Vibration actuator

Abstract

To improve durability of a resin film of a vibration actuator.SOLUTION: A vibration actuator includes a vibrator generating vibration, and a mover which comes in contact with the vibrator and is relatively movable to the vibrator by the vibration, wherein one of a first surface contacting the mover of the vibrator, and a second surface contacting the vibrator of the mover is formed of a resin containing carbide.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a vibration actuator.

Background Art

[0002] In a conventional vibration actuator, the friction caused by the contact surface between the vibrator and the moving body has a great influence on the driving stability, efficiency, lifespan, etc. of the vibration actuator (for example, refer to Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The vibration actuator which is the first aspect of the technology disclosed in the present application includes a vibrator that generates vibrations, and a moving body that contacts the vibrator and moves relative to the vibrator by the vibrations. One of the first surface of the vibrator that contacts the moving body and the second surface of the moving body that contacts the vibrator is formed of a resin containing carbide.

[0005] The lens barrel which is the second aspect of the technology disclosed in the present application includes the vibration actuator which is the first aspect of the technology disclosed in the present application.

[0006] The electronic device which is the third aspect of the technology disclosed in the present application includes the vibration actuator which is the first aspect of the technology disclosed in the present application.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0008] The vibration actuator according to the present embodiment has a vibrator in which an electromechanical conversion element and an elastic body are joined, and generates a progressive vibration wave (hereinafter referred to as a progressive wave) in the elastic body by utilizing the expansion and contraction of the electromechanical conversion element. By this progressive wave, the vibration actuator frictionally drives a moving body that is in pressure contact with the vibrator in an elliptical motion of about several [μm]. Hereinafter, the vibration actuator will be described with reference to the accompanying drawings.

[0009] [First Embodiment] Figure 1 is an explanatory diagram showing the configuration of a camera according to the first embodiment. In the first embodiment, an ultrasonic motor that utilizes the ultrasonic vibration range will be described as an example of the vibration actuator. Also, in the first embodiment, a camera will be described as an example of the electronic device.

[0010] The camera 1 includes a camera body 2 having an image sensor 6 and a lens barrel 3. The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. Note that the camera 1 of the first embodiment shows an example in which the lens barrel 3 is an interchangeable lens, but it is not limited thereto. For example, the lens barrel 3 may be integrally formed with the camera body 2.

[0011] The lens barrel 3 includes a lens 4, a cam barrel 5, and a ultrasonic motor 10. In the first embodiment, the ultrasonic motor 10 is, for example, substantially annular in shape and is arranged in the lens barrel 3 such that the central axis direction of the annulus substantially coincides with the optical axis direction (the direction of arrow A in FIG. 1).

[0012] The ultrasonic motor 10 is used as a driving source for driving the lens 4 during the focus operation of the camera 1. The driving force obtained from the ultrasonic motor 10 is transmitted to the cam barrel 5. The lens frame 4a of the lens 4 is in cam engagement with the cam barrel 5. When the cam barrel 5 rotates around the optical axis of the lens 4 by the driving force of the ultrasonic motor 10, the lens 4 moves in the optical axis direction and focus adjustment is performed. Note that the ultrasonic motor 10 may be used as a driving source for driving the lens 4 during the zoom operation of the camera 1.

[0013] In FIG. 1, a subject image is formed on the imaging surface of the image sensor 6 by a lens group (including the lens 4) (not shown) provided in the lens barrel 3. The subject image formed by the image sensor 6 is converted into an electrical signal, and image data is obtained by A / D converting the signal.

[0014] FIG. 2 is an external view showing the ultrasonic motor 10 of the first embodiment. The ultrasonic motor 10 includes a vibrator 13 including a piezoelectric body 11 and an elastic body 12, a moving body 15, a flexible printed circuit board 14, a vibration absorber 16, and a support 17.

[0015] The piezoelectric body 11 converts electrical energy into mechanical energy. In the first embodiment, a piezoelectric element is used as the piezoelectric body 11, but an electrostrictive element may also be used. This piezoelectric body 11 is fixed to a support 17 provided on the lens barrel 3 via a vibration absorber 16 such as felt.

[0016] An electrode portion (not shown) is formed on the piezoelectric body 11. The piezoelectric body 11 expands and contracts by a drive signal supplied from a flexible printed circuit board 14 that is electrically connected to this electrode portion, and excites the elastic body 12.

[0017] The elastic body 12 is a member that generates a traveling wave by the excitation of the piezoelectric body 11. The elastic body 12 is formed of a ferroalloy such as stainless steel or invar steel having a high elastic modulus. The elastic body 12 is formed of, for example, SUS303. The elastic body 12 is a substantially annular member. The piezoelectric body 11 is adhered to one surface of the elastic body 12 by an electrically conductive adhesive or the like. A comb tooth portion 12a formed by cutting a plurality of grooves 12b is provided on the other surface of the elastic body 12.

