JP5486039B2 - Spacer used in magnetic disk device and magnetic disk device - Google Patents

Description

  The present invention relates to a magnetic disk device used for reading and writing information, and more particularly to a spacer inserted between magnetic disks of a magnetic disk device having a plurality of magnetic disks and a magnetic disk device using the spacer. .

  A magnetic disk device (hard disk) used for reading and writing information rotates a magnetic disk by a spindle motor in a sealed case-like shroud for fixing the mechanism of the magnetic disk device and protecting it from dust in the atmosphere. A swing arm is mounted by a voice coil motor while a magnetic head is attached to the tip of the slider and lightly pressed against the surface of the magnetic disk by a flexure consisting of a leaf spring. Is rotated to the left and right to move the magnetic head to an arbitrary track on the magnetic disk to read and write information. In recent years, with the miniaturization of OA equipment, the size, thickness, Capacity is increasing. In particular, a large-capacity magnetic disk device usually has a plurality of magnetic disks. In that case, a plurality of magnetic disks are inserted into a rotating hub of a spindle motor by inserting a spacer between the magnetic disks. A disk-shaped clamper is fastened to the upper end of the rotating hub with a screw, and the inner periphery of the magnetic disk is pressed by the elastic deformation of the clamper so that the magnetic disk and the spacer are placed between the large-diameter portion of the bottom of the rotating hub and the clamper It is supposed to hold on.

  However, the expansion of the data area on the magnetic disk surface and the increase in recording density have become more and more necessary as the magnetic disk device becomes smaller, thinner and larger in capacity. As the magnetic disk drive becomes smaller and thinner and has a larger capacity, and as the data area on the magnetic disk surface increases and the recording density increases, data recording / reproduction becomes inaccurate, There has been a problem that positioning to the target track, writing and reading of data cannot be performed accurately, or a failure such as contact with the magnetic disk occurs due to a decrease in flying height. The cause of this is that the magnetic disk is distorted or wavy due to the non-uniform force applied in the circumferential direction of the magnetic disk, and the magnetic head and magnetic disk are instantaneously caused by this distortion or waviness. It is thought that the fluctuation of the floating gap occurs. FIG. 4 shows the state of distortion of the magnetic disk in the conventional magnetic disk apparatus. In FIG. 4, 3 is a magnetic disk, 10 is a rotary hub, 11 is a clamper, and 12 is a screw for fastening the clamper 11 and the rotary hub 10. Due to the non-uniform elastic deformation of the clamper 11 due to the concentrated axial force of the screw 12 on the inner peripheral portion of the magnetic disk in the conventional magnetic disk apparatus, distortion and waviness as shown by thin lines in FIG. Occur.

  Therefore, the cause of distortion and undulation in the magnetic disk is the concentration of the axial force of the screw that fastens the clamper so that the magnetic disk and the spacer are pressed and held by the elastic deformation of the clamper between the large diameter part of the bottom of the rotating hub. As a result, non-uniform elastic deformation may occur in the magnetic disk, and the gap between the upper end of the cylindrical portion on which the magnetic disk and spacer of the rotating hub are mounted and the protrusion provided on the cylindrical protrusion at the top of the hub. By press-fitting the inner diameter part of the clamper into the magnetic disk, the magnetic disk and the spacer can be pressed and held without using a screw. Therefore, the inner peripheral part of the magnetic disk that occurs when the clamper pressing the magnetic disk and the upper surface of the hub are screwed together Deformation of the magnetic head can be prevented, and the flying of the magnetic head can fluctuate at the inner periphery of the magnetic disk during the operation of the magnetic disk device. It has been proposed that positioning accuracy can be improved by making the magnetic head output uniform, data writing and reading accuracy can be improved, and the reliability of the magnetic disk device can be improved (for example, Patent Documents). 1).

JP-A-6-60513

  However, in recent years, magnetic disk devices have become smaller, thinner, larger capacity, and faster (up the disk rotation speed), and the data area on the magnetic disk surface and the recording density have increased. It has been found that deformation such as distortion and undulation of the magnetic disk cannot be sufficiently prevented by simply pressing and holding the magnetic disk and the spacer without using screws by pressing the clamper into the rotating hub as proposed. It was.

