JPH0334153A - Spindle motor for hard disk device - Google Patents

Abstract

PURPOSE:To prevent the deformation of a disk due to the fluctuation of an ambient temperature from occurring and to reduce a manufacturing cost by directly fitting a disk in a cylindrical yoke part having a slit. CONSTITUTION:It is assumed that the inside diameter of the mounting hole 22a of the disk 22 is reduced than the original outside diameter of the yoke part 18 due to the fluctuation of the ambient temperature after assembling and the difference of thermal expansion between the disk 22 and the yoke part 18. At such a case, since the yoke part 18 receives a tightening force from periphery, the yoke part 18 is deformed in a direction to reduce the width of the slit 19, and thermal stress can be relaxed. Adversely, when the inside diameter of the mounting hole 22a of the disk 22 is increased than the original outside diameter of the yoke part 18, the yoke part 18 is deformed in a direction to expand the width of the slit 19 since the tightening force applied on the yoke part 18 from the periphery is weakened, which maintains a stable fitting state between the yoke part 18 and the disk 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a spindle motor for a hard disk drive having an improved rotor structure.

(Prior Art) For example, in a 365-inch type hard disk device, if the structure of a conventional disk drive section is illustrated,
The result will be as shown in the figure.

In the figure, a stator 2 equipped with an armature coil 1 is fitted and fixed to the outer periphery of a bearing device 3, and a rotary shaft 4 is rotatably supported by the bearing device 3. This rotating shaft 4
A cylindrical container-shaped hub 5 is fixed to the upper end of the stator 2 so as to cover the stator 2, and a plurality of magnetic recording disks 6 are fitted around the outer periphery of the hub 5. Also,
A cylindrical rotor yoke 7 is fitted on the inner periphery of the hub 5, and a field magnet 8 is further fitted on the inner periphery. Here, the disk 6 is generally made of aluminum, and the hub 5 is manufactured by cutting magnetic stainless steel or the like.

(Question 8 to be solved by the invention) By the way, the coefficient of thermal expansion of the stainless steel that is the material of the hub 5 is about 1. 1 x 10-'/°C, and the thermal expansion of aluminum, which is the material of the disk 6, is approximately 2.3 x 10-'/°C.
5/'C, and the two are significantly different. For this reason,
For example, when calculating the standard size of a 3.5-inch type and assuming that the temperature is 25° C. higher than the temperature at the time of assembly, the inner diameter of the mounting hole of the disk 6 will be 75 μm smaller than the outer diameter of the hub 5.

As a result, in the above configuration, the disk 6 is warped as shown in an exaggerated manner in FIG. 6, and errors in writing and reading are likely to occur. Furthermore, with the above configuration, the hub 5 must be manufactured by cutting, which is expensive.
The structure is complicated, such as assembling the rotor yoke 7 to the hub 5, and the overall manufacturing cost is high.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a spindle motor with 6 I/D disks that can prevent deformation of the disks due to fluctuations in ambient temperature and also reduce manufacturing costs. .

[Structure of the Invention] (Means for Solving the Problems) A spindle motor of the present invention includes a rotor having an end plate portion fixed to a rotating shaft, and a cylindrical end plate portion having a slit. It is composed of a yoke part made of a magnetic material connected to the outer periphery in a fitted state, and a field permanent magnet provided on the inner periphery of this yoke part, and a magnetic recording disk is fitted to the outer periphery of the yoke part. It is characterized by being made to fit together.

In this case, it is desirable that the slits in the yoke portion be provided corresponding to the magnetic pole boundary portions of the field permanent magnets.

(Operation) Since the disc is directly fitted into the cylindrical yoke, the hub, which was conventionally formed by cutting, is no longer required.
The number of parts is reduced. In addition, since the yoke part has a cylindrical shape with slits, there is a difference in thermal expansion between the yoke part and the disk, so even if the mounting hole of the disk deforms to shrink or expand due to fluctuations in ambient temperature, it will not change. The deformation is absorbed by the expansion of the slit width, and no excessive stress is applied to the disk.

In this configuration, the field permanent magnet is exposed through the slit in the yoke, but if the slit is provided corresponding to the magnetic pole boundary of the field permanent magnet, the field permanent magnet can be exposed from the field permanent magnet. leakage flux can be minimized.

(Example) Hereinafter, a first example in which the present invention is applied to a 3.5-inch type hard disk device will be described with reference to FIGS. 1 and 2.

The stator 11 includes a plurality of armature windings 13 on a stator core 12.
The bearing sleeve 15 is fixed to the outer periphery of a bearing sleeve 15 erected at the center of the bracket 14 . A pair of upper and lower rolling bearings 15a and 15b are installed inside the pongee receiving tube 15, and a rotary shaft 16 is rotatably supported via these.

A disk-shaped end plate 17 is fixed to the upper end of the rotating shaft 16, and the upper end of a cylindrical yoke 18 is connected to the end plate 17 in a fitted manner. A flexible rubber adhesive is applied to this connecting portion, thereby integrating the two. The yoke part 18 is formed by rolling a plate made of magnetic material into a cylindrical shape, and by setting the length of the plate slightly shorter than the outer circumferential dimension of the end plate part 17, As shown, a slit 19 extending in the axial direction is formed.

A field permanent magnet 20, which also has a cylindrical shape, is fixed to the inner periphery of the yoke portion 18 in a fitted state. This field permanent magnet 20 is magnetized so as to have different poles alternately in the circumferential direction, so that, for example, eight poles are formed. It is arranged so as to be located at the center of one width direction. The end plate portion 17, yoke portion 18, and field permanent magnet 20 described above constitute the rotor 21 as a whole, and the stator 11
It also operates as a brushless DC motor.

On the other hand, four magnetic recording disks 22 are provided in this embodiment, and their mounting structure will be described next.

Each disk 22 has a circular mounting hole 22a formed in its center (eg, inner diameter 25 mm) and is made of aluminum. A ring 23 made of aluminum is fitted into the lower end of the yoke portion 18 of the rotor 21 . All of the four disks 22 are directly fitted into the yoke part 18, of which the lowermost one has the above-mentioned receiver resting on the upper surface of the ring 23, and the other disks are stacked in multiple stages with a spacer ring 24 interposed between them. ing. A retaining plate 26 fixed to the end plate 17 with screws 25 is in contact with the inner circumference of the upper surface of the uppermost disk 22, and each disk 22 is sandwiched between the receiver and the ring 23. .

In the above configuration, the inner diameter of the mounting hole 22a of the disk 22 is larger than the original outer diameter of the yoke portion 18 due to the difference in thermal expansion between the disk 22 and the yoke portion 18 due to fluctuations in the ambient temperature after assembly. Suppose that also becomes smaller. In this case, since the yoke part 18 receives a tightening force from the surroundings, the yoke part 18 deforms in a direction that narrows the width of the slit 19, thereby relieving the thermal stress. Also,
Conversely, the assembly may be difficult due to later ambient temperature fluctuations in the disk 22.
If the inner diameter of the mounting hole 22a of the yoke part 18 becomes larger than the original outer diameter dimension of the yoke part 18, the tightening force of the yoke part 18 from the surroundings can be weakened.
8 deforms in a direction to widen the width of the slit 19, thereby maintaining a stable fitted state between the yoke portion 18 and the disk 22.

As described above, according to this embodiment, it is possible to alleviate the thermal stress caused by the difference in materials, and it is possible to prevent distortion from occurring in the disk 22, so that stable operation as a hard disk device can be expected. In addition, since the disk 22 is directly fitted into the yoke portion 18, there is no need for a hub like in the past, and there is no need for expensive cutting, which also reduces manufacturing costs. can.

In addition, as in this embodiment, the slit 1 of the yoke portion 18
According to the configuration in which the magnetic poles 9 are aligned with the magnetic pole boundary portion 20a of the field permanent magnet 20, leakage magnetic flux is reduced compared to the configuration in which they are shifted as in the second embodiment of the present invention shown in FIG. The occurrence of can be reduced.

Note that the present invention is not limited to the above embodiments,
For example, as in the third embodiment shown in FIG.
If one of the magnets is inclined with respect to the radial direction of the field permanent magnet 20, leakage flux can be further reduced. In addition, in order to reduce cogging, when the field permanent magnet is magnetized at an angle with respect to the axial direction, the slit is also formed diagonally along the magnetic pole boundary.
Various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As described above, according to the present invention, deformation of the disk due to fluctuations in ambient temperature can be prevented, and manufacturing costs can also be reduced. Furthermore, in the configuration in which the slits of the yoke portion are provided corresponding to the magnetic pole boundary portions of the field permanent magnets, leakage flux can be minimized even though the slits are provided.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a longitudinal cross-sectional view of the whole, FIG. 2 is a cross-sectional view, and FIG. 3 is a schematic diagram showing a second embodiment of the present invention. FIG. 4 is a cross-sectional view of the main part showing a third embodiment of the present invention, FIG. 5 is a vertical cross-sectional view showing a conventional spindle motor, and FIG. 6 shows a deformed state of the disk. FIG. 3 is a partially enlarged vertical cross-sectional view. In the drawing, 11 is fixed, 16 is a rotating shaft, 17 is an end plate part,
18 is a yoke portion, 19 is a slit, 20 is a field permanent magnet, 20a is a magnetic pole boundary portion, 21 is a rotor, and 22 is a disk.

Claims (1)

[Claims] 1. An external rotor is provided to cover the stator,
In a device to which a magnetic recording disk is fitted, the rotor is connected to an end plate portion fixed to a rotating shaft and a cylindrical end plate portion having a slit and fitted to the outer periphery of the end plate portion. A hard disk drive comprising a yoke made of a magnetic material and a field permanent magnet provided on the inner periphery of the yoke, and the disk is fitted on the outer periphery of the yoke. spindle motor. 2. The spindle motor for a hard disk drive according to claim 1, wherein the slit in the yoke portion is provided corresponding to a magnetic pole boundary portion of the field permanent magnet.