JP2000175387A - Multistage, long and multipole polarizing cylindrical magnet rotor and permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of torque irregularity by stacking cylindrical magnets manufactured by a vertical magnetic field forming method and oriented in one direction perpendicular to a cylindrical shaft in a multi-stage in an axial direction for formation of a long cylindrical magnet in multipole-polarizing its outer peripheral surface so as to serve as a rotor of a permanent magnet motor. SOLUTION: A cylindrical magnet whose orientation is turned 90 deg. so as to have one-way anisotropy is 6-pole polarized to obtain large magnetic flux density at oriented A and D poles, and the magnetic flux density becomes small at a part in the perpendicular direction to the orientation of B, C, E, and F poles. On the other hand, when the one-way anisotropy cylindrical magnet is sliced, divided into two in a cylindrical- axial direction, turned, stacked in two stages, and polarized, the total amount of magnetic flux increase at the A, D poles and decreases at the B, C, E, and F poles. The cylindrical magnet manufactured by a vertical magnetic field forming method and oriented in one direction perpendicular to the axial direction is axially stacked in two stages and multipole-polarized. It is thus possible to reduce variations in the amount of magnetic field for suppression of torque irregularity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical magnet rotor for a synchronous permanent magnet motor such as a servo motor and a spindle motor, and to an improvement of a permanent magnet motor using the same.

[0002]

2. Description of the Related Art Anisotropic magnets made by pulverizing crystalline magnetic anisotropic materials such as ferrites and rare earth alloys and press-molding them in a specific magnetic field are used for speakers, motors, measuring instruments,
Widely used for other electrical equipment. this house,
In particular, rare earth sintered magnets having anisotropy in the radial direction
It has excellent magnetic properties and can be freely magnetized in the axial direction.
Further, since there is no need to reinforce magnet fixing such as segment magnets, they are used for AC servomotors, DC brushless motors, and the like. Particularly in recent years, it has been used in a wide range of applications such as power steering for automobiles.

[0003] Magnets having a radial orientation are produced by molding in a magnetic field (molding in a magnetic field) or by backward extrusion (backward extrusion). In the forming method in a magnetic field, a magnetic field is applied from the opposite direction through a core to obtain radial orientation. However, since the height of a magnet that can be oriented is determined by the shape of the core, one compact can be formed from one press. In other words, only one-piece molding can be performed. For this reason, the productivity of the cylindrical radial anisotropic magnet is extremely low and extremely expensive. Further, since a magnetic field is generated through the core, a sufficient magnetic field cannot be obtained, and it is difficult to obtain a high orientation. On the other hand, the rear-extrusion method requires a large facility, has a low yield, and it is difficult to manufacture an inexpensive magnet. As described above, it is difficult to manufacture the radial anisotropic magnet by any method, and it is difficult to manufacture the radial anisotropic magnet inexpensively in large quantities.

[0004]

SUMMARY OF THE INVENTION A multi-pole magnet can be applied to a cylindrical magnet without using a radially anisotropic magnet, a high magnetic flux density, and a small variation in magnetic flux density between poles can provide a high performance permanent magnet. It can be a magnet for a type motor. For this purpose, a magnet is manufactured by a vertical magnetic field press, and a cylindrical magnet oriented in a certain direction perpendicular to the cylinder axis (hereinafter referred to as a radially oriented cylindrical magnet) is multipolarly magnetized in the circumferential direction to obtain a radially anisotropic magnet. A method of fabricating a multi-pole magnet without using a conductive magnet has been proposed.
-85-120, 1985).

[0005] The radially oriented cylindrical magnet manufactured by the vertical magnetic field press can be made as long as possible (50 mm or more) as long as the cavity of the press machine can be used. In addition, multiple presses can be performed. Thus, a compact can be obtained and can be supplied at a low cost in place of a radially anisotropic magnet which is expensive as a cylindrical magnet for a motor. However, a cylindrical magnet that has been subjected to multipolar magnetization on a magnet oriented in one direction in the radial direction, which was actually produced by a vertical magnetic field press, has a high magnetic flux density in the pole near the orientation direction and a pole in the direction perpendicular to the orientation direction. Since the magnetic flux density is small, when incorporated in a motor and rotated, torque unevenness that reflects variations in magnetic flux density between the poles occurs.
A motor magnet that could be used practically could not be obtained.

