JPH05168212A - Brushless motor - Google Patents

Abstract

PURPOSE:To enable a motor to be easily made thinner, and enable the precision of rotation to be ensured without requiring high precision for component parts for fixing ball bearings. CONSTITUTION:A brushless motor consists of a rotor consisting of a magnet 1, and a rotor yoke 2 with the magnet to be fitted on, a stator consisting of a coil 3, and a back yoke 4 or a core with the coil to be set on, and a bearing for supporting the rotor rotatably on the stator. In this case, the bearing is formed with one ball bearing, and with magnetic attraction between the magnet of the rotor and the back yoke or core of the stator, pre-pressure is to be applied to the ball bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and more particularly to a brushless motor characterized in that the bearing is composed of one ball bearing.

[0002]

2. Description of the Related Art Conventionally, two ball bearings are often used as bearings for motors that require highly accurate rotation. However, in such a case, the central axes of the two ball bearings need to be accurately aligned, and high precision is required for parts that fix the ball bearings. For this reason, the cost of the bearing portion increases. Further, since two ball bearings are used, it is difficult to make the motor thinner. If two ball bearings are used and the motor is made thin, a sufficient distance cannot be obtained between the bearings and the bearing becomes unstable, and there is a problem that the rotation accuracy cannot be ensured.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems.
(EN) Provided is a brushless motor which can easily reduce the thickness of a motor and can secure rotation accuracy without requiring high accuracy for a component for fixing a ball bearing.

[0004]

According to the present invention, there is provided a rotor including a magnet, a rotor yoke to which the magnet is attached, a coil, a stator including a coil and a back yoke or an iron core, and the rotor. In a brushless motor including a bearing rotatably supported with respect to the stator, the bearing is composed of one ball bearing, and a magnetic attraction force between a magnet of the rotor and a back yoke or an iron core of the stator. It is characterized in that the ball bearing is preloaded.

In the brushless motor described above,
An accommodating portion for fixing the ball bearing is provided in at least one of the rotor yoke and the back yoke in a step shape or a cut-and-raised shape by press molding.

[0006]

With the brushless motor of the present invention having the above-mentioned structure, only one ball bearing is required, so that the bearing portion can be shortened and the motor can be easily thinned. Moreover, since it is not necessary to align the central axes of the ball bearings, it is not necessary to have high precision in the parts that fix the ball bearings. Since the ball bearing is preloaded by the magnetic attraction between the rotor magnet and the stator back yoke or iron core,
The accuracy of rotation can be secured.

[0007]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. First, FIG. 1 is a sectional view showing a first embodiment of the brushless motor of the present invention. In FIG. 1, the brushless motor of the first embodiment is a flat magnet 1
A rotor including a rotor yoke 2 to which the magnet 1 is attached, a stator including an air-core flat coil 3, and a back yoke 4 in which the coil 3 is arranged, and the rotor rotatably with respect to the stator. It comprises a ball bearing 5 as a bearing for supporting. That is, it is a face-to-face flat type brushless motor.

The inner ring of the ball bearing 5 is fixed to the stepped storage portion 2a of the rotor yoke 2, and the outer ring is fixed to the cut-and-raised storage portion 4a of the back yoke 4 of the stator. The stepped storage portion 2a of the rotor yoke 2 and the cut-and-raised storage portion 4a of the back yoke 4 of the stator are both formed by press molding when the rotor yoke 2 and the back yoke 4 are formed by press molding.

A feature of the present invention is that there is only one ball bearing 5 as a bearing. In order to stabilize the rotation of the motor, a preload is applied to the ball bearing 5, and the preload is applied by the magnetic attraction between the flat magnet 1 of the rotor and the back yoke 4 of the stator. Next, a second embodiment of the brushless motor of the present invention will be described with reference to the sectional view of FIG. In FIG. 2, the second
The brushless motor of the embodiment has a cylindrical magnet 11
A rotor including a rotor yoke 12 to which the magnet 11 is attached, a coil 13, a stator including an iron core 14 around which the coil 13 is wound, and a stator housing 16 supporting the iron core 14, and the rotor, Ball bearing 5 as a bearing for rotatably supporting the stator
Consists of That is, the motor is a cylindrical outer rotation type brushless motor.

The inner ring of the ball bearing 5 is fixed to the stepped storage portion 12a of the rotor yoke 12, and the outer ring is fixed to the stator housing 16. The stepped storage portion 12a of the rotor yoke 12 is simultaneously formed by press molding when the rotor yoke 12 is formed by press molding. A feature of the present invention is that there is only one ball bearing 5 as a bearing. In order to stabilize the rotation as a motor, a preload is applied to the ball bearing 5, and the preload is deviated between the magnetic center of the cylindrical magnet 11 of the rotor and the magnetic center of the iron core 14 of the stator (FIG. 2). Is indicated by A) and is applied by a magnetic attraction force.

As described above, since only one ball bearing 5 is required, the bearing portion can be shortened and the motor can be easily thinned. Further, since it is not necessary to align the central axes of the ball bearings 5 with each other, a component for fixing the ball bearings 5, that is, in the first embodiment, the rotor yoke 2 having the stepped storage portion 2a and the cut-and-raised storage portion. High accuracy is not required for the back yoke 4 having the portion 4a and, in the second embodiment, for the rotor yoke 12 having the stepped storage portion 12a.

Since the ball bearing 5 is preloaded by the magnetic attraction between the magnets 1 and 11 of the rotor and the back yoke 4 or the iron core 14 of the stator, the rotation accuracy can be secured. In addition, since the inner side of the inner ring of the ball bearing 5 is supported by the storage portions 2a and 12a of the rotor yokes 2 and 12, it is possible to have a structure without a shaft, and the space inside the storage portions 2a and 12a For example, when it is used as a spindle motor for a floppy disk or the like, it can be effectively used as a space for a chuck device for media.

When the back yoke 4 and the stator housing 16 are used as a spindle motor for a floppy disk or the like, they may be integrated with the chassis of the floppy disk drive. Further, the rotor yokes 2, 12 and the back yoke 4 including the stepped or cut-and-raised ball bearing housings 2a, 12a, 4a provided on at least one of the rotor yokes 2, 12 and the back yoke 4 can be manufactured by press molding. It is possible to manufacture at low cost.

[0014]

As described above, since the brushless motor of the present invention requires only one ball bearing,
The bearing can be shortened, and the motor can be easily thinned. Moreover, since it is not necessary to align the central axes of the ball bearings, it is not necessary to have high precision in the parts that fix the ball bearings. Since the ball bearing is preloaded by the magnetic attraction between the magnet of the rotor and the back yoke of the stator or the iron core, the accuracy of rotation can be ensured.

In addition, it is possible to have a structure without an axis, and when the space inside the inner ring of the ball bearing is used as a spindle motor of, for example, a floppy disk or the like, it can be effectively utilized as a space of a chuck device for media. There is. Further, by providing the storage portion for fixing the ball bearing to at least one of the rotor yoke and the back yoke in a stepped shape or a cut-and-raised shape by press molding, it is possible to manufacture the rotor yoke and the back yoke at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a brushless motor according to a first embodiment of the invention.

FIG. 2 is a sectional view of a second embodiment of the brushless motor of the present invention.

[Explanation of symbols]

 1, 11 Magnet 2, 12 Rotor yoke 2a, 12a Stepped storage part 3, 13 Coil 4 Back yoke 4a Cut and raised storage part 14 Iron core 5 Ball bearing 16 Stator housing

Claims (2)

[Claims] 1. A rotor including a magnet, a rotor yoke to which the magnet is attached, a coil, a stator including a coil, a back yoke or an iron core, and a rotor rotatably with respect to the stator. In a brushless motor including a supporting bearing, the bearing is composed of one ball bearing, and the ball bearing is preloaded by a magnetic attraction force between a magnet of the rotor and a back yoke or an iron core of a stator. Brushless motor characterized by doing so. 2. The brushless motor according to claim 1, wherein an accommodating portion for fixing the ball bearing is provided in at least one of the rotor yoke and the back yoke by press molding.