JPH0152830B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a slider for a magnetic head of a magnetic disk storage device, and particularly to a slider for a small high-density hard disk device with a small disk diameter and high magnetic recording density. The present invention relates to a preferred slider for a magnetic head.

[Background of the invention]

A magnetic disk storage device writes and reads information by floating a magnetic head mounted on a slider across a small gap over the surface of a magnetic recording disk. A slider carrying this magnetic head is supported against the disk surface so as to allow pitching and rolling movements. Further, this slider is provided with a plurality of rails having the same width and extending in the longitudinal direction with gaps in the lateral direction on the surface facing the disk surface. As a result, when the disk rotates, air is drawn between the rail and the disk to generate pressure, and the slider is pushed away from the disk surface, producing a flying height g. This flying height g has a characteristic that the higher the disk rotation speed and the wider the rail width, the larger the flying height g becomes. Therefore, the flying height g of the slider differs between the rail portion located on the outer circumferential side of the disk and the rail portion located on the inner circumferential side of the disk, depending on the circumferential speed of the disk.

Originally, it is better to bring the magnetic head closer to the disk, but as mentioned above, the flying height g is smaller on the inner circumference side of the slider than on the outer circumference side, so the contact between the slider and the disk, and by extension, , both have the disadvantage of being susceptible to damage.

This drawback becomes a particular problem as the flying height g has to be made smaller as disks are made smaller and more dense.

This will be explained in more detail below. First, FIG. 1 shows the relationship between the difference in flying height between the inner and outer peripheral rails of the slider and the disk speed.
In the figure, ranges a, b, c, d, and e indicated by arrows are
14 inch, 10 inch, 8 when rotating at 3600 rpm
Speed ranges for inch, 5 inch and 3 inch disks are shown. The horizontal axis is the disk speed, and the vertical axis is the flying height g _a of the outer rail and the flying height of the inner rail.
The amount obtained by dividing the difference in g _b by the floating height g ₀ of the center rail is shown in %. (g _a − _{g b} )/g ₀ is about 3% at most in a large disk device with a 14-inch disk diameter, but 7% in a small disk device with a 3-inch disk diameter.
It has also reached If the recording density is the same, the flying height
Since g ₀ must also be the same, the floating amount g _b of the inner rail becomes smaller as the disk diameter becomes smaller. For example, if the flying height g ₀ is 0.3 μm, the inner rail flying height g _b for a 14-inch disk is 0.296 μm, which is only 0.004 μm smaller than g ₀ , but it is 3 inches. 0.289μ for disk
m and 0.011μm smaller.

Next, problems caused by the small flying height g _b of the inner rail will be explained from the perspective of contact between the disk and the slider.

The causes of contact between the slider and disk are the vertical movement of the disk surface due to disk vibration, the surface roughness of the disk surface, the vertical movement of the slider due to vibration from the support material that holds the slider in the air, and the slider and disk surface. It is known that various factors are involved, such as the dynamic characteristics of the air film formed between the two. Although it is difficult to quantify the influence of each of these factors on the contact between the slider and the disk, the following experimental facts show the influence of the surface roughness of the disk surface and other factors. I found out that.

Currently, the standard deviation δ of the disk surface roughness is approximately 0.07μ.
m, rotation speed of a 14-inch disk with a thickness of 1.9 mm
Rotate at 3600 rpm (peripheral speed 60 m/s) and float the slider above it. At this time, a piezo element is attached to the slider so that the impact when the slider contacts the disk can be detected. When the flying height of the slider is varied, contact between the slider and the disk is detected when the flying height is 0.3 μm or less.

Now, we assume that the roughness of the disk surface has a normal distribution, and furthermore, the flying height detected by the piezo element
It is assumed that the collision at 0.3 μm has a roughness of 3δ (=0.21 μm). This assumption does not undermine the generality of the following discussion. This assumption and (g _a −
Based on the value of g _b )/g ₀ , the floating height of the inner rail g _b
Let's calculate the increase in contact frequency due to the decrease in Here, the value of the cumulative distribution function of normal distribution is used as the contact frequency. Here, based on the above assumption that when the circumferential speed of the 14-inch disk is 60 m/s, g ₀ = 0.3 μm and a roughness of 3δ is detected, the contact frequency is
It is 0.135%. On the other hand, with the 3-inch disk, the floating height of the inner rail has decreased to 0.287μm as mentioned above, so it is thought that contact with roughness up to 2.8δ will occur. Therefore, the contact frequency is 0.256%, which is 14
The contact frequency is about twice that of the inch disk. By the way, it has been found that in the above-mentioned experimental device for impact detection using piezo elements, even if the flying height is 0.32 μm, the disk surface will be scratched if left for a long time. Since the contact frequency in this case is 0.05%,
From this, it can be understood that the increase in the frequency of contact is important from the standpoint of ensuring the reliability of the disk device.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a slider which eliminates the drawback of a conventional slider in that the flying height of the inner rail is reduced, and which is less likely to cause damage to the head and disk.

[Summary of the invention]

The flying height of the slider largely depends on the disk circumferential speed at the rail position and the rail width. Among conventional sliders having the same rail width, the floating heights of the outer rails are different because the circumferential speeds of the inner and outer rails are different. In the present invention, the ratio B _a / _{B b of} the inner rail width B _b of the slider floating rail to the outer rail width B a is D, and the disk diameter at the innermost position of the slider movement range is D. When the rail interval on the inner and outer circumferential sides of the slider is W, The feature is that the floating height of the rails on the inner and outer circumferential sides is the same.

[Embodiments of the invention]

Hereinafter, one embodiment of the magnetic disk slider of the present invention will be described with reference to FIGS. 2 to 4.

FIG. 2 is a plan view illustrating how the magnetic head slider and disk of the present invention are installed, and FIG. 3 is a plan view thereof. A magnetic head slider 2 on which a magnetic head 1 is mounted is supported by a gimbal 3 for allowing pitching and rolling movements of the slider 2, and a load arm 5 for pressing the slider 2 against a disk 4 rotating in the direction of the arrow. In this example, the slider 2 has two
Book rails 6a and 6b are provided. When the disk 4 rotates, the rails 6a, 6b and the disk 4
Air is drawn in between the
occurs. FIG. 4 is a diagram of the slider 2 in FIGS. 1 and 2 viewed from the disk 4 side. The disk 4 rotates in the direction of the arrow, and the magnetic head 1 is provided on the downstream side. And rail 6a
is located on the outer circumferential side of the disk 4, and the rail 6b is located on the inner circumferential side of the disk 4. Also, the width B _b of the inner rail 6b is the width of the outer rail 6a.
B It is made larger than _a . The higher the speed of the disk surface and the wider the rail width,
The flying height g has a characteristic of increasing. Therefore,
In such a structure, the slider 2 has a width B _b of the inner rail 6b where the circumferential speed is lower than the width B _a of the outer circumferential side rail 6a where the circumferential speed is high. _b and the floating height g _a on the rail 6a side
become equal.

Next, a case will be described in which the magnetic head slider of the present invention is implemented in a small high-density magnetic disk device having a disk outer diameter of 90 mm, a rotational speed of 3600 rpm, and a magnetic head flying height _g0 of 0.3 μm. Figure 5 shows the relationship between the flying height and peripheral speed of the slider under the above conditions, where the horizontal axis represents the peripheral speed v of the disk, and the vertical axis represents the ratio of the flying height of the rail section to the flying height of the magnetic head. It represents. In the figure, curve A is the rail width
In the case of 0.738 mm, curve B shows the ratio of the flying height when the rail width is 0.695 mm. As can be seen from the figure, the flying height g of the slider rapidly decreases as the peripheral speed v decreases, and increases as the rail width B increases. Therefore, the flying height g becomes minimum when the slider moves to the innermost diameter side, at a circumferential speed of 10 m/s. At this time, since the difference in circumferential speed v _Sb between the inner rail v _Sb and the outer rail is 1 m/s, the width of the inner rail and outer rail is the same as in the conventional case (0.738 mm in this example). ), the difference in flying height reaches 7% of the flying height _g0 of the magnetic head. In this embodiment, on the other hand, the width of the rail on the outer diameter side is set to B=0.695, so that the flying height on the inner diameter side and the outer diameter side can be kept the same. Furthermore, this reduces the frequency of contact between the rail and disk by approximately 1/2.
The reliability of the device can be improved.

Here, in order to make the floating height of the inner and outer rails the same, the inner rail width B _b and the outer rail width
Consider what the ratio to B _a should be.
Now, the center rail 7 of the slider 2 shown in FIG.
Suppose that the disk is at a position with a disk diameter D and is floating at a rotational speed n. In addition, the inner peripheral side rail 6
Let W be the distance between b and the outer peripheral side rail 6a. Furthermore, the floating height of the inner rail 6b is g _b , the disk speed is v _b , the floating height of the outer rail 6a is g _a , and the disk speed is v _a . By comparing the analysis considering the bearing action between the slider and the disk with the actual measurement of the flying height, we discovered that the following proportional relationship holds.

That is, when the rail width is constant, ( _ga / g _b ) = (V _a / V _b ) ^0.7±0.1 ... (1) Also, when the circumferential speed is constant ( _ga / - / g _b ) = (B _a /B _b ) ^1.7±0.1 ...(2). However, in order to distinguish between the flying heights in equations (1) and (2), the flying heights are expressed as _a and _b in equation (2). Furthermore, the range of the exponent in equations (1) and (2) is shown to be within the above range even when considering the pressing load on the slider and the influence of the tilt angle of the slider with respect to the slider's circumferential direction. ing.

The present invention aims to equalize the flying heights of the inner and outer peripheral rails by compensating for the difference in flying height based on the circumferential speed expressed by equation (1) with the rail width shown by equation (2). The following equation (3) must hold true.

g _a ／g _b・ga _／ ―／g _b ≡(V _a ／V _b ) ^0.7±0.1・(B _a ／B _b ) ^1.7±0.1 = 1 ……(3) Here, V _a =V _b +2πW・n/60...(5) V _b ≒V _a ≒n/60πD... Substituting (6) into equation (4), we get becomes.

The effect of the difference in disk diameter between the inner rail 6b and the outer rail 6a of the slider 2 is noticeable, so when the disk diameter is small, that is, the slider 2 is at the innermost position of its movement range. Therefore, it is appropriate to use the disk diameter at the innermost position of the slider 2's movement range as the disk diameter D in equation (7). In other words, the width B _b of the inner rail 6b and the outer rail 6
The ratio of the width B _a of a to the width B a may be selected within the range of equation (7) using the disk diameter D at the innermost circumferential position of the slider 2's movement range and the rail spacing W.

As described above, the present invention is particularly effective in small magnetic disk devices. Moreover,
It can also be applied to large magnetic disk devices, and its effects can be expected. That is, although dust is removed as much as possible from the inside of the magnetic disk device to create a clean environment during assembly, a small amount of dust may still remain. These dust particles may be collected in the fine floating gap between the slider and the disk, causing contact between the two. Based on our experience with conventional 14-inch class large disks, we know that the above-mentioned collection tends to occur on the inner rail, and the difference in the flying height between the inner and outer rails in large magnetic disk devices also has a large effect. There is. Therefore, the effects of the present invention can be expected even in large-sized magnetic disk devices.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent an increase in the frequency of contact due to a decrease in the flying height of the inner rail, and it is possible to improve the reliability of the device.

Furthermore, if the reduction in contact frequency is used to reduce the flying height of the magnetic head, the recording density can be increased.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the disk speed and the flying height imbalance of the slider, FIG. 2 is a diagram for explaining the device status of the magnetic head slider and disk of the present invention, and FIG. 3 is a side view of FIG. 2. 4 is a view showing the surface of the magnetic head slider in FIGS. 2 and 3 facing the disk surface, and FIG. 5 is a view showing the relationship between the flying height of the slider and the circumferential speed of the disk. 1...Magnetic head, 2...Slider for magnetic head, 3...Gimbal, 4...Magnetic disk, 5...
...Load arm, 6a, 6b...Rail.

Claims (1)

[Scope of Claims] 1. In a slider for a magnetic head of a magnetic disk device having floating rails on both sides of the surface facing the disk surface, the width B _b of the inner rail of the floating rail and the width of the outer rail The ratio of width B _a is B _a /B _b ,
When the disk diameter at the innermost position of the slider movement range is D, and the rail spacing between the inner and outer circumferences of the slider is W, A slider for a magnetic head characterized by the following.