Patent Publication Number: US-2016226401-A1

Title: Piezoelectric drive device, robot, and drive method of robot

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a piezoelectric drive device, a robot, and a drive method of a robot. 
     2. Related Art 
     JP-A-2004-260990 discloses that one driven body and multiple actuators for driving the driven body are provided so as to drive the driven body by causing the respective actuators to cooperate with each other. 
     However, JP-A-2004-260990 does not sufficiently consider that driving the respective actuators may cause vibrations or a backlash of the driven body. 
     SUMMARY 
     An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples. 
     (1) An aspect of the invention provides a piezoelectric drive device. The piezoelectric drive device includes multiple piezoelectric drive units that drive a driven member. Each of the multiple piezoelectric drive units has a vibrating plate, a piezoelectric vibrating body which is disposed in the vibrating plate, and a contact member which can come into contact with the driven member. The multiple piezoelectric drive units belong to a first piezoelectric drive unit group and a second piezoelectric drive unit group. The respective contact members of the multiple piezoelectric drive units belonging to the first piezoelectric drive unit group are arranged at a position which is symmetrical to a movement center axis or a movement center line of the driven member. The respective contact members of the multiple piezoelectric drive units belonging to the second piezoelectric drive unit group are arranged at a position which is symmetrical to a movement center axis or a movement center line of the driven member. A timing when the respective contact members of the first piezoelectric drive unit group press the driven member is different from a timing when the respective contact members of the second piezoelectric drive unit group press the driven member. According to this aspect, the respective contact members of the multiple piezoelectric drive units belonging to the first piezoelectric drive unit group are arranged at the position which is symmetrical to the movement center axis or the movement center line of the driven member. The respective contact members of the multiple piezoelectric drive units belonging to the second piezoelectric drive unit group are arranged at the position which is symmetrical to the movement center axis or the movement center line of the driven member. Therefore, it is possible to minimize vibrations or a backlash of the driven member. 
     (2) In the piezoelectric drive device, timings when the respective contact members of the first piezoelectric drive unit group press the driven member may be the same as each other, and timings when the respective contact members of the second piezoelectric drive unit group press the driven member may be the same as each other. According to this aspect, the timings when the respective contact members of the first piezoelectric drive unit group press the driven member are the same as each other, and the timings when the respective contact members of the second piezoelectric drive unit group press the driven member are the same as each other. Therefore, it is possible to minimize vibrations or a backlash of the driven member. 
     (3) In the piezoelectric drive device, the driven member may have a disc shape, the respective contact members of the first piezoelectric drive unit group may be arranged at a point symmetry position or a rotation symmetry position with respect to the movement center axis, and the respective contact members of the second piezoelectric drive unit group may be arranged at a point symmetry position or a rotation symmetry position with respect to the movement center axis. According to this aspect, when the driven member has the disc shape, it is possible to minimize vibrations or a backlash of the driven member. 
     (4) In the piezoelectric drive device, the geometric center of gravity of a contact point with which the respective contact members of the first piezoelectric drive unit group come into contact, and the geometric center of gravity of a contact point with which the respective contact members of the second piezoelectric drive unit group come into contact may be located at a position of the movement center axis. According to this aspect, the geometric center of gravity of the contact point with which the respective contact members of the first piezoelectric drive unit group come into contact, and the geometric center of gravity of the contact point with which the respective contact members of the second piezoelectric drive unit group come into contact are located at the position of the movement center axis. Therefore, it is possible to minimize vibrations or a backlash of the driven member. 
     (5) In the piezoelectric drive device, the respective contact members of the first piezoelectric drive unit group may be separately arranged at opposite positions across the driven member, and the respective contact members of the second piezoelectric drive unit group may be separately arranged at opposite positions across the driven member. According to this aspect, the respective contact members of the first piezoelectric drive unit group are separately arranged at the opposite positions across the driven member, and the respective contact members of the second piezoelectric drive unit group are separately arranged at the opposite positions across the driven member. Therefore, it is possible to minimize vibrations or a backlash of the driven member. 
     (6) Another aspect of the invention provides a robot. The robot includes multiple link portions, a joint portion that connects the multiple link portions to each other, and the piezoelectric drive device that pivotally moves the multiple link portions in the joint portion according to any one of (1) to (5) described above. In this case, the piezoelectric drive device can be used for driving the robot. 
     (7) Still another aspect of the invention provides a drive method of a robot. The drive method includes driving the piezoelectric drive device by applying a cyclically varying voltage to the piezoelectric vibrating body, and pivotally moving the multiple link portions in the joint portion. 
     The invention can be implemented in various aspects. For example, in addition to the piezoelectric drive device, the invention can be implemented in various aspects such as a drive method of the piezoelectric drive device, a manufacturing method of the piezoelectric drive device, a robot having the piezoelectric drive device mounted thereon, a drive method of the robot having the piezoelectric drive device mounted thereon, a liquid feeding pump, a medication pump, and the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIGS. 1A and 1B  are respectively a plan view and a sectional view which illustrate a schematic configuration of a piezoelectric drive unit. 
         FIG. 2  is a plan view of a vibrating plate. 
         FIG. 3  is a view for describing an electrical connection state between the piezoelectric drive unit and a drive circuit. 
         FIGS. 4A and 4B  are views for describing an example of bending vibrations of the piezoelectric drive unit. 
         FIGS. 5A to 5D  are views for describing an arrangement of the piezoelectric drive unit in a piezoelectric drive device according to a first embodiment. 
         FIGS. 6A to 6C  are views for describing an arrangement of the piezoelectric drive unit in a piezoelectric drive device according to a second embodiment. 
         FIGS. 7A and 7B  are views for describing an arrangement of the piezoelectric drive unit in a piezoelectric drive device according to a third embodiment. 
         FIG. 8  is a view for describing a force applied to a rotor by a piezoelectric drive unit of a first piezoelectric drive unit group. 
         FIGS. 9A to 9C  are views for describing an arrangement of the piezoelectric drive unit in a piezoelectric drive device according to a fourth embodiment. 
         FIGS. 10A to 10C  are views for describing a piezoelectric drive device according to a modification example of the fourth embodiment. 
         FIG. 11  is a sectional view of a piezoelectric drive unit according to another embodiment of the invention. 
         FIGS. 12A and 12B  are plan views of a piezoelectric drive unit according to further another embodiment of the invention. 
         FIG. 13  is a view for describing an example of a robot which uses the above-described piezoelectric drive unit. 
         FIG. 14  is a view for describing a wrist portion of the robot. 
