JP2000116090A - Permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make uniform scattering of the magnetic flux density between poles and to reduce torque irregularity by making specific the number of gears of a stator that is combined with a cylindrical magnet when the number of magnetization in a peripheral direction in the cylindrical magnet is set to an even number that is equal to or more than four. SOLUTION: When the number of magnetization in a peripheral direction in a cylindrical magnet 23 that is orientated in one direction being vertical to a cylindrical shaft is set to k (k is a positive even number that is equal to or more than four), the number of stator gears 21 being combined with the cylindrical magnet 23 is set to 3k.n/2 (n is a positive integer that is equal to or more than one). Also, the skew angle of the cylindrical magnet 23 ranges from 1/10 to 2/3 of the angle (360/k) for one pole and is made of k multiple-pole skew magnetization. Further, the skew angle of the stator gears 21 ranges from 1/10 to 2/3 of an angle (360/k) for one pole similarly and is provided with 3k.n/2 skew gears. For example, by setting the number k of magnet poles to 6 and the number 3k.n/2 of gears to 9 (n=1) in the combination of the pole of the magnet and the stator gears 21, the magnetic flux scattering can be relaxed also in a cylindrical magnet being orientated in a diameter direction with scattering in the magnetic flux density and suppressing rotation irregularity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a permanent magnet motor such as a servo motor and a spindle motor.

[0002]

2. Description of the Related Art Anisotropic magnets made by crushing crystalline magnetic anisotropic materials such as ferrites and rare earth alloys and pressing them in a specific magnetic field are used to produce loudspeakers, motors, measuring instruments, and other electric machines. Widely used for equipment and the like. Of these, rare earth sintered magnets that have anisotropy in the radial direction in particular have excellent magnetic properties, can be freely magnetized in the axial direction, and do not require reinforcement for fixing magnets such as segment magnets. Therefore, they are used for AC servomotors, DC brushless motors, and the like. In particular, in recent years, a long radial anisotropic magnet has been demanded as the performance of a motor becomes higher. Magnets with radial orientation are manufactured by molding in a magnetic field or by backward extrusion.In the molding method in a magnetic field, a magnetic field is applied from the opposite direction through a core to obtain radial orientation, but the magnet height that can be oriented is determined by the core shape. It is difficult to manufacture long products. In addition, the backward extrusion method requires large facilities, 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 mass-produce it inexpensively, and there is a disadvantage that the cost of the motor using the radial anisotropic magnet is very high. Was.

[0003]

If a cylindrical magnet can be multipolar magnetized without using a radial anisotropic magnet, the magnetic flux density is high, and the variation in magnetic flux density between the poles is small, a high-performance permanent magnet can be used. It can be a magnet for a motor. The magnet is oriented in one direction perpendicular to the cylinder axis by a vertical magnetic field press, and only the magnetization is multipole, so that a cylindrical multipole magnet for a permanent magnet motor is manufactured without using a radial anisotropic magnet. A method has been proposed (magnetics workshop of the Institute of Electrical Engineers of Japan, MAG-85-120, 1985). Magnets manufactured by the perpendicular magnetic field molding method and oriented in one direction perpendicular to the cylinder axis (hereinafter referred to as radially oriented cylindrical magnets) can be made as long as possible (50 mm or more) as long as the cavity of the press machine allows. In addition, since multiple presses can be performed, a large number of molded bodies can be obtained by one press, and a cylindrical magnet for a motor can be supplied at a low cost in place of an expensive radial anisotropic magnet. However, magnets that are multipole magnetized on a radially oriented cylindrical magnet actually produced by a vertical magnetic field press have a high magnetic flux density at poles near the orientation direction and a low magnetic flux density at poles perpendicular to the orientation direction. When the motor is assembled with the motor and the motor is rotated, uneven torque reflecting the variation in the magnetic flux density between the poles occurs, and it cannot be said that the magnet is a motor magnet that can withstand practical use.