[0018] The tip surface of the comb tooth portion 12a is a contact surface that comes into pressure contact with a moving body 15 described later, and the moving body 15 is rotationally driven by the traveling wave generated on this contact surface. A composite resin film 18 (see FIG. 3) in which polytetrafluoroethylene (hereinafter referred to as PTFE), which is an example of a fluororesin, polyetheretherketone (hereinafter referred to as PEEK), which is an example of a binder resin, and silicon carbide (hereinafter referred to as SiC), which is an example of a carbide, are combined is formed on the tip surface of the comb tooth portion 12a.

[0019] The moving body 15 is a substantially annular member formed of a metal such as stainless steel, for example. The moving body 15 is formed of a stainless steel alloy. The moving body 15 is brought into pressure contact with the vibrator 13 (elastic body 12) and is frictionally driven by a traveling wave. A hard anodized film layer 19 (see FIG. 3) is formed on the contact surface of this moving body 15 with respect to the vibrator 13 by anodic oxidation treatment.

[0020] The flexible printed circuit board 14 is electrically connected to a predetermined electrode portion of the piezoelectric body 11 and is a member that supplies a drive signal to the piezoelectric body 11. A control device 101 for controlling the camera 1 is connected to the flexible printed circuit board 14.

[0021] A temperature sensor 102 is connected to the control device 101. The control device 101 adjusts the frequency of the drive signal supplied to the piezoelectric body 11 so that the rotational speed of the moving body 15 becomes constant according to the detection result of the temperature sensor 102.

[0022] FIG. 3 is an enlarged cross-sectional view of the contact portion between the elastic body 12 and the moving body 15 of the ultrasonic motor 10 according to the first embodiment. Note that in FIG. 3, a part of the circumferential cross-section of the ultrasonic motor 10 is enlarged and shown.

[0023] A composite resin film 18 is provided on the tip surface of the comb-tooth portion 12a which is the contact surface of the elastic body 12 with the moving body 15. A hard anodized film layer 19 is provided on the contact surface of the moving body 15 with the elastic body 12. Therefore, the region where the vibrator 13 and the moving body 15 are in frictional contact is where the composite resin film 18 and the hard anodized film layer 19 are in contact. The composite resin film 18 is, for example, a polymer alloyed resin film formed by applying a paint mainly composed of PTFE, PEEK, and SiC to the tip surface of the comb-tooth portion 12a and baking it at about 350 degrees.

[0024] In the baked composite resin film 18, 42 [wt (weight)%] of PTFE, 28 [wt%] of PEEK, and 30 [wt%] of SiC are blended. Also, the surface of the composite resin film 18 is polished by, for example, about 15 [μm]. The surface roughness Sa (ISO25278) at that time is, for example, 1 [μm] (measurement range 675 [μm] × 506 [μm]), and the film thickness after polishing is, for example, 30 [μm].

[0025] The coating film made of PEEK is superior in terms of hardness, plastic deformation resistance, adhesion and peel strength, stability of friction coefficient, abrasion resistance, heat resistance, paint stability, processability, moisture resistance, etc. compared to the case where other resins are used as the coating film. Furthermore, by forming the composite resin film 18 through the compounding of PTFE and SiC, the following effects (a) to (d) can be expected.

[0026] (a) Since the composite resin film 18 has higher heat resistance compared to other resin films with low heat resistance (heat resistance temperature of 200 degrees Celsius or less) such as epoxy resin, the abrasion resistance and plastic deformation resistance of the contact surface with the hard anodized film layer 19 are improved.

[0027] (b) Since the composite resin film 18 contains SiC having high hardness and high elastic modulus, the mechanical properties of the composite resin film 18 are improved.

[0028] (c) By containing SiC, the heat resistance and thermal conductivity of the composite resin film 18 are improved, suppressing the alteration of the composite resin film 18 due to frictional heat generated during the driving of the ultrasonic motor 10.

[0029] (d) Since the composite resin film 18 has PTFE, PEEK, and SiC, its moisture resistance is improved, suppressing the chemical and physical alteration of the composite resin film 18 by moisture in the environment.

[0030] Also, for example, if the film thickness of the composite resin film 18 is 30 [μm], the average particle size of PTFE contained in the composite resin film 18 is 5 to 10 [μm]. However, the particle size of PTFE may be appropriately selected and used according to the film thickness of the composite resin film 18, the mixing characteristics with other raw materials, etc.