         FIG. 15  is a view for describing an example of a liquid feeding pump which uses the above-described piezoelectric drive unit. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Configuration of Piezoelectric Drive Unit 
       FIG. 1A  is a plan view illustrating a schematic configuration of a piezoelectric drive unit  10  which is used in the invention.  FIG. 1B  is a sectional view of the piezoelectric drive unit  10 , which is taken along line B-B in  FIG. 1A . The piezoelectric drive unit  10  includes a vibrating plate  200  and two piezoelectric vibrating bodies  100  which are respectively arranged on both surfaces (first surface  211  (also referred to as a “front surface”) and second surface  212  (also referred to as a “rear surface”)) of the vibrating plate  200 . The piezoelectric vibrating body  100  includes a substrate  120 , a first electrode  130  which is formed on the substrate  120 , a piezoelectric substance  140  which is formed on the first electrode  130 , and a second electrode  150  which is formed on the piezoelectric substance  140 . The first electrode  130  and the second electrode  150  interpose the piezoelectric substance  140  therebetween. The two piezoelectric vibrating bodies  100  are arranged symmetrical to each other around the vibrating plate  200 . The two piezoelectric vibrating bodies  100  have the same configuration as each other. Thus, unless otherwise specified in the following, a configuration of the piezoelectric vibrating body  100  located on an upper side of the vibrating plate  200  will be described. 
     The substrate  120  of the piezoelectric vibrating body  100  is used as a substrate for forming the first electrode  130 , the piezoelectric substance  140 , and the second electrode  150  through a film forming process. The substrate  120  also has a function as a vibrating plate for mechanical vibrating. For example, the substrate  120  can be formed of Si, Al 2 O 3 , and ZrO 2 . For example, as the substrate  120  made of silicon (hereinafter, also referred to as “Si”), it is possible to use a Si wafer for semiconductor manufacturing. According to this embodiment, a planar shape of the substrate  120  is rectangular. For example, preferably, the thickness of the substrate  120  is set to a range of 10 □μm to 100 μm. If the thickness of the substrate  120  is set to 10 □μm or greater, the substrate  120  can be relatively easily handled when the film forming process on the substrate  120  is performed. If the thickness of the substrate  120  is set to 100 □μm or smaller, the substrate  120  can be easily vibrated in response to expansion or contraction of the piezoelectric substance  140  formed of a thin film. 
     The first electrode  130  is formed as one continuous conductive layer which is formed on the substrate  120 . In contrast, as illustrated in  FIG. 1A , the second electrode  150  is divided into five conductive layers  150   a  to  150   e  (also referred to as “second electrodes  150   a  to  150   e ”). The second electrode  150   e  located in the center is formed in a rectangular shape extending over the substantially whole body in the longitudinal direction of the substrate  120 , in the center in the width direction of the substrate  120 . The other four second electrodes  150   a ,  150   b ,  150   c , and  150   d  have the same planar shape, and are formed at positions of four corners of the substrate  120 . In an example illustrated in  FIGS. 1A and 1B , both the first electrode  130  and the second electrode  150  have a rectangular planar shape. For example, the first electrode  130  or the second electrode  150  is a thin film formed by means of sputtering. For example, as a material of the first electrode  130  or the second electrode  150 , it is possible to use any highly conductive material such as Aluminum (Al), nickel (Ni), gold (Au), platinum (Pt), and iridium (Ir). Instead of configuring the first electrode  130  to include one continuous conductive layer, the first electrode  130  may be divided into five conductive layers having substantially the same planar shape as that of the second electrodes  150   a  to  150   e . Wiring (or a wiring layer and an insulating layer) for electrical connection between the second electrodes  150   a  to  150   e , and wiring (or a wiring layer and an insulating layer) for electrical connection between the first electrode  130  and the second electrodes  150   a  to  150   e  are omitted in the illustration in  FIGS. 1A and 1B . 
     The piezoelectric substance  140  is formed as five piezoelectric layers having substantially the same planar shape as that of the second electrodes  150   a  to  150   e . Alternatively, the piezoelectric substance  140  may be formed as one continuous piezoelectric layer having substantially the same planar shape as that of the first electrode  130 . Five piezoelectric elements  110   a  to  110   e  (refer to  FIG. 1A ) are configured to include a layered structure of the first electrode  130 , the piezoelectric substance  140 , and the second electrodes  150   a  to  150   e.    
     For example, the piezoelectric substance  140  is a thin film formed using a sol-gel method or a sputtering method. As a material of the piezoelectric substance  140 , it is possible to use any material which shows a piezoelectric effect, such as ceramics employing a Perovskite structure of ABO 3  type. For example, as the ceramics employing the Perovskite structure of ABO 3  type, it is possible to use lead zirconate titanate (PZT), barium titanate, lead titanate, potassium niobate, lithium niobate, lithium tantalate, sodium tungstate, zinc oxide, barium strontium titanate (BST), strontium bismuth tantalate (SBT), lead metaniobate, lead zinc niobate, scandium lead niobate, and the like. For example, in addition to the ceramic, it is also possible to use a material which shows a piezoelectric effect, such as polyvinylidene fluoride, a crystal, and the like. For example, preferably, the thickness of the piezoelectric substance  140  is set to a range of 50 nm (0.05 □μm) to 20 □μm. A thin film of the piezoelectric substance  140  having the thickness in this range can be easily formed using a thin film forming process. If the thickness of the piezoelectric substance  140  is set to 0.05 □μm or greater, a sufficiently strong force can be generated in response to expansion or contraction of the piezoelectric substance  140 . If the thickness of the piezoelectric substance  140  is set to 20 □μm or smaller, the piezoelectric drive unit  10  can be sufficiently miniaturized. 
       FIG. 2  is a plan view of the vibrating plate  200 . The vibrating plate  200  has a rectangular vibrating body portion  210 , and connection portions  220  which respectively triply extend from the right and left long sides of the vibrating body portion  210 . In addition, the vibrating plate  200  has two attachment portions  230  which are respectively connected to the three connection portions  220  on the right and left sides. In  FIG. 2 , for convenience of illustration, the vibrating body portion  210  is hatched. The attachment portion  230  is used in order to attach the piezoelectric drive unit  10  to other members by using a screw  240 . For example, the vibrating plate  200  can be formed of metal such as silicon, silicon compound, stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, copper, copper alloy, iron-nickel alloy, and the like, metal oxide, or materials such as diamond and the like. 
     The piezoelectric vibrating bodies  100  (refer to  FIGS. 1A and 1B ) respectively adhere to an upper surface (first surface) and a lower surface (second surface) of the vibrating body portion  210  by using an adhesive. Preferably, a ratio between a length L and a width W of the vibrating body portion  210  is set to L:W=approximately 7:2. The ratio is a preferred value used in order to perform ultrasonic vibrations (to be described later) by which the vibrating body portion  210  is bent to the right and left along its plane. For example, the length L of the vibrating body portion  210  can be set to a range of 0.1 mm to 30 mm. For example, the width W can be set to a range of 0.05 mm to 8 mm. Preferably, the length L is set to 50 mm or smaller in order for the vibrating body portion  210  to perform the ultrasonic vibrations. For example, the thickness (thickness of the vibrating plate  200 ) of the vibrating body portion  210  can be set to a range of 20 □μm to 700 □μm. If the thickness of the vibrating body portion  210  is set to 20 □μm or greater, the vibrating body portion  210  has sufficient rigidity in order to support the piezoelectric vibrating body  100 . If the thickness of the vibrating body portion  210  is set to 700 □μm or smaller, the vibrating body portion  210  is enabled to have sufficiently large deformation in response to deformation of the piezoelectric vibrating body  100 . 
