JP2004079126A - Magnetic disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk device in which reproduction errors caused at a low temperature by equivalent magnetic spacing between a magnetic disk and a magnetic head are reduced, simultaneously a head medium crash which occurs between the magnetic head and the magnetic disk in the magnetic disk device for which recording density is increased especially is prevented and a using temperature range is enlarged while securing high reliability and high stability. <P>SOLUTION: On the magnetic disk device 100, a head floating height control part 27 which executes a preceding pseudo recording (PDW) operation under a low temperature environment is loaded. Also, it is provided with a function of executing a series of operations of low temperature error judgement, recess amount control by the preceding pseudo recording (PDW) operation, normal read and write back. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic disk drive for recording or reproducing information signals on a magnetic disk.
[0002]
[Prior art]
In recent years, the recording density of a magnetic disk device has been increasing year by year, and although the density has been slightly decreasing, the momentum has not yet declined. In addition, while the focus has been on the competition for recording density and storage capacity, additional factors such as high reliability and high stability have been focused on. In addition, the magnetic disk device is not only positioned as an auxiliary storage device of a computer, but has also begun to enter into other fields such as application to a car navigation system and audio equipment.
[0003]
Under these circumstances, in conventional conventional development, research has been made on how to narrow the gap between the magnetic disk and the magnetic head as one method of improving the recording density.
[0004]
If the flying height of the magnetic head from the surface of the magnetic disk is simply reduced, the direction of development is relatively easy. However, the flying height of a magnetic head includes physical spacing and magnetic spacing. As the physical spacing is reduced, the gap between the magnetic disk and the magnetic head becomes narrower. The risk of an accident that leads to physical destruction of data, that is, a so-called magnetic head / magnetic disk failure problem (called Head Media Interference (HDI)) is acceleratingly increasing.
[0005]
Therefore, how to reduce the magnetic spacing and at the same time, ensure the reliability and stability has been increasingly attracting attention as a technical problem required for the magnetic disk device in the future.
[0006]
In addition, as the recording density has been increasing, the use range has expanded to the automobile industry field and the home appliance field other than the computer field as described above, and accordingly, the use environment temperature range of the magnetic disk drive has also been expanded. I have.
[0007]
For example, the operating environment temperature assurance range of a conventional magnetic disk device for a general personal computer is + 5 ° C. to + 80 ° C., whereas a magnetic disk device mounted on an automobile is −40 ° C. to + 80 ° C. It is an unusual extreme operating environment temperature range such as temperature.
[0008]
Under such an operating temperature environment, a new problem arises.
[0009]
As a major new problem, there is a problem of a flying height of the magnetic head due to a temperature change of a recess amount of the magnetic head described below. The problem caused by the temperature change of the recess amount is that the head slider is depressed from an ABS (Air Bearing Surface) surface that is in contact with the magnetic disk so that the recording / reproducing portion of the magnetic head does not directly collide with the magnetic disk. This is a problem related to the protrusion of the (recess) portion, which is a so-called magnetic head / magnetic disk failure (called Head Media Interference (HDI)) that occurs as a result of a collision between a magnetic head and a projection of a magnetic disk.
[0010]
Hereinafter, the problem related to the change in the recess amount will be described with reference to the drawings.
[0011]
FIG. 9 is an enlarged schematic diagram of a main part showing a state where the magnetic head main body part is recessed from the head slider surface and a state where the surface part of the magnetic disk has irregularities.
[0012]
As shown in FIG. 9, since the material used for the magnetic head main body 3b and the material used for the head slider 3c are different from each other, the recessed portion 3a has a difference in expansion coefficient depending on temperature, and has Change. In particular, experimental results show that when the temperature rises, the recess 3a tends to approach from the design position A to a position such as a position B indicated by a broken line.
[0013]
FIG. 3 shows actually measured data showing the fluctuation of the recess with respect to the temperature. As shown in FIG. 3, for example, the fluctuation of the recess at a temperature lower than the normal temperature (−40 ° C.) extends to 5 nm.
[0014]
In the prior art, even if the environmental temperature becomes high and the recess 3a approaches the position B, the magnetic head 3 contacts the protrusion 1b of the magnetic disk 1 so that the magnetic disk 1 crashes. The point of design is to form a recess to such an extent that the magnetic head 3 does not change the magnetoresistance of the magnetic head caused by the magnetic head 3 hitting the protrusion 1b of the magnetic disk 1.
