JP2015089291A - Vibration actuator, lens barrel and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration actuator in which drive efficiency of a vibration wave motor is enhanced.SOLUTION: A vibration actuator includes an electromechanical conversion element vibrating with a drive signal, an elastic body bonded to the electromechanical conversion element, and converting the vibration thereof into a traveling wave, a rotor in contact with the elastic body and rotating by the traveling wave thereof, and a control unit 41 for supplying a drive signal to the electrode of the electromechanical conversion element. The electrodes of the electromechanical conversion element are arranged so that the phases are different spatially by 120 degrees, and the control unit 41 supplies any one of drive signals of 3-phase or 2-phase, selectively, to the electrode of the electromechanical conversion element.

Description

  The present invention relates to a vibration actuator, a lens barrel, and a camera.

  2. Description of the Related Art Conventionally, an annular vibration wave motor in which an input portion of an electromechanical conversion element is a three-phase type is known (see Patent Document 1).

JP-A-11-341846

  In the above conventional example, the drive signal is always input in three phases to the input portion of the electromechanical conversion element, resulting in a decrease in drive efficiency.

  An object of the present invention is to provide a vibration actuator, a lens barrel, and a camera that improve the driving efficiency of a vibration wave motor.

The present invention solves the above problems by the following means.
The invention according to claim 1 is an electromechanical transducer that vibrates by a drive signal, an elastic body that generates a traveling wave by the vibration of the electromechanical transducer, and a rotor that rotates by the traveling wave of the elastic body; And a control unit that selectively supplies one of three-phase or two-phase drive signals having different phases to the electromechanical transducer.
According to a second aspect of the present invention, in the vibration actuator according to the first aspect of the present invention, electrodes are arranged on the electromechanical transducer so that the phases are spatially different by 120 degrees.
According to a third aspect of the present invention, in the vibration actuator according to the first aspect, when the three-phase input is performed, the control unit supplies a drive signal having a phase difference of 120 degrees in time to the three phases, and when the two-phase input is performed. A drive signal having a phase difference of 60 degrees in time is supplied to the two phases, and the phase difference of the drive signal is gradually changed at the transition between the three-phase input and the two-phase input.
According to a fourth aspect of the present invention, in the vibration actuator according to the third aspect, in the transition from the three-phase input to the two-phase input, the control unit drives to one phase that does not supply a drive signal at the two-phase input. It is characterized by gradually reducing the signal.
According to a fifth aspect of the present invention, in the vibration actuator according to the third aspect, in the transition from the two-phase input to the three-phase input, the control unit drives to one phase that supplies a drive signal at the time of the three-phase input. It is characterized by gradually increasing the signal.
According to a sixth aspect of the present invention, in the vibration actuator according to any one of the first to fifth aspects, the electromechanical transducer is provided with the electrode for each half wave, and the wave number of the traveling wave is 3N + 1 ( N: integer of 2 or more), in the case of three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to a wave number N + 0.5, and sends the remaining one-phase drive signal to a wave number N−. The two-phase input signal is supplied to only the electrode corresponding to the wave number N + 0.5.
According to a seventh aspect of the present invention, in the vibration actuator according to any one of the first to fifth aspects, the electromechanical transducer is provided with the electrode for each half wave, and the wave number of the traveling wave is 3N + 2 ( N: integer of 1 or more), in the case of three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to a wave number N + 0.5, and sets the remaining one-phase drive signal to a wave number N. The two-phase input is supplied to the corresponding electrode, and the two-phase drive signal is supplied only to the electrode corresponding to the wave number N + 0.5.
According to an eighth aspect of the present invention, in the vibration actuator according to any one of the first to fifth aspects, the electromechanical transducer has the electrode provided for every half wave, and the wave number of the traveling wave is 3N + 2 ( N: integer of 1 or more), in the case of three-phase input, the control unit supplies a two-phase drive signal to the electrode corresponding to the wave number N, and the remaining one-phase drive signal corresponds to the wave number N + 1. The two-phase input is supplied to the electrode, and the two-phase drive signal is supplied only to the electrode corresponding to the wave number N.
According to a ninth aspect of the present invention, in the vibration actuator according to any one of the first to fifth aspects, the electromechanical transducer is provided with the electrode for each half wave, and the wave number of the traveling wave is 3N ( N: an integer of 2 or more), in the case of three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to the wave number N, and sets the remaining one-phase drive signal to a wave number N-1. The two-phase input is supplied to the corresponding electrode, and the two-phase drive signal is supplied only to the electrode corresponding to the wave number N.
According to a tenth aspect of the present invention, in the vibration actuator according to any one of the first to fifth aspects, the electromechanical transducer is provided with the electrode for each half wave, and the wave number of the traveling wave is 3N ( N: an integer of 2 or more), in the case of three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to the wave number N-0.5, and the remaining one-phase drive signal has a wave number. The two-phase drive signal is supplied to only the electrode corresponding to the wave number N-0.5.
According to an eleventh aspect of the present invention, an electromechanical transducer that vibrates by a drive signal, an elastic body that is joined to the electromechanical transducer and converts vibrations of the electromechanical transducer into a traveling wave, and the elastic body A vibration actuator comprising: a rotor that is contacted and rotated by a traveling wave of the elastic body; and a control unit that supplies a drive signal to the electrode of the electromechanical conversion element. In the case of rotating a driven body having a small torque difference from the torque in the electromechanical conversion element, the number of remaining one-phase electrodes is smaller than the number of two-phase electrodes having the same number of electrodes. An electrode is disposed on the electromechanical conversion element, and the controller selectively supplies either a three-phase input signal or a two-phase input drive signal to the electrode of the electromechanical transducer.
According to a twelfth aspect of the present invention, in the vibration actuator according to the eleventh aspect, the driven body having a small torque difference between the required torque at the start-up and the torque in the steady state is the required torque at the start x 0. 8 is less than the torque in a steady state.
According to a thirteenth aspect of the present invention, there is provided an electromechanical transducer that vibrates in response to a drive signal, an elastic body that is joined to the electromechanical transducer and converts vibrations of the electromechanical transducer into a traveling wave, and the elastic body. A vibration actuator comprising: a rotor that is contacted and rotated by a traveling wave of the elastic body; and a control unit that supplies a drive signal to the electrode of the electromechanical conversion element. In the case of rotating a driven body having a large torque difference from the torque in the electromechanical conversion element, the number of remaining one-phase electrodes is larger than the number of two-phase electrodes having the same number of electrodes. An electrode is disposed on the electromechanical conversion element, and the controller selectively supplies either a three-phase input signal or a two-phase input drive signal to the electrode of the electromechanical transducer.
According to a fourteenth aspect of the present invention, in the vibration actuator according to the thirteenth aspect, the driven body having a large torque difference between the required torque at the time of starting and the torque in a steady state is the required torque at the time of starting x 0. 8 exceeds the torque in a steady state.
According to a fifteenth aspect of the present invention, in the vibration actuator according to any one of the first to fourteenth aspects, the electromechanical transducer is a single plate type.
A sixteenth aspect of the present invention is a lens barrel including the vibration actuator according to any one of the first to fifteenth aspects.
According to a seventeenth aspect of the present invention, in the lens barrel according to the sixteenth aspect, the vibration actuator is a hollow type, and an optical path is disposed in the hollow portion.
The invention described in claim 18 is a camera provided with the lens barrel described in claim 16 or 17.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration actuator, lens barrel, and camera which improved the drive efficiency of the vibration wave motor can be provided.

