JPH089606A - Rotor for induction motor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a rotor for an induction motor which can make both stray loss and resistance loss sufficiently lower when operated by an inverter. CONSTITUTION:A bar 71 is composed of a group formed by bundled plural (for example, 9) copper wires coated with insulating layers of a thermosetting adhesive resin so that the cross section of the bar 71 can become nearly equal to that of a slot 61 (namely, an eggplant-like shape which is elongated in the radial direction). The wires are twisted around the axial direction (left-right direction in the Figure). The number of twisting times is adjusted to one or two in the peripheral direction of the eggplant-like cross section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor,
In particular, it relates to a rotor of an induction motor and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, electric vehicles have been put to practical use as measures against pollution. Induction motors are a favorite for passenger car class drive motors because of their structural robustness and low price, and variable speed operation with an inverter is used to control them. And in order to extend the mileage, high efficiency is important.

The rotor windings of this induction motor are generally
Copper is used as a rotor material in large- and medium-sized electric motors to improve efficiency, and in small-sized machines such as induction motors for electric vehicles, aluminum die-casting is mainly used from the viewpoint of manufacturability.

The following are known techniques relating to the production of rotor windings by this aluminum die casting. According to this known technique, a bundle of thin Cu wires is displaced in the axial direction to form a stranded wire, and the periphery thereof is cast by aluminum die casting to be a conductor of a rotor of an induction motor. Make up. As a result, compared with the case where the conductor is manufactured only by aluminum die casting, the resistance loss to the fundamental wave during the operation of the inverter is reduced and the stray loss to the harmonics is suppressed.

[0005]

However, the above-mentioned known techniques have the following problems. That is, the known technology aims to reduce stray loss by transposing the bundled wires into stranded wires, but the insulation coating of the wires is partially destroyed by the high temperature during aluminum die casting, and conduction occurs. However, there is a disadvantage that the effect of dislocations is reduced and the stray loss may not be sufficiently reduced. Further, the Cu element wire portion contributes to the reduction of the resistance loss, but since the aluminum having a high specific resistance is filled around the Cu element wire, the reduction of the resistance loss was insufficient. Therefore, it is difficult to improve the efficiency during the operation of the inverter, and there are problems such as a rise in the temperature of the rotor / bearing and a difficulty in extending the service life.

On the other hand, as a known technique regarding a stranded wire,
For example: JP, 61-33726, A This publicly known art is on a stranded wire of a super-strength steel wire of circular section,
After twisting a plurality of twisted wires of odd-shaped cross-section wires so as to be arranged in layers, the twisted wires are compressed so that the voids between these twisted wires are reduced. SUMMARY OF THE INVENTION In this known technique, a wire-shaped insulated conductor formed by twisting a plurality of wires is arranged around a circular cooling pipe for cooling a coil, and then the wires are compressed to form a cross section. Is a square shape.

However, when the above-mentioned known technique is applied to the structure of the rotor of the induction motor, there are the following problems. That is, the configuration of the known technology is based on the premise that a stranded wire for strength retention is provided in the center, and stranded wires having different cross-sectional shapes are twisted around the stranded wire, which is not applicable to a conductor of a rotor of an induction motor. Have difficulty. Further, the configuration of the known technique is a configuration on the stator side of the coil, which is premised on the presence of the cooling pipe, and is difficult to apply to the conductor of the rotor of the induction motor.

An object of the present invention is to provide a rotor of an induction motor and a method of manufacturing the same, which can sufficiently reduce both stray loss and resistance loss during inverter operation.

[0009]

In order to achieve the above-mentioned object, according to the present invention, a shaft is provided in an induction motor, a substantially cylindrical iron core fixed to the shaft, and a diameter of the iron core. In a rotor of an induction motor having a plurality of slots formed in the axial direction in the vicinity of the outer periphery in the direction and a plurality of conductors accommodated in the slots, each of the plurality of conductors is provided with a plurality of insulating coatings. Of copper wires are bundled into one, and the cross-sectional shape is formed to be substantially the same as the cross-sectional shape of the slot. A rotor for an induction motor is provided, each of which is twisted in the axial direction and displaced.

