JPH0982014A - Magnetic disk drive - Google Patents

Abstract

A magnetic disk device capable of appropriately controlling the head flying height according to the track position of the magnetic head and the operation mode of the magnetic disk device. A rotating magnetic disk (101) and a head slider (106) arranged to face the magnetic disk (101).
And a magnetic head 103 having an electromagnetic converter supported by the head, a head slider 103, and a magnetic disk 101.
And a voltage generating circuit 108 for applying a voltage according to at least one of the track position of the magnetic head 103 and the operation mode of the magnetic disk device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device.

[0002]

2. Description of the Related Art Generally, a magnetic disk device rotates a disk-shaped magnetic recording medium called a magnetic disk, and a magnetic head positioned at an arbitrary radial position on the magnetic disk records information on a plurality of concentric tracks. It is also a device for reproducing recorded information.

In such a magnetic disk device, the magnetic head is moved over the magnetic disk by the dynamic pressure effect of air.
There are fixed magnetic disk devices and magneto-optical disk devices as a method of levitating a very small amount of about 0 nm. In such a magnetic disk device, the magnetic head is mechanically applied with a constant load in the magnetic disk direction by the suspension supporting the magnetic head, and the force generated by the dynamic pressure bearing and the load applied by the suspension are balanced. Ascend to the surface.

Although the magnetic head moves to an arbitrary position on the magnetic disk, the flow velocity of the air passing through the air bearing portion becomes larger at the outer peripheral position than at the inner peripheral position, so that the levitation force generated by the dynamic pressure air bearing increases. , The flying height increases. Since there is a negative correlation between the head flying height and the recording density, there is a problem that the recording density decreases toward the outer circumference. In order to avoid this problem and to make the recording density uniform over the inner and outer circumferences, a method is used to keep the flying height as constant as possible by providing an angle between the magnetic head and the airflow, and the flying shape is made constant by devising the bearing shape. The scheme is known. However, the former method can simplify the air bearing part, but the fluctuation of the flying height cannot be reduced so much, and the latter method makes it difficult to shape the air bearing part, and cannot accurately keep the flying height constant. .

Further, as described above, it is difficult to make the flying characteristics of the individual magnetic heads uniform at each track position, and it is also difficult to make the flying characteristics of the heads uniform. That is, in addition to the air bearing portion, there are many error factors such as an error in the suspension mounting position and an error in the suspension load. It is virtually impossible to remove the flying height error between the heads. At present, we are designing equipment with a margin in mind.

Further, in the case where the flying height of the head fluctuates due to a change with time after the magnetic disk device is assembled and the magnetic disk device is placed in an environment with extremely low atmospheric pressure such as high altitude,
No method has been found for optimizing the head flying height.

By the way, in the magnetic disk device for floating the magnetic head as described above, in general, when the magnetic disk starts to rotate, the magnetic disk is brought into contact with the magnetic disk, and the CSS (contact start) for floating the magnetic head only when the number of rotations becomes high.・ A system called "stop" is used. Since the load of the magnetic head is applied by the suspension, almost the same load is applied during contact as when flying. Therefore, the magnetic disk may be destroyed by the load of the magnetic head during CSS. The load of the magnetic head is preferably large in order to enhance the stability against external disturbances during flying, but the load of the head is 3 to 3 in order to prevent destruction.
A light load of about 10 grams is used.

There is also a system in which the magnetic head is always kept in contact with the magnetic disk without being levitated. A typical one is a floppy disk, but recently, a contact type has been proposed for use in a fixed magnetic disk device. Even when the magnetic head is brought into contact with the magnetic disk, air enters the gap due to the surface roughness of the contact surface, so if the sliding speed increases depending on the position of the magnetic head, the contact surface pressure decreases, the head touch deteriorates, and the reproduction signal May result in a decrease in S / N. Therefore, even a contact type magnetic head needs a constant pressing load, but it is difficult to apply a sufficient load to avoid deterioration of the magnetic disk due to sliding.

Since the load of the magnetic head is mechanically given by a support spring such as a suspension which supports the magnetic head, if there is a manufacturing error in the magnetic head, the magnetic disk, etc., the load will also fluctuate, and the flying height will decrease. There is also a problem that variations such as the above tend to become large.

In addition to the above-mentioned device for mechanically obtaining the pressing force of the flying head, as disclosed in Japanese Patent Laid-Open No. 61-151839, a magnetic disk surface protrusion removing device is provided between the flying head and the disk. There is a technique in which a voltage is applied to control the flying height to be low. According to this document, the pressing force of the head is increased by applying a voltage, but it is not described in detail whether or not the head floats stably. Further, the head and the disk are supposed to scrape off the protrusions by making contact with each other, but when they come into contact with each other, an electric charge flows between the head and the disk, so that the electric charge cannot be controlled.

Further, Japanese Patent Laid-Open No. 20824/1993 discloses a magnetic head and a magnetic disk in which electric charges are applied and the head is levitated by using an electrostatic reaction force. In this case, the inside of the magnetic disk must be decompressed in order to suppress the levitation force due to air.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic disk device capable of appropriately controlling the head flying height according to the track position of the magnetic head and the operation mode of the magnetic disk device.

More specifically, the present invention aims to provide the following magnetic disk device.

(1) A uniform recording density is achieved over the inner and outer circumferences of the magnetic disk by applying a head load that gives a constant head flying height regardless of the position of the magnetic head.

(2) In the flying head, the head load is reduced during CSS or idle, and in the case of the contact head, the head load is reduced to reduce damage to the magnetic disk.

(3) High density recording is realized with an optimum head flying height by applying an appropriate load to the magnetic head irrespective of manufacturing errors of the suspension and the like.

[0017]

A magnetic disk device according to the present invention has a rotating magnetic disk, a head slider arranged to face the magnetic disk, and an electromagnetic conversion portion supported by the head slider. A magnetic head for recording / reproducing information on / from the magnetic disk, a track position on the magnetic disk where the magnetic head is located between the head slider and the magnetic disk, and / or at least one of operation modes of the magnetic disk device. It has a voltage application means for applying a voltage.

As described above, in the present invention, by applying the voltage between the head slider and the magnetic disk,
Charges of opposite signs are generated on the facing surfaces of the head slider and the magnetic disk, and a suction force proportional to the square of the potential difference is generated.
The head slider has a slider surface that forms an air bearing so as to fly above the magnetic disk, and a levitation force is generated on the magnetic disk due to the dynamic pressure effect of air due to the rotation of the magnetic disk. Therefore, the magnetic head is levitated to a predetermined height by applying a voltage that gives a suction force equal to the levitation force between the head slider and the magnetic disk.

Further, according to the present invention, a voltage is applied between the head slider and the magnetic disk in accordance with at least one of the track position of the magnetic head and the operation mode of the magnetic disk device, and thereby the track position of the magnetic head and the magnetic disk device. The flying height of the head is appropriately controlled according to the operation mode of.

The preferred embodiments of the present invention are listed below.

(1) The voltage applying means increases the voltage applied between the head slider and the magnetic disk as the track position of the magnetic head shifts from the inner circumference side to the outer circumference side of the magnetic disk, thereby magnetically A head load that gives a constant head flying height is applied regardless of the position of the head, and a uniform recording density is achieved over the inner and outer circumferences of the magnetic disk.

(2) The voltage applying means sets the voltage applied between the head slider and the magnetic disk to zero or a minute voltage when the operation mode of the magnetic disk device is the contact start / stop mode, and the seek mode. In the case of, the flying head is set to a higher voltage than that in the contact start / stop mode, and in the read / write mode it is set to a higher voltage than that in the seek mode. Reduces the load on the head during sliding and reduces damage to the magnetic disk. Furthermore, by applying an appropriate load to the magnetic head regardless of the manufacturing error of the suspension or the like, high density recording can be realized by the optimum head flying height.

(3) The maximum track diameter of the magnetic disk is R
[M] and the rotational angular velocity of the magnetic disk is ω [1 / s], the upper limit of the voltage applied by the voltage applying means is 3 ×.
By setting (ωR) ^1/2 [V], the magnetic head is surely levitated above the magnetic disk.

