WO2010027007A1

WO2010027007A1 - Ultrasonic actuator

Info

Publication number: WO2010027007A1
Application number: PCT/JP2009/065387
Authority: WO
Inventors: 勝一浦谷; 茂昭栃本; 昭広沖
Original assignee: コニカミノルタオプト株式会社
Priority date: 2008-09-04
Filing date: 2009-09-03
Publication date: 2010-03-11
Also published as: JPWO2010027007A1; JP5152336B2

Abstract

An ultrasonic actuator provided with a vibrating body comprising a piezoelectric vibrator for generating vibration by means of an electrical signal, a protruding section, and a contact section for transmitting the vibration; a moving body which comprises a section to be contacted where a vibration-high-receiving section susceptible to receiving the vibration from the protruding section and a vibration-low-receiving section not susceptible to receiving the vibration therefrom are formed, and which moves in response to the vibration of the piezoelectric vibrator via the vibration-high-receiving section; a calculating section which detects a change, in the resonance state of the piezoelectric vibrator, generated when the vibration-low-receiving section of the moving body passes through the protruding section of the vibrating body, and which calculates the positional information of the moving body according to the change in the resonance state; and a control section for controlling the drive of the moving body according to the positional information calculated by the calculating section. The ultrasonic actuator is compact and is capable of an accurate positional control.

Description

Ultrasonic actuator

The present invention relates to an ultrasonic actuator that drives a moving body by vibration of a piezoelectric vibrator having a piezoelectric element.

The ultrasonic actuator is configured such that a fixed portion including a piezoelectric vibrator having a piezoelectric element and a moving body are in contact with each other, and the moving body is driven by the vibration of the piezoelectric vibrator. Specifically, a traveling wave is generated on the surface of the fixed part by the vibration of the piezoelectric vibrator, and the fixed part comes into contact with the moving body only at the top of the wave. Since the top of the wave is rotating elliptically, the moving body is driven so as to be pushed by the fixed part. Since the ultrasonic actuator is driven in this manner, there is a possibility that slip occurs between the fixed portion and the moving body, and it is necessary to control the moving amount of the moving body. Conventionally, in order to control the amount of movement of a moving body, a method of providing a position detection device such as a rotary encoder has been used. That is, the moving amount of the moving body is detected by the position detection device, and the moving body is controlled by feedback control. However, attaching the rotary encoder has a problem that the space for installing the ultrasonic actuator increases.

Recently, various methods have been proposed to solve this problem. For example, the invention described in Patent Document 1 is an ultrasonic actuator including a fixed portion and a moving body, and a non-uniform portion is formed by a slot or a protrusion on the moving body. The nonuniform portion is formed in order to emphasize the change in the envelope of the peak value of the drive current supplied to the piezoelectric vibrator. By performing electrical signal processing on the detected envelope of the peak value of the drive current, the amount of movement of the moving body is detected and the amount of movement is controlled.

The invention described in Patent Document 2 discloses an ultrasonic motor composed of a vibrator and a moving body, and 2 arc protrusions or ring-shaped protrusions 2 facing each other on the lower surface of the moving body. Heterogeneous portions are formed at one location, thereby forming a non-uniform portion for detecting the position and rotational speed of the moving body. The vibrator is provided with vibration detection means, which compares the fluctuation period of the phase difference between the detection signal detected by the vibration detection means and the applied voltage to obtain the fluctuation period, and detects the position and rotation speed from the fluctuation period. ing.

In the inventions described in Patent Document 1 and Patent Document 2, the configuration and the number of rotations are detected without a sensor that detects the position of a moving body such as an encoder, by the configuration as described above.

However, in the ultrasonic actuator of Patent Document 1, since the change in the peak value of the drive current of the piezoelectric vibrator is small, accurate detection is difficult, and high-accuracy position control is difficult. In addition, it is possible to increase the crest value change by increasing the shape of the slot and protrusion compared to other locations, but this will reduce the driving efficiency and maintain the flatness at the time of contact. The new problem of becoming difficult arises.

In the ultrasonic motor of Patent Document 2, since the circular protrusion or ring-shaped protrusion formed on the lower surface of the moving body is in surface contact with the upper surface of the vibrator, the moving amount of the moving body is averaged, and high-precision detection is difficult. There is a problem that it is. Furthermore, since the heterogeneous part is formed on the two lower surfaces of the two arcuate protrusions or ring-shaped protrusions facing each other on the lower surface of the moving body, a phase difference signal of two cycles is generated during one rotation of the moving body. It is only output. For this reason, in order to improve the resolution of position detection, it is necessary to provide a plurality of detection units whose phases are shifted, which causes a problem that the structure is complicated and the scale of the detection circuit is increased.

JP-A-6-225550 JP-A-6-133570

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an ultrasonic actuator that is small and capable of accurate position control.

An ultrasonic actuator according to an aspect of the present invention includes a piezoelectric vibrator that generates vibration by an electric signal, a vibrating body having a curved portion or a needle-like protrusion, and a contact portion that transmits the vibration. A piezoelectric high vibration receiving portion that is easy to receive vibration from the protrusion and a low contact receiving portion that is difficult to receive vibration from the protruding portion; and the piezoelectric vibration through the high vibration receiving portion. Detecting a resonance state change of the piezoelectric vibrator that occurs when the vibration low-accepting portion of the moving body passes through the protrusion of the vibrating body, A calculation unit that calculates position information of the moving body based on a state change, and a control unit that controls driving of the moving body based on the position information calculated by the calculation unit.

In this way, the resonance state change of the piezoelectric vibrator is detected, the position information such as the moving amount and position of the moving body is calculated, and the moving amount and the like of the moving body are thereby controlled. A small ultrasonic actuator can be provided without the need.

In addition, since the uppermost portion of the protrusion provided on the vibrating body is curved or needle-shaped, the contact area of the moving body with the vibration contacted portion is extremely small, and the force from the moving body is a protrusion close to point contact. The resonance state change of the piezoelectric vibrator can be detected with high resolution. Therefore, a phase difference appears remarkably, a change in phase difference can be detected with higher accuracy, and position control with higher accuracy can be performed.

It is a schematic block diagram which shows the structure of the lens drive unit using the ultrasonic actuator which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the internal structure of the said ultrasonic actuator. It is a block diagram which shows the electric constitution of the said ultrasonic actuator. FIGS. 4A and 4B are views showing an external appearance of a vibrating body provided in the ultrasonic actuator, FIG. 4A is a plan view of the vibrating body, and FIG. 4B is a diagram in which drive electrodes of the vibrating body are installed. FIG. 4C is a side view of the vibrating body on which the vibration detection electrode is installed. FIG. 5A is a cross-sectional view showing an electrode configuration in each layer of the piezoelectric vibrator of the vibrator, FIG. 5A is a cross-sectional view taken along the line VA-VA of FIG. 4B, and FIG. It is a VB-VB sectional view taken on the line B). It is a conceptual diagram which shows the bending primary mode of the said vibrating body. FIGS. 7A and 7B are conceptual diagrams illustrating a rotational movement of a protrusion provided on a contact portion of the vibrating body, FIG. 7A is a side view of the contact portion, and FIG. 7B is a plan view of the contact portion. . It is a disassembled perspective view of the rotor and the contact portion of the ultrasonic actuator. It is a perspective view which shows the shape of the surface facing the said contact part of the said rotor. It is a principal part expanded sectional view which shows the contact state of the said rotor and the said contact part. It is a principal part expanded sectional view which shows the contact state of another rotor and the said contact part. It is a principal part expanded sectional view which shows the contact state of another rotor and the said contact part. It is a graph which shows the relationship between the vibration detection voltage in the said piezoelectric vibrator, and the frequency of a drive signal. It is a graph which shows the relationship between the phase difference between the vibration detection voltage and drive voltage in the said piezoelectric vibrator, and the frequency of a drive signal. It is a block diagram which shows the electric constitution of the ultrasonic actuator which concerns on Embodiment 2 of this invention. It is a figure which shows the equivalent circuit of a piezoelectric vibrator. FIG. 17A is a graph showing the phase difference between the driving current and the driving voltage in the piezoelectric vibrator, and FIG. 17A is a graph showing the waveforms of the driving current and the driving voltage in the first embodiment. ) Is a graph showing waveforms of the drive current and the drive voltage in the second embodiment. It is a circuit diagram which shows the structural example of a current converter or a voltage converter. It is a graph which shows conversion to a pulse signal. 6 is a graph showing the positioning of the ultrasonic actuator according to the second embodiment. 6 is a circuit diagram showing a part of a specific circuit configuration of an ultrasonic actuator according to Embodiment 2. FIG. FIG. 22A is a graph showing the drive current and drive voltage of the ultrasonic actuator according to Embodiment 2, FIG. 22A is a graph showing the drive current and drive voltage in the first embodiment, and FIG. It is a graph which shows the drive current and drive voltage in a 2nd form. FIG. 23A is a graph showing an output signal from the logic circuit of the ultrasonic actuator according to Embodiment 2 and a signal after low-pass filter processing, and FIG. 23A is a graph in the first embodiment, and FIG. Is a graph in the second form. 6 is a graph showing a signal after a high-pass filter process and a signal after a low-pass filter process of an ultrasonic actuator according to a second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(Embodiment 1)
An ultrasonic actuator according to Embodiment 1 of the present invention will be described. First, the configuration of a lens driving unit using the ultrasonic actuator according to Embodiment 1 of the present invention will be described. FIG. 1 is a diagram for explaining a configuration of a lens driving unit using the ultrasonic actuator according to the first embodiment. The lens driving unit 300 is used for AF and zooming of digital cameras and digital video cameras, and driving of aberration correction of a pickup lens of a DVD. As shown in FIG. 1, a lens support portion 22b that is partially screwed with a lead screw 21 that is integrally coupled to the rotation shaft of the ultrasonic actuator 100 according to the first embodiment, and is supported by the lens support portion 22b. The lens 22, two guide rails 22 a installed in parallel with the lead screw 21 that controls the movement of the lens 22, a case 23 covering these, and the ultrasonic actuator 100 are provided. In FIG. 1, the electrical components of the ultrasonic actuator 100 are not shown.

