Patent Publication Number: US-2006012363-A1

Title: Method of production of magnetic disk device and apparatus for inspection of magnetic disk device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      The present invention contains subject matter related to Japanese Patent Application No. 2004-205505 filed in the Japan Patent Office on Jul. 13, 2004, the entire contents of which being incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a method for producing for example a self-servo type magnetic disk device and an apparatus for inspection of the magnetic disk device.  
      2. Description of the Related Art  
      There is known, for example, a method for producing a hard disk drive (HDD) including a disk drive unit including a magnetic disk and a drive unit for driving that and made sealed in structure for preventing dust etc. from entering from outside and a control unit for access control to the disk drive unit.  
      The HDD records a servo signal for defining a magnetic head position in advance on the magnetic disk and records and reproduces data on the basis of the servo signal. As methods of writing this servo signal on the magnetic disk, the disk servo write method and the self-servo write method are known.  
      In the disk servo write method, the servo signal is stored in the magnetic disk in advance when assembling the disk drive unit. In this disk servo write method, it is necessary to separately provide a device for writing the servo signal on the magnetic disk. Further, it is necessary to be careful about disk eccentricity, and a high precision is required at the time of mechanical assembly.  
      In the self-servo write method, after assembling the disk drive unit and the control unit, the control unit controls the drive unit to store the servo signal in the magnetic disk. In the self-servo write method, in comparison with the disk servo write method, no write device other than the magnetic disk device is necessary for writing the servo signal. Further, since the self-servo write method has the control unit write the servo signal on the magnetic disk after assembly, it is possible to achieve a higher density and improve access in comparison with the disk servo write method.  
      Turning to the issue focused on it the present invention, in the self-servo write method, since the servo signal is written in the magnetic disk after the assembly, if the servo signal is not correctly recorded on the magnetic disk, sometimes the entire HDD has to be discarded after assembly, it suffers from the disadvantage of waste.  
     SUMMARY OF THE INVENTION  
      It is desirable to provide a method of production of a magnetic disk device and an apparatus for inspection of a magnetic disk device able to avoid the wasteful cost when producing a magnetic disk device having a magnetic disk and a control unit for controlling access to it and having the control unit write a servo signal on the magnetic disk after assembly.  
      According to a first aspect of the present invention, there is provided a method of producing a magnetic disk device having a disk drive part including a magnetic disk and a drive unit for driving the magnetic disk and a control part for controlling the drive unit to control access to the magnetic disk and write a servo signal in the magnetic disk, including a first step of inspecting magnetic conversion characteristics of the drive unit and a second step of connecting the disk drive part and the control part when it is judged by the inspection of the first step that the magnetic conversion characteristics of the drive unit are proper.  
      Preferably, the method further includes a third step of having the control part control the drive unit after the second step to write the servo signal on the magnetic disk.  
      The first step may include a step of writing an inspection signal in the magnetic disk by the drive unit, a step of reading the inspection signal from the magnetic disk, and a step of comparing the inspection signal written on the magnetic disk and the inspection signal read out from the magnetic disk, and in the second step, the disk drive part and the control part are connected when it is judged as a result of the comparison of the inspection signals that the magnetic conversion characteristics of the drive unit are proper.  
      More preferably, the inspection signal may include an inspection signal having a single frequency characteristic or the inspection signal may include an inspection signal having a predetermined modulation pattern.  
      More preferably, in the step of writing the inspection signal, the inspection signal is written into part of the tracks of the magnetic disk.  
      According to a second aspect of the present invention, there is provided an inspection apparatus for inspecting a magnetic disk device having a disk drive part including a magnetic disk and a drive unit for driving the magnetic disk and a control part for controlling the drive unit to control access to the magnetic disk and write a servo signal in the magnetic disk, including an inspecting part for inspecting the magnetic conversion characteristics of the drive unit before connecting the disk drive part and the control part.  
      Preferably, the inspecting part outputs a control signal for connecting the disk drive means and the control means when it is judged by the inspecting means that the magnetic conversion characteristics of the drive unit are proper.  
