JPH09285047A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the cogging and the whirling of a shaft by a method wherein the magnetic circuit of a magnet motor is composed of a core which has (6n) salient poles arranged with the same angular pitches and a core which are so magnetized as to have (8n) poles and the widths of the salient poles in the left half of the core and the right half of the core are changed within the range of 15/n degrees ± 5%. SOLUTION: The magnetic circuit of a motor is composed of a core 1 which has (6n) salient poles arranged with same angular pitches and a core which are so magnetized as to have (8n) poles. The widths of the salient poles in the left half 1a and the right half 1b of the core 1 are changed within the range of 15/n degrees ± 5%. The left half of the core 1 is a core 1a in which the angles of the salient poles are α deg.and the right half of the core 1 is a core 1b in which the angles of the salient poles are βSo and the core 1 consists of the combination of the core 1a and the core 1b. The relation between the magnet of the core la and the core 1 and the relation between the magnet of the core 1b and the core 1 are completely equal to each other. The cogging torque of the core 1 is obtained by synthesizing a half of the cogging torque of the core 1a and a half of the cogging torque of the core 1b. With this constitution, the cogging torque can be reduced and the shaft is pressed against one side and the whirling is suppressed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an information device, an image,
The present invention relates to a disk drive motor used in a disk drive device such as a magnetic disk or an optical disk used in audio equipment or the like.

[0002]

2. Description of the Related Art In recent years, disk drive devices such as magnetic disks and optical disks used in information equipment, video equipment, audio equipment and the like are required to have a motor with high rotational accuracy in accordance with high density recording of equipment. .

The cogging torque due to the change in the attraction force between the core and the magnet is the first factor that deteriorates the rotation accuracy of the motor. If the cogging torque becomes large, the jitter of the motor deteriorates, causing a read / write error.

Secondly, in the case of a motor having a bearing having a clearance between the shaft and the bearing, such as an oil-impregnated metal bearing, the shaft swings within the clearance between the shaft and the bearing. It appears as vibration in the track direction and causes a tracking error.

Conventionally, as a motor, first, as a measure against the cogging torque, the one described in Japanese Patent Application Laid-Open No. 4-304151 is known.

FIG. 6 shows the core shape of the conventional motor of the first embodiment. In FIG. 6, the core salient poles are formed by changing the angle by a predetermined angle from the position where 360 ° is equally divided. By shifting the positions of the salient poles, there is no one in which the magnet and the core have the same positional relationship, and the cogging torque is reduced.

Secondly, as a measure against whirling of the shaft, the one described in JP-A-1-152947 is known.

FIG. 7 shows a core shape of a conventional second embodiment motor. In FIG. 7, the magnetic center of the core is vertically displaced for each half circumference of the core. With this configuration, a force that tilts the shaft in a certain direction is applied to the magnet, so that whirling of the shaft can be suppressed.

[0009]

However, although the above-mentioned conventional methods are effective in reducing the cogging torque and suppressing the whirling of the shaft, the problems of the cogging torque and the whirling of the shaft are not solved. It does not solve at the same time.

It is an object of the present invention to provide a motor that simultaneously realizes reduction of cogging torque which causes deterioration of rotational accuracy and suppression of whirling of a shaft.

[0011]

In order to solve this problem, the present invention provides a core having 6n pole salient poles arranged at an equal angular pitch, and a magnetizing magnet having 8n poles arranged at an equal angular pitch. In a motor having a core and a magnet forming a magnetic circuit, the width of the core salient pole is changed in the range of 5% before and after 15 / n ° between the right half and the left half of the core. .

As a result, the phases of the cogging torques generated by the right and left halves of the core differ by 180 °, so that the cogging torques of both sides cancel each other out, reducing the cogging torque, and at the same time reducing the cogging torque between the core and the magnet. The attraction force acting on the rotor becomes unbalanced on the left and right, and the magnet fixed to the rotor receives a force that presses the shaft in one radial direction of the bearing, and the whirling of the shaft is restricted. Due to the synergistic effect of these two actions, it is possible to provide a motor with extremely high rotational accuracy without using special parts.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises a core having salient poles of 6n poles arranged at an equiangular pitch, and magnetizing of 8n poles arranged at an equiangular pitch. In a motor having a core and a magnet forming a magnetic circuit, the width of the salient pole of the core is 1 for the right half and the left half of the core.
By changing within 5% before and after 5 / n °, the cogging torque generated by one half of the core and the other half of the core are 180 ° out of phase with each other, so that the cogging torques cancel each other and the cogging torque is reduced. At the same time, the magnet exerts a force that presses the shaft to one side of the bearing, which has the effect of suppressing whirling of the shaft in the motor.

According to a second aspect of the present invention, the core and the magnetic circuit are constituted by the core having the slots of 6n poles arranged at an equal angular pitch and the magnetization of the 6n poles arranged at an equal angular pitch. And a magnet having a magnet, the slot width of the core is 15 / n ° between the right half and the left half of the core.
By changing within the range of 5% before and after, the same effect as in claim 1 can be obtained.

The embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a view showing a shape of a core according to a first embodiment of the present invention, and FIG. 2 is an exploded view showing a shape of a core according to the first embodiment of the present invention. is there. As shown in FIG. 2, the core 1 in FIG. 1 has a half on the left side of the core 1a having a core salient pole angle of α ° and a half on the right side of the core 1b having a core salient pole angle of β °. It has a shape combined with. Since the relationship between the magnet of the core 1a and the core is the same on the left and right, it is considered that the cogging torque is half when the cogging torque is half on one side. This also applies to the core 1b. Therefore, it is considered that the cogging torque of the core 1 is a combination of half the cogging torques of the core 1a and the core 1b.

Here, the cogging torque of the core 1a (or the core 1b) alone will be considered. 3A shows the relationship between the width (angle) of the salient pole of the core and the cogging torque, and FIG. 3B shows the width (angle) of the salient pole of the core and the stationary position of the rotor due to the cogging torque. It is a figure. From this, it can be seen that the cogging torque and the salient pole width have a certain law. The law is that cogging torque of almost the same absolute value appears every 15 ° salient pole width, and salient pole width 7.
It means that the stationary position of the rotor is reversed by 7.5 ° around 5 °, 22.5 °, 37.5 ° and 52.5 °. Considering the cogging torque when the width of the salient pole is different by 15 °, the absolute values of the cogging torque are almost the same in all cases, and the stationary position of the rotor is different by 7.5 °. This angle of 7.5 ° is 2 which is the basic cycle of the cogging torque.
One in one.

From the above, when the angle α-β = 15 ° is set, the cogging torque of the core 1 has the same absolute value.
The cogging torques of which the phases are different by 0 ° are halved, and the cogging torques of the two cancel each other out to reduce the cogging torque.

Further, in the case of the present embodiment, the attraction force acting between the core and the magnet becomes unbalanced on the left and right, and the rotor to which the magnet is attached is always in a state in which a force pressing in one radial direction is applied. As a result, the shaft is pressed in one direction of the bearing, and whirling of the shaft can be suppressed.

Due to these two synergistic effects, the motor using the core of the present embodiment can obtain a very high rotation accuracy in spite of its simple structure.

Further, although the above embodiment has been described for the case where the core has 6 poles and the magnet has 8 poles, the core 6n is generally used.
The same effect can be obtained for the pole and the magnet 8n pole by changing the width of the left and right core salient poles by 15 / n °.

Although the angle difference between the left and right is set to 15 ° in the above-mentioned embodiment, the point where the cogging torque becomes minimum due to the influence of magnetic saturation of the core in an actual motor is from the above angle. In many cases, the motor is present at a position slightly displaced, and by designing in consideration of this displacement, the cogging torque can be further reduced and a motor with high rotation accuracy can be provided.

(Embodiment 2) FIG. 4 is a view showing the shape of a core according to a second embodiment of the present invention, and FIG. 5 is an exploded view showing the shape of a core according to the second embodiment of the present invention. It is a figure. In FIG. 4, the core 1 is, as shown in FIG. 5, the core 1a whose slot opening angle is α ° in the left half of the core 1.
And the right half have a shape in which the half of the core 1b whose core slot opening angle is β ° is combined. The shape of the core shown in FIG. 4 is different from that of the first embodiment, but in fact, it is constructed based on exactly the same idea. In the core of FIG. 1, the joint between the left and right cores is in the slot portion, but in FIG. 4, the joint between the left and right is replaced with a salient pole portion. Therefore, by setting the angle α-β = 15 °,
The same effect can be obtained. Further, in the present embodiment, three slots having a wide opening angle are evenly arranged on the left side of the core, which is an optimum space for arranging the Hall element or the like for detecting the rotor position.

[0023]

As described above, according to the present invention, the cogging torque can be reduced and the whirling of the shaft can be suppressed at the same time only by the shape of the core. The synergistic effect of these two effects makes it possible to achieve a very simple structure and a high rotational accuracy. It can provide a very high motor.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape of a core according to a first embodiment of the present invention.

FIG. 2 is an exploded view showing a shape of a core according to the first embodiment of the present invention.

FIG. 3A is a diagram showing the relationship between the width (angle) of the salient pole of the core and the cogging torque. (B) A diagram showing the width (angle) of the salient pole of the core and the stationary position of the rotor due to the cogging torque.

FIG. 4 is a diagram showing a shape of a core according to a second embodiment of the present invention.

FIG. 5 is an exploded view showing a shape of a core according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a core shape of a conventional motor according to a first embodiment.

FIG. 7 is a diagram showing a core shape of a conventional motor according to a second embodiment.

[Explanation of symbols]

 1 core 1a, 1b core

Claims (2)

[Claims] 1. A motor including a core having 6n poles of salient poles arranged at an equiangular pitch, and a magnet having a magnetization of 8n poles arranged at an equiangular pitch and constituting a magnetic circuit with the core. In the motor, the width of the core salient pole is changed in the range of 5% before and after 15 / n ° between the right half and the left half of the core. 2. A motor having a core having slots of 6n poles arranged at an equiangular pitch, and a magnet having 6n poles arranged at an equiangular pitch and constituting a magnetic circuit with the core. A motor characterized in that the width of the slot of the core is changed in the right half and the left half of the core within a range of 5% before and after 15 / n °.