JP2014236572A - Method for manufacturing rotor for inductive rotating electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rotor for an inductive rotating electric machine capable of efficiently performing shrink fitting using heat of molten metal in a casting step in a shrink fitting step.SOLUTION: A method for manufacturing a rotor for an inductive rotating electric machine 1 performs a casting step and a shrink fitting step. The casting step casts molten metal for forming a conductor 31 into a plurality of slots 22 in a rotor core 2 formed by laminating a magnetic steel sheet 20. The shrink fitting step assembles a shaft 4 having a larger outer diameter than an inner diameter of a central hole 21 of the rotor core 2 into the central hole 21 of the rotor core 21. When the rotor core 2 is heated by the casting step, the inner diameter of the central hole 21 of the rotor core 2 becomes larger than the outer diameter of the shaft 4. The shrink fitting step inserts the shaft 4 into the central hole 21 and cools the rotor core 2 in a state in which the inner diameter of the central hole 21 is larger than the outer diameter of the shaft 4.

Description

  The present invention relates to a method for manufacturing a rotor for an induction rotating electrical machine formed by providing a conductor on a rotor core.

In manufacturing a rotor (rotor) of a rotating electric machine such as an induction motor, a shaft (rotating shaft) is attached, a conductor material is cast into a through hole of a rotor core, and the like.
For example, in the rotor for electric motors of Patent Document 1, a rotor conductor that penetrates a laminated rotor core and an end ring that connects end portions of the rotor conductor are integrally formed by aluminum die casting. In this rotor for electric motors, a cylindrical sleeve is inserted into the inner wall of the rotor core by shrink fitting or press fitting before aluminum die casting.

JP-A-6-253512

  However, the electric motor rotor of Patent Document 1 requires a large heat source when the cylindrical sleeve is inserted into the inner wall of the rotor core by shrink fitting. Further, when a cylindrical sleeve is inserted into the inner wall of the rotor core by press-fitting, a large amount of power is required to perform the press-fitting.

  The present invention has been made in view of such a background, and provides a method for manufacturing a rotor for an induction rotating electrical machine capable of efficiently performing shrink fitting by using the heat of a molten metal in a casting process in a shrink fitting process. It was obtained as.

One aspect of the present invention is a casting process in which molten metal for forming a plurality of conductors is cast into a plurality of slots in a rotor core formed by laminating electromagnetic steel sheets,
When a shaft having an outer diameter larger than the inner diameter of the center hole is assembled to the center hole of the rotor core, the inner diameter of the center hole of the rotor core becomes larger than the outer diameter of the shaft by being heated in the casting process. And a shrink-fitting step of cooling the rotor core after inserting the shaft into the center hole.

In the method for manufacturing a rotor for an induction rotating electrical machine, the heat stored in the rotor core from the molten metal in the casting process is used when the shaft is assembled to the rotor core in the shrink fitting process.
Specifically, in the casting process, when casting molten metal into a plurality of slots in the rotor core, the rotor core is heated by the heat of the molten metal. At this time, the rotor core expands and the center hole of the rotor core becomes larger.

  Next, in the shrink fitting process, a shaft having an outer diameter larger than the inner diameter of the center hole is assembled to the center hole of the rotor core. At this time, because the rotor core is heated in the casting process, the inner diameter of the central hole of the rotor core is larger than the outer diameter of the shaft. Therefore, the shaft can be easily inserted into the center hole of the rotor core. Thereafter, when the rotor core is cooled, the rotor core contracts and the shaft can be shrink-fitted into the center hole of the rotor core.

  Thus, according to the method for manufacturing a rotor for an induction rotating electric machine, the heat of the molten metal in the casting process can be used for the shrink fitting process to efficiently perform the shrink fitting.