[0031] This PTFE has high lubricating properties compared to other resins, has the effect of reducing the coefficient of friction, and improving the starting performance of the ultrasonic motor 10 at low speeds. Further, PTFE has high water repellency compared to other solids (other types of resins and inorganic materials), and can suppress adhesion between the hard anodized film layer 19 facing the composite resin film 18 under high temperature and high humidity conditions (for example, in the range of a temperature of 40 degrees or more and a relative humidity of 80% or more).

[0032] Since the composite resin film 18 contains SiC, it is desirable that the counter material, the hard anodized film layer 19, is not a material that increases wear due to sliding with SiC. As the particle size of SiC becomes larger than 11 [μm], the surface roughness increases, which becomes an obstacle during driving.

[0033] Since the composite resin film 18 contains SiC, the strength and denseness of the coating film are improved compared to the case where SiC is not contained. As a result, there is an effect of improving the hardness, plastic deformation resistance, and elastic modulus.

[0034] Further, since the heat generated in the contact surface between the composite resin film 18 and the hard anodized film layer 19 by frictional driving is conducted to the outside of the contact surface, the retention of heat in the contact surface is suppressed. As a result, there is an effect of reducing the softening of the resin and improving the driving efficiency.

[0035] Further, since SiC increases the coefficient of friction between the vibrator 13 and the moving body 15 (that is, the coefficient of friction between the composite resin film 18 and the hard anodized film layer 19), the transmission efficiency of the vibrator 13 is improved. As a result, there is an effect that the holding torque and the maximum load torque are higher compared to the case where SiC is not contained.

[0036] <Production Example of Composite Resin Film 18> The composite resin film 18 is formed through the following steps. First, degreasing treatment is performed on the tip surface of the comb teeth portion 12a, which is the contact surface between the elastic body 12 and the moving body 15. At this time, a treatment for roughening the surface such as blast etching may be performed for further improving the adhesion.

[0037] Mix PEEK with PTFE, SiC, and a solvent to make a stirred solution. Apply this solution to the contact surface of the elastic body 12 (the tip surface of the comb teeth portion 12a), leave it under a high temperature of about 350 [°C] after calcination, and let it dry and harden. After hardening, polish the surface of the composite resin film 18 using an abrasive such as green carborundum to make it flat and reduce the surface roughness.

[0038] On the other hand, the hard anodized film layer 19 is formed by subjecting the surface of the moving body 15 made of an aluminum alloy (A6061) to a hard anodizing treatment. After the hard anodized film layer 19 is formed, polish its surface with GC (green carborundum) abrasive paper of #320 to #8000 mesh to make the hard anodized film layer 19 have a desired roughness. For example, it is preferable that the maximum height roughness of the surface of the hard anodized film layer 19 is in the range of 0.13 to 1.3 [μm]. If the maximum height roughness is within this range, the composite resin film 18 that is the friction mating material will not be worn compared to the case outside this range.

[0039] Next, bond the piezoelectric body 11 to the elastic body 12 on which the composite resin film 18 is formed to form the vibrator 13. Arrange the vibrator 13 and the moving body 15 so that the composite resin film 18 of the vibrator 13 and the hard anodized film layer 19 of the moving body 15 are in contact under pressure, and assemble each member. Through these steps, the ultrasonic motor 10 is manufactured.

[0040] Here, ultrasonic motors 10 with different mixing ratios of PEEK, PTFE, and SiC are prepared, and their respective f (driving frequency)-N (motor rotation speed) characteristics, wear amount of the composite resin film 18, and holding torque are investigated.

[0041] Figure 4 is a table showing the measurement results of the mixing ratios of PEEK, PTFE, and SiC. In each measurement example 1 to 7, when the content rate of PEEK in the composite resin film 18 is X [wt%], the content rate of PTFE is Y [wt%], and the content rate of SiC is Z [wt%], it is preferable to satisfy the following formulas (1) to (4). X + Y + Z = 100 [wt%] ··· (1) 24 [wt%] ≤ Y ≤ 42 [wt%] ··· (2) 15 [wt%] ≤ Z ≤ 30 [wt%] ··· (3) 39 [wt%] ≤ Y + Z ≤ 72 [wt%] ··· (4)

[0042] If the content rate Z of SiC is too small, the durability of the composite resin film 18 will deteriorate. For example, in Measurement Example 8, since the content rate Z of SiC was lower than 15 [wt%] and did not satisfy the above formulas (3) and (4), the stability of the wear coefficient was not good. Also, if the content rate X of PEEK was less than 28 [wt%] or the content rate Z of SiC was more than 30 [wt%], the performance as a resin would decline, for example, the appearance would become poor.

