JPH078154B2 - Vibration wave motor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive circuit for an oscillatory wave motor, and more particularly to an oscillatory wave for detecting a deviation amount between a resonance frequency and a drive frequency of the motor using a phase difference detection device. The present invention relates to a motor device.

[Prior art]

When driving a vibration wave motor efficiently, it is desired to drive the motor at the resonance frequency.As a method of solving this problem, the vibration state of the motor is detected by providing a monitor electrode and a signal from this monitor electrode is detected. The applicant of the present application has proposed Japanese Patent Application No. 60-226566, which controls the frequency of the drive signal so that the phase difference from the drive signal is constant.

In this type of motor, the resonance tracking control can be performed by the phase difference control in the frequency band near the resonance point, but when the starting frequency of the motor is far from the resonance point, the resonance tracking control can be performed by the phase difference control. It is inappropriate to do.

In order to solve this problem, a method of gradually lowering the frequency from the starting frequency and shifting the frequency in the resonance direction so that the frequency is set to a desired frequency can be considered. There is a possibility that the point may be crossed and the resonance point may continue to move toward a lower frequency direction.

Although the above inconvenience can be prevented to some extent by predefining the shift frequency range with the frequency setting circuit so that the above frequency shift can be performed only from the starting frequency to near the resonance frequency, the resonance frequency is determined by the external environment of the motor. However, in such a case, the frequency shifts to a low frequency beyond the resonance point.

[Object] In view of the above matters, the present invention detects the phase difference between the signal from the monitor electrode and the drive signal when the frequency setting circuit gradually lowers the frequency from the starting frequency to shift the frequency in the resonance direction. However, when the phase difference is in the vicinity of resonance, it is prohibited to shift the frequency by the frequency setting circuit toward the lower frequency side, and the driving frequency exceeds the resonance frequency due to the action of the setting circuit. It is intended to provide a vibration wave motor device which is prevented from being continuously shifted in the low frequency direction.

〔Example〕

FIG. 1 is a cross-sectional view of a vibration wave motor according to the present invention as seen from the circumferential direction. In FIG. 1, 1 is a rotor, 3 is a vibrating body, and 4 is a vibrating body. Piezoelectric bodies 5 are electrodes. The vibrating body 3 and the piezoelectric body 4 constitute a stator, and the rotor 1 is in frictional contact with the vibrating body 3.

In the electrode 5, the wavelength of the bending traveling wave in the vibrating body 3 is
Then, 5a is a driving electrode which is arranged on the piezoelectric body 4 at a λ / 2 interval, and 5b is a driving electrode which is also arranged on the piezoelectric body 4 at a λ / 2 interval. 5S is a vibration detection electrode, and the driving electrode 5a and the vibration detection electrode 5S are out of phase with each other by λ / 2 (that is, in phase). Further, the electrodes 5b and 5a are out of phase with each other by 3λ / 4, and the piezoelectric body to which the driving voltage is applied at the electrode 5a constitutes an A-phase piezoelectric body, and the driving voltage is applied at the electrode 5b. The B-phase piezoelectric body is composed of the piezoelectric body. Since the polarization treatment of these piezoelectric bodies and the electrode arrangement configuration itself are well known, detailed description thereof will be omitted.

In the above-mentioned configuration, by applying the frequency voltages of 90 ° out of phase to the electrodes 5a and 5b, progressive vibration waves are generated on the vibrating body 3, and the rotor 1 is driven by the vibration waves. To be done. This vibrating state is detected by the output signal from the piezoelectric body to which the electrode 5S is attached, and the phase difference of the signal waveform between the electrode 5S and the electrode 5a at that time is as shown by line A in FIG. That is, when the drive signal to the electrode 5a has the resonance frequency fr, the signal waveform from the electrode 5S is in a state of being -9 ° out of phase with the drive signal of the electrode 5a, and when the drive signal deviates from the resonance frequency,
As indicated by line A in FIG. 2, the phase difference between the electrodes 5a and 5S deviates from 90 °. Therefore, in the present invention, the phase difference is detected to detect the deviation of the drive frequency from the resonance frequency fr.

The resonance frequency and the phase difference between the signals of the electrodes 5a and 5S are
It deviates from the above −90 ° depending on the positions of the electrodes 5a and 5a.
Since there is a specific relationship between the phase difference of the signal of, the detection of the deviation from the specific phase difference of the signal between the electrodes 5a and 5S can also detect the deviation of the drive frequency from the resonance frequency fr in this case as well. Becomes

FIG. 3 is a circuit diagram showing an embodiment of the drive circuit for the vibration wave motor according to the present invention.

In the figure, 2 is a stator of the vibration wave motor shown in FIG. 12 is a voltage controlled oscillator that oscillates at a frequency according to the input voltage, 14 is an amplifier, 16 is a matching coil, and the frequency signal from the oscillator 12 is applied to the electrode 5a via these amplifiers and coils. Reference numeral 7 is a comparator for shaping the waveform of the output of the amplifier 14 through the coil 16 (that is, the voltage waveform applied to the stator of the vibration wave motor) into a pulse signal, and 8 is for shifting the pulse from the comparator 7 by 90 °. In the shift register, the pulse from the register 8 is transmitted through the rotation direction switching switch 13 to the amplifier 15 and the coil.
It is applied to the electrode 5b via 17. Electrode 5a with the above configuration
Frequency voltages with 90 ° different phases are applied between and 5b. 18
In the edge trigger type phase comparator, the output of the oscillator 12 is input as one input of the comparator 18, and the output of the N frequency dividing circuit (32 frequency dividing circuit) 21 is input as the other input.
Reference numeral 20 denotes a voltage controlled oscillator that generates a frequency according to the output of the comparator 18 via the lag lead filter 19. The comparator 18 is in an open state when the phase difference between the input signals is zero, maintains the output of the oscillator 20 in that state, and when a phase difference occurs between the input signals, the phase shift direction and the amount of the phase difference are changed. Accordingly, signals with different duties are output to increase or decrease the output frequency of the voltage controlled oscillator 20. With this configuration, the two inputs of the comparator 15 are controlled to have the same phase, and as a result, the output of the frequency divider circuit 21 has the same phase as the output of the oscillator 12 and the same frequency. Therefore, the output of the oscillator 20 becomes an N signal (32 signals) of the output frequency of the oscillator 12, and since this signal is the clock signal of the shift register 8, the output of the N / 4th stage of the register 8 is a comparator. The output of the oscillator 7, that is, the output of the oscillator 12, becomes a signal having a 90 ° phase difference, and as described above, the electrode 5b
A frequency signal with a phase difference of 90 ° is supplied between points 5a and 5a.

Reference numeral 6 is a comparator for shaping the signal from the electrode 5S into a pulse waveform, and 9 is an edge trigger type phase comparator, which is constructed as shown in FIG. 4 (a). The comparator has inputs R ₁ , V
Detecting the _first pulse phase, the input R ₁ FIG. 4 (b) the phase difference low and without the output V ₁ when the phase of the input R ₁ is ahead input V ₁ as indicated, conversely When the phase is delayed from the input V ₁ , the output D _{1 is set} to the phase difference low level, and when the phases are further matched, the output V ₁ , D ₁
Both send out a high level. The output waveform of the other output terminal out of the comparator 9 with respect to the inputs R ₁ and V ₁ is as shown in FIG. 25 is an open or closed rape control switching switch, and in the open loop control mode, the output out of the comparator 9 and the filter 11
In the closed loop control mode, the output out of the comparator 9 is connected to the filter 11. Reference numeral 12 is a voltage controlled oscillator whose output frequency is variable in accordance with the signal from the output out of the comparator 9 in the closed loop control mode. Reference numeral 10 is an AND gate connected to the outputs U ₁ and D ₁ of the comparator 9, 22 is a reset terminal connected to the NAND gate 10, and when the output of the NAND gate 10 is at a high level, the reset state is released and the clock pulse of the oscillator 20 is generated. Counter for counting, 24 for numerical information setting device, 23 for counter 22
It is a comparator that compares the count value of and the set value of the numerical information setting device and outputs a high level when the count value <the set value. Reference numeral 27 is a micro computer which sends a switching signal for switching the switch 25 to the closed loop mode when the high level is continuously sent from the comparator 23 for a predetermined time or longer.

