JP2000032783A - Drive control device for vibrating-wave device and vibrating-wave motor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive control device for vibrating-wave device which is capable of proper drive control through phase difference detection. SOLUTION: The drive control device is provided with a first controlling means which varies the frequency of an alternating signal applied to the piezoelectric element of a vibrating-wave device and thereby controls driving speed, a second controlling means which stops the variation of the frequency based on the phase difference between a signal of detection of the actual state of vibration and the alternating signal, and a third controlling means which controls driving speed by a method different from that using the variation of frequency after the stop of the variation of the frequency. The second controlling means is so arranged that it is not actuated until the above-mentioned detection signal detects the specified state of vibration (steps 106, 107).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a vibration wave device and a vibration wave motor device.

[0002]

2. Description of the Related Art A vibrating body in a vibration wave device such as a vibration wave motor is, for example, a type in which a piezoelectric element as an electro-mechanical energy conversion element is bonded or sandwiched and fixed to an elastic body.
Alternatively, a type composed only of a piezoelectric element has been proposed, and by applying an alternating signal as a drive signal to a piezoelectric element as an electro-mechanical energy conversion element, for example, a plurality of bending vibrations are formed on a vibrating body, By forming a plurality of bending vibrations, a circular or elliptical motion is formed on the driving surface of the vibrating body.

Various types of piezoelectric elements have been proposed depending on the shape of the vibrating body. For example, in the case of a ring-shaped vibrating body, the piezoelectric element is polarized so as to have a predetermined phase relationship with the ring-shaped piezoelectric element. It has two groups of drive piezoelectric elements that have been processed, a vibration detector that uses electrodes (empty electrodes) that are not used for drive, and the like.

The frequency of the drive signal and the number of rotations (rotational speed) are suitable for control because the high frequency side is gradual from the resonance frequency at which the number of rotations reaches a peak. Has a driving characteristic that the frequency increases and the number of rotations decreases as the frequency increases.

[0005] As the vibration wave device, for example, a sheet member such as paper is brought into contact with the driving surface of the vibrating body and conveyed, or a moving body or the like is brought into pressure contact with the vibrating body to rotate the moving body. Alternatively, there has been proposed a type in which the contact body is a fixed body (for example, a rail shape) and the vibrating body is moved with respect to the fixed body.

As a drive control method of such a vibration wave device, there is a method of controlling a rotation speed by changing a drive frequency. In this drive control method, the vibration state of the vibration wave device (the vibration state of the vibrating body) is simultaneously detected, and the amount of change in the drive frequency is limited so that the input power does not exceed.

[0007] This is because the rotational speed changes due to the fluctuation of the load torque, and the input power is excessive only by controlling the rotational speed.

More specifically, the drive frequency of the vibration wave motor is gradually lowered from the initially set high frequency.
At the same time as detecting the rotational speed of the vibration wave motor by the encoder, the vibration state of the vibration wave motor is detected by detecting the phase difference between the output voltage waveform of the free electrode of the piezoelectric element of the vibration wave motor and the input voltage waveform of the vibration wave motor. (Depending on the position of the vacant electrode and the positional phase of the driving piezoelectric element portion, the phase difference increases or decreases as the resonance state is approached), and when at least one of the detection signals reaches the first predetermined value, vibration occurs. The driving frequency of the wave motor is stopped to be lowered to stop the acceleration.

Thereafter, when the at least one of the detection signals reaches a second predetermined value, the drive frequency of the vibration wave motor is increased to control the rotational speed of the vibration wave motor to decrease.

[0010]

However, the above-described drive control is performed immediately after the drive of the vibration wave motor is started (immediately after the start).
Therefore, the vibration amplitude of the vibration wave motor is very small, and the phase difference between the output voltage waveform of the empty electrode of the piezoelectric element of the vibration wave motor and the input voltage waveform of the vibration wave motor may lack accuracy (this In this case, since the output voltage waveform of the empty electrode is very small, an accurate phase difference cannot be obtained. Therefore, the phase difference may be the first predetermined value to be compared. Therefore, at that time, the control for lowering the driving frequency of the vibration wave motor is stopped, and as a result, the acceleration of the vibration wave motor is not performed, and there is a problem that the predetermined rotation speed is not reached.

[0011] In a remarkable case, the rotational speed is significantly different from the original rotational speed (control is performed in a lower frequency region than the resonance point), and a so-called malfunction may occur.

An object of the invention according to the present application is to provide a drive control device of a vibration wave device and a vibration wave motor device which can perform appropriate drive control by detecting a phase difference.

[0013]

A first configuration of a drive control device of an oscillatory wave device for realizing the object of the invention according to the present application is as follows.
First control means for controlling the driving speed by changing the frequency of an alternating signal applied to the electro-mechanical energy conversion element of the vibration wave device, and a phase difference between a detection signal of an actual vibration state and the alternating signal. A second control means for stopping the change of the frequency based on the second control means, and a third control means for controlling the driving speed after the stop of the change of the frequency by a method different from the change of the frequency. The control means does not operate until the detection signal detects a predetermined vibration state.

A second configuration of the drive control device of the vibration wave device for realizing the object of the invention according to the present application is that the drive is performed by changing the frequency of an alternating signal applied to the electromechanical energy conversion element of the vibration wave device. First control means for controlling the speed, second control means for stopping the change in the frequency based on the phase difference between the detection signal of the actual vibration state and the alternating signal, and after stopping the change in the frequency. And a third control means for performing the drive speed control by a pulse width modulation method, wherein the second control means does not operate until the detection signal detects a predetermined vibration state.

A third configuration of the drive control device of the vibration wave device for realizing the object of the invention according to the present application is characterized in that the second control means sets the vibration state at a frequency higher than the resonance frequency to a predetermined vibration state. Is what you do.

According to a fourth configuration of the drive control device of the vibration wave device for realizing the object of the invention according to the present application, the actual vibration state includes an output voltage waveform of an electric signal converted by an electro-mechanical energy conversion element. Of the amplitude.

A first configuration of a vibration motor device for realizing the object of the invention according to the present application is provided with an electro-mechanical energy conversion element for vibration detection and an electro-mechanical energy conversion element for driving. A driving signal is applied to the conversion element to obtain a driving force, and a vibration state is detected by detecting a phase difference between the drive signal applied to the conversion element for driving and the signal from the conversion element for detection. Then, in the vibration wave motor device for regulating the frequency of the drive signal, while applying a drive signal to the conversion element in response to a pulse,
First speed control means for changing the frequency of the drive signal by changing the frequency of the pulse to change the speed, and second speed control means for changing the duty by changing the duty of the pulse.
Speed control means, a level detection means for detecting an output signal level from the conversion element for detection, and when a phase difference becomes a predetermined phase difference during frequency change by the first speed control means. Prohibiting means for prohibiting the shift of the frequency of the pulse to a lower frequency, the second speed control means being provided after the prohibition means has inhibited the shift in the frequency decreasing direction. And when the output level detected by the level detecting means is equal to or less than a predetermined value, the prohibiting means is held inactive regardless of the phase difference.

According to a second configuration of the vibration motor device for realizing the object of the invention according to the present application, the device comprises a speed detecting means for detecting a speed of the motor, a target speed and a speed detected by the speed detecting means. Comparing means for comparing speeds, wherein the second speed control means increases the duty when the detected speed is lower than the target speed based on the output of the comparing means,
When the detected speed is higher than the target speed, the duty is changed to a small value, and when the duty reaches a predetermined minimum value, the second speed control means is shifted to an inactive state. Speed control is restarted.

According to a third configuration of the vibration motor device for realizing the object of the invention according to the present application, the first speed control means includes:
Based on the output of the comparing means, the frequency at which the detected speed is lower than the target speed is decreased, and the frequency at which the detected speed is higher than the target speed is increased.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 and 2
Shows a first embodiment in which the vibration wave device of the present invention is applied to a vibration wave motor.

In the control block diagram shown in FIG. 1, 1 is a control circuit composed of a microcomputer, 2 is an oscillation circuit which can vary the oscillation frequency by the output of the control circuit 1,
Numeral 3 indicates that the output of the oscillation circuit 2 is PWM-controlled by the output of the
(Pulse width modulation). 4 and 5 are PW
This is an output circuit that amplifies the output of the M circuit 3 with power.

Reference numeral 6 denotes a position / speed detection circuit, which is a photo interrupter 2 having light emitting and receiving elements (not shown) arranged on both sides of a light shielding plate 22 which rotates integrally with the rotation of the vibration wave motor 21.
The rotational position and rotational speed of the vibration wave motor 21 are detected from the output of the light receiving element 3.

The piezoelectric element disposed on the vibrating body of the vibration wave motor 21 includes an A electrode 21a to which a drive signal (A-phase drive signal) from the output circuit 4 is applied, and a drive signal (B-phase drive) from the output circuit 5. B electrode 21b to which a drive signal is applied, an empty electrode (vibration detection electrode) S, an electrode G1 provided on the opposite side to these electrodes (disposed opposite to the A electrode 21a and the S electrode), G2 (disposed opposite to the B electrode 21b).

Reference numeral 7 denotes a phase difference detection circuit for detecting a phase difference between output signals of the vibration wave motor 21. A drive signal applied to the electrodes A and B of the piezoelectric element and a detection of a vibration state from the electrode S are detected. Signals are input respectively.

The resistances 11, 12, the resistances 13, 14, the resistances 15, 1 connected to the input side of each signal of the phase difference detection circuit 7
The voltage is divided by a voltage dividing resistor constituted by 6 to an inputtable voltage, and a DC voltage component is removed by capacitors 8, 9 and 10, and a signal having an accurate waveform is inputted. The driving voltage applied to the electrodes A and B of the vibration wave motor 21 is increased by the coils 17 and 18 and the capacitors 19 and 20. A power supply voltage detection circuit 24 detects the power supply voltage of the output circuits 4 and 5 and transmits the detected power supply voltage to the control circuit 1.

An amplitude detecting circuit 25 detects the vibration amplitude of the vibration body of the vibration wave motor based on the vibration state detection signal (output voltage from the electrode S) detected by the sensor electrode S. In the above configuration, the control circuit 1 includes a position / speed detection circuit 6, a phase difference detection circuit 7, a power supply voltage detection circuit 2,
4. Based on the output of the amplitude detection circuit 25, the oscillation frequency of the oscillation circuit 2 and the duty ratio of the PWM circuit 3 are changed as described later.

In FIG. 2, a waveform (b) is a reference oscillation signal in the oscillation circuit 2, which is 1 / (1) of the period applied to each piezoelectric element.
It is Tfrq / 4 in a cycle of four times.

In FIG. 2, waveforms (c) and (d) are two output signals from the oscillation circuit 2 to the PWM circuit 3, and have a period Tfrq from the reference oscillation signal of waveform (b).
The signals are 90 degrees out of phase necessary for driving the vibration wave motor 21 of FIG.

The waveforms (e) and (f) in FIG.
The output signals to the output circuits 4 and 5 of the M circuit 3 vary the ON and OFF times according to the duty ratio set by the output of the control circuit 1 for the signals of the waveforms (c) and (d). ing. The signal (e) rises at the rise of the signal (c) and falls at the rise of the signal (d). On the other hand, the signal (f) rises when the signal (d) rises, and falls when the signal (c) falls. Incidentally, in this embodiment, the duty ratio is 25%.

FIGS. 3 to 6 are motor diagrams showing input / output characteristics of the vibration wave motor according to the first embodiment of the present invention. FIG. 3 shows curves A1, A2, A3 of the driving frequency f and the rotation speed N. FIG. 4 shows a curve B1 of the driving frequency f and the input power P,
B2 and B3. The curves B1, B2, and B3 are set so that the inputs are different depending on the PWM3.
These correspond to the outputs of curves A1, A2, and A3, respectively.

In this embodiment, the voltage applied to the vibration wave motor is made substantially constant, and the input current is changed by changing the duty of the high frequency applied voltage by the PWM 3.

In FIG. 4, for example, the duty of the curve B3 is set to 50% of the maximum, so that the output of the curve A3 of the driving frequency f and the rotation speed N can take the maximum value.

Next, the curve B1 is obtained by setting the duty to a sufficiently small value by the PWM 3 so that the curve A1 of the driving frequency f and the rotation speed N shown in FIG. 3 can obtain a sufficiently small output. As a result, the start (start) frequency can be set low, so that the duty is 50%.
Therefore, the input power P can be made sufficiently smaller than in the case of (1).
The curve B2 has a duty between the curves B1 and B3, and corresponds to the curve A2 representing the relationship between the drive frequency f and the rotation speed N.

FIG. 5 shows curves C1, C2, and C3 of the drive frequency f and the phase difference θ representing the vibration state of the vibration wave motor. In this embodiment, the phase difference signal representing the vibration state of the vibration wave motor is It is a phase difference between the output voltage waveform and the input voltage waveform of the electrode S of the piezoelectric element of the wave motor.

When the duty of the high frequency applied voltage is changed by the PWM 3, the curve of the drive frequency f and the phase difference θ representing the vibration state of the vibration wave motor also changes. For example, the curve C3 corresponds to the output of the curve A3 of the drive frequency f and the rotation speed N with the duty set to 50% of the maximum.

Next, in the curve C1, the duty is set to a sufficiently small value by the PWM 3 so that the curve A1 of the drive frequency f and the rotation speed N can obtain a sufficiently small output. At this time, it is necessary to take care that the phase difference does not become smaller than a predetermined phase difference so that the vibration state of the vibration wave motor is stabilized.

The curve C2 corresponds to the curve A2 representing the relationship between the drive frequency f and the rotation speed N at an intermediate duty between the curves C1 and C3.

FIG. 6 shows input / output characteristics, which are curves S1, S2, and S3 of the drive frequency f and the amplitude S representing the vibration state of the vibration wave motor.
S3. When the duty of the high frequency applied voltage is changed by the PWM 3, the curve of the drive frequency f and the amplitude S representing the vibration state of the vibration wave motor also changes. For example, the curve S3 corresponds to the output of the curve A3 of the drive frequency f and the rotation speed N with the duty set to 50% of the maximum. Next, the curve S1 corresponds to the output of the curve A1 of the driving frequency f and the rotation speed N. The curve S2 corresponds to a curve A2 representing the relationship between the driving frequency f and the rotation speed N at an intermediate duty between the curves S1 and S3.

The above-mentioned phase difference signal has high accuracy when the vibration amplitude of the vibration wave motor is larger than a predetermined value.
When the amplitude is small, the error becomes large. Therefore, when the phase difference signal is used, the amplitude output needs to be larger than a predetermined value.

Next, the operation of the first embodiment of the present invention will be described with reference to the flow chart of FIG. 7 and the motor diagram showing the input / output characteristics of the vibration wave motor of FIGS.

In FIG. 7, when a drive start command to the vibration wave motor comes, in step (101), the duty of the PWM control is changed to the start duty (at the time of starting which is set in advance based on the output of the power supply voltage detection circuit 24). (Duty), and proceeds to step (102).

In step (102), the drive frequency is set to the start frequency fa (FIG. 3), and the flow advances to step (103).

In step (103), the drive frequency is lowered by a predetermined amount, and the flow advances to step (104).

In step (104), the rotational speed of the vibration wave motor is detected, and it is determined whether the speed is lower than the set speed. If the speed is lower, the process proceeds to step (105). Otherwise, the process proceeds to step (114). . Since the vibration wave motor is not rotating at the initial stage of the startup, the process proceeds to step (105).

In step (105), the output voltage waveform of the piezoelectric element of the vibration wave motor is detected, and it is determined whether the amplitude is larger than a predetermined amplitude.
Go to 6), otherwise return to step (103).

At the initial stage of starting, the amplitude of the vibration wave motor cannot be detected so small that the process returns to step (103).
Step (104) and Step (105) are repeated,
Thereby, acceleration is performed.

Then, the driving frequency is fb (FIGS. 3 and 6).
And the vibration wave motor starts to rotate. Even if the vibration wave motor starts to rotate, the amplitude is still smaller than the predetermined output, so that the process normally returns to step (103).

When the vibration wave motor starts rotating, in step (104), at the start of acceleration,
Since the number of revolutions (motor speed) is usually lower than the set speed, the process proceeds to step (105). In the case of minute drive, the process may proceed to step (114) by speed servo.

In step (106), the phase difference (FIG. 5) between the input voltage waveform of the vibration wave motor and the output (signal from the electrode S) voltage waveform of the piezoelectric element is detected, and it is determined whether the phase difference is smaller than a predetermined phase difference. If it is smaller, the process proceeds to step (107); otherwise, the process proceeds to step (10).
Return to 3). At the start of acceleration, since the phase difference is large, the process returns to step (103) and this operation is repeated to perform acceleration.
When this operation is further repeated and acceleration is performed, if it is determined in step (104) that the rotation speed has become faster than the set rotational speed, the flow proceeds to step (114).

