JP2003219587A - Outer rotor type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To assure torque when a rotor type motor, in which the rotor of permanent magnet rotates around the outside of a stator, is rotated at a low speed, while attaining reduced cogging torque, when it is rotated at a high speed. <P>SOLUTION: A rotor 20 of a permanent magnet 24 of an rotor type motor rotates around the outside of a stator 10. A gap between a stator-side magnetic pole 12 and a rotor-side permanent magnet 24 becomes smaller at a low speed, while becomes larger at a high speed due to the centrifugal force caused by the rotation of the motor. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer rotor type motor (rotary electric motor) in which a rotor using a permanent magnet rotates outside a stator, and is effectively applied to, for example, a spindle motor in which a shaft is directly connected to drive a load. Related technology.

[0002]

2. Description of the Related Art An outer rotor type motor using a permanent magnet as a rotor is suitable for downsizing, especially thinning, and it is easy to obtain a relatively high torque. Drives) are used for spindle motors that rotate at high speed.

As shown in FIG. 3, this type of motor has a structure in which a cup-shaped rotor 20 rotates outside the stator 10. The rotor 20 includes an annular permanent magnet 2 on the inner wall surface of a flat circular cup 22 having a rotation shaft 26 at the center.
4 is fixed. The permanent magnet 24 is magnetized in multiple poles so that N poles and S poles are alternately arranged at predetermined intervals in the circumferential direction. A rotating shaft 26 of the cup 22 is rotatably supported by a bearing device 16 penetrating the stator 10.

The stator 10 has a plurality of fixed magnetic poles 12, called teeth, arranged radially. Each magnetic pole 12
Each of them has an excitation winding 14 wound around it, and its magnetic pole tip (magnetic action end) is faced with a predetermined gap (gap) g on the inner peripheral side surface of the permanent magnet 24. Each excitation winding 14 is driven by multi-phase energization by a drive circuit (not shown). The permanent magnet 24, that is, the rotor 2 is generated by the rotating magnetic field generated by this multi-phase energization drive.
0 is rotationally driven.

[0005]

In the outer rotor type motor described above, the gap g between the magnetic pole 12 on the stator side and the permanent magnet 24 on the rotor side is related to the output characteristics of the motor. That is, if the gap g is reduced, the magnetic attraction force acting between the stator 10 and the rotor 20 is increased, and the torque during low speed rotation can be increased.

However, the magnetic attraction force acting between the stator 10 and the rotor 20 causes cogging torque. The cogging torque is a kind of rotational torque unevenness that occurs when the magnetic attraction force between the stator 10 and the rotor 20 changes depending on the rotation angle of the rotor 20, and if this is large,
Vibration and noise are generated during high-speed rotation, and motor efficiency is greatly reduced.

Therefore, for example, in a spindle motor which drives a load such as a CD directly at a high speed to drive the spindle at a high speed, it is necessary to secure a torque at a low speed necessary to reliably start the rotation of the motor and to prevent vibration and noise at a high speed. There is a problem that it is in conflict with reducing the cogging torque which is the cause.

The present invention has been made in view of the above contradictory problems, and it is an outer rotor type that can achieve both torque securing at low speed rotation and reduction of cogging torque at high speed rotation. To provide a motor.

[0009]

The means according to the present invention is an outer rotor type motor in which a rotor using a permanent magnet rotates outside the stator, and the gap between the stator side magnetic pole and the rotor side permanent magnet is the rotation of the motor. It is characterized in that it is configured to be small at low speed and large at high speed due to the centrifugal force generated. According to this means, it is possible to achieve both the securing of torque during low speed rotation and the reduction of cogging torque during high speed rotation.

As a concrete means of the above construction, an annular permanent magnet formed by being divided into a plurality of segments is arranged on the inner wall surface of a flat circular cup, and the centrifugal force is provided between each segment and the inner wall surface of the cup. A configuration in which an elastic member that is elastically deformed according to a force is interposed is suitable. As the elastic member, an elastic cushion material made of an elastic material such as sponge or rubber is convenient. To make it even simpler, an elastic cushion material formed in a sheet shape in advance is used. Further, a metal spring member can be used as the elastic member. Since the metal spring member has little deterioration or deterioration of the material such as sponge or rubber, it is possible to expect stable motor characteristics for a long period of time.

[0011]

1 shows an embodiment of an outer rotor type motor to which the technique of the present invention is applied. The motor shown in the figure has a structure in which a cup-shaped rotor 20 using a permanent magnet 24 rotates outside the stator 10.

In the rotor 20, permanent magnets 24 are annularly arranged along the inner wall surface of a flat circular cup 22 having a rotating shaft 26 at the center. The annular permanent magnet 24 is formed by being divided into a plurality (four in the figure) of arc-shaped segments 24a to 24d. A rotating shaft 26 of the cup 22 is rotatably supported by a bearing device 16 penetrating the stator 10.

Each of the segments 24a to 24d is an independent member made of a hard magnetic material, and is arranged on the inner wall surface of the cup 22 so as to form a ring as a whole.
The segments 24a to 24d are magnetized so that the N poles and the S poles are alternately arranged at predetermined intervals in the circumferential direction of the ring.

