JPH11273016A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of the magnetic disk device by simultaneously obtaining the reproduced output from an MR head or the MR sensor provided in the vicinity of an MR element for a monitoring during the recording of data on a magnetic disk medium. SOLUTION: When thermal asperity signals, which are generated by the contact between the vicinity of an MR sensor section or the vicinity of an MR element section and dust, are detected in amplified reproduced signals while conducting a recording of data by a recording and reproducing control circuit 9, a retrial of the data recording is conducted or a data recording is conducted in an alternative sector. The timing, with which a sense current is generated to monitor the presence or the absence of the intrusion of dust, is preferably matched to the timing of the data recording operation, if a read head is also used as it is. A thermal asperity detecting circuit 6 sets a slice level against the reproduced output from a control section 7 or a drive controller 11. If the level is exceeded, it is recognized that thermal asperity is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive equipped with a magnetoresistive head (MR head) using a magnetoresistive element (MR element) or an MR sensor.

[0002]

2. Description of the Related Art In order to reduce the size and density of magnetic disk drives,
In the actual machine, the slider shape has been reduced in size and the magnetic head has been reduced in flying height, and the frequency of contact between the magnetic head and minute projections or minute dust on the magnetic disk medium has increased.
On the other hand, magnetic heads are also shifting from conventional inductive heads to MR heads utilizing the magnetoresistance effect, which has excellent electromagnetic conversion characteristics. The principle of reading signals from an MR head utilizes the fact that the electric resistance of an MR element, which is a ferromagnetic material, changes due to an external magnetic field from the medium due to the magnetoresistance effect of the MR element.

That is, to reproduce a signal with an MR head, a change in the electric resistance value is taken out as a change in voltage by flowing a sense current, which is a constant current, and is reproduced. Therefore, when there is contact between the magnetic disk medium or dust and the vicinity of the MR head element portion, frictional heat is generated between the MR head and the magnetic disk medium, and the frictional heat causes an abrupt temperature increase in the MR element portion. A rise occurs. As a result, the electric resistance of the MR element also increases, resulting in a change in the DC component of the reproduction signal. This phenomenon is called a thermal asperity phenomenon.

The thermal asperity phenomenon often occurs due to the contact between the vicinity of the MR element and the magnetic disk medium, particularly the minute projection existing on the magnetic disk medium, but the thermal asperity phenomenon floats in the magnetic disk device. In many cases, hard dust or the like is generated by entering between the magnetic head and the magnetic disk medium and coming into contact with the vicinity of the MR element.

Generally, in a conventional magnetic disk drive,
When dust or the like enters between the magnetic head and the magnetic disk medium during the data recording operation, the flying height of the magnetic head, which is a gap between the magnetic disk medium and the magnetic head, may temporarily increase. For this reason, it is not possible to sufficiently magnetize the magnetic disk medium.
Since the reproduction output was locally insufficient, a read error sometimes occurred.

[0006]

Generally, a data recording operation in a magnetic disk drive is realized by moving a head to a predetermined sector position on a magnetic disk and supplying a current to a write head at a certain timing. To confirm whether the data recording operation was performed normally,
It is determined by the recording timing and the confirmation that the write current has flowed, etc. In order to prevent the performance of the magnetic disk drive from deteriorating, it is not confirmed at present whether the data was recorded normally. . That is, it is necessary to detect whether the data recording is normal or not by the MR element after one round of the disk (verification by the MR element during the recording operation depends on the recording current leakage magnetic flux from the magnetic head and the magnetic flux from the disk). It is difficult to distinguish this from the reproduction magnetic flux), which leads to a decrease in performance.

Therefore, for example, dust or the like enters between the magnetic head and the magnetic disk medium during the recording operation, and the floating amount of the magnetic head, which is a gap between the magnetic disk medium and the magnetic head, temporarily rises. Even if the magnetic disk medium cannot be magnetized, it cannot be recognized as a write error. As a result, when data is reproduced from that portion later, the reproduction output is locally insufficient, which may result in a read error.

Generally, in a magnetic disk device equipped with an MR head, performing a reproducing operation by supplying a sense current to the MR head during a data recording operation is, as described above, the noise from the write head and the data recording. It is difficult to realize this due to the influence of leakage magnetic flux at the time, and it has not been actually performed.

