Abstract:
A head actuator mechanism characterized has a head that records and reproduces data; a suspension that holds the head; a support arm; a drive means for moving the support arm; a coupling section for coupling the support arm and the suspension together in such a way that the head can move relatively to the support arm; and at least one piezoelectric element for coupling the support arm and the suspension together to move the head relatively to the support arm for fine tuning, the piezoelectric element being fixed to the support arm and suspension at both ends.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a head actuator mechanism used for a disc apparatus such as a hard disc apparatus using a disc as an information storage medium. 
     2. Related Art of the Invention 
     Magnetic disc apparatuses such as hard disc and floppy disc apparatuses conventionally use the same magnetic head to write and read data. On the contrary, attention is being paid to the application to magnetic disc apparatuses of very sensitive read-only heads using a magnetic-resistance effect element (MR elements), including so-called magnetic-resistance magnetic heads. Of course, the use of such a read-only head requires a separate write-only magnetic head to be provided. 
     FIG. 40 shows an example of such a magnetic head formed by integrating a write and a read elements as a thin-film structure. This is a head based on a “piggyback” method which is constituted by laminating an MR element  22  acting as a read element and a lead conductor  23  connected to the MR element, via an insulating layer  21  on a head slider  20 , and laminating thereon via an insulating layer  24  a write element comprising a lower and an upper cores  25  and  26  and a write gap  27  and a coil conductor  28  provided between the cores. The magnetic head is disposed so as to be opposed to the magnetic disc  29  as shown in the figure. 
     Currently, instead of the linear motor method, the rotary actuator method enabling the magnetic head to be moved at a high speed using a small apparatus is often used as a method for driving the magnetic head in the magnetic disc apparatus. As shown in FIG. 41, this method uses a rotating shaft  32  as a support point to rotate an arm  31  with a magnetic head  30  attached to its tip in order to move the magnetic head  30  in the radial direction between the inner and outer circumferences of the magnetic disc  29  for seeking. According to this method, the relative angle between the track direction and the magnetic head  30  is not constant in each track. In other words, the azimuth angle (between the gap direction and track width direction of the magnetic head  30 ) of the magnetic head  30  varies with the track. If the magnetic head  30  is used for both writes and reads, no problem occurs even if the relative angle between the track direction and the magnetic head varies with the track. 
     If, however, the magnetic head  30  comprises the individually configured write and read elements arranged on the same slider in parallel as shown in FIG.  40  and the relative angle varies with the track, the trace position may be different for a write element  40  and a read element  41  laminated as shown in FIG.  42 . FIG. 42 shows a difference in the trace position for the write and read elements  40  and  41  caused by the difference in the relative angle between the track direction and the magnetic head. As shown in FIG.  42 ( a ), when the relative angle between the track direction and the write and read elements  40  and  41  is 90° (corresponding to the azimuth angle of 0°), the write and read elements  40  and  41  trace the same position (shown by arrow  43 ) in the same track  42 . On the contrary, if the relative angle between the track direction and the write and read elements  40  and  41  becomes different from 90°, for example, the track  44  is displaced toward the outer circumference relative to the state in FIG.  42 ( a ), as shown in FIG.  42 ( b ), the write element  40  traces the position shown by arrow  45 , while the read element  41  the position shown by arrow  46  which is slightly closer to the inner circumference, resulting in a difference in traced track  44  position (this is called a “track offset”) between writes and reads. Consequently, the read output from the read element  41  decreases in such a way as to correspond to the rate of track offset relative to the track width. The decrease in read output caused by the track offset increases with decreasing track width due to the increasing density of the track, causing an increase in error rate. 
     As described above, when a magnetic head comprising a write and a read elements that are individually configured is driven by a rotary actuator as in the prior art, the track offset may occur between writes and reads to reduce the read output. 
     This invention is provided in view of this point, and its object is to provide a magnetic disc apparatus that prevents the track offset between writes and reads even if a magnetic head comprising a write and a read elements that are individually configured is driven by a rotary actuator. 
     SUMMARY OF THE INVENTION 
     A head actuator mechanism of the present invention has: 
     a head that records and reproduces data; 
     a suspension that holds the head; 
     a support arm; 
     a drive means for moving the support arm; 
     a coupling section for coupling said support arm and said suspension together in such a way that said head can move relatively to said support arm; and 
     at least one piezoelectric element for coupling said support arm and said suspension together to move said head relatively to said support arm for fine tuning, 
     said piezoelectric element being fixed to said support arm and suspension at both ends. 
     And the head actuator mechanism according to the above invention is such that said coupling section is another piezoelectric element both ends of which are fixed to said support arm and said suspension. 
     And the head actuator mechanism according to the above invention is such said coupling section is present on the side of the position at which said piezoelectric element is coupled to said support arm. 
