JP2017055554A - Vibration actuator, lens unit, and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable driving performance.SOLUTION: The vibration actuator includes: an electromechanical transducer for converting electric power into mechanical vibrations; a vibrating part which is vibrated by the electromechanical transducer; a contact part which is in contact with the vibrating part and moves relative to the vibrating part by vibrations. The contact part has a contact surface which is in contact with the vibrating part, and a side surface which is in contact with the vibrating part and provided in a direction crossing the contact surface. The side surface is provided with a layer containing a lubricant.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vibration actuator, a lens unit, and an imaging apparatus.

  Vibration actuators that convert electric power into mechanical vibrations are known. For example, in an ultrasonic motor, in order to improve starting characteristics, it has been proposed to bond a slider material to the surface of a rotor that contacts the stator (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 5-137358

  The vibration actuator of the present invention is an electromechanical conversion unit that converts electric power into mechanical vibration, a vibration unit that vibrates by the electromechanical conversion unit, and contacts with the vibration unit and moves relative to the vibration unit by vibration. A contact portion, and the contact portion has a contact surface in contact with the vibration portion, and a side surface provided in a direction adjacent to the contact surface and intersecting the contact surface, and a layer including a lubricant is provided on the side surface. It has been.

  The lens unit of the present invention includes the vibration actuator and a lens driven by the vibration actuator.

  The imaging apparatus of the present invention includes the vibration actuator, a lens driven by the vibration actuator, and an imaging element that captures a subject image formed by an optical component including the lens.

2 is a schematic cross-sectional view showing the entire vibration actuator 100. FIG. It is an enlarged view of the A section in FIG. 3 is a perspective view of an electromechanical conversion unit 22. FIG. FIG. 6 is a diagram for explaining the operation of the piezoelectric laminate 20. It is a graph which shows the change of the rotation speed of the rotor with respect to the rotation time of the rotor after leaving for 30 minutes in the state which does not drive. It is a graph which shows the change of the friction coefficient of the contact part 42 and the stator 30 with respect to the waiting time of a vibration actuator. It is a graph which shows the change of the oxygen concentration of the iron powder which remained on the stator with respect to waiting time. It is a table | surface which shows stand-up performance and the presence or absence of the oxidation of iron powder. The amount of wear of the stator 30 after driving for 60 minutes is shown. The enlarged view of another contact part is shown. 2 is a schematic cross-sectional view of a camera 200 including a vibration actuator 100. FIG. 2 is a schematic diagram of an optical apparatus 300 including a vibration actuator 101. FIG. FIG. 6 is a perspective view of an assembly in which an electromechanical conversion unit 322 and a transmission unit 331 are integrated. 6 is a schematic diagram for explaining the operation of the vibration actuator 101. FIG. 3 is a side view of the vibration actuator 102. FIG. 4 is a perspective view of an assembly of an electromechanical conversion unit 422 and a transmission unit 431 of the vibration actuator 102 and an abutting unit 442 of a rotor 440. FIG. FIG. 6 is a development view for explaining the operation of the vibration actuator 102.

  FIG. 1 is a schematic cross-sectional view showing the entirety of the vibration actuator 100. In the following description, the direction of each element is described with the upper side in the figure as “up” and the lower side in the figure as “down”. However, these descriptions do not mean that the vibration actuator 100 is used only in the illustrated direction.

  The vibration actuator 100 includes a shaft portion 90 as a central axis, a base plate 10 that is sequentially stacked upward with the shaft portion 90 as a center, a piezoelectric laminate 20, a stator 30, a rotor 40, and an output gear 60. And a top plate 80. The base plate 10 is coupled to the lower end of the shaft portion 90. The top plate 80 is tightened downward by the nut 92 along the axial direction of the shaft portion 90. The piezoelectric laminate 20, the stator 30, the rotor 40, and the output gear 60 are sandwiched between the base plate 10 and the top plate 80 and pressed against each other in the axial direction of the shaft portion 90.

  The piezoelectric laminate 20 includes a plurality of electromechanical transducers 22 laminated together in the thickness direction, and is supported from below by the base plate 10. A stator 30 is overlaid on the upper surface of the piezoelectric laminate 20. Thereby, the stator 30 is supported by the piezoelectric laminate 20 from below. The upper surface of the stator 30 forms a contact surface with the rotor 40.

  The stator 30 is coupled to the lower end of the vibrating body 32 arranged coaxially with the shaft portion 90. Thereby, when the stator 30 swings, the vibrating body 32 also swings integrally. When the swing of the stator 30 is regarded as vibration, the vibrating body 32 forms a single vibration system together with the stator 30. Therefore, when the dimensions and mass of the vibrating body 32 are changed, the natural frequency of the stator 30 also changes. The stator 30 is an example of a vibration part.

  The rotor 40 abuts on the upper surface of the stator 30 via the contact portion 42. The contact part 42 is fixed to the rotor 40, and rotates together with the rotor 40 when the rotor 40 rotates around the shaft part 90. Further, the contact portion 42 has elasticity, and is deformed when an external force is applied. For this reason, even when the stator 30 vibrates in the axial direction of the shaft portion 90, the contact portion 42 is deformed following the contact surface, so that contact with the stator 30 is maintained.

