JP2023101232A - Rotor manufacturing method - Google Patents

Abstract

To provide a method of manufacturing rotor capable of suppressing heat generation during operation of a cage-type induction motor.SOLUTION: A method of manufacturing a rotor equipped with a first short-circuit ring disposed on one end side in a direction along a rotation axis of a rotor core, a second short-circuit ring disposed oppositely to the first short-circuit ring across the rotor core, and a plurality of rod-shaped portions inserted in the rotor core to connect the first short-circuit ring and the second short-circuit ring, includes: a molding step of pressing a conductive material lump to mold the first short-circuit ring and the rod-shaped portion extending from the first short-circuit ring; an insertion step of inserting the rotor core in the rod-shaped portion from a free end portion side of the rod-shaped portion; and a machining step of providing the second short-circuit ring at the free end portion of the rod-shaped portion after the rotor core is inserted.SELECTED DRAWING: Figure 3

Description

The present invention relates to a rotor manufacturing method.

Conventionally, a squirrel cage induction motor is known that has a rotor in which short-circuit rings arranged at both ends of a rotor core and rod-shaped portions connecting the short-circuit rings are combined in a cage shape. As a rotor in such a squirrel cage induction electric machine, there is known a mode in which a short-circuit ring and a bar-shaped portion are formed by casting (see, for example, Patent Document 1).

JP 2009-124879 A

However, when the rod-shaped portion and the short-circuit ring are formed by casting, cavities called blowholes may be formed in the rod-shaped portion and the short-circuit ring. Since the blowholes increase electrical resistance, the electrical resistance of the rod-shaped portion and the short-circuit ring is increased. Therefore, when a squirrel-cage induction motor having a rotor formed by casting a rod-shaped portion and a short-circuit ring is operated, the rotor may generate heat due to the blowholes.

Accordingly, an object of the invention disclosed in the present specification is to provide a manufacturing method capable of obtaining a rotor capable of suppressing heat generation during operation of a squirrel cage induction motor.

A rotor manufacturing method disclosed in the present specification includes a first short-circuit ring arranged on one end side in a direction along a rotation axis of a rotor core, and a first short-circuit ring facing the first short-circuit ring across the rotor core. A method for manufacturing a rotor comprising: second short-circuit rings arranged; and a plurality of bar-shaped portions inserted through the rotor core and connecting the first short-circuit rings and the second short-circuit rings, a forming step of pressing a conductive material block to form the first short-circuit ring and the rod-shaped portion extending from the first short-circuit ring; an inserting step of inserting the core; and a processing step of providing the second short-circuit ring at the free end of the rod-shaped portion after the rotor core is inserted.

In the rotor manufacturing method described above, the first short-circuit ring and the rod-shaped portion may be formed by pressing a side wall of a cylindrical material block having conductivity.

Further, in the rotor manufacturing method described above, the forming step includes a first step of pressing a conductive solid columnar mass of material to form an intermediate body having a bottom plate portion and an annular wall portion; A second step of removing the bottom plate portion to form the first short-circuit ring, and a third step of processing the annular wall portion into a comb tooth shape to form the rod-shaped portion may be provided. .

In the rotor manufacturing method described above, the third step may be configured to remove the removed portion set adjacent to the portion formed as the rod-shaped portion.

The removed portion may be removed by cutting with a cutting tool.

In the rotor manufacturing method described above, the step of providing the second short-circuit ring includes bending the free end protruding from the rotor iron core in the circumferential direction, and bringing the free ends adjacent in the circumferential direction into contact with each other. It can be set as the aspect which provides the said 2nd short circuit ring.

Further, in the above rotor manufacturing method, the step of providing the second short-circuit ring includes placing a conductive plate in contact with the free end projecting from the rotor iron core, and It is also possible to adopt a mode in which the contact portion between the portion and the plate is welded.

The invention disclosed in this specification can provide a manufacturing method capable of obtaining a rotor capable of suppressing heat generation during operation of a squirrel cage induction motor.

