Patent Publication Number: US-2022239237-A1

Title: Vibration wave driving apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a vibration wave driving apparatus, which is suitable for a lens interchangeable type digital single-lens reflex camera, a digital still camera, a digital video camera, a lens interchangeable type digital video camera, etc. 
     Description of the Related Art 
     In driving a vibration wave driving apparatus (ultrasonic motor) that has a driving source in deformations of a piezoelectric element, the vibration generated by the friction contact between a vibrator and a friction member may be transmitted to a holding member that holds the vibrator, and may cause the rocking vibration and the abnormal noise. Japanese Patent Laid-Open No. (“JP”) 2016-19354 discloses a vibration wave driving apparatus that includes a damper member provided between the vibrator and the holding member. JP 2010-158127 discloses a vibration wave driving apparatus that includes a vibration suppressing member that suppresses the unnecessary vibration from the vibrator. 
     The vibration wave driving apparatus disclosed in JP 2016-19354 directly pressurizes the holding member, the piezoelectric element may be separated from the vibrator, and the driving characteristic may deteriorate. The vibration wave driving apparatus disclosed in JP 2010-158127 cannot suppress the vibration of the holding member and may cause abnormal noise. 
     SUMMARY OF THE INVENTION 
     The present invention provides a vibration wave driving apparatus that can maintain a good driving characteristic while suppressing the vibration of a holding member that holds a vibrator. 
     A vibration wave driving apparatus according to one aspect of the present invention includes a vibrator configured to vibrate and movable relative to a friction member to generate a driving force, a pressing member configured to pressurize the vibrator, a transmission member configured to transmit a pressing force by the pressing member to the vibrator, a holding member configured to hold the vibrator, and a viscoelastic member configured to connect the holding member and the transmission member to each other. An apparatus according to another aspect of the present invention includes the above vibration wave driving apparatus, and a driven member driven by a driving force from the vibration wave driving apparatus. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  explain a holding member and its surrounding members according to the first embodiment. 
         FIGS. 2A and 2B  compare the holding member according to the first embodiment and a conventional holding member. 
         FIGS. 3A and 3B  compare a transmission member according to the first embodiment and a conventional transmission member. 
         FIGS. 4A to 4C  explain vibration modes of a vibrator. 
         FIG. 5  is a sectional view of a vibration wave driving apparatus according to the first embodiment. 
         FIGS. 6A and 6B  illustrate positions at which viscoelastic members according to the first embodiment are to be disposed. 
         FIGS. 7A and 7B  explain a holding member and its surrounding members according to a second embodiment. 
         FIGS. 8A and 8B  compare the holding member according to the second embodiment and a conventional holding member. 
         FIGS. 9A and 9B  compare a transmission member according to the second embodiment and a conventional transmission member. 
         FIG. 10  is a sectional view of a vibration wave driving apparatus according to the second embodiment. 
         FIG. 11  is a sectional view of an image pickup apparatus according to a third embodiment. 
         FIG. 12  is a perspective view of a conventional vibration wave driving apparatus. 
         FIG. 13  is a sectional view of a driving force extractor in the conventional vibration wave driving apparatus. 
         FIG. 14  is an exploded perspective view of the conventional vibration wave driving apparatus. 
         FIG. 15  is a sectional view of a conventional vibration wave driving apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Referring now to the accompanying drawings, a detailed description will be given of embodiments according to the present invention. Corresponding elements in respective figures will be designated by the same reference numerals, and a duplicate description thereof will be omitted. 
     In each embodiment, an X-axis direction is set to a direction in which a vibrator and a friction member move relative to each other, a Y-axis direction is set to a direction (pressurizing direction) orthogonal to the X-axis direction, in which the vibrator is pressurized against the friction member, and a Z-axis direction is a direction orthogonal to the X-axis direction and the Y-axis direction. The coordinate system in each embodiment is set for description purposes, and the present invention is not limited to this definition. 
     Referring now to  FIGS. 12 to 15 , a description will be given of a problem of the conventional vibration wave driving apparatus.  FIGS. 12 to 15  are a perspective view, a sectional view of a driving force extractor, an exploded perspective view, and a sectional view in the X-axis direction of a conventional vibration wave driving apparatus  1000 , respectively. 