  The upper end of the rotor 40 engages with the lower portion of the output gear 60 in the rotation direction with the shaft portion 90 as the rotation axis. As a result, when the rotor 40 rotates with the shaft portion 90 as the rotation axis, the output gear 60 also rotates accordingly.

  The output gear 60 is pivotally supported from the shaft portion 90 via the bearing portion 70. As a result, even when a load is applied to the output gear 60, the output gear 60 rotates smoothly around the shaft portion 90. A pinion gear is cut on the outer periphery of the output gear 60, and the output gear 60 can output the rotation of the output gear 60 to the outside.

  The pressurizing unit 50 is, for example, a coil spring biased in the extending direction, and the upper end thereof abuts on the lower surface of the output gear 60. The lower end of the pressurizing part 50 abuts on a step formed upward on the inner surface of the rotor 40.

  The output gear 60 has a step formed upward on the inner surface. The step formed upward of the output gear 60 contacts the lower surface of the bearing portion 70. Since the upper surface of the bearing portion 70 is in contact with the top plate 80, the output gear 60 is not displaced upward. Therefore, the pressurizing unit 50 whose upper end is in contact with the output gear 60 urges the rotor 40 whose lower end is in contact toward the stator 30.

  FIG. 2 is an enlarged view of a portion A in FIG. The contact portion 42 has a contact surface 120 that contacts the stator 30, and side surfaces 122 and 124 that are adjacent to the contact surface 120 and provided in a direction intersecting the contact surface 120. A resin layer 110 containing a lubricant is formed on the side surface 122 of the contact portion 42, and a resin layer 112 containing the lubricant is also formed on the side surface 124.

  The thickness of the resin layers 110 and 112 is determined in a direction orthogonal to the relative movement direction of the contact portion 42 with respect to the stator 30. The contact portion 42 rotates about the shaft portion 90 with respect to the stator 30. Therefore, the direction orthogonal to the relative movement direction with respect to the stator 30 is a direction toward the left and right outer sides around the shaft portion 90 in FIG. Therefore, the thickness of the resin layer 110 is the dimension 114, and the thickness of the resin layer 112 is the dimension 116.

  In the vibration actuator 100, the dimension 114 is 10 μm and the dimension 116 is 10 μm. The dimension 44, which is the thickness of the contact portion 42, is 80 μm. Therefore, the thickness of the resin layers 110 and 112 is 25% of the thickness 44 of the contact portion 42. The thickness of the resin layer is preferably 15% or more and less than 30% with respect to the thickness of the contact portion 42. When the thickness of the resin layer is made smaller than 15% with respect to the thickness of the contact portion 42, the effect of preventing iron powder to be described later is reduced. Further, even if the thickness of the resin layer is set to 30% or more with respect to the thickness of the contact portion 42, the effect of preventing the iron powder from being oxidized cannot be enhanced, and the manufacturing cost of the vibration actuator 100 is improved.

  Further, the contact portion 42 is worn more than the stator 30 due to contact with the stator 30. For example, the contact portion 42 is formed of stainless steel, and the stator 30 is formed of ceramic. In general, since stainless steel has a lower hardness than ceramic, the contact portion 42 wears more than the stator 30 due to contact with the stator 30.

  The contact surface of the contact portion 42 has a hole that forms a gap with the stator 30. Ceramics inevitably contain voids because they are produced by a solid phase reaction of raw material powders. For this reason, a space is formed on the surface of the stator 30 formed of ceramics.

  As an example of ceramics, ceramics sintered using powders of metal oxides, metal nitrides, metal carbides and the like as raw materials can be used. More specifically, any of aluminum oxide, zirconium oxide, magnesium oxide, silicon oxide, titanium nitride, silicon carbide, and silicon nitride, or a material containing two or more of these can be used. In this embodiment, zirconium oxide was used.

As examples of stainless steel, martensitic stainless steels such as SUS431, 403, 410, 420, and 440 can be used in addition to SUS420J2 that can be used as an elastic material by baking. Further, depending on the specification of the vibration actuator 100, other stainless steel such as austenitic stainless steel such as SUS304, iron-based alloy, or the like may be used. In this embodiment, SUS420J2 was used.
As the lubricant contained in the resin layers 110 and 112, a fluorine-based resin can be used. More specifically, PTFE (tetrafluoroethylene resin), PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), FEP (perfluoroethylene-propylene copolymer), ETFE (ethylene-tetrafluoroethylene copolymer) Coalescence), PCTFE (polychlorotrifluoroethylene), ECTFE (ethylene-chlorotrifluoroethylene copolymer), PVDF (polyvinylidene fluoride), PVF (polyvinyl fluoride), TFE / PDD (tetrafluoroethylene-perfluoro) Any of the dioxole copolymers) or a material containing two or more of these can be used. In this embodiment, an FC-103 heat resistant TFE coat manufactured by Fine Chemical Co., which contains PTFE was used.