[0004]

Means for Solving the Problems The present inventors have made intensive efforts to solve the above problems, and as a result, the present invention has been accomplished. The permanent magnet motor of the present invention has the following features. The number of magnetic poles in the circumferential direction of a cylindrical magnet manufactured by the method and oriented in one direction perpendicular to the cylindrical axis is k (k
Is a positive even number of 4 or more), and the number of teeth of the stator combined with the cylindrical magnet is 3 k · n / 2 (n is a positive integer of 1 or more). The skew angle of the cylindrical magnet oriented in one direction perpendicular to the axis is 1/10 to 2/3 of the angle of one pole of the cylindrical magnet (360 / k), and is composed of k multipole skew magnetized. ,
(3) The skew angle of the stator teeth is 1/10 to 2/3 of the angle of one pole of the cylindrical magnet (360 / k), and is 3kn.
/ 2 skew teeth. According to the present invention, it has become possible to supply a high-performance synchronous magnet motor in large quantities at low cost.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will now be described with reference to Nd-F
An eB-based radially oriented cylindrical magnet will be described, but the present invention is not limited to an Nd-Fe-B-based magnet. FIG.
FIG. 3 is an explanatory plan view of a magnetizer for magnetizing a cylindrical magnet. In the figure, 1 is a radially oriented cylindrical magnet, 10 is a magnetizer, 1
Numeral 1 denotes magnetic pole teeth of the magnetizer, and numeral 12 denotes a coil of the magnetizer. FIG. 2 is a diagram showing the surface magnetic flux density when the Nd-Fe-B-based cylindrical magnet produced by the perpendicular magnetic field press is subjected to six-pole magnetization by the magnetizer shown in FIG. As described above, when a radially oriented cylindrical magnet is manufactured by the vertical magnetic field molding method and the magnet is subjected to six-pole magnetization, a very large surface magnetic flux density can be obtained in the B, C, E, and F orientation directions. In addition, the surface magnetic flux density is small in portions A and D perpendicular to the orientation direction. In addition, in the orientation direction and its perpendicular direction, the magnetization width is wide in the orientation direction, even though the magnetization is performed using the magnetizing apparatus having the same angular width as in FIG. It becomes very narrow in the vertical direction. Therefore, in the radially oriented cylindrical magnet produced by the vertical magnetic field press, there are a pole having a large total magnetic flux generated from one pole and a pole having only a very small magnetic flux. Variations in the amount of magnetic flux between the poles result in uneven rotation when incorporated in the motor, causing vibration and noise. Therefore, by reducing the variation in the amount of magnetic flux between the respective poles, smooth and even rotation can be performed.

FIG. 3 is a plan view of a three-phase motor having nine stator teeth (stator teeth). In the three-phase motor 20, the stator teeth 21 of α, β, and γ are arranged in the order of α, β, and γ, and the wires are connected while winding the stator teeth in a coil shape, and become the input lines of the motor as U, V, and W phases. . A current flows through the U, V, and W phases to generate a magnetic field in the coil 22, and the magnetic field generated by the coil and the cylindrical magnet 2
The motor rotates due to the repulsive force and the attractive force acting between the motor 3.
UV, VW and WU are each one of the total number of stator teeth.
When a current flows through U-V, a magnetic field is generated from α of the stator core, and similarly, a magnetic field is generated in β by VW and γ in W-U. FIG.
The three-phase motor having such a stator having nine teeth incorporates a radially oriented cylindrical magnet 23 magnetized to six poles.

In the figure, UV (α) is located at the center of the pole of the magnet and becomes the peak of the motor torque. At this time, U-
The poles that act on V (α) to generate rotational force are F, B, and D poles. The F and B poles are poles in the vicinity of the orientation direction and have a high magnetic flux density, and D is a pole located in a direction perpendicular to the orientation direction. And the magnetic flux density is small. Next, the magnet rotates, and E (V)
The A and C poles approach. The E and C poles are poles near the orientation direction and have a high magnetic flux density, and A is a pole located in a direction perpendicular to the orientation direction and has a low magnetic flux density. However, 3 /
Due to having twice as many as nine teeth, the amount of magnetic flux linked to the U-V (α) coil is E, E,
The sum of the A and C poles is always equal. This relationship is the same for VW (β) and WU (γ).
Thus, the combination of the number of magnet poles and the number of teeth of the stator of the motor is determined by the number of magnet poles k = 6 and the number of teeth 3k · n / 2 = 9 (k =
6, n = 1), the magnetic flux variation is reduced even in a radially oriented cylindrical magnet in which the magnet has a pole in the direction near the orientation and a pole in the direction perpendicular to the orientation direction and the magnetic flux density varies. A motor without rotation unevenness can be obtained.