  The conventional spacer uses a steel bar made of stainless steel or a hot rolled steel bar as it is, and as shown in FIG. Is made into a pipe-shaped material B, and this is made into a ring C to make a ring C, which is used as it is as a spacer. Therefore, there is distortion, the surface hardness of the outer peripheral part is high, and as it goes to the inner side (inner peripheral part) The hardness tends to be low, and the variation in surface hardness is very large, and the variation in crystal grain size and residual strain is also very large. Therefore, when multiple magnetic disks and spacers are mounted on the spindle motor's rotating hub and the clamper is fastened with screws, the spacer's distortion increases due to the pressure caused by the elastic deformation of the clamper. It is a factor of deformation. Also, when the clamper is press-fitted into the rotating hub without using screws, the spacer is also distorted due to the pressure caused by the elastic deformation of the clamper, which causes deformation of the magnetic disk, such as waviness. .

  Conventional spacers that are manufactured by cutting a round bar and drilling holes can also reduce the variation in surface hardness and reduce the variation in crystal grain size and residual strain by heat treatment. However, the manufacturing cost is extremely high.

  The present invention relates to a magnetic disk device in which a plurality of magnetic disks are inserted in a spacer between the magnetic disks and mounted on a rotary hub of a spindle motor and held by pressing with a clamper. The purpose of the present invention is to make it possible to sufficiently prevent the deformation of the magnetic disk device and to cope with the increase in the data area on the magnetic disk surface and the increase in recording density. .

  In order to solve the above-mentioned problems, the present inventors have studied the materials and functions of all members of the magnetic disk device. As a result, the material of the spacer used when mounting a plurality of magnetic disks to the rotating hub, and the mechanical, physical, and electrical characteristics of the magnetic disk are greatly related to the deformation of the magnetic disk, such as waviness. Finally, the present invention has been made.

The spacer used in the magnetic disk apparatus of the present invention is a clamper in which a plurality of magnetic disks are inserted into a rotating hub of a spindle motor with spacers inserted between the magnetic disks, and a disc-shaped clamper is attached to the upper end of the rotating hub. The spacer is inserted between the magnetic disks of the magnetic disk apparatus configured to press the inner peripheral portion of the magnetic disk by elastic deformation of the magnetic disk and hold the magnetic disk and the spacer between the large diameter portion of the bottom of the rotating hub and the clamper. It is produced by processing a rolled sheet of ferritic stainless steel into a ring shape by punching, and the variation in surface hardness is within 4% above and below the average value.

This spacer is manufactured by stamping a ferritic stainless steel rolled plate, so that the following steps can be taken by creating uniform hardness, crystal grain size, residual stress, etc. in the state of the rolled plate. However, the accuracy is maintained, the variation in surface hardness is small, and the variation in crystal grain size and residual strain is also small. Since the variation of the surface hardness is very small, the distortion of the spacer when the mounting a plurality of magnetic disks and spacers rotating hub of a spindle motor clamper fastened with screws is reduced, the magnetic disk distortion, waviness or the like Even if the data area on the magnetic disk surface increases or the recording density increases, the magnetic disk device is still in operation. The flying height of the magnetic head can be maintained in a stable state with no fluctuation at the inner periphery of the magnetic disk, and the positioning accuracy is improved by making the magnetic head output uniform, the data writing and reading accuracy is improved, and the magnetic disk device Reliability can be improved. Further, since the rolled plate material is punched and manufactured, the accuracy is improved and the cost is very advantageous, and the productivity is improved because the machining process is shortened.

Further, this spacer has a crystal grain size corresponding to a value of G of 5.0 to 9.0 calculated by an equation of m = 8 × 2 ^G using an average number of crystal grains m per 1 mm ^2. Features.

This spacer has a very small crystal grain size, so when the magnetic disk and spacer are attached to the rotating hub of the spindle motor and the clamper is tightened with screws, the distortion of the spacer is reduced and the magnetic disk is distorted and swelled. Even if the data area on the magnetic disk surface increases or the recording density increases, the magnetic disk device is still in operation. The flying height of the magnetic head can be maintained in a stable state with no fluctuation at the inner periphery of the magnetic disk, and the positioning accuracy is improved by making the magnetic head output uniform, the data writing and reading accuracy is improved, and the magnetic disk device Reliability can be improved. Further, since the rolled plate material is punched and manufactured, the accuracy is improved and the cost is very advantageous, and the productivity is improved because the machining process is shortened. In particular, since the ferrite crystal grain size is fine, heat generation is low, residual magnetism is low, magnetic resistance is low, heat is difficult to maintain, and therefore distortion is low and speed is increased (disk rotation speed is increased). However, the accuracy does not decrease due to heat, and the failure due to heat is greatly reduced.

Further, this spacer is characterized in that the residual compressive stress is 80 MPa or less.

This spacer, since the residual stress is very small, the distortion of the spacer when the mounting a plurality of magnetic disks and spacers rotating hub of a spindle motor clamper fastened with screws is reduced, the magnetic disk distortion, waviness or the like Even if the data area on the magnetic disk surface increases or the recording density increases, the magnetic disk device is still in operation. The flying height of the magnetic head can be maintained in a stable state with no fluctuation at the inner periphery of the magnetic disk, and the positioning accuracy is improved by making the magnetic head output uniform, the data writing and reading accuracy is improved, and the magnetic disk device Reliability can be improved. Further, since the rolled plate material is punched and manufactured, the accuracy is improved and the cost is very advantageous, and the productivity is improved because the machining process is shortened. In particular, since the residual stress is very small, there is little distortion, positioning accuracy, data writing accuracy, and data reading accuracy can be improved, the failure rate can be reduced, and the rotation speed can be increased.

In the magnetic disk apparatus of the present invention, a plurality of magnetic disks are inserted into a rotating hub of a spindle motor by inserting a spacer between the magnetic disks, and a disk-shaped clamper is mounted on the upper end of the rotating hub to elastically deform the clamper. The magnetic disk device is configured to hold the magnetic disk and the spacer between the large-diameter portion of the bottom portion of the rotating hub and the clamper by pressing the inner peripheral portion of the magnetic disk, and the spacer is formed by rolling ferritic stainless steel. It is produced by punching a plate material into a ring shape, the surface hardness variation is within 4% above and below the average value, and the crystal grain size is m = 8 × using the average number of crystal grains m per mm ² This corresponds to a G value of 5.0 to 9.0 calculated by the formula of 2G, and the residual compressive stress is 80 MPa or less.

This magnetic disk unit has small variations in spacer surface hardness and small variations in crystal grain size and residual strain. For this reason, multiple magnetic disks and spacers are mounted on the spindle motor rotating hub and the clamper is fastened with screws. The distortion of the spacer is small, and the deformation of the magnetic disk, undulation, etc. can be sufficiently prevented, and the miniaturization, thinning and large capacity of the magnetic disk device are accelerated, and the data area on the magnetic disk surface is increased. Even if the expansion or increase in recording density progresses, the magnetic head flying can be kept stable and stable at the inner periphery of the magnetic disk during the operation of the magnetic disk device, and positioning by uniformizing the magnetic head output It is possible to improve accuracy, write data, improve reading accuracy, improve the reliability of magnetic disk devices, And, since fabricating a spacer by punching a rolled sheet, becomes very advantageous cost on to improve the machining accuracy of the spacer, also, machining process is also shortened to improve the productivity.

  According to the present invention, it is possible to sufficiently prevent distortion, swell, and the like of the inner peripheral portion of the magnetic disk that has been received from fastening of screws between the clamper and the upper surface of the hub that press the magnetic disk and elastic deformation of the clamper and the like. For this reason, even if the magnetic disk device has become smaller and thinner and has a larger capacity, and the data area on the magnetic disk surface has been expanded and the recording density has increased, the magnetic head can be The flying can be held in a stable state without fluctuation, and the positioning accuracy can be improved by improving the magnetic head output, the data writing and reading accuracy can be improved, and the reliability of the magnetic disk device can be improved.