It is a figure explaining electronic camera 1 of an embodiment. It is a figure explaining the lens barrel. FIG. 3 is a partially broken perspective view of a vibrator 11 and a mover 15. 3 is a block diagram illustrating a driving device 40. FIG. It is a schematic diagram which shows the electrode pattern of the piezoelectric material 13 in case the wave number of a traveling wave is 3N + 1. It is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 1 and the C-phase assist force is weakened. It is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 2 and the C-phase assist force is weakened. It is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 2 and the C-phase assist force is increased. It is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N and the assist force of the C phase is weakened. It is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N and the C-phase assist force is increased.

  Hereinafter, embodiments of a vibration actuator, a lens barrel, and a camera according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating an electronic camera 1 according to this embodiment.
The electronic camera 1 of the present embodiment includes an imaging optical system (lens barrel 20), an imaging element 30, an AFE (Analog front end) circuit 60, an image processing unit 70, an audio detection unit 80, and a buffer memory 110. And the recording interface 120, the monitor 140, the operation member 90, the memory 130, and the CPU 100, and can be connected to the PC 150 as an external device.

  The lens barrel 20 includes a plurality of optical lenses, and forms a subject image on the light receiving surface of the image sensor 30. In FIG. 1, the optical lens system is simplified and illustrated as a single lens L. In addition, the optical lens L for AF in the optical lens group is driven by driving the vibration wave motor 10.

  The image sensor 30 is configured by a CMOS image sensor or the like in which light receiving elements are two-dimensionally arranged on a light receiving surface. The image sensor 30 photoelectrically converts the subject increase caused by the light beam that has passed through the imaging optical system 20 to generate an analog image signal. The analog image signal is input to the AFE circuit 60.