[0043] When the above formulas (1) to (4) are satisfied, the ultrasonic motor 10 can be manufactured without degrading the durability of the composite resin film 18 and the performance as a resin. Furthermore, when 24 [wt%] ≤ Y ≤ 42 [wt%] and 21 [wt%] ≤ Z ≤ 30 [wt%], the measurements shown in the following FIGS. 5 to 7 were carried out. In order to further improve the durability of the composite resin film 18, the content rate Z of SiC was set to 21 [wt%] or more in the measurements shown in FIGS. 5 to 7.

[0044] FIG. 5 is a graph showing the f-N characteristics of ultrasonic motors with different mixing ratios of PTFE and SiC. FIG. 6 is a graph showing the wear amounts of ultrasonic motors with different mixing ratios of PTFE and SiC. FIG. 7 is a graph showing the holding torques of ultrasonic motors with different mixing ratios of PTFE and SiC.

[0045] In FIGS. 5 to 7, the horizontal axis represents the PTFE mixing ratio in the composite resin film 18, and the vertical axis represents the SiC mixing ratio in the composite resin film 18. In FIGS. 5 to 7, the centers of the concentric circles of each Measurement Example 1 to 5 are the points where the PTFE mixing ratio and the SiC mixing ratio shown in FIG. 4 are plotted. Also, in each of Measurement Examples 1 to 5, the numerical value indicating the size (diameter) of the concentric circle represents the normalized measured value. The bold numerical values on the circles of each of Measurement Examples 1 to 5 represent the average values of the respective measured values of Measurement Examples 1 to 5.

[0046] Also, in FIGS. 5 to 7, since the number of prototype lots and the number of evaluation individuals vary depending on the mixing ratio, the number of measurements n of the measured values varies depending on the measurement example. For example, in FIG. 5, the number of measurements n for measurement example 1 is n = 2, for measurement example 2 is n = 4, for measurement example 3 is n = 2, for measurement example 4 is n = 1, and for measurement example 5 is n = 4. In FIGS. 6 and 7, the number of measurements n for measurement example 1 is n = 2, for measurement example 2 is n = 4, for measurement example 3 is n = 2, for measurement example 4 is n = 2, and for measurement example 5 is n = 4.

[0047] In FIG. 5, the measured values indicating the sizes of the concentric circles for measurement examples 1 to 5 are proportional to the change width of the f-N characteristics, indicating that the smaller the value, the higher the stability. The number of measurements n for measurement example 5 is three measured values of "2.5", "3.0", and "3.5", but since "3.5" was measured twice, the number of measurements n for measurement example 5 is n = 4. Looking at the average values, the stability is high in the order of measurement examples 3, 5, 4, 1, 2 (the average value is small).

[0048] In FIG. 6, the sizes of the concentric circles for measurement examples 1 to 5 are proportional to the wear amount of the composite resin film 18, indicating that the smaller the size, the less the wear amount, that is, the better. The number of measurements n for measurement example 2 is three measured values of "22.0", "25.0", and "35.0", but since "25.0" was measured twice, the number of measurements n for measurement example 2 is n = 4. In FIG. 6, looking at the average values, the wear amount is small (good) in the order of measurement examples 5, 4, 3, 2, 1.

[0049] In FIG. 7, the sizes of the concentric circles for measurement examples 1 to 5 are proportional to the magnitude of the holding torque of the ultrasonic motor 10, indicating that the larger the size, the better, and the target value is set to "10.5". The target value is, for example, the holding torque in an ultrasonic motor without applying the composite resin film 18.

[0050] In Measurement Example 2, the number of measurements n is three values: 12.5, 13.5, and 15.0. However, since 13.5 was measured twice, the number of measurements n for Measurement Example 2 is n = 4. Also, in Measurement Example 4, the number of measurements n is one value: 18.0. However, since 18.0 was measured twice, the number of measurements n for Measurement Example 4 is n = 2. Further, in Measurement Example 5, the number of measurements n is two values: 13.5 and 14.0. However, since 13.5 was measured three times, the number of measurements n for Measurement Example 4 is n = 4. In Figure 7, the average value of each of Measurement Examples 1 to 5 exceeds the target value.

[0051] From the results shown in Figures 5 to 7, considering the f-N characteristics, wear amount, and holding torque, it can be seen that Measurement Examples 3, 4, and 5 are better than Measurement Examples 1 and 2.

[0052] SiC and PTFE contribute to suppressing performance changes such as wear resistance and durability. Therefore, as the sum of the content rate Y of PTFE and the content rate Z of SiC increases as a proportion of the total blending ratio of PEEK, PTFE, and SiC, both the f-N characteristics and the wear amount become better. For example, the sum of the content rate Y of PTFE and the content rate Z of SiC shown in Figure 4 is 54 [wt%] for Measurement Example 1 and 45 [wt%] for Measurement Example 2, whereas it is 66 [wt%] for Measurement Example 3, 57 [wt%] for Measurement Example 4, and 72 [wt%] for Measurement Example 5. Thus, the higher the sum of the content rate Y of PTFE and the content rate Z of SiC is (43 wt% or less of PEEK), the more stable the f-N characteristics are, the lower the wear amount is, and the more the durability is improved.

