JP4924726B2 - Vibration wave motor, lens barrel and camera - Google Patents

Description

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

  The vibration wave motor generates a traveling vibration wave (hereinafter abbreviated as a traveling wave) on a driving surface of an elastic body by using expansion and contraction of a piezoelectric body, as known in Patent Document 1 and the like. Due to this traveling wave, an elliptical motion is generated on the drive surface, and the moving element in pressure contact with the wavefront of the elliptical motion is driven. Such a vibration wave motor is characterized by having a high torque even at a low rotation. For this reason, when mounted on the drive device, the gear of the drive device can be omitted, and there is an advantage that quietness can be achieved and positioning accuracy can be improved by eliminating gear noise.

  On the other hand, since this vibration wave motor uses a vibration amplitude of about 1 μm generated in the stator, its characteristics are unstable. In order to solve this problem, Patent Document 2 discloses that the driving efficiency and driving performance are improved by setting the amplitude to 1.5 times or more the surface roughness of the driving surface.

Japanese Patent Publication No. 1-17354 JP-A-61-35178

According to the technique described in the above-mentioned Patent Document 2, when the amplitude is large to some extent, a suitable driving performance is obtained and the driving is performed silently. However, if the vibration amplitude becomes too large, there is a problem that pressurization on the moving element will not work, abnormal noise will be generated, and proper frictional contact will not be obtained between the moving element and the vibrator. As a result, good driving performance cannot be obtained.
In recent years, the wear resistance of the material of the drive surface has improved, it has become possible to reduce the frictional wear when the vibrator is driven by generating a large vibration amplitude, and to generate a large amplitude in the vibrator. Yes. Therefore, a new problem has arisen for optimization of speed control when driven with a large amplitude.

  An object of the present invention is to solve such problems and to provide a vibration wave motor, a lens barrel, and a camera that can obtain suitable driving performance and can be driven silently.

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.
The invention according to claim 1 is joined to the electromechanical conversion element (13, 113) excited by the drive signal and the electromechanical conversion element (13, 113), and the drive surface (18a, 118a) is driven by the excitation. An elastic body (14, 114) that generates a progressive vibration wave on the surface, and a sliding surface that is in pressure contact with the drive surface (18a, 118a) of the elastic body (14, 114). In a vibration wave motor (10, 110) comprising a relative motion member (12, 112) driven by the motor and a drive device (50) for providing the drive signal to the electromechanical transducer (13, 113). The drive device (50) defines a vibration amplitude generated on the drive surface (18a, 118a) of the elastic body (14, 114) as a value, and the drive surface (18a) of the elastic body (14, 114). , 118a When the wavelength of the traveling wave generated in λ is defined as λ, a driving signal for generating a traveling vibration wave satisfying a value / λ ≦ 0.00025 on the driving surface (18a, 118a) is transmitted to the electromechanical transducer (13 113), the vibration wave motor (10, 110).
The invention according to claim 2 is joined to the electromechanical conversion element (13, 113) excited by the drive signal and the electromechanical conversion element (13, 113), and the drive surface (18a, 118a) is driven by the excitation. And an elastic body (14, 114) that generates a progressive vibration wave, and a sliding surface that is in pressure contact with the drive surface (18a, 118a) of the elastic body (14, 114). In a vibration wave motor (10, 110) comprising a relative motion member (12, 112) driven by a wave and a drive device (50) for providing the drive signal to the electromechanical transducer (13, 113). The drive device (50) defines a vibration amplitude generated on the drive surface (18a, 118a) of the elastic body (14, 114) as a value, and drives the drive surface (18a) of the elastic body (14, 114). , 118a When the amount of deformation in the pressing direction of the sliding surface of the relative motion member (12, 112) in pressure contact with the pressure is defined as b value, a progressive vibration wave satisfying a value / b value ≦ 3 is driven. The vibration wave motor (10, 110) is characterized in that a drive signal generated on the surfaces (18a, 118a) is applied to the electromechanical transducer (13, 113).
According to a third aspect of the present invention, in the vibration wave motor (10, 110) according to the first aspect, the driving device (50) includes the driving surface (18a, 118a) of the elastic body (14, 114). Is defined as a value, and the sliding surface of the relative motion member (12, 112) in pressure contact with the driving surface (18a, 118a) of the elastic body (14, 114) is pressed. When the amount of deformation in the direction is defined as b value, the electromechanical transducer (13, 113) generates a drive signal for generating a progressive vibration wave on the drive surface (18a, 118a) that satisfies a value / b value ≦ 3. A vibration wave motor (10, 110) characterized in that
Invention of Claim 4 is a vibration wave motor (10,110) of any one of Claim 1 to 3, Comprising: The said drive device (50) is 0.000003 <= a value / (lambda). The vibration wave motor (10, 110) is characterized in that the electromechanical conversion element (13, 113) is provided with a drive signal for generating a progressive vibration wave satisfying the above condition on the drive surface (18a, 118a).
Invention of Claim 5 is a vibration wave motor (10,110) of any one of Claim 1 to 4, Comprising: The said drive device (50) is 0.04 <= a value / b. A vibration wave motor (10, 110) characterized in that a drive signal for generating a progressive vibration wave satisfying a value on the drive surface (18a, 118a) is applied to the electromechanical transducer (13, 113). .
The invention according to claim 6 is the vibration wave motor (10, 110) according to any one of claims 1 to 5, wherein the drive surface (18a, 118a) of the elastic body (14, 114), Or it is a vibration wave motor (10,110) characterized by the durable thin film being apply | coated to the sliding surface of the said relative motion member (12,112).
The invention according to claim 7 is the vibration wave motor (10, 110) according to claim 6, wherein the thin film is mainly composed of polyamideimide, has a Young's modulus of 4 GPa to 10 GPa, and a film thickness of 50 μm or less. The vibration wave motor (10, 110) is characterized by the following.
The invention described in claim 8 is a lens barrel (3, 103) including the vibration wave motor (10, 110) described in any one of claims 1 to 6.
The invention described in claim 9 is a camera (1) including the vibration wave motor (10, 110) according to any one of claims 1 to 6.

  Note that the configuration described with reference numerals may be modified as appropriate, and at least a part of the configuration may be replaced with another component.

  According to the present invention, it is possible to provide a vibration wave motor, a lens barrel, and a camera that can obtain suitable driving performance and can be driven silently.

It is a figure explaining a camera provided with a vibration wave motor of a first embodiment. It is a figure explaining the vibration wave motor of a first embodiment. It is a figure explaining the contact state of the vibrator of a vibration wave motor using a traveling wave, and a mover. It is a figure explaining the contact state of the vibrator of a vibration wave motor using a traveling wave, and a mover. It is a block diagram explaining the drive device of the vibration wave motor of a first embodiment. It is a figure explaining the relationship between the frequency of a vibration wave motor, and speed. It is a figure explaining the vibration wave motor of 3rd embodiment of this invention.

(First embodiment)
Hereinafter, embodiments of a vibration wave motor 10 according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a camera 1 including a vibration wave motor 10 according to the first embodiment.
The camera 1 includes a camera body 2 having an image sensor 8 and a lens barrel 3 having a lens 7. The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. In the present embodiment, the lens barrel 3 is an interchangeable lens. However, the present invention is not limited to this. For example, the lens barrel 3 may be a lens barrel integrated with the camera body.

The lens barrel 3 includes a lens 7, a cam barrel 6, gears 4 and 5, a vibration wave motor 10, and the like. In the present embodiment, the driving force obtained from the vibration wave motor 10 is transmitted to the cam cylinder 6 via the gears 4 and 5. The lens 7 is held by the cam barrel 6 via a lens frame 7a, and is moved substantially parallel to the optical axis direction (the direction of arrow L shown in FIG. 1) by the driving force of the vibration wave motor 10.
In FIG. 1, a subject image is formed on the imaging surface of the imaging element 8 by a lens group (including the lens 7) (not shown) provided in the lens barrel 3. The imaged subject image is converted into an electrical signal by the image sensor 8, and image data is obtained by A / D converting the signal.

FIG. 2 is a diagram illustrating the vibration wave motor 10 according to the first embodiment of the present invention.
In the present embodiment, the vibrator 11 side is fixed and the relative motion member (moving element) 12 is driven.

  As will be described later, the vibrator 11 joins an electromechanical conversion element (hereinafter referred to as a piezoelectric body 13) such as a piezoelectric element or an electrostrictive element that converts electrical energy into mechanical energy, and the piezoelectric body 13. And the elastic body 14. The traveling wave is generated in the vibrator 11, but in the present embodiment, it will be described as four traveling waves as an example.

The elastic body 14 is made of a metal material having a high resonance sharpness, and has an annular shape. A groove 17 is cut on the opposite surface to which the piezoelectric body 13 is joined, and the tip surface of the protruding portion 18 (a place where the groove 17 is not provided) serves as a driving surface 18 a and is brought into pressure contact with the moving element 12.
The reason for cutting the groove 17 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 18a. In this embodiment, the portion where the groove 17 is not cut is referred to as a base portion 19. The piezoelectric body 13 is bonded to the surface of the base portion 19 opposite to the groove 17 side.

  The drive surface 18a of the elastic body 14 is lubricated to ensure wear resistance when driven at a high speed. The material is composed of polyamideimide as a main component and added with PTFE, and has a Young's modulus of about 4 to 10 GPa, preferably 8 GPa or less. Further, the thickness is set to 5 μm or more and 50 μm or less.

The piezoelectric body 13 is generally made of a material such as lead zirconate titanate, commonly called PZT. In recent years, lead-free materials such as potassium sodium niobate, potassium niobate, and sodium niobate are used because of environmental problems. , Barium titanate, bismuth sodium titanate, potassium bismuth titanate and the like.
Electrodes (not shown) are arranged on the surface of the piezoelectric body 13 and are divided into two phases (A phase and B phase) along the circumferential direction. In each phase, the electrodes are arranged so that they are alternately polarized every ½ wavelength, and an interval of ¼ wavelength is left between the A phase and the B phase.

  The mover 12 is made of a light metal such as aluminum, and the surface of the sliding surface 12a is anodized to improve wear resistance.

  The output shaft 20 is coupled to the moving element 12 via a rubber member 21 so as to rotate integrally with the moving element 12. The rubber member 21 between the output shaft 20 and the mover 12 has a function of coupling the mover 12 and the output shaft 20 with adhesiveness due to rubber, and vibration for not transmitting vibration from the mover 12 to the output shaft 20. A function of absorption is required, and butyl rubber or the like is preferable.

The pressure member 22 is provided between the gear member 23 fixed to the output shaft 20 and the bearing receiving member 24. The gear portion 23 material is inserted so as to fit in the D cut of the shaft, is fixed by a stopper 25 such as an E clip, and is integrated with the output shaft 20 in the rotation direction and the axial direction. Further, the bearing receiving member 24 is inserted on the inner diameter side of the bearing 26, and the bearing 26 is inserted on the inner diameter side of the fixing member 27.
With this structure, the movable element 12 is brought into pressure contact with the vibrator 11 drive surface 18a.

3 and 4 are diagrams for explaining the contact state between the vibrator 11 and the moving element 12 of the vibration wave motor 10 using traveling waves.
A traveling wave is generated in the vibrator 11 and its amplitude is a value (pp) and the wavelength of the wave is λ. Since the size of the elliptical motion generated at the traveling wave front in the pressurizing direction and the size in the circumferential direction are approximately 1: 1, the magnitude of the a value is approximated by the following equation.

a = No-load rotation speed (rpm) / 60 × π × D × 2π × f × 2

here,
D: Diameter of sliding surface 12a of moving element 12 (mm)
f: The frequency (Hz) of the drive signal.
Since the sliding surface 12a has a width, D is defined as the median value of the outer diameter and the inner diameter.

On the other hand, since the moving element 12 is in pressure contact with the drive surface 18a of the vibrator 11, the sliding surface 12a is deformed along the traveling wave. Let the deformation amount be b value. The magnitude of the b value is approximated by the following equation.

b = 1/384 × p × λ 4 ÷ (E × (B × H 3/12))

here,
p: Load (N) ÷ (D × π) Load per unit length (N / mm)
E: Young's modulus (N / mm ² ) of the sliding portion of the slider 12
B: Width of sliding portion of moving element 12 (mm)
H: Height of sliding portion of moving element 12 (mm)
It is.

The relationship between the a value, the b value, and λ has been considered to be irrelevant until now, but as a result of experiments, it has been found that there is an appropriate range. The experimental results are shown in Table 1.

  When the rotational speed is changed by changing the drive frequency of the drive signal, the drive efficiency gradually increases, but starts to decrease from a certain value. This is because when the amplitude is small, there is a conversion loss from the vibration energy of the vibrator 11 to the rotational kinetic energy to the moving element 12, but the conversion loss decreases as the amplitude increases. If the amplitude value is greater than or equal to the amplitude value, the amplitude becomes too large, and the vibration itself may be lost. The threshold is considered to be determined by the ratio of amplitude to wavelength (ie, a value / λ).

The state in which the vibration itself is lost is a state in which the vibration is unstable. Therefore, the vibration wave motor 10 is difficult to control in this unstable region.
According to this measurement, the driving efficiency decreases when a value / λ ≦ 0.00025 is exceeded. Therefore, the relationship of a value / λ ≦ 0.00025 is preferable.
In order to obtain a stable rotation, a relationship of 0.000003 ≦ a value / λ is preferable.
The driving efficiency is calculated from: = rotational speed × torque / input power.

  Further, when the drive frequency of the drive signal is changed and the rotation speed is changed, abnormal noise starts to occur at a certain rotation speed or higher. This is because when the amplitude is small, the vibrator 11 drive surface 18a and the slider 12 sliding surface 12a are in close contact with each other by pressurization, but when the amplitude increases and the rotation speed increases, This is probably because the slider 12 sliding surface 12a starts to float, and a gap is generated between the vibrator 11 and the driving surface 18a.

The threshold is considered to be determined by the ratio of the amplitude to the amount of deformation of the slider 12 sliding surface 12a (ie, a value / b value). In the state where the noise is generated, the rotational speed is unstable, and therefore the vibration wave motor 10 is difficult to control in this unstable region.
According to this measurement, the relationship of a value / b value ≦ 3.0 is preferable. Further, in order to obtain a stable rotation, a relationship of 0.04 ≦ a value / b value is preferable.

In addition, although it is a definition of B value and H value, as shown to (a) of FIG. 4, it is the width | variety and height of the sliding part of the slider 12. As shown in FIG. In (a), the support member of the sliding portion extends to the inner diameter side, but even if it extends to the outer diameter side as in (b), the definition is the same.
Further, as shown in (c), when the polymer sliding material 12c is pasted on the sliding surface 12a, the sliding material has an extremely smaller Young's modulus than the metal. Define the part excluding the part.

FIG. 5 is a block diagram illustrating the driving device 50 of the vibration wave motor 10 of the first embodiment.
First, driving / control of the vibration wave motor 10 will be described.
The oscillating unit 51 generates a drive signal having a desired frequency according to a command from the control unit 52.
The phase shifter 53 divides the drive signal generated by the oscillator 51 into two drive signals having different phases.
The amplification unit 54 boosts the two drive signals divided by the phase shift unit 53 to desired voltages, respectively.
A drive signal from the amplifying unit 54 is transmitted to the vibration wave motor 10, and a traveling wave is generated in the vibrator 11 by the application of this drive signal, and the moving element 12 is driven.

The rotation detection unit 55 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 12, and transmits the detected value to the control unit 52 as an electric signal.
The control unit 52 controls the driving of the vibration wave motor 10 based on a driving command from the CPU in the lens barrel 3 or the camera 1 main body. The control unit 52 receives the detection signal from the rotation detection unit 55, obtains position information and speed information based on the value, and determines the frequency of the oscillation unit 51 and the voltage of the amplification unit 54 so that the position information is positioned at the target position. To control.

  Although driving in the forward direction and driving in the reverse direction, when driving in the driving forward direction, the phase difference between the two driving signals (frequency voltage signals) in the phase shift unit 53 is set to a positive value, for example, +90 degrees, When driving in the reverse direction, the phase difference between the two drive signals (frequency voltage signals) in the phase shifter 53 may be set to a negative value, for example, -90 degrees.

