JPH0785409A - Magnetic recording / reproducing apparatus and data reading method - Google Patents

Abstract

(57) [Summary] [Object] It is an object of the present invention to eliminate the reduction of the reproduction output level from the head at low temperature, and to prevent the deterioration of the S / N ratio due to the distortion of the waveform, thereby causing the read error. It is an object of the present invention to provide a magnetic recording / reproducing apparatus capable of preventing the above-mentioned problem. The HDC 3 executes error detection processing of read data from a read signal from the head 1 during a read operation. When the read error is detected, the CPU 4 outputs a control signal HU for switching the current value of the write current. The write current switching circuit 5 supplies the write current increased from the normal current value to the coil of the head 1 according to the control signal HU. As a result, the core temperature of the head 1 rises, and as a result, the reproduction output level of the head 1 increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing device such as a hard disk device.

[0002]

2. Description of the Related Art Conventionally, a hard disk device (HDD)
Has a head for reading / writing data from / to a recording medium (disk). The head 1 is shown in FIG.
As shown in the side view of FIG. 9A and the plan view of FIG. 9B, the actuator 10 is supported by the actuator 10 and moves in the radial direction on the disk as the actuator 10 is rotationally driven. The actuator 10 is configured to be rotationally driven in the radial direction of the arrow 11 about the rotation shaft 10a by a voice coil motor (VCM) not shown. Further, the actuator 10 has a signal line 10b that connects the head 1 and a read / write circuit (R / W circuit) (not shown). R / W circuit is a head IC
Which is an integrated circuit referred to as, and processes a read signal from the head 1 or a write signal (write current) to the head 1.
Supply.

The head 1 is a thin film head, for example. As shown in FIG. 6 (a side view in FIG. 6A, a plan view in FIG. 6B and a front view in FIG. 6C), the thin film head is
The slider 12 and the magnetic thin film 13 formed on the side surface of the slider 12 are included. As shown in FIG. 6C, the magnetic thin film 13 includes a core 13c having a magnetic gap 13a and a coil 13b. The slider 12 has a flat surface 12b facing the disk surface, as shown in FIG.
It is a head main body that floats by receiving the pressure of the air flow accompanying the rotational drive of the disk. In the slider 12, a flat surface 12b facing the disk surface is processed into a convex shape called a crown 12a. Here, in the plane 12b of the slider 12, the height to the top of the crown 12a with respect to the reference plane parallel to the disk surface is the crown amount CL.
It is defined as

The crown amount CL changes the flying height when the head 1 is positioned on the disk. To be precise, the flying height is the distance between the surface of the disk and the magnetic gap 13a. Therefore, when the crown amount CL increases, the flying height increases, and the magnetic gap 13a is relatively separated from the disk surface. On the contrary, when the crown amount CL becomes smaller, the flying height decreases and the magnetic gap 1
3a relatively approaches the disk surface.

By the way, it is well known that the shape of the crown and the amount of crown vary depending on the temperature change, although there is some variation depending on the coefficient of thermal expansion of the material of the slider 12 and the processing strain of the crown. Normally, as shown in FIG. 9 (B), the crown amount CL decreases as the temperature rises (therefore, the flying height decreases), and conversely the crown amount CL increases as the temperature lowers (see FIG. 9B). Therefore, the flying height tends to increase. When the flying height of the head 1 changes as the crown amount CL changes, the head output (read signal level) naturally changes.

Specifically, as shown in FIG. 7, when the head output at high temperature is compared with the head output at low temperature, the change in resolution becomes very large. Here, the resolution is the ratio of the head output at the lowest frequency LF and the head output at the highest frequency HF. If the resolution is lowered, the peak shift of the read signal is increased during the read operation, and the read error is more likely to occur. That is, at a low temperature, the resolution is lowered and the read error tends to occur easily.

[0007]

In the conventional head, the amount of crown of the slider, which affects the flying height, fluctuates due to temperature changes. In particular, when the temperature is lowered, the crown amount is increased accordingly, and the floating amount is increased. For this reason, the resolution is lowered, the reproduction output level from the head is reduced, and a read error tends to occur. In order to eliminate such a defect, a boost (boos) for amplifying a high frequency band of a read signal by a filter is used.
There is a method of compensating for the deterioration of resolution at low temperature by the circuit t) or the waveform equalization circuit. However, in such a method, there is a problem in that all high frequencies of the read signal waveform are amplified, waveform distortion occurs, and the reproduction output S / N ratio deteriorates.

An object of the present invention is to eliminate the reduction of the reproduction output level from the head at a low temperature, and to prevent the occurrence of a read error without causing the deterioration of the S / N ratio due to the generation of the waveform distortion. An object of the present invention is to provide a magnetic recording / reproducing apparatus capable of performing the magnetic recording and reproducing.