Specifically, a through hole is formed in the lens support portion 22b that supports the outer peripheral portion of the lens 22, and a guide rail 22a is passed through the through hole, and the lens support portion 22b is connected to the guide rail 22b. Can move only along the direction. The lens support portion 22b is screwed with the lead screw 21, and the lens support portion 22b is driven along the guide rail 22a as the lead screw 21 rotates about its axis.

In such a lens driving unit 300, by driving the ultrasonic actuator 100, the lead screw 21 is rotated clockwise or counterclockwise, whereby the lens support portion 22b integrated with the lens 22 is moved in the horizontal direction in FIG. Moving. That is, the lens driving unit 300 constitutes a linear movement lens feed mechanism.

As described above, the ultrasonic actuator 100 according to the first embodiment is used for the lens driving unit 300, for example, but is not limited thereto, and can be used for various other purposes.

Next, the mechanical configuration of the ultrasonic actuator will be described. FIG. 2 is a view for explaining the mechanical configuration of the ultrasonic actuator. In FIG. 2, the electrical configuration of the ultrasonic actuator is not shown. As shown in FIG. 2, the ultrasonic actuator 100 includes a moving body having a contacted portion, that is, a rotor 1, a contact portion 2 a having a protrusion 2 c that contacts the contacted portion of the rotor 1, and a piezoelectric vibrator 2 b. A vibrating body (stator) 2, a weight portion 5 installed at an end of the vibrating body 2, a rotating shaft 3 installed integrally with the rotor 1 at the rotation center of the rotor 1, a bearing 27 of the rotating shaft 3, A case 7 that covers them, a pressurizing unit 6 that is connected to the bottom surface of the case 7 and the vibrating body 2 and includes an elastic body such as a spring that presses the vibrating body 2 against the rotor 1 with a predetermined urging force; The connected support frame 24, a cap 26 installed so as to penetrate the support frame 24, and a bearing 25 that is a sphere that is rotatably fitted in a recess 26 a formed in the cap 26.

The rotor 1 has a disk shape. The rotating shaft 3 is the center of the rotor 1 and is disposed so as to extend in a direction perpendicular to the surface of the disk. The rotating shaft 3 is connected to the rotor 1 integrally or by caulking or the like. The vibrating body 2 includes a disk-shaped contact portion 2a centering on the rotation shaft 3 and a piezoelectric vibrator 2b joined to the contact portion 2a. The contact portion 2 a has a protrusion 2 c, and the protrusion 2 c comes into contact with the rotor 1. Since the rotor 1 is driven by the frictional force between the protrusion 2c and the rotor 1, the contact portion 2a including the protrusion 2c is made of a material having high wear resistance such as ceramics such as alumina and zirconia, cemented carbide, and the like. Is formed. The contact portion 2a is fixed to the piezoelectric vibrator 2b using an adhesive having high rigidity and strong adhesive force such as epoxy. The piezoelectric vibrator 2b is configured by alternately laminating piezoelectric thin plates exhibiting piezoelectric characteristics and internal electrodes. In consideration of ease of manufacture, the piezoelectric vibrator 2b preferably has a rectangular parallelepiped shape. As the piezoelectric thin plate, for example, a thin plate of a piezoelectric element such as a piezoelectric ceramic made of PZT (lead zirconate titanate) or the like may be used. The piezoelectric vibrator 2b vibrates by sending a predetermined electric signal to the piezoelectric vibrator 2b via the internal electrode. Due to the vibration, the contact portion 2a connected to the piezoelectric vibrator 2b vibrates, and the protrusion 2c in contact with the rotor 1 also vibrates. The uppermost part of the projection 2c is formed in a curved surface or a needle shape, and makes the contact area with the rotor 1 as small as possible. The bearing 27 rotatably supports the rotary shaft 3. Specifically, the rotary shaft 3 is supported in the radial direction by the bearing 27. In the piezoelectric vibrator 2b, the weight part 5 is installed at the end opposite to the end joined to the contact part 2a. By installing the weight portion 5, the vibration balance of the vibrating body 2 is improved. Moreover, since the position of the vibration node of the piezoelectric vibrator 2b moves to the weight part 5 side by installing the weight part 5, the vibration of the protrusion part 2c can be increased. For example, the weight portion 5 is formed of tungsten having a high specific gravity, copper, or an iron-based tungsten alloy.

The rotor 1, the vibrating body 2, the rotating shaft 3, the bearing 27, the weight portion 5, and the pressurizing portion 6 are disposed in the case 7. The rotating shaft 3 protrudes from the inside of the case 7 to the outside. A part of the bearing 27 is exposed to the outside of the case 7. The vibrating body 2 is restricted from rotating with respect to the case 7, and is pressed from the bottom surface of the case 7 toward the rotor 1 by the pressurizing unit 6. Thereby, the contact part 2a is in contact with the rotor 1 in a state where high pressure is applied. The support frame 24 is installed on the end surface of the case 7 on the side from which the rotary shaft 3 protrudes, and the rotary shaft 3 protruding from the case 7 extends into the support frame 24. A concave surface is formed at the end of the rotating shaft 3, and a bearing 25, which is a sphere fitted in a recess 26 a of a cap 26 installed on the support frame 24, is disposed so as to fit in the concave surface, and the rotating shaft 3 rotates. The bearing 25 is freely supported. Specifically, the rotary shaft 3 is supported by the bearing 25 in the radial and thrust directions. The cap 26 is threadedly engaged with the support frame 24 and penetrates. That is, the support frame 24 and the cap 26 are threaded, and the position of the cap 26 in the direction along the rotation shaft 3 can be adjusted by tightening or loosening the cap 26. Since the vibrating body 2 is pressed against the rotor 1 by the pressurizing unit 6, the rotating shaft 3 coupled to the rotor 1 receives a reaction force from the bearing 25, but the reaction force is at the center of rotation of the rotating shaft 3. Therefore, the friction loss between the rotating shaft 3 and the bearing 25 which is a sphere can be minimized. When the ultrasonic actuator is manufactured, the position of the cap 26 is adjusted to adjust the pressing force between the vibrating body 2 and the rotor 1. And if adjustment is completed, the position of the cap 26 will be fixed by adhere | attaching. By doing in this way, while the rotation of the vibrating body 2 is restricted with respect to the case 7, the axis center with the rotor 1 is positioned and held.

Next, the electrical configuration of the ultrasonic actuator will be described. FIG. 3 is a diagram for explaining an electrical configuration of the ultrasonic actuator. As shown in FIG. 3, the ultrasonic actuator 100 includes a control unit 11, a drive voltage generation unit 12, a vibration state detection unit 14, a detection voltage conversion unit 15, and a drive voltage other than those shown in FIG. 2. A conversion unit 16 and a calculation unit 17 are provided. In FIG. 3, the mechanical configuration shown in FIG. 2 shows members necessary for the description of the electrical configuration, and the other components are not shown. The control unit 11, the drive voltage generation unit 12, the drive current generation unit 13, the detection voltage conversion unit 15, the drive voltage conversion unit 16, and the calculation unit 17 are, for example, a resistor, a capacitor, and a coil on a substrate. An electronic element such as is arranged.

The control unit 11 generates a drive signal that is an electrical signal so that the rotor 1 is rotationally driven. Specifically, the rotor 1 is driven so that the drive signal is driven by the protrusion 2c by vibrating the piezoelectric vibrator 2b so that the protrusion 2c (not shown) of the contact portion 2a generates an elliptical rotational motion. Moving.

The drive voltage generator 12 generates a drive voltage according to the drive signal instructed by the controller 11. In addition, since the drive control of the piezoelectric vibrator 2b is performed by a current, the drive current generation unit 13 generates a drive current based on the drive voltage. The drive current generated by the drive current generator 13 is output from the drive current generator 13 and input to the piezoelectric vibrator 2b.

The vibration state detection unit 14 detects a vibration detection voltage indicating the vibration state of the piezoelectric vibrator 2b. Specifically, when the piezoelectric vibrator 2b vibrates, the vibration state detection unit 14 outputs a voltage (vibration detection voltage) that is a signal indicating the vibration state of the piezoelectric vibrator 2b. Note that the vibration state of the piezoelectric vibrator 2b changes according to the resonance state of the piezoelectric vibrator 2b.

The detection voltage conversion unit 15 converts the vibration detection voltage output from the vibration state detection unit 14 into a pulse signal and inputs the pulse signal to the calculation unit 17. The drive voltage conversion unit 16 converts the drive voltage generated by the drive voltage generation unit 12 into a pulse signal and inputs the pulse signal to the calculation unit 17. As described above, the arithmetic processing is facilitated by converting the pulse signal.

The calculation unit 17 calculates the phase difference between the vibration detection voltage from the detection voltage conversion unit 15 and the drive voltage from the drive voltage conversion unit 16. The calculation unit 17 calculates position information such as the movement amount of the rotor 1 based on the calculated phase difference, and instructs the control unit 11. The control unit 11 generates a drive signal in consideration of the position information from the calculation unit 17. The position information is information calculated by the calculation unit 17 regarding the movement amount, position, etc. of the rotor 1.

In FIG. 2, the vibration state detection unit 14 is described separately from the piezoelectric vibrator 2b in consideration of easy viewing. However, for example, the vibration state detection unit 14 is installed as an internal electrode of the piezoelectric vibrator 2b. Also good. Thereby, the vibration state of the piezoelectric vibrator 2b can be directly detected, and high-precision detection is possible. Below, the case where the vibration state detection part 14 is installed in the inside of the piezoelectric vibrator 2b is demonstrated.

Next, the configuration of the vibrating body 2 will be described. FIG. 4 is a view showing the appearance of a vibrating body provided in the ultrasonic actuator, FIG. 4 (A) is a plan view of the vibrating body, and 4 (B) is a diagram showing a drive electrode of a piezoelectric vibrator installed. FIG. 4C is a side view of the side on which the vibration detection electrode of the piezoelectric vibrator is installed. As shown in FIGS. 4 (A) to 4 (C), the vibrating body 2 includes a piezoelectric vibrator 2b having a configuration in which a circular contact portion 2a provided with a protrusion 2c and a piezoelectric thin plate are stacked via an internal electrode. It has. For example, as shown in FIG. 4A, the protrusions 2c have a substantially spherical surface, and are formed at three equal intervals (120 degree intervals) concentrically with the central axis of the contact portion 2a. Each vertex of these protrusions 2 c is in contact with the rotor 1. The protrusion 2c may be formed in a cone shape such as a cone or a pyramid, the uppermost portion may be a needle shape, the lower portion may be square, and the upper portion may be hemispherical. In other words, the uppermost portion of the protrusion 2c is curved or needle-shaped, and the protrusion 2c may be in contact with the contacted portion on the lower surface of the rotor 1 with a minute area as close to point contact (or line contact) as possible. . Further, as shown in FIGS. 4B and 4C, driving electrodes 2b-1, 2b for inputting signals to or outputting signals from the respective internal electrodes stacked on the piezoelectric vibrator 2b. -2, 2b-3, 2b-4, vibration detection electrode 2b-5, and ground electrode 2b-6 are provided on each side surface of the piezoelectric vibrator 2b. These drive electrodes 2b-1, 2b-2, 2b-3, 2b-4, vibration detection electrode 2b-5, and ground electrode 2b-6 are not shown, but lead wires, flexible wires, etc. are solder or conductive. It is joined by an adhesive or the like to send and receive signals.

5 is a cross-sectional view showing the electrode configuration in each layer of the piezoelectric vibrator according to Embodiment 1, and FIG. 5 (A) is a cross-sectional view taken along the line VA-VA of FIG. 4 (B). ) Is a cross-sectional view taken along line VB-VB in FIG. The piezoelectric vibrator 2b includes a piezoelectric thin plate 20 on which the internal electrodes 2d to 2h shown in FIGS. 5A and 5B are formed, and a piezoelectric thin plate on which the internal electrode 2i that is the vibration state detector 14 is formed. 20 is a multilayer structure in which 20 and 20 are alternately stacked. That is, the internal electrode layer having the internal electrodes 2d to 2h and the internal electrode layer having the internal electrode 2i are alternately laminated, and the piezoelectric thin plate 20 is inserted between the internal electrode layers. The internal electrodes 2d to 2i are formed by printing silver palladium on the piezoelectric thin plate 20. The internal electrodes 2d to 2g are formed in the vicinity of each corner of the piezoelectric thin plate 20, respectively. Further, the internal electrode 2h is disposed on at least a part of the portion on the piezoelectric thin plate 20 where the portion where any of the protrusions 2c is arranged is moved along the direction perpendicular to the rotor 1. With this arrangement, the internal electrode 2i can accurately detect the vibration state of the piezoelectric vibrator 2b. That is, the vibration detection voltage is output from the internal electrode 2i according to the vibration of the piezoelectric vibrator 2b. The internal electrode 2 i is formed on substantially the entire surface of the piezoelectric thin plate 20. The

internal electrodes

2d, 2e, 2f, and 2g are connected to the drive electrodes 2b-1, 2b-2, 2b-3, and 2b-4, respectively. The internal electrode 2h is connected to the vibration detection electrode 2b-5. The internal electrode 2i is connected to the ground electrode 2b-6. The drive electrodes 2b-1, 2b-2, 2b-3, 2b-4 are connected to the drive current generator 13, the vibration detection electrode 2b-5 is connected to the detection voltage converter 15, and the ground electrode 2b-6 is Grounded. The connection and grounding are not shown, but are performed via lead wires, FPC (flexible printed wiring board), or the like. In order for the piezoelectric thin plate 20 to exhibit piezoelectric characteristics, it is necessary to perform a predetermined polarization process on these.

Next, the vibration of the piezoelectric vibrator 2b and the vibration of the protrusion 2c caused thereby will be described. FIG. 6 is a conceptual diagram showing the bending primary mode of the vibrating body. 7A and 7B are diagrams for explaining the rotation of the protruding portion. FIG. 7A is a side view of the contact portion, and FIG. 7B is a plan view of the contact portion. As described above, in the piezoelectric vibrator 2b, when a high frequency drive signal (drive current) is applied to the drive electrodes 2b-1, 2b-2, 2b-4, 2b-3 with a phase shifted by 90 degrees, the internal electrodes The 2d, 2e, 2g, and 2f regions perform stretching vibrations that are 90 degrees out of phase. When the frequency of the drive signal is brought close to the resonance frequency, the bending primary mode is excited 90 degrees out of phase in the piezoelectric vibrator 2b. Here, when the bending primary mode is excited, the piezoelectric vibrator 2b, which is a rectangular parallelepiped, repeats the primary bending deformation motion to the left and right by two nodes P as shown in FIG. In the case of the ultrasonic actuator 100, the high-frequency drive signals applied to the drive electrodes 2b-1, 2b-2, 2b-4, and 2b-3 are 90 degrees out of phase with each other. Is generated by the

internal electrodes

2d, 2e, 2g, and 2f while the vibration in the bending primary mode is shifted. Thereby, the tip of the piezoelectric vibrator 2b joined to the contact portion 2a performs a revolving motion (oscillation vibration). As the piezoelectric vibrator 2b moves in this manner, the protrusion 2c of the contact portion 2a installed on the piezoelectric vibrator 2b is indicated by an arrow in FIGS. 7A and 7B. Elliptical vibration is performed. Note that the phases of the elliptical vibrations of the adjacent protrusions 2c are shifted by 120 degrees. As described above, the rotor 1 is pressed against the contact portion 2a. Therefore, the friction coefficient between the rotor 1 and the protrusion 2c is large. Therefore, each protrusion 2c performs the above-described elliptical vibration whose phase is shifted by 120 degrees, so that the rotor 1 is rotationally driven so as to be moved by the protrusion 2c.

