JP4701641B2 - Composite bond magnet, method for producing composite bond magnet, rotor of DC brushless motor equipped with composite bond magnet. - Google Patents

Description

  The present invention relates to a technique such as a DC brushless motor, and more particularly to magnetic field orientation molding of a bonded magnet for a permanent magnet type rotor.

  Conventionally, in the bonded magnet world, a rare earth compound that is expensive but has a high energy product and excellent magnetic properties and a ferrite compound that has a low energy product but is inexpensive have been blended at an arbitrary mixing ratio to create a hybrid compound, which is then injection molded. Attempts have been made to obtain bonded magnets with arbitrary magnetic properties at an optimal price, but rare-earth bonded magnets and ferrite-based bonded magnets with completely different thermal properties must be injection molded under the same conditions. This hybrid compound, which cannot be obtained, has a problem that it is very difficult to exert its original magnetic characteristics, and the cost is often high.

For this purpose, there has been proposed a rotor for a small motor in which an annular rare earth magnet is integrally molded and fixed to a rotating shaft of a motor via a bonded magnet containing ferrite. Here, in the bonded magnet containing ferrite, the rotating shaft and the rare earth magnet are integrated by insert molding. In other words, in a state where the rare earth magnet previously produced by compression molding or injection molding is inserted into the mold together with the shaft, the melt-plasticized ferrite bond magnet is injection molded and integrated. (For example, see Patent Document 1)
JP-A-9-93842 (2nd to 3rd pages, FIGS. 1 and 2)

  When a conventional composite bonded magnet is actually manufactured, if the inserted rare earth magnet is a bonded magnet, the rare earth bonded magnet receives twice the heat history during injection molding, and the injection temperature during molding of the ferrite-based bonded magnet However, the magnetic properties of the rare earth bonded magnet deteriorate due to oxidation deterioration due to high temperature and a decrease in coercive force.

  Incidentally, Nd-Fe-B system composed of neodymium (Nd), iron (Fe), and boron (B), and Sm composed of samarium (Sm), iron (Fe) nitrogen (N), which are put into practical use as rare earth bonded magnets. -Fe-N system is very oxidatively deteriorated and is applied with anti-oxidation surface treatment on magnetic powder. However, it is still easily oxidized and deteriorated due to the heat history at the time of manufacture. Magnetic properties cannot be obtained.

  In other words, when using magnetic anisotropy material, when placing an electromagnet or permanent magnet in a mold and applying a magnetic field to the bond magnet during injection molding, magnetic field orientation molding is performed. Since the force is lowered and the magnetic properties are deteriorated, in the form described in JP-A-9-93842 in which a rare earth magnet is inserted and a ferrite-based bonded magnet is injection-molded, a specific magnetic field orientation is applied to the rare earth magnet. This is difficult, and the surface magnetic flux distribution cannot be arbitrarily controlled. Therefore, there is a problem that it is difficult to optimally design the rotor with respect to magnetic characteristics and sound / vibration.

  Nd-Fe-B rare earth bonded magnets often use isotropic materials that are not magnetically oriented during molding. However, even when the rare earth magnets are isotropic, the ferrite bonded magnets are injected and integrated. There is a big problem that the holding power decreases due to high-temperature oxidative degradation during molding.

  The composite bonded magnet according to the present invention has been made to solve these problems, and has an optimum design for improving the surface magnetic flux density distribution and demagnetization resistance, improving the performance of the rotor, and reducing sound and vibration. In addition, by changing the material of the rare earth bonded magnetic material, it is possible to support models from standard to high grade, enabling common use of molds and integration of parts. The aim is to be able to respond quickly.

The composite bonded magnet of the present invention comprises a primary bonded magnet molded body obtained by injection molding of a primary bonded magnet containing ferrite or soft magnetic iron and oriented in a polar anisotropic magnetic field. A secondary bonded magnet including a magnetic material is injection-molded to provide a secondary bonded magnet molded body that is oriented in an anisotropic magnetic field, and the primary bonded magnet molded body and the secondary bonded magnet molded body are melt bonded. The anisotropic magnetic field orientation molding is continuously performed, the thickness of the layer of the secondary bonded magnet molding is different between the polar center part and the interpolar part of the polar anisotropic magnetic field orientation, and the surface magnetic flux density distribution is substantially It is a sine wave waveform.

