JPH08107687A - Oscillatory wave motor - Google Patents

Abstract

PURPOSE: To make it possible to drive a motor at a drive frequency which makes the efficiency of electromechanical energy conversion almost the maximum even though environmental temperature or an alternating voltage applied changes. CONSTITUTION: A motor comprises an electromechanical transducer for converting electrical energy to mechanical energy; an elastic member 1 that vibrates according to the mechanical displacements of the transducer; exciting circuits 6A and 6B for applying an alternating voltage through an inductance element having a predetermined inductance to the electromechanical transducer; and a circuit for varying the inductance or equivalent inductance of the exciting circuits so that a predetermined relation can be maintained between the frequency of the alternating voltage that maximizes the transducer efficiency and the resonance frequency determined by the equivalent circuit of the exciting circuit and the electromechanical transducer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration wave motor called an ultrasonic motor or a piezoelectric motor.

[0002]

2. Description of the Related Art Conventionally, this type of vibration wave motor applies an alternating voltage to an element such as a piezoelectric element or an electrostrictive element that converts electrical energy into mechanical energy (hereinafter simply referred to as an electromechanical conversion element). By doing so, it was driven by utilizing the mechanical vibration of the electromechanical conversion element. The vibration wave motor is classified into a standing wave type motor and a traveling wave type motor according to the form of vibration generated in the electromechanical conversion element.

FIG. 9 is a circuit diagram showing a drive circuit of a conventional traveling wave type vibration wave motor. The vibrating body 1 is composed of a combination of two sets of electromechanical conversion elements and an elastic body, and an alternating voltage is applied thereto via the electrodes 1a, 1b, 1c. The oscillator 2 is for generating an alternating voltage, and its output is branched and one is connected to the amplifier 4A and the other is connected to the amplifier 4B via the π / 2 phase shifter 3. The outputs of the amplifiers 4A and 4B are connected to the inductance elements 5A and 5B that form the excitation circuit, respectively.

As shown in FIG. 9, the vibrator 1 is composed of two sets of electromechanical conversion elements, and the phase of the alternating voltage applied to each electromechanical conversion element is ± π by the π / 2 phase shifter 3.
Since there is no difference other than a shift of / 2 rad, a drive circuit for a vibrating body composed of a pair of electromechanical conversion elements is shown in FIG.
Will be explained.

FIG. 10 is a circuit diagram for explaining the operation of a conventional vibration wave motor. The equivalent circuit 7 of the vibrating body 1 is an LCR series circuit of the mechanical vibration part (equivalent coil of self-inductance Lm, equivalent capacitor of electrostatic capacity Cm, resistance value R).
equivalent resistance of m) and an equivalent capacitor of the intrinsic capacitance Co connected in parallel with these.

The rectangular signal of frequency f generated from the oscillator 2 is amplified by the amplifier 4A into a rectangular voltage having a large amplitude voltage difference, and applied to the inductance element 5A. At this time, a high-voltage alternating sine voltage is applied to the vibrating body 1 between the electrodes 1a and 1c due to resonance of the intrinsic capacitance Co of the vibrating body 1 and the inductance element 5A.
This vibrating body 1 converts electric energy into mechanical energy of vibration by an electromechanical conversion element, and the vibration wave motor is driven by utilizing this vibration.

Such a vibrating body 1 is driven by an alternating voltage having a frequency fe, which is most efficiently determined from the equivalent constants (Lm, Cm, Rm, Co) of the vibrating body 1 and is capable of electromechanical energy conversion. Is desirable. On the other hand, the size of the inductance element 5A is determined to be a predetermined value according to the equivalent circuit constant of the vibrating body 1.

FIG. 11 shows the frequency of the alternating voltage (hereinafter referred to as the driving frequency), the current value I (solid line) flowing through the inductance element 5A and the vibrating body 1 in FIG. 10, and the electro-mechanical energy of the vibrating body 7. The conversion efficiency η (broken line) (hereinafter referred to as the conversion efficiency η) is shown. The drive frequency fe that maximizes the conversion efficiency η exists between the two resonance frequencies f1 and f2 that maximize the current value I (f1 <fe <.
f2). The relative relationship between the frequencies f1, f2 and fe is determined by the equivalent constants (Lm, Cm, Rm, Co) of the vibrating body 1 and the size of the inductance element 5A.