Each of the segments 24a to 24d is provided with a cup-shaped elastic cushioning material 30 in the form of a cup 2.
It is attached to the inner wall surface of 2. The cushion material 30 is an elastic member made of sponge, rubber, or the like, and when the segments 24a to 24d receive a centrifugal force due to the rotation of the rotor 20, they are pressed by the segments 24a to 24d and elastically compressed. Has become. That is,
Each of the segments 24a to 24d is attached to the inner wall surface of the cup 22 via the cushion material 30. The inner wall surface of the cup 22 and the cushion material 30 and the cushion material 30 and the segments 24a to 24d are joined by an adhesive or the like.

The stator 10 has a plurality of fixed magnetic poles 12, called teeth, arranged radially. Each magnetic pole 12
Each of them has an excitation winding 14 wound around it, and its magnetic pole tip (magnetic action end) is faced with a predetermined gap (gap) g on the inner peripheral side surface of the permanent magnet 24. Each excitation winding 14 is driven by multi-phase energization by a drive circuit (not shown). The permanent magnet 24, that is, the rotor 2 is generated by the rotating magnetic field generated by this multi-phase energization drive.
0 is rotationally driven.

Next, the operation will be described. The outer rotor type motor described above includes the annular permanent magnet 2 on the rotor 20 side.
4 is formed by being divided into a plurality of segments 24a to 24d, and each of the segments 24a to 24d is attached to the inner wall surface of the cup 22 via the elastic cushion material 30, so that the magnetic pole 1 on the stator 10 side is formed.
The gap g between the permanent magnet 24 on the side of the rotor 20 and the permanent magnet 24 on the rotor 20 side changes according to the centrifugal force accompanying the rotation of the motor, as shown in FIGS.

That is, at the time of stop or low speed rotation,
As shown in (a), each of the segments 24a to 24d is supported by the elastic cushion material 30 in the non-compressed state, and is in the position closest to the magnetic pole 12 on the stator 10 side. At this time, the gap g is minimized, and a magnetic attraction force sufficient to secure low-speed rotation torque at the time of starting and acceleration can be applied between the stator 10 and the rotor 20.

On the other hand, at the time of high speed rotation, as shown in (b), each of the segments 24a to 24d receives a centrifugal force to compress the elastic cushion material 30. This compression is elastic compression, and the amount of compression depends on the rotation speed. As a result, the gap g is enlarged during high-speed rotation, and the cogging torque can be reduced. Therefore, at the time of high speed rotation, there is little vibration or noise, and the motor efficiency can be stably and efficiently rotated without lowering the motor efficiency. Further, by using the sheet-shaped elastic cushion material 30 made of sponge, rubber or the like as the elastic member, the means for obtaining the above-mentioned effect can be very easily configured.

As described above, it is possible to secure both the low-speed torque required to reliably start the rotation of the motor and reduce the cogging torque that causes vibration and noise during high-speed rotation. Can be achieved.

Although the change in the gap g is exaggerated in FIG. 2 in order to make the operation easy to understand, the actual change in the gap g may be very small, and therefore the thickness of the elastic cushion member 30 may be small. Does not affect the size or shape of the motor.

Although the present invention has been described above based on its typical embodiment, the present invention can have various modes other than those described above. For example, in the above-described embodiment, the sheet-shaped elastic cushion material 3 is provided as the elastic member step to be interposed between the segments 24a to 24d and the inner wall surface of the cup 22.
Although 0 is used, the elastic cushion material 30 may have a shape other than a sheet shape, for example, a granular shape or an embossed shape. In addition to elastic materials such as sponge and rubber, metal spring members can be used. In the case of a metal spring member, it is possible to avoid a change in elastic characteristics due to material deterioration or alteration that is likely to occur in sponge, rubber or the like.

[0022]

According to the present invention, in a motor of an outer rotor type in which a rotor using a permanent magnet rotates outside the stator, it is possible to secure torque during low speed rotation and reduce cogging torque during high speed rotation. Can be achieved.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view showing an embodiment of a main part of an outer rotor type motor according to the present invention.

FIG. 2 is a diagram schematically showing an operation of the motor shown in FIG.

3A and 3B are a plan view and a cross-sectional view showing a configuration of a conventional outer rotor type motor.

[Explanation of symbols]

10 Stator 12 magnetic poles 14 Excitation winding 16 Bearing device 20 rotor 22 cups 24 annular permanent magnet 24a to 24d Segments forming an annular permanent magnet 26 rotation axis 30 Elastic cushion material (elastic member) g gap

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H002 AA01 AB07 AC04                 5H622 AA02 AA03 CA02 CA05 CA11                       CB06 PP04 PP19 QB02

Claims (6)

[Claims] 1. In an outer rotor type motor in which a rotor using permanent magnets rotates outside a stator, a gap between a stator side magnetic pole and a rotor side permanent magnet is small at low speed and large at high speed due to centrifugal force generated by rotation of the motor. An outer rotor type motor characterized by being configured as follows. 2. The annular permanent magnet according to claim 1, which is divided into a plurality of segments, is arranged on the inner wall surface of the flat circular cup, and the centrifugal force is applied between each segment and the inner wall surface of the cup. An outer rotor type motor characterized by interposing an elastic member that is elastically deformed accordingly. 3. The outer rotor type motor according to claim 2, wherein an elastic cushion material is interposed as the elastic member. 4. The outer rotor type motor according to claim 3, wherein the elastic cushion material has a sheet shape. 5. The outer rotor type motor according to claim 3, wherein an elastic material such as sponge or rubber is used as the elastic cushion material. 6. The outer rotor type motor according to claim 2, wherein a metal spring member is used as the elastic member.