FIG. 1 is an explanatory diagram showing the inside of a squirrel-cage induction motor in which a rotor manufactured by the rotor manufacturing method of the first embodiment is assembled. FIG. 2 is a perspective view of a punch used in the rotor manufacturing method of the first embodiment. 3(A) to 3(I) are explanatory diagrams showing part of the steps of the rotor manufacturing method according to the first embodiment, and FIG. 3(A) shows a state in which a lump of material is set in a die. FIG. 3(B) is a plan view of a material block set in a die, and FIG. 3(C) is a cross-sectional view taken along line X1-X1 in FIG. 3(B). FIG. 3(D) is a diagram showing how a material block is pressed by a punch, FIG. 3(E) is a plan view of a deformed material block, and FIG. 3(F) is a cross-sectional view along line X2-X2 in FIG. 3(E). is. FIG. 3(G) is a diagram showing a state in which the punch has been pushed in, FIG. 3(H) is a diagram showing a state in which the first short-circuit ring and the rod-shaped portion are formed, and FIG. ) is a cross-sectional view taken along line X3-X3. FIG. 4 is a plan view of an electromagnetic steel sheet forming a rotor core. 5(A) to 5(C) are three views showing a state in which the rotor core is inserted through the rod-shaped portion, FIG. 5(A) being a plan view, FIG. 5(B) being a front view, and FIG. (C) is a bottom view. FIG. 6 is an explanatory view schematically showing how the free end of the rod-shaped portion is bent. 7(A) to 7(C) are three views of the rotor manufactured by the rotor manufacturing method of the first embodiment, FIG. 7(A) being a plan view, and FIG. A front view, and FIG. 7C is a bottom view. FIG. 8 is a perspective view of a punch used in the rotor manufacturing method of the second embodiment. 9(A) to 9(F) are explanatory diagrams showing part of the steps of the rotor manufacturing method according to the second embodiment, and FIG. 9(A) shows a state in which a lump of material is set in a die. FIG. 9(B) is a plan view of a material block set in a die, and FIG. 9(C) is a cross-sectional view taken along line X4-X4 in FIG. 9(B). FIG. 9(D) is a diagram showing how the intermediate is formed by punching, FIG. 9(E) is a plan view of the intermediate, and FIG. 9(F) is a cross-sectional view taken along the line X5-X5 in FIG. be. 10(A) to 10(E) are explanatory diagrams showing part of the steps of the rotor manufacturing method according to the second embodiment, and FIG. 10(B) is a diagram showing how the bottom plate portion is punched out, FIG. 10(C) is a plan view of the intermediate body after the bottom plate portion is punched out, and FIG. 10(D) is an annular wall 10(E) is a cross-sectional view taken along the line X6-X6 in FIG. 10(D). FIG. 11(A) is a front view showing a removed portion set in the intermediate, and FIG. 11(B) is a plan view showing a removed portion set in the intermediate. 12(A) and 12(B) are two side views of a rotor manufactured by the rotor manufacturing method of the third embodiment, FIG. 12(A) being a plan view and FIG. 12(B) being a front view. It is a diagram.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated so as to completely match the actual ones. In some drawings, details may be omitted. Furthermore, the scale of each element depicted in each figure may be different.

(First embodiment)
[Configuration of squirrel cage induction motor]
First, referring to FIG. 1, a schematic configuration of a squirrel cage induction motor 1 incorporating a rotor 4 manufactured by the manufacturing method of the present embodiment will be described. The squirrel cage induction motor 1 is used, for example, as a drive source for a hybrid vehicle, an electric vehicle, a fuel cell vehicle, or another electric vehicle, or a drive source for a pump or a fan. be done.

A squirrel cage induction motor 1 includes an annular stator 3 provided in a case 2 and a rotor 4 arranged inside the stator 3 so as to face the stator 3 in the radial direction. The rotor 4 is provided rotatably around the rotation axis AX within the stator 3 . The rotor 4 is arranged to face the first short-circuit ring 6 arranged on one end side of the rotor iron core 5 in the direction along the rotation axis AX direction, and the first short-circuit ring 6 with the rotor iron core 5 interposed therebetween. A second short-circuit ring 7 is provided. The rotor 4 also includes a plurality of rod-shaped portions 8 that connect the first short-circuit ring 6 and the second short-circuit ring 7 . A rotating shaft member 9 is provided in the central portion of the rotor core 5. The rotating shaft member 9 includes a first bearing member 10a provided on one end side of the rotor 4, It is supported by the case 2 by the second bearing member 10b provided on the side. This allows the rotor 4 to rotate. In this embodiment, as shown in FIG. 3(H), the rod-shaped portions 8 are arranged in the circumferential direction, and the number thereof is 12. However, the number of the rod-shaped portions 8 is limited to this. Any other number may be used.