Sectional explanatory drawing which shows the die-cast apparatus before casting a molten metal in the casting process concerning Example 1. FIG. Sectional explanatory drawing which shows the die-casting apparatus of the state which poured the molten metal in the casting process concerning Example 1. FIG. Sectional explanatory drawing which shows the die-casting apparatus of the state which casts the molten metal in each cavity in the casting process concerning Example 1. FIG. Sectional explanatory drawing which shows the die-cast apparatus of the state which raised the other shaping | molding die from one shaping | molding die after casting in the casting process concerning Example 1. FIG. Sectional explanatory drawing which shows the die-cast apparatus of the state which extracts a rotor core and a die-cast molded object from the other shaping | molding die in the casting process concerning Example 1. FIG. The top view which shows the rotor core and die-cast molded object concerning Example 1 in the state seen from the axial direction one side of the rotor core. Sectional explanatory drawing which shows the support jig of the state before inserting a shaft in the center hole of a rotor core in the shrink fitting process concerning Example 1. FIG. Sectional explanatory drawing which shows the support jig of the state which inserted the shaft in the center hole of the rotor core in the shrink fitting process concerning Example 1. FIG. Sectional explanatory drawing which shows the state which cuts the unnecessary part in a die-cast molded object with the cutting blade of a cutting jig in the cutting process concerning Example 1. FIG. FIG. 3 is an explanatory diagram illustrating the rotor according to the first embodiment. Sectional explanatory drawing which shows the state which inserts a shaft in the center hole of a rotor core using the support jig | tool which has an induction heating coil in the shrink fitting process concerning Example 2. FIG.

A preferred embodiment of the above-described method for manufacturing a rotor for an induction rotating electrical machine will be described.
In the method for manufacturing a rotor for an induction rotating electric machine, in the shrink fitting process, only the heat of the molten metal in the casting process is used, and the shaft can be shrink fitted in the center hole of the rotor core without further heating. . Further, in the shrink fitting process, the heat of the molten metal in the casting process can be used, and the rotor core can be further heated by another heating source to shrink the shaft in the center hole of the rotor core.

In the casting process, the molten metal forms annular end plates connected to both axial end portions of the plurality of conductors on the outer sides of the axial end surfaces of the rotor core, and the shaft of the rotor core. An unnecessary part connected to the end plate on one side in the direction may be formed, and after performing the shrink fitting process, an excision process of excising the unnecessary part may be performed. In the shrink fitting process, the shaft may be inserted from the other axial side of the center hole of the rotor core.
The portion on one side in the axial direction of the rotor core where the unnecessary portion is formed is formed by connecting the unnecessary portion to the end plate over the circumference. Therefore, the portion on one side in the axial direction of the rotor core is affected by thermal contraction when the unnecessary portion is cooled, and the inner diameter of the center hole becomes smaller than the portion on the other side in the axial direction of the rotor core. Therefore, the shaft can be easily inserted into the center hole of the rotor core by inserting the shaft from the other axial side of the rotor core having a relatively large inner diameter of the center hole.

Further, in the shrink fitting process, the shaft supported and fixed to a jig is inserted into the center hole of the rotor core, and in the cutting process, the shaft inserted into the center hole of the rotor core is inserted into the jig. The unnecessary portion may be excised while being supported and fixed.
In this case, the jig used to support and fix the shaft used in the shrink fitting process can also be used in the cutting process. Therefore, it is not necessary to prepare a jig separately in the excision process, and it is possible to eliminate the need to change the stage in the excision process.

Hereinafter, embodiments of a method for manufacturing a rotor for an induction rotating electrical machine will be described with reference to the drawings.
Example 1
In the manufacturing method of the rotor 1 for induction rotating electrical machines of this example, a casting process and a shrink fitting process are performed. In the casting process, as shown in FIGS. 1 to 3, molten metal 30 for forming conductors 31 is cast into a plurality of slots 22 in the rotor core 2 formed by laminating electromagnetic steel plates 20. In the shrink fitting process, as shown in FIGS. 6 and 7, the shaft 4 having an outer diameter larger than the inner diameter of the center hole 21 is assembled to the center hole 21 of the rotor core 2. At that time, the shaft 4 is inserted into the center hole 21 in a state where the inner diameter of the center hole 21 of the rotor core 2 is larger than the outer diameter of the shaft 4 by heating in the casting process, and then the rotor core 2 is cooled. .