In addition, in the method for manufacturing a composite bonded magnet according to the present invention , a magnetic field orientation permanent magnet and a magnetic field orientation yoke are provided in a mold so as to form a polar anisotropic magnetic field having a similar shape in the circumferential direction. Forming a circuit and injection-molding a primary bonded magnet containing ferrite or soft magnetic iron in the mold to produce a primary bonded magnet molded body oriented in an anisotropic magnetic field; and in the mold Generating a secondary bonded magnet formed by injection molding a secondary bonded magnet containing a magnetic anisotropic rare earth magnetic material and oriented in a polar anisotropic magnetic field inside or outside the primary bonded magnet formed body. The primary bonded magnet molded body and the secondary bonded magnet molded body are melt-bonded and continuously subjected to polar anisotropic magnetic field orientation molding, and the layer thickness of the secondary bonded magnet molded body is the polar anisotropic It differs between the pole center part and the pole part of the magnetic field orientation, One surface magnetic flux density distribution is characterized in that a substantially sinusoidal waveform. Thus, since the primary bond magnet and the secondary bond magnet are formed by magnetic field orientation molding using the same magnetic circuit, these two layers are melt-bonded with a binder resin such as a thermoplastic resin, and are continuously different from each other. It is possible to apply a magnetic field orientation.

The composite bonded magnet of the present invention comprises a primary bonded magnet molded body obtained by injection molding of a primary bonded magnet containing ferrite or soft magnetic iron and oriented in a polar anisotropic magnetic field. A secondary bonded magnet including a magnetic material is injection-molded to provide a secondary bonded magnet molded body that is oriented in an anisotropic magnetic field, and the primary bonded magnet molded body and the secondary bonded magnet molded body are melt bonded. The anisotropic magnetic field orientation molding is continuously performed, the thickness of the layer of the secondary bonded magnet molding is different between the polar center part and the interpolar part of the polar anisotropic magnetic field orientation, and the surface magnetic flux density distribution is substantially Since it is characterized by a sinusoidal waveform, the surface magnetic flux density distribution and demagnetization resistance can be improved, enabling high performance of the rotor and optimum design for reducing sound and vibration, as well as rare earth Changing the material of the bond magnetic material Only by the model corresponding standard to high grade becomes possible, common mold, and allowing the integration of components, quickly in limited production of diversified products is equal great effects can accommodate.

In addition, in the method for manufacturing a composite bonded magnet according to the present invention , a magnetic field orientation permanent magnet and a magnetic field orientation yoke are provided in a mold so as to form a polar anisotropic magnetic field having a similar shape in the circumferential direction. Forming a circuit and injection-molding a primary bonded magnet containing ferrite or soft magnetic iron in the mold to produce a primary bonded magnet molded body oriented in an anisotropic magnetic field; and in the mold Generating a secondary bonded magnet formed by injection molding a secondary bonded magnet containing a magnetic anisotropic rare earth magnetic material and oriented in a polar anisotropic magnetic field inside or outside the primary bonded magnet formed body. The primary bonded magnet molded body and the secondary bonded magnet molded body are melt-bonded and continuously subjected to polar anisotropic magnetic field orientation molding, and the layer thickness of the secondary bonded magnet molded body is the polar anisotropic It differs between the pole center part and the pole part of the magnetic field orientation, One the surface magnetic flux density distribution is characterized in that a substantially sinusoidal waveform, minimizing thermal degradation of the rare earth bonded magnet, applying any continuous magnetic field orientation, such as polar anisotropic orientation In addition, the magnetic characteristics of the anisotropic bonded magnet can be maximized, and a rotor using the bonded magnet that is superior to sound and vibration can be easily obtained.

Embodiment 1 FIG.
FIG. 1 is a schematic view showing a mold for injection molding of a primary bonded magnet of a composite bonded magnet according to Embodiment 1 of the present invention, and FIG. 2 is a secondary bonded magnet of the composite bonded magnet according to Embodiment 1 of the present invention. FIG. 3 is a plan view showing a rotor formed of a composite bonded magnet mold according to Embodiment 1 of the present invention, and FIG. 4 is a composite bond according to Embodiment 1 of the present invention. FIG. 5 is a characteristic diagram showing the surface magnetic flux density, and FIG. 6 is a molding in which the composite bonded magnet mold according to the first embodiment of the present invention is applied to the outer rotor molding. It is a schematic diagram which shows the metal mold | die. In FIG. 1, a magnetic field orientation permanent magnet 3 and a magnetic field orientation yoke 4 are arranged in an outer shell mold 2 of a mold 1 so that a similar orientation magnetic field 5 is formed in the circumferential direction. It is configured to allow polar anisotropic orientation molding.

  As a first step, a mold for injection molding of a primary bonded magnet of the composite bonded magnet shown in FIG. 1, the magnetic field orientation permanent magnet 3 and the magnetic field orientation yoke 4 are placed in the outer shell mold 2 of the mold 1. And an inner core 7 is arranged at the center via a non-magnetic ring 6 and a ferrite-based bonded magnet is injection-molded to obtain a primary bonded magnet molded body 8 oriented in an anisotropic magnetic field. Here, a dummy insert 10 is inserted in the cavity 9 for forming the secondary bonded magnet, and the ferrite-based bonded magnet contains about 1 to 3 microns of ferrite magnetic powder in a volume of about 70%, and the binder resin is PA12 ( A commercially available compound as polyamide 12) was used.

  Next, as a second step, in the mold for injection molding of the secondary bonded magnet of the composite bonded magnet shown in FIG. 2, the cavity 9 for molding the secondary bonded magnet in the mold 1 shown in FIG. Using the mold 1 with the inserted dummy insert 10 removed, the mold 1 with the primary bonded magnet molded body 8 shown in FIG. N-bond magnet is injection molded, and the portion where the surface magnetic flux density is the highest by concentrating the magnetic field is the pole center portion A, and conversely, the portion where the surface magnetic flux density is the lowest is the interpole portion B. The body 11 is molded, and the thermoplastic resin portion of the primary bonded magnet molded body 8 and the secondary bonded magnet molded body 11 is melt-bonded to obtain a composite bonded magnet molded body that is integrated and continuously magnetically oriented. .

  Here, the Sm-Fe-N-based bonded magnet contains 60% by volume of Sm-Fe-N magnetic powder having a magnetic anisotropy particle size of about 1 to 5 microns, and is a binder resin that is a thermoplastic resin. A commercially available compound with PA12 (polyamide 12) was applied.

  The binder resin is not limited to PA12, but PA6 (polyamide 6), PA66 (polyamide 66), PBT (polybutylene terephthalate), PET (polyethylene terephthalate), depending on the required heat resistance and moldability. PPS (polyphenylene sulfide), LCP (liquid crystal polymer), or the like may be used.

  Thus, since the primary bonded magnet molded body 8 and the secondary bonded magnet molded body 11 are formed by magnetic field orientation molding using the same magnetic circuit, these two layers are melt-bonded with a thermoplastic resin such as a binder resin, It is possible to easily carry out polar anisotropic magnetic field orientation continuously.

  Further, since the primary bonded magnet molded body 8 using ferrite magnetic powder and the secondary bonded magnet molded body 11 using Sm-Fe-N magnetic powder are close in particle size, the particle size is relatively large. Compared to the Nd-Fe-B system, it is easy to ensure the continuity between the two layers in the continuous magnetic field orientation molding, and has an effect of obtaining a smooth magnetic flux density distribution. Further, the thickness of the secondary bonded magnet molded body 11 is as thin as 3 mm or less. Even in this case, since the primary bonded magnet molded body 8 serves as a back yoke, it has an effect that polar anisotropic orientation can be easily obtained.

