JPH0795783A - Ultrasonic motor and its controlling method - Google Patents

Abstract

PURPOSE:To provide an ultrasonic motor which can stably control the oscillation of elastic progressive waves which are excited from an oscillatory body with accuracy by detecting the oscillation from a plurality of oscillation detecting electrodes. CONSTITUTION:A plurality of oscillation detecting electrodes F1 and F2 are installed to a piezoelectric body for detecting the oscillation of elastic progressive waves and the amplitudes of the output signals of the electrodes F1 and F2 are respectively detected by means of amplitude detecting circuits. The detected amplitudes are added to each other by at an adding circuit and the drive of an ultrasonic motor is controlled by using the added result as a control signal. Therefore, the oscillation of the elastic progressive waves excited from an oscillatory body can be stably controlled without being affected by residual standing wave components in the progressive waves and the positional deviations of the electrodes F1 and F2 from standing waves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an ultrasonic motor which uses elastic vibration excited by a piezoelectric body as a driving force and a method of controlling the ultrasonic motor.

[0002]

2. Description of the Related Art In recent years, attention has been paid to an ultrasonic motor which excites elastic vibration in a vibrating body formed of a piezoelectric body such as a piezoelectric ceramic and uses this as a driving force.

A conventional ultrasonic motor will be described below with reference to the drawings. FIG. 18 is a cutaway perspective view showing a schematic configuration of a disk-type ultrasonic motor, in which the piezoelectric body 2 is bonded to one of the main surfaces of the elastic substrate 1 to form the vibrating body 3. Further, the protrusion 1a is provided on the other main surface of the elastic substrate 1. An elastic body and a wear-resistant friction material are bonded together to form the moving body 4. The moving body 4 is in pressure contact with the vibrating body 3. By applying an electric field to the piezoelectric body 2 and generating two standing waves having a phase difference of 90 ° in the circumferential direction of the vibrating body 3, a traveling wave of bending vibration is excited,
The moving body 4 is driven by frictional force.

FIG. 19 shows an example of the electrode structure of the piezoelectric body 2 in the disk type ultrasonic motor, which is constructed so as to excite a primary bending vibration in the radial direction and a tertiary bending vibration in the circumferential direction. .

FIG. 19 (a) is a plan view of the first surface of the piezoelectric body 2 of the disc type ultrasonic motor, and FIG. 19 (b) is shown in FIG.
It is a top view of the 2nd surface of the piezoelectric material 2 shown to (a).

In FIG. 19B, on the second surface of the piezoelectric body 2, electrodes DD and EE having a phase difference corresponding to a quarter wavelength of the standing wave relative to each other and a half of the traveling wave. The electrode FF corresponding to one wavelength is formed.

In FIG. 19 (a), on the first surface of the piezoelectric body 2, a half wavelength of the electrode groups AA and BB having a phase difference corresponding to a quarter wavelength of the traveling wave relative to each other. A corresponding electrode CC is constructed.

The electrode group AA includes small electrode portions aa1 and aa2 corresponding to a half wavelength of the traveling wave and a small electrode portion aa3 corresponding to a quarter wavelength. Similarly, the electrode group BB includes small electrode portions bb1 and bb2 corresponding to a half wavelength of the traveling wave and a small electrode portion bb3 corresponding to a quarter wavelength of the traveling wave. These electrodes are used to polarize the piezoelectric body 2, and are polarized in opposite directions in the thickness direction, as indicated by + -in the figure.

The electrode groups AA and BB on the first surface and the electrodes CC
Are respectively configured to correspond to the electrodes DD, EE, FF on the second surface. That is, by turning over FIG.
When superposed on (b), the electrode group AA is placed on the electrode DD,
The electrode group BB faces the electrode EE, and the electrode CC faces the electrode FF.

The piezoelectric body 2 constitutes the vibrating body 3 by bonding the first surface to the elastic substrate 1. The bonding surface of the piezoelectric body 2 with the elastic substrate 1 is the first surface opposite to the surface shown in the figure, and the electrode is a solid electrode. At the time of use, the electrode groups AA and BB are short-circuited and used as indicated by the diagonal lines in the figure.

In the area of the electrode groups AA and BB, the electrode D
By applying the voltage V1 represented by the equation 1 and the voltage V2 represented by the equation 2 from D and EE, respectively, V1 = V0 sin (ωt) (Equation 1) V2 = V0 cos (ωt) (Equation 2) The traveling wave of bending vibration is excited in the vibrating body 3 from the two standing waves traveling in the circumferential direction, which are represented by Equation 3. However,
V0 is the instantaneous value of the voltage, ω is the angular frequency, and t is the time.

Ξ = ξ0 (cos (ωt) cos (kx) + sin (ωt) sin (kx)) = ξ0 cos (ωt−kx) (Equation 3) where ξ is the amplitude value of the bending vibration, ξ0 is the instantaneous value of the bending vibration amplitude, k is the wave number, λ is the wavelength, and x is the position.

FIG. 20 shows a sectional view of the piezoelectric body 2 and the electrode structure shown in FIG. 18, which shows a standing wave excited by the drive electrode of the piezoelectric body 2. Applying electrical signals 90 degrees out of phase to the electrode D
The standing wave τ is excited by D, and the standing wave υ is generated by the electrode EE.
1 (solid line) is excited.

The standing wave υ2 (broken line) is excited when an electric signal whose phase is different by 90 degrees with respect to the electric signal applied to the electrode DD is applied to the electrode EE, and the moving body 4 is moved. Rotate in the opposite direction.

In FIG. 21, a point A on the surface of the vibrating body 3 excites a traveling wave to make an elliptical motion of the major axis 2w and the minor axis 2u, and the moving body 4 is installed on the vibrating body 3 under pressure. By contacting in the vicinity of the apex P of the ellipse, the frictional force causes the wave to move in the direction opposite to the traveling direction of the wave at a velocity v represented by Expression 4.

V = ω × u (Equation 4) In order to control the rotation speed of the ultrasonic motor, the rotation speed is detected and the drive signal is controlled. To detect the rotation speed,
In addition to the method of installing a detector such as an encoder, there is a method of detecting the vibration excited in the vibrating body. Since the amplitude of the vibration excited on the vibrating body is related to the rotation speed, it is possible to control the drive signal and control the rotation speed by detecting the vibration of the vibrating body.

When a vibration detecting electrode is provided on the piezoelectric body, a charge is generated in the vibration detecting electrode on the piezoelectric body, which is substantially proportional to the amplitude of the vibration excited in the piezoelectric body. If we detect the charge induced by the vibration at
The amplitude of the vibration excited by the vibrating body can be detected. In FIG. 19, the electrode FF is used as the vibration detection electrode. The electrode FF is installed corresponding to a half wavelength centered on the half wave position of the second wave of the standing wave υ1 in FIG.

FIG. 22 shows a block diagram of the rotation speed control of the ultrasonic motor utilizing the vibration detection. By detecting the amplitude of the output signal from the vibration detection electrode on the piezoelectric body by the amplitude detection circuit, an index of the magnitude of vibration in the vibration body is obtained, and this is sent to the control circuit to obtain the desired rotation speed. Adjust the drive circuit to generate the drive waveform.

[0019]

However, as shown in FIG.
In the piezoelectric body having the electrode configuration shown in Fig. 20, as shown in Fig. 20, the standing waves ν1 and ν2 excited by the electrode DD are
Since both have the vibration abdomen at the center of the electrode FF,
The component of the standing wave ν1 or the standing wave ν2 of the elastic traveling wave excited by the piezoelectric body can be detected by the electrode FF.

However, the standing wave τ excited by the electrode EE has a vibration node at the center of the electrode FF,
Since the amplitudes at both ends of F are the same amplitude but in different directions, the components of the charges induced by the standing wave τ cancel each other out, and among the elastic traveling waves excited by the piezoelectric body, the standing wave τ The component cannot be detected by the electrode FF.