     The vibration wave driving apparatus  1000  is a direct action type linear actuator, and generates a driving force in the X-axis direction. A connecting protrusion  17   a  of a driven member  17  is inserted into a groove-shaped driving force extractor  16   a  of a move plate  16 . Thereby, the vibration wave driving apparatus  1000  is connected to the driven member  17  and can drive the driven member  17  in the X-axis direction. 
     A tension coil spring  7  urges a pressure plate  8  in the Y-axis direction. A transmission member  6  receives a pressing force from the pressure plate  8  (pressing member) toward the piezoelectric element  1  in the Y-axis direction, and transmits the pressing force to a vibrator  3  via a felt  5 . 
     A description will now be given of a mechanism by which the vibration wave driving apparatus  1000  generates the driving force. The vibration wave driving apparatus  1000  includes the vibrator  3  that includes a piezoelectric element  1  and a boss plate  2  fixed to each other by an adhesive or the like. A flexible substrate  12  is mechanically and electrically connected to the piezoelectric element  1  with an anisotropic conductive paste or the like. The piezoelectric element  1  is provided with two electrodes. When two-phase high-frequency voltages having different phases are applied to the two electrodes, the vibrator  3  generates two vibration modes illustrated in  FIGS. 4A and 4B .  FIG. 4A  illustrates a deformed state of the vibrator  3  in a push-up vibration mode in which the vibrator  3  generates a bending vibration in the Y-axis direction. The tint represents a change in the Y-axis direction. In the push-up vibration mode, the vibrator  3  generates a primary bending deformation (having two vibration nodes) in the short side direction of a central rectangular portion that is a joint with the piezoelectric element  1  and does not deform (or has no vibration nodes) in the long side direction.  FIG. 4B  illustrates a deformed state of the vibrator  3  in a feed vibration mode in which the vibrator  3  shows a secondary bending deformation (having three vibration nodes) in the long side direction of the rectangular portion and does not deform (or has no vibration nodes) in the short side direction. When the voltages are applied to the two electrodes of the piezoelectric element  1  with a temporal phase difference of π/2, the two vibration modes are temporally shifted and overlap each other, and an elliptical motion occurs at projections (convex portions) of the boss plate  2 . By changing the frequency and phase of the high-frequency voltages applied to the piezoelectric element  1 , the rotation direction and elliptic ratio of the elliptical motion can be properly changed, and the vibrator  3  can be made to move as desired. The vibrator  3  can generate a driving force that moves relative to a friction member  14  by a frictional contact with the friction member  14  fixed to a base member  13 . That is, the vibrator  3  can move relative to the friction member  14  in the X-axis direction. A ball base  15  is disposed on the opposite side of the vibrator  3  with respect to the friction member  14 . Three rolling balls (not shown) are disposed between the ball base  15  and the move plate  16 . 
     A description will now be given of a connection between the holding member  4  that holds the vibrator  3  and a holding member holding frame  11 . The boss plate  2  has two holes  2   b  separated from each other in the X-axis direction. The holding member  4  has fixing pins  4   a  facing the two holes  2   b . The pin  4   a  is inserted into the hole  2   b  and then fixed with an adhesive or the like. The holding member holding frame  11  is connected to the move plate  16  by a screw and engaged with the holding member  4 . 
     At each end of the holding member  4  in the X-axis direction, the holding member  4  is disposed inside roller members  9  and the holding member holding frame  11  is disposed outside the roller members  9 . A leaf spring  10  is fixed to the holding member holding frame  11  by an adhesive or the like, and urges the holding member  4  in the X-axis direction via the roller member  9 . That is, the holding member  4  is urged to the holding member holding frame  11  via the roller members  9 . The holding member  4  is not only urged in the X-axis direction, but also moved in the Y-axis direction by rolling of the roller members  9 . That is, the holding member holding frame  11  can be equalized in the X-axis direction and the Y-axis direction. 
     Due to the above structure, in the connection between the holding member  4  and the holding member holding frame  11 , there is no play in the X-axis direction that is the driving direction, and there is almost no sliding resistance due to the rolling action of the rolling member  9  in the Y-axis direction. 