For example, the equivalent constant (L
m, Cm, Rm, Co) is constant, and the frequency characteristic when the value of the inductance element 5A is reduced is shown in FIG.
FIG. 12B shows the frequency characteristic when the value of the inductance element 5A is increased in FIG. FIG. 12 (a),
In both (b), the value of fe is almost the same, whereas in (a) of the figure, f1 and f2 move to the high frequency side, and f1 and f
The frequency difference of e becomes small (the frequency difference between f2 and fe becomes large). This tendency becomes more remarkable as the value of the inductance element 5A becomes smaller, and approaches f1 = fe as much as possible. On the other hand, in the same figure (b), f1 and f2 move to the low frequency side, and the frequency difference between f2 and fe becomes small (f1 and fe
The difference in frequency will increase). This tendency becomes more remarkable as the value of the inductance element 5A increases, and f2 = f
Get closer to e. Similarly, the inductance element 5A
Even when the value of is constant, the equivalent constant (L
m, Cm, Rm, Co), f1, f2,
The relative relationship of fe changes.

[0010]

Generally, the equivalent circuit constants (Lm, Cm, Rm,
Co) changes depending on the environmental temperature of the vibration wave motor or the temperature of the electromechanical conversion element (hereinafter simply referred to as “temperature”) and the magnitude of the applied alternating voltage.
Even when the value of the inductance element 5A is selected such that the relative relationship between 1, f2 and fe is as shown in FIG. 11, when the temperature or the magnitude of the alternating voltage changes, this relative relationship changes as follows.

For example, FIG. 12A corresponds to the case where the temperature of the vibration wave motor is lowered. However, although the frequency fe at which the conversion efficiency η is maximum moves to the low frequency side, f1,
Since it is smaller than the movement amount of f2, it is ignored. Such a change in the relative relationship between the frequencies f1, f2 and fe shows a similar tendency when the applied alternating voltage is reduced. On the other hand, FIG. 12B corresponds to the case where the temperature of the vibration wave motor rises. However, although the frequency fe at which the conversion efficiency η is maximum moves to the high frequency side, f1, f
Since it is smaller than the movement amount of 2, it is ignored. Such a change in the relative relationship between the frequencies f1, f2 and fe is
A similar tendency is exhibited when the applied alternating voltage is increased. As is clear from the figure, in FIG.
And the value of fe approaches, and the current value I at fe increases. Further, in FIG. 12B, as the values of f2 and fe approach each other, the current value I at fe increases.

In such a case, the following problems occur. As a well-known characteristic of a vibration wave motor, when the current flowing through the vibration body exceeds a certain value, the vibration body 1
Vibration becomes unstable, the conversion efficiency η is extremely lowered, and further, the rotation of the motor is stopped. This characteristic is represented by the curve of the conversion efficiency η in FIGS. 11, 12A, and 12B that is sharply lowered.
For this reason, when the states of FIGS. 12 (a) and 12 (b) proceed, as shown in FIGS. 13 (a) and 13 (b), driving is performed at the maximum value frequency fe of the ideal conversion efficiency curve (dashed line). There was a problem that I could not.

An object of the present invention is to provide a vibration wave motor which can be driven at a driving frequency which maximizes the conversion efficiency of electromechanical energy even when the environmental temperature or the applied alternating voltage changes.

[0014]

In order to solve the above-mentioned problems, the invention of claim 1 vibrates by an electromechanical conversion element for converting electric energy into mechanical energy and a mechanical displacement of the electromechanical conversion element. In a vibration wave motor including an elastic body and an excitation circuit that applies an alternating voltage to the electromechanical conversion element via a dielectric element having a predetermined inductance, the conversion efficiency of the electromechanical conversion element is substantially maximum. The inductance of the excitation circuit or an equivalent inductance thereof so that the frequency of the alternating voltage and the resonance frequency determined by the equivalent circuit of the excitation circuit and the electromechanical conversion element are maintained in a predetermined relative relationship. It is characterized in that it has an inductance variable section for changing the size of the.

According to a second aspect of the present invention, in the vibration wave motor according to the first aspect, the inductance variable section of the excitation circuit is arranged in accordance with the environmental temperature of the vibration wave motor or the temperature of the electromechanical conversion element. It is characterized in that the magnitude of the inductance or equivalent inductance is changed.

The invention of claim 3 is the invention of claim 1 or claim 2.
In the vibration wave motor described in the paragraph [1], the inductance varying unit changes the magnitude of the inductance of the excitation circuit or an equivalent magnitude of inductance in accordance with the magnitude of the alternating voltage.