     And the head actuator mechanism according to the above invention is such that said coupling section is present on the side of the position at which said piezoelectric element is coupled to said suspension. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing a configuration of a first embodiment of this invention; 
     FIG. 2 is a top view showing a configuration of a first embodiment of this invention; 
     FIG.  3 ( a ) shows the periphery of a fine-motion actuator according to the first embodiment (prior to the application of electric fields), and FIG.  3 ( b ) shows the periphery of the fine-motion actuator according to the first embodiment (after the application of electric fields); 
     FIG. 4 is a characteristic diagram showing the characteristics of piezoelectric ceramic and a piezoelectric singlecrystal material; 
     FIG. 5 is a characteristic diagram showing the characteristics of the displacement of piezoelectric ceramic; 
     FIG. 6 is a top view showing a configuration of electrodes in the piezoelectric element according to the first embodiment of this invention; 
     FIG. 7 is a block diagram showing driving executed by the first embodiment of this invention; 
     FIG. 8 shows an applied structure of a head actuator mechanism according to the first embodiment; 
     FIG. 9 shows an applied structure of the head actuator mechanism according to the first embodiment; 
     FIG. 10 shows an applied structure of the head actuator mechanism according to the first embodiment; 
     FIG. 11 is a perspective view showing a configuration of a second embodiment of this invention; 
     FIG. 12 is a top view showing a configuration of the second embodiment of this invention; 
     FIG. 13 is a top view showing another configuration of the second embodiment of this invention; 
     FIG. 14 is a top view showing another configuration of the second embodiment of this invention; 
     FIG. 15 shows the periphery of a fine-motion actuator according to a third embodiment of this invention; 
     FIG. 16 shows the periphery of a fine-motion actuator of another configuration according to the third embodiment of this invention; 
     FIG. 17 is a perspective view showing a configuration of a fourth embodiment of this invention; 
     FIG. 18 shows an applied structure of a head actuator mechanism according to the fourth embodiment; 
     FIG. 19 shows an applied structure of the head actuator mechanism according to the fourth embodiment; 
     FIG. 20 is a perspective view showing a configuration of a fifth embodiment of this invention; 
     FIG. 21 is a top view showing a configuration of the fifth embodiment of this invention; 
     FIG. 22 shows the periphery of a fine-motion actuator according to a sixth embodiment of this invention; 
     FIG. 23 is a top view showing another configuration of the sixth embodiment of this invention; 
     FIG. 24 is a perspective view showing a configuration of the seventh embodiment of this invention; 
     FIG. 25 shows a method for manufacturing the seventh embodiment; 
     FIG. 26 is a perspective view showing another configuration of the seventh embodiment of this invention; 
     FIG. 27 is a top view showing another configuration of the seventh embodiment of this invention; 
     FIG. 28 is a top view showing another configuration of the seventh embodiment of this invention; 
     FIG. 29 is a top view showing another configuration of the seventh embodiment of this invention; 
     FIG. 30 is a top view showing another configuration of the seventh embodiment of this invention; 
     FIG. 31 is a top view showing a configuration of an eighth embodiment of this invention; 
     FIG. 32 describes the assembly of the eighth embodiment of this invention; 
     FIG. 33 is a top view showing a configuration of a ninth embodiment of this invention; 
     FIG. 34 is a top view showing a configuration of a piezoelectric element according to the ninth embodiment of this invention; 
     FIG. 35 is a top view showing another configuration of the ninth embodiment of this invention; 
     FIG. 36 is a top view showing another configuration of the ninth embodiment of this invention; 
     FIG. 37 shows a method for manufacturing the ninth embodiment of this invention; 
     FIG. 38 is a top view showing a configuration of a tenth embodiment of this invention; 
     FIG. 39 shows a method for manufacturing the tenth embodiment of this invention; 
     FIG. 40 is a sectional view showing a magnetic head comprising a write and a read elements integrated together; 
     FIG. 41 is an explanatory drawing of a rotary actuator in a magnetic disc apparatus; and 
     FIG. 42 describes a track direction and a track offset between a write and a read caused by the variation of the relative angle of a magnetic head according to the prior art. 
     DESCRIPTION OF SYMBOLS 
       1  Support arm 
       2  Suspension 
       3  Head 
       4  Coil or the voice coil motors (VCM) 
       5  Shaft and Bearing 
       6   a ,  6   b ,  6   c ,  6   d  Piezoelectric elements consisting of piezoelectric bodies 
       7 ,  7   a ,  7   b  Hinge composed of an elastic bodies 
       8   a ,  8   b ,  8   c ,  8   d  Element-fixing hinges 
       9   a  Driving electrode 
       9   b  Detection electrode 
       10  Signal generating circuit 
       11  Amplifier 
       12  Control circuit 
       13   a ,  13   b ,  13   c ,  13   d ,  13   e ,  13   f  Actuator body blocks 
       14   a ,  14   b ,  14   c ,  14   d  Reinforcing materials 
       15   a ,  15   b ,  15   c ,  15   d  hinge substitution sections 
       16  Shaft plate 
       17   a ,  17   b  Piezoelectric bodies 
       18   a ,  18   b  Joining members 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A first embodiment of this invention is described below with reference to the drawings. 
     FIG. 1 is a perspective view of a head actuator mechanism according to the first embodiment of this invention. FIG. 2 is a top view of the head actuator mechanism according to the first embodiment of this invention. The present head actuator is composed of a coarse-motion actuator and a fine-motion actuator each consisting of a voice coil motors. 
     In the figures,  1  is a support arm,  2  is a suspension,  3  is head,  4  is a coil for the voice coil motors (VCM),  5  is a shaft and a bearing, and  6   a  and  6   b  are piezoelectric elements consisting of piezoelectric bodies each having one end fixed to the support arm  1  and the other end connected to the suspension  2  using an adhesive, respectively. The piezoelectric elements  6   a  and  6   b  are polarized in the same thickness direction, and electrodes are formed in part of the front and rear surfaces of the element so that the stretching vibration of the piezoelectric elements  6   a  and  6   b  is excited in the longitudinal direction when electric fields are applied to the electrodes in the front and rear surfaces. 