[0053] Also, it can be seen that PTFE, which is a fluororesin, is better in the range of 36 to 42 [wt%], and SiC is better in the range of 21 to 30 [wt%].

[0054] Also, from the results shown in FIGS. 5 to 7, considering the f-N characteristics, wear amount, and holding torque, it can be seen that Measurement Example 5 is better than Measurement Examples 1 to 4. In Measurement Example 5, the content rate X of PEEK is less than each of the content rates Y of PTFE and Z of SiC. In other words, in Measurement Example 5, each of the content rates Y of PTFE and Z of SiC is more than the content rate X of PEEK. Measurement Example 5 where the content rate X of PEEK is less than each of the content rates Y of PEFE and Z of SiC has more stable f-N characteristics, reduced wear amount, and improved durability compared to Measurement Examples 1 to 4 where this is not the case.

[0055] In addition, when increasing the blending ratio (Y + Z) of PTFE and SiC above that of Measurement Example 5 (72 [wt%]), the amount of PEEK, which is the binder component, decreases, and it becomes difficult to form a composite material of PTFE and SiC. Therefore, 39 [wt%]% ≦ Y + Z ≦ 72 [wt%] is favorable for the formation of the composite resin film 18.

[0056] FIG. 8 is a table showing the measurement results of the yield stress and wear resistance of the composite resin film 18. The composite resin film 18 interposed between the vibrator 13 and the moving body 15 is pressurized by a spring or the like. The numerical value of the pressure may be determined by dividing the required torque by the friction coefficient of the contact surface where the composite resin film 18 contacts the hard anodized coating layer 19.

[0057] Although wear may increase when increasing the pressure, it is desirable that the wear amount of the composite resin film 18 is not a problem even when increasing the pressure to increase the torque. Therefore, the yield contact pressure, which is one of the strength parameters of the composite resin film 18, was measured by the indentation method. The yield contact pressure decreases when increasing Y in the above formula (1) and increases when increasing Z. When Y = 24 [wt%] and 39 [wt%] ≦ Y + Z ≦ 54 [wt%], the yield contact pressure shows 60 [MPa] or more.

[0058] For example, if the surface pressure is lower than the yield contact pressure measured for each material (Measurement Example 9 and Measurement Example 10), the material will not yield. The composite resin film 18 of Measurement Example 9 contains PEEK, which is an example of a binder resin, PTFE, and SiC, which is an example of an inorganic substance (the same applies to Measurement Example 11 and Measurement Example 12 described later). The mixing ratios of PEEK, PTFE, and SiC in Measurement Example 9 are the same as those in Measurement Example 2.

[0059] The composite resin film 18 of Measurement Example 10 contains polyamideimide (PAI), which is an example of a binder resin, PTFE, and SiC, which is an example of an inorganic substance. The mixing ratio of Measurement Example 10 is the same as that of Measurement Example 9, except that PAI is used instead of PEEK. Since PAI has inferior wear resistance compared to PEEK and is effective only when the applied surface pressure is lower than its yield contact pressure, its range of use is limited.

[0060] When friction sliding under pressure was performed on the materials of Measurement Example 9 and Measurement Example 10 such that the surface pressure was greater than the yield contact pressure, a difference appeared in the wear amount. Measurement Example 9 has good wear resistance, and as a result of pressurization below the pressure, it became clear that the resin film of Measurement Example 9 having the same components as the present embodiment can withstand pressurization of 50 [MPa] or less even considering variations in the yield contact pressure.

[0061] Figure 9 is a table showing the measurement results of the ratio of the average value of the interparticle distance and the ratio of the wear amount of the composite resin film 18. Measurement Example 11 and Measurement Example 12 are samples in which the mixing ratios of PEEK, PTFE, and SiC are the same as those in Measurement Example 9. In Measurement Example 11 and Measurement Example 12, among the composite resin films 18 laid on the contact surface where the composite resin film 18 in the ultrasonic motor 10 contacts the hard anodized coating layer 19, those with a wider average interparticle distance of PTFE had more wear. Even when the mixing ratios of PEEK, PTFE, and SiC are the same, the wear amount tends to increase as the interparticle distance widens. The average interparticle distance from the particle center of gravity of PTFE was 12 [μm] on average when measured by the triangle division method.

[0062] The triangular division method is a method of performing image processing on an observation image of a group of PTFE particles, generating triangles by connecting the centers of gravity of adjacent particles with lines through computer analysis, and calculating the average distance between the particles. The average distance between the particles is the average value estimated when the distribution of the inter-particle distances is assumed to be a lognormal distribution.

[0063] Also, in the case of Measurement Example 2, the average distance between the particles from the center of gravity of the PTFE particles was 9 [μm] on average when measured by the triangular division method, and the distance dispersion was 7 [μm]. The average distance between the particles from the center of gravity of the SiC particles was 18 [μm] on average when measured by the triangular division method, and the distance dispersion was 9 [μm].

[0064] Also, in the case of Measurement Example 5, the average distance between the particles from the center of gravity of the PTFE particles was 12 [μm] on average when measured by the triangular division method, and the distance dispersion was 9 [μm]. The average distance between the particles from the center of gravity of the SiC particles was 16 [μm] on average when measured by the triangular division method, and the distance dispersion was 8 [μm]. Regarding the average distance between the particles from the center of gravity of the SiC particles as well, the larger the distance, the more the wear amount. Therefore, if the average distance between the particles from the center of gravity of the SiC particles is in the range of 12 to 16 [μm], the wear resistance will be good, similar to the case of PTFE.

[0065] Thus, the composite resin film 18 of the first embodiment contains a carbon material such as SiC. Therefore, for example, compared with a tetrafluoroethylene resin, the durability of the composite resin film 18 is improved, and wear can be reduced.

[0066] Also, the composite resin film 18 is different from a SiC film composed of SiC alone. In the case of a SiC film, for example, it is necessary to form a SiC film on the elastic body 12 using a PI-CVD apparatus using plasma. However, since the composite resin film 18 is a resin, it can be easily coated on the elastic body 12, for example, it can be coated with a brush. This facilitates the manufacture of the ultrasonic motor 10.

[0067] Also, for example, even if the composite resin film 18 is pressure-applied and pressed between the elastic body 12 and the moving body 15 and comes into contact with the opposing surfaces, when driving the moving body 15 by friction, breakage and detachment of the composite resin film 18 are reduced. When breakage and detachment of the composite resin film 18 are reduced, even if the frequency-rotation speed characteristics change during driving of the ultrasonic motor 10, generation of abnormal noise is reduced. Therefore, the ultrasonic motor 10 can be easily started, and a decrease in driving efficiency and service life can be suppressed.

[0068] That is, by using the composite resin film 18 in the ultrasonic motor 10, generation of frictional wear under pressure contact can be suppressed, and quietness of the ultrasonic motor 10 can be maintained.

[0069] Also, the composite resin film 18 has a higher thermal conductivity and thermal diffusivity than, for example, a tetrafluoroethylene resin, so an increase in the contact surface temperature due to the generated frictional heat is suppressed. Therefore, roughening of the composite resin film 18 that becomes the frictional contact surface is suppressed, and the relative moving body can be moved well by the elliptical motion on the order of μm generated in the vibrator 13.

[0070] Also, the composite resin film 18 can maintain the frictional wear characteristics, frequency-rotation characteristics, thrust and torque-rotation speed characteristics as a friction material even if its mechanical properties change due to moisture absorption, compared to, for example, a tetrafluoroethylene resin.

[0071] Therefore, in the first embodiment, it is possible to provide a vibration actuator, a lens barrel 3, and an electronic device that are easy to manufacture, do not generate abnormal noise, have good and stable driving performance, are excellent in environmental resistance, and have improved durability under pressure application.

[0072] [Second Embodiment] FIG. 10 is a cross-sectional view showing an ultrasonic motor 20 according to the second embodiment. The ultrasonic motor 20 is provided in the lens barrel 3 of the same camera 1 as the ultrasonic motor 10 of the first embodiment, and is used as a drive source for driving the lens 4 when performing a focusing operation or a zoom operation. The ultrasonic motor 20 is different from the first embodiment in that it transmits a driving force to a cam cylinder (not shown) via a gear (not shown) and drives the lens 4 held by this cam cylinder.

[0073] The ultrasonic motor 20 includes a vibrator 23, a moving body 25, an output shaft 28, and a pressurizing portion 29. The vibrator 23 is a substantially annular member having an elastic body 22 and a piezoelectric body 21 joined to the elastic body 22. The vibrator 23 generates a traveling wave by the expansion and contraction of the piezoelectric body 21.

[0074] The elastic body 22 is a substantially annular member formed of stainless steel. A piezoelectric body 21 is joined to one surface of the elastic body 22, and a comb-tooth portion 22a formed by cutting a plurality of grooves in the circumferential direction is provided on the other surface. The tip surface of this comb-tooth portion 22a is a contact surface that is brought into pressure contact with the moving body 25, and the moving body 25 in contact with this contact surface is driven by the traveling wave.

[0075] A composite resin film 31 is formed on the contact surface of the vibrator 23 with the moving body 25, similarly to the vibrator 13 shown in the first embodiment. The composite resin film 31 is formed of a resin film equivalent to Measurement Example 1 in FIG. 4. Also, the film thickness of the composite resin film 31 is 30 [μm].

[0076] The elastic body 22 has a flange portion 22b formed by expanding in the radial direction on the inner peripheral side thereof, and is supported by a support body 26 by this flange portion 22b.

[0077] The piezoelectric body 21 has a function of converting electrical energy into mechanical energy. Similar to the first embodiment, a piezoelectric element is used as the piezoelectric body 21, but an electrostrictive element may also be used. An electrode portion (not shown) is formed on the piezoelectric body 21. The piezoelectric body 21 expands and contracts by a drive signal supplied from a flexible printed circuit board 24 that is electrically connected to this electrode portion, and causes vibration in the elastic body 22.

[0078] A control device 201 for controlling a camera equipped with the ultrasonic motor 20 is connected to the flexible printed circuit board 24. A temperature sensor 202 is connected to the control device 201. The control device 201 adjusts the frequency of the drive signal supplied to the piezoelectric body 21 so that the rotation speed of the moving body 25 becomes constant according to the detection result of the temperature sensor 202.

[0079] The moving body 25 is in pressure contact with the vibrator 23 and is rotationally driven by the elliptical motion caused by the traveling wave generated at the tip surface of the comb-tooth portion 22a which is the contact surface of the vibrator 23. The moving body 25 is a member formed of stainless steel. The moving body 25 is fitted to the output shaft 28. The moving body 25 is formed of an aluminum alloy, and a hard anodized film layer 32 is formed on the contact surface of the moving body 25 with the vibrator 23. Therefore, in the region where the moving body 25 and the vibrator 23 are in frictional contact, the hard anodized film layer 32 and the composite resin film 31 are in contact. The composite resin film 31 is the same resin film as the composite resin film 18 of the first embodiment.

[0080] The output shaft 28 has a substantially cylindrical shape. One end portion of the output shaft 28 is fitted to the moving body 25 via a rubber member 30. The other end portion of the output shaft 28 is rotatably attached to the support body 26 via a bearing 27. The output shaft 28 rotates integrally with the moving body 25 and transmits the rotational motion of the moving body 25 to a driven member such as a gear (not shown).

[0081] The pressing portion 29 is a mechanism for pressing the vibrator 23 and the moving body 25. The pressing portion 29 includes a spring 29a, a retaining ring 29b, a retaining ring 29c, and an E-ring 29d. The spring 29a generates a pressing force. The retaining ring 29b is disposed in contact with the bearing 27 and presses one end of the spring 29a. The E-ring 29d is inserted into a groove formed in the output shaft 28 to regulate the position of the retaining ring 29c.

[0082] Also in the ultrasonic motor 20, by forming the composite resin film 31 on the friction contact surface of the vibrator 23, it is possible to reduce the wear amount, reduce abnormal noise, improve durability, stabilize the driving performance, improve the starting characteristics, and the like.

[0083] Furthermore, since the ultrasonic motor 20 is often manufactured as a small-sized ultrasonic motor having a smaller diameter than the ultrasonic motor 10 of the first embodiment, heat generation becomes a problem. However, according to the second embodiment, the composite resin film 31 of Measurement Example 5 uses SiC and thus has excellent heat dissipation properties.

[0084] In each of the above embodiments, a hard anodized film is shown as the sliding film (composite resin films 18 and 31) of the moving bodies 15 and 25. However, the present invention is not limited to this, and surface treatments such as hard chrome plating and electroless nickel (composite) plating, films by other manufacturing methods such as PVD methods (vacuum evaporation, sputtering, etc.), CVD methods, thermal spraying methods, epitaxial methods, and electrodeposition methods may be used. Further, instead of forming a film, a single metal (alloy) or a resin film may be used. A composite film such as forming hard anodized film or electroless nickel plating on the substrate treatment may also be used.

[0085] In each of the above embodiments, an example of forming the composite resin films 18 and 31 on the contact surfaces (tip surfaces of the comb teeth portions 12a and 22a) of the vibrators 13 and 23 is shown. However, the present invention is not limited to this, and the composite resin films 18 and 31 may be formed on the contact surfaces of the moving bodies 15 and 25. Further, the composite resin films 18 and 31 may be formed on both the contact surface of the vibrators 13 and 23 and the contact surface of the moving bodies 15 and 25.

[0086] Furthermore, it may be applied to a vibration actuator in a form in which the piezoelectric bodies 11 and 21 are in frictional contact with the moving bodies 15 and 25 without using the elastic bodies 12 and 22. In this case, the composite resin films 18 and 31 may be formed on at least one of the contact surface of the piezoelectric bodies 11 and 21 with respect to the moving bodies 15 and 25 and the contact surface of the moving bodies 15 and 25 with respect to the piezoelectric bodies 11 and 21.

