JPH0327992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a floating head mechanism that flies over the surface of a rotating disk-shaped magnetic recording medium with a minute flying gap.

[Prior art]

Conventionally, in magnetic disk drives, in order to avoid wear and tear caused by contact between the magnetic head, which controls electromagnetic conversion, and the surface of the magnetic recording medium, a slider that floats using the viscous flow of air that accompanies the surface of the rotating recording medium has conventionally been used. A floating head slider with an electromagnetic conversion section is used. This floating head slider is designed in such a way that the load applied by the external load spring and the pressure generated by the slider are balanced to maintain a certain gap, but in order to increase the recording density, the floating head slider is It is required to make the floating gap as small as possible. On the other hand, in order to satisfy this requirement, the surface of a traveling recording medium is finished to have a smooth, mirror-like surface; however, not only microscopic surface roughness but also sparse protrusions remain on the surface of the recording medium. When this protrusion collides with the floating head slider, the flying clearance of the floating head slider fluctuates, which not only disturbs the reproduction signal of the magnetic head but also damages the floating head slider or the recording medium. Therefore, the flying clearance of the floating head slider must be set within a range that does not contact these protrusions on the surface of the recording medium.

FIG. 1 is a sectional view showing a conventional example of a magnetic disk device equipped with this type of floating head slider.This will be briefly explained based on the figure. A spindle that is freely arranged and rotated at high speed by a motor 4,
A plurality of disks (recording media) 5 (three disks are shown in the figure) are arranged on this spindle 1 with a predetermined gap maintained in the thickness direction. Reference numeral 6 denotes a carriage disposed on the base 2 via a bearing 7, and three head arms 8 extending below each recording medium 5 are attached to the carriage 6.
A floating head slider 10 is attached to each of the leading ends of the recording medium 5, corresponding to each recording medium 5. Further, a coil 12 is attached to the carriage 6 in correspondence with the magnetic circuit 11.

FIGS. 2a and 2b show the floating head slider 10 taken out, and this floating head slider 10 is usually a twin-cylinder slider 13 having two slider surfaces 14A and 14B on the surface facing the recording medium surface. and a magnetic head 16 comprising a core 17 and a coil 18 and constituting a magnetic transducer.A tapered surface 15 is formed at the air inflow end of each slider surface 14A, 14B, and the core 17 and the slider 13 A gap 19 is formed between them. Further, a slider surface 20 having a minute width is provided at the center of the slider 13 adjacent to the core 17.
It has the function of determining the width of 9, and hardly contributes to levitation. The floating head slider 10 configured in this manner is supported by a cymbal spring 22 via a rear groove 21 of the slider 13, and a load is applied by a load beam 23, as shown in FIG. 2b. . A dimple 24 is formed at the tip of the load beam 23, and a hemispherical convex portion (not shown) is formed on the cymbal spring 22 at a position corresponding to the dimple 24, so that the load by the load beam 23 is transferred to the slider 13. It is designed to act on one point in the widthwise center of the back surface. This is to ensure that the degree of freedom of movement of the floating head slider 10, especially rolling and pitching movements, is not restricted.

Figures 3a and 3b are schematic diagrams showing the floating state of the floating head slider 10, in which a is a side view seen from a direction perpendicular to the disk traveling direction (direction of arrow A), and b is a rear view seen from behind in the disk traveling direction. It is. In the figure, pressure is generated on the slider surfaces 14A and 14B due to the disk running, and the load beam 23
(see FIG. 2b), it floats above the disk surface while maintaining a state of balance with the load W applied thereto.

Here, the floating clearance h ₀ of the floating head slider 10
The factors that cause deviation from the set value can be broadly classified as follows.

(1) Static error: A deviation in the flying clearance due to errors in flying parameters such as the shape and dimensions of the slider surface, the load W, and the location of its point of application (indicated by in Figure 3).

(2) Dynamic error: Dynamic flying clearance fluctuation due to undulations and vibrations of the running disk surface or vibrations of the cymbal spring 22, load beam 23, etc.

The flying clearance of the floating head slider 10 is set in consideration of these static and dynamic flying clearance fluctuations so that it does not come into contact with the recording medium surface, so reducing these flying clearance fluctuations is a matter of designing the floating head mechanism. is considered to be the most important issue in the world.

