JP2002298525A - Magnetic disk unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disk unit which is small in necessary volume, light in weight, also reduces the resonance gain of a resonance frequency of a rotary actuator and can improve the stability of a positioning servo system. SOLUTION: The voice coil motor of this magnetic disk unit comprises a driving coil formed integrally with the rotary actuator, a pair of magnetic circuits arranged on both sides of the driving coil, a magnet arranged on a surface facing the driving coil of one of the magnetic circuits, and a viscoelastic body arranged between one of the magnetic circuits and the magnet and for connecting the one of the magnetic circuits and the magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive for recording and reproducing information on a rotating magnetic disk.

[0002]

2. Description of the Related Art A magnetic disk drive rotates a magnetic disk and records or reads information on a plurality of concentric circles by a magnetic head positioned at an arbitrary radial position on the magnetic disk. And is positioned on an arbitrary track. The rotary actuator is made of aluminum or a magnesium alloy, and is integrally formed with a suspension made of a stainless steel plate for supporting the magnetic head fixed thereto. Alternatively, a thin plate suspension made of a stainless steel plate is stacked before the head arm. The rotary actuator is driven to rotate in the radial direction of the magnetic disk by a voice coil motor (VCM) about a rotation axis that supports and rotates the rotary actuator. As a voice coil motor of a small device, a planar type in which a coil is wound on a plane parallel to a moving plane is generally used.

Here, the rotary actuator having the above configuration has a problem that the positioning accuracy of the magnetic head cannot be improved due to the resonance frequency generated by the rotary actuator itself. That is, since the magnetic head is positioned by the positioning servo system, if the resonance frequency of the rotary actuator affecting the servo system is low, servo for positioning control cannot be stably performed by the servo system. Also,
Normally, even when servo is stably applied, vibration of the resonance frequency of the rotary actuator occurs due to sudden disturbance or the servo band cannot be increased much, and as a result, positioning accuracy cannot be improved. For this reason, it is necessary to increase the resonance frequency of the rotary actuator as much as possible or to lower the resonance peak.
Either measure can reduce the influence of disturbance or improve the positioning accuracy by improving the servo band.

FIGS. 8 and 9 show an example of a resonance mode caused by a voice coil motor of a rotary actuator made of a stainless steel arm. FIG. 8 shows a state in which a resonance frequency in the vertical vibration mode is generated in the rotary actuator. In this example, the entire rotary actuator is tilted in the seek direction, and an unstable sub-peak occurs near 1 kHz. FIG. 9 shows a state in which the rotary actuator vibrates in the seek direction. In this example, the rotary actuator is 6.6k
A mode with a main resonance frequency of Hz has occurred. 8 and 9
As shown in the figure, the resonance frequency generated in the rotary actuator becomes an obstacle, and the modes of these resonance frequencies are excited to cause unstable phenomena such as oscillation. Therefore, it is desired to raise the servo band higher than the resonance frequency generated in the rotary actuator. I couldn't raise it.

To prevent this, it is necessary to increase the value of the resonance frequency generated in the rotary actuator. However, since there is a limit in a method of increasing the value of the resonance frequency, it is necessary to reduce the resonance gain by increasing the damping for the rotary actuator. As a method for damping the rotary actuator, Japanese Patent Application Laid-Open No. 3-173342 discloses a method in which a member having a viscous resistance and a restraining plate are attached to the upper part of a magnetic circuit. This is proposed to reduce residual vibration during seeking, and absorbs vibration of a magnetic circuit by deformation of a viscous resistance member sandwiched between a restraint plate of a stationary member and the magnetic circuit.

[0006]

However, in the above-mentioned conventional method, the restraining of the restraining plate is insufficient, so that the damping effect is small and the positioning servo system becomes unstable. Since it is necessary, there is a problem that the magnetic circuit itself becomes large and heavy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a small volume and a light weight, and can reduce a resonance gain of a resonance frequency of a rotary actuator. It is an object of the present invention to provide a magnetic disk drive capable of improving the stability of a system.