  The AFE circuit 60 performs gain adjustment (signal amplification according to ISO sensitivity) for the analog image signal. Specifically, the imaging sensitivity is changed within a predetermined range in accordance with a sensitivity setting instruction from the CPU 100. The AFE circuit 60 further converts the image signal after analog processing into digital data by a built-in A / D conversion circuit. The digital data is input to the image processing unit 70.

The image processing unit 70 performs various types of image processing on the digital image data.
The buffer memory 110 temporarily records image data in the pre-process and post-process of image processing by the image processing unit 70.
The sound detection unit 80 includes a microphone and a signal amplification unit (not shown). The sound detection unit 80 mainly detects and captures sound from the subject direction during moving image shooting, and transmits the data to the CPU 100.

The recording interface 120 has a connector (not shown). A memory card 121 is connected to the connector, and data is written to the connected memory card 121 and data is read from a recording medium.
The monitor 140 is composed of a liquid crystal panel, and displays an image, an operation menu, and the like according to an instruction from the CPU 100.

  The operation member 90 indicates a mode dial, a cross key, an enter button, and a release button, and sends an operation signal corresponding to each operation to the CPU 100. Settings for still image shooting and moving image shooting are set by the operation member 90.

The CPU 100 comprehensively controls operations performed by the electronic camera 1 by executing a program stored in a ROM (not shown). For example, AF (autofocus) operation control, AE (automatic exposure) operation control, auto white balance control, and the like are performed.
The memory 130 records a series of image data subjected to image processing.

  FIG. 2 is a diagram for explaining the lens barrel 20 and is a view showing a state in which the ring-shaped vibration wave motor 10 is incorporated in the lens barrel 20. FIG. 3 is a partially broken perspective view of the vibrator 11 and the moving element 15. 2 and 3, the direction toward the subject is defined as the Z direction at the camera position (hereinafter referred to as a normal position) when the photographer takes a horizontally long image with the optical axis OA being horizontal.

  The vibrator 11 is joined to the piezoelectric body 13 and an electromechanical transducer (hereinafter referred to as a piezoelectric body) 13 that converts electrical energy into mechanical energy, such as a single-plate piezoelectric element or electrostrictive element. And an elastic body 12. In the vibrator 11, traveling waves having wave numbers 4, 5, 3N (N: integer of 2 or more), 3N + 1, 3N + 2,.

  The elastic body 12 is made of a metal material having a high resonance sharpness and has an annular shape. In the elastic body 12, a groove 12c is cut on the opposite side of the bonding surface 12d to which the piezoelectric body 13 is bonded. Then, the tip surface of the protruding portion 12b (a portion where the groove 12c is not provided) becomes the driving surface 12a and is brought into pressure contact with the moving element 15. The reason for cutting the groove 12c is to make the neutral surface of the traveling wave as close to the piezoelectric body 13 as possible, thereby amplifying the amplitude of the traveling wave on the drive surface 12a.

  The piezoelectric body 13 is divided into three phases (A phase, B phase, and C phase) along the circumferential direction. In each phase, the first divided region 13A, the second divided region 13B, and the third divided region 13C divided in the radial direction are arranged so that the phases are spatially different by 120 degrees ( FIG. 5 to FIG. 10). On the back surface side of the piezoelectric body 13, electrodes corresponding to each divided region are provided for each half wave. The electrodes corresponding to the respective divided regions (hereinafter also referred to as electrode patterns) differ depending on the wave number of traveling waves and the strength of assist force (described later) in the C phase, as will be described later.

Under the piezoelectric body 13, a non-woven fabric 16, a pressure plate 17, and a pressure member 18 are disposed.
The nonwoven fabric 16 is made of, for example, a felt material, and is disposed under the piezoelectric body 13 and functions so as not to transmit the vibration of the piezoelectric body 13 to the pressure plate 17 and the pressure member 18.
The pressure plate 17 is pressurized by the pressure member 18.
The pressure member 18 is disposed under the pressure plate 17 and generates a pressurizing force. In this embodiment, the pressure member 18 is a disc spring, but it may be a coil spring or a wave spring instead of a disc spring. The pressure member 18 is held by being fixed to a pressing ring 19 fixed to the fixing member 14.

  The mover 15 is a rotor that converts the vibration of the piezoelectric body 13 into a rotational force through a traveling wave. The mover 15 is made of a light metal such as aluminum, and a sliding material for improving wear resistance is provided on the surface of the sliding surface 15a.

  On the side opposite to the sliding surface 15a of the mover 15 (Z plus direction in FIG. 3, the optical axis direction subject side), rubber is absorbed in order to absorb vibration in the vertical direction (Z direction in FIG. 3) of the mover 15. Such a vibration absorbing member 23 is disposed, and an output transmission member 24 is disposed in the Z plus direction.

  The output transmission member 24 regulates the pressurizing direction (Z direction) and the radial direction by a bearing 25 provided on the fixed member 14. Thereby, the moving element 15 is regulated in the pressurizing direction and the radial direction.

  The output transmission member 24 has a protrusion 24 a from which a fork 35 connected to the cam ring 36 is engaged, and the cam ring 36 is rotated as the output transmission member 24 rotates.

  A key groove 37 is obliquely cut in the cam ring 36, and a fixing pin 38 provided in the AF ring 34 is engaged with the key groove 37. The AF ring 34 is driven in the straight direction in the axial direction so that it can stop at a desired position.

  The fixing member 14 has a pressing ring 19 attached thereto by screws, and by attaching this, the output transmission member 24, the moving element 15, the piezoelectric body 13, and the pressing member 18 can be configured as one motor unit.

FIG. 4 is a block diagram illustrating the driving device 40 (FIG. 2).
The oscillating unit 42 generates a drive signal having a desired frequency according to a command from the control unit 41.
The phase shift unit 43 divides the drive signal generated by the oscillating unit 42 into three drive signals having different phases in response to a command from the control unit 41.
The amplification unit 44 boosts the three drive signals divided by the phase shift unit 43 to desired voltages, respectively.

  The drive signal from the amplifying unit 44 is transmitted to the vibration wave motor 10 (the electrode of the piezoelectric body 13). By applying this drive signal, a traveling wave is generated in the elastic body 12 of the vibration wave motor 10, and the moving element 15 is Rotate.

  The rotation detection unit 46 includes an optical encoder, a magnetic encoder, and the like, detects the position and speed of a driven body (optical lens L) driven by driving the moving element 15, and uses the detected value as an electrical signal to control the control unit. 41.

  The control unit 41 controls the driving of the vibration wave motor 10 based on a driving command from the CPU 100 in the lens barrel 20 or the camera 1 main body. The control unit 41 receives the detection signal from the rotation detection unit 46, obtains position information and speed information based on the value, and controls the frequency, phase difference, etc. of the oscillation unit 42 so as to be positioned at the target position. To do. The control unit 41, the piezoelectric body 13, the elastic body 12, and the mover 15 constitute a vibration actuator in the present embodiment.

  The control unit 41 of this embodiment is characterized in that the vibration wave motor 10 is selectively supplied with either a three-phase input or a two-phase input drive signal.

  Specifically, in the piezoelectric body 13, when the wave number of the traveling wave is 3N + 1 (N is an integer equal to or larger than 1), the control unit 41 sends the drive signal of the three-phase input to the electrode corresponding to the wave number N of each phase. To supply each. On the other hand, the control unit 41 supplies a two-phase input drive signal to two electrodes (for example, A phase and B phase) corresponding to the wave number N.

  In the present embodiment, the three phases of the piezoelectric body 13 are spatially shifted by 120 degrees, and the electrode areas corresponding to the respective phases are substantially the same for all three electrodes. A drive signal is supplied only to any two phases.

  The control unit 41 uses a three-phase input when the output power of the vibration wave motor 10 is more necessary, and a two-phase input when there is no need to increase the output power. For example, the control unit 41 uses a three-phase input when the vibration wave motor 10 is activated, and transitions to a two-phase input when reaching a predetermined rotation region.

  It should be controlled so that at least one phase input is not performed when the vibration wave motor 10 reaches the predetermined rotation region. That is, a transition from a three-phase input to a one-phase or two-phase input may be performed. The predetermined rotation area is, for example, when the moving element 15 of the vibration wave motor 10 rotates more than 1/10000 or more than the entire circumference, or when the moving element 15 rotates about 20 to 30% of the rated rotation. Say.

  Further, the control unit 41 gradually changes the phase difference of the drive signal in the transition between the three-phase input and the two-phase input. Specifically, in the transition from the three-phase input to the two-phase input, the control unit 41 gradually changes the phase of the drive signal supplied to each of A, B, and C from 120 degrees to 60 degrees. Moreover, the control part 41 changes gradually the drive signal supplied to each phase of A, B, C from 60 degree | times to 120 degree | times in the transition from 3 phase input to 2 phase input.

  Further, the control unit 41 is characterized in that, in the transition from the three-phase input to the two-phase input, the drive signal to one phase that does not supply the drive signal at the time of the two-phase input is gradually reduced. For example, when transitioning to a two-phase input, the drive signal to the C phase that has supplied the voltage of the drive signal at the three-phase input is gradually reduced.

  In addition, the control unit 41 is characterized by gradually increasing the drive signal to one phase for supplying the drive signal at the time of three-phase input in the transition from the two-phase input to the three-phase input. For example, when transitioning to a three-phase input, the drive signal to the C phase that is not supplying the drive signal at the two-phase input is gradually increased.