An object of the present invention is to perform multipolar magnetization without using a radially anisotropic magnet, to have a high magnetic flux density and a small variation in magnetic flux density between poles. An object of the present invention is to provide a multi-stage long multi-pole magnetized cylindrical magnet rotor that can be mass-produced at low cost without causing unevenness, and a permanent magnet motor using the same.

[0007]

Means for Solving the Problems The present inventors have made intensive efforts to solve the above-mentioned problems, and have made the following improvements in order to reduce the variation in magnetic flux between the poles. The magnet for motors, which can realize smooth rotation without uneven torque, that is, a multi-stage long multi-pole magnetized cylindrical magnet rotor and a permanent magnet type motor using the same can be manufactured. (1) When a cylindrical magnet manufactured by a perpendicular magnetic field molding method and oriented in one direction perpendicular to the cylindrical axis is multipole magnetized on its outer peripheral surface to form a rotor of a permanent magnet type motor, a multistage (in the axial direction) (Two or more stages) to form a long cylindrical magnet, and this multi-stage long cylindrical magnet is used as a rotor for a permanent magnet type motor. (2) The number of stacked multi-stage cylindrical magnets is i (i is 2 or more and 10
(Positive integers below), the orientation direction of each cylindrical magnet is shifted by an angle of 180 / i, i-pieces are stacked and multi-pole magnetized, and the orientation-dispersed multi-stage multi-pole magnet for a permanent magnet motor. It is a cylindrical magnet rotor. (3) When the number of poles of multipolar magnetization is n (n is a positive integer of 1 or more and 50 or less), there is a relationship of i = n / 2 between the number of stacked poles i and the number of magnetized poles n. An orientation dispersion type multi-stage multi-pole magnetized cylindrical magnet rotor is used. (4) When performing n multipolar magnetizations on the outer peripheral surface of the multistage cylindrical magnet, the angle of one pole is set to 360 / n, and 1 / of this angle is set.
A long multi-pole skew-magnetized cylindrical magnet rotor with skew magnetization at an angle of 10 to 2/3. (5) A permanent magnet motor is obtained by using the multi-stage long cylindrical magnet as a rotor for a permanent magnet motor. With such a configuration, there is no uneven torque,
We have realized mass supply of inexpensive and excellent multi-pole magnets and permanent magnet motors using them.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a radially oriented cylindrical magnet of the present invention will be described with respect to an Nd-Fe-B-based cylindrical magnet.
The invention is not limited to this type of magnet. FIG. 1 (a)
FIG. 1B shows a state in which the cylindrical magnet 1 is magnetized using the magnetizer 10, and FIG. 1B shows a state in which the orientation direction of the cylindrical magnet is rotated by 90 ° with respect to (a). FIG. Reference numeral 11 denotes a magnetic pole tooth of the magnetizer, and reference numeral 1 denotes
2 is a magnetizer coil. FIG. 2 shows the Nd—Fe—B-based cylindrical magnet produced by the perpendicular magnetic field press, which was subjected to six-pole magnetization in the orientation direction shown in FIG. 1A, and the surface magnetic flux density was measured. As a result, it can be seen from FIG. 2 that a very large surface magnetic flux density is obtained in the B, C, E, and F poles in the orientation direction, but a small surface magnetic flux density is obtained in the A and D poles in the direction perpendicular to the orientation direction. Is recognized. Despite magnetizing using a magnetizing device having the same angular width as shown in FIG. 1, the magnetizing width is different between the orientation direction and the direction perpendicular thereto, and is wider in the orientation direction. It becomes very narrow in the vertical direction. For this reason, in a unidirectional anisotropic cylindrical magnet produced by a vertical magnetic field press, there are a pole having a large total magnetic flux generated by the pole and a pole having only a very small magnetic flux, and when used as a motor, A torque difference occurs between the poles, and smooth rotation cannot be performed due to the uneven torque.