[0015]
For these reasons, the overall design of the magnetic head 3 is designed so that the recess amount α is as large as possible from the viewpoint of the magnetic head / magnetic disk failure problem, and the flying height β from the magnetic disk surface 1a is as low as possible. Has been done.
[0016]
However, since the head slider 3c and the magnetic head main body 3b are formed of different materials as described above, the recess 3a approaches the position B at a high temperature due to environmental temperature or temperature change of the head slider 3c. On the other hand, when the temperature becomes low, a phenomenon occurs in which the wire is retracted to the position C indicated by the broken line.
[0017]
As a result, when used at an extremely low temperature such as when mounted on an automobile, the recess of the recess may cause a problem of magnetic disk reproduction error (BER performance).
[0018]
However, at the present stage of the above-mentioned situation, there is no example in which a measure for preventing a magnetic head / magnetic disk failure problem and a measure for improving BER performance are compatible. This is because the BER performance cannot be improved unless the flying height of the magnetic head is reduced, which are mutually contradictory characteristics.
[0019]
The solution to the above-described problem is a major problem in further increasing the recording density.
[0020]
[Problems to be solved by the invention]
Although the nominal value of the flying height of the conventional magnetic head is about 10 nm, if the recess fluctuation amount is as large as 5 nm as described above, even if the crisis of the magnetic head / magnetic disk failure problem can be eliminated, There has been a problem that the possibility of frequent reproduction errors of the magnetic disk is included.
[0021]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a magnetic disk drive having a magnetic head provided with a recess, data reproduction by an equivalent increase in magnetic spacing particularly caused by recession of the recess at a low temperature. It is an object of the present invention to provide a magnetic disk device which has an effect of reducing errors and at the same time preventing a magnetic disk from crashing by a magnetic head, and which is highly reliable, highly stable, and capable of expanding a use environment temperature.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, a magnetic disk device of the present invention includes a magnetic disk as a magnetic recording / reproducing medium, a spindle motor for rotating the magnetic disk, and recording information on the magnetic disk. And a magnetic head for performing reproduction, an actuator arm for mounting and rotating the magnetic head, a voice coil motor for magnetically driving the actuator arm, and a base plate for mounting these constituent members, In a magnetic disk drive comprising a top cover forming a package with the base plate, a temperature detecting means for detecting a temperature inside the magnetic disk drive and outputting the temperature data, and corresponding to an operating environment temperature of the magnetic head. Then, data indicating the physical variation amount of the recessed portion of the magnetic head was stored A degree-recess amount correlation table, and a reference data table in which a reference recess amount of the recess portion is stored in correspondence with the operating environment temperature, based on the temperature data output from the temperature detecting means, Calculating the recess amount for the temperature from the recess amount correlation table, comparing the obtained recess amount with the reference recess amount for the temperature obtained from the reference data table, and comparing the difference in the recess amount obtained from the comparison; The recess amount of the magnetic head is controlled based on data.
[0023]
Further, the magnetic disk device of the present invention estimates the flying height of the magnetic head from the data of the recess amount for the temperature obtained from the temperature-recess amount correlation table, and the estimated flying height is the reference recess amount. If the height is higher, a pseudo dummy recording operation is performed to raise the temperature of the recessed portion of the magnetic head, thereby controlling the amount of recess, and making the flying height appropriate.
[0024]
Further, in the magnetic disk device of the present invention, the magnetic space between the magnetic head and the magnetic disk surface is temporarily reduced by generating heat in the magnetic head by performing the preceding pseudo recording operation. It is characterized by.
[0025]
Further, the magnetic disk apparatus of the present invention is characterized in that before performing the preceding pseudo recording operation, the magnetic head is temporarily moved to an unload position to perform the preceding pseudo recording operation.
[0026]
Further, the magnetic disk device of the present invention provides a dedicated area for the preceding pseudo-recording operation at a predetermined position on the magnetic disk as an area for performing the preceding pseudo-recording operation, and executes the preceding pseudo-recording operation. Further, the preceding pseudo recording operation is performed by temporarily moving the magnetic head to the predetermined position.
[0027]
Further, the magnetic disk device of the present invention is characterized in that when performing the preceding pseudo recording operation at the unload position or the operation-dedicated area, recording is performed with a recording current larger than a normal recording current.
