Patent Publication Number: US-2023154490-A1

Title: Head driving device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2021-186537, filed Nov. 16, 2021, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a head driving device of a data storage device using tape as a recording medium. 
     2. Description of the Related Art 
     Data storage devices which use tape (magnetic tape) as a recording medium are known. Examples of data storage devices are described in U.S. Pat. No. 10,971,184 B (Patent Literature 1) and JP 2020-129424 A (Patent Literature 2). These data storage devices comprise a case, tape accommodated in the case, a tape winding mechanism, a head assembly, etc. Data is magnetically recorded in the tape. The head assembly includes a magnetic head, a head driving device which relatively moves the magnetic head with respect to the tape, etc. An element provided in the magnetic head performs access such as reading of data recorded in the tape and wiring of data. 
     The head driving device of the data storage device described in Patent Literature 1 includes a head stack assembly and a voice coil motor for moving the head stack assembly. A head arm comprising a spring function is provided at the distal end of the head stack assembly. A magnetic head is mounted on the head arm. The magnetic head moves in the width direction of the tape by the voice coil motor. 
     The head driving device of the data storage device described in Patent Literature 2 includes a coarse motion actuator and a micromotion actuator to correspond to the increase in the recording density of tape. The coarse motion actuator moves the magnetic head with a stroke which is relatively large. The micromotion actuator moves the magnetic head with a stroke which is relatively small. A stepping motor or a voice coil motor (VCM) is used for the coarse motion actuator. A piezoelectric element such as lead zirconate titanate (PZT) may be used for the micromotion actuator. 
     In the head driving device of Patent Literature 1, a small magnetic head moves in the width direction of the tape by the voice coil motor. In this type of conventional device, the tape may be damaged by contact with the magnetic head. In addition, in the conventional device, it is difficult to stably hold the magnetic head in a predetermined position with respect to the tape which moves at high speed. In another conventional device, a large magnetic head having a length corresponding to the width of tape may be used. However, the large magnetic head is heavy. Thus, it is difficult to stably support the magnetic head by a head arm comprising a suspension function. 
     The head driving device of Patent Literature 2 comprises the coarse actuator consisting of a voice coil motor, and the micromotion actuator consisting of a piezoelectric element. This type of conventional device has some problems. For example, the structure is complicated, and the number of components is increased. 
     Hard disk drives which use a disk as a recording medium are known. In the case of hard disk drives, an air bearing is formed between the surface of the disk and a magnetic head. In the head driving device of Patent Literature 2, tape is used as a recording medium. Therefore, in the head driving device of Patent Literature 2, to prevent the damage of the tape when the tape is fast wound or fast rewound, a structure in which the tape is in contact with the magnetic head is adopted. However, in this conventional device, the structure of the head driving device is further complicated. 
     An object of the present invention is to provide a head driving device which can stably hold a head member and function as a micromotion actuator. 
     BRIEF SUMMARY OF THE INVENTION 
     According to an embodiment, a head driving device comprises a head supporting portion supporting a head member, a first beam, a first base side hinge portion, a first head side hinge portion, a second beam, a second base side hinge portion, a second head side hinge portion, a first piezoelectric unit, and a second piezoelectric unit. The head driving device comprises first and second base portions facing each other across an intervening space. The head supporting portion is provided between the first base portion and the second base portion. The first beam extends from the first base portion to the head supporting portion. The first base side hinge portion connects a base portion of the first beam to the first base portion. The first head side hinge portion connects a distal end of the first beam to the head supporting portion. 
     The second beam is provided on an opposite side of the first beam across the intervening head supporting portion. The second beam extends from the second base portion to the head supporting portion. The second base side hinge portion connects a base portion of the second beam to the second base portion. The second head side hinge portion connects a distal end of the second beam to the head supporting portion. The first piezoelectric unit is provided between the first base portion and the base portion of the first beam. The first piezoelectric unit displaces the distal end of the first beam by deforming in a state where voltage is applied. The second piezoelectric unit is provided between the second base portion and the base portion of the second beam. The second piezoelectric unit displaces the distal end of the second beam by deforming in a state where voltage is applied. 
     The head driving device of the present invention can stably hold the head member and function as a micromotion actuator. 
     A width of the first base side hinge portion may be less than a width of the base portion of the first beam, and a width of the first head side hinge portion may be less than a width of the distal end of the first beam. A width of the second base side hinge portion may be less than a width of the base portion of the second beam, and a width of the second head side hinge portion may be less than a width of the distal end of the second beam. 
     According to the embodiment, the head driving device has a taper shape. Here, the taper shape indicates that a planar shape of the first beam is a shape in which a width is decreased from the base portion of the first beam to the distal end of the first beam. Further, a planar shape of the second beam is a shape in which a width is decreased from the base portion of the second beam to the distal end of the second beam. 
     In the head driving device, first element accommodation portions may be provided on both sides of the first base side hinge portion. A pair of first piezoelectric elements constituting the first piezoelectric unit is provided in the first element accommodation portions. Second element accommodation portions may be provided on both sides of the second base side hinge portion. A pair of second piezoelectric elements constituting the second piezoelectric unit is provided in the second element accommodation portions. 
     According to the embodiment, one of the first piezoelectric elements may be provided in the first element accommodation portion with a predetermined polarity. The other one of the first piezoelectric elements is provided in the first element accommodation portion such that it turns around thereby having an opposite polarity. One of the paired second piezoelectric elements may be provided in the second element accommodation portion with a predetermined polarity. The other one of the paired second piezoelectric elements is provided in the second element accommodation portion such that it turns around thereby having an opposite polarity. 
     According to the embodiment, as exemplarily shown in  FIG.  3   , the head driving device may comprise first and second suspensions made of a metal plate member. The first suspension includes the first beam, the first base side hinge portion and the first head side hinge portion. The second suspension includes the second beam, the second base side hinge portion and the second head side hinge portion. The second suspension forms a line-symmetric shape with the first suspension with respect to an axis which passes through a center of the head supporting portion. 
     For example, as shown in  FIG.  10   , the head driving device comprising the first suspension and the second suspension may comprise a first bent portion and a second bent portion. The first bent portion is formed in the first suspension. The second bent portion is formed in the second suspension. The first bent portion bends at an angle less than or equal to 90° in a thickness direction of the plate member with respect to the head supporting portion. The second bent portion bends at a same angle with the first bent portion on a same side as the first bent portion with respect to the head supporting portion. 
