JP2008206298A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator that is high in control band and excellent in positioning accuracy to be ready for high-density magnetic disks. <P>SOLUTION: A moving mechanism includes: a driving member whose size in the direction of length varies according to applied voltage; an auxiliary member that is so formed that it is shorter than the driving member, is bonded to a side face of the driving member substantially parallel to the direction in which the length of the driving member varies, and prevents following to variation in length; and a driven body that is rotationally driven by interaction between the driving member and the auxiliary member. The remaining portion of the side face of the driving member other than the portion where the auxiliary member is bonded is bonded onto the outer circumferential surface of the driven body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator using a piezoelectric element.

  In recent years, miniaturization and refinement of information equipment have progressed. For example, in the focus correction and tilt angle control of an optical system, the head actuator of an ink jet printer device, a magnetic disk device, etc., there is an actuator that can move and control a minute distance. It is necessary. Under such circumstances, the increase in the storage capacity of the magnetic disk apparatus has become more and more important as the market expands and the performance of the apparatus increases. Generally, an increase in capacity of a magnetic disk device is achieved by increasing a storage capacity per disk. However, in order to increase the recording density without changing the diameter of the disk, it is necessary to increase the number of tracks (TPI) per unit length. In other words, it is essential to narrow the track width. For this reason, it is indispensable that the positional accuracy of the head in the track width direction is high, and a head actuator capable of high positioning accuracy is desired.

Conventional head positioning has been performed by an electromagnetic actuator in a fixed portion of a suspension holding a head (slider). Conventionally, the recording density of the medium is in a range that can be sufficiently covered by this method. However, due to the increase in recording density accompanying the recent increase in capacity of recording apparatuses, there is a risk that head reading and writing defects may occur in the conventional method due to inaccurate head positioning. In order to make positioning accurate, there is a system in which a microactuator that directly moves the slider is disposed between the slider and the suspension. The actuator according to this system can finely move the head attached to the tip of the arm independently of the operation of the core earth actuator (electromagnetic actuator).
JP 2001-84723 A

  In the above-mentioned methods, there are a type in which a microactuator is arranged between a slider and a suspension, and a type in which a microactuator is arranged on the same plane (side surface of the slider) as the slider. In the former method, it is necessary to secure a space corresponding to the thickness of the microactuator, and there are cases where the number of mounted disks is limited in a magnetic disk device mounted with a plurality of disks. In the latter method, depending on the driving method, it is difficult to increase the control band by translating the slider and exciting the resonance of the suspension. Further, simply disposing the unimorph type microactuator on the side surface of the slider makes a difference between the direction of rotation of the slider and the direction of warping of the microactuator, making it difficult to increase the amount of displacement of the slider.

  An object of the present invention is to provide an actuator excellent in a positioning system with a high control band corresponding to a high-density magnetic disk.

The present invention employs the following means in order to solve the above problems. In other words, the moving mechanism of the present invention is configured such that the length in the length direction changes according to the applied voltage, and is formed shorter than the drive member, and is substantially parallel to the direction in which the length of the drive member changes. An auxiliary member that is bonded to a side surface and prevents follow-up to the change in length, and a driven body that is rotationally driven by the interaction between the driving member and the auxiliary member, and an outer peripheral surface of the driven body The remaining part of the side surface to which the auxiliary member is bonded is fixed to the driving member.

  According to the moving mechanism of the present invention, the auxiliary member formed shorter than the driving member is bonded to the side surface of the driving member, and the remaining portion of the side surface of the driving member to which the auxiliary member is bonded is on the outer peripheral surface of the driven body. It is fixed. Therefore, when a voltage is applied to the drive member provided in the moving mechanism of the present invention, the direction of warpage of the drive member and the rotational drive direction of the driven body are alleviated, and the auxiliary formed with the same length as the drive member The displacement amount of the driven body can be increased as compared with the moving mechanism including the member.

  In the moving mechanism of the present invention, the drive member may be at least one set in a rotationally symmetric position on the outer peripheral surface of the driven body. In the moving mechanism of the present invention, the driving member may be a laminated piezoelectric element having a plurality of active layers. Furthermore, in the moving mechanism of the present invention, the auxiliary portion may be any one of zirconia, stainless steel, and alumina.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the actuator excellent in the positioning system with a high control band corresponding to a high-density magnetic disk.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.

<Outline of the invention>
FIG. 1 is a plan view of a magnetic disk apparatus to which the present invention is applicable. A magnetic disk device 1 shown in FIG. 1 includes a rotatable magnetic disk 2 and a slider 3 having a magnetic head for reading information from the magnetic disk 2 and writing information to the magnetic disk 2. The slider 3 corresponds to the driven body of the present invention.