      The inspecting part may write an inspection signal in the magnetic disk by the drive unit, read out the inspection signal from the magnetic disk, then compare the inspection signal written on the magnetic disk and the inspection signal read out from the magnetic disk.  
      More preferably, the inspection signal may include an inspection signal having a single frequency characteristic or the inspection signal may include an inspection signal having a predetermined modulation pattern.  
      More preferably, the inspection part writes the inspection signal by writing the inspection signal into part of the tracks of the magnetic disk.  
      According to the present invention, it is possible to provide a method of production of a magnetic disk device and an apparatus for inspection of a magnetic disk device able to avoid the wasteful cost when producing a magnetic disk device having a magnetic disk and a control unit for controlling access to it and having the control unit write a servo signal on the magnetic disk after assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments with reference to the accompanying drawings, in which:  
       FIG. 1  is a view of the overall configuration of a magnetic disk device to be inspected by an inspection apparatus according to an embodiment of the present invention;  
       FIG. 2  is a functional block diagram of an inspection apparatus according to an embodiment of the present invention;  
       FIG. 3  is a flow chart for explaining the operations of the magnetic disk device and the inspection apparatus shown in  FIG. 1  and  FIG. 2 ; and  
       FIG. 4  is a flow chart for explaining a specific example of the operations of the inspection apparatus and a processing unit shown in  FIG. 3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Below, preferred embodiments of the present invention will be described with reference to  FIG. 1  to  FIG. 4 .  
      Magnetic Disk Device  
       FIG. 1  is a view of the overall configuration of a magnetic disk device  1  to be inspected by an inspection apparatus according to an embodiment of the present invention. As shown in  FIG. 1 , the magnetic disk device  1  has for example a hard disk assembly (HDA)  10  and a processing unit  30 . The magnetic disk device  1  is for example a portable system for recording/reproducing audio data. In the magnetic disk device  1 , the HDA  10  and the processing unit  30  are assembled at the time of shipping. The processing unit  30  writes the servo signal on the magnetic disk  12  of the HDA  10 , that is, the self-servo write method is employed.  
      Below, an explanation will be given of the HDA  10  and the processing unit  30  shown in  FIG. 1 .  
      HDA  10   
      As shown in  FIG. 1 , the HDA  10  has for example a magnetic disk  12 , spindle motor  14 , VCM  16 , head  17 , signal processor  18 , and interface  20 . The HDA  10  has a sealed structure for preventing entry of dust from the outside.  
      The magnetic disk  12  has a memory region divided into a plurality of sectors in for example concentric circles. Further, the magnetic disk  12  has a plurality of tracks formed in concentric circles. The spindle motor  14  rotates the magnetic disk  12 . The VCM  16  runs a current from a driver  40  of the processing unit  30  to a coil and moves the head  17  in the radial direction of the magnetic disk  12  by magnetic induction. Due to this, the head  17  is moved to the access position on the magnetic disk  12 . The head  17  moves close to the recording region on the magnetic disk  12  and writes a signal, for example, an audio signal, into the sectors and tracks and reads a signal from the sectors and the tracks on the basis of the servo signal defining the position of the head  17 .  
      The signal processor  18  amplifies the signal read out from the magnetic disk  12  by the head  17  and outputs it to the processing unit  30  via the interface  20 . Further, the signal processor  18  outputs the signal to be stored input from the processing unit  30  to the head  17 .  
      Processing Unit  30   
      As shown in  FIG. 1 , the processing unit  30  has for example an HDA interface  31 , liquid crystal display (LCD)  32 , power supply circuit  34 , flash memory  36 , synchronous DRAM (SDRAM)  38 , driver  40 , LCD driver  52 , interface  54 , universal serial bus (USB) interface  56 , CODEC  58 , conversion circuit  60 , hard disk controller (HDC)  62 , direct memory access controller (DMAC)  64 , and central processing unit (CPU)  66 .  
      In the present embodiment, the LCD driver  52 , interface  54 , USB interface  56 , CODEC  58 , conversion circuit  60 , HDC  62 , DMAC  64 , and CPU  66  are integrally configured by for example a semiconductor integrated circuit  59 .  
      The HDA interface  31  is connected to the interface  20  of the HDA  10  and inputs/outputs data with the HDA  10 . The LCD  32  displays an image on a screen under the control of the LCD driver  52 . The screen is for example an operation screen. The power supply circuit  34  supplies power to components of the processing unit  30 . The flash memory  36  stores a program PRG for defining the processing of the CPU  66 . The program PRG is F/W (Firm Ware). The SDRAM  38  stores the data concerning the processing of the processing unit  30 . The driver  40  outputs a control signal to the spindle motor  14  and the VCM  16  of the HDA  10  under the control of the HDC  62 .  
      The LCD driver  52  controls the display of the LCD display  32  on the basis of the control signal from the CPU  66 . The interface  54  and the USB interface  56  input/output data with the outside of the processing unit  30 . The CODEC  58  decodes the audio data read out from for example the HDA  10  and encodes the audio data to be stored in the HDA  10 . The conversion circuit  60  performs processing such as filtering (equalization) and A/D conversion of the signal read out from the HDA  10  and outputs the audio data obtained by the processing to the HDC  62 . Namely, the conversion circuit  60  functions as a so-called read channel. Further, the conversion circuit  60  performs D/A conversion of the audio data to be stored input from the HDC  62  to generate an audio signal and outputs this to the HDA  10 .  
      The HDC  62  centrally controls the access to the HDA  10  under the control of the CPU  66 . For example, the CPU  66  controls operations according to the program PRG read out from the flash memory  36 .  
      The CPU  66  performs the processing of writing the servo signal into the HDA  10  at the time of the assembly of for example the HDA  10  and the processing unit  30  into the magnetic disk device  1 . Specifically, the CPU  66  controls the spindle motor  14  serving as the drive unit, the VCM  16 , head  17 , signal processor  18 , etc. and writes the servo signal on the magnetic disk  12  at the time of the assembly of the HDA  10  and the processing unit  30  into the magnetic disk device  1 .  
      For example, the CPU  66  may instruct a write operation triggered by detection of the HDA  10  and the processing unit  30  being electrically connected at the time of assembly or may instruct a write operation triggered by a signal instructing a write operation from the outside.  
      Inspection Apparatus  70   
       FIG. 2  is a functional block diagram of the inspection apparatus  70  according to an embodiment of the present invention. As shown in  FIG. 2 , the inspection apparatus  70  has for example an inspection unit  700 .  
      Inspection Unit  700   
      The inspection unit  700  inspects the magnetic conversion characteristics of the magnetic disk  12  before assembling the HDA  10  into the magnetic disk device  1 . Further, the inspection unit  700  assembles the HDA  10  and the processing unit  30  into the magnetic disk device  1  conditional on the magnetic conversion characteristics of the magnetic disk device  12  being found to be proper by that inspection. In more detail, the inspection unit  700  outputs a signal instructing assembly of the HDA  10  and the processing unit  30  into the magnetic disk device  1  to a not illustrated assembly apparatus conditional on the magnetic conversion characteristics of the magnetic disk  12  being found to be proper by that inspection. The assembly apparatus assembles the HDA  10  and the processing unit  30  into the magnetic disk device  1  when that signal is input.  
      Further, the inspection unit  700  writes an inspection signal having for example a single frequency characteristic into the magnetic disk  12 , then reads out the inspection signal from the magnetic disk and inspects the magnetic conversion characteristics on the basis of the read out signal. The inspection signal is an RF signal having a single frequency characteristic of for example about 2 MHz to several tens MHz as the frequency characteristic. This inspection signal is used when inspecting the magnetic conversion characteristics of the magnetic disk  12 , that is, whether or not a signal written on the magnetic disk  12 , by the head  17  can be read out as a signal having a predetermined intensity by the head  17 . As the frequency of this inspection signal, a frequency optimum for inspecting the magnetic conversion characteristics of the magnetic disk  12  to be inspected is set.  
      Below, an explanation will be given of a preferable example of the inspection unit  700 . As shown in  FIG. 2 , the inspection unit  700  has for example an HDA interface  71 , LCD  72 , LCD driver  73 , power supply circuit  74 , memory  75 , driver  76 , conversion circuit  77 , HDC  78 , and CPU  79 .  
      The HDA interface  71  is connected to the interface  20  of the HDA  10  and inputs and outputs data with the HDA  10 . The LCD  72  displays an image on a screen under the control of the LCD driver  73 . The screen is for example an inspection operation screen. The LCD driver  73  controls the display of the LCD  72  on the basis of the control signal from the CPU  79 . The power supply circuit  74  supplies power to the components of the inspection apparatus  70 .  
      The memory  75  stores a program PRG for realizing the functions according to an embodiment of the present invention for defining the processing of the CPU  79 . The driver  76  outputs, under the control of the HDC  78 , control signals to the spindle motor  14  and the VCM  16  of the HDA  19 , for example, a control signal for controlling the head position for writing and reading the inspection signal and a control signal for rotating the spindle motor  14 .  
      The conversion circuit  77  outputs for example an inspection signal via the HDA interface  71  to the signal processor  18  of the HDA  10  under the control of the HDC  78 . Further, the conversion circuit  77  performs the signal processing of the inspection signal read out from the HDA  10  under the control of the HDC  78  and outputs the same to the HDC  78 .  
      The HDC  78  centrally controls the access to the HDA  10  under the control of the CPU  79 . The CPU  79  inspects the magnetic conversion characteristics of the magnetic disk  12  by controlling the drive unit of the HDA  10  before assembling the HDA  10  into the magnetic disk device  1 . In more detail, the CPU  79  outputs a control signal for writing an inspection signal on the magnetic disk to for example the HDC  78 , outputs a control signal for reading the inspection signal from the magnetic disk  12  to the HDC  78 , and inspects the magnetic conversion characteristics on the basis of the read out signal.  
      Below, the operation according to an embodiment of the present invention will be explained.  
      Example of Operation  
       FIG. 3  is a flow chart for explaining the operations of the magnetic disk device and the inspection apparatus shown in  FIG. 1  and  FIG. 2 . Referring to  FIG. 3 , an explanation will be given of the method for producing the magnetic disk device  1  centering on the operations of the CPU  79  of the inspection apparatus  70  and the CPU  66  of the magnetic disk device  1 .  
      At step ST 1 , the HDA  10  is produced. In more detail, the HDA  10  is produced by assembling the magnetic disk  12 , spindle motor  14 , VCM  16 , head  17 , signal processor  18 , etc. into the HDA  10  by for example a not illustrated assembly apparatus. At this time, the servo signal for defining the head position of the head  18  is not written on the magnetic disk  12 .  
      At step ST 2 , the inspection unit  700  of the inspection apparatus  70  inspects the magnetic conversion characteristics of the magnetic disk  12  before assembling the HDA  10  into the magnetic disk device  1 . For example, the inspection is carried out by electrically connecting the HDA interface  71  of the inspection apparatus  70  and the interface  20  of the HDA  10 . The detailed operation for inspection of the magnetic conversion characteristics will be explained later.  
      At step ST 3 , the inspection unit  700  of the inspection apparatus  70  judges whether or not the magnetic conversion characteristics of the magnetic disk  12  are proper by the inspection. For example, when the magnetic conversion characteristics of the magnetic disk  12  are found to be proper by the inspection, the inspection unit  700  of the inspection apparatus  70  outputs an instruction for assembling the HDA  10  and the processing unit  30  into the magnetic disk device  1  to a not illustrated assembly apparatus.  
      At step ST 4 , conditional on the magnetic conversion characteristics being proper, the HDA  10  and the processing unit  30  are assembled into the magnetic disk device  1 . In more detail, when an instruction for assembling the HDA  10  and the processing unit  30  into the magnetic disk device  1  is input from the inspection apparatus  70 , a not illustrated assembly apparatus, assembles the HDA  10  and the processing unit  30  into the magnetic disk device  1  and electrically connects the interface  20  of the HDA  10  and the HDA interface  31 .  
