JPH10222826A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stopping or preventing a discharge in a magnetic head using an MR head and a magnetic disk device using it. SOLUTION: In the magnetic disk device using an R/W IC using a one side source, a recording coil part is grounded during an operation mode excepting data recording operation, and the discharge is prevented. During the data recording operation, when a write error or a discharge waveform is confirmed, the recording coil part 10 is grounded temporarily, and further, by performing seek or CSS operation, the discharge is stopped and a re-discharge is prevented by forcedly discharging a residual charge on the magnetic head to a magnetic disk surface. The discharge between the magnetic head using the MR head and the magnetic disk is stopped or prevented without changing the structure of the magnetic head, and the magnetic disk device with high reliability is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for stopping discharge between a magnetic head and a magnetic disk in a magnetic disk drive.

[0002]

2. Description of the Related Art In a recording / reproducing circuit including a magnetic head in a conventional magnetic disk drive, a recording coil section of a recording head and an MR element section of a head using an MR head as a reproducing head are R / A amplifiers. Connected to WIC. The R / WIC is adapted to amplify a reproduction signal from a magnetic disk or to supply a recording signal sent to a recording head of a disk device to a current flowing through a coil. In addition, this R / WIC may use a single power supply in order to use a personal computer power supply of 5 V or 12 V in consideration of mounting on a personal computer. In the R / WIC using such a single power supply, a constant positive voltage is constantly applied to the recording coil portion of the magnetic head. Generally, the recording coil portion and the MR element portion of the recording head are insulated from the slider, magnetic core, and shield portion by photoresist or the like to form a capacitance, and the magnetic head slightly flies above the magnetic disk. Each element of the magnetic head forms a parasitic capacitance with the surface of the magnetic disk. For this reason, a slider insulated from the recording coil portion and the MR element portion of the recording head,
The magnetic core and the magnetic shield are charged to a potential determined by the capacitance ratio of the capacitance.

The electric charge charged in the slider, the magnetic core, and the shield portion is reduced when the flying height of the magnetic head is reduced.
Or, in a place where the flying height is low, discharge is performed at a distance between the magnetic disk. Further, once discharged, the discharge is continued even if the flying height increases due to the influence of the residual charge, thereby causing an error in the reproduced data.

As a method of solving the problem caused by the discharge, a DC voltage substantially equal to the DC voltage applied from the R / WIC is applied to the magnetic disk so that the DC voltage level of the magnetic disk surface and the magnetic core is substantially the same level. A method for preventing charging has been reported in Japanese Patent Application Laid-Open No. 2-246048.

[0005]

Discharge occurs when the difference between the DC voltage applied from the R / WIC and the DC voltage on the surface of the magnetic disk, that is, the potential difference exceeds the withstand voltage of the system. In the above method, a DC voltage is applied to the surface of the magnetic disk to reduce the potential difference to 0 V. Therefore, when a magnetic head using an MR element is used, discharge occurs between the MR element and the magnetic disk, one of which is grounded. .

Therefore, when a magnetic head using an MR element is used, the surface of the magnetic disk needs to be grounded, and a method for preventing or stopping discharge in this state is required.

[0007]

In a magnetic disk drive using a magnetic head using an MR element, as means for stopping discharge, a slider, a magnetic core, and a magnetic shield are grounded, and charged electric charges are discharged. There is a method of releasing, and a method of grounding the recording coil to prevent the slider, the magnetic core, and the magnetic shield from being charged.

In the former method, the structure of the magnetic head needs to be changed because the slider, the magnetic core, and the magnetic shield are grounded. In the latter, on the other hand, the discharge can be prevented without changing the structure of the magnetic head, but the possibility remains during the recording operation when the recording coil cannot be grounded. Therefore, a discharge occurs during the recording operation, and write occurs.
If an e-error occurs, the recording operation is interrupted, and the discharge is stopped by temporarily grounding the recording coil. Also, once discharge occurs, the withstand voltage of the system is drastically reduced due to the effect of the residual charge, and becomes about several hundred mV. Therefore, temporarily performing a seek or CSS operation with the recording coil grounded temporarily Levitation or contact with the surface of the magnetic disk, and the residual charge is forced to escape to the surface of the magnetic disk. By performing this operation, the withstand voltage can be ensured even after once discharging, and the discharging can be completely stopped.

Therefore, by using this method, in a magnetic disk drive using an MR head, discharge from the slider, the magnetic core, and the magnetic shield can be prevented without changing the structure of the magnetic head.