[0028]
According to the present invention, since the function of optimizing the flying height of the magnetic head by controlling the recess amount of the magnetic head by detecting the temperature inside the magnetic disk device and reproducing the magnetic disk even in a low temperature environment is provided. Errors can be reduced, and even in a magnetic disk device with a high recording density, it is possible to prevent a magnetic disk from crashing due to a magnetic head, and a highly reliable magnetic disk device with a high recording density can be realized.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0030]
FIG. 1 is a block diagram showing a main part of a magnetic disk drive according to an embodiment of the present invention. FIG. 2 is a block diagram showing a main part of a head flying height control unit which is a core of the present invention.
[0031]
1 and 2, the magnetic disk drive 100 includes a mechanism unit 10 having a head assembly unit provided with a head amplifier unit (HA) 6 and a control unit 20 for controlling the mechanism unit 10. The control unit 20 is connected by an interface signal line 60 for transmitting and receiving a control signal from a host system 50 such as a PC.
[0032]
The mechanism unit 10 includes a magnetic disk 1 serving as a magnetic recording medium, a spindle motor (SPM) 2 for rotating the magnetic disk 1 at a high speed, and a unit for recording and reproducing recorded information on the magnetic disk 1. A magnetic head 3 comprising a recording head and a reproducing head; an actuator arm 4 attached to the tip of the magnetic head 3 to rotate on the surface of the magnetic disk 1; and a drive source for rotating the actuator arm 4 A voice coil motor (VCM) 5 and a head amplifier (HA) 6 for transmitting and receiving recording and reproduction signals between the controller 20 and the magnetic disk 1 is not rotating at a steady speed. Meanwhile, a ramp mechanism 7 for retracting the magnetic head 3 from above the surface of the magnetic disk 1 is provided.
[0033]
The head amplifier (HA) 6 has a recording amplifier for supplying a recording current to the recording head 3 and a reproduction amplifier for amplifying a reproduction signal from the reproduction head.
[0034]
The head amplifier (HA) 6 is provided with a temperature sensor 6 a for detecting an environmental temperature near the magnetic head 3, and outputs temperature data detected by the temperature sensor 6 a according to an instruction from the control unit 20. Further, the head amplifier (HA) 6 has a register (not shown) for setting a current value of the recording current, and this register is accessed by a CPU / control logic unit 26 described later. I have.
[0035]
The control unit 20 transmits an information signal line 30 for transmitting and receiving an information signal necessary for recording and reproduction to and from the magnetic disk 1 and a motor control signal for the spindle motor (SPM) 2 and the voice coil motor (VCM) 5. It is connected to the mechanism section 10 by a control signal line 40 for performing transmission and reception.
[0036]
The control unit 20 includes a reproduction / recording (R / W) channel 21, a hard disk controller (HDC) 22, a VCM / SPM control unit 23, and a nonvolatile IC memory on a printed circuit board (PCB) (not shown). (EEPROM) 24, a buffer memory (DRAM) 25, a CPU / control logic unit (hereinafter referred to as CPU) 26, and a head flying height control unit 27 are mounted.
[0037]
The reproduction / recording (R / W) channel 21 is a processing unit for a reproduction / recording signal, and has an encoder function for encoding recording data transferred from the host system 50 and reproduction data from the reproduction signal read by the reproduction head. It has a decoder function of decoding (RD).
[0038]
The hard disk controller (HDC) 22 receives the recording data (WD) and the command transferred from the host system 50 via the interface signal line 60, and sends the reproduction data read from the magnetic disk 1 and reproduced to the host. It has a data transfer function for transferring data to the system 50. In addition to the interface function and the data transfer control function, the hard disk controller (HDC) 22 has an ECC (Error Correction Code) function of reproduced data.
[0039]
The VCM / SPM control unit 23 controls the drive of the spindle motor (SPM) 2 and the voice coil motor (VCM) 5 under the control of the CPU 26 and supplies a drive current.
[0040]
A non-volatile IC memory (EEPROM) 24 is a memory for storing various data necessary for control processing of the CPU 26, and stores a recording current value related to the embodiment, and error information indicating an error pattern and an error rate. are doing.
[0041]
The buffer memory (DRAM) 25 is a memory for temporarily storing reproduction / recording data that is transfer-controlled by the hard disk controller (HDC) 22.
[0042]
The CPU 26 is composed of a microprocessor (CPU) and a logic circuit constituting a main control device of the magnetic disk device 100, and has a function of controlling a recording current value of the magnetic head 3 related to the embodiment other than various control processes. have.
[0043]
The control unit 20 includes a head flying height control unit 27 having a function essential to the present invention. The head flying height control unit 27 functions as a part of the CPU 26 in cooperation with the CPU 26.