Below, it demonstrates in full detail with reference to FIGS. 1-10 about the manufacturing method of the rotor 1 for induction rotating electrical machines of this example.
As shown in FIG. 1, in the casting process, a die casting apparatus 5 having one mold 51 for sandwiching the rotor core 2 from one side 201 in the axial direction and the other mold 52 for sandwiching the rotor core 2 from the other side 202 in the axial direction. Use. One mold 51 is provided with a casting port 511, a plunger 512 that can be moved forward and backward with respect to the casting port 511, a positioning pin 513 that is inserted into the center hole 21 of the rotor core 2, and the like. The other mold 52 is provided with an ejector 521 for extruding the die cast molded body 300 integrated with the rotor core 2. The ejector 521 is provided on the eject base 522 and can advance and retreat.
A runner 53 that is a path from the casting port 511 to the gate 531 is formed at a position where one mold 51 and the other mold 52 face each other. A first cavity 54 </ b> A in which the rotor core 2 is disposed is formed from the runner 53 toward the other mold 52.

  FIG. 10 shows the rotor 1 with the shaft 4 assembled thereto. As shown in the figure, end plates 32 formed in an annular shape are formed on the outer sides of both end surfaces in the axial direction of the rotor core 2 so as to be connected to the conductors 31 filled in the slots 22. As shown in FIG. 1, the one mold 51 is provided with a second cavity 54B for forming the end plate 32 on one axial side 201 with respect to the first cavity 54A. The runner 53 and the second cavity 54 </ b> B are connected by a gate 531 located at the most downstream end of the runner 53. The gate 531 is formed on substantially the entire circumference in the circumferential direction of the second cavity 54B. The other mold 52 is provided with a third cavity 54C for forming the end plate 32 on the other axial side 202 with respect to the first cavity 54A.

As shown in FIG. 10, the rotor 1 is formed by providing a cage-type conductor portion 3 in which end plates 32 at both axial ends are connected to a rotor core 2 by a plurality of conductors 31. The plurality of slots 22 in the rotor core 2 are formed by twisting around the center of the rotor core 2, and the plurality of conductors 31 are formed along the twist of the slot 22. In FIG. 1 to FIG. 9, the slot 22 is simply shown in a state parallel to the central axis of the rotor core 2.
In the die-casting device 5, each of the conductors 31 filled in the slots 22 by the molten metal 30 and an annular end connected to both axial end portions of the plurality of conductors 31 on the outer side of both axial end surfaces of the rotor core 2. A pair of plates 32 are formed.

  As shown in FIGS. 2 and 3, the die casting apparatus 5 has a structure in which the molten metal 30 is pressed between one mold 51 and the other mold 52. In the die casting apparatus 5, the molten metal 30 cast from the casting port 511 passes through the runner 53 and the gate 531 to the second cavity 54B, the plurality of slots 22 of the rotor core 2 in the first cavity 54A, and the third cavity 54C. And filled. The cage conductor 3 is formed by the molten metal 30 in each of the cavities 54A, 54B, 54C.

The other mold 52 has a presser for pressing the rotor core 2 in the first cavity 54 </ b> A against the positioning pin 513 in the one mold 51 when the other mold 52 is closed by the one mold 51. A portion 523 is formed. The positioning pin 513 is formed such that the tip side portion inserted into the first cavity 54 </ b> A of the other mold 52 is reduced in diameter via the step portion 514. When the one mold 51 and the other mold 52 are closed, the rotor core 2 is sandwiched between the pressing portion 523 and the step portion 514.
Further, as shown in FIG. 6, in one molding die 51, a hot water pool for allowing molten metal to flow from the gate 531 into the second cavity 54B substantially simultaneously around the second cavity 54B for molding the end plate 32. A portion 55 is formed. The hot water reservoir 55 is formed so as to be connected to the runner 53.

As shown in FIGS. 3 and 4, the molten metal 30 of this example is aluminum (including an aluminum alloy). In the casting process, the molten metal 30 left in the runner 53 is formed as an unnecessary portion 33 connected to the end plate 32 facing the end surface on the one axial side 201 of the rotor core 2. The unnecessary portion 33 is formed as an unnecessary portion with respect to the plurality of conductors 31 and the pair of end plates 32 which are the cage conductor portions 3 as the product portion.
As shown in FIG. 5, in the shrink-fitting process, the rotor core 2 after the conductor 31 and the end plate 32 are die-cast is taken out from the die casting device 5, and the center hole 21 of the rotor core 2 is taken as shown in FIGS. The shaft 4 is inserted from the other axial side 202. The shaft 4 is a portion that becomes a central axis portion when the rotor 1 rotates. The shaft 4 is formed in a hollow shape having a shaft center hole 41.

