JP2009118661A - Actuator, magnetic head assembly, and magnetic disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator which can finely displace an object in a predetermined surface and has high-speed followability and is hardly spatially constrained in a direction vertical to the predetermined surface, and also to provide a magnetic head assembly and a magnetic disc device using the same. <P>SOLUTION: The actuator 20 comprises of two piezoelectric elements 21 disposed on both sides of a slider 13 equipped with a magnetic head 13a. These piezoelectric elements 21 have such a mechanism that a piezoelectric structure contracts corresponding to the application of voltage and then an arm section of a tabular hinge disposed on the top face of the piezoelectric structure deforms due to the contraction of the piezoelectric structure and rotates a slider 13 about the center of gravity thereof. As a result, the magnetic head 13a is finely displaced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an actuator suitable for controlling a minute displacement of a magnetic head used in a magnetic disk device, a magnetic head assembly using the actuator, and a magnetic disk device.

  In many information devices, an actuator is used for movement control of a small part at a minute distance. For example, in information equipment equipped with an optical system, an actuator is used for focus correction and tilt angle control. In an ink jet printer or a magnetic disk device, an actuator is used for movement control of the printer head or the magnetic head. In recent years, miniaturization and high performance of these information devices have been promoted, and accordingly, an actuator capable of controlling movement of a minute distance with high accuracy is desired.

  In the case of a magnetic disk device, the recording capacity per magnetic disk has been remarkably increased with the demand for larger capacity. In order to increase the recording capacity without changing the size of the magnetic disk, the number of tracks per unit length (track per inch: TPI) must be increased, that is, the track width should be narrowed and arranged at a high density. Is essential. For this reason, it is necessary to precisely control the position of the magnetic head in the radial direction of the magnetic disk.

  The magnetic head (recording element and reproducing element) is disposed on an end face of a substantially rectangular parallelepiped member called a slider. In a conventional magnetic disk apparatus, a suspension arm that supports a slider is rotated within a predetermined angle range in a direction parallel to the surface of the magnetic disk by an electromagnetic actuator (voice coil motor) to position the magnetic head. However, as the track density increases, it has become difficult to precisely control the positioning of the magnetic head by simply rotating the suspension arm with an electromagnetic actuator.

In Patent Document 1, a pair of piezoelectric elements are arranged between the proximal end side and the distal end side of a suspension arm, and the distal end side of the suspension arm is minutely displaced within the plane parallel to the surface of the magnetic disk by these piezoelectric elements. It has been proposed to let Patent Documents 2 to 4 propose that a small actuator is disposed between the slider and the suspension arm, and the slider is slightly displaced in a plane parallel to the surface of the magnetic disk.
JP-A-11-242864 JP 2004-30823 A JP 2006-14557 A WO2004 / 093205

  However, in the method described in Patent Document 1, the distance between the actuator and the slider is relatively large. In the methods described in Patent Documents 2 to 4, an actuator is disposed between the slider and the suspension, so that high-speed followability is good, but the actuator is disposed in a direction perpendicular to the surface of the magnetic disk. Space is required, and in a magnetic disk device having a plurality of magnetic disks mounted thereon, it may be necessary to reduce the number of mounted disks.

  As described above, an object of the present invention is an actuator that can displace a target object within a predetermined plane, is excellent in high-speed followability, and is hardly subject to space restrictions in a direction perpendicular to the predetermined plane. Is to provide.

  Another object of the present invention is that the magnetic head can be minutely displaced in a plane parallel to the surface of the magnetic disk, has excellent high-speed followability, and has a space perpendicular to the surface of the magnetic disk. It is an object of the present invention to provide a magnetic head assembly and a magnetic disk device that are hardly restricted.

  According to one aspect of the present invention, there is provided an actuator that is interposed between a support member and an object and rotates the object within a predetermined angle range around its center of gravity, and is disposed on both sides of the object. And a pair of piezoelectric elements supported by the support member, wherein the piezoelectric element expands and contracts according to an applied voltage, and the surface of the piezoelectric structure on the support member side or the support An actuator having a plate-like member disposed on a surface opposite to the member and connected to the object is provided.