[0009]

The first aspect of the present invention is to provide head means having a slider whose crown amount varies with temperature changes, error detecting means for executing error detection processing of read data, and the extent to which the crown amount varies. The magnetic recording / reproducing apparatus is provided with write current switching means for increasing the write current.

A second aspect of the present invention is to provide a head means having a slider whose crown amount fluctuates due to a temperature change, an error detecting means for executing error detection processing of read data, and a write for increasing the write current to the extent that the crown amount fluctuates. The magnetic recording / reproducing apparatus is provided with a retry unit for re-executing the read operation by the current switching unit and the head unit.

[0011]

According to the first aspect of the present invention, the error detecting means executes the error detecting process of the read data reproduced from the read signal output from the head means during the read operation. The write current switching means, when an error of the read data is detected by the error detection means, increases the current value of the write current to a normal value to such an extent that the crown amount fluctuates, and the increased write current is applied to the head. Supply to the coil of means.

In the second aspect of the present invention, the error detecting means executes an error detecting process of read data reproduced from the read signal output from the head means during the read operation. The write current switching means, when an error of the read data is detected by the error detection means, increases the current value of the write current to a normal value to such an extent that the crown amount fluctuates, and the increased write current is applied to the head. Supply to the coil of means. The retry means re-executes the read operation by the head means after the write current is supplied to the coil by the write current switching means.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a read / write circuit of an HDD according to the same embodiment and a main part around it, FIG. 2 is a block diagram showing a configuration of a write current switching circuit 5 according to the embodiment, and FIG. FIG. 4 is a block diagram showing the main part of the HDD according to the example, and FIG. 4 is a flow chart for explaining the operation of the same embodiment.

As shown in FIG. 3, the HDD has a single or a plurality of disks 6 and a head 1 for reading / writing data from / to the disks 6. The head 1 has a slider 12 as shown in FIG.
The magnetic gap 13a, the core 13c, and the coil 1 on the side surface of the
3b is a thin film head on which each is formed. In the slider 12, the flat surface 12b facing the disk 6 is processed into a convex shape called a crown 12a. Crown amount C
As shown in FIG. 9B, L has a variation characteristic with respect to a temperature change.

The disk 6 is rotated by a spindle motor 9. Spindle motor 9 is motor driver 10
The drive is controlled by the CPU 4 via the. CPU4
It is a control microcomputer for controlling the motor driver 10 and the VCM driver 8. VCM driver 8
Drives a voice coil motor (VCM) 7. VCM
As shown in FIG. 5, the reference numeral 7 rotationally drives the actuator 10 supporting the head 1 to move the head 1 to the disk 6 by rotating.
Move in the radial direction.

The read / write (R / W) circuit 2 is a constituent element according to the gist of the present invention, and supplies a write current to the head 1 and receives a read signal from the head 1 to a read system circuit. It is a head IC (integrated circuit) for outputting. The read system circuit is a circuit for reproducing read data from a read signal from the head 1, and includes an automatic gain control amplifier (AGC) 11 and a low pass filter (LPF) 1.
2, pulse generation circuit 13, PLL circuit 15, delay circuit 16, data separator 7 and encoder / decoder (EN
DEC) 18. The ENDEC 18 demodulates the data pulse output from the data separator 7 into, for example, an NRZ signal of the NRZ recording modulation method, and outputs the NRZ signal to the HDC 3.

The LPF 12 is an element constituting a filter system (for example, including a boost circuit etc.) for removing noise of the read signal from the AGC 11. The servo circuit 14 is
Servo signal (burst signal) output from the LPF 12
Is received, a positioning control signal for the head 1 is generated and output to the CPU 4. The HDC 3 is a hard disk controller that forms an interface between the host computer and the HDD. The HDC 3 receives the NRZ signal from the ENDEC 18 and transfers the reproduced data after the ECC check processing to the host computer. Also, HD
The C3 receives the write data transferred from the host computer and outputs it to the ENDEC 18. ENDEC
Reference numeral 18 generates write data WD obtained by modulating the write data from the HDC 3 into an NRZ signal and outputs the write data WD to the R / W circuit 2. The HDC 3 has a write gate signal W during a write operation.
G is output to the R / W circuit 2. The buffer RAM 19 is
The HDC 3 is a buffer memory used when exchanging read / write data with the host computer.

In the present invention, as shown in FIG. 1, a write current switching circuit 5 for switching the write current WC of the R / W circuit 2 is provided. The write current switching circuit 5 has a C
When the control signal (heat up signal) HU from the PU 4 is significant (logic level “H”), the write current WC having a current value larger than the normal current value flows from the R / W circuit 2 to the coil of the head 1. It is a circuit for switching.