By the way, as mentioned above, floating head slider 1
0 is generally equipped with a double copper slider 13 having two slider surfaces 14A and 14B. This is to increase the restoring moment of the floating head slider 10 in the rolling direction and to reduce the static and dynamic flying clearance fluctuations mentioned above.

If the gap between the slider surfaces 14A and 14B is defined as _yb in FIG. 3b, most sliders 13 have a value of _yb of about 3 to 4 mm. In this way, the floating head slider 10 having a finite width has the following characteristics:
Fluctuations in the flying clearance different from the above-described fluctuation factors in the set flying clearance occur as shown below.

As is well known, in a magnetic disk device, a floating head slider 10 is positioned at a certain radial position on the surface of a disk that rotates at a constant rotation speed at high speed, and performs recording and reproducing, and changes the radial position as necessary to perform recording and reproducing. . That is, since the traveling speed differs depending on the radial position, the flying clearance of the floating head slider 10 to which a constant load W is applied changes.
Specifically, since the traveling speed is fast at a position with a large radius, the floating clearance becomes large. The amount of change in the flying clearance is not positioned as an error in the set flying clearance, but is a value that is determined once the radial position in which the floating head slider 10 operates, the rotation speed of the disk, etc. are determined.

Furthermore, changes in the flying clearance of the floating head slider 10 due to different radii occur even when the radial position of the slider 13 is fixed. That is, as shown in FIG. 4a and b, the two slider surfaces 1
Since there is a speed difference between 4a and 14b corresponding to the radius ratio r _p / _ri , the slider 13 flies while tilting in the width direction. Here, the radius r _c of the disk is the slider surface 1
If the gap y _b between 4A and 14B is sufficiently large, the speed difference corresponding to the radius ratio r _p /r _i will be minute,
The difference Δh in the floating clearance becomes a negligible value. but,
In the case of a small magnetic disk device using a disk with a small diameter, the speed difference cannot be ignored, and the above-mentioned difference in flying clearance Δh becomes obvious. Note that the reason why the flying clearances of the slider surfaces 14A and 14B are different is not only due to a difference in running speed, but also to a difference in local velocity vector within the slider surface due to a difference in curvature of the disk surface running. That is, the fourth
At the air inflow end and outflow end of the slider 13 set as shown in Figure a, the angle (θ _i , θ _p ) between the slider longitudinal direction and the disk running direction becomes large, and the angle is on the inner circumferential side. The slider surface 14A is larger than the outer slider surface 14B. As the angle between the longitudinal direction of the slider and the traveling direction of the disk increases, the levitation force decreases even if the absolute value of the speed is the same, so this effect has the same effect as the speed difference explained earlier, that is, Δh It acts in the direction of increasing it.

These levitation characteristics can be obtained by solving the following Reynozzle equation regarding the gas lubricant film.

∂/∂x [ph ³ (1+6λ/h) ∂p/∂x] + ∂/∂y [ph ³ (1+6λ/h) ∂p/∂y] = 6μUx∂(ph)/∂x+6μUy∂(ph) /∂y...(1) However, x, y: coordinates, p: pressure, h: gap,
λ: Mean free path, μ: Viscosity coefficient, Ux,
Uy: Speed Figure 5 shows the relationship between the radial position of the disk and the difference Δh in the flying clearance between the slider surfaces 14A and 14B of No. 2, taking into account the difference in speed vectors mentioned above.
A calculation example of solving equation (1) is shown below. The calculation conditions are: disk traveling speed at radius r _c 6.5 m/s, l = 3.7 mm,
y _b = 2.6mm, b = 0.5mm, /l = 0.55, /y _b =
0.5 h _p =0.2 μm. As can be seen from the figure, r _c
As becomes smaller, Δh increases, and when r _c = 20 mm, Δh = 0.02 μm, that is, the average flying clearance h _p =
Reaching 10% of 0.2μm.

This tendency becomes more pronounced as the dimensions of the slider 13, l and _yb, become larger, so Δh can be reduced by reducing l and _yb . However, as mentioned above, the restoring moment in the rolling direction is reduced, so extreme miniaturization is not possible. When designing a floating head slider for such a small-diameter disk, it is necessary to set the center flying clearance by taking into consideration the Δh explained here in addition to the static and dynamic errors mentioned above. However, there was a problem in that it was difficult to create minute gaps for high-density recording.

One way to solve this problem is to make the inner slider surface 14A wider than the outer slider surface 14B. In other words, the slider surface 14
This is a method for determining the widths of A and 14B. The biggest drawback of this method is that by making the normally symmetrical floating head slider asymmetrical, two types of sliders must be prepared: one located above the disk surface and the other located below. It is. In other words, for the sake of explanation, FIGS. 3 and 4 show the slider located above the disk surface, but in a typical magnetic disk device, the slider is arranged to sandwich the disk on the top and bottom surfaces of the disk, respectively. , and the running direction is the same, so the widthwise asymmetric slider is different for the upper surface and the lower surface. Dividing two types of parts instead of one type not only complicates the management of parts processing and assembly processes, but also complicates inventory management that takes into account the yield of parts, resulting in high costs. There is a drawback.

[Summary of the invention]

The present invention has been made in view of the above-mentioned points, and the innermost radial position on the disk surface where the floating head slider is located is r _c , the total width of the floating head slider is y _b , and the two main slider surfaces are When each width is b, set the slider width direction position of the load force point applied to the slider to be shifted from the slider width direction center line to the outer circumference side of the disk by Δ(y-b) ² / (4r _c ). It has excellent stability,
The object of the present invention is to provide a floating head mechanism capable of preventing tilting of a slider in the width direction, which occurs in small-diameter disks.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

〔Example〕

Figure 6 is a calculation example in which the above equation (1) is solved for the relationship between the non-dimensional load force point position y/y _b in the slider width direction and the slope Δh/h _p of the slider floating gap, and the radial position r _c of the slider is Dimensionless parameter (y _b - b)/
It is expressed as r _c . From this result _{, the load force point position/y b is} (y _b −
b) varies depending on /r _c , for example, in (y _b - b)/r _c = 0.102 shown by straight line M, /y _b =
It becomes 0.524.

When looking for the specific dimensions of this value, y _b =
2.6mm, b = 0.5mm, r _c = 20.5mm, Δh is 0
The load force point position is 1.362 mm, that is, by setting the load force point position approximately 60 μm on the outer circumferential side from the center of the slider, the inclination in the width direction of the slider can be eliminated. Note that N is (y _b - b)/r _c =
0.145, P indicates the straight line when (y _b −b)/r _c =0.064.

A more general expression of this optimal load force point position will be described below.

FIG. 7 is a model diagram showing the balanced state of forces on the slider 13' floating when the inclination in the slider width direction is 0, where f _i and f _p are respectively on the inner circumferential side,
The floating force Δ generated on the outer slider surfaces 14A and 14B is the amount of deviation of the load force point position from the slider center. Since f _i and f _p can approximately be assumed to act on the center of each slider surface 14A, 14B, the moment balance equation is {y _b − b)/2+Δ}・f _i = {(y _b − b)/2−Δ}·f _p (2)

On the other hand, since the levitation force is approximately proportional to the speed, that is, the radius, the following equation holds true.

f _p /f _i =r _c +(y _b -b)/2/r _c -(y _b -b)/2...
(3) Calculating Δ from equations (2) and (3) yields the following equation.

Δ=(y _b − b) ² /(4r _c )...(4) Since equation (4) is an approximate equation obtained from the speed difference corresponding to the radius ratio of the slider surfaces 14A and 14B, strictly speaking, In addition to this is the effect of the difference in velocity vector within the slider plane due to the curvature difference mentioned above.

Figure 8 shows the calculation results of approximate equations (4) and (1) for the relationship between (y _b - b)/r _c and the load force point position [/y _b ] 〓 _h = 0, where Δh is 0. This is a comparison.
Although the accuracy of approximation formula (4) tends to decrease somewhat as (y _b −b)/r _c increases, it can be said that it is a fairly good approximation.

That is, by setting the load force point position to be shifted from the center in the width direction of the slider to the outer circumferential side by the value expressed by equation (4), the slider 13' can be levitated substantially parallel to the width direction.

Moreover, since the parts of the floating head slider shown in FIG.
The components of the gimbal/load beam shown in Figure b are also common for both the upper and lower surfaces of the disk. In other words, as a specific method for setting the load force point position by shifting the load force point position, it is also possible to shift the relative position of the slider 13' and the gimbal/load beam by the amount expressed by equation (4), or to set the load force point position in advance. Gimbal spring 9 that determines the point of force position
The convex portion formed on the load beam 8 and the dimple 7 formed on the load beam 8 may be formed to be shifted, but the direction of the shift may be different when viewed as a slider/gimbal/load beam assembly shown in Fig. 2b. It is common in the fixed end direction of the load beam 8.

In the slider/gimbal/load beam assembly itself shown in FIG. 2B, since the slider 13' is asymmetrical in the longitudinal direction, there are two types, one for the upper surface and one for the lower surface with respect to the disk, as is conventional.

By the way, Δ ^y expressed by equation (4) will be an extremely small value if, for example, r _c is large enough, and Δ
Not only does it have almost no effect to set it by shifting it by a certain amount, but it may also have no practical meaning when taking into account the tolerances of the assembly jig or parts.

Therefore, the practically effective value of Δ will be further explained below.

Figure 9 shows r _c and Δ obtained based on equation (4) for commonly used slider dimensions.
This shows the relationship between Here, r _c is the disk radius corresponding to the slider position as shown in FIG. 7, but more specifically, it can be considered to be approximately the innermost radial position of the slider moving in the radial direction. The minimum clearance of the slider is determined at the innermost radial position, and if it is floating parallel to the width direction at that position, it will move to the outer radial side and Δh
This is because even if increases, the floating gap will not become less than the floating gap at the innermost radial position.

As can be seen from Fig. 9, Δ becomes larger as r _c is smaller and (y _b - b) is larger. For example, when y _b = 3 mm and b = 0.5 mm, Δ is Δ when r _c = 80 mm.
20μm, Δ40μm at r _c = 40mm, Δ at r _c = 20mm
y reaches 80μm.

The fact that Δ is large means that when the load force point position is set at the center of the slider in the width direction, the inclination Δh of the slider is correspondingly large.

That is, the smaller the innermost radius of the magnetic disk device, the greater the effect of setting the load force point position by Δ.

In the above explanation, Fig. 2b is shown as a specific structural example of the gimbal and load beam, but even if other slider support mechanisms have the functions of the gimbal and load beam, the load force point position explained here may not be the same. It is clear that the effect of setting the values in a different manner is the same.

〔Effect of the invention〕

As explained above, in the floating head mechanism according to the present invention, the position of the load force point applied to the slider in the slider width direction is set to be shifted from the slider width direction center line to the disk outer circumferential side. This prevents the floating head slider from tilting in the width direction, which occurs in disk devices.
This improves flying stability and makes the flying gap smaller, in other words, enables high-density recording. Also,
Since parts such as the slider or its support mechanism are common for the upper and lower surfaces of the disk, the processing and assembly processes are not complicated, which is a great advantage.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional magnetic disk device, FIGS. 2a and 2b are perspective views showing a floating head slider taken out and a partially omitted perspective view of its gimbal/load beam assembly, and FIG. 3 a and b are schematic diagrams showing the floating state of the floating head slider;
a is a side view seen from a direction perpendicular to the disk running direction, b is a rear view seen from the rear in the disk running direction,
Figures 4a and b are diagrams showing a floating head slider that flies at an angle depending on the radius ratio, Figure 5 is a diagram showing calculation results showing the relationship between the disk radius and the difference in flying clearance, and Figure 6 is a diagram showing the results of calculations showing the relationship between the disk radius and the difference in flying clearance. A diagram showing the calculation results showing the load force point position and the inclination of the floating gap, Figure 7 is a model diagram showing the force balance state of the slider, and Figure 8 is an exact diagram showing the load force point position with the slider width direction inclination as 0. FIG. 9 is a diagram showing the calculation results of the solution and the approximate solution, and FIG. 9 is a diagram showing the calculation results showing the relationship between the disk radius and the load point movement amount. 10... Magnetic head slider, 13, 13'...
...Slider, 14A, 14B...Slider surface, 1
6... Magnetic head, 17... Core, 18... Coil, 19... Gap, 22... Cymbal spring, 23... Load beam.

Claims (1)

[Claims] 1 In a floating head mechanism that has at least two main slider surfaces on both sides and performs recording and reproduction by floating above the surface of a rotating disk-shaped magnetic recording medium, the innermost periphery on the disk surface where the floating head slider is located. When the radial position is rc, the total width of the floating head slider is yb, and the two main slider surface widths are each b, the position of the load force point applied to the slider in the slider width direction is from the center line in the slider width direction to the outer circumferential side of the disk, A floating head mechanism characterized by being set to be shifted by Δ(y _b −b) ² /(4r _c ).