[0010] Preferably, in the rotor of the induction motor, the rotor of the induction motor is provided, wherein the cross section of the slot forms an elongated opening in the radial direction.

Further, preferably, in the rotor of the induction motor, the wires included in the wire group are twisted in the circumferential direction of the cross section of the slot for one rotation or more and two rotations or less. An induction motor rotor is provided.

In order to achieve the above object, according to the present invention, a slot formed in the axial direction near the radial outer circumference of a substantially cylindrical iron core provided in an induction motor and fixed to a shaft, and A method of manufacturing a rotor for an induction motor, comprising: a conductor housed in a slot; and two end rings, which are respectively provided at both ends in the axial direction of the iron core and short-circuit connect both ends of the conductor, a plurality of insulating coatings are applied. A first step of bundling the copper wires of a book into an elongated ring shape,
A second step of twisting the plurality of elongated ring-shaped strands around the axis in the longitudinal direction by one rotation or more and two rotations or less; and the transposed plurality of strands having a cross-sectional shape A third step of compression-molding so as to be substantially equal to the cross-sectional shape of the slot, and a fourth step of cutting both longitudinal ends of the compression-molded strands to form the conductor.
And a method of manufacturing a rotor of an induction motor.

Preferably, in the method of manufacturing a rotor for an induction motor, the first to fourth steps are repeated to form the same number of conductors as the number of slots, and before the slots are housed in the slots. There is provided a method of manufacturing a rotor of an induction motor, which further comprises a fifth step of pre-bonding a conductor with one of the two end rings.

[0014]

In the present invention having the above-described structure, the conductor is composed of a group of a plurality of wires each of which is provided with an insulating coating, and the copper has a specific resistance higher than that of aluminum. Since the value of is small, the resistance loss is smaller than that in the case where the conductor is formed only by the conventional die casting of aluminum and the case where the periphery of the copper wire is filled with aluminum.
At this time, since the cross-sectional shape of this wire group is formed to be almost the same as the cross-sectional shape of the slot, each wire originally having a circular cross-section is deformed into an elliptical shape, etc. Since the cross-sectional area of the conductor occupying the area, that is, the space factor is improved, the reduction of the space factor does not increase the resistance loss. Therefore, the resistance loss can be sufficiently reduced. Further, since each of the wires included in the wire group is twisted in the axial direction in a spiral shape and rearranged, stray loss during operation of the inverter can be reduced. At this time, the effect of dislocation is effectively exerted without the insulation being broken by aluminum die casting as in the conventional case and the effect of dislocation is reduced, so that stray loss during inverter operation can be sufficiently reduced.

Further, the cross section of the slot has an elongated opening in the radial direction, so that the wires accommodated in the slot can be distributed over a large distance in the radial direction. Furthermore, by suppressing the number of twists of the wires included in the wire group in the circumferential direction of the cross section of the slot to be 1 rotation or more and 2 rotations or less, the length is increased by a large number of windings and the effective cross-sectional area is reduced. It is possible to secure the effect of dislocation while preventing this.

Further, in the present invention, in the first step, a plurality of insulating coated copper wires are bundled into an elongated ring shape, and in the second step, the elongated ring-shaped wires are aligned in the longitudinal direction. The shaft is made to be an axis and twisted about 1 axis or more and 2 times or less to displace, and the plurality of strands displaced in the third step are compression-molded so that the cross-sectional shape is substantially equal to the cross-sectional shape of the slot, By cutting both ends in the longitudinal direction of the plurality of strands compression-molded in the fourth step to form conductors, a rotor capable of sufficiently reducing resistance loss and stray loss during inverter operation can be manufactured. .

Further, after repeating the first to fourth steps to form the same number of conductors as the number of slots, and before putting the conductors in the slots in the fifth procedure, one of the two end rings is provided with these conductors. By pre-coupling with each other, when the conductors are housed in the slots, the conductors do not fall apart and are easy to handle.