FIG. 6 is a diagram for explaining the relationship between the frequency and speed of the vibration wave motor 10.
In the case of the vibration wave motor 10, speed change and control are generally performed at the drive frequency. The speed increases as the frequency is lowered, and the speed decreases as the frequency is increased.
According to this embodiment, the drive device 50 of the vibration wave motor 10 is operated as follows.
First, the setting in the factory before shipment will be described.
First, D: The diameter (mm) of the sliding surface 12 a of the moving element 12 (see FIG. 2) and λ: the wavelength (mm) of the vibrator 11 are input to the control unit 52.

Next, preliminary driving is performed. As the method, first, a drive signal is generated from the oscillation unit 51. The signal is divided into two drive signals having a phase difference of 90 degrees by the phase unit, and is amplified to a desired voltage by the amplification unit 54.
The drive signal is applied to the piezoelectric body 13 of the vibration wave motor 10 to generate a traveling wave on the drive surface 18 a of the vibrator 11.
The mover 12 that is in pressure contact with the drive surface 18a is frictionally driven by this elliptical motion.
An optical encoder is disposed in the driving body driven by driving the moving element 12, and an electric pulse is generated therefrom and transmitted to the control unit 52, whereby the speed can be obtained.
1) Speed value, 2) Driving frequency at that time, 3) Amplitude a value of traveling wave is calculated from input D value, and 4) From input λ value, a value / λ ≦ 0.00025 Get the drive frequency to be kept.
Let that frequency be the lower limit frequency A. This is the factory setting before shipment.

As an actual drive / control operation, a drive command is issued from the control unit 52 and a drive signal is generated from the oscillation unit 51. The signal is divided into two drive signals having a phase difference of 90 degrees by the phase unit, and is amplified to a desired voltage by the amplification unit 54.
The drive signal is applied to the piezoelectric body 13 of the vibration wave motor 10, and the piezoelectric body 13 is excited. Due to the excitation, fourth-order bending vibration is generated in the elastic body 14.
The piezoelectric body 13 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 phase is shifted by 90 degrees, the two bending vibrations are combined into four traveling waves.

  Elliptic motion occurs at the front of the traveling wave. Accordingly, the movable element 12 that is in pressure contact with the drive surface 18a is frictionally driven by this elliptical motion. An optical encoder is arranged in the driving body driven by driving the moving element 12, and an electric pulse is generated therefrom and transmitted to the control unit 52. Based on this signal, the control unit 52 can obtain the current position and the current speed. The control unit 52 performs control by changing the frequency so that the target speed matches the actual speed, but the frequency is prevented from falling below the lower limit frequency A.

  By performing such a control method, a suitable driving efficiency can always be obtained, and a silent driving is possible.

In the present embodiment, the drive surface 18a of the elastic body 14 is subjected to a lubricious surface treatment.
The material is composed mainly of polyamideimide and added with PTFE. The physical properties are Young's modulus of 4 GPa or more and thickness of 50 μm or less.

When the Young's modulus of the lubricant material on the surface is smaller than this or when the thickness is larger than this, biting deformation occurs at the position of the driving surface 18a that contacts the sliding surface 12a of the moving element 12, and complicated friction driving occurs. Thus, the relationship between the vibration amplitude found by the author and the driving efficiency may be different. When the lubricating surface treatment of the drive surface 18a is a Young's modulus of 4 GPa or more and a thickness of 50 μm or less, the relationship between the vibration amplitude found by the author and the drive efficiency can be obtained, and thus the effect of the present invention can be obtained.
The upper limit of Young's modulus is 10 GPa or less in production. Moreover, since it becomes easy to peel when the film thickness becomes thin, the lower limit of the film thickness is preferably 5 μm or more.

  For example, in a combination of a Young's modulus and a thin lubricating film in which the conventional vibrator 11 drive surface 18a is a metal material or metal plating, and the slider 12 sliding surface 12a is a metal material or metal plating, the friction drive between metals is performed. For this reason, when the driving speed is high, frictional wear increases and the value a cannot be increased (vibration amplitude cannot be increased). For this reason, it is not possible to drive to the control range defined by this embodiment, and numerical values as in this embodiment are not necessary. However, if the driving surface 18a or the sliding surface 12a has a large Young's modulus and a thin lubricating film is applied, frictional wear will not occur even if the vibration amplitude is increased to increase the driving speed. For this reason, the control method of this embodiment becomes effective.