1 is a cross-sectional view of a magnetic disk device according to an example of an embodiment of the present invention. It is explanatory drawing of the manufacturing method of the spacer which concerns on an example of embodiment of this invention. It is a top view which shows the hardness measurement location of a spacer. It is explanatory drawing which shows the state of the distortion of the magnetic disc in the conventional magnetic disc apparatus. It is explanatory drawing of the manufacturing method of the conventional spacer.

  FIG. 1 shows the structure of a magnetic disk device (hard disk) according to an example of an embodiment of the present invention. In this magnetic disk apparatus, a magnetic disk 3 is rotated by a spindle motor 2 in a hermetically sealed shroud 1 for fixing the mechanism of the magnetic disk apparatus and protecting it from dust in the atmosphere, and a magnetic head 4 is mounted at the tip. The voice coil motor 7 is moved while the slider 6 lightly pressed against the surface of the magnetic disk 3 by the flexure 5 made of a leaf spring is levitated from the surface of the magnetic disk 3 by the pressure of the airflow generated on the surface of the magnetic disk 3 by the rotation of the magnetic disk 3. Thus, the swing arm 8 is rotated left and right to move the magnetic head 4 to an arbitrary track on the magnetic disk 3 to read and write information.

  There are a plurality of magnetic disks 3 (three in the example shown in the figure are not limited to this), and a spacer 9 is inserted between the plurality of magnetic disks 3 and the rotating hub of the spindle motor 2 is inserted. 10, a disc-shaped clamper 11 is fastened to the upper end of the rotating hub 10 with a screw 12, and the inner periphery of the magnetic disk 3 is pressed by elastic deformation of the clamper 11 to rotate the magnetic disk 3 and the spacer 9. The hub 10 is held between the large diameter portion at the bottom of the hub 10 and the clamper 11.

  In the example shown in the figure, there are three magnetic disks 3 and two spacers 9, and the lowermost magnetic disk 3 is supported by the large-diameter portion at the bottom of the rotating hub 10 and the inner periphery of the upper surface on the lower side. The intermediate magnetic disk 3 is supported by the upper surface of the lower spacer 9 and pressed by the lower surface of the upper spacer 9, and the uppermost magnetic disk 3 is The inner peripheral portion is supported by the upper surface of the upper spacer 9 and the upper inner peripheral portion is pressed by the clamper 11.

  In FIG. 1, reference numeral 13 denotes a spindle motor base fixed in the shroud 1, and reference numeral 14 denotes a bearing held by the spindle motor base 13. The rotary hub 10 is configured integrally with the rotary shaft of the spindle motor 2 and is rotatably supported on the spindle motor base 13 via a bearing 14. Reference numeral 15 denotes a stator iron core mounted on the spindle motor base 13, 16 denotes a stator winding wound around the stator iron core 15, and 17 denotes a permanent magnet attached to the rotary hub 10 against the stator iron core 15. . Reference numeral 19 denotes a rotating shaft of the swing arm 8, 20 denotes a coil of the voice coil motor 7, 21 denotes an upper magnet, 22 denotes a lower magnet, 23 denotes a circuit board on which a signal processing circuit is mounted, 24 denotes a shroud 1 and a circuit board 23 It is a frame for integrating and fixing to other devices.

  In the magnetic disk apparatus of this embodiment, the spacer 9 inserted between the magnetic disks 3 is produced by punching a ferritic stainless steel rolled plate D into a ring shape as shown in FIG. It is.

The rolled steel sheet D of ferritic stainless steel has a small surface hardness variation within 4% above and below the average value, and the grain size is the grain size number defined in JIS G0551 (average grain size per mm ² (A value of G calculated by the formula m = 8 × ^2G using a number m) of 5.0 to 9.0, and heat treatment is performed so that the residual compressive stress is reduced to 80 MPa or less. Therefore, the accuracy is maintained even after the punching process, and the manufactured spacer 9 has a small variation in surface hardness and a small variation in crystal grain size and residual strain.

  The magnetic disk apparatus of this embodiment has a very small variation in the surface hardness of the spacer 9, a very small crystal grain size, and a very small residual stress. Due to the action, the distortion of the spacer 9 is reduced when the plurality of magnetic disks 3 and the spacers 9 are mounted on the rotating hub 10 of the spindle motor 2 and the clamper 11 is fastened with the screws 12. The deformation of the magnetic disk device can be sufficiently prevented, and the magnetic disk device can be reduced in size, thickness and capacity, and even if the data area on the surface of the magnetic disk 3 and the recording density increase, During operation, the flying of the magnetic head 4 can be held in a stable state without fluctuation at the inner periphery of the magnetic disk 3, and the magnetic head output Improvement in the positioning accuracy by equalizing, data write, improving reading accuracy, it is possible to improve the reliability of the magnetic disk device. In addition, since the rolled plate material D is manufactured by punching, the accuracy is improved and the cost is very advantageous, and the productivity is improved because the machining process is shortened. In particular, since the ferrite crystal grain size is fine, heat generation is low, residual magnetism is low, magnetic resistance is low, and heat is hard to keep, so there is little distortion and high speed (disc rotation speed is increased). However, the accuracy does not decrease due to heat, and the failure due to heat is greatly reduced. In particular, since the residual stress is very small and distortion is small, positioning accuracy, data writing accuracy, and data reading accuracy can be improved, the failure rate can be reduced, and the rotation speed can be increased. Further, since the processing steps are shortened, the productivity is improved by 1.5 to 2 times.

  In this embodiment, the clamper 11 is attached to the rotary hub 10 with the screw 12 so as to press and hold the magnetic disk 3 and the spacer 9. However, the structure for attaching the clamper 11 is not limited to this. For example, a protrusion is provided on the peripheral surface of the cylindrical protrusion on which the uppermost clamper 11 of the rotating hub 10 is mounted, and the clamper is disposed between the upper end of the cylindrical portion on which the magnetic disk 3 and the spacer 9 are mounted and the protrusion. For example, a structure in which the screw 12 is not used, such as press-fitting the inner diameter portion, may be used.

  A rolled steel plate made of ferritic stainless steel (430) is punched into a ring shape, and spacers having an outer diameter of 23.8 mm, an inner diameter of 20.0 mm, and a thickness of 1.865 mm are formed in Example 1, Example 2, and Example 3. In addition, the same steel was manufactured by drilling a hole in a steel bar (round bar) manufactured by cold drawing of ferritic stainless steel (430) and cutting it into a pipe shape. Three types of spacers (external diameter 23.8 mm, internal diameter 20.0 mm, thickness 1.865 mm) were prepared as Conventional Example 1, Conventional Example 2, and Conventional Example 3.

  Example 1, Example 2 and Example 3 were manufactured by changing the processing conditions of the refining and steelmaking processes so that the crystal grain sizes were different. Conventional Example 1, Conventional Example 2, and Conventional Example 3 were also crystallized. It is manufactured by changing the processing conditions of the refining and steelmaking processes so that the particle size is different.

  And the surface hardness (HRV) of these Examples 1-3 and the prior art examples 1-3 was measured. For this measurement, Mitutoyo HM211 was used, the load was 100 g, and the measurement locations were 6 locations in the radial direction (0.5 mm pitch) in the circumferential direction shown in FIG. Table 1 shows the measurement results of Example 1 and Conventional Example 2.

  As can be seen from Table 1, in Example 1, the surface hardness is within 3.7% above and below the average value, and the hardness variation is very small and stable, whereas in Conventional Example 1, the surface hardness is above 7% above and below. The outer periphery is high in hardness but is significantly lower as it comes to the inner periphery. Here, the examples and the conventional examples are shown one by one, but similar results were obtained in the other examples.

Further, the crystal grain sizes (ferrite crystal grain sizes) of Examples 1 to 3 and Conventional Examples 1 to 3 were measured. The measurement of the crystal grain size is based on the measurement method defined in JIS G0551. The value of G calculated by the formula of m = 8 × 2 ^G using the crystal grain size number, that is, the average number of crystal grains m per 1 mm ^2. It was evaluated with. The results are shown in Table 2.

  As can be seen from Table 2, the crystal grain sizes of Examples 1 to 3 are finer than that of Conventional Examples 1 to 3.

  Moreover, the residual stress of the said Examples 1-3 and the prior art examples 1-3 was measured. For this measurement, X'PERT PRO MPD manufactured by PANalytical was used, and X-ray diffraction measurement was performed at Young's modulus: 211.160 Gpa and Poisson's ratio: 0.28820. The results are shown in Table 3.

  As can be seen from Table 3, the crystal grain sizes of Examples 1 to 3 are smaller than those of Conventional Examples 1 to 3.

  Residual stress is the stress generated inside as a result of the compositional deformation of the metal. It is caused by a sudden change or non-uniform change caused by cold working or heat treatment. There are compressive stress and tensile stress. The compressive stress is negative and the tensile stress is positive. Once generated, it can be removed by subsequent heat treatment or the like.

  A magnetic disk device (shown in FIG. 1) was assembled using the spacers of Examples 1 to 3 and the spacers of Conventional Examples 1 to 3, and an operation test was performed. At that time, in order to make it easy to confirm the effect, the operation was confirmed by increasing the rotational speed of the magnetic disk (by increasing the number of revolutions by 15%). As a result, it can be confirmed that the magnetic disk device using the spacer of Example 1 has improved positioning accuracy, data writing accuracy, and data reading accuracy over the magnetic disk device using the spacer of Conventional Example 1. It was. Specifically, the positioning accuracy, data writing accuracy, and data reading accuracy were improved by about 5%. In addition, failures such as contact of the magnetic disk and the magnetic head have been greatly reduced. It is thought that the fact that the variation in hardness is very small and stable greatly contributes to this effect. In addition, in Examples 1 to 3, the ferrite crystal grain size is very fine, heat generation is very small, and even if the rotational speed is 1.5 times, the accuracy does not decrease, and failure due to heat is also possible. This is considered to be a factor that greatly decreases. If the crystal grain size is small, the residual magnetism is small and the magnetic resistance is small, so it is difficult to keep heat. In Examples 1 to 3, the small residual stress contributes to the improvement of positioning accuracy, data writing accuracy, and data reading accuracy, and the failure rate is reduced (20% reduction) and allowable rotation is achieved. It is thought that the number can be increased (more than 10%).

2 Spindle motor 3 Magnetic disk 9 Spacer 10 Rotating hub 11 Clamper D Rolled plate

Claims (2)

Insert a spacer between multiple magnetic disks and insert it into the rotating hub of the spindle motor. Attach a disk-shaped clamper to the upper end of the rotating hub, and move the inner periphery of the magnetic disk by elastic deformation of the clamper. A spacer that is inserted between the magnetic disks of the magnetic disk device configured to press and hold the magnetic disk and the spacer between the large-diameter portion of the bottom of the rotating hub and the clamper ,
By punching a rolled sheet of ferritic stainless steel are produced by processing in a ring shape, the variation of surface hardness within 4% vertically around a mean value, grain size, the average crystal grain number m per 1 mm ² A spacer used for a magnetic disk drive, which corresponds to a G value of 5.0 to 9.0 calculated by an equation of m = 8 × 2 ^G and has a residual compressive stress of 80 MPa or less . Insert a spacer between multiple magnetic disks and insert it into the rotating hub of the spindle motor. Attach a disk-shaped clamper to the upper end of the rotating hub, and move the inner periphery of the magnetic disk by elastic deformation of the clamper. A magnetic disk device configured to press and hold a magnetic disk and a spacer between a large-diameter portion of the bottom of the rotating hub and a clamper,
The spacer is manufactured by punching a ferritic stainless steel rolled plate material into a ring shape, and the surface hardness variation is within 4% above and below the average value, and the crystal grain size is an average crystal per 1 mm ^2. corresponds to 5.0 to 9.0 of the value of G calculated by the formula of m = 8 × 2 ^G using a particle number m, the magnetic disk apparatus characterized by residual compressive stress is less than 80 MPa.

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