An object of the present invention is to eliminate the above-mentioned problems, and to provide a new means for improving the reliability of a magnetic disk drive.

[0010]

In order to solve the above problems, the present invention mainly employs the following configuration.

A magnetic disk medium; a spindle motor for rotating the magnetic disk medium at a constant speed; a write head for recording data on the magnetic disk medium;
A magnetic head comprising an MR head for reproducing data using an element and / or an MR sensor for data detection; and an actuator for positioning the magnetic head at a predetermined position on the magnetic disk medium. A magnetic disk drive for obtaining and monitoring a reproduction output from the MR head or from an MR sensor provided near an MR element at the same time as recording data on the magnetic disk medium.

A magnetic disk medium; a spindle motor for rotating the magnetic disk medium at a constant speed;
A magnetic head comprising a write head for recording data on the magnetic disk medium, an MR head for reproducing data using an MR element, and / or an MR sensor for data detection; and a magnetic head having a predetermined position on the magnetic disk medium. A magnetic disk drive comprising: an actuator for positioning a read head and a read current by supplying a sense current to the MR head or an MR sensor provided near the MR element during a data recording operation by the write head. A magnetic disk drive for detecting a change in the DC level of the reproduction output to detect the occurrence of a thermal asperity phenomenon.

Further, in the magnetic disk device, when the thermal asperity phenomenon is detected, at least one retry of the data recording operation is performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
This will be described below with reference to FIG. Here, 1 is a magnetic disk medium (disk), 2 is a rotating body (motor), 3 is a magnetic head, 4 is an actuator, 5 is a head disk assembly, 6 is a thermal asperity detection circuit, and 7 is a control unit ( Microcomputer, 8 a servo control circuit, 9 a recording / reproduction control circuit, 10 a magnetic disk drive (drive), 11 a drive controller, 12 dust, 13
Is a gap between the magnetic head and the disc (normal), 14 is a gap between the magnetic head and the disc (abnormal), 15 is an MR element, and 16 is M
R sensor, 17 indicates a shield, 18 indicates a shield, and 19 indicates a write head.

The magnetic head 3 includes a magneto-resistance effect element (MR)
Element), a magnetoresistive head (MR head) for reproducing data using an element, an MR sensor for data detection, and a write head including an inductive head.

FIG. 1 shows a magnetic disk drive 10 according to an embodiment of the present invention when dust 12 floating in a head disk assembly 5 enters between a magnetic head 3 and a magnetic disk medium 1. FIG. Although the gap between the magnetic head 3 and the magnetic disk medium 1 is temporary due to the intrusion of dust or the like, the gap extends from 13 to 14 in the figure, and if such a phenomenon occurs during the data recording operation,
It is feared that the magnetic disk medium cannot be sufficiently magnetized.

FIG. 2 shows that in the magnetic disk drive 10 according to the embodiment of the present invention, dust 12 floating in the head disk assembly 5 enters between the magnetic head 3 and the magnetic disk medium 1, Near MR sensor or M
FIG. 7 is a diagram showing a reproduced waveform when a contact is made in the vicinity of an R element portion. Here, FIG. 2A is a normal reproduction waveform diagram, and FIG. 2B is a reproduction waveform diagram in the case of dust intrusion, which is a waveform generally showing a thermal asperity phenomenon. Compared with the normal waveform when there is no contact shown in FIG. 2A, the reproduction output voltage D
It can be seen that the C component fluctuates.

FIG. 3 shows the configuration of the magnetic disk drive. When dust 12 enters between the magnetic head 3 and the magnetic disk medium 1 during data recording, the MR sensor or M
FIG. 6 is a block diagram showing detection of a thermal asperity waveform reproduced by an R element and a method for dealing with the case.

The magnetic head 3 is scanned by the actuator 4 on at least one magnetic disk medium 1 fastened to the rotating body 2 in the radial direction of the magnetic disk medium.
The mechanism 5 including the magnetic disk medium 1, the rotating body 2, the magnetic head 3, and the actuator 4 is called a head disk assembly. The servo control circuit 8 performs scanning control of the magnetic head 3. The concentric positioning signal written in advance in the magnetic disk medium 1 in the head disk assembly manufacturing process is reproduced by the magnetic head 3 during scanning, and the track position is recognized.