[0008]

According to the present invention, there is provided a magnetic disk drive comprising: a magnetic disk for recording information; a magnetic head for recording and reproducing information on and from the magnetic disk;
A rotary actuator that movably supports the magnetic head with respect to the magnetic disk; and a voice coil motor that drives the rotary actuator to rotate in a radial direction of the magnetic disk. A drive coil formed integrally with the drive coil, a pair of magnetic circuits disposed on both sides of the drive coil, a magnet disposed on one surface of the magnetic circuit facing the drive coil, and one of the magnetic circuits And a viscoelastic body that is arranged between the magnet and one of the magnetic circuits and joins the magnet.

According to another aspect of the present invention, there is provided a magnetic disk device for recording information, a magnetic head for recording and reproducing information on and from the magnetic disk, and a movable magnetic head for the magnetic disk. A rotary actuator for supporting, comprising a voice coil motor that drives the rotary actuator to rotate in the radial direction of the magnetic disk, the voice coil motor,
A drive coil formed integrally with the rotary actuator, a pair of magnetic circuits disposed on both sides of the drive coil, and a magnet disposed on a surface of the magnetic circuit facing one of the drive coils, At least one of the magnetic circuits has a configuration in which a viscoelastic body is sandwiched therebetween.

As a result, in the magnetic disk drive of the present invention, the required volume is small and light, and the resonance gain of the resonance frequency of the rotary actuator can be reduced, so that the stability of the positioning servo system can be improved. It is possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the magnetic disk drive according to the present invention will be described below with reference to the drawings. FIG.
FIG. 1 is a diagram showing an overview of an HDD of the present invention.

As shown in FIG. 1, in the magnetic disk drive of the present invention, a housing 1 on a rectangular box having an open upper surface and an upper end opening of the housing screwed to the housing 1 with a plurality of screws are provided. And a top cover (not shown) for closing. A magnetic disk 2, a spindle motor 3 as driving means for supporting and rotating the magnetic disk 2, a magnetic head 4 for recording and reproducing information on the magnetic disk 2, and a magnetic head 4 A rotary actuator 5 having a suspension mounted on a magnetic head 4 movably supporting a magnetic head 4, a rotary shaft 6 rotatably supporting the rotary actuator 5, and a voice for rotating and positioning the rotary actuator 5 via the rotary shaft 6. A coil motor 7 and a head amplifier circuit 8 are housed therein. (First Embodiment) FIG. 2 shows a configuration of a voice coil motor 7 which is a feature of the present invention. The voice coil motor 7 is applied to, for example, a 2.5-inch magnetic disk drive. A magnet 13 having a thickness of about 1.8 [mm] is provided on a lower magnetic circuit 11 having a thickness of about 1.8 [mm].
Are joined via a viscoelastic body 4. Upper magnetic circuit 1
2 and the lower magnetic circuit 11 are configured by a magnetic pair such as iron.

The thicker the viscoelastic body 4 is, the higher the damping effect is. However, if the thickness is too large, the efficiency of the lower magnetic circuit 11 is reduced. Therefore, the thickness is preferably about 50 to 100 [μm]. Further, the viscoelastic body 4 has a size of 1 to 10 so as to suppress the resonance frequency of the rotary actuator 5.
Those having a damping effect of suppressing resonance in a frequency band of [kHz] are preferable. Further, as a material of the viscoelastic body 4, it is preferable that silicon (Si) is not contained at all, or even if it is contained, a very small amount is contained. Further, as the material of the viscoelastic body 4, a material which does not generate gas or has a very small amount of gas generation even if gas is generated is preferable.

There is a magnetic gap of about 1.7 [mm] between the magnet 13 and the upper magnetic circuit 12, between which a magnetic gap of about 1.
The drive coil 15 having a thickness of 25 [mm] is arranged. A magnetic flux runs in the vertical direction in the magnetic gap, and when an electric current is applied to the planar drive coil 15, a driving force in the left and right direction is generated. The distance between the drive coil 15 and the magnet 13 and the distance between the drive coil 15 and the upper magnetic circuit 12 are each 0.1 mm.
It is set to about 3 [mm]. This value is desired to be as small as possible in order to increase the driving force. However, if the value is too small, the driving coil 15 may come into contact with the magnet 13 or the upper magnetic circuit 12 due to an assembly error. It is about 3 [mm].

