Vibration wave motor

Abstract

To obtain good vibration characteristics with a vibrator formed by bonding a lead-free element and an elastic body.SOLUTION: A vibration wave motor has an annular elastic body that has a bottom surface to come into contact with an element and a drive surface having a groove, and that drives a mover with a vibration wave generated in the drive surface by displacement of the element. The density of the element is 4.2 to 6.0×103 kg / m3, and the value of [(T / B) / W] ranges from 0.84 to 1.94 wherein T represents the depth of the groove, B represents the distance from a bottom of the groove to the bottom surface, and W represents a radial-direction width of the elastic body.SELECTED DRAWING: Figure 7

Description

Incorporation by reference

[0001] This application claims the priority of Japanese Patent Application No. 2017-202118, filed on October 18, 2017, and incorporates the contents thereof by reference into this application. 017-202118 and incorporates the contents thereof by reference into this application. Incorporate.

Technical Field

[0002] The present invention relates to a lens barrel and an imaging device.

Background Art

[0003] A vibration wave motor generates a progressive vibration wave (hereinafter abbreviated as a progressive wave) on the driving surface of an elastic body by utilizing the expansion and contraction of a piezoelectric body (see Patent Document 1 below). Such a vibrator of a vibration wave motor generally includes an electromechanical conversion element (hereinafter referred to as a piezoelectric body) and an elastic body. Conventionally, the piezoelectric body has generally been composed of a material such as lead zirconate titanate commonly called PZT. In recent years, however, lead-free materials have been studied due to environmental problems, and their mounting on vibration wave motors has been considered. A vibration wave motor generates a progressive vibration wave (hereinafter abbreviated as a progressive wave) on the driving surface of an elastic body by utilizing the expansion and contraction of a piezoelectric body (see Patent Document 1 below). Such a vibrator of a vibration wave motor generally includes an electromechanical conversion element (hereinafter referred to as a piezoelectric body) and an elastic body. Conventionally, the piezoelectric body has generally been composed of a material such as lead zirconate titanate commonly called PZT. In recent years, however, lead-free materials have been studied due to environmental problems, and their mounting on vibration wave motors has been considered. Generally, it is composed of an electromechanical conversion element (hereinafter referred to as a piezoelectric body) and an elastic body. Conventionally, the piezoelectric body has generally been composed of a material such as lead zirconate titanate commonly called PZT. In recent years, however, lead-free materials have been studied due to environmental problems, and their mounting on vibration wave motors has been considered. Conventionally, the piezoelectric body has generally been composed of a material such as lead zirconate titanate commonly called PZT. In recent years, however, lead-free materials have been studied due to environmental problems, and their mounting on vibration wave motors has been considered. Conventionally, the piezoelectric body has generally been composed of a material such as lead zirconate titanate commonly called PZT. In recent years, however, lead-free materials have been studied due to environmental problems, and their mounting on vibration wave motors has been considered. In recent years, however, lead-free materials have been studied due to environmental problems, and their mounting on vibration wave motors has been considered.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] A vibration wave motor according to one aspect of the technology disclosed in the present application includes an element that is displaced by the application of a voltage, and a driving surface having a bottom surface and a groove that are in contact with the element. The displacement of the element causes a moving element to be driven by a vibration wave generated on the driving surface by an annular elastic body. The density of the element is 4.2 to 6.0×10 A vibration wave motor according to one aspect of the technology disclosed in the present application includes an element that is displaced by the application of a voltage, and a driving surface having a bottom surface and a groove that are in contact with the element. The displacement of the element causes a moving element to be driven by a vibration wave generated on the driving surface by an annular elastic body. The density of the element is 4.2 to 6.0×10 A vibration wave motor according to one aspect of the technology disclosed in the present application includes an element that is displaced by the application of a voltage, and a driving surface having a bottom surface and a groove that are in contact with the element. The displacement of the element causes a moving element to be driven by a vibration wave generated on the driving surface by an annular elastic body. The density of the element is 4.2 to 6.0×10 The density of the element is 4.2 to 6.0×103 kg / m 3 where T is the depth of the groove, B is the distance from the bottom of the groove to the bottom surface, and W is the radial width of the elastic body. When [( T / B)÷W], the value ranges from 0.84 to 1.94. T / B)÷W] has a value in the range of 0.84 to 1.94.

[0006] An imaging device, which is another aspect of the technology disclosed in the present application, includes a lens barrel and a camera body and is provided with an element that is displaced by the application of a voltage, a contact surface that contacts the element, and a driving surface on which a vibration wave is generated by the displacement of the element. An elastic body in which a plurality of grooves are formed, a mover that contacts the driving surface and rotates by the vibration wave, a rotating ring that rotates by the rotation of the mover, and a lens that moves in the optical axis direction by the rotation of the rotating ring. The element is composed of a material mainly containing potassium sodium niobate, potassium niobate, sodium niobate or barium titanate. When T is the depth of the groove, B is the distance from the bottom of the groove to the contact surface, and W is the radial width of the elastic body , [(T / B)÷W] has a value in the range of 0.84 to 1.94. , [(T / B)÷W] has a value in the range of 0.84 to 1.94.

