JP2017118772A - Motor, and manufacturing method of rotor constituting motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor which prevents a plastic magnet from being divided, by forming an assembly of a yoke and the plastic magnet by molding the plastic magnet on an outer diameter surface of the yoke using the same metal mold even in the case where a shaft specification such as a shaft length or a coupling position is changed, and a manufacturing method of a rotor constituting the motor.SOLUTION: The motor comprises a stator that is formed from a stator yoke and a coil, and a rotor 20 that is disposed at an inner diameter side of the stator. The rotor 20 includes: a yoke 22 which is formed from a material having magnetism; a plastic magnet 23 which is disposed on an outer diameter surface of the yoke 22, uses PPS as a binder and contains a neodymium powder; and a shaft 21 that is fitted to a center of the yoke 22.SELECTED DRAWING: Figure 3

Description

* This invention relates to the manufacturing method of the rotor which comprises a motor and a motor.

  Conventionally, a general rotor and shaft fitting of a brushless motor is firmly joined to the shaft by heating the rotor yoke at a high temperature and fitting the shaft to the expanded portion to cool the rotor yoke. The manufacturing method is taken. Further, the shaft fitting of the yoke was formed to be slightly smaller than the diameter of the shaft to be used, and was firmly joined by press fitting.

  However, in these structures, since the yoke is heated at a high temperature, it is impossible to fit a magnet, particularly a plastic magnet by injection molding, to the outer periphery of the rotor before fitting to the shaft. Even in the case of press-fitting, since there is a concern about deformation of the yoke and shaft, a magnet is formed on the outer periphery of the rotor by assembling the yoke and shaft after injection. Therefore, even if the yoke and the magnet are the same, if the length of the shaft and the position where the yoke is fixed are different, an injection mold suitable for the model has been required.

  In Patent Document 1, since a low thermal expansion alloy is used for the yoke, in the method of heating the yoke as described above, the shaft fitting portion does not expand and fitting by heat cannot be employed. For this reason, the shaft is cooled to reduce the diameter and then fitted to the yoke. The magnet used in Patent Document 1 is an NdFeB magnet, which is a sintered magnet. Therefore, the magnet and the yoke are joined by adhesion. When the material of the yoke of Patent Document 1 is adopted for a plastic magnet as in the present application, the difference in thermal expansion coefficient between the magnet and the yoke is further generated, which may lead to breakage of the magnet.

JP-A-6-261477

  In view of the above-mentioned problems, the present invention forms an assembly of a yoke and a plastic magnet by molding a plastic magnet on the outer diameter surface of the yoke with the same mold even if the shaft specifications such as the shaft length and the fastening position change. And it aims at providing the manufacturing method of the rotor which comprises a motor and a motor which does not raise | generate a plastic magnet crack.

The present invention is grasped by the following composition in order to achieve the above-mentioned object.
(1) A first aspect of the present invention is a motor, comprising a stator formed by a stator yoke and windings, and a rotor disposed on an inner diameter side of the stator, wherein the rotor is magnetic. A yoke formed of a material having a plastic magnet having a neodymium powder disposed on an outer diameter surface of the yoke and having PPS as a binder, and a shaft fitted in the center of the yoke. .

(2) In the configuration of (1) above, the material of the yoke may include stainless steel.

(3) A second aspect of the present invention is a method for manufacturing a rotor constituting a motor, the method comprising: (a) forming a hole having a diameter smaller than the diameter of the shaft at the center of the yoke; A step (b) of joining a plastic magnet to the radial surface by injection molding to form an assembly of the yoke and the plastic magnet; and a step of cooling the shaft and fitting it into the hole of the yoke (c) And.

  According to the present invention, even if the shaft specifications such as the shaft length and the fastening position are changed, the plastic magnet is molded on the outer diameter surface of the yoke with the same mold to form the assembly of the yoke and the plastic magnet. It is possible to provide a motor and a method of manufacturing a rotor constituting the motor that do not cause magnet breakage.

It is a perspective view which shows the yoke which concerns on embodiment of this invention. It is a perspective view which shows the state which couple | bonded the magnet with the outer diameter surface of the yoke which concerns on embodiment of this invention. 1 is a perspective view showing a rotor according to an embodiment of the present invention, in which a shaft is fitted to a yoke and magnet assembly.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the accompanying drawings. Note that the same number is assigned to the same element throughout the description of the embodiment.

<Motor>
First, the configuration of the motor according to the present embodiment will be described. Note that the motor in this embodiment is a brushless motor.

  The motor includes a motor housing that forms the outer periphery of the motor, a stator that is fixed to the inner wall of the motor housing, formed by a stator yoke and a winding, and a bearing that is disposed on the inner diameter side of the stator and is fixed to the motor housing. And a rotor 20 that is pivotally supported. As shown in FIGS. 1 to 3, the rotor 20 includes an assembly 25 of a yoke 22 and a plastic magnet 23. The assembly 25 of the yoke 22 and the plastic magnet 23 includes a yoke 22 and a plastic magnet 23 which is disposed on the outer diameter surface of the yoke 22 and uses PPS as a binder and neodymium powder. The plastic magnet 23 is disposed on the outer diameter surface of the yoke 22 by injection molding. The shaft 21 is inserted through a hole 24 provided in the center of the yoke 22.

