JP3586804B2 - Plastic magnet rotor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plastic magnet rotor used for a rotor such as a DC brushless motor and a stepping motor.
[0002]
[Prior art]
9A and 9B show a conventional rotor formed by integrally molding a plastic magnet, wherein FIG. 9A is a perspective view and FIG. 9B is a plan view. The plastic magnet rotor is easy to manufacture, and is integrally molded with the rotor shaft 21 to form the field magnet portion 22, the fixing portion 23 between the rotor shaft 21 and the field magnet portion 22, and the bearing support for fixing the position of the bearing. Since the ribs 25 arranged at positions corresponding to the respective magnetic poles for reinforcing the portion 24 and the fixing portion 23 are simultaneously formed, the processing cost can be reduced. Therefore, it is most suitable for a small-capacity home electric motor.
[0003]
In such an integrally molded rotor made of a plastic magnet, there is no equivalent to the back yoke of the field magnet, so the magnetic resistance in the magnetic path of the magnet increases, and a sufficient amount of magnetic flux cannot be obtained. could not. However, by performing the molding while forming the orientation magnetic field in the molding die, the magnet in the plastic magnet is polar-oriented, and even without the back yoke, good performance can be obtained. Since the orientation of the plastic magnet can be changed by changing the magnetic field in the mold, various magnetizing methods for the rotor have become possible.
[0004]
However, when a DC motor is used for an air blower, noise reduction is one of the issues. One means for reducing noise is to reduce ripple in output torque and reduce cogging torque due to sine wave magnetization of the magnet. Sinusoidal magnetization is possible with conventional polar orientation technology, but the peak of the amount of magnetic flux is determined by the shape of the field magnet, such as the thickness of any magnetized waveform. The amount of magnetic flux of the rotor decreased, and a sufficient amount of magnetic flux could not be obtained with respect to the amount of the plastic magnet of the rotor.
On the other hand, FIG. 10 shows a plastic magnet rotor disclosed in Japanese Utility Model Unexamined Publication No. 61-171470 having a rotor shaft 31, a field magnet portion 32, and a fixing portion 33. Here, a thin groove 34 is provided in the axial direction between the magnetic poles N and S on the outer periphery of the field magnet portion 32 to clarify the direction of the magnetic flux of each magnetic pole to increase the magnetic force of the rotor. From the viewpoint of sine wave magnetization for the purpose of (1), it is not always sufficient.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problem, and to obtain a plastic magnet rotor having a magnetized sinusoidal shape of a rotor integrally molded with a plastic magnet and having sufficient characteristics with respect to the amount of the plastic magnet. It is intended for.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a plastic magnet rotor formed by molding a field magnet portion having a plurality of magnetic poles around a rotor shaft. It is constituted by a curved surface whose thickness is greater than the thickness of both ends.
[0007]
Further, the curved surface of the outer periphery is formed of a circular arc smaller than a virtual circumscribed circle circumscribing the outer periphery of the field magnet portion.
[0008]
A notch along the axial direction is provided at the boundary between the magnetic poles on the outer periphery of the field magnet portion.
[0009]
Further, in a plastic magnet rotor formed by molding a field magnet portion having a plurality of magnetic poles around a rotor shaft, the inner circumference of the field magnet portion is formed by adjusting the thickness of a central portion in the circumferential direction of each magnetic pole at both ends thereof. It is constituted by a curved surface having a shape thinner than the wall thickness.
[0010]
Further, the inner peripheral curved surface is formed of an arc which makes the boundary between the adjacent magnetic poles the thickest.
[0011]
A notch along the axial direction is provided at the center of each magnetic pole on the inner periphery of the field magnet portion.
[0012]
Further, in a plastic magnet rotor formed by molding a field magnet portion having a plurality of magnetic poles around a rotor shaft, a depression is formed at a boundary portion of each magnetic pole on the outer periphery of the field magnet portion, and a depth of the depression is formed. From the both end faces of the field magnet portion to gradually decrease along the axial direction of the shaft, and set the depth to a minimum or zero at a position closer to one end face side than a center position between the both end faces. It is characterized by having.
[0013]
Further, the recess is formed by two planes.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
1A and 1B show a first embodiment of the present invention, wherein FIG. 1A is a perspective view and FIG. 1B is a plan view. A field magnet portion 2, a fixing portion 3 for fixing the field magnet portion 2 to the rotor shaft 2, and a bearing support portion 4 for defining a bearing position are integrally formed on a rotor shaft 1 with a plastic magnet. . Further, the fixing portion 3 is provided with ribs 5 for reinforcement, the number of which is equal to the number of magnetic poles at the center of each of the magnetic poles 6a to 6h. In this example, the field magnet portion has eight poles, and eight ribs are formed correspondingly.
Note that the above basic configuration is the same in other embodiments described later.
[0015]
The inner peripheral surface of the field magnet portion 2 is formed in a circular shape concentric with the rotor shaft 1, and the outer peripheral surface of the field magnet is formed in an uneven shape. The uneven shape corresponds to a gentle arc-shaped curved surface for each magnetic pole so that the central portion 7 of each of the magnetic poles 6a to 6h is the thickest and the boundary 8 between the magnetic poles is the thinnest. Are connected.
[0016]
Then, when molding the rotor, a magnetic field is formed in the molding die so that the orientation of the rotor can be sufficiently performed and the amount of magnetic flux can be obtained most. As a result, the magnetic flux distribution on the magnet surface becomes trapezoidal, but the gap between the stator and the rotor used together is large at the boundary 8 of each magnetic pole and gradually narrows toward the center 7 of the magnetic pole. Almost the same magnetic flux distribution as wave magnetization can be obtained.
By adopting this configuration, compared to a conventional plastic magnet rotor in which the inner and outer peripheries of the field magnet portion 2 have concentric circle shapes, the amount of plastic magnet of the rotor is reduced by the amount of unevenness in the rotor outer shape. As a result, an effective magnetic flux amount can be obtained, and sine wave magnetization contributing to low noise can be achieved.
[0017]
Note that, in the above example, the outer peripheral surface of the field magnet is formed into a shape in which arc-shaped curved surfaces corresponding to the respective magnetic poles are connected. However, the curved surface does not necessarily have to be arc-shaped, and may be a curved surface using a plurality of planes. Good.
[0018]
Embodiment 2 FIG.
2A and 2B show a second embodiment of the present invention, wherein FIG. 2A is a perspective view and FIG. 2B is a plan view. This is a modification of the rotor shape of the first embodiment, in which a notch 9 is formed along the axial direction of the rotor at the boundary 8 between the magnetic poles 6a to 6h on the outer periphery of the field magnet portion 2. The rest is exactly the same as the first embodiment. The broken line in the figure is a virtual circumscribed circle circumscribing the outer periphery of the field magnet unit 2.
Since the gap between the magnetic poles is increased by the notch 9, the magnetic resistance increases, the magnetic flux generated from the magnetic pole surface flows to the stator, and the magnetization waveform changes from a sine wave to a trapezoidal wave. This magnetization waveform can be relatively easily operated by changing the width and depth of the notch 9. Further, since the shape of the notch 9 can be configured by a combination of two planes, machining and correction of the mold are easy. Further, since the notch 9 can absorb the distortion of the rotor caused by the shrinkage of the plastic generated during the molding of the rotor, a plastic magnet which is stable in dimensions and balance can be obtained.
[0019]
Embodiment 3 FIG.
3A and 3B show a third embodiment of the present invention, wherein FIG. 3A is a perspective view and FIG. 3B is a plan view. Here, the outer peripheral surface of the field magnet portion 2 is formed in a circular shape concentric with the rotor shaft 1, and the inner peripheral surface of the field magnet portion 2 is formed in an uneven shape. The concavo-convex shape is such that the centers of adjacent magnetic poles are gently circled such that the boundary 8 between adjacent magnetic poles (indicated by a broken line) is thickest and the center 7 of each of the magnetic poles 6a to 6h is thinnest. It is formed by connecting with arcuate curved surfaces. At this time, if the plastic magnet is polar-oriented, the magnetic path in the magnet is oriented along the curve of the inner peripheral surface, so that the orientation is improved, the characteristics of the plastic magnet are improved, and the amount of magnetic flux is further reduced. A sine wave magnetized rotor can be obtained.
