JP6389662B2 - Ultrasonic motor and lens driving device using ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor used for a lens barrel or the like of an imaging apparatus and a lens driving device using the ultrasonic motor.

  An ultrasonic motor using the ultrasonic vibration of a piezoelectric element is characterized by being small in size and capable of obtaining a high driving force, capable of supporting a wide speed range, low vibration and low noise. Ultrasonic motors having such characteristics are known in various principles and shapes depending on the application.

  As one of the methods, a method is known in which one or a plurality of resonance modes are simultaneously excited in a chip-type vibrator provided with a contact portion with a driven member. In this method, a large reciprocating motion or elliptical motion is generated at the contact portion by the excited resonance mode, and this motion is transmitted to the driven member to drive the driven member. The apparatus disclosed in Patent Document 1 is an example of an ultrasonic motor using a chip-type vibrator.

  The feature of this method is that the vibrator is relatively small among the ultrasonic motors and that the driven member can be driven not only in rotation but also in straight drive. Therefore, an ultrasonic motor using a chip-type vibrator is suitable as an actuator for linearly driving a lens in a lens barrel or the like of a camera that requires a small and high driving force motor.

JP 2010-183816 A

  A retractable small lens barrel used for a compact camera or the like is folded in the direction of the optical axis when not in use and is stored in the camera body. Therefore, the size of each part inside the lens barrel is limited particularly in the optical axis direction of the lens barrel. In such a lens barrel, when the lens is linearly driven in the optical axis direction by the ultrasonic motor using the chip-type vibrator, it is required to reduce the size of the motor in the driving direction of the motor itself. However, when the conventional chip-type vibrator is similarly reduced in order to reduce the dimension in the driving direction, there is a problem that the resonance frequency of the resonance mode becomes high and the amplitude necessary for driving cannot be obtained.

  Therefore, an object of the present invention is to provide an ultrasonic motor in which the resonance frequency does not increase and the amplitude does not decrease even when the vibrator is downsized in the driving direction.

In order to solve the above problems, an ultrasonic motor according to the present invention includes a vibrator having a piezoelectric element, a contact portion provided in the vibrator, and a first contact with the vibrator in contact with the contact portion. A driven member held so as to be relatively movable in the direction and a biasing force in a second direction perpendicular to the contact surface between the contact portion and the driven member, to bias the contact portion and the driven member And the vibrator has a dimension in a third direction orthogonal to the first direction and the second direction larger than a dimension in the first direction, and the contact portion has the first direction . The driven member is moved relative to the vibrator in the first direction using a first resonance mode having a displacement in the first direction, and the first resonance mode is a bending primary vibration. It is characterized by that.

  According to the present invention, it is possible to provide an ultrasonic motor in which the resonance frequency does not increase and the amplitude does not decrease even when the vibrator is downsized in the driving direction.

It is a figure showing the block diagram of the ultrasonic motor by 1st Embodiment of this invention, and the mode of a vibration. It is a figure explaining the drive principle of the ultrasonic motor by 1st Embodiment of this invention. It is a figure explaining the subject of the conventional ultrasonic motor. It is a figure explaining the effect of the ultrasonic motor of the present invention. It is a figure explaining the drive system of 1st embodiment of the ultrasonic motor of this invention. It is a figure explaining the lens-barrel using 1st embodiment of the ultrasonic motor of this invention. It is a figure explaining the effect of the lens-barrel using the ultrasonic motor of this invention. It is a figure explaining the holding | maintenance method of the ultrasonic motor of this invention. It is a figure showing the block diagram of the 2nd Embodiment of the ultrasonic motor of this invention, and the mode of a vibration. It is a figure explaining the drive principle of 2nd Embodiment of the ultrasonic motor of this invention.

Embodiments for carrying out the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same members.
First, the ultrasonic motor 1 which is the 1st Embodiment of this invention is demonstrated.

(First embodiment)
FIG. 1A shows the configuration of the ultrasonic motor 1 according to the first embodiment of the present invention. The ultrasonic motor 1 includes a vibrator 11 and a driven member 12. The vibrator 11 includes a piezoelectric element 111, and the resonance mode is excited in the vibrator 11 by expansion and contraction of the piezoelectric element 111.

  The vibrator 11 is configured by attaching a plate-like piezoelectric element 111 to an elastic body 112, and the elastic body 112 is provided with a contact portion 113 that contacts other members and generates a frictional force. The driven member 12 is brought into contact with the contact portion 113 and is held so as to be movable relative to the vibrator 11 in a predetermined direction (D1 direction in FIG. 1) by a holding structure (not shown).

