JP2010009663A - Actuator, magnetic head assembly, and magnetic disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an actuator which are achieved easily and wherein a floating height of a magnetic head is controlled speedily and precisely; a magnetic head assembly; and a magnetic disk device using the magnetic head assembly. <P>SOLUTION: The actuator 20 comprises two piezoelectric elements 21 and a connecting plate 22. The piezoelectric elements 21 are arranged on both sides of a slider 14 provided with a magnetic head 13. The connecting plate 22 is bonded on the piezoelectric elements 21 and the slider 14 using adhesive 23. When applying voltage to the piezoelectric elements 21, the piezoelectric elements 21 contract in a direction parallel to the surface of the connecting plate 22. The contraction of the piezoelectric elements 21 curves the connecting plate 22 to depress the end on the magnetic head 13 side of the slider 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an actuator suitable for controlling a flying height 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.

  A magnetic disk device is a device that magnetically records information by magnetizing the surface of a magnetic disk (recording medium) rotating at high speed with a recording element. Information recorded on the magnetic disk is read by a reproducing element, converted into an electrical signal, and output. Hereinafter, the recording element and the reproducing element are collectively referred to as a magnetic head.

  With the demand for increasing the capacity of magnetic disk devices, the recording capacity per magnetic disk has increased remarkably. 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.

  The magnetic head is disposed on an end face of a substantially rectangular parallelepiped member called a slider. The slider is supported at the tip of a leaf spring-like suspension and floats slightly from the magnetic disk due to the air flow generated by the rotation of the magnetic disk. The distance between the magnetic head and the magnetic disk is determined by the strength of the air flow generated by the rotation of the magnetic disk and the urging force of the suspension against the slider.

  In recent years, with the increase in recording density of magnetic disk devices, write errors and read errors have occurred with slight fluctuations in the distance between the magnetic head and the magnetic disk. For this reason, it has been required to control the gap between the magnetic head and the magnetic disk (hereinafter also referred to as “flying height”) with higher accuracy.

In order to respond to such demands, it has been proposed to control the flying height by arranging a piezoelectric element (actuator) on the rear end side of the suspension and curving the suspension by the piezoelectric element. In addition, it has been proposed to arrange a heating element around the magnetic head and control the flying height using thermal expansion. Further, it has been proposed to attach a piezoelectric element to the tip of the slider and control the flying height by the piezoelectric element. In addition, it has been proposed to use a piezoelectric element for tracking control of a magnetic head.
JP 07-262726 A JP 2005-11413 A JP 2000-348321 A Japanese Patent No. 3558266 Japanese Patent No. 3225510

  When the piezoelectric element is disposed on the rear end side of the suspension, the distance between the piezoelectric element and the slider is large, so that it is considered that the high-speed followability is not sufficient. Also, the method of controlling the flying height using thermal expansion is considered to be insufficient in high-speed follow-up in consideration of the response characteristics and heat conduction of the heating element. Since the method described in Patent Document 3 uses the piezoelectric element in a shear mode (d15 mode), the piezoelectric element needs to be polarized in advance and then bonded to the end face of the slider. As a result, the manufacturing process becomes complicated, and there is a risk of a decrease in yield and an increase in cost. In addition, since the magnetic head (recording element and reproducing element) is formed after the piezoelectric element is bonded to the slider, the piezoelectric element may be exposed to a high temperature in the magnetic head manufacturing process, and the piezoelectric characteristics may deteriorate.

  Accordingly, it is an object of the present invention to provide an actuator, a magnetic head assembly, and a magnetic disk device using the magnetic head assembly that can be easily realized and can control the flying height of the magnetic head with high speed and high accuracy.

  In the magnetic head assembly used in the magnetic disk apparatus, the above-described object is to provide a slider having a magnetic head for recording and reproducing information on the magnetic disk, piezoelectric elements respectively disposed on both sides of the slider, and elasticity. And a connecting plate commonly bonded to the slider and the surface of the piezoelectric element opposite to the magnetic disk, the piezoelectric element extending and contracting in a direction parallel to the surface of the connecting plate Is achieved.

  In addition, the above-described object is to provide 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 the magnetic of the slider according to an applied voltage. An actuator that pushes down the end on the side where the head is provided toward the magnetic disk, a suspension arm that supports the slider and the actuator, and the suspension arm that drives the slider moves in the radial direction of the magnetic disk. A connecting means that is elastically connected to the slider and the surface of the piezoelectric element on the side of the suspension arm. And the piezoelectric element is in a direction parallel to the surface of the connecting plate. It is achieved by a magnetic disk device that is condensation.

  In the magnetic head assembly and the magnetic disk device having the above-described configuration, the piezoelectric elements respectively disposed on both sides of the slider and the connection connected to the surface on one side (surface opposite to the magnetic disk) of the slider and the piezoelectric element. And a board. The piezoelectric element is formed by alternately laminating piezoelectric films and interlayer electrode films, for example, and contracts in a direction parallel to the surface of the connecting plate when a voltage is applied.

  Since such a piezoelectric element performs a polarization process by applying a voltage in a direction perpendicular to the expansion / contraction direction of the piezoelectric film, it can be polarized using an interlayer electrode film. Therefore, the step of forming the electrode for polarization treatment and the step of removing the electrode for polarization treatment after the polarization treatment are unnecessary, and the production is easy. In addition, the flying height (the distance between the magnetic head and the magnetic disk) is controlled by pushing down the tip of the slider directly with an actuator composed of a piezoelectric element and a connecting plate, so that the flying height can be controlled at high speed and with high accuracy. Can do.

  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 configuration of a magnetic disk device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an outline of the configuration of the magnetic disk device.

  As shown in FIGS. 1 and 2, the magnetic disk device according to this embodiment includes a metal housing 10, a disk-shaped magnetic disk 11 housed in the housing 10, and the magnetic disk 11 rotating. A spindle motor 12 to be moved, a slider (object) 14 provided with a magnetic head 13 (recording element 13a and reproducing element 13b), a suspension arm 15 for supporting the slider 14, and a voice coil motor 16 for driving the suspension arm 15. In addition, information is written (recorded) and read (reproduced) to and from the magnetic disk 11 via the flying height control actuator 20 and the magnetic head 13, and the spindle motor 12, voice coil motor 16 and actuator 20 are controlled. And a control unit (electronic circuit) 18.

  The magnetic disk 11 is fixed to the rotary shaft 12 a of the spindle motor 12 and is rotated at a high speed by the spindle motor 12. The suspension arm 15 has a carriage arm 15a on the proximal end side and a leaf spring-like suspension 15b (support member) on the distal end side. The slider 14 is disposed on the surface on the magnetic disk 11 side of a portion called a gimbal at the tip of the suspension 15b.

  The suspension arm 15 is driven and controlled by a voice coil motor 16 and rotates within a predetermined angular range around the rotation shaft 16 a to move the slider 14 (magnetic head 13) in the radial direction of the magnetic disk 11.

  FIG. 3 is an exploded view showing the slider 14, the actuator 20, and the suspension 15b. 3 indicates the moving direction (rotation direction) of the magnetic disk 11, and for convenience of explanation, the leading end side of this arrow is referred to as the leading end side, and the opposite side is referred to as the trailing end side.

  As shown in FIG. 3, the actuator 20 of the present embodiment has a pair of piezoelectric elements 21 arranged on both sides in the width direction of the slider 14 and a common joint on the pair of piezoelectric elements 21 and the slider 14 by an adhesive 23. The connecting plate 22 is provided. The slider 14 is formed in a substantially rectangular parallelepiped shape with ceramics such as AlTiC (AlTiC), for example.

  The connecting plate 22 is made of stainless steel having a thickness of 20 μm, for example. If the mass of the coupling plate 22 is large, the position control response characteristic of the magnetic head is degraded, so that the coupling plate 22 is preferably lightweight. The connecting plate 22 may be formed of a material lighter than stainless steel, for example, zirconia. However, the connecting plate 22 is required to have appropriate elasticity.