Therefore, when different load fluctuations occur between the electrodes DD and EE, the vibration detection signal from the electrode FF can cope with the change on the electrode DD side, but can cope with the change on the electrode EE side. The effect of this load variation, which cannot be done, is described more generally.

Due to various causes, the elastic traveling wave that excites the vibrating body has a bias δt with respect to time as shown in equation 5,
In many cases, the deviation δx with respect to the position and the deviation m with respect to the amplitude occur, and the standing wave component remains.

Ξ = ξ0 cos (ωt) cos (kx) + mξ0 sin (ωt + δt) sin (kx + δx) (Equation 5) The deviation with respect to time is often due to the difference in the impedance of the piezoelectric body and the deviation with respect to the position. This is often caused by a shift in the electrode pattern. The deviation with respect to the amplitude is caused by variations in the composition of the piezoelectric body and variations in the drive circuit.

Further, since the vibration detecting electrode and the driving electrode are provided on the opposite surface of the piezoelectric body and the electrode for polarization in order to generate the standing wave, when the electrodes are formed on the piezoelectric body, the position is particularly great. However, there is a problem that it is difficult to align them accurately, and a shift easily occurs. When the vibration detection electrode is displaced from the predetermined position, the positional relationship with respect to the standing wave generated in the vibrating body varies.

When such a standing wave component remains and the vibration detection electrode is displaced, the speed of the elliptical vibration of the apex of the vibrating body due to the elastic traveling wave is the same even if the rotation direction changes, and the rotation speed is 23, the output from the vibration detection electrode changes depending on the rotation direction of the ultrasonic motor as shown in FIG. In the case of FIG. 23, the amplitude of the output from the vibration detection electrode was smaller when rotating counterclockwise.

FIG. 24 shows the relationship between the ratio of the output from the amplitude detection circuit in the case of the counterclockwise direction and the case of the clockwise direction in the case where there is a deviation δt with respect to time, and the displacement amount of the vibration detection electrode. When the displacement of the vibration detection electrode becomes large, the difference in the amplitude depending on the rotation direction becomes remarkable. -9 with the same amplitude
When the drive signals having different phases of 0 degrees are input to change the rotation direction, the output amplitude from the vibration detection electrode changes significantly.

FIG. 25 shows the relationship between the rotation speed and the amplitude of the output from the vibration detecting electrode in the ultrasonic motor having the structure having the output from the vibration detecting electrode. The rotation speed and the amplitude are proportional to each other, but differ depending on the rotation direction. In this figure, the amplitude is smaller in the clockwise direction than in the opposite direction even at the same rotation speed.

This is due to the deviation due to the positional deviation between the standing wave and the vibration detecting electrode, the non-uniformity of the pressure applied, and the like, as described above.

For this reason, in the ultrasonic motor having the same structure, the counterclockwise direction may become larger, and the relationship between the rotation speed and the amplitude does not correspond one-to-one.

Therefore, there is a problem that the rotation speed cannot be controlled by using the amplitude of the output from the vibration detecting electrode as an index.

In order to avoid this, there is a problem that the position of the vibration detection electrode must be precisely positioned with respect to the standing wave.

A common potential is required to apply a drive signal to the two drive electrodes on the piezoelectric body and generate an electric field in the thickness direction of the piezoelectric body. Generally, a ground potential is used as the common potential, and a lead wire or the like is connected to an elastic substrate, which is often made of metal, to obtain the common potential.

A flexible lead pattern or the like is used as a lead wire for connecting the drive electrode or the vibration detection electrode on the piezoelectric body to the external circuit. To facilitate the connection,
In many cases, a common electrode electrically connected to the elastic substrate is provided on the piezoelectric body, and a common potential is extracted from this common electrode by a flexible lead pattern.

The common electrode of the piezoelectric body is connected to the lead wire or the like by using the elastic substrate to which the piezoelectric body is bonded or a part of the same circumference of the drive electrode of the piezoelectric body as the common electrode.

When the elastic substrate of the vibrating body is connected to the lead wire, if the outer peripheral portion of the vibrating body is connected, the lead wire is excited when the vibrating body is excited in a vibration mode such that the outer periphery becomes a free end. Etc. and the mass of the connection part impedes vibration as a load, driving efficiency is reduced, and if the elastic substrate and lead wires are connected by a method involving heating, the entire vibrator is affected by heating. The problem is that it affects the polarization state of the piezoelectric body.

The present invention solves the above-mentioned problems, and even when the load is deviated or the standing wave component remains and the position of the vibration detecting electrode is displaced, the vibration detecting electrode is rotated depending on the rotation direction. To provide a highly efficient ultrasonic motor and a method of controlling the ultrasonic motor that can reduce the output difference of the motor, stably control the rotation speed of the rotor, do not hinder the vibration of the vibrating body, and have no deterioration in the vibration characteristics. It is intended.

[0037]

In order to solve the above-mentioned problems, the ultrasonic motor of the present invention is provided with a plurality of vibration detection electrodes as well as drive electrodes on a piezoelectric body. The amplitude detection circuit detects the amplitude of the vibration or a value related to the amplitude from the signal output to each vibration detection electrode, and the drive signal is controlled using the value obtained by numerically adding this value to determine the rotation speed. To control.

Alternatively, output signals of different electrodes of the vibration detection electrodes are selected as control signals according to the traveling direction of the elastic traveling wave excited in the vibrating body, the drive signal is controlled, and the rotation speed is controlled.

Further, it has a structure in which a plurality of vibration detection electrodes are provided on the piezoelectric body together with the drive electrodes, and a common electrode is provided in the vicinity of the inner peripheral portion of the piezoelectric body.

[0040]

By using the result of adding the amplitude values of the outputs from the plurality of vibration detecting electrodes provided on the piezoelectric body for controlling the drive signal, the standing wave component remains in the elastic traveling wave that excites the vibrating body. Even when the position of the vibration detection electrode is displaced with respect to the standing wave, the added value can be substantially unchanged depending on the rotation direction. By using this added value,
The rotation speed of the ultrasonic motor can be controlled.

Further, by selecting the vibration detecting electrode, stable speed control can be performed without being affected by the load variation between the driving electrodes.

Further, by providing the common electrode on the inner peripheral portion where the vibration is the smallest, it is possible to minimize the inhibition of the vibration due to the connection of the lead wires, and it is possible to obtain a high driving efficiency.

[0043]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an ultrasonic motor according to a first embodiment of the present invention. In the main body of the ultrasonic motor shown in the sectional view, the piezoelectric body 2 is attached to one of the main surfaces of the elastic substrate 1 to form the vibrating body 3. Further, the protrusion 1a is provided on the other main surface of the elastic substrate 1. The moving body 4 is composed of an elastic body and a wear resistant friction material.

The moving body 4 is in pressure contact with the vibrating body 3 by using the pressing spring 5 as a pressing means. The circuit system 6 is composed of a drive circuit, a control circuit, an amplitude detection circuit, an addition circuit, etc., and is connected to the electrodes of the piezoelectric body 2. Further, the elastic substrate is used as a reference potential and electrically connected to an external circuit. By applying an electric field from the circuit system to the piezoelectric body 2 and creating two standing waves having a phase difference of 90 ° in the circumferential direction of the vibrating body 3, a traveling wave of bending vibration is excited and the moving body 4 is caused by frictional force. Driven.

FIG. 2A is a plan view of the first surface of the piezoelectric body 2 of the disk type ultrasonic motor shown in FIG. 1, and FIG.
It is a top view of the 2nd surface of the piezoelectric body shown to (a), A radial vibration primary-circumferential tertiary flexural vibration is excited to a disk-shaped vibration body.