Data is recorded in the drive controller 1
1 and a command from the control unit 7 to record / record on the magnetic head 3 whose track positioning is controlled by the above-described method.
This is performed by the reproduction control circuit 9. At this time, the reproduction signal amplified by the recording / reproduction control circuit 9 at the same time is
The signal shown in (b), that is, the thermal asperity signal generated by the contact of the dust or the like with the vicinity of the MR sensor unit or the MR element unit is detected, and if detected, retry data recording as described later. Alternatively, a means for recording data in a replacement sector is used.

When a sense current for monitoring the presence or absence of intrusion of dust or the like during the data recording operation is supplied, the timing is set when the read head is used as it is (the MR for data reproduction).
It is desirable that the element be synchronized with the timing of the data recording operation when the element also serves as an MR sensor for data detection (thermal asperity signal detection). In addition, when a new MR sensor is added and mounted (see FIG. 4C), the magnetic sensor may be constantly flowing while the magnetic disk device is operating. However, from the viewpoint of power consumption, head current life, etc.,
It is desirable to match with the data recording operation timing.

Next, a detection method performed by the thermal asperity detection circuit 6 will be described. Detection circuit 6
Sets at least one slice level for the reproduction output from the control unit 7 or the drive controller 11, and recognizes that a thermal asperity has occurred when the level is exceeded. In this case, the reproduction output is a low-pass filter (LPF: cut-off frequency = about several MHz) or a band-pass filter (BPF: cut-off frequency =) in the recording / reproduction control circuit 9 which passes the frequency component of thermal asperity. Several hundred KHz-several M
(Approximately Hz).

When the thermal asperity is detected in this manner, if the thermal asperity is due to dust floating in the head disk assembly 5, the thermal asperity can be obtained by retrying the recording operation at least twice (write retry). In many cases, the recording operation ends normally and the occurrence of a write error due to intrusion of dust or the like can be avoided. The number of times of retry is desirably about ten times, but it is considered that the number of times may be slightly changed depending on the hardness and size of the floating dust.

If thermal asperity continues to be detected even after retrying several times,
For example, it is considered that this is due to a defect existing on the magnetic disk medium, the sector is unusable, and a method of recording data in a replacement sector under the control of the control unit 7 is desirable. Japanese Patent Laid-Open No. 57-186268 discloses a method of preparing a replacement sector and controlling the defective portion of the magnetic disk medium so as not to use the defective portion.
And JP-A-61-236002.

According to the embodiment of the present invention, preventive measures against device failure such that data recording fails due to the intrusion of dust or the like between the magnetic head and the magnetic disk medium during the data recording operation, resulting in a read error. , A replacement sector is used. After performing the series of operations, a data reproducing operation may be performed to confirm whether data recording has been performed normally. Of course, a write error due to intrusion of dust or the like should be prevented by always performing a reproducing operation after data recording and confirming whether data recording was normally performed.

Next, a method for realizing an MR sensor for detecting thermal asperity will be described with reference to FIG. FIG.
(A), (b) and (c) are cross-sectional views of the element portion of the magnetic head. FIG. 4A shows a magnetic head including an inductive write head 19 and a general MR head on which the MR element 15 is mounted. In this magnetic head, when data is recorded, a sense current may be applied to the MR element at the same time to perform a monitoring operation (reproduction operation) for dust and the like, but the reproduction is slightly affected by a magnetic flux leaking from the write head 19 and noise. It will be difficult.

On the other hand, FIG. 4B shows a case in which a shield 18 is mounted between the write head 19 and the MR element 15 so that the MR element is hardly affected by the data recording operation from the write head. Shield 17 and shield 1 shown
8 may be connected at the upper part, and it is desirable to use CoNbZr or the like as the material. By doing so, actually S / N
Although it is difficult to reproduce data due to such problems as above, it is possible to detect the presence or absence of thermal asperity caused by the intrusion of dust or the like (the MR element 15 is used as an MR sensor).