  Next, a method for forming the resin layer will be described using the resin layer 110 as an example. First, the contact part 42 washed with ethanol and dried is prepared, and masking is performed on a region where the resin layer 110 is not formed. Next, PTFE is uniformly applied to the side surface 122 of the contact portion 42 using an FC-103 heat-resistant TFE coat. When the weight of the contact portion 42 is increased by 2 mg due to the application of PTFE, baking is performed at 200 ° C. for 20 minutes using an oven. In this manner, a resin layer 110 having a thickness of 10 μm containing a solid PTFE lubricant was formed on the side surface 122 of the contact portion 42. The coating amount of 2 mg is the weight of PTFE necessary to make the film thickness 10 μm, calculated from the coating area and the density of PTFE.

  Note that the fluorine resin may be applied to the contact portion 42 by immersing the contact portion 42 in the solution in which the fluorine resin is dissolved. In addition, the thickness of the resin layer 110 may be adjusted by forming it to be thicker than a predetermined thickness, and then shaving it to a predetermined thickness.

  FIG. 3 is a perspective view of the electromechanical transducer 22 that forms the piezoelectric laminate 20. Each of the electromechanical conversion units 22 includes a piezoelectric material plate 24, drive electrodes 21, 23, 25, and 27 and a common electrode 26, and converts electric power into mechanical vibration.

  The piezoelectric material plate 24 is a disk-shaped member made of a piezoelectric material such as PZT. The lower surface of the piezoelectric material plate 24 is covered with a common electrode 26. On the upper surface of the piezoelectric material plate 24, a plurality of drive electrodes 21, 23, 25, 27 arranged in a circumferential direction are arranged. The drive electrodes 21, 23, 25, 27 and the common electrode 26 are formed by directly attaching an electrode material such as nickel or gold to the surface of the piezoelectric material by a method such as plating, vapor deposition, or thick film printing.

  Thereby, for example, when the common electrode 26 is fixed to the ground potential and the drive voltage is applied to any one of the drive electrodes 21, 23, 25, 27, the region is limited to the region of the drive electrodes 21, 23, 25, 27 The thickness of the piezoelectric material plate 24 changes.

  The piezoelectric laminate 20 is formed by laminating a plurality of electromechanical transducers 22 as described above via an insulating layer. In the plurality of electromechanical transducers 22 of the piezoelectric laminate 20, the same drive voltage is applied to the drive electrodes 21, 23, 25, and 27 at the same position at the same timing.

  4A to 4D are views for explaining the operation of the piezoelectric laminate 20 in the vibration actuator 100. FIG. In the piezoelectric laminate 20, when a driving voltage is selectively applied to any of the plurality of driving electrodes 21, 23, 25, 27 of the electromechanical conversion unit 22, the position of the driving electrodes 21, 23, 25, 27 is determined. In FIG. 2, the change in the thickness of the piezoelectric material plate 24 is superimposed. Thereby, the inclination of the stator 30 with respect to the base plate 10 changes greatly.

  In the state shown in FIG. 4A, a voltage for extending the piezoelectric body is applied to the drive electrode 27 on the front side of the paper, and a voltage for contracting the piezoelectric body is applied to the drive electrode 23 on the back side of the paper. As a result, the stator 30 that was initially parallel to the base plate 10 is inclined rearward as shown in the drawing.

  Next, when the stator 30 is viewed from above, the drive electrodes 21, 23, 25, and 27 to which the voltage is applied are sequentially switched clockwise, as shown in FIGS. 4 (b) to 4 (d), The direction in which the stator 30 tilts can be rotated clockwise. Note that when the order of applying the voltages is reversed, the rotation direction of the inclination of the stator 30 is reversed.

  Referring again to FIG. 1, in the vibration actuator 100, the rotor 40 is biased by the pressurizing unit 50, so that the contact unit 42 is constantly pressed against and in contact with the stator 30. For this reason, the rotor 40 obtains a frictional driving force from the stator 30 that swings while rotating in the tilt direction, and rotates relative to the stator 30.

  At this time, the rotor 40 rotates in the direction opposite to the rotation of the stator 30 in the tilt direction. Therefore, when the vibration actuator 100 is looked down from above, when the tilt direction of the stator 30 is rotated clockwise as described above, the rotation direction of the rotor 40 is counterclockwise. Thus, the vibration actuator 100 in which the rotor 40 rotates when the driving voltage is supplied to the piezoelectric laminate 20 is formed.

  Note that the frequency of the drive voltage of the vibration actuator 100 is preferably close to the natural frequency of a portion that vibrates when the vibration actuator 100 operates, such as the piezoelectric laminate 20, the stator 30, the vibration body 32, and the shaft portion 90. Thereby, a driving force can be efficiently generated with respect to the input electric power.

  The rotational driving force generated by the vibration actuator 100 is generated by the frictional force between the stator 30 and the rotor 40. Here, according to the principle of “F (friction force) = μ (friction coefficient) × N (load load)”, the relationship of friction force F∝friction coefficient μ is established if the load N is constant. Therefore, in the vibration actuator 100, the driving force can be improved and the output torque can be increased by increasing the friction between the stator 30 and the rotor 40 by increasing the biasing force of the pressurizing unit 50.