  Furthermore, since the thickness of the secondary bonded magnet molded body 11 is different between the pole center portion and the inter-pole portion, there is an effect that the distribution waveform of the surface magnetic flux density can be controlled to an arbitrary shape, and the surface is formed at the pole center portion. When it is desired to concentrate the magnetic flux density, the thickness of the secondary bonded magnet molded body 11 located at the pole center may be made thicker than the periphery.

  Further, as a third step, as shown in the plan view of FIG. 3 and the cross-sectional view of FIG. A rotating body of the rotor 14 for the brushless motor is configured.

  In addition, shaft insert molding may be performed in the first step, in which case the third step is omitted, but the horizontal axis indicates the phase angle and the vertical axis indicates the surface according to the characteristic diagram showing the surface magnetic flux density in FIG. If the magnetic flux density is plotted, a clean sine wave waveform is obtained, so that problems of sound and vibration due to cogging torque generation and rectangular waves can be suppressed.

  Next, in another example of the first embodiment, the primary bonded magnet molded body 8 includes soft magnetic iron powder in a volume ratio of 60%. In the first step, the soft magnetic iron powder is mixed in a volume ratio. The primary bonded magnet molded body 8 was subjected to magnetic field orientation molding using a bond magnetic body containing about 60% and a binder resin of PA12. The following steps are the same as those in the first embodiment.

  As another feature of the embodiment, a bonded magnetic body containing soft magnetic iron powder can be effectively acted on the primary bonded magnet molded body 8 as a rotor back yoke. Incidentally, in the case of a laminated body of electromagnetic steel sheets generally used as a rotor back yoke, it was difficult to integrally form with a bond magnet due to the effect of thickness variation and spring back. Has the effect of facilitating

  In still another embodiment, the secondary bonded magnet molded body 11 is isotropic with 30% magnetic anisotropic Sm-Fe-N magnetic powder in the first embodiment or the other embodiments. Nd-Fe-B magnetic powder 30% and binder resin PA12 are 40% (volume ratio).

  In this way, as described in the other embodiments, it is possible to support models from standard to high grade by simply changing the material of the rare earth bonded magnetic material, sharing molds, and integrating parts. And can respond quickly to small-lot production of various varieties.

  Furthermore, another embodiment of the first embodiment will be described. It is an application schematic diagram to the outer rotor of the composite bond magnet by other embodiment shown in FIG. In the figure, in the case of an outer rotor, the working surface is opposite to that of the inner rotor. That is, a bond magnetic body containing ferrite or soft magnetic body, which is the primary bonded magnet molded body 8, is injection molded on the outer diameter side, and a rare earth bonded magnet, which is the secondary bonded magnet molded body 11, is disposed on the inner diameter side. The orientation magnetic field 5 circuit is different from the embodiment of the inner rotor described above except that a permanent magnet is provided on the inner core 7 side in the mold in FIG.

  In the above-described magnetic field orientation method, the formation of the 8-pole polar anisotropic orientation has been described. However, the magnetic field orientation is not limited to 8 poles, and the magnetic field orientation shaping is continuously performed with other pole numbers. Of course, it is possible.

It is a schematic diagram which shows the injection mold of the primary bond magnet of the composite bond magnet by Embodiment 1 of this invention. It is a schematic diagram which shows the injection die of the secondary bond magnet of the composite bond magnet by Embodiment 1 of this invention. It is a top view which shows the rotor shape | molded with the composite bond magnet metal mold | die by Embodiment 1 of this invention. It is an axial sectional view showing a rotor formed with a composite bonded magnet mold according to Embodiment 1 of the present invention. It is a characteristic view which shows the surface magnetic flux density of the composite bond magnet by Embodiment 1 of this invention. It is a schematic diagram which shows the metal mold | die for which the composite bond magnet metal mold | die by Embodiment 1 of this invention was applied to outer rotor shaping | molding.

Explanation of symbols

1 mold,
2 Outer shell mold,
3 permanent magnets for magnetic field orientation,
4 Magnetic field orientation yoke,
5 orientation magnetic field,
6 Non-magnetic ring,
7 inner core,
8 Primary bonded magnet molded body,
9 Cavity for secondary bonded magnet molding,
10 Dummy nesting,
11 Secondary bonded magnet molded body,
12 wheels,
13 shaft,
14 Rotor.