(4) An insulating layer is provided on at least one of the facing surfaces of the magnetic disk and the head slider, and the voltage applied by the voltage applying means is set to be less than the dielectric breakdown voltage of the insulating layer. It protects electrically and mechanically and prevents the insulation layer from being destroyed by an applied voltage.

(5) The volume of the head slider is 15 mm ³
By the following, when a voltage is applied between the head slider and the magnetic disk, a large electrostatic attraction force is generated with respect to the mass of the head slider, and stable head flying characteristics are obtained.

(6) When the flying height of the magnetic head with respect to the magnetic disk in the recording / reproducing mode of the magnetic disk device is set to 100 nm or less, a slight voltage is applied between the head slider and the magnetic disk to fly the head. Allows control of quantity.

(7) By providing current limiting means for limiting the current flowing between the magnetic head and the magnetic disk when the magnetic head and the magnetic disk come into contact with each other, destruction of the magnetic disk and the magnetic head due to an excessive current is prevented.

The current limiting means is formed of an insulating layer provided on at least one of the facing surfaces of the magnetic disk and the head slider, or is constituted by a resistor inserted between the magnetic head and the voltage applying means. To be done. When a resistor is used as the current limiting means, its resistance value is preferably larger than the contact resistance value when the magnetic head and the magnetic disk are in contact with each other.

(8) An actuator electrically connected to the head slider for moving the head slider in the radial direction of the magnetic disk is provided, and the voltage applying means is provided between the head slider and the magnetic disk via the actuator. By applying a voltage to the magnetic disk, a special wiring for applying a voltage between the magnetic disk and the magnetic head is unnecessary.

(9) Flying height detecting means for detecting the flying height of the magnetic head with respect to the magnetic disk, and control means for controlling the applied voltage by the voltage applying means based on the flying height detected by the flying height detecting means. By providing, the applied voltage is controlled more appropriately.

(10) In the case of having a plurality of magnetic heads,
By applying different voltages according to the flying characteristics of the individual magnetic heads between the head slider and the magnetic disk by the voltage applying means, variations in the flying characteristics of the individual magnetic recording media are corrected.

(11) In the case of having a plurality of magnetic heads,
A magnetic head selected from a plurality of magnetic heads by applying a voltage between the head slider of the desired magnetic head selected and a magnetic disk by the voltage application means for limiting the flying characteristics of the magnetic head. For the magnetic heads other than the above, the reliability of the device is improved by making the flying height safer.

(12) By applying a slight head pressing force that presses the magnetic head toward the magnetic disk from the suspension supporting the magnetic head, the applied voltage between the head slider and the magnetic disk is zero or very small. It is possible to stabilize the load amount and flying height of the magnetic head even when the voltage is varied.

(13) The magnetic head is preferably a magnetic flux sensitive type such as an MR head as a reproducing head.

[0035]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a magnetic disk device according to the present invention. As shown in the figure, the housing 100 of the magnetic disk device has a rectangular box shape with an open upper end. The top opening of the housing 100 is closed by the top cover 150 via packing. The top cover 150 is fixed to the housing 100 with a plurality of screws.

Inside the housing 100, one or a plurality of magnetic disks 101 and a disk drive mechanism (not shown) for rotationally driving the magnetic disks 101 are arranged. The magnetic disk 101 is driven by the disk drive mechanism. They are coaxially fitted to the hubs of the spindle motors (not shown) that are the sources, and are arranged along the axial direction of the hubs.
An annular fixing ring 151 is screwed to the upper end of the hub, and the magnetic disk 101 is sandwiched between the fixing ring 151 and a flange (not shown) provided at the lower end of the hub.

The magnetic disk 101 comprises a glass substrate having a center hole and magnetic layers formed on both sides of this glass substrate.

Further, the housing 100 has a suspension 1
07, a head unit including the head slider 106, a mount unit for indicating the head unit, a cylindrical head actuator 104 rotatably supported by the housing 100, and the head unit moved to a desired position. And a voice coil motor 152 for driving the motor.

Before describing specific embodiments of the present invention, the principle of the present invention will be described.

When a voltage is applied between the head slider (or the conductive film on the head slider) and the magnetic disk according to the present invention, charges of opposite signs are generated on the facing surfaces of the head slider and the magnetic disk, and are proportional to the square of the applied voltage. Generated suction force is generated. The head slider has a slider surface which forms an air bearing so as to fly above the magnetic disk, and a levitation force is generated when the magnetic disk rotates due to the dynamic pressure effect of air. For this reason, the magnetic head can be floated to a predetermined height by applying an applied voltage between the head slider and the magnetic disk that gives a suction force equal to the floating force.

Consider the force balance in the head slider at this time. The generated force of the air bearing is Fa, the electrostatic attraction force is Fe, and the constant load applied from the suspension supporting the head slider to the head slider is Fn. Fa
Is inversely proportional to the square of the distance between the magnetic disk surface and the head slider, and is proportional to the head slider working area S and the relative speed (peripheral speed) U between the magnetic disk and the head slider. Where U is the angular velocity ω due to the rotation of the magnetic disk
And the disk radius R of the track on which the magnetic head is positioned (U = ωR). Fe is applied voltage V
Is proportional to the square of the distance between the surface of the magnetic disk and the head slider, and is proportional to the square of the head slider operating area S. These relationships are expressed by the following equations.

Fa = ε _a US / H ² (1) Fe = ε _e V ² S / H ² (2) Fn = ε _f (3) where ε _a , ε _e and ε _f are proportional constants. . The force balance equation is Fa = Fe + Fn, and (1) (2)
From the equation (3), ε _a US / H ² = ε _e V ² S / H ² + ε _f (4) By solving this equation for H, the following solution is obtained.

H = [(ε _a U−ε _e V ² ) S / ε _f ] ^1/2 (5) Looking at the equation (5), the head flying height H increases as the peripheral speed U increases.
As the applied voltage V increases, the head flying height H increases.
It can be seen that becomes smaller. In the conventional magnetic disk device corresponding to the case where the applied voltage V is zero, the radius R changes when the position of the magnetic head changes from the inner circumference to the outer circumference, so that the head flying height H changes.

Therefore, in the present invention, the head flying height H is always maintained by controlling the applied voltage V according to the track position.
Constant. If the applied voltage V is always constant, the flying height of the head changes depending on the peripheral speed, and it is meaningless to apply the applied voltage.

As can be seen from the equation (1), the levitation force generated by the magnetic head has a positive correlation with the rotational speed of the magnetic disk at the place where the magnetic head is located. Therefore, when the flying height H of the magnetic head to which a constant pressing force is applied by the suspension is compared in the inner and outer circumferences, the head flying height at the outer peripheral portion is higher than the head flying height at the inner peripheral portion. Therefore, the recording density of the outer peripheral portion must be lower than the recording density of the inner peripheral portion. In recent years, some heads have a substantially uniform flying height over the inner and outer circumferences in order to increase the recording density in the outer circumference. The method is to make the air bearing shape such that the flying height of the head does not depend on the disk peripheral speed, or to angle the magnetic head with respect to the magnetic disk toward the outer circumference so that the airflow strikes the magnetic head obliquely. There is a method to suppress the increase in the amount. According to the present invention, the head flying height H is kept constant by applying an appropriate voltage V determined between the air peripheral velocity and the attitude of the magnetic head between the head slider and the magnetic disk without applying such a special device. Can be

Even when a contact type magnetic head is used, the airflow enters the surface roughness gaps on the surface of the magnetic disk, so that when the peripheral speed of the magnetic disk increases, a levitation force is generated, and the head against the magnetic disk is generated. The pressing force of the slider is reduced. Since the magnetic head floats up from the surface of the magnetic disk when disturbance vibration enters, it is necessary to apply a pressing force of disturbance acceleration × head mass to the magnetic head. In the contact type magnetic head, the pressing force decreases as it is located closer to the outer peripheral portion of the magnetic disk, but the pressing force can be made uniform by increasing the applied voltage between the head slider and the magnetic disk toward the outer peripheral portion.

Further, in the present invention, the applied voltage V between the head slider and the magnetic disk is controlled according to the operation mode of the magnetic disk device. That is, when the rotational speed of the magnetic disk is reduced to save power in the idle mode where reading / writing is not performed, the levitation force of the magnetic head also decreases, and the head levitation amount H decreases. Contact with the magnetic disk may cause a head crash. Therefore, in the idle mode, the applied voltage V between the head slider and the magnetic disk is controlled to prevent the head flying height H from decreasing or increase it. Since the possibility of head crash decreases as the head flying height H increases, it is effective to increase the head flying height H during idling in this way.

