JPH05252676A - Manufacture of rotor for brushless motor - Google Patents

Abstract

PURPOSE:To enhance efficiency and output and to reduce manhour in the manufacture of a rotor for brushless motors having a plurality of conductive permanent magnet pieces. CONSTITUTION:Conductive permanent magnet pieces 2 are arranged through predetermined spaces into which mixture 3 of fine powder of permanent magnet and insulating fluid is injected thus molding a rotor integrally. Since the mixture of fine powder of permanent magnet and insulating fluid has specific resistance much higher than that of the conductive permanent magnet 2, high eddy current is not induced in the magnet even if high frequency flux interlinks with the rotor during operation of brushless motor. Furthermore, since the rotor can be molded integrally by simply injecting the mixture 3 of fine powder of permanent magnet and insulating fluid, manhour can be reduced remarkably in the manufacture of the rotor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rotor of a brushless motor using a permanent magnet for the rotor.

[0002]

2. Description of the Related Art In recent years, brushless motors using a permanent magnet in a rotor have been widely used for the purpose of improving control performance, high efficiency, and low noise of rotating electric machines. Further, in order to improve the efficiency and increase the output of brushless motors, permanent magnets having a high magnetic flux density represented by rare earth-based permanent magnets have been adopted.

As a control method for changing the rotation speed of the brushless motor, a PAM method for changing the value of the voltage applied to the stator winding and a control method for keeping the voltage constant and a voltage waveform having a relatively high frequency (several kHz to several kHz). There is a PWM method in which the average applied voltage is changed by turning on / off at several tens of kHz and changing the on / off time ratio.

FIG. 4 is a main connection circuit diagram of a control circuit of a three-phase full-wave drive system and a brushless motor, and FIG. 5 shows an example of a voltage waveform and a current waveform applied to a motor stator winding by the PWM system. In FIG. 4, 12 is an AC power supply (in the figure, a single phase is shown, but it may be three phases), 13 is a rectifying diode, 14 is a smoothing capacitor, 15 is a three-phase full-wave drive transistor, 16 is a brushless motor, Vu is a voltage applied to any one lead terminal of the brushless motor 16 and the negative side of the smoothing capacitor 14, and Iu is a current flowing through the lead terminal of the brushless motor 16 measuring Vu. As shown in FIG. 5, since Vu of Iu has a PWM waveform, a high frequency current corresponding to the PWM frequency is superimposed on the fundamental wave current. On the other hand, even in the PAM system, the brushless motor that operates at a particularly high speed has a sudden current Iu when the energization of the three-phase full-wave driving transistor 15 is switched.
And the high frequency current is superimposed on the fundamental wave current as in the PWM method.

[0005]

However, when a permanent magnet having a high magnetic flux density represented by a rare earth permanent magnet is adopted, a high frequency magnetic flux is generated corresponding to the high frequency current superposed on the current Iu shown in FIGS. 4 and 5. The generated high-frequency magnetic flux is linked to the rare-earth permanent magnet. The rare earth permanent magnet has a relatively large electrical resistance of about 10 ⁻⁴ Ωcm and has relatively large conductivity, and a current easily flows, so that a large eddy current is generated inside the magnet. Since this eddy current causes a loss of the motor, the efficiency of the brushless motor is significantly deteriorated as a result, and it is meaningless to improve the efficiency of the brushless motor and increase the output thereof by using an expensive rare earth magnet.

In order to solve this problem, a conductive permanent magnet typified by a rare earth permanent magnet and a non-conductive permanent magnet typified by a ferrite permanent magnet (electrical resistivity is about 10 ⁴ Ωcm) are used. It is conceivable to arrange the rotors alternately to form a rotor, or to use a semi-conductive permanent magnet made by mixing rare earth-based permanent magnet fine powder and an insulating fluid instead of the ferrite permanent magnet. However, it is necessary to attach a large number of permanent magnets in order to manufacture one rotor, and the number of manufacturing steps increases, resulting in a costly brushless motor.

An object of the present invention is to solve the above problems and to provide a method of manufacturing a brushless motor rotor which has high efficiency and high output and which requires less manufacturing steps.

[0008]

In order to achieve the above object, a method for manufacturing a brushless motor rotor according to the present invention is a rotor for a brushless motor having a plurality of conductive permanent magnet pieces. After arranging the magnet pieces in a predetermined space, a mixture of permanent magnet fine powder and an insulating fluid is poured into the space to integrally mold the rotor.

[0009]

As described above, according to the present invention, since the mixture of the permanent magnet fine powder and the insulating fluid has the electric resistivity much larger than that of the conductive permanent magnet, it is possible to operate the brushless motor during operation. Even if the high-frequency magnetic flux links the rotor, no large eddy current is generated inside the magnet. further,
After arranging the conductive permanent magnet pieces in a predetermined space, the mixture of the permanent magnet fine powder and the insulating fluid is injected into the space and the rotor is integrally molded. Since it is not necessary to install the permanent magnet, the number of manufacturing steps will be greatly reduced.

[0010]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view showing a method for manufacturing a brassless motor rotor according to a first embodiment of the present invention. (A) is a perspective view of a cylindrical rotor core, (b) is a perspective view of a plurality of conductive permanent magnet pieces, (c) is a cylindrical rotor core, and a plurality of conductive permanent magnet pieces are axially predetermined. Is a perspective view showing a state where the space is opened, and (d) is a state of (c) in which a mixture of permanent magnet fine powder and an insulating fluid is injected into the space,
The perspective view of the completed state which integrally molded the rotor is shown. As shown in FIG. 1, a rotor 1 comprises a cylindrical rotor core 1 and a plurality of conductive permanent magnet pieces 2 arranged axially in a predetermined space. The mixture 3 of the body is injected to integrally mold the rotor. In addition, 4 is a groove formed in the outer periphery of the cylindrical rotor core 1 in the axial direction, and 5 is a finished rotor product.

FIG. 2 is a sectional view showing a step of injecting the mixture 3 of the permanent magnet fine powder and the insulating fluid into the space in the manufacturing method of the present invention. A cylindrical rotor iron core 1 and a plurality of conductive permanent magnet pieces 2 are mounted in injection molds 6a, 6b, 6c, and a mixture 3 of permanent magnet fine powder and insulating fluid is injected from an injection port 7 into a cylindrical rotor. It is injected into the space through a groove 4 provided in the outer periphery of the iron core 1 in the axial direction. The insulating fluid referred to here is a molding resin such as nylon, PPS, or polyester, and may be thermosetting or thermoplastic.

In the brushless motor manufactured as described above, the electric resistivity of the mixture of the permanent magnet fine powder and the insulating fluid is much larger than that of the conductive permanent magnet. Therefore, even if the high-frequency magnetic flux links the rotor during operation of the brushless motor, a large eddy current is not generated inside the magnet. Furthermore, the rotor can be integrally molded only by injecting the mixture of the permanent magnet fine powder and the insulating fluid. Therefore, it is possible to improve the efficiency and increase the output of the brushless motor, and at the same time, to use an expensive conductive permanent magnet and an inexpensive mixture of permanent magnet fine powder and an insulating fluid, it is possible to conduct everything. It is possible to provide a brushless motor that is significantly cheaper in terms of material than a brushless motor that is composed of conductive permanent magnets. In addition, the number of rotor manufacturing steps is significantly reduced,
Significant improvements can be made in terms of man-hours.

In this embodiment, the conductive permanent magnet pieces are stacked in the rotational axis direction, but it goes without saying that the same effect can be obtained by arranging them in the circumferential direction.

Further, in this embodiment, the inversion type brushless motor in which the stator is on the outer side and the rotor is on the inner side is shown. It goes without saying that you can get it.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG.

FIG. 3 shows an embodiment of a brushless motor in which conductive permanent magnet pieces are arranged in the radial direction from the center.
(A) is a cross-sectional view of a completed brushless motor, and (b) is a perspective view of only a rotor. A flat plate-shaped rotor is provided so as to face the magnetic pole surface of the flat plate-shaped stator core 8. The flat plate rotor includes a rotor core 9 and a plurality of conductive permanent magnet pieces 10.
Are arranged in the radial direction from the center, and the conductive permanent magnet piece 1
By injecting the mixture 11 of the permanent magnet fine powder and the insulating fluid into the space provided between 0 in the same manner as in the first embodiment, the number of manufacturing steps of the rotor can be greatly reduced. .

Needless to say, the same effect can be obtained with a brushless motor that does not use a rotor core.

[0019]

As is apparent from the above description of the embodiments, the present invention is a rotor of a brushless motor having a plurality of conductive permanent magnet pieces, in which the conductive permanent magnet pieces are opened in a predetermined space. After arranging, the mixture of permanent magnet fine powder and insulating fluid was injected into the space, and the rotor was integrally molded, so that the electrical resistivity of the mixture of permanent magnet fine powder and insulating fluid became conductive. Since the electric resistance of the permanent magnet is much larger than that of the permanent magnet, a large eddy current is not generated inside the magnet even if the high-frequency magnetic flux links the rotor during operation of the brushless motor. Furthermore, since the rotor is integrally molded by simply injecting a mixture of the permanent magnet fine powder and the insulating fluid, it is not necessary to attach many permanent magnets to manufacture the rotor, and the number of manufacturing steps is greatly reduced. This means that the number of man-hours can be greatly improved.

[Brief description of drawings]

1A is a perspective view of a cylindrical rotor core of a brassless motor according to a first embodiment of the present invention, FIG. 1B is the same, and FIG. 1C is a perspective view of a plurality of conductive permanent magnet pieces. , A perspective view of a cylindrical rotor core in which a plurality of conductive permanent magnet pieces are arranged with a predetermined space opened in the axial direction, and (d) is the same as that in the state of (c), which is insulated from the permanent magnet fine powder. Perspective view of a completed state in which a mixture of a volatile fluid is injected into the space and the rotor is integrally molded

FIG. 2 is a sectional view showing a step of injecting a mixture of permanent magnet fine powder and an insulating fluid of the present invention.

FIG. 3A is a cross-sectional view of a finished brassless motor of the second embodiment of the present invention, and FIG. 3B is a perspective view of only the brushless motor rotor.

FIG. 4 is a main connection circuit diagram of a control circuit of a three-phase full-wave drive PWM system and a brushless motor.

5A is a waveform diagram of an applied voltage by a PWM method, and FIG. 5B is a current waveform diagram of the same.

[Explanation of symbols]

 2 Conductive permanent magnet pieces 3 Mixture of permanent magnet fine powder and insulating fluid 5 Rotor

Claims (4)

[Claims] 1. A plurality of conductive permanent magnet pieces are provided, the conductive permanent magnet pieces are arranged with a predetermined space between them, and then a mixture of permanent magnet fine powder and an insulating fluid is injected into the space. Manufacturing method for a brushless motor rotor in which the rotor is integrally molded. 2. The method of manufacturing a brushless motor rotor according to claim 1, wherein the magnetic pole surface is formed in a cylindrical shape, and the conductive permanent magnet pieces are arranged in the rotational axis direction or the circumferential direction. 3. The method for manufacturing a brushless motor rotor according to claim 1, wherein, when the magnetic pole surface is orthogonal to the rotation axis, the conductive permanent magnet pieces are arranged radially or radially from the center. 4. The method for manufacturing a brushless motor rotor according to claim 1, wherein a rotor core is not used.