  The slider 3 has a substantially rectangular shape and is attached to the tip portion of the suspension 4. The base part of the suspension 4 is fixed to the carriage arm 5. The carriage arm 5 is rotated about an arm shaft 7 by an electromagnetic actuator 6. As shown by the arrows in FIG. 1, the slider 3 can move in the radial direction of the magnetic disk 2.

  FIG. 2 is a perspective view showing a configuration example of a magnetic head support mechanism having a microactuator 22. This magnetic head support mechanism includes a slider 3 provided with an electromagnetic conversion element 21 and a suspension 4 that supports the slider 3, and a microactuator 22 is provided on a side surface (outer peripheral surface) of the slider 3. . The microactuator 22 slightly displaces the slider 3 with respect to the suspension 4. The slider 3 of this embodiment has a vertical dimension of 1250 microns and a horizontal dimension of 1000 microns. However, these are examples, and the present invention is not limited to these dimensions.

  FIG. 2 shows a tip portion of the suspension 4, and the tip of the suspension 4 is notched inside. A gimbal portion 23 is disposed in the notch. What is a part of the gimbal part 23 and the tip of the suspension 4? I'm scared. The upper surface side of the slider 3 and the lower surface side of the gimbal portion 23 are bonded via the microactuator 22, and the slider 3 is fixed to the gimbal portion 23.

The microactuator 22 includes a piezoelectric element (piezo element) 24 and a member 25, and bonds the side surface of the piezoelectric element 24 and the side surface of the member 25 with an adhesive. The piezoelectric element 24 according to the present embodiment has a thickness of 152 microns, and the member 25 has a thickness of 20 microns. These are merely examples, and the present invention is not limited thereto. The piezoelectric element 24 corresponds to the driving member of the present invention. The member 25 corresponds to an auxiliary member of the present invention.

  FIG. 3 shows a side view of the piezoelectric element 24. The piezoelectric element 24 has a multilayer structure including a piezoelectric layer 31 and an electrode layer 32. When a voltage is applied to the electrode layer 32, the active layer 33 sandwiched between the electrode layers 32 expands and contracts. That is, the piezoelectric layer 31 is polarized in the thickness direction, the active layer 33 sandwiched between the electrode layers 32 expands and contracts due to the piezoelectric lateral effect, and the piezoelectric element 24 expands and contracts in the length direction. In other words, the piezoelectric element 24 expands and contracts in a direction intersecting with the stacking direction of the piezoelectric layers 31.

  When a drive voltage is applied to the electrode layer 32, the length in the length direction of the piezoelectric element 24 is reduced, and when the drive voltage applied to the electrode layer 32 is released, the length of the piezoelectric element 24 is reduced. Return to the original. In the present embodiment, PNN-PT-PZ ceramics is used as the piezoelectric material constituting the piezoelectric layer 31 of the piezoelectric element 24. In the present embodiment, Pt is used as an electrode material constituting the electrode layer 32 of the piezoelectric element 24.

  In the present embodiment, zirconia, stainless steel, or alumina can be used as the member 25. The length of the member 25 is shorter than the length of the piezoelectric element 24. Therefore, when the member 25 is bonded to the side surface of the piezoelectric element 24, there is a portion that is not in contact with the member 25 on the side surface of the piezoelectric element 24. The side surface of the slider 3 is bonded to the portion of the side surface of the piezoelectric element 24 to which the member 25 is bonded, that is not in contact with the member 25. In this case, an adhesive portion 26 is provided between the piezoelectric element 24 and the slider 3 to bond the piezoelectric element 24 and the slider 3. In this way, the microactuator 22 is disposed on the side surface of the slider 3.

  When a plurality of microactuators 22 are arranged on the side surface of the slider 3, the microactuators 22 are arranged at rotationally symmetric positions around the center of gravity of the slider 3.

  When the microactuator 22 is disposed on the slider 3, two microactuators 22 are disposed on the side surface of the slider 3. In this case, the microactuator 22 is provided on one of the side surfaces of the slider 3, and the microactuator 22 is further provided on the side surface rotated 180 degrees around the center of gravity. By doing so, the microactuator 22 is arranged at the rotationally symmetric position of the slider 3.

  When a driving voltage is applied to the piezoelectric element 24, the length of the piezoelectric element 24 is reduced in the length direction of the piezoelectric element 24. As for the portion where the piezoelectric element 24 and the member 25 are bonded, the piezoelectric element 24 is warped to the outside where the member 25 is not bonded because the member 25 is warped to the piezoelectric element 24 side. Therefore, the member 25 generates a warp of the microactuator 22 in cooperation with the piezoelectric element 24 according to the contraction of the piezoelectric element 24 in the length direction.

