Stator for rotary electric machine

Abstract

To provide a stator for a rotary electric machine capable of dividing eddy currents generated in a coil wire and reducing eddy current loss without reducing a ratio of the coil wire to a slot.SOLUTION: A stator for a rotary electric machine of the present invention includes a stator core and a coil wire disposed in slots in the stator core. In addition, the coil wire is formed of a conductor group, in which a plurality of rectangular wires are bundled together, and has a shape whose cross section is rectangular and around which is covered with an insulating film. A longitudinal direction of the cross section of the rectangular wire is directed in a circumferential direction and the rectangular wires are arranged side by side in a radial direction to form the conductor group, at least the surface roughness of the side face of the long side abutting against another adjacent rectangular wire is larger than the surface roughness of the side face of the short side, and thereby it is possible to provide the stator for a rotary electric machine capable of reducing AC loss over the entire rotation range from low to high rotation ranges.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a stator for a rotating electric machine, and more particularly to a stator for a rotating electric machine in which copper loss caused by using a coil wire having a large cross-sectional area is suppressed. [Background technology]

[0002] In motors for electric vehicles, the proportion of the coil wire in the stator slot is increased to reduce the resistance of the coil wire and suppress temperature increases caused by copper loss in the coil wire.

[0003] However, if a coil wire with a large cross-sectional area is used, a bias in current density occurs in the coil wire due to eddy currents at high rotation speeds, resulting in large losses.

[0004] Patent Document 1 discloses that the coil wire is made of multiple divided copper wires so that eddy currents generated in the coil wire at the portion where leakage magnetic flux intersects are divided, and insulating members are provided between adjacent copper wires to reduce eddy currents. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6522312 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technique described in Patent Document 1, insulating material is placed between the copper wires that make up the coil wire, which reduces the copper wire occupancy rate due to the insulating material, making it impossible to reduce the resistance of the coil wire, and resulting in increased losses at low rotation speeds.

[0007] The present invention has been made in consideration of the problems associated with the conventional technology, and has an object to provide a stator for a rotating electric machine that can decouple eddy currents generated in the coil wire and reduce copper loss without reducing the proportion of the coil wire in the slot. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that by roughening the contact surfaces between the flat wires that make up the coil wire to increase the contact resistance, it is possible to disrupt the eddy currents generated in the coil wire without providing an insulating member between the flat wires, thereby achieving the above-mentioned objective and thus completing the present invention.

[0009] That is, the stator for a rotating electric machine of the present invention includes a stator core and a coil wire arranged in the slot of the stator core. The coil wire is formed of a conductor group of a plurality of rectangular wires, has a rectangular cross section, and is covered with an insulating film. The flat wire has a cross-sectional longitudinal direction oriented in the circumferential direction and is arranged radially to form the group of conductors, and is characterized in that the surface roughness of at least the long side surface that abuts other adjacent flat wires is greater than the surface roughness of the short side surface. Effect of the Invention

[0010] According to the present invention, the contact surfaces between the rectangular wires that make up the coil wire are roughened to increase the contact resistance, thereby making it possible to provide a stator for a rotating electric machine that can reduce AC losses over the entire rotation range, from low to high rotation ranges. [Brief description of the drawings]

[0011] [Figure 1] 1 is a partial cross-sectional view taken in a direction perpendicular to an axis, showing an example of a stator for a rotating electric machine according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a coil wire of the present invention. [Diagram 3]2 is an enlarged view of the circled portion in FIG. 1 for explaining the arrangement of the coil wires in the slots. FIG. [Figure 4] 1A and 1B are diagrams illustrating how eddy currents are divided when a coil wire is formed using multiple rectangular wires. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The stator for a rotating electric machine according to the present invention will now be described in detail. As shown in FIG. 1, a stator for a rotating electric machine according to the present invention includes a stator core and coil wires arranged in slots of the stator core.

[0013] As shown in FIG. 2, the coil wire is formed from a group of conductors in which multiple flat wires, each with a rectangular cross section, are stacked together. The group of conductors, each with a square cross section, is covered with an insulating film to insulate it from other components such as the stator core.

[0014] In addition, as shown in FIG. 3, the coil wire is arranged in the slots of the stator core so that the longitudinal direction of the cross section of the flat wire faces the circumferential direction of the stator, and the flat wire constituting the coil wire is aligned in the radial direction of the stator.

[0015] As shown in Fig. 3, the coil wires are arranged in a radial line with their longitudinal direction facing the circumferential direction. When the rotor rotates at high speed, changes in magnetic flux cause large eddy currents to be generated in the coil wire, as shown in the top of Fig. 4. This causes a bias in the current density distribution in the coil and increases copper loss.

[0016] The coil wire of the present invention is formed from multiple flat wires divided radially. The radial thickness of the flat wires that make up the coil wire is reduced, and the electrical resistance between the flat wires is increased. This prevents eddy currents from flowing beyond the contact surfaces between the flat wires. As shown in the bottom of Figure 4, this reduces the eddy currents generated in the coil wire and suppresses copper loss.

[0017] In this case, if the electrical resistance between the rectangular wires is increased by the insulating film, the proportion of the rectangular wire occupying the slot is reduced by the thickness of the insulating film, resulting in an increase in the resistance of the coil wire.

[0018] The coil wire of the present invention does not provide an insulating film between the rectangular wires, but rather roughens the contact surfaces between adjacent rectangular wires to increase the contact resistance, as shown in Figure 2, thereby preventing eddy currents from flowing beyond the contact surfaces between the rectangular wires.

[0019] Therefore, the proportion of the rectangular wire in the slot does not decrease, so that AC loss can be reduced over the entire rotation range from low to high rotation.

[0020] The surface roughness (Ra) of the contact surface between adjacent rectangular wires varies depending on the material of the rectangular wire, but it is preferable that Ra is 10 μm or more and Rz is 100 μm or less.

[0021] By performing surface treatment so that the surface roughness (Ra) is 10 μm or more, it is expected that the contact resistance will increase by more than 10 times compared to untreated rectangular copper wire.

[0022] Furthermore, by having a surface roughness (Rz) of 100 μm or less, the gap between adjacent rectangular wires becomes smaller than the thickness of the insulating film, so that a reduction in the proportion of rectangular wire occupying the slot can be suppressed.

[0023] Examples of methods for roughening the side surface of the rectangular wire include laser texturing and shot peening.

[0024] Laser texturing can form the surface shape of the rectangular wire into any desired shape, such as a convex lattice, a concave lattice, a protrusion shape, or a dimple shape, so that the apexes of opposing convex parts come into contact with each other to form point contact, thereby reliably increasing the contact resistance.

[0025] In addition, shot peening is a cold processing method in which countless metal particles are collided with the surface of a rectangular wire at high speed, forming depressions on the surface of the wire. Since the surface of the rectangular wire becomes harder due to work hardening, when the laminated rectangular wire is pressed to produce coil wire, the protrusions formed on the surface are less likely to deform. This means that even if copper material is used for the rectangular wire, the contact resistance can be stably increased.

[0026] The above-mentioned roughening process needs to be performed on the long side surface that abuts other adjacent rectangular wires, and does not need to be performed on the short side surface covered with the insulating film or on the other long side surface covered with the insulating film that does not abut other rectangular wires.

[0027] Therefore, the surface roughness of the long side surface that abuts against another adjacent rectangular wire is greater than the surface roughness of the short side surface and the other long side surface that does not abut against another rectangular wire.

[0028] Furthermore, the above-mentioned surface roughening may be performed only in the longitudinal direction of the rectangular wire, that is, on the portion that is to be placed in the slot of the stator, but it is preferable to perform the surface roughening over the entire longitudinal direction of the rectangular wire.

[0029] In a flat wire that has been roughened in this manner, the relationship between the surface roughness of the longitudinal side surface that abuts adjacent flat wires and the surface roughness of the other sides is the same throughout the entire length, and there is no need to specify the part that will be placed within the slot, making the roughening process easy.

[0030] In addition, outside the slots, multiple flat wires may be bundled together and bent, or their tips may be welded, which may cause contact between adjacent flat wires. Therefore, by roughening the entire length, copper loss can be reduced even outside the slots.

[0031] The coil wire of the present invention can be produced by stretching a conductor wire to form a flat wire of the desired shape, annealing it to soften it, roughening it as described above, stacking and pressing the flat wire so that the roughened longitudinal sides abut each other to form a conductor wire group, and applying an insulating film around this conductor wire group and baking it. [Explanation of symbols]

[0032] 1 Stator core 11 Slots 2 Coil wire 21 Rectangular wire 22 conductor group 23 Insulating film 3. Varnish

Claims

1. A stator for a rotating electric machine comprising a stator core and a coil wire disposed in a slot of the stator core, The coil wire is formed of a conductor group of a plurality of rectangular wires, has a rectangular cross section, and is covered with an insulating film. The rectangular wire has a cross-sectional longitudinal direction oriented in the circumferential direction and is arranged radially to form the group of conductors, and the surface roughness of at least the long side surface that abuts other adjacent rectangular wires is greater than the surface roughness of the short side surface.

2. 2. The stator for a rotating electric machine according to claim 1, wherein the rectangular wire has a surface on at least one of the longitudinal sides thereof that contacts an adjacent rectangular wire, the surface being work-hardened.

3. 2. The stator for a rotating electric machine according to claim 1, wherein the surface roughness of the longitudinal side surface of the rectangular wire that abuts against adjacent rectangular wires is greater than the surface roughness of the side surface covered with the insulating film.

4. The stator for a rotating electric machine as described in claim 1, characterized in that the relationship between the surface roughness of the longitudinal side surface that abuts adjacent rectangular wires and the surface roughness of the other side surfaces is the same throughout the entire length.

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