     The head driving device of each of some embodiments may comprise a damper member provided in at least part of the first beam, the second beam and the head supporting portion as shown in  FIG.  5    to  FIG.  9   . 
     As shown in  FIG.  14    to  FIG.  17   , a first milliactuator assembly and a second milliactuator assembly may be provided. The first milliactuator assembly includes a first head supporting portion, a first suspension and a second suspension. The second milliactuator assembly includes a second head supporting portion, a third suspension and a fourth suspension. These first to fourth suspensions may consist of a common metal plate member and may comprise substantially a common structure. 
     The first suspension and the second suspension are line-symmetric with respect to an axis which passes through a center of the first head supporting portion. The third suspension and the fourth suspension are line-symmetric with respect to an axis which passes through a center of the second head supporting portion. The first head supporting portion and the second head supporting portion may be connected to each other by a connection portion. 
     For example, like the three-dimensional head driving device shown in  FIG.  18    to  FIG.  22   , a first bent portion, a second bent portion, a third bent portion and a fourth bent portion may be provided. The first bent portion is formed in the first suspension. The first bent portion bends at an angle less than or equal to 90° in a thickness direction of the plate member with respect to the first head supporting portion. The second bent portion is formed in the second suspension. The second bent portion bends on a same side as the first bent portion at a same angle as the first bent portion with respect to the first head supporting portion. 
     The third bent portion is formed in the third suspension. The third bent portion bends on the same side as the first bent portion at the same angle as the first bent portion with respect to the second head supporting portion. The fourth bent portion is formed in the fourth suspension. The fourth bent portion bends on a same side as the second bent portion at a same angle as the second bent portion with respect to the second head supporting portion. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG.  1    is a plan view of a head driving device according to a first embodiment. 
         FIG.  2    is a cross-sectional view of the head driving device along the F 2 -F 2  line of  FIG.  1   . 
         FIG.  3    is a plan view of the plate member of the head driving device shown in  FIG.  1   . 
         FIG.  4    is a cross-sectional view of part of the head driving device along the F 4 -F 4  line of  FIG.  1   . 
         FIG.  5    is a plan view of a head driving device according to a second embodiment in which a damper member is shown by hatching. 
         FIG.  6    is a cross-sectional view of the head driving device along the F 6 -F 6  line of  FIG.  5   . 
         FIG.  7    is a plan view of a head driving device according to a third embodiment in which a damper member is shown by hatching. 
         FIG.  8    is a plan view of a head driving device according to a fourth embodiment in which each damper member is shown by hatching. 
         FIG.  9    is a plan view of a head driving device according to a fifth embodiment in which a damper member is shown by hatching. 
         FIG.  10    is a side view of the head driving device comprising a first bent portion and a second bent portion. 
         FIG.  11    is a diagram showing the vibration property of 0 to 1.5 kHz of the head driving devices according to the second embodiment to the fifth embodiment. 
         FIG.  12    is a diagram showing the vibration property of 8 to 9.5 kHz of the head driving devices according to the second embodiment to the fifth embodiment. 
         FIG.  13 A  is a plan view showing head driving device comprising a damper member according to a comparative example 1. 
         FIG.  13 B  is a plan view showing head driving device comprising a damper member according to a comparative example 2. 
         FIG.  14    is a perspective view of a head driving device according to a sixth embodiment. 
         FIG.  15    is a plan view of the head driving device shown in  FIG.  14   . 
         FIG.  16    is a plan view of a head driving device according to a seventh embodiment. 
         FIG.  17    is a plan view of a head driving device according to an eighth embodiment. 
         FIG.  18    is a front view schematically showing a data storage device comprising a head driving device according to a ninth embodiment. 
         FIG.  19    is a perspective view of the actuator assembly of the data storage device shown in  FIG.  18   . 
         FIG.  20    is an exploded perspective view of the actuator assembly shown in  FIG.  19   . 
         FIG.  21    is a diagram in which the head driving device of the actuator assembly shown in  FIG.  19    is viewed in the direction shown by arrow F 21  of  FIG.  19   . 
         FIG.  22    is a perspective view showing the head driving device and the terminal portion shown in  FIG.  19   . 
         FIG.  23    is a diagram showing the vibration property of the head driving device shown in  FIG.  19    and the vibration property of the head driving device shown in  FIG.  14   . 
         FIG.  24    is a plan view of a plate member comprising a connection portion for connecting two head supporting portions. 
         FIG.  25    is a plan view of a head driving device according to a tenth embodiment. 
         FIG.  26    is a plan view of a plate member comprising a connection portion for connecting three head supporting portions. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     [First Embodiment] (FIG.  1  to FIG.  4 ) 
     This specification hereinafter explains a head driving device  10 A according to a first embodiment with reference to  FIG.  1    to  FIG.  4   . 
       FIG.  1    is a plan view of the head driving device  10 A.  FIG.  2    is a cross-sectional view of the head driving device  10 A along the F 2 -F 2  line of  FIG.  1   . The head driving device  10 A comprises a flat plate member  11  formed of metal (for example, stainless steel).  FIG.  3    is a plan view of the plate member  11 . The thickness of the plate member  11  is 0.1 to 0.3 mm (for example, 0.15 mm). For example, length L 1  of the plate member  11  is 20 mm. However, length L 1  may be different from this example. 
     A frame portion  12  is formed in part of the plate member  11 . The frame portion  12  includes a first base portion  13  and a second base portion  14 . The first base portion  13  faces the second base portion  14  across an intervening space. The first base portion  13  and the second base portion  14  are connected to each other by a bridge portion  15 . Thus, the relative locations of the first base portion  13  and the second base portion  14  do not substantially change. For example, distance L 2  (shown in  FIG.  3   ) between the first base portion  13  and the second base portion  14  is 15 mm. However, distance L 2  may be different from this example. 
     In the center between the first base portion  13  and the second base portion  14 , a head supporting portion  16  is provided. The head supporting portion  16  supports a head member  17  which functions as a magnetic head. The head member  17  may be called a head bar or a slider. The head member  17  is fixed to the head supporting portion  16  by a fixing means such as an adhesive. 
     The head member  17  extends in the width direction T 1  of magnetic tape  18  (partly shown by two-dot chain lines in  FIG.  1   ) as a recording medium. The head member  17  is an example of a recording medium. 
     Elements which can convert a magnetic signal into an electric signal such as an MR (Magneto Resistive) element are provided in the head member  17 . By these elements, access such as data writing or reading with respect to the magnetic tape  18  is performed. 