Brief Description of the Drawings

[0007]

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DETAILED DESCRIPTION OF THE INVENTION

[0008] <Schematic Configuration Example of Camera> FIG. 1 is a schematic cross-sectional view of a camera including a lens barrel equipped with a vibration wave motor. The camera 100 is an optical device capable of taking still images and moving images, and has an imaging element and an image processing unit. The lens barrel 20, which is an imaging optical system, is detachably attached to the camera body 1. Note that the camera 100 may be an integrated imaging device of the camera body 1 and the lens barrel 20.

[0009] The lens barrel 20 includes an outer fixed cylinder 31, an inner fixed cylinder 32, and a vibration wave motor 10. The outer fixed cylinder 31 has, for example, a cylindrical shape and covers the outer peripheral portion of the lens barrel 20. The outer fixed cylinder 31 has a protruding piece 31a that protrudes from its inner peripheral surface toward the optical axis OA. The protruding piece 31a supports the inner fixed cylinder 32. The inner fixed cylinder 32 has, for example, a cylindrical shape and is provided on the inner peripheral side of the outer fixed cylinder 31. The vibration wave motor 10 is provided between the outer fixed cylinder 31 and the inner fixed cylinder 32.

[0010] In the inner fixed cylinder 32, a first lens group L1, a second lens group L2, a third lens group L3, and a fourth lens group L4 are arranged on the same optical axis OA from the subject side. The third lens group L3 It is an AF (Auto Focus) lens held by an annular AF ring 34. The first lens group L1, the second lens group L2, and the fourth lens group L4 are fixed to the inner fixed cylinder 32 . The third lens group L3 is configured to be movable in the direction of the optical axis OA (hereinafter referred to as the optical axis direction) with respect to the inner fixed cylinder 32 when the AF ring 34 moves.

[0011] The vibration wave motor 10 includes a vibrator 11, a mover 15, a pressing member 18, etc. For example, the vibrator 11 is used as a stator, and the mover 15 is used as a rotor that is rotationally driven.

[0012] The vibrator 11 is an annular member and is composed of an elastic body 12 and a piezoelectric body 13. The elastic body 12 is joined to the piezoelectric body 13. The elastic body 12 generates a traveling wave. Here, the traveling wave is, for example, a 9-wave traveling wave. The elastic body 12 is composed of a metal material with a large resonance sharpness. The shape of the elastic body 12 is an annular shape.

[0013] The piezoelectric body 13 is an element that is displaced by the application of a voltage. Specifically, for example, it is an electro-mechanical conversion element such as a piezoelectric element or an electrostrictive element that converts electrical energy into mechanical energy. The piezoelectric body 13 is generally composed of a material such as lead zirconate titanate commonly called PZT, but other materials may be used instead of PZT.

[0014] For example, the piezoelectric body 13 may be composed of potassium sodium niobate, potassium niobate, sodium niobate, barium titanate, bismuth sodium titanate, bismuth potassium titanate, etc., which are lead-free materials. The details of the vibrator 11 will be described later with reference to FIG. 2. ​

[0015] On the side opposite to the side where the piezoelectric body 13 and the elastic body 12 are joined, a non-woven fabric 16, a pressure plate 17, and a pressing member 18 are arranged. The non-woven fabric 16 is composed of, for example, felt. The non-woven fabric 1 6 is a vibration transmission prevention member that prevents the vibration from the vibrator 11 from being transmitted to the pressure plate 17 and the pressing member 18.

[0016] The pressure plate 17 is configured to receive the pressure from the pressing member 18. The pressing member 18 is, for example, composed of a disc spring and generates a pressing force on the pressure plate 17. The pressing member 18 may be a coil spring or a wave spring in addition to the disc spring. The retaining ring 19 is an annular member and holds the pressing member 18 by being fixed to the fixing member 14.

[0017] The mover 15 is, for example, an annular member made of a light metal such as aluminum. The mover 15 has a sliding surface 15a that contacts and slides on the elastic body 12 at one end thereof. The sliding surface 15a is surface-treated with a sliding material or the like to improve wear resistance.

[0018] A vibration absorption member 23 is arranged on the other end side of the mover 15. The vibration absorption member 23 is, for example, composed of an elastic member such as rubber and absorbs the longitudinal vibration of the mover 15. The vibration absorption member 23 has an output transmission member 24 arranged on the side opposite to the side that contacts the mover 15.

[0019] The output transmission member 24 regulates the displacement of the mover 15 in the pressing direction PD and the radial direction DD by means of a bearing 25 provided on the fixing member 14.

[0020] ​​​The output transmission member 24 has a protrusion 24a. The protrusion 24a is fitted into a fork 35 connected to the cam ring 36. The cam ring 36 is an annular member and rotates as the output transmission member 24 rotates.

[0021] A key groove 37 is formed obliquely (spirally) with respect to the circumferential direction of the cam ring 36. A fixing pin 38 is provided on the outer peripheral side of the AF ring 34. The fixing pin 38 is fitted into the key groove 37. Thus, when the cam ring 36 is rotationally driven, the AF ring 34 is driven in the forward direction of the third lens group L3 on the optical axis OA (the direction toward the subject side; hereinafter referred to as OA+). and stops at a desired position on the optical axis OA. Note that the backward direction of the third lens group L3 on the optical axis OA (the direction toward the camera body 1 side) is denoted as "OA-".

[0022] The fixing member 14 fixes the pressing ring 19 with a screw (not shown). By attaching the pressing ring 19 to the fixing member 14, the moving element 15, the vibrator 11, and the pressing member 18 can be configured as one motor unit from the output transmission member 24.