As shown in FIG. 7, in the shrink fitting process, a support jig 6 for supporting and fixing the shaft 4 is used. The support jig 6 is provided with a holding portion 61 for holding the shaft 4 and a guide 62 for guiding the rotor core 2 to be disposed on the support jig 6. The support jig 6 is configured to support the shaft 4 upward.
In the shrink fitting process, the shaft 4 supported and fixed to the support jig 6 is inserted into the center hole 21 of the rotor core 2. At this time, the shaft 4 is inserted into the center hole 21 of the rotor core 2 by lowering the rotor core 2 with respect to the shaft 4 standing upward from the support jig 6. Further, as shown in FIG. 8, in the shrink fitting process, the unnecessary portion 33 due to the molten metal 30 formed on the runner 53 is connected to the cage-shaped conductor portion 3 while being connected to the central hole 21 of the rotor core 2. The shaft 4 is shrink-fitted.

As shown in FIG. 9, in the manufacturing method of this example, after performing the shrink fitting process, as an excision process, the unnecessary portion 33 formed connected to the cage conductor 3 is excised. The unnecessary portion 33 in this example is a molded product formed in the runner 53 from the casting port 511 to the gate 531 connected to the end plate 32 on the one axial side 201.
In the cutting step, the shaft 4 inserted into the center hole 21 of the rotor core 2 is maintained and fixed to the support jig 6 and the unnecessary portion 33 is cut off.

In the excision process, the excision jig 7 provided with an excision blade 71 for excising the unnecessary portion 33 and a guide shaft 72 inserted into the shaft center hole 41 is used. The cutting blade 71 and the guide shaft 72 are provided to hang downward from the base portion 70 of the cutting jig 7. In addition, the cutting blade 71 is provided in the base portion 70 so as to face the formation position of the gate 531 between the runner 53 and the second cavity 54B.
In a state where the rotor core 2 is supported and fixed to the support jig 6, the excision jig 7 is lowered with respect to the shaft 4 standing upward from the support jig 6, whereby the guide shaft is inserted into the shaft center hole 41 of the shaft 4. 72 is inserted.

  As shown in FIGS. 6 and 9, when the guide shaft 72 is inserted into the shaft center hole 41, the cutting blade 71 is a part of the unnecessary portion 33 formed on the gate 531 when the molten metal 30 is cast. A certain molded product 331 is contacted, and the molded product 331 is cut. Thus, in the state where the guide shaft 72 is inserted into the shaft center hole 41, the unnecessary portion 33 unnecessary for the cage-type conductor portion 3 which is a product portion is cut by the cutting blade 71.

Next, the manufacturing method and effects of this example will be described.
In the manufacturing method of this example, the heat stored in the rotor core 2 from the molten metal 30 in the casting process is used when the shaft 4 is assembled to the rotor core 2 in the shrink fitting process.
Specifically, first, as shown in FIG. 1, the rotor core 2 is arranged on the positioning pins 513 in one mold 51 in the casting process. In the die casting apparatus 5, one mold 51 is disposed on the lower side, and the other mold 52 is disposed above the one mold 51.

  Next, as shown in FIG. 2, the molten metal 30 is poured into the casting port 511 of the one mold 51 with the plunger 512 lowered. Next, the other mold 52 is lowered with respect to the one mold 51, the one mold 51 and the other mold 52 are closed, and a pressure is applied between the one mold 51 and the other mold 52. Add At this time, the rotor core 2 is inserted into the first cavity 54A, and the rotor core 2 is sandwiched between the pressing portion 523 and the step portion 514.

  Next, as shown in FIG. 3, the plunger 512 is advanced to push the molten metal 30 toward the runner 53 and the cavities 54A, 54B, 54C. At this time, the molten metal 30 flows from the runner 53 to the hot water reservoir 55, and flows from the hot water reservoir 55 to the second cavity 54 </ b> B via the gate 531. The molten metal 30 is temporarily stored in the hot water reservoir 55 and then flows to the gate 531, so that the molten metal 30 can flow into the second cavity 54 </ b> B simultaneously from substantially the entire circumference of the gate 531. Further, the molten metal 30 flows from the second cavity 54B to the first cavity 54A and the third cavity 54C.