     The head driving device  10 A includes a first beam  21  and a second beam  22 . The first beam  21  extends from the first base portion  13  to the head supporting portion  16 . The second beam  22  is provided on the 180-degree opposite side of the first beam  21  across the intervening head supporting portion  16 . The second beam  22  extends from the second base portion  14  to the head supporting portion  16 . 
       FIG.  1    is a plan view of the head driving device  10 A. As shown in  FIG.  1   , the planar shape of the first beam  21  is a taper shape in which the width is decreased from a base portion  21   a  to a distal end  21   b . In this specification, the planar shape refers to the shape of the first beam  21  when the first beam  21  is viewed in a direction facing the plane of the plate member  11  (plan view). The planar shape of the second beam  22  is also a taper shape in which the width is decreased from the base portion  22   a  to the distal end  22   b  of the second beam  22 . 
     A first base side hinge portion  31  is formed between the base portion  21   a  of the first beam  21  and the first base portion  13 . Width W 1  (shown in  FIG.  3   ) of the first base side hinge portion  31  is less than width W 2  of the base portion  21   a  of the first beam  21 . By the first base side hinge portion  31 , the base portion  21   a  of the first beam  21  is connected to the first base portion  13 . On the both sides of the first base side hinge portion  31 , element accommodation portions  32  and  33  consisting of a recess portion are formed. 
     A first head side hinge portion  35  is provided between the distal end  21   b  of the first beam  21  and the head supporting portion  16 . On the both sides of the first head side hinge portion  35 , slits  36  and  37  are formed. The width of the first head side hinge portion  35  is equal to the width of the distal end  21   b  of the first beam  21  or less than the width of the distal end  21   b.  By the first head side hinge portion  35 , the distal end  21   b  of the first beam  21  is connected to the head supporting portion  16 . 
     A second base side hinge portion  41  is provided between the base portion  22   a  of the second beam  22  and the second base portion  14 . Width W 3  (shown in  FIG.  3   ) of the second base side hinge portion  41  is less than width W 4  of the base portion  22   a  of the second beam  22 . By the second base side hinge portion  41 , the base portion  22   a  of the second beam  22  is connected to the second base portion  14 . On the both sides of the second base side hinge portion  41 , element accommodation portions  42  and  43  consisting of a recess portion are formed. 
     A second head side hinge portion  45  is provided between the distal end  22   b  of the second beam  22  and the head supporting portion  16 . On the both sides of the second head side hinge portion  45 , slits  46  and  47  are formed. The width of the second head side hinge portion  45  is equal to the width of the distal end  22   b  of the second beam  22  or less than the width of the distal end  22   b.  By the second head side hinge portion  45 , the distal end  22   b  of the second beam  22  is connected to the head supporting portion  16 . 
     A first piezoelectric unit  51  is provided between the first base portion  13  and the base portion  21   a  of the first beam  21 . The first piezoelectric unit  51  includes a pair of first piezoelectric elements  51   a  and  51   b.  These piezoelectric elements  51   a  and  51   b  are formed of piezoelectric bodies such as lead zirconate titanate (PZT). The piezoelectric bodies have a property of deforming in a state where voltage is applied. The first piezoelectric elements  51   a  and  51   b  are inserted into the first element accommodation portions  32  and  33 , respectively. These first piezoelectric elements  51   a  and  51   b  are fixed to the plate member  11  by an electrically insulating adhesive. 
       FIG.  4    is a cross-sectional view along the F 4 -F 4  line of  FIG.  1   .  FIG.  4    shows the element accommodation portion  32  and the piezoelectric element  51   a . Thickness t 1  of the piezoelectric element  51   a  is less than thickness t 2  of the plate member  11 . For example, thickness t 1  of the piezoelectric element  51   a  is 0.1 mm. However, thickness t 1  may be different from this example. On a surface of the piezoelectric element  51   a,  a first electrode  55  consisting of a metal thin film is formed. On the other surface of the piezoelectric element  51   a,  a second electrode  56  consisting of a metal thin film is formed. When voltage is applied to these electrodes  55  and  56 , the piezoelectric element  51   a  deforms (expands and contracts) based on a direction in which current flows. The direction in which the piezoelectric elements  51   a  and  51   b  expand and contract is the length direction of the first beam  21 . The piezoelectric elements  51   a  and  51   b  comprise a common structure. 
     The piezoelectric element  51   a  is accommodated in the element accommodation portion  32  with a predetermined polarity so as to expand or contract based on the polarity of the applied voltage. The polarity is plus or minus. The piezoelectric element  51   b  is also accommodated in the element accommodation portion  32  with a predetermined polarity so as to expand or contract based on the polarity of the applied voltage. In  FIG.  1   , the piezoelectric element  51   b  is shown by hatching. In the case of the present embodiment ( FIG.  1   ), the piezoelectric element  51   a  and the piezoelectric element  51   b  are accommodated in the element accommodation portion  33  such that they face opposite directions. Thus, the piezoelectric element  51   a  and the piezoelectric element  51   b  have opposite polarities. 
     When the piezoelectric element  51   a  contracts by the application of voltage, and the piezoelectric element  51   b  expands, the distal end  21   b  of the first beam  21  is displaced in a first direction (shown by arrow Y 1  in  FIG.  1   ). When the piezoelectric element  51   a  expands and the piezoelectric element  51   b  contracts, the distal end  21   b  of the first beam  21  is displaced in a second direction (shown by arrow Y 2  in  FIG.  1   ). 
     A second piezoelectric unit  61  is provided between the second base portion  14  and the base portion  22   a  of the second beam  22 . The second piezoelectric unit  61  includes a pair of second piezoelectric elements  61   a  and  61   b.  These piezoelectric elements  61   a  and  61   b  are inserted into the second element accommodation portions  42  and  43 , respectively. These piezoelectric elements  61   a  and  61   b  are fixed to the plate member  11  by an electrically insulating adhesive. The second piezoelectric elements  61   a  and  61   b  consist of piezoelectric bodies comprising the same structure as the first piezoelectric elements  51   a  and  51   b.    
     The piezoelectric element  61   a  of the second piezoelectric unit  61  shown in  FIG.  1    is accommodated in the element accommodation portion  42  with a predetermined polarity so as to expand or contract based on the polarity of the applied voltage. The piezoelectric element  61   b  is accommodated in the element accommodation portion  43  such that it faces the opposite direction of the piezoelectric element  61   a  thereby having the opposite polarity of the piezoelectric element  61   a.  The piezoelectric element  61   b  is shown by hatching. 