[0023] The drive circuit 40 is fixed to the protruding piece 31a. The drive circuit 40 controls the rotational drive of the vibration wave motor 10. The drive circuit 40 is electrically connected to the piezoelectric body 13 by a signal line 21 and supplies a voltage signal to the piezoelectric body 13.

[0024] <Schematic configuration example of the vibrator 11 and the moving element 15> FIG. 2 is a perspective view showing a part of the vibrator 11 and the moving element 15 cut away. As described above, the vibrator 11 is composed of an elastic body 12 and a piezoelectric body 13. The elastic body 12 is formed by the piezoelectric body On the side opposite to the joint surface 12d with 13, it has a driving surface 12a. The driving surface 12a is subjected to a surface treatment for lubricity.

[0025] The driving surface 12a is in pressure contact with the sliding surface 15a of the mover 15 to rotationally drive the mover 15. A groove 12c is formed in the driving surface 12a. Also, the elastic body 12 has a plurality of protrusions 12b so as to sandwich the groove 12c. In other words, a groove 12c is formed between adjacent protrusions 12b. The tip surface of the protrusion 12b is the driving surface 12a.

[0026] The vibration wave motor 10 drives the third lens group L3 by driving the mover 15 using the driving force generated on the driving surface 12a by the excitation of the piezoelectric body 13. The reason for forming the groove 12c in the elastic body 12 is to bring the neutral plane 800 of the traveling wave in the width direction of the vibrator 11 along the optical axis as close as possible to the piezoelectric body 13 side, thereby amplifying the amplitude of the traveling wave on the driving surface 12a.

[0027] In the elastic body 12, the portion without the protrusion 12b from the joint surface 12d where the piezoelectric body 13 contacts to the driving surface 12a that is in pressure contact with the sliding surface 15a of the mover 15 is referred to as the base portion 12e. That is, the elastic body 12 is composed of the base portion 12e and the protrusions 12b arranged in the circumferential direction on the base portion 12e, and a groove 12c is formed between adjacent protrusions 12b, making it comb-shaped.

[0028] Note that B is the thickness of the base portion 12e. C is the thickness of the piezoelectric body 13 in the optical axis direction. T is the depth of the groove 12c provided between adjacent protrusions 12b, in other words, the length of the protrusion 12b in the optical axis direction. W is the width of the elastic body 12 in the radial direction DD. ​​​​​​​​​​​​​​

[0029] The mover 15 has a sliding surface 15a that is in pressure contact with the drive surface 12a. Further, the mover 15 has a joint surface 15b that joins with the output transmission member 24 on the side opposite to the sliding surface 15a of the mover 15 of the mover 15.

[0030] <Piezoelectric body 13> FIG. 3 is an explanatory diagram showing the piezoelectric body 13. (a) shows an annular first surface 13A that joins with the joint surface 12d of the elastic body 12 and (b) shows an annular second surface 13B that is the back surface of the first surface 13A of the elastic body 12 and contacts the nonwoven fabric 16.

[0031] The piezoelectric body 13 is separated into two phases (phase A and phase B) along the circumferential direction. In each phase , elements with alternating polarization are arranged every half wavelength of the traveling wave, and a 1 / 4 wavelength interval is provided between phase A and phase B.

[0032] In (a), on the first surface 13A, in phase A, a plurality (eight in this example) of first electrodes 131A are provided along the circumferential direction of the first surface 13A , and in phase B, a plurality (eight in this example) of second electrodes 131B are provided along the circumferential direction of the first surface 13A . In particular, one end of the plurality of first electrodes 131A is denoted as the first electrode 131A1 and the other end of the first electrode 1 31A is denoted as the first electrode 131A2. Similarly, one end of the plurality of second electrodes 131B is denoted as the second electrode 131B1 and the other end of the second electrode 131B is denoted as the second electrode 131 B2.

[0033] The first surface 13A has a third electrode 131C of a quarter wavelength of the traveling wave between the first electrode 131A1 and the second electrode 131B1 , and between the first electrode 131A2 and the second electrode 131B2 ​​It has a fourth electrode 131D that is 3 / 4 wavelength of the traveling wave. These electrodes 131A, 131B, 1 31C, 131D are polarized into a plus electrode (+) and a minus electrode (-) alternately along the circumferential direction between adjacent electrodes 131A, 131B, 131C, 131D respectively.

[0034] (b) On the second surface 13B, on the back side of the A phase, it has a first electrode 132A and on the back side of the B phase, it has a second electrode 132B. Also, on the second surface 13B, on the back side of the third electrode 131C that is 1 / 4 wavelength of the traveling wave, it has a third electrode 132C that is 1 / 4 wavelength of the traveling wave, and on the back side of the fourth electrode 131D that is 3 / 4 wavelength of the traveling wave, it has a fourth electrode 132D that is 3 / 4 wavelength of the traveling wave.

[0035] When a drive voltage is applied to the first electrode 132A, the drive voltage is transmitted to the A phase, and when a drive voltage is applied to the second electrode 132B the drive voltage of the B phase is transmitted. The third electrode 132C that is 1 / 4 wavelength of the traveling wave is short-circuited to the elastic body 12 with a conductive paint and grounded (GND).

[0036] <Block configuration example of drive circuit 40> FIG. 4 is an explanatory diagram showing a block configuration example of the drive circuit 40. The drive circuit 40 supplies a drive signal that repeatedly varies to the vibration wave motor 10. The drive circuit 40 includes an oscillation unit 60, a phase shift unit 62, an amplification unit 64, a vibration wave motor 10, a rotation detection unit 66, and a control unit 68.