[0044]
FIG. 2 is a block diagram showing a detailed configuration of the head flying height control unit 27. 2, the head flying height control unit 27 includes a temperature-recess conversion unit 201, a temperature-recess dependency table 202, a comparison determination unit 203, a determination criterion data table 204, a recess amount estimation unit 205, a recess amount It is composed of the main parts of a control unit 206 and a low temperature error limit determination unit 207, and has the following functions.
[0045]
The temperature-recess conversion unit 201 receives the temperature data measured by the temperature sensor 6a via the head amplifier (HA) 6, and converts the transmitted temperature data based on a temperature-recess dependency table 202 described later. It has a function of calculating the amount of recess at the measured temperature.
[0046]
The temperature-recess dependency table 202 is data stored in a memory table in advance when the magnetic disk 100 is manufactured, and is correlation data indicating a relationship between the temperature near the magnetic head and the recess amount. That is, the recess amount is stored here corresponding to each temperature (for example, −40 ° C. to 80 ° C.).
[0047]
The comparison determination unit 203 has a function of comparing the recess amount data sent from the temperature-recess conversion unit 201 with the reference data in the determination reference data table 204 and calculating the difference between the two data.
[0048]
The determination reference data table 204 is design value data serving as a reference for the flying height of the magnetic head 3, and is stored in a memory table different from the memory table in which the temperature-recess dependence table 202 is stored. Here, reference design value data of the recess amount for each temperature (for example, −40 ° C. to 80 ° C.) is stored.
[0049]
The recess amount estimating unit 205 has a function of estimating a correction amount of the recess amount at the temperature based on the data calculated by the comparison determining unit 203, and controls the control operation of the correction amount to the recess amount control unit 206. Instruct the operation.
[0050]
The recess amount control unit 206 performs control for retracting the magnetic head 3 to a predetermined position based on the estimation result data from the recess amount estimation unit 205 via the VCM / SPM control unit 23. . Then, after performing this control, the control of a preceding pseudo recording (PDW) operation described later is performed.
[0051]
The preceding pseudo recording (PDW) operation is a basic control operation of the present invention. In the preceding pseudo recording (PDW) operation, the recording current value of the magnetic head 3 is set to a larger current value than during the normal recording operation. You can do it. Due to this large current, the recessed portion of the magnetic head 3 is warmed, and the recessed portion that has been drawn in expands to maintain the reference flying height.
[0052]
The low temperature error limit determination unit 207 stores limit value data as reference data for determining a reproduction error. When a reproduction error occurs during reproduction of the magnetic disk 1, the reproduction error value data indicates the low temperature error limit. The reproduction error value data input to the determination unit 207 is compared with the limit value data stored therein. If the reproduction error value data exceeds the limit value data, the recess amount is given to the CPU 26. Is output.
[0053]
Further, the head flying height control unit 27 takes in the temperature data detected by the temperature sensor 6a and sent to the control unit 20, and determines whether or not the temperature data exceeds a preset temperature To. Is stored, and it is determined whether or not the temperature exceeds a temperature range in which it is determined that the recess amount has changed. The threshold value of the temperature data may be stored in the temperature-recess conversion unit 201 or may be stored in another place.
[0054]
FIG. 3 is actually measured data showing the variation of the recess amount due to the temperature of the recess portion of the magnetic head. The measurement data shows the actual measurement data of the two magnetic disk devices. However, in any of the measurement data, it is assumed that the recess fluctuation increases in the minus (-) direction as the environmental temperature decreases, that is, the recess portion is retracted. Is shown.
[0055]
FIG. 4 is measured data showing the amount of change in the error rate (BER) when the reproduction flying height changes. According to this, the error rate (BER) becomes worse as the floating fluctuation amount on the horizontal axis increases in the negative direction. That is, the higher the flying height, the worse the error rate (BER).
[0056]
FIG. 5 is actually measured data showing the transition of the deterioration of the reproduction error rate (BER) at a low temperature. This indicates that the error rate (BER) becomes worse as the temperature on the horizontal axis increases in the minus direction (as the temperature decreases).
[0057]
FIG. 6 is actually measured data showing a change in the amount of protrusion of the recess due to the recording current of the magnetic head 3 when the pseudo dummy recording (PDW) operation is actually performed. According to this, as the recording current of the recording head on the horizontal axis increases, the amount of protrusion of the recess of the magnetic head 3 increases. This means that the temperature of the magnetic head rises due to the heat generated by the recording current of the recording head, and the recess protrudes due to the temperature.
