JP6007788B2 - Vibration actuator driving apparatus, driving method, and optical apparatus - Google Patents

Description

  The present invention relates to a vibration actuator driving apparatus, a driving method, and an optical apparatus.

  Conventionally, in order to drive a vibration actuator, two vibration signals having different phases are applied to the piezoelectric element. The frequency of the input vibration signal is a frequency between the drive frequency used to drive the vibration actuator and the resonance frequency of the next higher vibration mode of the vibration mode (drive mode) including the drive frequency ( Starting from the starting frequency, the driving frequency is gradually lowered (for example, see Patent Document 1).

JP-A-3-22873

However, the startup frequency is limited to a frequency between the drive frequency and the resonance frequency of the next higher vibration mode of the drive mode, and thus cannot be set to a very high frequency. Therefore, at the time of activation, since it does not start from a sufficiently high frequency, the vibrator 20 suddenly starts to vibrate and sudden sound may occur.
In recent years, a vibration actuator is often used in a moving image shooting camera. In this case, this sudden sound is recorded at the time of moving image shooting or the like. In particular, during moving image shooting, a wobbling operation is performed and the power supply is frequently turned on and off, so that the generation of this abnormal noise becomes more obvious.

  An object of the present invention is to provide a vibration actuator driving device, a driving method, and an optical apparatus that are made silent.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

According to the first aspect of the present invention, there is provided a vibration part having an electromechanical energy conversion element to which two drive signals capable of changing a phase difference are input, and a drive generated in the vibration part due to vibration of the electromechanical energy conversion element The two drives with a starting frequency higher than the driving frequency used for driving in a state where the relative moving unit is moved relative to the vibrating unit by force and the phase difference is set so that the relative moving unit is stopped. When the signal is input to the electromechanical energy conversion element and the frequency of the two drive signals is gradually decreased from the activation frequency to reach the drive frequency, the phase difference is determined by the relative movement unit and the vibration unit. And a control unit for making a phase difference that can be moved relative to the vibration actuator.
Invention of Claim 2 is a drive device of the vibration actuator of Claim 1, Comprising: The said starting frequency is a frequency more than the resonance frequency of the higher vibration mode following the vibration mode containing the said drive frequency. It is the drive device of the vibration actuator characterized by being.
A third aspect of the present invention is the vibration actuator driving apparatus according to the first aspect, wherein the phase difference at which the relative movement unit maintains the stop state is ± 15 degrees of 0 degrees or 180 degrees. The drive device of the vibration actuator characterized by these.
According to a fourth aspect of the present invention, there is provided a vibration part having an electromechanical energy conversion element to which two drive signals capable of changing a phase difference are inputted, and a drive generated in the vibration part due to vibration of the electromechanical energy conversion element A vibration actuator driving method comprising: a relative movement section that moves relative to the vibration section by force, wherein the relative movement section maintains a stopped state based on a mutual phase difference when the vibration actuator is activated. The two drive signals are input to the electromechanical energy conversion element at a starting frequency higher than the drive frequency used for driving the vibration actuator while maintaining the phase difference, and the frequencies of the two drive signals are When the driving frequency is gradually decreased from the starting frequency, the phase difference is determined so that the relative moving unit can move relative to the vibrating unit. That the difference is a method of driving a vibration actuator according to claim.
A fifth aspect of the present invention is an optical apparatus including the driving device according to the first to third aspects.

  According to the present invention, it is possible to provide a drive device, a drive method, and an optical apparatus for a vibration actuator that has been silenced.

It is a figure explaining the camera containing the lens-barrel provided with the vibration actuator driven with the drive device of embodiment. It is a block diagram explaining the drive device of the vibration actuator and vibration wave actuator of embodiment. It is a figure explaining a lens barrel provided with the vibration actuator driven with the drive device of an embodiment. It is a figure which shows the relationship between the phase difference between A phase and B phase, and the rotational speed of a slider. It is a figure which shows the relationship between the frequency of a drive signal, and the impedance of a vibration actuator. It is the figure which showed the example of the lens drive by the vibration actuator by this embodiment.

FIG. 1 is a diagram illustrating a camera 2 including a lens barrel 1 including a vibration actuator 100 driven by a driving device according to an embodiment of the present invention.
In the present embodiment, the lens barrel 1 can be attached to and detached from the main body of the camera 2, but the present invention is not limited to this and may be non-detachable.

The camera 2 of this embodiment includes an imaging optical system (lens) 3 in a lens barrel 1.
In the main body of the camera 2, an image pickup device 4, an AFE (Analog front end) circuit 5, an image processing unit 6, a sound detection unit 7, a buffer memory 8, a recording interface 9, a monitor 10, and an operation Consists of a member 11, a memory 12, and a CPU 13, and can be connected to a PC 14 as an external device.

The imaging optical system 3 includes a plurality of optical lenses, and forms a subject image on the light receiving surface of the imaging element 4. In FIG. 1, the optical lens system is simplified and denoted by reference numeral 3 as a single lens.
In the optical lens group, the optical lens for AF is driven by driving the vibration actuator 100.

The exposure time (shutter speed) for the image sensor 4 is determined according to the state of the operation member 11 or the image.
The imaging element 4 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 4 photoelectrically converts a subject image by a light beam that has passed through the imaging optical system 3 to generate an analog image signal. The analog image signal is input to the AFE circuit 5.

  The AFE circuit 5 performs gain adjustment (signal amplification according to ISO sensitivity) on the analog image signal. Specifically, the imaging sensitivity is changed within a predetermined range in accordance with a sensitivity setting instruction from the CPU 13. The AFE circuit 5 further converts the analog-processed image signal into digital data by a built-in A / D conversion circuit. The digital data is input to the image processing unit 6.

The image processing unit 6 performs various types of image processing on the digital image data.
The memory 12 temporarily records image data in a pre-process and post-process of image processing by the image processing unit 6.
The sound detection unit 7 includes a microphone and a signal amplification unit 105, and detects and captures sound from the subject direction mainly during moving image shooting, and transmits the data to the CPU 13.

The recording interface 9 has a connector (not shown), and a recording medium 15 is connected to the connector, and data is written to and read from the recording medium 15 connected thereto.
The monitor 10 is composed of a liquid crystal panel, and displays an image, an operation menu, and the like according to an instruction from the CPU 13.
The operation member 11 indicates a mode dial, a cross key, a determination button, and a release button, and sends an operation signal corresponding to each operation to the CPU 13. Settings for still image shooting and moving image shooting are set by the operation member 11.

The CPU 13 comprehensively controls operations performed by the camera 2 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 12 records a series of image data subjected to image processing.
In the camera 2 having such a configuration, the present invention captures an image corresponding to a moving image.

  FIG. 2 is a block diagram illustrating the vibration actuator 100 and the driving device 101 of the vibration wave actuator according to the embodiment. The drive device 101 includes an oscillation unit 102, a phase shift unit 104, an amplification unit 105, a detection unit 106, and a control unit 103 that controls them.

The oscillation unit 102 generates a drive signal having a desired frequency according to a command from the control unit 103.
The phase shift unit 104 divides the drive signal generated by the oscillation unit 102 into two drive signals having different desired phases in response to a command from the control unit 103.
The amplification unit 105 boosts the two drive signals divided by the phase shift unit 104 to desired voltages, respectively.
The drive signal from the amplifying unit 105 is transmitted to the vibration actuator 100, and by applying this drive signal, a traveling wave is generated in the vibrator 20 described later of the vibration actuator 100, and the moving element 28 is driven.

The rotation detection unit 106 includes an optical encoder, a magnetic encoder, and the like, detects the position and speed of a driven object driven by driving the moving element 28, and transmits the detected value to the control unit 103 as an electric signal. .
The control unit 103 controls the drive of the vibration actuator 100 and the operation of the vibration wave actuator based on a drive command from the CPU 13 in the lens barrel 1 or the camera body. The control unit 103 receives the detection signal from the rotation detection unit 106, obtains position information and speed information based on the values, and determines the frequency and phase difference of the oscillation actuator 100 oscillation unit 102 so as to be positioned at the target position. Control etc.

  FIG. 3 is a diagram for explaining the lens barrel 1 including the vibration actuator 100 driven by the drive device according to the embodiment of the present invention, and is a view showing a state in which the ring-shaped vibration actuator 100 is incorporated in the lens barrel 1. is there.

  The vibrator 20 includes an electromechanical energy conversion element (hereinafter referred to as a piezoelectric body) 21 such as a piezoelectric element or an electrostrictive element that converts electrical energy into mechanical energy, and an elastic body 22 joined with the piezoelectric element 21. It is composed of In the vibrator 20, nine traveling waves are generated as an example in the present embodiment.

  The elastic body 22 is made of a metal material having a high resonance sharpness, and has a ring shape. A groove is cut in the opposite surface of the elastic body 22 to which the piezoelectric element 21 is bonded, and the tip surface of the protruding portion (a portion where there is no groove) becomes the driving surface 22a and is brought into pressure contact with the moving element 28. The reason for cutting the groove is to make the neutral surface of the traveling wave as close to the piezoelectric element 21 as possible, thereby amplifying the amplitude of the traveling wave on the drive surface 22a.

  The piezoelectric element 21 is divided into two phases (A phase and B phase) along the circumferential direction, and in each phase, elements in which polarization is alternated every 1/2 wavelength are arranged, An interval of 1/4 wavelength is provided between the A phase and the B phase.

Under the piezoelectric element 21, a non-woven fabric 23, a pressure plate 24, and a pressure member 25 are disposed.
The nonwoven fabric 23 is, for example, felt and is disposed under the piezoelectric element 21 so that the vibration of the vibrator 20 is not transmitted to the pressure plate 24 and the pressure member 25.

The pressure plate 24 is configured to receive pressure from the pressure member 25.
The pressure member 25 is disposed under the pressure plate 24 and generates pressure. In this embodiment, the pressure member 25 is a disc spring, but it may be a coil spring or a wave spring instead of a disc spring.
The pressing member 25 is held by a pressing ring 26, and the pressing ring 26 is fixed to a fixing member 27.

The mover 28 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.
A vibration absorbing member 29 such as rubber is disposed on the moving element 28 in order to absorb the vertical vibration of the moving element 28, and an output transmission member 30 is disposed thereon.

The output transmission member 30 is regulated in the pressurizing direction and the radial direction by a bearing 31 provided on the fixed member 27, and thereby the pressurizing direction and the radial direction of the moving element 28 are regulated.
The output transmission member 30 has a protrusion 32, from which a fork connected to the cam ring 33 is engaged, and the cam ring 33 is rotated as the output transmission member 30 rotates.

In the cam ring 33, a key groove 34 is obliquely cut in the cam ring 33, and a fixing pin 36 provided in the AF ring 35 is engaged with the key groove 34.
Then, the cam ring 33 is rotationally driven, so that the AF ring 35 is driven in the straight direction in the optical axis direction and can be stopped at a desired position.
In the fixing member 27, the pressing ring 26 is attached with a screw, and by attaching this, the output transmission member 30, the moving element 28, the vibrator 20, and the pressing member 25 can be configured as one motor unit.

The phase shifter 104 in FIG. 2 separates the drive signal generated from the oscillator 102 into A-phase and B-phase drive signals having different phases. The A phase and B phase drive signals are applied to the respective electrodes of the piezoelectric element 21.
When there is a phase difference between the A-phase and B-phase drive signals, the wave generated on the drive surface 22a of the elastic body 22 by the vibration excited by the piezoelectric element 21 becomes a traveling wave and rotates the moving element 28. .

FIG. 4 is a diagram showing the relationship between the phase difference between the A phase and the B phase and the rotational speed of the moving element 28.
As shown in the figure, when the phase difference between the A phase and the B phase is ± 90 degrees, the rotational speed of the moving element 28 is the fastest. When the phase difference is close to 0 (or 180 degrees), the wave generated on the drive surface 22a becomes a standing wave, not a traveling wave, and the rotation of the moving element 28 stops.

FIG. 5 is a diagram illustrating the relationship between the frequency of the drive signal and the impedance of the vibration actuator 100. The portion indicated by fs in the figure is the drive frequency used when driving the lens.
When driving the vibration actuator 100, it is preferable to start the vibration actuator 100 from a low speed. Therefore, the frequency of the drive signal applied to the piezoelectric element 21 starts from a frequency higher than the drive frequency (hereinafter referred to as a start-up frequency). Generally, the driving frequency is gradually lowered.

In order to facilitate explanation of this activation frequency, first, a comparison with this embodiment will be described. In the comparative embodiment, when the vibration actuator 100 is driven, the phase difference of the drive signals applied to the piezoelectric element 21 between the A phase and the B phase is fixed at 90 degrees, for example.
In this case, the start-up frequency starts from a frequency f1 between the drive frequency fs and the resonance frequency f3 of the next higher vibration mode of the vibration mode (drive mode) including the drive frequency fs, and gradually The drive frequency is lowered to fs.

  Thus, the reason why f1 is not used is higher than the resonance frequency f3 of the vibration mode next to the vibration mode because the impedance of the vibration actuator 100 is higher when the frequency of the drive signal exceeds the resonance frequency f3. This is because it becomes difficult to control the operation.

  However, in the case of this comparative form, at the same time as the power is turned on, the phase difference is 90 degrees and the A phase and the B phase of the starting frequency f1 are applied to the piezoelectric element 21. Since the activation frequency f1 is smaller than f3, the activation frequency f1 cannot be set to a sufficiently high frequency, and there is a possibility that the vibrator 20 of the vibration actuator 100 suddenly starts a large vibration and sudden sound is generated.

Therefore, in the present embodiment, the application of power to the piezoelectric element 21 is started from the frequency f2 that exceeds the resonance frequency f3 of the next higher vibration mode after the drive vibration mode.
Also in the present embodiment, the resonance frequency f3 must be exceeded when the frequency is lowered to the drive frequency fs.
If the moving element 28 is driven when the resonance frequency f3 is exceeded, the operation of the vibration actuator 100 may become unstable as described above.

Therefore, in the present embodiment, the phase difference between the A phase and the B phase is set to 0 or 180 degrees until the drive frequency fs is reached. However, 0 degrees and 180 degrees are not strict values, and as long as the movable element 28 does not rotate, for example, up to about ± 5 degrees is an allowable range.
When the vibration frequency reaches the drive frequency fs, the phase difference between the A phase and the B phase is set to about 90 degrees. When the phase difference reaches 90 degrees, the moving element 28 starts rotating, and the lens can be driven by the vibration actuator 100.

  According to this embodiment, until the vibration frequency reaches the drive frequency fs, a standing wave is generated on the drive surface 22a of the vibrator 20 instead of a traveling wave, so that no rotational force is transmitted to the moving element 28. Accordingly, since the vibration actuator 100 is stopped, there is no problem in operation. On the other hand, since the vibration of the vibrator 20 starts from a small vibration, the possibility of sudden sound is low.

FIG. 6 is a diagram illustrating an example of lens driving by the vibration actuator 100 according to the present embodiment.
First, at the time t1 when the voltage supply to the vibration actuator 100 is started, the phase difference is 0, so the lens remains stopped. Therefore, the lens does not suddenly start driving and sudden sound does not occur.
Then, the frequency of the drive signal is decreased, and a phase difference is generated between the A phase and the B phase at t2 that exceeds the resonance frequency f3 and enters the drive frequency fs. In this embodiment, it is about 90 degrees. In addition, although 90 degree | times is efficient, it is not limited to this.
Then, the phase difference is set to about 0 degree at time t3 when the lens 3 reaches a desired position. As a result, the lens 3 stops.
A phase difference is generated between the A phase and the B phase at the time t4 when the lens 3 needs to be driven again. At this time, when the lens 3 is driven in the direction opposite to the movement from the time t2 to the time t3, the phase difference is set to minus 90 degrees.

As described above, this embodiment has the following effects.
(1) Conventionally, when the vibration actuator 100 is activated, the power supply voltage is slowly applied or activated at a frequency slightly higher than the drive frequency. However, the sudden sound at power-on did not disappear. During movie shooting, sudden sound occurred every time the actuator was turned on. Also, in order to suppress the generation of abnormal noise, conventionally, the frequency at the time of startup has been expanded only before the resonance point of the next mode.
However, in the present invention, the frequency at the time of activation is extended to the next drive mode, and the activation is started from a state where vibration is sufficiently small, thereby reducing the occurrence of sudden sound at the time of activation.
(2) By setting the phase difference of the drive signal when the power is turned on to 0 or 180 degrees, even if the vibrator 20 starts to vibrate, the moving element 28 does not start, and the vibration frequency of the drive signal is the resonance frequency. There is no problem when exceeding.

(Deformation)
The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
(1) In the present embodiment, the lens barrel 1 can be attached to and detached from the main body of the camera 2, but the present invention is not limited to this and may be detachable.
(2) Further, in the present embodiment, the vibration actuator 100 is described as an annular type in which a lens is mounted inside. However, the present invention is not limited to this, and the axis of the holding cylinder is different from the axis of the holding cylinder outside the lens holding cylinder. It may be a small one that rotates around.
In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  1: lens barrel, 2: camera, 20: vibrator, 21: piezoelectric element, 22: elastic body, 22a: driving surface, 28: moving element, 100: vibration actuator, 101: driving device, f1: starting frequency, f3: resonance frequency, fs: drive frequency

Claims (5)

A vibrating section having an electromechanical energy conversion element to which two drive signals capable of changing the phase difference are input;
A relative movement part that moves relative to the vibration part by a driving force generated in the vibration part by vibration of the electromechanical energy conversion element;
The two drive signals are input to the electromechanical energy conversion element at a start frequency higher than the drive frequency used for driving in a state where the relative movement unit is held at a phase difference that is stopped. And a controller that gradually reduces the frequency of the starting frequency to the driving frequency so that the phase difference is a phase difference that allows the relative movement unit to move relative to the vibration unit. about,
A drive device for a vibration actuator characterized by the above. A drive device for a vibration actuator according to claim 1,
The start-up frequency is a frequency equal to or higher than a resonance frequency of a vibration mode next to a vibration mode including the driving frequency;
A drive device for a vibration actuator characterized by the above. A drive device for a vibration actuator according to claim 1,
The phase difference at which the relative movement unit holds the stopped state is 0 ° or ± 15 ° of 180 °,
A drive device for a vibration actuator characterized by the above. A vibrating section having an electromechanical energy conversion element to which two drive signals capable of changing the phase difference are input;
A relative movement part that moves relative to the vibration part by a driving force generated in the vibration part by vibration of the electromechanical energy conversion element;
A driving method of a vibration actuator comprising:
When starting the vibration actuator,
The electromechanical energy conversion of the two drive signals in a state in which the relative phase difference is maintained at a phase difference in which the relative movement unit maintains a stopped state and at a start frequency higher than the drive frequency used for driving the vibration actuator Input to the element,
When the frequency of the two drive signals is gradually decreased from the starting frequency to reach the drive frequency, the phase difference is set to a phase difference that allows the relative movement unit to move relative to the vibration unit. ,
A driving method of a vibration actuator characterized by the above.   An optical apparatus comprising the driving device according to claim 1.

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