JP2003168273A - Floating head slider - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve follow-up properties to the waviness of a disk surface in the floating micro-space region of the floating head slider of a magnetic disk recorder. <P>SOLUTION: The head position of the slider is made coincident with the center of pressure of a bearing pad at a rear part. Each bearing pad length at a front and rear parts is made nearly coincident with the wavelength of the waviness corresponding to a resonance frequency in the primary and secondary modes of a slider pitch oscillation. The center of pressure of a bearing pad at the front part is set to be 20 to 30% of slider length from the front end of the slider. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flying head slider in a magnetic disk storage device for positioning a recording / reproducing element on a rotating disk medium surface in a non-contact manner up to a minute and constant clearance. More specifically,
The present invention relates to a flying head slider that can follow the waviness of a disk surface without changing the clearance up to a nanometer-level ultrafine clearance.

[0002]

2. Description of the Related Art In a magnetic disk storage device which is an important external storage device in a computer system, in order to perform high density and high reliability recording by a recording / reproducing element (hereinafter referred to as a head) on the magnetic disk surface, the head is placed at the rear end Non-contact recording has been performed by floating a mounted slider on the surface of a rotating disk medium by the principle of an air bearing. In order to increase the recording density of the disk medium, it is necessary to reduce the clearance between the head and the disk. Since the disk surface rotating at high speed has undulations and vibrations, the air bearing of the slider has the function of a spring and a dashpot for positioning the head at the rear end of the slider to the disk surface that fluctuates to a minute and constant clearance.

FIG. 11 shows a taper flat type flying head slider which is generally used in the era when the flying clearance of the head position was reduced from 500 nm to 50 nm from 1974 to 1995.
Air bearing rail surfaces 2a, 2b having a length equal to the slider length and a narrow width are provided on both sides of a rectangular flat plate-shaped slider 1. When the disk surface is run as indicated by arrow 3 and a load of 100 mN to 30 mN is applied to the slider central back surface via a flexible support spring, the slider rear end on which the head 4 is installed is several tens of nanometers. When the clearance is reached, balance with the reaction force of the air film. When the clearance is reduced, the pressure on the air bearing surface increases rapidly, and the rigidity of the air film near the head is about 10 ⁴ times the stiffness of the support spring, so even if the disk surface vibrates, the head / disk A certain clearance can be maintained between the surfaces.

FIG. 12 shows a taper flat type negative pressure slider having a negative pressure generating bearing area by providing a reverse step portion 5 at the center of the positive pressure generating bearing surface of the taper flat surface of FIG. In this case, even if the slider load is reduced, the slider load during steady rotation of the disk can be applied with a negative pressure, so that the disk easily floats from a region where the peripheral speed of the disk is small, and in the operating speed region, the outer circumference of the disk
Even if the disk surface velocity is different on the inner circumference, a nearly constant clearance can be maintained, and the change in clearance due to the change in atmospheric pressure can be suppressed. Recently, it is possible to reduce not only the speed change due to the outer and inner circumferential positions of the disk but also the change in the clearance due to the skew (tilt) of the slider.
A flying head slider such as No. 4 is used. Figure 1
The slider No. 3 has a wide bearing surface 6 at the rear end of the center rail, and in FIG. 14, a rear bearing pad 7 is independent at the central rear end. Here, numeral 8 in FIG. 14 is a stiction removing pad for preventing the air bearing surface from being attracted to the disk surface by the meniscus force when the slider is in contact with the disk surface.

The areal recording density of the currently practical disk device is 30.
It is gigabit / square inch, and the clearance between the head and the medium is about 15 nanometers. Next 10
In order to realize 0 gigabits / square inch, it is necessary to realize a head-medium clearance of about 6 nanometers. In such a minute clearance region, if the air bearing surface is long, the slider cannot follow the minute waviness of the disk, and the slider easily contacts the disk surface. For this reason, recently, there has been proposed a slider as shown in FIGS. 15 and 16 in which the front bearing surface is also shortened to form the front bearing pad 9 and the rear end also has a short rear bearing pad surface 7.

By the way, in the clearance region of several nanometers, the slider intermittently comes into contact with the roughness projections on the disk surface, and if the surface roughness is reduced, the stiction force increases and the crash easily occurs. For this reason, a slider for near-contact recording has been developed which allows intermittent contact due to the design of surface roughness, lubricant, coating material and the like. Further, in magnetic recording, it is necessary to suppress the fluctuation of the clearance between the head and the medium to a certain value or less, but since the allowable fluctuation value decreases as the absolute value of the clearance decreases, it becomes difficult to suppress the variation below the allowable value. ing. Therefore, a contact slider has been developed in which variations and fluctuations in the clearance are greatly reduced by continuously contacting the slider with the disk surface and the clearance loss is small. FIG. 17
Is an example of a slider for the purpose of near contact and contact recording. The front side is a relatively long air bearing rail, and the short pad 10 at the rear end is a contact pad. In this case, the trailing contact pad is in the mixed lubrication region.
Here, the case where the contact rigidity is dominant is called contact recording, and the case where the air film rigidity is dominant is called near contact recording. FIG. 18 shows another embodiment of the contact recording slider, in which the rear contact pad 10 is considerably short because it does not generate a levitation force. Also, the front bearing pads 9a, 9b
Is also considerably shorter.

[0007]

In the region where the clearance between the head and the disk surface is 10 nanometers or less, in both non-contact recording, near contact recording, and contact recording, a very small amount called a micro waviness of the disk surface is called. It is important to reduce fluctuations in the clearance between the head and disk surfaces due to waviness. The wavelength of the waviness on the disk surface, which affects the clearance variation, is calculated from the low frequency component of the waviness that has a wavelength of about 10 times the slider length where the clearance between the slider surface and the disk surface changes depending on the location within the slider length.
Even the high frequency component having a wavelength equal to the length of the trailing edge pad becomes a problem. These waviness components differ depending on the peripheral speed of the disk. For example, when the slider length is 1.25 mm, the trailing pad length is 50 μm, and the peripheral speed of the disk is 15 m / s, it is made to follow the slider bearing surface design. Therefore, the frequency of the waviness of the disk surface to be considered is in the range of about 1 kHz to about 300 kHz. Wavelength components smaller than this and high frequency swell components do not have the function of following the trailing end air bearing pad and contact pad of the slider, so the size of the swell needs to be small enough not to affect clearance fluctuation. Generally, the amplitude of the waviness on the disk surface has a property of decreasing in proportion to the first power of the frequency to the second power of the frequency, and therefore, 1 kHz
It is an important issue to design a slider bearing surface having a high followability to the waviness of the disk surface from z to several hundred kHz. The slider constitutes an air film spring by front and rear air bearings and a vibration system having a natural frequency and a natural mode of three degrees of freedom, and the slider does not follow the waviness of the disk surface above these natural frequencies. Therefore, conventionally, slider designs have been made to increase the natural frequency of these sliders. However, as the clearance decreases, the air film rigidity increases, and the lowest-order natural frequency of the slider becomes 50 kHz or higher. On the other hand, as the swell frequency with the slider length as the wavelength becomes approximately 10 kHz, the bearing surface becomes longer and it becomes impossible to follow. The effect has become noticeable. Therefore, a slider bearing surface has been shortened and a slider having the pad type bearing surface and contact surface shown in FIGS. 16 and 18 has already been developed. In this case, if the bearing pad length is 200 μm, the undulation frequency at which the pad cannot completely follow is 75 kHz which is the undulation frequency having the same wavelength as the pad length, which is about the same as the natural frequency of the slider. However, since the slider has two natural vibrations in which vertical translation and pitch rotation are coupled, it is unclear how to design the positions and lengths of the front and rear bearing pads with respect to the two natural frequencies of the slider. Met. Further, when the bearing surface is shortened and the width is increased, there is a problem that the damping performance of the air film deteriorates and a large peak occurs at the resonance frequency. Further, although the recording / reproducing conversion element is generally formed at the rear end of the slider, sufficient consideration has not been given to the positional relationship with the pressure center of the rear bearing pad. Therefore, as the clearance becomes smaller, the followability to the waviness of the disk surface deteriorates, and not only the clearance fluctuation but also the contact with the disk surface is likely to occur.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flying head slider having a clearance on the nanometer level, in which the head position can best follow the waviness of the disk surface. The present invention proposes design conditions regarding the head position, the position and size of the air bearing surface and the contact surface before and after the slider. More specifically, based on an analysis of the followability that considers that the slider is a vibrating system having two degrees of freedom of vertical translation and pitch rotation with respect to the waviness in the traveling direction of the disk surface, the clearance of the head position is the best. A slider having a head position that follows is proposed. It also proposes front and rear bearing pad lengths so that the amplitude near the resonance frequency does not increase even if the air bearing has no damping performance. Further, even though it is a two-degree-of-freedom vibration system, a slider bearing pad position is proposed in which the head position clearance variation exhibits the follow-up characteristics of an ideal one-degree-of-freedom vibration system of a higher-order mode. . The embodiment will be shown below, and the principle of mechanics used therein and the bearing pad design conditions based on the principle will be described in detail.

[0009]

FIG. 1 shows an embodiment of the non-contact recording head slider of the present invention. The slider has two small front bearing pads 9a, 9b on the left and right of the front side,
Further, one rear bearing pad 7 having a small length is provided at the center of the rear end of the slider. The rear bearing pad 7 is located at the center of the slider.
Instead of one, there may be two on each side as in the conventional slider of FIG. The two bearing pad surfaces on the left and right of the slider are for increasing the followability of the slider to the disk surface for roll vibration. The present invention focuses only on the followability to the waviness in the running direction of the disk surface, and therefore only the bearing characteristics that contribute to the pitch vibration of the slider. There is no special regulation regarding the width direction of the slider and the width of the bearing surface regarding roll vibration, and the follow-up function of the slider for roll vibration is basically the same as that of the conventional technology.

The feature of the slider bearing surface of the present invention is that the head is set at the center of the pressure of the rear bearing pad by ± (±) of the slider length.
The accuracy is 1% or ± 10% of the rear bearing pad length. When the disk average running speed is V and the resonance frequencies of the first and second modes of slider pitch vibration are f ₁ and f ₂ , respectively, the front bearing pad length and the rear bearing pad length are V / f ₁ ,
That is, it is 1.0 to 1.4 times V / f ₂ .
Further, the pressure center of the front bearing pad is not in the vicinity of the slider front end like the conventional slider, but in the range of 20% to 30% of the slider length from the slider mass center to the front side (range of 20% to 30% of the slider length from the slider front end). ) Is the position.

(Analytical model for clarifying the effect) Here, the fact that the present head slider has excellent follow-up characteristics will be described using the results of a dynamic analysis of the follow-up performance with respect to the waviness of the disk surface. The reason for the optimum dimensions of the front and rear bearing pads will be described. Fig. 2 shows a dynamic analysis model. As a design parameter that affects the follow-up characteristics, as shown in FIG.
₁ , 1 and ₂ and the equivalent translational air film rigidity when the slider makes a translational movement, k ₁ and k ₂ , from the center of mass of the slider (usually located at the center since the slider is a rectangular parallelepiped block with a small thickness). The pressure center positions of the front and rear bearing pads are d ₁ and d _2, and the distance from the slider mass center to the head position of the recording / reproducing element is d _h . Since the bearing reaction force against the disk surface waviness 11 is related to the distributed clearance in the bearing pad, as shown in FIG. 2, the front bearing pad surface has a stiffness of k _i / n per element l ₁ / n. The distributed pressure of the bearing pad against the waviness of the disk surface was calculated assuming that there is a distributed spring having a stiffness of k ₂ / m per element l ₂ / m on the rear bearing pad surface. In the calculation of the followability, the clearance variation of the head position was analyzed by considering the reaction force of the distributed spring proportional to the local clearance between the bearing pad and the disk waviness in the equation of the translational motion and the pitch motion of the slider. The results described below are the results calculated with m = n = 100. As the disc surface waviness 11, in addition to the harmonic waviness, the followability to random waviness was also examined. Slider length l =
Targeting a 1.25 mm pico slider, the mass m = 1.
59 mg, pitch moment of inertia I _p = 2.2 × 10
The ^-13 Nm ² was used. The running speed V of the disc is
2.5-inch type that will become popular in the future, with a rotation speed of 5400 rpm
Was set to 15 m / s. The calculation example shown below is under this condition, but the definition of the present invention is not restricted to these specific disk running conditions.

(Effect of head position on tracking characteristics and maximum
Proper position) The front bearing rail length shown in Fig. 17 is 1₁= 0.
8l, l at the rear_Two== 0.1 l bearing pad
Ru-shaped slider (d₁= 0.1 l, d_Two= 0.45l, k
₁= 10⁵N / m, k_Two= 2 x 10⁵N / m) and FIG.
On the front shown in₁= 0.2l bearing pad, l on rear
_Two= 0.1l bearing pad pad slider (d
₁= 0.4 l, d_Two= 0.45l, k₁= 10⁵N /
m, k_Two= 2 x 10 ⁵(N / m) Disc harmonious waviness
Z_dsin (2πf_dAmplitude Z of t)_dAgainst head
Clearance fluctuation amplitude Z_hThe frequency characteristic of the ratio of_h
0.5l (a), 0.475l (b), 0.45l
FIG. 3 shows the case of changing to (c). Z on the vertical axis
_h/ Z_dIs the tracking error ratio, so smaller than 1 is small
It means that the followability is high. Resonance of slider
The frequency of the rail slider is f ₁= 44 kHz, f_Two
= 106 kHz, pad type slider is f₁= 61 kH
z, f_Two= 107 kHz. Also, the damping effect of the air film
Is equivalent to when the slider vibrates vertically.
The damping coefficient value is used so that the damping ratio is 0.05.
It From these figures, the head
Position d_hWill shift from the center of the rear bearing pad
It can be seen that the deterioration is remarkable. This is the rear bearing pad
Air film spring allows clearance between bearing pad center and disk surface
Is kept constant, so swells will occur at positions deviating from here.
This is because the clearance changes due to the phase shift of. d_h
= 0.475l means that when l = 1.25mm,
The distance from the center of the bearing is 31 μm.
Followability even with slight deviation from the center of pressure of the rear bearing pad
Can be said to worsen. Also d_hPad in small area
Type sliders have better tracking characteristics than rail type sliders.
Rail-type sliders have poor trackability in the low frequency range.
I understand.

FIGS. 4 (a) and 4 (b) show the rms value σ _h of the clearance variation of the head position with respect to the random waviness, with the horizontal axis representing the head position and the vertical axis representing the rail type slider and the pad type slider. It is a thing. The random waviness used here has a standard deviation of sigma = 1 nm when the measurement distance is 1 mm, and the amplitude is inversely proportional to the 1.25th power of the frequency as a frequency characteristic of the waviness (hereinafter, the power exponent of the frequency is β In this case, β = 1.25). FIG. 4 shows a case where three types of air film rigidity are changed. From these figures, the head position is d _h
= D ₂ = 0.45l, σ _h is almost the minimum. Even considering the variation, d _h /l=0.45±
It can be seen that it is desirable that the head position coincides with the center of the rear bearing pad pressure with an accuracy of 0.01, that is, ± 1% of the slider length. The rear bearing pad has a slider length of about 10
%, It is desirable that the head position be aligned with the center of the rear bearing pad pressure with an accuracy of about 10% of the pad length. Further, since the minimum value of σ _h is smaller in (b) the pad slider than in (a) the rail slider, the pad type has better followability than the rail type. This is because, as can be seen from FIG. 3 (c), the trackability in the low frequency region is deteriorated in the rail type even under the condition of d _h = d _2. Therefore, it is preferable that the front bearing pad be short. This is because the front bearing spring acts so as to resist the positioning effect of the rear bearing spring with respect to the waviness of the disk. From the viewpoint of reducing this resistance effect, it is desirable that the front bearing pad be short. However, the front bearing pad has an optimum value from other viewpoints described later.

In the case of the pad type slider shown in FIG.
Resonance is observed at 0 to 70 kHz, which is the first-order mode resonance. Although the damping ratio is as small as 0.05, the resonance of the secondary mode is not so often seen because the rear bearing pad length is l.
₂ = 0.1l = 0.125 mm, the undulation frequency corresponding to this wavelength is 125 kHz, and since the resonance frequency f ₂ = 107 kHz of the secondary mode is close, the undulation excitation force is suppressed from the rear bearing pad. From this viewpoint, the optimum design condition of the rear bearing pad length will be described later. The design conditions of the front bearing pad that will not cause the resonance of the first-order mode will also be described later.

As described above, in the flying head slider according to the present invention, the front bearing is of a pad type, and the head position is located at the pressure center position of the rear bearing pad with an accuracy of ± 1% of the slider length or the rear bearing pad length. The first feature is that they are matched with an accuracy of ± 10%. In the embodiment of FIG. 1, a drawing is drawn in which the pressure center of the rear bearing pad (which is slightly behind the center of the bearing pad surface) is made to coincide.

(Effects of Rear Bearing Pad Length on Tracking Characteristics
Results and optimum value) Next, the optimum value of the rear bearing pad length is described.
Bell. 5A and 5B show d₁= 0.4 l, d_Two= D
_h= 0.45l, l₁= 0.2l pad type slider
By the way, l_TwoCharacteristic Z when changing_h/ Z_dof
It is a frequency characteristic. Below this, the head position is rear
Discuss only if it matches the bearing pad pressure center
It 5 (A) is k₁= 10⁵N / m, k_Two= 2.0 x
10⁵In the case of N / m, the resonance frequency of the slider is f₁=
61 kHz, f_Two= 107 kHz. Also in FIG.
(B) is k₁= 4.0 × 10⁵N / m, k_Two= 4.0 ×
10⁵In case of N / m, f₁= 113 kHz, f_Two= 1
It is 63 kHz. From now on, in FIG._Two=
When 0.1l, f_Two= 107 kHz second-order mode
The vibration amplitude is suppressed, but l_Two= 0.075l, and
As it becomes as small as 0.05l, the resonance amplitude of the secondary mode
It can be seen that it will increase. In addition, in FIG._Two=
F when 0.1l and 0.05l_Two= 2 at 163 kHz
The next mode resonance appears, but l_Two= 0.075l
At that time, the resonance of the secondary mode hardly appears. this
The reason is that the resonance of the secondary mode is due to the clearance of the rear bearing pad position.
This is a mode in which the
Is oscillated via the spring of the rear bearing pad length l_TwoBut
Resonance frequency f of secondary mode_TwoWavelength (= V / f
_Two), The undulation excitation force is flat on the bearing pad surface.
This is because even if there is undulation and there is swell, it will not be excited.
In FIG. 5A, (a) l_Two= 0.1l, no excitation force
Frequency becomes V / l_Two= 120 kHz and f_Two= 107
Since the value is close to kHz, (a) l_Two= 0.1l
Second-order mode resonance does not appear much. Also in FIG. 5 (B)
Is (b) l _Two= 0.075l, V / l_Two= 16
F at 0 kHz_Two= 163kHz, so this resonance is suppressed
Is under pressure. Generally, rear bearing pads are V / l_TwoMore than
It has the effect of smoothing the excitation force of the undulation frequency.
In (b) and (c) of (A) and (c) of FIG.
The resonance of the secondary mode appears at these resonance frequencies.
Is lower than the frequency averaged by the bearing pads
It Regarding the resonance of the first-order mode, the node point is
Excited because it is not too far from the center of the rear bearing pad
The effect and observed effect are relatively small. Figure 5
F appearing in (A)₁= Primary mode near 60 kHz
Resonances are better than those excited at the rear bearing pads
Because it was excited by the front bearing pad.
It These calculation results show that the damping ratio of the air bearing is 0.05.
This is an example of calculation in the case of
Since the resonance amplitude amplification factor is considerably large,
The resonance suppression effect by selecting the optimum bearing pad length
Will be extremely important.

From the above, the rear bearing pad length is generally
(L_Two) Is l_Two≧ V / f_TwoIs designed so that
Can be said to be desirable. But l_TwoIs V / f_TwoMore sweet
If it is larger, the averaging effect on the waviness of the rear bearing is f
_TwoIt occurs even in a smaller frequency range, so swell
The followability of the bearing pad, that is, the head, is deteriorated. this
Is the vibration of 100 kHz or less in (a) and (b) of FIG.
Comparing the widths, (a) is larger than (b)
I understand from that. Therefore, the rear bearing pad is
The resonant frequency of the cord is set to zero and
It is desirable to follow the lower frequencies, so
The optimum value of the rear bearing pad length is l_Two= V / f _TwoIs. Shi
However, this condition is that the pressure distribution is evenly distributed along the air bearing.
When the actual air bearing surface is
It may be numerically distributed, and this condition requires correction.
It is important. With this in mind, generally rear bearing pads
Optimal length is l_Two= ΑV / f_Two(1.0 ≦ α ≦ 1.4)
Becomes In the case of a magnetic disk device, the slider is
Depending on whether it is near the inner diameter or the outer diameter of the
However, the air film resonance frequency of the slider
Since the number does not change as much as the running speed,
V / f evaluated by uniform speed_Two1.0-1.4 times the rear shaft
It is desirable to design the receiving pad length. Therefore, in the present invention
Rear bearing pad length is the average running speed of the used disc
Degree V and the resonance frequency f of the secondary mode at that time_TwoAgainst
l_Two= ΑV / f_TwoThe range is (1.0 ≦ α ≦ 1.4)
It

(Effect of length and position of front bearing pad and its
These optimum values) Next, the effect of the position of the front bearing pad and its
The optimum value of the length will be described. FIG. 6A shows d_Two= D_h
= 0.45l, l₁= 0.2 l, l_Two= 0.1 l, k₁
= 10 ⁵N / m, k_Two= 2 x 10⁵Before under the condition of N / m
Side bearing pad position d₁0.2l, 0.3l, 0.4l
Response ratio of clearance to harmonic swell
Z_h/ Z_dIs the frequency characteristic of. Further, FIG. 6B shows d_Two
= D_h= 0.45l, l ₁= 0.2 l, l_Two= 0.1
l, k₁= 4 x 10⁵N / m, k_Two= 4 x 10⁵N / m
Front bearing pad position d₁= 0.2l, 0.3
It is the result when changing to l and 0.4 l. these
The head position is aligned with the rear bearing pad position.
The rear bearing pad length suppresses the resonance of almost secondary modes.
I choose the length. The position of the front bearing pad is now d
₁= 0.4 l, f in FIG.₁= About 60
The resonance of the primary mode of kHz appears, and FIG.
In (B), f₁= Resonance of the primary mode of about 110 kHz
Appears, d₁= 0.3l is quite small
And then d₁= 0.2l completely disappeared
There is. The reason for this will be described below.

When the inertia moment of the pitch motion with respect to the center of mass of the slider is I _p and the mass is m, if the front and rear bearing pads are short and the bearing rigidity can be approximated to a concentrated spring, then I _p = m for the rear bearing and the front bearing. If they have a relationship of × d ₁ × d ₂ , they are in a relationship of mutual impact center positions. At this time, the center of the rear bearing pad becomes a node point of the primary mode regardless of the value of the bearing rigidity, and the primary mode becomes pitch vibration around the pressure center position of the rear bearing pad. The center position of the front bearing pad pressure becomes the node point of the secondary mode,
The next vibration mode is pitch vibration around the center of the front bearing pad. In the case of this slider close to the pico slider, d ₂ =
When 0.45 l, d ₁ = 0.19 l becomes the impact center position, at which time the primary mode is not excited at the rear bearing position, and the primary mode excited at the front bearing pad is not observed. Moreover, only the influence of the primary mode appears in the clearance variation of the front bearing pad. This is the reason why the resonance of the first-order mode does not appear when (a) d ₁ = 0.2 l in FIGS. 6A and 6B. It is natural that such a design is desirable from the viewpoint of followability. . However, when d ₁ = 0.3 _{l, a} fairly good followability is exhibited. This is because the deviation from the impact center position influences by the square, and the effect of the error is less likely to appear even if the impact center position deviates to some extent.If the distance between the front and rear bearing pads is increased, the restoring rigidity against pitch vibration increases, Since the resonance frequency of the mode increases,
This is because the tracking error ratio in the low frequency region decreases as can be seen from (b) and (c) of FIGS. 6A and 6B. Therefore, the tracking error with respect to the random waviness is d ₁ = 0.3l
In many cases, the minimum is. Therefore, the recommended value d ₁ of the center position of the front bearing pad of the present invention is set in the range of d ₁ ^* ≦ d ₁ ≦ d ₁ ^* + 0.1 l, where the impact center position is d ₁ ^* .

On the other hand, regarding the length of the front bearing pad,
It does not matter if the front bearing pad does not affect the secondary vibration mode that affects the clearance variation of the rear bearing as long as it is near the impact center. However, the law that the impact center position is always the node of each vibration mode is the result when the bearing rigidity is expressed by the concentrated spring. When the bearing pad length becomes long, the front bearing pad has an effect of resisting the secondary mode as a rotary spring, which hinders follow-up positioning by the rear bearing spring. That is, in this sense, it is desirable that the front bearing pad length is short. However, as can be seen from the case of d ₁ = 0.4l in FIGS. 6 (A-c) and 6 (B-c), the slider has a primary mode resonance in which the rear bearing vibrates greatly, and is not shown in the figure. However, at this time, the front side of the slider vibrates greatly, and if the damping ratio is small, the front edge of the slider may contact the disk surface. Therefore, the front bearing pad length is 1.0 to 1.0 of the wavelength V / f ₁ corresponding to the resonance frequency f ₁ of the primary mode, so that the undulation component that resonates the secondary mode is suppressed by the rear bearing pad length.
It is desirable to set 1.4 times and average the excitation force of the waviness component that resonates the primary vibration mode. Now, assuming that the front and rear bearing stiffnesses are equal, the natural frequency f ₂ of the secondary mode is approximately 1.55 times the natural frequency f ₁ of the primary mode. Therefore, the optimum front bearing pad length l ₁ is 1.55 times the rear bearing pad length l ₂ designed optimally as described above. Since the front bearing pad generally has a larger clearance, it is necessary to make the front bearing pad larger in order to design the front and rear bearing pads with the same rigidity. In order to increase the bearing rigidity up to a large clearance, it may not be sufficient to multiply the bearing pad length by 1.55, and at this time the bearing width must be increased.

The front bearing pad length l ₁ in the present invention has the same accuracy as the rear bearing pad length l ₁ = αV / f ₁ (1.
It is designed so that 0 ≦ α ≦ 1.4). However, when the front bearing pad length becomes 0.3 l or more, the clearance fluctuation of the head position starts to increase due to the above reason. Therefore, when V / f ₁ is larger than 0.3 _{l, it} should be 0.3 _l or less. desirable. In the case of V = 15 m / s as in the present embodiment, f ₁ = about 60 kHz when α = 1.2 in FIG. 6A, so l ₁ = αV / f ₁ = 0.3 mm = 0.
24, and in the case of FIG. 6B, f ₁ = about 110 k
Since it is Hz, 1 ₁ = αV / f ₁ = 0.15 mm = 0.12
It becomes l.

The present invention firstly proposes a head position for matching the variation of the clearance between the head and the disk with the ideal following characteristic of one degree of freedom, and secondly, the head position of the rear bearing pad. This is to propose a rear bearing pad length that can suppress the resonance amplitude of the tracking characteristic by eliminating the excitation force component of the undulation of the resonance frequency of the secondary mode in which the clearance of the rear bearing pad position fluctuates even if the damping is small. In addition, the front bearing pad length condition for suppressing the resonance amplitude of the first-order mode in which the front bearing pad fluctuates and for removing the constraint effect of the front bearing pad that deteriorates the followability of the slider at the head position is proposed. Fourthly, the clearance variation of the rear bearing pad has a tracking performance close to that of a one-degree-of-freedom vibration system with only a secondary mode determined by the rigidity of the rear bearing pad's air film and the moment of inertia of the slider. One is to propose a front bearing pad position to be so. The effect on the followability of the clearance of the head portion is large in this order, and the effect is additive. Therefore, if all of them are adopted, a high-density recording slider having the most ideal follow-up characteristic can be realized. However, the present invention may employ a part of each of them, and can provide superior follow-up performance to a slider that does not employ them.

(Method of Forming Head Position at Pressure Center of Rear Bearing Pad) The front and rear bearing pad shapes in the embodiment of the present invention shown in FIG. 1 can be realized by a conventional slider machining method, but the head is rear bearing. Since it is not mounted in the center of the pad in the past, an example of this processing method will be described.
FIG. 7 shows an embodiment in which the head is mounted at the pressure center position of the rear bearing pad, and corresponds to an enlarged view of the rear portion of the slider in FIG.
However, here, the case where the rear bearing pad is not rectangular but trapezoidal is shown, and the shape of the rear bearing pad is not particularly specified. The head 4 projects from the maximum bearing surface of several nanometers so that when the slider is tilted and floats, the head gap position has a flying clearance that is substantially the same as the rear end of the rear bearing pad. This means that the head gap portion is likely to be damaged except during normal flying. Therefore, in FIG.
And stiction prevention contact pad 8 as shown in FIGS.
Is provided in front of the rear bearing pad, and the height of this stiction prevention contact pad is set higher than the head gap surface. The stiction prevention contact pads are also on the front side of the slider as shown in FIG. 1, so that these stiction prevention contact pads make contact when the slider surface contacts the stationary disk surface. Further, since the slider tilts during normal flying, the flying height is larger on the stiction preventing contact pad surface.

Slider An example of a method of processing the slider shown in FIG. 7 is shown in FIGS. First, as shown in FIG. 8A, the head 4 is formed by a process technique on the slider block material 12 such as Al ₂ O ₃ TiC according to the conventional processing method. In the conventional slider, alumina (Al ₂ O ₃ ) or the like is laminated as the head protection layer 13 by several μm, but here, the distance from the pressure center of the bearing pad length to the rear end, for example, 40
μm is laminated as shown in FIG. And FIG. 8 (b)
After cutting out the slider along the broken lines 14a and 14b, the air bearing surface is formed by lapping and etching. At this time, the bearing surface around the head gap is lowered as shown in FIG. Bearing pad length is 12
If the pitch angle is 0 μm and the slider pitch is 100 microradians, the maximum is about 5 nanometers.

In FIG. 9, instead of projecting the head gap surface from the rear bearing pad surface, the rear end portion of the rear bearing pad is machined so as to be substantially parallel to the disk surface during normal flying. This is an example in which a head is provided near the boundary between and. With such a structure, the floating clearance at the head position can be made as small as possible without the head position protruding from the bearing surface. When contact between the head and the disk becomes a problem, it is desirable to provide the head on the inclined surface side of the rear bearing surface in an area where the clearance is slightly increased. In this case as well, the head is of course designed to match the center of pressure of the rear bearing pad. The shape of the bearing surface, the center of pressure on the bearing surface, the amount of protrusion of the head, and the like can be predicted using a calculation program based on the lean gas lubrication theory, and the clearance at the head position is designed in advance to a desired value.

[0026]

Although the above description of the present invention is applied to the flying slider for non-contact recording, the same applies to the slider for near contact recording in which the rear bearing pad is the contact pad in the mixed lubrication region. Clearly applicable to In this case, when the rear bearing pad is read as the rear contact pad in the above discussion, the same excellent follow-up characteristic can be obtained.

FIG. 10 shows a negative pressure generating reverse step unit 5 according to the present invention.
It is an example applied to a negative pressure slider having. Also in this case
Slide the head to the pressure center of the rear bearing pad.
1% accuracy of length, 10% accuracy of rear bearing pad length
I am letting you. Also, the rear bearing pad length l_TwoIs the secondary mode
Resonance frequency f_TwoAgainst l_Two= ΑV / f_Two(1.0 ≦
α ≦ 1.4). Also, the front bearing pad length l₁Is l₁
= ΑV / f₁(1.0 ≦ α ≦ 1.4), and before
Center position of bearing pad d₁Is d₁ ^*≤d ₁≤d₁
^*+ 0.1l (d₁ ^*Is the range of the impact center position)
Has been.

Although the bearing surface design which suppresses the clearance variation with respect to the skew and the bearing surface design which suppresses the clearance variation with respect to the ambient pressure change are not described here, in an actual slider, the slider bearing surface is formed in consideration of these effects. The present invention also includes a slider having a bearing surface additionally having these effects.

(Difference from Conventional Pad Type Slider) Incidentally, the recent pad type sliders shown in FIGS. 16, 17 and 18 are also similar to the slider of the present invention. However, first of all, the slider of FIG. 17 is not a pad slider, and the head position is considerably deviated from the pressure center position of the rear bearing pad. On the other hand, since the pad sliders of FIGS. 16 and 18 are all in the development stage, there is no literature describing their dimensions in detail, but the literature regarding the contact slider of FIG. There is no. Also, from the measurement of the pad shape dimensions in the photograph of the slider surface, it is expected that the head position is not at the pressure center position with an accuracy of 10% of the rear bearing pad length in any case. In particular, since FIG. 18 is a slider for the purpose of contact recording, the rear pad is not an air bearing. Further, the rear bearing pad length is considerably reduced in order to prevent the generation of the levitation force as compared with the case of the non-contact recording or the near contact recording of the present invention. Further, the length of the front bearing pad is as small as 1 ₁ = 0.082l, and it is unlikely that the effects of suppressing the resonance of the secondary and primary modes are considered. Further, since the rear end of the front bearing pad is located 0.21 l from the front end of the slider, its center of pressure is expected to be smaller than 0.2 l from the front end. Meanwhile, Figure 1
The slider of No. 6 has a front bearing pad length of 0.3 l, which is too large, and the bearing surface is not rectangular, so that the center of pressure is expected to be less than 0.2 l from the front end of the slider. The length of each bearing pad depends on the disk running speed used and 1
Although it depends on the resonance frequency of the second and second modes, there is no description that the design concept of the present invention is applied.

In contrast to these sliders, in the slider of the present invention shown in FIGS. 1 and 9, the head position is at the pressure center position of the rear bearing pad position, and the front bearing pad moves slightly to the center of the slider. The center position of the pressure is at least 0.2 l or more from the front end of the slider. Also, the front and rear bearing pad lengths are respectively
It is almost equal to the wavelength of the swell corresponding to the next resonance frequency. However, the present invention also includes a slider that satisfies some of these conditions.

[0031]

The effect of the present invention is that by matching the head position with the pressure center position of the rear bearing pad, it is possible to remarkably improve the follow-up characteristic to the swell in the region lower than the resonance frequency due to the air film spring of the slider.

Further, by matching the length of the rear bearing pad to 1.0 to 1.4 times the wavelength of the undulation corresponding to the resonance frequency of the secondary mode, the resonance amplitude is suppressed even if the rear bearing pad has no damping effect. can do.

Further, the resonance amplitude of the primary mode can be suppressed by making the front bearing pad length equal to 1.0 to 1.4 times the wavelength of the undulation corresponding to the resonant frequency of the primary mode.

Further, by setting the position of the front and rear bearing pads with respect to the slider within the range of about 10% of the slider length on the front side from the positional relationship of the impact center, it is possible to prevent the vibration of the primary mode from appearing in the variation of the head clearance. The fluctuation of the clearance between the head and the disk surface with respect to the slight waviness of the disk surface is equivalent to the one-degree-of-freedom vibration system by the spring of the rear bearing pad, and can have an ideal follow-up characteristic without resonance.

[Brief description of drawings]

FIG. 1 is an embodiment of a head slider of the present invention.

FIG. 2 is an analytical model of the follow-up characteristic of a head slider showing the effect of the present invention.

FIG. 3 Influence of head position on follow-up characteristics for disc surface harmonic waviness

FIG. 4 Influence of head position on follow-up characteristics for random waviness on disk surface

[Fig. 5] Effect of rear bearing pad length on follow-up characteristics

[Fig. 6] Effect of position of front bearing pad on tracking characteristics

FIG. 7 is an example of a head mounted at the center position of the rear bearing pad pressure.

FIG. 8 is an example of a processing method in which a head is installed at a pressure center position of a rear bearing pad.

FIG. 9 is an embodiment in which the head is located at the center of pressure on the same surface as the rear bearing pad surface, and the rear end of the bearing is removed to reduce the flying height at the head position.

FIG. 10 is another embodiment of the present invention.

FIG. 11 Conventional taper flat type flying head slider

FIG. 12 Conventional taper flat type negative pressure slider

FIG. 13 shows an example of a conventional flying head slider with a center rail bearing.

FIG. 14 shows an example of a conventional flying head slider with a stiction removal pad.

FIG. 15 Conventional one bearing pad on the front and two on the rear
Example of flying head slider with two bearing pads

FIG. 16: Conventional, two bearing pads on front, one on rear
Example of flying head slider with two bearing pads

FIG. 17 is an example of a conventional 2-rail / 1-pad type near-contact recording slider.

FIG. 18: Example of conventional pad-type contact recording slider

[Explanation of symbols]

1 ----- Slider 2 ----- Air bearing rail surface 3 ----- Arrow indicating the disc running direction 4 --- head (recording / reproducing element) 5 ----- Negative pressure generation Reverse step unit 6 ----- Center rail bearing 7 ----- Rear bearing pad 8 ---- Stiction prevention contact pad 9 ----- Front bearing pad 10 --- Contact pad 11 --- Disk surface undulation 12 --- Slider block material 13 --- Head protection layer 14 --- Slider cutting line

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masami Yamane             2-93-Kosugi Gotencho, Nakahara-ku, Kawasaki-shi, Kanagawa             3 Highness Kosugi 202 F-term (reference) 5D042 NA02 PA01 PA05 QA02

Claims (4)

[Claims] 1. In a flying head slider having air bearing pad surfaces at the front and rear of the slider, and positioning the recording / reproducing element on the recording medium surface to a minute and constant clearance, the recording / reproducing element is pressured by the rear bearing pad. A flying head slider characterized in that the center position is matched within an accuracy of ± 1% of the slider length or within a range of ± 10% of the rear bearing pad length. 2. The wavelength of the undulation of the disk surface corresponding to the resonance frequency of the secondary mode in which the rear bearing pad of the slider vibrates, with the length in the scanning direction of the rear air bearing pad surface being 1.0 to
The flying head slider according to claim 1, wherein the flying head slider has a range of 1.4 times. 3. The length of the front air bearing pad surface in the scanning direction is in the range of 1.0 to 1.4 times the wavelength of the undulation corresponding to the resonance frequency of the primary mode in which the front air bearing pad vibrates. The flying head slider according to claim 1 or 2, wherein 4. The pressure center position of the front bearing pad is 10% of the slider length from the position corresponding to the center of impact of the slider with respect to the pressure center position of the rear bearing pad.
It has been installed in a range up to the distance of 1.
Alternatively, the flying head slider according to claim 2 or 3.