  FIG. 4 shows a top view of a conventional microactuator 41. In the conventional microactuator 41, the piezoelectric element 24 and the member 42 have the same length.

  FIG. 5 shows the behavior of the conventional microactuator 41. In the conventional microactuator 41, the length of the piezoelectric element 24 and the length of the member 42 are the same length, and the entire side surface of the piezoelectric element 24 and the entire side surface of the member 42 are bonded. Therefore, when a driving voltage is applied to the piezoelectric element 24, the length of the piezoelectric element 24 is reduced in the length direction of the piezoelectric element 24, so that the member 42 warps toward the piezoelectric element 24. And when the member 42 warps to the piezoelectric element 24 side, the piezoelectric element 24 warps to the outside where the member 42 is not bonded. That is, when a driving voltage is applied to the piezoelectric element 24, the conventional microactuator 41 exhibits a warping behavior.

FIG. 6 shows a top view of the microactuator 22 according to the present embodiment. As shown in FIG. 6, in the microactuator 22 according to the present embodiment, the length of the member 25 is shorter than the length of the piezoelectric element 24.

  FIG. 7 shows the behavior of the microactuator 22 according to the present embodiment. The microactuator 22 has a member 25 shorter than the piezoelectric element 24. When a driving voltage is applied to the piezoelectric element 24, the length of the piezoelectric element 24 is reduced, so that the member 25 is warped toward the piezoelectric element 24 side. Then, when the member 25 is warped to the piezoelectric element 24 side, a portion of the end portion of the piezoelectric element 24 where the member 25 is bonded is warped to the outside where the member 25 is not bonded.

  As described above, when the driving voltage is applied to the piezoelectric element 24, the length of the piezoelectric element 24 is shortened, so that the length of the portion where the member 25 is not bonded is reduced. As a result, the microactuator 22 according to the present embodiment exhibits a behavior that combines both warpage and shrinkage. That is, in the microactuator 22 according to the present embodiment, when a drive voltage is applied to the piezoelectric element 24, the portion of the piezoelectric element 24 where the member 25 is bonded warps to the side where the member 25 is not bonded, A portion of the member 24 to which the member 25 is not bonded exhibits a behavior of moving in a direction in which the length is reduced.

  FIG. 8 shows a top view of the slider 3 provided with the conventional microactuator 41. As shown in FIG. 8, a pair of microactuators 41 are provided on the side surface of the slider 3 so as to face each other. In the conventional microactuator 41, the length of the member 42 is the same as the length of the piezoelectric element 24.

  FIG. 9 shows the displacement of the slider 3 provided with the conventional microactuator 41 when a driving voltage is applied to the piezoelectric element 24. When a voltage of 30 V is applied to the piezoelectric element 24, the slider 3 rotates in the direction of the arrow A around the center of gravity, so that the slider 3 is displaced by 166 nm in the direction of the arrow A.

  FIG. 10 shows a top view of the slider 3 provided with the microactuator 22 of the present embodiment. As shown in FIG. 10, a pair of microactuators 22 are provided on the side surface of the slider 3 so as to face each other. In the microactuator 22 shown in FIG. 10, the length of the member 25 is 40% of the length of the piezoelectric element 24. However, the ratio of the length of the member 25 to the length of the piezoelectric element 24 is an example, and the present invention is not limited to this.

  FIG. 11 shows the behavior of the microactuator 22 and the movement of the slider 3 when the driving voltage is applied to the piezoelectric element 24. When a driving voltage is applied to the piezoelectric element 24A and the piezoelectric element 24B, the length of the piezoelectric element 24A contracts in the direction of arrow B in FIG. 11, and the length of the piezoelectric element 24B contracts in the direction of arrow C in FIG.

  When the length of the piezoelectric element 24A is reduced, the end portion of the piezoelectric element 24A bonded to the slider 3 moves in the direction in which the length of the piezoelectric element 24A is reduced (the direction of arrow B in FIG. 11). Further, since the length of the piezoelectric element 24A is shortened, the portion of the piezoelectric element 24A bonded to the member 25 warps to the outside where the member 25 is not bonded. Thus, the microactuator 22 exhibits the behavior of shrinkage and warping.

  By reducing the length of the piezoelectric element 24B, the end of the piezoelectric element 24B bonded to the slider 3 moves in the direction in which the length of the piezoelectric element 24B is reduced (the direction of arrow C in FIG. 11). Further, since the length of the piezoelectric element 24B is shortened, the portion of the piezoelectric element 24B bonded to the member 25 warps to the outside where the member 25 is not bonded. Thus, the microactuator 22 exhibits the behavior of shrinkage and warping.

  When the microactuator 22 shows the behavior of contraction and warpage, the slider 3 bonded to the microactuator 22 rotates in the direction of arrow D in FIG.

  FIG. 12 shows the displacement of the slider 3 provided with the microactuator 22 of the present embodiment when a driving voltage is applied to the piezoelectric element 24. When a voltage of 30 V is applied to the piezoelectric element 24, the slider 3 rotates in the direction of arrow E around the center of gravity, so that the slider 3 is displaced by 238 nm in the direction of arrow E. The displacement amount 238 nm of the slider 3 provided with the microactuator 22 is increased by about 40% with respect to the displacement amount 166 nm of the slider 3 provided with the conventional microactuator 41.

  When a driving voltage is applied to the piezoelectric element 24 of the conventional microactuator 41, the conventional microactuator 41 is only warped, so that distortion occurs in the rotation direction of the slider 3 and the movement direction of the microactuator 41.

  On the other hand, when a driving voltage is applied to the piezoelectric element 24 of the microactuator 22, the portion of the end portion of the microactuator 22 that is bonded to the member 25 warps, and the length of the portion that is not bonded to the member 25 is reduced. Therefore, distortion in the rotation direction of the slider 3 and the movement direction of the microactuator 22 is alleviated, and the displacement amount of the slider 3 increases.

  FIG. 13 shows the relationship between the length of the member 25 and the amount of displacement of the slider 3. The vertical axis of FIG. 13 indicates the displacement amount (nm) of the slider 3, and the horizontal axis indicates the ratio (%) of the length of the member 25 to the length of the piezoelectric element 24. As the ratio (%) of the length of the member 25 to the length of the piezoelectric element 24 decreases, that is, as the length of the member 25 decreases, the displacement (nm) of the slider 3 increases. When the ratio (%) of the length of the member 25 to the length of the piezoelectric element 24 is 20% or less, the saturation state is approached.

  If the ratio (%) of the length of the member 25 to the length of the piezoelectric element 24 is too small, the ratio of the piezoelectric element 24 that supports the slider 3 increases, and the piezoelectric element 24 may be damaged. The ratio (%) of the length of the member 25 to the length of the piezoelectric element 24 may be determined by the desired amount of displacement of the slider 3 and the strength of the microactuator 22. For example, in the case of a notebook computer, priority is given to strength, and the ratio (%) of the length of the member 25 to the length of the piezoelectric element 24 is increased. In the case of a personal computer used for a server, the amount of displacement is increased. The ratio (%) of the length of the member 25 to the length of the piezoelectric element 24 is preferentially reduced.

  Next, a manufacturing method of the microactuator 22 of this embodiment will be described. In this embodiment, PNN-PT-PZ ceramic is used as the piezoelectric material, and Pt is used as the electrode material. In this case, instead of using PNN-PT-PZ ceramics as the piezoelectric material, PZT ceramics or other ceramics may be used as the piezoelectric material. Further, instead of using Pt as an electrode material, AgPd or the like may be used as an electrode material.

  A desired number of Pt electrodes are screen-printed and stacked on a PNN-PT-PZ ceramic green sheet. After that, the piezoelectric element 24 is obtained by firing at 1050 ° C. in the atmosphere and cutting with a dicing saw with a predetermined width. Thus, the obtained piezoelectric element 24 has a structure in which a plurality of active layers 33 made of a piezoelectric material are stacked.

In the present embodiment, zirconia, stainless steel, and alumina are used as the member 25, but other materials may be used as the member 25. The microactuator 22 is manufactured by bonding the piezoelectric element 24 and the member 25 with an adhesive.

  According to the present embodiment, when a driving voltage is applied to the piezoelectric element 24 of the microactuator 22, the portion of the microactuator 22 that is bonded to the member 25 warps, while the length of the portion that is not bonded to the member 25 is long. Therefore, the distortion in the rotation direction of the slider 3 and the movement direction of the microactuator 22 can be reduced. As a result, an increase in the amount of displacement of the slider 3 can provide an actuator excellent in a positioning system with a high control band corresponding to a high-density magnetic disk.

<Modification 1>
In the above-described embodiment, the configuration in which the slider 3 is provided with a set of microactuators 22 has been described. However, the present invention is not limited to this. That is, the slider 3 may be provided with two sets of microactuators 22.

  A configuration example in which two sets of microactuators 22 are provided on the slider 3 is shown in FIG. As shown in FIG. 14, the microactuator 22 </ b> A and the microactuator 22 </ b> B are provided on the slider 3 in the same manner as in the above embodiment. In the first modification, the above-described embodiment is further modified as follows so that the microactuator 22C and the microactuator 22D are provided on the slider 3.

  First, a microactuator 22C that is symmetrical to the microactuator 22A is provided on the same side as the side of the slider 3 provided with the microactuator 22A. That is, the microactuator 22C is provided on the slider 3 so as to be symmetrical with respect to the microactuator 22A with the center line 1401 as the axis of symmetry.

  A microactuator 22D that is symmetrical to the microactuator 22B is provided on the same side as the side of the slider 3 provided with the microactuator 22B. That is, the microactuator 22D is provided on the slider 3 so as to be symmetrical with respect to the microactuator 22B with the center line 1401 as the axis of symmetry.

  By deforming in this way, the rotation direction of the slider 3 can be made two. That is, when a driving voltage is applied to the piezoelectric element 24A and the piezoelectric element 24B, the microactuator 22A and the microactuator 22B exhibit the behavior of contraction and warping, so that the slider 3 rotates in the direction of the arrow F around the center of gravity. Moving. On the other hand, when a driving voltage is applied to the piezoelectric element 24C and the piezoelectric element 24D, the microactuator 22C and the microactuator 22D exhibit the behavior of contraction and warping, so that the slider 3 rotates in the direction of the arrow G around the center of gravity. Moving.

  According to the first modification, it is possible to increase the amount of displacement of the slider 3 by relaxing the distortion in the rotation direction of the slider 3 and the movement direction of the microactuator 22, and to further increase the number of rotation directions of the slider 3. It becomes.

  Further, the present invention may have a configuration in which the microactuator 22 is provided on a polygonal slider. For example, the micro actuator 22 may be provided on a hexagonal or octagonal slider. In this case, as described in the above embodiment, the microactuator 22 is arranged at a rotationally symmetric position around the center of gravity of the polygonal slider.

1 is a plan view of a magnetic disk device to which the present invention is applicable. 3 is a perspective view of a configuration example of a magnetic head support mechanism having a microactuator 22. FIG. 3 is a side view of a piezoelectric element 24. FIG. FIG. 6 is a top view of a conventional microactuator 41. It is a figure showing the behavior of the conventional microactuator 41. It is a top view of the microactuator 22 of this embodiment. It is the figure which showed the behavior of the microactuator 22 of this embodiment. It is a top view of the slider 3 provided with the conventional microactuator 41. FIG. It is the figure which showed the displacement of the slider 3 provided with the conventional microactuator 41. FIG. It is a top view of the slider 3 provided with the microactuator 22 of this embodiment. FIG. 6 is a diagram illustrating the behavior of the microactuator 22 and the movement of the slider 3 when a driving voltage is applied to the piezoelectric element 24. It is the figure which showed the displacement of the slider 3 provided with the microactuator 22 of this embodiment. FIG. 6 is a diagram showing the relationship between the length of a member 25 and the amount of displacement of a slider 3. FIG. 4 is a diagram showing a configuration example in which two sets of microactuators 22 are provided on the slider 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic disk apparatus 2 Magnetic disk 3 Slider 4 Suspension 5 Carriage arm 6 Electromagnetic actuator 7 Arm axis | shaft 21 Electromagnetic conversion element 22 Microactuator 23 Gimbal part 24 Piezoelectric element 25 Member 26 Adhesion part 31 Piezoelectric layer 32 Electrode layer 33 Active layer 41 Microactuator 42 members

Claims (4)

A drive member whose length in the length direction changes according to the applied voltage;
An auxiliary member that is formed shorter than the drive member, is bonded to a side surface substantially parallel to the direction in which the length of the drive member changes, and prevents follow-up to the change in length;
A driven body that is rotationally driven by the interaction between the driving member and the auxiliary member;
A moving mechanism in which a remaining portion of a side surface of the driving member to which the auxiliary member is bonded is fixed to an outer peripheral surface of the driven body.   2. The moving mechanism according to claim 1, wherein at least one set of the driving member is located at a rotationally symmetric position on an outer peripheral surface of the driven body.   The moving mechanism according to claim 1, wherein the driving member is a laminated piezoelectric element having a plurality of active layers.   The moving mechanism according to claim 1, wherein the auxiliary member is any one of zirconia, stainless steel, and alumina.

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