      At step ST 5 , the assembled processing unit  30  controls the drive unit such as VCM  16  of the HDA  10  and the signal processor  18  and writes the servo signal to (in) the magnetic disk  12  (self-servo write).  
      On the other hand, if the CPU  70  of the inspection unit  700  judges at step ST 3  that the magnetic conversion characteristics are not proper, the HDA  10  is discarded (ST 6 ). In more detail, when the CPU  79  of the inspection unit  700  judges that the magnetic conversion characteristics are not proper, it outputs a signal indicating that to the assembly apparatus. When that signal is input, the assembly apparatus discards the HDA  10 .  
      Inspection of Magnetic Conversion Characteristic  
       FIG. 4  is a flow chart for explaining a specific example of the operations of the inspection apparatus  70  and the processing unit  30  shown in  FIG. 3 . A more detailed explanation will be given of the operation according to the inspection of the magnetic conversion characteristics of steps ST 2  to ST 4  shown in  FIG. 3  by referring to  FIG. 4 .  
      At step ST 11 , the inspection unit  700  of the inspection apparatus  70  writes the inspection signal to the HDA  10  before assembly. In more detail, the CPU  79  of the inspection unit  700  outputs a control signal for writing the inspection signal to the HDC  78 . The HDC  78  receives the control signal and controls the driver  76  and the conversion circuit  77  and controls the drive unit of the HDA  10  to write the inspection signal in (on) the magnetic disk  12 .  
      At step ST 12 , the inspection unit  700  then reads out the inspection signal from the HDA  10 . In more detail, the CPU  79  of the inspection unit  700  outputs a control signal for reading the inspection signal from the HDA  10  in (to) the HDC  78 . The HDC  78  receives the control signal and controls the driver  76  and the conversion circuit  77  and controls the drive unit of the HDA  10  to read out the inspection signal and outputs the same to the CPU  79 .  
      At step ST 13 , the CPU  79  judges whether or not the magnetic conversion characteristics of the magnetic disk  12  are proper on the basis of for example the written inspection signal and the read out inspection signal. In more detail, where an inspection signal having a single frequency characteristic is written on the magnetic disk  12  as the inspection signal, the CPU  79  judges whether or not the magnetic conversion characteristics of the magnetic disk  12  are proper by comparing the level of the inspection signal read out from the magnetic disk  12  and a predetermined value.  
      At step ST 15 , when judging that the magnetic conversion characteristics are proper, the HDA  10  and the processing unit  30  are assembled into the magnetic disk device  1 . In more detail, for example the CPU  79  outputs a signal instructing assembly of the HDA  10  and the processing unit  30  into the magnetic disk device  1 . When the signal instructing assembly is input, a not illustrated assembly apparatus assembles the HDA  10  and the processing unit  30  into the magnetic disk device  1  and electrically connects the interface  20  of the HDA  10  and the HDA interface  31 .  
      On the other hand, when judging at step ST 14  that the magnetic conversion characteristics are not suitable, the HDA  10  is discarded. In more detail, when judging that the magnetic conversion characteristics are not proper, the CPU  79  outputs a signal indicating that to the assembly apparatus. When that signal is input, the assembly apparatus discards the HDA  10  (ST 16 ).  
      As explained above, before assembling the HDA  10  into the magnetic disk device  1 , the magnetic conversion characteristics of the magnetic disk  12  are inspected. Conditional on that inspection showing that the magnetic conversion characteristics of the magnetic disk  12  are proper, the HDA  12  and the processing unit  30  are assembled into the magnetic disk device  1  and the assembled processing unit  30  controls the drive unit of the HDA  10  to write the servo signal on the magnetic disk  12 , so it is possible to reduce the ratio of the magnetic disk devices into which defective magnetic disks are assembled. Further, since the ratio of the magnetic disk devices  1  in which defective magnetic disks are assembled becomes smaller after the assembly, it is possible to reduce the wasteful cost in comparison with the case where defects of the magnetic disks are discovered after assembly and the entire magnetic disk devices are discarded.  
      In more detail, before assembling the HDA  10 , if the magnetic conversion characteristics of the magnetic disk  12  of the HDA  10  are found to not be proper, for example if the magnetic conversion characteristics are smaller than predetermined values, the HDA  10  is discarded at that stage. Therefore, the entire magnetic disk device  1  after assembly will not be discarded.  
      Further, by inspecting the magnetic conversion characteristics by the simple inspection of writing an inspection signal having a single frequency characteristic on the magnetic disk  12  of the HDA  10  as an inspection signal, reading out that signal, and judging whether or not the signal level thereof is a predetermined value or more, it is possible to inspect for problems in the magnetic disk  12  of the HDA  10  in a shorter time in comparison with the case of for example writing a servo signal on the entire magnetic disk  12  before assembly and reading out that signal for inspection.  
      Further, it is also possible for example for the CPU  79  of the inspection unit  700  to write an inspection signal having a predetermined modulation pattern on the magnetic disk  12  as the inspection signal, then read out the inspection signal from the magnetic disk and inspect the magnetic conversion characteristics on the basis of the read out signal. The predetermined modulation pattern may be for example an inspection signal having a plurality of frequency characteristics or may be an inspection signal having a modulation pattern simpler than that of the servo signal as well. By doing this, it is possible to inspect the more detailed magnetic conversion characteristics of the magnetic disk  12 .  
      Further, as the inspection signal, the CPU  79  of the inspection unit  700  may write an inspection signal into only part of the tracks of the magnetic disk  12 , then read out the inspection signal from part of the tracks and inspect the magnetic conversion characteristics on the basis of the read out signal. For example, it is possible to inspect any of the outer tracks, middle tracks, or inner tracks of the magnetic disk  12  or combinations of these tracks, desired tracks, etc. By doing this, it is possible to inspect the magnetic conversion characteristics of the magnetic disk  12  in a shorter time in comparison with the case for example of writing the inspection signal into all tracks of the magnetic disk  12 , reading out that signal, and inspecting the magnetic conversion characteristics of the magnetic disk  12 .  
      First, an explanation will be given of correspondence between the configuration of the embodiment and the configuration of the present invention as expressed in the claims. A magnetic disk device  1  shown in  FIG. 1  corresponds to the magnetic disk device according to the present invention. An inspection apparatus  70  shown in  FIG. 2  corresponds to the inspection apparatus according to the present invention, and an inspection unit  700  corresponds to the inspecting means according to the present invention. A magnetic disk  12  shown in  FIG. 1  corresponds to the magnetic disk according to the present invention, and a spindle motor  14 , a voice control motor (VCM)  16 , and a head  17  correspond to the drive unit according to the present invention.  
      Step ST 2  shown in  FIG. 3  corresponds to a first step of the first aspect of the invention, and steps ST 3  to ST 6  correspond to a second step of the first aspect of the invention. Further, step ST 2  shown in  FIG. 3  corresponds to the first step of the third aspect of the invention, and step ST 3  corresponds to the second step of the third aspect of the invention.  
      It should be understood by those skilled in the art that various modifications, combinations, sub-combinations, and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.  
      For example, the inspection unit  700  of the inspection apparatus  70  need not have the above-mentioned configuration. For example, it may have components able to perform the processing according to the above embodiment of the present invention. For example, it may be provided with an oscillation device for writing an inspection signal having a single frequency characteristic or desired modulation pattern on the magnetic disk  12 , a measurement device for measuring the level of the read RF signal for the inspection signal read out from the magnetic disk  12 , and a control unit for controlling them to realize the functions of the embodiment of the present invention.  
      Further, in the above embodiment, the HDA  10  inspected by the inspection apparatus  70  was configured by a magnetic disk  12  and a drive unit, but the invention is not limited to this. For example, a control circuit for performing the function of the processing unit  30  may be provided in the HDA  10  as well. In that case as well, the inspection apparatus  70  realizes the functions according to the above embodiment of the present invention via that processing circuit.