     A contact member  20  is disposed on one short side of the vibrating plate  200 . The contact member  20  can come into contact with a driven body so as to apply a force to the driven body. Preferably, the contact member  20  is formed of a durable material such as ceramics (for example, Al 2 O 3 ). 
       FIG. 3  is a view for describing an electrical connection state between the piezoelectric drive unit  10  and a drive circuit  300 . Among the five second electrodes  150   a  to  150   e , a pair of the second electrodes  150   a  and  150   d  which are located at opposite angles are electrically connected to each other via a wire  151 . A pair of the second electrodes  150   b  and  150   c  which are located other opposite angles are also electrically connected to each other via a wire  152 . The wires  151  and  152  may be formed using a film forming process, or may be realized by means of wire-shaped wiring. The three second electrodes  150   b ,  150   e , and  150   d  located on the right side in  FIG. 3  and the first electrode  130  (refer to  FIGS. 1A and 1B ) are electrically connected to the drive circuit  300  via wires  310 ,  312 ,  314 , and  320 . The drive circuit  300  applies a cyclically varying AC voltage or pulsating voltage between a pair of the second electrodes  150   a  and  150   d  and the first electrode  130 . In this manner, the piezoelectric drive unit  10  is caused to perform the ultrasonic vibrations, thereby enabling a rotor (driven body) coming into contact with the contact member  20  to be rotated in a predetermined rotation direction. Here, the “pulsating voltage” means a voltage obtained by adding a DC offset to the AC voltage. A direction of the voltage (electric field) is one direction from one electrode toward the other electrode. The rotor coming into contact with the contact member  20  can be rotated in the opposite direction by applying the AC voltage or the pulsating voltage between the other pair of the second electrodes  150   b  and  150   c  and the first electrode  130 . The voltage is simultaneously applied in the two piezoelectric vibrating bodies  100  disposed on both surfaces of the vibrating plate  200 . Wiring (or a wiring layer and an insulating layer) configuring the wires  151 ,  152 ,  310 ,  312 ,  314 , and  320  illustrated in  FIG. 3  is omitted in the illustration in  FIGS. 1A and 1B . 
       FIGS. 4A and 4B  are views for describing an example of bending vibrations of the piezoelectric drive unit  10 . The contact member  20  of the piezoelectric drive unit  10  is in contact with an outer periphery of a rotor  50  functioning as a driven body. In an example illustrated in  FIGS. 4A and 4B , the drive circuit  300  (refer to  FIG. 3 ) applies the AC voltage or the pulsating voltage between a pair of the second electrodes  150   a  and  150   d  which are arranged at first opposite angles and the first electrode  130 , and the piezoelectric elements  110   a  and  110   d  expand and contract in a direction of an arrow x in  FIGS. 4A and 4B . In response to this, the vibrating body portion  210  of the piezoelectric drive unit  10  is alternately deformed into a straight shape which does not meander as illustrated in  FIG. 4A  and into a meandering shape (S-shape) which is bent inside a plane of the vibrating body portion  210  as illustrated in  FIG. 4B . A distal end of the contact member  20  performs elliptical movement in a direction of an arrow y. As a result, the rotor  50  is rotated around a center  51  thereof in a first direction z (clockwise direction in  FIGS. 4A  and  4 B). According to the embodiment, the description that the vibrating body portion  210  is alternately deformed into the straight shape which does not meander as illustrated in  FIG. 4A  and into the meandering shape (S-shape) which is bent inside the plane of the vibrating body portion  210  as illustrated in  FIG. 4B  is referred to as bending vibrations. The three connection portions  220  (refer to  FIG. 2 ) of the vibrating plate  200  described with reference to  FIG. 2  are disposed at a position of a vibration knot (joint) of the vibrating body portion  210  described above. When the drive circuit  300  applies the AC voltage or the pulsating voltage between the other pair of the second electrodes  150   b  and  150   c  which are arranged at second opposite angles different from the first opposite angles and the first electrode  130 , the rotor  50  is rotated in the opposite direction (second direction or counterclockwise direction). In the bending vibrations, the two piezoelectric elements  110   a  and  110   d  which are driven during clockwise rotation are located at a point symmetry position with respect to a center  205  of the vibrating body portion  210  (or the piezoelectric vibrating body  100 ). The two piezoelectric elements  110   b  and  110   c  which are driven during counterclockwise rotation are located at a point symmetry position with respect to the center  205  of the vibrating body portion  210  (or the piezoelectric vibrating body  100 ). If the same voltage as that of a pair of the second electrodes  150   a  and  150   d  (or the other pair of the second electrodes  150   b  and  150   c ) is applied to the second electrode  150   e  in the center, the piezoelectric drive unit  10  expands or contracts in the longitudinal direction. Accordingly, it is possible to increase a force applied from the contact member  20  to the rotor  50 . The piezoelectric element which is driven during the bending vibrations by the drive circuit  300  may not be located at the point symmetry position. For example, the piezoelectric element may be positioned at a position deviated from the center  205 . This operation of the piezoelectric drive unit  10  (or the piezoelectric vibrating body  100 ) is disclosed in Patent Document 1 described above (JP-A-2004-320979 or corresponding U.S. Pat. No. 7,224,102), the content of which is incorporated by reference. 
     First Embodiment 
       FIGS. 5A to 5D  are views for describing an arrangement of a piezoelectric drive unit in a piezoelectric drive device  1000  according to a first embodiment.  FIG. 5A  illustrates a view when the piezoelectric drive unit is viewed in a normal direction of the rotor  50 .  FIG. 5B  illustrates a view when the piezoelectric drive device  1000  is viewed in a direction of an arrow B illustrated in  FIG. 5A . In  FIG. 5B , since it becomes difficult to view the drawing, piezoelectric drive units  10   s   3  and  10   t   2  and the contact member  20  are omitted. The piezoelectric drive device  1000  includes six piezoelectric drive units  10   s   1  to  10   s   3  and  10   t   1  to  10   t   3 . The piezoelectric drive units  10   s   1  to  10   s   3  and  10   t   1  to  10   t   3  are classified to two groups, that is, a first piezoelectric drive group and a second piezoelectric drive group. The first piezoelectric drive group includes the piezoelectric drive units  10   s   1  to  10   s   3 , and the second piezoelectric drive group includes the piezoelectric drive units  10   t   1  to  10   t   3 . The contact member  20  of the three piezoelectric drive units  10   s   1  to  10   s   3  of the first piezoelectric drive group is arranged along the outer periphery of a disc shape of the rotor  50  (driven member  50 ) at a third rotation symmetry position around the center  51  of the rotor  50 . The geometric center of gravity of three contact points between the three contact members  20  of the three piezoelectric drive units  10   s   1  to  10   s   3  and the rotor  50  is coincident with the center  51  of the rotor  50 . The contact member  20  of the three piezoelectric drive units  10   t   1  to  10   t   3  of the second piezoelectric drive group is also arranged along the outer periphery of the rotor  50  at a third rotation symmetry position around the center  51  of the rotor  50 . The geometric center of gravity of three contact points between the three contact members  20  of the three piezoelectric drive units  10   t   1  to  10   t   3  and the rotor  50  is coincident with the center  51  of the rotor  50 . The “geometric center of gravity” means the center of gravity of a convex and polygonal shape (triangular shape according to the embodiment) configured to include three or more contact points. 
     The contact member  20  of the piezoelectric drive units  10   s   1  to  10   s   3  and  10   t   1  to  10   t   3  comes into contact with an outer peripheral surface  52  (also referred to as a “contact surface  52 ”) of the rotor  50  in the center of the thickness of the rotor  50 . A trajectory TR (also referred to as a “movement trajectory TR”) of the contact point shows a circle formed along the outer peripheral surface  52 . The center  51  of the rotor  50  corresponds to a “movement center axis” which is the center of the movement trajectory TR of the outer peripheral surface  52 . In other words, on the assumption of the movement trajectory TR on the contact surface  52  of the rotor  50  with which the multiple contact members  20  of the multiple piezoelectric drive units  10   s   1  to  10   s   3  and  10   t   1  to  10   t   3  come into contact, the center  51  of the rotor  50  is the movement center axis which is located in the center of the movement trajectory TR. 
     In the piezoelectric drive device  1000 , the three piezoelectric drive units  10   s   1  to  10   s   3  of the first piezoelectric drive unit group press the rotor  50  at the same timing. However, the pressing timings of the respective piezoelectric drive units  10   s   1  to  10   s   3  may have a mutual difference of approximately 5% when the length of a pressing cycle is presumed to be 100%. If the difference falls within this degree, vibrations or a backlash of the rotor  50  can be sufficiently suppressed and minimized. In addition, the three piezoelectric drive units  10   t   1  to  10   t   3  of the second piezoelectric drive unit group also press the rotor  50  at the same timing. Similarly, the pressing timings of the respective piezoelectric drive units  10   t   1  to  10   t   3  may also have a mutual difference of approximately 5% when the length of a pressing cycle is presumed to be 100%. The timing at which the piezoelectric drive units  10   s   1  to  10   s   3  of the first piezoelectric drive unit group press the rotor  50  and the timing at which the piezoelectric drive units  10   t   1  to  10   t   3  of the second piezoelectric drive unit group press the rotor  50  are different from each other. The pressing is alternately performed. 
       FIG. 5C  is a view for describing pressing forces F 10   s   1  to F 10   s   3  applied to the rotor  50  from the piezoelectric drive units  10   s   1  to  10   s   3  of the first piezoelectric drive unit group. The pressing forces F 10   s   1  to F 10   s   3  have the same magnitude, and are oriented in a tangent line direction at the contact point between the rotor  50  and the contact member  20 . If a rotation symmetry force is applied in this way from the contact point located at a rotation symmetry position, no force except for the rotating force is applied to the rotor  50 . The pressing forces F 10   s   1  to F 10   s   3  applied to the rotor  50  from the piezoelectric drive unit of the first piezoelectric drive unit group serve only to rotate the rotor  50 , and a force in a translation direction is not applied to the rotor  50 . As a result, it is possible to suppress the vibrations or the backlash of the rotor  50 . 
       FIG. 5D  is a view for describing a case where the pressing forces F 10   s   1  to F 10   s   3  are oriented in a direction other than the tangent line direction of the outer peripheral surface  52  of the rotor  50 . The pressing force F 10   s   1  can be divided into a force F 10   s   1   a  acting in the tangent line direction of the outer peripheral surface  52  and a force F 10   s   1   b  acting in the center direction (radial direction) of the rotor  50 . Similarly, the pressing forces F 10   s   2  and F 10   s   3  can also be respectively divided into forces F 10   s   2   a  and F 10   s   3   a  acting in the tangent line direction, and forces F 10   s   2   b  and F 10   s   3   b  acting in the center direction. In a case of the forces  10   s   1   b , F 10   s   2   b , and F 10   s   3   b , a line of action passes through the center  51  of the rotor  50 , and a total sum of the forces  10   s   1   b , F 10   s   2   b , and F 10   s   3   b  becomes zero. Accordingly, the force acting in the translation direction is not applied to the rotor  50 . As described with reference to  FIG. 5C , the forces  10   s   1   a , F 10   s   2   a , and F 10   s   3   a  acting in the tangent line direction serve only to rotate the rotor  50 , and a force acing in the translation direction is not applied to the rotor  50 . Therefore, even when the pressing forces F 10   s   1  to F 10   s   3  are oriented in the direction other than the tangent line direction of the outer peripheral surface  52  of the rotor  50 , the pressing forces F 10   s   1  to F 10   s   3  serve only to rotate the rotor  50 , and a force acing in the translation direction is not applied to the rotor  50 . As a result, it is possible to suppress the vibrations or the backlash of the rotor  50 . 
     As described above, according to the first embodiment, the respective contact members  20  of the three piezoelectric drive units  10   s   1  to  10   s   3  belonging to the first piezoelectric drive unit group are arranged at the third rotation symmetry position with respect to the center  51  (movement center axis) of the rotor  50 . The respective contact members  20  of the three piezoelectric drive units  10   s   1  to  10   s   3  belonging to the second piezoelectric drive unit group are arranged at the third rotation symmetry position with respect to the center  51  (movement center axis) of the rotor  50 . After the respective contact members  20  of the first piezoelectric drive unit group press the rotor  50 , the respective contact members  20  of the second piezoelectric drive unit group press the rotor  50 . Accordingly, it is possible to minimize the vibrations or the backlash of the rotor  50 . 
     Second Embodiment 
       FIGS. 6A to 6C  are views for describing an arrangement of a piezoelectric drive unit in a piezoelectric drive device  1000   s  according to a second embodiment.  FIG. 6A  is a view when the piezoelectric drive unit is viewed in the normal direction of the rotor  50 , and  FIG. 6B  illustrates a view when the piezoelectric drive device  1000   s  is viewed in a direction of an arrow B illustrated in  FIG. 6A . In  FIG. 6B , since it becomes difficult to view the drawing, a piezoelectric drive unit  10   t   1  and the contact member  20  are omitted. The piezoelectric drive device  1000   s  includes four piezoelectric drive units  10   s   1 ,  10   s   2 ,  10   t   1 , and  10   t   2 . The first piezoelectric drive group includes the piezoelectric drive units  10   s   1  and  10   s   2 , and the second piezoelectric drive group includes the piezoelectric drive units  10   t   1  and  10   t   2 . The contact member  20  of the two piezoelectric drive units  10   s   1  and  10   s   2  of the first piezoelectric drive group is arranged along the outer periphery of the rotor  50  at a point symmetry position around the center  51  (which is the rotation center of the rotor  50  and corresponds to a movement center axis” in the appended claims) of the rotor  50 . The geometric center of gravity of the two piezoelectric drive units  10   s   1  and  10   s   2  is coincident with the center  51  of the rotor  50 . The contact member  20  of the two piezoelectric drive units  10   t   1  and  10   t   2  of the second piezoelectric drive group is also arranged along the outer periphery of the rotor  50  at a point symmetry position around the center  51  of the rotor  50 . The geometric center of gravity of the two piezoelectric drive units  10   t   1  and  10   t   2  is coincident with the center  51  of the rotor  50 . 
     The contact member  20  of the piezoelectric drive units  10   s   1 ,  10   s   2 ,  10   t   1 , and  10   t   2  comes into contact with the outer peripheral surface  52  (also referred to as the “contact surface  52 ”) of the rotor  50  in the center of the thickness of the rotor  50 . The trajectory TR (also referred to as the “movement trajectory TR”) of the contact point shows a circle formed along the outer peripheral surface  52 . 
     The two piezoelectric drive units  10   s   1  and  10   s   2  of the first piezoelectric drive unit group press the rotor  50 , and the two piezoelectric drive units  10   t   1  and  10   t   2  of the second piezoelectric drive unit group press the rotor  50 . The pressing performed on the rotor  50  by the piezoelectric drive units  10   s   1  and  10   s   2  of the first piezoelectric drive unit group and the pressing performed on the rotor  50  by the piezoelectric drive units  10   t   1  and  10   t   2  of the second piezoelectric drive unit group are alternately performed. 
       FIG. 6C  is a view for describing the pressing forces F 10   s   1  and F 10   s   2  applied to the rotor  50  from the piezoelectric drive units  10   s   1  and  10   s   2  of the first piezoelectric drive unit group. The pressing forces F 10   s   1  and F 10   s   2  have the same magnitude. The pressing forces F 10   s   1  and F 10   s   2  are respectively oriented in the tangent line direction in the contact point between the rotor  50  and the contact member  20 , and the orientations are opposite to each other. The pressing forces F 10   s   1  and F 10   s   2  are not on the same straight line. Accordingly, the pressing forces F 10   s   1  and F 10   s   2  configure a couple of forces. Therefore, the pressing forces F 10   s   1  and F 10   s   2  serve only to rotate the rotor  50 , and force acting in the translation direction is not applied to the rotor  50 . As a result, it is possible to minimize the vibrations or the backlash of the rotor  50 . The above-described configuration is similarly applied to the pressing force applied to the rotor  50  from the piezoelectric drive units  10   t   1  and  10   t   2  of the second piezoelectric drive unit group. 
     As described above, according to the second embodiment, the respective contact members  20  of the piezoelectric drive units  10   s   1  and  10   s   2  of the first piezoelectric drive unit group are arranged along the outer periphery of the rotor  50  at the point symmetry position around the center  51  of the rotor  50 . The respective contact members  20  of the piezoelectric drive units  10   t   1  and  10   t   2  of the second piezoelectric drive unit group are arranged along the outer periphery of the rotor  50  at the point symmetry position around the center  51  of the rotor  50 . After the respective contact members  20  of the first piezoelectric drive unit group press the rotor  50 , the respective contact members  20  of the second piezoelectric drive unit group press the rotor  50 . Therefore, it is possible to minimize the vibrations or the backlash of the rotor  50 . 
     Third Embodiment 
       FIGS. 7A and 7B  are views for describing an arrangement of a piezoelectric drive unit in a piezoelectric drive device  1000   t  according to a third embodiment.  FIG. 7A  illustrates a state where the piezoelectric drive device  1000   t  is viewed in a direction parallel to the rotor  50 , and  FIG. 7B  illustrates a state where the piezoelectric drive device  1000   t  is viewed in the normal direction of the rotor  50 . The piezoelectric drive device  1000   t  includes 12 piezoelectric drive units  10   s   1   u  to  10   s   3   u ,  10   s   1   d  to  10   s   3   d ,  10   t   1   u  to  10   t   3   u , and  10   t   1   d  to  10   t   3   d . The first piezoelectric drive unit group includes the piezoelectric drive units  10   s   1   u  to  10   s   3   u  and  10   s   1   d  to  10   s   3   d , and the second piezoelectric drive unit group includes the piezoelectric drive units  10   t   1   u  to  10   t   3   u  and  10   t   1   d  to  10   t   3   d.    
     The contact member  20  of the piezoelectric drive units  10   s   1   u  to  10   s   3   u  of the first piezoelectric drive unit group is arranged on one surface  50   u  side of the rotor  50  at a third rotation symmetry position. The contact member  20  of the piezoelectric drive units  10   s   1   d  to  10   s   3   d  is arranged on the other surface  50   d  side of the rotor  50  at a third rotation symmetry position. The piezoelectric drive unit  10   s   1   u  and  10   s   1   d  are paired with each other, and are separately arranged at opposite positions across the rotor  50 . The configuration is similarly applied to the piezoelectric drive units  10   s   2   u  and  10   s   2   d , and the piezoelectric drive units  10   s   3   u  and  10   s   3   d . The piezoelectric drive units  10   t   1   u  to  10   t   3   u  of the second piezoelectric drive unit group are arranged similarly to the piezoelectric drive units  10   s   1   u  to  10   s   3   u  of the first piezoelectric drive unit group. 
     The contact member  20  of the piezoelectric drive units  10   s   1   u  to  10   s   3   u  of the first piezoelectric drive unit group comes into contact with the one surface  50   u  of the rotor  50 . The movement trajectory TR of the contact point is a circle formed around the center  51  of the rotor  50 . The center  51  of the rotor  50  corresponds to the “movement center axis” which is the center of the movement trajectory TR on the outer peripheral surface  52 . In other words, on the assumption of the movement trajectory TR on the outer peripheral surface  52  of the rotor  50  with which the multiple contact members  20  of the multiple piezoelectric drive units  10   s   1  to  10   s   3  and  10   t   1  to  10   t   3  come into contact, the center  51  of the rotor  50  is the movement center axis which is located in the center of the movement trajectory TR. The contact member  20  of the piezoelectric drive units  10   t   1   u  to  10   t   3   u  of the second piezoelectric drive unit group similarly comes into contact with the surface  50   u , and similarly forms a circular movement trajectory formed around the center  51  of the rotor  50 . The movement trajectory TR formed by the contact member  20  of the piezoelectric drive units  10   s   1   u  to  10   s   3   u  of the first piezoelectric drive unit group and the movement trajectory formed by the contact member  20  of the piezoelectric drive units  10   t   1   u  to  10   t   3   u  of the second piezoelectric drive unit group may overlap each other, or may not overlap each other. The contact member  20  of the piezoelectric drive units  10   s   1   d  to  10   s   3   d  of the first piezoelectric drive unit group and the piezoelectric drive units  10   t   1   d  to  10   t   3   d  of the second piezoelectric drive unit group similarly come into contact with the other surface  50   d  of the rotor  50 . The configuration is similarly applied to the movement trajectory. The movement trajectory TR formed by the contact member  20  of the piezoelectric drive units  10   s   1   u  to  10   s   3   u  of the first piezoelectric drive unit group and the movement trajectory formed by the contact member  20  of the piezoelectric drive units  10   s   1   d  to  10   s   3   d  of the first piezoelectric drive unit group oppose each other. The movement trajectory formed by the contact member  20  of the piezoelectric drive units  10   t   1   u  to  10   t   3   u  of the second piezoelectric drive unit group and the movement trajectory formed by the contact member  20  of the piezoelectric drive units  10   t   1   d  to  10   t   3   d  of the second piezoelectric drive unit group oppose each other. 
       FIG. 8  is a view for describing forces F 10   s   1 , F 10   s   3 , and F 10   s   2  applied to the rotor  50  by the piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u ,  10   s   2   d ,  10   s   3   u , and  10   s   3   d  of the first piezoelectric drive unit group. The force applied by the piezoelectric drive unit  10   s   1   u  and the force applied by the piezoelectric drive unit  10   s   1   d  are applied in the same direction with the same magnitude. Thus,  FIG. 8  collectively illustrates the forces as the force F 10   s   1 . The configuration is similarly applied to the forces F 10   s   2  and F 10   s   3 . The forces F 10   s   1 , F 10   s   2 , and F 10   s   3  have the same magnitude, and are applied in the tangent line direction of the movement trajectory TR. Therefore, similarly to the first embodiment, the forces F 10   s   1 , F 10   s   2 , and F 10   s   3  serve only to rotate the rotor  50 , and the force acting in the translation direction is not applied to the rotor  50 . As a result, it is possible to suppress the vibrations or the backlash of the rotor  50 . 
     The piezoelectric drive units  10   s   1   u  and  10   s   1   d ,  10   s   2   u  and  10   s   2   d , and  10   s   3   u  and  10   s   3   d  respectively oppose each other across the rotor  50 , and press the rotor  50 . The force acting in the normal line direction of the rotor  50  (direction along the rotation axis of the rotor  50 ) is offset, and thus the force to swing the rotation axis of the rotor  50  is not applied. Therefore, it is possible to minimize the vibrations or the backlash of the rotor  50 . The configuration is similarly applied to the piezoelectric drive units  10   t   1   u  to  10   t   3   u  and  10   t   1   d  to  10   t   3   d  of the second piezoelectric drive unit group. 
     As described above, according to the third embodiment, the respective contact members  20  of the six piezoelectric drive units  10   s   1   u  to  10   s   3   u  and  10   s   1   d  to  10   s   3   d  belonging to the first piezoelectric drive unit group are arranged at a third rotation symmetry position with respect to the center  51  (movement center axis) of the rotor  50 . The respective contact members  20  of the six piezoelectric drive units  10   t   1   u  to  10   t   3   u  and  10   t   1   d  to  10   t   3   d  belonging to the second piezoelectric drive unit group are arranged at a third rotation symmetry position with respect to the center  51  (movement center axis) of the rotor  50 . A timing when the respective contact members  20  of the first piezoelectric drive unit group press the rotor  50  and a timing when the respective contact members  20  of the second piezoelectric drive unit group press the rotor  50  are different from each other. The pressing is alternately performed. Therefore, it is possible to minimize the vibrations or the backlash of the rotor  50 . 
     If the first to third embodiments are collectively described, the respective contact members  20  of the multiple (n-number, n is an integer of two or more) piezoelectric drive units belonging to the first piezoelectric drive unit group are arranged at a symmetry position (generally, the n-th rotation symmetry posit ion or the point symmetry position) with respect to the center  51  (movement center axis) of the rotor  50 . The respective contact members  20  of the multiple (n-number) piezoelectric drive units belonging to the second piezoelectric drive unit group are arranged at a symmetry position (the n-th rotation symmetry position or the point symmetry position) with respect to the center  51  of the rotor  50 . The timing when the respective contact members  20  of the first piezoelectric drive unit group press the rotor  50  and the timing when the respective contact members  20  of the second piezoelectric drive unit group press the rotor  50  are different from each other. The pressing is alternately performed. Therefore, it is possible to minimize the vibrations or the backlash of the rotor  50 . 
     According to the above-described first to third embodiments, preferably, the timings when the respective contact members  20  of the first piezoelectric drive unit group press the rotor  50  are the same as each other, and the timings when the respective contact members  20  of the second piezoelectric drive unit group press the rotor  50  are the same as each other. It is possible to further suppress the vibrations or the backlash of the rotor  50 . However, with regard to the timing when the respective contact members  20  of the first piezoelectric drive unit group or the second piezoelectric drive unit group press the rotor  50 , at least the two piezoelectric drive units which are paired with each other, for example, the piezoelectric drive units  10   s   1   u  and  10   s   1   d  may simultaneously press the rotor  50 . A pair of the piezoelectric drive units  10   s   1   u  and  10   s   1   d  and a pair of the piezoelectric drive units  10   s   2   u  and  10   s   2   d  may not necessarily simultaneously press the rotor  50 . 
     Fourth Embodiment 
       FIGS. 9A to 9C  are views for describing an arrangement of a piezoelectric drive unit of a piezoelectric drive device  1000   u  according to a fourth embodiment.  FIG. 9A  is a side view of the piezoelectric drive device  1000   u ,  FIG. 9B  is a top view of the piezoelectric drive device  1000   u , and  FIG. 9C  is a bottom view of the piezoelectric drive device  1000   u . The first to third embodiments employ the rotor  50  as the driven member, but a driven member  53  according to the fourth embodiment is a rectangular flat plate. 
     The piezoelectric drive device  1000   u  includes eight piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u ,  10   s   2   d ,  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d . The piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u , and  10   s   2   d  configure the first piezoelectric drive unit group. The piezoelectric drive units  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d  configure the second piezoelectric drive unit group. 
     With regard to the first piezoelectric drive unit group, the piezoelectric drive units  10   s   1   u  and  10   s   2   u  are arranged on one surface  53   u  side of the driven member  53 , and the piezoelectric drive units  10   s   1   d  and  10   s   2   d  are arranged on the other surface  53   d  side of the driven member  53 . The piezoelectric drive units  10   s   1   u  and  10   s   1   d  are paired with each other, and are arranged so as to oppose each other across the driven member  53 . The piezoelectric drive units  10   s   2   u  and  10   s   2   d  are similarly paired with each other, and are arranged so as to oppose each other across the driven member  53 . The piezoelectric drive units  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d  of the second piezoelectric drive unit group are similarly arranged. According to the embodiment, as arranged on the surface  53   u  side of the driven member  53  in the order of the piezoelectric drive units  10   s   1   u ,  10   t   1   u ,  10   s   2   u , and  10   t   2   u  from the left side in the drawing, the piezoelectric drive units of the first piezoelectric drive unit group and the piezoelectric drive units of the second piezoelectric drive unit group are alternately arranged. 
     The contact member  20  of the piezoelectric drive units  10   s   1   u ,  10   s   2   u ,  10   t   1   u , and  10   t   2   u  comes into contact with the one surface  53   u  of the driven member  53 . A movement trajectory TRu of the contact point shows a straight line along the movement direction of the driven member  53  of the one surface  53   u  of the driven member  53 . The contact member  20  of the piezoelectric drive units  10   s   1   d ,  10   s   2   d ,  10   t   1   d , and  10   t   2   d  comes into contact with the other surface  53   d  of the driven member  53 . A movement trajectory TRd of the contact point shows a straight line along the movement direction of the driven member  53  of the other surface  53   d  of the driven member  53 . The driven member  53  moves along the movement trajectories TRu and TRd. If an intermediate line between the movement trajectories TRu and TRd is referred to as a movement center line  54 , the respective contact members  20  of the piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u ,  10   s   2   d ,  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d  are arranged at a symmetry position with respect to the movement centerline  54 . In other words, on the assumption of the movement trajectories TRu and TRd on the surfaces  53   u  and  53   d  of the driven member  53  with which the multiple contact members  20  of the multiple piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u ,  10   s   2   d ,  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d  come into contact, the center line of the driven member  53  is the movement center line  54  located in the center (intermediate portion) of the movement trajectories TRu and TRd. 
     According to the embodiment, the respective contact members  20  of the multiple piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u , and  10   s   2   d  belonging to the first piezoelectric drive unit group are arranged at a symmetry position with respect to the movement center line  54  of the driven member  53 . The respective contact members  20  of the multiple piezoelectric drive units  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d  belonging to the second piezoelectric drive unit group are arranged at a symmetry position with respect to the movement center line  54  of the driven member  53 . A timing when the four piezoelectric drive units  10   s   1   u ,  10   s   1   d ,  10   s   2   u , and  10   s   2   d  of the first piezoelectric drive unit group press the driven member  53  and a timing when the four piezoelectric drive units  10   t   1   u ,  10   t   1   d ,  10   t   2   u , and  10   t   2   d  of the second piezoelectric drive unit group press the driven member  53  are different from each other. The pressing is alternately performed. Therefore, it is possible to suppress the vibrations or the backlash of the driven member  53 . 
     Preferably, the piezoelectric drive units which are arranged so as to oppose each other across the movement center line  54  of the driven member  53  and which are paired with each other, for example, the piezoelectric drive units  10   s   1   u  and  10   s   1   d  simultaneously press the driven member  53 . In this manner, it is possible to further suppress the vibrations or the backlash of the driven member  53 . 
       FIGS. 10A to 10C  are views for describing a piezoelectric drive device  1000   v  according to a modification example of the fourth embodiment. In the piezoelectric drive device  1000   u  according to the fourth embodiment, as arranged in the order of the piezoelectric drive units  10   s   1   u ,  10   t   1   u ,  10   s   2   u , and  10   t   2   u  from the left side in the drawing, the piezoelectric drive units of the first piezoelectric drive unit group and the piezoelectric drive units of the second piezoelectric drive unit group are alternately arranged. In contrast, the piezoelectric drive device  1000   v  according to the modification example is different therefrom in that a surface  55  perpendicular to the movement center line  54  serves as a symmetry surface, and the piezoelectric drive units of the first piezoelectric drive unit group and the piezoelectric drive units of the second piezoelectric drive unit group are arranged at a surface symmetry position. Similarly to the third embodiment, the piezoelectric drive device  1000   v  according to the modification example of the third embodiment can also further suppress the vibrations or the backlash of the driven member  53 . 
     In the above-described respective embodiments, a case of two piezoelectric drive unit groups has been described as an example. However, a configuration may be adopted in which the number of piezoelectric drive unit groups is three or more, in which timings when the piezoelectric drive units of the three piezoelectric drive unit groups press the driven member are different from each other, and in which the pressing is sequentially and alternately performed. In this manner, it is possible to suppress the vibrations or the backlash of the driven member. 
     Another Embodiment of Piezoelectric Drive Device 
       FIG. 11  is a sectional view of a piezoelectric drive unit  10   a  according to another embodiment of the invention, and is a view corresponding to  FIG. 1B  according to the first embodiment. In the piezoelectric drive unit  10   a , the piezoelectric vibrating body  100  is arranged in the vibrating plate  200  in a state where the arrangement in  FIG. 1B  is upside down. That is, here, the second electrode  150  is arranged close to the vibrating plate  200 , and the substrate  120  is arranged farthest from the vibrating plate  200 . Similarly to  FIG. 1B ,  FIG. 11  also omits the illustration of wiring (or a wiring layer and an insulating layer) for electrical connection between the second electrodes  150   a  to  150   e , and wiring (or a wiring layer and an insulating layer) for electrical connection between the first electrode  130  and the second electrodes  150   a  to  150   e . This piezoelectric drive unit  10   a  can also achieve the same advantageous effect as that according to the first embodiment. Similarly to the second embodiment, the substrate  120  of the piezoelectric vibrating body  100  may protrude from the vibrating plate  200 . A shape of the contact member may be the shape similar to that according to the third embodiment. 
       FIGS. 12A and 12B  are plan views of a piezoelectric drive unit  10   b  according to further another embodiment of the invention, and are views corresponding to  FIG. 1A  according to the first embodiment. In  FIGS. 12A and 12B , for convenience of illustration, the connection portion  220  and the attachment portion  230  of the vibrating plate  200  are omitted in the illustration. In the piezoelectric drive unit  10   b  in  FIG. 12A , a pair of the second electrodes  150   b  and  150   c  is omitted. The piezoelectric drive unit  10   b  can also rotate the rotor  50  in one direction z as illustrated in  FIGS. 4A and 4B . The same voltage is applied to the three second electrodes  150   a ,  150   e , and  150   d  in  FIG. 12A . Accordingly, the three second electrodes  150   a ,  150   e , and  150   d  may be formed as one continuous electrode layer. 
       FIG. 12B  is a plan view of a piezoelectric drive unit  10   c  according to further another embodiment of the invention. In the piezoelectric drive unit  10   c , the second electrode  150   e  located in the center of  FIG. 1A , and the other four second electrodes  150   a ,  150   b ,  150   c , and  150   d  are formed so as to have an area which is larger than that in  FIG. 1A . This piezoelectric drive unit  10   c  can also achieve substantially the same advantageous effect as that according to the first embodiment. 
     As is understood from  FIGS. 1A, 1B, 12A, and 12B , at least one electrode layer can be disposed as the second electrode  150  of the piezoelectric vibrating body  100 . However, as in the embodiments illustrated in  FIGS. 1A, 1B, 12A, and 12B , if the second electrode  150  is disposed at an opposite angle position of the rectangular piezoelectric vibrating body  100 , it is preferable since the piezoelectric vibrating body  100  and the vibrating plate  200  can be deformed into a meandering shape which is bent inside a plane thereof. 
     Embodiment of Device Employing Piezoelectric Drive Device 
     The above-described piezoelectric drive unit  10  applies a great force to the driven body by utilizing resonance, and can be applied to various devices. For example, the piezoelectric drive unit  10  can be used as a drive device for various apparatuses such as a robot (also including an electronic component conveying apparatus (IC handler)), a medication pump, a timepiece calendar feeding device, a printing apparatus (for example, a sheet feeding mechanism. However, not applicable to a head since the vibration plate is not caused to resonate in the piezoelectric drive device used for the head). Hereinafter, a representative embodiment will be described. 
       FIG. 13  is a view for describing an example of a robot  2050  which employs the above-described piezoelectric drive unit  10 . The robot  2050  has an arm  2010  (also referred to as an “arm unit”) which includes multiple link portions  2012  (also referred to as a “link member”) and multiple joint portions  2020  for connecting the link portions  2012  to each other in a pivotable or bendable state. The above-described piezoelectric drive unit  10  is incorporated in the respective joint portions  2020 , and the joint portions  2020  can be pivotally moved or bent at any desired angle by using the piezoelectric drive unit  10 . A robot hand  2000  is connected to a distal end of the arm  2010 . The robot hand  2000  includes a pair of gripping portions  2003 . The piezoelectric drive unit  10  is also incorporated in the robot hand  2000 . The robot hand  2000  can grip an object by using the piezoelectric drive unit  10  so as to open and close the gripping portions  2003 . The piezoelectric drive unit  10  is also disposed between the robot hand  2000  and the arm  2010 . The robot hand  2000  can be rotated with respect to the arm  2010  by using the piezoelectric drive unit  10 . 
       FIG. 14  is a view for describing a wrist portion of the robot  2050  illustrated in  FIG. 13 . The joint portions  2020  on the wrist interpose a wrist pivotally moving portion  2022  therebetween, and the link portion  2012  on the wrist is attached to the wrist pivotally moving portion  2022  so as to be pivotally movable around a central axis O of the wrist pivotally moving portion  2022 . The wrist pivotally moving portion  2022  includes the piezoelectric drive unit  10 . The piezoelectric drive unit  10  pivotally moves the link portion  2012  on the wrist and the robot hand  2000  around the central axis O. The multiple gripping portions  2003  are erected in the robot hand  2000 . A proximal end portion of the gripping portion  2003  is movable inside the robot hand  2000 . The piezoelectric drive unit  10  is mounted on a base portion of the gripping portion  2003 . Therefore, the gripping portions  2003  are moved so as to grip a target by operating the piezoelectric drive unit  10 . 
     As the robot, without being limited to a single arm robot, the piezoelectric drive unit  10  can also be applied to a multi-arm robot in which the number of arms is two or more. Here, in addition to the piezoelectric drive unit  10 , the joint portion  2020  on the wrist or the inside of the robot hand  2000  includes a power line for supplying power to various devices such as a force sensor and a gyro sensor or signal line for transmitting a signal. Accordingly, enormous wiring is needed. Therefore, it was very difficult to arrange the wiring inside the joint portion  2020  or the robot hand  2000 . However, the piezoelectric drive unit  10  according to the above-described embodiments can decrease a drive current compared to a normal electric motor or the piezoelectric drive device in the related art. Therefore, it is possible to arrange the wiring even in a small space such as the joint portion  2020  (particularly, a distal end joint portion of the arm  2010 ) and the robot hand  2000 . 
       FIG. 15  is a view for describing an example of a liquid feeding pump  2200  employing the above-described piezoelectric drive unit  10 . In the liquid feeding pump  2200 , a case  2230  internally has a reservoir  2211 , a tube  2212 , the piezoelectric drive unit  10 , a rotor  2222 , a deceleration transmission mechanism  2223 , a cam  2202 , and multiple fingers  2213 ,  2214 ,  2215 ,  2216 ,  2217 ,  2218 , and  2219 . The reservoir  2211  is an accommodation section for accommodating a liquid which is a transport target. The tube  2212  is used in order to transport the liquid fed from the reservoir  2211 . The contact member  20  of the piezoelectric drive unit  10  is disposed in a state of being pressed against a side surface of the rotor  2222 , and the piezoelectric drive unit  10  rotatably drives the rotor  2222 . A rotation force of the rotor  2222  is transmitted to the cam  2202  via the deceleration transmission mechanism  2223 . The fingers  2213  to  2219  are members for blocking the tube  2212 . If the cam  2202  is rotated, the fingers  2213  to  2219  are sequentially pressed radially outward by a protrusion portion  2202 A of the cam  2202 . The fingers  2213  to  2219  block the tube  2212  sequentially from the upstream side (reservoir  2211  side) in the transport direction. In this manner, the liquid inside the tube  2212  is sequentially transported to the downstream side. According to this configuration, an extremely small amount of the liquid can be accurately fed. Moreover, a miniaturized liquid feeding pump  2200  can be realized. An arrangement of each member is not limited to the illustrated example. A configuration may be adopted in which a ball disposed in the rotor  2222  blocks the tube  2212  without providing the fingers. The above-described liquid feeding pump  2200  can be utilized for a drug dispensing apparatus which administers a drug solution such as insulin to a human body. Here, a drive current is decreased by using the piezoelectric drive unit  10  according to the above-described embodiments, compared to the piezoelectric drive unit in the related art. Accordingly, it is possible to minimize power consumption of the drug dispensing apparatus. Therefore, the piezoelectric drive unit  10  is particularly effective when the drug dispensing apparatus is driven by a battery. 
     Modification Example 
     Without being limited to the above-described examples or embodiments, the invention can be embodied in various aspects within the scope not departing from the gist of the invention. For example, the invention can also be modified as follows. 
     Modification Example 1 
     According to the above-described embodiments, the first electrode  130 , the piezoelectric substance  140 , and the second electrode  150  are formed on the substrate  120 . However, the substrate  120  may be omitted, and the first electrode  130 , the piezoelectric substance  140 , and the second electrode  150  may be formed on the vibrating plate  200 . 
     Modification Example 2 
     According to the above-described embodiments, each one of the piezoelectric vibrating bodies  100  is disposed on both surfaces of the vibrating plate  200 . However, any one of the piezoelectric vibrating bodies  100  can be omitted. However, if each of the piezoelectric vibrating bodies  100  is disposed on both surfaces of the vibrating plate  200 , it is preferable since the vibrating plate  200  is more easily deformed into a meandering shape which is bent inside a plane thereof. 
     Hitherto, the embodiments of the invention have been described with reference to some examples. However, the above-described embodiments are provided in order to facilitate the understanding of the invention, and are not intended to limit the invention. The invention can be modified or improved without departing from the gist and the scope of the appended claims, and the invention includes its equivalents as a matter of course. 
     The entire disclosure of Japanese Patent Application No. 2015-016928, filed Jan. 30, 2015 is expressly incorporated by reference herein.