  Next, in a vibration actuator in which the resin layers 110 and 112 are not provided, a description will be given of a situation in which stable driving performance cannot be obtained if the vibration actuator is left driven without being driven and then driven again. FIG. 5 is a graph showing a change in the number of rotations of the rotor with respect to the rotation time of the rotor after being left for 30 minutes without being driven, and shows a case where driving is performed three times in succession. In FIG. 5, the vertical axis represents the rotation speed [rpm], and the horizontal axis represents the rotation time [sec]. From the graph of FIG. 5, it can be seen that in the vibration actuator not provided with the resin layers 110 and 112, the rotor 40 hardly rotates for 0.4 seconds from the start of rotation in the first drive. Thereafter, the rotor 40 gradually begins to rotate, and reaches a rotational speed close to 150 rpm after about 5 seconds.

  In the second measurement performed immediately after the first measurement, the rotational speed of 150 rpm or more has been reached after 0.1 seconds. Further, in the third measurement performed immediately after the second measurement, the rotation speed reaches 150 rpm or more after 0.1 second. Therefore, if the vibration actuator without the resin layers 110 and 112 is left in a state where it is not driven for 30 minutes, the rotational speed of the rotor 40 does not increase in the subsequent first drive, and the drive performance of the vibration actuator is stable. It turned out to be no longer.

  FIG. 6 is a graph showing changes in the friction coefficient between the contact portion 42 and the stator 30 with respect to the standby time of the vibration actuator. In FIG. 6, the vertical axis represents the friction coefficient, and the horizontal axis represents the standby time [min]. It can be seen from the graph of FIG. 6 that the friction coefficient between the contact portion 42 and the stator 30 decreases with the standby time. Specifically, the friction coefficient decreased from 0.8 to 0.4 with a waiting time of 60 minutes. Such a decrease in the coefficient of friction due to the standby time is considered to be a cause of difficulty in increasing the rotational speed of the rotor 40 at the start of driving as shown in FIG.

  FIG. 7 is a graph showing a change in the oxygen concentration of iron powder remaining on the stator with respect to the standby time. In FIG. 7, the vertical axis represents the oxygen concentration [a. u. ] (Arbitrary unit), and the horizontal axis is the waiting time [min]. From the graph of FIG. 7, the oxygen concentration of the iron powder increases with the waiting time, and the oxygen concentration becomes 0.60 a. u. To 0.67a. u. Increased to. Thus, both the increase in the oxygen concentration and the decrease in the friction coefficient were changed in the standby time of 60 minutes, and the tendency of the change was consistent. From this, it was considered that the friction coefficient between the contact portion 42 and the stator 30 was lowered due to the oxidation of the iron powder interposed between the contact portion 42 and the stator 30. The results shown in FIGS. 5, 6, and 7 use the same vibration actuator as the vibration actuator 100 except that the resin layers 110 and 112 are not formed.

  FIG. 8 is a table showing the rising performance and the presence or absence of iron powder oxidation. In FIG. 8, “○” in the column of “rise performance” indicates that the rotational speed approaching 150 rpm has been reached after 0.1 seconds from the start of driving even after being left undriven for 1 hour, and “×” indicates the start of driving. After 0.1 second, the rotation was hardly observed. In FIG. 8, “O” in the “Oxidation presence / absence” column indicates that the oxidation of the iron powder existing on the stator 30 is suppressed, and “X” indicates that the oxidation of the iron powder existing on the stator 30 is suppressed. Indicates no.

  As shown in the table of FIG. 8, the vibration actuator 100 on which the resin layers 110 and 112 were formed had a rotation speed of 150 rpm after 0.1 seconds even when left for 1 hour without being driven. On the other hand, in the vibration actuator in which the resin layers 110 and 112 are not formed, only about 10 rpm was obtained after 0.1 second as shown in FIG. Further, in the vibration actuator 100 in which the resin layers 110 and 112 are formed, the oxygen concentration of the iron powder existing on the stator 30 does not increase when not driven, whereas the resin layers 110 and 112 are formed. No vibration actuator showed an increase in oxygen concentration, as shown in FIG.

  In the vibration actuator 100 in which the resin layers 110 and 112 are formed, the contact portion 42 is worn by friction with the stator 30, and iron powder containing a lubricant is generated. Iron powder containing a lubricant is interposed between the stator 30 and the contact portion 42. In this state, when the contact portion 42 and the stator 30 rotate while being in contact with each other, the lubricant is spread so as to cover the periphery of the iron powder. Thereby, the oxidation of the iron powder interposed between the contact part 42 and the stator 30 is suppressed. By suppressing the oxidation, in the vibration actuator 100 in which the resin layers 110 and 112 are formed, the friction coefficient between the stator 30 and the contact portion 42 does not decrease even after being left untreated for a long time. As a result, even when left untreated for a long time, the initial drive performance does not become unstable, and a vibration actuator having stable drive performance can be realized.

  In addition, the iron powder interposed between the stator 30 and the contact portion 42 is sequentially replaced with iron powder generated thereafter by friction with the stator 30. Since the resin layers 110 and 112 containing the lubricant are formed on the side surfaces 122 and 124 of the contact portion 42, the iron powder generated by the wear contains the lubricant. Since the iron powder containing the lubricant is continuously supplied between the stator 30 and the contact portion 42, it is interposed between the stator 30 and the contact portion 42 even after the contact portion 42 is worn out after being driven for a long time. Oxidation of iron powder is suppressed. Therefore, even if the vibration actuator 100 is driven for a long period of time and left untreated for a long period of time, the driving performance does not become unstable.

  Thus, it can be said that the vibration actuator 100 of this embodiment has a short period of time until it reaches the steady rotational speed, that is, the target rotational speed, and is excellent in the rising characteristics after energization. Further, even if the vibration actuator 100 according to the present embodiment is left untreated for a long period of time, it exhibits the same drive responsiveness as before being left untreated for a long period of time. It can be said that the sex is constant.

  On the other hand, when the resin layer containing the lubricant is provided only on the contact surface 120, after the contact surface 120 is worn, iron powder not containing the lubricant is generated. Then, after the iron powder interposed between the stator 30 and the contact portion 42 is replaced with the iron powder not containing the lubricant, the oxidation of the iron powder interposed between the stator 30 and the contact portion 42 is suppressed. Not. For this reason, stable drive performance cannot be obtained after being left untreated for a long time.

  In the present embodiment, an example in which the resin layers 110 and 112 are formed on the side surfaces 122 and 124 is shown. However, the present invention is not limited to this, and the side surface on which the resin layer is formed may be either the side surface 122 or 124.

  FIG. 9 shows the amount of wear of the stator 30 after driving for 60 minutes. In FIG. 9, the vertical axis represents the wear amount [μm], and the horizontal axis represents the material of the contact portion 42 and the presence or absence of the resin layer. As shown in FIG. 9, in the vibration actuator 100 provided with the resin layers 110 and 112, the wear amount of the stator 30 after driving for 60 minutes was 0.4 μm. On the other hand, in the vibration actuator not provided with the resin layers 110 and 112, the wear amount of the stator 30 after driving for 60 minutes was 1.5 μm. Thus, it has been found that by providing the resin layers 110 and 112 on the side surfaces 122 and 124 of the contact portion 42, a vibration actuator capable of reducing the amount of wear of the stator 30 can be realized.

  FIG. 10 shows an enlarged view of another contact portion. FIG. 10A shows another contact portion 46. The portion in contact with the stator 30 in the contact portion 46 has a tapered shape in which the thickness on the side in contact with the stator 30 is reduced. In this case, the contact area with the stator 30 increases with wear of the contact portion 46. The resin layers 130 and 132 may be formed with a thickness corresponding to the contact area. For example, the contact portion 46 shown in FIG. 10A is formed so that the resin layers 130 and 132 become thicker upward corresponding to the contact portion 46 becoming thicker toward the upper side. .

  When the contact portion 46 wears due to friction with the stator 30, the contact area between the stator 30 and the contact portion 46 increases. Thus, the thickness of the resin layers 130 and 132 is changed according to the contact area that changes due to the wear of the contact portion 46, and the ratio of the thickness of the resin layer to the contact area is within a predetermined range, for example, 15 % Or more and less than 30%. Thereby, even if the contact part 46 is worn out, the lubricant can be supplied at the same rate with respect to the contact area, so that the iron powder can be stably prevented from being oxidized.

  FIG. 10B shows another contact portion 48. In the other contact portion 48, the resin layer 130 further includes a protective layer 136 that covers the outside of the resin layer 130. The resin layer 132 further includes a protective layer 138 that covers the outside of the resin layer 132. As described above, the resin layer may include the protective layers 136 and 138 that cover the outside of the resin layer. By providing the protective layers 136 and 138, peeling of the resin layers 130 and 132 can be prevented. Further, the resin layers 130 and 132 may contain a curing agent to increase the hardness of the resin layers 130 and 132. Glass fiber can be used as the curing agent.

  FIG. 11 is a schematic cross-sectional view of a camera 200 provided with the vibration actuator 100. The camera 200 includes a lens unit 202 and a camera body 201.

  The lens unit 202 is detachably attached to the camera body 201 via the mount system 203. The lens unit 202 includes an optical system 280 composed of optical components such as lenses, a lens barrel 270 that houses the optical system 280, and a vibration actuator 100 that is provided inside the lens barrel 270 and drives the optical system 280. Prepare.

  The optical system 280 includes a front sphere 282, a variable power lens 284, a focusing lens 286, and a main lens 288, which are sequentially arranged from the incident end corresponding to the left side in the drawing. A diaphragm device 290 is disposed between the focusing lens 286 and the main lens 288.

  The vibration actuator 100 is disposed in the middle of the lens barrel 270 in the optical axis direction and below the focusing lens 286 having a relatively small diameter. Accordingly, the vibration actuator 100 is accommodated in the lens barrel 270 without increasing the diameter of the lens barrel 270. For example, the vibration actuator 100 moves the focusing lens 286 forward or backward in the direction of the optical axis X.

  The camera body 201 houses the viewfinder 240, the control unit 250, and the main mirror 262. The main mirror 262 is provided with an oblique position that is inclined on the optical path of the subject light beam incident through the optical system 280 of the lens unit 202 and a retreat position that is lifted while avoiding the subject light beam (indicated by a dotted line in the figure). ).

  The main mirror 262 in the oblique position guides most of the subject light flux to the focusing plate 266 disposed above. The focus plate 266 is in an optically conjugate position with the image sensor 220, and the subject image formed on the focus plate 266 is observed as an erect image from the viewfinder 240 through the pentaprism 248. Further, a part of the subject luminous flux is guided to the photometry unit 252 by the pentaprism 248. The photometry unit 252 measures the intensity and distribution of the subject luminous flux according to the subject brightness.

  The finder 240 includes an eyepiece 242, a finder display 244 and a half mirror 246. The finder display unit 244 generates a display image representing information such as the shooting conditions set in the camera 200. The half mirror 246 superimposes the display image generated on the finder display unit 244 on the image on the focusing screen. Accordingly, the user can observe the subject image formed on the focusing screen 266 and the display image formed on the finder display unit 244 together from the eyepiece unit 242.

  The main mirror 262 has a sub mirror 264 on the back surface. The sub mirror 264 guides a part of the subject light beam that has passed through the half mirror part of the main mirror 262 to the focusing part 254 disposed below. Thereby, when the main mirror 262 is in the oblique position, the in-focus position of the in-focus lens 286 is detected. When the main mirror 262 moves to the retracted position, the sub mirror 264 also retracts from the subject light beam.

  In the camera body 201, a shutter 230, an optical filter 222, and an image sensor 220 are sequentially arranged behind the main mirror 262 with respect to the lens unit 202. When the shutter 230 is opened, the main mirror 262 moves to the retracted position immediately before that, so that the subject luminous flux goes straight and enters the image sensor 220. As a result, the image formed by the incident light is converted into an electrical signal in the image sensor 220.

  In the camera 200, the lens unit 202 is also electrically coupled to the camera body 201. Accordingly, the lens unit 202 receives supply of power from the camera body 201 and operates in cooperation with the camera body 201 under the control of the control unit 250 of the camera body 201. Therefore, for example, the autofocus mechanism can be formed by controlling the rotation amount and the rotation direction of the vibration actuator 100 based on the information on the distance to the subject detected by the focusing unit 254 on the camera body 201 side.

  Although the case where the focusing lens 286 is moved by the vibration actuator 100 is illustrated, the vibration actuator 100 may drive the opening / closing of the aperture device 290, the movement of the variator lens in the variable power lens 284, and the like. Also in this case, the vibration actuator 100 contributes to automation of exposure, execution of a scene mode, execution of bracket photography, and the like by referring to information with the photometric unit 252 and the finder display unit 244 via an electrical signal. .

  The vibration actuator 100 can also be used for applications other than optical systems such as a photographing machine and binoculars. For example, a precision stage, more specifically, an electron beam drawing apparatus, various stages for an inspection apparatus, a moving mechanism of a cell injector for biotechnology, a power source such as a moving bed of a nuclear magnetic resonance apparatus, and the like can be exemplified.

  FIG. 12 is a schematic diagram of an optical device 300 including the vibration actuator 101. The optical apparatus 300 includes an optical component 302, a holding frame 304, a guide shaft 306, and the vibration actuator 101.

  The holding frame 304 holds an optical component 302 such as a lens. The holding frame 304 is slidably supported by being inserted through the pair of guide shafts 306. The guide shafts 306 are arranged in parallel to each other in the optical axis direction of the optical component 302.

  The holding frame 304 has a cylindrical shape as a whole, but has a flat contact surface 308 in the lower part of the side peripheral surface in the figure. The contact surface 308 is formed in parallel with the axial direction of the guide shaft 306 and forms a part of the vibration actuator 101. The contact surface 308 may be formed by processing a part of the holding frame 304, or may be formed by adding another member to the side peripheral surface of the holding frame 304.

  The vibration actuator 101 further includes an electromechanical conversion unit 322 and a transmission unit 331. The electromechanical conversion unit 322 and the transmission unit 331 are arranged on the lower side in the drawing with respect to the holding frame 304 and abut on a contact surface 308 located on the side peripheral surface of the holding frame 304.

  In the vibration actuator 101, the electromechanical conversion unit 322 and the transmission unit 331 transmit driving force to the contact surface 308 of the holding frame 304 in a state where the relative position with respect to the guide shaft 306 is fixed. As a result, the optical component 302 moves in the optical axis direction along the guide shaft 306 together with the holding frame 304. As a result, the characteristics of the optical system including the optical component 302 change.

  FIG. 13 is a perspective view of an assembly in which the electromechanical conversion unit 322 and the transmission unit 331 are integrated. The transmission unit 331 has a rectangular plate shape, and has an electromechanical conversion unit 322 on the lower surface in the drawing. On the upper surface of the transmission portion 331, a pair of projection portions 342 that are spaced apart in the longitudinal direction and project upward in the figure are provided. In the optical device 300, the tip of the protrusion 342 contacts the contact surface 308 of the holding frame 304.

  The electromechanical conversion unit 322 includes a pair of piezoelectric blocks formed of a piezoelectric material. The piezoelectric blocks are spaced apart from each other in the longitudinal direction of the transmission portion 331. The pair of piezoelectric blocks are insulated from each other, and a driving voltage can be applied individually. As a result, the transmission portion 331 can be deformed while being in contact with the contact surface 308 of the holding frame 304.

FIG. 14 is a schematic diagram for explaining the operation of the vibration actuator 101. In FIG 14, (A) sequence, the driving voltage A two-phase applied to the pair of piezoelectric block, the change in the effective value of B, submitted over time, from the timing t ₁ to timing t _9. The drive voltages A and B periodically change in a state where the phases are shifted by 90 degrees.

  In FIG. 14, column (B) shows temporal changes in lateral vibration generated in the transmission unit 331 by the electromechanical conversion unit 322 to which the drive voltages A and B are applied. Here, the lateral vibration means vibration that causes displacement in a direction perpendicular to the longitudinal direction of the transmission unit 331 when the transmission unit 331 is bent and deformed by the electromechanical conversion unit 322 expanding and contracting with a phase difference. The transmission unit 331 has a fourth-order transverse vibration mode with respect to the fluctuation cycle of the drive voltages A and B.

  In FIG. 14, column (C) shows temporal changes in longitudinal vibration generated in the transmission unit 331 by the electromechanical conversion unit 322 to which the drive voltages A and B are applied. Here, the longitudinal vibration means vibration that causes displacement in the longitudinal direction of the transmission unit 331 as the transmission unit 331 expands and contracts with expansion and contraction of the electromechanical conversion unit 322. The transmission unit 331 has a primary longitudinal vibration mode with respect to the fluctuation cycle of the drive voltages A and B.

  In FIG. 14, column (D) shows temporal changes in elliptical motion generated at the tip of the protrusion 342 of the transmission unit 331 due to the combination of the lateral vibration and the longitudinal vibration. The protrusion 342 is disposed at the antinode position of the fourth vibration mode of the transmission unit 331. Moreover, the transmission part 331 is fixed relatively with respect to the guide shaft 306, for example in the center of a longitudinal direction. As a result, the tip of the protrusion 342 generates a driving force that pushes the contact surface 308 of the holding frame 304 in the longitudinal direction of the guide shaft 306. As a result, the holding frame 304 moves along the longitudinal direction of the guide shaft 306.

  Also in the vibration actuator 101 as described above, one of the contact surface 308 and the protrusion 342 is formed of a metal material, and the other is formed of ceramic. Then, a resin layer containing a lubricant is provided on the side surface of the member formed of the metal material. For example, in the example shown in FIG. 13, the contact surface 308 formed on the surface of the holding frame 304 is formed of a ceramic material or the like, and the transmission portion 331 integrated with the protrusion 342 is formed of a metal material. Then, a resin layer containing a lubricant is formed on the side surface 332 of the protrusion 342. As a result, a vibration actuator having a stable driving performance can be obtained even when left untreated for a long period of time.

  FIG. 15 is a side view of the vibration actuator 102. The vibration actuator 102 includes a base plate 410, a pressurization unit 450, a pressurization plate 451, an electromechanical conversion unit 422, a transmission unit 431, a rotor 440, a buffer plate 463, and an output unit 461, which are sequentially stacked from the lower side in the drawing.

  The pressurizing portion 450 is fixed to the base plate 410 at the lower end in the drawing. Further, the pressurizing unit 450 exerts an urging force that pushes the pressure plate 451 upward. The pressure plate 451 presses the electromechanical conversion unit 422 and the transmission unit 431 that are integrated with each other toward the upper rotor 440. Thereby, the transmission part 431 is pressed against the contact part 442 formed on the lower surface of the rotor 440 in the drawing.

  The rotor 440 is disposed to be rotatable with respect to the base plate 410. The rotor 440 is coupled to the output unit 461 with the buffer plate 463 interposed therebetween. As a result, of the motion generated in the rotor 440, the rotational motion is transmitted to the output unit 461, and the rotor 440 and the output unit 461 rotate integrally around the rotation axis parallel to the paper surface. Further, the vibration in the height direction generated in the rotor 440 is absorbed by the buffer plate 463. Thereby, the output part 461 can transmit a rotational motion to the exterior efficiently.

  FIG. 16 is a perspective view of the assembly of the electromechanical conversion unit 422 and the transmission unit 431 of the vibration actuator 102 and the contact unit 442 of the rotor 440. Elements that are the same as those in FIG. 15 are given the same reference numerals, and redundant descriptions are omitted.

  In the vibration actuator 102, the electromechanical conversion unit 422 includes a plurality of piezoelectric blocks arranged on the lower surface of the annular transmission unit 431 in the drawing. The plurality of piezoelectric blocks are spaced apart from each other in the circumferential direction of the transmission portion 431. The pair of piezoelectric blocks are insulated from each other, and a driving voltage can be applied individually. Thereby, the transmission part 431 can be partially deformed in a state where the contact part 442 of the rotor 440 is brought into contact.

  Moreover, the transmission part 431 has the some groove | channel 435 formed in radial direction on the upper surface in the figure. Thereby, the bending rigidity of the transmission part 431 becomes low, and the deformation | transformation of the transmission part 431 by the electromechanical conversion part 422 becomes easy.

  The rotor 440 has an annular shape as a whole, and has a contact portion 442 having a narrow radial width at the lower end. As a result, the contact portion 442 is strongly pressed against the transmission portion 431.

  FIG. 17 is a development view for explaining the operation of the vibration actuator 102. As described with reference to FIG. 16, by applying a drive voltage that periodically varies with a phase difference to the plurality of piezoelectric blocks arranged in the longitudinal direction of the transmission unit 431, Lateral vibration and longitudinal vibration can be generated.

  In the vibration actuator 102, since the transmission part 431 is annular, a traveling wave traveling in the circumferential direction is generated in the transmission part 431 by sequentially moving the position where the lateral vibration occurs. Therefore, the circumferential driving force is transmitted to the annular contact portion 442 that contacts the transmission portion 431, and the rotor 440 rotates.

  Also in the vibration actuator 102 as described above, one of the contact portion 442 and the transmission portion 431 is formed of a metal material, and the other is formed of ceramic. Then, a resin layer containing a lubricant is provided on the side surface of the member formed of the metal material. For example, in the example shown in FIG. 16, the contact portion 442 that is not deformed is formed of a ceramic material, and the transmission portion 431 that is deformed when a traveling wave is generated is formed of a metal material. Then, a resin layer containing a lubricant is formed on the side surface 432 of the transmission portion 431. As a result, even when the vibration actuator 102 is left undriven, stable driving can be obtained.

10, 410 Base plate, 20 Piezoelectric laminate, 21, 23, 25, 27 Drive electrode, 22, 322, 422 Electromechanical converter, 24 Piezoelectric material plate, 26 Common electrode, 30 Stator, 32 Vibrator, 40, 440 Rotor 42, 46, 48 Contact part, 44, 114, 116 Dimensions, 50, 450 Pressurizing part, 60 Output gear, 70 Bearing part, 80 Top plate, 90 Shaft part, 92 Nut, 100, 101, 102 Vibration actuator, 110, 112, 130, 132 Resin layer, 120 Contact surface, 122, 124, 332, 432 Side surface, 136, 138 Protective layer, 200 Camera, 201 Camera body, 202 Lens unit, 203 Mount system, 220 Image sensor, 222 Optical Filter, 230 Shutter, 240 Fine 242 Eyepiece unit, 244 Display unit for viewfinder, 246 Half mirror, 248 Penta prism, 250 Control unit, 252 Photometric unit, 254 Focus unit, 262 Main mirror, 264 Sub mirror, 266 Focus plate, 270 Lens barrel, 280 Optics System, 282 front sphere, 284 zoom lens, 286 focusing lens, 288 main lens, 290 aperture device, 300 optical equipment, 302 optical components, 304 holding frame, 306 guide shaft, 308 abutting surface, 331, 431 transmission section 342 Protruding part 435 Groove 442 Abutting part 451 Pressure plate 461 Output part 463 Buffer plate

Claims (12)

An electromechanical converter that converts electrical power into mechanical vibration;
A vibrating section that vibrates by the electromechanical converter;
A contact part that contacts the vibration part and moves relative to the vibration part by the vibration;
The contact portion has a contact surface in contact with the vibration portion and a side surface provided in a direction adjacent to the contact surface and intersecting the contact surface, and a layer including a lubricant is provided on the side surface. Vibration actuator.   The vibration actuator according to claim 1, wherein the contact portion has a lower hardness than the vibration portion.   The vibration actuator according to claim 1, wherein the contact portion wears more than the vibration portion due to contact with the vibration portion.   The vibration actuator according to any one of claims 1 to 3, wherein the contact surface of the contact portion includes a hole portion that forms a gap with the vibration portion.   5. The vibration actuator according to claim 1, wherein the contact portion is made of ceramic, and the vibration portion is made of stainless steel.   The vibration actuator according to claim 1, wherein the lubricant is a fluororesin.   The vibration actuator according to claim 1, wherein the layer including the lubricant is formed with a thickness corresponding to a contact area of the contact surface with the vibration part.   The thickness of the layer containing the lubricant is 15% or more and less than 30% with respect to the length of the contact portion in the direction orthogonal to the relative movement direction of the vibration portion. The vibration actuator described in 1.   The vibration actuator according to any one of claims 1 to 8, wherein the layer including the lubricant is formed so that a thickness thereof is changed according to a distance from the contact surface.   The vibration actuator according to claim 1, wherein the lubricant is a solid phase lubricant. The vibration actuator according to any one of claims 1 to 10,
A lens unit including a lens driven by the vibration actuator. The vibration actuator according to any one of claims 1 to 10,
A lens driven by the vibration actuator;
An image pickup apparatus comprising: an image pickup device that picks up a subject image formed by an optical component including the lens.

Images