  The molten metal 30 in each of the cavities 54A, 54B, 54C is cooled by the coolant flowing in the cooling pipe formed in the other mold 52, and the plunger 512 is retracted after a few seconds. Next, as shown in FIG. 4, the other mold 52 is raised from one mold 51, and the rotor core 2 held by the other mold 52 is extracted from the positioning pins 513. At this time, the die-cast molded body 300 as the cage-shaped conductor portion 3 and the unnecessary portion 33 rises together with the other molding die 52 in a state of being integrated with the rotor core 2.

  When casting the molten metal 30 into the plurality of slots 22 in the rotor core 2, the rotor core 2 is heated by the heat of the molten metal 30. When the other mold 52 is lifted from one mold 51, the rotor core 2 is in an expanded state by the heat of the molten metal 30, and the center hole 21 of the rotor core 2 is larger than the specified dimension.

Next, as shown in FIG. 5, the other mold 52 holding the rotor core 2 and the die cast molded body 300 is moved from above with respect to the one mold 51. Then, the ejector 521 in the other mold 52 is operated to extract the rotor core 2 and the die-cast molded body 300 from the first cavity 54A and the third cavity 54C.
Next, as shown in FIGS. 7 and 8, in the shrink-fitting process, the rotor core 2 integrated with the die-cast molded body 300 is lowered with respect to the shaft 4 rising upward from the support jig 6, and the rotor core 2. The shaft 4 having an outer diameter larger than the inner diameter of the center hole 21 is assembled to the center hole 21. At this time, the rotor core 2 integrated with the die-cast molded body 300 is turned upside down, and the shaft 4 is inserted from the other axial side 202 of the center hole 21 of the rotor core 2.

  And the unnecessary part 33 shape | molded by the gate 531 and the hot water sump part 55 is connected with the end plate 32 in the circumferential shape in the part of the axial direction one side 201 of the rotor core 2 in which the unnecessary part 33 is formed. Part. Therefore, the portion on the one axial side 201 of the rotor core 2 is affected by thermal contraction when the unnecessary portion 33 is cooled, and the inner diameter of the center hole 21 is larger than the portion on the other axial side 202 of the rotor core 2. Get smaller. Therefore, the shaft 4 can be easily inserted into the center hole 21 of the rotor core 2 by inserting the shaft 4 from the other axial side 202 of the rotor core 2 having a relatively large inner diameter of the center hole 21.

In addition, the gate 531 and the hot water reservoir 55 can be formed in the axial direction with respect to the second cavity 54B in which the end plate 32 is formed. In this case, it is possible to obtain the same effect as when the gate 531 and the hot water reservoir 55 are formed on the outer peripheral side with respect to the second cavity 54B.
The mechanism by which the portion of the rotor core 2 on one side 201 in the axial direction contracts is as follows. That is, when the diameter of the gate 531 is reduced, the end plate 32 is reduced in diameter, and the relative positions of the plurality of conductors 31 connected to the end plate 32 are moved in the diameter reduction direction, so that the rotor core 2 is deformed to be reduced in diameter.

Further, when the shaft 4 is assembled to the center hole 21 of the rotor core 2, the inner diameter of the center hole 21 of the rotor core 2 is larger than the outer diameter of the shaft 4 because the rotor core 2 is heated by the molten metal 30. Therefore, the shaft 4 can be easily inserted into the center hole 21 of the rotor core 2.
Thereafter, when the rotor core 2 and the die-cast molded body 300 are cooled, the rotor core 2 contracts and the shaft 4 can be shrink-fitted into the center hole 21 of the rotor core 2.

  In the shrink fitting process of this example, shrink fitting is performed before the inner diameter of the center hole 21 of the rotor core 2 heated by the molten metal in the casting process returns to the original state smaller than the outer diameter of the shaft 4. In the shrink fitting process, shrink fitting is performed without further heating by the heating means. Thereby, in the shrink fitting process, the heating source for heating the rotor core 2 can be made unnecessary, and the energy efficiency in the shrink fitting process can be improved. In addition, the time required for the shrink fitting process can be shortened.