FIG. 3 shows a sectional view of the piezoelectric body 2 and a standing wave excited by the drive electrodes of the piezoelectric body 2. In the figure, λ
Indicates the wavelength of the standing wave.

In FIG. 2B, on the second surface of the piezoelectric body 2, electrodes D and E having a phase difference corresponding to a quarter wavelength of the traveling wave relative to each other and four of the traveling wave are located. Electrodes F1 and F2 corresponding to one-half wavelength are formed.

In FIG. 2A, on the first surface of the piezoelectric body 2, electrode groups A and B having a phase difference positionally corresponding to a quarter wavelength of the traveling wave and a quarter thereof. Electrode C corresponding to wavelength
1 and C2 are configured. The electrode group A includes small electrode portions a1 and a2 corresponding to a half wavelength of the traveling wave and small electrode portions a3 and a4 corresponding to a eighth wavelength. Similarly, the electrode group B includes small electrode portions b1 and b2 corresponding to a half wavelength of the traveling wave and small electrode portions b3 and b4 corresponding to a eighth wavelength.

The electrode groups A and B on the first surface and the electrodes C1 and C2
Are respectively formed corresponding to the electrodes D, E, F1 and F2 on the second surface. That is, FIG.
When superposed on (b), the electrode group A faces the electrode D, the electrode group B faces the electrode E, the electrode C1 faces the electrode F1, and the electrode C2 faces the electrode F2.

When the piezoelectric body 2 is polarized, the second surface is placed on a conductor such as metal so that the first electrode serves as a common electrode.
Using the small electrode portions of the surface electrode groups A and B and the electrode C, the piezoelectric body 2 is polarized as indicated by the symbol shown in FIG.

The piezoelectric body 2 after polarization has the elastic substrate 1 on the first surface.
The vibrating body 3 is formed by adhering to the.

The polarization direction is not limited to the direction shown in FIG. When electric signals having 90-degree temporally different phases are applied to the electrodes D and E of the piezoelectric body 2 having 90-degree temporally different phases, bending vibration of radial primary and circumferential tertiary is applied to the vibrating body 3. Can be excited.

Therefore, the electrodes used to drive the vibrating body of the piezoelectric body 2 are the electrodes D and E, and only the electrodes F1 and F2 are not used as drive electrodes, so that half of the traveling wave is generated.
Only the wavelength equivalent is not used for driving, ensuring a high driving force.

FIG. 3 shows a standing wave which constitutes an elastic traveling wave excited in the vibrating body 3 when electric signals having 90 degrees different phases in time are applied to the electrodes D and E, respectively. .

When electric signals whose phases are different by 90 degrees with respect to time are applied to the electrodes D and E, the standing wave α is excited by the electrode D and the standing wave β1 (solid line) is excited by the electrode E.

The standing wave β2 (broken line) is excited when an electric signal whose phase is different by −90 degrees in time from the electric signal applied to the electrode D is applied to the electrode E. The moving body rotates in the opposite direction to when the standing wave β1 (solid line) is excited.

The electrodes F1 and F2 are used as vibration detection electrodes. As shown in FIG. 3, the electrode F1 is provided for 1/4 wavelength from 1/8 wavelength to 3/8 wavelength centering on the position of the 1/4 wavelength of the second wave of the standing wave α. And the electrode F2 is centered at the position of 1/2 wavelength of the second wave, and 3 /
It is provided for a quarter wavelength corresponding to 8 to 5/8 wavelengths.

In other words, the vibration detecting electrodes are provided for the quarter wave centering around the abdominal portions of the two standing waves α and β.

FIG. 4 is a block diagram of the rotation speed control by detecting the vibration of the circuit system in this embodiment.

From the electrodes F1 and F2 on the second surface of the piezoelectric body, electric signals due to the electric charges induced by the vibration of the vibrating body are taken out. The electric signal taken out from the electrodes F1 and F2 becomes an AC signal which changes with time as shown in FIG. This signal is sent to the amplitude detection circuit in the circuit system, and the amplitude of the vibration is detected by this amplitude detection circuit.

The amplitude detection circuit is composed of a rectifier circuit and the like, and detects a value corresponding to the peak-peak of the input signal (maximum amplitude of the input signal) as a DC voltage.

These two DC voltages are sent to the adding circuit and the DC voltages are added. This added DC voltage is sent to the control circuit, and as a control index, the control circuit controls the drive circuit and changes parameters such as frequency and voltage so that the drive signal can obtain a desired rotation speed.

In this way, the rotation speed of the moving body is controlled. A half-wave rectifier circuit or the like may be used in the amplitude detection circuit, which is half the amplitude of the output signal from the vibration detection electrode.
(Peak and ground) may be converted into a DC voltage and used as a value indicating the amplitude of vibration.

Alternatively, the output signal from the vibration detecting electrode may be integrated for a certain period of time, converted into a DC voltage, and this voltage may be added.

The voltage detected by the amplitude detection circuit may be analog-digital converted into a digital value and then added, and the resulting digital value may be used to control the drive signal by the control circuit. It is easy to handle as a control index when performing digitally. The method of detecting the magnitude of the vibration generated in the vibrating body from the output signal from the vibration detection electrode is not limited to the above.

In FIG. 5, the output signals from the amplitude detection circuit when the signals output to the electrodes F1 and F2 of the piezoelectric body having the electrode structure shown in FIG. The relationship between the ratio of the value and the added value when rotating clockwise and the amount of positional deviation of the vibration detection electrodes F1 and F2 with respect to the standing wave is shown.

In this case, the deviation δt with respect to time was the same regardless of the rotation direction. As shown in FIG. 5, even if the position of the vibration detection electrode with respect to the standing wave is largely deviated, there is no direction dependency of the added value.

Therefore, a drive signal having the same amplitude without control and only the phase relationship changed to change the rotation direction is input, and the same elastic traveling waves with different directions are excited in the vibrating body. Even when there is a residual standing wave component or a positional deviation of the electrodes, the added value does not change depending on the rotation direction, and the rotation speed can be controlled accurately regardless of the rotation direction.

FIG. 6 (a) shows that the adder circuit adds the output signals from the amplitude detection circuit in the case of counterclockwise rotation of the signals output to the electrodes F1 and F2 when the deviation δt with respect to time differs depending on the rotation direction. The relationship between the ratio between the added value and the added value when rotating clockwise and the amount of positional deviation of the vibration detection electrodes F1 and F2 with respect to the standing wave. Also in this case, the added value was substantially constant regardless of the rotation direction and the amount of displacement of the vibration detection electrode.

FIG. 6 (b) is a diagram showing the relationship between the rotational speed of the ultrasonic motor constructed by using the piezoelectric body having the electrode structure of this embodiment and the added value of the output from the vibration detection electrode. The rotation speed and the added value are proportional to each other regardless of the rotation direction.

Therefore, the added value has a one-to-one correspondence with the rotation speed and can be used as an index of the rotation speed. The relationship between the added value and the rotation speed is stored in advance in the storage area in the control circuit of FIG. When a desired rotation speed is input to the control circuit, an added value corresponding to this rotation speed is obtained. The drive signal is controlled so that the same value as this added value is obtained.

Generally, when changing the rotation speed of the ultrasonic motor, the frequency and voltage of the drive signal are changed. As the frequency of the drive signal is closer to the resonance frequency of the vibrating body, the vibration amplitude of the vibrating body increases and the rotation speed increases. Further, the higher the voltage of the drive signal, the larger the amplitude of the vibrating body and the higher the rotation speed.

Therefore, the frequency or voltage of the drive signal is changed by the control circuit so that the added value of the output from the vibration detection electrode matches the added value corresponding to the desired rotation speed. A desired rotation speed can be obtained by inputting a drive signal having a frequency and a voltage with which the added values match, to the drive electrode. With the above method, the rotation speed of the ultrasonic motor can be accurately controlled.