[Production method]
A method for manufacturing the rotor 4 will be described below.
<Extrusion molding process>
A method of manufacturing the rotor 4 includes an extrusion process. FIG. 2 shows a punch 20 used in the extrusion process. The punch 20 is a pin-shaped tool, and has a cylindrical guide portion 21 at its tip. In addition, the punch 20 has a stepped portion 22 having a larger diameter than the guide portion 21 on the proximal end side of the guide portion 211 . The height of the stepped portion 22 is set to correspond to the thickness of the first short-circuit ring 6 . The punch 20 includes a plurality of projecting portions 23 projecting radially toward the base end side from the stepped portion 22, and a groove portion 24 formed between the projecting portions 23 adjacent in the circumferential direction. ing. The protrusions 23 and the grooves 24 are provided alternately along the circumferential direction, and both extend along the longitudinal direction of the punch 20 . As will be described later in detail, part of the material block 40 (see FIG. 3A and the like) flows into the groove 24 to form the rod-shaped portion 8 (see FIG. 1).

Referring now to FIG. 3A, extrusion is performed using a punch 20 and a die 30. As shown in FIG. The die 30 includes a first housing recess 31 into which the guide portion 21 of the punch 20 is inserted, and a second housing recess 31 into which the portion of the punch 20 where the step portion 22, the projecting portion 23 and the groove portion 24 are formed is inserted. A storage recess 32 is provided. The inner peripheral diameter of the second housing recess 32 is larger than the inner peripheral diameter of the first housing recess 31, and is set to a dimension that allows the projecting portion 23 of the punch 20 to come into sliding contact therewith.

The operator first sets the conductive tubular material mass 40 in the second housing recess 32 of the die 30 . The material lump 40 is cylindrical, as shown in FIGS. 3(B) and 3(C). The material lump 40 in this embodiment is made of pure copper (tough pitch copper), but may contain a slight amount of impurities. In addition, the material block 40 can be appropriately selected from materials having electrical conductivity and workability capable of being plastically deformed. In addition to copper, it can be appropriately selected from, for example, aluminum, gold, silver, copper alloys, aluminum alloys, and the like.

As shown in FIG. 3A, the operator sets the material block 40 in the second housing recess 32 of the die 30 and then inserts the punch 20 into the die 30 . Then, the operator moves the punch 20 to press the material block 40 as indicated by an arrow 15a shown in FIG. 3(D). As a result, the material mass 40 is spread in a direction opposite to the pressing direction of the punch 20 as indicated by an arrow 15b in FIG. flow into the space formed between them. As a result, the material mass 40 gradually changes its shape as shown in FIGS. 3(E) and 3(F). It should be noted that when the material lump 40 is extrusion-molded, the volume of the material lump 40 does not change before and after molding.

From the state shown in FIG. 3(D), when the operator further pushes the punch 20 as indicated by arrow 15c in FIG. , are further pushed apart in the direction opposite to the pressing direction of the punch 20 . When the stepped portion 22 of the punch 20 reaches the boundary between the first recessed portion 31 and the second recessed portion 32 of the die 30, an annular shape is formed as shown in FIGS. 3(H) and 3(I). The first short-circuit ring 6 and the plurality of rod-shaped portions 8 extending in a state of being connected to the first short-circuit ring 6 at the connecting portion 8a are formed at once. The end of the bar-shaped portion 8 opposite to the connecting portion 8a is a free end 8b. Since the first short-circuit ring 6 and the rod-shaped portion 8 are formed by extrusion molding, unlike the case where they are formed by casting, blowholes do not occur in these portions.

In the present embodiment, processing using plastic deformation is adopted in order to avoid the occurrence of blowholes, and extrusion molding is adopted among the processing utilizing plastic deformation. For example, press working is known as a working that utilizes plastic deformation. However, with press working, it is difficult to secure the necessary length dimension for the bar-shaped portion 8 . In other words, press work includes a process of pulling the material, but it is difficult to form a long portion in the process of pulling. On the other hand, in the case of extrusion molding, the necessary length dimension of the rod-shaped portion 8 can be secured.