     In the conventional vibration wave driving apparatus  1000 , the sliding resistance in the Y-axis direction is hardly generated in the holding member  4 . Therefore, when the vibration is excited due to vibration or the like from another member, the rocking vibration is generated in the arrow direction in  FIG. 15  in the holding member  4 . 
     First Embodiment 
       FIGS. 1A and 1B  explain a holding member and its surrounding members according to this embodiment.  FIGS. 1A and 1B  are a perspective view and an exploded perspective view of the holding member and its surrounding members, respectively. The components in this embodiment, which are corresponding components in the prior art, will be designated by the same reference numerals, and a detailed description thereof will be omitted. 
     The vibration wave driving apparatus  100  according to this embodiment includes a holding member  41  and a transmission member  61  having shapes different from those of the conventional holding member  4  and the conventional transmission member  6 . The vibration wave driving apparatus  100  according to this embodiment further includes viscoelastic members  18 . 
     The transmission member  61  directly transmits the pressing force to the piezoelectric element  1 . The viscoelastic member  18  connects the holding member  41  and the transmission member  61  to each other. The viscoelastic member  18  is a member having a high damping property, and is made, for example, of an adhesive or butyl rubber using an elastomer system as a main component. 
       FIGS. 2A and 2B  compare the holding member  41  according to this embodiment and the conventional holding member  4 .  FIGS. 2A and 2B  illustrate the holding member  41  according to this embodiment and the conventional holding member  4 , respectively. In  FIGS. 2A and 2B , an upper figure is a perspective view and a lower figure is a side view.  FIGS. 3A and 3B  compare the transmission member  61  according to this embodiment and the conventional transmission member  6 .  FIGS. 3A and 3B  illustrate the transmission member  61  according to this embodiment and the conventional transmission member  6 , respectively. In  FIGS. 3A and 3B , the upper figure is an illustration viewed from the + side in the Y-axis direction, and the lower figure is an illustration viewed from the − side in the Y-axis direction. 
     The holding member  41  has a notch portion (connector)  41   a  having a concave shape when viewed from the X-axis direction (first direction). The transmission member  61  includes an arm portion  61   a  that fits into the notch portion  41   a  with a certain gap. Four convex portions  61   b  that come into contact with the vibrator  3  are provided on the surface of the transmission member  61  on the piezoelectric element  1  side. 
     Referring now to  FIGS. 4A to 4C , a description will be given of the positions of the convex portions  61   b .  FIG. 4C  illustrates common nodes in which nodes in a plurality of standing wave vibrations excited by the vibrator  3  in the two vibration modes of the vibrator  3  intersect and overlap each other. In  FIG. 4A , the center of the vibrator  3  is a portion (vibration antinode) that has a maximum displacement of the bending vibration (the largest vibration amplitude). The portions that are illustrated by L 1  and L 2  in  FIG. 4A  are portions (vibration nodes) in which the displacement in the bending vibration is almost zero. In a case where these nodes exist at points, they are also called node points. In the vibration of the rectangular plate as in this embodiment, the nodes are formed in a line shape instead of the points and thus these nodes in the present invention will be particularly referred to as a node line (in a case where the vibration plate has a disk shape, the node line formed in the radial direction becomes concentric and thus will be referred to as a node circle in this case). The node lines L 3  to L 5  in  FIG. 4B  are formed along the directions orthogonal to the node lines L 1  and L 2 .  FIG. 4C  illustrates the node lines L 1  to L 5  of the two vibration modes. The intersections between the node lines L 1  and L 2  and the node lines L 3  to L 5 , that is, common nodes of the two vibration modes are the common nodes Q 1  to Q 6 . The convex portion  61   b  is located at any one of the positions of the common nodes Q 1  to Q 6 . In this embodiment, the convex portions  61   b  are located at the positions of the common nodes Q 1 , Q 2 , Q 5 , and Q 6 . Q 3  and Q 4  serve as support portions of the vibrator  3 . 