  However, even if the conventional vibrator 11 drive surface 18a is a metal material or metal plating, and the slider 12 sliding surface 12a is a metal material or metal plating, the frictional wear during high-speed driving does not occur. The method of the embodiment is effective and produces an effect.

(Second embodiment)
Next, a second embodiment will be described. In the second embodiment, the vibration amplitude is controlled based on the deformation amount of the movable element 12 in the pressurized state.
In this embodiment, the vibration wave motor control device operates as follows. First, the setting in the factory before shipment will be described.
First, D: the diameter (mm) of the sliding surface 12a of the moving element 12, λ: the wavelength (mm) of the vibrator 11, and the deformation amount b value (mm) of the moving state of the moving element 12 are calculated. 52.
Next, preliminary driving is performed. As a method thereof, a drive signal is generated from the oscillating unit 51, and the signal is divided into two drive signals having a phase difference of 90 degrees by the phase unit, and is amplified to a desired voltage by the amplification unit 54. The drive signal is applied to the piezoelectric body 13 of the vibration wave motor 10 to generate a traveling wave on the drive surface 18 a of the vibrator 11. The mover 12 that is in pressure contact with the drive surface 18a is frictionally driven by this elliptical motion. An optical encoder is arranged in the driving body 30 driven by driving the moving element 12, and an electric pulse is generated therefrom and transmitted to the control unit 52, so that the speed can be obtained.

  Similarly, 1) velocity value, 2) driving frequency at that time, 3) amplitude a value of traveling wave is calculated from input D value, and 4) a value / b value ≦ 3.0 from input b value. A drive frequency that maintains the relationship is obtained. Let that frequency be the lower limit frequency B. In order to obtain a stable rotation, 0.04 ≦ a value / b value. This is the factory setting before shipment.

  As an actual drive / control operation, a drive command is issued from the control unit 52, a drive signal is generated from the oscillation unit 51, and the signal is divided into two drive signals having a phase difference of 90 degrees by the phase unit. Amplified to a desired voltage by the amplifying unit 54. The drive signal is applied to the piezoelectric body 13 of the vibration wave motor 10, and the piezoelectric body 13 is excited. Due to the excitation, fourth-order bending vibration is generated in the elastic body 14. The piezoelectric body 13 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 phase is shifted by 90 degrees, the two bending vibrations are combined into four traveling waves.

  Elliptic motion occurs at the front of the traveling wave. Accordingly, the movable element 12 that is in pressure contact with the drive surface 18a is frictionally driven by this elliptical motion. An optical encoder is arranged in the driving body driven by driving the moving element 12, and an electric pulse is generated therefrom and transmitted to the control unit 52. Based on this signal, the control unit 52 can obtain the current position and the current speed. The control unit 52 performs control by changing the frequency so that the target speed matches the actual speed, but the frequency is prevented from falling below the lower limit frequency B.

  In the first embodiment, control is performed so that the relationship of a value / λ ≦ 0.00025 is maintained, and in the second embodiment, control is performed so that the relationship of a value / b value ≦ 3.0 is maintained. However, it may be controlled so that both are maintained.

(Third embodiment)
FIG. 7 is a diagram illustrating the vibration wave motor 110 according to the third embodiment of the present invention, and is a view showing a state in which the ring-shaped vibration wave motor 110 is incorporated in the lens barrel 103.
The vibrator 111 includes an electromechanical conversion element (hereinafter referred to as a piezoelectric body) 113, which is an example of a piezoelectric element or an electrostrictive element that converts electrical energy into mechanical energy, and an elastic body 114 joined with the piezoelectric body 113. It is configured. Although a traveling wave is generated in the vibrator 111, in the present embodiment, description will be made assuming that the traveling wave is 9 waves as an example.