     Although this embodiment defines the polarization direction of the piezoelectric elements, the stretching direction of the elements is actually determined by the relationship between the direction of polarization and the direction of applied electric fields. Thus, it is sufficient to apply electric fields in an appropriate direction taking the direction of polarization during the driving into consideration. 
     FIG. 3 shows the principle that the suspension  2  is deflected. 
     FIG. 3 a  shows the periphery of the fine-motion actuator prior to the application of electric fields, and FIG. 3 b  shows the periphery of the fine-motion actuator after the application. 
     By applying electric fields of the same strength in opposite directions, between the front and rear electrodes of each of the piezoelectric elements  6   a  and  6   b , the piezoelectric elements  6   a  and  6   b  are simultaneously stretched or contracted by the same amount as shown in FIG. 3 b . In addition, since the support arm  1  is fixed to the shaft  5  via the bearing, the suspension  2  is rotationally moved. This rotational motion is expanded according to the length of the suspension  2 , thereby enabling the head  3  attached to the tip of the suspension to be moved in the direction shown by the arrow in FIGS. 1 and 2. 
     With this mechanism, the strength of electric fields applied to the piezoelectric elements  6  can be varied to accurately position at a target position the head  3  that has been coarsely moved by the voice coil motor. 
     To allow the suspension  2  to rotate more efficiently, it is necessary that the adhered portion between the suspension  2  and the piezoelectric elements  6  can be rotationally moved. Accordingly, the suspension  2  and the piezoelectric elements  6  are desirably adhered together using an adhesive such as a silicon one having a relatively low rigidity. 
     Furthermore, the slight non-linearity of the piezoelectric elements must be accounted for in order to improve the moving resolution of the head  3 . FIG. 4 shows the results of experiments obtained by plotting the amount of displacement at the tips of the piezoelectric elements of piezoelectric ceramics when sinusoidal signals are applied to the elements with the voltage varied. Even with a small applied voltage, non-linearity is observed in the relationship between the applied voltage and the amount of displacement. However, a similar plot using piezoelectric elements of a piezoelectric singlecrystal material shows linearity from low to high voltages. Thus, by configuring this embodiment using piezoelectric elements of a piezoelectric singlecrystal material, the moving resolution of the head  3  (precision controllability) can be improved easily. 
     Furthermore, displacement creeps (the variation of displacement that occurs when a potential continues to be applied) such as those shown in FIG. 5 are seen in piezoelectric elements of piezoelectric ceramics (No displacement creep phenomenon is observed in the piezoelectric elements of a piezoelectric singlecrystal material). This is the temporal variation of the amount of displacement during DC driving, the amount of displacement increases as the voltage increases as understood from FIG. 5, and is very disadvantageous to very precise position control applications such as this invention. To solve this problem, the applied voltage (applied fields) may be reduced or control may be provided such that the amount of displacement is monitored and maintained constant. 
     In particular, the latter method can be relatively easily implemented by using part of the electrodes in the surfaces of the piezoelectric element as detective electrodes. FIG. 6 shows an example of an electrode structure. In this example, the electrodes  9   a  and  9   b  are divided in the longitudinal direction of the elements, but similar effects can be obtained by setting the dividing direction so as to have an arbitrary angle from the longitudinal direction. The piezoelectric elements  6   a  and  6   b , however, desirably have an electrode configuration using the centerline of the first embodiment as a symmetry axis. In principle, electric fields applied to the drive electrode  9   a  of the element distort the piezoelectric element due to a counter-piezoelectric effect. This configuration converts this distortion into charges using a piezoelectric effect in order to detect a variation in the distortion of the element as a variation in voltage, and if the creep phenomenon increases the distortion of the element, the output voltage from the detective electrode  9   b  increases. Thus, by effecting feedback control using a feedback circuit such as that shown in the drive block diagram shown in FIG. 7, the creep phenomenon in the element can be eliminated. This does not need to be considered for piezoelectric elements of a piezoelectric singlecrystal material because they do not exhibit the displacement creep phenomenon. Further,  10  stands for a signal generating circuit and  12  stands for a control circuit. 
     In addition, the piezoelectric singlecrystal material has a better thermal characteristic for a piezoelectric constant than piezoelectric ceramics, so piezoelectric elements composed of the above material have an excellent thermal characteristic for displacement. 
     Accordingly, the head actuator mechanism using these piezoelectric elements has an excellent thermal characteristic for the amount of displacement, so it can be controlled precisely and easily. 
     FIGS. 8 to  10  show a configuration to which the head actuator mechanism shown in FIG. 1 is applied. 
     The applied structure shown in FIG. 8 is characterized by the simplification of the coarse-motion actuator using only one VCM coil despite the presence of a plurality of heads. 
     In addition, the head actuator mechanism can also be simplified by driving two suspensions using one set of piezoelectric elements as shown in FIG.  9 . Moreover, the head actuator mechanism can further be simplified by integrating a plurality of suspensions together and driving them using one set of piezoelectric elements, as shown in FIG.  10 . 
     Second Embodiment 
     A second embodiment of this invention is described below with reference to the drawings. 
     FIG. 11 is a perspective view of a head actuator mechanism according to the second embodiment of this invention. 
     FIG. 12 is a top view of the head actuator mechanism according to the second embodiment of this invention. 
     In the figures,  1  is a support arm,  2  is a suspension,  3  is head,  4  is a coil for the voice coil motors (VCM),  5  is a shaft and a bearing, and  6   a  and  6   b  are piezoelectric elements consisting of piezoelectric bodies, and  7  is a hinge composed of an elastic body. 
     The piezoelectric elements  6   a  and  6   b  each have one end fixed to the suspension arm  1  and the other end fixed to the suspension  2 , using an adhesive, respectively. 
     Electrodes are formed in part of the front and rear surfaces of the piezoelectric elements  6   a  and  6   b , and these elements are polarized in the same thickness direction. 
     Although this embodiment defines the polarization direction of the piezoelectric elements, the stretching direction of the elements is actually determined by the relationship between the direction of polarization and the direction of applied electric fields. Thus, it is sufficient to apply electric fields in an appropriate direction taking the direction of polarization during the driving into consideration. 
     By applying electric fields of the same strength in opposite directions, between the front and rear electrodes of each of the piezoelectric elements  6   a  and  6   b , the piezoelectric elements  6   a  and  6   b  are simultaneously stretched or contracted by the same amount. 
     Since the support arm  1  is fixed to the shaft  5  via the bearing, the suspension  2  is rotationally moved. This rotational motion is expanded according to the length of the suspension  2 , thereby enabling the head  3  attached to the tip of the suspension to be moved in the direction shown by the arrow in FIGS. 11 and 12. 
     Furthermore, the hinge mechanism  7  acts as a rotational center for rotational motions of the suspension  2  to enable the stretching and contraction of the piezoelectric elements  6   a  and  6   b  to be efficiently converted into the rotational motion of the suspension  2 , thereby enabling the head  3  to move over a wider range. The hinge mechanism  7  is formed by extending to the support arm  1  the support arm  1  side of the plate constituting the suspension  2  in FIG.  1  and coupled to the support arm  1  at a narrow portion P. In addition, the hinge mechanism  7  serves to improve the strength of the fine-motion actuator, thereby improving the response frequency. 
     With this mechanism, the strength of electric fields applied to the piezoelectric elements  6  can be varied to accurately position at a target position the head  3  that has been coarsely moved by the voice coil motor. 
     To allow the suspension  2  to rotate more efficiently, it is necessary that the adhered portion between the suspension  2  and the piezoelectric elements  6  can be rotationally moved. Accordingly, the suspension  2  and the piezoelectric elements  6  are desirably adhered together using an adhesive such as a silicon one having a relatively low rigidity. 
     Of course, the moving resolution of the head  3  (precision controllability) can be improved by configuring this embodiment using piezoelectric elements of a piezoelectric singlecrystal material. 
     Although this embodiment has been described in conjunction with the hinge  7  formed on the support arm  1  side, similar effects can be obtained by extending the support arm  1  side of the plate to the suspension  2  side and forming the hinge on this side as shown in FIG.  13 . In addition, by forming the hinge on both the support arm  1  and suspension  2  sides, the stress occurring in each hinge can be reduced to improve reliability. 
     FIG. 14 shows another structure of the second embodiment. This structure is characterized in that only one piezoelectric element is used compared to the two piezoelectric elements in the embodiment shown in FIG. 11 . Consequently, this configuration has a simpler structure, and requires only one signal compared to the two types of drive signals of phases offset by 180° required in the configuration shown in FIG.  11 . 
     Of course, by providing detective electrodes in the piezoelectric element as in the first embodiment, effects similar to those of the first embodiment can be obtained. 
     Third Embodiment 
     A third embodiment of this invention is described below with reference to the drawings. 
     FIG. 15 is a top view of a fine-motion actuator in a head actuator mechanism according to the third embodiment of this invention. 
     In the figure,  1  is a support arm,  2  is a suspension,  6   a  and  6   b  are piezoelectric elements consisting of piezoelectric bodies,  7  is a hinge composed of an elastic body, and  8   a  and  8   b  are hinges used to fix the piezoelectric elements  6   a  and  6   b  to the suspension  2 . 
     The coarse-motion actuator and head are similar to those in the first embodiment. The piezoelectric elements  6   a  and  6   b  each have one end fixed to the support arm  1  and the other end fixed to the suspension  2  via the element-fixing hinges  8   a  and  8   b , using an adhesive, respectively. 
     Since the support arm  1  is fixed to the shaft  5  via the bearing, the suspension  2  is rotationally moved. This rotational motion is expanded according to the length of the suspension  2 , thereby enabling the head  3  attached to the tip of the suspension to be moved. 
     Furthermore, the hinge mechanism  7  acts as a rotational center for rotational motions of the suspension  2  to enable the stretching and contraction of the piezoelectric elements  6   a  and  6   b  to be efficiently converted into the rotational motion of the suspension  2 , thereby enabling the head  3  to move over a wider range. 
     In addition, the hinge mechanism  7  serves to improve the strength of the fine-motion actuator, thereby improving the response frequency. 
     In addition, to allow the suspension  2  to rotationally move, an angular moment acts on the adhered portion between the piezoelectric elements  6   a  and  6   b  and the suspension  2 . Embodiments 1 and 2 use an adhesive such as a silicon one having a relatively low elastic strength to adhere the piezoelectric elements  6   a  and  6   b  and the suspension  2  together in order to reduce the angular moment occurring in the adhered portion. An adhesive of a low elastic strength may cause large losses in converting the stretching and contraction of the elements  6   a  and  6   b  into the rotation of the suspension  2 . 