     Referring now to  FIGS. 1A, 1B, and 5 , a description will be given of the effect of the structure according to this embodiment.  FIG. 5  is a sectional view of the vibration wave driving apparatus  100 . In this embodiment, the transmission member  61  directly pressurizes common nodes different from those of the support portion of the vibrator  3  among the common nodes to the two vibration modes of the vibrator  3 . The transmission member  61  receives a pressing force from the pressure plate  8  toward the piezoelectric element  1  in the Y-axis direction, and transmits the pressing force to the piezoelectric element  1  via the convex portions  61   b . Since the convex portions  61   b  contact the common nodes of the vibrator  3 , the transmission member  61  can pressurize the vibrator  3  without being affected by the vibration. Thereby, the transmission member  61  can become stable. In this embodiment, the common nodes Q 1 , Q 2 , Q 5 , and Q 6  on both sides of the vibrator  3 , that is, the common nodes disposed symmetrically with respect to the centerline in the short side direction of the vibrator  3  are pressurized. Thereby, the transmission member  61  can transmit the pressing force over the entire area of the vibrator  3 , so that deterioration of the driving characteristics can be suppressed. 
     As described above, the transmission member  61  is substantially integrated with the vibrator  3  and is stable during driving, so that it serves as a damper together with the viscoelastic member  18 . This structure can suppress the rocking vibration of the holding member  41  and the abnormal noise. 
     This embodiment provides four convex portions  61   b , but the present invention is not limited to this embodiment. A number may be provided that can stabilize the transmission member  61 , that is, there may be at least three or more convex portions  61   b . In this embodiment, the common nodes Q 1 , Q 2 , Q 5 , and Q 6  are pressurized, but the present invention is not limited to this embodiment. In order to transmit the pressing force over the entire area of the vibrator  3 , the common nodes may be pressed which are disposed symmetrically with respect to the center line in the short side direction of the vibrator  3 . Such common nodes may include common nodes close to both ends in the long side direction of the vibrator  3 . 
     A description will now be given of the position where the viscoelastic member  18  connects the holding member  41  and the transmission member  61  to each other. The viscoelastic member  18  connects the side surface of the arm portion  61   a  of the transmission member  61  and the side surface of the notched portion  41   a  of the holding member  41  to each other. That is, the viscoelastic member  18  is disposed between the holding member  41  and the transmission member  61  in the Z-axis direction (second direction). Thereby, even in a case where a member that shrinks after the application such as a silicone resin adhesive is used for the viscoelastic member  18 , the force due to the shrinkage acts on the side surface, and no forces are applied to the pins  41   b  of the holding member  41  and the holes  2   b  in the boss plate  2 . Thus, the deterioration of the driving characteristic due to peeling of the piezoelectric element  1  and the boss plate  2  etc. can be suppressed. The viscoelastic member  18  may be provided so as to connect the holding member  41  and the pressure plate  8  to each other. This structure can further suppress the vibration of the holding member  41 . 
     In this embodiment, after each member is assembled, the viscoelastic members  18  are disposed at positions indicated by arrows in  FIG. 6A  that illustrates part of the vibration wave driving apparatus viewed from one side in the moving direction, and at positions indicated by arrows in  FIG. 6B  that illustrates part of the vibration wave driving apparatus viewed from the other side in the moving direction. 
     That is, after it is confirmed that the transmission member  61  receives the pressing force and is stable, the viscoelastic member  18  connects the holding member  41  and the transmission member  61  to each other. This structure can remove factors that deteriorate the driving characteristic such as the transmission member  61  connected in an inclined state. 
     Second Embodiment 
       FIGS. 7A and 7B  explain the holding member  42  and its surrounding members in this embodiment.  FIGS. 7A and 7B  are a perspective view and an exploded perspective view of the holding member  42  and its surrounding members, respectively. This embodiment will discuss changes from the first embodiment. In this embodiment, the same reference numerals are given to structures according to the first embodiment corresponding to the conventional structures, and a detailed description thereof will be omitted. 
     The vibration wave driving apparatus  100  according to this embodiment includes a holding member  42 , a transmission member  62 , and a viscoelastic member  182  having shapes different from those of the holding member  41 , the transmission member  61 , and the viscoelastic member  18  of the first embodiment. 
