JP2000102207A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor with a simple constitution having a high precise hub setting surface. SOLUTION: This spindle motor is equipped with a stator part 11, which contains a bearing 16 fixed on a motor base 12 and a winding coil 15 arranged around the bearing, and a rotor part 20 which is supported by the bearing 16 and contains a rotating shaft 21 and a rotor magnet 24. A boss part 22, having a hub setting surface 22a of a disk medium, is installed in the vicinity of one end of the rotating shaft 21. The rotor magnet 24 faces the winding coil 15 and is integrally fixed to the rotating shaft 21. A trench 21a for cutting work is formed on the other end of the rotating shaft 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor used for rotating a disk medium such as a large-capacity floppy disk.

[0002]

2. Description of the Related Art FIG. 5 is a sectional side view showing an example of a conventional spindle motor. This spindle motor 1 is
It comprises a fixedly arranged stator section 2 and a rotor section 3 rotatably supported by the stator section 2. The stator unit 2 includes a motor base 2a, a bearing housing 2b attached to the motor base 2a, and a winding coil wound around a laminated iron core 2c fixed and arranged so as to surround the bearing housing 2b in the circumferential direction. 2d and a pair of bearings 2 held in the bearing housing 2b by press fitting or the like.
e.

The rotor 3 is mounted on a rotating shaft 3a rotatably held by a bearing 2e via a boss 4a to be described later.
a flat cylindrical rotor case 3b whose lower end is open so as to surround d from the outside, a rotor magnet 3c attached to the inner peripheral surface of the rotor case 3b by bonding or the like,
And a disk medium chucking portion 4 attached near the upper end of the rotating shaft 3a.

The chucking portion 4 includes a boss 4a mounted near the upper end of the rotating shaft 3a and a disk chucking magnet 4b provided on the upper surface of the rotor case 3b radially outside the boss 4a. And a disc chucking pin 4c. further,
The upper surface 4d of the boss 4a is formed as a hub seating surface of the disk medium so as to be perpendicular to the center axis of the rotating shaft 3a. And on the hub seating surface 4d,
In order to enhance the slidability during chucking of the disk medium, a seating sheet 5 made of, for example, a tetrafluoroethylene film or the like is attached with an adhesive, an adhesive, or the like.

[0005] The spindle motor 1 thus configured
According to the above, when the disk medium is placed on the seat 5 attached to the hub seating surface 4d of the boss portion 4a, the center hole of the center hub of the disk medium is placed at one end of the rotating shaft 3a. The hub is engaged with the chucking magnet 4
The magnetic force is applied to the chucking portion 4 to be fixed and held on the chucking portion 4. When the winding coil 2d is appropriately energized, the magnetic field generated in the winding coil 2d interacts with the magnetic field generated by the rotor magnet 3c of the rotor section 3 and the rotor case 3b acting as a rotor yoke, and the rotor The unit 3 is driven to rotate. At this time, the rotation of the rotor unit 3 is reliably transmitted to the disk medium by engaging the chucking pins 4c with the chucking holes provided in the disk medium, and the disk medium is reliably rotated. It is supposed to be.

[0006]

Generally, a floppy disk drive (hereinafter referred to as FDD), which is widely used as a computer peripheral, has a capacity of, for example, about 2 MB per disk medium when unformatted. However, in recent years, an FDD having a large capacity per disk medium and a high data transfer speed has been developed.
Have been developed and are being marketed.

In the case of such a so-called large-capacity FDD,
In order to increase the capacity, the track pitch of the disk medium has been greatly reduced, and the rotation speed of the disk medium has been increased in order to increase the data transfer speed. For this reason, in the FDD, it is necessary to perform high-accuracy tracking control of the recording / reproducing head and to suppress vibration due to an increase in the motor rotation speed.
It is necessary to suppress surface runout of the disk medium during DD mounting as much as possible.

However, in the conventional spindle motor 1 as shown in FIG. 5, the hub seating surface 4d for determining the runout of the disk medium is defined by the boss 4a which is attached to the rotary shaft 3a by press fitting or the like. Have been. Therefore, in order to suppress the surface runout of the disk medium at the time of FDD mounting, the bearing housing 2b and the bearing 2
e, it is necessary to increase the dimensional accuracy of each component of the rotating shaft 3a and the boss portion 4a, and also to increase the assembly accuracy thereof.
There has been a problem that parts costs and assembly costs are increased.

In view of the above, it is an object of the present invention to provide a spindle motor having a simple structure and a highly accurate hub seating surface.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a stator portion including a bearing mounted on a motor base and a winding coil disposed around the bearing.
A rotor supported by the bearing, and integrally fixed to the rotating shaft such that a boss having a hub seating surface of a disk medium is provided near one end and opposed to the rotating shaft and the winding coil; In a spindle motor for rotating a disk medium provided with a rotor unit including a magnet, a cutting groove is formed at the other end of the rotating shaft.

According to the above configuration, since the cutting groove is formed at the other end of the rotary shaft, the cutting groove such as a cutting drive is formed in the cutting groove at the final stage of assembling the spindle motor. By engaging the driving tool, the rotating shaft can be rotationally driven by the cutting driving tool. Then, the hub seating surface of the boss portion attached near one end of the rotating shaft can be cut by the cutting tool. As a result, the hub seating surface is cut with high precision with respect to the rotary shaft in the assembled state, so that the surface runout of the hub seating surface is significantly reduced, and highly accurate surface runout accuracy is obtained.

Since the cutting of the hub seating surface is performed only by engaging the cutting drive tool with the cutting groove provided at the other end of the rotary shaft, the cutting of the rotary shaft and the bearing is performed. The load at the time is small, and there is no damage to the rotating shaft and the bearing due to the cutting process. In addition, except for a cutting groove formed at the other end of the rotating shaft, the configuration is the same as that of the conventional spindle motor, so that chucking of the disk medium can be performed in the same manner as the conventional spindle motor. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are added. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

FIGS. 1 and 2 show an embodiment of a spindle motor according to the present invention. The spindle motor 10 includes a fixedly arranged stator unit 11 and a rotor unit 20 rotatably supported by the stator unit 11. The stator part 11 is a motor base 1
2, a bearing housing 13 attached to the motor base 12, a winding coil 15 wound around a laminated iron core 14 fixedly arranged so as to surround the bearing housing 13 in the circumferential direction, and the inside of the bearing housing 13. And a pair of bearings 16 by press fitting or the like.

The motor base 12 is made of, for example, a galvanized steel plate and functions as a stator substrate. The bearing housing 13 is fixed to the motor base 12 by caulking or the like. The laminated iron core 14 is configured by laminating, for example, electromagnetic steel sheets such as a silicon steel sheet. Power is supplied to the winding coil 15 from a drive circuit (not shown) through a harness and the like and wiring provided on the motor base 12.

The bearing 16 is held at a predetermined interval by inserting a spacer 17 in the bearing housing 13. Each bearing 16 and spacer 17 are fixed in the bearing housing 13 by bonding or the like. Further, on the motor base 12, a support column 18 for mounting to a floppy disk drive is mounted by caulking or the like.

The rotor portion 20 includes a rotating shaft 21 rotatably held by the bearing 16 and a boss portion 22 mounted near one end (the upper end in the drawing) of the rotating shaft 21.
A flat cylindrical rotor case 23 attached to the boss portion 22 and having an open lower end so as to surround the winding coil 15 from the outside; and a rotor attached to the inner peripheral surface of the rotor case 23. It includes a magnet 24 and a chucking portion 25 for a disk medium provided near one end of the rotating shaft 21.

The boss 22 is made of, for example, brass, and is fixed to the rotating shaft 21 by press-fitting or the like. Further, the boss portion 22 is formed so that its upper surface 22a is perpendicular to the center axis of the rotating shaft 21 as a hub seating surface of the disk medium. And the hub seating surface 22
A seating sheet 26 made of, for example, a tetrafluoroethylene film or the like is adhered on the sheet a with an adhesive or an adhesive in order to enhance the slidability during chucking of the disk medium. This seat 26 has a thickness of, for example, 0.1 m.
m to 0.2 mm.

The rotor case 23 is made of a magnetic material such as a galvanized steel plate, and is fixed to the boss 22 by caulking or the like. The rotor magnet 24 is magnetized so that N poles and S poles are alternately arranged along the circumferential direction, and is fixed to the inner peripheral surface of the rotor case 23 by bonding or the like. The chucking portion 25 includes a disk chucking magnet 25 a and a disk chucking pin 25 b provided on the upper surface of the rotor case 23.

The above configuration is substantially the same as that of the conventional spindle motor 1 shown in FIG. 5, but in the spindle motor 10 according to the present invention, as shown in detail in FIGS. The configuration is different in that a cutting groove 21a for engaging a cutting drive tool is formed at the lower end of the shaft 21. This cutting groove 21
As shown in FIG. 4, a is formed at the lower end surface of the rotating shaft 21 so as to extend in the diametrical direction, and the width thereof is selected to be substantially equal to the thickness of the tip of the cutting drive tool. .

The spindle motor 10 according to the present invention is configured as described above, and is assembled as follows. That is, after the rotor unit 20 previously assembled except for the seat 26 is assembled to the stator unit 11, these are fixed to the cutting device by the columns 18 fixed to the motor base 12. Is done. Then, a cutting drive tool 30 such as a cutting drive knurl of the cutting device 30
Is engaged in the cutting groove 21 a at the lower end of the rotating shaft 21.

From this state, the cutting drive tool 30 is moved from the state shown in FIG.
Is rotated around the longitudinal axis as shown by the arrow A, whereby the rotating shaft 21 rotates around its central axis. Then, the cutting tool of the cutting device, such as a cutting tool 31 made of, for example, carbide steel or diamond, is positioned on the upper surface of the boss portion 22 that rotates together with the rotating shaft 21, that is, the hub seating surface 22a. Face 22
The cutting process a is performed.

Thus, the hub seating surface 22 of the boss portion 22
In the assembled state, a is cut so as to be perpendicular to the center axis of the rotating shaft 21. Therefore, the runout of the hub seating surface 22a is greatly reduced, and the runout accuracy is improved. And after the end of the above cutting process,
The assembly of the spindle motor 10 is completed by attaching the seat 26 to the hub seating surface 22a with an adhesive, an adhesive, or the like.

According to the spindle motor 10 assembled in this manner, when the disk medium is placed on the seat 26 on the hub seating surface 22a of the boss 22, the disk medium is moved to the center hub. The center hole is engaged with one end of the rotating shaft 21, and the hub is magnetically attracted by the chucking magnet 25a. As a result, the hub is pressed against the seat 26 and is fixedly held to the chucking portion 25.

When the winding coil 15 is appropriately energized, the magnetic field generated in the winding coil 15 interacts with the magnetic field generated by the rotor magnet 24 of the rotor section 20 to rotate the rotor section 20. Will be done. At this time, since the seat 26 to which the disk medium comes in contact has a relatively small thickness of, for example, 0.1 mm to 0.2 mm, the surface runout accuracy is determined by the hub seating surface 22 a of the boss 22. Is determined by the surface runout accuracy.

Therefore, as described above, the hub seating surface 22a of the boss portion 22 is cut so as to be perpendicular to the center axis of the rotating shaft 21 at the final stage of assembly, so that the surface runout is reduced. Since it is greatly reduced, the surface deflection accuracy of the disk medium actually chucked by the chucking unit 25 increases. As described above, even when the track pitch of the disk medium is narrow and the rotation speed of the disk medium is high, as in a large-capacity floppy disk drive, highly accurate tracking control of the recording / reproducing head is possible. In addition, the vibration generated due to the rotation of the spindle motor is reduced, and a spindle motor optimal for a large-capacity floppy disk drive can be obtained.

The cutting of the hub seating surface 22a of the boss portion 22 in the final stage of the above-described assembly is performed by cutting the cutting groove 2 provided with the cutting drive tool 30 at the other end of the rotary shaft 21.
1a, the cutting is performed by the cutting tool 31, so that the load on the rotating shaft 21 and the bearing 16 during the cutting process can be reduced, and the rotating shaft 21 and the bearing 1 can be cut by the cutting process.
No damage to 6. Except for a cutting groove 21a formed at the other end of the rotary shaft 21, the disk medium has the same configuration as the conventional spindle motor 1 shown in FIG. And the spindle motor 10
There is no significant increase in manufacturing costs and component costs.

In the above-described embodiment, the rotor case 23 and the rotor magnet 24 provided on the inner peripheral surface thereof are arranged so as to surround the wound coil 14 arranged in an annular shape from the outside. However, the present invention is not limited to such a configuration, and the present invention can be applied to a spindle motor in which a rotor case and a rotor magnet are disposed so as to face the winding coil 15 in the axial direction. it can. In the above-described embodiment, the spindle motor for rotating and driving a disk medium such as a floppy disk has been described. However, the present invention is not limited to this, and the spindle motor for rotating and driving any disk-shaped member to be rotated. The present invention can be applied to further,
In the embodiment described above, the rotor case 23 is fixed to the rotating shaft 21 via the boss portion 22. However, the present invention is not limited to this. The present invention can be applied to a motor.

[0029]

As described above, according to the present invention, since the hub seating surface is formed with high precision, the surface runout of the disk medium during mounting can be greatly suppressed.

[Brief description of the drawings]

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

FIG. 2 is a schematic plan view of the spindle motor of FIG.

FIG. 3 is an enlarged side view of a rotating shaft in the spindle motor of FIG. 1;

FIG. 4 is an enlarged bottom view showing a lower end surface of the rotation shaft of FIG. 3;

FIG. 5 is a schematic sectional view showing an example of a conventional spindle motor.

[Explanation of symbols]

10 ... spindle motor, 11 ... stator part,
12 ... motor base, 13 ... bearing housing,
14 ... Laminated iron core, 15 ... Wound coil, 16 ...
・ Bearing, 17 ・ ・ ・ Spacer, 18 ・ ・ ・ Post, 20 ・
..Rotor part, 21 ... Rotary shaft, 21a ... Cutting groove, 22 ... Boss part, 22a ... Hub seating surface,
Reference numeral 23: rotor case, 24: rotor magnet, 25: chucking portion, 30: cutting drive tool (vertical), 31: cutting tool (bite)

Claims (2)

[Claims] 1. A bearing mounted on a motor base and a stator including a winding coil disposed around the bearing, and a boss supported by the bearing and having a hub seating surface of a disk medium. And a rotor section including a rotor magnet integrally fixed to the rotating shaft so as to face the rotating shaft provided near one end and the winding coil. A spindle motor, wherein a cutting groove is formed at the other end of the rotating shaft. 2. The spindle motor according to claim 1, wherein the cutting groove is a groove for engaging a cutting drive tool for rotating the rotating shaft during cutting of the hub seating surface.