JPH07320475A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To suppress wear of internal mechanisms by controlling the internal atmosphere of a hermetically closed device. CONSTITUTION:An oxygen concn. maintaining mechanism is mounted within the magnetic disk device of a hermetic type. A spindle 5, a pivot 6, an actuator magnet 7, etc., are mounted on a base 4. Further, plural sheets of disks 8 are supported on the spindle 5. A carriage 9, a head 10 and other necessary parts are mounted at the magnet 7. The base 4 and a cover 11 are fixed via packings. Further, an oxygen adsorbent unit 13 is mounted at one corner of the base. This unit 13 houses an oxygen adsorbent 1 consisting of fine iron powder, etc. An oxygen diffusion and inflow part 3 is composed of a polyethylene film, etc. The wear resistant strength of the magnetic disks depends upon the oxygen pressure and the oxygen partial pressure is recommended to be controlled to a range of prescribed Pa to kPa value in order to maximize the strength thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to a hermetically sealed magnetic disk device having an internal atmosphere adjusted.

[0002]

2. Description of the Related Art A magnetic disk device currently mainly used as an external storage device of a computer is one in which a magnetic signal is written to and read from a rotating disk-shaped magnetic recording medium (hereinafter referred to as a disk) by a magnetic head. . In a magnetic disk device, a disk and a magnetic head move relative to each other at a speed of several tens m / s. When the magnetic head and the disk come into direct contact with each other, both are worn and the life of the device is shortened. Particularly, the case where the magnetic film of the disk is destroyed by abrasion is called a disk crash, and the information on the disk is destroyed on a large scale. In order to avoid this, for example, the shape of the slider on which the magnetic head is mounted is generally sled-shaped, and the magnetic head is levitated by the airflow during disk rotation, so that direct contact between the two during steady operation is avoided. There is. Both of them come into contact when the device is started or stopped, but against this, by forming a protective film on the magnetic film of the disk and applying a lubricant on it, durability against wear is improved. ing.

In this magnetic disk device, it is desired to further improve the recording density. For that purpose, it is desirable to make the distance between the magnetic head and the disk as small as possible. In the latest model, the distance is already 100n.
It is reduced to m or less. In such a situation, the probability of contact between the magnetic head and the disk during steady operation cannot be ignored, and it is considered that the magnetic head and the disk are in contact with each other at a constant frequency. If the distance between the two is further reduced, the probability of contact is further increased. In order to further improve the recording density,
Attempts have also been made to perform recording and reproduction with the magnetic head and the disk in continuous contact.

It has already been described that a protective film is formed on the surface of the disk in order to reduce wear when the magnetic head / disk comes into contact, but in many cases a carbon film is used as the material for the protective film. It is believed that contact causes oxidative wear. Oxygen may also be involved in the deterioration of the lubricant on the disk surface. For this reason, it has been proposed to suppress wear by eliminating oxygen inside the magnetic disk device (Japanese Patent Laid-Open No. 1-57480). On the other hand, it has been reported that destructive wear is more likely to proceed in an extremely clean atmosphere in which oxygen is completely removed (War et al., “Durability of Magnetic Thin Film Rigid Disc in Nitrogen and
Helium Environments, "Advanced Information of Storage Systems, Vol. 1, pages 327-336, AD 1991). As described above, the influence of the oxygen atmosphere on the durability of the disk was not always clear.

As a method for reducing oxygen, attempts have been made to mix oxygen and an inert gas, for example, helium, and to seal the mixture in a hermetically sealed magnetic disk device (for example, JP-A-61-292289). Gazette). Moreover,
It has also been devised to remove oxygen in the magnetic disk device with an oxygen adsorbent (for example, JP-A-3-254835).
Issue). However, simply installing an oxygen adsorbent changes the performance of the adsorbent over time, so that the oxygen concentration inside the magnetic disk device cannot be kept constant for a long period of time.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a magnetic disk device capable of controlling the atmosphere so as to keep the wear of the internal mechanism of the magnetic disk device most suppressed.

[0007]

As a result of a detailed study on the above problems, the inventors of the present invention have found that the wear resistance strength of a magnetic disk depends on the oxygen partial pressure, and oxygen in the atmosphere for maximizing the strength is high. Concentration is 10 Pa to 10 kPa in oxygen partial pressure
It was found that the wear was stably reduced by positively controlling the oxygen concentration inside the magnetic disk device within this range. Furthermore, the method of controlling this stably and easily was devised.

As described above, it is already known to simply mix oxygen into an inert gas as an atmospheric gas.
However, simply using an inert gas mixed with a low concentration of oxygen causes oxygen to enter from the outside of the device through an organic member such as packing and increase its concentration, so that a constant oxygen concentration is stable for a long period of time. It's not always easy to maintain. It is possible to completely seal the magnetic disk device with a metal seal to prevent the inflow of oxygen, but it is difficult to repair after assembling the device, and the device may be distorted during sealing. There is.

The present invention has found that by introducing an oxygen concentration control means into the magnetic disk device, the oxygen concentration in the device can be maintained within the optimum range in which the wear strength is improved. Specifically, the oxygen concentration is controlled by balancing the inflow amount of oxygen from the outside of the device to the inside of the device and the inflow amount of oxygen from the inside of the device to the oxygen adsorbent unit.

An example of the oxygen adsorbent unit is shown in FIG.
It typically consists of an oxygen adsorbent 1, a unit housing 2, and an oxygen diffusion inlet 3. Examples of the oxygen adsorbent 1 include metal / alloy powder, metal / alloy lower oxide, and oxidizable organic substance. Further, some of them are processed to prevent their rapid oxidation. However, the essence of the present invention is not limited to merely limiting the type of oxygen adsorbent. The unit housing 2 is made of synthetic resin, metal or the like, and is usually fixed to the HDA housing with screws, an adhesive, an adhesive or the like. Also, the oxygen diffusion inflow part 3
May be simple pores, may be a porous body, or may be a membrane or bulk material that allows a small amount of oxygen to permeate. Further, various materials such as a composite material in which a reinforcing material is attached to the membrane and rubber containing a filler are conceivable. Furthermore, the unit housing 2 itself can be made of a material that also serves as the oxygen diffusion / inflow portion 3.

Oxygen is introduced into the HDA from the outside or H
In the case of diffusively flowing into the oxygen adsorbent unit from the inside of the DA, the inflow rate depends on the concentration difference between the two sides. The external oxygen concentration is Po, the oxygen concentration inside the HDA is Pi, and the oxygen concentration inside the oxygen adsorbent unit is Pa. Po is the oxygen concentration in the atmosphere and is usually constant. When the oxygen inflow rate from the outside to the inside of the HDA is J1, the oxygen inflow rate from the inside of the HDA to the oxygen adsorbent unit is J2, and the rate constants at that time are K1 and K2, respectively, the following equations hold.

[0012]

## EQU1 ## J1 = K1. (Po-Pi) J2 = K2. (Pi-Pa) If Pa is constant, J1 = J2 after a certain time.
And Pa is uniquely determined. To keep Pa constant, Pa << Pi may be set. Normally, the equilibrium partial pressure of oxygen adsorbent is extremely low, so the above condition can be easily achieved by using an excessive amount of oxygen adsorbent.

Therefore, it is important to always keep the oxygen partial pressure inside the oxygen adsorbent unit sufficiently lower than the oxygen partial pressure inside the HDA, whereby the inflow rate of oxygen into the oxygen adsorbent unit is increased in the oxygen diffusion inflow section. As the diffusion rate control of
It is possible to keep it constant. Here, "sufficiently low" means that there is no problem if it is 1/10 or less in view of the accuracy of control required for this purpose.

Further, by optimizing the structure and material of the oxygen diffusion / inflow part, the temperature coefficient of the oxygen inflow rate from the outside of the apparatus to the inside of the apparatus and the oxygen inflow rate from the inside of the apparatus to the oxygen adsorbent unit are made equal to each other, It is possible to keep the oxygen concentration inside the device constant regardless of the temperature.

Controlling the wear by controlling the oxygen partial pressure of the internal atmosphere in this way is particularly desirable for application to a high recording density type magnetic recording device in which the flying height of the head is reduced.
Further, it can be applied to so-called contact recording in which recording and reproduction are performed in a state where the head and the disk are in continuous contact with each other.

[0016]

【Example】

(Embodiment 1) FIG. 2 shows a sealed magnetic disk device in which an oxygen concentration maintaining mechanism is installed in the device. In this magnetic disk device, a spindle 5, a pivot 6, an actuator magnet 7 and the like are mounted on a base 4.
Further, four disks 8 having a diameter of 95 mm are supported on the spindle 5, and a carriage 9, a head 10 and other necessary parts are mounted on the actuator magnet 7. The base 4 and the cover 11 are fixed to each other via a packing 12. Furthermore, according to the present invention in one corner of the base,
The oxygen adsorbent unit 13 is attached. The oxygen adsorbent unit 13 includes an oxygen adsorbent 1 made of fine iron powder or the like.
The oxygen diffusion / inflow part 3 is made of a polyethylene film.

Example 2 In order to verify the effect of maintaining the oxygen concentration, the apparatus shown in Example 1 was operated for 1000 hours, and the change in oxygen concentration before and after the operation was measured by gas chromatography. As a result, the oxygen concentration before the test was 40
0Pa, concentration after testing 500 hours is 450Pa, 1
The concentration after 000 hours was 480 Pa.

On the other hand, with the same structure, the oxygen adsorbent unit 1
In the case of not having 3, the oxygen concentration before the test is 450P
a, the concentration after the start of the test 500 hours is 1600 Pa, 10
The concentration after 00 hours was 2500 Pa.

As described above, the oxygen concentration maintaining effect of the oxygen adsorbent unit 13 was confirmed.

(Embodiment 3) In order to clarify the optimum range of oxygen concentration in the atmosphere, an apparatus equipped with a spindle for disc rotation in which a motor unit is isolated by a magnetic fluid seal is used in an ultrahigh vacuum compatible chamber. Then, a friction test was performed in an atmosphere of mixed gas of oxygen and nitrogen with various ratios. In the test, a sputter disk was used as the disk, and an alumina-titanium carbide composite ceramic head was used as the head. The flying height of the head was set to about 20 nm under the test conditions, and was adjusted so as to always contact the disk even during steady rotation. FIG. 3 shows the result of measuring the time until the disk is worn and destroyed.

From the above results, the oxygen partial pressure in the atmosphere inside the magnetic disk device is 10 Pa or more and 10 kP.
It has been found that a or less is desirable.

[0022]

According to the present invention, the oxygen concentration in the magnetic disk device can be maintained in a constant range for a long period of time. As a result, the atmosphere inside the magnetic disk device can be maintained in a region where wear is reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an oxygen adsorbent unit.

FIG. 2 is a structural diagram of a magnetic disk device equipped with an oxygen concentration control mechanism.

FIG. 3 is a diagram showing the atmospheric oxygen partial pressure dependency of the wear strength of a magnetic disk.

[Explanation of symbols]

 1 ... Oxygen adsorbent, 2 ... Unit housing, 3 ... Oxygen diffusion inflow part, 4 ... Base, 5 ... Spindle, 6 ... Pivot, 7 ... Actuator magnet, 8 ... Disk, 9 ... Carriage, 10 ... Head, 11 ... Cover, 12 ... Packing, 13 ... Oxygen adsorbent unit.

Claims (5)

[Claims] 1. A magnetic disk device for recording or reproducing information on a rotating magnetic recording medium by a magnetic head, comprising a mechanism for controlling oxygen concentration in a gas atmosphere inside the magnetic disk device to 10 Pa or more and 10 kPa or less. A magnetic disk device characterized by the above. 2. The magnetic disk device according to claim 1, wherein the magnetic disk device includes an oxygen adsorbent unit having an oxygen diffusion / inflow portion. 3. An oxygen concentration control mechanism keeps the oxygen concentration constant by equilibrium between diffusion and inflow of oxygen from the outside of the device to the inside of the device and absorption of oxygen from the inside of the device to an oxygen adsorbent unit having a diffusion inflow part. Claim 1 characterized in that it is kept at
Alternatively, the magnetic disk drive described in 2. 4. The magnetic according to claim 1, wherein the oxygen partial pressure inside the oxygen adsorbent unit is 1/10 or less of the oxygen partial pressure inside the magnetic disk device. Disk device. 5. The magnetic disk device according to claim 1, wherein the path of oxygen inflow from the outside of the device to the inside of the device is mainly volume diffusion inside the organic member. Magnetic disk device.