JPH11266554A - Flat fan motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat fan motor which is able to reduce the vibration of its rotor by reducing the fluctuations of a thrust load, when the motor is rotated and moreover can obtain stable rotation by obtaining a large thrust load. SOLUTION: In a flat fan motor, a stator yoke 2 which faces opposite to a magnet 1 fitted to a rotor is constituted of an annular outer yoke 2a and a polygonal inner yoke 2b. The fan motor mainly obtains a thrust load by means of the outer yoke 2a and less-fluctuating cogging torque by means of the inner yoke 2b. Since the thrust load fluctuates little, stable motor rotation can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat type (axial gap type) motor, and more particularly, to a stator yoke used for the motor.

[0002]

2. Description of the Related Art FIGS. 4A and 4B show an example of a yoke shape of a conventional fan motor. FIG. 4A is a front sectional view, FIG. 4B is a plan view, and FIG. A magnet 12 attached to the rotor and having six magnet poles and a substantially triangular stator yoke 13 attached to the stator are arranged facing each other.

[0003] By forming the stator yoke 13 in a polygonal shape, the suction force in the thrust direction fluctuates according to the rotor rotation angle θ, and a pulsating flow characteristic as shown in FIG. Since the number of magnet poles is six, it changes every 60 degrees of rotation. In the structure of the yoke of the conventional flat motor, the permeance of the magnetic circuit fluctuates greatly during rotation, and the magnetic attraction force in the thrust direction fluctuates greatly, which causes vibration. In addition, fluctuations in the suction force cause rotation unevenness, and the stability during rotation of the rotor has also deteriorated.

[0004]

By the way, in a flat motor, the outer peripheral shape of a stator yoke is generally made non-uniform with respect to a rotor magnet in order to obtain a coking torque. To obtain the necessary thrust load (a single-bearing type motor requires a certain thrust load to stabilize rotation), the larger the outer shape of the yoke, the better, but the larger the yoke, the larger the coking torque. Therefore, there is a problem that the fluctuation of the thrust load increases. SUMMARY OF THE INVENTION It is an object of the present invention to provide a flat motor capable of reducing the fluctuation of the thrust load during rotation to reduce the vibration of the rotor and obtaining a stable rotation by obtaining a large thrust load.

[0005]

In order to achieve the above-mentioned object, a flat fan motor according to the present invention comprises a yoke arranged to face a stator side with respect to a multi-pole magnet mounted on a rotor side. The inner yoke on the side closer to the axis is polygonal, the outer yoke on the outer circumference is ring-shaped,
The polygonal portion is configured to obtain a coking torque and the ring-shaped portion is configured to mainly obtain a thrust load. In the above configuration, the inner yoke and the outer yoke are connected at a connecting portion and are integrally formed. Further, the flat fan motor can be applied to a single-bearing fan motor.

[0006]

According to the above construction, a strong magnetic attraction force acts to stabilize the magnetic attraction force by the ring-shaped yoke portion, and a coking torque can be obtained by the inner polygonal yoke portion, thereby stabilizing the flat motor. You can get a good rotation.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a front sectional view showing an embodiment of a flat fan motor according to the present invention, which is an example of a single-bearing fan motor. The outermost periphery of the motor housing is a venturi 4, a multi-pole magnet 1 is mounted on the lower surface, and a rotor 7 having a fan 5 formed on the outer periphery is housed. The shaft 8 fixed to the rotor 7 is supported by one bearing, that is, one ball bearing 9, and an E-ring is locked at an end of the shaft 8 to prevent the shaft 8 from coming off.

On the stator side, a coil 6 and a yoke 2 are arranged facing the magnet 1. York 2
Since the inner yoke has a polygonal shape and the outer yoke has a ring shape, the rotor 7 is always attracted to the stator with a large magnetic attraction in the thrust direction, and this magnetic attraction serves as a preload for the ball bearing 9. At the same time, the coking torque exerted by the polygonal inner yoke is small, and the fluctuation of the thrust load is small. Therefore, stable rotation is obtained with less vibration of the rotor.

FIGS. 2A and 2B show a yoke-shaped embodiment. FIG. 2A is a side sectional view, FIG. 2B is a plan view, and FIG. 2C is a characteristic diagram of a thrust load. The outer yoke portion 2a and the inner yoke portion 2b have a ring shape and a hexagonal shape, respectively, and the two yoke portions 2a and 2b are connected by a connecting portion 2c and are integrally formed. The further the outer periphery, the greater the attraction force between the yoke 2 and the magnet 1, so that the ring-shaped outer yoke 2 a mainly generates a thrust load. The hexagonal inner yoke portion 2b generates a cogging torque with little fluctuation.

In (c), B is a suction force by the outer yoke 2a, C is a suction force for generating a coking torque by the inner yoke 2b, and a combined suction force A obtained by combining B and C works as a slide load. By arranging the yoke for obtaining the coking torque inside the ring, the fluctuation of the synthetic suction can be reduced. The characteristic that the magnetic attraction force is large but the permeance fluctuation of the magnetic circuit is small can be obtained.

FIG. 3 is a plan view showing another embodiment of the yoke shape. The connection between the ring-shaped outer yota 3a and the hexagonal inner yoke 3b has a structure in which the hexagonal top is directly connected to the inner peripheral portion of the ring, and is integrally formed. By arranging the polygon as the inner yoke, the thrust load can be increased by the ring-shaped outer yoke without increasing the fluctuation of the permeance of the magnetic circuit, but by changing the polygon from a triangle to a hexagon, Variations in the permeance of the magnetic circuit can be reduced. Further, since the outer yoke and the inner yoke can be integrally formed, the number of parts of the yoke does not increase.

[0012]

As described above, according to the present invention, since the yoke is constituted by the polygonal inner yoke and the ring-shaped outer yoke, a large thrust load can be obtained and the fluctuation of the thrust load can be reduced. In this case, the rotor can be stabilized. Further, in the one-ball bearing, a sufficient preload to the ball bearing can be obtained.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of a fan motor according to the present invention.

2A and 2B are diagrams showing an embodiment of a yoke shape, wherein FIG. 2A is a front sectional view, FIG. 2B is a plan view, and FIG. 2C is a characteristic diagram of a thrust load.

FIG. 3 is a plan view showing another embodiment of a yoke shape.

4A and 4B are diagrams showing an example of a yoke shape of a conventional fan motor, wherein FIG. 4A is a side sectional view, FIG. 4B is a plan view, and FIG. 4C is a characteristic diagram of a thrust load.

[Explanation of symbols]

 1,12 magnet 2,3,13 stator yoke 2a outer yoke 2b inner yoke 4 venturi 5 fan 6 coil 8 shaft 9 ball bearing 10 printed circuit board 11 lead wire

Claims (3)

[Claims] 1. A multi-pole magnet mounted on a rotor side has a yoke shape facing the stator side, the inner yoke near the rotation axis has a polygonal shape, and the outer yoke on the outer circumference has a ring shape. A flat fan motor, wherein a coking torque is obtained in the polygonal portion and a thrust load is mainly obtained in the ring-shaped portion. 2. The apparatus according to claim 1, wherein the inner yoke and the outer yoke are connected at a connecting portion and are integrally formed.
The flat fan motor as described. 3. The flat fan motor according to claim 1, wherein the flat fan motor is a single-bearing fan motor.