  Hereinafter, the direction in which the driven member 12 can move relative to the vibrator 11 is referred to as a first direction. The contact portion 113 and the driven member 12 are urged by receiving an urging force F in a direction perpendicular to the contact surface of the contact portion 113 and the driven member 12 (direction D2 in FIG. 1) by an urging means (not shown). Hereinafter, a direction perpendicular to the contact surface between the contact portion 113 and the driven member 12 is referred to as a second direction. Further, a direction orthogonal to the first direction and the second direction is referred to as a third direction (D3 direction in FIG. 1).

  Here, when the dimension in the first direction of the vibrator 11 is W, the dimension in the second direction is T, and the dimension in the third direction is L, the vibrator 11 of the ultrasonic motor 1 has the first dimension. The dimension L in the third direction is designed to be larger than the dimension W in the direction and the dimension T in the second direction.

  In such a configuration, a resonance mode (described later) is excited in the vibrator 11, and the driven member 12 is relatively driven in the first direction. For example, PZT (lead zirconate titanate) is used for the piezoelectric element 111, and stainless steel is used for the elastic body 112, the contact portion 113, and the driven member 12, for example. However, the elastic body 111, the contact portion 113, and the driven member 12 do not have to be made of the same material, and can be made of different materials.

  Examples of a method of holding the driven member 12 so as to be movable relative to the vibrator 11 include a method of fixing the vibrator 11 and providing a guide hole in the driven member 12 and guiding the driven member 12 with a guide bar. Further, as the urging means, for example, a leaf spring is used.

  FIGS. 1B and 1C are diagrams showing resonance modes excited by the vibrator 11. FIG. 1B shows a state of a resonance mode (hereinafter referred to as a first resonance mode) in which the contact portion 113 of the vibrator 11 has a displacement in the first direction. The present invention is characterized in that bending primary vibration is used as the first resonance mode.

  FIG. 1C shows a state of a resonance mode (hereinafter referred to as a second resonance mode) in which the contact portion 113 of the vibrator 11 is displaced in the second direction. In this embodiment, an example in which bending primary vibration is used in the second resonance mode as in the first resonance mode will be described.

  When the vibrator 11 is excited with an appropriate phase delay in the resonance mode shown in FIGS. 1B and 1C, the contact portion 113 on the vibrator 11 becomes an ellipse indicated by r in FIG. Do exercise. At this time, in the configuration shown in FIG. 1A, the driven member 12 that is in contact with the contact portion 113 is drawn out by the frictional force with the contact portion 113 and is relatively driven in the first direction.

  Note that the shape, configuration, and material of the vibrator 11 are not limited to those described above, and it is sufficient that the vibrator 11 can be excited as a first resonance mode by the expansion and contraction of the piezoelectric element 111.

  FIG. 2 is a diagram for explaining the principle of driving the ultrasonic motor 1 by exciting the vibration shown in FIGS.

  First, an electrode pattern for applying a voltage to the piezoelectric element 111 will be described with reference to FIG. In the ultrasonic motor 1, the piezoelectric element 111 is composed of a single piezoelectric element layer, and electrode patterns are formed on the top and bottom surfaces of the piezoelectric element 111.

  FIG. 2A-2 is a front view of the vibrator 11. 2A-1 is a top view of the vibrator 11 and shows an electrode pattern on the top surface of the piezoelectric element 111 provided in the vibrator 11. FIG. 2A-3 is a cross-sectional view of the boundary layer between the piezoelectric element 111 and the elastic member 112 (AA cross-sectional view of FIG. 2A-2), and shows an electrode pattern on the bottom surface of the piezoelectric element 111. FIG.

  As shown in FIG. 2A-1, two electrodes 111 a and 111 b divided in the short side direction are arranged on the upper surface of the piezoelectric element 111. As shown in FIG. 2A-3, an electrode 111c is disposed on the entire bottom surface of the piezoelectric element 111. The electrode 111c is used as a common ground electrode when an AC voltage is applied to the electrodes 111a and 111b.

  In addition, since the bottom surface of the piezoelectric element 111 is in close contact with the elastic member 112, an extending portion 111c 'is provided for energizing from the outside. The piezoelectric element 111 is polarized in the thickness direction (P direction in FIG. 2).

