US-12627205-B2 - Method for manufacturing rotor

US12627205B2US 12627205 B2US12627205 B2US 12627205B2US-12627205-B2

Abstract

A method for manufacturing a rotor includes, with a magnet accommodated in a magnet housing hole of a rotor core, causing a first die to contact a first end face of the rotor core and causing a second die to contact a second end face of the rotor core. The method also includes injecting the thermoplastic into the magnet housing hole through a passage of the second die in a state in which the first die and the second die are respectively in contact with the first end face and the second end face and the first die is heated.

Inventors

Makoto Kitahara
Masaki Sugiyama

Assignees

TOYOTA BOSHOKU KABUSHIKI KAISHA

Dates

Publication Date: 20260512
Application Date: 20240422
Priority Date: 20230425

Claims (8)

1 . A method for manufacturing a rotor, the rotor including a rotor core that includes a magnet housing hole and a magnet that is accommodated in the magnet housing hole and fixed to the rotor core with a thermoplastic, the rotor core having a first end face and a second end face, which is located on a side opposite to the first end face, the magnet housing hole opening in the first end face and the second end face, the method comprising: with the magnet accommodated in the magnet housing hole, causing a first die to contact the first end face and causing a second die to contact the second end face, the second die including a passage through which the thermoplastic flows; and injecting the thermoplastic into the magnet housing hole through the passage in a state in which the first die and the second die are respectively in contact with the first end face and the second end face and the first die is heated, wherein the first die is heated by energizing a first heater provided in the first die, and the first die is in direct contact with the first end face during the injecting of the thermoplastic into the magnet housing hole.
2 . The manufacturing method according to claim 1 , wherein the injecting the thermoplastic includes injecting the thermoplastic in a state in which the second die is heated.
3 . The manufacturing method according to claim 1 , wherein the rotor core includes stacked iron core pieces, the method further comprises, prior to injecting the thermoplastic, pressing the second end face with the second die, thereby pressing the first end face against the first die, and the injecting the thermoplastic includes injecting the thermoplastic in a state in which the first end face is pressed against the first die.
4 . The manufacturing method according to claim 3 , wherein the rotor core has a stacking height, the stacking height being a dimension from the first end face to the second end face, a length of the magnet in a stacking direction of the iron core pieces is shorter than the stacking height, and the pressing the second end face with the second die includes pressing the second end face such that a flow space in which the thermoplastic flows is created between the second die and the magnet in the stacking direction, while reducing the stacking height by causing the iron core pieces to closely contact each other in the stacking direction.
5 . The manufacturing method according to claim 1 , wherein the rotor core includes stacked iron core pieces, the iron core pieces include: first iron core pieces that include tabs that bulge on one side in a stacking direction of the iron core pieces, the first iron core pieces being stacked with the tabs being joined to each other; and a second iron core piece including a through-hole into which the tab of the first iron core piece adjacent to the second iron core piece in the stacking direction is inserted, the second iron core piece forming the first end face or the second end face, and the method further comprises, prior to injecting the thermoplastic, pressing a protruding end of the tab protruding from the through-hole, thereby crushing the tab such that the protruding end is located inside the through-hole.
6 . The manufacturing method according to claim 1 , wherein the rotor core includes stacked iron core pieces, the iron core pieces include: first iron core pieces that include tabs that bulge on one side in a stacking direction of the iron core pieces, the first iron core pieces being stacked with the tabs being joined to each other; and a second iron core piece including a through-hole into which the tab of the first iron core piece adjacent to the second iron core piece in the stacking direction is inserted, the second iron core piece forming the first end face, and the injecting the thermoplastic includes injecting the thermoplastic in a state in which a protruding end of the tab protruding from the through-hole is accommodated in an accommodating recess formed in the first die.
7 . The manufacturing method according to claim 2 , wherein the second die is heated by energizing a second heater provided in the second die.
8 . A method for manufacturing a rotor, the rotor including a rotor core that includes a magnet housing hole and a magnet that is accommodated in the magnet housing hole and fixed to the rotor core with a thermoplastic, the rotor core having a first end face and a second end face, which is located on a side opposite to the first end face, the magnet housing hole opening in the first end face and the second end face, the method comprising: with the magnet accommodated in the magnet housing hole, causing a first die to contact the first end face and causing a second die to contact the second end face, the second die including a passage through which the thermoplastic flows; and injecting the thermoplastic into the magnet housing hole through the passage in a state in which the first die and the second die are respectively in contact with the first end face and the second end face and the first die is heated, wherein the injecting the thermoplastic includes injecting the thermoplastic in a state in which the second die is heated.