[0037] The oscillation unit 60 generates a drive signal of a desired frequency according to a command from the control unit 68 and outputs it to the phase shift unit 6 2. The phase shift unit 62 separates the drive signal generated by the oscillation unit 60 into two drive signals with different phases. The amplification unit 64 amplifies the two drive signals separated by the phase shift unit 62 ​ Boost them to the desired voltages respectively. The drive signal from the amplifier unit 64 is transmitted to the traveling wave motor 10. Upon the application of this drive signal, a traveling wave is generated in the vibrator 11, and the mover 15 is driven.

[0038] The rotation detection unit 66 is constituted by, for example, an optical encoder or a magnetic encoder, and detects the position and speed of the cam ring 36 driven by the drive of the mover 15, and transmits the detected values (detection position and detection speed) to the control unit 68 as an electrical signal (detection signal).

[0039] The control unit 68 controls the drive of the traveling wave motor 10 based on a drive command from within the lens barrel 20 or from the processor 70 of the camera body 1. The control unit 68 receives the detection signal from the rotation detection unit 66, and calculates information indicating the target position and moving speed of the cam ring 36 based on the detected value.

[0040] Then, the control unit 68 controls the frequency of the oscillation signal from the oscillation unit 60 so as to position the cam ring 36 at the target position. When switching the normal and reverse rotations of the cam ring 36 in the rotation direction, the control unit 68 changes the phase difference of the phase shifter 62 to 90 degrees or minus 90 degrees.

[0041] <Operation example of the traveling wave motor 10> Next, the operation of the traveling wave motor 10 of the embodiment will be described. When a drive command is issued from the control unit 68, the oscillation unit 60 generates a drive signal and outputs it to the phase shifter 62. The drive signal is split by the phase shifter 62 into two drive signals having a 90-degree phase difference, and amplified to the desired voltage by the amplifier unit 64.

[0042] The amplified drive signal is applied to the piezoelectric body 13 of the traveling wave motor 10, and the piezoelectric body 13 is excited. This excitation generates ninth-order bending vibration in the elastic body 12. The piezoelectric body 13 is divided into a phase A and a phase B, and drive signals are applied to the phase A and the phase B, respectively. The ninth-order bending vibration generated from the phase A and the ninth-order bending vibration generated from the phase B are shifted in positional phase by 1 / 4 wavelength. Also, the drive signal applied to the phase A and the drive signal applied to the phase B are shifted in phase by 90 degrees. Therefore, the two bending vibrations are combined to form a traveling wave of nine waves.

[0043] Elliptical motion occurs at the wave crest of the traveling wave. Accordingly, the mover 15 in pressure contact with the drive surface 12a is frictionally driven by this elliptical motion. A rotation detection unit 66 is disposed on the cam ring 36 driven by the mover 15, and an electric pulse is generated therefrom and transmitted to the control unit 68 as a detection signal. Based on this detection signal, the control unit 68 can obtain the current position and the current speed of the cam ring 36.

[0044] In the vibration wave motor 10 described above, a lead-free material is used as the piezoelectric body 13 in consideration of environmental problems. However, as a result of intensive studies by the present inventors, when a lead-free piezoelectric body 13 is mounted on the vibration wave motor 10, it has been found that it is difficult to obtain the same driving performance as that of a piezoelectric body of PZT (lead zirconate titanate) under the same conditions.

[0045] To investigate the cause, examination was made using CAE (computer aided engineering g) analysis or the like, and it was found that the densities of the lead-free piezoelectric body 13 and PZT are different. The density of the lead-free piezoelectric body 13 is, for example, in the case of a niobium-based material 4.2 to 4.7×10 3 [kg / m 3In the case of barium titanate-based materials, it is 5.5 ~6.0×10 3 kg / m 3 .

[0046] On the other hand, for PZT, it is 7.7~7.8×10 3 [kg / m 3 . That is, the lead -free piezoelectric body 13 has a density that is 20 to 40% lower than that of PZT. Due to this , it was found that the vibration characteristics of the vibrator 11 in which the lead-free piezoelectric body 13 and the elastic body 12 are joined cannot be obtained .

[0047] <Equivalent circuit> Fig. 5 is an explanatory diagram showing the equivalent circuit of the vibrator 11 of the vibration wave motor 10. The equivalent circuit is shown in (a), and the calculation formula for the mechanical quality factor Qm is shown in (b). In (a), Lm is the equivalent inductor tance, Cm is the equivalent capacitance, R is the resonance resistance, and Cd is the electrostatic capacitance of the piezoelectric body 13. The values of Lm and Cm affect the resonance characteristics of the vibrator 11. The mechanical quality factor Qm in (b) is a measure showing the resonance characteristics, and the larger this Qm value, the better the resonance characteristics. The mechanical quality factor Q m increases as the value of Lm increases .

[0048] Table 1 shown below shows the values of Lm and Cm calculated by CAE analysis when each material is used as the piezoelectric body 13. Here, the model of the piezoelectric body 13 was configured as follows .

[0049] Outer diameter: 62 [mm] Inner diameter: 55 [mm] Thickness of the vibrator 11: 4.22 [mm] Number of grooves 12c provided on the drive surface 12a side: 48 Depth of the groove 12c: 1.92 [mm]

[0050]

Table 1

[0051] As shown in Table 1, while the Lm value of PZT is 0.341, the Lm value of the barium titanate system is 0.325, and the Lm value of the niobate system is 0.313. That is, the smaller the density becomes, the smaller the Lm value becomes. When the lead-free piezoelectric body 13 is incorporated into the vibrator 11 , the Lm value becomes smaller compared to the case where the piezoelectric body of PZT is incorporated.

[0052] That is, the mechanical quality factor Qm when the lead-free piezoelectric body 13 is incorporated is smaller than that when the piezoelectric body of PZT is incorporated. For this reason, when the lead-free piezoelectric body 13 is incorporated compared to the case where the piezoelectric body of PZT is incorporated, it has been found that it is difficult to obtain the desired resonance characteristics.

[0053] In addition, since the vibration wave motor 10 operates on the principle of utilizing resonance, if the desired vibration characteristics cannot be obtained for the vibrator 11, it is difficult to obtain the driving performance in the state where the mover 15 is combined. Therefore, for the vibrator 11 using the lead-free piezoelectric body 13, there is a tendency to be difficult to obtain the desired driving performance.

[0054] Therefore, in order to improve the resonance characteristics of the vibrator 11 using the lead-free piezoelectric body 13, the tendency of the dimensions of the vibrator 11 with an improved L m value was investigated. Here, the depth of the groove 12c provided between the adjacent protrusion parts 12b of the elastic body 12 is T, the thickness of the base part 12e from the bottom of the groove 12c to the joint surface 1 2d with the piezoelectric body 13 is B, the width of the elastic body 12 in the radial direction DD is W, and the wavelength of the traveling wave generated in the vibrator 11 is λ.

[0055] <Example of CAE analysis results> Figure 6 is a graph showing the CAE analysis results. (a) is the graph showing the CAE analysis results and (b) shows the dimensions of the vibrator 11. Specifically, for example, Figure 6 shows T value: 1.9 - 2.8, B value: 1.0 - 1.9, W value: 2.4 - 4.5, are respectively changed within the range, and the results of calculating the Lm value by CAE analysis are shown. From the calculation results, it can be seen that there is a correlation between the calculation results, the value of [(T / B)÷W], and the Lm value . Specifically, for example, the Lm value tends to be larger as the T value is larger, smaller as the B value is smaller and larger, and also tends to be larger as the W value is smaller, and larger as the λ value is larger .

[0056] Therefore, for a niobium-based material (4.2 - 4.7×10 3 [kg / m 3 ) with a density smaller than that of PZT, when the [(T / B)÷W] value is changed, the CAE analysis calculates what values the Lm value of the vibrator 11 will take in the material of each piezoelectric body 13. The calculation results are shown in Table 2 .

[0057]

Table 2

[0058] Note that Table 2 shows T value: 1.9 - 3.5 B value: 1.0 - 2.9 W value: 2.4 - 4.5 are respectively changed within the range, and the results of calculating the Lm value when the [(T / B)÷W] value becomes 0.51, 0.84, 1 .02, 1.94 are shown. 4.2 - 4.7×10 3 [k g / m 3The range is within the density range of common niobium-based piezoelectric materials, so CAE analysis was performed using the upper limit density value and the lower limit density value.

[0059] According to Table 2, the smaller the density, the smaller the Lm value. On the other hand, it was found that if the [(T / B)÷W] value is increased, a value larger than that of the vibrator 11 equipped with PZT can be obtained. However, since there are also possible drawbacks when increasing the [(T / B)÷W] value, the inventors made a prototype of a vibration with a niobium-based material and decided to investigate the resonance characteristics as the vibration wave motor 10 .

[0060] The material of the piezoelectric body 13 is mainly potassium sodium niobate, and the elastic body 12 is stainless steel. Twelve types of vibrators 11 with different T, B values of the elastic body 12 and the width W of the radial DD were prototyped, and the voltage (driving voltage ) of the driving signal that can drive each prototype of the twelve types of vibrators 11 was investigated.

[0061] The prototypes were T value: 1.5 - 2.0 B value: 0.35 - 0.75 W value: created in the range of 2.4 - 2.7. Also, the density of the piezoelectric body 13 of the prototype is 4.4 ×10 3 [kg / m 3 .

[0062] The lower the voltage of the driving signal that can drive, the better the resonance characteristics of the actual vibration wave motor 10. It is considered that the higher the voltage of the driving signal, the better the resonance characteristics of the actual vibration wave motor 10 . The measurement results are shown in Fig. 7.

[0063] <Example of measurement results of [(T / B)÷W] value> ​​FIG. 7 is a graph showing the measurement results of the [(T / B)÷W] value according to the drive voltage. When the [(T / B)÷W] value was 0.82, the vibration wave motor 1 0 did not start even when a drive voltage of 100 [V] was applied.

[0064] On the other hand, in the range where the [(T / B)÷W] value is 0.84 to 1.94, it was found that the vibration wave motor 10 can be driven with an appropriate drive voltage of 100 [V] or less.

[0065] Also, when the [(T / B)÷W] value was 2.29, the vibration wave motor 10 was driven, but the rotational state of the mover 15 was in a somewhat unstable state.