It should be noted that the drive signal is controlled by using the added value of the output from the vibration detection circuit even in the other electrode structure having the positional relationship between the two standing waves and the vibration detection electrode shown in FIG. 3 in the present embodiment. If so, the rotation speed can be accurately controlled regardless of the rotation direction.

As described above, according to this embodiment, an ultrasonic wave whose rotational speed can be controlled extremely stably and highly accurately without being affected by the residual standing wave component of the elastic traveling wave and the positional deviation of the vibration detection electrode. Motor and control method can be realized.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 7A is a plan view of the first surface of the piezoelectric body of the disc type ultrasonic motor, and FIG. 7B is a plan view of the second surface of the piezoelectric body shown in FIG. 7A. That is, the disk-shaped vibrating body excites the bending vibration of the primary in the radial direction and the tertiary in the circumferential direction.

FIG. 8 shows a sectional view of the piezoelectric body 2 and a standing wave excited by the drive electrodes of the piezoelectric body 2.

In FIG. 7B, on the second surface of the piezoelectric body 2, electrodes K and J having a phase difference corresponding to a quarter wavelength of the traveling wave relative to each other and four of the traveling wave are provided. Electrodes L1 and L2 corresponding to one-half wavelength are formed.

In FIG. 7A, on the first surface of the piezoelectric body 2, there are electrode groups G and H having a phase difference positionally corresponding to a quarter wavelength of the traveling wave and a quarter. Electrode I corresponding to wavelength
1 and I2 are configured. The electrode group G includes small electrode portions g1 and g2 corresponding to a half wavelength of the traveling wave and a small electrode portion g3 corresponding to a quarter wavelength. Similarly, the electrode group H includes small electrode portions h1 and h2 corresponding to a half wavelength of the traveling wave and a quarter electrode portion.
It consists of a small electrode portion h3 corresponding to the wavelength.

The electrode groups G and H on the first surface and the electrodes I1 and I2
Are respectively configured to correspond to the electrodes J, K, L1 and L2 on the second surface. That is, FIG. 7 (a) is turned over and FIG.
, The electrode group G faces the electrode J, the electrode group H faces the electrode K, the electrode I1 faces the electrode L1, and the electrode I2 faces the electrode L2.

By placing the piezoelectric body 2 on the second surface on a conductor such as a metal, a group of electrodes G on the first surface is formed as a common electrode.
The small electrode portion of H and the electrode I are polarized as indicated by the symbols shown in FIG. Even if the electrode on the first surface is small, it corresponds to a quarter wavelength, so that the polarization is easier than in the previous embodiment.

The piezoelectric body 2 after polarization has the elastic substrate 1 on the first surface.
The vibrating body 3 is formed by adhering to the.

The polarization direction is not limited to the direction shown in FIG. When electric signals whose phases are different by 90 degrees with respect to time are applied to the electrodes J and K of the piezoelectric body 2 which are connected to an external circuit by using the elastic substrate as a reference potential and the phases are different by 90 degrees, the vibrating body 3 has a diameter of 90 degrees. It is possible to excite bending vibration of the first-order direction and the third-order circumferential direction.

The electrodes used for driving occupy 5/6 of the whole and a high driving force is secured. FIG. 8 shows electrodes J and K.
In addition, a standing wave that constitutes an elastic traveling wave excited in the vibrating body 3 when electric signals whose phases are different by 90 degrees with respect to time is applied is shown.

When electric signals whose phases are different by 90 degrees with respect to time are applied to the electrodes J and K, the standing wave γ is excited by the electrode J and the standing wave ε1 (solid line) is excited by the electrode K. The standing wave ε2 (broken line) is excited when an electric signal whose phase is different by −90 degrees in time from the electric signal applied to the electrode J is applied to the electrode K. In this case, the standing wave ε1 The moving body rotates in the opposite direction to the case where (solid line) is excited.

The electrodes L1 and L2 are used as vibration detecting electrodes. As shown in FIG. 8, the electrode L1 is provided at a position corresponding to a quarter wavelength from a quarter wavelength to a half wavelength centered on the position of the third wave of the second wave of the standing wave γ. The electrode L2 is centered at the position of the 5/8 wavelength of the second wave, and
The wavelengths corresponding to the 1/4 wavelength from 2 wavelengths to 3/4 wavelength are provided.

In other words, a quarter-wave vibration detection electrode that divides the position corresponding to the abdomen of one standing wave of the two standing waves into two equal parts is installed. Alternatively,
A quarter-wave vibration detection electrode that bisects a position corresponding to the node is installed between the nodes. Although the vibration detection electrode is provided at the position of the second wave in this embodiment, the same effect can be obtained with the first wave and the third wave.

The output signals due to the electric charges induced in the electrodes L1 and L2 are detected separately by the method shown in FIG. 4 to detect the amplitude of the vibration of the vibrating body, and this value is added by the addition circuit. , Calculate the added value.

Here, the peak values of the signals output from the electrodes L1 and L2 are each converted into a DC voltage to obtain a value indicating the magnitude of vibration generated in the vibrating body, and this current value is integrated by an adding circuit. Then, the speed of the moving body was controlled to a desired value by controlling the drive circuit using the integrated result as a control index. The drive signal is controlled using this added value.

The ratio between the added value of the amplitude of the signal output to the electrodes F1 and F2 when it rotates counterclockwise and the added value of the signal when it rotates clockwise is the same as in FIG.
The value was 1 regardless of the amount of displacement of L2 with respect to the standing wave.

FIG. 9 shows the ratio of the added value of the amplitude when the signal output to the electrodes L1 and L2 rotates in the counterclockwise direction and the added value when the signal rotates to the clockwise direction when the deviation δt with respect to time differs depending on the rotating direction. And the positional deviation amount of the vibration detection electrodes F1 and F2 with respect to the standing wave.

Also in this case, when the amount of displacement is 0, the ratio of the added values does not become 1.0, but it is extremely close to 1.0. Therefore, even though the standing wave component remains in the elastic traveling wave, the added value can be considered to be almost constant regardless of the rotation direction and the displacement amount of the vibration detection electrode, and is used as a control index of the rotation speed. The rotation speed could be controlled to a desired value with high precision.

As described above, according to this embodiment, in order to exclude the influence of the residual standing wave component of the elastic traveling wave on the vibration detection, the vibration detection electrodes need not be precisely aligned with the standing wave. It is possible to realize an ultrasonic motor and control method that can control the rotation speed with extremely high stability and high accuracy.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 10A is a plan view of the first surface of the piezoelectric body of the disc type ultrasonic motor, and FIG. 10B is a plan view of the second surface of the piezoelectric body shown in FIG. 10A. That is, the disk-shaped vibrating body excites the bending vibration of the primary in the radial direction and the tertiary in the circumferential direction.

FIG. 11 shows a sectional view of the elastic substrate 1 and the piezoelectric body 2 and a standing wave excited by the drive electrode of the piezoelectric body 2. λ indicates the wavelength of the standing wave.

In FIG. 10A, the first surface of the piezoelectric body 2 is formed with electrode groups M and N which are positional relative to each other and have a phase difference corresponding to a quarter wavelength of the traveling wave. The electrode group M is composed of small electrode portions m1, m2, m3 corresponding to one-half wavelength of the traveling wave. Similarly, the electrode group N includes small electrode portions n2 and n3 corresponding to a half wavelength of the traveling wave and a small electrode portion n corresponding to a quarter wavelength.
It consists of 1 and n4.

In FIG. 10B, on the second surface of the piezoelectric body 2, the electrodes P1, P2 and Q connected at the outer peripheral portion are connected.
1, the electrode Q2 and electrodes R1 and R2 corresponding to a quarter wavelength of the standing wave are installed on the inner peripheral portion.