[0018]

Embodiments of the present invention will be described below with reference to FIGS. A first embodiment of the present invention will be described with reference to FIGS. This embodiment is an embodiment of the rotor of the induction motor. The vertical cross-sectional structure of the induction motor is shown in FIG. In FIG. 2, the induction electric machine 1 includes a housing 9 and the housing 9.
A stator 2 having a stator core 4 fixed to the inner peripheral surface of the rotor and a multi-phase stator winding 5 wound around the stator core 4.
A rotor 8 having a shaft 8, a substantially cylindrical rotor core 6 fixed to the shaft 8, and a rotor winding 7 provided on the rotor core 6, an end bracket 10, and an end bracket 10. And a bearing 11 that holds the shaft 8 rotatably.

This embodiment relates to the structure of the rotor 3, the details of which will be described below. FIG. 1 is a partially cutaway perspective view of the rotor 3 according to the present embodiment, and FIG. 3 is a front view (partial transverse sectional view) viewed from the direction A in FIG. 1 and 3
In the above, as described above, the rotor 3 includes the shaft 8,
A rotor core 6 and a rotor winding 7 are provided. The rotor core 6 is made of laminated silicon steel plates, and has a plurality of slots 61 formed in the axial direction near the outer circumference in the radial direction. As shown in FIG. 3, the cross section of the slot 61 forms an opening of a shape elongated in the radial direction. Also rotor winding 7
Is a plurality of bars 71 housed in a plurality of slots 61.
And two end rings 72a, 72b which are respectively provided on both ends in the axial direction of the stator core 6 and short-circuit connect both ends of the plurality of bars 71. Both of the end rings 72a and 72b are made of copper and are electrically connected to the plurality of bars 71.

The detailed structure of the bar 71 is shown in FIG. Bar 7
1 is composed of a group of a plurality of (for example, 9) copper wires 71A whose outer periphery is insulated and coated with a thermosetting adhesive resin, which are bundled into one, and a cross-sectional shape of which is a slot. 61
Is formed so as to have almost the same cross-sectional shape (that is, a shape elongated in the radial direction). And strand 7
1A is distorted by being twisted in a spiral shape in the axial direction (left-right direction in the drawing). As the number of times of this twist,
In the circumferential direction of the eggplant-shaped cross section (for example, in the direction of arrow B in the figure),
It is twisted only once or twice. By suppressing the number of twists in this way, it is possible to secure the effect of dislocation while preventing the length from increasing and the effective cross-sectional area decreasing due to a large number of turns. Also, at both ends of the strand 71A,
Insulation peeling portion 7 for connecting to the end rings 72a, 72b
1A _a and 71A _b are provided, and these insulation peeling parts 7 are provided.
The 1A _a , 71A _b and the end rings 72a, 72b are joined by, for example, silver brazing or welding.

Next, the operation of this embodiment will be described. In the rotor 3 of the induction motor according to the present embodiment, the bar 71 is formed by a group of wire bundles in which a plurality of copper wires 71A having an insulating coating are bundled together. Since copper has a smaller specific resistance value than aluminum, the resistance loss can be made smaller than in the case of forming a conductor only by conventional aluminum die casting or in the case of aluminum die casting around the copper wire. Further, at this time, the cross-sectional shape of this wire group is formed so as to be substantially the same as the cross-sectional shape of the slot 61, and each wire 71A originally having a circular cross-section is deformed into an elliptical shape or the like. The product factor (= cross-sectional area of bar 71 / cross-sectional area of slot 61) is improved. Therefore, it is possible to sufficiently reduce the resistance loss without increasing the resistance loss due to the decrease of the space factor. Further, since each of the strands 71A of the bar 71 is twisted in the axial direction in a spiral shape to be displaced, stray loss during operation of the inverter can be reduced. Since the strand 71A is formed as described above, the space factor does not become small as in the case where the round strand is simply transposed. Further, unlike the conventional case, the insulation is not destroyed by aluminum die casting and the effect of dislocation is not reduced, so that the effect of dislocation works effectively and the stray loss during inverter operation can be sufficiently reduced. Further, generally, in the rotor bar, current is difficult to flow because the inductance is large on the shaft side,
Since the inductance is small on the outer peripheral side of the bar, current tends to flow easily. This tendency is particularly large in a bar having a shape in which the radial direction is longer than the circumferential direction. This is called the deep groove effect and has a resistance value several times higher than the actual resistance, causing a loss. During the operation of the inverter, a harmonic current flows through the bar, resulting in a loss comparable to several tens of times the actual resistance value of the bar, thus lowering the efficiency. Here, the slots 61 of the rotor 3 of this embodiment are
The cross section of the above has an opening of a shape that is elongated in the radial direction, and as described above, originally, the deep groove effect is apt to be remarkably exhibited. However, in the rotor 3 of the present embodiment, the wires 71 stored in the slot 61 are
Since A is twisted in the axial direction and dislocated,
The strands 71A are distributed over a large radial distance of the slot 61. That is, the wire 71A that is closest to the outer periphery in the slot 61 at a certain axial position is
At the other twisted positions, the deep groove effect is located closest to the shaft 8 in the slot 61, and the deep groove effect can be effectively canceled. Therefore, it is possible to eliminate the imbalance of the inductance, sufficiently homogenize the current distribution, and suppress an increase in loss.

As described above, according to this embodiment,
Since the resistance loss and stray loss of the bar 71 are sufficiently reduced and the deep groove effect is canceled to suppress the loss increase, the loss of the rotor 3 as a whole can be reduced, and the one-charge traveling distance of the battery can be extended. . Further, since the burden on other parts such as bearings is lightened, it is possible to reduce failures and improve the reliability of the induction motor 1 as a whole.

In the above embodiment, the end rings 72a and 72b were both made of copper, but the material is not particularly limited, and they may be made of aluminum die casting or the like. Further, the materials may be different such that one is copper and the other is aluminum. Also in this case, the same effect is obtained.

A second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the bar structure is different. The same members as those in the first embodiment are designated by the same reference numerals. FIG. 5 shows the detailed structure of the bar 171 of the rotor of the induction motor of this embodiment. In FIG. 5, the bar 17 of this embodiment is
1 is different from the bar 71 of the first embodiment in that the bar 171
However, a plurality of (for example, four) rectangular copper wires 171 are provided.
This is a point composed of a group of strands of A. Also, as in the first embodiment, this group of strands is formed so that the cross-sectional shape is an elongated shape, and the strands 171A are spirally twisted and displaced. FIG. 6 shows the structure of the bar 171 before being shaped and dislocated in this way. As shown in FIG. 6, the strand 171A before forming / dislocation has a rectangular cross section. The other structure is almost the same as that of the first embodiment.

Also in this embodiment, the same effect as in the first embodiment can be obtained. A third embodiment of the present invention will be described with reference to FIG. This embodiment is an embodiment of a method of manufacturing the rotor 3 of the induction motor according to the first embodiment. The same members as those in the first and second embodiments are designated by the same reference numerals. The main part of the method of manufacturing the rotor according to the present embodiment relates to the manufacturing process of the bar 71 (see FIG. 1) of the rotor winding 7 of the rotor 3, and this process will be described with reference to FIG. A description will be given in order from a) to (d). In FIG. 7, first, a plurality (eg, 9) copper strands 71A whose outer periphery is insulation-coated with a thermosetting adhesive resin are provided.
Are bundled into an elongated ring shape (FIG. 7 (a)). Next, the plurality of elongated annular wires 71A are dislocated by twisting the shaft 12 in the longitudinal direction (left and right direction in the drawing) about the shaft 12 (for example, in the direction of an arrow C in the drawing) one rotation or more and two rotations or less. Let Further, the plurality of dislocated strands 71A are compression-molded so that the cross-sectional shape is substantially equal to the cross-sectional shape of the slot 61 (see FIG. 3) (FIG. 7 (c)).

The details of the compression molding step of FIG. 7C are shown in FIG. FIG. 7 before the compression molding step of FIG.
The VI of the plurality of strands 71A dislocated in the step (b)
A cross section of I-VII is shown in FIG. As shown in the drawing, each of the strands 71a has a circular cross section, and the plurality of strands 71A are bundled so that the cross section thereof has a substantially circular shape. Next, the plurality of strands 71A are pressed and molded by the molding means 13L, R having the same cross-sectional shape as those of the slots 61 (FIGS. 8B and 8C).
At this time, if necessary, the heating means (not shown) presses while heating. As a result, the plurality of strands 71A have a cross-sectional shape substantially equal to the cross-sectional shape of the slot 61 (FIG. 8 (d)).

After the compression molding process as described above, returning to FIG. 7, both ends of the plurality of strands 71A in the longitudinal direction are cut along the a ₁ -a ₂ plane and removed to form a bar 71 of a predetermined length. (FIG. 7 (d)). FIG. 7 is an enlarged perspective view of a section D, which is a cut surface.
It shows in (e).

According to the manufacturing method of this embodiment, it is possible to manufacture the rotor 3 having the bar 71 described in the first embodiment.

Although the rotor 3 having the bar 71 of the first embodiment is manufactured in the above embodiment, the rotor having the bar 171 described in the second embodiment is used. The same can be applied to the case of manufacturing, whereby the rotor 3 of the second embodiment can be manufactured. Also, the two end rings 72a, 72
b, for example, the end ring 72a and the bar 71.
There is also a configuration in which and are combined in advance. This modification will be described with reference to FIG. The same members as those in the first to third embodiments are designated by the same reference numerals. In this modification, FIG.
The above procedure described in (a) to (d) is repeated to form the same number of bars 71 as the number of slots 61 (for example, 12), and then these bars 71 are inserted into the slots 61.
The bar 71 is previously coupled to the end ring 72a before being stored in the. This state is shown in FIG. In FIG. 9, twelve bars 71 have an end ring 72 at one end.
It is preliminarily combined in the shape of a comb with a by silver brazing or welding. With the end ring 72a and the bar 71 thus joined together, each bar 71 is inserted into the slot 61 of the rotor core 6, and then the remaining end ring 72b and each bar 71 are silver brazed. Combined by welding etc. Accordingly, when the bars 71 are housed in the slots 61, the bars 71 are not disjointed and are easy to handle, and it is possible to prevent the bars 71 from moving and the positions being misaligned to cause non-uniformity for each product. Further, the above first to third
In the above embodiment, the case where the present invention is applied to the rotary type motor drive is shown, but the present invention can also be applied to the linear motor drive. It can also be used as a damper winding of a synchronous motor.

[0030]

According to the present invention, a conductor is constituted by a group of wires in which a plurality of copper wires with an insulating coating are bundled into one,
Since the cross-sectional shape of the wire group is formed to be substantially the same as the cross-sectional shape of the slot and the space factor does not decrease, the resistance loss can be sufficiently reduced as compared with the conventional case. Also,
Each of the strands included in the strand group is twisted in the axial direction in a spiral shape and dislocated, and the effect of this dislocation is not reduced as in the past, so stray loss during inverter operation is sufficiently reduced. It can be reduced. Therefore, it is possible to reduce the loss of the rotor, improve the efficiency, and extend the one-charge traveling distance of the battery. In addition, since the burden on other parts such as bearings is lightened, it is possible to reduce failures and improve the reliability of the induction motor as a whole.

Further, since the cross section of the slot forms an opening which is elongated in the radial direction, the wires accommodated in the slot are distributed over a large radial distance. Therefore, the deep groove effect, in which the current does not easily flow on the shaft side and the current easily flows on the outer peripheral side, is effectively canceled by displacing the accommodated wires, and the current distribution is made sufficiently uniform, and the increase in loss is suppressed. be able to. Furthermore, the number of twists of the wires included in the wire group in the circumferential direction of the cross section of the slot is set to 1
Since the number of turns is not less than two and not more than two, it is possible to secure the effect of dislocation while preventing the length from increasing and the effective cross-sectional area from decreasing due to many turns. Also, since the conductor is pre-coupled with one of the two end rings before it is stored in the slot, the conductor is easy to handle when it is stored in the slot, and the conductor moves and the position is misaligned. Can be prevented.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing the structure of a rotor according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing the structure of an induction motor.