<Insertion process>
After the extrusion molding process is finished, the insertion process is started. The inserting step is a step of inserting the rotor core 5 from the free end portion 8b side of the bar-shaped portion 8 formed by the extrusion molding step. An operator forms the rotor core 5 by laminating a plurality of plate-shaped electromagnetic steel sheets 5a. FIG. 4 shows a plan view of the electromagnetic steel sheet 5a. One electromagnetic steel sheet 5a is formed in a disc shape from a silicon steel sheet, and is provided with a first insertion hole 5a1 for inserting the rotating shaft member 9 (see FIG. 1) at the center thereof. Further, second insertion holes 5a2 are provided around the first insertion holes 5a1 at predetermined intervals in the circumferential direction. The rod-shaped portion 8 is inserted through each of the second insertion holes 5a2. Therefore, the arrangement of the second insertion holes 5a2 is set according to the arrangement of the rod-shaped portion 8. As shown in FIG. The electromagnetic steel sheet 5a itself is a conventionally known one, and a conventionally known method can be adopted for its manufacturing method, so detailed description thereof will be omitted here.

In the present embodiment, the second insertion hole 5a2 is provided for inserting the rod-shaped portion 8. However, instead of the second insertion hole 5a2, a notch in which the outer peripheral edge side of the electromagnetic steel plate 5a is open may be provided. can be

In the insertion step, as shown in FIGS. 5(A) to 5(C), the rod-shaped portion 8 is pushed from its free end portion 8b, that is, from the side opposite to the side where the first short-circuit ring 6 is provided. 2 insertion hole 5a2. The inserted electromagnetic steel sheets 5a are stacked on the first short-circuit ring 6 in order. After all the electromagnetic steel sheets 5a have been inserted, the free end 8b of the bar-shaped portion 8 protrudes above the uppermost electromagnetic steel sheet 5a as shown in FIG. 5(B). Although FIG. 5B shows a state in which six electromagnetic steel sheets 5a are stacked for convenience of drawing, this does not indicate the actual number of layers.

<Short-circuit ring forming step>
Next, a short-circuited ring forming step for forming the second short-circuited ring 7 will be described. As shown in FIG. 5(B), after all the electromagnetic steel sheets 5a are inserted, the free end 8b of the bar-shaped part 8 protrudes above the uppermost electromagnetic steel sheet 5a. In the short-circuit ring forming step, the operator bends the free end portion 8b. Specifically, as indicated by an arrow 15e in FIG. 6, the operator applies a lateral force to the free end portion 8b to bend the free end portion 8b in the circumferential direction, thereby bending the free end portion 8b adjacent in the circumferential direction. Bring them into contact. As a result, the free end portion 8b is circumferentially folded, and the second short-circuit ring 7 is formed. The portions where the free ends 8b are in contact with each other may be brazed to improve the strength.

Since the free end portion 8b is originally formed by extrusion molding from the material block 40 (see FIG. 3B, etc.), no blowholes are formed in the free end portion 8b, and the second short-circuit ring 7 heat generation is also suppressed.

As described above, the rotor 4 is formed. A rotating shaft member 9 is attached to the formed rotor 4 by press-fitting, and incorporated into the stator 3 as shown in FIG. For mounting the rotating shaft member 9, conventionally known methods such as shrink fitting, fixing with an adhesive, and welding can be adopted.

According to the method of manufacturing the rotor 4 of the first embodiment, the first short-circuit ring 6, the second short-circuit ring 7, and the rod-shaped portion 8 are formed by extrusion molding. In contrast, blowholes do not occur. As a result, heat generation during operation of the squirrel cage induction motor 1 is suppressed.

In this embodiment, each process is described as being performed by an operator, but each process may be automatically performed using a work machine. This point is also common in the second embodiment and the third embodiment described below.

(Second embodiment)
Next, the manufacturing method of the second embodiment will be described with reference to FIGS. 8 to 11B. Except for details, the rotor manufactured by the manufacturing method of the second embodiment is the same as the rotor 4 manufactured by the manufacturing method of the first embodiment. will be used for explanation.

