JP2015104254A - Driving device for vibration wave motor, optical equipment, and driving method for vibration wave motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device for a vibration wave motor, which is able to improve the starting performance of a vibration wave motor.SOLUTION: A driving device 100 for a vibration wave motor 10 according to the invention drives the vibration wave motor 10 comprising: a piezoelectric body 11 that vibrates by the input of a signal, an elastic body 12 joined to the piezoelectric body 11, vibrated by the vibration of the piezoelectric body 11, and used for generating a progressive wave in a drive surface 12a; and a mover 15 that is brought into pressure contact with the drive surface 12a and is driven by the progressive wave. When the mover 15 is driven by the progressive wave, a first signal for causing the elastic body 12 to generate vibration in a first direction and vibration in a second direction is generated for the piezoelectric body 11. Before the drive of the mover 15 by the progressive wave, a second signal for causing the elastic body 12 to generate vibration in a third direction different from the first and second directions is generated for the piezoelectric body 11.

Description

  The present invention relates to a vibration wave motor drive device, an optical apparatus, and a vibration wave motor drive method.

The vibration wave motor has an elastic body to which a piezoelectric body is bonded, and generates a traveling wave in the elastic body using expansion and contraction of the piezoelectric body. Then, the moving element in pressure contact with the elastic body is moved by the traveling wave.
In this vibration wave motor, the elastic body and the vibrator are fixed when driven, and the startup performance may become unstable during startup. Such instability of starting performance is a problem for a vibration wave motor that is required to have improved stability during driving.
Therefore, before starting, after applying a voltage in the vicinity of the resonance frequency higher than the vibration used for normal driving to the piezoelectric body to generate a standing wave with a large amplitude in the elastic body, the resonance frequency for normal driving is used. There is a technique for applying a nearby voltage. As a result, vibration with a large amplitude is generated in the vibrator before activation to reduce the occurrence of malfunction (see Patent Document 1).

JP-A-6-327271

  However, since the vibration generated in the elastic body in the above prior art and before the start-up is the vibration in the same direction, there is a possibility that the adhesion between the elastic body and the moving element cannot be sufficiently peeled off.

  An object of the present invention is to provide a vibration wave motor driving device, an optical apparatus, and a vibration wave motor driving method capable of improving the starting performance of the vibration wave motor.

The present invention solves the above problems by the following means.
According to a first aspect of the present invention, there is provided a piezoelectric body that vibrates by input of a signal, an elastic body that is bonded to the piezoelectric body, vibrates by vibration of the piezoelectric body, and generates a traveling wave on a driving surface, and the driving surface. A driving device that drives a vibration wave motor that includes a moving member that is in pressure contact and is driven by the traveling wave, wherein the vibration in the first direction and the second direction are driven when the moving member is driven by the traveling wave. A first signal that causes the elastic body to generate vibrations of the elastic body is generated with respect to the piezoelectric body, and before the moving element is driven by the traveling wave, the first direction is different from the second direction. The vibration wave motor driving device is characterized in that a second signal for generating vibration in the elastic body is generated for the piezoelectric body.
A second aspect of the present invention is the vibration wave motor driving apparatus according to the first aspect, wherein one of the contact surfaces of the elastic body and the moving element has a resin film. It is a drive device of a wave motor.
A third aspect of the present invention is the vibration wave motor drive device according to the first or second aspect, wherein the frequency of the second signal is lower than the frequency of the first signal. This is a motor drive device.
Invention of Claim 4 is a drive device of the vibration wave motor of any one of Claims 1-3, Comprising: The said elastic body is an annular shape, The vibration of the said 3rd direction is A vibration wave motor drive apparatus characterized by being a radial vibration.
Invention of Claim 5 is an optical apparatus provided with the drive device of the vibration wave motor of any one of Claims 1-4, and the said vibration wave motor.
According to a sixth aspect of the present invention, there is provided a piezoelectric body that vibrates by input of a signal, an elastic body that is bonded to the piezoelectric body, vibrates by the vibration of the piezoelectric body, and generates a traveling wave on a driving surface, and the driving surface. A driving method for driving a vibration wave motor including a moving element that is in pressure contact and driven by the traveling wave, wherein the vibration in the first direction and the second direction are driven when the moving element is driven by the traveling wave. A first signal that causes the elastic body to generate vibrations of the elastic body is generated with respect to the piezoelectric body, and before the moving element is driven by the traveling wave, the first direction is different from the second direction. A method for driving a vibration wave motor, characterized in that a second signal for generating vibration in the elastic body is generated for the piezoelectric body.
In addition, the said structure may be improved suitably, and at least one part may substitute for another structure.