[0010]

FIG. 1 shows the configuration of a magnetic head 1. The recording magnetic head includes a recording coil 10 and a magnetic core 11 formed so as to surround a part of the recording coil.
The reproducing magnetic head has a magnetic shield 12 formed to be paired with the magnetic core 11, and an MR electrode 13 and an MR element 14 between the magnetic core 11 and the magnetic shield 12. ing. These head element portions are connected to a slider 15 for flying the head through a magnetic shield 12, and a protective film 16 is provided on a surface facing the magnetic disk 17. Each part of the recording coil 10, the magnetic core 11, the MR element 14, and the magnetic shield 12 is insulated with a high resistance by an insulating layer 18 such as a photoresist. The MR element 14 is connected to the R / WIC via the MR electrode 13, one of which is grounded. Further, the recording coil 10 passes a recording current.
/ WIC. R / WIC using single power supply
In this case, the recording coil 10 is in a state where a positive or negative DC voltage is constantly applied. When the magnetic head 1 in such a state is floated on the grounded magnetic disk 17, the parasitic capacitance 20 and the parasitic resistance 21 due to the insulating layer 18 such as a photoresist and the parasitic capacitance 22 generated between the magnetic head magnetic disks are reduced. As a result, a potential is generated in the slider 15, the magnetic core 11, and the magnetic shield 12 in the electrically floating state, and the electric charge is charged.

When electric charges are charged in the magnetic core 11 and the magnetic shield 12, an electric field is generated in the air between the magnetic head 1 and the magnetic disk 17. When the intensity of the electric field exceeds a certain threshold value, air breakdown occurs, and the magnetic core 11
The electric charge charged to the field 12 is discharged through the magnetic disk. Due to this discharge, pulse-like noise is generated in the output of the MR element, that is, in the reproduced output, and an error occurs in the reproduced data.

The strength of the electric field required to cause air breakdown, that is, the threshold value, depends on the distance between the magnetic head 1 and the magnetic disk 17, ie, the flying height. Goes down. Therefore, the discharge phenomenon due to the dielectric breakdown of air occurs when the interval becomes narrow, for example, at a position where a protrusion on the magnetic disk is present.

Since the strength of the applied electric field is proportional to the magnitude of the DC voltage applied to the recording coil, the threshold value is changed by changing the DC voltage applied to the recording coil. You can know as.

The magnetic disk is rotated at 1500 rpm, and the magnetic head is lifted by a flying height of about 20 mm at a position having a radius of 25 mm.
When following in nm, 20V is applied to the recording coil.
Is applied, a pulse-like noise waveform as shown in FIG. 2 is detected from the MR element. This is noise due to the fluctuation of the potential of the magnetic core and the like due to the discharge. When the voltage applied to the recording coil is set to 0 V, the pulse-like noise waveform disappears. FIG. 3 shows the number of pulse-shaped noises, ie, the number of discharges, per round of the magnetic disk when the magnitude of the DC voltage applied to the recording coil was changed. DC voltage applied to the recording coil from 0V to 20V
, And a discharge stop voltage characteristic 31 when the voltage is lowered from 20V to 0V.

From the discharge starting voltage characteristic 30, the threshold value at the time of the occurrence of discharge, that is, the applied voltage of the recording coil is about 6 V. When a higher DC voltage is applied, discharge occurs. Conversely, from the discharge stop characteristic 31, the voltage applied to the recording coil needs to be 0.2 V or less to stop the discharge. As described above, since the threshold value is different between the discharge start characteristic and the stop characteristic, even if the voltage applied to the recording coil from the R / WIC is 6 V or less, if the applied voltage is 0.2 V or more, the flying height due to a protrusion or the like is increased. When the discharge becomes low and the discharge starts, the discharge continues even if the flying height returns to the original height. Therefore, to prevent or stop the discharge, it is necessary to ground the recording coil.

However, in a magnetic disk drive, data
During recording, the recording coil cannot be grounded. Therefore, if a write error or a discharge waveform is confirmed during recording, it is necessary to stop the data recording operation and stop the discharge by temporarily grounding the recording coil.

However, since the recording coil is temporarily grounded, the discharge is stopped, and the data recording operation is performed again, when a DC voltage is applied to the recording coil, the influence of the residual charge remaining on the magnetic head is obtained. Therefore, the discharge may be started even when the applied DC voltage is 6 V or less.