[0020]
Embodiment 4 FIG.
4A and 4B show a fourth embodiment of the present invention, wherein FIG. 4A is a perspective view and FIG. 4B is a plan view. Here, the outer peripheral surface of the field magnet portion 2 is formed in a circular shape concentric with the rotor shaft 1, and the inner peripheral surface of the field magnet portion 2 is formed in an uneven shape. Notches along the axial direction of the rotor at the center 7 of each of the magnetic poles 6a to 6h, so that the boundary 8 between adjacent magnetic poles (indicated by a broken line) is thicker than the center 7 of the magnetic poles. 9 is formed. The notch 9 makes the orientation of the magnet clear when polar orientation of the plastic magnet is performed, so that the orientation of the polar orientation is improved, and at the same time, a rotor capable of near-sinusoidal magnetization can be obtained. Can be
[0021]
In the third and fourth embodiments, the inner peripheral surface of the field magnet portion 2 does not necessarily have to have an arcuate shape as shown in FIG. The same effect can be achieved by forming any curved surface that is thin and symmetrically thicker at both ends 8 than at the center 7.
[0022]
Embodiment 5 FIG.
5A and 5B show a fifth embodiment of the present invention, wherein FIG. 5A is a perspective view and FIG. 5B is a plan view. The outer peripheral surfaces on the end surfaces 13 and 13 ′ of the field magnet portion 2 are basically such that the center 7 in the circumferential direction of the magnetic poles 6 a to 6 h is the thickest and the boundary 8 between the magnetic poles 6 a to 6 h is the thinnest. Thus, the magnetic poles are formed in a shape in which the magnetic poles are connected by a gentle arc-shaped curved surface. Therefore, the boundary 8 between the magnetic poles forms the depression 10. However, the depth of the depression, that is, the difference between the thick part and the thin part of each magnetic pole differs depending on the axial position, and becomes larger as the end faces 13 and 13 ′ of the field magnet unit 2 are closer. The depth of the depression 10 is set to a minimum or zero at a position deviated upward or downward with respect to the axial direction of the outer peripheral surface of the field magnet portion 2. FIG. 6 is a front view of the rotor, in which the axial center of the field magnet portion 2 in dimension is represented by 14, and the above-mentioned deviated position is represented by 15, which is the magnetic pole center of the rotor.
[0023]
As a result, the amount of magnetic flux in the portion where the depression depth is large is smaller than that in the portion where the depression depth is small, so that when this rotor is inserted into the stator, the magnetic balance in the axial direction can be achieved. The position is different from the case of a normal rotor, and is a position deviated upward or downward. In other words, in the conventional rotor, when the length of the rotor in the axial direction is made larger than the stack thickness of the stator and the rotor is inserted into the stator, the overhang dimension of the rotor becomes uniform on both sides, whereas In the case of the rotor of the present invention, one of them protrudes longer. Therefore, conversely, in the case of the rotor of the present invention, if the protruding dimension of the rotor is set to the same dimension, an axial force is generated. By utilizing this, the axial pressure applied to the bearing can be obtained, so that it is not necessary to use a spring washer.
[0024]
FIG. 7 is an exemplary view showing the use of the plastic magnet rotor according to the fifth embodiment of the present invention. If no axial force is generated and the rotor is largely protruded to either side as shown in FIG. 7, there is an advantage that the degree of freedom in mounting a sensor for detecting the magnetic pole position of the rotor can be increased. Here, 16 indicates a stator core, and 17 indicates a winding wound on the stator core.
[0025]
Embodiment 6 FIG.