In the three-phase motor, when the number of stator poles is set to 3 k · n / 2 with respect to the number of magnet poles k, the above relationship is always maintained, and a motor without rotation unevenness can be obtained. In this way, by performing multipolar magnetization on the radially oriented cylindrical magnet and setting the number of stator teeth to 3n / 2 times the number of magnetized poles, a radially oriented cylindrical magnet that is inexpensive and can be mass-produced is used. It has become possible to produce a motor having excellent motor characteristics without rotation unevenness.

A multi-pole magnetized radially oriented cylindrical magnet produced by a vertical magnetic field press is more magnetized near the gap than a multi-pole magnetized radial anisotropic ring magnet. And the magnetic properties are low, so the change of 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 or skewing the stator teeth. If the skew angle of the cylindrical magnet and the stator teeth is less than 1/10 of the angle of one pole of the cylindrical magnet, the effect of lowering the cogging torque due to the skew magnetization is small, and is larger than two thirds of the angle of one pole of the cylindrical magnet. The skew angle is 1 / the angle of one pole of the cylindrical magnet.
Angles of 10 to 2/3 are preferred.

[0010]

EXAMPLES (Example 1, Comparative Example 1)
7% by weight of Nd, Dy, Fe, Co, M (M is Al, S
Using i, Cu) and B having a purity of 99.5% by weight, an ingot was produced by melting and casting in a vacuum melting furnace. The ingot was coarsely pulverized with a jaw crusher, and further subjected to jet mill pulverization in a nitrogen stream to obtain a fine powder having an average particle size of 3.5 μm. This powder was molded with a vertical magnetic field press at a molding pressure of 1.0 t / cm ² in a magnetic field of 12 kOe. This molded body was sintered in Ar gas at 1090 ° C. for 1 hour, and subsequently heat-treated at 580 ° C. for 1 hour. Thereafter, processing was performed to obtain a cylindrical magnet of φ30 mm × φ25 mm × L30 mm. Using the same magnet powder as the present cylindrical magnet, molding was performed with a vertical magnetic field press at a molding pressure of 1.0 t / cm ² in a magnetic field of 12 kOe, sintering was performed at 1090 ° C. for 1 hour in Ar gas, and subsequently 580 ° C. The properties of the block magnet produced under the same conditions as this cylindrical magnet after heat treatment for 1 hour at
r: 13.0 kG, iHc: 15 kOe, (BH) ma
x: 40 MGOe. The above-mentioned radially oriented cylindrical magnet was arranged in a magnetizer so as to have the relationship shown in FIG. 1, and six-pole magnetization was performed. A motor was manufactured in which the magnet after magnetization was incorporated in a stator having the same height as the magnet and having the configuration shown in FIG. A ferromagnetic core serving as a motor shaft is inserted and bonded to the inner diameter of the magnet. The copper wire was wound 100 turns for each tooth. The amount of magnetic flux between the phases was measured using a flux meter. As Comparative Example 1, the same fine copper wire as in Example 1 was wound around only one of the stator teeth for 100 turns, and the amount of magnetic flux was measured with a flux meter. Table 1 shows peak values when the magnet makes one rotation. As shown in the table, in the comparative example, although the amount of magnetic flux due to the peak is very large, about three times as large as the small peak, the peak value is hardly changed in the first embodiment.