     When the piezoelectric element  61   a  contracts by the application of voltage, and the piezoelectric element  61   b  expands, the distal end  22   b  of the second beam  22  is displaced in the first direction (shown by arrow Y 1  in  FIG.  1   ). When the piezoelectric element  61   a  expands and the piezoelectric element  61   b  contracts, the distal end  22   b  of the second beam  22  is displaced in the second direction (shown by arrow Y 2 ). When the distal end  22   b  of the second beam  22  is displaced in the same direction as the distal end  21   b  of the first beam  21 , the head member  17  moves in the first direction Y 1  or the second direction Y 2 . 
     The first beam  21 , the first base side hinge portion  31  and the first head side hinge portion  35  constitute a first suspension SP 1 . The second beam  22 , the second base side hinge portion  41  and the second head side hinge portion  45  constitute a second suspension SP 2 . These suspensions SP 1  and SP 2 , the head supporting portion  16 , the first piezoelectric unit  51  and the second piezoelectric unit  61  constitute a milliactuator assembly MA 1 . 
     The first suspension SP 1  and the second suspension SP 2  are line-symmetric with respect to axis C 2  (shown in  FIG.  3   ) which passes through center Cl of the head supporting portion  16 . The first beam  21  and the second beam  22  extend in a direction perpendicular to axis C 2 . The first suspension SP 1  and the second suspension SP 2  consist of the common plate member  11  formed of stainless steel. The thickness of the first suspension SP 1  is equal to the thickness of the second suspension SP 2 . 
     [Second to Fifth Embodiments] (FIG.  5  to FIG.  9 ) 
       FIG.  5    shows a head driving device  10 B according to a second embodiment.  FIG.  6    is a cross-sectional view of the head driving device  10 B along the F 6 -F 6  line of  FIG.  5   . The head driving device  10 B comprises a damper member DM 1 . Since the other structures are common to the head driving device  10 A of the first embodiment and the head driving device  10 B, explanations thereof are omitted by adding common reference numbers to common structural elements. 
     As shown in  FIG.  6   , the damper member DM 1  comprises a viscoelastic material layer  70  and a constrained plate  71 . The viscoelastic material layer  70  is formed of a polymeric material which can exert viscosity resistance when it is deformed. For example, the polymeric material is acrylic resin and has viscosity. The constrained plate  71  is formed of synthetic resin such as polyester. The constrained plate  71  overlaps the viscoelastic material layer  70 . 
     The damper member DM 1  shown in  FIG.  5    covers a head supporting portion  16 , the entire part of a first beam  21  and the entire part of a second beam  22 . For convenience sake, in  FIG.  5   , the damper member DM 1  is shown by hatching. As shown in  FIG.  6   , the damper member DM 1  also covers slits  36 ,  37 ,  46  and  47 . 
       FIG.  7    shows a head driving device  10 C according to a third embodiment. This head driving device  10 C also comprises a damper member DM 2 . For convenience sake, the damper member DM 2  is shown by hatching. The damper member DM 2  is provided partway in the length direction of a first beam  21  from a head supporting portion  16  and partway in the length direction of a second beam  22  from the head supporting portion  16 . Since the other structures are common to the head driving device  10 B of the second embodiment and the head driving device  10 C of the third embodiment, explanations thereof are omitted by adding common reference numbers to common structural elements. The damper member DM 2  is provided in the head supporting portion  16 , and at least part of the first beam  21  and the second beam  22 . 
       FIG.  8    shows a head driving device  10 D according to a fourth embodiment. This head driving device  10 D comprises a pair of damper members DM 3 . The damper members DM 3  are separately provided in a first beam  21  and a second beam  22 . No damper member is provided in a head supporting portion  16 . When no damper member is provided in the head supporting portion  16 , each damper member may be attached to either the adverse side or back side of each of the first beam  21  and the second beam  22 . Since the other structures are common to the head driving device  10 B of the second embodiment and the head driving device  10 D of the fourth embodiment, explanations thereof are omitted by adding common reference numbers to common structural elements. 
       FIG.  9    shows a head driving device  10 E according to a fifth embodiment. A damper member DM 4  provided in this head driving device  10 E covers a head supporting portion  16 , the entire part of a first beam  21  and the entire part of a second beam  22 . None of slits  36 ,  37 ,  46  and  47  is covered with the damper member DM 4 . Since the other structures are common to the head driving device  10 B of the second embodiment and the head driving device  10 E of the fifth embodiment, explanations thereof are omitted by adding common reference numbers to common structural elements. 
     The head driving device shown in  FIG.  10    comprises a first bent portion  75  formed in the first suspension SP 1 , and a second bent portion  76  formed in the second suspension SP 2 . The first bent portion  75  is bent at angle θ 1  less than or equal to 90° in the thickness direction of the plate member  11  with respect to the head supporting portion  16 . The second bent portion  76  is bent at the same angle θ 2  as the first bent portion  75  to the same side as the first bent portion  75  with respect to the head supporting portion  16 . As the head driving device shown in  FIG.  10    comprises the bent portions  75  and  76 , the head driving device has a three-dimensional shape like a mountain. 
       FIG.  11    shows the vibration property of the first mode of 0 to 1.5 kHz regarding the head driving devices  10 A to  10 E of the first embodiment to the fifth embodiment. In  FIG.  11   , the horizontal axis indicates the frequency, and the vertical axis indicates the gain. 
     In  FIG.  11   , the broken line N 1  shows the vibration property of the head driving device  10 A of the first embodiment which does not comprise a damper member. In  FIG.  11   , the one-dot chain line DM 1  shows the vibration property of the head driving device  10 B ( FIG.  5   ) comprising the damper member DM 1  according to the second embodiment. The two-dot chain line DM 2  shows the vibration property of the head driving device  10 C ( FIG.  7   ) comprising the damper member DM 2  according to the third embodiment. The thin line DM 3  shows the vibration property of the head driving device  10 D ( FIG.  8   ) comprising the damper members DM 3  according to the fourth embodiment. The solid line DM 4  shows the vibration property of the head driving device  10 E ( FIG.  9   ) comprising the damper member DM 4  according to the fifth embodiment. 
     As shown by the broken line N 1  in  FIG.  11   , the peak of the resonance of the head driving device of the first embodiment which does not comprise a damper member is steep. To the contrary, in each of the head driving devices of the second to fifth embodiments which comprise the damper member, the peak of resonance is moderate. In particular, the peak of the resonance of the head driving device  10 E ( FIG.  9   ) of the fifth embodiment shown by the solid line DM 4  is the least. For this reason, regarding the vibration property of 0 to 1.5 kHz, the damper member DM 4  ( FIG.  9   ) of the fifth embodiment may be preferable. 
