JPH0884487A - Drive circuit for vibration wave motor - Google Patents

Abstract

PURPOSE: To start a motor smoothly by prohibiting the frequency holding operation of drive voltage and the shifting operation to high frequency side for a predetermined time after application of a drive voltage to a vibration wave motor and allowing the operations when the motor is started within a predetermined time. CONSTITUTION: A CPU 24 neglects the output from magnitude comparators 22, 25 for a predetermined time after sterting application of a drive voltage to a vibration wave motor and prohibits the drive frequency holding operation and the shifting operation to high frequency side. Immediately upon elapse of the predetermined time or upon starting rotation of the motor even within the predetermined time, the drive frequency holding operation and the shift operation to high frequency side are started based on the signals from the magnitude comparators 22, 25. Consequently, the vibration motor can be started smoothly and driven stably without being driven at a frequency lower than the resonance frequency.

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 drive circuit for driving and controlling a vibration wave motor.

[0002]

2. Description of the Related Art Progressive elastic wave vibration is applied to the surface of a vibrating body by applying a plurality of high-frequency AC voltages having different phases to an electromechanical energy conversion element such as a piezoelectric element integrated with the vibrating body. Is a known vibration wave motor configured to generate vibrations and convert the vibration energy of the vibrating body into a continuous mechanical motion for output. It's been a long time since it was made. As a control method of the vibration wave motor of the above type, a method by voltage control and a method by frequency control are theoretically known, but conventionally, a control method by frequency control is generally carried out. The frequency control method is a method of controlling the speed or motion of the motor by changing the frequency of the high frequency AC voltage applied to the electro-mechanical energy conversion element, and a vibration wave motor drive based on this control method. The circuit has also been put into practical use by the applicant.

A vibration wave motor of the above type can be driven most efficiently and at a high speed when the vibrating body is in a resonance state. However, during steady operation of the motor, the vibration of the vibrating body changes from the resonance state. If the motor shifts, a phenomenon occurs in which the motor suddenly stops. Therefore, in the drive control of the motor, a drive control method that does not cause the phenomenon is required.

Therefore, as a drive control method and apparatus capable of preventing the occurrence of the above phenomenon, the applicant of the present invention said, "The vibration state of the vibrating body is monitored by the detecting means, and the vibrating state of the vibrating body is predetermined. When in the first state, the frequency of the alternating voltage applied to the element is prohibited from shifting to a frequency lower than the resonance frequency, and the vibration state of the vibrating body becomes the predetermined second state. A drive control method and a drive circuit in which the frequency of the alternating voltage is sometimes shifted in a direction higher than the resonance frequency by a predetermined amount have been proposed (Japanese Patent Application No. 63-132151).

[0005]

However, there are the following problems to be further improved in the prior art of the above proposal.

That is, the driving state of the motor is not stable within a certain time from when two alternating voltages having different phases are applied to the element of the vibrating body.
Therefore, when the drive control according to the above-mentioned prior art is performed, an erroneous signal is output from the detection means, and as a result, the frequency change of the drive signal (alternating voltage) applied to the element is prohibited. Alternatively, there is a possibility that an erroneous control operation may be performed in which the frequency is shifted to a direction higher than the resonance frequency. Therefore, if the erroneous control as described above is performed, there is a possibility that the start of the motor may be delayed or that the motor may make a jerk.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved vibration wave motor drive circuit which can solve the above-mentioned problems of the conventional vibration wave motor drive circuit. The purpose of the present invention will be specifically described below.

