JPH0574436B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a piezoelectrically driven vibrator.

[Conventional technology and its problems]

Recently, various piezoelectric element-driven vibrators have been developed that use the expansion and contraction of the piezoelectric element obtained by applying an alternating current voltage to the piezoelectric element as an excitation source. For example, in the case of a vibration feeder, piezoelectric elements are attached to both sides of a leaf spring that connects the trough and the base, and when an alternating current voltage is applied to this, the leaf spring bends due to the expansion and contraction of these piezoelectric elements, and the trough is Vibrate. In other words, the piezoelectric element becomes the excitation source, and its frequency is the frequency of the AC power source, but this vibration feeder constitutes a two-mass vibration system consisting of the mass of the trough, the spring constant of the leaf spring, etc., and these generate natural vibrations. The number or resonant frequency is determined. The trough is normally excited with an excitation force at or near this natural frequency. That is, although a commercial power source is generally used as a driving power source, the vibration feeder is designed so that its natural frequency matches or is close to the frequency of the commercial power source. As a result, the magnitude of the excitation force required to obtain a predetermined swing width in the trough can be minimized or close to it. Therefore, the magnitude of the alternating current voltage applied to the piezoelectric element, which is the vibrating section, can be reduced, and power consumption can be reduced.

However, the trough is not supplied with any transfer material;
That is, there is no problem when the load is very small, but when the load increases to a certain extent, the amplitude of the trough becomes small even though the excitation force is constant. This is due to the synergistic effect of the increase in the weight of the vibrated body including the transferred material and the resulting fluctuation in the natural frequency. The natural frequency under no load was determined by taking into account the amount of time required.
However, if the load is constant, the objective is almost achieved, but if the load changes, the natural frequency and amplitude will change accordingly. Therefore, not only is the advantage of vibrating the trough at the natural frequency lost, but the desired effect cannot be obtained.

In addition, at the design stage of a vibration feeder, matching the natural frequency to the frequency of the AC power source used and setting the amplitude to a predetermined value imposes various design constraints, making the design that much more difficult. .

[Problem that the invention seeks to solve]

The present invention has been made in view of the above points, and it is possible to manufacture a piezoelectric element-driven vibrator driven by resonance with a simple design, and it is possible to always obtain a constant amplitude with minimum power consumption. An object of the present invention is to provide a control device for a piezoelectric element-driven vibrator. According to the present invention, this purpose is achieved by coupling the vibrated body and the base with a leaf spring, pasting a piezoelectric element on the leaf spring, and
In a control device for a piezoelectric element-driven vibrator in which an excitation source is an expansion and contraction force of the piezoelectric element obtained by applying an alternating current voltage to the piezoelectric element, a first control device for applying the alternating voltage to the piezoelectric element; A second electrode is attached to the piezoelectric element with a space between the electrode and the second electrode, the second electrode is connected to a vibration detection circuit, and the output of the vibration detection circuit is connected to the vibration of the vibrated body and the excitation. A phase detection means for detecting a phase difference between the vibration force and the excitation force, and a phase difference between the vibration and the excitation force at a natural frequency of the vibrator or a frequency close thereto, and an output of the phase detection means. The AC voltage as an output of the control circuit is supplied to a control circuit comprising a first comparison means and a second comparison means for comparing the amplitude of the vibration of the vibrated body with a predetermined amplitude, and the AC voltage as an output of the control circuit is The frequency of the excitation force is controlled to match the natural frequency or a frequency close to this based on the output of the first comparison means, and the magnitude of the excitation force is controlled based on the output of the second comparison means. This is achieved by a control device for a piezoelectric element-driven vibrator, characterized in that the amplitude of the vibration of the vibrated body is controlled so as to match the predetermined amplitude.

[Effect]

An alternating current voltage at a resonant frequency is applied to the piezoelectric element by a control circuit, and the object to be vibrated always vibrates in a resonant state. Further, the alternating current voltage is controlled so as to vibrate with a predetermined amplitude.