[0058]
Therefore, in the present invention, the distance from the recording surface of the magnetic disk 1 to the magnetic head 3 is increased by utilizing the characteristics of FIGS. 3 to 6 described above and the recessed portion is recessed in a low temperature environment. When the probability of occurrence of an error increases, a preceding pseudo recording (PDW) operation is performed to perform control to temporarily protrude the recess.
[0059]
Next, the operation of the present invention will be described with reference to FIGS. 1 and 2 while keeping the characteristics of FIGS. 3 and 6 in mind.
[0060]
1 and 2, when an error occurs during reproduction of the magnetic disk 1, the reproduction error value data is sent to the head flying height control unit 27 of the control unit 20, and the reproduction error value data is transmitted to the low temperature error limit determination unit. 207. Then, it is compared with the judgment reference value data stored in advance here. If the reproduction error value data exceeds the judgment reference value data, the control operation described below is performed.
[0061]
First, a control request signal is output from the low temperature error limit determination unit 207 to the CPU 26 to control the recess amount. Then, the CPU 26 receives this and outputs a recess amount control operation signal.
[0062]
The temperature sensor 6a measures the environmental temperature in the vicinity of the magnetic head 3 in response to the recess amount control operation signal from the CPU 26, and the measured temperature data is stored in the temperature-recess conversion section of the recess amount control section 27 of the control section 20. It is sent to 201. Then, the recess amount corresponding to the temperature data is output from the temperature-recess dependency table 202, and the recess amount βt is calculated.
[0063]
The calculated recess amount βt is sent to the comparison determination unit 203, where the reference design value data βo of the recess amount at the temperature is obtained from the determination reference data table 204 and compared with the recess amount βt. As a result, difference data Δx (= βt−βo) from the design value at the temperature is calculated.
[0064]
Next, the recess amount to be corrected is estimated by the recess amount estimating unit 205 based on the difference data Δx sent from the comparison determining unit 203, and a control operation is performed on the recess amount controlling unit 206. The recess amount control unit 206 controls the VCM / SPM control unit 23 to drive the voice coil motor (VCM) 5 so that the magnetic head 3 is first subjected to a retracting operation measure for the magnetic head 3 described below. Then, the magnetic head 3 is retracted to a predetermined position determined by the retracting operation measure.
[0065]
Here, the evacuation operation measures for evacuation of the magnetic head 3 are based on three types of evacuation operation measures from the movement level 1 to the movement level 3, and the movement level to be used is selected by the control program. ing.
[0066]
That is, at the movement level 1, the magnetic head 3 is forcibly unloaded.
[0067]
At the movement level 2, the head moves to a dummy area which is not used for reading and writing data in the innermost or outermost part.
[0068]
At the movement level 3, positioning is performed in the vicinity of a track on which data is to be reproduced or at a cylinder position where the data exists.
[0069]
Next, after moving the magnetic head 3 to the predetermined position, the recess amount control unit 206 performs a preceding pseudo recording (PDW) operation to control the recess amount. The temperature of the magnetic head 3 rises due to the preceding pseudo-recording (PDW) operation, and the recessed portion protrudes according to the graph shown in FIG. 6, so that the flying height becomes a value close to the reference design value data.
[0070]
As a result, when the reproduction error decreases, the low temperature error limit determination unit 207 receives the reduced reproduction error value data from the CPU 26, and the low temperature error limit determination unit 207 again compares the reproduction error value data with the determination reference value data to make a determination. When the reproduction error value data decreases and falls within the determination reference value data, it is determined that the recess amount control has been successful, and the control is terminated.
[0071]
On the other hand, even if a reproduction error occurs during reproduction of the magnetic disk 1, if the reproduction error value data input to the low temperature error limit determination unit 207 is small and does not exceed the predetermined determination reference value data, the CPU 26 The recess amount control request signal is not sent, and it is determined that the recess amount is not a change in the normal error range, that is, the change in the recess amount due to the environmental temperature.
[0072]
By performing the above operation, the low temperature error limit determination unit 207 determines whether the reproduction error is caused by the fluctuation of the recess amount due to the low temperature environment, or is a normal error, for example, a positioning error or the recording medium S / S. This is to determine whether the error is due to an accidental error such as N shortage or the like.