  FIG. 2B shows a state in which the first resonance mode is excited in the vibrator 11. 2B-1 and 2B-2 are respectively a top view and a front view of the vibrator 11 excited in the first resonance mode. When an AC voltage having an opposite phase is applied to the electrodes 111a and 111b, one of the piezoelectric elements near the electrode 111a and the piezoelectric elements near the electrode 111b expands and the other contracts. By repeating this alternately, the bending primary vibration in the D1 direction in FIG. 2B can be excited.

  At this time, in FIG. 1B, the position indicated by N is a vibration node, which is the point with the least displacement. Further, in FIG. 1B, the end portion and the center portion of the vibrator 11 indicated by A in the third direction are antinodes of vibration, and the displacement is the largest.

  FIG. 2C shows a state in which the second resonance mode is excited in the vibrator 11. When an alternating voltage having the same phase is applied to the electrodes 111a and 111b, both the piezoelectric element near the electrode 111a and the piezoelectric element near the electrode 111b expand and contract at the same timing. Thereby, bending vibration can be excited in the direction D2 in FIG. At this time, the position indicated by N in FIG. 1C is a vibration node, which is the point with the least displacement. Further, in FIG. 1C, the end portion and the center portion of the vibrator 11 indicated by A in the third direction are antinodes of vibration, and the displacement is the largest.

  In the electrodes 111a and 111b, the AC voltage for exciting the first resonance mode described above and the AC voltage for exciting the second resonance mode are superimposed and applied to each electrode to the vibrator 11. The first resonance mode and the second resonance mode can be excited.

  The electrode pattern and the polarization direction are not limited to the above, and the piezoelectric element 11 can be expanded and contracted by an AC voltage applied from the outside, and the vibrator 11 can be excited in the first resonance mode or the second resonance mode. If it is good.

  Here, the problem of the conventional ultrasonic motor and the effect of the present invention will be described with reference to FIGS.

  Conventionally, there has been a problem that if the vibrator is reduced in size, the resonance frequency of the vibration increases and the amplitude decreases. The device disclosed in Patent Document 1 uses a telescopic primary vibration as a first resonance mode for a chip-type vibrator. In order to explain the problems of the conventional ultrasonic motor, an AC voltage was applied to the vibrator, and the resonance frequency and amplitude when the expansion and contraction primary vibration was excited as the first resonance mode were obtained by piezoelectric simulation. A change in resonance frequency and a change in amplitude when the entire vibrator is similarly reduced in order to change the dimension in the driving direction will be described with reference to FIG. In addition, since a drive direction is synonymous with the 1st direction in the ultrasonic motor 1, a drive direction is called a 1st direction below.

  FIG. 3A shows a state in which a primary vibration is excited as a first resonance mode in a rectangular vibrator. At this time, the dimension in the first direction is represented by W in FIG. In order to change the dimension W in the first direction, the change in the resonance frequency of the first resonance mode when the whole vibrator is enlarged and reduced in a similar shape is shown in FIG. 3B, and the change in the amplitude is shown in FIG. Shown in However, the change in amplitude shown in FIG. 3C is compared by applying an electric field of the same magnitude to the piezoelectric element provided in the vibrator.

  As shown in FIG. 3B, the resonance frequency f0 of the first resonance mode becomes higher as the similarity is reduced so that the dimension W in the first direction becomes smaller. Further, as shown in FIG. 3C, the amplitude a0 of the first resonance mode becomes smaller as the similarity is reduced so that the dimension W in the first direction becomes smaller. For this reason, if the conventional vibrator is similarly reduced, the amplitude required for driving cannot be obtained. In particular, since the dimension in the first direction of the vibrator affects the resonance frequency and amplitude of the first resonance mode, even if the dimension in the first direction is small, the resonance frequency does not increase in the first resonance mode and the amplitude does not increase. It is necessary not to decrease.

  In order to explain the effect of the present invention, an AC voltage is applied to a beam-shaped vibrator, and the resonance frequency and amplitude when bending vibration is excited as the first resonance mode are obtained by piezoelectric simulation. FIG. 4 (a-1) shows a state where the vibrator is excited as a first resonance mode, and FIG. 4 (a-2) shows a state where the bending secondary vibration is excited. FIG. 4A-3 shows a state in which the tertiary vibration is excited. FIG. 4B shows the relationship between the dimension W of the vibrator in the first direction and the resonance frequency of the first resonance mode. FIG. 4C shows the relationship between the dimension W in the first direction of the vibrator and the amplitude of the first resonance mode. 4B and 4C, the solid line represents data of the bending primary vibration, the broken line represents the bending secondary vibration, and the alternate long and short dash line represents the bending tertiary vibration data.

  As shown in FIG. 4B, the smaller the dimension W in the first direction is at any of the resonance frequency f1 of the bending primary vibration, the resonance frequency f2 of the bending secondary vibration, and the resonance frequency f3 of the bending tertiary vibration. The resonance frequency tends to decrease. Further, when the resonance frequency f1 of the bending primary vibration, the resonance frequency f2 of the bending secondary vibration, and the resonance frequency f3 of the bending tertiary vibration are compared, the resonance frequency f1 of the bending primary vibration is the smallest.

  As shown in FIG. 4C, the amplitude increases as the dimension W in the first direction decreases in any of the amplitude a1 of the bending primary vibration, the amplitude a2 of the bending secondary vibration, and the amplitude a3 of the bending tertiary vibration. Tend to. Further, when comparing the amplitude a1 of the bending primary vibration, the amplitude a2 of the bending secondary vibration, and the amplitude a3 of the bending tertiary vibration, the amplitude a1 of the bending primary vibration is the largest.

  As described above, in the ultrasonic motor 1 of the present invention, the bending primary vibration is used as the first resonance mode, and therefore the dimension of the vibrator 11 in the first direction (W in FIG. 1A) is small. The characteristic that the resonance frequency is low and the amplitude is large is obtained. For the above reasons, the present invention can provide an ultrasonic motor in which the resonance frequency does not increase and the amplitude does not decrease even when the vibrator is downsized in the driving direction (first direction).

  In the ultrasonic motor 1 according to the first embodiment of the present invention, the vibrator 11 has a structure in which the elastic member 112 is attached to the piezoelectric element 111. In such a structure, the piezoelectric element 111 does not need to be laminated with a piezoelectric element layer, and the contact portion 113 can be integrated with the elastic body 112, so that the cost can be reduced. For the above reason, it is one of preferred embodiments that the vibrator 11 has a structure in which the elastic member 112 is attached to the piezoelectric element 111.

  In the ultrasonic motor 1, the example in which the driven member 12 is relatively driven by exciting the vibrator 11 with the two vibrations of the first resonance mode and the second resonance mode has been described. However, the second resonance mode is not necessarily required if the second resonance mode can be driven. For example, FIG. 5A shows an example in which the vibrator 11 is mechanically tilted with respect to the driven member 12 at an angle θ. At this time, the friction member 113 always generates a friction force in a predetermined direction with respect to the driven member 12 in the first resonance mode, so that the driven member 12 can be driven. However, in this method, the driving direction cannot be reversed unless a mechanism for mechanically changing the inclination θ is provided. In the method of causing the contact portion 113 to generate an elliptical motion by the first resonance mode and the second resonance mode, the phase of the AC voltage that excites the first resonance mode and the AC voltage that excites the second resonance mode is changed. Then, the direction of the elliptical motion can be changed as shown in FIG. Since this method does not require a mechanism for adjusting the tilt mechanically, the entire ultrasonic motor 1 can be reduced in size. For the above reason, it is preferable that the ultrasonic motor 1 of the present invention drives the driven member 12 in the first resonance mode and the second resonance mode.

  Here, an embodiment of a lens barrel that linearly drives the lens using the ultrasonic motor 1 of the present invention will be described.

  FIG. 6A is a perspective view of the compact camera 5 provided with the lens barrel 51. Here, an example in which the focus lens is driven in the direction of the optical axis a (FIG. 6A) inside the lens barrel 51 using the ultrasonic motor 1 will be described.

  FIG. 6B is a sectional view of the focus lens driving section taken along a plane (surface C in FIG. 6A) passing through the optical axis a of the lens barrel 51, and a plane perpendicular to the optical axis a (FIG. 6B). FIG. 6C is a cross-sectional view of the focus lens driving unit according to (DD cross section).

  A focus lens 511 is disposed inside the lens barrel 51 at the center of the optical axis, and the focus lens 511 is fixed to the lens holder 512. The lens holder 512 is provided with a round hole 512a and a long hole 512b, and a rod-shaped guide member 513 is passed through each hole. Accordingly, the focus lens 511 and the lens holder 512 are held so as to be movable only in the optical axis direction.

  Inside the lens barrel 51, the above-described ultrasonic motor 1 is disposed adjacent to the focus lens 511 and the lens holder 512. The ultrasonic motor 1 includes a vibrator 11 and a driven member 12. The vibrator 11 is held by the vibrator holder 514 via the holding member 13.

  The holding member 13 has a thin sheet metal shape, for example, and holds the vibrator 11 movably only in the direction of the driven member 12. A pressing member 516 is disposed on the vibrator 11 via a buffer member 517. For the buffer member 517, a felt or the like that hardly inhibits the vibration of the vibrator 11 is used. A leaf spring 14 is disposed between the pressing member 516 and the vibrator holder 514, and the contact portion 113 on the vibrator 11 is urged toward the driven member 12 via the pressing member 516 and the buffer member 517.

  The driven member 12 is fixed to the lens barrel exterior 518, and the vibrator holder 514 is held to be movable only in the optical axis direction with respect to the lens barrel exterior 518 via the rolling member 515. When the above-described vibration is excited in the vibrator 11 in this state, the vibrator 11 relatively drives the driven member 12 by a frictional force. At this time, since the driven member 12 is fixed to the lens barrel exterior 518, the vibrator 11, the vibrator holding member 13, the vibrator holder 514, the leaf spring 14, the pressing member 516, and the buffer member 517 are arranged in the optical axis direction. Moving. Since the vibrator holder 514 is connected to the lens holder 512 via the connecting portion 514a, the lens holder 512 and the focus lens 511 can be driven in the optical axis direction in synchronization with the movement of the vibrator 11.

  The advantages of the lens barrel 51 that drives the lens using the ultrasonic motor 1 will be described with reference to FIG.

  FIG. 7A is a diagram illustrating a state in which the lens 511 is extended most in the optical axis direction and a state in which the lens 511 is retracted most in the same cross section as FIG. 6B. FIG. 7B shows an example in which the conventional ultrasonic motor 3 having a large dimension in the driving direction is used for driving the lens 511 in FIG. 7A, instead of the ultrasonic motor 1 of the present invention. The structure of the lens barrel is the same as that of the lens barrel 51 except for the ultrasonic motor to be used.

  In FIGS. 7A and 7B, the distance when the lens 511 is most extended in the optical axis direction and the distance when the lens 511 is most retracted (hereinafter referred to as a lens driving distance) are d1a and d1b, respectively. Similarly, in FIGS. 7A and 7B, the dimensions of the movable portion including the lens 511 in the optical axis direction are d2a and d2b, respectively, and when the lens 511 moves the lens driving distances d1a and d1b, the movable portion moves in the optical axis direction. Let d3a and d3b be the maximum distances occupied by.

  When comparing the lens driving distances d1a and d1b with the same length in FIGS. 7A and 7B, the dimensions d1a and d1b in the optical axis direction of the movable part depend on the dimensions in the driving direction of the vibrator. ) Uses a small ultrasonic motor 1 in the driving direction, and d2a is smaller than d2b. For this reason, d3a is smaller than d3b in distances d3a and d3b occupied by the movable portion in the optical axis direction when the lens moves. Since d2a and d3b are smaller than d2b and d3b, the lens barrel 51 that drives the lens using the ultrasonic motor 1 can be reduced in size in the optical axis direction of the lens barrel or when the lens barrel is retracted. Thinning is possible.

  For the above reason, a lens driving device using the ultrasonic motor 1 such as the above-described lens barrel 51 is preferable.

  Note that one of the vibrator 11 and the driven member 12 is connected to the fixed side and the other is connected to the movable side to drive the object as a motor. The lens barrel 51 shown in FIG. 6 is an example in which the vibrator 11 is connected to the vibrator holder 514 on the movable side via the holding member 13. The vibrator 11 is excited in the first resonance mode or the second resonance mode, and there is a possibility that the vibration is hindered depending on the connection position of the holding member 13. For example, in the first resonance mode and the second resonance mode, if the holding member 13 is connected to a position where the displacement amount is large, the vibration is hindered and the driving efficiency is lowered.

  On the other hand, if the holding member 13 is connected to a position where the amount of displacement is small in the first resonance mode or the second resonance mode, the above-described reduction in efficiency can be prevented. In the first resonance mode, the position with the least displacement is in the vicinity of the vibration node indicated by N in FIG. In the second resonance mode, the position with the least displacement is in the vicinity of the vibration node indicated by N in FIG. In the vibrator 11 of the ultrasonic motor 1, since the first resonance node and the second resonance node coincide with each other, the holding member 13 may be connected and held in the vicinity of the two resonance nodes. FIG. 8 shows a state in which the holding member 13 is connected to the vibrator 11.

  In the vibrator 11, the node of the first resonance mode (N in FIG. 1B) and the node of the second resonance mode (N in FIG. 1C) are held at the position (H in FIG. 8). The member 13 is connected. The holding member 13 is a thin flat plate-like member, for example, and stainless steel is used as the material.

  The holding member 13 is provided with a fixing portion 13a, and is connected to a connection target via the fixing portion 13a. The fixing portion 13a is a through hole, for example, and is fixed to the connection target by screw fastening or the like. However, the holding member 13 may be manufactured separately from the elastic body 112 of the vibrator 11 and fixed by adhesion or welding, or may be manufactured integrally with the elastic body 112.

  The vibrator 11 is an example in which the node of the first resonance mode and the node of the second resonance mode coincide with each other, but the node of the first resonance mode and the node of the second resonance mode do not necessarily coincide with each other. When the nodes of the first resonance mode and the second resonance mode do not coincide with each other, at least the vicinity of the node of one resonance mode is preferably maintained. For the above reasons, it is preferable that the holding portion between the other member and the vibrator 11 holds the vicinity of at least one node of the first resonance mode or the second resonance mode.

  The contact portion 113 is provided on the vibrator 11 at a position where a large amount of displacement can be obtained in each of the first direction and the second direction, thereby increasing the driving speed and driving efficiency. In the first resonance mode, the position with the largest displacement is in the vicinity of the antinode of vibration indicated by A in FIG. In the second resonance mode, the position where the displacement is greatest is in the vicinity of the antinode of vibration indicated by A in FIG.

  In the vibrator 11 of the ultrasonic motor 1, the antinodes of the first resonance and the antinodes of the second resonance coincide with each other. Therefore, the contact portion 113 is preferably provided at the position of the antinodes of the two resonances. However, the antinodes of the second resonance mode and the second resonance mode do not necessarily coincide with each other. When the antinodes of the first resonance mode and the second resonance mode do not coincide with each other, the antinodes of at least one of the resonance modes are in contact with each other. A portion 113 may be provided. For the above reasons, the contact portion 113 is preferably provided in the vicinity of at least one antinode of the first resonance mode or the second resonance mode.

  In order to decrease the resonance frequency of the first resonance mode and increase the amplitude, it is preferable that the dimension W in the first direction is small as described above. Similarly, by reducing the dimension T in the second direction and increasing the dimension in the third direction, the resonance frequency of the first resonance mode can be lowered and the amplitude can be increased. In consideration of the above, it is preferable that the vibrator 11 has a small dimension W in the first direction, a small dimension T in the second direction, and a large dimension L in the third direction. It is preferable that the dimension L in the first direction is larger than the dimension W in the first direction and the dimension T in the second direction.

  As described above, the vibrator 11 preferably has a large dimension L in the third direction. In the vibrator 11 having such a shape, a vibration having a displacement in the second direction and having a low resonance frequency and a large amplitude includes bending vibration in the direction. For the above reasons, the second resonance mode is preferably bending vibration.

  In addition, when the bending primary vibration is used in the bending vibration as the second resonance mode like the vibrator 11 of the ultrasonic motor 1, the bending resonance primary vibration in which the first resonance mode and the second resonance mode are different in direction. It is. At this time, resonance nodes substantially coincide as indicated by N in FIGS. 1B and 1C, and resonance antinodes substantially coincide as indicated by A in FIGS. 1B and 1C. For this reason, the above-mentioned holding part can be provided at a position where the displacement is the smallest in the first resonance mode and the displacement is the smallest in the second resonance mode. Further, the contact portion 113 can be provided at a position where the displacement is the largest in the first resonance mode and the displacement is the largest in the second resonance mode. For the above reason, the second resonance mode is preferably a primary vibration.

  Next, the ultrasonic motor 2 which is the 2nd Embodiment of this invention is demonstrated.

(Second Embodiment)
FIG. 9A shows the configuration of the ultrasonic motor 2 according to the second embodiment of the present invention. The ultrasonic motor 2 includes a vibrator 21 and a driven member 22. The vibrator 21 has the piezoelectric element 211 as in the first embodiment, and the resonance mode is excited in the vibrator 21 by the expansion and contraction of the piezoelectric element 211. In this structure, a rectangular piezoelectric element 211 is attached with a contact portion 213 that comes into contact with another member and generates a frictional force.

  The description of the driven member 22, the holding method of the driven member 22, the description of the urging force F by the urging means (not shown), and the definitions of the first, second, and third directions are the same as in the first embodiment. . The shape of the vibrator, the material of the piezoelectric element and the driven member, examples of the biasing means, and the example of the method for holding the driven member are the same as those in the first embodiment. Therefore, these descriptions are omitted for convenience.