<Shaft>
The shaft 21 is made of a general stainless alloy.

<York>
The yoke 22 may be a generally used laminated yoke made of a silicon steel plate or soft iron made of a magnetic material. In this embodiment, magnetic stainless steel is used. The outer diameter surface of the yoke 22 may be devised to prevent cracking due to the difference in thermal shrinkage of the plastic magnet 23 or to prevent axial displacement due to high-speed rotation. In the present embodiment, grooves are formed at equal intervals in the outer peripheral axis direction of the yoke 22.

<Plastic magnet>
As the plastic magnet 23, a neodymium magnet using PPS as a binder is used. By using PPS as a binder, the shape can be stabilized even when the plastic magnet 23 reaches a high temperature.

<Assembly of yoke and plastic magnet>
The assembly 25 of the yoke 22 and the plastic magnet 23 is obtained by integrally molding the yoke 22 alone and the plastic magnet 23 with a mold. In the present embodiment, the plastic magnet 23 has the yoke 22 set in a mold and is insert-molded on the outer diameter surface thereof to form an assembly 25 of the yoke 22 and the plastic magnet 23. Here, by using PPS as a binder for the material of the plastic magnet 23, bonding with an adhesive is weakened, and therefore, integral molding by insert molding is preferable as described above.

<Rotor>
The rotor 20 is obtained by fitting the shaft 21 whose diameter has been reduced by cooling into the shaft mounting hole 24 of the yoke 22 (cooling swallow method). The hole 24 of the yoke 22 is formed to be slightly smaller than the diameter of the shaft 21 at normal temperature. When the shaft 21 returns to normal temperature, the diameter of the shaft 21 also returns to its original value and is firmly fastened to the yoke 22.

<Method for manufacturing rotor>
Next, the manufacturing method of the rotor which comprises the motor which concerns on this embodiment is demonstrated.

  In this embodiment, the yoke 22 alone and the plastic magnet 23 are integrally molded with a mold, and the shaft 21 is fixed to the cooled shaft 21 by assembling the yoke 22 and the plastic magnet 23 on which the plastic magnet 23 is formed. This is carried out by a cooling swallow method, which is inserted into the hole 24 of the yoke 22 and fixed. Each will be described below.

<Manufacture of shaft>
The shaft 21 is formed of a general stainless alloy. The fastening surface of the shaft 21 with the yoke 22 may be subjected to treatment such as knurling in order to further tighten the fastening.

<Manufacture of yokes and plastic magnets>
In the process of this embodiment, a hole 24 having a diameter smaller than the diameter of the shaft 21 is formed at the center of the yoke 22 (step (a)), the yoke 22 is set in a mold, and a plastic magnet 23 is formed on the outer diameter surface thereof. Are molded by insert molding by injection molding to form an assembly 25 of the yoke 22 and the plastic magnet 23 (step (b)).

<Fitting the shaft to the yoke>
Thereafter, the shaft 21 is cooled, and when it has a diameter smaller than the diameter of the hole 24 of the yoke 22, it is fitted into the shaft mounting hole 24 of the yoke 22 (step (c)). When the shaft 21 returns to room temperature by this process, the yoke 22 is firmly fastened.

<Effect of embodiment>
Even if the length of the shaft 21 and the fastening position change, if the dimensions of the yoke 22 do not change, the plastic magnet 23 can be fitted to the outer diameter surface of the yoke 22 and assembled with the shaft 21 with the same mold. become.

  Although the embodiments have been described above, the present invention is not limited to the specific embodiments and includes various modifications, which are claimed by those skilled in the art. It is clear from the description of the range.

DESCRIPTION OF SYMBOLS 1 ... Motor 10 ... Stator 20 ... Rotor 21 ... Shaft 22 ... Yoke 23 ... Plastic magnet 24 ... Hole 25 ... Assembly (of yoke 22 and plastic magnet 23)

Claims (3)

A motor,
A stator formed by a stator yoke and windings;
A rotor disposed on the inner diameter side of the stator,
The rotor is
A yoke formed of a magnetic material;
A plastic magnet disposed on the outer diameter surface of the yoke, having PPS as a binder, and having a neodymium powder;
And a shaft fitted in the center of the yoke.   The motor according to claim 1, wherein the material of the yoke includes stainless steel. A method of manufacturing a rotor constituting a motor,
Forming a hole having a diameter smaller than the diameter of the shaft in the center of the yoke (a);
A step (b) of forming an assembly of the yoke and the plastic magnet by bonding a plastic magnet to the outer diameter surface of the yoke by injection molding;
Cooling the shaft and fitting it into the hole of the yoke.

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