<Intermediate formation step>
A method for manufacturing the rotor 4 in the second embodiment includes an intermediate forming step. The worker forms an intermediate 71 as shown in FIG. 9(F) in the intermediate forming step. The intermediate body 71 refers to a form formed before reaching the form including the first short-circuit ring 6 and the rod-shaped portion 8 . Extrusion is also employed to form intermediates. FIG. 8 shows a punch 50 used for extrusion in the intermediate forming process. The punch 50 is a cylindrical tool, and has a cylindrical portion 51 and a tapered portion 52 formed at its base end.

Referring now to FIG. 9A, extrusion is performed using a punch 50 and a die 60. As shown in FIG. The die 60 has a housing recess 61 and a stopper section 62 provided at the upper edge of the opening of the housing recess 61 . The inner diameter of the storage recess 61 is larger than the diameter of the cylindrical portion 51 of the punch 50 . The distance of the gap between the storage recess 61 and the columnar portion 51 corresponds to the thickness of the annular wall portion 71b of the intermediate body 71, which will be described later, and thus to the radial dimension of the rod portion 8. As shown in FIG. The stopper portion 62 regulates the pushing amount of the punch 50 by contacting the tapered portion 52 when the punch 50 is pushed. The pushing amount of the punch 50 is set according to the thickness of the bottom plate portion 71a of the intermediate body 71, which will be described later.

First, a conductive solid columnar material block 70 is set in the housing recess 61 of the die 60 . As shown in FIGS. 9B and 9C, the material lump 70 has a solid columnar shape. The material lump 70 in this embodiment is made of the same material as the material lump 40 in the first embodiment.

As shown in FIG. 9A, the operator sets the material block 70 in the housing recess 61 of the die 60 and then inserts the punch 50 into the die 60 . Then, the operator moves the punch 50 to press the material block 40 as indicated by an arrow 15f shown in FIG. 9(D). As a result, the material block 70 is spread in a direction opposite to the pressing direction of the punch 50 and flows into the space formed between the punch 50 and the die 60 in the housing recess 61 . As a result, the material mass 70 gradually changes its shape and finally changes into an intermediate body 71 as shown in FIGS. 9(E) and 9(F).

The intermediate body 71 has a cup shape, and includes a bottom plate portion 71a and an annular wall portion 71b extending from an edge portion of the bottom plate portion 71a.
<Punching process>
Next, the punching process will be described with reference to FIGS. 10(A) to 10(E). The punching step is a step of punching a punched piece 71 a 1 from the bottom plate portion 71 a of the intermediate body 71 to form the first short-circuit ring 6 . First, an operator approaches the bottom plate portion 71a with the punch 80 arranged so as to face the bottom plate portion 71a, as indicated by an arrow 15g shown in FIG. 10(A). Then, the operator presses the punch 80 against the bottom plate portion 71a as indicated by an arrow 15h in FIG. 10(B) to punch out the punching piece 71a1. Thereby, the opening 71a2 is formed, and the ring-shaped first short-circuit ring 6 is formed. By punching out the punched piece 71a1 in a punching process, the first short-circuit ring 6 is formed with a flange 6a. It may be left as it is. The second embodiment differs from the first embodiment in that the brim portion 6a is formed.

In addition, in the present embodiment, punching is used to process the bottom plate portion 71a, but a processing method such as cutting or cutting may be used.

<Machining process>
Next, the machining process will be explained. The machining step is a step of forming the bar-shaped portion 8 by processing the annular wall portion 71b of the intermediate body 71 into a comb-teeth shape. Referring to FIGS. 11A and 11B, the removed portion 71b1 set adjacent to the portion formed as the rod-shaped portion 8 is shaded. In this embodiment, the removed portion 71b1 is cut and removed by a cutting tool 81 shown in FIG. 11(B). As a result, a state in which the first short-circuit ring 6 and the rod-like portion 8 are provided as shown in FIGS. 10(D) and 10(E) can be achieved. That is, by applying machining, in the first embodiment, a state equivalent to the states shown in FIGS. 3(H) and 3(I) can be realized.

In this embodiment, cutting is used as machining, but other conventionally known processing methods such as punching and cutting may be used. Also, in the present embodiment, the machining process is performed after the punching process, but the order of these processes may be changed, or both processes may be performed at the same time.

<Insertion process>
After the stamping and machining steps, the operator performs the inserting step. Since the inserting process is the same as in the first embodiment, detailed description thereof will be omitted here.

<Short-circuit ring forming step>
After the inserting step, the operator performs the short-circuit ring forming step. Since the short-circuit ring forming step is the same as in the first embodiment, detailed description thereof will be omitted here.

Even in the manufacturing method of the second embodiment, since the first short-circuit ring 6 and the rod-shaped portion 8 are formed by extrusion molding, for example, unlike the case where they are formed by casting, no blowholes are generated. . As a result, heat generation during operation of the squirrel cage induction motor 1 is suppressed.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. 12(A) and 12(B). The manufacturing method of the third embodiment differs from the first and second embodiments in the step of forming a short-circuit ring.

In the first embodiment and the second embodiment, the second short-circuit ring 7 is formed by bending the free end portion 8b of the rod-shaped portion 8 . On the other hand, the rotor 90 manufactured by the manufacturing method of the third embodiment includes a second short-circuit ring 91 made of a conductive plate, which is a copper plate in this embodiment. The second short-circuit ring 91 is formed by placing a copper plate in contact with the free end portion 8b of the rod-shaped portion 8 protruding from the rotor core 5 and welding the contact portion.

Even in such a rotor 90, the first short-circuit ring 6 and the rod-shaped portion 8 are formed through steps similar to those in the first and second embodiments. Therefore, since the first short-circuit ring 6 and the rod-like portion 8 are formed by extrusion molding, blow holes are not generated unlike, for example, the case where they are formed by casting. As a result, heat generation during operation of the squirrel cage induction motor 1 is suppressed.

The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited to these. Various modifications of these examples are within the scope of the present invention, and furthermore, the present invention can be modified. It is self-evident from the above description that many other embodiments are possible within the scope.

Reference Signs List 1 squirrel cage induction motor 2 case 3 stator 4 rotor 5 rotor core 5a magnetic steel plate 5a1 first insertion hole 5a2 second insertion hole 6 first short-circuit ring 6a flange 7 second short-circuit ring 8 rod-shaped portion 8a connected Part 8b Free end 9 Rotating shaft member 10a First bearing member 10b Second bearing member 20, 50 Punch 21 Guide part 22 Stepped part 23 Protruding part 24 Grooved part 30, 60 Die 31 First storage recess 32 Second storage Concave portions 40, 70 material block 51 cylindrical portion 52 tapered portion 61 storage concave portion 62 stopper portion 71 intermediate body 71a bottom plate portion 71a1 punched piece 71a2 opening portion 71b annular wall portion 71b1 removed portion 80 punch punch 81 cutting tool

Claims (7)

a first short-circuit ring disposed on one end side in a direction along the rotation axis of the rotor core; a second short-circuit ring disposed facing the first short-circuit ring across the rotor core; and the rotor. a plurality of rod-shaped portions that are inserted through an iron core and connect the first short-circuit ring and the second short-circuit ring, the method comprising:
a forming step of pressing a conductive mass of material to form the first short-circuit ring and the rod-shaped portion extending from the first short-circuit ring;
an inserting step of inserting the rotor core into the rod-shaped portion from the free end side of the rod-shaped portion;
a processing step of providing the second short-circuit ring at the free end portion of the rod-shaped portion after the rotor core is inserted;
including,
A rotor manufacturing method. The molding step includes
The first short-circuit ring and the rod-shaped portion are formed by pressing a side wall of a cylindrical material mass having conductivity,
A method for manufacturing a rotor according to claim 1 . The molding step includes
a first step of pressing a conductive solid columnar mass of material to form an intermediate body having a bottom plate portion and an annular wall portion;
a second step of removing the bottom plate portion to form the first short-circuit ring;
2. The method of manufacturing a rotor according to claim 1, further comprising: a third step of processing the annular wall portion into a comb shape to form the rod-like portion. The third step is
removing the removal portion set adjacent to the portion formed as the rod-shaped portion;
A method for manufacturing a rotor according to claim 3. The removed portion is removed by cutting with a cutting tool.
A method for manufacturing a rotor according to claim 4. The processing step includes
The free end protruding from the rotor iron core is bent in the circumferential direction, and the second short-circuit ring is provided with the free ends adjacent in the circumferential direction being in contact with each other.
A method for manufacturing a rotor according to claim 1 . The processing step includes
A conductive plate is placed in contact with the free end protruding from the rotor iron core, and a contact portion between the free end and the plate is welded.
A method for manufacturing a rotor according to claim 1 .

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