  ADVANTAGE OF THE INVENTION According to this invention, the drive device of a vibration wave motor, the optical apparatus, and the drive method of a vibration wave motor which can improve the starting performance of a vibration wave motor can be provided.

It is a schematic block diagram of the camera carrying the vibration wave motor of embodiment. It is a figure explaining the vibration wave motor of an embodiment. It is a perspective view of the moving element and elastic part of a vibration wave motor. It is a block diagram explaining the drive device of a vibration wave motor. It is a figure explaining the vibration mode excited when the drive signal input into a piezoelectric material is a drive frequency, (a) is the figure which looked at the elastic body from the side, (b) is a perspective view. It is a perspective view of the elastic body to which the vibration of the 3rd direction was added.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a vibration wave motor according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a camera 1 equipped with a vibration wave motor 10 of the embodiment.
The camera 1 includes a camera body 2 and a lens barrel 3. The camera body 2 includes an image sensor 6. The imaging element 6 is an imaging device that captures a subject image formed by the lens barrel 3. The lens barrel 3 is an interchangeable lens that is detachably attached to the camera body 2. In the camera 1 of the present embodiment, an example in which the lens barrel 3 is an interchangeable lens is shown. However, the present invention is not limited to this, and a lens barrel integrated with the camera body may be used.

  The lens barrel 3 includes a lens 4 as an optical member, a cam barrel 5, a vibration wave motor 10, and other members (not shown). The vibration wave motor 10 of the present embodiment is used as a drive source for driving the lens 4 when adjusting the focus of the camera 1. The driving force extracted from the vibration wave motor 10 is transmitted to the cam cylinder 5 through a power transmission mechanism (not shown). The cam cylinder 5 is engaged with the lens 4 by a cam mechanism. When the cam cylinder 5 is rotated by the driving force of the vibration wave motor 10, the lens 4 is moved in the direction of the optical axis A by the cam mechanism. Thereby, focus adjustment is performed.

  FIG. 2 is a diagram illustrating the vibration wave motor 10 according to the embodiment. FIG. 3 is a perspective view of the moving element 15 and the elastic body 12 of the vibration wave motor 10. The vibration wave motor 10 includes a mover 15 and a vibrator 13. As will be described later, the vibrator 13 includes an electromechanical transducer (hereinafter referred to as a piezoelectric body) 11, such as a piezoelectric element or an electrostrictive element that converts electrical energy into mechanical energy, and the piezoelectric body 11. And the vibrator 13 generates a progressive vibration wave.

  The elastic body 12 is made of a metal material having a high resonance sharpness, and has a circular shape. A groove 12b is cut on the opposite surface of the elastic body 12 to which the piezoelectric body 11 is bonded, and the tip surface of the protruding portion (a place where the groove 12b is not present) becomes the driving surface 12a and is brought into pressure contact with the moving element 15. The piezoelectric body 11 is joined to the side of the elastic body 12 where the groove 12b is not cut.

  The mover 15 is a substantially annular member formed of a light metal such as an aluminum alloy, a synthetic resin, or the like. The moving element 15 is brought into pressure contact with the vibrator 13 and is frictionally driven by a traveling wave. In the present embodiment, a resin film 12 c is formed on the drive surface 12 a of the elastic body 12.

FIG. 4 is a block diagram illustrating the driving device 100 of the vibration wave motor 10.
The oscillating unit 101 generates a drive signal having a desired frequency according to a command from the control unit 102.
The phase shifter 103 divides the drive signal generated by the oscillator 101 into two drive signals having a 90 ° phase difference.
The amplifying unit 104 boosts the two drive signals divided by the phase shift unit 103 to desired voltages, respectively.

A drive signal from the amplifying unit 104 is transmitted to the vibration wave motor 10, and a traveling wave is generated in the vibration body by the application of the drive signal, so that the moving element 15 is driven.
The rotation detection unit 105 includes an optical encoder, a magnetic encoder, and the like, and detects the position and speed of a driven object driven by driving the moving element 15.

  The control unit 102 controls driving of the vibration wave motor 10 based on a driving command from the CPU. The control unit 102 receives the detection signal from the detection unit, obtains position information and speed information based on the values, and controls the frequency of the oscillation unit 101 so as to be positioned at the target position.

Next, driving of the vibration wave motor 10 of the present embodiment will be described.
First, the target position is transmitted to the control unit 102. A drive signal is generated from the oscillation unit 101, and the signal is divided into two drive signals having a phase difference of 90 ° by the phase shift unit 103, and is amplified to a desired voltage by the amplification unit 104.
The drive signal is applied to the piezoelectric body 11 of the vibration wave motor 10, and vibration is excited in the piezoelectric body 11, and the fourth-order bending vibration is generated in the elastic body 12 due to the vibration. The piezoelectric body 11 is divided into an A phase and a B phase, and drive signals are applied to the A phase and the B phase, respectively.
The positional phase of the fourth-order bending vibration generated from the A-phase and the fourth-order bending vibration generated from the B-phase are shifted by ¼ wavelength, and the A-phase drive signal and the B-phase drive signal are Since the 90 ° phase is shifted, the two bending vibrations are combined into four traveling waves.

FIG. 5 is a diagram illustrating a vibration mode that is excited when the drive signal input to the piezoelectric body 11 is a drive frequency. (A) is the figure which looked at the elastic body 12 from the side, (b) is a perspective view.
The vibrations excited by the elastic body 12 when the drive signal input to the piezoelectric body 11 is the drive frequency are two signals shown in the figure. The drive frequency is a frequency of a signal applied to the piezoelectric body 11 when the vibration wave motor 10 is normally driven.
When a drive signal having a drive frequency is applied to the piezoelectric body 11, vibration in the circumferential direction (X direction in the figure) (vibration in the first direction, first vibration mode) and vibration in the vertical direction (Y direction in the figure) (first direction). (Bidirectional vibration, second vibration mode) occurs. As a result of these two vibrations, a traveling wave is generated in the elastic body 12 as shown in FIG.

The vibration wave motor 10 according to the present embodiment generates vibrations in directions different from the vibrations in the first direction and the second direction (the vibrations in the third direction) prior to generating the traveling wave and moving the moving element 15. , The third vibration mode) is generated in the elastic body 12.
In the present embodiment, the vibration in the third direction is a vibration in a direction perpendicular to the vibration in the first direction and the vibration in the second direction. FIG. 6 is a perspective view of the elastic body 12 to which the vibration in the third direction is applied. As illustrated, the vibration in the third direction is a vibration mode in the radial direction (Z direction in the figure) of the elastic body 12. That is, the vibration in the third direction is torsional vibration or the like that exists outside the driving frequency range and has a radial vibration component.

In the vibration wave motor 10, particularly when the resin film 12 c is present on the drive surface 12 a of the elastic body 12, the drive surface 12 a and the contact surface 15 a of the moving element 15 are fixed when the vibration wave motor 10 is not driven. There is a case. Due to this fixation, the startup performance becomes unstable when the vibration wave motor 10 is started.
However, according to the present embodiment, torsional vibration in the radial direction is generated in the elastic body 12 before activation. For this reason, when the drive surface 12a coated with the resin film 12c of the elastic body 12 and the contact surface 15a of the moving element 15 are fixed, they can be peeled off by applying vibration before activation.
Moreover, since the vibration at that time is a vibration in a direction different from the normal driving, the peeling effect is high.