FIG. 4 is a graph showing a discharge starting voltage characteristic when the DC voltage applied to the recording coil is increased from 0 V to 20 V again after the recording coil is temporarily grounded to stop the discharge in the discharged head. Figure 4 shows. After the recording coil is temporarily grounded, the discharge starting voltage characteristic 40 measured in the following state without any operation, and once with the recording coil grounded after the recording coil is temporarily grounded
Comparing the discharge start voltage characteristics 41 measured after performing the EK operation, the discharge start voltage characteristics 40 measured in the following state indicate that the threshold value at the time when discharge occurs is reduced to 2 V due to the residual charge of the magnetic head. ing. On the other hand, after the recording coil is temporarily grounded, and after the seek operation is performed once with the recording coil grounded, the discharge starting voltage characteristic 41 shows that the threshold value at the time when the discharge occurs is 6V. Return. This is because the seek operation causes a state where the flying height of the magnetic head is low or a state where the magnetic head is in contact with the surface of the magnetic disk, and the residual charge of the magnetic head is discharged to the surface of the magnetic disk and disappears. is there.

Instead of seeking, CSS (C
By releasing the residual charge of the magnetic head from the surface of the magnetic disk by a method of contacting the magnetic disk with the magnetic head, such as an on-chip start stop, it is possible to return the threshold value at the time of discharge to 6V. Thus, in the magnetic disk drive, if a write error or a discharge waveform is confirmed during the data recording operation, the data recording operation is stopped and the recording coil is temporarily grounded to discharge. Stop and simultaneously see
By forcibly eliminating the residual charge by performing k or CSS, it is possible to prevent discharge when performing the data recording operation again.

FIG. 5 shows the configuration of a magnetic disk drive having a circuit for stopping or preventing discharge. The magnetic disk device has a magnetic head 101 and a magnetic disk 102, and controls a spindle unit 103 for rotating the magnetic disk, an actuator unit 104 for moving the magnetic head, an R / WIC 105 for amplifying a recording / reproducing signal, and the whole. And a circuit unit 106.

FIG. 6 shows the discharge countermeasure circuit 107 added in this embodiment. The discharge countermeasure circuit 107 is provided with a switch that receives an R / W signal from the circuit unit 106 that outputs a different output value during recording than during reproduction, and that can ground the recording coil.

When the operation mode other than the recording operation is identified from the R / W signal, the recording coil is grounded. When it is determined that a recording operation is being performed, a temporary seek or CSS command is sent when a pulse rises to the error trigger signal, so that the seek or CSS is temporarily grounded with the recording coil grounded. It is done. Thus, the discharge between the magnetic head and the magnetic disk can be stopped and prevented.

[0023]

According to the present invention, unnecessary discharge phenomena between a magnetic head using an MR element and a magnetic disk can be stopped or prevented without changing the structure of the magnetic head.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a magnetic head.

FIG. 2 is a diagram showing a discharge waveform detected from an MR element.

FIG. 3 is a diagram illustrating a difference between a discharge start characteristic and a discharge stop characteristic.

FIG. 4 is a diagram illustrating the effect of seek.

FIG. 5 is an example of the overall configuration of a magnetic disk drive.

FIG. 6 is a configuration example of a discharge countermeasure circuit.

[Explanation of symbols]

Reference Signs List 10 recording coil 11 magnetic core 12 magnetic shield 13 MR electrode 14 MR element 15 slider 16 protective film 18 insulating layer 20 parasitic capacitance between recording coil and magnetic core 21 parasitic resistance between recording coil and magnetic core 22 magnetism Parasitic capacitance between head and magnetic disk 30 Discharge start voltage characteristic 31 Discharge stop voltage characteristic 40 Discharge start voltage characteristic in following state after discharge 41 Discharge start voltage characteristic after seek once after discharge 101 Magnetic head 102 Magnetic disk 103 Spindle 104 Actuator 105 R / WIC 106 Magnetic disk drive control circuit unit 107 Discharge countermeasure circuit.

Continued on the front page (72) Inventor Naoki Kodama 2880 Kofu, Odawara-shi, Kanagawa Storage Systems Division, Hitachi, Ltd.

Claims (2)

[Claims] An operation mode other than a data recording operation in a magnetic disk drive using an R / WIC using a single power supply.
A magnetic disk drive characterized in that during recording, the recording coil was grounded to prevent discharge. 2. In a magnetic disk drive using an R / WIC using a single power supply, a write operation is performed during a data recording operation.
If an error or a discharge waveform is confirmed, the recording coil section is temporarily grounded, and a seek or CSS operation is performed to force the residual charge of the magnetic head to escape to the surface of the magnetic disk. A magnetic disk drive characterized by stopping discharge and preventing re-discharge.