       FIG.  12    shows the vibration property of the first mode of 8 to 9.5 kHz regarding the head driving devices  10 A to  10 E of the first embodiment to the fifth embodiment. In  FIG.  12   , the horizontal axis indicates the frequency, and the vertical axis indicates the gain. 
     In  FIG.  12   , the broken line N 1  shows the vibration property of the head driving device  10 A of the first embodiment which does not comprise a damper member. In  FIG.  12   , the one-dot chain line DM 1  shows the vibration property of the head driving device  10 B ( FIG.  5   ) comprising the damper member DM 1  according to the second embodiment. The two-dot chain line DM 2  shows the vibration property of the head driving device  10 C ( FIG.  7   ) comprising the damper member DM 2  according to the third embodiment. The thin line DM 3  shows the vibration property of the head driving device  10 D ( FIG.  8   ) comprising the damper members DM 3  according to the fourth embodiment. The solid line DM 4  shows the vibration property of the head driving device  10 E ( FIG.  9   ) comprising the damper member DM 4  according to the fifth embodiment. 
     As shown by the broken line N 1  in  FIG.  12   , the peak of the resonance of the head driving device of the first embodiment which does not comprise a damper member is great. To the contrary, in each of the head driving devices of the second to fifth embodiments which comprise the damper member, the peak of resonance is less. In particular, each of the resonance mode of the head driving device  10 B comprising the damper member DM 1  of the second embodiment ( FIG.  5   ) and the resonance mode of the head driving device  10 C comprising the damper member DM 2  of the third embodiment ( FIG.  7   ) is substantially flat. For this reason, regarding the vibration property of 8 to 9.5 kHz, the damper member DM 1  of the second embodiment and the damper member DM 2  of the third embodiment may be preferable. 
     [Comparative Example 1] (FIG.  13 A) 
       FIG.  13 A  shows a head driving device  10 F according to comparative example 1. A damper member DM 5  provided in this head driving device  10 F comprises a first extending portion  81  and a second extending portion  82 . The first extending portion  81  extends from a first base side hinge portion  31  to a first base portion  13 . The second extending portion  82  extends from a second base side hinge portion  41  to a second base portion  14 . The other structures are common to the head driving device  10 B of the second embodiment and the head driving device  10 F of comparative example 1. 
     The vibration property of the head driving device  10 F of comparative example 1 is equivalent to that of the head driving device  10 B of the second embodiment. However, the damper member DM 5  of comparative example 1 has a drawback in respect that the shape is complicated and it is heavy compared to the damper member DM 1  of the second embodiment. 
     [Comparative Example 2] (FIG.  13 B) 
       FIG.  13 B  shows a head driving device  10 G according to comparative example 2. A damper member DM 6  provided in this head driving device  10 G comprises an extending portion  83  covering a first piezoelectric unit  51 , and an extending portion  84  covering a second piezoelectric unit  61 . The other structures are common to the head driving device  10 B of the second embodiment and the head driving device  10 G of comparative example 2. 
     Regarding the vibration property of the head driving device  10 G of comparative example 2, the gain of the first mode is large compared to the head driving device  10 B of the second embodiment. In addition, the damper member DM 6  of comparative example 2 has a drawback in respect that it is heavier than the damper member DM 1  of the second embodiment. These factors show that the damper member should be preferably provided so as not to cover the base side hinge portion  31  or  41 , or the piezoelectric unit  51  or  61 . 
     [Sixth Embodiment] ( FIG.  14    and  FIG.  15   ) This specification hereinafter explains a head driving device  10 H according to a sixth embodiment with reference to  FIG.  14    and  FIG.  15   .  FIG.  14    is a perspective view of the head driving device  10 H.  FIG.  15    is a plan view of the head driving device  10 H. 
     The head driving device  10 H comprises a first milliactuator assembly MA 1  and a second milliactuator assembly MA 2 . The first milliactuator assembly MA 1  is structured in the same manner as the milliactuator assembly MA 1  of the first embodiment ( FIG.  1    to  FIG.  4   ). For this reason, the second milliactuator assembly MA 2  is explained below. 
     The second milliactuator assembly MA 2  shown in  FIG.  14    and  FIG.  15    includes a third suspension SP 3  and a fourth suspension SP 4 . The third suspension SP 3  and a first suspension SP 1  comprise a common structure. The fourth suspension SP 4  and a second suspension SP 2  comprise a common structure. 
     In the center between a first base portion  13  and a second base portion  14 , a first head supporting portion  16  and a second head supporting portion  116  are provided. The second head supporting portion  116  is provided in another position in the length direction of a head member  17  with respect to the first head supporting portion  16 . By these first and second head supporting portions  16  and  116 , the head member  17  is supported. The head member  17  is fixed to the first head supporting portion  16  and the second head supporting portion  116  by a fixing means such as an adhesive. 
     The second milliactuator assembly MA 2  includes the second head supporting portion  116 , a third beam  121  and a fourth beam  122 . The third beam  121  extends from the first base portion  13  to the second head supporting portion  116 . The fourth beam  122  is provided on the 180-degree opposite side of the third beam  121  across the intervening second head supporting portion  116 . The fourth beam  122  extends from the second base portion  14  to the second head supporting portion  116 . 
       FIG.  15    is a plan view of the head driving device  10 H. The planar shape of the third beam  121  is a taper shape in which the width is decreased from the base portion  121   a  to the distal end  121   b  of the third beam  121 . The planar shape of the fourth beam  122  is also a taper shape in which the width is decreased from the base portion  122   a  to the distal end  122   b  of the fourth beam  122 . 
     A third base side hinge portion  131  is formed between the base portion  121   a  of the third beam  121  and the first base portion  13 . The width of the third base side hinge portion  131  is less than the width of the base portion  121   a  of the third beam  121 . By the third base side hinge portion  131 , the base portion  121   a  of the third beam  121  is connected to the first base portion  13 . On the both sides of the third base side hinge portion  131 , element accommodation portions  132  and  133  consisting of a recess portion are formed. 
     A third head side hinge portion  135  is provided between the distal end  121   b  of the third beam  121  and the second head supporting portion  116 . On the both sides of the third head side hinge portion  135 , slits  136  and  137  are formed. The width of the third head side hinge portion  135  is equal to the width of the distal end  121   b  of the third beam  121  or less than the width of the distal end  121   b.  By the third head side hinge portion  135 , the distal end  121   b  of the third beam  121  is connected to the second head supporting portion  116 . 
     A fourth base side hinge portion  141  is provided between the base portion  122   a  of the fourth beam  122  and the second base portion  14 . The width of the fourth base side hinge portion  141  is less than the width of the base portion  122   a  of the fourth beam  122 . By the fourth base side hinge portion  141 , the base portion  122   a  of the fourth beam  122  is connected to the second base portion  14 . On the both sides of the fourth base side hinge portion  141 , element accommodation portions  142  and  143  consisting of a recess portion are formed. 
     A fourth head side hinge portion  145  is provided between the distal end  122   b  of the fourth beam  122  and the second head supporting portion  116 . On the both sides of the fourth head side hinge portion  145 , slits  146  and  147  are formed. The width of the fourth head side hinge portion  145  is equal to the width of the distal end  122   b  of the fourth beam  122  or less than the width of the distal end  122   b.  By the fourth head side hinge portion  145 , the distal end  122   b  of the fourth beam  122  is connected to the second head supporting portion  116 . 
     A third piezoelectric unit  151  is provided between the first base portion  13  and the base portion  121   a  of the third beam  121 . The third piezoelectric unit  151  includes a pair of piezoelectric elements  151   a  and  151   b.  The piezoelectric elements  151   a  and  151   b  are formed of piezoelectric bodies such as lead zirconate titanate (PZT). The piezoelectric bodies deform in a state where voltage is applied. The piezoelectric elements  151   a  and  151   b  are inserted into the element accommodation portions  132  and  133 , respectively. The piezoelectric elements  151   a  and  151   b  are fixed to a plate member  11  by an electrically insulating adhesive. 
     The piezoelectric elements  151   a  and  151   b  expand or contract based on the polarity (plus or minus) of the applied voltage. For example, when the piezoelectric element  151   a  expands and the piezoelectric element  151   b  contracts, the distal end  121   b  of the third beam  121  is displaced in a first direction. When the piezoelectric element  151   a  contracts and the piezoelectric element  151   b  expands, the distal end  121   b  of the third beam  121  is displaced in a second direction. 
     A fourth piezoelectric unit  161  is provided between the second base portion  14  and the base portion  122   a  of the fourth beam  122 . The fourth piezoelectric unit  161  includes a pair of piezoelectric elements  161   a  and  161   b.  These piezoelectric elements  161   a  and  161   b  are inserted into the element accommodation portions  142  and  143 , respectively. The piezoelectric elements  161   a  and  161   b  are fixed to the plate member  11  by an electrically insulating adhesive. 
     The third beam  121 , the third base side hinge portion  131  and the third head side hinge portion  135  constitute the third suspension SP 3 . The fourth beam  122 , the fourth base side hinge portion  141  and the fourth head side hinge portion  145  constitute the fourth suspension SP 4 . These suspensions SP 3  and SP 4 , the second head supporting portion  116 , the third piezoelectric unit  151  and the fourth piezoelectric unit  161  constitute the second milliactuator assembly MA 2 . 
     As shown in  FIG.  15   , axis C 4  passes through center C 1  of the first head supporting portion  16 . Axis C 4  also passes through center C 3  of the second head supporting portion  116 . The third suspension SP 3  and the fourth suspension SP 4  are line-symmetric with respect to axis C 4 . The third beam  121  and the fourth beam  122  extend in a direction perpendicular to axis C 4 . The third suspension SP 3  and the fourth suspension SP 4  consist of the common plate member  11  formed of stainless steel. The thickness of the third suspension SP 3  is equal to the thickness of the fourth suspension SP 4 . 
     The head member  17  of the head driving device  10 H ( FIG.  15   ) of the sixth embodiment is supported by the first milliactuator assembly MA 1  and the second milliactuator assembly MA 2 . Thus, this head member  17  is supported in two positions in the length direction of the head member  17 . In this way, in three-dimensional directions (the directions of the X-axis, Y-axis and Z-axis shown in  FIG.  14   ), the rigidity of the head driving device  10 H can be increased, thereby stabilizing the head member  17 . 
     The four piezoelectric elements  51   b,    61   b,    151   b  and  161   b  shown in  FIG.  14    and  FIG.  15    are accommodated in the element accommodation portions  33 ,  43 ,  133  and  143  in a predetermined direction regarding the polarity. 
     The four piezoelectric elements  51   a,    61   a,    151   a  and  161   a  shown by hatching are accommodated in the element accommodation portions  32 ,  42 ,  132  and  142  such that they face the opposite direction thereby having the opposite polarity of the piezoelectric elements  51   b ,  61   b,    151   b  and  161   b.    
     As shown in  FIG.  15   , a plus input voltage of [d+y] is assumed to be applied to all of the piezoelectric elements. In this case, the piezoelectric elements  51   b,    61   b,    151   b  and  161   b  which are in the normal positions expand, and the piezoelectric elements  51   a,    61   a,    151   a  and  161   a  which are in a reverse state contract. By this structure, the head member  17  moves in a first direction (shown by arrow Y 1 ). 
     Contrary to  FIG.  15   , a minus input voltage of [−y] is assumed to be applied to all of the piezoelectric elements. In this case, the piezoelectric elements  51   b,    61   b,    151   b  and  161   b  which are in the normal positions contract, and the piezoelectric elements  51   a ,  61   a,    151   a  and  161   a  which are in a reverse state expand. By this structure, the head member  17  moves in a second direction (the opposite direction of arrow Y 1 ). Thus, in the case of the present embodiment, the head member  17  can be moved in the Y-axis direction by an input signal of [±y] of one system. 
     [Seventh Embodiment] (FIG.  16 ) 
       FIG.  16    shows a head driving device  10 J according to a seventh embodiment. Piezoelectric elements  51   a ,  51   b,    61   a,    61   b,    151   a,    151   b,    161   a  and  161   b  comprise a common structure. The piezoelectric elements  51   a,    51   b,    161   a  and  161   b  are accommodated in element accommodation portions  32 ,  33 ,  142  and  143  in a predetermined direction regarding the polarity. The piezoelectric elements  61   a,    61   b,    151   a  and  151   b  shown by hatching are accommodated in element accommodation portions  42 ,  43 ,  132  and  133  such that they turn around thereby having the opposite polarity. The other structures are the same as the sixth embodiment ( FIG.  14    and  FIG.  15   ). 