  Ordinarily, a 1-phase or 2-phase input may be used, and a 3-phase input may be performed only when an output is more necessary. The case where the output is more necessary is, for example, a case where the load is partially increased during the operation of the cam mechanism that moves the optical lens L in the optical axis direction. The increase in the load can be detected by monitoring the current value and voltage value of the drive signal output from the amplifying unit 44, for example.

  In addition, in the case of an electrode pattern in which the wave number of the traveling wave is 3N + 1 (N: an integer of 2 or more) and the assist force due to the C phase is weakened, the control unit 41 outputs a two-phase drive signal with a three-phase input. The electrode corresponding to the wave number N + 0.5 is supplied, and the remaining one-phase drive signal is supplied to the electrode corresponding to the wave number N-1. In the two-phase input, the control unit 41 supplies the two-phase drive signal only to the electrode corresponding to the wave number N + 0.5.

  The assist force is a driving force that increases by supplying a driving signal to the C phase. Normally, a traveling wave can be generated over the entire circumference of the piezoelectric body 13 by supplying driving signals whose phases are different by 60 degrees in time even with only the AB phase. At that time, the amplitude of the traveling wave can be further increased by supplying the drive signal to the C phase. If the assist force is weak, the driving force increases. If the assist force is high, the driving force increases. As will be described later, the electrode pattern of the piezoelectric body 13 differs depending on the strength of the assist force due to the C phase.

  In addition, in the case of an electrode pattern in which the wave number of the traveling wave is 3N + 2 (N: an integer of 1 or more) and the assist force due to the C phase is weakened, the control unit 41 outputs a two-phase drive signal with a three-phase input. The electrode corresponding to the wave number N + 0.5 is supplied, and the remaining one-phase drive signal is supplied to the electrode corresponding to the wave number N. In the two-phase input, the control unit 41 supplies the two-phase drive signal only to the electrode corresponding to the wave number N + 0.5.

  In addition, in the case of an electrode pattern in which the wave number of the traveling wave is 3N + 2 (N: an integer of 1 or more) and the assist force by the C phase is strengthened, the control unit 41 outputs a two-phase drive signal for a three-phase input. The electrode corresponding to the wave number N is supplied, and the remaining one-phase drive signal is supplied to the electrode corresponding to the wave number N + 1. In the two-phase input, the control unit 41 supplies the two-phase drive signal only to the electrode corresponding to the wave number N.

  In addition, in the case of an electrode pattern in which the wave number of the traveling wave is 3N (N: an integer of 2 or more) and the assist force due to the C phase is weakened, the control unit 41 outputs a two-phase drive signal for a three-phase input. The electrode corresponding to the wave number N is supplied, and the remaining one-phase drive signal is supplied to the electrode corresponding to the wave number N-1. In the two-phase input, the control unit 41 supplies the two-phase drive signal only to the electrode corresponding to the wave number N.

  In addition, in the case of an electrode pattern in which the traveling wave number is 3N (N: integer greater than or equal to 2) and the assist force by the C phase is increased, the control unit 41 outputs a two-phase drive signal for a three-phase input. The electrode corresponding to the wave number N−0.5 is supplied, and the remaining one-phase drive signal is supplied to the electrode corresponding to the wave number N. In the two-phase input, the control unit 41 supplies the two-phase drive signal only to the electrodes corresponding to the wave number N-0.5.

  The three phases in the piezoelectric body 13 may have a configuration in which two phases have the same electrode area, and the remaining one phase is smaller than that and larger than half a wave. In this case, at the time of two-phase input, drive signals are supplied only to two phases having the same area.

  Further, the three phases in the piezoelectric body 13 may have a configuration in which two phases have the same electrode area, and the remaining one phase is smaller than that and smaller than half a wave. In that case, at the time of two-phase input, drive signals are supplied only to two phases having the same area.

  Further, in the configuration in which the piezoelectric body 13 is N-phase input (N: integer of 4 or more) and the electrodes are arranged so that the N-phase is spatially different by 360 degrees, the N-phase of the piezoelectric body 13 is changed to N-phase input. Drive signals having different phases of 360 / N degrees may be input. In that case, a drive signal of one phase or more is not supplied as necessary.

  In the above configuration, at least two phases of the piezoelectric body 13 may have an electrode pattern for the same wavelength of one wave or more, and the remaining N-2 phase may have an electrode pattern for at least one wavelength. If a drive signal of one phase or more is not supplied as necessary, the drive signal is continuously input to two phases having electrode patterns for the same wavelength.