The rotor 1 has a structure in which the resonance state of the piezoelectric vibrator 2b changes according to the position of the piezoelectric vibrator 2b with respect to the rotor 1. Specifically, the rotor 1 has a configuration in which different forces are periodically applied to the piezoelectric vibrator 2b when the rotor 1 is rotationally driven. Specifically, in the contacted portion of the rotor 1, a vibration high receiving portion that easily receives vibration from the protrusion portion 2c of the contact portion 2a and a vibration low receiving portion that hardly receives vibration from the protrusion portion 2c of the contact portion 2a are formed. Thus, the contacted part of the rotor is not uniform. That is, the vibration high receiving portion and the low vibration receiving portion of the rotor 1 should not be made uniform in the shape of the surface in contact with the projection 2c, or the vibration high receiving portion and the low vibration receiving portion of the rotor 1 may be made of different materials. Thus, the phase difference between the driving voltage and the driving current is changed.

More specifically, the vibration high receiving portion of the rotor 1 is formed by a flat surface that comes into contact with the protruding portion 2c so as to receive vibration from the protruding portion 2c, and the vibration low receiving portion constitutes a vibration high receiving portion. A groove is formed on the flat surface so as not to come into contact with the protrusion 2c so as not to receive vibration from the protrusion 2c. A plurality of grooves are formed for accurate position control. In addition, the high vibration receiving portion of the rotor 1 has a rough surface to increase the coefficient of friction to make it easy to receive vibration from the protrusion 2c, and the low vibration receiving portion has a small surface roughness to make it slip easily and vibrate. It may be difficult to receive. Further, the high vibration receiving portion of the rotor 1 is made of a vibrating material such as a high density material or a low elastic material so as to be easily subjected to vibration from the protrusion 2c, and the low vibration receiving portion is a low density material or elastic. It may be made of a vibration-absorbing material such as a high-grade material so that it is difficult to receive vibration from the protrusion 2c. Thus, the phase difference between the drive voltage and drive current of the drive signal in the piezoelectric vibrator 2b is changed by making the contacted portion of the rotor 1 in contact with the contact portion 2a of the vibrating body 2 non-uniform. In other words, since the rotor 1 has the above structure when the rotor 1 is driven, there are a plurality of states in which different forces are applied to the vibrating piezoelectric vibrator 2b. Since the force applied to the piezoelectric vibrator 2b varies depending on the form of the rotor 1 where the piezoelectric vibrator 2b is located, the resonance state of the piezoelectric vibrator 2b changes. The ultrasonic actuator 100 detects the amount of movement of the rotor 1 based on the change in the resonance state.

The contacted portion in contact with the protrusion 2c in the rotor 1 will be described in more detail. As described above, high-precision positioning control is realized by periodically forming different forms in the contacted portion of the rotor 1. In the contacted portion of the rotor 1 that is in contact with the contact portion 2a of the vibrating body 2, a plurality of grooves (concave portions) extending along the radial direction are formed at equal intervals along the circumference to form a vibration low receiving portion. Yes. The contacted part of the rotor will be described with reference to FIGS. FIG. 8 is an exploded perspective view of the rotor 1 and the contact portion 2a. FIG. 9 is a diagram showing the shape of the contacted portion of the rotor 1. FIG. 10 is an enlarged cross-sectional view of the main part of the contacted portion of the rotor 1. FIG. 11 is an enlarged cross-sectional view of a main part showing another structure of the contacted portion of the rotor 1. FIG. 12 is an enlarged cross-sectional view of a main part showing still another structure of the contacted portion of the rotor 1.

As shown in FIG. 8, the contact portion 2a of the vibrating body 2 (not shown) includes a plurality of protrusions 2c on the surface on the rotor 1 side. A predetermined urging force is applied between the rotor 1 and the contact portion 2a, and these are in close contact with each other. In this case, the contact portion 2a is in contact with the contacted portion of the rotor 1 at the protrusion 2c. Therefore, the force is applied only from the rotor 1 to the protrusion 2c, and the force is not applied to the entire contact portion 2a.

As shown in FIG. 9, a plurality of grooves 1 a that extend along the radial direction through the center of the rotor 1, that is, vibration low receptive portions, are formed in the contacted portion that contacts the contact portion 2 a in the rotor 1. The grooves 1a are formed at equal intervals along the circumference. That is, the location where the groove 1 a is formed and the location where the groove 1 a is not formed are alternately arranged along the circumference of the rotor 1. With this configuration, when the piezoelectric vibrator 2b (not shown) vibrates, the protrusion 2c that is in contact with the contacted portion of the rotor 1 elliptically vibrates, whereby the rotor 1 is driven. Moreover, the protrusion 2c periodically passes through the groove 1a. The force applied to the contact portion 2a is different between the case where the protrusion 2c is located at the location where the groove 1a is formed (vibration low receiving portion) and the location where the groove 1a is not formed (vibration high accepting portion). . For this reason, since the force applied to the piezoelectric vibrator 2b is also different, the resonance state of the piezoelectric vibrator 2b changes. As shown in FIG. 10, the rotor 1 has a thin plate 1b attached so as to cover the surface on the contact portion 2a side. By adopting such a configuration, the flatness of the contacted portion of the rotor 1 is formed, and rattling when the protruding portion 2c passes through the groove 1a can be prevented. The rotor 1 is formed of a metal such as stainless steel, and the groove 1a is formed in the rotor 1 by machining or etching. The thin plate 1b is also formed of a metal such as stainless steel. The thin plate 1b is preferably subjected to nitriding treatment or the like in order to improve wear resistance. The rotor 1 and the thin plate 1b may be joined by forming a thin adhesive layer between them, or the vicinity of the center may be joined by spot welding or the like. In this case, the protrusion 2c and the thin plate 1b come into contact with each other and the thin plate 1b is moved by the elliptical vibration of the protrusion 2c, so that the rotational drive is reliably transmitted from the thin plate 1b to the rotor 1. In such a configuration, since the portion where the groove 1a is formed is a cavity, the spring constant of the thin plate 1b is different between the portion where the groove 1a is formed and the portion where the groove 1a is not formed. That is, in the thin plate 1b, the location where the groove 1a is formed is less rigid than the location where the groove 1a is not formed. Therefore, in the thin plate 1b, when the protrusion 2c is located at the position where the groove 1a is formed, the resonance frequency of the piezoelectric vibrator 2b is lowered. Thus, the resonance state of the piezoelectric vibrator 2b changes according to the position of the protrusion 2c with respect to the contacted portion of the rotor 1.

Further, on the same flat surface of the contacted portion in contact with the protrusion 2c in the rotor 1, a vibration high receiving portion having a non-sliding surface having a high friction coefficient and a vibration low receiving portion having a sliding surface having a low friction coefficient are formed. May be. The low vibration receiving portion is formed not by a groove but by a low friction region extending along the radial direction through the center of the rotor, and regions having different friction coefficients are alternately arranged along the circumference of the rotor 1. In order to make the friction coefficient different, for example, the surface roughness may be changed. With such a configuration, since the vibration high receiving portion and the vibration low receiving portion are formed on the same flat surface, there is no backlash when the rotor 1 is driven. Further, the force applied to the protrusion 2c varies depending on the friction coefficient of the region where the protrusion 2c is located. Therefore, since the force applied to the piezoelectric vibrator 2b is also different, the resonance state of the piezoelectric vibrator 2b changes.

Further, as shown in FIG. 11, the vibration low receiving portion 1 c formed of a material having a lower density, lower mass, or higher elasticity than the material forming the vibration high receiving portion is provided along the circumference of the rotor 1. May be arranged periodically. Further, the formation range of the low vibration receiving portion may be widened as shown in FIG. For example, the vibration low receiving portion 1c may occupy a half circumference of the rotor 1. With such a configuration, the contacted portion in contact with the protrusion 2c in the rotor 1 is formed of a plurality of different materials, and the force applied to the protrusion 2c varies depending on the material of the region where the protrusion 2c is located. Therefore, since the force applied to the piezoelectric vibrator 2b is also different, the resonance state of the piezoelectric vibrator 2b changes. In this configuration, only the material of the vibration high receiving portion and the vibration low receiving portion are different from each other, and the surfaces that come into contact with the protrusions 2c are the same flat surface, so that no rattling occurs when the rotor 1 is driven. Even when the rotor 1 is made of a different material, the surface of the rotor 1 on the side of the protrusion 2c may be covered with a thin plate as shown in FIG.

As described above, the resonance state of the piezoelectric vibrator 2b changes according to the relative position of the rotor 1. Since the groove 1a and the regions having different friction coefficients are formed, two types of regions are periodically arranged along the circumference of the rotor 1, so that the resonance state of the piezoelectric vibrator 2b can be changed. By monitoring, the position information of the rotor 1 can be calculated. Note that all of the protrusions 2c need to be located in one of the two types of regions at the same time. The shape of the surface of the rotor 1 that is in contact with the protrusion 2c needs to be configured to have such a relationship.

In addition, although two types of regions are provided periodically, one place having a shape or property different from those of the two types of regions is formed, and the position is set as the origin position of the rotor 1. May be. That is, three types of different forms may be provided in the contacted portion of the rotor 1 that is in contact with the protruding portion 2c, one of which may be formed in only one place, and the remaining two types may be formed alternately alternately. Also, more than three types of different forms may be formed on the contacted portion of the rotor 1. In addition, the structure which makes the to-be-contacted part of the rotor 1 which contact | connects the projection part 2c a non-uniform | heterogenous form is not limited to the example mentioned above. Any device that can change the resonance state of the piezoelectric vibrator 2b may be used.

Next, a specific method for detecting the resonance state will be described. A change in the resonance state is detected by a signal output from the vibration detection electrode 2b-5. That is, as the rotor 1 rotates, the force applied to the piezoelectric thin plate 20 at the location where the internal electrode 2h connected to the drive detection electrode 2b-5 is changed periodically. Thereby, the phase difference between the vibration detection voltage output from the internal electrode 2h and the drive voltage changes. FIG. 13 is a graph showing the relationship between the vibration detection voltage and the frequency of the drive signal, and FIG. 14 is a graph showing the relationship between the phase difference between the vibration detection voltage and the drive voltage and the frequency of the drive signal. In FIG. 13, the vertical axis represents voltage and the horizontal axis represents frequency. FIG. 13 shows a case where the groove 1a is formed in the contacted portion of the rotor 1 and the thin plate 1b is formed as shown in FIG. The relationship between the amplitude of the voltage and the frequency is shown for the case where the portion 2c is located at a location where the groove 1a is not formed. In FIG. 13, the solid line indicates the case where the protrusion 2c is located at the position where the groove 1a is formed, and the broken line indicates the case where the protrusion 2c is located where the groove 1a is not formed. . As described above, the amplitude of the vibration detection voltage is different between the case where the protrusion 2c is located at the position where the groove 1a is not formed and the case where the protrusion 2c is located at the position where the groove 1a is formed. In FIG. 13, the frequency at the maximum value is the resonance point in each line. Since the solid line has a lower frequency at the maximum value, the resonance frequency of the piezoelectric vibrator 2b is lower when the protrusion 2c is located at the position where the groove 1a is formed. Note that the phase difference between the vibration detection voltage and the drive voltage changes greatly in the vicinity of the resonance point.

In FIG. 14, the vertical axis represents the phase difference and the horizontal axis represents the frequency. FIG. 14 shows a case in which the groove 1a is formed in the contacted portion of the rotor 1 and the thin plate 1b is formed as shown in FIG. In the case where the part 2c is located at a location where the groove 1a is not formed, the relationship between the phase difference between the vibration detection voltage and the drive voltage and the frequency of the drive signal is shown. In FIG. 14, a solid line indicates a case where the protruding portion 2c is positioned at a position where the groove 1a is formed, and a broken line indicates a case where the protruding portion 2c is positioned where the groove 1a is not formed. As described above, the phase difference is different between the case where the protrusion 2c is located at a position where the groove 1a is not formed and the case where the protrusion 2c is located where the groove 1a is formed. Thus, since the vibration detection voltage and the phase difference differ depending on the position of the protrusion 2c with respect to the rotor 1, the change in the resonance state can be detected by calculating them based on the vibration detection voltage.

Next, the operation of the ultrasonic actuator 100 will be described. First, the control unit 11 outputs a drive signal that is an electric signal for a command to drive the rotor 1. The drive voltage generation unit 12 generates a drive voltage according to the drive signal from the control unit 11. At this time, the generated drive voltage is detected by the drive voltage converter 16 and converted into a pulse signal. Further, the drive voltage is input to the drive current generation unit 13, and the drive current generation unit 13 generates a drive current corresponding to the drive voltage. The drive voltage and drive current are alternating current. The drive current is input to the piezoelectric vibrator 2b, and when the piezoelectric vibrator 2b vibrates, the protrusion 2c performs elliptical vibration, thereby driving the rotor 1. The vibration detection voltage generated at this time is detected by the vibration state detection unit 14 (internal electrode 2h) and output to the detection voltage conversion unit 15. The detection voltage converter 15 converts the vibration detection voltage into a pulse signal. The calculating part 17 calculates | requires the phase difference of the drive voltage made into the pulse signal, and a vibration detection voltage. Thereby, the calculating part 17 can calculate the position etc. of the rotor 1, and can calculate position information, such as the moving amount | distance of the rotor 1. FIG. Further, the phase difference is detected as signal information (level) by converting the pulse signal. Thereby, the phase difference can be easily detected. Further, the calculation unit 17 may calculate position information such as the movement amount of the rotor 1 from the amplitude of the vibration detection voltage. Each protrusion 2c is in contact with the contacted portion of the rotor 1 at its apex. Therefore, in the detection of different regions, it is possible to detect accurately and with high accuracy even in the vicinity of the boundary between them.

The calculation of location information will be specifically described. As described above, the rotor 1 has three different forms. One is the origin form, and the rest is the first form and the second form. Therefore, when the protrusion 2c is located in each form, the resonance states are different from each other. For example, the first form and the second form are alternately formed at a predetermined angle with respect to the center of the rotor 1, and the number of passes through the first form and the second form is counted. That's fine. The rotation angle of the rotor 1 can be detected from the predetermined angle and the number of passes. In this way, the relative position relationship between the vibrating body 2 and the rotor 1 can be detected. In addition, since the origin form can also be detected, it is possible to easily detect how many times the rotor 1 has rotated by counting how many times the origin form has been passed. Thus, the absolute position relationship between the protrusion 2c and the rotor 1 can be detected. Further, by combining these, position information such as a movement amount and a movement amount of the rotor 1 can be detected.

Further, in the ultrasonic actuator 100, the contact portion 2a is in contact with the contacted portion of the rotor 1 at the apex of the projection 2c, so that the vibration state change (resonance state change) of the piezoelectric vibrator 2b is digitally changed. That is, it can be detected with high resolution. Changes in the vibration detection voltage and the phase difference appear remarkably, the phase difference can be easily detected, and more accurate position control is possible.

Thus, the position information of the rotor 1 detected by the calculation unit 17 is sent to the control unit 11, and the control unit 11 considers the position information of the rotor 1 detected by the calculation unit 17, and The drive can be controlled. Thereby, the ultrasonic actuator 100 capable of highly accurate position control can be realized without attaching a rotary encoder or the like.

(Embodiment 2)
Next, an ultrasonic actuator according to Embodiment 2 of the present invention will be described. The same members as those of the ultrasonic actuator 100 according to Embodiment 1 described above are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 15 is a block diagram showing an electrical configuration of the ultrasonic actuator 200 according to the second embodiment.

As shown in FIG. 15, the ultrasonic actuator 200 includes a rotor 1 that is a moving body, a vibrating portion (stator) having a contact portion 2 a having a protrusion 2 c (not shown) that contacts the rotor 1, and a piezoelectric vibrator 2 b. ) 2, the rotation shaft 3 integrally installed with the rotor 1 at the rotation center of the rotor 1, a control unit 11, a drive voltage generation unit 12, a drive current generation unit 13, a drive current detection unit 18, A drive current conversion unit 19, a drive voltage conversion unit 16, and a calculation unit 17 are provided. The control unit 11, the drive voltage generation unit 12, the drive current generation unit 13, the drive current detection unit 18, the drive current conversion unit 19, the drive voltage conversion unit 16, and the calculation unit 17 are, for example, on a substrate. Electronic elements such as resistors, capacitors and coils are arranged.

The mechanical configuration of the ultrasonic actuator 200 is the same as that of the ultrasonic actuator 100 according to the first embodiment. However, since the ultrasonic actuator 200 does not need to detect the vibration state, the vibration detection electrode 2b-5 and the internal electrode 2h connected to the vibration state detection unit shown in FIGS. 4 and 5 are provided. Absent.