[0087] In addition, in each of the above embodiments, stainless steel is used as the material for forming the elastic bodies 12 and 22, but other ferrous materials may also be used. For example, various steel materials such as SUS440C, S15C, S55C, SCr445, and SNCM630 may be used. Copper alloys such as phosphor bronze and aluminum-based alloys may also be used.

[0088] In addition, in each of the above embodiments, an example in which the moving bodies 15 and 25 are formed of an aluminum alloy is shown, but it is not limited thereto, and ferrous materials, stainless alloys, phosphor bronze, etc. may also be used. For example, various steel materials such as SUS440C, S15C, S55C, SCr445, and SNCM630 may be used.

[0089] In addition, in each of the above embodiments, an example in which PTFE is used as the fluororesin is shown, but it is not limited thereto, and an appropriate fluororesin may be appropriately selected and used. For example, PFA (tetrafluoroethylene-perfluoroalkylvinyl ether Copolymer), FEP (Tetrafluroethylene-hexafluoropropylene Copolymer), PCTFE (Polychloro-Trifluoroethylene Copolymer), ETFE (Ethylene Tetrafluoroethylene Copolymer), ECTFE (Ethylene Chlorotrifluoroethylene Copolymer), PVDF (Polyvinylidene Fluoride), PVF (Polyvinylfluoride), etc. may be mentioned. Also, each functional group may be changed.

[0090] In addition, in each of the above embodiments, an example in which the composite resin films 18 and 31 contain SiC as an example of a carbonaceous material is shown, but it is not limited thereto, and carbides such as SiC, WC, B4C, TaC, TiC, NbC, ZrC, and VC may also be used.

[0091] In addition, the composite resin films 18 and 31 of the above embodiments are made into polymer alloyed resin films by applying a paint containing PEEK as one of the main raw materials to the tip surfaces of the comb teeth portions 12a and 22a and baking them. However, modified PEEK may be used instead of PEEK. Modified PEEK is a resin obtained by modifying the properties of PEEK. For example, it is a resin obtained by polymer alloying PEEK with other resins such as PPS (Poly Phenylene Sulfide Resin) or PES (Polyethersulfone).

[0092] By using modified PEEK, the adhesion to the elastic body 12 and the hard anodized film layer 19 is further improved compared to non-modified PEEK, and the cost is reduced compared to non-modified PEEK.

[0093] In addition, in the above embodiments, the ultrasonic motors 10 and 20 in which the moving bodies 15 and 25 are rotationally driven are shown. However, the present invention is not limited to this, and the vibrators 13 and 23 or the moving bodies 15 and 25 may be linear drive type vibration actuators that are driven in a linear direction.

[0094] In addition, in the above embodiments, the ultrasonic motor using vibration in the ultrasonic region has been described as an example. However, the present invention is not limited to this, and for example, it may be applied to a vibration actuator using vibration other than the ultrasonic region.

[0095] In addition, in the above embodiments, the ultrasonic motors 10 and 20 are shown as an example of being used as a drive source for performing the focusing operation of the lens barrel 3 of the camera 1. However, the present invention is not limited to this, and for example, it may be applied to a drive source for performing the zoom operation of the lens barrel 3.

[0096] In addition, the ultrasonic motors 10 and 20 may be used as drive sources or drive parts for various electronic devices other than the camera 1, such as drive sources for copiers and the like, drive parts for automobile steering wheel tilt devices and headrests, and drive parts for various medical devices, particularly MRI that dislikes the generation of magnetism, robots, and care suits.

[0097] As described above, according to each of the above embodiments, it is possible to provide a vibration actuator, a lens barrel 3, and an electronic device that are easy to manufacture, reduce the generation of abnormal noise, have good and stable driving performance, and improved durability.

[0098] In addition, each of the above embodiments and its modified forms can be used in appropriate combinations, but detailed descriptions thereof are omitted. Further, the present invention is not limited to the above-described embodiments.

Description of Reference Numerals

[0099] 1: Camera, 3: Lens barrel 3, 10, 20: Ultrasonic motor, 11, 21: Piezoelectric body, 12, 22: Elastic body, 13, 23: Vibrator, 15, 25: Moving body, 18, 31: Composite resin film

Claims

Claim 1 An oscillator that generates vibrations, a moving body that contacts the oscillator and moves relative to the oscillator by the vibrations, and one of a first surface of the oscillator that contacts the moving body and a second surface of the moving body that contacts the oscillator is formed of a resin containing a carbide vibratory actuator.

Images