The electrode groups M and N on the first surface are configured respectively corresponding to the electrodes P1, P2, Q1 and Q2 on the second surface. That is, when FIG. 10A is turned over and overlapped with FIG. 10B, the electrode group M is the electrodes P1 and P2, and the electrode group N is the electrode Q.
Opposite 1 and Q2 respectively.

By placing the second surface of the piezoelectric body 2 on a conductor such as a metal, a group of electrodes M on the first surface are formed as a common electrode.
It was polarized by N according to the sign. The direction of polarization is not limited to the one indicated by the symbol.

After polarization, the piezoelectric body 2 has the elastic substrate 1 on the first surface.
Then, the vibrating body 3 is formed by bonding. The electrode P1 of the piezoelectric body 2,
When an electric signal having a phase difference of 90 degrees with respect to time is applied to P2 and the electrodes Q1 and Q2, in an ideal case, as shown in FIG.
Two standing waves η (solid line) and a standing wave θ1 (solid line) with different phases are generated, and the elastic substrate 1 has a radial direction 1
It is possible to excite bending vibrations of the second and third circumferential directions. The standing wave θ2 (broken line) is generated when drive signals whose phases are different by −90 degrees are input to the electrode group N, and the moving body rotates in the opposite direction.

The electrodes R1 and R2 are used as vibration detecting electrodes. As shown in FIG. 11, the electrode R1 is provided for 1/4 wavelength from 5/8 wavelength to 7/8 wavelength centered on the position of 3/4 wavelength of the first wave of the standing wave η. And
Electrode R2 is centered on the beginning of the third wave and
It is provided for ¼ wavelength from / 8 wavelength to ⅛ wavelength of the third wave. In other words, the electrode R1 is a vibration detection electrode for a quarter wavelength centered on the abdomen of the first standing wave η, and the electrode R2 is 1/4 centered on the abdomen of the second standing wave θ. This means that vibration detection electrodes for the respective wavelengths are installed.

An ultrasonic motor is constructed using the piezoelectric body shown in FIG. 10, and its rotation speed is detected by the amplitude detection circuit from the output signal from the vibration detection electrode shown in FIG.
The value obtained by adding the values was controlled as a control index. As a result, similar to FIGS. 5 and 6, a control index independent of the rotation direction was obtained without being affected by the residual standing wave component in the traveling wave and the positional deviation.

In the present embodiment, the vibration detection electrodes R1 and R2 are provided so as not to be adjacent to each other but to face each other. Distortion of the vibration waveform and residual standing wave components occur not only in the circumferential direction but also in the radial direction.

Further, the centers of the piezoelectric body and the elastic substrate may deviate from each other, resulting in poor concentricity. In the case of this embodiment, FIG.
As shown in (c), the primary vibration is excited in the radial direction.

Therefore, the vibration becomes larger toward the outer peripheral portion.
In the case of a piezoelectric body having adjacent vibration detection electrodes, if the concentricity deteriorates, the detection signal of any of the vibration detection electrodes increases or decreases. Therefore, if the ultrasonic motors have different concentricity, the vibration detection result varies.

However, when the vibrating electrodes are provided so as not to be adjacent to each other but to face each other as in the present embodiment, even if the vibration detection result of one becomes large, the other becomes small.
When this is added, a constant value is always obtained. Therefore, not only the effect of the positional deviation of the electrode pattern in the circumferential direction but also the effect of eliminating the effect of the radial deviation can be exhibited together.

The drive electrodes P1 and P2 and the drive electrodes Q1 and Q2 are spatially separated. However, by connecting at the outer peripheral portion, connection with an external circuit has become easier. Further, in the case of having a primary vibration mode in the radial direction as in the present embodiment, the vibration of the outer peripheral portion is the largest and the outer peripheral portion generates a large driving force. Therefore, since the outer peripheral portion is connected and this portion also contributes to the driving, a larger driving force can be generated. The method of connecting the outer peripheral portion is not limited to the one in this embodiment.

As described above, in this embodiment, it is possible to provide an ultrasonic motor capable of controlling the rotation speed without being affected by the residual component of the standing wave and the positional deviation of the electrodes while maintaining a high driving force.

(Embodiment 4) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 12A is a plan view of the first surface of the piezoelectric body of the disc type ultrasonic motor, and FIG. 12B is a plan view of the second surface of the piezoelectric body shown in FIG. 12A. That is, the disk-shaped vibrating body excites bending vibration in the radial first order and the circumferential third order.

FIG. 13 shows a cross-sectional view of the elastic substrate 1 and the piezoelectric body 2 and a standing wave excited by the drive electrode of the piezoelectric body 2. λ indicates the wavelength of the standing wave.

In FIG. 12A, on the first surface of the piezoelectric body 2, there are formed electrode groups S and T having a phase difference positional relative to each other by a quarter wavelength of the standing wave. The electrode group M is composed of small electrode portions s1, s2, s3 corresponding to a half wavelength of the standing wave. Similarly, the electrode group N includes small electrode portions t2 and t3 corresponding to a half wavelength of the standing wave and small electrode portions t1 and t4 corresponding to a quarter wavelength of the standing wave.
Consists of.

In FIG. 12B, on the second surface of the piezoelectric body 2, the electrode U1, the electrode U2 and the electrode V, which are connected at the inner peripheral portion, are connected.
1, electrode V2 and electrode W corresponding to 1/4 wavelength of standing wave
1, W2 is installed.

The electrode groups S and T on the first surface are configured respectively corresponding to the electrodes U1, U2, V1 and V2 on the second surface. That is, when FIG. 12 (a) is turned over and overlapped with FIG. 12 (b), the electrode group S is the electrodes U1 and U2, and the electrode group T is the electrode V.
1 and V2, respectively.

By placing the second surface of the piezoelectric body 2 on a conductor such as a metal, a group of electrodes S,
Using T, polarization was performed in the thickness direction as indicated by the symbol. The direction of polarization is not limited to the one indicated by the symbol.

The piezoelectric body 2 after polarization has the elastic substrate 1 on the first surface.
Then, the vibrating body 3 is formed by bonding. Electrode U1 of piezoelectric body 2,
When an electric signal whose phase is different by 90 degrees with respect to time is applied to U2 and the electrodes V1 and V2, in the ideal case, as shown in FIG.
Two standing waves μ (solid line) and a standing wave ν1 (solid line) with different phases are generated, and the elastic substrate 1 has a radial direction 1
It is possible to excite bending vibrations of the second and third circumferential directions. The standing wave ν2 (broken line) is generated when drive signals whose phases are different by −90 degrees are input to the electrode group T, and the moving body rotates in the opposite direction.

The electrodes W1 and W2 are used as vibration detecting electrodes. As shown in FIG. 13, the electrode W1 is provided for 1/4 wavelength from 5/8 wavelength to 7/8 wavelength centering on the position of 3/4 wavelength of the first wave of the standing wave μ. And
Electrode W2 is centered around the position of 1/2 wavelength of the third wave.
It is provided for ¼ wavelength from / 8 wavelength to 5/8 wavelength.

In other words, the electrode W1 has the first standing wave μ
Is a vibration detection electrode for a quarter wavelength centered on the abdomen of the second standing wave ν, and the electrode W2 is 1 / centered on the abdomen of the second standing wave ν.
This means that vibration detection electrodes for four wavelengths are installed respectively. It should be noted that both the electrodes W1 and W2 have a first wave and a third wave.
The position is not limited to the above position of the wave, but may be the second wave.

An ultrasonic motor was constructed using the piezoelectric body shown in FIG. The rotation speed was controlled using a value obtained by adding the peak-peak value of the output signal from the vibration detection electrode shown in FIG. 4 as a control index.

As a result, similar to FIGS. 5 and 6, a control index independent of the rotation direction was obtained without being affected by the residual standing wave component in the traveling wave and the positional deviation.