  Next, as shown in FIG. 9, in the excision process, the supporting jig 6 that supports and fixes the shaft 4 used in the shrink fitting process is also used. Then, the cutting jig 7 provided with the cutting blade 71 and the guide shaft 72 is lowered with respect to the supporting jig 6 in which the rotor core 2 is fixedly supported by the shaft 4. At this time, the guide shaft 72 in the excision jig 7 is inserted from above into the shaft center hole 41 of the shaft 4 rising upward from the support jig 6. Then, in a state where the guide shaft 72 is inserted into the shaft center hole 41, the molded product 331 that is a part of the unnecessary portion 33 formed on the gate 531 is cut by the cutting blade 71. Thus, the unnecessary portion 33 unnecessary for the cage-type conductor portion 3 is cut off, and as shown in FIG. 10, the rotor 1 in which the cage-type conductor portion 3 and the rotor core 2 are integrated can be formed.

  Thus, according to the manufacturing method of the rotor 1 for induction rotating electrical machines, the heat of the molten metal in the casting process can be used for the shrink fitting process to efficiently perform the shrink fitting. Further, the supporting jig 6 can also be used in the assembling process and the excision process, so that it is not necessary to change the jig for fixing and supporting the shaft 4 in the excision process.

(Example 2)
This example is an example in which the rotor core 2 is further heated using a heating means in the shrink fitting process.
The heating means of this example is an induction heating coil 63 that heats the rotor core 2 from the outer periphery, as shown in FIG. The induction heating coil 63 is provided above the guide 62 of the support jig 6 </ b> A, and is configured to heat almost the entire outer periphery of the rotor core 2.
In this example, the shaft 4 supported by the clamper 64 is inserted into the rotor core 2 heated by the induction heating coil 63 while being supported by the support jig 6A.

  The shrink fitting process of this example is effective in the following cases. For example, it is effective when the rotor core 2 heated by the molten metal in the casting process is cooled to some extent and the inner diameter of the central hole 21 of the rotor core 2 becomes smaller than the outer diameter of the shaft 4. Further, although the inner diameter of the center hole 21 of the rotor core 2 is larger than the outer diameter of the shaft 4, it is effective when the inner diameter is further increased to insert the shaft 4 more smoothly.

When the inner diameter of the center hole 21 of the rotor core 2 is smaller than the outer diameter of the shaft 4, the rotor core 2 is further heated by the induction heating coil 63 so that the inner diameter of the center hole 21 of the rotor core 2 becomes the shaft. The rotor core 2 can be expanded again to be larger than the outer diameter of 4. Thus, even when a certain amount of waiting time is possible after performing the casting process and before performing the shrink fitting process, the heat of the molten metal in the casting process is utilized for the shrink fitting process to perform the shrink fitting smoothly. Can do.
Also in the method for manufacturing the rotor for induction rotating electrical machine 1 of the present example, the other configurations and the reference numerals in the drawings are the same as those in the first embodiment, and the same effects as those in the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Rotor for induction rotating machines 2 Rotor core 201 One axial side 202 The other axial side 21 Center hole 22 Slot 3 Cage-type conductor part 30 Molten metal 31 Conductor 32 End plate 33 Unnecessary part 4 Shaft 41 Shaft center hole 5 Die casting apparatus 6 Supporting jig Tool 7 Cutting jig 71 Cutting blade 72 Guide shaft

Claims (4)

A casting step of casting molten metal for forming a plurality of conductors into a plurality of slots in a rotor core formed by laminating electromagnetic steel sheets;
When a shaft having an outer diameter larger than the inner diameter of the center hole is assembled to the center hole of the rotor core, the inner diameter of the center hole of the rotor core becomes larger than the outer diameter of the shaft by being heated in the casting process. And a shrink-fitting step of cooling the rotor core after that, and inserting the shaft into the center hole. In the casting process, the molten metal forms annular end plates connected to both axial ends of the plurality of conductors on the outer sides of both axial ends of the rotor core, and one axial direction of the rotor core. Form an unnecessary part connected to the end plate on the side,
The method for manufacturing a rotor for an induction rotating electrical machine according to claim 1, wherein after performing the shrink fitting process, a cutting process for cutting the unnecessary portion is performed.   The method for manufacturing a rotor for an induction rotating electrical machine according to claim 2, wherein, in the shrink fitting process, the shaft is inserted from the other axial side of the center hole of the rotor core. In the shrink fitting process, the shaft supported and fixed to the jig is inserted into the center hole of the rotor core,
4. The induction rotating electrical machine according to claim 2, wherein in the cutting step, the unnecessary portion is cut off in a state where the shaft inserted into the central hole of the rotor core is supported and fixed to the jig. Of manufacturing a rotor for an automobile.

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