  A notch 22a extending from the rear end side edge of the connection plate 22 to the vicinity of the front end side edge is provided between the region where the slider 14 of the connection plate 22 is joined and the region where the piezoelectric element 21 is joined. Yes. As shown in FIG. 3, the piezoelectric element 21 and the slider 14 are bonded to the connecting plate 22 with an adhesive 23 attached to the entire upper surface. In this embodiment, the structure of the actuator 20 and the slider 14 connected to the actuator 20 is called a magnetic head assembly.

  The magnetic head assembly is bonded to the lower side of the gimbal 15c provided at the tip of the suspension 15b by the adhesive 24. In the present embodiment, as will be described later, since the connecting plate 22 is curved in accordance with the control of the flying height, the adhesive 24 that joins the actuator 20 and the gimbal 15c so that the bending of the connecting plate 22 is not inhibited by the gimbal 15c. Is attached only to the upper surface on the rear end side of the connecting plate 22.

  Note that reference numeral 13 in FIG. 3 schematically shows a magnetic head provided on the end face of the slider 14. The magnetic head 13 is formed by laminating a recording element 13a and a reproducing element 13b. For example, a single pole head is used as the recording element 13a, and an MR (Magneto Resistive) element, a GMR (Giant Magneto Resistive) element, or a TMR (Tunnel Magneto Resistive) element is used as the reproducing element 13b. These recording element 13a and reproducing element 13b are formed by repeating a film forming process and a patterning process.

  4A is a front view of the magnetic head assembly, FIG. 4B is a top view thereof, and FIG. 4C is a right side view thereof. 4A to 4C, the same components as those in FIG. 3 are denoted by the same reference numerals.

  As described above, the magnetic head assembly is joined to the slider 14 provided with the magnetic head 13, the pair of piezoelectric elements 21 disposed on both sides of the slider 14, and the slider 14 and the piezoelectric element 21. And a connecting plate 22. In the present embodiment, the bottom surface of the piezoelectric element 21 is located on the same plane as the bottom surface of the slider 14 as shown in FIG. 4A, but the bottom surface of the piezoelectric element 21 is higher than the bottom surface of the slider 14. There may be.

  As shown in FIG. 4C, the piezoelectric element 21 is formed with an interlayer electrode film 32 sandwiched between a plurality of piezoelectric films 31. Collective electrodes 35 are respectively formed on the front end side end surface and the rear end side end surface of the piezoelectric element 21. The collective electrode 35 on one side (left side in FIG. 4C) is electrically connected to the odd-numbered interlayer electrode film 32 counted from above, and the collective electrode on the other side (right side in FIG. 4C). 35 is electrically connected to the even-numbered interlayer electrode film 32. These collective electrodes 35 are electrically connected to a wiring formed on the surface of the suspension 15b via an insulating film via a fine metal wire (bonding wire).

  5A and 5B are schematic side views showing the operation of the magnetic head assembly of this embodiment. However, in FIGS. 5A and 5B, for convenience of explanation, the position on the front end side of the slider 14 and the position on the front end side of the piezoelectric element 21 are shown shifted.

  When no voltage is applied to the piezoelectric element 21, when the magnetic disk 11 is rotated, the slider 14 slightly floats from the magnetic disk 11 as shown in FIG. 5A due to the air flow generated as the magnetic disk 11 rotates. The slider 14 and the magnetic disk 11 are substantially parallel.

  When a predetermined voltage is supplied to the piezoelectric element 21 of the actuator 20 through the collective electrode 35 in this state, the piezoelectric element 21 expands or contracts in the longitudinal direction (direction parallel to the surface of the connecting plate 22). In this embodiment, it is assumed that the same voltage is supplied to the two piezoelectric elements 21 arranged with the slider 14 interposed therebetween. The rate at which the piezoelectric element 21 expands or contracts is related to the applied voltage. In the present embodiment, a voltage is applied so that the piezoelectric element 21 contracts.