When the magnetic disk starts to rotate, the magnetic head is stationary on the magnetic disk, and when the disk starts to rotate, the buoyancy of the air bearing acts to start floating, so-called CSS (contact start). The magnetic head slides on the magnetic disk in the initial stage of rotation because it is in the (stop) mode. Therefore, it is necessary to cover and protect the magnetic layer of the magnetic disk. However, if the head pressing force is too large or it takes time for the magnetic head to float, the magnetic layer may be destroyed. Therefore, in the CSS mode, the applied voltage V between the head slider and the magnetic disk is reduced or set to zero to reduce the pressing force of the magnetic head against the magnetic disk and improve the CSS durability.

Recently, in order to prevent adsorption between the head and the disk, the surface of the CSS zone on the magnetic disk is roughened and R
A method called a zone texture method in which the surface roughness of the / W zone is improved has been proposed. However, a step is likely to be formed between the CSS zone and the data zone, and the conventional head has a drawback that the head easily crashes when the head moves. In the CSS zone, no voltage is applied or a low voltage is applied, the head flying height is high, the head is moved to the data zone, a larger voltage is applied after the head is moved, and the head flying height is lowered to prevent the head from adsorbing. And high density recording can be achieved at the same time.

Furthermore, at the time of seek for moving the magnetic head to the target track, or when the track is on-track, read / write is performed.
When writing is not performed, the applied voltage V between the head slider and the magnetic disk is lowered to increase the head flying height H, thereby avoiding the risk of head crash.

At the time of reading / writing, the applied voltage V between the head slider and the magnetic disk is increased to reduce the flying height of the head, and as described above, the applied voltage V is controlled according to the track position, so that the flying height of the head is increased. Try to keep the amount constant.

The pressing force balanced with the levitation force of the air bearing of the magnetic head is not limited to the attraction force by electrostatic force. If the applied voltage between the head slider and the magnetic disk disappears due to an electric circuit failure or the like, the attractive force disappears, making stable flying of the magnetic head difficult, which may lead to head crash. Therefore, it is effective to apply a minimum load that does not cause head crash by a mechanical method such as suspension. If the magnetic head load is applied only by the suspension, an overweight variation and a head flying height variation are caused by the influence of mounting error. However, in the present invention in which the load due to the suspension is small, the variation of the load and the head flying height is also small.

Next, the upper limit of the voltage V applied between the head slider and the magnetic disk will be described. For expression (5) to have meaning, the inside of [] must be zero or more.

Since this condition is (ε _a U−ε _e V ² ) ≧ 0 (6), V ≦ (ε _a U / ε _e ) ^1/2 = α · U ^1/2 (7) Thus, the upper limit of the applied voltage V is obtained.

The equal sign in equation (7) is the head flying height H =
Since 0 holds true, α is α = Vm / U ^1/2 (8) from the relationship between the applied voltage V _m when the head flying height is zero and the peripheral speed U, and is applied regardless of the head load or head flying height. Voltage V
And it can be obtained only by the peripheral speed.

The upper limit of the applied voltage V shown in the equation (7) is a condition necessary for the head slider to fly. When the applied voltage V is higher than this, the head slider cannot fly and falls.

FIG. 2 shows the measurement results of the head flying height with respect to the applied voltage V. This is because the volume of the head slider is 1.
The case was 4 mm ³ , and the peripheral speed was 13.2 m / s.
A point x is an actual measurement value, and a solid line is an extrapolation line. The applied voltage when the head flying height is zero is 11.2V. Therefore, α = 11.2 / (13.2) ^1/2 = 3.08 [V /
(M / s) ^1/2 ], and the peripheral speed is 13.2 m / s, the head flying height becomes zero when the maximum applied voltage becomes 11.2 V,
The magnetic head will not fly. Since the peripheral speed increases as the radius of the track on which the magnetic head is located increases, it is defined at the maximum radius of the magnetic disk.

From the above, the upper limit of the applied voltage V between the head slider and the magnetic disk is 3 × U ^1/2 = 3 × (ωR) ^1/2
[V].

Unlike the large magnetic disk device, the versatile small magnetic disk device does not have its own power source, but operates by receiving necessary power from the outside, mainly from the computer main body. Therefore, the power supply voltage required for the magnetic disk device has a practical industry standard depending on the size of the disk. This value is 1.8 "HDD and 2.5" HD
For D, 5V single, 3.5 "HDD and 5.25" HD
5V, 12V for D, -5V, 5 for 8 "HDD
It is V and 24V. When the applied voltage applied between the head slider and the magnetic disk is higher than these supplied voltages, a booster circuit is required, which increases power consumption, temperature rise, circuit mounting area, increases manufacturing cost, and downsizes the device. Will be at a disadvantage. Therefore, it is desirable that the upper limit value of the applied voltage applied between the head slider and the magnetic disk is 24 V, which is the same as the maximum supply voltage of the small magnetic disk device.

More specifically, the maximum radius of a magnetic disk used in a compact magnetic disk device having high recording density and versatility is 1.8 ", 2.5", 3.5 ",
24mm each for 5.25 "and 8" disks, 3
2.5 mm, 47.5 mm, 65 mm and 105 mm, the maximum allowable voltage applied to each disk is 9.7 V when the magnetic disk is rotating at 4200 rpm.
It becomes 1.3V, 13.7V, 16.0V, and 20.4V.

Next, the volume of the head slider will be described.

On the other hand, from the expressions (1) and (2), it can be seen that the force acting on the head slider is proportional to the head slider acting area S. On the other hand, since the flying posture and flying stability of the head slider are determined by the external force acting on the unit mass of the head slider, the ratio of the head slider working area S to the head slider volume Vol is significant. This ratio is k as follows.

K = S / Vol (9) When k is small, the force acting on the head slider unit mass becomes small, and the magnetic head cannot stably fly. On the contrary, k
Is large, the force acting on the unit mass of the head slider is large, and the flying stability of the magnetic head is increased.

FIG. 3 shows the relationship between the existing 36 types of head slider volumes and k that are often used in hard disk devices. From this figure, it is understood that when the head slider volume is 15 mm ³ and k becomes 1, and when the head slider volume Vol becomes smaller thereafter, k rapidly increases. As a result, when a voltage according to the operation mode of the magnetic disk device or the track position of the magnetic head is applied between the head slider having a head slider volume Vol of 15 mm ³ or less and the magnetic disk, the magnetic head is pressed in the direction of the magnetic disk. A large electrostatic attraction force can be applied to the head slider mass, and stable flying characteristics can be obtained.

From the above, it is desirable that the volume Vol of the head slider is 15 mm ³ or less.

Next, the head flying height H will be described.
From the equation (2), it can be seen that the suction force is larger as the head flying height H is smaller. That is, the electrostatic attraction force Fe is
It is inversely proportional to the head flying height H. The relationship between the electrostatic attraction force Fe and the flying height H is shown in FIG. It can be seen from FIG. 4 that the electrostatic attraction force rapidly increases when the flying height is 100 nm or less.

On the other hand, the flying force also increases as the flying height H of the head decreases, but the flying force is generated when air molecules collide with the head slider working surface, so that the flying height H is 100.
When the thickness is less than nm, the number of air molecules that collide decreases, and the increase in levitation force becomes smaller than the increase in suction force. Conversely,
The electrostatic attraction force increases in inverse proportion to the square of the distance.

Therefore, when the head flying height H becomes less than 100 nm, a slight voltage is applied between the head slider and the magnetic disk in accordance with the operation mode of the magnetic disk device and the track position of the magnetic head, and the head flying height is increased. An electrostatic force head flying height control method for controlling is effective.

(First Embodiment) FIG. 5 is a diagram showing a schematic configuration of a magnetic disk device according to the first embodiment.
As shown in the figure, a pindle motor 102 for rotating the magnetic disk 101 and a head actuator 104 for moving the magnetic head 103 in the radial direction of the magnetic disk 101 to position it on a desired track are provided on the frame 105. It is provided.

The magnetic disk 101 is formed by forming a conductive magnetic layer on a substrate made of an aluminum alloy or glass, and forming a protective layer such as SiO ₂ or diamond-like carbon (DLC) on the magnetic layer. . The magnetic layer of the magnetic disk 101 is electrically connected to the rotating part of the spindle motor 102 by a suitable means, and the rotating part of the spindle motor 102 is electrically connected to the frame 105 by means such as a brush not shown. The frame 105 is electrically connected to the ground level GND.

The magnetic head 103 includes the head slider 10
6 and the suspension 107, and is made of a conductive material such as Altic. When the magnetic head 103 is made of a non-conductive material, a conductive film is formed on at least the slider surface of the slider portion 106 facing the magnetic disk 101. Head slider 106
An unillustrated electromagnetic converter (transducer) for recording / reproducing is fixed to the tip of the device, and an air bearing is formed. For example, an induction type head is used as the recording electromagnetic converting section, and a magnetic flux sensitive head such as an MR head is used as the reproducing electromagnetic converting section. Also, one induction type head may be shared as an electromagnetic conversion unit for recording and reproduction.

The suspension 107 is made of a thin metal plate and supports the head slider 106. The head slider 106 and the suspension 107 are electrically insulated. Further, the suspension 107 is the magnetic disk 1.
When recording / reproducing information to / from 01 (when reading / writing)
The head slider 106 is mechanically provided with a pressing force that is about half the minimum value of the pressing force that causes a predetermined flying height.

The voltage generating circuit 108 is the head slider 10.
6 is a circuit for applying a positive or negative DC voltage between the magnetic layer of the magnetic disk 101 and the magnetic layer of the magnetic disk 101, the output terminal of which is connected to the head slider 106, and the reference potential terminal is the frame 1
05 is connected. With such a configuration, the voltage generation circuit 108 generates a voltage having a certain potential difference with respect to the ground level GND electrically connected to the magnetic layer of the magnetic disk 101, and supplies the electric charge to the head slider 106.

The head slider 106 is fixed and electrically connected to the suspension 107 with a conductive adhesive or the like, and the magnetic head 103 is connected to the actuator 10.
4 may be electrically insulated and the output terminal of the voltage generation circuit 108 may be connected to the suspension 107.

The voltage generating circuit 108 is used for the head slider 106 during CSS (contact start / stop).
By applying a zero or minute voltage between the magnetic disk 101 and the magnetic disk 101, damage to the magnetic disk 101 and the magnetic head 103 during CSS is reduced.

On the other hand, at the time of reading / writing, as shown in FIG. 6, when the magnetic head 103 is located inside the magnetic disk 101, the head slider 106 and the magnetic disk 10 are moved.
The flying voltage of the head slider 106 is made constant at any track position on the magnetic disk 101 by decreasing the voltage applied to the magnetic disk 101 and increasing the voltage applied to the outer peripheral portion.

Further, in the idle state waiting for the read / write, the rotation speed of the spindle motor 102 is lowered and the applied voltage between the head slider 106 and the magnetic disk 101 is made smaller than that during the read / write, so that the head slider 106 floats. Do not let the amount go down. Since the electrostatic capacitance of the head slider 106 is relatively small, when a voltage is applied between the head slider 106 and the magnetic disk 101, voltage control with good response can be performed.

Next, a method of controlling the applied voltage between the head slider 106 and the magnetic disk 101 by the voltage generating circuit 106 will be described.

For example, the reproduction output of the magnetic head 103 in the synchronous signal area of the servo area on the magnetic disk 101 is monitored, and if the reproduction output is too large, the applied voltage is reduced, and if it is too small, the applied voltage is increased. Thus, the flying height of the head is controlled. The control signal that serves as a reference for this control is a variation factor of the head flying height, such as the innermost track position of the magnetic disk 101 or the track position where the angle between the magnetic head 103 and the recording track becomes zero. It is desirable to use the reproduction output at the track position with the smallest number.

As a method of controlling the applied voltage V, for example, the following method may be adopted.

(1) Each time the magnetic head 103 is positioned on each track, the difference between the reproduction output and the reference output is obtained, and the applied voltage is controlled based on this difference.

(2) First, the reproduction output on all tracks is detected, the control signal of the applied voltage for each track is obtained from the difference between this reproduction output and the reference output, and stored in a memory as a table. The control signal corresponding to the track position is read from this table to control the applied voltage.

The control method (1) has a high accuracy, but the calculation time is long, and the control method (2) has a short calculation time, but the accuracy is slightly deteriorated. Therefore, it can be used properly according to the required specifications.

Further, the reproducing head of the magnetic head 103 has an M
When the R head (magneto-resistive magnetic head) is used, the reproduction output does not depend on the peripheral speed of the magnetic disk 103 (the relative speed of the magnetic disk 103 and the head 103), so that the isolated wave output of the reproduction output is the same for all tracks. Since the applied voltage V between the head slider 106 and the magnetic disk 101 may be controlled to control the head flying height as described above, there is an advantage that the control system becomes simple.

(Second Embodiment) FIG. 7 is a schematic configuration diagram of a magnetic disk device according to the present embodiment. In the present embodiment, the head slider 106 is electrically connected to the ground level GND, and the magnetic properties of the magnetic disk 101 are the same as those in the second embodiment. The output terminal of the voltage generation circuit 108 is connected to the layer. Therefore, the magnetic layer of the magnetic disk 101 is insulated from the ground level GND.

In a magnetic head having an unstable structure of an electromagnetic conversion portion such as an MR head, there is a risk of destroying the electromagnetic conversion portion when a voltage is applied to the electromagnetic conversion portion. 106 is the ground level GN
Since it is connected to the D ground, there is no risk of the electromagnetic conversion section being damaged. Further, since minute dust in the charged air is less likely to adhere to the magnetic head 103, the flying operation of the head slider 106 is not disturbed.

Next, the spacing between the magnetic disk 101 and the magnetic head 103 will be described with reference to FIGS.

As shown in FIG. 8, the magnetic disk 101 includes a buffer layer 11 on an insulating substrate 111 such as a glass plate.
2, a structure in which a magnetic layer 113 and an insulating layer 114 made of a dielectric material are laminated. That is, the magnetic layer 113 is covered with an insulating layer 114 made of a ceramic thin film such as SiO ₂ . Between the magnetic layer 113 and the head slider 106, a voltage V
Is applied.

Head slider 106 and magnetic disk 10
A certain amount of spacing 109 is generated between the distances 1 and 1. When the magnetic disk 101 is rotated, the air rotates at a speed U that is substantially the same as the peripheral speed of the disk 101, and as a result, the levitation force Fu is generated. Magnetic layer 1 of magnetic disk 101
When a potential difference V is applied between the head slider 13 and the head slider 106, positive and negative charges Q are generated, and an electrostatic attraction force Fd is generated on the head slider 106. Assuming that the pressing force applied from the suspension 107 to the head slider 106 is Fs, the magnetic head 103 stably flies with a spacing amount such that Fu = Fd + Fs. That is, as shown in FIG. 8, a stable spacing 109 is obtained at the equilibrium point where the sum of the electrostatic attraction force Fd and the pressing force Fs becomes equal to the levitation force Fu.

In addition, as shown in FIG.
The insulating layer 114 may be provided not only on the surface of No. 1 but also on the surface of the head slider 106.

Further, as shown in FIG. 10, the magnetic layer 113
Magnetic disk 101 in which is not covered with the dielectric layer 114
On the other hand, the head slider 10 covered with the insulating layer 110
6 may be used.

The insulating layers 110 and 114 also function as mechanical and electrical protective layers. The magnetic head 103 vibrates when a disturbance vibration or the like enters, and may come into contact with the magnetic disk 101. With the insulating layer 110 and the insulating layer 114, direct contact between the magnetic head 103 and the magnetic layer 113 can be prevented,
It is possible to prevent the magnetic layer 113 from being mechanically destroyed.

The thickness of the insulating layer 110 must be smaller than the distance between the magnetic layer 113 and the head slider 106. However, if the thickness of the insulating layer 110 is too thin, dielectric breakdown is likely to occur, and the insulating layer 110 cannot play its original role. Considering these, the thickness of the insulating layer 110 is preferably in the range of 1 to 100 nm.

Further, as shown in FIG. 9, the voltage generating circuit 1
A current limiter (for example, a resistor) 115 may be provided between the 08 and the head slider 106. Further, a similar current limiter is used for the voltage generation circuit 108 and the magnetic layer 1 of the magnetic disk 101.
13 may be provided between the voltage generating circuit 108 and the head slider 106, and between the voltage generating circuit 108 and the magnetic layer 113. By providing such a current limiter, it is possible to prevent the magnetic disk 101 and the magnetic head 103 from being broken by limiting the current flowing between the magnetic disk 101 and the magnetic head 103 when they come into contact with each other. Current limiter 11
The resistance value of the resistor used in No. 5 needs to be larger than the contact resistance value when the magnetic disk 101 and the magnetic head 103 are in contact with each other, and is preferably several times or more the contact resistance. Alternatively, as the current limiter 115, a current control circuit including an active circuit may be used.

Further, the insulating layer 11 shown in FIGS.
0 and 114 may also serve as the current limiting means.

By the way, the suction force is the head slider 106.
Is inversely proportional to the square of the distance between the conductive surfaces of the magnetic disk 101, and the levitation force is also inversely proportional to the square of the distance between the surface of the magnetic disk 101 and the magnetic head. Therefore, a stable force balance point does not always exist, and the suction force is large. Too much, the magnetic head 103 collides with the magnetic disk 101, and conversely, the levitation force becomes too large and the magnetic head 103 causes the magnetic disk 1 to move.
There is a possibility that it will be skipped from the surface of 01.

When the insulating layer 110 is formed on the surface of the magnetic disk 101 as shown in FIGS. 8 and 9, the distance between the air bearing portions can be reduced by the insulating layer 110 as shown in FIG. The problem of is solved. That is, since the distance between the air bearings is smaller than the distance between the head slider 106 and the conductive surface of the magnetic disk 101 by the thickness of the insulating layer 110, a force balance point C is obtained, and the magnetic head 103 is stabilized. You can surface with spacing.

When the insulating layers 110 and 114 are made of a dielectric material, the attractive force increases by the dielectric constant, so that the required attractive force can be generated with a small applied voltage, which is suitable for suppressing the applied voltage. Is.

The horizontal axis in FIG. 11 represents the spacing amount (excluding the thickness of the insulating layer), and the vertical axis represents various acting forces acting between the head head slider 106 and the magnetic layer of the magnetic disk 101. Indicates.

Further, as described above, the insulating layers 110, 1
14, the magnetic head 103 causes the magnetic disk 101
Since no current flows even when the magnetic recording layer 113 comes into contact with the magnetic recording medium, the magnetic layer 113 is not broken and the recorded contents can be prevented from being destroyed. This will be described in more detail.

FIG. 12 is a characteristic diagram showing the qualitative correlation between the two, with the horizontal axis representing the spacing amount (not including the thickness of the insulating layer) and the vertical axis representing the breakdown voltage. As is clear from the figure, there is an optimum spacing amount that minimizes the dielectric breakdown voltage of the air layer, and the breakdown voltage increases with decreasing or increasing values below this optimal spacing amount. .

As is known as Paschen's law, the dielectric breakdown voltage of the air layer decreases as the spacing becomes smaller in a large spacing region, but has a minimum value. At normal atmospheric pressure, the dielectric breakdown voltage of the air layer is about 300 V, so there is no problem with the voltage used in the magnetic disk device, but if the magnetic head may come into direct contact with the magnetic disk, the air layer Instead, the breakdown voltage of the insulating layers 110 and 114 becomes a problem. Therefore, it is preferable that the applied voltage V between the head slider 106 and the magnetic disk 101 be kept below the breakdown voltage of the insulating layers 110 and 114.

When the insulating layers 110 and 114 are made of a dielectric material, the attractive force increases by the dielectric constant, and the required attractive force can be generated with a small voltage. Therefore, by selecting a material having an appropriate dielectric constant. In some cases, it may be possible to adjust the required applied voltage V and suppress it to be equal to or lower than the withstand voltage of the insulating layers 110 and 114.

The pressing force balanced with the levitation force of the air bearing of the magnetic head 103 is not limited to the attraction force by the electrostatic force. When an electric circuit failure or the like occurs and the voltage applied between the head slider 106 and the magnetic disk 101 disappears, the attractive force disappears and stable flying of the magnetic head 101 becomes difficult, which may lead to head crash. Therefore, it is effective to apply a minimum load that does not cause head crash by a mechanical method such as suspension. Magnetic head with suspension only 1
When the load of 03 is applied, the amount of load and the amount of levitation are varied due to the influence of mounting error. However, in the present invention in which the load by the suspension is small, the variation in load and levitation amount is also small.

Head slider 106 and magnetic disk 10
More precise control can be performed by detecting the head flying height of the magnetic head 103 when controlling the applied voltage V between 1 and 1. The applied voltage V may be controlled only by the track position on the magnetic disk 101 where the magnetic head 103 is located without detecting the head flying height.
An error occurs due to the individual difference of 03. The head flying height is detected by using, for example, a servo signal previously written on the magnetic disk 101 to position the magnetic head 103 on a predetermined track. When the detection level of the servo signal is low, the head flying height is detected. When the detection level is high, the applied voltage is increased, and when the detection level is high, the head flying height is low. Therefore, the applied voltage is decreased to absorb individual differences of the magnetic heads 103, and to obtain a uniform information signal from all the magnetic heads. Can be played.

The head flying height can be detected by monitoring the output of an AE (acoustic emission) sensor. The surface of the magnetic disk 101 has minute irregularities, and even if the magnetic head 103 floats to a considerable extent, the convex portion on the surface of the magnetic disk 101 has the magnetic head 103.
Since it collides with, the number of impacts can be counted by the AE sensor. Therefore, the head flying height can be detected by integrating the AE sensor output per unit time. Further, since the electrostatic capacitance between the magnetic head 103 and the magnetic disk 101 has a negative correlation with the flying height of the head, the flying height of the head can also be detected by detecting the electrostatic capacitance.

Further, in the case where the head flying height fluctuates due to a change with time after the magnetic disk device is assembled or the magnetic disk device is placed in an environment where the atmospheric pressure is extremely low such as high altitude, the head flying height is conventionally optimized. However, if the head flying height is detected and the applied voltage between the head slider 106 and the magnetic disk 101 is controlled as described above, it is possible to cope with such a variation in the head flying height. Therefore, it is possible to improve the long-term reliability of the magnetic disk device and expand the usage environment.

The shape of the head slider constituting the air bearing portion of the magnetic head 103 may be a general twin barrel type taper flat type, but a shape with a minute crown instead of a perfect plane is preferable. In the taper flat type, the head flying height on the upstream side is larger than that on the downstream side with respect to the air flow,
Since the charge amount of each part is constant, the attraction force on the downstream side becomes larger than that on the upstream side, and the tilting direction of the head slider becomes larger. If this angle is too large, it becomes unstable, and a large suction force cannot be used.

On the other hand, as shown in FIG. 8, when the surface 106a of the head slider 106 is provided with a crown (a curved surface that gently swells in a convex shape in the center), the spacing at the center of the head slider 106 becomes small, The electrostatic attraction force Fd at the central portion increases, and the head slider 10 by the electrostatic force increases.
The slope of 6 is reduced.

(Third Embodiment) FIG. 13 is a block diagram showing a more specific embodiment of the magnetic disk device (hard disk device) according to the present invention. In the figure,
A hard disk controller (HDC) 201 exchanges necessary control signals and data with the outside of the magnetic disk device via an interface (IF).

The read / write (R / W) circuit 202 is
During recording, data input via the HDC 201 is supplied to the magnetic head 103 via the head drive circuit 203 and written to the magnetic disk 101, and during reproduction, a signal read by the magnetic head 103 from the magnetic disk 101 is supplied to the head drive circuit. The signal is received via 203, subjected to predetermined signal processing, and then transferred to the HDC 201. Further, the read / write circuit 202 includes the magnetic head 103.
Tracking servo data 211 generated based on the servo information read from the magnetic disk 101 by
Is sent to the servo control circuit 204. Servo control circuit 204
Is the tracking servo data 211 and the HDC 20.
VCM (voice coil motor) driver 20 based on the target cylinder number as a seek command input from 1
5 to control the movement of the magnetic head 103 in the radial direction of the magnetic disk 101.
Is positioned on a target track on the magnetic disk 101.

The servo control circuit 204 controls the magnetic head 10
No. 3 track position, that is, a track position signal 212 indicating which track the magnetic head 103 is located on the magnetic disk 101 is sent to the head flying height control circuit 206.
Send to The head flying height control circuit 206 receives the track position signal 212 and a mode signal (a signal representing the operation mode of the magnetic disk device) 21 input from the HDC 201.
Voltage control signal 214 to the voltage generation circuit 108 based on
Send. The voltage generation circuit 108 applies a voltage controlled based on the voltage control signal 214 between the head slider of the magnetic head 103 and the magnetic disk 101. This controls the flying height of the magnetic head 103.

Next, the operation of the head flying height control circuit 206 in this embodiment will be described with reference to the flow chart shown in FIG.

The head flying height control circuit 206 first determines the HD
The operation mode of the magnetic disk device is determined by the mode signal 213 input from C201, and the voltage control signal 24 is supplied to the voltage generation circuit 108 based on the operation mode.

As described above, in the magnetic disk device, especially the hard disk device, the CS
Perform S (contact start stop). That is, when the apparatus is started up, the magnetic head 103 is brought into contact with the magnetic disk 101 before the magnetic disk 101 starts rotating, and when the magnetic disk 101 starts rotating, the magnetic head 103 is moved from the magnetic disk 101 by the buoyancy of the air bearing. . On the other hand, when the apparatus is stopped, the magnetic head 103 is brought into contact with the magnetic disk 101 from a floating state. When the magnetic disk device is in the CSS mode, the pressing force of the magnetic head 103 against the magnetic disk 101 is as small as possible from the viewpoint of reducing the frictional force that causes damage to the magnetic disk 101 and the magnetic head 103 and shortening the CSS time. Smaller is preferable.

Therefore, the head flying height control circuit 206 first determines from the mode signal 213 whether the operation mode of the magnetic disk device is the CSS mode (step S1), and C
In the SS mode, the magnetic disk 101 and the magnetic head 1
A voltage control signal 214 for setting the voltage V applied between the head sliders No. 03 of No. 03 to 0 or a minute voltage is supplied to the voltage generation circuit 108 (step S2). When the applied voltage V is 0 or a minute voltage, the electrostatic attraction force between the magnetic disk 101 and the head slider 106 is small, so that the pressing force of the magnetic head 103 against the magnetic disk 101 can be suppressed to be small.

Next, the head flying height control circuit 206 determines from the mode signal 213 that the operation mode of the magnetic disk device is R /
It is determined whether the W mode has been entered (step S
3). Since the magnetic disk device performs the seek operation after the CSS and before the R / W mode, the fact that the R / W mode is not reached means that the seek mode is set. When it is determined in step S3 that the R / W mode is not set, that is, in the seek mode, the voltage control signal 214 that sets the applied voltage V to V = Vs is supplied to the voltage generation circuit 108 (step S4).

Next, the magnetic head 103 operates the magnetic disk 1
When the target track on 01 is reached and it is confirmed that the track is on-track, the mode is switched to the R / W mode. Upon confirming that the head flying height control circuit 206 has switched to the R / W mode, the head flying height control circuit 206 calculates an applied voltage V = Vc corresponding to the track position indicated by the track position signal 212 input from the servo control circuit 204 (step In S5), the voltage control signal 214 that makes the applied voltage V become Vc is supplied to the voltage generation circuit 108.

Here, the applied voltage V = Vs and R / W when the operation mode of the magnetic disk device is the seek mode
The relationship of the applied voltage V = Vc in the mode is set as follows.

In the seek mode, the magnetic head 103
Is different from the case of the R / W mode in which a signal is read / written by stopping at a fixed position of a desired track on the magnetic disk 101, movement of the head flying height by moving the magnetic head 103 in the radial direction of the magnetic disk 101. Therefore, it is preferable to slightly increase the set value of the head flying height in comparison with the case of the R / W mode in consideration of the margin. Therefore, the applied voltage V in the seek mode
= Vs is slightly higher than the applied voltage V = Vc in the R / W mode, and normally requires a signal recorded in the servo area at a recording density lower than the signal recorded in the data area on the magnetic disk 101. The head flying height is set to a value that can be read by the S / N.

The applied voltage V in the seek mode is R /
By setting the applied voltage lower than that in the W mode, it is possible to overcome the step difference between the media in the zone texture without crashing.

On the other hand, in the R / W mode, the dynamic fluctuation of the head flying height as in the seek mode is eliminated, so the applied voltage V = Vc is set according to the track position where the magnetic head 103 is located. By doing so, the same head flying height is obtained at all track positions for reading / writing.

As described above, in the third embodiment, the applied voltage V between the magnetic disk 101 and the head slider 106 is controlled according to the operation mode and the track position of the magnetic disk device, so that the head flying height is appropriately adjusted. Can be controlled.

(Fourth Embodiment) In the third embodiment,
The case where the applied voltage V is controlled by open loop control without monitoring the head flying height has been described, but it is also possible to monitor the head flying height and control the applied voltage V by feedback control.

FIG. 15 is a block diagram showing such a fourth embodiment. In addition to the configuration of FIG. 13, a flying height measuring sensor 215 and a flying height calculation section 216 are provided.
Based on the output signal 217 from the flying height measurement sensor 215, the flying height calculation unit 216 obtains the current head flying height, and inputs this to the head flying height control circuit 206 to calculate the current head flying height and the target flying height. The error, that is, the flying height error is calculated, and feedback is performed by correcting the reference voltage so that the flying height error becomes zero. Note that the other parts of FIG. 15 are the same as those of FIG. 13, and therefore description thereof will be omitted. As the flying height measurement sensor 215, for example, an electrostatic capacitance sensor may be used for the magnetic disk 101
A device that detects a change in capacitance between the magnetic head 103 and the magnetic head 103 can be used.

A known signal obtained from the R / W channel, for example, a sync signal area (syn) on the magnetic disk is used.
A signal reproduced by the MR head from the (c region) may be taken into the flying height control circuit 206, and the applied voltage may be controlled so that the flying height of the head becomes constant. In this case, it is not necessary to provide the flying height measuring sensor 215, so that the apparatus can be simplified and the cost can be reduced. In that case, for example, the read signal from the MR head of the magnetic head 103 is taken into the head flying height control circuit 206 via the read / write circuit 202, and the applied voltage V is controlled so that the read signal level becomes constant. You can do this.

FIG. 16 is a flow chart showing the operation of the head flying height control circuit 206 in this embodiment.
The processing of steps S11 to S14 is step S1 of FIG.
It is the same as the processing of S3. In the present embodiment, the head flying height control circuit 206 performs R / R after the processing of step S14.
After confirming the switching to the W mode, the reference voltage Vo of the applied voltage V corresponding to the track position indicated by the track position signal 212 input from the servo control circuit 204 is calculated (step S15). Next, the correction voltage ΔV is calculated from the flying height error obtained as described above (step S16), and this correction voltage ΔV is added to the reference voltage Vo calculated in step A15 to obtain V = Vo.
The applied voltage V is calculated as + ΔV (step S1)
7). That is, the head flying height control circuit 206 supplies the voltage generation circuit 108 with the voltage control signal 214 so that the applied voltage V becomes Vo + Δ.

As described above, according to the fourth embodiment, by forming a feedback loop for monitoring the head flying height and controlling the applied voltage V, the head flying height can always be kept at the target flying height.

In the third and fourth embodiments, the head flying height control circuit 206 calculates the applied voltage V = Vc in the R / W mode from the track position by a predetermined approximation formula. May be magnetic disk 1
The 01 data area is divided into several zones, and the applied voltage according to the track position, that is, the zone to which the track of interest belongs belongs to by referring to the memory table showing the relationship between the zone and the applied voltage created by calculation in advance. You may ask.

In the third and fourth embodiments, the applied voltage V is controlled according to both the operation mode and the track position. However, as in the case where a negative pressure slider is used as the head slider, the head flying height is increased. When the voltage does not change much depending on the track position, the applied voltage V may be controlled only by the operation mode. In this case, the applied voltage V may be a relatively low voltage. In addition, the magnetic head 10
It is also possible to change the applied voltage V so as to compensate for the variation of the head flying height due to the individual difference of No. 3.

Furthermore, in the third and fourth embodiments, the case where servo signals are recorded at the same frequency from the inner circumference to the outer circumference of the magnetic disk 101 has been described in mind, but some servo signals may be recorded depending on the configuration of the magnetic disk device. In some cases, the recording frequency is changed for each zone and recording is performed at a substantially constant recording density. In such a case, the applied voltage V in the servo mode may be calculated for each zone.

Further, in the case of a magnetic disk device having various operation modes such as an idle mode and a sleep mode which are not mentioned in the above embodiments for the purpose of power saving of the magnetic disk device, the CSS mode, seek mode, R The applied voltage V can be set not only by the / W mode but also by these other modes.

In the case where a rotary actuator type magnetic disk device is constructed by using an induction type thin film magnetic head as a recording head and a composite type thin film magnetic head in which an MR head is laminated as a reproducing head, respectively, an arm of a rotary actuator is used. Rotation of causes a skew angle variation. At this time, the skew angle θ causes a deviation between the recording track position and the reproducing head position on the magnetic disk. When the recording / reproducing head interval is D, the deviation Z between the recording track position and the reproducing head position
Is represented by Z = D · sin θ.

In Japanese Patent Laid-Open No. 5-298615, as shown in FIG. 17, the arm length (R:
The relationship between the distance from the rotation center of the rotary actuator to the center position of the composite read / write head) and the distance from the disk rotation center to the actuator rotation center (R0) is 1.
It has been shown that the skew density fluctuation is reduced by setting the optimum value in the range of 1R0 ≤R≤1.2R0, and thus the positional deviation between the recording track and the reproducing track is reduced, whereby the track density can be improved. There is.

However, in this method, since the arm tilt angle is substantially constant from the inner circumference to the outer circumference of the magnetic disk, a method that has been conventionally used to make the flying height of the head uniform over the inner circumference, that is,
(1) A method of suppressing the flying height on the inner and outer circumferences by setting a small skew angle on the inner circumference and a large skew angle on the outer circumference,
(2) A step is provided on the side of the ABS surface, and a change in the flying height is suppressed by utilizing the fact that the skew angle changes from the inner circumference to the outer circumference, so that a substantially constant flying height characteristic can be realized. So-called TP that sets the width appropriately
The method of utilizing the change of the skew angle such as C (Transverse Pressure Contour) technology cannot be applied.

On the other hand, since the flying height control methods described in the third and third embodiments can be applied even when there is no skew angle fluctuation, the flying height control method is combined with the MR composite head mounted rotary actuator having the optimum arm length. The same head flying height can be obtained in all tracks. As a result, it becomes possible to perform recording and reproduction at the same recording density on the entire surface of the magnetic disk, which is effective in increasing the storage capacity of the magnetic disk device.

The linear actuator is an actuator which does not cause recording / reproducing track deviation due to the skew angle. However, as in the case of the rotary actuator having the optimum arm length, the linear actuator is effectively combined with the present invention to effectively control the flying height. It can be performed.

(Fifth Embodiment) In the first to fourth embodiments, the output terminal of the voltage generating circuit 108 is directly electrically connected to the head slider 106 to apply a voltage between the magnetic disk 101 and the head slider 106. I applied it,
The voltage generating circuit 1 is provided in the head actuator for moving the magnetic head 103 in the radial direction of the magnetic disk 101.
08 output terminals are electrically connected, and the magnetic disk 101 and the head slider 1 are connected via this head actuator.
It is also possible to adopt a configuration in which a voltage is applied between 06.

18A and 18B are views showing the configuration of the magnetic head 103 and the head actuator 104 in this embodiment, FIG. 18A is a plan view, and FIG. 18B is a sectional view. The head actuator 104 is a rotary actuator configured to move the magnetic head 103 in the radial direction of the magnetic disk 101 by rotating around a pivot portion 122 such as a ball bearing by a coil 121.

Here, an insulating spacer 123 made of a viscoelastic material such as silicone is arranged between the main body of the head actuator 104 and the pivot part 122, and the main body of the head actuator 104 is formed by the insulating spacer 123. It is electrically insulated from the support frame 124. The body of the head actuator 104 is made of a conductive material, and the head slider 1
06 is electrically connected.

The output terminal of the voltage generating circuit 108 is connected to the main body of the head actuator 104 which is electrically connected to the head slider 106. The reference potential terminal of the voltage generation circuit 108 is electrically connected to the frame 102 as described in the first to third embodiments.
Therefore, according to the present embodiment, the head actuator 10
A voltage is applied between the magnetic disk 101 and the head slider 106 via the main body of No. 4.

In the above embodiment, two magnetic heads are provided for one magnetic disk, and the voltage is applied from the common voltage generating circuit between the head slider of each magnetic head and the magnetic disk. Alternatively, a voltage generating circuit may be provided for each head individually to individually apply the voltage, or the magnetic heads may be switched to apply the voltage only between the head slider and the magnetic disk of the selected magnetic head. May be. The same applies to the configuration having a plurality of magnetic disks as in the sixth embodiment described below.

(Sixth Embodiment) In each of the above embodiments, two magnetic heads are provided for one magnetic disk, and a voltage is supplied from a common voltage generating circuit between the head slider and the magnetic disk of each magnetic head. However, it is also possible to individually provide a voltage generation circuit for each head to individually apply the voltage, or to switch the magnetic heads and only between the head slider and the magnetic disk of the selected magnetic head. A voltage may be applied. The same applies to a configuration having a plurality of magnetic disks.

FIG. 19 shows a schematic structure of a magnetic disk device according to the sixth embodiment of the present invention having a plurality of such magnetic disks. In FIG. 19, the configuration of the magnetic disk device is the same as that in FIG. 1 except that a plurality of magnetic disks are provided, and therefore the description thereof is omitted.

(Seventh Embodiment) FIG. 20 is a schematic configuration diagram of a magnetic disk device according to a seventh embodiment of the present invention using a contact type head. The magnetic disk 301 includes an insulating substrate 311, such as a glass plate, a buffer layer 312,
It has a magnetic layer 313 and an insulating layer 314 made of a dielectric material. The insulating layer 314 is made of SiO ₂ , DLC or the like. Microscopically, the surface of the insulator has irregularities with a surface roughness of about several nm. The contact-type head 302 includes an insulating layer 321 made of a dielectric material such as DLC, a slider portion 322 with a transducer that rubs the insulating layer 314 on the magnetic disk at a predetermined peripheral speed while making contact, and a predetermined slider. And a spring portion 323 that supports the slider and presses it against the disk in order to apply a pressing force to the magnetic disk.
The spring portion 323 is supported by an actuator (not shown) and moves on the disk.

Even when the head and the disk are in contact with each other, the levitation force FAa is generated by air due to the surface roughness of the head and the disk surface. An appropriate voltage is applied between the slider 322 and the magnetic layer 313 by the voltage generation circuit 308, and the electrostatic attraction force Fe is generated. At this time, the equation of Fa = Fe + Fn holds. Fe
Is given by the same equation as the equation (2), but Fa is smaller than that given by the equation (1). However, the flying height H is the degree of surface roughness of the contact surface. Since the contact force Fc between the slider and the disk is Fc = Fn + Fe−Fa, a constant contact force can always be applied by operating the voltage so that Fe = Fa. In this case, the contact force can be reduced by applying the voltage only when R / W and increasing the contact force Fc, and by not applying the voltage or lowering the voltage at other times, thereby reducing the contact force. The life of the head can be extended.

The present invention can be implemented with various modifications. For example, if the same voltage is applied between the head sliders of many magnetic heads and the magnetic disks,
It is possible to prevent the head flying height from varying depending on the track position and make the head flying height uniform from the inner circumference to the outer circumference of the magnetic disk. Voltages are simultaneously applied between the head sliders of all the magnetic heads and the magnetic disks according to the operation mode of the magnetic disk device. In this case, therefore, the variation in the flying characteristics of the individual magnetic heads is kept within a predetermined range. Is desirable. Further, in this case, for example, the fourth
As described in the above embodiment, the head actuator 1
If 04 is common to each magnetic head and the main body of the head actuator 104 is connected to the voltage generation circuit, it is not necessary to perform wiring for voltage application to the head slider of each magnetic head. And the advantage is that the circuit is very simple.

When the voltage is individually applied between the head slider and the magnetic disk of each magnetic head, the head flying height of only the selected magnetic head is recorded / recorded.
Since it is possible to set the spacing suitable for reproduction and to make the flying height of other magnetic heads safer than that, there is an advantage that the reliability of the magnetic disk device is improved. Moreover, even if there are variations in the flying characteristics of the individual magnetic heads, optimal flying height control can be performed for the individual magnetic heads, and it is necessary to consider variations in the flying characteristics of the individual magnetic heads in device design. Since it does not exist, recording / playback with the smallest floating gap is possible,
The recording density can be dramatically improved. Further, since it is not necessary to select the magnetic head according to the flying characteristics, the process control becomes simple and the yield can be improved. Further, in this case as well, it is necessary to electrically connect the head slider of each magnetic head from other portions to apply a voltage, thereby providing wiring for applying a voltage up to near the tip of the magnetic head. Wiring is easy.

[0150]

According to the present invention, a load that gives a constant head flying height can be applied regardless of the track position of the magnetic head, and a uniform recording density can be achieved over the inner and outer circumferences. Further, by reducing the head load during CSS, sliding, idling, etc. to reduce damage to the magnetic disk, it is possible to prolong the life of the apparatus and further reduce power consumption.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a magnetic disk device according to the present invention.

FIG. 2 is a graph showing the relationship between the head flying height and the applied voltage between the head slider and the magnetic disk for explaining the present invention.

FIG. 3 is a diagram showing a relationship between a head slider volume and an area / volume ratio.

FIG. 4 is a diagram showing the relationship between electrostatic attraction force and head flying height.

FIG. 5 is a schematic configuration diagram schematically showing the magnetic disk device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a track position of a magnetic head and an applied voltage between a head slider and a magnetic disk.

FIG. 7 is a schematic configuration diagram schematically showing a magnetic disk device according to a second embodiment of the present invention.

FIG. 8 is an enlarged partial cross-sectional view showing a magnetic head and a magnetic disk for explaining the operation of the same embodiment.

FIG. 9 is an enlarged partial sectional view showing a magnetic head and a magnetic disk for explaining the operation of the same embodiment.

FIG. 10 is an enlarged partial sectional view showing a magnetic head and a magnetic disk for explaining the operation of the same embodiment.

FIG. 11 is a diagram showing the relationship between the flying height of a magnetic head and the electrostatic attraction force.

FIG. 12 is a diagram showing a relationship between spacing and dielectric breakdown voltage.

FIG. 13 is a diagram showing a configuration of a magnetic disk device according to a third embodiment of the present invention.

FIG. 14 is a flowchart for explaining the operation of the embodiment.

FIG. 15 is a diagram showing a configuration of a magnetic disk device according to a fourth embodiment of the present invention.

FIG. 16 is a flowchart for explaining the operation of the embodiment.

FIG. 17 is a diagram for explaining optimization of the arm length of the rotary actuator and the distance from the disk rotation center to the actuator rotation center for reducing the skew angle fluctuation in the known example.

FIG. 18 is a plan view and a cross-sectional view showing configurations of a magnetic head and a head actuator according to a fifth embodiment of the present invention.

FIG. 19 is a diagram showing a schematic configuration of a magnetic disk device having a plurality of magnetic disks according to a sixth embodiment of the present invention.

FIG. 20 is a diagram showing a schematic configuration of a magnetic disk device having a plurality of magnetic disks according to a seventh embodiment of the present invention.

[Explanation of symbols]

 101 ... Magnetic disk 102 ... Spindle motor 103 ... Magnetic head 104 ... Head actuator 105 ... Frame 106 ... Head slider 107 ... Suspension 108 ... Voltage generating circuit 109 ... Spacing 110 ... Insulating layer 111 ... Insulating substrate 112 ... Buffer layer 113 ... Magnetic layer 114 ... Insulating layer 115 ... Current limiter 201 ... Hard disk controller 202 ... Read / write circuit 203 ... Head drive circuit 204 ... Servo control circuit 205 ... VCM driver 206 ... Head flying height control circuit 211 ... Tracking servo data 212 ... Track Position signal 213 ... Mode signal 214 ... Voltage control signal 215 ... Flying height measurement sensor

Claims (13)

[Claims] 1. A magnetic disk that rotates, a head slider that is arranged so as to face the magnetic disk, and an electromagnetic conversion portion that is supported by the head slider, and record / reproduce information on / from the magnetic disk. A magnetic head for performing a voltage, and voltage applying means for applying a voltage according to at least one of a track position on the magnetic disk where the magnetic head is located between the head slider and the magnetic disk and an operation mode of a magnetic disk device. A magnetic disk device comprising: 2. The voltage applying means increases the voltage applied between the head slider and the magnetic disk as the track position of the magnetic head shifts from the inner circumference side to the outer circumference side of the magnetic disk. The magnetic disk device according to claim 1, wherein: 3. The voltage applying means sets the voltage applied between the head slider and the magnetic disk to zero or a minute voltage when the operation mode is the contact start / stop mode, and when the operation mode is the seek mode. 3. The voltage is higher than the voltage in the contact start / stop mode, and is higher in the read / write mode at a predetermined track position than in the seek mode. Magnetic disk device. 4. The maximum track diameter of the magnetic disk is R
[M], where the rotational angular velocity of the magnetic disk is ω [1 / s], the upper limit of the voltage applied by the voltage applying means is 3
X (ωR) ^1/2 [V] is set.
4. The magnetic disk device according to any one of items 1 to 3. 5. An insulating layer is provided on at least one of the facing surfaces of the magnetic disk and the head slider, and
5. The magnetic disk device according to claim 1, wherein the voltage applied by the voltage applying means is set to be less than the dielectric breakdown voltage of the insulating layer. 6. A head slider according to claim 1, wherein the volume of the head slider is 15 mm ³ or less.
The magnetic disk drive according to the item. 7. The flying height of the magnetic head with respect to the magnetic disk in the recording / reproducing mode of the magnetic disk device is 100 nm or less.
7. The magnetic disk device according to claim 1. 8. A current limiting means for limiting a current flowing between the magnetic head and the magnetic disk when the magnetic head and the magnetic disk are in contact with each other.
8. The magnetic disk device according to any one of items 1 to 7. 9. An electric connection with the head slider,
An actuator for moving the head slider in a radial direction of the magnetic disk, wherein the voltage applying means applies a voltage between the head slider and the magnetic disk via the actuator. 9. The magnetic disk device according to any one of 1 to 8. 10. A flying height detection means for detecting the flying height of the magnetic head with respect to the magnetic disk, and a control means for controlling the voltage applied by the voltage applying means based on the flying height detected by the flying height detection means. 10. The magnetic disk device according to claim 1, further comprising: 11. A magnetic disk that rotates, a head slider arranged to face the magnetic disk, and an electromagnetic converter supported by the head slider, respectively, to record / reproduce information on / from the magnetic disk. And a voltage applying unit for applying a voltage between the head slider and the magnetic disk, the voltage applying unit applying a voltage according to each flying characteristic of the magnetic heads. . 12. A magnetic disk that rotates, a head slider arranged to face the magnetic disk, and an electromagnetic converter supported by the head slider, respectively, and information is recorded / reproduced on / from the magnetic disk. And a voltage for applying a voltage between the head slider of the desired magnetic head selected from the plurality of magnetic heads and the magnetic disk to limit the flying characteristics of the magnetic head. A magnetic disk device comprising: an applying unit. 13. The head slider has at least one bearing having a fluid inflow end and a fluid outflow end and a magnetic gap, and the magnetic head is provided with a recording element and a reproducing device provided near the outflow end. An element, wherein a skew angle which is an angle formed by a magnetic gap length direction of the magnetic gap and a track direction on the magnetic disk is substantially constant from an innermost track to an outermost track on the magnetic disk, The bearing is arranged at a predetermined angle with respect to the track direction such that the inflow end is located closer to the outer peripheral side of the magnetic disk than the outflow end with respect to the track direction. Any one of 1 to 12
The magnetic disk drive according to the item.