FIG. 1B shows a cylindrical magnet having unidirectional anisotropy rotated by 90 ° with respect to FIG. 1A to perform six-pole magnetization. A large magnetic flux density is obtained in the A and D poles, and the magnetic flux density is small in a portion perpendicular to the orientation direction of the B, C, E and F poles. The one-way anisotropic cylindrical magnet is sliced and divided into two equal parts in the cylinder axis direction, one of which is gradually rotated to perform two-stage stacking, and the other is rotated to 90 ° to perform stacking. Thereafter, when the magnetization is performed in the arrangement shown in FIG. 1A, the total magnetic flux gradually increases as the rotation angle increases in the A and D poles, and B, C,
At the E and F poles, the total magnetic flux decreases. By stacking two or more stages in the axial direction of the cylindrical magnets manufactured by the perpendicular magnetic field molding and oriented in one direction perpendicular to the axial direction and performing multipolar magnetization, the amount of magnetic flux between the poles is reduced. Variation can be reduced, and torque unevenness when used as a motor can be suppressed.

By rotating the orientation direction of the divided magnets by a predetermined angle relatively and stacking them in multiple stages (two or more stages) and performing multi-pole magnetization, the variation in the amount of magnetic flux between the orientation direction and the direction perpendicular thereto is obtained. And the variation of the magnetic flux amount between the poles can be reduced. At this time, it is preferable that the magnets to be stacked are stacked with their orientation directions shifted by 180 / i degrees (i is the number of stacked magnets) to perform multipolar magnetization. Also,
The number of divisions is i in order to uniformly distribute the orientation direction to each pole.
= N / 2 steps (n is the number of poles), a portion having a large amount of magnetic flux in the orientation direction and a portion having a small amount of magnetic flux in a direction perpendicular thereto can be uniformly distributed to each pole. / I
By stacking the magnetic poles at different degrees and performing multi-pole magnetization, the total magnetic flux of each pole can be equalized. When n increases, the gap between the magnetized poles becomes narrow, and it becomes difficult to sufficiently magnetize.
Is preferably 50 or less. Also, if i is large and the number of stacks is large, the cost increases, so i is preferably 10 or less.

In the case where a cylindrical magnet having unidirectional anisotropy is multipolar magnetized by a vertical magnetic field press, the magnetized magnets near the gap between the poles are compared with the case where a radially anisotropic ring magnet is multipolar magnetized. Since the magnetism and magnetic properties are low, the change in the magnetic flux density between the poles is smooth, and the cogging torque of the motor is small. The cogging torque can be further reduced by skew-magnetizing the magnet or skewing the stator teeth. When the skew angle is 1/10 or less of the angle of one pole of the magnet (360 / n degrees), the effect of lowering the cogging torque due to the skew magnetization is small.
If it is larger than / 3, the decrease in the torque of the motor is large, so the skew angle is 1/10 to 2 of the angle of one pole of the magnet.
An angle of / 3 is preferred.

[0012]

Examples (Examples 1, 2 and Comparative Example 1) each having a purity of 9
9.7% by weight of Nd, Dy, Fe, Co, M (M is A
(1, Si, Cu) and B having a purity of 99.5% by weight were melt-cast in a vacuum melting furnace to produce an ingot. This ingot was coarsely pulverized with a jaw crusher, and further jet milled in a nitrogen stream to obtain an average particle size of 3.5 μm.
m was obtained. This powder was subjected to 1
Molding was performed at a molding pressure of 1.0 t / cm ² in a magnetic field of 2 kOe. The obtained molded body was sintered in Ar gas at 1090 ° C. for 1 hour, and subsequently heat-treated at 580 ° C. for 1 hour. After that, it is processed to 30mm outside diameter, 25m inside diameter
m, a cylindrical magnet having a thickness of 15 mm was obtained. Using the above magnet powder, a block magnet was produced under the same conditions as the cylindrical magnet.
The characteristics of this block magnet are as follows: Br: 13.0 kG, iH
c: 15 kOe, (BH) max: 40 MGOe.