  FIGS. 9B and 9C are diagrams showing resonance modes excited by the vibrator 21. FIG. FIG. 9B shows a state of the first resonance mode in which the contact portion 213 of the vibrator 21 is displaced in the first direction. The present embodiment is also characterized in that a bending primary vibration is used as the first resonance mode. FIG. 9C shows a state of the second resonance mode in which the contact portion 213 of the vibrator 21 is displaced in the second direction. The elliptical motion is generated in the contact portion 213 using the first resonance mode and the second resonance mode, as in the first embodiment.

  Note that the shape, configuration, and material of the vibrator are not limited to those described above, and it is only necessary to excite the bending primary vibration as the first resonance mode in the vibrator 21 by the expansion and contraction of the piezoelectric element 211 as in the first embodiment. is there.

  FIG. 10 is a diagram for explaining a method of driving the ultrasonic motor 2 by exciting the vibration shown in FIGS. 9B and 9C.

  First, an electrode pattern for applying a voltage to the piezoelectric element 211 will be described with reference to FIG. In the ultrasonic motor 2, the vibrator 21 uses a piezoelectric element 211 in which two piezoelectric element layers are laminated in the second direction, and the upper and lower surfaces of the piezoelectric element 211 and the boundary between the laminated piezoelectric element layers. An electrode is provided in the layer. FIG. 10A-2 is a front view of the vibrator 21. FIG. FIG. 10A-1 is a top view of the vibrator 21 and shows an electrode pattern on the top surface of the piezoelectric element 211. FIG. FIG. 10A-3 is a sectional view of the boundary layer of the piezoelectric element layer (a sectional view taken along line BB in FIG. 10A-2), showing an electrode pattern provided in the boundary layer. FIG. 10A-4 shows an electrode pattern on the bottom surface of the piezoelectric element 211. FIG.

  As shown in FIGS. 10A-1 and 10A-4, the electrodes 211a, 211b, 211c, and 211d, which are divided into two in the short side direction, are disposed on the top and bottom surfaces of the piezoelectric element 211, respectively. Yes. As shown in FIG. 10A-3, the electrode 211e is disposed on the entire surface of the boundary layer of the piezoelectric element layer of the piezoelectric element 211. The electrode 211e is used as a common ground electrode when an AC voltage is applied to the electrodes 211a, 211b, 211c, and 211d.

  Further, an extending portion 211e 'is provided to energize the electrode 211e from the outside. The upper surface side and the bottom surface side of the piezoelectric element layer are polarized in opposite directions, the upper surface side piezoelectric element layer is polarized in the P1 direction in FIG. 10, and the bottom surface side piezoelectric element layer is polarized in the P2 direction in FIG.

  FIG. 10B shows a state in which the first resonance mode is excited in the vibrator 21. FIGS. 10B-1, B-2, and B-3 are respectively a top view, a front view, and a bottom view of the vibrator 21 excited in the first resonance mode.

  An AC voltage having the same phase is applied to the electrodes 211a and 211c, and an AC voltage having a phase opposite to that of the AC voltage applied to the electrodes 211a and 211c is applied to the electrodes 211b and 211d. At this time, one of the piezoelectric elements near the electrodes 211a and 211c and the piezoelectric elements near the electrodes 211b and 211d expands and the other contracts. By repeating this alternately, the bending primary vibration in the D1 direction in FIG. 10B can be excited. At this time, the position represented by N in FIG. 10B is a vibration node, which is the point with the least displacement. Further, the end portion and the center portion of the vibrator 21 represented by A in FIG. 10B in the second direction are antinodes of vibration, and the displacement is the largest.

  FIG. 10C shows a state in which the second resonance mode is excited in the vibrator 21. An alternating voltage having the same phase is applied to the electrodes 211a and 211b, and an alternating voltage having a phase opposite to that of the alternating voltage applied to the electrodes 211a and 211b is applied to the electrodes 211c and 211d. At this time, one of the piezoelectric elements near the electrodes 211a and 211b and the piezoelectric elements near the electrodes 211c and 211d expands and the other contracts. By repeating this alternately, the bending primary vibration in the direction D2 in FIG. 10C can be excited. At this time, the position represented by N in FIG. 10C is a vibration node, which is the point with the smallest displacement. Further, in FIG. 10C, the end portion and the center portion of the vibrator 21 represented by A in the third direction are antinodes of vibration, and the displacement is the largest.

  In the electrodes 211a, 211b, 211c, and 211d, the AC voltage for exciting the first resonance mode and the AC voltage for exciting the second resonance mode are applied to the vibrator 21 in a superimposed manner. The first resonance mode and the second resonance mode can be excited.