In step (107), the frequency is fixed, the driving frequency is fc (FIG. 3), the rotational speed of the vibration wave motor is N1, and the process proceeds to step (108).

In step (108), the rotational speed of the vibration wave motor is detected to determine whether the rotational speed is lower than the set speed. If the rotational speed is lower than the set speed, the process proceeds to step (109). Otherwise, the process proceeds to step (112).

In step (109), the duty of the PWM control is increased by a predetermined amount from the start duty, and the routine proceeds to step (110). The vibration wave motor is further accelerated, and the rotation speed increases from N1 to N2 (FIG. 3).

In step (110), it is determined whether or not the rotational speed of the vibration wave motor is faster than the set speed. If it is faster, the process proceeds to step (111), otherwise, the process proceeds to step (116). At the start of acceleration, such as at the beginning of startup, the rotation speed is low, so the flow proceeds to step (116).

In step (116), it is determined whether the duty is equal to or greater than the upper limit value. If the duty is equal to or greater than the upper limit value, the process proceeds to step (117), and otherwise, returns to step (109). Since the duty is low at the beginning of the acceleration, the process returns to the step (109) and this operation is repeated to perform the acceleration. When the duty eventually reaches the upper limit value, the duty is fixed in step (117), and the duty is fixed in step (11).
Return to 0). At this time, the rotation speed of the vibration wave motor reaches N3 (FIG. 3).

In step (110), if the rotational speed of the vibration wave motor is lower than the set speed, step (1)
16), step (117) and step (110) are repeated, so that the rotational speed of the vibration wave motor remains at N3 and does not increase any more (the limit speed of the motor).

When it is time to start deceleration for stopping, in step (110), it is determined that the rotational speed of the vibration wave motor is faster than the set speed, and
Proceed to 1).

In step (111), the duty is reduced by a predetermined amount by the PWM control, and step (11)
Proceed to 2). At this time, the rotation speed of the vibration wave motor decreases from N3 to N2 (FIG. 3).

In step (112), it is determined whether the duty is the start duty. If the duty is the start duty, the process proceeds to step (113); otherwise, the process returns to step (110). At the beginning of deceleration, since the duty is sufficiently larger than the start duty, step (11)
0), and returns to step (111) and step (11).
2) Repeat step (110). Eventually, when the duty becomes the start duty, it is determined in step (112), and the process proceeds to step (113). At this time, the rotation speed of the vibration wave motor decreases from N2 to N1 (FIG. 3).

In step (113), it is determined whether or not the rotational speed of the vibration wave motor is faster than the set speed. If it is faster, the process proceeds to step (114); otherwise, the process returns to step (109). Normally, since the deceleration is further continued toward the stop, the process proceeds to step (114), and the drive frequency of the vibration wave motor is increased by a predetermined amount, and the process proceeds to step (1).
Proceed to 15).

In step (115), it is determined whether or not there is a command to stop the rotation of the vibration wave motor. If it is stopped, the driving is terminated. Otherwise, step (104) is performed.
Return to Then, step (104), step (114), and step (115) are repeated toward the stop. When the stop command of the vibration wave motor is issued, the driving ends.

The above operation is a simple representative example from the start to the end of driving. However, during the acceleration or deceleration,
It is also possible to perform acceleration / deceleration so as to follow a preset speed table, or to perform so-called speed servo that performs acceleration / deceleration to match a constant speed.

[0062]

As described above, according to the present invention,
When controlling the rotation speed by changing the drive frequency of a vibration wave device such as a vibration wave motor, the phase difference signal is used after reaching a predetermined amplitude, so a malfunction due to a large error in the phase difference signal when the amplitude is small When the predetermined phase difference is reached, the original control of the vibration wave device such as the vibration wave motor, in which the PWM control is performed to control the driving speed of the vibration wave device such as the vibration wave motor, can be realized. .

Further, according to the present invention, as compared with the conventional system in which only the drive frequency of a vibration wave device such as a vibration wave motor is changed to control the drive speed (rotation speed), the vibration wave in a high frequency region is particularly high. Power consumption at a frequency at which a vibration wave device such as a motor is not driven (rotated) can be greatly reduced, and an excellent effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a drive circuit according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of each part in FIG.

FIG. 3 is a characteristic diagram showing a relationship between frequency and rotation speed.

FIG. 4 is a characteristic diagram showing a relationship between frequency and input power.

FIG. 5 is a characteristic diagram showing a relationship between a frequency and a phase difference.

FIG. 6 is a characteristic diagram showing a relationship between frequency and input characteristics.

FIG. 7 is a flowchart showing the operation of the first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 control circuit 2 oscillation circuit 3 pulse width modulation (PWM) circuit 4, 5 output circuit 6 position / speed detection circuit 7 phase difference detection circuit 8, 9, 10, 19, 20 capacitor 11 to 16 resistor 17, 18 coil 21 vibration Wave motor (USM) 22 Light shielding plate 23 Photo interrupter 24 Power supply voltage detection circuit 25 Amplitude detection circuit

Continuation of the front page F term (reference) 5H680 AA06 AA09 BB13 CC02 DD01 DD15 DD23 DD53 DD59 DD87 EE21 EE22 EE23 EE24 FF08 FF23 FF25 FF27 FF30 FF33 FF38

Claims (7)

[Claims] 1. A first control means for controlling a driving speed by changing a frequency of an alternating signal applied to an electro-mechanical energy conversion element of a vibration wave device, a detection signal of an actual vibration state, and the alternating signal. Second control means for stopping the change in the frequency based on the phase difference with the control signal, and third control means for controlling the drive speed after the stop of the change in the frequency by a method different from the change in the frequency. The second control means does not operate until the detection signal detects a predetermined vibration state. 2. A first control means for controlling a driving speed by changing a frequency of an alternating signal applied to an electro-mechanical energy conversion element of a vibration wave device, a detection signal of an actual vibration state, and the alternating signal. A second control means for stopping the change of the frequency based on a phase difference between the control signal and a third control means for controlling the driving speed after the stop of the change of the frequency by a pulse width modulation method, The second control means does not operate until the detection signal detects a predetermined vibration state. 3. The drive control device for a vibration wave device according to claim 1, wherein the second control unit sets a vibration state at a frequency higher than a resonance frequency to a predetermined vibration state. 4. The vibration wave device according to claim 1, wherein the actual vibration state is an amplitude of an output voltage waveform of an electric signal converted by an electro-mechanical energy conversion element. Drive control device. 5. An electro-mechanical energy conversion element for detecting vibration and an electro-mechanical energy conversion element for driving are provided. A driving signal is applied to the conversion element for driving to obtain a driving force, and a driving force is obtained. A vibration wave motor device that detects a phase difference between a drive signal applied to the conversion element unit and a signal from the conversion element for detection, detects a vibration state, and regulates the frequency of the drive signal. A first speed control unit for changing the frequency of the drive signal by changing the frequency of the pulse and changing the speed while changing the frequency of the pulse, and changing the duty of the pulse. A second speed control means for changing the speed by performing the operation, a level detection means for detecting an output signal level from the conversion element for detection, and a frequency change by the first speed control means. Prohibiting means for prohibiting shifting of the frequency of the pulse to a lower frequency when the phase difference becomes a predetermined phase difference, wherein the prohibiting means prohibits the shifting in the frequency decreasing direction. After that, the speed control by the second speed control means is started, and when the output level detected by the level detection means is equal to or less than a predetermined value, the prohibition means is disabled regardless of the phase difference. A vibration wave motor device characterized by being held. 6. The apparatus according to claim 1, further comprising: a speed detecting means for detecting a speed of the motor; and a comparing means for comparing a target speed with a speed detected by the speed detecting means. When the detected speed is lower than the target speed based on the output of the comparing means, the duty is increased, and when the detected speed is higher than the target speed, the duty is changed to a small value and the duty reaches a predetermined minimum value. 6. The vibration wave motor device according to claim 5, wherein the second speed control means is shifted to an inactive state when the speed control is performed, and the speed control by the first speed control means is restarted. 7. The first speed control means, based on the output of the comparison means, decreases the frequency at which the detection speed is lower than the target speed, and increases the frequency at which the detection speed is higher than the target speed. The vibration wave motor device according to claim 6, wherein: