Abstract:
To provide a piezoelectric actuator that is small in size, large in displacement, high in rigidity, excellent in controllability, and excellent in stability, the present invention provides a piezoelectric actuator, including: a first piezoelectric member that is bent and displaced in a thickness direction; and a second piezoelectric member that is bent and displaced in a direction opposite to the first piezoelectric member. In the piezoelectric actuator, the first piezoelectric member and the second piezoelectric member are stacked on each other in the thickness direction of the first piezoelectric member and the second piezoelectric member, and the center portion in the longitudinal direction of the first piezoelectric member and the center portion in the longitudinal direction of the second piezoelectric member, or both ends of the first piezoelectric member and both ends of the second piezoelectric member are fixed to each other.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a piezoelectric actuator, and more particularly to an actuator that is incorporated into an electronic device such as a camera or an information recording device, and serves as a drive source that precisely moves a driven unit such as a lens, and an electronic device using the actuator. 
     2. Description of the Related Art 
     In recent years, improvements in function and performance of the electronic device have been advanced, and diverse principles are applied to the actuators used in the electronic devices. In particular, a piezoelectric actuator using the piezoelectric element can be precisely positioned, is superior in responsiveness, and can be directly driven. Therefore, an attempt is made to apply the piezoelectric actuator to the positioning of the lens or a pickup in the information recording device. In particular, the piezoelectric actuator of a bimorph type having a structure in which two piezoelectric elements are bonded together and generating a bend displacement is widely used because the displacement is larger than that of the piezoelectric actuators of other types. However, in order to address a need for larger displacement output, the length of a piezoelectric element must be lengthened, and the thickness of the piezoelectric element must be thinned. As a result, the piezoelectric actuator is not practical in view of the size, rigidity, and strength. 
     Under the circumstances, there has been known a structure in which a plurality of bimorph elements are stacked on each other in a thickness direction (direction of the bend displacement), and one ends of the respective bimorph elements are bonded together to obtain a large displacement. A structure has been proposed in which two or even number of units each having a pair of bimorph elements that cross each other in an X-shaped configuration are stacked on each other, and fixed to each other. 
     However, the actuator disclosed in JP 2006-121769 A has a portion where the bimorph elements cross each other in the X-shaped configuration, and therefore the structure is complicated, the assembling is difficult, and a gap must be defined between the bimorph elements that cross each other to provide the X-shaped configuration. This leads to an increase in the size of the actuator. Further, with the above configuration, the rigidity of the actuator is reduced, and a responsiveness and the positioning controllability are deteriorated. At the same time, there arises such a problem that the actuator is liable to be affected by a posture difference to be used or a disturbance such as vibrations from outside. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention is to provide a piezoelectric actuator that is small in size, large in displacement, high in rigidity, excellent in controllability, and excellent in stability. 
     In order to solve the above-mentioned problems, according to an aspect of the present invention, there is provided a piezoelectric actuator including: a first piezoelectric member that is bent and displaced (deformed) in a thickness direction; and a second piezoelectric member that is bent and displaced (deformed) in a direction opposite or inverse to the displacement direction of the first piezoelectric member. In the piezoelectric actuator, the first piezoelectric member and the second piezoelectric member are stacked or superposed over each other in spaced relation in the thickness direction of the first piezoelectric member and the second piezoelectric member, and a center portion in a longitudinal direction of the first piezoelectric member and a center portion in a longitudinal direction of the second piezoelectric member are fixed to each other. According to the structure, there can be realized the piezoelectric actuator that is high in rigidity and large in displacement. 
     Further, a plurality of piezoelectric actuators are disposed in a direction of the bend displacement, and both ends in the longitudinal direction of piezoelectric members are fixed to each other at a position where two piezoelectric actuators are adjacent to each other, to constitute the piezoelectric actuator. According to this configuration, the piezoelectric actuator that is larger in displacement can be realized. 
     According to another aspect of the present invention, there is provided a piezoelectric actuator, including: a first piezoelectric member that is bent and displaced in thickness; and a second piezoelectric member that is bent and displaced in a direction opposite to the first piezoelectric member. In the piezoelectric actuator, the first piezoelectric member and the second piezoelectric member are stacked on each other in the thickness direction of the first piezoelectric member and the second piezoelectric member, and both ends in a longitudinal direction of the first piezoelectric member and both ends in a longitudinal direction of the second piezoelectric member are fixed to each other. According to the structure, there can be realized the piezoelectric actuator that is high in rigidity and large in displacement. 
     Further, a plurality of piezoelectric actuators are disposed in a direction of the bend displacement, and both ends in the longitudinal direction of piezoelectric members are fixed to each other at a position where the piezoelectric actuators are adjacent to each other, to constitute the piezoelectric actuator. According to this configuration, the piezoelectric actuator that is larger in displacement can be realized. 
     Further, the plurality of piezoelectric actuators are disposed in the longitudinal direction of the piezoelectric member, and two adjacent piezoelectric members are fixed to each other to constitute the piezoelectric actuator. According to this configuration, the rigidity of the piezoelectric actuator is further increased. 
     According to the present invention, the piezoelectric actuator having a structure that is capable of generating the large displacement and has the high rigidity is obtained. Accordingly, the piezoelectric actuator according to the present invention is excellent in controllability and reliability. Further, it is possible to downsize the electronic device that incorporates the actuator and reduce the power consumption. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a diagram showing the entire structure of a piezoelectric actuator according to a first embodiment of the present invention; 
         FIGS. 2A to 2C  are diagrams showing an electrode structure of a piezoelectric element used in the piezoelectric actuator according to the first embodiment of the present invention; 
         FIG. 3  is a diagram showing a drive state of the piezoelectric actuator according to the first embodiment of the present invention; 
         FIG. 4  is a diagram showing the structure of a piezoelectric actuator according to a second embodiment of the present invention; 
         FIG. 5  is a diagram showing the structure of a piezoelectric actuator according to a third embodiment of the present invention; 
         FIG. 6  is a diagram showing the structure of a piezoelectric actuator according to a fourth embodiment of the present invention; 
         FIG. 7  is a diagram showing the structure of a piezoelectric actuator according to a fifth embodiment of the present invention; 
         FIG. 8  is a diagram showing the structure of a piezoelectric actuator according to a sixth embodiment of the present invention; 
         FIGS. 9A and 9B  are diagrams showing the structure of a piezoelectric actuator that is incorporated in an electronic device according to a seventh embodiment of the present invention; and 
         FIG. 10  is a block diagram showing the electric device according to the seventh embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a description will be given of embodiments of the present invention with reference to the accompanying drawings. 
     First Embodiment 
     A description will be given of the structure and operation of piezoelectric actuators  100  and  101  according to the present invention with reference to  FIGS. 1 ,  2 , and  3 .  FIG. 1  is a diagram showing the entire structure of piezoelectric actuators  100  and  101 .  FIGS. 2A to 2C  are diagrams showing the electrode structure of piezoelectric members  1  and  2 .  FIG. 2A  is a diagram showing electrodes that are disposed on the upper surfaces of piezoelectric elements  1   b  and  2   b  that constitute the piezoelectric members  1  and  2 , and  FIG. 2B  is a diagram showing electrodes  14  and  19  that are disposed on the upper surfaces of piezoelectric elements  1   a  and  2   a  that constitute the piezoelectric members  1  and  2 .  FIG. 2C  is a diagram showing electrodes that are disposed on the lower surfaces of the piezoelectric elements  1   a  and  2   a .  FIG. 3  is a diagram showing the drive state of the piezoelectric actuators  100  and  101 . 
     The piezoelectric actuator  101  according to the present invention includes the piezoelectric members  1  and  2  that are rectangular and stacked over each other in superposed spaced-apart relationship in the thickness direction. A fixing member  7  is disposed between the piezoelectric member  1  and the piezoelectric member  2  and fixes a center portion in the longitudinal direction of the piezoelectric member  1  and a center portion of the piezoelectric member  2 . The piezoelectric actuator  101  also includes an operative member  4  and a support member  3  which are arranged so as to sandwich the piezoelectric members  1  and  2  from both sides of the piezoelectric members  1  and  2  in the thickness direction, and a fixing members  8  and  9  that fix the piezoelectric member  1  and the operative member  4  at both sides (opposite ends) of the piezoelectric member  1  in the longitudinal direction. Further, the piezoelectric actuator  101  includes fixing members  5  and  6  that fix the piezoelectric member  2  and the support member  3  at both ends in the longitudinal direction of the piezoelectric member  2 . The piezoelectric actuator  100  indicates a portion made up of the piezoelectric member  1 , the piezoelectric member  2 , and the fixing member  7 . 
     The piezoelectric member  1  is of a structure in which the two piezoelectric elements  1   a  and  1   b  are stacked on each other, and functions as a so-called bimorph type piezoelectric actuator. Electrodes  10  and  11  are disposed on the upper surface of the piezoelectric element  1   b  in two divided regions except for a center portion in the longitudinal direction of the piezoelectric element  1   b . An electrode  14  is disposed on the entire upper surface of the piezoelectric element  1   a  except for both ends in the longitudinal direction of the piezoelectric member  2 . Electrodes  12  and  13  are disposed on the lower surface of the piezoelectric element  1   a  in two divided regions except for a center portion in the longitudinal direction of the piezoelectric element  1   a . The piezoelectric member  2  is also of the bimorph structure that is made up of two piezoelectric elements  2   a  and  2   b , which is identical with the structure of the piezoelectric member  1 . The electrodes  10 ,  11 ,  12 ,  13 , and  14  in the piezoelectric member  1  correspond to electrodes  15 ,  16 ,  17 ,  18 , and  19  in the piezoelectric member  2 , respectively. 
     The piezoelectric elements  1   a ,  1   b ,  2   a , and  2   b  are polarized in the directions indicated by arrows  1000  and  1001  in the figure. The polarization is conducted by applying a high voltage between the electrode  14  and the electrodes  10 ,  11 ,  12 , and  13 , and between the electrode  19  and the electrodes  15 ,  16 ,  17 , and  18 . A side electrode  21  is disposed at a side of the center portion in the longitudinal direction of the piezoelectric member  1 , and short-circuits the electrode  14 . Side electrodes  20  and  22  are disposed at sides of both ends in the longitudinal direction of the piezoelectric member  1 . The side electrode  20  short-circuits the electrodes  10  and  12 , and the side electrode  22  short-circuits the electrodes  11  and  13 . Further, a side electrode  24  is disposed at the side of the center portion in the longitudinal direction of the piezoelectric member  2 , and short-circuits the electrode  19 . Side electrodes  23  and  25  are disposed at the sides of both ends in the longitudinal direction of the piezoelectric member  2 . The side electrode  23  short-circuits the electrodes  15  and  17 , and the side electrode  25  short-circuits the electrodes  16  and  18 . Those side electrodes  20 ,  21 ,  22 ,  23 ,  24 , and  25  are polarized and thereafter applied. Alternatively, it is possible that an electrode is disposed on a side of the fixing member  7 , and short-circuits the side electrode  21  and the side electrode  24 . In this case, it is possible to reduce the number of lead wirings not shown in the figure which are connected to the electrode. 
     Now, a method of driving the piezoelectric actuators  100  and  101  will be described. A drive signal that is applied to the piezoelectric actuators  100  and  101  is a DC voltage, and voltages different from each other in the polarity are applied to the side electrodes  20 ,  22  and the side electrodes  23 ,  25  with the side electrodes  21  and  24  as GND. For example, a voltage of +10 V is applied to the side electrodes  20  and  22  with the side electrodes  21  and  24  as GND, and a voltage of −10V is applied to the side electrodes  23  and  25 . As a result, both of the piezoelectric member  1  and the piezoelectric member  2  which are the actuator of the bimorph type are bent and displaced in the thickness direction of the piezoelectric members  1  and  2  as shown in  FIG. 3 , but the displacement direction is opposite to each other. As a result, the displacement of the piezoelectric actuators  100  and  101  are in the y-axial direction in the figure. With the above principle, the amount of displacement twice as large as that in the case having only one piezoelectric member is obtained. Further, in order to reverse the displacement direction, the polarity of a signal that is applied to the side electrodes  20  and  22 , and the polarity of a signal that is applied to the side electrodes  23  and  25  can be reversed, respectively. Further, the amount of displacement of the piezoelectric actuators  100  and  101  is controlled by changing the magnitude of the voltage of the signal which is applied to the piezoelectric members  1  and  2 . 
     As described above, a portion where the piezoelectric member  1  and the piezoelectric member  2  are fixed to each other, a portion where the piezoelectric member  1  and the operative member  4  are fixed to each other, and a portion where the piezoelectric member  2  and the support member  3  are fixed to each other are non-driven portions where no distortion occurs due to the piezoelectric effect caused by supplying the drive signal. As a result, it is possible to prevent the members of the fixing portions from being peeled off from each other during driving. 
     Further, with the provision of the side electrodes  20 ,  21 ,  22 ,  23 ,  24 , and  25  on portions that are non-driven portions of the piezoelectric members  1  and  2 , the drive electrode can be disposed over the entire surface of other portions of the piezoelectric members  1  and  2 . For that reason, no unbalance occurs in the entire displacement distribution as the displacements of the piezoelectric actuators  100  and  101  become larger. 
     Incidentally, the structure and the polarization direction of the piezoelectric members  1  and  2  as well as the drive signal are described in detail above. The configuration of the piezoelectric members  1  and  2  is not limited when the piezoelectric members  1  and  2  function as the bimorph element. The piezoelectric members  1  and  2  can be constituted by a laminate piezoelectric element having three or more piezoelectric elements stacked on each other. 
     Further, in a method of fabricating the piezoelectric actuators  100  and  101 , the piezoelectric members  1  and  2 , the fixing members  5 ,  6 ,  7 ,  8  and  9 , the operative member  4 , and the support member  3  can be joined by using an adhesive. Alternatively, at least the piezoelectric members  1  and  2 , and the fixing member  7  are made of piezoelectric ceramics, to thereby make it possible to manufacture those members integrally. For example, a piezoelectric sheet having the piezoelectric element  2   a , a piezoelectric sheet having the piezoelectric element  2   b , a piezoelectric sheet having the fixing member  7 , a piezoelectric sheet having the piezoelectric element  1   a , and a piezoelectric sheet having the piezoelectric element  1   b  are stacked on each other, and then integrally sintered. In this example, when resin or carbon paste is disposed in the periphery of the fixing member  7  in the piezoelectric sheet having the fixing member  7 , since the resin or carbon paste is burned away or melted and dried up at the time of sintering, only the fixing portion  7  remains. With the application of the above process, it is possible to manufacture the piezoelectric actuator  100  that is high in the reliability, and small in the performance variation in large numbers and inexpensively. 
     Second Embodiment 
     A second embodiment of the present invention will be described with reference to  FIG. 4 . In this embodiment, differences between the piezoelectric actuators  100  and  101  described in the first embodiment will be mainly described. 
     A piezoelectric actuator  200  is constituted as follows. That is, two piezoelectric actuators  100  each having the piezoelectric members  1 ,  2 , and the fixing member  7  in the piezoelectric actuator  100  as described in the first embodiment are disposed in a direction of the bent displacement of the piezoelectric members  1  and  2  (y-axial direction indicated by an arrow in the figure). Both ends in the longitudinal direction of the piezoelectric members  1  and  2  that constitute the adjacent piezoelectric actuators are fixed to each other through fixing members  32  and  33  to constitute the piezoelectric actuator  200 . Further, the operative member  4  is fixed through the fixing members  30  and  31  by both ends in the longitudinal direction of two piezoelectric members  1 , which are positioned at both ends of the piezoelectric actuator  200  in the y-axial direction indicated by an arrow. Further, the support member  3  is fixed at both ends in the longitudinal direction of the piezoelectric member  2  through the fixing members  34  and  35  to constitute the piezoelectric actuator  201 . As in the piezoelectric actuators  100  and  101 , the piezoelectric member  1  and the piezoelectric member  2  are bent and displaced in directions opposite to each other. As a result, the piezoelectric actuators  200  and  201  are displaced in the y-axial direction in the figure as a sum of the displacements of the respective piezoelectric members  1  and  2 . 
     In this embodiment, two piezoelectric actuators  100  each having the piezoelectric members  1 ,  2 , and the fixing member  7  are disposed. When the number of piezoelectric actuators  100  is increased, the displacement of the piezoelectric actuators  200  and  201  is increased in proportion to the number of piezoelectric actuators  100 . 
     Third Embodiment 
     A third embodiment of the present invention will be described with reference to  FIG. 5 . In this embodiment, differences between the piezoelectric actuators  100  and  101  described in the first embodiment will be mainly described. 
     A piezoelectric actuator  300  is constituted as follows. That is, the piezoelectric members  1  and  2  in the piezoelectric actuator  100  described in the first embodiment are stacked on each other in the thickness direction thereof. Both ends in the longitudinal direction of the piezoelectric members  1  and  2  are fixed to each other through fixing members  37  and  38  to constitute the piezoelectric actuator  300 . Further, the operative member  4  is fixed at the center portion in the longitudinal direction of the piezoelectric member  2  through a fixing member  36 , and the support member  3  is fixed at the center portion in the longitudinal direction of the piezoelectric member  1  through a fixing member  39  to constitute a piezoelectric actuator  301 . Similarly, as in the piezoelectric actuators  100  and  101 , the piezoelectric member  1  and the piezoelectric member  2  are bent and displaced in directions opposite to each other. As a result, the piezoelectric actuators  300  and  301  are displaced in the y-axial direction in the figure as a sum of the displacements of the respective piezoelectric members  1  and  2 . 
     Fourth Embodiment 
     A fourth embodiment of the present invention will be described with reference to  FIG. 6 . In this embodiment, differences between the piezoelectric actuators  300  and  301  described in the third embodiment will be mainly described. 
     A piezoelectric actuator  400  is constituted as follows. That is, two piezoelectric actuators  300  each having the piezoelectric members  1 ,  2  and the fixing members  37 ,  38  in the piezoelectric actuator  301  described in the third embodiment are disposed in the direction of the bent displacement of the piezoelectric members  1  and  2  (y-axial direction). The center portions in the longitudinal direction of the piezoelectric members  1  and  2 , which constitute the adjacent piezoelectric actuators, are fixed to each other through a fixing member  41  to constitute the piezoelectric actuator  400 . Further, the operative member  4  is fixed through a fixing member  40  by the center portions in the longitudinal direction of the piezoelectric member  2  which are positioned at both ends of the piezoelectric actuator  400  in the y-axial direction. The support member  3  is fixed at the center portion in the longitudinal direction of the piezoelectric member  1  through a fixing member  42  to constitute a piezoelectric actuator  401 . Similarly, as in the piezoelectric actuators  300  and  301 , the piezoelectric member  1  and the piezoelectric member  2  are bent and displaced in directions opposite to each other. As a result, the piezoelectric actuators  400  and  401  are displaced in the y-axial direction in the figure as a sum of the displacements of the respective piezoelectric members  1  and  2 . 
     In this embodiment, two piezoelectric actuators  300  each having the piezoelectric members  1 ,  2 , and the fixing members  37 ,  38  are disposed. When the number of piezoelectric actuators  300  is increased, the displacement of the piezoelectric actuators  400  and  401  is increased in proportion to the number of piezoelectric actuators  300 . 
     Fifth Embodiment 
     A fifth embodiment of the present invention will be described with reference to  FIG. 7 . In this embodiment, differences among the piezoelectric actuators  100 ,  101 ,  300 , and  301  described in the first and third embodiments will be mainly described. 
     In a piezoelectric actuator  500  according to the present invention, the rectangular piezoelectric members  1 ,  2 , and another piezoelectric member  1  are sequentially stacked on each other in the thickness direction. The center portion in the longitudinal direction of the piezoelectric member  1  and the center portion in the longitudinal direction of the piezoelectric member  2  are fixed to each other through a fixing member  46 . Further, the piezoelectric member  2  and the another piezoelectric member  1  are fixed at both ends in the longitudinal direction of the piezoelectric members  1  and  2  through fixing members  44  and  45 . Then, the center portion in the longitudinal direction of the another piezoelectric member  1  is fixed to the operative member  4  through a fixing member  43 . Both ends in the longitudinal direction of the piezoelectric member  1  and the support member  3  are fixed to each other at both ends in the longitudinal direction of the piezoelectric element  1  through fixing members  47  and  48  to constitute the piezoelectric actuator  501 . 
     The piezoelectric member  1  and the piezoelectric member  2  are bent and displaced in directions opposite to each other. As a result, the piezoelectric actuators  500  and  501  are displaced in the y-axial direction in the figure as a sum of the displacements of the respective piezoelectric members  1  and  2 . The piezoelectric actuators  500  and  501  are configured in such a manner that the piezoelectric member  1  or the piezoelectric member  2  is further stacked on and connected to the piezoelectric actuators  100 ,  101  and the piezoelectric actuators  300 ,  301 . Accordingly, it is possible that the piezoelectric member  1  or the piezoelectric member  2  is further stacked on and connected to the piezoelectric actuator  200  described in the second embodiment or the piezoelectric actuator  400  described in the fourth embodiment to constitute the piezoelectric actuator. 
     In the case where the piezoelectric member  1  is connected to the piezoelectric actuator  200 , the piezoelectric actuator  200  is newly connected to the piezoelectric member  1  through a fixing member at both ends in the longitudinal direction of the piezoelectric member  2 , which constitutes the piezoelectric actuator  200  and is positioned at one end in the y-axial direction. In the case where the piezoelectric member  2  is connected to the piezoelectric actuator  200 , the piezoelectric actuator  200  is newly connected to the piezoelectric member  2  through a fixing member at both ends in the longitudinal direction of the piezoelectric member  1 , which constitutes the piezoelectric actuator  200  and is positioned at one end in the y-axial direction. 
     In the case where the piezoelectric member  1  is connected to the piezoelectric actuator  400 , the piezoelectric actuator  400  is newly connected to the piezoelectric member  1  through a fixing member at the center portion in the longitudinal direction of the piezoelectric member  2 , which constitutes the piezoelectric actuator  400  and is positioned at one end in the y-axial direction. In the case where the piezoelectric member  2  is connected to the piezoelectric actuator  400 , the piezoelectric actuator  400  is newly connected to the piezoelectric member  2  through a fixing member in the center portion in the longitudinal direction of the piezoelectric member  1 , which constitutes the piezoelectric actuator  400  and is positioned at one end in the y-axial direction. 
     Sixth Embodiment 
     A sixth embodiment of the present invention will be described with reference to  FIG. 8 . In this embodiment, differences between the piezoelectric actuators  200  and  201  described in the above embodiment will be mainly described. 
     A piezoelectric actuator  600  according to the present invention is made up of the respective two rectangular piezoelectric members  50  and  51 , and fixing members  52 ,  53 ,  54 ,  55 , and  56  which couple the piezoelectric members  50  and  51  with each other. The piezoelectric members  50  and  51  are arranged in the stated order of the piezoelectric members  50 ,  51 ,  50 , and  51  in the thickness direction thereof from above in the figure. The piezoelectric member  50  is of the structure in which two piezoelectric members  1  described in the first embodiment are arranged in the longitudinal direction of the piezoelectric member  1  and coupled with each other. The piezoelectric member  50  can be made up of one piezoelectric member, or two piezoelectric members  1  can be coupled with each other by adhering means or the like. The piezoelectric member  51  is structured in such a manner that two piezoelectric members  2  described in the first embodiment are arranged in the longitudinal direction of the piezoelectric member  1  and coupled with each other. The piezoelectric member  51  can be constituted by one piezoelectric member, or can be constituted by coupling two piezoelectric members  1  by the aid of the adhering means or the like. 
     In the figure, the uppermost piezoelectric member  50  and the second upper piezoelectric member  51  are coupled with each other through the fixing members  55  and  56  at the center portions in the longitudinal direction of the two piezoelectric member  1  and piezoelectric member  2  which constitute those piezoelectric members  50  and  51 . The second upper piezoelectric member  51  and the third upper piezoelectric member  50  are coupled with each other through the fixing members  52 ,  54 , and  53  at both ends in the longitudinal direction of those piezoelectric members  51  and  50  and in the center portions in the longitudinal direction thereof, respectively. The third upper piezoelectric member  50  and the fourth upper piezoelectric member  51  are coupled with each other through the fixing members  55  and  56  in the center portion in the longitudinal direction of the two piezoelectric member  1  and piezoelectric member  2  which constitute those piezoelectric members  50  and  51 . 
     A piezoelectric actuator  601  is made up of the piezoelectric actuator  600 , a support member  63  that fixes the piezoelectric actuator  600 , an operative member  49  that is driven by the piezoelectric actuator  600 , and fixing members  57 ,  58 ,  59 ,  60 ,  61 , and  62  which couple the piezoelectric actuator  600  with the support member  63  and the operative member  49 , respectively. The support member  63  and the piezoelectric actuator  600  are coupled with each other through the fixing members  60 ,  62 , and  61  at both ends and in the center portion of the fourth upper piezoelectric member  51  that constitutes the piezoelectric actuator  600 . The operative member  49  and the piezoelectric actuator  600  are coupled with each other through the fixing members  57 ,  59 , and  58  at both ends and in the center portion of the uppermost piezoelectric member  50  that constitutes the piezoelectric actuator  600 . 
     In a method of driving the piezoelectric actuators  600  and  601 , the piezoelectric member  50  and the piezoelectric member  51  are bent and displaced in directions opposite to each other. That is, the piezoelectric member  1  and the piezoelectric member  2  are bent and displaced in directions opposite to each other, as a result of which the piezoelectric actuators  600  and  601  are displaced in the y-axial direction in the figure as a sum of the displacements of the respective piezoelectric members  50  and  51  in the y-axial direction. 
     As described above, the piezoelectric actuators  600  and  601  can be configured in such a manner that the respective two piezoelectric actuators  200  and  201  are disposed in the longitudinal direction of the piezoelectric members  1  and  2  that apparently constitute the piezoelectric actuators  200  and  201 , and the adjacent piezoelectric members are coupled with each other. Accordingly, it is possible that the piezoelectric actuators  100 ,  101 ,  300 ,  301 ,  400 ,  401 ,  500 , and  501  are used, and at least one of the piezoelectric actuators  100 ,  101 ,  300 ,  301 ,  400 ,  401 ,  500 , and  501  having the same configuration is arranged in the longitudinal direction of the piezoelectric members that constitute the above piezoelectric actuators to be used, and the adjacent piezoelectric members are fixed to each other to constitute the piezoelectric actuator. As the number of piezoelectric actuators  200 ,  201 ,  300 ,  301 ,  400 ,  401 ,  500 , and  501  which are disposed in parallel is increased more, the rigidity of the piezoelectric actuator that has been finally constituted is increased more. 
     As described above, a plurality of piezoelectric actuators having the same configuration are arranged in a direction (x-axial direction) orthogonal to the displacement direction (y-axial direction), and coupled with each other, thereby making it possible to increase the rigidity while keeping the displacement as compared with a case using one piezoelectric actuator. Further, the piezoelectric actuator withstands a deformation that is caused by sintering the piezoelectric element that constitutes the piezoelectric actuator, thereby making it possible to reduce the manufacture variation. 
     Seventh Embodiment 
     A seventh embodiment of the present invention will be described with reference to  FIGS. 9 and 10 . 
       FIGS. 9A and 9B  are diagrams showing a piezoelectric actuator  700  that is incorporated into an electronic device according to the present invention.  FIG. 9A  is a top view of the piezoelectric actuator  700 , and  FIG. 9B  is a side view thereof. The piezoelectric actuator  700  is of the structure in which an operative member  71  and a support member  70  are fixed on the upper and lower surfaces of the two piezoelectric actuators  200  that are disposed in parallel, respectively. A lens  72  that is a controlled member is disposed in the center of the operative member  71 , and an image pickup element  73  is disposed on the support member  70 . In this embodiment, the image pickup element  73  is formed of a CCD or a C-MOS sensor. A drive signal is supplied to the two piezoelectric actuators  200 , and the operative member  71  and the controlled member (lens)  72  are driven in the y-direction in the figure. As a result, a light that has passed through the controlled member (lens)  72  is focused on the image pickup element  73 . With the above configuration, the piezoelectric actuator  700  functions as an auto focus driver device. 
       FIG. 10  is a block diagram showing an electronic device  800  incorporates the piezoelectric actuator  700  of the present invention. In this figure, the electronic device  800  is a digital camera. When a user touches a shutter not shown in the figure, a driving circuit  74  supplies the drive signal to the piezoelectric actuator  700  on the basis of an instruction signal from a control circuit  75 . The lens  72  that is a controlled unit operates on the basis of the operation of the piezoelectric actuator  700 , and the control circuit  75  outputs the instruction signal to the driving circuit  74  on the basis of the information from the image pickup element  73  not shown in the figure, and positions the lens  72  so as to be focused. When the shutter not shown in the figure is depressed in this state, an image that has been taken on the image pickup element  73  is retrieved into a memory not shown in the figure. 
     In this embodiment, the piezoelectric actuator  200  is shown as a drive source of the piezoelectric actuator  700 . However, any one of piezoelectric actuators described in the first to sixth embodiments can be used. Further, a digital camera is exemplified as the electronic device  800 . Alternatively, the piezoelectric actuator can be used for spherical aberration correction or the like of another electronic device, for example, a DVD. In any cases, the electronic device  800  using the piezoelectric actuator of the present invention can be downsized and reduced in the power consumption. 
     INDUSTRIAL APPLICABILITY 
     The piezoelectric actuator according to the present invention can generate a large displacement while keeping a small size, can conduct precise positioning, and is low in the power consumption. Therefore, the piezoelectric actuator of the present invention can be applied to the driving of a pickup in an optical disk or a magnetic disk, the driving of an adjusting mechanism (part such as a lens or a prism) of the optical system in the optical disk, or the lens driving in an auto focus mechanism of the camera, and the like. Further, since a plurality of piezoelectric actuators are used to enable multiaxial driving, the piezoelectric actuator of the present invention can also be applied as an x-y micromotion device in a microscope or a measuring device as well as an image stabilizer in the camera or a video camera.