3 is a partial cross-sectional front view showing the structure of the rotor shown in FIG.

FIG. 4 is a perspective view showing a detailed structure of the bar shown in FIG.

FIG. 5 is a perspective view showing the structure of a rotor bar according to a second embodiment of the present invention.

6 is a perspective view showing a state before processing of the bar shown in FIG.

FIG. 7 is a diagram showing a procedure of a method of manufacturing a rotor according to the third embodiment of the present invention.

8 is a diagram showing a detailed procedure of the compression molding step shown in FIG.

FIG. 9 is a perspective view showing a configuration of an end ring and a bar of a rotor according to a modified example of the third embodiment.

[Explanation of symbols]

 1 induction motor 2 stator 3 rotor 6 rotor iron core 7 rotor winding 8 shaft 13L, R forming means 61 slot 71 bar 71A wire 72a, b end ring 171 bar 171A wire

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Haruo Obaraki 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Ryoichi Naganuma 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1-1 Hitachi Ltd., Hitachi Research Laboratory (72) Inventor Koki Taneda, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Production Engineering Research Laboratory Hitachi, Ltd. (72) Masami Masuda Yokohama, Kanagawa 292 Yoshida-cho, Totsuka-ku, Hitachi Ltd., Production Engineering Laboratory (72) Inventor Suetaro Shibukawa 2520, Takaba, Katsuta-shi, Ibaraki Hitachi Automotive Systems Division (72) Inventor Osamu Koizumi Katsuta-shi, Ibaraki 2520, Takaba, Oita

Claims (5)

[Claims] 1. An induction motor equipped with a shaft, a substantially cylindrical iron core fixed to the shaft, a plurality of slots axially formed near the outer circumference of the iron core in the radial direction, and a plurality of slots housed in the slots. In the rotor of the induction motor having a plurality of conductors, each of the plurality of conductors is formed by bundling a plurality of copper wires coated with an insulating coating into one and having a cross-sectional shape of the slot. It is a group of strands formed to have a shape substantially equal to the cross-sectional shape, and each of the strands included in the strands is twisted in the axial direction and dislocated. Characteristic induction motor rotor. 2. The rotor for an induction motor according to claim 1, wherein the cross section of the slot forms an opening elongated in the radial direction. 3. The rotor for an induction motor according to claim 1, wherein the strands included in the strand group are twisted in the circumferential direction of the cross section of the slot once or more and twice or less. And induction motor rotor. 4. A slot formed in the axial direction in the vicinity of a radially outer periphery of a substantially cylindrical iron core provided in an induction motor and fixed to a shaft, and a conductor housed in the slot.
A method of manufacturing a rotor of an induction motor, comprising: two end rings that are respectively provided at both axial ends of the iron core and that short-circuit and connect both ends of the conductor; and a plurality of copper wires coated with insulation are bundled. And a second step of twisting the plurality of slender annular wire strands about the longitudinal direction as an axis for one rotation or more and two rotations or less, A third step of compression-molding the plurality of strands so that the cross-sectional shape thereof is substantially equal to the cross-sectional shape of the slot; and cutting both end portions in the longitudinal direction of the plurality of compression-molded strands. A fourth step of forming a conductor, and a method for manufacturing a rotor of an induction motor. 5. The method of manufacturing a rotor for an induction motor according to claim 4, wherein the first to fourth steps are repeated to form the same number of conductors as the number of slots and before the conductors are housed in the slots. 5. A method of manufacturing a rotor for an induction motor, further comprising a fifth step of preliminarily coupling these conductors to one of the two end rings.