JPS62129986A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To obtain a device which is prevented from breaking resulting from a difference in thermal expansion and suits to high-density recording by forming a metallic clamp of a metallic material which has a specific coefficient of thermal expansion as compared with the coefficient of thermal expansion of a disk substrate made of a brittle material. CONSTITUTION:Plural disks 1 which have a magnetic film on both top and reverse surfaces of a substrate made of the brittle material such as glass are stacked by being fitted on the outer periphery of a spindle 2 with a metallic spacer 3 between, and a stator coil 6 is fitted to a shaft 5 opposite a magnet 7 provided on the inner wall of the spindle 2 supported pivotally on a fixed shaft 5 by a bearing 11. The disks 1 are fixed with a set screw 8 by pressing the upper end surface of the spindle 2 with the metallic clamp 9, which is formed of a material whose coefficient of thermal expansion is within a range of + or -50X10<-7>/deg of that of the disk substrate. Consequently, the difference in heat expansion due to variation in ambient temperature is reduced to prevent the disk from breaking owing to the generation of thermal stress.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic disk device, and in particular, to prevent damage to a magnetic disk due to a difference in thermal expansion between a fastening portion that fixes the magnetic disk and a substrate of the magnetic disk. This has been improved to prevent this.

[Conventional technology]

2. Description of the Related Art Conventionally, magnetic disks used in this type of magnetic disk device generally have a magnetic film formed on a metal substrate made of An or A-1 alloy. The fastening portion for fixing the magnetic disk made of the gold fmH substrate to the magnetic disk device is made of An or Ai alloy.

However, recently, glass substrates or Reramix substrates have been attracting attention as substrate materials for magnetic disks in order to meet the demands for high recording density. The big reason is A1 and A
It has fewer surface defects than L alloy substrates and has N1-
It has the excellent feature that a magnetic film can be manufactured without requiring a highly hard underlayer such as P or alumite.

[Problem that the invention seeks to solve]

First, simply replacing the metal substrate with a glass or ceramic substrate has the problem that the magnetic disk is easily damaged. That is, the thermal expansion coefficient of a glass substrate or a ceramic substrate is usually 40 to 120.
x10'/deg Te, on the other hand, the tightening part is A,
Since the fastening fitting is made of 1 or AfL alloy, its coefficient of thermal expansion is 230 to 240 x 10''7/deg, which is significantly larger than that of a glass substrate.

Therefore, when the ambient temperature of the magnetic disk device changes, the glass or ceramic magnetic disk and A! L
There is a drawback that tensile stress due to the difference in thermal expansion between the magnetic disk and the fastening fittings of the magnetic disk acts on the magnetic disk, causing damage to the magnetic disk.

[Means for solving problems]

The present invention was made to eliminate the above-mentioned drawbacks, and
The feature is that it is rotatably arranged around a fixed axis, and
A spindle rotated by full drive, a plurality of magnetic disks fitted into the outer peripheral surface of this spindle and arranged in a VJ layer on a pedestal provided below the outer peripheral surface, and these magnetic disks. The magnetic disk includes a plurality of metal spacers that maintain a constant distance between the disks, and a tightening portion that is fixed to an upper end surface of the spindle and presses a portion of the magnetic disk that faces the pedestal. The substrate of the magnetic disk is made of a fragile material such as glass or ceramics, and the tightening portion has a coefficient of thermal expansion of ±50× of the material of the magnetic disk substrate made of the fragile material) l'3+. It is made of a material in the range of 10'/deg.

[For production]

In the present invention, the tightening part has a coefficient of thermal expansion of ±50X 10-
Since it is made of a material in the range of 7/de(), it is possible to reduce the difference in thermal expansion between the magnetic disk substrate and the clamping part due to changes in the ambient temperature of the magnetic disk drive. No thermal stress is applied, preventing damage to the magnetic disk.

〔Example〕

An embodiment of the magnetic disk device of the present invention will be described in detail with reference to FIG. In addition, Figure 1 shows 5, which has a built-in motor.
FIG. 2 is a sectional view of a disk rotating portion of a 25-inch Winchester type magnetic disk device.

First, in the Winchester-type magnetic disk device of this embodiment, a plurality of magnetic disks 1 are inserted and stacked on the outer peripheral surface of a spindle 2 via metal spacers 3, and a motor 4 is arranged inside the spindle 2. The shaft of the motor 4 is a stationary shaft (fixed shaft) 5, a coil is attached to this stationary shaft 5 to form a stator 6, and the spindle 2
A magnet 7 is attached to the inner wall of the motor 4, and the outer periphery of the motor 4, that is, the magnet 7 and the spindle 2 are rotated together at high speed (for example, 3600 rpm) by driving the motor 4. Note that 11 is a bearing.

Here, the magnetic disk 1 is pressed by a fastening fitting 9 fixed to the upper end surface of the spindle 2 by a set screw 8, so that the magnetic disk 1 is placed on a pedestal portion 10 that is integrally provided on the outer peripheral surface of the lower end portion of the spindle 2. This prevents the magnetic disk 1 from rotating idly with respect to the spindle 2 due to the moment of inertia acting on the magnetic disk 1, and at the same time prevents the magnetic disk 1 from relative displacement.

The substrate of the magnetic disk 1 has a coefficient of thermal expansion of 94×10'/
Outer diameter 130m with deg soda lime glass
m, an inner diameter of 40 mm, a thickness of 1.9 mm, and on the front and back surfaces thereof, a base layer made of Cr of a predetermined thickness by a known technique such as a vacuum evaporation method, and a Co-Ni11Q magnetic layer, Each magnetic film is formed of a C film layer that covers and protects this Co--Ni film magnetic layer.

The tightening fitting 9 is made of 13-Cr stainless steel (e.g. 5US
420J2) and its thermal expansion coefficient is 110X
10-7/dcg. Further, the spindle 2 is made of mild steel with a coefficient of thermal expansion of 105 to 110 x 10-7/dcg, and the metal spacer 3 is made of 13-Cr with a coefficient of thermal expansion of 110 x 10-7/dcg, similar to the fastening fitting 9.
Made of stainless steel.

Further, the set screw 8 is made of nickel chromium strong steel, and its coefficient of thermal expansion is 107 x 10'/deg.

Hiddenly, according to the magnetic disk device according to this embodiment,
Because the difference between the coefficient of thermal expansion of the magnetic disk cover plate and the coefficient of thermal expansion of the fastening metal fittings is small, the temperature is -40°C to
In the permissible temperature range up to 70° C., thermal stress, ie, tensile stress, applied to the magnetic disk could be reduced, and damage to the magnetic disk could be prevented. In addition, in this example, the coefficient of thermal expansion of the spindle and the metal spacer is not much different from the coefficient of thermal expansion of the magnetic disk substrate, and the difference in thermal expansion between the spindle and the metal spacer is also small. In this permissible temperature range, the force generated due to the difference in thermal expansion in the direction of the fixed axis of the spindle can be minimized as much as possible.

Therefore, damage to the magnetic disk due to thermal stress can be effectively prevented, and damage to the magnetic disk can also be effectively prevented by preventing the tightening fitting from bending outward and creating locally high contact pressure. can.

The present invention is not limited to the above embodiments, but may include the following. First of all, the fastening fittings are not limited to 13-Cr stainless steel, but have a thermal expansion coefficient of ±50 relative to the magnetic disk substrate.
It is sufficient if the material is in the range of
For brittle materials of deg, 310C mild steel (coefficient of thermal expansion: 110x10-7/dcg), high carbon steel with carbon content 06-16% (coefficient of thermal expansion: 96-107x10
-7/dcg) and U titanium alloys (e.g. EVA Ti-6
A,! Cr and Su for rust prevention.

A material plated with Ni, 7N, etc. may also be used.

Furthermore, the tightening portion need not be made of metal like the tightening fittings, but may be made of other materials.

In addition, if the thickness of the tightening part, for example, the part of the metal fitting that presses the magnetic disk in the example of the above embodiment, is 3 mm or more, the bending rigidity value of the tightening part can be improved. can be prevented. Furthermore, if the tightening fittings of the above embodiments are hardened, this will prevent the tightening fittings from being deformed and will prevent local high pressure from being applied to the part that contacts the magnetic disk. Therefore, damage to the magnetic disk substrate can be prevented.

That is, damage can be further prevented by reducing the difference in thermal expansion between the magnetic disk substrate and the clamping part, and by adjusting the thickness and/or hardening of the pressing part of the clamping fitting.

Further, in the present invention, if the spacer, spindle, and set screw are made of a material with a coefficient of thermal expansion of ±50 x 10'/deg relative to the magnetic disk substrate as in the above embodiment, the damage will be further reduced. It has a preventive effect.

Further, the magnetic film of the magnetic disk in the present invention is not limited to the three-layer structure of the Cr film underlayer, co-Ni magnetic layer, and C film layer described above, but may include a Zr 02 film, a Zr 02 film,
It may also have a two-layer structure from which a base layer such as a Cr film is removed. Further, the substrate of the magnetic disk may be made of glass other than soda lime glass, such as aluminosilicone glass.In short, any fragile material such as glass or ceramics may be used.

Further, a magnetic disk device other than a Reinchesov type magnetic disk device may be used.

Furthermore, as shown in FIG.
0. Metal spacer 3. The parts that directly contact the magnetic disk 1, such as the clamping member 9 that presses the disk 1, are made of synthetic resin or synthetic rubber with a thickness of 0.1
By interposing a thin spacer 21 of about mm,
It is also possible to prevent the magnetic disk from being damaged due to the surface finish accuracy of each metal component.

As the material for the spacer 21, synthetic resins such as polyester, polyimide, polyamide, polyethylene, polyvinyl chloride, fluororesin, polyurethane, or synthetic rubbers such as urethane rubber, acrylic rubber, silicone rubber, and ethylene propylene rubber are used. Furthermore, it may be a mixture of these or a composite material in which these are laminated.

Note that the spacer 21 is not placed on the front and back surfaces of each magnetic disk 1 as shown in FIG. A sufficient effect can be expected even if the fastener is interposed only in the space between the fastener and the magnetic disk 1. In addition, the spacer 21 between the fastening fitting and the magnetic disk 1 may be made of synthetic resin or synthetic rubber, even if it is a metal spacer having a coefficient of thermal expansion in the range of ±50 x 10'/deg with respect to the magnetic disk substrate. has the same effect.

〔Effect of the invention〕

As described above, in the magnetic disk device according to the present invention, the fastening portion is formed of a material having a thermal expansion coefficient of ±50×10'/deg with respect to the coefficient of thermal expansion of the magnetic disk substrate made of a brittle material. Despite being made of fragile materials such as glass and ceramics, within the allowable storage temperature range, a large force is applied to the magnetic disk due to the difference in thermal expansion between the clamping part and the magnetic disk substrate.
Therefore, damage to the magnetic disk can be prevented and a magnetic disk device suitable for high-density recording can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a rotating part of a poly disk showing one embodiment of the present invention applied to Winchester type magnetic disk loading, and FIG. 2 is a cross-sectional view of a rotating part of a disk showing another embodiment of the present invention. It is.

Claims (1)

[Claims] (1) A spindle that is rotatably arranged around a fixed shaft and rotated by a motor drive, and a pedestal that is fitted onto the outer circumferential surface of the spindle and provided below the outer circumferential surface. a plurality of magnetic disks arranged, a plurality of metal spacers interposed between these magnetic disks to maintain a constant disk spacing; and a metal spacer fixed to an upper end surface of the spindle and facing the pedestal part. It is equipped with a tightening part that presses the part of the magnetic disk,
The substrate of the magnetic disk is made of a fragile material such as glass or ceramics, and the tightening portion has a coefficient of thermal expansion of ±50×10^-^7/deg of the material of the magnetic disk substrate made of the fragile material. A magnetic disk device characterized in that it is made of a material in the range of.