The drive electrodes U1 and U2 and the drive electrodes V1 and V2 are spatially separated. However, by connecting at the inner peripheral portion, the connection to the external circuit is also made at one location, respectively, and it becomes easy even for a piezoelectric body having a small diameter.

Further, as in this embodiment, when the primary vibration mode is in the radial direction, the vibration at the outer peripheral portion is the largest. Therefore, even if the inner peripheral portion is used for connecting the drive electrodes, the vibration of this portion is small. Therefore, when the vibration detecting electrode is provided on the outer peripheral portion side, the output signal is not so small and the control is not hindered.

The method of connecting the inner peripheral portion is not limited to the one in this embodiment, and may be a linear shape or the like. Further, the inner peripheral portion and the outer peripheral portion may be connected, the vibration detecting electrodes may be separated and connected at the center, and the vibration detecting electrodes may be respectively taken out by two leads and connected respectively.

In this embodiment, similarly to the third embodiment, the vibration detection electrodes W1 and W2 are provided so as not to be adjacent to each other but to face each other. In addition, the effect of being able to eliminate the influence of the radial deviation is also exhibited.

As described above, in the present embodiment, the drive signal can be easily input while holding the high vibration detection signal, and the rotation speed can be controlled without being affected by the residual component of the standing wave and the positional deviation of the electrodes. An ultrasonic motor can be provided.

(Embodiment 5) A fifth embodiment of the present invention will be described below with reference to the drawings.

FIG. 14A is a plan view of the first surface of the piezoelectric body of the disc type ultrasonic motor, and FIG. 14B is a plan view of the second surface of the piezoelectric body shown in FIG. 14A. Is. The X in FIG. 14A and the X ′ in FIG. 14B, and the X ′ in FIG. 14A and the Y ′ in FIG. 14B face each other across the piezoelectric body 2.

Therefore, the electrode structure of FIG. 14 has the same positional relationship between the standing wave and the vibration detection electrode as in FIG. The second surface of the piezoelectric body 2 is the same as that shown in FIG.

The first surface of the piezoelectric body 2 is the small electrode a shown in FIG.
3, b4 and electrodes C1 and C2 are collectively referred to as electrode ab1, and small electrodes a4 and b3 are collectively referred to as electrode ab2. By applying different AC voltages, elastic traveling waves of primary in the radial direction and tertiary in the circumferential direction can be obtained. Even if the directions of the signs are reversed, elastic traveling waves of primary in the radial direction and tertiary in the circumferential direction can be similarly obtained.

Vibration detection electrode electrodes F1 and F2 shown in FIG.
Is centered on the position of the 1/4 wavelength of the second wave of the standing wave α in FIG. 3, and is provided for 1/4 wavelength from 1/8 wavelength to 3/8 wavelength, and the electrode F2 is Centering on the position of the second wavelength of 1/2 wavelength, 1 / from 3/8 wavelength to 5/8 wavelength
It is provided for four wavelengths.

In other words, the vibration detecting electrodes are installed for the quarter wavelength centering on the abdominal portions of the two standing waves α and β.

Since the electrodes F1 and F2 have a positional relationship with the standing wave shown in FIG. 3, as shown in the block diagram of FIG.
The output signals from the vibration detection electrodes F1 and F2 are sent to the vibration detection circuit, the outputs from this vibration detection circuit are added, and by using the added value, the standing wave residual component and the electrode position deviation are not affected, The rotation speed of the moving body can be stably controlled as in the case of using the piezoelectric body having the electrode structure shown in FIG.

In the electrode structure shown in FIG. 14A, the electrodes ab
2 corresponds to a quarter wavelength of the elastic traveling wave, and the other electrodes correspond to a half wavelength. Unlike the electrode structure shown in FIG. 2, since there is no electrode corresponding to 1/8 wavelength and the electrode is large, it is easy to cause polarization, and it is possible to obtain the effect that the piezoelectric body is less likely to crack during polarization. .

As described above, in the present embodiment, the area of the electrode for polarization can be kept large and the polarization can be easily performed, and the piezoelectric body is hardly damaged or destroyed during polarization, and the standing wave It is possible to provide an ultrasonic motor capable of controlling the rotation speed without being affected by the positional deviation between the residual component and the electrode.

(Embodiment 6) A sixth embodiment of the present invention will be described below with reference to the drawings.

FIG. 15A is a plan view of the first surface of the piezoelectric body of the disc type ultrasonic motor, and FIG. 15B is a plan view of the second surface of the piezoelectric body shown in FIG. 15A. Is. The X in FIG. 15A and the X ′ in FIG. 15B, and the X ′ in FIG. 15A and the Y ′ in FIG. 15B face each other across the piezoelectric body 2.

Therefore, the electrode structure of FIG. 15 has the same positional relationship between the standing wave and the vibration detection electrode as in FIG. The second surface of the piezoelectric body 2 is provided with an annular electrode Z on the inner peripheral portion, and the other electrodes are reduced in the radial direction only by the portion of the electrode Z. The relationship is the same as in FIG.

The first surface has the same arrangement as in FIG. 15A, but the portion facing the electrode Z is removed. This electrode Z is used as a common electrode and is connected to the elastic substrate. In order to apply the drive signal to the piezoelectric body, an electrically common potential as a reference is required.

The elastic substrate is often composed of a metal body, and this metal body is used as a common potential. However, if there is no common electrode, a large number of leads and the like must be connected to the metal body. In addition, connection is not easy depending on the type of metal forming the metal body.

By forming a common electrode on the piezoelectric body and connecting it to the elastic substrate with a conductive paste or the like as in the present embodiment, the common potential can be easily obtained without extending the lead wire for a long time.

The direction of polarization is not limited to the signs shown in FIG. The polarization electrode may be provided near the inner peripheral portion.

Since the inner peripheral portion provided with the common electrode Z has the smallest vibration and contributes very little to the driving, even if the driving electrode and the vibration detecting electrode are not present in this portion, the driving force and the vibration are not detected. Absent.

The vibration detection electrode electrode F1 'of FIG.
Since F2 'has a positional relationship with the standing wave shown in FIG. 3 as in the fifth embodiment, as shown in the block diagram shown in FIG. 4, the output signals from the vibration detection electrodes F1' and F2 'are sent to the vibration detection circuit. To the piezoelectric body of the electrode structure of FIG. 2 without being influenced by the standing wave residual component and the electrode position deviation by adding the outputs from the vibration detection circuit and using the added value. As in the case of using, stable control can be performed.

As described above, in the present embodiment, the common potential can be easily obtained by providing the common electrode on the inner peripheral portion of the piezoelectric body, and it is affected by the residual component of the standing wave and the displacement of the electrodes. It is possible to provide an ultrasonic motor that can control the rotation speed without rotating.

FIG. 16 is a diagram showing another embodiment of the piezoelectric body provided with the common electrode. 16A is a plan view of the first surface of the piezoelectric body of the disc type ultrasonic motor, FIG. 16B is a sectional view of the piezoelectric body, and FIG. 16C is the piezoelectric body shown in FIG. It is a top view of the 2nd surface of a body. 16 in FIG. 16A and FIG.
X ′ in (c), X ′ in FIG. 16 (a) and Y ′ in FIG. 16 (c) face each other with the piezoelectric body 2 in between.

Therefore, the electrode structure of FIG. 16 has the same positional relationship between the standing wave and the vibration detection electrode as in FIG. FIG.
FIG. 3C shows an electrode configuration similar to that of FIG.
6A is different from FIG. 15A in that the electrode ZA is provided on the inner peripheral portion of the piezoelectric body 2.

This electrode ZA has a shape in which the first surface and the second surface of the piezoelectric body 2 are connected, as shown in FIG. 16 (b). Therefore, as in the case of FIG. 3, the electrode ZA can be electrically connected to the elastic substrate 1 only by adhering the first surface of the piezoelectric body 2 to the elastic substrate 1.

Therefore, as shown in FIG. 16D, after the piezoelectric body 2 is bonded to the elastic substrate 1, the electrodes D ', E', F1 ', F2' and ZA on the piezoelectric body are connected. It is only necessary to connect the external circuit with the flexible lead 10. The connecting means is not limited to this.

As described above, by adopting the shape in which the common electrode is connected to the two main surfaces of the piezoelectric body, in addition to the effect of the second embodiment, an ultrasonic motor having a small number of manufacturing steps is realized. be able to.

(Embodiment 7) Hereinafter, a seventh embodiment of the present invention will be described with reference to the drawings.

In this embodiment, a method of selecting and controlling the output signal from the vibration detecting electrode will be described. The electrode configuration of the piezoelectric body of the disc type ultrasonic motor is the same as that shown in FIG. 7, and the vibration shown in FIG. 8 is excited by the vibrating body.

When electric signals whose phases are different by 90 degrees with respect to time are applied to the electrodes J and K, the standing wave γ is excited by the electrode J and the standing wave ε1 (solid line) is excited by the electrode K. Further, the standing wave ε2 (broken line) is excited when an electric signal whose phase is temporally different by −90 degrees from the electric signal applied to the electrode J is applied to the electrode J.

The standing wave γ is excited by the electrode J, and the electrode E
When the standing wave ε1 is excited by, the standing wave γ and the standing wave ε1 have different phases in the electrode F1 but have the same amplitude in the same direction. Is detected as the sum of the electric charge induced by the standing wave γ and the electric charge induced by the standing wave ε1.

In the electrode L2, the standing wave γ and the standing wave ε1 are different in phase from each other by 90 degrees and have the same amplitude in different directions. Therefore, the electric charge induced by the standing wave γ and
The charges induced by the standing wave ε1 cancel each other out.

On the other hand, the standing wave γ is excited by the electrode J,
When the standing wave ε2 is excited by the electrode E, the standing wave γ and the standing wave ε2 are detected by the electrode L2 in the electrode L2 because the phases of the standing wave γ and the standing wave ε2 are different from each other by 90 degrees. The charge induced by the standing wave γ and the standing wave ε
It is detected as the sum of the charges induced by 2.

In the electrode L1, the standing wave γ and the standing wave ε2 are different in phase from each other by 90 degrees and have the same amplitude in different directions. Therefore, the electric charge induced by the standing wave γ and
The charges induced by the standing wave ε1 cancel each other out.

Therefore, when the elastic traveling wave excited in the vibrating body 3 is composed of the standing wave γ and the standing wave ε1 depending on the traveling direction, the signal from the electrode L1 is selected and the standing wave is selected. γ
And the standing wave ε2, the signal from the electrode F2 can be selected so that the electrodes J and K can be driven when the ultrasonic motor is driven.
Even if a load change occurs between them, the state can be detected, so that stable driving can be realized.

FIG. 17 shows a block diagram of the circuit system of the present invention. The output from the vibration detection electrode is sent to the vibration detection circuit to detect the amplitude. A selection circuit is provided for switching the detection result depending on the rotation direction. One of the amplitude detections is sent to the control circuit. The control circuit controls the drive circuit to control the rotation speed.

A similar effect can be obtained by using another configuration in which a circuit for selecting the output signals of the vibration detection electrodes L1 and L2 is provided, the amplitude is detected by the vibration detection circuit after the output signal is selected.

As described above, according to the present embodiment, the drive electrode area can be made large despite the fact that the vibration detecting section is installed on the piezoelectric body, and the traveling elastic wave excited by the vibrating body travels. Since the vibration detection signal is selected according to the direction, it is possible to obtain an ultrasonic motor with stable operation and good driving efficiency.

In the above embodiment, the disk type ultrasonic motor using the flexural vibration of the primary disk in the radial direction and the tertiary disk in the circumferential direction has been described, but the present invention is also effective in other vibration modes. Of course, the present invention is also effective for an annular ultrasonic motor using flexural vibration of an annulus.
Further, the same effect can be obtained in the above-mentioned embodiment even with respect to δx and m other than δt shown in the equation 5 which generate the residual standing wave component, and even when these are combined, a sufficient effect can be obtained.

[0165]

By arranging the piezoelectric drive electrodes and the vibration detection electrodes as described above, the drive electrode area can be increased and the electrode alignment can be performed while keeping the vibration detection output large. Ultrasonic motor that can control the rotation speed stably and accurately without using an encoder etc. by using the vibration detection signal without being affected by the residual prominent wave component of the elastic traveling wave Can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2A is a plan view of a first surface of a piezoelectric body of the motor of the embodiment, and FIG. 2B is a plan view of a second surface of the piezoelectric body.

FIG. 3 is a diagram showing a relationship between a piezoelectric body and a standing wave of the motor of the embodiment.

FIG. 4 is an explanatory view of a control method of the motor of the embodiment.

FIG. 5 is a diagram showing a vibration detection result of the motor of the embodiment.

FIG. 6A is a diagram showing a vibration detection result of the motor of the embodiment, and FIG. 6B is a diagram showing an addition value of a rotation speed and an output from the vibration detection electrode.

FIG. 7A is a plan view of a first surface of a piezoelectric body of a disk type ultrasonic motor according to a second embodiment of the present invention, and FIG. 7B is a plan view of a second surface of the same piezoelectric body.

FIG. 8 is a relationship diagram between a piezoelectric body and a standing wave of the motor of the same embodiment.

FIG. 9 is a diagram showing a vibration detection result of the motor of the embodiment.

FIG. 10A is a plan view of a first surface of a piezoelectric body of a disk type ultrasonic motor according to a third embodiment of the present invention, and FIG. 10B is a plan view of a second surface of a piezoelectric body of the motor of the same embodiment. Figure (c) is a diagram showing radial vibration.

FIG. 11 is a relationship diagram between a piezoelectric body and a standing wave of the motor of the example.

FIG. 12 (a) is a plan view of a first surface of a piezoelectric body of a disk type ultrasonic motor according to a fourth embodiment of the present invention, and FIG. 12 (b) is a second surface of a piezoelectric body of the same embodiment motor. Plan view

FIG. 13 is a relationship diagram between a piezoelectric body and a standing wave of the motor of the example.

FIG. 14A is a plan view of a first surface of a piezoelectric body of a disk type ultrasonic motor according to a fifth embodiment of the present invention, and FIG. 14B is a second surface of a piezoelectric body of the same embodiment motor. Plan view

FIG. 15A is a plan view of a first surface of a piezoelectric body of a disk type ultrasonic motor according to a sixth embodiment of the present invention, and FIG. 15B is a second surface of a piezoelectric body of the motor of the same embodiment. Plan view

16A is a plan view of the first surface of the piezoelectric body of the same embodiment motor, FIG. 16B is a cross-sectional view of the piezoelectric body of the same embodiment motor, and FIG. 16C is a first view of the piezoelectric body of the same embodiment motor. The two-sided plan view (d) shows a lead taken out from the piezoelectric body.

FIG. 17 is a diagram showing a method of controlling an ultrasonic motor according to a seventh embodiment of the present invention.

FIG. 18 is a cutaway perspective view of a disc type ultrasonic motor.

FIG. 19A is a plan view of a first surface of a piezoelectric body showing a conventional electrode structure of a disc type ultrasonic motor, and FIG. 19B is a plan view of a second surface of the same piezoelectric body.

FIG. 20 is a diagram showing the relationship between a piezoelectric body of an ultrasonic motor and a standing wave in a conventional electrode structure.

FIG. 21 is an explanatory diagram of the operation principle of the ultrasonic motor.

FIG. 22 is an explanatory diagram of a conventional ultrasonic motor control method.

FIG. 23 is a diagram showing a vibration detection signal in a conventional ultrasonic motor.

FIG. 24 is a diagram showing a vibration detection result of a conventional ultrasonic motor.

FIG. 25 is a diagram showing a rotation speed and an output from a vibration detection electrode in a conventional ultrasonic motor.

[Explanation of symbols]

 1 Elastic substrate 1a Projection body 2 Piezoelectric body 3 Vibrating body 4 Moving body 5 Pressure spring 6 Circuit system

Front page continued (72) Inventor Osamu Kawasaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takashi Nojima, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Invention Inventor Katsumi Imada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Katsushi Takeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A vibrating body composed of a piezoelectric body and an elastic body, a moving body that comes into pressure contact with the vibrating body via a pressure means, and two vibrating bodies that are temporally and positionally different in phase. A drive circuit for generating a drive signal for exciting an elastic traveling wave by generating a standing wave, a drive electrode for inputting the drive signal to the piezoelectric body, and the vibrating body for the piezoelectric body. A plurality of vibration detection electrodes for detecting the vibration of the vibration detection circuit, an amplitude detection circuit for detecting the magnitude of the vibration of the vibrating body by the output signals from the plurality of vibration detection electrodes, and a plurality of the vibration detection circuits An ultrasonic motor comprising: an adder circuit for adding output signals and a control circuit for controlling rotation of the moving body by using an output of the adder circuit. 2. A vibrating body composed of a piezoelectric body and an elastic body, a moving body which comes into pressure contact with the vibrating body via a pressure means, and a first phase which is temporally and positionally different in phase from the vibrating body. And the second 2
A drive circuit for generating a drive signal for exciting the elastic traveling wave by generating two standing waves; a drive electrode for inputting the drive signal to the piezoelectric body; and a drive electrode for inputting the drive signal to the piezoelectric body. The first vibration detection electrode is located at a position centered on the abdomen of the first standing wave, and the second vibration detection electrode is located at a position centered on the node of the second standing wave. The two amplitude detection circuits that detect the magnitude of the vibration of the vibrating body by the output signals from the vibration detection electrodes, the addition circuit that adds the output signals from the two vibration detection circuits, and the output of the addition circuit. An ultrasonic motor having a control circuit for controlling the rotation of the moving body. 3. A vibrating body composed of a piezoelectric body and an elastic body, a moving body that comes into pressure contact with the vibrating body via a pressing means, and two vibrating bodies having different phases in terms of time and position. A drive circuit for generating a drive signal for exciting the elastic traveling wave by generating a standing wave, a drive electrode for inputting the drive signal to the piezoelectric body, and one of the piezoelectric body for the piezoelectric body. A first vibration detection electrode and a second vibration detection electrode that divide the position corresponding to the abdomen of the standing wave between the abdomens or between the nodes to the second vibration detection electrode, and the first and second vibrations. The magnitude of vibration of the vibrating body is detected by the output signal from the detection electrode 2
An ultrasonic motor having one amplitude detection circuit, an addition circuit for adding output signals from the two vibration detection circuits, and a control circuit for controlling rotation of the moving body by using an output of the addition circuit. . 4. A vibrating body composed of a piezoelectric body and an elastic body, a moving body which comes into pressure contact with the vibrating body via a pressing means, and two vibrating bodies having different phases temporally and positionally. A drive circuit for generating a drive signal for exciting an elastic traveling wave by generating a standing wave, a drive electrode for inputting the drive signal to the piezoelectric body, and the vibrating body for the piezoelectric body. A plurality of vibration detection electrodes, an amplitude detection circuit that detects the magnitude of vibration of the vibrating body based on output signals from the plurality of vibration detection electrodes, and a plurality of vibration detection circuits 2. An ultrasonic motor comprising: a selection circuit for selecting whether to use the output signal of 1) for control and a control circuit for controlling the rotation of the moving body by using the output of the selection circuit. 5. A vibrating body composed of a piezoelectric body and an elastic body, a moving body which comes into pressure contact with the vibrating body via a pressing means, and two vibrating bodies having different phases temporally and positionally. A drive circuit for generating a drive signal for exciting an elastic traveling wave by generating a standing wave, a drive electrode for inputting the drive signal to the piezoelectric body, and the vibrating body for the piezoelectric body. A plurality of vibration detection electrodes for detecting the vibration of the, and a selection circuit for selecting which output signal of the plurality of vibration detection electrodes is used for control and an output signal from the selected vibration detection electrode An ultrasonic motor comprising: an amplitude detection circuit that detects the magnitude of vibration of a vibrating body; and a control circuit that controls the rotation of the moving body. 6. A vibrating body composed of a piezoelectric body and an elastic body, a moving body that comes into pressure contact with the vibrating body via a pressing means, and two vibrating bodies having different phases temporally and positionally. A drive circuit for generating a drive signal for exciting an elastic traveling wave by generating a standing wave, a drive electrode for inputting the drive signal to the piezoelectric body, and the vibrating body for the piezoelectric body. An ultrasonic motor comprising a plurality of vibration detection electrodes for detecting the vibration of the piezoelectric body, and a common electrode provided near the inner peripheral portion of the piezoelectric body. 7. The ultrasonic motor according to claim 1, wherein the driving electrode provided on the piezoelectric body is divided into a plurality of parts. 8. The ultrasonic motor according to claim 1, wherein the vibration detecting electrode provided on the piezoelectric body is provided only on a part of the piezoelectric body in the radial direction. 9. The drive electrode provided on the piezoelectric body is divided into a plurality of parts, and at least one set of the separated drive electrodes is connected on the piezoelectric body.
7. The ultrasonic motor according to any one of 1 to 7. 10. The ultrasonic motor according to claim 6, wherein the common electrodes provided on both surfaces of the piezoelectric body are electrically connected to each other at the inner peripheral portion of the piezoelectric body. 11. The ultrasonic sensor according to claim 1, wherein the plurality of vibration detection electrodes provided on the piezoelectric body are not adjacent to each other but are located at positions substantially opposite to the center of the piezoelectric body. Sonic motor. 12. A piezoelectric body is driven by an alternating voltage to generate two standing waves having different phases in a vibrating body composed of the piezoelectric body and an elastic body to excite an elastic traveling wave. In a method of controlling an ultrasonic motor that moves a moving body that is placed in pressure contact with the vibrating body, a plurality of output signals from a plurality of vibration detection electrodes that detect elastic vibration of the vibrating body are extracted, and Converting a plurality of output signals into a signal indicating the magnitude of vibration of the vibrating body, adding signals indicating the magnitude of vibration of the vibrating body, and controlling the ultrasonic motor using the added value. Characteristic ultrasonic motor control method. 13. A piezoelectric body is driven by an AC voltage to generate two standing waves having different phases in a vibrating body composed of the piezoelectric body and an elastic body to excite an elastic traveling wave. In a method of controlling an ultrasonic motor that moves a moving body that is placed in pressure contact with the vibrating body, a plurality of output signals from a plurality of vibration detection electrodes that detect elastic vibration of the vibrating body are extracted, and A signal indicating the magnitude of vibration of the vibrating body is converted from a plurality of output signals, and a signal indicating the magnitude of vibration of the vibrating body is selected as a control signal according to the traveling direction of an elastic traveling wave excited in the vibrating body. A method for controlling an ultrasonic motor, which is characterized in that 14. A piezoelectric body is driven by an alternating voltage to generate two standing waves having different phases in a vibrating body composed of the piezoelectric body and an elastic body to excite an elastic traveling wave. In a method of controlling an ultrasonic motor that moves a moving body that is placed in pressure contact with the vibrating body, an output signal from a plurality of vibration detection electrodes for detecting elastic vibration of the vibrating body is extracted, A method for controlling an ultrasonic motor, comprising selecting from the output signal according to a traveling direction of an elastic traveling wave excited in the above, converting the output signal into a signal indicating the magnitude of vibration of the vibrating body, and controlling the signal as a control signal.