The elastic body 114 is made of a metal material having a high resonance sharpness, and has an annular shape. A groove 117 is cut on the opposite surface to which the piezoelectric body 113 is bonded, and the tip surface of the protrusion 118 (where the groove 117 is not provided) serves as a driving surface 118a and is brought into pressure contact with the moving element 112.
The reason for cutting the groove 117 is to make the traveling wave neutral surface as close to the piezoelectric body 113 as possible, thereby amplifying the amplitude of the traveling wave on the drive surface 18a.

  The piezoelectric body 113 is divided into two phases (A phase and B phase) along the circumferential direction, and in each phase, the 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.

A non-woven fabric (not shown), a pressure plate 120, and a pressure member 122 are disposed under the piezoelectric body 113. The non-woven fabric is an example of felt, and is disposed under the piezoelectric body 113 so that the vibration of the vibrator 111 is not transmitted to the pressure plate 120 or the pressure unit.
The pressure plate 120 is configured to receive pressure from the pressure member 122.

  The pressurizing member 122 is disposed under the pressurizing plate 120 and generates pressure. In this embodiment, the pressure member 122 is a disc spring, but it may be a coil spring or a wave spring instead of a disc spring. The pressure member 122 is held by fixing the holding ring to the fixing member 127.

The mover 112 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 12a.
On the moving element 112, a vibration absorbing member 131 such as rubber is arranged to absorb the vertical vibration of the moving element 112, and an output transmission unit 132 is arranged thereon.

In the output transmission unit 132, the pressurizing direction and the radial direction are regulated by a bearing 134 provided on the fixed member 127, and thereby the pressurizing direction and the radial direction of the moving element 112 are regulated.
The output transmission part 132 has a protrusion 135 from which a fork connected to the cam ring 136 is fitted. As the output transmission part 132 rotates, the cam ring 136 is rotated.

  In the cam ring 136, a key groove 140 is obliquely cut in the cam ring 136. A fixing pin 142 provided in the AF ring 141 is fitted in the key groove 140, and the cam ring 136 is driven to rotate. As a result, the AF ring 141 is driven in the straight direction along the optical axis direction, and can be stopped at a desired position.

  In the fixing member 127, the pressing ring 123 is attached by a screw, and by attaching this, the components from the output transmission unit 132 to the moving element 112, the vibrator 111, and the spring can be configured as one motor unit.

The experimental results in this embodiment are described in Table 2.

When the rotational speed is changed by changing the drive frequency of the drive signal, the drive efficiency gradually increases, but starts to decrease from a certain value. This is because when the amplitude is small, there is a conversion loss from the vibration energy of the vibrator 111 to the rotational kinetic energy to the moving element 112, but the conversion loss decreases as the amplitude increases. If the amplitude value is greater than or equal to the amplitude value, it is considered that the vibration itself is lost because the amplitude becomes too large. The threshold is considered to be determined by the ratio of amplitude to wavelength (ie, a value / λ).
Since the vibration is unstable when the vibration is lost, the vibration wave motor 110 is difficult to control in this unstable region.

According to this measurement, the relationship of a value / λ ≦ 0.00025 is preferable. In order to obtain a stable rotation, a relationship of 0.000003 ≦ a value / λ is preferable.
The driving efficiency is calculated from: = rotational speed × torque / input power.
Also, if the rotational speed is changed by changing the drive frequency of the drive signal, abnormal noise begins to occur at a certain rotational speed or higher. This is because when the amplitude is small, the vibrator 111 drive surface 18a and the slider 112 sliding surface 12a are in close contact with each other by pressurization, but when the amplitude increases and the rotation speed increases, This is probably because the slider 112 sliding surface 12a starts to float, and a gap is generated between the vibrator 111 and the driving surface 18a.

The threshold is considered to be determined by the ratio of amplitude to the amount of deformation of the slider 112 sliding surface 12a (ie, a value / b value). In the state where the noise is generated, the rotational speed is unstable. Therefore, the vibration wave motor 110 is difficult to control in this unstable region.
According to this measurement, the relationship of a value / b value ≦ 3.0 is preferable. Further, in order to obtain a stable rotation, a relationship of 0.04 ≦ a value / b value is preferable.