As a concrete example, the write current switching circuit 5 has a write current terminal W of the R / W circuit 2 as shown in FIG.
It is composed of a circuit having a transistor 20 and a parallel circuit of resistors R1 and R2 connected between C and ground. Transistor 2
0 is turned on when the control signal HU from the CPU 4 is significant and forms a parallel circuit of the resistors R1 and R2. That is, the resistance value of the circuit is reduced and the write current value is increased by the parallel resistance circuit including the resistors R1 and R2. When the control signal HU is invalid (logic level "L"), the transistor 20 is turned off and the resistor R2 is cut off.
Therefore, the resistance value (R1) of the circuit relatively increases,
The write current value decreases to the normal current value.

The R / W circuit 2 is, as shown in FIG.
Various interface signals are exchanged with C3. The interface signal WUS is a write unsafe signal and is output when the HDC 3 detects an error in the read signal by the ECC check processing. The interface signal WG is a write gate signal and determines the timing of the write operation. Interface signal RD
Is a read signal from the head 1. The interface signal HS is a head select signal. The interface signal WD is write data. The interface signal CS is a chip select signal.

Next, the operation of the embodiment will be described. Since the present invention relates only to the read operation, the description of the write operation will be omitted. First, as shown in step S1 of FIG. 4, during the read operation, the head 1 drives the disk 6
The data is read from, and the read data is reproduced by the read system circuit shown in FIG. That is, as shown in FIG. 1, the read signal output from the R / W circuit 2 is reproduced into read data RD by the read system circuit and output to the HDC 3. Here, in the head 1, the VCM 7 is driven and controlled by the servo circuit 14 and the CPU 4,
The read operation is executed by moving to the target cylinder on the disk 6.

The HDC 3 executes an ECC check process for the received read data RD and determines whether a read error has occurred (step S2). This ECC
If a read error is detected by the check process, CP
U4 controls to move the head 1 to a predetermined position which is a predetermined cylinder or CSS zone (YES in step S3, S4). Further, the CPU 4 outputs a control signal HU for switching the write current WC.

The write current switching circuit 5 supplies the write current WC increased from the normal current value from the R / W circuit 2 to the coil of the head 1 in response to the significant control signal HU from the CPU 4 (step S5). . At this time, the HDC 3 outputs the write gate signal WG for a predetermined time. The write current flows through the coil of the head 1 only during the output time of the write gate signal WG. Write gate signal W
The predetermined time of G is preset by the heat capacity of the head 1 and the temperature rise characteristic of the core.

When a write current flows through the coil of the head 1, the core temperature of the head 1 rises depending on the current value and the energization time. Specifically, as shown in FIG. 9A, for example, when the normal write current value is 40 mA and the write current value is increased to 50 mA, the core temperature of the head 1 is the same for the same energization time. It will rise relatively. When the core temperature of the head 1 rises, the ambient temperature of the head 1 changes, and the crown amount CL of the slider 12 changes. That is, as shown in FIG. 9B, when the temperature rises, the crown amount CL decreases. Therefore, the flying height of the head 1 becomes small, and the reproduction output of the head 1 becomes relatively large. Specifically, as shown in FIG.
The output level of the head 1 (that is, the read signal level) is
It increases with increasing core temperature.

When a predetermined time of the write gate signal WG, that is, an energizing time of the increased write current has passed for a set time, the CPU 4 invalidates the control signal HU and switches the write current switching circuit 5 to a normal current value (step). YES in S6, S7). The CPU 4 moves the head 1 to the target cylinder where the read error has occurred (step S
8). Then, the retry operation for re-executing the read operation by the head 1 is executed (step S9). HDC3
Is the EC for the read data RD due to the retry operation.
The C check process is executed to determine whether a read error has occurred (step S10). If a read error is detected again by this ECC check processing, HDC
3 executes an error process prepared in advance (step S1)
3). If no read error is detected, the process moves to the next read operation or write operation (step S12).

In this way, according to the present invention, when a read error is detected during the read operation, the read operation is temporarily stopped and the current value of the write current WC is increased above the normal value, and the coil 13b of the head 1 is increased. Supply to. By supplying this coil current, the core temperature of the head 1 is raised.
Therefore, the crown amount CL of the slider 12 can be reduced, the flying height of the head 1 can be reduced, and the reproduction output level of the head 1 can be increased.

Utilizing such a variation characteristic of the crown amount due to the temperature change, the reproduction output of the head 1 is increased when a read error is detected, and the retry operation is executed. At the time of this retry operation, the reproduction output of the head 1 is increased and the resolution is improved. Therefore, it is highly possible that the occurrence of the read error at the time of the read operation can be eliminated. In other words, H
When the ambient temperature of the DD is low, it is possible to eliminate the occurrence of a read error caused by the reduction of the reproduction output level from the head.

