 252a of the inner sheaths 25a, it is consequently possible to prevent the cracks from propagating further beyond these boundaries to the inner layers 251a of the inner sheaths 25a. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire. [Eighth comparative example]

[0134] Fig. Figure 26 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21 according to an eighth comparative example.

[0135] As in Fig. As shown in Figure 26, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the eighth embodiment, except that, unlike in the eighth embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is lower than the bond strength between the inner and outer layers 251a and 252a of the inner sheaths 25a.

[0136] In this comparative example, if cracks induced in the lacquer 28 reach the boundaries between the inner and outer layers 251a and 252a of the inner sheaths 25a, the cracks will propagate beyond these boundaries to the inner layers 251a of the inner sheaths 25a. In the worst case, the cracks can thus eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Ninth embodiment]

[0137] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0138] As in Fig. As shown in Figure 27, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section in its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured in two layers, comprising an inner layer 251a and an outer layer 252a, while the outer sheath 25b is structured in two layers, comprising an inner layer 251b and an outer layer 252b.

[0139] Each of the inner and outer layers 251a and 252a of the inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. Each of the inner and outer layers 251b and 252b of the outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0140] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251a and 252a of the inner sheath 25a are formed from the same insulating material, and the inner and outer layers 251b and 252b of the outer sheath 25b are formed from the same insulating material. More precisely, both the inner and outer layers 251a and 252a of the inner sheath 25 are formed from, for example, a polyamide imide (Al), while both the inner and outer layers 251b and 252b of the outer sheath 25b are formed from, for example, polyimide (Pi).

[0141] In the present embodiment, the inner and outer layers 251a and 252a of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer layers 251a and 252a of the inner sheath 25, the bond strength between the inner and outer sheaths 25a and 25b, and the bond strength between the inner and outer layers 251b and 252b of the outer sheath 25 can also be easily adjusted to the desired values ​​by adapting the curing times and curing temperatures of the inner and outer layers 251a and 252a of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b.

[0142] In the present embodiment, the tensile strength of the outer sheaths 25b of the segments 23 of an electrical wire is higher than the adhesive strength between the inner and outer layers 251b and 252b of the outer sheaths 25b.

[0143] Even if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251b and 252b of the outer sheaths 25b, it is consequently possible to prevent the cracks from propagating further beyond the boundaries to the inner layers 251b. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire. [Ninth comparative example]

[0144] Fig. Figure 28 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21 according to a ninth comparative example.

[0145] As in Fig. As shown in Figure 28, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the ninth embodiment, except that, unlike in the ninth embodiment, the tensile strength of the outer sheaths 25b of the segments 23 of an electrical wire is lower than the bond strength between the inner and outer layers 251b and 252b of the outer sheaths 25b.

[0146] In this comparative example, if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251b and 252b of the outer sheaths 25b, the cracks will propagate further beyond these boundaries to the inner layers 251b. In the worst case, the cracks will eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Tenth embodiment]

[0147] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0148] As in Fig. As shown in Figure 29, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured in two layers, comprising an inner layer 251a and an outer layer 252a, while the outer sheath 25b is structured in two layers, comprising an inner layer 251b and an outer layer 252b.

[0149] Each of the inner and outer layers 251a and 252a of the inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. Each of the inner and outer layers 251b and 252b of the outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0150] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251a and 252a of the inner sheath 25a are formed from the same insulating material, and the inner and outer layers 251b and 252b of the outer sheath 25b are formed from the same insulating material. More precisely, both the inner and outer layers 251a and 252a of the inner sheath 25a are formed from, for example, a polyamide imide (Al), while both the inner and outer layers 251b and 252b of the outer sheath 25 are formed from, for example, polyimide (Pi).

[0151] In the present embodiment, the inner and outer layers 251a and 252a of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer layers 251a and 252a of the inner sheath 25a, the bond strength between the inner and outer sheaths 25a and 25b, and the bond strength between the inner and outer layers 251b and 252b of the outer sheath 25b can also be easily adjusted to the desired values ​​by adapting the curing times and curing temperatures of the inner and outer layers 251a and 252a of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b.

[0152] In the present embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is higher than the adhesive strength between the outer layers 252a of the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b of the segments 23 of an electrical wire.