[0011]

[Table 1]

(Embodiment 2) The motor of Embodiment 1 is
The induced voltage when rotating at rpm and the motor
The size of the torque ripple was measured by a load cell when rotating at 5 rpm. Table 2 shows the difference between the maximum value of the absolute value of the induced voltage and the maximum value and the minimum value of the torque ripple. From the table, it can be seen that this motor has a sufficient amount of induced voltage in use and has sufficiently small torque ripple.

(Embodiment 3) When magnetizing the radially oriented cylindrical magnet of Embodiment 1, the skew angle is set to one angle of one pole of the magnet.
Skew magnetization at 20 degrees of / 3
Table 2 shows values obtained by measuring the induced voltage and the torque ripple in the same manner as in Example 2 by assembling the motor. From the table, it can be seen that the amount of torque ripple is smaller than that of the product without skew, and the reduction of the induced voltage is slight. FIG. 4 shows a change in the induced voltage with respect to the electrical angle at this time. FIG. 4 shows that the induced voltage has a smooth sine wave, and the generated induced voltage is not uneven. The curve a is the U-V phase in FIG. 3, the curve b is the V-W phase, and the curve c is the W-phase.
The induced voltage curve in the -U phase is shown.

(Comparative Example 2) When the radially oriented cylindrical magnet of Example 1 was magnetized, the angle of one pole of the skew angle magnet was 5/5.
6, the skew magnetization was performed at 50 degrees, the magnet was assembled into the motor of Example 1, and the values of the induced voltage and the torque ripple measured in the same manner as in Example 2 are shown in Table 2. From the table, it can be seen that the amount of torque ripple is smaller than that of the product without skew, but the induced voltage is so large that it is not suitable for practical use.

(Embodiment 4) A radially oriented cylindrical magnet is magnetized in the same manner as in Embodiment 1, and a skew angle is equal to that of Embodiment 1 having 20 degrees of 1/3 of the angle of one magnet. Table 2 shows the values obtained by measuring the induced voltage and the torque ripple in the same manner as in Example 2 by assembling into a motor having the same dimensions. From the table,
It can be seen that the amount of torque ripple is smaller than that of the non-skewed product, and the induced voltage is slightly reduced.

[0016]

[Table 2]

[0017]

According to the present invention, a multi-unit, long product can be easily produced without using a radially anisotropic magnet which is low in productivity and can be supplied stably at low cost and in large quantities. A high-performance permanent magnet motor can be realized using a radially oriented cylindrical magnet by a magnetic field press.
It is useful for lowering the price of high-performance motors such as C brushless motors, and has a very high industrial utility value.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view of a magnetizer for magnetizing a cylindrical magnet.

FIG. 2 Nd-Fe-B produced by a vertical magnetic field press
FIG. 2 is a diagram showing a surface magnetic flux density when six-pole magnetization is performed on a system cylindrical magnet by the magnetizer shown in FIG. 1.

FIG. 3 is a plan view of a three-phase motor in which a cylindrical magnet multipolarized to six poles and nine stator teeth are combined.

FIG. 4 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.

[Explanation of symbols]

 1. 10. Radially oriented cylindrical magnet Magnetizer 11. Magnetizer magnetic pole teeth 12. Magnetizer coil 20.3 phase motor 21. Motor stator teeth 22. Motor coil 23. Radially oriented cylindrical magnet

Claims (3)

[Claims] When the number of circumferentially magnetized poles of a cylindrical magnet manufactured by a vertical magnetic field molding method and oriented in one direction perpendicular to a cylindrical axis is k (k is a positive even number of 4 or more),
The number of teeth of the stator combined with this cylindrical magnet is 3kn
/ 2 (n is a positive integer greater than or equal to 1) peripherally magnetized permanent magnet motor. 2. The skew angle of a cylindrical magnet oriented in one direction perpendicular to the cylindrical axis is equal to the angle of one pole of the cylindrical magnet (360 /
2. The permanent magnet motor according to claim 1, wherein k multipole skew magnetization is 1/10 to 2/3 of k). 3. The skew angle of the stator teeth is equal to that of the cylindrical magnet 1.
3/10 from 1/10 to 2/3 of the pole angle (360 / k)
2. The permanent magnet motor according to claim 1, having kn / 2 skew teeth.