Patent Publication Number: US-2012038247-A1

Title: Ultrasonic motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2010-179612, filed Aug. 10, 2010, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotary ultrasonic motor used as, for example, an image vibration correcting unit of a digital camera or an actuator of an autofocus (AF) lens or the like. 
     2. Description of the Related Art 
     Recently, ultrasonic motors have been attracting attention as new motors that replace electromagnetic motors. The ultrasonic motors use the vibration of a transducer such as a piezoelectric device. As compared with the conventional electromagnetic motors, the ultrasonic motors have the following advantages: low-rotation high torque obtained without any gears, high coercive force, high resolution, a high degree of silence, no generation of magnetic noise, no influence of magnetic noise, etc. 
     Such an ultrasonic motor has been disclosed in, for example, Jpn. Pat. Appin. KOKAI Publication No. 9-117168. In this ultrasonic motor, a transducer comprises plate-like piezoelectric devices stacked on each other, elastic bodies that vertically catch the piezoelectric devices from both sides, and an abrasion-resistant material which is a driven body affixed to the surface of the elastic bodies provided on the upper side of the piezoelectric devices. The abrasion-resistant material is pressed by a rotor. 
     In this ultrasonic motor, the plate-like piezoelectric devices are stacked on each other, such that the transducer simultaneously induces a longitudinal vibration and a torsional vibration, and from these two vibrations, generates an elliptical vibration. A driving force generated at this moment from the elliptical vibration generating surfaces of the piezoelectric devices is transmitted to the abrasion-resistant material, and rotates the rotor via the abrasion-resistant material. 
     In an ultrasonic motor different from the above-mentioned ultrasonic motor, a transducer comprises a piezoelectric device, a holding member which holds the piezoelectric device, and friction contact members arranged in the piezoelectric device. A rotor is in direct contact with the friction contact members. Thus, if a voltage is applied to the piezoelectric device, a longitudinal vibration and a torsional vibration are induced, and an elliptical vibration is generated. This elliptical vibration is directly transmitted to, via the friction contact members, a rotor which is a driven body, and the rotor is driven by friction. 
     In such an ultrasonic motor, versatility of the ultrasonic motor and stabilization of the characteristics of the ultrasonic motor are attained by packaging primary components as a unit. 
     The configuration of the above-described ultrasonic motor disclosed in Jpn. Pat. Appin. KOKAI Publication No. 9-117168 may be complicated because the plate-like piezoelectric devices are stacked and the elastic bodies catch the piezoelectric devices. 
     Furthermore, a shaft which passes through the transducer and extends from the upper elastic body is only utilized as part of a pressing mechanism for pressing the rotor. Therefore, it is difficult for this shaft to transmit a rotation force to the rotor in an axial direction. That is, it might be difficult to apply this ultrasonic motor to an instrument or the like having no space in a diameter direction of the rotor. 
     Moreover, as described above, when the friction contact members are in direct contact with the rotor and the rotor is driven by the friction contact members, the accuracy of the relative positions of the central (rotation) shaft of the rotor and the friction contact members may be decreased by the processing and assembly of the ultrasonic motor. 
     When the piezoelectric devices are pressed by a pressing member and the friction contact members are thus pressed toward the rotor, the point of application for pressing (a contact point between the pressing member and the piezoelectric device) is displaced by the assembly of the transducer. 
     As a result, the posture of the transducer is tilted, and the contact surfaces of the rotor and the transducer may be out of equal contact. This may lead to the deterioration of the driving characteristics of the ultrasonic motor. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has been made under these circumstances, and is directed to provide an ultrasonic motor having packaged primary components, having a simple configuration, and having stable driving characteristics. 
     According to an aspect of embodiments, an ultrasonic motor includes a piezoelectric device, the section of the piezoelectric device perpendicular to its central axis having a length ratio of a rectangle, the piezoelectric device inducing a longitudinal vibration and a torsional vibration in response to a voltage, and generating an elliptical vibration from the longitudinal vibration and the torsional vibration, a holding member configured to hold the piezoelectric device at the position of a node of the torsional vibration, a friction contact member configured to be provided in an elliptical vibration generating surface of the piezoelectric device, a transducer configured to be assembled as one unit by the piezoelectric device, the holding member, and the friction contact member, a hollow rotor configured to contact the friction contact member, the rotor rotating around a shaft in a direction perpendicular to a plane direction of the elliptical vibration generating surface when a driving force is transmitted to the rotor from the friction contact member, a first driving force transmitting member configured to be adhesively fixed to the rotor and which rotates together with the rotor, a case member configured to have a positioning groove to position the transducer and configured to house the transducer, a press member configured to press the transducer housed in the case member toward the rotor; and a support mechanism configured to be disposed in the case member and configured to drivably support the first driving force transmitting member so that the rotor is drivable, wherein the support mechanism includes a second driving force transmitting member configured to contact a proximal end of the first driving force transmitting member at a distal end of the second driving force transmitting member and configured to be driven together with the first driving force transmitting member, a transmission shaft bearing having an inner ring in which the second driving force transmitting member is fitted, and a bearing support member configured to be disposed in the upper surface of the case member, the bearing support member supporting the transmission shaft bearing so that the second driving force transmitting member is drivable together with the first driving force transmitting member and so that the transmission shaft bearing is drivable. 
     Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a perspective view of an ultrasonic motor according to a first embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of the ultrasonic motor; 
         FIG. 3  is a front view of the ultrasonic motor; 
         FIG. 4  is a side view of the ultrasonic motor; 
         FIG. 5  is a sectional view along the line  5 - 5  shown in  FIG. 3 ; 
         FIG. 6  is a sectional view along the line  6 - 6  shown in  FIG. 4 ; 
         FIG. 7  is a perspective view of an ultrasonic motor according to a second embodiment of the present invention; 
         FIG. 8  is an exploded perspective view of the ultrasonic motor; 
         FIG. 9  is a front view of the ultrasonic motor; 
         FIG. 10  is a side view of the ultrasonic motor; 
         FIG. 11  is a sectional view along the line  11 - 11  shown in  FIG. 9 ; and 
         FIG. 12  is a sectional view along the line  12 - 12  shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 
     The first embodiment is described with reference to  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5 , and  FIG. 6 . 
     From now on, the width directions of a transducer  11  and a piezoelectric device  13  are an X-axis direction, the thickness directions of the transducer  11  and the piezoelectric device  13  perpendicular to the X-axis direction are a Y-axis direction, and the height directions of the transducer  11  and the piezoelectric device  13  perpendicular to the X-axis direction and the Y-axis direction are a Z-axis direction. 
     An ultrasonic motor  10  has the transducer  11  which is a primary component of the ultrasonic motor  10 . 
     As shown in  FIG. 2 , the transducer  11  has the piezoelectric device  13 , piezoelectric device holding members (hereinafter, holding members  15 ), and friction contact members  17 . In response to a voltage, the piezoelectric device  13  induces longitudinal vibration that expands and contracts in the direction of the rotation axis of the transducer  11 , and a torsional vibration that is generated on the rotation axis of the transducer  11  as a torsion axis. From these two vibrations, the piezoelectric device  13  generates an elliptical vibration. The holding members  15  hold the piezoelectric device  13  at the position of a node of the torsional vibration of the piezoelectric device  13 . The friction contact members  17  are arranged in one surface of an elliptical vibration generating surface of the piezoelectric device  13 . 
     As shown in  FIG. 2 ,  FIG. 5 , and  FIG. 6 , the section of the piezoelectric device  13  perpendicular to its central axis has a length ratio of a rectangle. An upper surface  13   a  of the piezoelectric device  13  serves as the elliptical vibration generating surface of the piezoelectric device  13  for generating an elliptical vibration from the longitudinal vibration and the torsional vibration. 
     As shown in  FIG. 2 , the holding members  15  are Π shaped (depressed). Each of the holding members  15  is fitted at the position of the node of the torsional vibration of the piezoelectric device  13 , and is fixedly attached to the position of the node by, for example, an adhesive agent. 
     Two friction contact members  17  are arranged in the elliptical vibration generating surface, and are fixedly attached thereto by, for example, an adhesive agent. 
     As shown in  FIG. 2 , the holding member  15  and the friction contact members  17  are fixedly attached to the piezoelectric device  13  as described above, so that the transducer  11  is assembled as one unit by the piezoelectric device  13 , the holding members  15 , and the friction contact members  17 . The transducer  11  assembled as one unit is packaged (enveloped) by the later-described case member  31 . 
     The friction contact members  17  are in contact with a rotor  19  which is a driven body in contact surfaces  17   c , and transmit, to the rotor  19 , a driving force to rotate the rotor  19 . That is, the rotor  19  as a driven body, which is driven (rotated) by the elliptical vibration that is its driving (rotation) force transmitted from the friction contact members  17 , is in contact with the friction contact members  17 . 
     As described above, the rotor  19  contacts the friction contact members  17 , and when the driving force is transmitted to the rotor  19  from the friction contact members  17 , the rotor  19  rotates around a (rotation) shaft in a direction (Z-axis direction) perpendicular to a plane direction of the elliptical vibration generating surface. The rotor  19  has a hollow circular shape having an opening  19   a.    
     As shown in  FIG. 5  and  FIG. 6 , a proximal end  61   b  of a first transmission shaft  61 , which is a central (rotation) shaft of the rotor  19 , is adhesively fixed to the opening  19   a  of the rotor  19 . Therefore, when the rotor  19  rotates, the first transmission shaft  61  also rotates together with the rotor  19 . The first transmission shaft  61  is T-shaped. 
     As shown in  FIG. 5  and  FIG. 6 , the first transmission shaft  61  is fitted in an opening  51   a  of a rotation force transmission gear  51  between a distal end  61   a  and a proximal end  61   b . The first transmission shaft  61  rotates together with the rotor  19 , and thereby transmits a driving force (turning force) to the rotation force transmission gear  51  and rotates the rotation force transmission gear  51 . Thus, the first transmission shaft  61  is a first driving force transmitting member for transmitting the driving force to the rotation force transmission gear  51 . 
     The rotation force transmission gear  51  is mounted on the rotor  19 , and is toothed with an unshown external device on the side surface of the case member  31 . As shown in  FIG. 2 , the rotation force transmission gear  51  has the opening  51   a  which the first transmission shaft  61  is fitted in and passed through, as described above. This rotation force transmission gear  51  rotates when a driving force (turning force) is transmitted thereto from the first transmission shaft  61  via the friction contact members  17  and the rotor  19 . The rotation force transmission gear  51  transmits this driving force to the unshown external device, and drives the device. The rotation force transmission gear  51  is disposed in the rotor  19  coaxially with the rotor  19  by passing the first transmission shaft  61  through the opening  51   a.    
     The first transmission shaft  61  that passes through the opening  51   a  is also adhesively fixed to the rotation force transmission gear  51  in its surface contacting the rotation force transmission gear  51 . The first transmission shaft  61  in the present embodiment is a device side driving force transmitting member for transmitting a driving force to the unshown external device via the rotation force transmission gear  51 . 
     As shown in  FIG. 2 ,  FIG. 5 , and  FIG. 6 , the first transmission shaft  61  has a conical recess  61   d  in an upper surface  61   c  of the proximal end  61   b . A second transmission shaft  63  which is a second driving force transmitting member is provided above the recess  61   d . The second transmission shaft  63  has, at its distal end  63   a , a semispherical protrusion  63   d  that contacts the recess  61   d . The size of the semispherical shape of the protrusion  63   d  is smaller than the size of the conical shape of the recess  61   d.    
     The second transmission shaft  63  rotates together with the first transmission shaft  61 . The second transmission shaft  63  is fitted in an inner ring of a transmission shaft bearing  23  such as a bearing. When the transmission shaft bearing  23  is a bearing, the transmission shaft bearing  23  is driven (rotated) together with the second transmission shaft  63 . The transmission shaft bearing  23  may be a slide bearing that uses, for example, a highly slidable resin. 
     As shown in  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5 , and  FIG. 6 , the transducer  11  is housed in the substantially Π shaped (depressed) case member  31  which catches the piezoelectric device  13  from the sides of a bottom surface  13   b  and a side surface  13   c  of the piezoelectric device  13 . That is, the case member  31  packages (envelopes/houses) the transducer  11  assembled as one unit, as described above. 
     As shown in  FIG. 2 ,  FIG. 5 , and  FIG. 6 , the case member  31  has the positioning grooves  33  for positioning the transducer  11 . The positioning groove  33  is Π shaped (depressed) like the holding members  15 . The positioning groove  33  is a long groove which is provided along the longitudinal axis direction of the case member  31  and in which the holding member  15  is slidable. The positioning grooves  33  are disposed at two positions corresponding to the holding members  15 . The holding members  15  slide in the positioning grooves  33  under the guidance of the positioning grooves  33  and are thus positioned. As a result, the transducer  11  including the piezoelectric device  13  is positioned in the X-axis direction and the Y-axis direction, and the transducer  11  is enveloped in the case member  31  in a positioned state. That is, the case member  31  positions and holds the piezoelectric device  13  (transducer  11 ) via the holding members  15  and the positioning grooves  33  in the X-axis direction and the Y-axis direction. 
     As shown in  FIG. 5  and  FIG. 6 , the case member  31  has a Π shaped (depressed) groove  35  at the bottom. The groove  35  is provided with a press member  37  which contacts a bottom surface  13   b  of the piezoelectric device  13  housed in the case member  31  and which presses the friction contact members  17  (transducer  11 ) toward the rotor  19  via the piezoelectric device  13 . The press member  37  is, for example, a coil spring or a leaf spring. 
     The case member  31  also has a cut-out  39  on the bottom side. An unshown flexible member for applying a voltage to the piezoelectric device  13  is inserted through the cut-out  39 . The flexible member extends outward from the case member  31 . 
     As shown in  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5 , and FIG,  6 , the case member  31  is provided with a support mechanism  70 . The support mechanism  70  urges, via the first transmission shaft  61 , the rotor  19  toward the friction contact members  17  housed in the case member  31 , and drivably supports the first transmission shaft  61  so that the rotor  19  is drivable. 
     The support mechanism  70  has the above-mentioned second transmission shaft  63 , the above-mentioned transmission shaft bearing  23 , and a bearing support member  53 . The second transmission shaft  63  contacts, at its distal end  63   a , the proximal end  61   b  of the first transmission shaft  61 , and is driven together with the first transmission shaft  61 . The second transmission shaft  63  is fitted in the inner ring of the transmission shaft bearing  23 . The bearing support member  53  is provided in an upper surface  31   a  of the case member  31 . The bearing support member  53  supports the transmission shaft bearing  23  so that the second transmission shaft  63  can be driven together with the first transmission shaft  61  and so that the transmission shaft bearing  23  can be driven. 
     The bearing support member  53  has a substantially planar shape. The bearing support member  53  has an opening  53   a  which holds the transmission shaft bearing  23  so that the transmission shaft bearing  23  can be driven (rotated) and which fixes the transmission shaft bearing  23  in a fitted state and which supports the transmission shaft bearing  23 . The bearing support member  53  is also a rotation force transmission gear support member which supports the rotation force transmission gear  51  via the transmission shaft bearing  23  and the second transmission shaft  63  and the first transmission shaft  61  so that the rotation force transmission gear  51  can be rotated. The bearing support member  53  is also a rotor support member which rotatably supports the rotor  19  via the transmission shaft bearing  23  and the second transmission shaft  63  and the first transmission shaft  61  so that the rotor  19  can be rotated. 
     The bearing support member  53  has positioning protrusions  53   b . The protrusions  53   b  position the transmission shaft bearing  23  and the second transmission shaft  63  so that the second transmission shaft  63  is aligned with the central axis of the transducer  11  by fitting the protrusions  53   b  in the positioning grooves  33  when the bearing support member  53  is disposed in the upper surface  31   a  of the case member  31 . Two protrusions  53   b  are provided to correspond to the positioning grooves  33 . 
     The bearing support member  53  has a thickness and a width that are substantially similar to the thickness and width of the case member  31 . 
     The bearing support member  53  is fastened to an edge  31   b  of the upper surface  31   a  of the case member  31  by fastening members  55  such as screws when the protrusions  53   b  are fitted in the positioning grooves  33 . When the bearing support member  53  is fastened to the edge  31   b  by the fastening members  55  and covers the rotor  19 , the above-mentioned press member  37  bends in a desired amount, thereby generating a press force. As a result, the piezoelectric device  13  is pressed along the positioning grooves  33  via the holding members  15 , and the friction contact members  17  are pressed against the rotor  19 . 
     Here, the recess  61   d  and the protrusion  63   d  are described in detail. 
     The transducer  11  is positioned in the X-axis direction and the Y-axis direction by the holding members  15  and the positioning grooves  33 . Moreover, the second transmission shaft  63  is fitted in the inner ring of the transmission shaft bearing  23 , the transmission shaft bearing  23  is supported in the opening  53   a  by the bearing support member  53 , and the bearing support member  53  is fastened to the edge  31   b  by the fastening members  55 , such that the second transmission shaft  63  is positioned in the X-axis direction and the Y-axis direction. 
     As the recess  61   d  contacts the protrusion  63   d  at this moment, the first transmission shaft  61  is positioned in the X-axis direction and the Y-axis direction similarly to the second transmission shaft  63 . The rotor  19  is also positioned in the X-axis direction and the Y-axis direction via the first transmission shaft  61 . 
     At the same time, the first transmission shaft  61  is adhesively fixed to the rotation force transmission gear  51  and the rotor  19 . 
     The transducer  11 , the case member  31 , the bearing support member  53 , the transmission shaft bearing  23 , and the second transmission shaft  63  are configured in one unit. 
     As described above, the recess  61   d  is conical, the protrusion  63   d  is semispherical, and the protrusion  63   d  is smaller than the recess  61   d . Thus, the first transmission shaft  61  can be tilted around the X-axis and the Y-axis by the recess  61   d  and the protrusion  63   d.    
     Therefore, as described above, the recess  61   d  and the protrusion  63   d  permit the first transmission shaft  61 , the rotation force transmission gear  51 , and the rotor  19  on the side of the recess  61   d  to be tilted relative to the second transmission shaft  63 , the transducer  11 , the case member  31 , the bearing support member  53 , and the transmission shaft bearing  23  on the side of the protrusion  63   d.    
     The rotor  19  is then pressed against the friction contact members  17  by pressurization when the fastening members  55  fasten the bearing support member  53  to the edge  31   b  of the upper surface  31   a  of the case member  31 . At this moment, the rotor  19  can be tilted around the X-axis and the Y-axis by the above-mentioned pressurization and by the recess  61   d  and the protrusion  63   d  so that the rotor  19  contacts the friction contact members  17  and follows the contact surfaces  17   c  of the friction contact members  17  when the rotor  19  is positioned in the X-axis direction and the Y-axis direction by the recess  61   d  and the protrusion  63   d.    
     Now, a method of assembling the ultrasonic motor  10  in the present embodiment is described. 
     The press member  37  is provided in the groove  35 . 
     The holding members  15  are fixedly attached to the position of the node of the torsional vibration of the piezoelectric device  13  by, for example, an adhesive agent. The friction contact members  17  are fixedly attached to the elliptical vibration generating surface (upper surface  13   a ) by, for example, an adhesive agent. As a result, the transducer  11  is assembled as one unit. The transducer  11  then slides in the positioning grooves  33  via the holding members  15  and is thus positioned, such that the transducer  11  is positioned in the X-axis direction and the Y-axis direction, and the transducer  11  is packaged (enveloped) by the case member  31  in a positioned state. 
     At the same time, the press member  37  contacts the bottom surface  13   b  of the piezoelectric device  13 . 
     The rotor  19  is then mounted on the friction contact members  17 , and the rotation force transmission gear  51  is mounted on the rotor  19 . The distal end  61   a  of the first transmission shaft  61  passes through the opening  51   a  and is disposed in the opening  19   a , and the first transmission shaft  61  is adhesively fixed to the rotation force transmission gear  51  and the rotor  19 . 
     The protrusion  63   d  of the second transmission shaft  63  contacts the recess  61   d  of the first transmission shaft  61 . The second transmission shaft  63  is fitted in the inner ring of the transmission shaft bearing  23 . 
     The transmission shaft bearing  23  is supported by the bearing support member  53  via the opening  53   a . The bearing support member  53  is fastened to the edge  31   b  of the upper surface  31   a  of the case member  31  by the fastening members  55 . At the same time, the press member  37  presses the friction contact members  17  toward the rotor  19  via the piezoelectric device  13 . 
     When the ultrasonic motor  10  is assembled, for example, when the rotor  19  is mounted on the friction contact members  17 , the position of the first transmission shaft  61  which is the central (rotation) shaft of the rotor  19  may be displaced relative to the positions of the friction contact members  17  as a result of the processing of the components of the ultrasonic motor  10  and the assembly of the ultrasonic motor  10 . 
     Moreover, after the transducer  11  is assembled, the point of application for pressing (the contact point between the press member  37  and the bottom surface  13   b ) may be displaced by the assembly of the transducer  11  when the piezoelectric device  13  is pressed by the press member  37  and the friction contact members  17  are pressed toward the rotor  19 . 
     However, in the present embodiment, as the recess  61   d  contacts the protrusion  63   d , the rotor  19  is brought into contact with the friction contact members  17  by pressurization when the fastening members  55  fasten the bearing support member  53  to the edge  31   b  of the upper surface  31   a  of the case member  31  when the first transmission shaft  61  and the rotor  19  are positioned in the X-axis direction and the Y-axis direction as described above. Accordingly, the rotor  19  can be tilted around the X-axis and the Y-axis by the recess  61   d  and the protrusion  63   d  so that the rotor  19  follows the contact surfaces  17   c  of the friction contact members  17 . Thus, the rotor  19  is pressed against the contact surfaces  17   c  of the friction contact members  17  by the pressurization of the fastening members  55 , and the fastening members  55  fasten the bearing support member  53  to the edge  31   b , such that the rotor  19  always uniformly contacts the contact surfaces  17   c  of the friction contact members  17 . 
     As described above, in the present embodiment, the fastening members  55  are pressurized from the side of the rotor  19  to the side of the transducer  11 , such that the rotor  19  is tilted around the X-axis and the Y-axis by the recess  61   d  and the protrusion  63   d , and the rotor  19  always uniformly contacts the contact surfaces  17   c.    
     As the friction contact members  17  are positioned in the X-axis direction and the Y-axis direction by the case member  31  via the piezoelectric device  13 , the holding members  15 , and the positioning grooves  33 , the rotor  19  always uniformly contacts the contact surfaces  17   c  owing to the first transmission shaft  61  that tilts around the X-axis and the Y-axis. 
     The displacement of the contact point between the press member  37  and the bottom surface  13   b  is prevented because the press member  37  is disposed in the groove  35  and because the transducer  11  is positioned in the X-axis direction and the Y-axis direction by the holding members  15  and the positioning grooves  33  as described above. 
     The protrusions  53   b  are fitted in the positioning grooves  33 , such that the transmission shaft bearing  23  and the second transmission shaft  63  can be quickly positioned, and the second transmission shaft  63  is quickly aligned with the central axis of the transducer  11 . 
     When a voltage is applied to the piezoelectric device  13  via the flexible member, the piezoelectric device  13  induces a longitudinal vibration and a torsional vibration, and from these two vibrations, generates an elliptical vibration. A driving force is transmitted to the rotation force transmission gear  51  from the elliptical vibration generating surface of the piezoelectric device  13  via the friction contact members  17 , the rotor  19 , and the first transmission shaft  61 , and rotates the rotation force transmission gear  51 . In this case, as the rotor  19  always uniformly contacts the contact surfaces  17   c  of the friction contact members  17 , stable driving characteristics can be obtained. This rotation force is then transmitted to the unshown device from the side surface of the case member  31  through the rotation force transmission gear  51 , and drives the device. 
     As described above, in the present embodiment, the transducer  11  can be assembled as one unit, and the transducer  11  can be packaged by the case member  31 , thereby allowing the transducer  11  and the ultrasonic motor  10  to be simpler in configuration. 
     Furthermore, in the present embodiment, even if the position of the first transmission shaft  61  which is the central (rotation) shaft of the rotor  19  is displaced relative to the positions of the friction contact members  17  as a result of the processing of the components of the ultrasonic motor  10  and the assembly of the ultrasonic motor  10 , the rotor  19  can be positioned in the X-axis direction and the Y-axis direction by the recess  61   d  and the protrusion  63   d , and the positioned rotor  19  can be tilted around the X-axis and the Y-axis by the recess  61   d  and the protrusion  63   d . Thus, in the present embodiment, as the rotor  19  can always uniformly contact the contact surfaces  17   c  of the friction contact members  17 , stable driving characteristics can be obtained. 
     Still further, in the present embodiment, the press member  37  can be disposed in the groove  35 , and the transducer  11  is positioned in the X-axis direction and the Y-axis direction as described above. Thus, after the transducer  11  is assembled, the point of application for pressing (the contact point between the press member  37  and the bottom surface  13   b ) is not displaced by the assembly of the transducer  11 , so that the displacement of the point of application can be prevented. 
     Still further, in the present embodiment, even if the axial direction of the second transmission shaft  63  is displaced relative to the central axis of the transducer  11 , the rotor  19  can be tilted by the recess  61   d  and the protrusion  63   d , and the rotor  19  can always uniformly contact the friction contact members  17 , so that stable driving characteristics can be obtained. 
     Still further, in the present embodiment, as the driving force can be externally transmitted from the side surface of the case member  31  by the rotation force transmission gear  51 , the ultrasonic motor  10  can be reduced in thickness. Therefore, in the present embodiment, the ultrasonic motor  10  can be easily disposed in a device that does not have enough space for the diametrical direction of the rotor  19 . 
     Still further, in the present embodiment, the transmission shaft bearing  23  and the second transmission shaft  63  can be quickly positioned by the protrusions  53   b , and the second transmission shaft  63  can be quickly aligned with the central axis of the transducer  11 . 
     Still further, in the present embodiment, the protrusion  63   d  is smaller than the recess  61   d , thereby ensuring that the protrusion  63   d  and the recess  61   d  can contact each other, enabling the recess  61   d  to function as a guide, and enabling the second transmission shaft  63  to be easily positioned relative to the first transmission shaft  61 . 
     Although the first transmission shaft  61  has the recess  61   d  and the second transmission shaft  63  has the protrusion  63   d  in the present embodiment, the present invention is not limited to this. One of the proximal end  61   b  of the first transmission shaft  61  (first driving force transmitting member) and the distal end  63   a  of the second transmission shaft  63  (second driving force transmitting member) may have the recess  61   d , and the other may have the protrusion  63   d.    
     Now, the second embodiment according to the present invention is described with reference to  FIG. 7 ,  FIG. 8 ,  FIG. 9 ,  FIG. 10 ,  FIG. 11 , and  FIG. 12 . The same components as those in the first embodiment are provided with the same reference marks as those in the first embodiment and are thus not described. 
     In the present embodiment, a second transmission shaft  63  may be eliminated. In this case, a first transmission shaft  61  may have a semispherical protrusion  61   f  at a proximal end  61   b , and a transmission shaft bearing  23  may contact the protrusion  61   f  of the first transmission shaft  61  in its inner ring. 
     The protrusion  61   f  of the first transmission shaft  61  is semispherical. 
     Thus, in the present embodiment, the second transmission shaft  63  can be dispensed with, thereby allowing an ultrasonic motor  10  to be simpler in configuration. 
     The present invention is not completely limited to the embodiments described above, and the components can be modified at the stage of carrying out the invention without departing from the spirit thereof. Moreover, various inventions can be made by a proper combination of the components disclosed in the embodiments described above. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.