Since the vibrator does not have to be designed to vibrate in a resonant state with respect to an alternating current voltage of a constant frequency, its design and manufacture are easy. Cost reduction becomes possible. Furthermore, since the expansion and contraction force of the piezoelectric element is used as the drive source, the drive section is much simpler than conventional drive sections, such as electromagnetic drive sections, and the total weight is reduced. Furthermore, according to the present invention,
A second electrode is attached between the first electrode and the second electrode, and by applying the above-mentioned controlled AC voltage to the first electrode, the vibrator always vibrates at a constant amplitude in a resonant state. However, in order to detect this vibration, the vibration of the vibrated body is detected from a second electrode attached to the same piezoelectric element, so its structure is simpler than that of conventional vibration detection means. is simple, and can be connected to the control circuit simply by connecting a lead wire to the second electrode, so manufacturing is very simple and costs can be significantly reduced.

〔Example〕

First, a vibration feeder as a vibrator applied to this embodiment will be explained with reference to FIGS. 1 and 2.

In FIG. 1, a trough 1 having a linear transfer path is connected to a base 2 by a pair of front and rear piezoelectric element driving leaf spring assemblies 4a, 4b arranged at an angle. The base 2 is supported on the floor by anti-vibration rubbers 3,3.

Since the piezoelectric element driving leaf spring assemblies 4a and 4b have the same structure, only one 4a will be described as a representative.Plate-shaped piezoelectric elements 8a and 8b are attached to both sides of the main leaf spring 7, and these elements 8
Electrode layers 9a and 9b are deposited on the surfaces of electrodes a and 8b. One electrode layer 9b is provided with a slit S to form an electrode surface 10 for amplitude detection.

As shown in FIG. 2, the main plate spring 7 has bolt insertion holes 12 at its upper and lower ends, through which bolts are inserted, and the lower end is fixed to a mounting portion 6 integral with the base 2. The upper end portion is fixed to the auxiliary leaf spring 11 with bolts and nuts. The upper end of the auxiliary leaf spring 11 is fixed to a mounting portion 5 integral with the trough 1 with a bolt.

The vibration feeder applied to this embodiment is constructed as described above, and the electrode layers 9a and 9b as the first electrodes are connected to the control AC power source 20 as shown in the figure.
electrically connected to. Further, amplitude detection terminals a and b are led out from the amplitude detection electrode surface 10 as a second electrode and the main plate spring 7.

In operation, as is well known, the piezoelectric elements 8a, 8b expand and contract by applying an alternating current voltage to the electrode layers 9a, 9b, which causes the main leaf spring 7 and the auxiliary leaf spring 11 to perform a bending motion, thereby creating a trough. 1 vibrates in the direction shown by arrow C. Note that the trough width can be increased by the auxiliary leaf spring 11,
Harmful twisting of the piezoelectric elements 8a and 8b can be prevented.

Since there is a certain relationship between the amplitude of the trough 1 and the amplitude at a position corresponding to the electrode surface 10 of the piezoelectric element 8b, the amplitude of the trough 1 can be calculated from the potential generated due to distortion of the piezoelectric element 8b in this part. can be detected. That is, the amplitude of the trough 1 can be detected from the output voltage between the output terminals a and b.

FIG. 3 shows a block circuit diagram of the control device according to the embodiment.
It works in synchronization with the commercial AC power supply 14, and AC →
A gate circuit 16 that generates a pulse to control the DC output level of the DC converter 15, and a DC → DC output for exchanging the DC output of the AC → DC exchanger 15 to AC.
The AC converter 17, the amplitude detection circuit 18 for detecting the vibration of the trough 1 of the vibration feeder F, that is, the amplitude, and the phase difference between the AC output of the DC to AC converter 17 and the output of the amplitude detection circuit 18. and a comparator 1 to compare the output of this phase detector 19 with a set phase.
20 and the output of this comparator 120, PI
Performs control and generates voltage according to this magnitude
PI (Proportional Integral) controller 21 and this
A VE converter 22 receives the output of the PI controller 21 and generates a pulse with a frequency corresponding to the magnitude of the output.
A pulse distributor 23 for distributing the output pulse of the V-F converter 22 to four transistors in the DC to AC converter 17, which will be described in detail later, and the output of the amplitude detection circuit 18 are set. It consists of a comparator 24 for comparing the amplitude with the amplitude, and a PI controller 25 that receives the output of the comparator 24, performs PI control, and generates a voltage according to the magnitude.

The output of the PI controller 25 is supplied to the gate circuit 16, which controls the phase of the gate pulse for the AC to DC exchanger 15. Therefore, an AC voltage whose magnitude and frequency are controlled according to the output of the amplitude detection circuit 18 and the output of the phase detector 19 is obtained from the DC to AC converter 17, and this is applied to the piezoelectric element of the vibrating feeder F. 8a and 8b. The piezoelectric elements 8a and 8b generate an excitation force at the frequency of this alternating current and a magnitude corresponding to the magnitude of this alternating current.

Next, details of the above-mentioned AC to DC converter 15 and DC to AC converter 17 will be explained with reference to FIG. 4.

In the AC → DC exchanger 15, the diode
D ₁ , D ₂ and thyristors SCR ₁ , SCR ₂ constitute a bridge circuit, and a commercial AC power supply 14 is connected to this bridge circuit.
is connected. The gate pulse of the gate circuit 16 shown in FIG. 3 is supplied to the gate electrodes of the thyristors SCR ₁ and SCR ₂ from the gate signal supply terminal G via the diodes D ₃ and D ₄ . A rectified output in which the conduction angles of thyristors SCR ₁ and SCR ₂ are controlled by this gate pulse is obtained from the bridge circuit, and the diode
The DC output is smoothed by a smoothing circuit including D ₉ , reactor L, and capacitor C ₁ and is supplied to DC to AC converter 17 via protection circuit 30 (not shown in FIG. 3).

In the DC to AC converter 17, transistors TR ₂ and TR ₅ form one pair;
TR ₃ and TR ₄ form the other pair. Further, overvoltage absorbing diodes _D5 to _D8 are connected in parallel with each of the transistors _TR2 to _TR5 , respectively. Connection point of transistors TR ₂ and TR ₄ and diodes D ₅ and D ₇
The connection point with the transistors TR ₃ TR ₅ and the connection point with the diodes D ₆ and D ₈ are connected to one electrode surface of the piezoelectric elements 8a, 8b.
It is connected to the other electrode surface of 8b or the leaf spring 7. Base electrode B ₂ of transistor TR ₂ ~ TR _{5 ~
B5} is supplied with _a rectangular waveform pulse as _a base signal from _the pulse distributor ₂₃ in FIG. Transistor TR ₃ ,
A base signal is alternately supplied to base electrodes B ₃ and B ₄ of TR ₄ . Therefore, when one pair of transistors TR ₂ and TR ₅ are in a conductive state, the other pair of transistors TR ₃ and TR ₄ are in a non-conductive state,
Also, when transistors TR ₂ and TR ₅ of one pair are in a non-conducting state, the transistors of the other pair
TR ₃ and TR ₄ are in a conductive state.

The protection circuit 30 includes a detection coil 3 wound around the track.
5. Consists of a series circuit of a resistor R and a transistor TR ₁ , and when an overcurrent is detected by the detection coil 35, a cutoff circuit (not shown) shuts down the gate to the gate signal supply terminal G in the AC to DC converter 15. The pulse is cut off and the DC to AC converter 17
Base electrodes of transistors TR ₂ to TR ₅ in
Base signals to _B2 - _B5 are blocked. At the same time, the base electrode B ₁ of the transistor TR ₁
A base signal is supplied to the transistor TR1, and the transistor _TR1 becomes conductive, and the charge stored in the capacitor _C1 in the AC to DC converter 15 is discharged via the resistor R. This protects each of the above-mentioned circuit elements from overcurrent. Furthermore, the capacitor
The voltage between both electrodes of C ₁ may be detected, and when an overvoltage is detected, the above-mentioned protective action may be performed.

The gate circuit 16 of this embodiment is also configured as follows. That is, although not shown, when the start button of this device is pressed, a start command signal is given to the gate circuit 16, whereby the gate circuit 16 generates a gate pulse as shown in FIG. 5B. ing. 5A to 5D show temporal changes in the signals of each part immediately after startup, but the commercial AC power supply 1 shown in FIG. 5A
The phase θ of the gate pulse is configured to change as θ=180°−k ₁ t (where t is time and k ₁ is a constant) with reference to when the instantaneous value of alternating current No. 4 is zero. That is _{, as} shown in FIG _.
The output _of the _bridge circuit composed of ing. This predetermined value α is determined by the amplitude value set in the comparator 24. Although not shown, when the stop button of this device is pressed, a stop command is given to the gate circuit 16, which causes the gate circuit 16 to change as θ=α+k ₁ t until the phase of the game pulse reaches 180°.
is configured.

