JPS62212968A - Spindle structure - Google Patents

Abstract

PURPOSE:To prevent a rotating central shaft from decentering and inclining even when the temperature of one's own magnetic disk device and the circumference are changed by constituting the parts abutting on the upper/lower and radius directions of a bearing of a material having the approximately same linear expansion coefficient as the bearing. CONSTITUTION:For bearings 7 and 8, a linear expansion coefficient is 12.5X10<-6>/ deg.C in a bearing steel, and the linear expansion coefficient (for example, a SUS 440C is 10.1X10<-6>/ deg.C) of the parts (interval pipe 10', shaft 4 and housing 6') of the circumference is approximately the same (comes to be a little smaller than the bearing, and when the diameter of the bearing is smaller, it does not matter). Thus, the thermal expansion of the radius direction and the thickness direction of the bearings 7 and 8 and the ambient parts can be approximately equal, the vibration and turning of a spindle at the time of high temperature which is generated by the thermal expansion difference can be suppressed, and the decrease of the off-track is attained.

Description

[Detailed Description of the Invention] [Summary] A spindle structure for a magnetic disk drive, in which parts that touch the bearing in the upper, lower, and radial directions are made of a material having approximately the same coefficient of linear expansion as the bearing, and the magnetic disk drive itself and Even if the surrounding temperature changes, the central axis of rotation will not become eccentric or tilted.

[Industrial application field]

The present invention relates to a spindle structure in a magnetic disk device that suppresses the whirling of the central axis of rotation caused by changes in the temperature of the spindle and reduces off-track.

A magnetic disk drive is used as a peripheral device for computers and other devices.A head is held on the surface of a magnetic disk that rotates at high speed with a small gap, and information is recorded on a large number of concentric trunks on the surface of the magnetic disk. Generally, multiple magnetic disks and heads are stacked to increase recording capacity.

Recently, with the increase in the density of magnetic recording, the track spacing has become narrower, and the requirement for precision in positioning the head to the target track has increased. The misalignment of the head can no longer be ignored.

Therefore, there is a need for a spindle structure that prevents the center axis of rotation of the spindle from whirling around due to temperature changes.

[Conventional technology]

FIG. 4 is a diagram illustrating a conventional spindle structure.

FIG. 4 shows the spindle part of a sealed magnetic disk device. In the figure, the spindle part is sealed by a base 1 and a cover (not shown) to prevent dust from entering. It is attached to a disk mounting member (hereinafter referred to as hub) 5 fixed to a spindle shaft (hereinafter referred to as shaft) 4 having (motor) 3. The shaft 4 is held and rotated via bearings 7.8 above and below a housing 6 fixed to the base 1. Further, a head 9 for reading/writing information on the disk 2 is attached to an actuator (not shown) via a head arm 11.

In addition, 10 is a spacer tube that takes the space between the upper and lower bearings, 1
2 is a servo head, and 13 is a preload spring.

The upper and lower bearings 7.8 are generally made of bearing steel (linear expansion coefficient 12.5 x 10/''c) due to durability.
The shaft 4 is SO5440G (coefficient of linear expansion 10.l) to match the thermal expansion with the bearing 7.8 and for corrosion resistance.
XX0->°C) is used. This is because the inner ring of the bearing 7.8 is tightly fitted onto the shaft 4, so if there is a large difference in linear expansion coefficient, the radial clearance will fluctuate greatly, causing the center of the shaft 4 to swing around. The housing 6 is made of cast aluminum (coefficient of linear expansion 23.5 x 10/'C) due to its light weight, and the spacer tube 10 is generally made of 5US303 (coefficient of linear expansion 17.3 x 10/'C) due to its workability and corrosion resistance. Use.

[Problem that the invention seeks to solve]

A plurality of disks 2 stacked on a spindle are rotated at high speed (3600 rpm), and information is recorded concentrically on the disks 2 at pitches of about 25 μm. The temperature of the magnetic disk device increases by about 15° C. until it stabilizes about two hours after the start of rotation due to rotational frictional heat (windage loss) between the disk disk 2 and the air. In order to guarantee operation at an ambient temperature of 10 DEG C. to 40 DEG C., the device is required to perform recording and reproducing operations at a temperature range of 10 DEG C. to 55 DEG C. (temperature span 45 DEG C.).

However, when the temperature rises, each component thermally expands and deforms, but the magnetic disk drive has a servo radius 12 for head positioning, and the read/write disk 2 and head arm 11 move radially toward the servo. If the disk 2 and the head arm 11 undergo the same linear expansion, there will be no deviation (off-track) between the written information position and the head positioning position during reproduction.

However, a magnetic disk drive is a composite of parts having various coefficients of linear expansion, and it is difficult to minimize this off-trunk.

Furthermore, in the required high-density recording 25 μm pitch magnetic disk device, this off-track is 2.5 μm.
Otherwise, the recorded information cannot be accurately reproduced due to head position misalignment during recording and reproduction. Furthermore, if writing is performed in a shifted state, there is a risk that previously recorded information on adjacent tracks will be destroyed, making it impossible to reproduce it.

It has been found that one of the major factors that increases this off-track is the difference in linear expansion between the upper and lower bearings 7.8 and the parts in contact with them.

When the spindle temperature increases by 45°C, bearing 7.
The distance between the outer ring 8 and the inner diameter of the housing 6 is the bearing diameter φ
40 Tsuru, the increase was 19.8 μm, causing play between the outer ring of the bearing 7.8 and the inner diameter of the housing 6, which caused the bearing to rotate around the center axis A as shown in Figure 5 (a) at low temperatures. At high temperatures, this is one of the causes of the whirling phenomenon like A' shown in FIG. 5(b).

Furthermore, when paying attention to the thickness direction of the bearings 7.8, there is a difference of 13 μm between the shaft 4 and the spacer tube 10, and a pressure on the order of 100 nm is applied to the upper and lower bearings 7.8. This pressure distorts the ball starting surface of the bearing 7.8, deforms the rotational trajectory, and causes a whirling phenomenon.

This whirling phenomenon at high temperatures results in a difference in rotational trajectory between low and high temperatures, which poses a problem in that it causes the above-mentioned off-track.

[Means for solving problems]

FIG. 1 is a diagram explaining the present invention in detail.

FIG. 1 shows the spindle structure of the present invention. In the figure,
The spindle B has a plurality of discs 2 as before.
is attached to a hub 5 fixed to a shaft 4 having a drive section (motor) 3 at the bottom. The shaft 4 is held and rotated via bearings 7.8 above and below a housing 6' fixed to the base 1. In addition, 1
0' indicates a spacer tube, and 13 indicates a preload spring.

The present invention provides the bearing 7.8 and its surrounding parts that cause the whirling phenomenon of the rotational center axis, namely the spacing tube lO' for maintaining the distance between the upper and lower bearings 7.8 of the spindle, the shaft 4, and the outer ring of the bearing. In order to suppress the difference in thermal expansion of the holding housing 6', it is desirable to use bearing steel equivalent to that of the bearing. The structure is unified to martensitic stainless steel.

[Effect]

That is, the bearing 7.8 is made of bearing steel and has a coefficient of linear expansion of 12.
．． 5xlO/”c, and surrounding parts (interval tube 10
', shaft 4, and housing 6) (for example, 5US440C is 10.1 x 10/°C) are almost the same (slightly smaller than the bearing, but there is no problem if the bearing diameter is small). Bearing 7.8
The thermal expansion in the radial direction and the thickness direction of the surrounding parts can be made almost equal, and the whirling of the spindle at high temperatures caused by the difference in thermal expansion [Figure 2 (a) shows the center axis of rotation A1 at low temperatures. (See Fig. 2 (b), the central axis of rotation A' at high temperatures) can be suppressed, and off-track can be reduced.

〔Example〕

FIG. 3 is a diagram explaining the present invention in detail.

Note that common symbols throughout the figures indicate the same objects.

FIG. 3 shows the spindle portion of a sealed magnetic disk device. In the figure, the spindle portion is sealed by a base 1 and a cover (not shown) to prevent dust from entering, and a plurality of disk disks 2 are inside the spindle portion, and a drive portion is located at the bottom. Shaft 4 with (motor) 3
It is attached to a hub 5 fixed to. The shaft 4
are held and rotated via bearings 7.8 above and below a housing 6' fixed to the base 1. Further, a head 9 for reading/writing information on the disk 2 is attached to an actuator (not shown) via a head arm 11. In addition, 10' is the upper and lower bearing 7.8
12 is a servo head, and 13 is a preload spring.

The upper and lower bearings 7.8 are made of bearing steel (linear expansion coefficient 12).
．． 5 x 10/'c), and the shaft 4 has a coefficient of linear expansion that is almost close to that of SO5440C (10,1
"C) is used. As a result, the shaft 4, which is closely fitted to the inner ring of the bearing 7.8, has less variation in the radial clearance due to thermal expansion, and can prevent the center shaft from whirling around when the spindle rotates.

In addition, in order to make the housing 6' lightweight, it is made of aluminum casting (linear expansion coefficient 23.5 x 10/'c) with 5US
The spacer tube 10' is also formed from 5US440G to match the coefficient of thermal expansion with the bearing link 7.8. This makes it possible to make the thermal expansion in the thickness direction (vertical direction) almost equal, and it is possible to suppress whirling of the spindle at high temperatures caused by a difference in thermal expansion.

Therefore, off-track can be reduced.

〔Effect of the invention〕

As explained above, according to the present invention, the spindle whirling phenomenon at high temperatures can be minimized by unifying the materials of the surrounding parts of the bearing to materials that have a coefficient of linear expansion that is approximately the same as that of the bearing. The off-track phenomenon can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the present invention in detail. FIG. 2 is a diagram explaining the central axis of rotation of the spindle of the present invention at low temperature and high temperature. FIG. 3 is a diagram explaining the present invention in detail. Figure 4 is a diagram explaining the conventional spindle structure, and Figure 5 (
(a) and (b) are diagrams illustrating the rotation center axis of a conventional spindle at low temperature and high temperature. In the figure, 1 is the base, 2 is the disk disc, 3 is the drive unit (motor), 4 is the spindle shaft (shaft), 5 is the hub, 6' is the housing, 7.8 is the bearing, 10' is the spacer tube, Wood shavings ≦ Tan H fire tree color Iku, LC section date f [3 river grass 3 hearing

Claims (1)

[Claims] A housing (6) on a base (1) is connected to a rotating spindle shaft (4) supported by upper and lower bearings (7, 8) through a disk mounting member (5). A spindle structure (B) of a magnetic disk device configured with a disk disk (2) attached, the spindle shaft (4) and the upper and lower bearings (7, 8) of the spindle shaft (4).
), and a housing (6') that holds the outer rings of the upper and lower bearings (7, 8), which have approximately the same coefficient of linear expansion as the bearings (7, 8). A spindle structure characterized in that it is made of a material that has.