[0017]

In the present invention, the alternating voltage is applied to the drive electrode of the vibration wave motor through the excitation circuit that changes the inductance value or the equivalent inductance value to an ideal value. Even if the temperature or the applied alternating voltage changes, it can be driven at a driving frequency that maximizes the conversion efficiency of electro-mechanical energy.

[0018]

【Example】

(Embodiment 1) Hereinafter, the present invention will be described in detail with reference to the drawings and the like. FIG. 1 is a circuit diagram showing a first embodiment of a vibration wave motor according to the present invention. In addition,
In FIG. 1, the same symbols as in FIG. 9 represent members having the same function. The vibration wave motor of the first embodiment has the inductance element 5A of the conventional drive circuit shown in FIG.
Instead of 5B, the excitation circuits 6A and 6B having variable inductance values or equivalent inductance values are connected to the electrodes 7a,
Amplifiers 4A and 4B are connected by 7b, and the vibrating body 1 is connected by electrodes 1a and 1b, respectively.

In this embodiment, two excitation circuits 6
Since A and 6B have the same configuration and function, one side (6A)
Will be described only. In the first embodiment,
As shown in FIG. 2, the excitation circuit 6A includes a plurality of inductance elements L1 having the same or different inductance values.
L2, L3 (inductance values λ1, λ2,
λ3) are connected in series, and the inductance element L
One terminal of 1 is connected to the external electrode 7a, and one terminal of the inductance element L3 is connected to the external electrode 1a. Such inductance elements L1, L2, L
Examples of the method 3 include a method of using a plurality of independent coils, a method of using a plurality of intermediate taps, and a coil wound around the same bobbin or core.

Further, the inductance elements L1, L2, L
As shown in FIG. 2, switch elements S1 and S2 are respectively connected between the connection points of the three electrodes and the external electrode 1a. Opening / closing of these switch elements S1 and S2 is controlled by the control circuit 8.

The control circuit 8 has therein a temperature detecting section and a detecting section for detecting the magnitude of the alternating voltage applied to the vibrating body 1, and based on the information from these detecting sections,
It is a circuit that controls the opening and closing of the switch elements S1 and S2.

In such an excitation circuit 6A, the magnitude L of the inductance between the external electrode 1a and the electrode 7a is λ1 + λ2 + when all the switch elements S1 and S2 are open.
λ3, λ2 + λ3 when only the switch element S1 is closed, and λ3 when only the switch element S2 is closed, so that it is possible to change to three kinds of values.

First, the operation of the present embodiment will be described only when the temperature changes. For example, assume that the temperature range in which the vibration wave motor is to be operated is divided into three ranges of low temperature, medium temperature, and high temperature. The control circuit 8 detects this temperature, and when the temperature is in the low temperature range, all the switch elements S1,
Control is performed so that S2 is opened, and only the switch element S1 is closed in the medium temperature range, and only the switch element S2 is closed in the high temperature range.

First, in the medium temperature range, the switch element S1
Is closed, an alternating voltage is applied to the vibrating body 1 of FIG. 1 via an inductance whose size is λ2 + λ3. The magnitude of this inductance (λ
2 + λ3) is an equivalent circuit constant (Lm, Cm, Rm, C of mechanical vibration of the vibration wave motor if the temperature is in the medium temperature range.
0) is changed and the relative relationship between the frequencies f1, f2, and fe is also changed, the value is set to a predetermined value so that the driving can be performed at the frequency fe that maximizes the conversion efficiency η.

When the temperature falls from this state to reach the low temperature range, all the switch elements S1 and S2 are
, The size of the vibrating body 1 is λ1 + λ2
An alternating voltage will be applied through the inductance of + λ3. The magnitude of this inductance (λ1
+ Λ2 + λ3), the equivalent circuit constant of the mechanical vibration of the vibration wave motor changes within the range of low temperature and the frequencies f1 and f
Even if the relative relationship between 2 and fe changes, it is possible to drive at the frequency fe at which the conversion efficiency η is almost maximum.
It is set to a predetermined value.

On the contrary, when the temperature rises and reaches the high temperature range, the switch element S2 is closed,
An alternating voltage is applied to the vibrating body 1 via an inductance whose size is λ3. The magnitude of the inductance λ3 is such that even if the relative relationship between the frequencies f1, f2 and fe changes due to a change in the equivalent circuit constant of the mechanical vibration of the vibration wave motor in the low temperature range, It is set to a predetermined value so that it can be driven at the frequency fe at which the conversion efficiency η becomes almost maximum.

Then, the control circuit 8 detects the magnitude of the alternating voltage in the same manner when it responds to the change in the applied alternating voltage, so that the conversion efficiency η of the vibrating body 1 does not drop sharply. The switch elements S1 and S2 are controlled so that the magnitude of the inductance having a predetermined value is selected. When the alternating voltage is large and a rapid decrease in conversion efficiency η is expected, the opening / closing of the switch elements S1 and S2 is controlled so that the inductance value becomes small, and conversely,
When the alternating voltage is small, and when the conversion efficiency η is expected to drop sharply, the opening / closing of the switch elements S1 and S2 is controlled so that the inductance value becomes large.

When the temperature and the alternating voltage change at the same time, the switch element S is selected so that the optimum inductance value is selected in advance from the combination of the temperature and the alternating voltage.
The opening and closing patterns of S1 and S2 are recorded in a memory device,
The control circuit 8 may control the opening and closing of the switch elements S1 and S2 accordingly.

The first embodiment has been described by using an example in which three inductance values can be selected in order to correspond to the three temperature ranges and the magnitude of the applied alternating voltage value. However, the present invention is not limited to this. The number of inductance elements and switching elements are arranged as shown in FIG. 3 so that four or more inductance values can be selected, and a wider temperature range and applied alternating voltage value are used. It is possible to correspond to. Of course, two inductance values may be selectable by using two inductance elements and one switch element, and the inductance may be selected depending on the operating temperature range of the vibration wave motor and the applied alternating voltage range. The size and number of may be set.

(Second Embodiment) FIG. 4 is a circuit diagram showing an exciting circuit of a vibration wave motor according to a second embodiment. In the second embodiment, a plurality of inductance elements (L1, L2, ..., Ln) having different inductance values are used, one ends of which are both connected to the electrode 1a, and the other ends thereof are
Switch elements (S1, S2, ..., Sn) are connected in series. All switch elements (S1, S2, ..., S
The other end of n) is connected to the external electrode 7a.

The control circuit 8 has the same function as that of the first embodiment, and like the first embodiment, the external electrode 7a depends on the temperature of the vibration wave motor and the applied alternating voltage. −
An inductance element (L1, L2, ..., Ln) having a predetermined inductance value between 1a is selected, and control is performed so that only the switch element connected to the inductance element is closed. Further, if a plurality of switch elements are simultaneously closed by an appropriate combination, it is possible to configure a new inductance value by connecting the inductance elements in parallel. In this way, by combining a plurality of inductance elements and switching elements, it is possible to selectively insert inductance elements having different values between the amplifier 4A and the vibrating body 1.

In the first and second embodiments,
Two examples of the combination of the inductance element and the switch element have been described, but the combination method is not limited to these, and in order to realize the present invention,
It is sufficient that the inductance value can be changed.

(Third Embodiment) FIG. 5 is a circuit diagram showing an exciting circuit of a vibration wave motor according to a third embodiment. In the third embodiment, the excitation circuit 6A includes one end of one inductance element L (whose value is λ), as shown in FIG.
A plurality of capacitive elements having different capacitance values (C1, C2, ..., C
n) are switching elements (S1, S2, ..., Sn), respectively.
5 through each other as shown in FIG. 5 (the capacitive element described here may be a general capacitor).

The other end of the inductance element L is connected to the external electrode 1a, and all capacitive elements (C1, C2,
, Cn) is connected to the external electrode 7a at the other end. The switch element S0 has one end connected to the electrode 7a and the other end connected to the inductance element L without a capacitive element. Opening and closing of the switch elements S0, S1, ..., Sn are controlled by the control circuit 8.

The control circuit 8 has the same function as that of the first and second embodiments described above, and has a temperature detecting section and an alternating voltage value detecting section applied to the vibrating body therein. Based on the information from those detection units, the switch element S
0, S1, ..., Sn are controlled to be opened and closed. The reactance of a circuit in which an inductance element L having a value of λ and a capacitive element having a capacitance value of c is connected in series is ω (λ−ω ⁻² c ⁻¹ ) (1) ( However, ω = 2πf, f: drive frequency), which is smaller by ω ⁻¹ c ⁻¹ than when only the inductance element is used (ωλ), and becomes smaller as the capacitance value c is smaller. This has the same effect as reducing the inductance value equivalently.