     Thus, this embodiment provides the element-fixing hinges  8   a  and  8   b  of a structure that reduces the angular moment occurring in the adhered portion to minimize the losses in converting the stretching and contraction of the elements  6   a  and  6   b  into the rotation of the suspension  2 . The hinges  8   a  and  8   b  enable the suspension  2  to rotate through a larger angle to enable the head section to move over a wider range. In addition, since the spring coefficient of the hinge mechanism relative to bending deformation is constant compared to the adhesive, the relationship between the amount of distortion of the piezoelectric element and the amount of movement of the head section exhibits linearity. As a result, the relationship between electric fields applied to the piezoelectric elements  6   a  and  6   b  and the amount of movement of the head section exhibits an almost linear characteristic despite a slight non-linearity between the distortion of the piezoelectric elements and applied electric fields, thereby improving precision controllability. 
     Of course, the moving resolution of the head  3  (precision controllability) can be improved by configuring this embodiment using piezoelectric elements of a piezoelectric singlecrystal material as in the first and second embodiments. 
     Although this embodiment has been described in conjunction with the hinge  7  formed on the support arm  1  side, similar effects can be obtained by forming the hinge on the suspension  2  side as in FIG. 13 showing the second embodiment. In addition, by forming the hinge on both the support arm  1  and suspension  2  sides, the stress occurring in each hinge can be reduced to improve reliability. 
     Moreover, although the element-fixing hinges  8   a  and  8   b  are formed only on the coupled portion between the piezoelectric elements  6   a  and  6   b  and the suspension  2 , similar effects can be obtained by forming the hinges on the coupled portion between the piezoelectric elements  6   a  and  6   b  and the support arm  1 . 
     In addition, by forming the element-fixing hinge on both the coupled portions between the piezoelectric elements  6   a  and  6   b  and the suspension  2  and between the piezoelectric elements  6   a  and  6   b  and the support arm  1 , the stress occurring in each hinge can be reduced to improve reliability. 
     FIG. 16 shows another structure of the third embodiment. This structure is characterized in that only one piezoelectric element is used compared to the two piezoelectric elements in the preceding invention. Consequently, this configuration has a simpler structure, and requires only one signal compared to the two types of drive signals with phases offset by 180° required in the preceding invention. 
     Of course, by providing detective electrodes in the piezoelectric element as in the first embodiment, effects similar to those of the first embodiment can be obtained. 
     Fourth Embodiment 
     A fourth embodiment of this invention is described below with reference to the drawings. 
     FIG. 17 is a perspective view of a head actuator mechanism according to the fourth embodiment of this invention. 
     In the figure,  1  is a support arm,  2  is a suspension,  3  is head,  4  is a coil for the voice coil motors (VCM),  5  is a shaft and a bearing, and  6   a ,  6   b ,  6   c , and  6   d  are piezoelectric elements consisting of piezoelectric bodies each having one end fixed to the support arm  1  and the other end are connected to the suspension  2  using an adhesive, respectively. 
     Electrodes are formed in part of the front and rear surfaces of each of the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d , and the elements are polarized in the thickness direction. 
     Furthermore, the polarizing direction and the direction of electric fields applied between the electrodes in the front and rear surfaces are determined so that the displacement of the piezoelectric elements  6   a  and  6   c  is opposite to the displacement of the piezoelectric elements  6   b  and  6   d.    
     Consequently, if the stretching of the piezoelectric elements  6   a  and  6   c  is excited, the same amount of contraction of the piezoelectric elements  6   b  and  6   d  is excited. The other part of this embodiment is similar to that of the embodiment in FIG.  1 . 
     In addition, the use of four piezoelectric elements improves the strength of the fine-motion actuator section to enable the control frequency to be set at a high value. 
     Besides, by arbitrarily setting the strength of electric fields applied to the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d , the head  3  can be moved three-dimensionally. 
     Of course, this embodiment can provide effects equivalent to those of the first embodiment. 
     FIGS. 18 and 19 show an applied configuration of the head actuator mechanism shown in FIG.  17 . 
     In the applied structure in FIG. 18, the coarse-motion actuator can be simplified using only one VCM coil despite the presence of a plurality of heads. 
     In addition, the head actuator mechanism can further be simplified by integrating a plurality of suspensions together and driving them using one set of piezoelectric elements, as shown in FIG.  19 . 
     Fifth Embodiment 
     A fifth embodiment of this invention is described below with reference to the drawings. 
     FIG. 20 is a perspective view of a head actuator mechanism according to the fifth embodiment of this invention. 
     FIG. 21 is a top view of the head actuator mechanism according to the fifth embodiment of this invention. 
     In the figures,  1  is a support arm,  2  is a suspension,  3  is head,  4  is a coil for the voice coil motors (VCM),  5  is a shaft and a bearing, and  6   a ,  6   b ,  6   c , and  6   d  are piezoelectric elements consisting of piezoelectric bodies, and  7  is a hinge composed of an elastic body. 
     The piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  each have one end fixed to the support arm  1  and the other end fixed to the suspension  2 , using an adhesive, respectively. The other configuration is similar to that of the embodiment in FIG.  1 . 
     Since the support arm is fixed to the shaft  5  via the bearing, the stretching motion of the piezoelectric elements  6   a ,  6   c  and  6   b ,  6   d  causes the suspension  2  to be rotationally moved. This rotational motion is expanded according to the length of the suspension  2 , thereby enabling the head  3  attached to the tip of the suspension to be moved in the direction shown by the arrow in FIGS. 20 and 21. 
     Furthermore, the hinge mechanism  7  acts as a rotational center for rotational motions of the suspension  2  to enable the stretching and contraction of the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  to be efficiently converted into the rotational motion of the suspension  2 , thereby enabling the head  3  to move over a wider range. In addition, the hinge mechanism  7  serves to improve the strength of the fine-motion actuator, thereby enabling the control frequency to be set at a high value. 
     With this mechanism, electric fields applied to the piezoelectric elements  6  can be varied to accurately position at a target position the head  3  that has been coarsely moved by the voice coil motor. 
     To allow the suspension  2  to rotate more efficiently, it is necessary that the adhered portion between the suspension  2  and the piezoelectric elements  6  can be rotationally moved. Accordingly, the suspension  2  and the piezoelectric elements  6  are desirably adhered together using an adhesive such as a silicon one having a relatively low rigidity. 
     Besides, even if electric fields applied to the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  vary individually, information destruction caused by the contact between the head  3  and a recording medium can be prevented because the hinge  7  defines the moving direction of the head  3 . Consequently, a reliable magnetic disc apparatus can be realized. 
     In addition, the use of four piezoelectric elements improves the strength of the fine-motion actuator section to enable the control frequency to be set at a high value. 
     Of course, this embodiment can provide effects equivalent to those of the second embodiment. 
     Sixth Embodiment 
     A sixth embodiment of this invention is described below with reference to the drawings. 
     A head actuator according to this invention is composed of a coarse-motion actuator and a fine-motion actuator each consisting of a VCM. 
     FIG. 22 is a top view of a fine-motion actuator in a head actuator mechanism according to the sixth embodiment of this invention. 
     In the figure,  1  is a support arm,  2  is a suspension,  6   a ,  6   b ,  6   c , and  6   d  are piezoelectric elements consisting of piezoelectric bodies,  7  is a hinge composed of an elastic body, and  8   a  and  8   b  are hinges used to fix the piezoelectric elements to the suspension  2 . 
     The piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  each have one end fixed to the support arm  1  and the other end fixed to the suspension  2  via the element-fixing hinges  8   a  and  8   b , using an adhesive, respectively. 
     The other configuration is similar to that in FIG.  21 . 
     The above configuration can provide a reliable magnetic disc apparatus and thus a head actuator mechanism having excellent precision controllability. 
     Although this embodiment has been described in conjunction with the hinge  7  formed on the support arm  1  side, similar effects can be obtained by forming the hinge on the suspension  2  side as in FIG. 13 showing the second embodiment. In addition, by forming the hinge on both the support arm  1  and suspension  2  sides, the stress occurring in each hinge can be reduced to improve reliability. 
     Moreover, although the element-fixing hinges  8   a  and  8   b  are formed only on the coupled portion between the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  and the suspension  2 , similar effects can be obtained by forming the hinges on the coupled portion between the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  and the support arm  1 . 
     In addition, by forming the element-fixing hinges  8   a  and  8   b  on both the coupled portions between the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  and the suspension  2  and between the piezoelectric elements  6   a ,  6   b ,  6   c , and  6   d  and the support arm  1 , the stress occurring in each hinge can be reduced to improve reliability (FIG.  23 ). 
     Of course, this embodiment can provide effects similar to those of the third embodiment. 
     Seventh Embodiment 
     A seventh embodiment of this invention is described below with reference to the drawings. 
     FIG. 24 is a perspective view of a head actuator mechanism according to the seventh embodiment of this invention. 
     In the figure,  1  is a support arm,  2  is a suspension,  3  is a head,  4  is a coil for voice coil motors (VCM),  5  is a shaft and a bearing, and  6   a  and  6   b  are piezoelectric elements consisting of piezoelectric bodies each having one end fixed to the support arm  1  and the other end fixed to the suspension  2 , using an adhesive, respectively. Electrodes are formed in part of the front and rear surfaces of each of the piezoelectric elements  6   a  and  6   b , and the elements are polarized in the same thickness direction. The stretching vibration of the piezoelectric elements  6   a  and  6   b  is excited in the longitudinal direction when electric fields are applied to the electrodes in the front and rear surfaces. 
     Since the support arm  1  is fixed to the shaft  5  via the bearing, the suspension  2  is rotationally moved. This rotational motion is expanded according to the length of the suspension  2 , thereby enabling the head  3  attached to the tip of the suspension to be moved. 
     This embodiment differs from the first embodiment in the mounting positions of the piezoelectric elements. 
     According to the configuration in FIG. 1, the rigidity of the head actuator in the direction of its height is determined by the thickness of the piezoelectric element and the Young&#39;s modulus, so the impact resistance of the actuator mechanism in the direction of its thickness significantly decreases as the thickness of the piezoelectric element decreases to decrease a driving voltage. According to this embodiment, however, since the impact resistance in the direction of the height is determined by the width of the piezoelectric element and the Young&#39;s modulus, the thickness of the piezoelectric element can be reduced while the impact resistance is maintained, thereby enabling driving with a low driving voltage. 
     Moreover, the other structure is the same as in the first embodiment, so this configuration can provide effects similar to those of the configuration in FIG.  1 . 
     FIG. 25 shows a method for manufacturing the configuration of this invention shown in FIG.  24 . According to this manufacturing method, a block  13   a  (a suspension material corresponding to a suspension mounted portion) and a block  13   b  (a support arm material corresponding to a support arm mounted portion) constituting an actuator mechanism section that is large in the direction of its thickness are first manufactured using an appropriate working method such as cutting work. Next, piezoelectric element materials  6   a  and  6   b  that are sufficiently large in the direction of their width are joined with the blocks  13   a  and  13   b  at predetermined positions. Finally, these blocks are sliced into pieces of an appropriate thickness using a dicer or a wire saw. A head actuator is then completed by merging the suspension mounted portion with the suspension body section and merging the support arm mounted portion with the support arm body section. This manufacturing method enables a large number of actuators to be manufactured relatively inexpensively. 
     Of course, the effects described in Embodiments 2 and 3 are added by providing the hinges  7   a  and  7   b  in the middle of the actuator mechanism or providing the hinges  8   a ,  8   b ,  8   c , and  8   d  on the mounted portions of the piezoelectric elements as in Embodiments 2 and 3 as shown in FIGS. 26 to  30 . 
     To allow the piezoelectric elements to act like the hinge mechanism on the mounted portion of the piezoelectric element that is added to the form in FIG. 28, the form in FIG. 29 has reinforcing materials  14   a  to  14   d  mounted on part of the piezoelectric element. Consequently, hinge substitution sections  15   a  to  15   d  act like the hinge mechanism to provide characteristics equivalent to those in FIG.  28 . 
     Like the form in FIG. 29, the form in FIG. 30 allows the piezoelectric elements to act like the hinge mechanism on the mounted portion of the piezoelectric element. Specifically, thin portions are formed at the respective ends of the piezoelectric element and used as the hinge substitution sections  15   a  to  15   d . Of course, this configuration provides effects similar to those in FIG.  28 . 
     Eighth Embodiment 
     An eighth embodiment of this invention is described below with reference to the drawings. 
     FIG. 31 is a top view of a fine-motion actuator in a head actuator mechanism according to the eighth embodiment of this invention. 
     In the figure,  6   a  and  6   b  are piezoelectric elements consisting of piezoelectric bodies,  13   a ,  13   b ,  13   c ,  13   d ,  13   e , and  13   f  are body blocks consisting of elastic bodies, and  16  is a shaft plate consisting of an elastic body. According to this configuration, the body blocks  13   a  and  13   b , the body blocks  13   c  and  13   d , and the blocks  13   e  and  13   f  are respectively joined together in such a way as to be mutually opposed and to sandwich the shaft plate  16 . The piezoelectric element  6   a  has its respective ends joined with the body blocks  13   a  and  13   c , while the piezoelectric element  6   b  has its respective ends joined with the body blocks  13   b  and  13   d.    
     FIG. 32 shows an assembly process for this actuator structure. As shown in this figure, the actuator of this configuration is configured by combining small members together. 
     Besides, this assembly method is applicable to the manufacturing method for slicing actuator blocks to form actuators as shown in FIG.  25 . 
     This configuration is similar to the configuration in the seventh embodiment (FIG. 27) and has similar operational principles and effects. Since, however, this configuration is obtained by combining several members, the shaft plate  16  can comprise a material having the nature of a spring to allow the hinge sections  7   a  and  7   b  to be formed of the plate  16  in order to improve the reliability of the hinge sections during the driving of the actuator and thus the reliability of the actuator. 
     In addition, the body plates  13   a  and  13   b  located on the head side can comprise a material of a small specific gravity to allow the position of the gravity of the actuator to approach the shaft section supporting the entire suspension in order to improve the resonance frequency of a head actuator, thereby improving the control frequency of the actuator at a high value. As a result, a head actuator having a higher operational speed can be realized. 
     Moreover, if the piezoelectric elements comprise a piezoelectric singlecrystal material, the joined portion of the body block  13  can comprise a material that can be joined with the piezoelectric singlecrystal material easily, thereby eliminating the needs for adhesion with resin that is a factor preventing precision control. As a result, a head actuator mechanism that can be more easily precision-controlled can be realized. 
     Ninth Embodiment 
     A ninth embodiment of this invention is described below with reference to the drawings. 
     FIG. 33 is a top view of a fine-motion actuator in a head actuator mechanism according to the ninth embodiment of this invention. 
     This embodiment differs from FIG. 27 showing the seventh embodiment in the configuration of the piezoelectric elements. 
     FIG. 34 shows a configuration of the piezoelectric element. 
     Piezoelectric elements  6   a  and  6   b  comprise two piezoelectric bodies  17   a  and  17   b  opposed at a predetermined distance in such a way as to sandwich joining members  18   a  and  18   b.    
     Electrodes are formed in the respective surfaces of each of the piezoelectric bodies  17   a  and  17   b , and the inter-electrode wiring and the polarization direction are determined so that the piezoelectric bodies  17   a  and  17   b  follow the same stretching-deformation process. The piezoelectric bodies  17   a  and  17   b  are connected in parallel. 
     This configuration can easily increase the cross section of the piezoelectric element while maintaining the drive voltage constant. Consequently, the force generated by the piezoelectric element can be increased to realize a head actuator having an increased amount of displacement. Besides, the thickness of the element increases to improve the strength of the actuator mechanism, thereby substantially improving the impact resistance. 
     On the contrary, by maintaining the thickness of the piezoelectric element constant, the thickness of each piezoelectric body can be reduced without changing the rigidity of the actuator. Accordingly, the drive voltage can be significantly reduced while maintaining a constant amount of displacement, thereby realizing a head actuator that enables driving with a low voltage. 
     The other structure is the same as in the first embodiment, so this configuration provides effects similar to those of the configuration in FIG.  1 . 
     FIGS. 35 and 36 show similar piezoelectric elements applied to other configurations of Embodiment 7, and of course, these elements provide both the above effects and the effects described in Embodiment 7. FIG. 35 shows an application to FIG.  28  and FIG. 36 shows an application to FIG.  29 . 
     Although these piezoelectric elements are laminated using joining members, similar effects can be obtained using laminated piezoelectric elements each comprising piezoelectric bodies that are simply stuck together. 
     In addition, if a piezoelectric singlecrystal material is used as piezoelectric bodies having electrodes on their surfaces, it is normally difficult to directly join these piezoelectric bodies together. According to the configuration of the present piezoelectric element, however, the piezoelectric bodies can be joined together easily by avoiding providing electrodes in the junctions between the joining members and the piezoelectric bodies. Consequently, the characteristics of the piezoelectric singlecrystal material can be fully provided. In addition, it is difficult to directly join different types of piezoelectric singlecrystal materials together due to a releasing phenomenon caused by the difference in thermal expansion coefficient, but this releasing problem during junction can be solved by forming the joining members of the same singlecrystal material as the piezoelectric bodies. 
     FIG. 37 shows an example of a method for manufacturing the present actuator. This manufacturing method constructs the actuator by joining together members into which two blocks have been cut. A block for an actuator mechanism section (composed of  13   a  to  13   f  and  16 ) is first produced and sliced into pieces of an appropriate size using a processing machine such as a dicer in order to form the actuator mechanism section. Furthermore, a block is produced that comprises piezoelectric bodies  17   a  and  17   b  that are sufficiently large in the direction of its width and that are jointed together using similar joining members  18   a  and  18   b . This block is similarly sliced to form piezoelectric elements  6   a  and  6   b . Finally, these members are joined together at predetermined positions to obtain finished products. 
     This manufacturing method enables a large number of actuators to be manufactured relatively inexpensively. 
     Tenth Embodiment 
     A tenth embodiment of this invention is described below with reference to the drawings. 
     FIG. 38 is a perspective view of a head actuator mechanism according to the tenth embodiment of this invention. 
     In the figure,  6   a  and  6   b  are piezoelectric elements formed by joining piezoelectric bodies  17   a  and  17   b  in such a way as to sandwich joining members  18   a  and  18   b ;  13   a ,  13   b ,  13   c ,  13   d ,  13   e , and  13   f  are body blocks consisting of elastic bodies; and  16  is a shaft plate consisting of an elastic body. According to this configuration, the body blocks  13   a  and  13   b , the body blocks  13   c  and  13   d , and the blocks  13   e  and  13   f  are respectively joined together in such a way as to be mutually opposed and to sandwich the shaft plate  16 . The piezoelectric element  6   a  has its respective ends joined with the body blocks  13   a  and  13   c , while the piezoelectric element  6   b  has its respective ends joined with the body blocks  13   b  and  13   d . Furthermore, hinge sections  8   a  to  8   d  are formed between the piezoelectric element  6   a  and the body blocks  13   a  and  13   c  and between the piezoelectric element  6   b  and the body blocks  13   b  and  13   d.    
     This configuration can easily increase the cross section of the piezoelectric element while maintaining the drive voltage constant. Consequently, the force generated by the piezoelectric element can be increased to realize a head actuator having an increased amount of displacement. Besides, the thickness of the element increases to improve the strength of the actuator mechanism, thereby substantially improving the impact resistance. 
     On the contrary, by maintaining the thickness of the piezoelectric element constant, the thickness of each piezoelectric body can be reduced without changing the rigidity of the actuator. Accordingly, the drive voltage can be significantly reduced while maintaining a constant amount of displacement, thereby realizing a head actuator that enables driving with a low voltage. 
     This configuration has operational principles and effects similar to those of the eighth embodiment. This embodiment, however, further enables the rigidity in the head moving direction to be determined by the Young&#39;s modulus and width of the piezoelectric element, thereby enabling the resonance frequency of vibration in the moving direction to be set at a high value to increase the control frequency for the actuator. As a result, a head actuator capable of fast operations can be realized. 
     FIG. 39 shows an example of a method for manufacturing the present actuator. This manufacturing method constructs the actuator by joining together members into which two blocks have been cut. A block for an actuator mechanism section (composed of  13   a  to  13   f  and  16 ) is first produced and sliced into pieces of an appropriate size using a processing machine such as a dicer in order to form the actuator mechanism section. Furthermore, a block is produced that comprises piezoelectric bodies  17   a  and  17   b  that are sufficiently large in the direction of its width and that are jointed together using similar joining members  18   a  and  18   b . This block is similarly sliced to form piezoelectric elements  6   a  and  6   b . Finally, these members are joined with the thin plates serving as the hinge substitution sections  8   a  and to  8   d  together at predetermined positions to obtain finished products. 
     This manufacturing method enables a large number of actuators to be manufactured relatively inexpensively. 
     Of course, if a piezoelectric singlecrystal material is used as piezoelectric elements, not only the above effects but also the effects described in Embodiment 8 can be obtained. 
     Although the above embodiments have been described in conjunction with the head actuator mechanism of a rotary moving type, this invention is applicable to a linear moving type. 
     As described above, this invention uses the stretching vibration of the group of piezoelectric elements provided between the suspension and support arm in order to enable the fine motion of the head attached to the tip of the suspension. 
     This configuration eliminates track offsets between writes and reads to prevent the read output from decreasing depending on the position of the track, thereby providing a reliable magnetic disc.