  Since the driving method and the control method of this embodiment are the same as those of the first embodiment or the second embodiment, description thereof is omitted.

  From the above, as shown in Table 1 of the first embodiment and Table 2 of the third embodiment, in both the first embodiment and the third embodiment, regardless of the shape, the wave number of the traveling wave, and the wavelength, a The relationship of value / λ ≦ 0.00025 is preferred. In order to obtain a stable rotation, a relationship of 0.000003 ≦ a value / λ is preferable. The relationship of a value / b value ≦ 3.0 is preferable. Further, in order to obtain a stable rotation, a relationship of 0.04 ≦ a value / b value is preferable.

As described above, controlling the vibration wave motor in consideration of this relationship is considered to be effective for many traveling wave vibration wave motors.
In the present embodiment, the vibration wave motor using the progressive vibration wave is disclosed with the wave numbers 4 and 9, but the other wave numbers of 5, 6, 7, 8, 10 and more have the same configuration. If controlled in the same way, the same effect can be obtained.

  10, 110: vibration wave motor, 12, 112: mover, 13, 113: piezoelectric body, 14, 114: elastic body, 18a, 118a: driving surface, 50: driving device

Claims (9)

An electromechanical transducer that is excited by a drive signal;
An elastic body that is bonded to the electromechanical transducer and generates a progressive vibration wave on a driving surface by the excitation;
A relative motion member having a sliding surface in pressure contact with a driving surface of the elastic body and driven by the progressive vibration wave;
In a vibration wave motor comprising: a drive device that provides the drive signal to the electromechanical conversion element;
The driving device includes:
When the vibration amplitude generated on the driving surface of the elastic body is defined as a value and the wavelength of the traveling wave generated on the driving surface of the elastic body is defined as λ, a value / λ ≦ 0.00025 is satisfied. Providing the electromechanical transducer with a drive signal for generating a progressive vibration wave on the drive surface;
Vibration wave motor characterized by An electromechanical transducer that is excited by a drive signal;
An elastic body that is bonded to the electromechanical transducer and generates a progressive vibration wave on a driving surface by the excitation;
A relative motion member having a sliding surface in pressure contact with the drive surface of the elastic body and driven by the progressive vibration wave;
In a vibration wave motor comprising: a drive device that provides the drive signal to the electromechanical conversion element;
The driving device includes:
The vibration amplitude generated on the drive surface of the elastic body is defined as a value, and the deformation amount in the pressurizing direction of the sliding surface of the relative motion member in pressure contact with the drive surface of the elastic body is defined as b value. Providing the electromechanical transducer with a drive signal for generating a progressive vibration wave on the drive surface that satisfies a value / b value ≦ 3 when defined,
Vibration wave motor characterized by The vibration wave motor according to claim 1,
The driving device includes:
The vibration amplitude generated on the drive surface of the elastic body is defined as a value, and the deformation amount in the pressurizing direction of the sliding surface of the relative motion member in pressure contact with the drive surface of the elastic body is defined as b value. Providing the electromechanical transducer with a drive signal for generating a progressive vibration wave on the drive surface that satisfies a value / b value ≦ 3 when defined,
Vibration wave motor characterized by The vibration wave motor according to any one of claims 1 to 3,
The driving device includes:
Providing the electromechanical transducer with a driving signal for generating a progressive vibration wave satisfying 0.000003 ≦ a value / λ on the driving surface;
Vibration wave motor characterized by The vibration wave motor according to any one of claims 1 to 4,
The driving device provides the electromechanical transducer with a driving signal for generating a progressive vibration wave on the driving surface that satisfies 0.04 ≦ a value / b value;
Vibration wave motor characterized by In the vibration wave motor according to any one of claims 1 to 5,
A vibration wave motor, wherein a durable thin film is applied to the drive surface of the elastic body or the sliding surface of the relative motion member. The vibration wave motor according to claim 6,
The vibration film motor is characterized in that the thin film is mainly composed of polyamideimide, has a Young's modulus of 4 Gpa to 10 GPa, and a film thickness of 50 μm or less.   A lens barrel comprising the vibration wave motor according to claim 1.   A camera comprising the vibration wave motor according to claim 1.

Images