JPS6337874A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent sucking between a disk and a head slider by reducing the disk contact area in the slider face of a head. CONSTITUTION:Projections 14a, 14b, 15a, 15b are provided to the slider faces 13a, 13b so as to reduce the contact area between a magnetic disk 20 and a slider 11 of a magnetic head 10. Thus, the adsorption of the disk/slider is prevented or the adsorbing force is reduced. Since the surface of the projections 14a, 14b, 15a, 15b is flat, inconvenience such as the change in the surface shape due to sliding is not caused. Thus, the disabled starting due to the adsorption of the disk and slider is prevented surely over a long period.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic disk device that is the core of a file storage device, and particularly to a magnetic disk device that uses a contact start-stop method or a contact running method. Related to magnetic disk devices.

(Prior Art) In recent years, in the field of magnetic disk devices, vigorous research and development has been carried out to improve recording density. In particular, the development of magnetic layers and miniaturization of the spacing between the head and disk when the magnetic head runs is remarkable. The former involves the commercialization of continuous thin film media in which a metal thin magnetic layer is formed by sputtering, etc., and the latter concerns the flatness of the disk head surface.

By miniaturizing the surface roughness, it has become possible to achieve a spacing of 0.2 μm or less.

However, in this type of magnetic disk drive, both the disk head and both surfaces are finished smooth, so if the magnetic disk is not rotating for a long time, adhesion will occur between the magnetic disk surface and the slider surface of the magnetic head. arise. In this case, the coefficient of static friction between the magnetic disk surface and the slider surface of the magnetic head increases, making it impossible to start the spindle motor.

Conventionally, the following measures (1) to (3) have been taken to prevent this adsorption.

(1) Roughen the slider running surface of the magnetic disk.

(2) Roughen the slider surface.

(3) Make the slider surface cylindrical.

However, the above measures have the following problems.

In other words, (1) and (2) are intended to prevent adhesion by roughening the surface that causes adhesion and increasing the average gap, but the surface that causes adsorption is caused by contact start/stop or contact. This is a sliding surface during running, and as shown in FIG. 4, the tips of the surface roughness protrusions are worn out due to sliding. That is, even if the surface shape is as shown by the solid line in the figure, due to wear due to sliding, the tip of the protrusion becomes flat as shown by the broken line in the figure. Therefore, an adsorption phenomenon appears as the sliding distance increases. If the surface roughness is made too large to avoid this, the helad core will be damaged in case (1), and the disk magnetic layer will be damaged in case (2). Furthermore, in case (2), if the slider is made of a very hard material in order to reduce the wear rate, this will not be a fundamental solution because it will damage the disk magnetic layer.

Furthermore, in case (3), machining the cylindrical surface is much more difficult than machining the flat surface, and the curvature of the cylindrical surface varies greatly. This variation in curvature results in variation in bearing acting force when the slider runs, that is, variation in spacing during recording and reproduction, and is not suitable for high-density magnetic disk drives.

(Problems to be Solved by the Invention) As described above, in the conventional device, there was a risk that the spindle motor would not be able to start due to the attraction between the magnetic disk and the slider of the magnetic head. In addition, conventional methods for preventing adsorption lose their effectiveness as the disk slides, or cause variations in spacing during recording and reproduction.

The present invention has been made in consideration of the above circumstances, and its purpose is to reliably prevent startup failure caused by adhesion between the magnetic disk and the slider over a long period of time without causing variations in spacing. The object of the present invention is to provide a highly reliable magnetic disk device that is suitable for high-density storage.

[Structure of the Invention (Means for Solving Problems)] The gist of the present invention is to prevent the disk from adhering to the head slider by reducing the disk contact area on the slider surface of the magnetic head.

That is, the present invention provides a magnetic disk device that performs recording and reproduction while maintaining a constant gap between the magnetic disk and the magnetic head when the magnetic disk rotates, and that maintains the disk and the magnetic head in contact when the magnetic disk is stopped. In the above, the disk contact surface of the magnetic head when the magnetic disk is stopped is constituted by a plurality of convex portions formed on the slider surface of the head, and the total area S of the disk contact surface of these convex portions is defined as When a water film is formed between the head and the disk, which increases in proportion to the area S, the force required to move the head in the in-plane direction of the disk, the starting torque of the motor that rotates the disk, and the number of heads to start one rotation. This value is set to be smaller than the permissible starting force F per head, which is determined by the radial position of the disk.

More specifically, when the coefficient of friction due to solid contact is μ, the load for pressing is P (g weight), the gap is h (μm), the surface tension of water is γ, and the contact angle is θ (deg), the above Area S(M
The relationship between 2) and the above-mentioned allowable starting force F (g weight) is set so that it becomes.

(Function) The present inventors conducted research on the adsorption phenomenon caused by water molecules (humidity) in the air, and after repeating various experiments, discovered the following facts.

That is, adsorption of water molecules occurs in the following process.

First, as shown in FIG. 5(a), a nucleus 54 of adsorbed water molecules is formed at the real contact portion 53 between the slider 5I of the magnetic head and the magnetic disk 52. Next, Fig. 5 (b
), the nucleus 54 has a relative humidity P due to the capillary condensation phenomenon.
/Ps (P is water vapor pressure, PS is saturated vapor pressure at that humidity)
It grows to a radius of curvature (gap: h) corresponding to , and a water film 55 is formed in the gap.

P/Ps (relative humidity) and h (gap) in the above process
The relationship with is expressed as shown in FIG. this is,
This means that as the relative humidity increases, the gap where a water film is formed becomes larger; for example, at a relative humidity of 65%, the gap becomes 0.0%.
A water film grows to a gap of 2 [μm], and the relative humidity is 90 [μm].
%] means that the water film grows to a gap of 0.08 [μ7'Il].

When a water film is formed between the disks in the slider in this way, the force F required to move the slider in the in-plane direction of the disk is expressed as 2Sγ COSθ F, -μ(+P)...■ . However, (μ: friction coefficient due to solid contact,
S: Area filled with water film, γ: Surface tension of water, θ
: contact angle, P: pressing is load).

On the other hand, the allowable starting force F per head by a spindle motor or the like is given by the following equation.

F-T/nr...■However, (
Starting torque of T-varnish spindle motor, n: number of heads,
r - slider radial position when starting rotation).

From equation 00, the condition for preventing the spindle motor from becoming unable to start even if adsorption occurs is F>FN, and solving this for S yields the following equation.

Here, the maximum permissible value of the area S is determined from various measurement results. The table below shows the friction coefficient μ of various types of disk heads.
, the contact angle θ of water in the gap h1 at rest and the pressure show the measurement results of the maximum and minimum values of the load P.

In the table, the minimum value of the load P for pressing was set to 0g in consideration of the negative pressure type slider. Minimum value of P, maximum value of h, minimum value of μ, maximum value of θ (values marked * in the table) and surface tension of water (20℃) 7.34xlO'9 weight/cII of S It can be seen that the maximum allowable value is approximately 0.1F. Therefore, if the total area of the disk contact area on the slider surface is set to a certain value of 0.1 F or less, the spindle motor will not stop rotating even if adsorption occurs, and the reliability of the magnetic disk drive will be improved. It is possible to make it L.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a perspective view showing the main structure of a magnetic disk device according to an embodiment of the present invention, and FIG. 2 is an enlarged perspective view showing a head section used in the device. In the figure, 10 is a magnetic head, and 20 is a magnetic disk. magnetic head lO
A slider 11 is used to maintain a predetermined gap between the magnetic head 10 and the magnetic disk 20 when the magnetic disk 20 rotates.
A core portion (thin film head) 12 (12a) is formed on the side surface of the slider 11.

12b). Top surface 13 of slider 11
(The slider surfaces 13a, 13b) have four convex portions 14.
(14a.

14b) and 15 (15a, 15b) are provided, and the upper surfaces of these convex portions 14 and 15 are processed to be flat.

Further, the slider 11 is fixed to a fixed end via a plate spring 30, and is biased toward the disk 20 by the spring 30. As a result, when the rotation of the magnetic disk 20 is stopped, the convex portions 14 and 15 come into contact with the disk surface. Further, the magnetic disk 20 is rotated by a spindle motor 40.

Here, the starting torque of the spindle motor 40 varies greatly depending on the type of magnetic disk drive, but the starting force F per head is generally designed to be lO~209 from the viewpoint of cost, power consumption, etc.

In this embodiment, the convex portion (4 is a circular plane of φ0.4 l1lI, and the convex portion 15 is a semicircular plane of φ0.4 ax.

Therefore, the total area S of the flat parts in contact with the disk is approximately 0.3811112, and O,lF (F-109
Therefore, it is set to a value smaller than 1+u2). Also, the height difference between the convex portion 14.15 and the slider surface 13 is 0.08.
μm to prevent the water film from spreading to the entire slider surface 13 even if the relative humidity reaches 90%. Furthermore, since the core section 12 for recording and reproducing is provided on the side surface of the contact plane by thin film formation technology, recording and reproducing can be performed with smaller spacing and high recording density can be achieved. Since the contact surface (upper surface of the convex portions 14, 15) or the flat surface is worn due to sliding during head travel, the wear rate is much lower than that of a roughened surface, and adsorption can be prevented for a long period of time.

Regarding the processing method, ion etching is suitable because the step difference is as small as 0.1 μm or less, and in this case, reproducibility of shape and dimensions can be expected, so variations in spacing during recording and playback can be kept small. becomes possible.

In this way, according to this embodiment, the convex portion 1 is formed on the slider surface 13.
4.15 makes the contact area between the magnetic disk 20 and the slider 11 of the magnetic head 10 small, so it is possible to prevent the disk/slider from adhering or to reduce the adsorption force. Furthermore, since the surfaces of the convex portions 14 and 15 are flat, there is no problem such as the surface shape changing due to sliding. Therefore, the inability to start due to adsorption of the disk slider can be reliably prevented for a long period of time. Furthermore, there is no inconvenience such as variations in spacing during recording and reproduction, and the reliability of the magnetic disk device can be improved.

FIG. 3 is a perspective view showing the main structure of another embodiment of the present invention. The same parts as in Fig. 1 are given the same reference numerals.
A detailed explanation thereof will be omitted.

This embodiment differs from the previously described embodiments in that the number of convex portions constituting the contact plane is increased and the area of each convex portion is decreased. That is, in this embodiment, 50 convex portions 44 (44a,
44b) on the slider surface 13 so that the total contact area is 0.
．． The length is 39m, m2. Further, as the core portion 42, a monolithic type which has been commonly used in the past was used. In this case as well, since there is a step with the contact plane, the core part 4
2 can be expected to have improved durability without wear.

Even with such a configuration, the disk contact area of the slider 11 can be made sufficiently small as in the previous embodiment, and the same effects as in the previous embodiment can be obtained.

Note that the present invention is not limited to each of the embodiments described above. For example, the combined area S of the contact plane increases by 119 in proportion to the area S. When a water film is formed between the slider and the disk, the force necessary to move the slider in the in-plane direction of the disk moves the disk. The starting torque of the rotating motor and the number of 11 spatulas.

It may be any value that is smaller than the allowable starting force F per head, which is determined by the radial position of the disk at which rotation starts. Specifically, the relationship between the total area S (m112) and the above-mentioned allowable starting force F (1 load) should satisfy the above-mentioned formula 0.

In addition, the number of convex portions provided on the slider surface and the area of each convex portion are as follows:
The window may be appropriately set within a range that satisfies the above formula 0. moreover,
The shape of the convex portion is not limited to a circular shape, but can be changed to an elliptical shape, a rectangular shape, or the like as appropriate. Furthermore, the type of head section attached to the slider can also be changed as appropriate. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, by providing a plurality of convex portions on the slider surface of the magnetic head and reducing the contact area between the disk and the slider, variations in spacing can be avoided. Therefore, it is possible to reliably prevent startup failures caused by adhesion between the magnetic disk and the slider over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the main part configuration of a magnetic disk device according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing a head section used in the above device, and FIG. A perspective view showing the main structure of another embodiment, FIG. 4 is a schematic diagram for explaining how the roughened surface changes due to sliding between the head and the disk, and FIG. FIG. 6 is a schematic diagram for explaining how a water film is formed in the gap between the head and the disk. FIG. 6 is a characteristic diagram showing the relationship between relative humidity and the gap in which the water film is formed. lO...Magnetic head, 11...Slider, 12.4
2... Core part (thin film head), 13... Slider surface, 14, 15.44... Convex part, 20... Magnetic disk, 30... Leaf spring, 40... Spindle motor. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (2)

[Claims] (1) In a magnetic disk device that performs recording and reproduction while maintaining a constant gap between the disk and the magnetic head when the magnetic disk rotates, and maintains the disk and the magnetic head in contact when the magnetic disk is stopped, The disk contact surface of the magnetic head when the magnetic disk is stopped is constituted by a plurality of convex portions formed on the slider surface of the head, and the total area S of the disk contact surfaces of these convex portions is defined as the area S. When a water film is formed between the head and the disk, the force required to move the head in the in-plane direction of the disk increases in proportion to the starting torque of the motor that rotates the disk, the number of heads, and the disk that starts rotating. A magnetic disk device characterized in that the drive force is set to a value smaller than the permissible starting force F per head determined by the radial position. (2) The area S (mm^2) and the allowable starting force F (g
2. The magnetic disk device according to claim 1, wherein the relationship between S<(F-μP)h/2μγcosθ is set as follows. However, μ is the friction coefficient due to solid contact, and P is the pressing load (
h is the gap (μm), γ is the surface tension of water, and θ is the contact angle (deg).