  According to another aspect of the present invention, a suspension, a magnetic head that records and reproduces information on and from a magnetic disk, a slider disposed at the tip of the suspension, and a slider disposed on both sides of the slider are applied. An actuator composed of a pair of piezoelectric elements having a piezoelectric structure that expands and contracts in response to a voltage, and the actuator has the center of gravity of the slider according to a voltage applied to the piezoelectric structure A magnetic head assembly is provided that rotates within a predetermined angular range as a center.

  According to still another aspect of the present invention, a magnetic disk capable of magnetically recording information, a slider provided with a magnetic head for recording and reproducing information on the magnetic disk, and arranged on both sides of the slider An actuator configured to include a pair of piezoelectric elements including a piezoelectric structure that expands and contracts according to an applied voltage, and rotates the slider within a predetermined angular range around its center of gravity, and supports the slider and the actuator There is provided a magnetic disk device having a suspension arm that moves and a moving unit that drives the suspension arm to move the slider in the radial direction of the magnetic disk.

  In the present invention, an actuator is constituted by piezoelectric elements respectively disposed on both sides of an object to be minutely displaced (for example, a slider provided with a magnetic head), and the object is rotated around the center of gravity by the actuator. Thereby, the member (magnetic head etc.) arrange | positioned at the end surface of a target object can be minutely displaced within a predetermined surface. In the present invention, since the object is driven by a pair of piezoelectric elements arranged on the side thereof, the high-speed followability is good and the space in the direction perpendicular to the predetermined plane is hardly restricted.

  Further, in the present invention, since the object is rotated around the center of gravity, the center of gravity does not move, and even if the present invention is applied to the magnetic head assembly, the control band caused by suspension resonance accompanying the movement of the center of gravity. Is avoided.

  In one embodiment of the present invention, a plate-like member connected to the object is disposed on the surface of the piezoelectric structure on the support member side or the surface opposite to the support member, and the object is interposed through the plate-like member. Displace the object. In this case, the plate-like member includes first and second joint portions that are joined to both ends of the piezoelectric member structure on the support member side or in the expansion and contraction direction of the surface opposite to the support member, An arm portion connected to an object, a first beam portion provided along a side of the piezoelectric structure on the object side and communicating between the first joint portion and the arm portion; It is preferable to have a second beam portion that is provided along a side opposite to the object of the body structure and communicates between the second joint portion and the arm portion. By adopting such a structure, the tip of the arm portion is greatly displaced due to expansion and contraction of the piezoelectric structure accompanying voltage application, and the object can be displaced greatly.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, an example in which the actuator according to the present invention is applied to a magnetic head assembly of a magnetic disk device will be described.

  FIG. 1 is a plan view showing a magnetic disk device including a magnetic head assembly according to an embodiment of the present invention. As shown in FIG. 1, a magnetic disk device includes a disk-shaped magnetic disk 11, a spindle motor (not shown) for rotating the magnetic disk 11, and a magnetic head (recording element and reproducing device) in a metal casing. A slider 13 provided with an element), a suspension arm (support member) 14 that supports the slider 13, an electromagnetic actuator (voice coil motor) 15 that drives the suspension arm 14, and a magnetic disk 11 via a magnetic head. And an electronic circuit (not shown) for recording and reproducing information.

  The magnetic disk 11 is fixed to the rotating shaft 12a of the spindle motor and is rotated at a high speed by the spindle motor. The suspension arm 14 includes a carriage arm 14a on the base end side (center axis 15a side) and a leaf spring suspension 14b on the tip end side. The slider 13 is disposed on the surface on the magnetic disk 11 side of a portion called a gimbal at the tip of the suspension 14b. The suspension arm 14 is driven and controlled by an electromagnetic actuator 15 and rotates within a predetermined angular range about a central axis 15a.

  FIG. 2 is a schematic diagram showing the slider 13, the actuator 20, and the suspension 14b. As shown in FIG. 2, the actuator 20 according to this embodiment includes a pair of piezoelectric elements 21 disposed on both sides of the slider 13. The slider 13 is disposed below the gimbal 14c provided at the tip of the suspension 14b via the actuator 20. The actuator 20 (the two piezoelectric elements 21) is joined to the lower surface of the gimbal 14c at two diagonal portions shaded in FIG. Note that reference numeral 13 a in FIG. 2 schematically shows a magnetic head (recording element and reproducing element) provided on the end face of the slider 13. As the recording element, for example, a single magnetic pole head is used, and as the reproducing element, for example, an MR (Magneto Resistive) element, a GMR (Giant Magneto Resistive) element, or a TMR (Tunnel Magneto Resistive) is used. These recording elements and reproducing elements are formed by repeating a film forming process and a patterning process.