Therefore, the capacitive elements (C1, C2,
, Cn) has a capacitance of C1>C2>...> Cn,
Consider the magnitude of equivalent inductance between the external electrodes 7a-1a. First, when only the switch element S0 is closed, the inductance value is naturally λ, and thereafter, by selecting the switch elements to be closed as S1, S2, ..., Sn, the equivalent inductance value becomes small. On the other hand, the control circuit 8 detects the temperature and the magnitude of the alternating voltage in the same manner as the above-described embodiment, and the conversion efficiency η does not suddenly decrease with the increase in the current flowing through the vibrating body 1 in a predetermined equivalent manner. The switch element is controlled so that a typical inductance value is selected. Since the capacitive element is used in the third embodiment, there is an advantage that it is smaller and less expensive than the inductance element.

As described above, as the switch element used in the first to third embodiments, a mechanical relay, a semiconductor relay or the like can be used. Further, it is also possible to use a temperature-sensitive reed switch or the like that opens and closes the switch element by sensing the temperature by itself without depending on the control circuit 8. Furthermore, since these excitation circuits have no directivity, it does not matter which of the two external electrodes is 7a or 1a.

(Embodiment 4) In the first to third embodiments, an example is given in which discrete inductance values or equivalent inductance values are selected. In each of the following embodiments, the case where the value of the inductance is continuously variable according to the temperature will be described. FIG. 6 is a diagram showing a fourth embodiment of the vibration wave motor according to the present invention. In the fourth embodiment, the coil 11 in which an electric wire is wound around a toroidal magnetic core having a size of the gap 11a of δ is used. The value of the inductance of this coil 11 is expressed by the following equation. λ≈μ ₀ AN ² δ ^-1 (2) (μ ₀ : permeability of vacuum A: cross-sectional area of magnetic core N: number of coil turns)

From this equation (2), the size δ of the void 11a
It can be seen that the inductance value λ becomes smaller as is increased. Therefore, when used in the present invention, the gap 11a may be made larger as the temperature rises. As this method, a suitable substance 12 having a positive coefficient of thermal expansion may be inserted into the void 11a, and the magnitude of δ may be controlled by the substance 12.

Since the substance 12 expands in the vertical direction in FIG. 6 when the temperature rises, the coil 11 has a large void 11a and a small inductance value.
As the substance 12, a shape memory alloy having a large coefficient of thermal expansion can be used.

Further, as shown in FIG. 7, a material 15 having a large thermal expansion coefficient and a thickness of t is fixed so that the position of the magnetic core 14 having a large relative permeability in the solenoid coil 13 is changed.
Even if it is installed between the magnetic core 6 and the magnetic core 14, the same effect can be obtained. Further, even if the substances 12 and 15 are piezoelectric bodies and the thickness thereof is electrically changed, the same effect can be obtained. In this case, the inductance value can be changed by changing the thickness of the applied voltage. In a toroidal coil or a solenoid coil having no air gap, its inductance value increases in proportion to the relative magnetic permeability of the core. Therefore, a core material having a negative relative permeability temperature coefficient may be selected. For example, Mn
Examples thereof include core materials such as -Zn ferrite and Fe-Ni alloys.

(Fifth Embodiment) FIG. 8 is a diagram for explaining a fifth embodiment of the vibration wave motor according to the present invention. The fifth embodiment is a transformer 1 having a mutual induction coefficient (coupling coefficient) of M.
6 is arranged, the inductance value on the primary side is λ1, and the two terminals are connected to the external electrodes 7a, 1a. The inductance value on the secondary side is λ2, and a resistor having a resistance value R is connected between the two terminals. The magnitude of the equivalent inductance between the terminals 7a and 1a is expressed by the following equation. λ 1 −ω ² M ² λ ² (R ² + ω ² λ ^{2 2} ) ^-1 (3)

Here, since it is possible to bring the above-mentioned mutual induction coefficient M close to 1, if M = 1 and omitted from equation (3), the inductance value between the electrodes 7a-1a is equivalent to L1. It is equal to (λ ² + R ² / ω ² λ ² ) ⁻¹ , and when R = ∞, the electrode 7 a
The inductance value between -1a is .lambda.1, and the equivalent inductance value decreases as the resistance value R decreases. Therefore, in this embodiment, a resistance element whose resistance value increases as the temperature rises may be used as the resistance R in FIG. As such a resistance element, a PTC (Positive T
A thermistor etc. can be used. Further, a resistance element whose resistance value can be electrically changed discretely or continuously based on the result of detecting the temperature or the alternating voltage value may be used.