In the first embodiment, the produced cylindrical magnets are stacked with the orientation directions shifted by 60 ° and arranged so that the orientation direction of the first-stage magnet has the relationship shown in FIG. went. In Example 2, the shift angle was 90 ° and six-pole magnetization was performed in the same manner. Further, as Comparative Example 1, an outer diameter of 30 mm, an inner diameter of 25 mm, and the same magnet powder as in Example 1 were used under the same conditions.
A cylindrical magnet having a thickness of 30 mm was prepared and subjected to six-pole magnetization.

(Embodiment 3) Using the same magnet powder as in Embodiment 1, under the same conditions, an outer diameter of 30 mm, an inner diameter of 25 mm, and a thickness of 10 m
m are produced, and the orientation direction is shifted by 60 ° and stacked in three stages.
Six-pole magnetization was performed with the arrangement shown in FIG. This is shown in FIG. The large arrow in the figure indicates the orientation direction of each stage of the cylindrical magnet. Reference numeral 23 denotes a motor core.

In order to evaluate these magnets, a horizontal 10.
A coil was prepared by winding a copper thin wire in a square having a length of 5 mm and a length of 30 mm with 50 turns. Move this coil away from the state in which it is in contact with the cylindrical magnet to a distance that is not affected by the magnetic force of the magnet, measure the amount of magnetic flux crossing the coil using a flux meter, and measure the amount of magnetic flux in the outer peripheral direction of the cylindrical magnet at this time. Table 1 shows the measured values.

[0016]

[Table 1]

(Embodiments 4 and 5) FIG. 4 is a plan view showing a three-phase permanent magnet motor 20 having nine motor stator teeth 21. FIG. A motor was manufactured by incorporating a magnetized cylindrical magnet into a stator having the same height as the magnet.
A ferromagnetic core serving as a motor shaft is inserted and bonded to the inner diameter of the cylindrical magnet. 150 fine copper wires on each tooth
Turn wound. This motor is rotated at 1000 rpm, and the absolute value of the induced voltage at this time is the maximum, and 1 to 5
After rotating at rpm, the size of the torque ripple was measured using a load cell. Reference numeral 22 denotes a motor coil. In the fourth embodiment, as in the second embodiment, the magnets are overlapped in two stages at a shift angle of 90 °, and the skew angle is set to １ ／ of the angle of one pole of the magnet.
The skew magnetization is performed at 20 °, and this magnet is incorporated in the motor of FIG.

In the fifth embodiment, a cylindrical magnet having the same dimensions as in the third embodiment is used. Magnets are stacked in three stages at a shift angle of 60 ° in FIG. 3 and magnetized without skew. FIG. 5 is incorporated into the motor of FIG. 4 having skew stator teeth that are 20 degrees, one third of the angle. In addition, a cylindrical magnet without stacking was used as Comparative Example 2, the induced voltage and the torque ripple were measured, and the maximum and minimum differences of the torque ripple are shown in Table 2 together with the induced voltage.

[0019]

[Table 2]

From Table 2, it can be seen that each of the examples has an induced voltage that can withstand practical use and the torque ripple is sufficiently small, whereas Comparative Example 2 has a large torque ripple and is not suitable for practical use. FIG. 5 shows a change in the induced voltage with respect to the electrical angle in the fifth embodiment. The induced voltage draws a smooth sine wave, and it is recognized that the generated induced voltage is not uneven. The curve a is the U-V phase in FIG.
The phase and the curve c show the induced voltage curve in the WU phase, respectively.

(Comparative Example 3) When the radially oriented cylindrical magnet of Example 4 was magnetized, skew magnetization was performed at 50 ° which is 5/6 of the angle of one pole of the skew angle magnet. It was assembled in a motor, and the induced voltage and the torque ripple were measured in the same manner as in Example 4, and the results are shown in Table 2. From Table 2, it can be seen that although the amount of torque ripple is small, the drop in induced voltage is large and is not suitable for practical use.