FIG. 3 shows the measurement results of the resonance gain of the rotary actuator 5 when the above-described voice coil motor is applied to a 2.5-inch magnetic disk drive. The solid line shows the measurement result in the case of the present invention, and is 50%.
A [μm] thick viscoelastic body 4 is used. The two-dot chain line shows the measurement results in the conventional case where no viscoelastic body is used. As can be seen from FIG. 3, the value of the resonance peak of the present invention is reduced by about 3 [dB] in the vicinity of the resonance frequency of 6.7 [kHz] where the value of the resonance peak is the largest. Even at other resonance frequencies, the present invention
The value of the resonance peak has decreased. As described above, the value of the resonance peak can be reduced, and as a result, the stability of the positioning servo system can be improved.

As the viscoelastic body, for example, a damping material such as "LA-50" manufactured by Nitto Denko Corporation is used.
Further, three or four convex portions having a height of about 0.4 [mm] are provided on the upper portion of the lower magnetic circuit 11 in order to position the magnet 13. Due to this convex portion, the magnet 13 is installed at a correct position of the lower magnetic circuit 11. Even if the magnet 13 rises from the lower magnetic circuit 11 due to an unexpectedly large impact or the like, the magnet 13 rises only about 0.3 [mm], which is the distance to the drive coil 15, so that the projection 13 There is no departure from. When the shock disappears, the magnet 1
3 automatically returns to the original position by a magnetic attraction force acting between the lower magnetic circuit 11. (Second Embodiment) Next, the configuration of the voice coil motor 7 of the magnetic disk drive of the second embodiment shown in FIG. 4 will be described. The lower magnetic circuit 21 having a thickness of about 1.8 [mm] has a thickness of about 1.
An 8 [mm] magnet 23 is joined. The upper magnetic circuit 22 includes a magnetic circuit 22a having a thickness of 0.7 [mm] and a magnetic circuit 22b having a thickness of 0.7 [mm] having a thickness of 0.1 [mm].
It is configured to be joined via a thick viscoelastic body 24. That is, the present embodiment is characterized in that the upper magnetic circuit 22 has a configuration in which two magnetic circuits 22a and 22b having substantially the same thickness sandwich the viscoelastic body 24. Here, the viscoelastic body 24 is disposed between the magnetic circuit 22a and the magnetic circuit 22b by bonding or simply sandwiching the magnetic circuit 22a and the magnetic circuit 22b. There is a magnetic gap of about 1.7 [mm] between the magnet 23 and the upper magnetic circuit 22, and about 1.0 [mm] formed integrally with the rotary actuator 5 during this time.
The drive coil 25 having a thickness of 25 [mm] is arranged.

The magnetic circuits 21 and 22 are made of a magnetic material such as iron. The magnetic flux generated from the magnet 23 passes through the magnetic circuits 22a and 22b to form a magnetic field in the magnetic gap. When the rotary actuator 5 resonates, the reaction force of the driving force generated by the driving coil 25 enters the magnetic circuits 22a and 22b.
b vibrates independently across the viscoelastic body 24. For this reason, a large distortion is generated in the viscoelastic body 24, and as a result, energy loss of resonance of the rotary actuator 5 is caused. Therefore, the resonance of the rotary actuator 5 is damped (attenuated), and the positioning servo system is further improved. Can be stabilized. Magnetic circuits 22a, 22b
The viscoelastic body 24 can be reduced in cost by forming a commercially available plate having the same configuration as a damping steel plate by pressing or the like. (Third Embodiment) Next, the configuration of the voice coil motor 7 of the magnetic disk drive of the third embodiment shown in FIG. 5 will be described. In FIG. 5, the drive coil is omitted. 5 is different from the configuration of FIG. 4 in that the magnetic circuit 32a and the magnetic circuit 32b constituting the magnetic circuit 32 have different plate thicknesses. That is, in the present embodiment, the plate thickness of the magnetic circuit 32 b close to the magnet 33 is smaller than the magnetic circuit 32
The feature is that it is thicker than a. Magnet 3
By increasing the plate thickness of the magnetic circuit 32b close to the magnetic circuit 32, the efficiency of the magnetic circuit is increased and a drive coil (not shown)
2b and the magnet 33) can be increased.

The thickness of each component is determined, for example, by the magnetic circuit 32a.
Is about 0.2 [mm], and the magnetic circuit 32b is 1.2 [m].
m], the viscoelastic body 34 is 0.1 [mm], and the lower magnetic circuit 3
1 is 1.8 [mm], and the magnet 33 is 1.8 [m].
m], the drive coil (not shown) is 1.25 [mm], and the gap between the magnetic circuit 32b and the magnet 33 is 1.7 [m].
m]. (Fourth Embodiment) Next, the configuration of the voice coil motor 7 of the magnetic disk drive of the fourth embodiment shown in FIG. 6 will be described. In FIG. 6, the drive coil is omitted. In FIG.
A sheet-like thin plate 45 is provided in the upper magnetic circuit 42 by the viscoelastic body 4.
There is a feature in the configuration bonded by No. 4. Thin plate 45
May be either a magnetic material or a non-magnetic material.
4, it is necessary to set the plate thickness to about 0.1 to 0.2 [mm]. By making the thickness of the thin plate 45 extremely thin and making the thickness of the magnetic circuit 44 sufficiently large, it becomes possible to generate a large driving force in a driving coil (not shown). When the rotary actuator 5 resonates, the upper magnetic circuit 42 vibrates in the thickness direction and the viscoelastic body 44 also tries to be distorted in the vertical direction. However, since the longitudinal direction of the viscoelastic body 44 is restrained by the thin plate 45, a large shear Since distortion occurs, large damping can be provided.

The thickness of each component is, for example, about 0.05 [mm] for the thin plate 45, 0.05 [mm] for the viscoelastic body 44,
The upper magnetic circuit 42 is 1.4 [mm], and the lower magnetic circuit 41
Is 1.8 [mm], the magnet 43 is 1.8 [mm],
The drive coil (not shown) is 1.25 [mm], and the gap between the upper magnetic circuit 42 and the magnet 43 is 1.7 [mm]. (Fifth Embodiment) Next, the configuration of the voice coil motor 7 of the magnetic disk drive of the fifth embodiment shown in FIG. 7 will be described. In FIG. 7, the drive coil is omitted. FIG. 7 is characterized in that the lower magnetic circuit 51 has a configuration in which a viscoelastic body 54 is sandwiched between the magnetic circuit 51a and the magnetic circuit 51b. Here, the viscoelastic body 54 is a magnetic circuit 51a.
And the magnetic circuit 52b is disposed in the middle by bonding or simply sandwiching it. When the rotary actuator 5 resonates, a reaction force of a driving force generated by a driving coil (not shown) enters the magnetic circuits 51a and 51b, and the magnetic circuits 51a and 51b vibrate independently with the viscoelastic body 54 interposed therebetween. For this reason, a large distortion is generated in the viscoelastic body 54. As a result, energy loss of resonance of the rotary actuator 5 is caused, and the resonance can be damped (attenuated).

The thickness of each component is determined, for example, by the magnetic circuit 51a.
Is about 0.9 [mm], the viscoelastic body 54 is 0.1 [mm],
The magnetic circuit 51b is 0.8 [mm], the upper magnetic circuit 52 is 1.4 [mm], the magnet 53 is 1.8 [mm], the drive coil (not shown) is 1.25 [mm], and the upper magnetic circuit 5 is not shown.
The gap between 2 and the magnet 53 is 1.7 [mm].

[0021]

As described in detail above, according to the present invention, the required volume is small and the weight is small, and the resonance gain of the resonance frequency of the rotary actuator can be reduced.
It is possible to improve the stability of the positioning servo system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overview of a magnetic disk drive according to the present invention.