     As shown in  FIG.  16   , when a plus input voltage of [+x] is applied to all of the piezoelectric elements, the piezoelectric elements  51   a,    51   b,    161   a  and  161   b  which are in the normal positions expand, and the piezoelectric elements  61   a,    61   b,    151   a  and  151   b  which are in a reverse state contract. By this structure, a head member  17  is displaced in the skew directions shown by arrows X in  FIG.  16   . 
     Contrary to  FIG.  16   , when a minus input voltage of [−x] is applied to all of the piezoelectric elements, the piezoelectric elements  51   a,    51   b,    161   a  and  161   b  which are in the normal positions contract, and the piezoelectric elements  61   a,    61   b,    151   a  and  151   b  which are in a reverse state expand. By this structure, the head member  17  moves in the opposite skew directions of arrows X. In this way, the head member  17  can be driven in a skew direction by an input signal of [±x] of one system. 
     [Eighth Embodiment] (FIG.  17 ) 
       FIG.  17    shows a head driving device  10 K according to an eighth embodiment. This head driving device  10 K and the head driving device  10 J of the seventh embodiment ( FIG.  16   ) comprise a common structure. Piezoelectric elements  51   a,    51   b,    161   a  and  161   b  are accommodated in element accommodation portions  32 ,  33 ,  142  and  143  in a predetermined direction regarding the polarity. The piezoelectric elements  61   a,    61   b,    151   a  and  151   b  shown by hatching are accommodated in element accommodation portions  42 ,  43 ,  132  and  133  such that they turn around regarding the polarity. 
     As shown in  FIG.  17   , an input voltage of [x+y] is assumed to be applied to the piezoelectric elements  51   b,    61   a,    151   a  and  161   b,  and an input voltage of [x−y] is assumed to be applied to the piezoelectric elements  51   a,    61   b,    151   b  and  161   a.  In this case, a head member  17  moves in the skew directions shown by arrows X, and the head member  17  moves in a first direction (shown by arrow Y 1 ). 
     Contrary to  FIG.  17   , an input voltage of [−x−y] is assumed to be applied to the piezoelectric elements  51   b,    61   a,    151   a  and  161   b,  and an input voltage of [−x+y] is assumed to be applied to the piezoelectric elements  51   a,    61   b,    151   b  and  161   a.  In this case, the head member  17  moves in the opposite directions of arrows X, and moves in the opposite direction of arrow Y. In this way, the head member  17  can be driven in a skew direction and a Y-axis direction by the input signals of two systems. 
     [Ninth Embodiment] (FIG.  18  to FIG.  23 ) 
       FIG.  18    schematically shows a data storage device  200  comprising a head driving device  10 L according to a ninth embodiment. For example, the data storage device  200  includes a case  201 , an actuator assembly  202 , a first winding device  203 , a second winding device  204  and a plurality of guide rollers  205 . The data storage device  200  is not limited to the example shown in  FIG.  18    and can be structured in various modes depending on the need. 
     Tape  18  as a recording medium is wound around tape reels  210  and  211 . A head member  17  is provided in the actuator assembly  202 . The actuator assembly  202  comprises a function of moving the head member  17  in the width direction of the tape  18  (Y-axis direction) and a skew direction. By the head member  17 , access (data writing or reading) with respect to the tape  18  is performed. 
       FIG.  19    shows an example of the actuator assembly  202  comprising the head driving device  10 L. The two-headed arrow PT 1  shown in  FIG.  19    is the pitching direction of the head member  17 .  FIG.  20    is an exploded perspective view of the actuator assembly  202 .  FIG.  21    is a diagram in which the head driving device  10 L is viewed in the direction shown by arrow F 21  of  FIG.  19   . 
     The actuator assembly  202  includes a slide member  222 , coarse motion voice coil motors  223  and  224 , a skew driving block  225  and the head driving device  10 L. The slide member  222  can move along a pair of guide members  220  and  221 . The voice coil motors  223  and  224  move the slide member  222 . The skew driving block  225  is attached to the slide member  222 . The skew driving block  225  rotates in a skew direction around a skew axis  226 . 
     The pair of voice coil motors  223  and  224  respectively comprise yokes  230  and  231 , magnets  232  and  233 , and coils  234  and  235 . The voice coil motors  223  and  224  move the slide member  222 , the head driving device  10 L and the skew driving block  225  along the guide members  220  and  221 . The voice coil motors  223  and  224  rotate the head driving device  10 L and the skew driving block  225  around the skew axis  226 . 
     As shown in  FIG.  21   , the head driving device  10 L comprises a first milliactuator assembly MA 1 ′ having a three-dimensional shape, and a second milliactuator assembly MA 2 ′ having a three-dimensional shape. The first milliactuator assembly MA 1 ′ comprises a first bent portion  241  and a second bent portion  242 . The second milliactuator assembly MA 2 ′ comprises a third bent portion  243  and a fourth bent portion  244 . The first milliactuator assembly MA 1 ′ and the second milliactuator assembly MA 2 ′ comprise a common structure. 
     The first milliactuator assembly MA 1 ′ is structured in the same manner as the milliactuator assembly MA 1  of the sixth embodiment ( FIG.  14    and  FIG.  15   ) except for the structure in which the first milliactuator assembly MA 1 ′ comprises the bent portions  241  and  242 . The second milliactuator assembly MA 2 ′ is structured in the same manner as the milliactuator assembly MA 2  of the sixth embodiment ( FIG.  14    and  FIG.  15   ) except for the structure in which the second milliactuator assembly MA 2 ′ comprises the bent portions  243  and  244 . Regarding the milliactuator assemblies MA 1 ′ and MA 2 ′ of the present embodiment, portions in common with the milliactuator assemblies MA 1  and MA 2  of the sixth embodiment are denoted by common reference numbers, explanations thereof being omitted. 
     As shown in  FIG.  21   , the first bent portion  241  is formed in a first head side hinge portion  35 . The second bent portion  242  is formed in a second head side hinge portion  45 . The first bent portion  241  is bent at angle θ 1  less than 90° in the thickness direction of a plate member  11  with respect to a first head supporting portion  16 . The second bent portion  242  is bent at angle θ 2  on the same side as the first bent portion  241  in the thickness direction of the plate member  11  with respect to the first head supporting portion  16 . Angle θ 1  of the first bent portion  241  is equal to angle θ 2  of the second bent portion  242 . Each of angle θ 1  and angle θ 2  is, for example, 45°. 