The above-mentioned constant k ₁ is determined in consideration of the following points. In other words, in general, when an excitation force of a certain frequency is applied to a vibrator, depending on the viscosity coefficient and the height of the natural frequency of the vibrating system, the vibration as shown in Fig. 6 A occurs when starting and stopping.
It vibrates in a transient state as shown in . Therefore, the amplitude is very large immediately after starting and immediately after stopping, and eventually reaches a steady value or zero, but such a transient state may adversely affect the desired action of the vibrator. In this embodiment, in consideration of this point, the constant _k1 is determined so that the vibrator starts and stops smoothly as shown in FIG. 6B.

Due to the gate pulse shown in FIG. 5B, a rectified output as shown in FIG. 5C is obtained from the bridge circuit in the AC to DC converter 15, and this is smoothed by the smoothing circuit to convert AC to DC. Vessel 1
5, a DC voltage as shown in FIG. 5D is obtained. This DC voltage reaches a steady value E as the phase θ of the gate pulse becomes α, but E≒k ₂ α
(k ₂ is a constant), and depending on the height of E, trough 1
Since the amplitude of trough 1 is uniquely determined, the amplitude of trough 1 is ultimately determined by α.

Next, the phase value set in the comparator 120 will be explained.

In terms of vibration engineering, the phase difference δ between the excitation force generated by the piezoelectric elements 8a and 8b and the amplitude of the trough 1 that vibrates in response to the excitation force is generally expressed by the following relational expression.

tanδ=2γλ/1−λ ² In the above equation, γ is the viscous drag coefficient of the vibration system, and λ=f/fo=frequency of excitation force/resonance frequency of the vibration system. Therefore, when f=fo, that is, when λ=1, there is a resonance state, and in this case, from the above equation, δ=‖/~/2. Further, when λ→0, δ→0, and when λ→∞, δ→‖~. Therefore, δ becomes 0→‖/~/2→‖ as f increases.
〜, but the appearance of this change is determined by the viscous drag coefficient γ
When γ=0, f=fo and δ goes from 0 to |~ in steps. However, in reality, the viscous drag coefficient γ cannot be zero, so δ=‖/~/2 in the resonance state. However, in this embodiment, the comparator 10 estimates a value slightly smaller than |/~/2 due to control stability.

Note that the AC output of the DC to AC converter 17 is applied to the piezoelectric elements 8a and 8b, and this stretching force becomes an excitation force, but the phases of the AC output and the excitation force are the same.

The control device according to the embodiment of the present invention is constructed as described above, and its operation will be explained next.

Now, when the start button (not shown) is pressed, a start command signal is supplied to the gate circuit 16, and as shown in FIG.
The gate signal as shown in the figure shows the AC to DC converter 15.
is supplied to the gate electrodes of thyristors SCR ₁ and SCR ₂ . This allows the bridge circuit to be
A rectified output as shown in FIG. .

On the other hand, a pulse with a frequency that varies depending on the difference between the output of the phase detector 19 and the set phase value at this time is transmitted from the pulse distributor 23 to the base electrodes B 2 of the transistors TR ₂ and TR ₅ in the DC to AC converter _17. ，
B ₅ and the base electrodes B ₃ and B ₄ of TR ₃ and TR ₄ are alternately supplied. Now, if this pulse is supplied to the base electrodes B ₂ and B ₅ of one pair of transistors TR ₂ and TR 5, these transistors TR ₂ and _{TR 5 become} conductive, and one electrode of the piezoelectric elements 8a and 8b becomes conductive. The surface has a positive potential. then the other pair of transistors
When a pulse is supplied to the base electrodes B ₃ and B ₄ of TR ₃ and TR ₄ , these transistors R ₃ and TR ₄ become conductive, and the other electrode surfaces of the piezoelectric elements 8a and 8b have a positive potential. In this way, an AC output having a magnitude corresponding to the level of the DC output of the AC to DC converter 15 is applied to the piezoelectric elements 8a and 8b, thereby exciting the trough 1.

At startup, a DC output with a rising characteristic as shown in FIG. 5D is supplied to the DC to AC converter 17, so that the trough 1 is started extremely stably as shown in FIG. 6B. The DC output of the AC to DC converter 15 eventually reaches a level E corresponding to the set amplitude, but if DC at this level is supplied to the DC to AC converter 17 at the same time as startup, the trough 1 Vibration starts in a transient state as shown in Figure 6A, which has a negative effect on its operation.

The phase detector 19 generates an output that detects the phase difference between the AC output of the DC to AC converter 17 and the output of the amplitude detection circuit 18, which is detected by the comparator 120.
is compared with the set phase value (in this example, a value slightly smaller than ‖/~/2), and the difference between them is set to zero.
Pulses with a frequency controlled by the PI controller 21 are supplied from the pulse distributor 23 to the DC to AC converter 17. The trough 1 is therefore controlled to vibrate at a frequency very close to the resonant frequency.

On the other hand, the output of the amplitude detection circuit 18 is compared with the set amplitude value by a comparator 24, and a gate signal whose phase is controlled by a PI controller 25 so that the difference between them becomes zero is applied to the AC to DC converter 15. As a result, the converter 15 obtains a DC output at a level corresponding to the set amplitude value. Therefore, the trough 1 will vibrate with the desired amplitude value.

As described above, in a steady state, the trough 1 is generated at a frequency approximately equal to the resonant frequency and with a desired amplitude.
is vibrating, but now the material transferred to this trough 1,
For example, assume that sand is supplied from a hopper (not shown) provided above the right end of the trough 1. The sand is transferred to the left in the figure by the transfer force caused by the vibration of trough 1, and is discharged from the left end of the trough, but when subjected to such a load, the width of trough 1 tends to become smaller and the sand is transferred. The resonant frequency of the vibration system containing the material decreases. However, according to this embodiment,
The amplitude of the trough 1 is detected by the amplitude detection circuit 18,
It is compared with the set amplitude value by the comparator 24, and the AC to DC converter 15 emits a DC output so that the set amplitude value is always reached, so that it vibrates at the desired amplitude value even in a loaded state. Although the resonant frequency decreases with the load, the excitation force at this time, that is, the AC output of the converter 1 and the amplitude (or vibration. In this sense, the amplitude detection circuit 18 can also be called a vibration detection circuit) The phase difference of decreases, but still remains resonant.

When a stop button (not shown) is pressed to stop the vibration of the trough 1, a stop command signal is supplied to the gate circuit 16. As a result, the phase θ of the gate signal is forced to change according to the equation θ=α+k ₁ t (where α is a value in a steady state with no load) until it reaches 180°. Therefore, the gate signal changes in the opposite direction to the change shown in FIG. 5B, and the AC to DC converter 1
The rectified output of the bridge circuit at 5 also changes in the opposite direction to the change shown in FIG. 5C. As a result, the DC output of the AC to DC converter 15 changes in the opposite direction to the change shown in FIG. 5D and approaches zero. Therefore, it comes to a quiet stop as shown in FIG. 6B. If the DC output level is directly reduced from E to zero without providing such a falling characteristic, the trough 1 will undergo transient vibrations as shown in FIG. 6A.

If an excessive current flows for some reason during operation of the trough 1 or at startup, this is detected by the detection coil 35 in the protection circuit 30 and a base signal is supplied to the base electrode B ₁ of the transistor TR ₁ . The transistor _TR1 becomes conductive. As a result, the charge in the capacitor _C1 is discharged through the resistor R, and the thyristor
The gate signals to the gate electrodes of SCR ₁ and SCR ₂ are cut off, and the base electrodes B ₂ - of transistors TR ₂ - _{R 5}
The base signal to _B5 is blocked. This results in
Each circuit element is protected. Although the embodiments have been described above, various modifications are possible.

For example, instead of the piezoelectric element-driven vibration feeder shown in FIGS. 1 and 2, those shown in FIGS. 7 and 8 may be applied.

7 and 8, trough 1' is connected to base 2' by drive leaf spring assemblies 20a', 20b';
Since 0b' has the same configuration, only 20a' will be explained.

That is, in this modification, only one leaf spring 10' is used in the assembly 20a', and no auxiliary leaf spring is required as in the example of FIGS. 1 and 2. The upper end of the leaf spring 10' is fixed to the block 8' by a bolt 21', and the lower end is fixed to the block 8' by a bolt 21'.
2' is fixed to the base 2'. Leaf spring 10'
Plate-shaped piezoelectric elements 11a', 11b' and 12a', 12b' are attached to both surfaces near both ends of the board, respectively, and electrode surfaces are formed on their outer surfaces (not shown), and these and the board The spring 10' is electrically connected to the above-mentioned controlled AC power source 20 as shown. Piezoelectric elements 11a', 11b', 12a', 12
The electrode surfaces b' are at the same potential, but the piezoelectric elements 11a', 11b', 12a',
The polarity of 12b' is determined. Therefore, when an alternating current voltage is applied to these electrode surfaces, the leaf spring 10'
Regarding the central part of the upper piezoelectric elements 11a', 11
The leaf spring portion to which b' is attached and the leaf spring portion to which the lower piezoelectric elements 12a' and 12b' are attached are displaced in opposite directions.

Further, as shown in FIG. 8, notches 10a' and 10b' are formed at both edges of the central portion of the leaf spring 10', thereby reducing the spring constant of the leaf spring 10'.
13 is a hole through which the bolts 21 and 22 are passed.

The vibrating feeder as described above can also be driven by the above-mentioned control device always in a resonant state and with a predetermined amplitude. In the configuration shown in FIG. 7, a part of the piezoelectric elements 11a', 11b' or 12a', 12b' may be used as the amplitude detection element as shown in FIG.

Furthermore, although the above embodiments have described a vibrating feeder, the present invention is also applicable to other piezoelectric element-driven vibrators, such as a vibrating parts feeder having a spiral track or a vibrating spiral elevator.

Furthermore, it goes without saying that the circuit of the control device is not limited to that shown in the drawings.

〔Effect of the invention〕

As described above, according to the control device for a piezoelectric element-driven vibrator of the present invention, the vibrator can always be driven in a resonant state and with a predetermined amplitude, reducing power consumption and increasing the range of use of the vibrator. can be expanded. Moreover, since it is a piezoelectric element drive type, the structure of the drive section is simplified, and the overall weight can be reduced, thereby reducing costs. In order to detect the vibration of the vibrated body, the first electrode and Since vibrations are detected from the latter of the second electrodes, the vibration detection means is extremely easy to attach, and the vibrations of the vibrated body can always be accurately detected.

[Brief explanation of drawings]

FIG. 1 is a side view of a vibration feeder to which a control device according to an embodiment of the present invention is applied, FIG. 2 is a front view of the main parts thereof, FIG. 3 is a block circuit diagram of a control device according to an embodiment of the present invention, and FIG. The figure is a detailed circuit diagram of the AC to DC converter, DC to AC converter and parts related to these in Figure 3, and Figure 5 is a graph for explaining the action of the gate circuit in Figure 3, and 6
The figure is a graph for explaining the action of the embodiment, and the seventh
FIG. 8 is a side view showing a modification of the piezoelectric element-driven vibration feeder applied to this embodiment, and FIG. 8 is a front view of the main parts thereof. In the figure, 8a, 8b, 11a', 11
b', 12a', 12b'... piezoelectric element, 18... amplitude detection circuit, 19... phase detector, 120, 24...
...Comparator.

Claims (1)

[Claims] 1. The object to be vibrated and the base are connected by a leaf spring, a piezoelectric element is attached to the leaf spring, and the expansion and contraction force of the piezoelectric element obtained by applying an alternating voltage to the piezoelectric element is used as an excitation source. In the control device for a piezoelectric element-driven vibrator, a first electrode for applying the alternating current voltage to the piezoelectric element and a second electrode spaced apart from the first electrode are attached to the piezoelectric element, and the second electrode The electrode is connected to a vibration detection circuit, and the output of the vibration detection circuit is connected to a phase detection means for detecting a phase difference between the vibration of the vibrating body and the excitation force, and a phase detection means that detects the phase difference between the vibration of the vibrating body and the excitation force, and the natural frequency of the vibrator or a frequency close to this. A first comparison means that compares the phase difference between the vibration and the excitation force at the frequency and the output of the phase detection means; and a first comparison means that compares the amplitude of the vibration of the vibrated body with a predetermined amplitude. The alternating current voltage as an output of the control circuit is supplied to a control circuit having a second comparison means, and the alternating current voltage as an output of the control circuit adjusts the frequency of the excitation force to the natural frequency or close to the natural frequency based on the output of the first comparison means. and the magnitude of the excitation force is controlled so that the amplitude of the vibration of the vibrated body coincides with the predetermined amplitude based on the output of the second comparing means. A control device for a piezoelectric element-driven vibrator, characterized in that: