JPH06267219A - Magnetic disk device and method for controlling its head floating height - Google Patents

Abstract

PURPOSE:To gain uniform reading/writing performance by making head floating heights on all tracks constant at the time of reading/writing. CONSTITUTION:A piezoelectric element is buried in a head slider 20 and crown quantity control circuit 19 is provided so as to generate strain by impressing a control voltage to the piezoelectric element and to control the crown quantity of the head slider 20. The optimum value of the control voltage to be supplied to a piezoelectric element 22 is selected by the crown quantity control circuit 19 based on a cylinder address indicating the track position of a current magnetic head 12, and is impressed to the piezoelectric element 22 to keep the head floating height constant over all the tracks.

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 and a head flying height control method thereof.

[0002]

2. Description of the Related Art In the case of a magnetic disk drive using a flying head, it is important to keep the flying height of the head small and constant in order to improve reliability. The head slider on which the magnetic head core is mounted plays a role of levitating the head by an appropriate amount by the dynamic pressure of the air flow generated between itself and the head slider by the rotation of the disk.

The shape of the head slider is, for example, as shown in FIG.
The following are examples. This head slider 7
As shown in FIG. 8, No. 1 receives the dynamic pressure of the air flow generated by the rotation of the disk 81 to obtain the required flying height h.

Such a head slider 71 is provided, for example, with a CDR (Constant Density Recordi) having a constant linear recording density.
ng) system magnetic disk device.
In this case, (1) the rotation speed of the disk becomes faster as the track position of the magnetic head is closer to the outer circumference of the disk, (2) FIG.
As shown in FIG. 10, since the yaw angle θ spreads as the magnetic head 91 approaches the outermost circumference from a certain track position on the disk 92, the relationship between the track position of the magnetic head and the head flying height h is shown in FIG. As shown in. In short, the head flying height h changes depending on the track position of the magnetic head.

Such a change in the flying height h of the head is
Due to the situation (2), it is a problem that is common to all types of magnetic disk devices, not limited to the CDR system.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve such problems, and at least the head flying height at the time of read / write is made constant on all tracks to obtain uniform read / write performance. It is an object of the present invention to provide a magnetic disk device and a head flying height control method therefor.

[0007]

In order to achieve the above-mentioned object, a magnetic disk device according to a first aspect of the present invention comprises a magnetic head having a magnetic head core mounted on a head slider, and an air flow generated as the disk rotates. In a magnetic disk device which is read from and written to the disk by being levitated from the surface of the disk by the dynamic pressure of the head slider. A piezoelectric element for causing the opposing surface to project in a substantially curved shape along the flow direction of the air flow,
The optimum control voltage to be applied to the piezoelectric element is selected based on the information indicating the current track position of the magnetic head obtained from the signal reproduced from the disk, and the control voltage is applied to the piezoelectric element. And a control means for controlling the flying height of the magnetic head to be constant over all tracks.

In order to achieve the above-mentioned object, the magnetic disk device of the second invention uses a magnetic head having a magnetic head core mounted on a head slider by a dynamic pressure of an air flow generated as the disk rotates. In a magnetic disk device that floats from the surface and performs read / write,
Embedded in the head slider, for causing a shape displacement of a magnitude according to an applied control voltage to cause the disk facing surface of the head slider to project in a substantially curved shape along the direction of the air flow. A first control voltage is applied to the piezoelectric element during reading / writing during rotation of the piezoelectric element and the disk, and the first control voltage is applied except during reading / writing.
And a control means for applying a second control voltage different from the above control voltage to the piezoelectric element so as to control the flying height of the magnetic head to be larger than that during read / write.

Further, in order to achieve the above-mentioned object, the magnetic disk device of the third invention uses a magnetic head having a magnetic head core mounted on a head slider, by means of a dynamic pressure of an air flow generated as the disk rotates. In a magnetic disk device that floats above the surface to perform read / write, it is embedded in the head slider and causes a shape displacement of a magnitude according to an applied control voltage to cause the disk facing surface of the head slider to move toward the air surface. A piezoelectric element for protruding in a substantially curved shape along the flow direction, and should be applied to the piezoelectric element based on information indicating the current track position of the magnetic head obtained from a signal reproduced from the disk. Select an optimum control voltage and apply this control voltage to the piezoelectric element to keep the flying height of the magnetic head constant over all tracks. Performs control so as to, except when read / write and a control means for variably controlling the control voltage such that the flying height is increased than when the read / write.

[0010]

That is, in the magnetic disk device of the first invention,
The control means selects an optimum control voltage to be applied to the piezoelectric element according to the current track position of the magnetic head and applies this control voltage to the piezoelectric element, so that the protrusion amount of the disk facing surface of the head slider is increased. Adjust (crown amount). The amount of crown and the flying height of the head are almost proportional,
By optimally controlling this crown amount according to the track position of the magnetic head, the head flying height can be made constant over all tracks.

In the magnetic disk device of the second invention, the control means applies the first control voltage to the piezoelectric element during read / write, and the second control voltage different from the first control voltage except during read / write. Since a control voltage is applied to the piezoelectric element to control the flying height of the head to be larger than that during read / write, the risk of collision between the magnetic head and the disk during seek operation can be largely eliminated.

In the magnetic disk drive of the second invention, the control means performs optimum control of the crown amount according to the track position of the magnetic head, and the head flying height is higher than that during read / write except during read / write. Since the control voltage is variably controlled to increase, the head flying height can be made constant over all tracks, and the risk of collision between the magnetic head and the disk during seek operation can be greatly eliminated. .

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining the configuration of a magnetic disk device according to an embodiment of the present invention.

In the figure, 11 is a disk, and 12 is a magnetic head for reading / writing signals from / to the disk 11. The magnetic head 12 is a flying head in which a magnetic head core is mounted on a head slider. A read / write circuit unit 13 is a circuit for performing head amplifiers, generation of write signals to be supplied to the head amplifiers, generation of read data from read signals input through the head amplifiers, and code modulation / demodulation of read / write data. have. Reference numeral 14 is an actuator for moving the magnetic head 12 in the radial direction on the disk surface. The actuator 14 has an arm that supports the head slider via a leaf spring, and a drive mechanism (including a voice coil motor) that rotates the arm within a certain angle range about a support shaft. ..
An actuator drive circuit 15 drives the actuator 14, and supplies a required drive current to the voice coil motor in order to align the magnetic head 12 on a target track based on a control signal from a positioning circuit section 16 described later. Reference numeral 16 denotes a positioning circuit unit that controls the positioning of the magnetic head 12 based on servo data obtained from the read / write circuit unit 13 and a command including read / write address information input from the host through the interface unit 18. Reference numeral 17 denotes a control circuit section that controls the entire magnetic disk device. An interface unit 18 controls the input / output of various commands and read / write data between the magnetic disk device and the host. Reference numeral 19 denotes a crown amount control circuit for optimally controlling the crown amount of the head slider by applying a control voltage to the piezoelectric element built in the head slider.

FIG. 2 is a perspective view of the head slider as seen from the disk facing surface side (air bearing surface side), and FIG. 3 is a side view showing the position of the piezoelectric element in the head slider of FIG.

As shown in these figures, the head slider 20 is equipped with two magnetic head cores 21, 21, one of which is a spare magnetic head core and the other magnetic head core is unusable. Used when The air bearing surface of the head slider 20 is recessed at its intermediate portion in the short side direction over the entire length in the longitudinal direction. Each one end of both ends in the short side direction except this recess is tapered and the other end is The magnetic head cores 21, 21
Are arranged respectively.

The above-mentioned piezoelectric elements 22, 22 are provided in the respective convex portions (both ends in the short side direction) on the air bearing surface side of the head slider 20, one behind each of the thin plates forming the air bearing surface of the head slider 20. It is buried in a state where one side is closely attached to. The piezoelectric elements 22 and 22 are electrically connected to the crown amount control circuit 19 and generate a strain (shape displacement) of a magnitude corresponding to the control voltage applied from the crown amount control circuit 19. Therefore, as shown in FIG.
Due to this shape displacement, the air bearing surface of the head slider 20 is lifted in a substantially curved shape along the air flow direction, and the crown amount C is variably controlled.

Next, the control of the flying height of the head will be described.

FIG. 5 shows the head flying height h and the crown amount C.
It is a graph which shows the relationship with. As is clear from this graph, the head flying height h is almost proportional to the crown amount C. Therefore, if the crown amount C is optimally controlled according to the track position of the magnetic head 12, the head flying height h can be kept constant on all tracks on the disk 11.

Details of a series of operations in this case will be described below. When a read command or a write command is input from the host through the interface unit 18, the control circuit unit 17 causes the read / write circuit 13, the positioning circuit unit 16, the crown amount control circuit 19, a spindle drive circuit (not shown), and the like. Issue an operation command to.

When the disk 11 starts to rotate, the positioning circuit section 16 first outputs a control signal to the actuator drive circuit 15 to move the magnetic head 12 to a target track, thereby driving the actuator 14.

When the movement of the magnetic head 12 is completed, reading / writing on the disk 11 is started. During this read / write operation, the control circuit unit 17 decodes the cylinder address, which is the information indicating the current track position of the magnetic head 12, from the servo pattern reproduced from the disk 11 through the read / write circuit 13, and reads it. It is given to the crown amount control circuit 19.

The crown amount control circuit 19 holds the optimum value of the control voltage to be supplied to the piezoelectric element 22 for each cylinder address in the form of a table. When the cylinder address is obtained from the control circuit unit 17, the optimum value of the control voltage corresponding to this cylinder address is selected from the table and this control voltage is supplied to the piezoelectric element 22 in the head slider 20.

The table information can be created based on the graph of FIG. 10 described in the conventional example.

As a result, the piezoelectric element 22 in the head slider 20 has a strain (shape displacement) of a magnitude corresponding to the control voltage.
Is generated, the air bearing surface of the head slider 20 is lifted in a substantially curved shape to variably control the crown amount C, and the head flying height h is controlled to be constant over all tracks.

Also, read / read for one command
A period during which the read / write is not actually performed even when the disc 11 is rotating, such as a disc rotation waiting period until the read / write for the next command is started after the write is finished and a seek operation period, The quantity control circuit 19 applies a control voltage obtained by adding, for example, a constant value to the value of the control voltage according to the current cylinder address, to the piezoelectric element 22, and causes the distortion (shape displacement) of the piezoelectric element 22 to be larger than that during read / write. Control to increase. As a result, the flying height h of the head is increased by several μm as compared with the read / write operation.
The danger of collision with can be greatly eliminated.

As described above, according to the magnetic disk apparatus of the present embodiment, the crown amount of the head slider 20 which influences the head flying height is optimally controlled according to the track position of the magnetic head 12, so that all the tracks are recorded. Therefore, the flying height of the head slider 20 can be kept constant. Therefore, uniform read / write performance can be obtained over all tracks, and reliability can be improved.

In this embodiment, a CDR type magnetic disk device having a constant linear recording density is taken as an example, but the present invention is also applicable to other systems, for example, a magnetic disk device having a constant disk rotation speed. Applicable.

Further, in this embodiment, the crown amount is controlled according to the track position of the magnetic head 12, and at the same time, the crown amount is further changed at the time of read / write and at the time of other than read / write. Even if the crown amount is controlled in two steps at the time of writing and at the time other than reading / writing, a unique effect for improving reliability can be obtained, for example, collision avoidance between the magnetic head 12 and the disk 11 at the seek operation. .

Further, in the above-mentioned embodiment, the head flying height other than during read / write is also made constant, but the present invention is not limited to this, and the servo pattern is reproduced from the disk 11 to decode the cylinder address. It does not have to be constant as long as it is within the range.

Further, the position of the piezoelectric element arranged in the head slider may be, for example, as shown in FIG. 6, on the side opposite to the air bearing surface of the head slider 61.
In this case, by distorting the piezoelectric element 62 in the direction of the arrow, the head slider 61 is entirely curved, and a required crown amount is secured.

[0032]

As described above, according to the magnetic disk device and the head flying height control method of the present invention, the crown flying amount is optimally controlled according to the track position of the magnetic head, so that the head flying height is controlled. It can be constant over the track. Further, the head flying height can be increased more than during read / write except during read / write, and the risk of collision between the magnetic head and the disk during seek operation can be greatly eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a configuration of a magnetic disk device according to an embodiment of the present invention.

2 is a perspective view of the head slider in the magnetic disk device of FIG. 1 as viewed from the disk facing surface side (air bearing surface side).

FIG. 3 is a side view showing the position of a piezoelectric element in the head slider of FIG.

FIG. 4 is a side view showing the action of the piezoelectric element in the head slider of FIG. 2 and the positional relationship between the head slider and the disk.

FIG. 5 is a graph showing a relationship between a head flying height and a crown height.

6A and 6B are a perspective view and a side view showing a head slider of another embodiment of the present invention.

FIG. 7 is a perspective view showing an external shape of a conventional head slider.

FIG. 8 is a side view showing how the head slider flies over the disk surface.

FIG. 9 is a plan view showing a positional relationship between a magnetic head and a disk on a plane.

FIG. 10 is a graph showing a relationship between a head flying height and a head track position in a conventional magnetic disk device.

[Explanation of symbols]

11 ... Disk, 12 ... Magnetic head, 13 ... Read / write circuit section, 14 ... Actuator, 15 ... Actuator drive circuit, 16 ... Positioning circuit section, 17 ... Control circuit section, 18 ... Interface section, 19 ... Crown amount control circuit , 20 ... Head slider, 21 ... Magnetic head core, 2
2 ... Piezoelectric element.

Claims (6)

[Claims] 1. A magnetic head in which a magnetic head core is mounted on a head slider is levitated from a disk surface by the dynamic pressure of an air flow generated as the disk rotates to read / write.
In a magnetic disk device for writing, embedded in the head slider, a shape displacement having a magnitude corresponding to a control voltage applied is generated to cause a disk facing surface of the head slider along a flow direction of the air flow. A piezoelectric element for projecting in a substantially curvature shape, and an optimum control voltage to be applied to the piezoelectric element based on information indicating the current track position of the magnetic head, which is obtained from a signal reproduced from the disk, is selected, A magnetic disk device comprising: a control unit that applies the control voltage to the piezoelectric element to control the flying height of the magnetic head to be constant over all tracks. 2. A magnetic head having a magnetic head core mounted on a head slider is levitated from the disk surface by the dynamic pressure of an air flow generated by the rotation of the disk to read / write.
In a magnetic disk device for writing, embedded in the head slider, a shape displacement having a magnitude corresponding to a control voltage applied is generated to cause a disk facing surface of the head slider along a flow direction of the air flow. A piezoelectric element for projecting in a substantially curved shape; a first control voltage is applied to the piezoelectric element during read / write during rotation of the disk, and the first control voltage except during read / write And a control means for applying a second control voltage different from the above to the piezoelectric element so as to control the flying height of the magnetic head to be larger than that during read / write. 3. A magnetic head having a magnetic head core mounted on a head slider is levitated from the disk surface by the dynamic pressure of an air flow generated by the rotation of the disk, and is read / written.
In a magnetic disk device for writing, embedded in the head slider, a shape displacement having a magnitude corresponding to a control voltage applied is generated to cause a disk facing surface of the head slider along a flow direction of the air flow. A piezoelectric element for projecting in a substantially curvature shape, and an optimum control voltage to be applied to the piezoelectric element is selected based on information indicating a current track position of the magnetic head obtained from a signal reproduced from the disk. The control voltage is applied to the piezoelectric element to control the flying height of the magnetic head to be constant over all tracks, and the flying height is larger than that during read / write except during read / write. And a control means for variably controlling the control voltage. 4. A magnetic head having a magnetic head core mounted on a head slider is levitated from the disk surface by the dynamic pressure of an air flow generated by the rotation of the disk so as to read / write.
In a head flying height control method for a magnetic disk device for writing, a shape displacement having a magnitude corresponding to a control voltage applied is generated in the head slider to cause the air flow to flow on a disk facing surface of the head slider. Optimum to be applied to the piezoelectric element based on the information indicating the current track position of the magnetic head, which is obtained from the signal reproduced from the disk, by embedding the piezoelectric element for protruding in a substantially curved shape along the direction. Head voltage control of a magnetic disk device, wherein a control voltage is selected and applied to the piezoelectric element to control the magnetic head flying height to be constant over all tracks. Method. 5. A magnetic head in which a magnetic head core is mounted on a head slider is levitated from a disk surface by dynamic pressure of an air flow generated as the disk rotates to read / write.
In a head flying height control method for a magnetic disk device for writing, a shape displacement having a magnitude corresponding to a control voltage applied is generated in the head slider to cause the air flow to flow on a disk facing surface of the head slider. A piezoelectric element for protruding in a substantially curved shape along the direction is embedded, a first control voltage is applied to the piezoelectric element during read / write during rotation of the disk, and other than during read / write. The first
And a second control voltage different from the above control voltage are applied to the piezoelectric element to control the flying height of the magnetic head to be larger than that during reading / writing. Method. 6. A magnetic head having a magnetic head core mounted on a head slider is levitated from a disk surface by a dynamic pressure of an air flow generated by the rotation of the disk so as to read / write.
In a head flying height control method for a magnetic disk device for writing, a shape displacement having a magnitude corresponding to a control voltage applied is generated in the head slider to cause the air flow to flow on a disk facing surface of the head slider. A piezoelectric element for projecting in a substantially curved shape along the direction is embedded, and when the disk rotates, it is obtained from a signal reproduced from this disk,
The optimum control voltage to be applied to the piezoelectric element is selected based on the information indicating the current track position of the magnetic head, and the control voltage is applied to the piezoelectric element to set the flying height of the magnetic head to all tracks. Head flying height control of a magnetic disk device, characterized in that the control voltage is variably controlled so that the flying height increases more than during reading / writing, while performing control so that the flying height is constant over time. Method.