Example 6, Comparative Example 4 Using the Nd magnet alloy of Example 1, a uniaxially oriented ring magnet was produced by a vertical forming method. Magnet size is outer diameter 25mm, inner diameter 20m
m, thickness 15 mm. As shown in FIG. 6, this was stacked in six stages while changing the orientation direction by 60 ° to produce a magnet rotor. Further, this rotor was magnetized with 6 poles at a skew angle of 7 degrees. Further, as Comparative Example 4, a rotor was prepared using the same magnet and the orientation direction was aligned in one direction, and six poles were similarly magnetized at a skew angle of 7 degrees. These were assembled in a stator and torque ripple was measured.
The results are as shown in Table 2. In Example 6, the torque ripple was significantly reduced as compared with the comparative example.
It can be seen that the effect of the dispersion of the orientation of the magnet according to the present invention is remarkable.

[0023]

According to the present invention, a vertical magnetic field which can be easily produced in multiple units and long products without using an expensive radial anisotropic magnet having low productivity and which can be stably supplied at a low cost and in large quantities. A motor-oriented rotor is manufactured by laminating radially oriented cylindrical magnets using a press in the axial direction, magnetizing the poles in a multi-pole manner, and incorporating this into a permanent magnet type motor to produce an AC servo motor, DC
It greatly contributes to higher performance of brushless motors and the like and lower prices of motors.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are schematic diagrams showing a state in which a cylindrical magnet is magnetized by using a magnetizer; FIG.
The state where the orientation direction of the cylindrical magnet is rotated by 90 ° with respect to (a) to perform magnetization is shown.

Fig. 2 Nd-Fe- fabricated by vertical magnetic field press
FIG. 2 is a diagram showing a surface magnetic flux density when six-pole magnetization is performed on a B-system cylindrical magnet by the magnetizer shown in FIG.

FIG. 3 is a perspective view showing a rotor for a permanent magnet type motor of the present invention in which radially oriented cylindrical magnets are stacked in three stages shifted by 60 ° each.

FIG. 4 is a plan view showing a three-phase motor of the present invention in which cylindrical magnets magnetized into six poles are combined with nine stator teeth.

FIG. 5 is a diagram showing a relationship between an induced voltage and an electrical angle when a three-phase motor incorporating a radially oriented cylindrical magnet is rotated at 1000 rpm.

FIG. 6 is a perspective view showing a rotor for a permanent magnet type motor of the present invention in which radially oriented cylindrical magnets are stacked in six stages shifted by 60 °.

[Explanation of symbols]

 1. Cylindrical magnet 10. Magnetizer 11. Magnetizer magnetic pole teeth 12. Magnetizer coil 20. Permanent magnet type motor 21. Motor stator teeth 22. Motor coil 23. Motor core

Claims (5)

[Claims] When a cylindrical magnet manufactured by a vertical magnetic field forming method and oriented in one direction perpendicular to a cylindrical axis is used for a rotor of a permanent magnet type motor by magnetizing the outer peripheral surface of the cylindrical magnet in a multipolar manner. A multi-stage long multi-pole magnetized cylindrical magnet rotor characterized in that a uniaxially anisotropic cylindrical magnet is stacked in two or more stages in the axial direction to form a long cylindrical magnet, which is used as a rotor for a permanent magnet motor. . 2. When the number of stacked cylindrical magnets is i (i is a positive integer of 2 or more and 10 or less), i cylindrical magnets are stacked with the orientation direction shifted by 180 / i. 2. The multi-stage long multi-pole magnetized cylindrical magnet rotor according to 1. 3. When the number of poles of the multipolar magnetization is n (n is a positive integer of 1 to 50), the number i of stacks and the number n of poles have a relationship of i = n / 2. 3. The multi-stage long multi-pole magnetized cylindrical magnet rotor according to 2. 4. When performing multi-pole magnetization of n poles on the outer peripheral surface of a cylindrical magnet, the angle of one pole is set to 360 / n, and skew magnetization is performed at an angle of 1/10 to 2/3 of this angle. The multi-stage long multi-pole magnetized cylindrical magnet rotor according to any one of claims 1 to 3. 5. A permanent magnet motor using the multi-stage long multi-pole magnetized cylindrical magnet rotor according to any one of claims 1 to 4.