[0066] Thus, the larger the [(T / B)÷W] value, the larger the Lm value of the vibrator 11 becomes, and the Qm value improves. On the other hand, the electromechanical coupling coefficient Kvn of the vibrator 11 may decrease, resulting in a drawback that the conversion efficiency from electrical energy to mechanical energy deteriorates.

[0067] When the [(T / B)÷W] value was 2.29, that drawback occurred, and it is considered that the rotational state of the mover 15 became somewhat unstable. Based on the above examination results, the vibration wave motor 10 of Example 1 has the following configuration.

Example

[0068] The piezoelectric body 13 contains potassium sodium niobate. Specifically, for example, the piezoelectric body 1 3 has potassium sodium niobate as a main component (for example, 90%), and the rest is made of materials such as lithium or antimony. Also, the density of the piezoelectric body 13 is set to 4.2 to 4.7×10 3 kg / m 3 . ​​​​​

[0069] Also, stainless steel was used for the elastic body 12, and the range of the [(T / B)÷W] value was set to 0.84 to 1.94. With such a configuration, even if the density of the piezoelectric body 13 becomes smaller than the case where PZT is the main component the resonance characteristics can be ensured for the vibrator 11, and the driving performance in the combined state of the mover 15 can be ensured.

[0070] Specifically, for example, when the [(T / B)÷W] value is 0.84, the calculated result by CAE analysis shows that the Lm value of the vibrator 11 is about 0.65, and when the [(T / B)÷W] value is 1.94, the Lm value of the vibrator 11 is about 1.4.

[0071] In the above-described embodiment, the [(T / B)÷W] value was set to 0.84 to 1.94. However, from the viewpoint of further reducing the driving voltage, 0.90 to 1.94 is preferable, and further 1.01 to 1.94 is preferable, and 1.01 to 1.71 is more preferable.

Example

[0072] Example 2 shows an example in which the material of the piezoelectric body 13 is changed with respect to Example 1. Specifically, for example, the piezoelectric body 13 is a material mainly composed of barium titanate, and its density is 5.5 to 6.0 ×10 3 [kg / m 3 . Also, stainless steel was used for the elastic body 12, and the range of the [(T / B )÷W] value was set to 0.84 to 1.94.

[0073] As shown in Table 1, even when the piezoelectric body 13 is barium titanate, since the density of the piezoelectric body 13 is smaller than the case where PZT is the main component, the Lm value of the vibrator 11 decreases, and the vibrator 1 Sufficient resonance characteristics cannot be obtained as 1. Even if the carriers 15 are combined in this state, the driving performance cannot be obtained.

[0074] Therefore, in Example 2, the [(T / B)÷W] value was changed, and the Lm value of the vibrator 11 was calculated by CAE analysis. The calculation results are shown in Table 3.

[0075]

Table 3

[0076] Table 3 shows the results of calculating the Lm values of each vibrator 11 when the density of the piezoelectric body 13 is 5.5×10 3 [kg / m 3 and 6.0×10 3 [kg / m 3 , and the [(T / B)÷W] value is changed to 0.51, 0.84, 1.2, 1 .94.

[0077] When the density of the piezoelectric body 13 is in the range of 5.5~6.0×10 3 [kg / m 3 , since this is the density range of a general barium titanate-based piezoelectric material, CA E analysis was performed at the upper and lower density values. Note that CAE analysis was performed in the range of T value: 1.9~3.5 B value: 1.0~2.9 W value: 2.4~4.5 . The wavelength λ of the traveling wave generated in the vibrator 11 is λ = 2 0.4.

[0078] When the piezoelectric body 13 is barium titanate, when the [(T / B)÷W] value is 0.84, the L m value is about 0.65, and when the [(T / B)÷W] value is 1.94, the Lm value of the vibrator 11 is about 1. 4. When the density of the piezoelectric body 13 is 5.5~6.0×103 [kg / m 3 of the material In the case of barium titanate, regarding the relationship between the [(T / B)÷W] value and the Lm value, the density of the piezoelectric body 13 is 4.2~4.7×10 [kg / m 3 [kg / m 3 of the niobate-based material (see Table 2 ). Therefore, the [(T / B)÷W] value is considered to be in the appropriate range of 0.84~ 1.94.

[0079] When the material of the piezoelectric body 13 is the niobate-based material (density: 4.2~4.7×10 3 [kg / m 3 ) and the Lm value when the material of the piezoelectric body 13 is the barium titanate-based material (density: 5.5~6.0×10 3 [kg / m 3 ) shown in Table 3, the same relationship holds when the [(T / B)÷W] value is in the range of 0. 84~1.94. Therefore, for the density of the piezoelectric body 13 of 4 .2~6.0×10 3 [kg / m 3 , the [(T / B)÷W] value of 0.84~1. 94 is considered to be in the appropriate range.

[0080] In the above embodiments, the [(T / B)÷W] value was set to 0.84~1.94. However, from the viewpoint of further reducing the driving voltage, 0.90~1.94 is preferable, and further 1.01~1.94 is preferable, and 1.01~1.71 is more preferable. preferable, and 1.01~1.71 is more preferable.

Example

[0081] Example 3 will be described. In Examples 1 and 2, the range of the [(T / B)÷W] value was determined so as to increase the Lm value of the equivalent circuit when the lead-free piezoelectric body 13 was mounted. It has been shown that the value is larger than when PZT is mounted as the piezoelectric body 13. There is a tendency to become.

