JP2601915Y2 - Brushless motor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor applicable to, for example, a magnetic disk drive.

[0002]

2. Description of the Related Art Conventionally, a brushless motor is known as one of motors applied to, for example, a magnetic disk drive. FIG. 6 shows an example of such a brushless motor. In FIG. 6, a hole is formed in the center of an iron substrate 45, and a cup-shaped housing 37 is fitted and fixed in the hole. An outer ring of a bearing 38 is fixed to the inside of the peripheral wall of the housing 37, and the rotating shaft 31 is press-fitted into an inner ring of the bearing 38. The rotating shaft 31 is supported by an inner ring of a bearing 38 so as to be rotatable. A stator core 44 is mounted on the outer surface of the housing 37 on the upper surface of the substrate 45. The stator core 44 is configured by stacking a plurality of core bodies. Further, the stator core 44 has a plurality of salient poles on the outer periphery, and the coil 41 is wound around each salient pole.

[0003] A hub table 39 on which a recording medium such as a disk is mounted is fitted to the upper end of the rotating shaft 31.
A cup-shaped rotor yoke 32 is fixed to the hub base 39 by caulking or the like. A drive magnet 33 is attached to the inner surface of the peripheral wall of the rotor yoke 32 via a yoke 43. The inner surface of the drive magnet 33 faces the salient poles of the stator core 44 with a certain gap. Therefore, the coils 4 wound around the salient poles of the stator core 44
By controlling the energization of 1, the drive magnet 33 and the rotor yoke 32 are urged, and the rotating shaft 31 is driven to rotate. A frequency power generation magnet 42 is attached outside the yoke 43 on the opening side of the rotor yoke 32.

[0004]

[Problems to be Solved by the Invention] In recent years, the above-described brushless motors have been increasingly thinned. As a method for reducing the thickness, a method such as reducing the number of stacked stator cores is used. However, if the number of stacked stator cores is reduced, a sufficient output cannot be obtained, and the characteristics of the motor are significantly deteriorated. The brushless motor as shown in FIG.
There is a disadvantage that the rotor yoke 32 rotates while rattling due to the gap between the rotating shaft 31 and the bearing 38.

In order to obtain a high output while reducing the dimension in the direction of the rotation axis, a large-diameter portion is formed on the inner diameter of the stator core and disposed on a substrate as described in Japanese Patent Application Laid-Open No. 3-243145. What is necessary is just to make it the structure which a part etc. is accommodated in the large diameter part of a stator core. However, in such a configuration, the dimension that can be reduced in thickness is small, and in order to further reduce the thickness, there is no other way but to reduce the stacked dimension of the stator core.

In order to prevent rattling of the rotor yoke 32 during rotational driving of the brushless motor, see Japanese Patent Application Laid-Open No.
As described in Japanese Patent No. 23346, a cushioning material may be provided on the bearing, and the rattling of the rotating shaft may be prevented by the cushioning material. However, providing a cushioning material in the bearing requires processing for forming a concave portion or the like on the inner surface of the bearing, which increases the manufacturing cost.

The present invention has been made to solve the above problems, and has as its object to provide a brushless motor that is thin and can obtain a sufficient output.

[0008]

Means for Solving the Problems The present invention has been made to achieve the above object, and has a rotating shaft, a rotor yoke fixed to the rotating shaft, and an inner peripheral surface of the rotor yoke. In a brushless motor including an annular driving magnet, a stator core facing the inner peripheral surface of the driving magnet, and an iron plate substrate on which the stator core is mounted , an upper surface facing an axial end surface of the driving magnet is provided.
90 ° to 270 ° angle range in the circumferential direction on the iron plate substrate
In you, characterized in that the formation of the magnetic flux reduction unit comprising a hole cut away.

[0009]

The magnetic path is interrupted by the magnetic flux reducing portion formed on the surface of the iron member facing one of the axial end faces of the drive magnet, so that the magnetic flux concentrates on the stator core, and the brushless motor is driven. When the output becomes high and a constant output is to be obtained, the number of stacked stator cores can be reduced. In addition, when the magnetic flux reducing portion is formed, magnetic imbalance occurs, and the rotor yoke rotates while tilting in one direction.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the brushless motor according to the present invention will be described below with reference to the drawings. In FIG. 1, a hole is formed in the center of an iron substrate 5, and a cup-shaped housing 7 is fitted and fixed in the hole.
An outer ring of a bearing 8 is fixed to the inside of a peripheral wall of the housing 7, and the rotating shaft 1 is press-fitted into an inner ring of the bearing 8.
The rotating shaft 1 is supported by an inner ring of a bearing 8 so as to be rotatable. The stator core 4 is mounted on the upper surface of the substrate 5 and on the outer periphery of the housing 7. The stator core 4 is configured by laminating a plurality of core bodies. As shown in FIG. 2, the outer periphery of the stator core 4 has a plurality of salient poles extending radially outward, and a coil 11 is wound around each salient pole.

In FIG. 1, a hub base 9 on which, for example, a disk is placed is fitted and fixed to the upper end of the rotating shaft 1. The cup-shaped rotor yoke 2 is fixed to the lower surface of the hub base 9 by caulking or the like. The drive magnet 3 is attached to the inner surface of the peripheral wall of the rotor yoke 2 via a yoke 13. The inner surface of the drive magnet 3 faces the salient pole of the stator core 4 with a gap corresponding to the dimension g. Therefore, by controlling the energization of the coil 11 wound around the salient poles of the stator core 4, the drive magnet 3 and the rotor yoke 2 are energized, and the rotating shaft 1 is driven to rotate. On the opening side of the rotor yoke 2, a magnet 12 for frequency generation is attached to the lower surface of the outer periphery of the yoke 13.

A magnetic flux reducing portion 6 which is a through hole is formed on a portion of the substrate 5 which faces the axial end surface of the drive magnet 3 with a gap therebetween. As shown in FIG. 2, the magnetic flux reduction unit 6 is formed so as to have a C-shape around the rotation shaft 2. The magnetic flux reducing portion 6 is formed from the root of the umbrella-shaped portion at the tip of the salient pole of the stator core 4 to the outer peripheral surface side of the drive magnet 3, and its width dimension L is equal to the gap dimension g described above, or It is set to be larger than that. By forming the magnetic flux reducing portion 6 on the substrate 5, the magnetic path from the driving magnet 3 to the substrate 5 which is a magnetic material is cut off, and the magnetic flux from the driving magnet 3 is concentrated on the salient poles of the stator core 4, and the effective magnetic flux Therefore, a brushless motor having an extremely high output can be obtained. Therefore, even if the number of stacked stator cores 4 is reduced and the physique is made thin, a sufficient output can be obtained. FIG. 4 shows the relationship between the notch amount (opening of the C-shape) of the magnetic flux reduction unit 6 and the effective magnetic flux ratio, and the effective magnetic flux ratio increases as the notch amount increases. In order to obtain a sufficient output, the notch amount is preferably set to 90 ° or more.

In the brushless motor having the above-described magnetic flux reduction section 6, an inexpensive magnet material having somewhat inferior characteristics may be used for the drive magnet 3 for cost reduction. Since the effective magnetic flux can be increased by the magnetic flux reducing section 6, the brushless motor can obtain a sufficient output in performance even with a magnet material having somewhat poor characteristics. Further, the salient poles of the stator core 4 and the driving magnets 3
High output can be obtained without reducing the gap size g of the brushless motor, thereby improving the productivity of the brushless motor,
Manufacturing costs can be further reduced.

The magnetic flux reducing section 6 is formed by cutting the substrate 5 into a C shape.
As a result, the suction force between the drive magnet 3 and the iron substrate 5 is unbalanced in the circumferential direction, and the rotor yoke 2 rotates in a state inclined in one direction as shown in FIG. When the rotor yoke 2 is tilted, the rotating shaft 1
Since the bearing also rotates while abutting on a specific portion of the bearing 8, smooth rotation can be achieved without rattling. Notch amount of looseness circumferential smallest flux reduction unit, can be seen that the graph shown in FIG. 5, the moment ratio of the inclination of the rotor yoke 2 is an angle range of about 180 ° of maximum . Also, as can be seen from FIG.
For smooth rotation without rattling, the magnetic flux reduction unit 6
Angle range of 90 ° to 270 °
No. Since the rotor yoke 2 is tilted by the magnetic flux reducing portion 6 to prevent the rotation shaft 2 from rattling, members such as a cushioning member are not required, so that the manufacturing cost can be further reduced.

[0015] Incidentally, the magnetic flux reduction unit 6 consisting of hole may be plural number, shape is not limited to C-shape, but it may also be formed, for example, the multiple C-shape.

[0016]

[0017]

According to the present invention, the rotating shaft, the rotor yoke fixed to the rotating shaft, the annular driving magnet fixed to the inner peripheral surface of the rotor yoke, and the inner peripheral surface of the driving magnet are opposed to each other. A brushless motor including a stator core and an iron plate substrate on which the stator core is mounted;
The above iron plate substrate facing the axial end face of the drive magnet
Cutout in the angular range of 90 ° to 270 ° in the circumferential direction
The magnetic flux path between the drive magnet and the iron member can be cut off, and the magnetic flux from the drive magnet can be concentrated on the stator core, resulting in a thin and sufficient output. Can be. Also drive
Imbalance of magnetic attraction between magnet and iron plate substrate
As a result, the rotor yoke is tilted in one direction
It can rotate smoothly without rattling.

[Brief description of the drawings]

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

FIG. 2 is a plan view showing a stator unit of the brushless motor.

FIG. 3 is a side view showing the inclination of a rotor yoke of the brushless motor.

FIG. 4 is a graph showing a relationship between a notch amount and an effective magnetic flux ratio of the brushless motor according to the present invention.

FIG. 5 is a graph showing a relationship between a notch amount and a rotor suction moment ratio of the brushless motor according to the present invention.

FIG. 6 is a sectional view showing an example of a conventional brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation axis 2 Rotor yoke 3 Drive magnet 4 Stator core 5 Iron plate substrate 6 Magnetic flux reduction part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Ishikawa 14-888 Ako, Komagane-shi, Nagano Co., Ltd. Sankyo Seiki Seisakusho Co., Ltd. Komagane Factory (56) References Really open Showa 64-37369 (JP, U) Really open Hei 3-106870 (JP, U) Actually open Hei 3-11368 (JP, U) (58) Fields studied (Int. Cl. ⁶ , DB name) H02K 29/00 H02K 21/22

Claims (1)

(57) [Scope of request for utility model registration] A rotating shaft, a rotor yoke fixed to the rotating shaft, an annular drive magnet fixed to an inner peripheral surface of the rotor yoke, a stator core facing the inner peripheral surface of the drive magnet, and a stator core. A brushless motor including an iron plate substrate to be mounted, wherein the iron plate opposes an axial end surface of the drive magnet.
Cut at 90 ° to 270 ° in the circumferential direction on the substrate
A brushless motor that has a magnetic flux reduction section consisting of a missing through-hole .