FIG. 4C shows a case in which an MR sensor 16 is newly added to the general head shown in FIG. Also in this case, it is desirable to adopt a structure surrounded by the shield 17 in order to make it less susceptible to the data recording operation. In order to take this structure, it is desirable to prepare two MR driving circuits (reproducing circuits) in the recording / reproducing control circuit. However, when a sense current is supplied to the MR sensor 16 during the data recording operation, A case where a sense current is supplied to the MR head 15 during the data reproducing operation may be distinguished, and the switching may be performed by one drive circuit. Also,
The mounting position of at least one MR sensor is shown in FIG.
Is located on the left side of the write head 19, but may be mounted on the right side in the figure. It is desirable that the MR sensor be mounted widely in the radial direction (track direction) of the disk in order to increase the sensitivity of determining the intrusion of dust or the like.

As described above, the embodiment of the present invention adds a function of detecting thermal asperity during a data recording operation. If a function is detected, dust or the like is placed between the magnetic head and the magnetic disk medium. Is determined to have entered,
This is to provide a method of retrying the recording operation to prevent a write error from occurring. By doing so, it is possible to prevent a write error due to intrusion of dust between the magnetic head and the magnetic disk medium during a data recording operation of the magnetic disk device, that is, a magnetic disk device failure due to data loss, and prevent the magnetic disk device from malfunctioning. The reliability of the device can be improved.

[0030]

In the magnetic disk device, dust or the like enters between the magnetic head and the magnetic disk medium during the data recording operation, and the flying height of the magnetic head is temporarily increased to sufficiently magnetize the magnetic disk medium. Even if you ca n’t,
It cannot be recognized as a write error. As a result, when data is reproduced from that portion later, since the reproduced output is locally insufficient, a read error occurs and a device failure occurs.

According to the present invention, it is possible to prevent a write error due to dust intrusion between the magnetic head and the magnetic disk medium, that is, a device failure due to data loss during a data recording operation at the time of operating the magnetic disk apparatus. Reliability is improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram when dust enters between a magnetic head and a magnetic disk medium.

FIG. 2 is a diagram showing reproduction waveforms in a normal state and when a thermal asperity occurs.

FIG. 3 is a block diagram showing a thermal asperity detection and operation control method.

FIG. 4 is a diagram showing an MR head element, an MR sensor, a write head, and a shield constituting a magnetic head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic disk medium (disk) 2 Rotating body (motor) 3 Magnetic head 4 Actuator 5 Head disk assembly 6 Thermal asperity detection circuit 7 Control part (microcomputer) 8 Servo control circuit 9 Recording / reproduction control circuit 10 Magnetic disk device (Drive) 11 Drive controller 12 Dust 13 Magnetic head-disc gap (normal) 14 Magnetic head-disc gap (abnormal) 15 MR element 16 MR sensor 17 Shield 18 Shield 19 Write head

Claims (4)

[Claims] A magnetic disk medium; a spindle motor for rotating the magnetic disk medium at a constant speed; a write head for recording data on the magnetic disk medium;
A magnetic disk drive comprising: a magnetic head comprising an MR head for reproducing data using an R element and / or an MR sensor for data detection; and an actuator for positioning the magnetic head at a predetermined position on the magnetic disk medium And simultaneously recording data on the magnetic disk medium,
MR provided from the MR head or in the vicinity of the MR element
A magnetic disk drive which obtains and monitors a reproduction output from a sensor. 2. A magnetic disk medium, a spindle motor for rotating the magnetic disk medium at a constant speed, a write head for recording data on the magnetic disk medium,
A magnetic disk drive comprising: a magnetic head comprising an MR head for reproducing data using an R element and / or an MR sensor for data detection; and an actuator for positioning the magnetic head at a predetermined position on the magnetic disk medium The data recording operation by the write head;
To the head or to the MR sensor provided near the MR element,
A magnetic disk drive, wherein a reproduction output is obtained by flowing a sense current, and a change in the DC level of the reproduction output is detected to detect occurrence of a thermal asperity phenomenon. 3. The magnetic disk drive according to claim 2, wherein at least one retry of the data recording operation is performed when the thermal asperity phenomenon is detected. 4. The magnetic disk drive according to claim 2, wherein when the thermal asperity phenomenon is detected, the thermal asperity phenomenon is detected even after retrying the data recording operation a specified number of times. A magnetic disk drive, wherein data is recorded in alternate sectors of the magnetic disk medium.