[0073]
If the recording magnetization state of the magnetic disk 1 is defective, a reproduction error is more likely to occur during a reproduction operation in a low temperature environment. In this case, it is possible to recover the reproduction error margin by taking measures to improve the recording magnetization state by a rewriting operation (write-back sequence) at the movement level 3 in the evacuation operation described later.
[0074]
When performing the preceding pseudo recording (PDW) operation, the preceding pseudo recording (PDW) operation of at least the data amount of one sector is required.
[0075]
In addition, the number of preceding pseudo recording (PDW) operations may be set according to the movement level of the magnetic head 3 in order to easily control the recess amount, and the recording current value at that time may be set together. Is also possible.
[0076]
Next, a description will be given of a preceding pseudo recording (PDW) operation at the moving level of the magnetic head 3.
[0077]
As described above, three types of movement levels are set for the movement level of the magnetic head 3. The movement level 1 is the most basic movement level.
[0078]
As described above, the correction control operation of the recess amount is performed by using the determination of the reproduction error value data in the low temperature error limit determination unit 207 as a trigger, thereby performing the pseudo dummy recording (PDW) operation. If the recording operation is performed at an arbitrary position, there is a possibility that data previously recorded by the preceding pseudo recording (PDW) operation is overwritten and data is destroyed.
[0079]
For this reason, at the reference movement level 1, the magnetic head 3 is temporarily unloaded to the ramp loading mechanism 7 to perform the preceding pseudo recording (PDW).
[0080]
FIG. 7 is a diagram showing the position of the preceding pseudo recording (PDW) operation of the magnetic head 3 in the case of this movement level 1.
[0081]
If the pseudo dummy recording (PDW) operation is performed at the position where the ramp load mechanism 7 is unloaded, data recorded on the magnetic disk 1 is not adversely affected.
[0082]
Note that the preceding pseudo recording (PDW) operation at the movement level 1 is an operation for increasing the temperature of the recessed portion of the magnetic head 3, and is only an operation of flowing a predetermined current to the recording coil of the magnetic head 3. . Therefore, at the moving level 1, after performing the preceding pseudo recording (PDW) operation, the recess generated in the low temperature environment can be protruded by the heat generated by the current flowing through the recording coil, The physical flying height can be returned to a predetermined flying height.
[0083]
As a result, the readability of the magnetic head 3 is also restored (improved), and a reproduction error can be recovered. Then, the recording data on the magnetic disk 1 can be read by the subsequent control operation.
[0084]
Next, at the movement level 2, the magnetic head 3 is moved to an area on the innermost or outermost part of the recording disk 1 where data is not originally read or written, and a preceding pseudo recording (PDW) operation is performed in this area. is there.
[0085]
FIG. 8 is a diagram showing the preceding pseudo recording (PDW) operation position of the magnetic head 3 at this movement level 2. In FIG. 8, the magnetic head 3 moves to a magnetic head position A in an outer non-data area or a magnetic head position B in an inner non-data area.
[0086]
In this non-data area on the outer circumference or inner circumference, after performing a pseudo dummy recording (PDW) operation a predetermined number of times or a predetermined amount with a predetermined recording current, the target data recording surface of the magnetic disk 1 is accessed. I do.
[0087]
As in the case of the movement level 1, the recess portion which has been recessed in the low temperature environment can be protruded by the preceding pseudo recording (PDW) operation, and the physical flying height can be returned to the predetermined flying height.
[0088]
As a result, the readability of the magnetic head 3 is also restored (improved), and a reproduction error can be recovered. Then, the recording data on the magnetic disk 1 can be read by the subsequent control operation.
[0089]
The feature of the moving level 2 is that the magnetic head 3 does not have to be retracted to the ramp mechanism 7 when performing the preceding pseudo recording (PDW) operation as compared with the moving level 1, so that the time is shortened. However, when the preceding pseudo recording (PDW) operation is performed at the movement level 2, the magnetic head 3 is located in the dedicated area on the magnetic disk 1, so there is no possibility of destroying the recording data area. There is a possibility of destruction. Therefore, the recording timing of the preceding pseudo recording (PDW) operation is performed according to a normal data write sequence.
[0090]
Finally, the movement level 3 will be described.
[0091]
The movement level 3 is a level at which the access speed is highest.
[0092]
In the case where the flying state of the magnetic head 3 is dynamically fluctuating during the reproducing operation, the recessed portion of the magnetic head 3 is retracted due to the low temperature environment, so that even if the sector is located in the same cylinder of the magnetic disk 1, In a readable sector and a sector in which the recording magnetization state is not good, there are sectors in which a read error is relatively likely to occur.
