JPH05175039A - Cutout anisotropic cylindrical magnet - Google Patents

Abstract

PURPOSE:To effectively alleviate change of the magnetic density at the gap of the boundaries of stator magnetic field and thereby prevent generation of cogging by forming cutout portions to non-effectuating surface regions including a part of the effectuating surface and gradually reducing the area of the cutout part at the effectuating surface at least in its circumferential direction. CONSTITUTION:While a synthetic resin magnet material supplied into a cylindrical cavity 1 is still in the soft condition, a magnetic field is applied to this magnet material to orient the axes of easy magnetization of magnetic particles in the magnet material along the direction of the line of magnetic force. Thereby, a cylindrical magnet converges both in the sections in the longitudinal direction and in the sections in the lateral direction. Even in this case, the cutout portions in which the areas thereof are gradually reduced in the one circumferential direction are provided within the cavity 1. Accordingly, generation of cogging can be prevented by effectively alleviating change of magnetic flux density at the gap of the boundaries of stator magnetic field and moreover torque can further be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a notched anisotropic cylindrical magnet suitable for use in a permanent magnet type stator of a motor, an outer rotor, etc., and particularly to cogging and vibration and noise caused by the cogging, and rotation. This is to effectively prevent the occurrence of unevenness.

[0002]

2. Description of the Related Art Conventionally, as a two-pole cylindrical magnet used in a motor, which has a relatively large surface magnetic field, the orientation direction of the easy axis of magnetization of magnetic powder particles is as shown in FIG. A cross section having an orientation shown in FIG. 1A has been used. In the figure, the thin line is the orientation direction of the easy axis of magnetization of the magnetic powder particles, and the orientation shown in FIG. 1A is usually called radial orientation.

By the way, when the two-pole cylindrical magnet having the radial orientation is used as the stator, when the magnetic pole surface of the rotating rotor crosses the magnetic field formed by the stator, the gap magnetic flux density at the boundary changes greatly. Therefore, an adverse effect called cogging has occurred. Regarding this point, the same applies to the case where a two-pole cylindrical magnet is used as the outer rotor, and since the change amount of the magnetic flux density with the inner fixed stator is also large, the occurrence of cogging cannot be avoided. Such cogging is not preferable because it causes delicate vibrations, resulting in noise and uneven rotation.

For this reason, conventionally, particularly for applications in which cogging is a problem, exceptionally, a long cylindrical magnet is used while the orientation degree of magnetic powder is lowered, or a short magnet is used. The magnetic properties themselves have been deteriorated by reducing the content rate. However, with such a method of coping, although the cogging can be reduced, the absolute value of the surface magnetic field becomes small, which causes a problem that the torque, which is a basic characteristic, is reduced.

Regarding cogging prevention, the orientation direction of the easy axis of magnetization of the magnetic powder particles in the cross section of the magnet is shown in FIG.
The so-called axial orientation magnet as shown in (b) is more advantageous than the radial orientation magnet,
After all, a decrease in torque was unavoidable.

Other measures against cogging are shown in FIG.
As shown in (b), so-called skew magnetization is known in which the rotor is magnetized obliquely to the axis.
According to this skew-magnetized rotor, the crossing area between the rotor magnetic pole surface and the working surface of the stator gradually increases as the rotor rotates, so that the occurrence of cogging can be effectively suppressed. However, the manufacturing process of the above method is more complicated than in the usual case, and there is a problem in that the cost is high.

Further, the substantial working width in the longitudinal direction of the conventional motor stator is as shown by symbol a in FIG. 3, and because of the existence of the bearing 9, the washer 10, the leaf spring 11, the brush 12, etc., the rotor. It was only as narrow as the magnetic pole width of. Since the width of the stator was not fully utilized as described above, the obtained torque could not be said to be an effective use of the width of the magnet. In the figure, numeral 13 is a cylindrical magnet, 14 is a rotor magnetic pole, 15 is a rotor exciting coil, 16 is a shaft, and 17 is a ferromagnetic case.

[0008]

SUMMARY OF THE INVENTION The present invention advantageously solves the above problems and effectively alleviates the change in the gap magnetic flux density due to the rotation of the rotor to prevent the occurrence of cogging. By effectively utilizing both longitudinal ends of the cylindrical magnet that has not been effectively utilized,
It is an object of the present invention to propose a two-pole cylindrical magnet that realizes further improvement in torque.

[0009]

That is, according to the present invention, among the inner peripheral surface or the outer peripheral surface of a cylinder whose cross section is O-shaped,
A cylindrical magnet having two working areas facing each other with an axis in between, and having a notch in a non-working surface area including a part of the working surface, and the area of the notch shape in the working surface. Is a notched anisotropic cylindrical magnet (first invention) that gradually decreases in at least one circumferential direction.

According to the first aspect of the present invention, in the first aspect of the invention, the easy axis of magnetization of the magnetic powder particles in the longitudinal cross section including the working surface and the axis of the cylindrical magnet is focused and oriented in the central region of the working surface. It is a cylindrical cylindrical magnet (second invention).

The present invention will be described in detail below. Figure 4
(A) to (e) show perspective views of preferred examples of the notched anisotropic cylindrical magnet according to the present invention. Further, FIG. 2A illustrates a motor incorporating such a notched anisotropic cylindrical magnet as a stator. By providing the notch as shown in the figure to the cylindrical magnet, the amount of change in the magnetic flux density of the gap between the stator magnet and the rotor magnetic pole face due to the rotation of the rotor is reduced without skewing the rotor. Therefore, it is possible to effectively prevent the occurrence of cogging without requiring a troublesome work such as skew-magnetizing the rotor.

Further, in the present invention, the axis of easy magnetization of the magnetic powder particles in the longitudinal cross section of the cylindrical magnet is focused and oriented so as to be focused on the substantial working surface in the central area of the working surface to further improve the torque. You can Figure 1
(B) and (C) show examples in which the easy axis of magnetization of the magnetic powder particles is focused on the substantial working surface in the central region of the magnet according to the present invention. In the same figure (b), when the light is focused linearly from the outer peripheral surface to the central area (simple focusing orientation), in the same figure (c), the central portion of the outer surface and both end surfaces are focused on the substantially working surface. This is the case (side-end side-face focusing orientation).

5 and 6 show a state in which the cylindrical magnet according to the present invention is incorporated as a stator of a DC motor. As is clear from comparing FIGS. 5 and 6 with FIG. 3 in which the conventional motor is incorporated, there is a wasteful magnetic flux in the conventional magnet as shown in FIG. On the other hand, in the magnet of the present invention as shown in FIGS. 1B and 1C, all the magnetic fluxes are focused and oriented on the substantially working surface, and therefore higher than those in the axial orientation. It is possible to obtain the gap magnetic flux density, and thus to improve the torque.

In order to further improve the torque, as shown in FIGS. 1 (e) and 1 (f), the orientation direction of the magnetic powder particles in the working area of the magnet cross section is set to the simple focusing orientation as described above or It suffices that the both ends are laterally focused.

Plastic magnets are more advantageous than sintered magnets that require high-temperature firing, because they do not have cracks when a notch is formed and yield is improved.

[0016]

The magnet material of the present invention may be either a sintered magnet or a synthetic resin magnet. For example, as a magnetic powder in a sintered magnet and a synthetic resin magnet, a ferrite-based material,
Alnico-based, samarium-cobalt-based, neodymium-iron-boron-based, or any other known material can be used. Also, the average particle size of the magnetic powder particles can be used within a known range. For example, it is generally 1.5 μm for ferrite type and 10 to 50 μm for rare earth type.

As the synthetic resin, a conventionally known one can be used. For example, polyamide-based synthetic resins such as polyamide 12 and polyamide 6, polyvinyl chloride, vinyl acetate copolymer thereof, homo- or copolymerized vinyl-based synthetic resins such as MMA, PS, PPS, PE and PP, urethane,
Silicone, Polycarbonate, PBT, PET, PE
EK, CPE, Hypalon, Neoprene, SBR, NB
A synthetic resin such as R or a thermosetting synthetic resin such as an epoxy resin or a phenol resin can be used. Further, the compounding ratio of the magnetic powder and the synthetic resin as the binder depends on the application, but it is generally desirable to set the magnetic powder to 40 to 70 vol%. In addition, it goes without saying that appropriate amounts of conventional plasticizers, lubricants, antioxidants, surface treatment agents and the like can be used according to the purpose.

Next, the magnetic circuit device of the magnetic field orientation molding die according to the present invention will be described. 7 to 11 and 12 to 17
Each of them schematically shows a preferred example of a magnetic circuit device of an injection mold suitable for use in manufacturing a cylindrical magnet. 7 to 11 are longitudinal cross sections of the product, and FIG.
8 shows a radial type alignment, FIG. 9 shows an axial type simple focusing alignment, FIG. 10 shows a radial type simple focusing alignment, and FIG. 11 shows an axial type both end side face focusing alignment. Fig. 12 ~
17 is a transverse cross section, and FIGS. 12 and 13 show an axial orientation, FIGS. 14 and 17 show a radial orientation, FIG. 15 shows a simple focusing orientation, and FIG. 16 shows both end side focusing orientations. In the figure, reference numeral 1 is a cavity provided in the die 2, 3 is a main pole, 4 is an intermediate magnetic pole, 5 is a counter pole, 6 is a yoke, 7 is an exciting coil, and 8 is an auxiliary magnetic pole.

The magnet of the present invention can be manufactured by appropriately combining magnetic circuits as shown in FIGS. 7 to 11 whose longitudinal sections are shown above and FIGS. 12 to 17 whose transverse section is shown above. That is, for example, the combination of FIG. 7 and FIG.
A magnetic circuit of a dipole-cylindrical magnet having an axial orientation, which is already known, in which a notch according to the present invention is provided in the cavity of the magnetic circuit.

Considering a case where a cylindrical magnet according to the present invention is manufactured by an injection molding die which is a combination of FIGS. 9 and 15, the synthetic resin magnet material introduced into the cylindrical cavity 1 is in a softened state. When a magnetic field is applied to the magnet material, the lines of magnetic force in the longitudinal cross section of the cavity 1 converge from the outer circumference of one working surface area to the central area inside the working surface. 4 and then permeate from this intermediate magnetic pole 4 so as to diverge toward the outer periphery of the other working surface region, and in the cross section, the intermediate magnetic pole 4 is focused from the outer periphery of the working surface region to the inside of the working surface. Through the intermediate magnetic pole 4 so as to diverge toward the outer circumference of the arc of the other working surface area, and therefore the easy axis of magnetization of the magnetic powder particles in the magnet material is oriented along the direction of the magnetic force line. That result, longitudinal cross-section in FIG. 1
(B) As a result, a cylindrical magnet having a horizontal cross-section as shown in FIG. 1 (e) can be obtained. Even in this case, needless to say, it is necessary to provide a notch having a shape as shown in FIG. 4 in the cavity.

As the main pole 3, the intermediate magnetic pole 4, the counter pole 5, the yoke 7 and the auxiliary magnetic pole 8, carbon steel such as S55C, S50C and S40C, die steel such as SKD11 and SKD61 and pamenjour,
A ferromagnetic material such as pure iron is used, while the die 2 is a non-magnetic material such as stainless steel, copper-beryllium alloy, high-manganese steel, bronze, brass and non-magnetic cemented carbide N-7. As the magnetic field molding method, magnetic field orientation injection molding, magnetic field orientation compression molding, magnetic field orientation RIM molding and the like are suitable.

[0022]

Example 1 A mold having an appropriate combination of magnetic circuits whose longitudinal cross sections are shown in FIGS. 7 to 11 and transverse cross sections shown in FIGS. 12 to 17 is used, and the shape and dimensions shown in FIG. 18 are obtained. The following cylindrical magnet was manufactured under the conditions shown in Tables 1 to 3 below. Here, the notch shape is a drum shape, and the sizes thereof are α = 70 ° and β = 35 ° in terms of the opening degree in the cross section as shown in FIG. The aperture width ratio is (b
/ A) × 100 (%) = 80%. Further, in the focusing orientation form in the longitudinal cross section of the magnetic powder particles, in the case of the overall focusing orientation as shown in FIG. 20 (a), the inner surface focusing angle is 50 °, while the side surface focusing at both ends as shown in FIG. In the case of orientation, the side surface focusing rate Z [= (a−b) / a × 100%] =
80%.

The rotor used in the present invention is shown in FIG.
The standard winding rotor shown in (a) was used. When using rare earth magnetic powder, pulsed high magnetic field treatment was performed immediately before the introduction into the cavity in order to align the magnetic moment in the easy axis of magnetization in advance.

[0024]

[Table 1] Raw magnetic powder A: Ferrite magnetic powder (magnetoplumbite strontium ferrite with an average particle size of 1.5 μm) Magnetic powder B: samarium-cobalt magnetic powder (2-17 system; average particle size 15 μm)

[0025]

TABLE 2 - formulation formulation A (plastic magnet formulation) magnetic powder: 63 vol% Polyamide 12: 36 vol% aminosilane A-1100: 1 vol% formulation B (sintered orientation) magnetic powder: 50 wt% Water: 50 wt%

[0026]

[Table 3] Molding method A: Plamag injection molding conditions Pellets used: Mixing A Molding machine: Magnetic field orientation injection molding machine with built-in coil Injection cylinder temperature: 300 ℃ Mold temperature: 100 ℃ Injection pressure: 1500 kg / cm ² Excitation Time: 15 seconds Cooling time: 20 seconds Injection cycle: 40 seconds ・ Molding method B: Sintered magnet making conditions Slurry used: Mixing B Molding machine: Coil-mounted magnetic field orientation compression molding machine Draining method: Injection method Excitation direction: Vertical Magnetic field Molding temperature: 20 ℃ Firing temperature: 1250 ℃ ・ Hall element 70μm square gallium-arsenic is used

The results of the measurement of the surface magnetic flux density and the motor detent torque on the effective working surface of the thus obtained two-pole cylindrical magnet are shown in Table 4, Table 5, Table 6 and Table 7 together with the evaluation of the cogging phenomenon.

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

[Table 7]

As is apparent from the table, the two-pole cylindrical stator magnet according to the present invention is provided with a notch having a shape in which the intersecting area between the rotor magnetic pole surface and the working surface of the stator gradually increases as the rotor rotates. By providing the cogging, the generation of cogging can be effectively prevented, and further, when the magnetic powder particles in the longitudinal cross section are focused and oriented on the substantially working surface, the torque can be improved together.

[0033]

As described above, according to the present invention, the non-active surface area including a part of the active surface of the two-pole cylindrical magnet is provided with a notch having a shape in which the area is gradually reduced in at least one circumferential direction. For example, when such a two-pole cylindrical magnet is used as a stator, it is possible to effectively alleviate the change in the gap magnetic flux density at the boundary of the stator magnetic field and prevent the occurrence of cogging. By converging and aligning with the substantially acting surface, the torque can be further improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an orientation state of an easy axis of magnetization of magnetic powder particles in a transverse section and a longitudinal section of a cylindrical magnet.

FIG. 2A is an exploded view of a conventional motor.
(B) is an exploded view of a motor incorporating a cylindrical magnet according to the present invention.

FIG. 3 is a sectional view of a motor incorporating a conventional cylindrical magnet.

FIG. 4 is a perspective view showing a suitable cutout shape.

FIG. 5 is a cross-sectional view of a motor incorporating a cylindrical magnet according to the present invention.

FIG. 6 is a cross-sectional view of a motor incorporating another cylindrical magnet according to the present invention.

FIG. 7 is a longitudinal cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having an axial orientation.

FIG. 8 is a longitudinal cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having a radial orientation.

FIG. 9 is a longitudinal cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having an axial simple focusing orientation.

FIG. 10 is a longitudinal cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having a radial type simple focusing orientation.

FIG. 11 is a longitudinal cross-sectional view of a magnetic circuit device that is suitable for use in the manufacture of a cylindrical magnet that has an axial-type side face-focusing orientation.

FIG. 12 is a cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having an axial orientation.

FIG. 13 is a transverse cross-sectional view of a magnetic circuit device that is also suitable for manufacturing a cylindrical magnet that also has an axial orientation.

FIG. 14 is a cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having a radial orientation.

FIG. 15 is a cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet whose cross section has a simple focusing orientation.

FIG. 16 is a transverse cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet whose transverse cross section has side-end side-focusing orientation.

FIG. 17 is a cross-sectional view of a magnetic circuit device suitable for use in manufacturing a cylindrical magnet having a radial orientation.

FIG. 18 is a diagram showing the shape of a cylindrical magnet manufactured in an example.

FIG. 19 is a diagram showing the dimensions and notch dimensions and shape of the cylindrical magnet manufactured in the example.

FIG. 20 is a diagram showing the orientation state of the easy axis of magnetization of the magnetic powder particles in the longitudinal cross section of the cylindrical magnet manufactured in the example.

[Explanation of symbols]

 1 Cavity 2 Die 3 Main pole 4 Intermediate pole 5 Counter pole 6 Yoke 7 Excitation coil 8 Auxiliary pole 9 Bearing 10 Washer 11 Leaf spring 12 Brush 13 Cylindrical magnet 14 Rotor pole 15 Rotor excitation coil 16 Shaft 17 Ferromagnetic case

Claims (2)

[Claims] 1. A cylindrical magnet having, as an acting surface, two regions facing each other with an axis center among the inner circumferential surface or the outer circumferential surface of a cylinder having an O-shaped cross section, and a part of the acting surface. A notched anisotropic cylindrical magnet having a notch in a non-acting surface region including a notch, and the area of the notch shape in the acting surface gradually decreases in at least one circumferential direction. 2. The two-pole cylindrical magnet according to claim 1, wherein an easy axis of magnetization of the magnetic powder particles in a longitudinal cross section including a working surface and an axial center of the cylindrical magnet is focused and oriented in a central region of the working surface.