JPS59136054A - Specifying method of axial position of rotational shaft of rotor and apparatus for executing the same - Google Patents

Abstract

PURPOSE:To specify the axial direction of a rotational shaft so that the insertion of the shaft and the removal of a rotor from a mold are not disturbed by oppositely opening a pin point gate and through holes for inserting the shaft of the rotor at the center of an openable nonmagnetic mold provided at the hole of a cylindrical cavity. CONSTITUTION:A cavity 18 is formed via a bottom 26 and a cylindrical inner peripheral wall via a stationary side mold 25 made of a nonmagnetic material. Magnetized yokes 28 made of a ferromagnetic material having a plurality of poles at equal central angles are arranged on the raidal outer periphery of the cavity 18. A through hole 32, to which a rotational shaft 30 of a rotor is inserted, is opened at a stationary mold 24 formed with a bottom 26 in coincidence with the central axis of the cavity 18. A movable mold 40 made of a nonmagnetic material is arranged above the caivity 18, a pin point gate 44 for injecting molten mixture is opened at the center of the raised part 42 of the conical trapezoid formed in the mold 40 in coincidence to the central axis to the hole 32. Thus, the shaft 30 is forcibly axially pressed by hydraulic pressure of the mixture 54 at the time of injecting from the gate 44, and specified at the position as prescribed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for regulating the axial position of a rotor rotating shaft when manufacturing a rotor for a rotating electric machine in which the rotating shaft is integrally attached to an anisotropic cylindrical magnet, and a method for regulating the axial position of the rotating shaft. The invention relates to a device for carrying out this process.

Generally, in order to manufacture a rotor for a rotating electric machine, for example a rotor for a bicycle generator in which a rotating shaft is inserted and fixed through a cylindrical magnet, isotropic ferrite 1 to 1 such as Ba ferrite magnet powder or Sr ferrite magnet powder is used. A small amount of binder is added to the ferromagnetic powder and press-molded at a pressure of about 1 to 2 tz/c% to obtain a cylindrical molded body having a through hole in the center,
This molded body is sintered at a high temperature of 1150°C to 1250'C, and the outer periphery is polished by centerless processing to form the rotor body 1.
0, the rotary shaft 12 is inserted into the center through hole 14 of the rotor main body 10 as shown in FIG. , S poles are alternately magnetized.

However, the method for manufacturing a rotor for a rotating electric machine according to the prior art described above requires a large number of steps, and the inner diameter of the through hole 14 varies due to the thermal influence during sintering after press forming. The problem is that the centering accuracy is low and center runout is likely to occur. In addition, isotropic ferrite magnet powder is magnetized after sintering as described above, but since the arrangement of the powder particles is already fixed, the degree of orientation is increased by aligning the axis of easy magnetization of the particles with the magnetization direction. It is possible,
Therefore, there was a limit to the improvement in magnetic properties.

Therefore, the inventor of this application simplified the complicated manufacturing process and improved the centering accuracy of the rotating shaft to eliminate center runout.
In addition, we devised a method and device for manufacturing rotors for rotating electric machines with significantly improved magnetic properties, and filed a separate patent application on the same date as the present application.

The method for manufacturing a rotor for a rotating electric machine according to the above patent application includes a cylindrical cavity of a mold, in which a rotor rotation axis is aligned with the axis thereof, and a plurality of poles are equally divided from the outside in the radial direction of the cylindrical cavity. Injecting a molten mixture of ferromagnetic powder and synthetic resin into the cavity while applying a magnetic field of It is characterized by:

By the way, when manufacturing a rotor for a rotating electrical machine using the above-mentioned manufacturing method, it is necessary to set the rotor rotating shaft in a cylindrical cavity of a mold so that its axis coincides with each other. For this reason, as shown in FIG. 2, the rotor rotation shaft 12 is inserted into a through hole 20 bored in the center of the bottom of the cylindrical cavity 18 to ensure accurate centering. In order to facilitate demolding from the mold, the inner diameter of the through hole 20 is set to be slightly larger than the outer diameter of the rotating shaft, so the rotating shaft 12 slides in the through hole 20 in the axial direction. Therefore, it is difficult to control the axial position of the rotary shaft 12 so that it always faces a predetermined position in the cavity 18. In particular, in the case of a left-right open type mold in which the mold dividing plane of the injection mold is vertical, the rotary shaft 12 is inserted horizontally into the through hole 20, so the bottom end of the shaft is held by the contact plate 22. Even if it is regulated, the rotary shaft 12 tends to slide toward the top due to vibrations of the mold, and an effective countermeasure is required. In this case, in order to facilitate demolding of the rotor after injection molding and to vent air from the cavity during molding, the through hole 20 for inserting the rotating shaft has a slight annular shape relative to the rotating shaft 12 as described above. It is necessary to simultaneously satisfy both contradictory requirements: it is necessary to have a narrow gap, and it is also necessary to be regulated at a predetermined position without shifting the rotating shaft 12 in the axial direction.

The present invention has been newly proposed in response to such demands, and when injection molding a molten mixture of ferromagnetic powder and synthetic resin, a rotating shaft facing into a cylindrical cavity is An object of the present invention is to provide a method for regulating the axial direction of a rotary shaft so that the rotary shaft is always centered in a fixed position, and which does not impede the insertion of the rotary shaft into a cavity or the removal of the rotor from a mold. .

In order to achieve this object, the method for regulating the axial position of the rotor rotating shaft according to the present invention is such that the rotor rotating shaft is aligned in the cylindrical cavity of the mold and faces the radially outer side of the cylindrical cavity. When manufacturing a rotor for a rotating electric machine by injecting a molten mixture of ferromagnetic powder and synthetic resin into the cavity while applying a magnetic field of multiple poles equally divided from The molten mixture is vertically injected toward the top of the rotor rotation shaft, and the fluid pressure at the time of injection of the molten mixture presses the rotor rotation shaft in the axial direction to move it to a predetermined position in the cylindrical cavity. It is characterized by

Further, an axial position regulating device for a rotor rotating shaft according to another invention of the present application, which is suitably used to carry out the method, includes:
a mold made of a non-magnetic material defining a cylindrical cavity;
A multi-pole magnetizing yoke made of a ferromagnetic material connected to the magnetizing coil and facing the radial outer circumference of the cylindrical cavity at equal central angles; It consists of a through hole, a pin point 1-key that opens facing into the cylindrical cavity, and a mold made of a non-magnetic material that closes the opening part of the cylindrical cavity so that it can be opened and closed. The invention is characterized in that the pinpoint gate is bored in the center of the non-magnetic mold which can be freely opened and closed and faces the area, facing the through-hole.

Next, a method for regulating the axial position of a rotor rotating shaft according to the present invention and an apparatus for implementing the method will be described in detail below with reference to the accompanying drawings, citing preferred embodiments.

First, the axial position regulating device for the rotor rotating shaft shown in Fig. 3 (this is also the rotor manufacturing device for rotating electric machines itself)
In this embodiment, reference numeral 8 indicates a cylindrical cavity formed in the mold, and this cavity 18 has a bottom portion 26 and a cylindrical inner circumferential wall surface defined by a fixed mold 24 made of a non-magnetic material. has been completed. Also, A-A in Figure 3
As shown in FIG. 4, which is a line cross section, magnetizing yokes 2B made of a ferromagnetic material and having multiple poles are arranged at equal central angles on the radial outer periphery of the cavity 18, and the tips of each magnetizing yokes 28 are directly connected to each other. It faces into the cavity 18 and forms a part of the inner peripheral wall surface of the cavity 18. The magnetizing yoke 28 is composed of an even number of 4 or more poles, and has an S pole and an N pole.
The poles are arranged alternately at a predetermined central angle, and in this embodiment, the poles are arranged in a four-pole structure. Further, the magnetizing yoke 28 is connected to a magnetizing coil (not shown), and by exciting the magnetizing coil, the cylindrical cavity 1 is
A strong magnetic field will be applied during the test.

The fixed mold 24 forming the bottom part 26 of the cylindrical cavity 18 has a through hole 32 at the center of the bottom part for inserting the rotor rotation @ 30 as described later. It is perpendicularly drilled in line with the axis. In this case, the inner diameter of the through hole 32 is set in advance so that an annular gap of about 2/100 to 3/100 of the outer diameter of the rotating shaft 30 is formed, and further, the inner diameter of the through hole 32 is A large-diameter stepped hole portion 34 is integrally formed below. This is to reduce the frictional resistance that comes into contact with the rotating shaft 30 and the inner wall of the through hole 32 when the rotor is demolded after injection molding. Further, a plurality of through holes 36 are bored adjacent to the periphery of the central through hole 32 (
(FIG. 4), a knockout pin 38 is inserted into this through hole 36 so as to be able to move up and down, and can protrude into the cavity 18.

It is preferable that the abutment plate 22 is removably positioned at the externally open end of the central through-hole 32, and that the position of the rotary shaft 30 in the cavity is regulated by the abutment plate 22.

Further, a movable mold 40 made of a non-magnetic material is placed above the opening of the cylindrical cavity 18 and can freely open and close the opening.
is arranged so that it can be raised and lowered freely. A truncated conical protuberance 42 that slightly protrudes inward of the cavity is integrally formed in the portion of the movable mold 40 facing the opening of the cavity 18, and the molten mixture is injected into the center of the protrusion 42. A pinpoint gate 44 is vertically drilled.

That is, this pinpoint gate 44 has its central axis aligned with the through hole 32 for inserting the rotor rotation shaft,
They are arranged opposite to each other with a space in the cavity 18 interposed therebetween.

Furthermore, another movable mold 46 made of a non-magnetic material is arranged above the movable mold 40 so as to be movable up and down, and a boundary surface between the top of the movable mold 40 and the side movable mold 46 is ,
As shown, a runner 48 is formed and is connected to a sprue 50 and a nozzle port 52 formed in the movable mold 46. In addition, each mold 24, 40
As the non-magnetic material constituting 46 and 46, for example, austenitic stainless steel is preferably used.

Regarding the method of regulating the axial position of the rotor rotating shaft using the position regulating device according to the present invention configured as described above,
This will be explained next. First, as shown in FIG. 3, the rotary shaft 30 is inserted into a through hole 32 formed at the bottom of the cylindrical cavity 18, and the narrow center of the rotary shaft 30 is aligned with the axis of the cavity 18.

In this case, by closing the lower opening of the center through hole 32 with the contact plate 22, the lower end of the rotating shaft 30 is connected to the contact plate 22.
2 and is regulated in a predetermined position, so that the rotating shaft 3
0 is always set so as to face into the cavity 18 by a predetermined length.

By the way, the through hole 32 has a slight annular slit formed therein as described above, and the rotating shaft 30 is only loosely inserted into the through hole 32.

Therefore, due to external vibrations applied to the mold or other factors, the rotary shaft 30 may move in the axial direction as shown in FIG. If injection molding is performed with the rotary shaft 30 being shifted in the axial direction with the cavity 18 open, the rotor as a product will be rejected as a defective product that does not meet the dimensional standards, resulting in a decrease in yield. Therefore, in order to cope with such a situation, in the apparatus according to the present invention, a pin point for injecting the molten mixture is installed in the center of the openable and closable non-magnetic mold 40 facing the opening of the cavity 18 as described above. The case 1-44 is bored oppositely to the through-hole 32 in exact alignment. And this pinpoint gate 4
Due to the fluid pressure during injection of the molten mixture from 4, the rotating shaft 30
By forcibly pushing down in the axial direction, the predetermined position can always be regulated.

That is, a mixture consisting of a ferromagnetic powder with a large magnetic anisotropy constant and a synthetic resin is heated and melted, this molten mixture is injected through the nozzle 52 of the movable mold 46, and the sprue 5
0 and into the cylindrical cavity 18 through the pinpoint gate 44. At this time, as shown in FIG. 5(b), the molten mixture 54 injected into the cavity 18 collides with the top of the rotating shaft 30 with considerable fluid pressure, and this pressure pushes the rotating shaft 30 in the axial direction. The position is regulated by lowering it (to a predetermined position where the shaft end comes into contact with the contact Fj, 22).

Also, in synchronization with this, a magnetizing coil (not shown) is excited,
A strong magnetic field is applied to the cavity 18 from the outside in the radial direction via the magnetizing yoke 28. In this way, by applying a multi-pole magnetic field while the mixture of magnet powder and synthetic resin is in a molten state and the particle arrangement is not solidified, it is possible to orient the axis of easy magnetization of the magnet powder particles in the radial direction. Cylindrical anisotropic magnet or cavity 1 with excellent magnetic properties
It is molded into 8.

Regarding the components of the molten mixture injected into the cavity, examples of ferromagnetic powder with a large magnetic anisotropy constant include Ba ferrite magnet powder, Sr ferrite magnet powder, or rare earth magnet powder (RCos type or R2C017 type). .Here 艮 indicates one or more rare earth elements) its regionally anisotropic manganese aluminum (Al-C)
Magnetic powder or the like is preferably used.

Note that it is desirable that the particle size of these ferromagnetic powders be around the single magnetic domain particle size.

Synthetic resins are used as organic binders; for example, thermoplastic resins such as polyethylene, nylon, polypropylene, polyphenyl cyphite, and thermosetting resins such as phenol and epoxy can be used.

In addition, the desirable blending ratio of ferromagnetic powder and synthetic resin is
The magnet powder volume fraction is about 50 to 65%. Further, the molding temperature of the molten mixture during injection molding is preferably in the range of 150 to 350°C, and the applied magnetic field needs to be 300,000 or more.

In this way, the molten mixture is injected into the cavity 18, magnetized, and then cooled and solidified.
The rotating shaft 30, which was previously set so as to face inside the cavity, is inserted into the center of a cylindrical resin magnet 56 molded in the cavity and fixed integrally therewith, thereby forming a rotor for a rotating electric machine as shown in FIG. is obtained. According to the present invention, during injection molding of this molten mixture, the rotating shaft 30 of the rotor for the rotating electric machine is positioned at a predetermined position in the axial direction in the cylindrical cavity 18 and is always regulated, so that the product obtained is All of them conform to standard dimensions, and manufacturing yields can be greatly improved. Moreover, it requires a special jig or other complicated special structure to regulate the rotary shaft to a predetermined position in the axial direction, and it is also difficult to remove the rotor from the mold by inserting the rotary shaft 30 into the through hole 32. It has many advantages such as not causing any trouble.

In the embodiments of the present invention, axial position regulation was explained when manufacturing the rotor of a bicycle generator, but it can also be widely and suitably used when manufacturing magnet rotors of general rotating electric machines, such as rotors of other surface current motors. It is something that

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a rotor for a rotating electric machine according to the prior art;
Fig. 2 is a schematic cross-sectional view showing a state in which the rotating shaft is inserted into the cavity, Fig. 3 is a longitudinal cross-sectional view of the axial position regulating device according to the present invention, and Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3. Figures 5(a) and 5(b) are cross-sectional views showing the state in which the rotating shaft is slid in the axial direction in the cavity, and Figure 6 is a longitudinal cross-sectional view of a rotor for a rotating electric machine manufactured by the method of the present invention. It is. 18... Cylindrical cavity 24... Fixed side mold 28... Magnetizing yoke 3
0...Rotor rotation axis 32...Through hole 40...
・Movable mold 44...Pinpoint gate FIG, 5 -282- FIG, 6 56

Claims (2)

[Claims] (1) Synthesize ferromagnetic powder by aligning the axes and facing the rotor rotation axis into the cylindrical cavity of the mold, and applying a magnetic field of multiple equally divided poles from the outside in the radial direction of the cylindrical cavity. When manufacturing a rotor for a rotating electric machine by injecting a molten mixture with a resin into the cavity, the molten mixture is injected from a vertical direction toward the top of the rotor rotation shaft inserted through and supported at the center of the bottom of the cylindrical cavity. A method for regulating the axial position of a rotor rotating shaft, characterized in that the rotor rotating shaft is axially suppressed by fluid pressure during injection of the molten mixture and moved to a predetermined position in a cylindrical cavity. (2) Magnetization of a mold made of a non-magnetic material defining a cylindrical cavity and multiple poles made of a ferromagnetic material connected to one magnetizing coil and facing the radial outer circumference of the cylindrical cavity at equal central angles. A yoke, a through hole for inserting the rotor rotating shaft drilled in the center of the bottom of the cylindrical cavity, a pinpoint gate that opens facing into the cylindrical cavity, and a gate that closes the opening of the cylindrical cavity so that it can be opened and closed. The pinpoint gate is formed in the center of the non-magnetic mold which faces the cylindrical cavity opening and can be opened and closed, facing the through-hole. Axial position regulating device for rotor rotation axis.