     The third bent portion  243  is formed in a third head side hinge portion  135  (shown in  FIG.  15   , etc.). As shown in  FIG.  19    and  FIG.  20   , the third bent portion  243  is bent in the same direction as the first bent portion  241 . Thus, the third bent portion  243  is bent at the same angle θ 1  (for example, 45°) as the first bent portion  241  in the thickness direction of the plate member  11  with respect to a second head supporting portion  116 . 
     The fourth bent portion  244  is formed in a fourth head side hinge portion  145  (shown in  FIG.  15   , etc.). As shown in  FIG.  19    and  FIG.  20   , the fourth bent portion  244  is bent in the same direction as the third bent portion  243 . Thus, the fourth bent portion  244  is bent at the same angle θ 2  (for example, 45°) as the third bent portion  243  in the thickness direction of the plate member  11  with respect to the second head supporting portion  116 . 
     As the bent portions  241 ,  242 ,  243  and  244  are provided, the head driving device  10 L of the present embodiment has a three-dimensional shape like a mountain. This structure allows the head driving device  10 L of the present embodiment to have a great rigidity compared to the head driving device  10 H of the sixth embodiment ( FIG.  14    and  FIG.  15   ) having a planar shape. 
     As shown in  FIG.  22   , a terminal portion  300  is provided in the frame portion  12  of the head driving device  10 L. Similarly, a terminal portion  301  is provided in the head member  17 . Terminals  310 ,  311 ,  312  and  313  are provided in piezoelectric elements  61   a,    61   b,    161   a  and  161   b,  respectively. The terminal portion  300  of the frame portion  12  is electrically connected to the terminal portion  301  of the head member  17 , and the terminals  310 ,  311 ,  312  and  313  of the piezoelectric elements  61   a,    61   b,    161   a  and  161   b.    
       FIG.  23    shows the vibration property of the head driving device  10 L of the ninth embodiment ( FIG.  19    to  FIG.  22   ) and the vibration property of the head driving device  10 H of the sixth embodiment ( FIG.  14   ). In  FIG.  23   , the solid line shows the vibration property of the head driving device  10 L comprising the bent portions  241 ,  242 ,  243  and  244 . The angle of each of the bent portions  241 ,  242 ,  243  and  244  is 45°. In  FIG.  23   , the broken line shows the vibration property of the head driving device  10 H which does not comprise a bent portion. 
     In  FIG.  23   , R 1  shows the pitching mode of the head driving device  10 H which does not comprise a bent portion. The pitching mode of the head driving device  10 H which does not comprise a bent portion arises at around 1 kHz. In  FIG.  23   , R 2  shows the pitching mode of the head driving device  10 L comprising the bent portions. The pitching mode of the head driving device  10 L comprising the bent portions arises at around 11 kHz. The head driving device  10 L comprising the bent portions has a three-dimensional shape. According to the head driving device  10 L having a three-dimensional shape, the frequency of the pitching mode can be largely increased compared to the frequency of the head driving device  10 H having a planar shape. 
     In a manner similar to that of the plate member  11  shown in  FIG.  24   , a connection portion  270  connecting the first head supporting portion  16  to the second head supporting portion  116  may be provided. By providing the connection portion  270 , the locational relationship between the first head supporting portion  16  and the second head supporting portion  116  is stabilized. This structure can prevent the positions of the first head supporting portion  16  and the second head supporting portion  116  from changing when the bent portions  241 ,  242 ,  243  and  244  are bent. Further, by providing the connection portion  270 , the adhesive surface property of the head member  17  can be increased. In addition, the use of the connection portion  270  allows the support of the head member  17  in a stable state. 
       FIG.  25    shows a head driving device  10 M according to a tenth embodiment. This head driving device  10 M comprises a first milliactuator assembly MA 1 , a second milliactuator assembly MA 2  and a third milliactuator assembly MA 3 . The third milliactuator assembly MA 3  includes a third head supporting portion  416 , a fifth beam  421 , a sixth beam  422 , a fifth piezoelectric unit  451  and a sixth piezoelectric unit  461 . 
     The third head supporting portion  416  is provided between a first base portion  13  and a second base portion  14 . The third head supporting portion  416  supports a head member  17 . The fifth beam  421  extends from the first base portion  13  to the third head supporting portion  416 . The first base portion  13  is connected to the base portion of the fifth beam  421  by a fifth base side hinge portion  431 . The distal end of the fifth beam  421  is connected to the third head supporting portion  416  by a fifth head side hinge portion  435 . 
     The sixth beam  422  is provided on the opposite side of the fifth beam  421  across the intervening third head supporting portion  416 . The sixth beam  422  extends from the second base portion  14  to the third head supporting portion  416 . The second base portion  14  is connected to the base portion of the sixth beam  422  by a sixth base side hinge portion  441 . The distal end of the sixth beam  422  is connected to the third head supporting portion  416  by a sixth head side hinge portion  445 . 
     The fifth piezoelectric unit  451  is provided between the first base portion  13  and the base portion of the fifth beam  421 . The fifth piezoelectric unit  451  displaces the distal end of the fifth beam  421  by deforming in a state where voltage is applied. The sixth piezoelectric unit  461  is provided between the second base portion  14  and the base portion of the sixth beam  422 . The sixth piezoelectric unit  461  displaces the distal end of the sixth beam  422  by deforming in a state where voltage is applied. 
     The milliactuator assemblies MA 1 , MA 2  and MA 3  comprise a common structure. Each of the milliactuator assemblies MA 1 , MA 2  and MA 3  is structured in the same manner as the milliactuator assembly MA 1  shown in  FIG.  14    and  FIG.  15   . As the head driving device  10 M of the present embodiment comprises three milliactuator assemblies MA 1 , MA 2  and MA 3 , rigidity can be further increased. In these milliactuator assemblies MA 1 , MA 2  and MA 3 , bent portions  241 ,  242 ,  243  and  244  similar to those of the head driving device  10 L of the sixth embodiment may be formed. The milliactuator assemblies comprising the bent portions  241 ,  242 ,  243  and  244  have a three-dimensional shape. The number of milliactuator assemblies may be four or more. 
     The plate member  11  shown in  FIG.  26    comprises a connection portion  470 . The connection portion  470  connects a first head supporting portion  16 , a second head supporting portion  116  and the third head supporting portion  416 . By providing the connection portion  470 , the locational relationships of the head supporting portions  16 ,  116  and  416  can be kept constant. 
     When the present invention is implemented, the specific mode of each of the elements constituting each head driving device can be modified in various ways. In addition, various forms can be applied to the data storage device depending on the need. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.