  3A is a front view of the piezoelectric element 21 (viewed from the direction of arrow A in FIG. 2), FIG. 3B is a top view thereof, and FIG. 3C is a right side view thereof. is there.

  As shown in FIG. 3A, the piezoelectric element 21 has a piezoelectric structure 30 configured by sandwiching an interlayer electrode 32 between a plurality of piezoelectric films 31. On the piezoelectric structure 30, a hinge (plate-shaped member) 40 made of a metal plate such as stainless steel is disposed. The hinge 40 is joined to both ends in the longitudinal direction of the piezoelectric structure 30 by an adhesive 33. Further, collective electrodes 35 are formed on both end faces of the piezoelectric structure 30 in the longitudinal direction. The collective electrode 35 on one side (left side in FIG. 3A) is electrically connected to the odd-numbered interlayer electrodes 32 counted from above, and the collective electrode 35 on the other side (right side in FIG. 3B). Are electrically connected to the even-numbered interlayer electrode 32. These collective electrodes 35 are electrically connected to wiring (not shown) formed on the surface of the suspension 14b via an insulating film via a fine metal wire (bonding wire) 23 as shown in FIG. Yes. In addition, the code | symbol 25 in FIG. 4 has shown the adhesive agent which joins the piezoelectric element 21 to the gimbal 14c.

  As shown in FIG. 3 (b), the hinge 40 is joined to both ends of the piezoelectric structure 30 in the longitudinal direction by an arm portion 41 that projects from the center portion to the slider side and is joined to the slider, and an adhesive 33. The first joint portion 42a and the second joint portion 42b are arranged along the side on the slider 13 side of the piezoelectric body structure 30 and communicated between the arm portion 41 and the first joint portion 42a. 1 beam portion 43a and a second beam portion 43b disposed along the side opposite to the slider 13 of the piezoelectric structure 30 and communicating between the arm portion 41 and the second joint portion 42b. Have. In the present embodiment, as shown in FIG. 3B, the second beam portion 43b is formed wider than the first beam portion 43a.

  5 and 6 are schematic views showing the operation of the actuator of this embodiment. 5A and 5B show the operation of the piezoelectric element 21 alone, and FIGS. 6A and 6B show the displacement of the slider 13. As shown in FIG. 6A, the arm portions 41 of the two piezoelectric elements 21 constituting the actuator 20 are joined to a point-symmetrical position with the center of gravity of the slider 13 as the center.

  As shown in FIG. 5A, when no voltage is applied to the piezoelectric element 21, the arm portion 41 extends in a direction perpendicular to the longitudinal direction of the piezoelectric element 21. In this case, as shown in FIG. 6A, the central axis of the slider 13 coincides with the direction in which the track of the magnetic disk extends (indicated by a one-dot chain line in the figure).

  When a predetermined voltage is supplied to the piezoelectric element 21 via the collective electrode 35, the piezoelectric structure 30 constituting the piezoelectric element 21 expands or contracts in the longitudinal direction. In the present embodiment, the same voltage is supplied to the two piezoelectric elements 21 constituting the actuator 20. The rate at which the piezoelectric structure 30 expands or contracts corresponds to the applied voltage. Here, it is assumed that a voltage is applied so that the piezoelectric structure 30 contracts.

  By applying a voltage to the piezoelectric element 21, the piezoelectric structure 30 contracts as shown in FIG. 5B, but the lengths of the beam portions 43a and 43b made of metal such as stainless steel hardly change. Therefore, reverse stress is applied to the arm portion 41 from the beam portions 43a and 43b. As a result, the arm portion 41 tilts and the position of the tip thereof changes greatly.