FIG. 2 is a diagram illustrating a configuration of a rotary actuator according to the first embodiment.

FIG. 3 is a diagram showing a measurement result of a resonance gain of a rotary actuator.

FIG. 4 is a diagram illustrating a configuration of a rotary actuator according to a second embodiment.

FIG. 5 is a diagram illustrating a configuration of a rotary actuator according to a third embodiment.

FIG. 6 is a diagram illustrating a configuration of a rotary actuator according to a fourth embodiment.

FIG. 7 is a diagram illustrating a configuration of a rotary actuator according to a fifth embodiment.

FIG. 8 is a diagram showing a state when a resonance frequency of a vertical vibration mode of a rotary actuator is generated.

FIG. 9 is a diagram showing a state where the rotary actuator vibrates in a seek direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Case, 2 ... Magnetic disk, 3 ... Spindle motor, 4 ... Magnetic head, 5 ... Rotary actuator, 6 ... Rotation axis, 7 ... Voice coil motor, 8 ... Head amplifier circuit, 11, 21, 31, 41, 51: Lower magnetic circuit, 12, 22, 32, 42, 52: Upper magnetic circuit, 13, 23, 33, 43, 53: Magnet, 1
4, 24, 34, 44, 54 ... viscoelastic body, 15, 25 ...
Drive coil, 22a, 22b, 32a, 32b, 51
a, 51b: magnetic circuit, 45: thin plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D068 AA01 BB01 CC12 EE01 EE17 GG25 5H633 BB02 BB15 GG03 GG06 GG08 HH02 HH05 HH14 HH24 JA04

Claims (5)

[Claims] A magnetic disk for recording information; a magnetic head for recording and reproducing information on and from the magnetic disk; a rotary actuator movably supporting the magnetic head with respect to the magnetic disk; A voice coil motor that drives a rotary actuator to rotate in a radial direction of the magnetic disk, wherein the voice coil motor includes a drive coil formed integrally with the rotary actuator, and a pair of coils disposed on both sides of the drive coil. A magnetic circuit, a magnet disposed on a surface of the magnetic circuit facing one of the drive coils, and joining one of the magnetic circuit and the magnet disposed between one of the magnetic circuits and the magnet. A magnetic disk device comprising: 2. A magnetic disk for recording information, a magnetic head for recording and reproducing information on and from the magnetic disk, a rotary actuator movably supporting the magnetic head with respect to the magnetic disk, A voice coil motor that drives a rotary actuator to rotate in a radial direction of the magnetic disk, wherein the voice coil motor includes a drive coil formed integrally with the rotary actuator, and a pair of coils disposed on both sides of the drive coil. And a magnet disposed on a surface of the magnetic circuit facing one of the drive coils, wherein at least one of the magnetic circuits has a configuration in which a viscoelastic body is sandwiched therebetween. Magnetic disk drive. 3. The magnetic circuit having a configuration in which the viscoelastic body is sandwiched between the viscoelastic body and the plate near the drive coil is thicker than the plate far from the drive coil. 3. The magnetic disk drive according to claim 2, wherein: 4. A magnetic disk for recording information, a magnetic head for recording and reproducing information on and from the magnetic disk, a rotary actuator for movably supporting the magnetic head with respect to the magnetic disk, A voice coil motor that drives a rotary actuator to rotate in a radial direction of the magnetic disk, wherein the voice coil motor includes a drive coil formed integrally with the rotary actuator, and a pair of coils disposed on both sides of the drive coil. And a magnet arranged on a surface of the magnetic circuit facing one of the drive coils, and at least one of the magnetic circuits has a viscoelastic body on a surface opposite to a surface facing the drive coil. A magnetic disk drive characterized in that it has a configuration in which a thin plate is adhered through the intermediary. 5. The viscoelastic body has a thickness of 50 μm to 10 μm.
5. The magnetic disk drive according to claim 1, wherein said magnetic disk drive has a thickness of 0 [mu] m.