As described above, in the present invention,
The inductance of the excitation circuit or equivalent inductance value so that the frequency of the alternating voltage that maximizes the conversion efficiency of electric-mechanical energy and the resonance frequency determined by the equivalent circuit of the excitation circuit and the vibration body maintain a predetermined relative relationship. Should be variable, and the method is not limited to the above embodiments. Further, the present invention can be applied to any type such as a linear type or an annular type as long as it is a vibration wave motor. Further, the vibration of the electromechanical conversion element is transmitted via the horn to the wedge-shaped vibrating piece that is in contact with the rotor surface at a small angle, and the present invention can also be applied to the wedge-shaped rotor that rotates the rotor.

[0045]

As described in detail above, according to the present invention, an alternating voltage is applied to the drive electrode of the vibration wave motor through the excitation circuit that changes the inductance value or equivalent inductance value to an ideal value. Therefore, there is an effect that even if the temperature of the vibration wave motor or the applied alternating voltage changes, the vibration frequency motor can always be driven by the drive frequency that maximizes the conversion efficiency of the electromechanical energy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a drive circuit for a vibration wave motor according to the present invention.

FIG. 2 is a circuit diagram showing an excitation circuit of the vibration wave motor according to the first embodiment.

FIG. 3 is a circuit diagram showing a modification of the excitation circuit of the vibration wave motor according to the first embodiment.

FIG. 4 is a circuit diagram showing an excitation circuit of a vibration wave motor according to a second embodiment.

FIG. 5 is a circuit diagram showing an excitation circuit of a vibration wave motor according to a third embodiment.

FIG. 6 is a circuit diagram showing an excitation circuit of a vibration wave motor according to a fourth embodiment.

FIG. 7 is a circuit diagram showing a modification of the excitation circuit of the vibration wave motor according to the fourth embodiment.

FIG. 8 is a circuit diagram showing an excitation circuit of a vibration wave motor according to a fifth embodiment.

FIG. 9 is a circuit diagram showing an example of a conventional vibration wave motor.

FIG. 10 is a circuit diagram illustrating an operation of a conventional vibration wave motor.

FIG. 11: Characteristics of current flowing in the vibrating body with respect to the alternating voltage frequency applied to the vibrating body of the vibrating wave motor and electricity of the vibrating body.
It is a figure explaining the conversion efficiency characteristic of mechanical energy.

FIG. 12 shows the characteristics of the current flowing in the vibrating body with respect to the alternating voltage frequency applied to the vibrating body of the vibrating wave motor, and the electricity of the vibrating body.
It is a figure explaining the conversion efficiency characteristic of mechanical energy.

FIG. 13 shows the characteristics of the current flowing through the vibrating body with respect to the alternating voltage frequency applied to the vibrating body of the vibrating wave motor, and the electricity of the vibrating body.
It is a figure explaining the conversion efficiency characteristic of mechanical energy.

[Explanation of symbols]

 1 Vibrating body 1a, 1b, 1c Electrode 2 Oscillator 3 Phase shifter 4A, 4B Amplifier 5A, 5B Inductance element 6A, 6B Excitation circuit 7a, 7b Electrode 8 Control circuit L, L1, L2, ..., Ln Inductance element S0, S1 , S2, ..., Sn switch element C1, C2, ..., Cn capacitive element

Claims (3)

[Claims] 1. An electromechanical conversion element for converting electric energy into mechanical energy, an elastic body vibrating by mechanical displacement of the electromechanical conversion element, and a dielectric element having a predetermined inductance in the electromechanical conversion element. In an oscillatory wave motor including: an excitation circuit that applies an alternating voltage via the excitation circuit, the frequency of the alternating voltage at which the conversion efficiency of the electromechanical conversion element is substantially maximum, and the equivalent of the excitation circuit and the electromechanical conversion element. A vibration wave including an inductance variable section that changes the magnitude of the inductance of the excitation circuit or an equivalent inductance so that the resonance frequency determined by the circuit and the resonance frequency are maintained in a predetermined relative relationship. motor. 2. The vibration wave motor according to claim 1, wherein the variable inductance section has an inductance or an equivalent inductance of the excitation circuit according to an environmental temperature of the vibration wave motor or a temperature of the electromechanical conversion element. A vibration wave motor characterized in that the magnitude of the inductance is changed. 3. The vibration wave motor according to claim 1, wherein the inductance variable section sets the inductance of the excitation circuit or the equivalent inductance according to the magnitude of the alternating voltage. Vibration wave motor characterized by changing.