  In the present embodiment, as shown in FIGS. 6A and 6B, the two piezoelectric elements 21 constituting the actuator 20 are disposed at point-symmetrical positions with the center of gravity of the slider 13 as the center. Along with the movement of the distal end portion of the arm portion 41 of 21, a force in the rotation direction around the center of gravity acts on the slider 13. That is, according to the voltage applied to the piezoelectric element 21, as shown in FIG. 6B, the slider 13 is inclined with respect to the direction in which the track of the magnetic disk extends, and the magnetic head (recording element and The reproducing element) is displaced by Δx in the track width direction. In this manner, in the present embodiment, the position of the magnetic head can be displaced by applying a voltage to the two piezoelectric elements 21 constituting the actuator 20.

  In the present embodiment, the suspension arm 14 is driven by the electromagnetic actuator 15 to determine the position of the slider 13, and the position of the magnetic head is further determined by the actuator 20 (piezoelectric element 21) interposed between the suspension 14 b and the slider 13. Since the fine adjustment is performed, the magnetic head can follow the track of the magnetic disk having a high track density. In the present embodiment, since the slider 13 is directly displaced by the actuator 20 fixed to the suspension 14b (gimbal 14c), the magnetic head has good high-speed followability and the magnetic recording medium rotates at high speed. It can be applied to the device. Further, in this embodiment, since the two piezoelectric elements 21 constituting the actuator 20 are arranged on both sides of the slider 13, a space required in a direction perpendicular to the surface of the magnetic disk can be reduced, and the magnetic disk can be reduced. Even in a magnetic disk device mounted with a plurality of disks, it is not necessary to reduce the number of disks mounted.

  In this embodiment, the position of the magnetic head is displaced by rotating the slider 13 around the center of gravity of the slider 13 by the actuator 20, but the slider 50 is tracked by the actuator 50, for example, as schematically shown in FIG. It is also conceivable to translate in the width direction (direction indicated by the arrow in the figure). However, if the slider 13 is translated in the width direction of the track, the position of the center of gravity of the suspension 51 also changes, so it becomes difficult to excite the resonance of the suspension 51 to increase the control band, and the high-speed followability is reduced. To do.

  On the other hand, in the present embodiment, as shown in FIGS. 6A and 6B, the center of gravity of the slider 13 does not change even if the position of the magnetic head is displaced. High-speed followability can be obtained.

  Hereinafter, the manufacturing method of the actuator and the magnetic head assembly according to this embodiment will be described with reference to FIGS.

  First, for example, a PNN (lead niobate niobate) -PT (lead titanate) -PZ (lead zirconate) ceramic green sheet is prepared as a material of the piezoelectric structure 30 shown in FIG. Instead of the PNN-PT-PZ ceramic green sheet, a sheet of piezoelectric material such as PZT may be used.

  Next, the conductive paste which has Pt (platinum) as a main component is screen-printed on the surface of a PNN-PT-PZ ceramic green sheet. Thereafter, a predetermined number of PNN-PT-PZ ceramic green sheets printed with this conductive paste are laminated and fired at 1050 ° C. in the atmosphere to form a piezoelectric laminated ceramic sheet. Next, the piezoelectric multilayer ceramic sheet is cut into a desired size to obtain the piezoelectric structure 30. Then, a conductor film such as Pt is formed on both end faces of the piezoelectric structure 30 to form a collective electrode 35.

  On the other hand, the stainless steel plate is processed into a predetermined shape to form the hinge 40. Then, the first joint portion 42 a and the second joint portion 42 b of the hinge 40 are joined to the piezoelectric structure 30 by the adhesive 35. In this way, the piezoelectric element 21 is completed.

  After that, as shown in FIG. 2, the two piezoelectric elements 21 are arranged with the slider 13 interposed therebetween, and the tip of the arm portion 41 of the piezoelectric element 21 is joined to the slider 13. Then, the piezoelectric element 21 and the suspension 14b (gimbal 14c) are joined. In this way, a magnetic head assembly including the actuator 20 according to this embodiment is completed.

  Hereinafter, the result of examining the displacement amount of the magnetic head of the magnetic head assembly according to the present embodiment will be described. As shown in FIG. 8, a pair of piezoelectric elements 21 provided with a hinge 40 made of a stainless steel plate having a length L1 of 850 μm, a width W1 of 180 μm, a length A1 of the arm portion 41 of 355 μm, and a thickness of 20 μm was formed. . Then, a 100 μm portion at the tip of the arm portion 41 of these piezoelectric elements 21 was joined to the slider 13. The slider 13 has a length L2 of 850 μm, a width W2 of 700 μm, and a height of 240 μm. Note that the bottom surface of the piezoelectric element 21 needs to be higher than the bottom surface of the slider 13. Further, the thickness of the hinge 40 is set to 50 μm or less, more preferably 20 μm or less from the viewpoint of securing a space in a direction perpendicular to the surface of the magnetic disk. However, if the hinge 40 is excessively thinned, the strength necessary for driving the slider 13 cannot be secured, so the thickness of the hinge 40 needs to be set as appropriate.

  A simulation calculation was performed on the magnetic head assembly to calculate the amount of displacement of the magnetic head disposed on the end face of the slider 13. FIG. 9 is a diagram showing the result of the simulation calculation. As a result of this simulation, the displacement of the magnetic head was 140 nm.

(Modification)
FIG. 10 is a view showing a modification of the actuator according to the present embodiment. In the actuator 20 shown in FIG. 2, the two piezoelectric elements 21 constituting the actuator 20 are separated from each other. However, in the actuator shown in FIG. 10, the tips of the arm portions 62 of the two piezoelectric elements 61 are connected. The structure, that is, the hinge of the two piezoelectric elements 61 is integrated. Also in this modification, the same effect as the above-described embodiment can be obtained.

  In the above-described embodiment, the example in which the actuator according to the present invention is applied to the magnetic head assembly has been described. Of course, it may be used.

  In the above-described embodiment, the case where the hinge (plate-shaped member) is disposed on the surface of the piezoelectric structure on the suspension (support member) side is described. You may arrange | position on the surface on the opposite side to a supporting member.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1) An actuator that is interposed between a support member and an object and rotates the object within a predetermined angle range around its center of gravity,
A piezoelectric structure that is arranged on both sides of the object and is supported by the support member, the piezoelectric element expanding and contracting according to an applied voltage, and the support of the piezoelectric structure An actuator comprising: a plate-like member disposed on a member-side surface or a surface opposite to the support member and connected to the object.

  (Appendix 2) The plate-like members are first and second joints that are joined to both ends of the piezoelectric member structure in the expansion / contraction direction of the surface on the support member side or the surface opposite to the support member, respectively. A first portion that is provided along a side of the piezoelectric body structure on the object side and communicates between the first joint portion and the arm portion. A beam portion and a second beam portion provided along a side opposite to the object of the piezoelectric structure and communicating between the second joint portion and the arm portion. The actuator according to Supplementary Note 1, which is characterized.

(Appendix 3) Suspension;
A slider provided with a magnetic head for recording and reproducing information with respect to a magnetic disk and disposed at a tip of the suspension;
An actuator composed of a pair of piezoelectric elements disposed on both sides of the slider and including a piezoelectric structure that expands and contracts according to an applied voltage;
A magnetic head assembly, wherein the actuator rotates the slider within a predetermined angular range around its center of gravity in accordance with a voltage applied to the piezoelectric structure.

  (Additional remark 4) The said piezoelectric element has a plate-shaped member arrange | positioned on the said suspension side surface of the said piezoelectric material structure, and connects with the said suspension side surface of the said slider. The magnetic head assembly described.

  (Supplementary Note 5) The plate-shaped member includes first and second joint portions that are joined to both ends of the piezoelectric structure in the direction of expansion and contraction of the surface on the suspension side, and an arm portion that is coupled to the slider. A first beam portion provided along the slider-side edge of the piezoelectric structure to communicate between the first joint portion and the arm portion; and the slider of the piezoelectric structure. The magnetic head assembly according to claim 4, further comprising: a second beam portion provided along a side opposite to the second portion and communicating between the second joint portion and the arm portion.

  (Supplementary note 6) The magnetic head assembly according to supplementary note 5, wherein an arm portion of one of the pair of piezoelectric elements and an arm portion of the other piezoelectric element are integrated.

  (Additional remark 7) The magnetic head assembly of Additional remark 4 characterized by the thickness of the said plate-shaped member being 50 micrometers or less.

  (Supplementary note 8) The magnetic head assembly according to supplementary note 3, wherein the piezoelectric structure has a structure in which sheet-like piezoelectric films and interlayer electrodes are alternately laminated.

(Appendix 9) a magnetic disk capable of magnetically recording information;
A slider provided with a magnetic head for recording and reproducing information to and from the magnetic disk;
An actuator that is arranged on both sides of the slider and is configured by a pair of piezoelectric elements including a piezoelectric structure that expands and contracts according to an applied voltage, and rotates the slider within a predetermined angular range around its center of gravity;
A suspension arm that supports the slider and the actuator;
And a moving means for driving the suspension arm to move the slider in the radial direction of the magnetic disk.

FIG. 1 is a plan view showing a magnetic disk device including a magnetic head assembly according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a slider, an actuator, and a suspension. 3A is a front view of the piezoelectric element, FIG. 3B is a top view thereof, and FIG. 3C is a right side view thereof. FIG. 4 is a schematic diagram showing electrical connection between the actuator and wiring provided on the surface of the suspension. 5A and 5B are schematic views showing the operation of a single piezoelectric element. 6A and 6B are schematic views showing the displacement of the slider accompanying the operation of the actuator. FIG. 7 is a diagram showing a problem when the slider is translated in the track width direction by the actuator. FIG. 8 is a diagram showing the size of each part of the actuator. FIG. 9 is a diagram showing the result of simulation calculation of the displacement amount of the magnetic head. FIG. 10 is a view showing a modification of the actuator according to the embodiment of the present invention.

Explanation of symbols

11 ... Magnetic disk,
13 ... Slider,
14 ... Suspension arm,
14a ... carriage arm,
14b, 51 ... suspension,
14c ... Gimbal,
15 ... Electromagnetic actuator (voice coil motor),
20, 50 ... Actuator (piezoelectric actuator),
21, 61 ... Piezoelectric element,
23 ... fine metal wire,
25, 33 ... adhesive,
30: Piezoelectric structure,
31 ... piezoelectric film,
32 ... interlayer electrode,
35 ... Batch electrode,
40 ... Hinge,
41, 62 ... arm part,
42a, 42b ... joints,
43a, 43b ... Beams.

Claims (5)

An actuator that is interposed between a support member and an object and rotates the object within a predetermined angular range around its center of gravity;
A piezoelectric structure that is arranged on both sides of the object and is supported by the support member, the piezoelectric element expanding and contracting according to an applied voltage, and the support of the piezoelectric structure An actuator comprising: a plate-like member disposed on a member-side surface or a surface opposite to the support member and connected to the object. Suspension,
A slider provided with a magnetic head for recording and reproducing information with respect to a magnetic disk and disposed at a tip of the suspension;
An actuator composed of a pair of piezoelectric elements disposed on both sides of the slider and including a piezoelectric structure that expands and contracts according to an applied voltage;
A magnetic head assembly, wherein the actuator rotates the slider within a predetermined angular range around its center of gravity in accordance with a voltage applied to the piezoelectric structure.   3. The magnetism according to claim 2, wherein the piezoelectric element has a plate-like member that is disposed on the suspension-side surface of the piezoelectric structure and is connected to the suspension-side surface of the slider. Head assembly.   The plate-shaped member includes first and second joint portions that are respectively joined to both ends of the surface on the suspension side of the piezoelectric structure in the expansion / contraction direction, an arm portion coupled to the slider, and the piezoelectric member A first beam portion provided along a side of the body structure on the slider side and communicating between the first joint portion and the arm portion; and a side opposite to the slider of the piezoelectric structure. 4. The magnetic head assembly according to claim 3, further comprising a second beam portion provided along a side and communicating between the second joint portion and the arm portion. A magnetic disk capable of magnetically recording information;
A slider provided with a magnetic head for recording and reproducing information to and from the magnetic disk;
An actuator that is arranged on both sides of the slider and is configured by a pair of piezoelectric elements including a piezoelectric structure that expands and contracts according to an applied voltage, and rotates the slider within a predetermined angular range around its center of gravity;
A suspension arm that supports the slider and the actuator;
And a moving means for driving the suspension arm to move the slider in the radial direction of the magnetic disk.

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