  In addition, although the example using the piezoelectric element 211 which laminated | stacked the two piezoelectric element layers in the 2nd direction was shown in the ultrasonic motor 2, the lamination direction may be a 1st direction. The electrode pattern is not limited to the above.

  Further, in the ultrasonic motor 2 of the second example, the resonance frequency is lower and the amplitude is smaller as the dimension in the first direction of the vibrator 21 (dimension W in FIG. 9A) is smaller as in the first embodiment. Is obtained. For the above reasons, the ultrasonic motor 2 of the second embodiment does not increase the resonance frequency and does not decrease the amplitude even when the vibrator is downsized in the driving direction (first direction).

  In the ultrasonic motor 2 according to the second embodiment of the present invention, the vibrator 21 has a structure in which the contact portion 213 is attached to the piezoelectric element 2 laminated in at least two layers. In such a structure, since the volume of the piezoelectric element is large, there is an advantage that a large stretching force is generated in the vibrator 21 and the amplitude of the first resonance mode and the second resonance mode can be increased. For the above reasons, it is preferable that the vibrator 21 has a structure in which the contact portion 213 is attached to the piezoelectric element 211 laminated in at least two layers in the biasing direction by the biasing means or in the relative movement direction with the driven member 22. One of the forms.

  For the same reason as in the first embodiment, the second resonance mode is not necessarily required for driving the driven member 22, but the driven member 22 is driven by the first resonance mode and the second resonance mode. It is preferable to do.

  Further, a lens barrel that drives the lens linearly by using the ultrasonic motor 2 using the ultrasonic motor 2 is the same as that in the first embodiment, and thus will be omitted.

For the same reason as in the first embodiment, it is preferable that the vibrator 21 holds the vicinity of at least one node of the first resonance mode or the second resonance mode.
Further, for the same reason as in the first embodiment, the contact portion 213 is preferably provided in the vicinity of at least one antinode of the first resonance mode or the second resonance mode.

As the shape of the vibrator 21, the dimension L in the third direction is preferably larger than the dimension W in the first direction and the dimension T in the second direction.
For the same reason as in the first embodiment, the second resonance mode is preferably bending vibration.
For the same reason as in the first embodiment, the second resonance mode is preferably a primary vibration.

  INDUSTRIAL APPLICABILITY The present invention can be used for lens driving or the like in a lens barrel of a camera that requires a small and high output motor.

DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2 Ultrasonic motor 11 Vibrator 111 Piezoelectric element 112 Elastic member 113 Contact part 12 Driven member 21 Vibrator 211 Piezoelectric element 213 Contact part 22 Driven member

Claims (9)

A vibrator having a piezoelectric element;
A contact portion provided on the vibrator;
A driven member held in contact with the contact portion so as to be movable relative to the vibrator in a first direction;
An urging means for urging the contact portion and the driven member by an urging force in a second direction perpendicular to a contact surface between the contact portion and the driven member;
In the vibrator, a dimension in a third direction orthogonal to the first direction and the second direction is larger than a dimension in the first direction, and the contact portion has a displacement in the first direction. Using the resonance mode of 1 to move the driven member relative to the vibrator in the first direction;
The ultrasonic motor, wherein the first resonance mode is a bending primary vibration. The transducer includes a first resonance mode relative to the driven member in the first direction relative to the vibrator by a second resonance mode in which the contact portion has a displacement in the second direction The ultrasonic motor according to claim 1, wherein the ultrasonic motor is moved . Ultrasonic motor according to claim 2, characterized in that for holding the vicinity of at least one section of the said oscillator and the first resonance mode and the second resonance mode. Ultrasonic motor according to claim 2 or 3, characterized in that the contact portion is provided in the vicinity of at least one belly of the first resonance mode and the second resonance mode in the vibrator. The ultrasonic motor according to any one of claims 2 to 4, wherein the second resonance mode is a bending vibration. Ultrasonic motor according to any one of claims 2 to 5, wherein the second resonant mode is a vibration of the primary. Ultrasonic motor according to any one of claims 1 to 6 wherein the transducer is characterized by a structure in which stuck the elastic member to the piezoelectric element. Any The vibrator of claims 1 to 6, characterized in that a structure in which stuck the contact portion to the piezoelectric element laminated on at least two layers in the relative movement direction of the biasing direction or the driven member The ultrasonic motor of Claim 1. Lens driving device using the ultrasonic motor according to any one of claims 1 to 8.

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