[0082] In order to increase the [(T / B)÷W] value, (1) Increase the T / B value, or (2) Decrease the W value There are two ways, but in both cases, when the speed change is large at the start of the vibration wave motor 10, the vibration wave motor 10 may not be able to be driven. Using FIG. 8, the reason will be explained.

[0083] <Behavior example of the protrusion 12b> FIG. 8 is an explanatory diagram showing the behavior of the protrusion 12b of the vibrator 11 due to the vibration wave. (a) is When the T / B value is smaller than that in (b) (the depth of the groove 12c is shallow), the vibration of the vibrator 11 due to the vibration wave shows the behavior of the protrusion 12b. (b) shows the behavior of the protrusion 12b of the vibrator 11 due to the vibration wave when the T / B value is larger than that in (a) ( the depth of the groove 12c is deep). (c) shows the behavior of the protrusion 12 b of the vibrator 11 due to the vibration wave when the W value is smaller than that in (a).

[0084] (1) When increasing the T / B value When a traveling wave of the vibrator 11 is generated, deformation occurs at the combined part of the thickness of the base part 12e and the thickness of the piezoelectric body 13 (that is, elastic deformation occurs in the elastic body 12 without the protrusion 12b). The neutral plane 800 of the bent elastic body 12 exists between the groove bottom of the groove 12c of the elastic body 12 and the joint surface 12d. And the protrusion 12b swings in the driving direction (the circumferential direction of the elastic body 12) due to the bending vibration generated at the combined part of the thickness B of the base part 12e and the thickness C of the piezoelectric body 13.

[0085] The neutral plane 800 of the bent elastic body 12 exists between the groove bottom of the groove 12c of the elastic body 12 and the joint surface 12d. And the protrusion 12b swings in the driving direction (the circumferential direction of the elastic body 12) due to the bending vibration generated at the combined part of the thickness B of the base part 12e and the thickness C of the piezoelectric body 13. C of the piezoelectric body 13 by the bending vibration generated at the combined part of the thickness B of the base part 12e and the thickness It occurs.

[0086] (a) When T / B is small, the movement of the tip surface (driving surface 12a) of the protrusion 12b in the driving direction is small. As in (b), when T / B is large, the movement in the driving direction becomes large. Here, the speed of the movement is estimated. The movement of the mover 15 in the driving direction that occurs in the portion where the thickness B of the base portion 12e and the thickness C of the piezoelectric body 13 are combined is taken as ((B + C) / 2). It is. It occurs.

[0087] ((B + C) / 2) is half of the distance obtained by combining the thickness B of the base portion 12e and the thickness C of the piezoelectric body 13, that is, the distance from the second surface 13B that joins the non-woven fabric 16 of the piezoelectric body 13 to the neutral plane 800. In this case, on the driving surface 12a, a movement in the driving direction that is (T + (B + C) / 2) / ((B + C) / 2) times that of the mover 15 occurs. For example, when T is increased, the swing of the driving surface 12a becomes larger accordingly. It occurs. Also, since the thickness C of the piezoelectric body 13 is several tenths or less compared to the thickness B of the base portion 12e, the above formula (T + (B + C) / 2) / ((B + C) / 2) can be approximated as (T + B / 2) / (B / 2). It occurs.

[0088] When T / B is large, since the movement in the driving direction is large, the force applied from the mover 15 to the driving surface 12a becomes large. For example, when the displacement of the movement of the elastic body 12 in the driving direction doubles, the speed and acceleration of the mover 15 also become twice as large. When trying to move the mover 15 that contacts the driving surface 12a, a force (load) twice as large is applied to the driving surface 12a. Due to this, when the speed change is large as in the case of starting the vibration wave motor 10,

[0089] in a state where the vibration is large, such as when starting the vibration wave motor 10, It occurs. the speed and acceleration of the mover 15 also become twice as large. When trying to move the mover 15 that contacts the driving surface 12a, a force (load) twice as large is applied to the driving surface 12a. Due to this, when the speed change is large as in the case of starting the vibration wave motor 10, in a state where the vibration is large, such as when starting the vibration wave motor 10, There are cases where the wave motor 10 cannot be driven.

[0090] (2) When reducing the W value When the traveling wave of the vibrator 11 is generated, the protrusion 12b, as described above, is at the base portion 12 Due to the bending vibration generated at the combined part of the thickness B of the e and the thickness C of the piezoelectric body 13, it swings in the driving direction ( circumferential direction of the elastic body 12).

[0091] When the outer inner diameter width W is small, that is, when the outer inner diameter width W is narrow, compared with the case where W is wide, the mass of the protrusion 12b of the vibrator 11 becomes small. Therefore, due to the small mass, the inertial force of the protrusion 12b in the driving direction becomes small, and the range of the driving resistance against the force in the driving direction applied from the mover 15 to the driving surface 12a is reduced. For example, when the outer inner diameter width W becomes 1 / 2 times, the mass of the protrusion 12b becomes 1 / 2 times. When trying to move the mover 15 in contact with the driving surface 12a, the range of the driving resistance against the force (load) from the driving surface 12a becomes 1 / 2 times. Due to this, in a state where the speed change is large like at the start of the vibration wave motor 10, there are cases where the vibration wave motor 10 cannot be driven.

[0092] There are cases where it cannot be driven.

[0093] From the above considerations, (1) when the T / B value is large and (2) when W is small, in a state where the speed change is large like at the start of the vibration wave motor 10, the force applied from the mover 15 to the driving surface 12a becomes large.

[0094] That is, the larger the value of [(T / B)÷W], in a state where the speed change is large like at the start of the vibration wave motor 10, the force applied from the mover 15 to the driving surface 12a ​​​​​​​​​As the force increases, the vibration wave motor 10 becomes difficult to start.

[0095] Also, according to the above considerations, (1) When the T / B value increases, the force applied from the mover 15 to the drive surface 12a increases almost in proportion to that value. On the other hand, when the T / B value increases, the force applied from the mover 15 to the drive surface 12a increases almost in proportion to that value. (2) When W decreases, the force applied from the mover 15 to the drive surface 12a increases almost semi-proportionally to that value. Based on the results of this consideration, a method for starting the vibration wave motor 10 was examined. .

[0096] <Example of drive sequence of vibration wave motor 10> FIG. 9 is an explanatory diagram showing an example of a drive sequence of the vibration wave motor 10. In FIG. 9, the temporal change in the drive frequency of the vibration wave motor 10, the temporal change in the drive voltage of the vibration wave motor 10, the temporal change in the phase difference between the two drive signals, and the temporal change in the rotational speed of the vibration wave motor 10 are shown.

[0097] In a state (t0) where there is no drive command from the control unit 68, Drive frequency: fs0 Drive voltage: voltage V0 (= 0 [V]) Phase difference between phase A and phase B: 0 degrees

[0098] When a drive command is given from the control unit 68 (t1), Drive frequency: fs0 Drive voltage: voltage V1 Phase difference between phase A and phase B: 90 degrees (-90 degrees during reverse drive)

[0099] When the drive frequency is gradually decreased and the frequency at t2 becomes f0, the mover 15 is rotationally driven.

[0100] At time t4, the frequency becomes flow, and the rotational speed reaches the target speed Rev1.

[0101] In Example 3, according to the [(T / B)÷W] value, when sweeping the frequency, the time for the change in frequency is lengthened. Specifically, for example, a relationship is established with the frequency difference between flow - fs0 and the time difference between t4 - t2 (hereinafter referred to as the rise time).

[0102] When the [(T / B)÷W] value is small, the rise time (t4 - t2) is shortened.

[0103] When the [(T / B)÷W] value is large, the rise time (t4 - t2) is lengthened.

[0104] This is because by increasing the rise time (t4 - t2), the reaction force from the mover 15 acting on the vibrator 11 of the vibration wave motor 1 at startup is reduced.

[0105] In the case of the vibration wave motor 10 equipped with PZT, [(T / B)÷W]: 0.51, and the frequency change rate during frequency sweeping at startup is set to about 1 [kHz / msec].

[0106] When the [(T / B)÷W] value is in the range of 0.84 - 1.02, the movement of the drive surface 12a in the driving direction increases by about 1.6 - 2 times compared to [(T / B)÷W] = 0.51. Therefore, if the rise time (t4 - t2) is doubled, that is, the frequency change rate of frequency sweeping is set to about 1 / 2 of it, for example, 0.5 [kHz / msec], the burden on the vibration wave motor 10 is about the same as or less than [(T / B)÷W]: 0.51 when PZT is mounted.

[0107] Also, when the [(T / B)÷W] value is in the range of 1.02 - 1.94, the drive surface 12a's The movement in the driving direction increases by about 2 to 3.8 times with respect to [(T / B)÷W]=0.51. Therefore, if the rise time (t4 - t2) is quadrupled, that is, the frequency change rate of the frequency sweep is reduced to about 1 / 4 of it, for example, to 0.25 [kHz / msec], the load on the vibration wave motor 10 will be the same as or less than [(T / B)÷W]:0.51 when the PZT is mounted.

[0108] By changing the amount of frequency change according to the [(T / B)÷W] value, even when the vibration wave motor 1 is in a state of large speed change like at the start-up (that is, when the load on the vibrator 11 of the vibration wave motor 10 is large), the vibration wave motor 10 can be surely started.

[0109] In this embodiment, the vibration wave motor 10 using a progressive vibration wave has been disclosed for the case of nine waves, but for other wave numbers of 4 to 8 waves and 10 waves or more, with the same configuration and the same control, the same effects can be obtained.

Explanation of Signs

[0110] 10 Vibration wave motor, 11 Vibrator, 12 Elastic body, 12a Driving surface, 12b Protrusion, 12c Groove, 12d Joint surface, 12e Base portion, 13 Piezoelectric body, 13A First surface, 13 B Second surface, 15 Mover, 15a Sliding surface, 15b Joint surface, 36 Cam ring, 40 Drive circuit, 60 Oscillation unit, 62 Phase shifter, 64 Amplifier, 66 Rotation detector, 68 Control unit 、70 Processor, 100 Camera, 800 Neutral plane, B Thickness of the base portion, T Depth of the groove 、W Outer inner diameter width​​​​

Claims

1. An element that is displaced by application of a voltage; The actuator has a bottom surface that contacts the element and a driving surface having a groove, and the actuator is driven by the displacement of the element. a ring-shaped elastic body that drives the moving element by vibration waves generated on the moving surface; The density of the elements is 4.2 to 6.0×10 ３ kg / m ３ and The depth of the groove is T, the distance from the bottom of the groove to the bottom surface is B, and the elastic body If the radial width is W, the value of [(T / B)÷W] is in the range of 0.84 to 1.

94. R, Oscillatory wave motor.

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