  In the above configuration, at least two phases of the piezoelectric body 13 have an electrode pattern for the same wavelength of 1.5 waves or more, and the remaining N-2 layer has an electrode pattern for at least 1.5 wavelengths or more. It is good also as a structure. If a drive signal of one phase or more is not supplied as necessary, the drive signal is continuously input to two phases having electrode patterns for the same wavelength.

Next, the operation of the control unit 41 in this embodiment will be specifically described.
First, a case where the wave number of the traveling wave is 3N + 1 (4, 7, 10, 13...) Will be described.

  FIG. 5 is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 1. FIG. 5 shows the arrangement of electrode patterns provided on the side in contact with the piezoelectric body 13 (the same applies to other similar drawings). An electrode common to the electrode patterns of each phase is provided on the side opposite to the surface in contact with the piezoelectric body 13. These electrodes are constituted by, for example, an FPC formed in an annular shape.

  As shown in FIG. 5, when the wave number of the traveling wave is 3N + 1, the A-phase, B-phase, and C-phase electrodes are arranged so that the phases are spatially different by 120 degrees. The electrodes of each phase are arranged so that the polarization directions are opposite to each other (+ -indicated in the figure) between the adjacent electrodes. Each phase is arranged with a phase shift of λ / 3. Three λ / 3 portions are provided. In the example of FIG. 5, the wave number is 2 in each phase, and when the wave number 1 in the three λ / 3 portions is added, a total of 7 traveling waves are formed.

  FIG. 6 is a schematic diagram illustrating an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 1 and the C-phase assist force is weakened.

  As shown in FIG. 6, when the assist force of the C phase is weakened, the wave number is 2.5 (total of 5 waves) in the A phase and the B phase, and the wave number of the C phase is 1. Therefore, when a wave number of 1 at three λ / 3 portions is added, a total of 7 traveling waves are formed.

  5 and FIG. 6, in the case of a three-phase input, by supplying drive signals having phases different by 120 degrees in time to the phases A, B, and C, it proceeds to the piezoelectric body 13. Waves can be generated. In the case of a two-phase input, for example, a traveling wave can be generated in the piezoelectric body 13 by supplying drive signals whose phases are different by 60 degrees in time to the AB phase.

Next, the case where the wave number of the traveling wave is 3N + 2 (5, 8, 11, 14...) Will be described.
FIG. 7 is a schematic diagram showing the electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 2 and the C-phase assist force is weakened. As shown in FIG. 7, when the assist force of the C phase is weakened, the wave number is 2.5 (total of 5 waves) in the A phase and the B phase, and the wave number of the C phase is 2. Therefore, a total of 8 traveling waves are formed.

  FIG. 8 is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N + 2 and the C-phase assist force is strengthened. As shown in FIG. 8, when the assist force of the C phase is increased, the wave number is 2 (total of 4 waves) in the A phase and the B phase, and the wave number of the C phase is 3. Therefore, a total of 8 traveling waves are formed.

  Also in the electrode patterns shown in FIGS. 7 and 8, in the case of three-phase input, by supplying drive signals whose phases are different by 120 degrees in time to the phases A, B, and C, the piezoelectric body 13 is supplied. A traveling wave can be generated. In the case of a two-phase input, for example, a traveling wave can be generated in the piezoelectric body 13 by supplying drive signals whose phases are different by 60 degrees in time to the AB phase.

Next, a case where the wave number of the traveling wave is 3N (6, 9, 12, 15 ...) will be described.
FIG. 9 is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N and the C-phase assist force is weakened. As shown in FIG. 9, when the assist force of the C phase is weakened, the wave number is 3 (total 6 waves) in the A phase and the B phase, and the wave number of the C phase is 2. Therefore, nine traveling waves are formed in total.

  FIG. 10 is a schematic diagram showing an electrode pattern of the piezoelectric body 13 when the wave number of the traveling wave is 3N and the C-phase assist force is increased. As shown in FIG. 10, when the C-phase assist force is increased, the wave number is 2.5 (total of 5 waves) in the A phase and the B phase, and the wave number of the C phase is 3. Therefore, nine traveling waves are formed in total.

  Also in the electrode patterns shown in FIGS. 9 and 10, in the case of a three-phase input, by supplying drive signals that are 120 degrees different in phase to the phases A, B, and C, the piezoelectric body 13 is supplied. A traveling wave can be generated. In the case of a two-phase input, for example, a traveling wave can be generated in the piezoelectric body 13 by supplying drive signals whose phases are different by 60 degrees in time to the AB phase.

Next, the relationship between the strength of the assist force and the electrode pattern of the piezoelectric body 13 will be described.
When the driven body (optical lens L) having a small torque difference between the required torque at the start and the torque in the steady state is rotated, the assist force due to the C phase is weakened. The electrodes are arranged so that the number of remaining one-phase electrodes is smaller than the number of two-phase electrodes. For example, as shown in FIGS. 6, 7, and 9, the electrodes are arranged so that the number of C-phase electrodes is smaller than the number of AB-phase electrodes having the same number of electrodes.

  The driven body having a small torque difference between the required torque at the start and the torque in the steady state refers to, for example, that the required torque at start × 0.8 is less than the torque in the steady state.

  Further, when the driven body having a large torque difference between the required torque at the start and the torque in the steady state is rotated, in order to increase the assist force due to the C phase, the piezoelectric body 13 has two phases having the same number of electrodes. The electrodes are arranged so that the number of remaining one-phase electrodes is larger than the number of electrodes. For example, as shown in FIGS. 8 and 10, the electrodes are arranged so that the number of C-phase electrodes is larger than the number of AB-phase electrodes having the same number of electrodes.

  The driven body having a large torque difference between the required torque at the start and the torque in the steady state refers to, for example, a case where the required torque at start × 0.8 exceeds the torque in the steady state.

  In the case of a three-phase input, the control unit 41 can generate a traveling wave in the piezoelectric body 13 by supplying drive signals having phases that are 120 degrees different in time to the phases A, B, and C. it can.

  In the case of a two-phase input, for example, a traveling wave can be generated in the piezoelectric body 13 by supplying drive signals whose phases are different by 60 degrees in time to the AB phase. In the two-phase input, in the electrode pattern in which the assist force by the C phase is set to be weak, a stronger traveling wave is generated even in the case of the two-phase input, so that the output reduction range can be reduced. Further, in the two-phase input, the electrode pattern in which the assist force by the C phase is set to be strong can further reduce the power consumption.

  In the vibration actuator of the above-described embodiment, either the three-phase input signal or the two-phase input drive signal is selectively supplied to the vibration wave motor 10. Therefore, when the vibration wave motor 10 is started, a three-phase input is used, and when the predetermined rotation region is reached, a transition to a two-phase input is performed, thereby reducing power consumption without affecting the rotation of the vibration wave motor 10. be able to. In addition, when the load becomes large while the vibration wave motor 10 is driven by the two-phase input, the vibration wave motor 10 can be driven more stably by changing to the three-phase input. . Therefore, in the vibration actuator of this embodiment, the driving efficiency of the vibration wave motor can be improved.

  Further, in the vibration actuator of this embodiment, the phase difference of the drive signal is gradually changed at the transition between the three-phase input and the two-phase input, so that the vibration wave is compared with the case where the phase difference is rapidly changed. Generation of sudden sound of the motor can be suppressed.

  Further, since the drive signal to the C phase is gradually changed at the same time as the phase difference is gradually changed, the transition between the three-phase input and the two-phase input can be made more smoothly.

  Although the configurations of the above embodiments can be used in appropriate combinations, the configurations of the embodiments are apparent from the drawings and description, and thus detailed description thereof is omitted. Furthermore, the present invention is not limited by the embodiment described above.

  1: Camera, 10: Vibration wave motor, 11: Vibrator, 12: Elastic body, 13: Piezoelectric body, 13A: First divided area, 13B: Second divided area, 13C: Third divided area, 15: Mover , 20: lens barrel, 40: driving device, 41: control unit

Claims (18)

An electromechanical transducer that vibrates in response to a drive signal;
An elastic body that generates traveling waves by vibration of the electromechanical transducer;
A rotor that is rotated by traveling waves of the elastic body;
A controller that selectively supplies the electromechanical transducer with any of three-phase or two-phase drive signals having different phases;
A vibration actuator comprising: The vibration actuator according to claim 1,
The electromechanical transducer has a vibration actuator characterized in that electrodes are arranged so that the phases are spatially different by 120 degrees. The vibration actuator according to claim 1,
The controller is
At the time of three-phase input, drive signals whose phases are different by 120 degrees in time are supplied to the three phases,
At the time of two-phase input, a driving signal having a phase difference of 60 degrees in time is supplied to the two phases,
In the transition between the three-phase input and the two-phase input, gradually changing the phase difference of the drive signal,
Vibration actuator characterized by The vibration actuator according to claim 3, wherein
The controller is
In the transition from the three-phase input to the two-phase input, gradually decrease the drive signal to one phase that does not supply the drive signal at the time of the two-phase input,
Vibration actuator characterized by The vibration actuator according to claim 3, wherein
The controller is
In the transition from 2-phase input to 3-phase input, gradually increase the drive signal to 1 phase that supplies the drive signal at the time of 3-phase input,
Vibration actuator characterized by The vibration actuator according to any one of claims 1 to 5,
When the electromechanical transducer is provided with the electrode for every half wave and the wave number of the traveling wave is 3N + 1 (N: an integer of 2 or more),
In the three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to a wave number N + 0.5, and supplies the remaining one-phase drive signal to an electrode corresponding to a wave number N-1.
In a two-phase input, a two-phase drive signal is supplied only to an electrode corresponding to a wave number N + 0.5,
Vibration actuator characterized by The vibration actuator according to any one of claims 1 to 5,
In the case where the electromechanical transducer is provided with the electrode for every half wave, and the wave number of the traveling wave is 3N + 2 (N is an integer of 1 or more),
In the three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to the wave number N + 0.5, and supplies the remaining one-phase drive signal to an electrode corresponding to the wave number N.
In a two-phase input, a two-phase drive signal is supplied only to an electrode corresponding to a wave number N + 0.5,
Vibration actuator characterized by The vibration actuator according to any one of claims 1 to 5,
The electromechanical conversion element is provided with the electrode every half wave, and when the wave number of the traveling wave is 3N + 2 (N: an integer of 1 or more),
In the three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to the wave number N, and supplies the remaining one-phase drive signal to an electrode corresponding to the wave number N + 1.
In the two-phase input, the two-phase drive signal is supplied only to the electrode corresponding to the wave number N.
Vibration actuator characterized by The vibration actuator according to any one of claims 1 to 5,
The electromechanical conversion element is provided with the electrode for each half wave, and when the wave number of the traveling wave is 3N (N: an integer of 2 or more),
In the three-phase input, the control unit supplies a two-phase drive signal to an electrode corresponding to the wave number N, and supplies the remaining one-phase drive signal to an electrode corresponding to the wave number N-1.
In the two-phase input, the two-phase drive signal is supplied only to the electrode corresponding to the wave number N.
Vibration actuator characterized by The vibration actuator according to any one of claims 1 to 5,
The electromechanical conversion element is provided with the electrode for each half wave, and when the wave number of the traveling wave is 3N (N: an integer of 2 or more),
In the three-phase input, the control unit supplies a two-phase drive signal to the electrode corresponding to the wave number N-0.5, and supplies the remaining one-phase drive signal to the electrode corresponding to the wave number N.
In a two-phase input, a two-phase drive signal is supplied only to an electrode corresponding to a wave number N-0.5,
Vibration actuator characterized by An electromechanical transducer that vibrates in response to a drive signal, an elastic body that is joined to the electromechanical transducer and converts vibrations of the electromechanical transducer into a traveling wave, and a traveling wave of the elastic body that is in contact with the elastic body A vibration actuator comprising: a rotor that is rotated by: a control unit that supplies a drive signal to an electrode of the electromechanical transducer;
When rotating a driven body having a small torque difference between a required torque at the time of startup and a torque in a steady state, the remaining number of the electromechanical conversion element is one more than the number of two-phase electrodes having the same number of electrodes. The electrodes are arranged so that the number of electrodes in the phase is reduced,
The control unit causes the electrodes of the electromechanical conversion element to selectively supply drive signals of a three-phase input or a two-phase input;
Vibration actuator characterized by The vibration actuator according to claim 11,
The driven body having a small torque difference between the required torque at the time of startup and the torque in the steady state is such that the required torque at startup × 0.8 is less than the torque in the steady state,
Vibration actuator characterized by An electromechanical transducer that vibrates in response to a drive signal, an elastic body that is joined to the electromechanical transducer and converts vibrations of the electromechanical transducer into a traveling wave, and a traveling wave of the elastic body that is in contact with the elastic body A vibration actuator comprising: a rotor that is rotated by: a control unit that supplies a drive signal to an electrode of the electromechanical transducer;
When rotating a driven body having a large torque difference between a required torque at startup and a torque in a steady state, in the electromechanical conversion element, the remaining one is more than the number of two-phase electrodes having the same number of electrodes. The electrodes are arranged so that the number of electrodes in the phase is large,
The control unit causes the electrodes of the electromechanical conversion element to selectively supply drive signals of a three-phase input or a two-phase input;
Vibration actuator characterized by The vibration actuator according to claim 13,
The driven body having a large torque difference between the required torque at the time of startup and the torque in the steady state is such that the required torque at startup x 0.8 exceeds the torque in the steady state,
Vibration actuator characterized by The vibration actuator according to any one of claims 1 to 14,
The electromechanical transducer is a single plate;
Vibration actuator characterized by   A lens barrel provided with the vibration actuator according to any one of claims 1 to 15.   17. The lens barrel according to claim 16, wherein the vibration actuator is a hollow type, and an optical path is disposed in the hollow portion.   A camera comprising the lens barrel according to claim 16.

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