An object of the present invention is to provide a vibration wave motor having a vibrating body excited by an electro-mechanical energy conversion element and driven by applying a plurality of alternating voltages having different phases to the element. As a configuration for controlling,
Frequency changing means for changing the frequency of the alternating voltage; and a first output when the vibration state of the vibrating body becomes a first state close to resonance, and a resonance state further than the first state. A first detection means for generating a second output when the second state is approached, and a prohibition means for prohibiting the frequency changing operation by the frequency varying means according to the first output;
A vibration wave motor drive circuit having frequency shift means for shifting the output frequency of the frequency variable means by a predetermined value in accordance with the second output, by detecting that the vibration wave motor is in a driving state. A second detecting means for generating a third output; and a time measuring means for detecting that a predetermined time has elapsed after starting to apply the alternating voltage to the element,
Restriction means for deactivating the prohibition means and the frequency shift means when the time measuring means detects that the elapsed time from when the alternating voltage is applied to the element is within the predetermined time, The third output is generated from the second detecting means even when the time measuring means detects that the elapsed time from the time when the alternating voltage is applied to the element is within the predetermined time. A vibration wave motor drive circuit, characterized in that it has deactivation means for deactivating the regulation means and deregulation means for activating the frequency shifting means. Is to provide.

[0009]

In order to solve the above-mentioned problems, the present invention discloses that "a plurality of alternating voltages having different phases are provided on a vibration body excited by an electro-mechanical energy conversion element. As a structure for controlling a vibration wave motor driven by applying a voltage, a frequency changing means for changing the frequency of the alternating voltage and a vibration state of the vibrating body are in a first state close to resonance. Depending on the first output, first detecting means for generating a second output when the second state is closer to the resonance state than the first state. In the vibration wave motor drive circuit, there is provided a prohibiting means for prohibiting the frequency changing operation by the frequency varying means, and a frequency shifting means for shifting the output frequency of the frequency varying means by a predetermined value according to the second output. , Second detecting means for generating a third output by detecting that the vibration wave motor is in a driving state, and detecting that a predetermined time has elapsed after starting to apply the alternating voltage to the element When the time measuring means and the time measuring means detect that the elapsed time from the time when the alternating voltage is applied to the element is within the predetermined time, the prohibiting means and the frequency shift means are deactivated. Even if the time counting means detects that the elapsed time from the time when the alternating voltage is applied to the regulating means and the element is within the predetermined time, the third output is the second output. A vibration wave motor drive circuit, characterized in that it has deregulation means for deactivating the regulation means and activating the prohibition means and the frequency shift means when the detection means generates the regulation wave. " provide.

The oscillatory wave motor drive circuit of the present invention is arranged such that "the regulating means is operated within a predetermined time from when the alternating voltage is started to be applied to the element of the motor to when the drive state of the motor is expected to be unstable. And prohibiting the change prohibiting operation of the frequency of the alternating voltage and the predetermined value shifting operation of the frequency, and determining that the third output is generated from the second detecting means within the predetermined time and the motor is started. If this occurs, the restriction release means immediately prohibits the frequency from being changed and shifts the frequency by a predetermined value. "Therefore, the above-mentioned problems relating to drive control of the motor can be solved.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
In the figure, 1 is a stator (vibrating body) of a vibration wave motor.
Then, it has drive electrodes 1-1 and 1-2, a resonance state detection electrode 1-3, and a common electrode 1-4. 2 is a phase comparator,
Reference numeral 3 is a high frequency elimination filter (low-pass filter), 4 is a voltage controlled oscillator (VCO), 5 is a 32 frequency divider, and a closed loop control system constituted by these is provided as an output of the oscillator 4 to an output of an oscillator 8 described later. On the other hand, a PLL (Phase Locked Loop) that generates a 32 times frequency
It constitutes the circuit. 6 and 7 are shift registers for the phase, and 6 is for making a signal (applied signal to the drive electrode 1-2) having a 90 ° phase difference with respect to the signal applied to the drive electrode 1-1 of the vibration wave motor. And 7 is for creating a phase difference necessary for making the drive frequency follow the resonance frequency of the vibration wave motor. 9 and 10 are AND
At the gate, one input terminal is connected to the output port of the CPU 24, and the start and stop of the vibration wave motor can be controlled by the output of the CPU. AND gate 9,1
The outputs of 0 are connected to amplifiers 11 and 12, respectively, and the outputs thereof are connected to drive electrodes 1-1 and 1-2 of the vibration wave motor through coils 13 and 14, respectively. Amplifier 1
Reference numerals 1 and 12 are provided to amplify the output signals of the AND gates 9 and 10 to a voltage necessary for driving the vibration wave motor,
Further, the coils 13 and 14 are provided for forming a series resonance circuit with the electrostatic capacity of the stator electrode of the vibration wave motor to amplify the drive signal and to select only a single frequency. 1
5 and 16 are level comparators, and 15 is a drive electrode 1-
In order to know the phase of the waveform of No. 1, 16 is connected to know the phase of the waveform of the resonance state detecting electrode 1-3. The output of the shift register 7 and the output of the level comparator 16 are connected to the input terminals of the phase comparator 20, respectively. The phase comparator 20 is configured to set the output to H during the time from the rise of the output signal of the shift register 7 to the rise of the output signal of the level comparator 16, and this output signal is the enable input terminal of the counter 21. It is connected to (enable input). The clock input terminal of the counter 21 is connected to the output terminal of the VCO 4 which generates the 32 times frequency. Therefore, one count of the counter 21 corresponds to a phase difference of 11.25 °. The output of the counter 21 is the magnitude
It is connected to one of the data input terminals of the comparators 22 and 25. Data latches 23 and 26 are provided for the CPU 24.
Latch the value output by. The output is connected to the other data input terminal of the magnitude comparators 22 and 25. The value set in the latch 26 is 23.
A value higher than the value set in is set.

Magnitude comparators 22 and 25
Compares two input data, and when the data output from the counter 21 becomes smaller, outputs H to the output terminal. It is connected to the CPU 24.

In the above configuration, when the CPU 24 drives the vibration wave motor by setting one of the input terminals of the AND gates 9 and 10 to H, the phase difference according to the frequency set in the oscillator OSC8 is input to the input terminal of the phase comparator 20. To be done. If the frequency set in the OSC 8 is higher than the resonance frequency, the phase of the output signal of the level comparator 16 lags behind that in the resonance state, so the period in which the output of the phase comparator 20 becomes H becomes long. That is, the period during which the counter 21 is permitted becomes longer and the output data becomes larger. The CPU presets certain data in the data latches 23 and 26, but when the drive frequency is higher than the resonance frequency, the data output by the counter 21 is more than the data set in the data latches 23 and 26. It is set to be large. Therefore, when the drive frequency is higher than the resonance frequency, the magnitude comparators 22 and 25 output L.

Next, among the operations of the circuit of FIG. 1, those related to the present embodiment will be described with reference to FIG.

Now, a value corresponding to the phase difference θ ₂ shown in FIG. 2A is set in the data latch 23, and a value corresponding to θ ₁ is set in the data latch 26. Normally, when the vibration wave motor is started, driving is started from a high frequency and the frequency is gradually lowered. Then, the frequency f1 shown in FIG. 2A is eventually reached,
The output OUT1 of the magnitude comparator 25 becomes H as shown in FIG. 2 (b). This signal OUT1 is C
It acts on the PU 24 to stop lowering the drive frequency. That is, the CPU 24 is
Stop decreasing the frequency set in SC8. The vibration wave motor is driven at a constant frequency at this point,
When the rotation speed of the motor changes or the pressure between the stator and the rotor of the vibration wave motor changes, the resonance frequency also changes and the output OU of the magnitude comparator 22 changes.
T2 may be H as shown in FIG. This signal OUT2 means that the set frequency is too low,
The CPU 24 acts to raise the frequency set in the OSC 8 slightly. That is, the CPU 24 raises the frequency set in the OSC 8 by one step when the UT 2 becomes H. As a result, the rotational speed of the vibration wave motor is slightly reduced, so that the vibration wave motor is normally driven at high speed and stably, and is never driven at a frequency lower than the resonance frequency.

As described above, when H is output from the comparator 25, the frequency is maintained in that state, and when H is output from the comparator 22, the frequency is shifted slightly higher to drive the motor drive frequency. Is set to be lower than the resonance frequency.

However, since the driving state of the vibration wave motor is unstable within a certain time immediately after the driving frequency is applied to the vibration wave motor, the comparator 22,
An incorrect signal may be output from 25. The CPU 24, which receives this erroneous signal, carries out the operation of holding the frequency or the operation of shifting the frequency to the higher side as described above. Then, when the vibration wave motor is started, the drive frequency should be smoothly shifted from the higher side to the lower side, but it may not be shifted or may be shifted to the higher side. Therefore, the vibration wave motor may start moving slowly or be jerky.

Therefore, in this embodiment, after the drive frequency signal is applied to the vibration wave motor, the output signals of the comparators 22 and 25 are ignored within the set time.
The frequency holding operation and the shift operation to the higher frequency are not performed.

In FIG. 1, 27 is a counter, the preset terminal PRESET is connected to the CPU 24, and
The time data is preset from. Terminal CLR is CP
It connects to U24 and starts the counter in response to the output H of CPU24. The counter 27 counts the clock of the terminal CLK at the start, and when the count value reaches a certain value according to the preset value, the output OUT becomes H and the H is transmitted to the CPU 24. Reference numeral 28 is a photo interrupter, which outputs a pulse signal wave corresponding to a code or slit of a pulse plate (not shown) attached to the vibration wave motor, and transmits it to the CPU 24.

The control operation and function of the vibration wave motor drive circuit of this embodiment will be described below with reference to FIG.

<Step 1> The frequency f _O of the drive frequency signal applied to the vibration wave motor is initialized to the initial value f _S , and the counter 27 is reset.

<Step 2> It is determined whether or not the vibration wave motor is to be driven. If it is to be driven, the procedure proceeds to step 4, and if not, the procedure proceeds to step 1.

<Step 3> T _S is set as a preset value of the counter 27 and counting is started.

<Step 4> The driving direction of the vibration wave motor is set.

<Step 5> Acceleration / deceleration of the driving speed of the vibration wave motor is determined, and if acceleration is to be performed, go to Step 6.
If it is decelerating, proceed to step 14, and if it is the same speed, proceed to step 13.

<Step 6> The drive frequency f _O is compared with the minimum drive frequency f _L, and if f _O is higher, the process proceeds to step 7, otherwise the process proceeds to step 13.

<Step 7> If the counter value T _S set in Step 3 has elapsed, proceed to Step 9, otherwise proceed to Step 8.

<Step 8> If it is judged from the output from the photo interrupter 28 that the motor is rotating, the process proceeds to step 9, and if it is stopped, the process proceeds to step 10.
Go to.

<Step 9> The output of the magnitude comparator 25 is read, and if L, it is judged that the current phase difference θ is larger than the set value θ ₁ , and if it is H, it is judged that it is small and the step is judged. Proceed to 11.

<Step 10> The drive frequency f _O is updated to a value lower by fΔ.

<Step 11> The output of the magnitude comparator 22 is read, and if it is L, it is judged that the current phase difference θ is larger than the set value θ ₂ , and the process proceeds to Step 13 and H
If so, it is determined to be small, and the process proceeds to step 12.

<Step 12> Set the drive frequency f _O to fΔ '
Only update to a higher value.

<Step 13> The drive frequency f _O is output.

<Step 14> The drive frequency f _O is compared with the highest drive frequency f _H, and if f _O is lower, the process proceeds to step 15, otherwise the process proceeds to step 13.

<Step 15> The drive frequency f _O is updated to a value higher by fΔ.

By performing the control as described above, the output of the magnitude comparators 22 and 25 is ignored within a predetermined time from the start of the application of the frequency voltage to the vibration wave motor, and the drive frequency holding operation and the higher operation are performed. It is possible to smoothly start the motor by not performing the shift operation of. Further, when the motor starts to rotate after the predetermined time passes or even within the predetermined time, the signals of the magnitude comparators 22 and 25 are immediately received to enable the driving frequency holding operation and the higher shifting operation. Therefore, the vibration wave motor can be stably driven without being driven at a frequency lower than the resonance frequency.

<Correspondence between Invention and Embodiment> The "frequency changing means" of claim 1 is the "oscillator OSC8" and "C" of the embodiment.
This is a concept including "PU 24", and the "first detecting means" in claim 1 is the "magnitude comparator 22" of the embodiment.
And 25 "," counter 21 ", and" phase comparator 2 "
0 "and" level comparators 15 and 16 that generate an input signal to the phase comparator 20 ". The "prohibiting means" in claim 1 is the "means configured in the CPU 24" of the embodiment, and the "frequency shift means" in claim 1 is also the "means configured in the CPU 24" of the embodiment. .

Further, the "second detecting means" in claim 1 is the "photo interrupter 28" of the embodiment, and the "clocking means" in claim 1 is the "counter 27" of the embodiment. “Regulation means and restriction release means” of 1 is “C of the embodiment”.
Means formed in the PU 24 ".

[0040]

As described above, according to the vibration wave motor drive circuit of the present invention, "the outputs of the magnitude comparators 22 and 25 are output within a predetermined time after the drive voltage is applied to the vibration wave motor. Ignoring this, the frequency holding of the drive voltage and the shift operation to the high frequency side are prohibited, and when the motor is started within the predetermined time, the drive voltage of the drive voltage is immediately changed according to the outputs of the magnitude comparators 22 and 25. The operation of "holding the frequency and permitting the shift operation to the high frequency side" is performed, so that the motor can be started smoothly, and a stable operation state can be achieved after a smooth transient operation state.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a vibration wave motor drive circuit according to an embodiment of the present invention.

FIG. 2A is a diagram showing a relationship between a frequency and a phase of vibration of a vibrating body of a vibration wave motor and a rotation speed of the motor.
2B is a diagram showing the outputs of the magnitude comparators 22 and 25 of FIG. 1 for the vibration wave motor having the characteristic shown in FIG.

3 is a flowchart showing a control operation of a CPU 24 in the configuration of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stator 2 ... Phase comparator 3 ... High frequency removal filter 4 ... Voltage controlled oscillator 5 ... 32 frequency divider 6, 7 ... Shift register 9, 10 ... AND gate 11, 12 ... Amplifier 13, 14 ... Coil 15, 16 ... Level comparator 20 ... Phase comparator 21 ... Counter 22,25 ... Magnitude comparator 23,26 ... Data latch 24 ... CPU 27 ... Counter 28 ... Photo interrupter

Claims (1)

[Claims] 1. A structure for controlling a vibration wave motor which has a vibrating body excited by an electro-mechanical energy conversion element, and is driven by applying a plurality of alternating voltages having mutually different phases to the element. As a frequency varying means for changing the frequency of the alternating voltage, a first output is generated when the vibrating state of the vibrating body becomes a first state close to resonance, and a resonance further than the first state is generated. A first detecting means for generating a second output when the second state close to the state is achieved, and a prohibiting means for prohibiting the frequency changing operation by the frequency varying means according to the first output,
A vibration wave motor drive circuit having frequency shift means for shifting the output frequency of the frequency variable means by a predetermined value in accordance with the second output, by detecting that the vibration wave motor is in a driving state. A second detecting means for generating a third output, a clocking means for detecting that a predetermined time has elapsed after starting to apply the alternating voltage to the element, and a time when the alternating voltage is applied to the element From the time when the alternating voltage is applied to the element, the restriction means that disables the prohibition means and the frequency shift means when the elapsed time is detected to be within the predetermined time. Even when the elapsed time of is within the predetermined time is detected by the time measuring means, when the third output is generated from the second detecting means, the regulating means is deactivated and the Prohibition measures and A vibration wave motor drive circuit comprising: a restriction releasing unit that operates the frequency shift unit.