       FIGS. 8A and 8B  compare the holding member  42  according to this embodiment and the conventional holding member  4 .  FIGS. 8A and 8B  illustrate the holding member  42  according to this embodiment and the conventional holding member  4 , respectively.  FIGS. 9A and 9B  compare the transmission member  62  according to this embodiment and the conventional transmission member  6 .  FIGS. 9A and 9B  illustrate the transmission member  62  according to this embodiment and the conventional transmission member  6 , respectively. In  FIGS. 9A and 9B , the upper figure is an illustration viewed from the + side in the Y-axis direction, and the lower figure is an illustration viewed from the − side in the Y-axis direction. 
     The holding member  42  has groove portions (connectors)  42   a  with a shape configured to accommodate the viscoelastic member  182  on the XZ plane orthogonal to the Y-axis direction along the Z-axis direction. The transmission member  62  has a rectangular portion  62   a  that fits into the groove portion  42   a  with a certain gap. Three convex portions  62   b  are provided on the surface of the transmission member  62  on the side of the piezoelectric element  1 . In this embodiment, the convex portions  62   b  pressurize the common nodes Q 1 , Q 4 , and Q 5  illustrated in  FIG. 4C . 
     In this embodiment, a method of assembling the vibration wave driving apparatus  100  is different from that of the first embodiment. Referring now to  FIGS. 7A, 7B, and 10 , a description will be given of a method of assembling the vibration wave driving apparatus  100  according to this embodiment.  FIG. 10  is a sectional view of the vibration wave driving apparatus  100  according to this embodiment. In this embodiment, the viscoelastic member  182  is disposed between the holding member  42  and the transmission member  62  in the Y-axis direction. In this embodiment, the viscoelastic member  182  is made of a material such as urethane rubber, which has a high damping property and does not shrink, and whose thickness in the Y-axis direction is adjustable. Once the thickness of the viscoelastic member  182  is controlled so that the convex portions  62   b  of the transmission member  62  definitely contact the piezoelectric element  1 , it is unnecessary to insert the viscoelastic member  182  into a space between the holding member  42  and the transmission member  62  at the end of the assembly. That is, since the viscoelastic member  182  can be disposed in advance in the groove portion  42   a  of the holding member  42 , the assembling property can be improved. Since the unshrinkable viscoelastic member  182  is used, no unnecessary force is applied to the pins  42   b  of the holding member  42  and the holes  2   b  in the boss plate  2 , and the deterioration of the driving characteristic can be suppressed due to peeling between the piezoelectric element  1  and the boss plate  2  or the like. 
     Third Embodiment 
       FIG. 11  is a sectional view of an image pickup apparatus (optical apparatus) that includes the vibration wave driving apparatus  100  according to the first or second embodiment. The image pickup apparatus according to this embodiment includes an imaging lens unit  200  and a camera body  300 . Inside the imaging lens unit  200 , the vibration wave driving apparatus  100  and a focus lens  400  attached to the vibration wave driving apparatus  100  are disposed. An image sensor  500  is disposed inside the camera body  300 . The focus lens  400  is moved along an optical axis O by the vibration wave driving apparatus  100  during imaging. An object image is imaged at the position of the image sensor  500 , and the image sensor  500  generates an in-focus image. In this embodiment, the vibration wave driving apparatus  100  is mounted on the image pickup apparatus, but the present invention is not limited to this embodiment. The vibration wave driving apparatus  100  may be mounted on another optical apparatus such as a lens unit, or may be mounted on an apparatus different from the optical apparatus. In this embodiment, the imaging lens unit  200  and the camera body  300  are integrated with each other, but the present invention is not limited to this embodiment. The imaging lens unit  200  may be attachable to and detachable from the camera body  300 . That is, the apparatus in the present invention refers to an apparatus that includes the vibration wave driving apparatus  100  according to each embodiment and a driven member driven by a driving force from the vibration wave driving apparatus  100 . 
     The above embodiment can provide a vibration wave driving apparatus that can maintain a good driving characteristic while suppressing the vibration of the holding member that holds the vibrator. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-011537, filed on Jan. 27, 2021, which is hereby incorporated by reference herein in its entirety.