8A and 8B show a sixth embodiment of the present invention, wherein FIG. 8A is a perspective view and FIG. 8B is a plan view. A concavity 11 is provided at the boundary 8 between the magnetic poles 6a to 6h on the outer periphery of the concentric field magnet portion 2 formed around the rotor shaft 1. The depth of the depression 11 increases as it approaches the end faces 13 and 13 ′ of the field magnet portion 2. The depth is set to a minimum or zero at a position (lower side in this figure) deviated vertically from the center with respect to the axial direction of the outer peripheral surface of the field magnet portion 2.
Unlike the fifth embodiment, the shape of the depression 11 is formed linearly by using two planes. Therefore, in addition to the effect of the fifth embodiment, the effect of facilitating creation of a molding die is also obtained. Have.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, while sine wave magnetization is attained and noise reduction is achieved, a sufficient magnetic flux amount can be obtained at low cost.
[0027]
Further, the cutout shape of the outer peripheral portion of the magnetic field magnet portion facilitates control of the magnetization waveform.
[0028]
In addition, the polar orientation is improved, sine wave magnetization is enabled, noise can be reduced, and a sufficient amount of magnetic flux can be obtained at low cost.
[0029]
The notch at the center of the magnetic pole on the inner circumference of the field magnet unit clarifies the direction of magnetic flux at the time of polar orientation, enables magnetization close to a sine wave, and increases the amount of magnetic flux.
[0030]
Further, by setting the depth of the depression at the boundary between the magnetic poles on the outer periphery of the field magnet portion as described in claim 1, the axial magnetic center position is shifted from the dimensional center , The force acting in the axial direction can be obtained, or the rotor position can be shifted to increase the degree of freedom of the mounting position of the magnetic sensor.
[0031]
As described in the second aspect, by forming the recess at the boundary between the magnetic poles by two planes, it is easy to form a molding die.
[Brief description of the drawings]
FIG. 1 is a plastic magnet rotor according to a first embodiment of the present invention, in which (A) is a perspective view and (B) is a plan view.
FIG. 2 is a plastic magnet rotor according to a second embodiment of the present invention, in which (A) is a perspective view and (B) is a plan view.
FIG. 3 is a plastic magnet rotor showing a third embodiment of the present invention, wherein (A) is a perspective view and (B) is a plan view.
FIG. 4 is a plastic magnet rotor showing a fourth embodiment of the present invention, wherein (A) is a perspective view and (B) is a plan view.
FIG. 5 is a plastic magnet rotor showing a fifth embodiment of the present invention, wherein (A) is a perspective view and (B) is a plan view.
FIG. 6 is a front view of the plastic magnet rotor of FIG.
FIG. 7 is an exemplary view showing the use of the plastic magnet rotor according to the fifth embodiment of the present invention.
8A and 8B are plastic magnet rotors according to Embodiment 6 of the present invention, wherein FIG. 8A is a perspective view and FIG. 8B is a plan view.
9 (A) is a perspective view and FIG. 9 (B) is a plan view showing a conventional example of a plastic magnet rotor.
10A and 10B show another conventional example of a plastic magnet rotor, in which FIG. 10A is a perspective view and FIG. 10B is a plan view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotor shaft, 2 field magnet part, 3 fixed part, 4 bearing support part, 5 rib, 6a-6h magnetic pole, 7 center part of each magnetic pole, 8 boundary part of each magnetic pole, 9 notch, 10 depression, 11 depression , 13, 13 'End faces of the field magnet portion.

Claims (2)

In a plastic magnet rotor formed by molding a field magnet portion having a plurality of magnetic poles around a rotor shaft,
A depression is formed at the boundary between the magnetic poles on the outer periphery of the field magnet portion, and the depth of the depression is gradually reduced along both ends of the field magnet portion along the axial direction of the shaft. A plastic magnet rotor wherein the depth is minimized or zero at a position deviated to one end face side from a center position between both end faces . 2. The plastic magnet rotor according to claim 1, wherein the depression is formed by two planes .

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