The control unit 11 generates a drive signal that is an electrical signal so that the rotor 1 is rotationally driven. The drive signal causes elliptical vibration to occur in the protrusion 2c installed on the contact portion 2a of the vibrating body 2. As described in the first embodiment, the protrusion 2c performs elliptical vibration as shown in FIG. 7 due to the vibration of the piezoelectric vibrator 2b. Then, the rotor 1 is driven so as to be pushed by the protrusion 2c.

The drive current detector 18 detects the drive current, and specifically detects the waveform and value of the drive current. The drive current detector 18 is installed between the drive current generator 13 and the piezoelectric vibrator 2b and detects the drive current in the piezoelectric vibrator 2b.

The drive current converter 19 converts the drive current detected by the drive current detector 18 into a pulse signal and inputs it to the calculator 17. The drive voltage conversion unit 16 converts the drive voltage generated by the drive voltage generation unit 12 into a pulse signal and inputs the pulse signal to the calculation unit 17. As described above, the arithmetic processing is facilitated by converting the pulse signal.

The calculation unit 17 calculates the phase difference between the drive current from the drive current conversion unit 19 and the drive voltage from the drive voltage conversion unit 16. The calculation unit 17 calculates position information such as the movement amount of the rotor 1 based on the calculated phase difference, and instructs the control unit 11. The control unit 11 generates a drive signal in consideration of the position information from the calculation unit 17. The position information is information calculated by the calculation unit 17 such as the movement amount and position of the rotor 1.

The rotor 1 has a structure in which the phase difference between the drive voltage and the drive current in the piezoelectric vibrator 2b changes according to the position of the piezoelectric vibrator 2b with respect to the rotor 1. Note that the change in the phase difference between the drive voltage and the drive current is caused by the change in the resonance state. The rotor 1 has a configuration in which the piezoelectric vibrator 2b is deformed when the rotor 1 is rotationally driven. Specifically, as in the first embodiment, the surface of the rotor 1 that contacts the protrusion 2c of the contact portion 2a is not uniform. In other words, the drive voltage and the drive current can be reduced by making the shape of the contacted part in contact with the protrusion 2c in the rotor 1 non-uniform or by configuring the contacted part of the rotor 1 with a plurality of materials having different properties. The phase difference is changed. As described above, the contacted portion in contact with the protrusion 2c in the rotor 1 is not uniform, so that the phase difference between the drive voltage and the drive current of the drive signal in the piezoelectric vibrator 2b changes. That is, when the rotor 1 is driven, the contacted portion of the rotor 1 has the above-described structure, and therefore there are a plurality of states in which different forces are applied to the vibrating piezoelectric vibrator 2b. become. Since the force applied to the piezoelectric vibrator 2b differs depending on the form of the rotor 1 where the piezoelectric vibrator 2b is located, the phase difference between the drive voltage and the drive current of the piezoelectric vibrator 2b changes. The ultrasonic actuator 200 detects the amount of movement of the rotor 1 based on this phase difference. Hereinafter, a method for detecting the moving amount of the rotor 1 based on the phase difference between the drive current and the drive voltage will be described in more detail.

The piezoelectric vibrator 2b is driven by receiving a drive signal as described above. In order for the piezoelectric vibrator 2b to vibrate, this drive signal is an alternating current. That is, the drive current and drive voltage based on the drive signal are alternating current. FIG. 16 is a diagram showing an equivalent circuit of the piezoelectric vibrator. As shown in FIG. 16, the piezoelectric transducer 2b is a capacitor of capacitance C _d, inductance L ₁ of the coil, the capacitance is a capacitor and resistance of C ₁ and a series circuit composed of the resistor element R ₁ is connected in parallel Circuit. The value of C _d is the capacitance determined by the dielectric constant and electrode size of the piezoelectric vibrator 2b. The L ₁ and C ₁ values are values determined by the piezoelectric mechanical vibration of the piezoelectric vibrator 2b, and are specifically determined by the vibration mode, dimensions, elastic constant, density, piezoelectric constant, etc. of the piezoelectric vibrator 2b. . The value of R ₁ is a value determined by the mechanical vibration loss of piezoelectric vibrators 2b.

The admittance observed from the electrical input side of the equivalent circuit shown in FIG.

In Equation 1, the first term is braking admittance, and the second term is dynamic admittance. Here, when the piezoelectric vibrator 2b is distorted, the dynamic admittance changes. Therefore, the relationship between voltage and current in dynamic admittance will be described. The dynamic admittance shown in the second term of Equation 1 is a series circuit of a resistance element, a coil, and a capacitor. Therefore, when the resistance of the resistance element is R, the inductance of the coil is L, the capacitance of the capacitor is C, and the input voltage applied to the series circuit is E _m sin ωt, the current that flows is assumed to be i. The relationship shown in is established.

Here, when i in Expression 2 is substituted into Expression 2 as i = Asinωt + Bcosωt, the following Expression 3 is obtained.

By comparing both sides of Formula 3, Formula 4 which is a simultaneous equation shown below is obtained.

When Equation 4 is solved to obtain A and B, and i is obtained from these, i is represented by Equation 5 shown below.

Here, I is the amplitude of the current (driving current), the amplitude of E _m is the input voltage. Θ represents the phase difference between the current (drive current) and the voltage (drive voltage) in the piezoelectric vibrator 2b. Equation 6 represents the value of θ.

From Equation 6, it can be seen that if the inductance L, capacitance C, and resistance R of the piezoelectric vibrator 2b are changed, the phase difference θ between the drive current and the drive voltage is shifted. For example, if the piezoelectric vibrator 2b is deformed, the resistance R can change. That is, when the cross-sectional area becomes large and the length becomes short, the resistance becomes small. For example, when the piezoelectric vibrator 2b is extended, its cross-sectional area is also reduced and the resistance value is increased. Thus, the phase difference between the drive current and the drive voltage changes as the piezoelectric vibrator 2b is deformed. Therefore, as described above, when the contacted portion of the rotor 1 has a different form, the phase difference between the drive current and the drive voltage of the piezoelectric vibrator 2b differs depending on the form.

FIG. 17 is a graph for explaining a difference in phase difference between the drive current and the drive voltage. FIG. 17A is a graph showing the waveforms of the drive current and the drive voltage in the first embodiment, and FIG. These are graphs showing the waveforms of the drive current and drive voltage of the second embodiment.

17A and 17B, the vertical axis represents voltage value or current value, respectively, and the horizontal axis represents time (t). The graph shown in the upper part is a drive voltage waveform, and the graph shown in the lower part is a drive current waveform. In addition, threshold values for the drive voltage and the drive current are also shown. In FIG. 17A, the phase difference between the drive voltage and the drive current is represented by ta. Further, when the surface state of the rotor 1 is the second form which is different from the first form, the phase difference between the drive voltage and the drive current is tb as shown in FIG. The value is different from the phase difference ta in FIG. In the ultrasonic actuator 200, a shape in which the phase difference between the drive voltage and the drive current is different is formed in the contacted portion of the rotor 1 in this way. The phase differences ta and tb are calculated based on the threshold value between the drive voltage and the drive current. This threshold value indicates the rising position of the pulse when the drive voltage and the drive current are converted into a pulse signal.

In the second embodiment, the drive voltage and the drive current are converted into pulse signals by using the drive voltage conversion unit 16 and the drive current conversion unit 19, respectively, and the phase difference is based on the pulse edge interval at the rising edge of the pulse signals. Is detected. The drive voltage converter 16 and the drive current converter 19 will be described. FIG. 18 is a circuit diagram illustrating a configuration example of the current conversion unit or the voltage conversion unit. FIG. 19 is a graph for explaining conversion to a pulse signal. As shown in FIG. 18, the drive current conversion unit 19 and the drive voltage conversion unit 16 include an operational amplifier, a resistance element having resistances R3 and R4, and a voltage source having a voltage of Vref. When the input voltage shown in the upper part of FIG. 19 is input to the drive current converter 19 and the drive voltage converter 16 having such a configuration, it is converted into a pulse waveform shown in the lower part and outputted. That is, the input voltage increases and is a constant output at the H level until the first threshold value ThH is reached. Furthermore, when the input voltage reaches the first threshold value ThH, the output becomes an L level, the input voltage decreases, and when the input voltage reaches the second threshold value ThL, the output becomes an H level. In this way, the analog signal indicating the drive voltage and drive current from the drive voltage generator 12 and the drive current detector 18 is converted into a pulse signal. Further, as can be seen from FIG. 19, a stable output signal can be obtained even if noise is added to the input signal which is an analog signal. The first threshold value ThH and the second threshold value ThL are expressed by Equation 7 using the resistors R3 and R4 and the voltage Vref. In Equation 7, Vout
min is an L level output voltage, and Vout max is an H level output voltage.

The difference between the first threshold value ThH and the second threshold value ThL is expressed by Expression 8 shown below.

As can be seen from Equation 8, the threshold voltage difference with respect to the output full scale can be changed by changing the ratio of the resistors R3 and R4.

In the ultrasonic actuator 200, as described above, the phase difference between the driving voltage and the driving current of the piezoelectric vibrator 2b is changed by driving the rotor 1. Further, since the phase difference is detected by the calculation unit 16 using a pulse signal, particularly based on the interval between the pulse edges, the phase difference can be easily detected.

As described in the first embodiment, the force from the rotor 1 is applied only to the protrusion 2c, and no force is applied to the entire contact portion 2a, so that the phase difference between the drive current and the drive voltage appears remarkably. Therefore, it is easy to detect the phase difference, and position control with higher accuracy is possible.

Note that the phase difference between the drive current and the drive voltage may be detected for at least one of the plurality of piezoelectric vibrators 2b.

Next, the operation of the ultrasonic actuator 200 according to the second embodiment will be described. First, the control unit 11 outputs a drive signal that is an electric signal for a command to drive the rotor 1. The drive voltage generation unit 12 generates a drive voltage according to the drive signal from the control unit 11. At this time, the generated drive voltage is detected by the drive voltage converter 16 and converted into a pulse signal. Further, the drive voltage is input to the drive current generation unit 13, and the drive current generation unit 13 generates a drive current corresponding to the drive voltage. The drive voltage and drive current are alternating current. The drive current is input to the piezoelectric vibrator 2b, and when the piezoelectric vibrator 2b vibrates, elliptical vibration is generated in the protrusion 2c, thereby driving the rotor 1. The drive current is detected by the drive current detector 18 and converted into a pulse signal by the drive current converter 19. The calculating part 17 calculates | requires the phase difference of the drive voltage made into the pulse signal, and a drive current. Thereby, position information such as the amount of movement of the rotor 1 can be calculated.

FIG. 20 is a graph for explaining the positioning of the ultrasonic actuator 200. In FIG. 20, the rotor 1 that is originally circular is developed and expressed in a straight line in consideration of easy understanding. As shown in FIG. 20, the contacted portion of the rotor 1 has three different forms as described above. One is the origin form, and the rest is the first form and the second form. Therefore, the phase difference between the drive voltage and the drive current differs in each form. In FIG. 20, when the piezoelectric vibrator 2b is located in the origin form, the phase difference is tz, and when the protrusion 2c is located in the first form, the phase difference is ta. When the protruding portion 2c is positioned in the form, the phase difference is tb. Thus, the phase difference varies depending on the form of the contacted portion of the rotor 1. Therefore, the calculating part 17 can calculate the position information of the rotor 1 by obtaining the phase difference. For example, the first form and the second form are alternately formed at a predetermined angle with respect to the center of the rotor 1, and the number of times the first form and the second form are passed is counted. What should I do? The rotation angle of the rotor 1 can be detected from the predetermined angle and the number of passes. Thus, the position information of the rotor 1 can be detected. In addition, since the origin form can also be detected, it is possible to easily detect how many times the rotor 1 has rotated by counting how many times the origin form has been passed. Thus, the absolute position relationship between the piezoelectric vibrator 2b and the rotor 1 can be detected. Further, by combining these, position information such as the movement amount and the movement amount of the rotor 1 can be calculated.

Further, in the ultrasonic actuator 200, since the contact portion 2a is in contact with the rotor 1 at the apex of the protrusion 2c, the change in the phase difference between the drive voltage and the drive current of the piezoelectric vibrator 2b (change in the resonance state) It can be detected digitally. That is, the vibration detection voltage and the phase difference change remarkably appear, the phase difference can be easily detected, and position control with higher accuracy is possible.

Thus, the position information of the rotor 1 detected by the calculation unit 17 is sent to the control unit 11, and the control unit 11 considers the position information of the rotor 1 detected by the calculation unit 17, and The drive can be controlled. Thereby, it is possible to realize the ultrasonic actuator 200 capable of highly accurate position control without attaching a rotary encoder or the like.

FIG. 21 is a circuit diagram showing a part of a specific circuit configuration of the ultrasonic actuator 200. In FIG. 21, among the ultrasonic actuator 200, the calculation unit 17, the drive current conversion unit 19, the drive voltage conversion unit 16, the drive current detection unit 18, the piezoelectric vibrator 2 b, the drive voltage generation unit 12, and the drive current generation unit 13. It is shown. Among these, the calculating part 17, the drive current conversion part 19, the drive voltage conversion part 16, the drive current detection part 18, and the piezoelectric vibrator 2b are represented by an electric circuit. The piezoelectric vibrator 2b is an equivalent circuit as described above. Here, the drive current detection unit 18 is a resistance element, and the drive current can be detected by detecting the voltage at both ends thereof. The drive current conversion unit 19 and the drive voltage conversion unit 16 are circuits having the same functions, although they are different from the circuit configuration described above. That is, the drive current and drive voltage are converted from an analog signal to a pulse signal. Specifically, the drive current converter 19 includes a differential amplifier circuit 19a and a pulse converter circuit 19b for amplifying a signal. Similarly, the drive voltage converter 16 includes a differential amplifier circuit 16a and a pulse converter circuit 16b. Prepare. The arithmetic unit 17 includes a logic circuit 17a, a low-pass filter 17b, and a high-pass filter 17c. Data actually measured using the circuit shown in FIG. 21 is shown in FIGS. 22 to 24 are graphs showing waveforms of data relating to the drive voltage and drive current obtained using the circuit shown in FIG.

FIG. 22 is a graph showing the drive current and drive voltage of the ultrasonic actuator 200, FIG. 22A is a graph showing the drive current and drive voltage in the first embodiment, and FIG. It is a graph which shows the drive current and drive voltage in the form. FIG. 23 is a graph showing an output signal from the logic circuit of the ultrasonic actuator 200 and a signal after the low-pass filter processing. FIG. 23A is a graph in the first embodiment, and FIG. Is a graph in the second form. FIG. 24 is a graph showing the signal after the high-pass filter processing and the signal after the low-pass filter processing of the ultrasonic actuator 200.

FIG. 22 shows a drive current waveform and a drive voltage converter output from the differential amplifier circuit 19a of the drive current converter 19 when the rotor 1 having the first and second forms different from each other is driven. The drive voltage waveforms output from the 16 differential amplifier circuits 16a are shown. Here, specifically, in the first embodiment, a recess (groove) is provided in the rotor 1, and in the second embodiment, no recess is provided. As can be seen by comparing FIGS. 22A and 22B showing the first mode and the second mode, respectively, the phase difference between the drive current and the drive voltage is different. The output from the differential amplifier circuit 19a and the output from the differential amplifier circuit 16a are input to the

pulse conversion circuits

19b and 16b, respectively, and then input to the logic circuit 17a. By being input to the logic circuit 17a, they are converted into a signal including the phase difference between the drive current and the drive voltage as information and output. Specifically, it is converted into a signal as shown in FIG. The signal waveform output from the logic circuit 17a and processed by the low-pass filter 17b is also shown in FIG. As shown in FIGS. 23A and 23B, the difference between the output signals from the logic circuit 17a in the first embodiment and the second embodiment is not clear, but by performing low-pass filter processing. These phase difference differences are expressed as signal level differences. Further, the signal after the low-pass filter processing is input to the high-pass filter 17c and subjected to high-pass filter processing. As shown in FIG. 24, the level difference of the signal after the high-pass filter processing is more noticeable than the level difference of the signal after the low-pass filter processing. Thus, by converting the signal, the phase difference can be detected as signal information (level), and the phase difference can be easily detected. In other words, the phase difference can be detected by reading the level of the signal after the high-pass filter processing, and it can be easily detected whether the protrusion 2c is located in the first form or the second form. By inputting the signal after the high-pass filter processing to the control unit 11 (not shown in FIG. 21), the control unit 11 can grasp the position information of the rotor 1, and in consideration of this position information, High-precision position control can be performed.

The ultrasonic actuator described above mainly has the following features.