When the core 1 is heated by heating the head 1 by increasing the write current WC, the head 1 is heated.
FIG. 8B shows the experimental result showing the change in the reproduction output of the.
As is clear from the experimental result shown in FIG. 8B, the reproduction output level of the head 1 can be increased by increasing the core temperature of the head 1.

[0029]

As described in detail above, according to the present invention, the reproducing output level from the head can be increased when a read error is detected by utilizing the variation characteristic of the crown amount of the slider with the temperature change. You can Therefore, it is possible to reliably eliminate the occurrence of a read error due to the reduction of the reproduction output level due to the low temperature, without causing the deterioration of the S / N ratio due to the distortion of the waveform of the read signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a read / write circuit of an HDD according to an embodiment of the present invention and a main part around the circuit.

FIG. 2 is a block diagram showing the configuration of a write current switching circuit 5 according to the same embodiment.

FIG. 3 is a block diagram showing a main part of the HDD according to the embodiment.

FIG. 4 is a flowchart for explaining the operation of the embodiment.

FIG. 5 is a diagram showing a structure of a head according to the embodiment.

FIG. 6 is a view showing the structure of a slider according to the embodiment.

FIG. 7 is a characteristic diagram showing the relationship between the conventional temperature and the reproduction output of the head.

8A is a characteristic diagram showing a relationship between a core temperature and a reproduction output of the head according to the embodiment, and FIG. 8B is a diagram showing an experimental result of the embodiment.

9A is a characteristic diagram showing a relationship between a current energization time of a coil and a core temperature according to the embodiment, and FIG. 9B is a characteristic diagram showing a relationship between a head temperature and a crown amount.

[Explanation of symbols]

1 ... Head, 2 ... R / W circuit, 3 ... HDC, 4 ... CP
U, 5 ... Write current switching circuit, 6 ... Disc.

Claims (4)

[Claims] 1. A write current supplied to a coil, comprising a slider having a crown formed on a side facing a recording medium, the crown amount of which fluctuates due to a temperature change, the recording magnetic field of the recording medium being converted into a read signal. A head means for converting write data into the recording magnetic field by means of; an error detecting means for executing an error detecting process of read data reproduced from the read signal outputted from the head means during a read operation; and the error detecting means. When an error in the read data is detected, the current value of the write current is increased to the extent that the crown amount fluctuates as compared with a normal value, and the increased write current is applied to the coil of the head means. A magnetic recording / reproducing apparatus comprising: a write current switching means for supplying. 2. A write current supplied to a coil, comprising a slider having a crown formed on a side facing a recording medium and having a crown amount fluctuated by a temperature change, the recording magnetic field of the recording medium being converted into a read signal. A head means for converting write data into the recording magnetic field by means of; an error detecting means for executing an error detecting process of read data reproduced from the read signal outputted from the head means during a read operation; and the error detecting means. When an error in the read data is detected, the current value of the write current is increased to the extent that the crown amount fluctuates as compared with a normal value, and the increased write current is applied to the coil of the head means. Write current switching means to be supplied, and after the write current is supplied to the coil by the write current switching means, A magnetic recording / reproducing apparatus comprising: a retry unit for re-executing the read operation by the head unit. 3. A write current supplied to a coil, which comprises a slider having a crown formed on a side facing a recording medium, the crown amount of which fluctuates due to a temperature change, the recording magnetic field of the recording medium being converted into a read signal. In a magnetic recording / reproducing apparatus equipped with a head means for converting write data into the recording magnetic field by means of: a step of reproducing read data from the read signal read by the head means during a read operation; A step of performing an error detection process of the read data, and a degree of fluctuation of the crown amount by comparing a current value of the write current with a normal value when an error of the read data is detected by the error detection process. And supplying the increased write current to the coil of the head means. After increased the write current is supplied to the coil, the data reading method characterized by comprising a step of re-executing the read operation by the head unit. 4. A write current supplied to a coil, which comprises a slider having a crown formed on a side facing a recording medium, the crown amount of which fluctuates due to temperature change, the recording magnetic field of the recording medium being converted into a read signal. In a magnetic recording / reproducing apparatus equipped with a head means for converting write data into the recording magnetic field by means of: a step of reproducing read data from the read signal read by the head means during a read operation; A step of performing an error detection process of the read data, and a degree of fluctuation of the crown amount by comparing a current value of the write current with a normal value when an error of the read data is detected by the error detection process. And supplying the increased write current to the coil of the head means. A method for reading data, comprising: