Abstract:
A drive mechanism has an ultrasonic motor having a rotor which is rotationally driven by vibration of a vibrating member having a piezoelectric element. The rotor has a projecting portion for rotation therewith. A driven member is connected to the rotor for undergoing movement along a surface extending in a radial direction of the rotor. A guide member restricts movement of the driven member and guides movement of the receiving member in a given direction. A receiving member contacts the projecting portion of the rotor to limit a range of rotation of the rotor and limit a range of movement of the driven member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a drive mechanism with an ultrasonic motor, and to an electronic device using the drive mechanism with the ultrasonic motor. 
     2. Description of the Related Art 
     Generally, optical apparatuses have an aperture or shutter mechanism for controlling the quantity of introduced light. Such an aperture mechanism is designed to control the quantity of introduced light by moving aperture blades which cover the aperture. To drive the blades, an electromagnetic actuator or a stepping motor is ordinarily used in combination with any of various motive power transmission mechanisms using toothed wheels, etc. 
     Conventionally, from an output shaft attached to the rotor of such an electromagnetic actuator or a stepping motor with little driving force, motive power is transmitted through a complicated power transmission mechanism. The conventional drive mechanisms for the above-mentioned purpose are large in size and have low positioning resolution. With respect to shutters, there is a limit to the shutter opening/closing speed. In the case of an aperture mechanism or the like, there is a need to keep a current running for maintaining the mechanism stopped in a certain position. In particular, there is a problem of fast exhaustion of batteries in portable devices such as cameras and video camera-recorders relating to such a need. 
     Further, the conventional electromagnetic actuators or motors are liable to generate electromagnetic noise such as to seriously affect communication and medical apparatuses. Conversely, they are caused to malfunction in the presence of magnetic fields. 
     SUMMARY OF THE INVENTION 
     In view of the above-described circumstances, an object of the present invention is to provide a drive mechanism using an ultrasonic motor for directly driving a driven member without a transmission mechanism using toothed wheels or the like. 
     To achieve the above-described object, the present invention employs, an ultrasonic motor as an actuator which is small in size and thickness, having a large torque, a stationary torque and has improved response, and is insensitive to magnetism, and provides a drive mechanism with an ultrasonic motor comprising an ultrasonic motor having a vibrating member including a piezoelectric element, and a rotor capable of rotating by receiving vibration of the vibrating member, at least one driven member linked to the rotor and driven by being linked to a rotary motion of the rotor, a guide member for restricting the rotation of the driven member to guide the driven member in a direction in which the driven member is to be driven. 
     The rotor of the ultrasonic motor is in the form of a plate because of the essential qualities of the ultrasonic motor. Therefore, the driven member can be rotatably attached to portions of the rotor other than the rotary shaft. 
     In this aspect of the present invention, a guide member is provided on the outside of the rotor to movably guide the driven member so that the driven member does not rotates with the rotation of the rotor, thereby enabling the moving member to move separately from the rotary motion of the rotor. 
     According to the present invention, therefore, it is possible to provide a drive mechanism which uses an ultrasonic motor to directly drive a driven member without a transmission mechanism using toothed wheels or the like, which is small in size, and which has high positioning accuracy. 
     The rotor may be directly pressed against the piezoelectric element or may be pressed against the piezoelectric element with a vibrating member interposed therebetween, the vibrating member amplifying elliptical vibration caused by expanding vibration of the piezoelectric element. 
     According to the present invention, the above-described drive mechanism with the ultrasonic motor may comprise the projecting portion (e.g., rotation range limiting member  15   b ) provided on the rotor, and a receiving member (e.g., spring seat  16   a ) for limiting the range of rotation of the rotor and limiting the range of movement of the driven member by receiving the projecting portion coming to the receiving member by a turning movement. 
     In this case, since the range of rotation of the rotor is limited, the moving member is inhibited from moving so as to exceed allowable limits, so that reliability of the drive mechanism with the ultrasonic motor can be improved. 
     More specifically, according to the present invention, there are provided a pressing spring (e.g., a plate spring  16 ) for pressing at least one of the rotor and the piezoelectric element against the other so that the pressure for contact therebetween is increased, and a spring seat ( 16   a ) for holding the pressing spring. This spring seat is constructed to also function as a receiving member. 
     Specifically, the driven member is linked to the rotor through the projecting portion. 
     In the above-described drive mechanism with the ultrasonic motor, a cushioning material for absorbing a shock may be provided between the projecting portion and the receiving member, thereby reducing the possibility of such a shock at the time of receiving seriously affecting the device incorporating the drive mechanism with the ultrasonic motor. 
     According to the present invention, in the above-described drive mechanism ( 1 ) with the ultrasonic motor, the driving direction in which the driven member is guided by the guide member ( 19   b ) is a rectilinear direction. 
     According to the present invention, it is possible to provide a drive mechanism with an ultrasonic motor capable of directly converting a rotary motion of a rotor into a rectilinear motion of a driven member. 
     According to the present invention, a plurality of driven members may be driven in different directions to each other. More specifically, separate driven members (e.g., aperture blades  21 ) are attached to the same rotor at two positions, and are moved in opposite directions to each other. 
     According to the present invention, it is also possible to obtain a drive mechanism ( 2 ) with an ultrasonic motor in which each of two driven members has an aperture ( 21 C), the two driven members are placed in an overlapping manner such that the aperture of one driven member is covered with the other driven member, and the amount of overlap of the two driven members is changed by rotational movement of the rotor to change the amount of opening ( 21   d ) of the aperture. 
     This mechanism can be used as an aperture mechanism for light quantity control or a shutter mechanism. 
     The present invention also provides a drive mechanism ( 3 ) with an ultrasonic motor comprising an ultrasonic motor having a vibrating member including a piezoelectric element, and a rotor capable rotating by receiving vibration of the vibrating member, a rotating member linked to the rotor and rotated by being linked to a rotary motion of the rotor, a driven member linked to the rotating member and driven with the rotation of said rotating member, and an axial member for rotatably supporting said driven member. 
     According to the present invention in this aspect, the driven member is a lever with the axial member and the rotor operating as a fulcrum and a point of action, respectively. Therefore, it is possible to provide, by utilizing the principle of the lever, a drive mechanism with an ultrasonic motor using a rotary motion of the drive mechanism rotor as a direct motive power source. 
     According to the present invention, it is also possible to obtain a drive mechanism with an ultrasonic motor comprising an aperture member (e.g., rotary member  31 ) having an aperture ( 31   a ), wherein the driven member is placed so that at least one portion overlaps the aperture of the aperture, and wherein the amount of overlap of the aperture and the driven member is changed with a rotational movement of the rotor to change the amount of opening of the aperture. 
     This mechanism can be used as an aperture mechanism for light quantity control or a shutter mechanism. 
     The present invention also provides a drive mechanism with an ultrasonic motor comprising an ultrasonic motor having a vibrating member including a piezoelectric element, and a rotor capable of being rotated by vibration of the vibrating member, a first driven member linked to the rotor and driven by being linked to a rotary motion of the rotor, a rotating member maintained in contact with the rotor and rotated by being linked to the rotary motion of the rotor, a second driven member linked to the rotating member and driven by being linked to the rotary motion of the rotating member, and an axial member for restricting the rotation of each of the first and second driven members and axially supporting the first and second driven members. 
     According to this aspect of the present invention, the two driven members can be used as hands for pinching and holding an object. Also, free end portions of the first and second driven members project toward each other and overlap with each other to have an overlap portion, and the amount of opening of the aperture ( 42   e ) formed by being surrounded by the first driven member and the second driven member is changed by a rotational movement of the rotor. 
     This mechanism can be further used as an aperture mechanism for light quantity control or a shutter mechanism. 
     The above-described drive mechanism with the ultrasonic motor may further be constructed to have rotation amount detection means (e.g., slit member  7  and light emitting and receiving device  16   b ) for detecting the amount of rotation of the rotor, and a control unit ( 18 ) for controlling the ultrasonic motor according to the amount detected by the rotation amount detection means. 
     In this case, since the ultrasonic motor is controlled by detecting the amount of rotation of the rotor, i.e., the amount of driving of the driven member, the drive mechanism with the ultrasonic motor can perform driving with improved accuracy. 
     This rotation amount detection means is, for example, a method of irradiating light on a slit member provided on the rotor, receiving transmitted light or reflected light obtained in a digital manner, and analyzing the number of pulses thereby obtained. 
     Further, the drive mechanism with ultrasonic motor may further be constructed to have a light quantity sensor for detecting the quantity of light passing through the aperture, and a control unit for changing the amount of opening of the aperture by controlling the ultrasonic motor according to the amount detected by the light quantity sensor. The amount of movement of the rotor is controlled while directly detecting the control-object light quantity, thus enabling highly accurate light quantity control. 
     The present invention also provides an electronic device with the ultrasonic motor having the above-described drive mechanism with the ultrasonic motor. 
     According to the present invention, the drive mechanism with the ultrasonic motor of the present invention is smaller and more accurate in positioning than the conventional drive mechanisms. Therefore, if the drive mechanism of the present invention is used, electronic devices, such as still cameras, video camera-recorders, electronic watches, measuring apparatuses, printers, printing machines, machine tools, robots, transfer apparatuses, and storage units, can be designed so as to reduce the overall size and the accuracy. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic top view of the construction of a drive mechanism with an ultrasonic motor, which represents a first embodiment of the present invention; 
     FIG. 2 is a schematic cross-sectional view of the ultrasonic motor of the drive mechanism with an ultrasonic motor shown in FIG. 1; 
     FIG. 3 comprises schematic top and side views for explaining a rotor used in an example of modification of the drive mechanism with an ultrasonic motor shown in FIG. 1; 
     FIG. 4 is a schematic top view of a drive mechanism with an ultrasonic motor, which represents a second embodiment of the present invention; 
     FIG. 5 is a schematic side view of an essential portion of the drive mechanism with an ultrasonic motor shown in FIG. 4; 
     FIG. 6 is a schematic top view explaining a drive mechanism with an ultrasonic motor, which represents a third embodiment of the present invention; and 
     FIG. 7 is a schematic top view explaining a drive mechanism with an ultrasonic motor, which represents a fourth embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     &lt;First Embodiment&gt; 
     FIG. 1 is a schematic top view of the construction of a drive mechanism  1  with an ultrasonic motor  10 , which represents a first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the construction of the ultrasonic motor  10  of the drive mechanism  1  with an ultrasonic motor. 
     The drive mechanism  1  is constituted essentially of the ultrasonic motor  10 , a control unit  18  for controlling the ultrasonic motor  10 , a drive rod  19   a  (driven member) linked rotatably to a rotor  15  of the ultrasonic motor  10 , a guide member  19   b  which holds the driven member  19   a  in such manner that the driven member  19   a  is slidably fitted thereto. 
     As shown in FIGS. 1 and 2, the ultrasonic motor  10  is constituted essentially of a disklike piezoelectric element  11 , a disklike vibrating member  12  fixed to the upper surface of the piezoelectric element  11 , a plurality of projections  13  integrally provided on the upper surface of the vibrating member  12 , a shaft  14  passing through central portions of the piezoelectric element  11  and the vibrating member  12 , a disklike rotor  15  rotatably supported by the shaft  14 , a plate spring  16  for pressing the rotor  15  against the projections  13 , and lead wires  11   a  for transmitting drive signals to electrodes of the piezoelectric element  11 . 
     The plate spring  16  has its one end fixed on a spring seat  16   a  spaced apart at a certain distance from the shaft  14 , and has its other end maintained in contact with the uppermost end portion of a press-down member  15   a , which protrudes beyond the upper surface of the rotor  15  at the center of the same, and which presses the rotor  15  downward. The uppermost end of the press-down member  15   a  is higher than the upper surface of the spring seat  16   a , so that the plate spring  16  is bent. 
     The rotor  15  has a pair of rotation range limiting members  15   b  each projecting from its side surface along the circumference in a direction perpendicular to the axial direction of the shaft  14 . The rotation range limiting members  15   b  are provided opposite from each other about the shaft  14 . The projecting length of the rotation range limiting members  15   b  is long enough to enable each of the rotation range limiting members  15   b  to be brought into contact with the spring seat  16   a  when the rotor  15  rotates. 
     Contact sensors  16   c  are provided on side surfaces of the spring seat  16   a . Each contact sensor  16   c  detects contact of the rotation range limiting member  15   b , and outputs a contact signal to the control unit  18 . 
     As shown in FIG. 2, a slit member  17  is provided along the side surface of the rotor  15 . The slit member  17  is formed in such a manner that a plate having a plurality of slits arranged at regular intervals and having its one surface mirror-finished is wrapped around an outer side surface of a disk having a central opening, with the two end portions of the plate joined to each other, and with the mirror-finished surface facing outward. The slit member  17  is placed on the rotor  15  in a capping manner. That is, the slits in the silt member  17  are formed so as to cover the side surface of the rotor  15  at regular intervals. 
     The spring seat  16   a  is formed by providing a light emitting and receiving device  16   b  in an inner side surface of a well-known spring seat. The light emitting and receiving device  16   b  emits light such as laser light toward the slit member  17 , receives reflected light from the slit member  17 , and converts the received light into an electrical signal. As the rotor  15  rotates, the light emitting and receiving device  16   b  intermittently receives light, generates an electrical signal formed of pulses, and outputs the signal to the control unit  18 . 
     That is, the control unit  18  computes the amount of rotation of the slit member  17 , i.e., the amount of rotation of the rotor  15  from the number of pulses in the electrical signal supplied from the light emitting and receiving device  16   b  and the total number of slits in the slit member  17 , controls the ultrasonic motor  10  while recognizing the computed amount of rotation, and stops the ultrasonic motor  10  when it receives a contact signal from the contact sensors  16   c.    
     The drive rod  19   a  has a generally rectangular hole  19   c  formed at its one end so as to extend laterally as viewed in FIG. 1. A shaft  15   c  projecting upward from an upper surface end portion of the rotation range limiting member  15   b  is inserted in the hole  19   c . Thus, the drive rod  19   a  is attached so as to be swingable relative to the hole  19   c  and so that the shaft  15   c  is movable in the hole  19   c.    
     The guide member  19   b  is provided separately from the ultrasonic motor  10 . The guide member  19   b  has a channel  19   e  in which a portion of the drive rod  19   a  is slidably fitted, and which supports the drive rod  19   a.    
     In the above-described drive mechanism  1  with the ultrasonic motor  10 , when the rotor  15  and the rotation range limiting members  15   b  of the ultrasonic motor  10  are rotated clockwise as viewed in FIG. 1, the drive rod  19   a  is thereby driven while being stopped from moving to the left or right as viewed in FIG. 1, since its one portion is fitted in the channel  19   e . The drive rod  19   a  therefore moves in a direction along the channel  19   e , i.e., upward as viewed in FIG. 1 while allowing the shaft  15   c  to move in the hole  19   c . When the rotor  15  and the rotation range limiting members  15   b  are rotated counterclockwise as viewed in FIG. 1, the drive rod  19   a  moves downward as viewed in FIG. 1 by a similar action. 
     That is, the drive mechanism  1  with the ultrasonic motor  10  is a drive mechanism for directly converting a rotary motion of the ultrasonic motor  10  into a longitudinal motion of the drive rod  19   a.    
     Thus, the small (thin) ultrasonic motor  10  having a high-precision positioning resolution and a stationary torque is used, and the power transmission mechanism is simplified in comparison with the conventional art, so that the size of the drive mechanism  1  with the ultrasonic motor  10  is small. If this drive mechanism is used, electronic devices having a mechanism for to-and-fro motions (still cameras, video camera-recorders, electronic watches, measuring apparatuses, printers, printing machines, machine tools, robots, transfer apparatuses, storage units, and so on) can be designed so as to reduce the overall size and the power consumption. 
     Since no toothed wheel is used for motive power transmission, the motive power transmission mechanism can operate with least play and can therefore position the drive rod  19   a  with improved accuracy. 
     Moreover, the control unit  18  controls the ultrasonic motor  10  while detecting the amount of rotation of the rotor  15  and the rotation range limiting members  15   b , and stops the ultrasonic motor  10  when it receives a contact signal. Therefore, the control unit  18  can precisely control the ultrasonic motor  10  by stopping the motor accurately and without overshooting the target point. Consequently, there is no possibility of the drive rod moving excessively, the accuracy of positioning of the drive rod  19   a  is further improved, and the reliability of the drive mechanism  1  with the ultrasonic motor is also improved. 
     This embodiment can be modified as desired within the scope of the present invention. 
     For example, if a through hole is formed in the guide member  19   b  instead of the channel  19   e , and the drive rod  19   a  is slidably inserted in this through hole, the same drive function can also be performed. 
     Also, the arrangement may alternatively be such that, as shown in a schematic side view of FIG. 3, a projection  15   d  is provided on the upper surface of the rotor  15  and is inserted in the hole  19   c  of the drive rod  19   a  to drive the drive rod  19   a . In this case, the drive mechanism is free from impact noise and also does not give a shock to the slide portions of the rotating member and the rotor of the ultrasonic motor, so that the life of the ultrasonic motor can be extended. Also, the elasticity of a cushioning material can produce a force in the rotor driving direction, thereby improving the mobility of the ultrasonic motor. 
     Cushioning members may be attached instead of the contact sensors  16   c  to absorb a shock when one of the rotation range limiting members  15   b  is brought into contact with the spring seat  16   a , thereby avoiding a detrimental effect on the device incorporating the drive mechanism with the ultrasonic motor. 
     &lt;Second Embodiment&gt; 
     A drive mechanism  2  with an ultrasonic motor, which represents a second embodiment of the present invention, will next be described in detail with reference to FIGS. 4 and 5. 
     FIG. 4 is a schematic top view showing the construction of the drive mechanism  2  with an ultrasonic motor, and FIG. 5 is a schematic side view of an essential portion of the drive mechanism  2  with an ultrasonic motor. 
     The drive mechanism  2  with an ultrasonic motor is a drive mechanism used as an aperture or shutter mechanism for optical apparatuses represented by a camera. As shown in FIG. 4, the drive mechanism  2  with an ultrasonic motor is constituted essentially of an ultrasonic motor  10 , two aperture blades  21  directly attached rotatably to a rotor  15  of the ultrasonic motor  10 , and a guide member  22  in which the aperture blades  21  are slidably fitted, and which supports the aperture blades  21 . 
     In this embodiment, the attached positions of two rotation range limiting members  15   b  of the rotor  15  are spaced apart by an angle of, for example, about 150° along the circumference of the rotation range limiting members  15   b , and stop pins  23  (receiving members) for limiting the range of rotation of the rotor  15  in association with the rotation range limiting members  15   b  are provided separately from a spring seat  16   a  on both sides of the spring  16   a  of the ultrasonic motor  10 . 
     Further, the rotor  15  has generally rectangular holes  15   e  extending in opposite radial directions from the vicinity of a shaft  14  so as to be symmetrical about the shaft  14 , respectively. 
     Each aperture blade  21  is formed of a rectangular plate  21   a  having a width approximately equal to the diameter of the ultrasonic motor  10  and having its one corner portion extended along its longitudinal direction. A shaft  21   b  is provided on the extended portion in the end thereof. The rectangular plate  21   a  has an aperture  21   c  formed at its center portion. 
     As shown in FIGS. 4 and 5, the two aperture blades  21  have their shafts  21   b  respectively inserted in the separate holes  15   e . Thus, the two aperture blades  21  are attached so as to be swingable relative to the holes  15   e  and movable in the holes  15   e . Since the aperture blades  21  are attached so as to have a symmetry about a line, the rectangular plates  21   a  are superposed one on another. 
     The guide member  22  is provided separately from the ultrasonic motor  10 . For example, the guide member  22  slidably supports only opposite side surfaces of the rectangular plates  21   a  of the two aperture blades  21 . 
     In the thus-constructed the drive mechanism  2  with the ultrasonic motor, each of the two aperture blades  21  moves by the same action as that of the above-described drive rod  19   a  in the drive mechanism  1  with the ultrasonic motor. While one of the two aperture blades  21  is moving upward as viewed in FIG. 4, the other is moving downward as viewed in FIG.  4 . 
     According to the direction of rotation of the rotor  15 , the overlap portion of the two rectangular plates  21   a  becomes larger and becomes smaller. When the overlap portion of the rectangular plates  21   a  becomes larger, the amount of overlap of the apertures  21   c , i.e., the amount of opening  21   d  becomes larger. Conversely, when the overlap portion of the rectangular plates  21   a  becomes smaller, the overlap of the apertures  21   c , i.e., the amount of opening  21   d  becomes smaller. 
     That is, the drive mechanism  2  with the ultrasonic motor  10  is capable of adjusting the amount of opening  21   d  by controlling the amount rotation and the direction of rotation of the rotor  15  through the drive of the ultrasonic motor  10 . Therefore, the drive mechanism  2  with the ultrasonic motor can be used as an aperture mechanism. If the rotor  15  is rapidly moved, the drive mechanism  2  with the ultrasonic motor can be used as a shutter mechanism. Specifically, by using the ultrasonic motor  10  having improved response, a shutter having a markedly high opening/closing speed can be realized. 
     Thus, the ultrasonic motor  10  having a reduced size (thickness) is used in combination with the motive power transmission mechanism simpler than the conventional ones, so that the accuracy with which the aperture blades  21  are positioned is high and the size of the drive mechanism  2  with the ultrasonic motor  10  is small. If this drive mechanism is used in an electronic device such as a camera, the overall size of the electronic device can be reduced. 
     If the drive mechanism  2  with the ultrasonic motor according to this embodiment is used in an automatic focusing (AF) camera, the amount of light passing through the drive mechanism  2  with the ultrasonic motor may be detected by the light quantity detection means used in combination with the automatic focusing mechanism, and the control unit  18  may control the drive mechanism  2  with the ultrasonic motor by recognizing the amount of opening  21   d  from the detected quantity of light. 
     &lt;Third Embodiment&gt; 
     A drive mechanism  3  with an ultrasonic motor, which represents a third embodiment of the present invention, will be described in detail with reference to the schematic top view of FIG.  6 . 
     The drive mechanism  3  with an ultrasonic motor is, for example, a mechanism used as an aperture or shutter mechanism for a camera. The drive mechanism  3  with an ultrasonic motor is constituted essentially of an ultrasonic motor  10  (of which only rotor  15  is shown in FIG.  6 ), a ring-shaped rotary member  31  having an aperture  31   a  for introduction of light formed at its center, and three aperture blades  32  (driven members) for covering the aperture  31   a  to adjust the amount of opening thereof. 
     The rotary member  31  has a generally rectangular hole  31   b  formed in its peripheral portion so as to extend in a radial direction, and also has, for example three generally rectangular holes  31   c  formed in its inner peripheral portions so as to extend in radial directions while being spaced apart from each other by an angle of 120°. The hole  31   b  is a hole in which the projection  15   d  on the upper surface of the rotor  15  is to be inserted fromlbelow. The holes  31   c  are holes in which projections  32   b  of the aperture blades  32  described below in detail are to be inserted from below. 
     Each of three aperture blades  32  is swingably attached at its one end to a component (not shown) other than the rotor  15  and the rotary member  31  by using its shaft  32   a . The three aperture blades  32  are attached in this manner at three positions located outside the rotary member  31  and spaced part from each other by 120°. Also, each aperture blade  32  has, at a position close to its center, the projection  32   b  to be inserted to the hole  31   c.    
     That is, the rotary member  31  is rotatably positioned on the shaft  32   a  through the aperture blades  32 . 
     The other ends of the three aperture blades  32  are placed so as to cover the aperture  31   a  of the rotary member  31 . 
     In the thus-constructed drive mechanism  3  with the ultrasonic motor, when the rotor  15  of the ultrasonic motor  10  rotates, the rotary member  31  rotates while allowing the projection  15   d  to slide in the hole  31   b . As the rotary member  31  rotates, the aperture blades  32  moves swingably on the shafts  32   a  while sliding the projections  32   b  in the holes  31   b , thereby changing the amount of covering over the aperture  31   a . So that, the amount of opening of the aperture  31   a  is thereby changed. The direction of swing of the aperture blades  32  to increase or reduce the amount of opening of the aperture  31   a  is determined by the direction of rotation of the rotor  15 . 
     That is, the drive mechanism  3  with the ultrasonic motor is capable of adjusting the amount of opening,of the aperture  31   a  by rotating the rotor  15 . Therefore, it can be used as a camera aperture mechanism. If the shape and the attached positions of the aperture blades  32  are suitably selected, the aperture  31   a  can be completely covered with the blades  32 . Therefore, the drive mechanism  3  with the ultrasonic motor can be used as a shutter. 
     Thus, the ultrasonic motor  10  having a reduced size (thickness), capable of high-precision positioning and having a stationary torque is used in an electronic device in combination with the motive power transmission mechanism simpler than the conventional ones, so that the accuracy with which the aperture blades  32  are positioned is high and the size of the drive mechanism  3  with the ultrasonic motor  10  is small. If this drive mechanism is used, the size and the power consumption of electronic devices, such as still cameras, video camera-recorders, robots having a charge-coupled device (CCD) camera, and measuring apparatuses can be reduced. 
     If the drive mechanism  3  with the ultrasonic motor according to this embodiment is used in an AF camera, the amount of light passing through the drive mechanism  3  with the ultrasonic motor may be detected by the light quantity detection means used in combination with the automatic focusing mechanism, and the control unit  18  may control the drive mechanism  3  with the ultrasonic motor by recognizing the amount of opening of the aperture  31   a  from the detected quantity of light. 
     &lt;Fourth Embodiment&gt; 
     A drive mechanism  4  with an ultrasonic motor, which represents a fourth embodiment of the present invention, will be described in detail with reference to the schematic top view of FIG.  7 . 
     The drive mechanism  4  with an ultrasonic motor is constituted essentially of an ultrasonic motor  10 , a disklike rotary member  41  having a side surface maintained in contact with a side surface of a rotor  15  of the ultrasonic motor  10 , and therefore capable of rotating with the rotation of the rotor  15 , aperture blades  42  (driven members) respectively attached to the rotor  15  and the rotary member  41  so as to be swingable and unidirectionally movable, and a shaft  43  for swingably positioning both the aperture blades  42 . 
     The rotor  15  and the rotary member  41  are equal in outside diameter and have equal amounts of rotation. The rotary member  41  has a projection  41   a  on its upper surface. The projection  41   a  is provided at such a position that the projection  41   a  and the projection  15   d  of the rotor  15  exhibit a point symmetry. The projection  41   a  and the projection  15   d  are inserted in holes  42   c  of the aperture blades  42  described below in detail. 
     Each of the two aperture blade  42  is generally L-shaped. The aperture blades  42  are attached in such a manner that one of them is flipped from side to side so that the extreme ends of their lower side portions  42   a  overlap each other. Further, each aperture blade  42  has a generally rectangular hole  42   c  formed neat the upper end of a vertical side portion  42   b  so as to extend in the vertical direction as viewed in the shape of L. As mentioned above, the projections  15   d  and  41   a  are inserted in the holes  42   c  to attach the aperture blades  42  so that the aperture blades  42  are swingable and the projections  15   d  and  41   d  are movable in the holes  42   c.    
     Central portions of the vertical side portions  42   b  project in the same direction as the lower side portions  42   a  and overlap each other. Through these overlapping portions  42   d , the aperture blades  42  are swingably positioned on the shaft  43 . 
     That is, the lower side portions  42   a  and the overlapping portions  42   d  of the two aperture blades  42  form an aperture  42   e.    
     In the thus-constructed drive mechanism  4  with the ultrasonic motor, when the rotor  15  of the ultrasonic motor  10  is rotated, the rotary member  41  rotates in the direction opposite to the direction of rotation of the rotor  15 . As the rotor  15  and the rotary member  41  rotate, the two aperture blades  42 , positioned by the shaft  43 , swing in opposite directions while allowing the projections  15   d  and  41   a  to slide in the holes  42   c , thereby changing the amount of opening of the aperture  42   e . The direction of swing of the aperture blades  42  to increase or reduce the amount of opening of the aperture  42   e  is determined by the direction of rotation of the rotor  15 . 
     That is, the drive mechanism  4  with the ultrasonic motor is capable of adjusting the amount of opening of the aperture  42   e  by rotating the rotor  15 . Therefore, it can be used as a camera aperture mechanism by placing a member  44  having a circular aperture  44   a  so as to overlap the aperture  42   e . If the shape and the attached positions of the aperture blades  42  are suitably selected, the aperture  44   a  can be completely covered with the blades  42 . Therefore, the drive mechanism  4  with the ultrasonic motor can be used as a shutter. Specifically, by using the ultrasonic motor  10  having improved response, a shutter having a markedly high opening/closing speed can be realized. 
     Thus, the ultrasonic motor  10  having a reduced size (thickness) and having a high-precision positioning resolution and a stationary torque is used in combination with the motive power transmission mechanism simpler than the conventional ones, so that the accuracy with which the aperture blades  42  are positioned becomes high and the size of the drive mechanism  4  with the ultrasonic motor  10  becomes small. The size and the power consumption of electronic devices such as cameras can be reduced by using this drive mechanism. 
     If the drive mechanism  4  with the ultrasonic motor according to this embodiment is used in an AF camera, the amount of light passing through the drive mechanism  4  with the ultrasonic motor may be detected by the light quantity detection means used in combination with the automatic focusing mechanism, and the control unit  18  may control the drive mechanism  4  with the ultrasonic motor by recognizing the amount of opening of the aperture  42   e  from the detected quantity of light. 
     In this embodiment, the rotary member  41  and the rotor  15  are maintained in contact with each other and a motion of the rotor  15  is converted into a motion of the rotary member  41  by frictional power transmission. However, any other transmission mechanisms using a belt, a cam, toothed wheels, or the like may alternatively be used. 
     According to the present invention, as described above, it is possible to provide a smaller drive mechanism which uses an ultrasonic motor to directly drive a driven member without a transmission mechanism using toothed wheels or the like, and which has a high positioning accuracy. 
     The range of rotation of the rotor is limited to inhibit the moving member from moving so as to exceed allowable limits, so that reliability of the drive mechanism with the ultrasonic motor can be improved. 
     Also, the possibility of a receiving a shock seriously affecting the device incorporating the drive mechanism with the ultrasonic motor can be reduced. 
     It is also possible to provide a drive mechanism with an ultrasonic motor capable of directly converting a rotary motion of a rotor into a rectilinear motion of driven members, and enabling the driven members to be used as an aperture for controlling the quantity of light. 
     A driven member can be a lever with a guide member and a rotor-operating as a fulcrum and a point of action, respectively. Therefore, it is possible to provide, by utilizing the principle of the lever, a drive mechanism with an ultrasonic motor capable of being used as an aperture mechanism for light quantity control with rotary motions of a drive mechanism rotor directly used as a motive power source. 
     Further, two driven members can be used as hands for pinching and holding an object, and also can be used as aperture members for light quantity control. 
     The ultrasonic motor is controlled by detecting the amount of rotation of the rotor, i.e., the amount of driving of the driven member, so that the drive mechanism with the ultrasonic motor can perform driving with improved accuracy. 
     The drive mechanism with the ultrasonic motor of the present invention is smaller than the conventional drive mechanisms. Therefore, if the drive mechanism of the present invention is used, electronic devices, such as still cameras, video camera-recorders, electronic watches, measuring apparatuses, printers, printing machines, machine tools, robots, transfer apparatuses, and storage units, can be designed so as to reduce the overall size and the power consumption.