[0093]
In such a case, the readable sector is read once, the same data is recorded in the same sector, the recess is protruded to improve the reproduction capability, and then the recording data is read from the recording sector where a reading error is likely to occur. By performing the writing anew, the recessed portion protrudes due to heat generated by the recording current of the recording head while preventing the recording data from being destroyed in the recording sector.
[0094]
That is, when a sector in which a reproduction error has occurred is detected, a sector in which no reproduction error occurs is searched for in the vicinity of the sector. In the sector search, the presence or absence of a reproduction error can be determined by reading a nearby sector where the relevant reproduction error has occurred, and examining an ECC (Error Correction Code).
[0095]
Next, when a sector in which a reproduction error has not occurred can be determined, the data is read and temporarily stored as reproduction data in an external cache memory or a temporary storage memory (for example, the DRAM 25). Thereafter, a rewrite operation is performed on the reproduced data in the same sector where no reproduction error has occurred. This is the moving level of the magnetic head 3 at the moving level 3 shown in the above-described embodiment, but by performing this rewriting operation, the recessed portion of the magnetic head 3 comes out due to the heat generated by the recording coil. That is, the rewrite operation has the same effect as the preceding pseudo recording (PDW) operation of the movement levels 1 and 2.
[0096]
As a result, the flying height of the magnetic head 3 can be temporarily reduced, and the reading performance is temporarily improved. Thereafter, a sector in which a predetermined reproduction error has occurred is read. In this case, since the flying height of the magnetic head 3 has been reduced in the preceding pseudo recording (PDW) operation, the state can be shifted to a more readable state. Therefore, a reproduction error is avoided.
[0097]
After the reproduction error is avoided, it is determined that the sector where the reproduction error has occurred can be read normally, and the read reproduction data is temporarily stored in the external cache memory or the temporary storage memory. Thereafter, the reproduction data is written back to the same sector.
[0098]
As described above, according to the present invention, when a reproduction error occurs, the flying height can be temporarily reduced by protruding the recessed portion, and thereby the reproduction error can be avoided. In addition, by performing a series of operations of reproduction error determination, recess amount control by preceding pseudo recording (PDW) operation, normal reproduction, and write-back, even if the recording magnetization state is relatively poor, the recording state can be reduced. Can be improved.
[0099]
The effect of this is that the flying height control of the magnetic head 3 can be performed in the vicinity of the sector where a read error is likely to occur, so that the best results can be obtained in both efficiency and effect.
[0100]
Incidentally, the recess amount control is performed by a method other than the preceding pseudo recording (PDW) operation, for example, as a heat source for increasing the temperature of the recess portion, a secondary component such as a coil separately provided in the magnetic head 3. , The recess amount control may be performed to avoid the reproduction error.
[0101]
The magnetic disk drive of the present invention thus configured is equipped with a controller for controlling the recess amount of the magnetic head by the preceding pseudo recording (PDW) operation, that is, a function of controlling the flying height of the magnetic head. Insufficient BER due to recessed recess below can be covered, and there is no need to design the steady-state flying height to be lower than necessary.
[0102]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a magnetic disk drive that improves read performance even in a low-temperature use environment and that improves reliability with respect to higher recording density.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main part of a magnetic disk drive according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a main part of a head flying height control unit shown in FIG. 1;
FIG. 3 is actually measured data showing recess fluctuations of a recess portion with respect to an environmental temperature.
FIG. 4 is actually measured data showing a change amount of a reproduction error rate (BER) when a reproduction flying height changes.
FIG. 5 is actually measured data showing a change in the reproduction error rate when the temperature is low.
FIG. 6 shows actually measured data indicating a change in flying height due to a recording current of a magnetic head when a pseudo dummy recording (PDW) operation is actually performed.
FIG. 7 is a diagram showing a leading pseudo recording (PDW) operation position of the magnetic head 3 at a movement level 1.
FIG. 8 is a diagram showing a preceding pseudo recording (PDW) operation position of the magnetic head 3 at a movement level 2.
FIG. 9 is an enlarged schematic diagram of a main part showing a state where the magnetic head main body is recessed from the head slider surface and a state where the surface of the magnetic disk 1 has irregularities.
[Explanation of symbols]
1 Magnetic disk
1a Magnetic disk surface
1b Projection (glide)
2 Spindle motor (SPM)
3 Magnetic head
3a recess
3b Magnetic head body
3c Head slider
4 Actuator arm
5 Voice coil motor (VCM)
6 Head amplifier (HA)
6a Temperature sensor
7 Ramp mechanism
10 mechanism
20 control unit
21 Playback / recording (R / W) channel
22 Hard Disk Controller (HDC)
23 VCM / SPM control unit
24 IC memory (EEPROM)
25 Buffer Memory (DRAM)
26 CPU / control logic section
27 Head flying height control unit
30 Information signal line
40 control signal line
50 Host system
60 Interface signal line
100 magnetic disk drive
201 Temperature-recess converter
202 Temperature-recess dependency table
203 Comparison judgment unit
204 criteria data
205 Recess amount estimation unit
206 Flying height control unit
207 Low temperature error limit judgment unit

Claims (10)

A magnetic disk serving as a magnetic recording / reproducing medium, a spindle motor for rotating and driving the magnetic disk, a magnetic head for recording and reproducing information on and from the magnetic disk, and a magnetic head mounted thereon. A magnetic disk drive comprising: an actuator arm for rotating; a voice coil motor for magnetically driving the actuator arm; a base plate on which these constituent members are mounted; and a top cover forming a package with the base plate. At
Temperature detecting means for detecting the temperature inside the magnetic disk device and outputting the temperature data;
A temperature-recess amount correlation table in which data indicating a physical variation amount of the recess portion of the magnetic head is stored in correspondence with the operating environment temperature of the magnetic head;
A reference data table in which a reference recess amount of the recess portion is stored corresponding to the operating environment temperature,
Based on the temperature data output from the temperature detecting means, a recess amount for the temperature is obtained from the temperature-recess amount correlation table, and the obtained recess amount and a reference recess for the temperature obtained from the reference data table are obtained. A magnetic disk drive for comparing the amount of the magnetic head and controlling the amount of recess of the magnetic head based on difference data of the amount of recess obtained from the comparison. The flying height of the magnetic head is estimated from the data of the recess amount with respect to the temperature obtained from the temperature-recess amount correlation table, and when the estimated flying height is higher than the reference recess amount, a preliminary pseudo recording operation is performed. 2. The magnetic disk drive according to claim 1, wherein the amount of the recess is controlled by increasing the temperature of the recess portion of the magnetic head, and the flying height is made appropriate. 2. The magnetic recording apparatus according to claim 1, wherein the magnetic head generates heat by performing the preceding pseudo recording operation, thereby temporarily reducing a magnetic space between the magnetic head and the surface of the magnetic disk. Disk device. 4. The magnetic disk drive according to claim 2, wherein the preceding pseudo recording has a data amount of at least one sector. 2. The magnetic disk drive according to claim 1, wherein, prior to performing the preceding pseudo recording operation, the magnetic head is temporarily moved to an unload position to perform the preceding pseudo recording operation. As an area for performing the preceding pseudo-recording operation, a dedicated area for the preceding pseudo-recording operation is provided at a predetermined position on the magnetic disk, and the magnetic head is temporarily moved before performing the preceding pseudo-recording operation. 2. The magnetic disk drive according to claim 1, wherein the preceding pseudo recording operation is performed while being moved to a predetermined position. 6. The magnetic disk device according to claim 4, wherein when performing the preceding pseudo recording operation at the unload position or the operation-dedicated area, recording is performed with a recording current larger than a normal recording current. 2. The magnetic disk drive according to claim 1, wherein when the reproduction error of the magnetic disk exceeds a predetermined error judgment reference value, the preceding pseudo recording operation is performed. 2. The magnetic disk drive according to claim 1, wherein the control of the flying height performs the control operation of the recess amount using heat generated by a heat generating means separately provided on the magnetic head. A magnetic disk serving as a magnetic recording / reproducing medium, a spindle motor for rotating and driving the magnetic disk, a magnetic head for recording and reproducing information on and from the magnetic disk, and a magnetic head mounted thereon. A magnetic disk drive comprising: an actuator arm for rotating; a voice coil motor for magnetically driving the actuator arm; a base plate on which these constituent members are mounted; and a top cover forming a package with the base plate. At
If the read error of the magnetic disk exceeds a predetermined error determination reference value, after reading data of a readable sector near the sector where the read error has occurred, the read data is written back to the same sector. Means for controlling the flying height of the magnetic head;
Means for reading the data of the sector where the reproduction error has occurred while the flying height is controlled by the means, and writing back the read data to the sector where the reproduction error has occurred to rewrite the data. A magnetic disk drive comprising:

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