Reference numeral 26 is a setting circuit for setting the free-running frequency f ₀ of the oscillator 12.

Next, the operation of the embodiment shown in FIG. 3 will be described.

First, it is assumed that the open loop / closed loop control switching switch 25 is set to the open loop mode. In this state, the voltage-controlled oscillator 12 oscillates at the free-running frequency f ₀ (higher than the mechanical resonance frequency fr of the vibration wave motor) independently of the output of the phase comparator 9. The signal from the voltage controlled oscillator 12 is applied to the electrode 5a of the vibration wave motor through the amplifier 14 and the coil 16. Further, the signal from the oscillator 12 is shaped by the A-phase comparator 7, and then input to the shift register 8 which shifts by a clock signal N times the frequency f ₀ .

As a result, ± 90 from the input signal from the register 8
A signal shifted by ゜ (± N / 4 steps) is taken out and passed through an amplifier 15 and a coil 17 via a switch 13 and an electrode of a vibration wave motor.
Apply signal to 5b.

By the above operation, the output of the oscillator 12 is applied to the electrode 5a, and the signal having a 90 ° phase shift with respect to the applied signal of the electrode 5a is applied to the electrode 5b.

In this way, when frequency voltages of 90 ° different phases are applied between the electrodes 5a and 5b, standing waves are formed in the A phase and B phase of the piezoelectric body, respectively, which are combined to generate a progressive vibration wave. Then, the rotor is driven.

Further, in this state, a frequency signal corresponding to the vibration state of the motor is generated from the electrode 5S, and the phase difference relationship between the signal waveforms of the electrode 5S and the electrode 5a at this time is the frequency to the driving electrode 5a. The relationship is as shown in FIG. That is, the resonance frequency fr
When driven by, the waveform relationship between electrodes 5S and 5a is −
It becomes 90 °, and its electrode corresponds to the deviation from the resonance frequency.
The phase difference relationship between 5S and 5a is as shown by line A in FIG.

The upper phase comparator 9 in which the signal from the electrode 5S is shaped by the comparator 6 to detect the phase difference between the electrodes 5S and 5a
An output of the oscillator 12 providing a driving signal to the electrode 5a is input to the R ₁ input at top register 8 of shaping by the comparator, is 90 degree phase shift at the register 8, the shift signal Is input to the input V ₁ of the comparator 9.

Since the frequency is now f ₀ > fr, there is a phase difference between the input signals to the comparator 9. Therefore, in this state, the output V ₁ or D ₁ of the comparator 9 intermittently outputs the low level, and the NAND gate 10 intermittently outputs the high level. The high level period from the NAND gate 10 is longer as the phase difference between the inputs R ₁ and V ₁ is larger, and the counter 22 is released from the set by the high level from the NAND gate 10. The number of clock pulses from the high-level period oscillator 20 is counted, and the count value indicates a value corresponding to the phase difference. This count value is compared with the set value of the setting device 24, and when the count value <the set value, a high level is sent from the comparator 23.

Assuming that the count value> the set value, the comparator 23 sends a low level, and the low level causes the computer 27 to send an instruction to decrease the set value of the setting device 26, thereby decreasing the output frequency of the oscillator 12. In this way, when the count value> the set value, the output frequency of the oscillator 12 gradually decreases and the resonance frequency fr approaches, and when the count value becomes the count value <the set value, the comparator is activated.
23 sends out a high level.

When the high level from the comparator 23 is detected by the computer 27, the switching switch 25 is switched to the open loop mode by an instruction from the computer.

In the closed loop mode, the output out of the comparator 9 is the filter 11
To the oscillator 12, and the output frequency of the oscillator 12 is controlled thereafter according to the signal from the output out of the comparator 9.

In the closed rape control, the output out of the comparator 9 exhibits the Y output characteristic as shown in FIG. Therefore, if the output of the electrode 5S and the signal of the electrode 5a differ by 90 ° or more, the output ou of the comparator 9
t becomes a high level and the frequency of the oscillator 12 is increased, whereby the signal of the electrode 5a is controlled so that the phase advances from the output of the electrode 5S, that is, the phase difference becomes 90 °.
Output ou of the comparator 9 where the signal phase difference between 5 and 5a is within 90 °
When t becomes low level, the frequency of the oscillator 12 is lowered to shift the phase difference between the signals of the electrodes in the 90 ° direction. With the above operation, in closed loop control, the phase difference between the signals of the electrodes is
Controlled to be 90 °.

[Modification] In the embodiment, if the outputs of the output terminals U ₁ and D ₁ of the comparator 9 are individually detected and the time when the low level is sent from each of the output terminals is detected, the lead or lag of the phase is detected. The directionality of can also be detected, and the frequency shift direction can also be detected.

Further, the set value of the setting device 24 is further increased each time a low level is sent from the comparator 23, that is, every time the counter value> the set value is detected, and the set value when the count value <the set value is reached. By reading, it is possible to read the amount of deviation of the frequency as a number.

[Effect]

As described above, according to the present invention, when the frequency setting circuit gradually lowers the frequency from the starting frequency to shift the frequency in the resonance frequency direction, the resonance frequency is detected by detecting the phase difference between the drive voltage and the monitor signal. Since the shift operation by the above setting circuit was prohibited when it became close,
It is possible to prevent the driving frequency from exceeding the resonance point and continuously shifting to a low frequency.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a vibration wave motor according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the present invention, and FIG. 3 is an implementation of a drive circuit for the vibration wave motor of the present invention. A circuit diagram showing an example, FIG. 4 (a) is a circuit diagram showing the configuration of the comparator 9 shown in FIG. 3, and FIG. 4 (b) is a waveform diagram explaining the operation of the comparator shown in FIG. 4 (a). 5 (a) to 5 (c) are waveform charts for explaining the operation of the comparator shown in FIG. 4 (a). 9 …… Comparator, 10 …… Nand gate 22 …… Counter, 23 …… Comparator 24 …… Setting device

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-61-251490 (JP, A) JP-A-56-10792 (JP, A) JP-A-62-203574 (JP, A) JP-A-63- 56178 (JP, A) JP 61-87428 (JP, A) JP 52-35621 (JP, A) REVIEW OF SCIENTIFIC INSTRUMENTS, Vol. 57, No. 57 11, November 1986, P.M. 2886-2890 (Fig. 6) "Ultrasonic motor actuator" by Trikeps, December 12, 1986, p. 70 to 71 (Figs. 14 and 15)

Claims (1)

[Claims] 1. A vibration wave motor device in which driving frequency signals having different phases are applied to a vibrating body on which a piezoelectric body is arranged to excite the vibrating body to obtain a vibrating wave, and the vibrating wave is used as a driving force. In, a vibration detection electrode for detecting a signal generated in the piezoelectric body, a detection circuit for detecting a phase difference between the signal from the electrode and the driving frequency signal, and a frequency of the driving frequency signal at a resonance frequency. Frequency setting circuit that varies in a predetermined range in the resonance frequency direction from a higher predetermined frequency, and the detection circuit when the frequency set by the setting circuit changes from a frequency higher than the resonance frequency to the resonance frequency direction The vibration characterized by having a prohibition circuit for prohibiting the setting of the frequency in the low frequency direction by the setting circuit when the phase difference detected in step 4 has become a predetermined phase difference indicating the vicinity of the resonance frequency. Wave motor equipment.