  Although the piezoelectric element 21 contracts by applying a voltage to the piezoelectric element 21, the length of the connecting plate 22 made of stainless steel or the like that is not a piezoelectric material does not change. Therefore, as shown in FIG. 5B, the actuator 20 is curved in an arc shape with the piezoelectric element 21 on the inside and the connecting plate 22 on the outside. Along with the bending of the connecting plate 22, the tip end side of the slider 14 joined to the connecting plate 22 is pushed down toward the magnetic disk 11. As a result, the distance (flying height) between the magnetic head 13 and the magnetic disk 11 is reduced.

  In order to control the flying height to be constant, it is necessary to detect a change in the flying height. Since the suspension 15b is curved as the slider 14 floats, for example, a change in the flying height can be detected using a strain sensor whose output changes according to the bending amount of the suspension 15b. Alternatively, predetermined data recorded in advance on the magnetic disk 11 may be read by the reproducing element 13b, and a change in the flying height may be detected by a change in the output of the reproducing element 13b. By controlling the voltage supplied to the piezoelectric element 21 according to the output of the strain sensor or the reproducing element 13b by the control unit 18, the flying height can be kept constant.

  Hereinafter, a method of manufacturing the magnetic head assembly according to the present embodiment will be described with reference to FIGS.

  First, as a material of the piezoelectric element 21 shown in FIG. 4, for example, a PNN (lead nickel niobate) -PT (lead titanate) -PZ (lead zirconate) ceramic green sheet is prepared. Instead of the PNN-PT-PZ ceramic green sheet, a sheet of piezoelectric material such as PZT may be used. As the PNN-PT-PZ ceramic green sheet, one having a thickness after firing of 20 μm, which will be described later, is used.

  Next, the conductive paste used as the interlayer electrode film 32 is screen-printed on the surface of the PNN-PT-PZ ceramic green sheet. As the conductive paste, for example, a paste containing Pt (platinum) as a main component is used, and the thickness of the conductive paste is adjusted so that the thickness after firing described later becomes 2 μm.

  A predetermined number of PNN-PT-PZ ceramic green sheets printed with this conductive paste are laminated, and then fired in the atmosphere at a temperature of 1050 ° C. to form a piezoelectric laminated ceramic sheet. Next, the piezoelectric laminated ceramic sheet is cut into a desired size to obtain the piezoelectric element 21. Thereafter, a conductor film such as Pt is formed on both end faces of the piezoelectric element 21 to form a collective electrode 35.

  On the other hand, the stainless steel plate is processed into a desired shape to form the connecting plate 22. Then, two piezoelectric elements 21 are arranged with the slider 14 on which the magnetic head 13 is formed being sandwiched, and a connecting plate 22 is bonded onto the slider 14 and the piezoelectric element 21 with an adhesive 23. In this way, the magnetic head assembly is completed.

  The piezoelectric element 21 needs to be polarized. In the present embodiment, since the piezoelectric element 21 is used in the d31 mode (a mode in which the piezoelectric element expands and contracts in the direction along the electrode surface), the polarization process applies a voltage in a direction orthogonal to the direction in which the piezoelectric film expands and contracts. . For this reason, the polarization process can be performed using the interlayer electrode film 32, and the process of forming the polarization process electrode and the process of removing the polarization process electrode after the polarization process are unnecessary. For example, after assembling the magnetic head assembly, a predetermined voltage may be applied to the interlayer electrode film 32 via the collective electrode 35 to perform polarization processing. Further, when the piezoelectric element 21 is driven with a voltage of about 10 to 30 V, the polarization process is performed by applying this driving voltage, so the polarization process does not have to be performed before being incorporated into the magnetic disk device.

  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. 6, the piezoelectric element 21 having a length L1 of 850 μm, a width W1 of 200 μm, and a thickness of 240 μm was formed. Then, two piezoelectric elements 21 were arranged with the slider 14 interposed therebetween, and a connecting plate 22 (refer to FIG. 3) made of a stainless plate having a thickness of 20 μm was joined thereon. The slider 14 has a length L2 of 850 μm, a width W2 of 700 μm, and a height of 240 μm.

  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 14. However, the voltage applied to the piezoelectric element 21 was 10V. FIG. 7 is a diagram showing the result of the simulation calculation. As a result of this simulation, the displacement amount of the magnetic head was 65 nm.

  In the present embodiment, the flying height (interval between the magnetic head and the magnetic disk) is controlled by pushing down the tip of the slider 14 directly by an actuator having the piezoelectric element 21 and the connecting plate 22 as constituent elements. It can be controlled with high accuracy. In the present embodiment, the piezoelectric film 31 can be polarized using the interlayer electrode film 32 of the piezoelectric element 21 after being assembled as a magnetic head assembly. Therefore, the process for forming the electrode for polarization treatment and the step for removing the electrode for polarization treatment after the polarization treatment are unnecessary, and the production is easy.

  Furthermore, in this embodiment, since the piezoelectric elements 21 are arranged on both sides of the slider 14, a space in the height direction (a direction perpendicular to the surface of the magnetic disk) can be reduced. As a result, even in a magnetic disk device that mounts a plurality of magnetic disks, it is not necessary to reduce the number of mounted disks.

FIG. 1 is a plan view showing a configuration of a magnetic disk device according to an embodiment of the present invention. FIG. 2 is a block diagram showing an outline of the configuration of the magnetic disk device. FIG. 3 is an exploded view showing the slider, the actuator, and the suspension. 4A is a front view of the magnetic head assembly, FIG. 4B is a top view thereof, and FIG. 4C is a right side view thereof. 5A and 5B are schematic side views showing the operation of the magnetic head assembly of this embodiment. FIG. 6 is a diagram showing the size of each part of the magnetic head assembly. FIG. 7 is a diagram showing the result of simulation calculation of the displacement amount of the magnetic head.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Housing, 11 ... Magnetic disk, 12 ... Spindle motor, 13 ... Magnetic head, 13a ... Recording element, 13b ... Reproducing element, 14 ... Slider, 15 ... Suspension arm, 15a ... Carriage arm, 15b ... Suspension, 15c ... Gimbal, 16 ... Voice coil motor, 18 ... Control unit, 20 ... Actuator, 21 ... Piezoelectric element, 22 ... Connecting plate, 23, 24 ... Adhesive, 31 ... Piezoelectric film, 32 ... Interlayer electrode film, 35 ... Collective electrode .

Claims (6)

In a magnetic head assembly used in a magnetic disk device,
A slider having a magnetic head for recording and reproducing information on a magnetic disk;
Piezoelectric elements respectively disposed on both sides of the slider;
It has elasticity, and has a connecting plate commonly joined to the surface of the slider and the piezoelectric element opposite to the magnetic disk,
The magnetic head assembly according to claim 1, wherein the piezoelectric element expands and contracts in a direction parallel to a surface of the connecting plate.   2. The magnetic head assembly according to claim 1, wherein the piezoelectric element is formed by alternately laminating piezoelectric films and interlayer electrode films in a direction perpendicular to the surface of the connecting plate.   A notch extending from the edge opposite to the magnetic head to the magnetic head side is provided between the area where the slider of the connecting plate is bonded and the area where the piezoelectric element is bonded. The magnetic head assembly according to claim 1, wherein the magnetic head assembly is a magnetic head assembly.   4. The magnetic head assembly according to claim 1, wherein a thickness of the piezoelectric element is equal to or less than a thickness of the slider. 5. 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 pushes an end of the slider on the side where the magnetic head is provided in accordance with an applied voltage toward the magnetic disk;
A suspension arm that supports the slider and the actuator;
Moving means for driving the suspension arm to move the slider in the radial direction of the magnetic disk;
The actuator is
Piezoelectric elements respectively disposed on both sides of the slider;
It has elasticity and has a connecting plate jointed on the slider and a surface of the piezoelectric element on the suspension arm side, and the piezoelectric element expands and contracts in a direction parallel to the surface of the connecting plate. Magnetic disk unit. An actuator that is interposed between a support member and an object and moves a tip portion of the object in a direction of coming into contact with or separating from the support member;
Piezoelectric elements respectively disposed on both sides of the object;
It has elasticity, and has a connecting plate that is commonly joined on the object and the surface of the piezoelectric element on the support member side,
The actuator, wherein the piezoelectric element expands and contracts in a direction parallel to the surface of the connecting plate.

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