Claims (6)

The primary bonded magnet comprising ferrite or soft iron by injection molding comprising a polar anisotropic magnetic field oriented primary bonded magnet molding, secondary bond magnet comprising magnetic anisotropy rare earth magnetic material to the inner or outer A secondary bonded magnet molded body having a polar anisotropic magnetic field orientation formed by injection molding, and the primary bonded magnet molded body and the secondary bonded magnet molded body are melt-bonded to continuously polar anisotropic magnetic field oriented. molded Rutotomoni,
A composite bonded magnet characterized in that the thickness of the layer of the secondary bonded magnet molded body is different between the pole center part and the pole part of the polar anisotropic magnetic field orientation and the surface magnetic flux density distribution is a substantially sinusoidal waveform. . The primary bonded magnet comprising ferrite or soft iron by injection molding comprising a polar anisotropic magnetic field oriented primary bonded magnet molding, secondary bond magnet comprising magnetic anisotropy rare earth magnetic material to the inner or outer A secondary bonded magnet molded body having a polar anisotropic magnetic field orientation formed by injection molding, and the primary bonded magnet molded body and the secondary bonded magnet molded body are melt-bonded to continuously polar anisotropic magnetic field oriented. molded Rutotomoni,
The secondary bonded magnet molded body is characterized in that the thickness of the pole central portion of the polar anisotropic magnetic field orientation is thicker than the thickness of the interpolar portion, and the surface magnetic flux density distribution is a substantially sinusoidal waveform. Composite bond magnet. A magnetic circuit is formed by arranging a permanent magnet for magnetic field orientation and a yoke for magnetic field orientation in the mold so that a similar polar anisotropic magnetic field is formed in the circumferential direction, and ferrite or soft magnetic material is formed in the mold. A step of generating a primary bonded magnet formed by injection molding of a primary bonded magnet containing magnetic iron and having a polar anisotropic magnetic field orientation; and a secondary bonded magnet containing a magnetic anisotropic rare earth magnetic material in the mold Forming a secondary bonded magnet molded body having an anisotropic magnetic field orientation by injection molding on the inner side or the outer side of the primary bonded magnet molded body, and the primary bonded magnet molded body and the secondary bond. The magnet compact is melt bonded and continuously subjected to polar anisotropic magnetic field orientation molding ,
A composite bonded magnet characterized in that the thickness of the layer of the secondary bonded magnet molded body is different between the pole center part and the pole part of the polar anisotropic magnetic field orientation and the surface magnetic flux density distribution is a substantially sinusoidal waveform. Manufacturing method. A magnetic circuit is formed by arranging a permanent magnet for magnetic field orientation and a yoke for magnetic field orientation in the mold so that a similar polar anisotropic magnetic field is formed in the circumferential direction, and ferrite or soft magnetic material is formed in the mold. A step of generating a primary bonded magnet formed by injection molding of a primary bonded magnet containing magnetic iron and having a polar anisotropic magnetic field orientation; and a secondary bonded magnet containing a magnetic anisotropic rare earth magnetic material in the mold Forming a secondary bonded magnet molded body having an anisotropic magnetic field orientation by injection molding on the inner side or the outer side of the primary bonded magnet molded body, and the primary bonded magnet molded body and the secondary bond. The magnet compact is melt bonded and continuously subjected to polar anisotropic magnetic field orientation molding ,
The secondary bonded magnet molded body is characterized in that the thickness of the pole central portion of the polar anisotropic magnetic field orientation is thicker than the thickness of the interpolar portion, and the surface magnetic flux density distribution is a substantially sinusoidal waveform. A method for producing a composite bonded magnet. The composite bonded magnet according to claim 1 or 2 , wherein the rare earth contains Sm-Fe-N. DC brushless motor rotor equipped with a composite bonded magnet, characterized in that mounting the composite bonded magnet according to any one of claims 1, 2, 5.

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