The ultrasonic actuator receives a vibration from the projection, a piezoelectric vibrator that generates a vibration by an electric signal, a vibrating body having a curved surface or a needle-like protrusion, and a contact portion that transmits the vibration. And a contacted part formed with a low vibration receiving part that is difficult to receive vibration from the protrusion, and is moved by receiving the vibration of the piezoelectric vibrator through the high vibration receiving part. Detecting a change in a resonance state of the piezoelectric vibrator that occurs when the vibration low-accepting portion of the moving body passes through the protrusion of the vibration body, and the movement is performed based on the change in the resonance state. A calculation unit that calculates body position information; and a control unit that controls driving of the moving body based on the position information calculated by the calculation unit.

With the above configuration, the resonance state change of the piezoelectric vibrator is detected, the positional information such as the moving amount and position of the moving body is calculated, and the moving amount and the like of the moving body are thereby controlled. A small ultrasonic actuator can be provided without the need.

It is preferable that the vibration low receiving portion is formed in a line shape in a direction orthogonal to the direction in which the vibration low receiving portion moves relative to the protrusion. By forming the low vibration receiving portion in a line shape in a direction perpendicular to the relative movement direction, the protrusion of the vibrating body can surely pass through the low vibration receiving portion. Accordingly, the resonance state change is surely generated in the piezoelectric vibrator, and accurate position control can be performed.

The contacted portion includes a vibration high receiving portion formed of a flat surface, a plurality of vibration low receiving portions formed by a plurality of grooves formed on the flat surface, and a cover member that covers the flat surface and the plurality of grooves. Is preferably provided.

In the above configuration, a plurality of grooves are formed on the flat surface to separate the vibration high receptive part and the vibration low receptive part, so that the boundary between the two parts is clear in shape and resonates with the piezoelectric vibrator with a simple structure. A state change can be caused. In addition, since the cover member that covers the flat surface and the groove is provided, the surface of the vibrating body that comes into contact with the protrusion is flat, thereby preventing rattling of the contact. Further, by forming a plurality of grooves, that is, by providing a plurality of vibration low receiving portions, the position information of the moving body can be obtained more accurately.

The high vibration receiving portion and the low vibration receiving portion are formed on the same flat surface, the high vibration receiving portion is formed of a vibrating material, and the low vibration receiving portion is formed of a vibration absorbing material. Also good.

Further, the high vibration receiving portion and the low vibration receiving portion may be formed on the same flat surface so that the surface of the high vibration receiving portion is non-sliding and the surface of the low vibration receiving portion is slid.

If it is these structures, since the to-be-contacted part of a moving body is formed in the flat surface, and the vibration high receiving part and the vibration low receiving part are formed in the flat surface, the said to-be-contacted part and the said vibrating body of said There is no backlash at the time of contact with the protrusion, and the contact can be maintained uniformly and stably.

The contact portion is provided with three protrusions, the three protrusions are arranged at equal intervals on a predetermined circumference, and the movable body is rotatable about a central axis passing through the center of the predetermined circumference, It is preferable that vibration low receiving portions of multiples of 3 are arranged at equal intervals in the circumferential direction.

In this configuration, since the three protrusions arranged at equal intervals in the circumferential direction come into contact with the moving body, the minimum number, that is, three, can stably contact the contacted part of the moving body. In addition, since the vibration low receptive portion is formed by a multiple of 3, the three protrusions can be simultaneously positioned on the vibration low receptive portion, and the resonance state of the piezoelectric vibrator can be reliably changed at a predetermined cycle. Can do.

The vibrating body is further provided with a vibration state detection unit that detects a vibration state of the piezoelectric vibrator and outputs a vibration detection voltage, and the arithmetic unit is configured to output a vibration voltage between the vibration detection voltage and the piezoelectric vibrator. The phase difference is preferably calculated as signal information.

With this configuration, a change in the resonance state of the piezoelectric vibrator can be easily detected by the phase difference between the vibration detection voltage and the driving voltage in the piezoelectric vibrator.

A pulse conversion unit that converts the vibration detection voltage and the drive voltage in the piezoelectric vibrator into pulse signals is further provided, and the calculation unit includes each pulse edge interval between the drive voltage converted into a pulse signal and the vibration detection voltage. The phase difference between the drive voltage and the vibration detection voltage is preferably calculated based on

With this configuration, the vibration detection voltage and the drive voltage are converted into pulse signals, and the phase difference is calculated based on each pulse edge interval, so that arithmetic processing can be performed easily.

The phase difference between the driving voltage and the driving current in the piezoelectric vibrator may be calculated as signal information.

With this configuration, the change in the resonance state of the piezoelectric vibrator can be easily calculated from the phase difference between the driving voltage and the driving current of the piezoelectric vibrator.

A pulse conversion unit that converts the drive voltage and drive current in the piezoelectric vibrator into pulse signals is further provided, and the calculation unit is based on each pulse edge interval of the drive voltage and the drive current converted into a pulse signal. It is preferable to calculate a phase difference between the drive voltage and the vibration detection voltage.

It is preferable that the vibration state detection unit is provided on a line perpendicular to the moving body and passing through the protrusion.

With this configuration, the vibration state detection unit is provided at a location that is more strongly affected by the pressing force from the moving body transmitted from the protrusion, so that the vibration state of the piezoelectric vibrator can be detected more accurately. It is.

In the resonance state, it is preferable that a form corresponding to the origin position of the moving body is formed in the contacted portion of the moving body.

This makes it possible to detect the absolute position of the moving body and the piezoelectric vibrator, and to control the position with higher accuracy.

In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. It is interpreted that it is included in

Claims

A piezoelectric vibrator that generates vibration by an electrical signal, and a vibrating body having a contact portion that has a curved surface or a needle-like protrusion at the top and transmits the vibration;
And a contacted portion formed with a vibration high receiving portion that easily receives vibration from the protrusion and a vibration low receiving portion that hardly receives vibration from the protrusion, and the piezoelectric through the vibration high receiving portion. A moving body that moves under the vibration of the vibrator;
Detecting a resonance state change of the piezoelectric vibrator that occurs when the vibration low-accepting portion of the moving body passes through the protrusion of the vibration body, and obtaining positional information of the moving body based on the resonance state change. A computing unit to calculate,
An ultrasonic actuator comprising: a control unit that controls driving of the moving body based on position information calculated by the calculation unit.
2. The ultrasonic actuator according to claim 1, wherein the low vibration receiving portion extends in a line shape in a direction orthogonal to a direction in which the low vibration receiving portion moves relative to the protrusion.
The contacted portion includes a vibration high receiving portion formed of a flat surface, a plurality of vibration low receiving portions formed by a plurality of grooves formed on the flat surface, and a cover member that covers the flat surface and the plurality of grooves. The ultrasonic actuator according to claim 2, wherein an outer surface of the cover member is flat.
The vibration high receiving portion and the vibration low receiving portion are formed on the same flat surface, the vibration high receiving portion is formed of a vibrating material, and the vibration low receiving portion is formed of a vibration absorbing material. The ultrasonic actuator according to claim 1.
The vibration high receiving portion and the vibration low receiving portion are formed on the same flat surface, the surface of the vibration high receiving portion is non-sliding, and the surface of the vibration low receiving portion is slidable. The ultrasonic actuator according to claim 1.
The contact portion has three protrusions, the three protrusions are arranged at equal intervals on a predetermined circumference, and the movable body is rotatable around a central axis passing through the center of the predetermined circumference. The ultrasonic actuator according to claim 1, wherein the vibration low-accepting portions having a multiple of 3 are arranged at equal intervals in the circumferential direction.
The vibrator further includes a vibration state detection unit that detects a vibration state of the piezoelectric vibrator and outputs a vibration detection voltage, and the calculation unit is configured to output a level of the vibration detection voltage and a drive voltage of the piezoelectric vibrator. The ultrasonic actuator according to claim 1, wherein the phase difference is calculated as signal information.
The apparatus further includes a pulse conversion unit that converts the vibration detection voltage and the drive voltage in the piezoelectric vibrator into pulse signals, respectively, and the calculation unit includes pulse pulse intervals of the drive voltage and the vibration detection voltage converted into pulse signals. The ultrasonic actuator according to claim 7, wherein a phase difference between the drive voltage and the vibration detection voltage is calculated based on the equation.
The ultrasonic actuator according to claim 1, wherein the calculation unit calculates a phase difference between a driving voltage and a driving current in the piezoelectric vibrator as signal information.
The apparatus further includes a pulse conversion unit that converts the drive voltage and the drive current in the piezoelectric vibrator into pulse signals, respectively, and the calculation unit is based on each pulse edge interval of the drive voltage and the drive current converted into a pulse signal. The ultrasonic actuator according to claim 9, wherein a phase difference between the drive voltage and the vibration detection voltage is calculated.