Description

BACKGROUND 1. Field The present disclosure relates to a method for manufacturing a rotor. 2. Description of Related Art The rotor of a typical magnet-embedded rotor includes a rotor core having magnet housing holes, and magnets accommodated in the magnet housing holes. The magnets are fixed to the rotor core with plastic filling the magnet housing holes. The plastic for filling the magnet housing holes may be a thermosetting plastic or a thermoplastic. Thermoplastics generally have a higher viscosity when melted than thermosetting plastics. Thus, the injection pressure required when filling magnet housing holes with thermoplastic using an injection device is more likely to increase than when filling magnet housing holes with thermosetting plastic. As a result, the rotor core may be deformed by the injection pressure of the thermoplastic. Japanese Laid-Open Patent Publication No. 2015-192575 discloses a method for manufacturing a rotor that injects thermoplastic into magnet housing holes in a state in which the outer circumferential surface of a rotor core is heated using a heating die. The heating die includes slide core blocks that are slidable in the radial direction of the rotor core. Each slide core block heats the outer circumferential surface of the rotor core while pressing the outer circumferential surface of the rotor core from the radially outer side. When the rotor core is heated by the heating die, the temperature of the thermoplastic is unlikely to decrease. Thus, the magnet housing holes are filled with the thermoplastic while limiting an increase in the viscosity of the thermoplastic. This limits an increase in the injection pressure of the thermoplastic and thus limits deformation of the rotor core. The method for manufacturing a rotor disclosed in the above-described publication requires a heating die having multiple slide core blocks. This may complicate the structure of the manufacturing apparatus for manufacturing a rotor. SUMMARY This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. In one general aspect, a method for manufacturing a rotor is provided. The rotor includes a rotor core that includes a magnet housing hole and a magnet that is accommodated in the magnet housing hole and fixed to the rotor core with a thermoplastic. The rotor core has a first end face and a second end face, which is located on a side opposite to the first end face. The magnet housing hole opens in the first end face and the second end face. The method includes, with the magnet accommodated in the magnet housing hole, causing a first die to contact the first end face and causing a second die to contact the second end face, the second die including a passage through which the thermoplastic flows. The method also includes injecting the thermoplastic into the magnet housing hole through the passage in a state in which the first die and the second die are respectively in contact with the first end face and the second end face and the first die is heated. Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a rotor that is manufactured through a manufacturing method according to one embodiment. FIG. 2 is a cross-sectional view of the rotor shown in FIG. 1. FIG. 3 is a cross-sectional view illustrating an apparatus for manufacturing the rotor shown in FIG. 1. FIG. 4 is a cross-sectional view illustrating a state in which a tab is crushed. FIG. 5 is a cross-sectional view showing a state in which a rotor core is placed on a first die. FIG. 6 is a cross-sectional view illustrating a state in which a first die and a second die are clamped. FIG. 7A is a cross-sectional view illustrating a state before the rotor core is pressed by the second die. FIG. 7B is a cross-sectional view illustrating a state in which the rotor core is pressed by the second die. FIG. 8 is a cross-sectional view illustrating a state in which plastic is injected into the magnet housing holes. FIG. 9 is a cross-sectional view of a first die according to a modification. Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION This description provides a comprehensive understanding of the methods, apparatuses, and/or systems described. Modifications and equivalents of the methods, apparatuses, and/or systems described are apparent to one of ordinary skill in the art. Sequences of operations a