JP2024070962A - Manufacturing method of coil segment - Google Patents

Abstract

[Problem] Suppressing an increase in the resistance value of a coil segment. [Solution] A manufacturing method for a coil segment according to an embodiment includes the steps of bending a coil wire to form a bent portion, and compressing the bent portion with metal powder placed thereon, thereby plastically flow bonding the metal powder to the bent portion. By forming an adhesion portion at the bent portion of the coil wire, a sufficient cross-sectional area of the bent portion can be secured, preventing an increase in electrical resistance and improving power consumption. In addition, because the processing is performed without heating, oxidation of the coil wire can be prevented. [Selected Figure] Figure 1

Description

The present invention relates to a method for manufacturing coil segments.

Patent document 1 discloses a method for manufacturing a rotating electric machine by inserting coil segments, in which coil wire is bent into an approximately U-shape, into slots in a stator core, then bending the ends of the coil segments and joining predetermined ends together.

JP 2003-143791 A

When creating a coil segment by bending coil wire, the plate thickness at the bent portion decreases, which may increase the resistance of the coil segment.

The present invention was made in consideration of these problems, and the object of the present invention is to provide a manufacturing method for coil segments that can suppress an increase in the resistance value of the coil segments.

A method for manufacturing a coil segment according to one embodiment of the present invention includes a step of bending a coil wire to form a bent portion, and a step of compressing the bent portion while placing metal powder in the bent portion, thereby plastically flow bonding the metal powder to the bent portion.

According to the present invention, it is possible to suppress an increase in the resistance value of the coil segment.

FIG. 4 is a flow diagram illustrating a method for manufacturing a coil segment according to an embodiment. 1A to 1C are diagrams illustrating an example of a coil segment manufactured using a coil segment manufacturing method according to an embodiment. FIG. 2 is a diagram illustrating plastic flow bonding used in the embodiment.

Embodiments of the present invention will be described below with reference to the drawings. For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate.

The embodiment relates to a method for manufacturing a coil segment used in a stator of a rotating electric machine. The stator has a stator core in which electromagnetic steel sheets are stacked in the axial direction, and a stator coil. The stator core includes a yoke formed in an annular shape and a number of teeth protruding from the inner peripheral surface of the yoke. The multiple teeth are formed at intervals on the inner peripheral surface of the yoke, and a slot is formed between each of the teeth.

The coil segment is made by bending a rectangular conductor wire with a rectangular cross section (specifically, a rectangle) into an approximately U-shape. This rectangular conductor wire is made of a highly conductive metal such as copper or aluminum. Here, the coil wire is made of copper.

Multiple coil segments are inserted into the slots from one axial end face of the stator core. The tip portions of the coil segments protrude a specified length from the other axial end face of the stator core. The protruding portions are bent, and the specified tips are joined together by welding or the like to form the stator coil.

A method for manufacturing a coil segment using a rectangular conductor wire includes, for example, edgewise bending a rectangular copper coil wire into an approximately U-shape. Edgewise bending refers to bending the short side of the cross section of a rectangular conductor wire. When the coil wire is bent into an approximately U-shape, it is in the form of bare copper wire. When such a coil wire is bent, a so-called plate shrinkage occurs in the bent portion. This plate shrinkage causes a reduction in the thickness of the bent portion, reducing the cross-sectional area of the segment coil.

The electrical resistance R of the coil segment is expressed by the following formula:
R = ρ l / A
R: Resistance l: Length of coil wire A: Cross-sectional area of coil wire ρ: Resistivity of coil wire (resistance value when cross-sectional area is 1 square meter and length is 1 meter)

The electrical resistance of a coil segment is proportional to the length of the coil wire and inversely proportional to the cross-sectional area. For this reason, when the cross-sectional area of a segment coil becomes smaller, there is a problem that the electrical resistance of the coil segment increases in some areas.

In addition, in order to adjust the radial position at the coil end, a shift section may be formed in the leg of the segment coil. The shift section may be formed by "flatwise bending," which bends the surface on the long side of the cross section of the rectangular wire. Even if the cross-sectional area of the bent portion formed by the edgewise bending process described above is the same, the electrical resistance may increase in the shift section of the coil segment. Therefore, the inventor has devised the following method of manufacturing a coil segment in order to suppress the increase in the resistance value of the coil segment.

Figure 1 is a flow diagram illustrating a method for manufacturing a coil segment according to an embodiment. Figure 2 is a diagram illustrating an example of a coil segment manufactured using the method for manufacturing a coil segment according to an embodiment.

As shown in Figure 1, first, the coil wire 1 is bent to form a bent portion (S11). In Figure 2, the coil wire 1 before bending is shown by a two-dot chain line. The coil wire 1 is a straight rectangular conductor wire, and no insulating coating is formed on the surface of the conductor wire. This coil wire 1 is then bent to form the bent portion 2. In Figure 2, the bent portion 2 is the area surrounded by a dashed circle. It can be seen from Figure 2 that the thickness of the bent portion 2 of the coil wire 1 has been reduced.

Returning to FIG. 1, next, the metal powder placed in the bent portion 2 is compressed to plastically flow bond the metal powder to the bent portion 2 (S12). Here, the metal powder placed in the bent portion 2 is copper powder. The copper powder adheres to the bent portion 2 by plastic flow to form an adhesion portion 3, which is integrated with the coil wire 1 without heating. As shown in FIG. 2, the adhesion portion 3 is formed along the outside of the bent portion 2.

In this way, by forming the adhesion portion 3 at the bent portion 2 of the coil wire 1, a cross-sectional area equal to or greater than that before the sheet was drawn can be secured, making it possible to realize a coil segment with low resistance. Note that adhesive may be mixed into the copper powder placed at the bent portion 2. However, since the copper space factor in the adhesion portion 3 decreases by the amount of adhesive, it is preferable to use only copper powder.

Here, the plastic flow bonding used in the embodiment will be described with reference to FIG. 3. For the purpose of explanation, FIG. 3 shows an example in which copper powder 21 is compressed and plastically deformed on a disk-shaped copper plate 20.

As shown in FIG. 3, the coil segment manufacturing device 10 includes a die 11 and a punch 13. A cavity 12 is formed in the die 11, which is a metal mold for pressure molding. A copper plate 20 is accommodated in the cavity 12. Only the surface of the copper plate 20 in the cavity 12 to which the copper powder 21 is to be adhered is open, and the other surfaces are closed by the die 11. A punch 13 is disposed on the die 11 so as to face the cavity 12. The punch 13 is raised and lowered by a well-known drive mechanism (not shown).

Copper powder 21 is filled onto the copper plate 20 inside the cavity 12. The punch 13 is lowered from above in the direction indicated by the white arrow to compress the copper powder 21, causing the copper powder 21 to plastically flow and form an adhesion portion on the upper surface of the copper plate 20. At this time, the surfaces of the copper plate 20 other than the surface to which the copper powder 21 is adhered are blocked by the die 11, so that the copper plate 20 can be prevented from spreading laterally.

This is used to suppress lateral thickening of the coil wire 1 when copper powder is compressed and plastically deformed around the coil wire 1. Specifically, the coil wire 1 is compressed without heating while all surfaces other than the surface that forms the adhesion portion are closed by a die. The load that causes the coil wire 1 to expand laterally is supported by the die. In other words, the formation of the adhesion portion in this embodiment is a closed forging type process.

It is preferable that the bottom surface of the punch 13 has an inclination angle α of less than 5 degrees. This makes it possible to promote the plastic flow of the copper powder 21.

The processing load P for realizing plastic flow bonding is expressed by the following formula.
P = k x Ks x L x t
k: Coefficient Ks: Yield stress of material (can be substituted with 80% of tensile strength)
L: processing line length t: plate thickness When α=0°, the processing load is maximum when k=1.

The coefficient k can be set to a predetermined value based on an empirical rule when an inclination angle of less than 5 degrees is provided on the lower surface 14 of the punch 13. For example, the value of the coefficient k for the inclination angle α of the lower surface 14 of the punch 13 is as follows:
α=0.5° or more and less than 2°: k=0.7
α=2° or more and less than 3°: k=0.6
α=3° or more and less than 5°: k=0.8

By providing an inclination angle to the lower surface 14 of the punch 13 that compresses the copper powder 21 in this way, the compression load can be reduced and the copper powder 21 can form an adhesion portion on the copper plate 20 without adhering to the die 11.

As an example, copper powder was supplied to a height of 0.67 mm on a pure copper plate of a given thickness of φ = 15 mm. The electrical resistance of both the copper plate and the copper powder was 0.5 Ω. By compressing the copper powder with the punch 13, a 0.61 mm adhesion portion was formed on the pure copper plate.

As described above, according to the embodiment, by forming the adhesion portion 3 at the bent portion 2 of the coil wire 1, it is possible to ensure a sufficient cross-sectional area of the bent portion 2, prevent an increase in electrical resistance, and improve power consumption. In addition, since the adhesion portion 3 is formed without heating, oxidation of the coil wire 1 can be prevented.

The present invention is not limited to the above embodiment, and can be modified as appropriate without departing from the spirit of the invention. In the example shown in FIG. 2, the adhesion portion 3 is formed on the outside of the bent portion 2, but it may be formed on the inside of the bent portion 2.

REFERENCE SIGNS LIST 1 Coil wire 2 Bent portion 3 Adhesion portion 10 Coil segment manufacturing device 11 Die 12 Cavity 13 Punch 14 Lower surface 20 Copper plate 21 Copper powder

Claims (1)

bending the coil wire to form a bent portion;
compressing the metal powder disposed in the bent portion to plastically flow bond the metal powder to the bent portion;
including,
A method for manufacturing a coil segment.

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