[0153] Even if cracks induced in the lacquer 27 reach the boundaries between the outer layers 252a of the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b, it is consequently possible to prevent cracks from propagating beyond these boundaries to the outer layers 252a of the inner sheaths 25a. It is therefore also possible to prevent the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire. [Tenth comparative example]

[0154] Fig. Figure 30 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21, according to a tenth comparative example.

[0155] As in Fig. As shown in Figure 30, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the tenth embodiment, except that, unlike in the tenth embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is lower than the adhesion strength between the inner and outer layers 252a of the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b of the segments 23 of an electrical wire.

[0156] In this comparative example, if cracks generated in the lacquer 27 reach the boundaries between the outer layers 252a of the inner sheaths 25a and the inner layers 251b of the outer sheaths 25b, the cracks will propagate further beyond these boundaries to the outer layers 252a of the inner sheaths 25a. In the worst case, the cracks can thus eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25. [Eleventh example]

[0157] This embodiment represents a rotating electric machine which has a configuration similar to the rotating electric machine according to the first embodiment; accordingly, only the differences between them are described below.

[0158] As in Fig. As shown in Figure 31, in the present embodiment, each of the segments 23 of an electrical wire forming the stator coil 21 is configured with an electrical conductor 24 and an insulating sheath 25 covering the outer surface of the electrical conductor 24. The electrical conductor 24 is, for example, made of copper and has a substantially rectangular cross-section perpendicular to its direction of extension. The insulating sheath 25 consists of an inner sheath 25a and an outer sheath 25b formed outside the inner sheath 25a. The inner sheath 25a is structured in two layers, comprising an inner layer 251a and an outer layer 252a, while the outer sheath 25b is structured in two layers, comprising an inner layer 251b and an outer layer 252b.

[0159] Each of the inner and outer layers 251a and 252a of the inner mantle 25a has a thickness in the range of, for example, 1 to 10 µm. Each of the inner and outer layers 251b and 252b of the outer mantle 25b also has a thickness in the range of, for example, 1 to 10 µm.

[0160] The inner and outer sheaths 25a and 25b are formed from different insulating materials, while the inner and outer layers 251a and 252a of the inner sheath 25a are formed from the same insulating material, and the inner and outer layers 251b and 252b of the outer sheath 25b are formed from the same insulating material. More precisely, both the inner and outer layers 251a and 252a of the inner sheath 25a are formed from, for example, a polyamide imide (Al), while both the inner and outer layers 251b and 252b of the outer sheath 25b are formed from, for example, polyimide (Pi).

[0161] In the first embodiment, the inner and outer layers 251a and 252a of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b are formed in the same way as the insulating sheaths 25 in the first embodiment. The bond strength between the inner and outer layers 251a and 252a of the inner sheath 25a, the bond strength between the inner and outer sheaths 25a and 25b, and the bond strength between the inner and outer layers 251b and 252b of the outer sheath 25b can also be easily adjusted to the desired values ​​by adapting the curing times and curing temperatures of the inner and outer layers 251a and 252a of the inner sheath 25a and the inner and outer layers 251b and 252b of the outer sheath 25b.

[0162] In the present embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is higher than the adhesive strength between the inner and outer layers 251a and 252a of the inner sheaths 25a.

[0163] Even if cracks induced in the lacquer 27 reach the boundaries between the inner and outer layers 251a and 252a of the inner sheaths 25a, it is consequently possible to prevent the cracks from propagating beyond these boundaries to the inner layers 251a. This also prevents the cracks from reaching the electrical conductors 24 of the segments 23 of an electrical wire. As a result, it is possible to reliably prevent a breakdown of the insulating sheaths 25 of the segments 23 of an electrical wire. [Eleventh comparative example]

[0164] Fig. Figure 32 represents the configuration of the segments 23 of an electrical wire forming the stator coil 21, according to an eleventh comparative example.

[0165] As in Fig. As shown in Figure 32, in this comparative example the segments 23 of an electrical wire have the same configuration as those in the eleventh embodiment, except that, unlike in the eleventh embodiment, the tensile strength of the inner sheaths 25a of the segments 23 of an electrical wire is lower than the bond strength between the inner and outer layers 251a and 252a of the inner sheaths 25a.

[0166] In this comparative example, if cracks that are generated in the lacquer 27 reach the boundaries between the inner and outer layers 251a and 252a of the inner sheaths 25a, the cracks will propagate further beyond these boundaries to the inner layers 251a. In the worst case, the cracks can thus eventually reach the electrical conductors 24 of the segments 23 of an electrical wire, resulting in a breakdown of the insulating sheaths 25.

[0167] Although the preceding particular embodiments have been shown and described, it is self-evident to those skilled in the art that various modifications, changes and improvements may have been made to them without departing from the spirit of the present invention.

[0168] As described above, in the first embodiment, for example, each of the insulating sheaths 25 of the segments 23 of an electrical wire is formed from a single insulating material and is structured in a single layer (see Fig. 10). In the second and third embodiments, each of the insulating sheaths 25 of the segments 23 of an electrical wire is formed from a single insulating material and is structured in two layers to have the inner and outer layers 251 and 252 (see Fig. 13 and Fig. 15). In the fourth embodiment, each of the insulating sheaths 25 of the segments 23 of an electrical wire consists of the inner and outer sheaths 25a and 25b, which are formed from different insulating materials and are each structured as a single layer (see Fig. 17). In the fifth and sixth embodiments, each of the insulating sheaths 25 of the segments 23 of an electrical wire consists of the inner and outer sheaths 25a and 25b, which are formed from different insulating materials; the inner sheath 25a is structured as a single layer, while the outer sheath 25b is structured as two layers to have the inner and outer layers 251b and 252b (see Fig. 19 and Fig. 21). In the seventh and eighth embodiments, each of the insulating sheaths 25 of the segments 23 of an electrical wire consists of the inner and outer sheaths 25a and 25b, which are formed from different insulating materials; the inner sheath 25a is structured in two layers to have the inner and outer layers 251a and 252a, while the outer sheath 25b is structured in a single layer (see Fig. 23 and Fig. 25). In the ninth, tenth and eleventh embodiments, each of the insulating sheaths 25 of the segments 23 of an electrical wire consists of the inner and outer sheaths 25a and 25b, which are formed from different insulating materials; the inner sheath 25a is structured in two layers to have the inner and outer layers 251a and 252a, while the outer sheath 25b is structured in two layers to have the inner and outer layers 251b and 252b (see Fig. 27, Fig. 29 and Fig. 31).

[0169] However, each of the insulating sheaths 25 of the segments 23 of an electrical wire can also have other configurations than those according to the first to eleventh embodiments.

[0170] As in Fig. 33 and Fig. As shown in Figure 34, for example, each of the insulating sheaths 25 of the segments 23 of an electrical wire can consist of an inner sheath 25a and an outer sheath 25b, which are formed from different insulating materials and each is structured in multiple layers to have three or more layers. In this case, it is further preferred that, for each adjacent pair of layers of the inner and outer sheaths 25a and 25b, the tensile strength of one of the two layers of the pair formed within the other layer is higher than the bond strength between the two layers of the pair.

[0171] As in Fig.As shown in Figure 35, each of the insulating sheaths 25 of the segments 23 of an electrical wire can otherwise consist of an inner layer 25a, an intermediate layer 25b, and an outer layer 25c, which are formed from different insulating materials. Each of the insulating sheaths 25 of the segments 23 of an electrical wire can further consist of four or more sheaths formed from different insulating materials. In those cases, each of the sheaths formed from different materials can additionally be either single-layered or multi-layered.

[0172] In the preceding embodiments, polyamide imide (AI) and polyimide (PI) are used as the insulating materials to form the insulating sheaths 25 of the segments 23 of an electrical wire.

[0173] Other insulating materials, such as PPS (polyphenylene sulfide) or PEEK (polyether ether ketone), can also be used to form the insulating sheaths 25. In the case of using PPS or PEEK, the insulating sheaths 25 of the segments 23 of an electrical wire can additionally be formed by extrusion to have a thickness of at least 10 µm (for example, 200 µm).

[0174] In the preceding embodiments, the lacquer 27 is implemented by the epoxy resin. However, the lacquer 27 can also be implemented by other insulating resins, such as polyester.

[0175] In the preceding embodiments, the present invention relates to a motor vehicle AC generator 1. However, the invention can also be applied to other rotating electrical machines, such as an electric motor and a motor-generator that can selectively function either as an electric motor or as an electric generator.

Claims

[1] Rotating electric machine (1) with: a rotor (3); a stator (2) comprising a stator core (22) and a stator coil (21) attached to the stator core (22), the stator core (22) having a plurality of slots (22a) formed therein, the stator coil (21) being partially received in the slots (22a) of the stator core (22) to form a pair of coil end parts projecting from the slots (22a) on opposite axial sides of the stator core (22), the stator coil (21) being formed from a plurality of segments (23) of an electrical wire connected to one another, each segment (23) of an electrical wire comprising an electrical conductor (24) and an insulating sheath (25; 25a, 25b; 25a, 25b, 25c) covering an outer surface of the electrical conductor (24); and an insulating resin (27) applied to the coil end parts of the stator coil (21) to cover outer surfaces of the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c) of the segments (23) of an electrical wire forming the stator coil (21), where a tensile strength of the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c) of the segments (23) of an electrical wire is higher than an adhesive strength between the insulating resin (27) and the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c). [2] Rotating electric machine (1) according to claim 1, wherein Each of the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c) of the segments (23) of an electrical wire is configured to have a plurality of layers (251, 252; 251b, 252b; 251a, 252a; 251a, 252a, 251b, 252b), each having a specific tensile strength, and at least one of the tensile strengths of the layers (251, 252; 251b, 252b; 251a, 252a; 251a, 252a, 251b, 252b) is higher than the bond strength between the insulating resin (27) and the insulating sheaths (25; 25a, 25b; 25a, 25b, 25c). [3] Rotating electric machine (1) according to claim 2, wherein for each adjacent pair of the layers of the insulating sheaths (25a, 25b) of the segments (23) of an electric wire the tensile strength of one of the two layers of the pair, which is formed within the other layer, is higher than an adhesion strength between the two layers of the pair. [4] Rotating electric machine (1) according to claim 1, wherein each of the segments (23) of an electric wire forming the stator coil (21) has a substantially rectangular cross-sectional shape. [5] Rotating electric machine (1) according to claim 1, wherein the stator coil (21) is attached to the stator core (22) in a manner of a distributed winding. [6] Rotating electric machine (1) with: a rotor (3); a stator (2) comprising a stator core (22) and a stator coil (21) attached to the stator core (22), the stator core (22) having a plurality of slots (22a) formed therein, the stator coil (21) being partially received in the slots (22a) of the stator core (22) to form a pair of coil end parts projecting from the slots (22a) on opposite axial sides of the stator core (22), the stator coil (11) being formed from a plurality of segments (23) of an electrical wire connected to one another, each segment (23) of an electrical wire comprising an electrical conductor (24) and an insulating sheath (25; 25a, 25b) covering an outer surface of the electrical conductor (24); and an insulating resin (27) applied to the coil end parts of the stator coil (21) to cover outer surfaces of the insulating sheaths (25; 25a, 25b) of the segments (23) of an electrical wire forming the stator coil (21), where each of the insulating sheaths (25; 25a, 25b) of the segments (23) of an electrical wire is configured to have an inner sheath (25a) and an outer sheath (25b) formed outside the inner sheath (25a), and a tensile strength of the inner sheath (25a) is higher than an adhesive strength between the inner and outer sheaths (25a, 25b). [7] Rotating electric machine (1) according to claim 6, wherein the inner and outer casings (25a, 25b) are formed from different insulating materials. [8] Rotating electric machine (1) according to claim 6, wherein each of the segments (23) of an electric wire forming the stator coil (21) has a substantially rectangular cross-sectional shape. [9] Rotating electric machine (1) according to claim 6, wherein the stator coil (21) is attached to the stator core (22) in a manner of a distributed winding. [10] Rotating electric machine (1) according to claim 6, wherein at least one of the inner and outer shells (25a, 25b) is configured to have a plurality of layers (251b, 252b; 251a, 252a; 251a, 252a, 251b, 252b). [11] Rotating electric machine (1) according to claim 10, in which for each adjacent pair of the plurality of layers (251b, 252b; 251a, 252a; 251a, 252a, 251b, 252b) the tensile strength of one (251b; 251a; 251a, 251b) of the two layers (251b, 252b; 251a, 252a; 251a, 252a, 251b, 252b) of the pair, which is formed within the other layer (252b; 252a; 252a, 252b), is higher than an adhesive strength between the two layers (251b, 252b; 251a, 252a; 251a, 252a, 251b, 252b) of the pair.

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