Furthermore, in this embodiment, in order to generate the vibration in the third direction by this initial driving, the driving device 100 generates a signal having a frequency lower than the frequency of the signal in the case of normal driving and inputs it to the piezoelectric body 11. To do.
This is because the lower the frequency, the greater the vibration that can be generated. According to the present embodiment, since a signal having a frequency lower than that in the case of normal driving is input to the piezoelectric body 11, vibration generated in the elastic body 12 is large, and the driving surface 12a on which the resin film 12c of the elastic body 12 is applied. And the peeling effect between the contact surface 15a of the moving element 15 further increases.
However, the present invention is not limited to this, and a peeling effect can be obtained even with a signal having a frequency higher than the signal frequency in the case of normal driving.

  The vibration wave motor 10 of the present embodiment is driven in a normal mode after once releasing the contact state between the elastic body 12 and the moving element 15.

  As described above, according to the present embodiment, after the elastic body is vibrated by the vibration in the third direction, the elastic body 12 is driven by the desired vibration such as bending vibration, so that the contact state between the elastic body 12 and the moving element 15 is reached. The startability of the vibration wave motor 10 can be improved by removing the influence.

  In this embodiment, in order to generate the vibration in the third direction by this initial driving, the driving device 100 generates a signal having a frequency lower than the frequency of the signal in the case of normal driving and inputs the signal to the piezoelectric body 11. For this reason, the vibration which generate | occur | produces in the elastic body 12 is large, and the peeling effect between the drive surface 12a to which the resin film 12c of the elastic body 12 was apply | coated and the contact surface 15a of the moving element 15 further increases.

  1: camera, 3: lens barrel, 10: vibration wave motor, 11: piezoelectric body, 12: elastic body, 12a: driving surface, 12b: groove, 12c: resin film, 13: vibrator, 15: mover, 15a: contact surface, 100: driving device, 101: oscillation unit, 102: control unit, 103: phase shift unit, 104: amplification unit, 105: rotation detection unit

Claims (6)

A piezoelectric body that vibrates in response to signal input, an elastic body that is bonded to the piezoelectric body, vibrates due to vibration of the piezoelectric body, and generates a traveling wave on the driving surface, and is in pressure contact with the driving surface and is driven by the traveling wave A driving device for driving a vibration wave motor including a movable element to be driven,
When the moving element is driven by the traveling wave, a first signal for causing the elastic body to generate a vibration in a first direction and a vibration in a second direction is generated for the piezoelectric body,
Generating a second signal for the piezoelectric body that causes the elastic body to vibrate in a third direction different from the first direction and the second direction before driving the moving element by the traveling wave;
A drive device for a vibration wave motor characterized by the above. It is a drive device of a vibration wave motor according to claim 1,
One of the contact surfaces of the elastic body and the mover has a resin film,
A drive device for a vibration wave motor characterized by the above. It is a drive device of the vibration wave motor according to claim 1 or 2,
The frequency of the second signal is lower than the frequency of the first signal;
A drive device for a vibration wave motor characterized by the above. It is a drive device of a vibration wave motor given in any 1 paragraph of Claims 1-3,
The elastic body has an annular shape, and the vibration in the third direction is vibration in a radial direction;
A drive device for a vibration wave motor characterized by the above.   An optical apparatus comprising the vibration wave motor drive device according to any one of claims 1 to 4 and the vibration wave motor. A piezoelectric body that vibrates in response to signal input, an elastic body that is bonded to the piezoelectric body, vibrates due to vibration of the piezoelectric body, and generates a traveling wave on the driving surface, and is in pressure contact with the driving surface and is driven by the traveling wave A driving method for driving a vibration wave motor including a movable element to be driven,
When the moving element is driven by the traveling wave, a first signal for causing the elastic body to generate a vibration in a first direction and a vibration in a second direction is generated for the piezoelectric body,
Generating a second signal for the piezoelectric body that causes the elastic body to vibrate in a third direction different from the first direction and the second direction before driving the moving element by the traveling wave;
A driving method of a vibration wave motor characterized by the above.

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