JP3268710B2 - Vibration wave motor drive circuit - Google Patents

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 driving circuit for driving and controlling a vibration wave motor.

[0002]

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

A vibration wave motor of the above type can be driven at the highest efficiency and at a high speed when the vibrating body is in a resonance state. However, during the 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.

[0004] Therefore, as a drive control method and apparatus capable of preventing the above-mentioned phenomenon from occurring, the applicant of the present application has stated that "the vibration state of the vibrating body is monitored by a detecting means, and the vibration state of the vibrating body is determined to be a predetermined value. 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 is in a predetermined second state. Sometimes the frequency of the alternating voltage is shifted by a predetermined amount in a direction higher than the resonance frequency ”(Japanese Patent Application No. 63-132151).

[0005]

However, the prior art proposed above has the following problems to be further improved.

That is, the driving state of the motor is not stable within a certain time after the start of applying two alternating voltages having different phases to the element of the vibrating body,
Therefore, when the driving control according to the above-described prior art is performed, an erroneous signal is output from the detection unit, and as a result, a change in the frequency of the driving signal (alternating voltage) applied to the element is prohibited. Alternatively, an erroneous control operation of shifting the frequency to a direction higher than the resonance frequency may be performed. Therefore, if the erroneous control is performed as described above, the start of the motor may be delayed, or the motor may perform a jerky movement at the start.

[0007]

An object of the present invention is an object of the invention, Ru der to provide an improved vibration wave motor driving circuit capable of solving the problems of the conventional vibration wave motor driving circuit described above.

[0008]

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a vibrating body excited by an electro-mechanical energy conversion element, and a plurality of alternating voltages having different phases from each other are applied to the element. As a configuration for controlling the vibration wave motor driven by being applied, a frequency variable means for changing the frequency of the alternating voltage and a vibration member
Phase difference between the signal from the detection electrode and the alternating voltage
Detects and generates a first output when the vibration state of the vibrating body is in a first state close to resonance, and generates a first output when the vibration state is in a second state closer to resonance than the first state. First detecting means for generating a second output, inhibiting means for inhibiting a frequency changing operation by the frequency varying means in accordance with the first output, and output of the frequency varying means in response to the second output. A frequency shifter that shifts the frequency by a predetermined value, in a vibration wave motor drive circuit having a second detection unit that generates a third output by detecting that the vibration wave motor is in a rotating state, A timer for detecting that a predetermined time has elapsed since the start of applying the alternating voltage to the element; and a timer for detecting that an elapsed time since the application of the alternating voltage to the element is within the predetermined time. When detected by means A prohibiting means and a regulating means for disabling the frequency shift means, and a case where it is detected by the timing means that the elapsed time from when the alternating voltage is applied to the element is within the predetermined time. Even if the third output is generated from the second detection means, the control means includes a restriction release means for disabling the restriction means and operating the prohibition means and the frequency shift means. It is characterized by the following.

In the conventional vibration wave motor drive circuit, the drive
Phase, the phase detection result is not stable, so it is far from resonance.
Nevertheless, the prohibition means and shift means are activated.
Cormorants but fear had, in the present invention, the predetermined time period from the start
During the period, the prohibition means and shift means are inoperative and malfunction
While the specified time has not elapsed since startup.
Even if it detects that the motor is rotating,
The stopping means and the shifting means are brought into the operating state. Because of this
The motor is rotating even when the specified time has not elapsed
If it is determined that the prohibition means and the shift means are
The resonance of the motor while it is rotating.
Too low frequency and the motor stops.
And prevent.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.
In the figure, reference numeral 1 denotes a stator (oscillator) of a vibration wave motor.
, And 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 denotes a high-frequency rejection filter (low-pass filter), reference numeral 4 denotes a voltage-controlled oscillator (VCO), and reference numeral 5 denotes a 32 frequency divider. PLL (Phase Locked Loop) that generates 32 times frequency
Make up the circuit. 6 and 7 are shift registers for the phase, and 6 is for generating a signal (a signal applied to the drive electrode 1-2) having a phase difference of 90 ° with respect to a signal applied to the drive electrode 1-1 of the vibration wave motor. Numeral 7 is for creating a phase difference necessary for causing the drive frequency to follow the resonance frequency of the vibration wave motor. 9 and 10 are AND
One input terminal of the gate 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 output of 0 is connected to amplifiers 11 and 12, respectively, and the output is further connected to drive electrodes 1-1 and 1-2 of the vibration wave motor through coils 13 and 14. 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.
The coils 13 and 14 are provided to amplify the drive signal by forming a series resonance circuit with the capacitance of the stator electrode of the vibration wave motor and to select only a single frequency. 1
5 and 16 are level comparators, and 15 is a drive electrode 1-.
16 is connected to know the phase of the waveform of the resonance state detecting electrode 1-3 to know the phase of the waveform of 1. 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 so that the output is set to H during the time from the rising of the output signal of the shift register 7 to the rising of the output signal of the level comparator 16. (Enable input). The clock input terminal of the counter 21 is connected to the output terminal of the VCO 4 that generates a 32-fold frequency. Therefore, one count of the counter 21 corresponds to a phase difference of 11.25 °. The output of the counter 21 is
It is connected to one of the data input terminals of the comparators 22 and 25. Reference numerals 23 and 26 denote data latches.
Latches the value output by. Its output is connected to the other data input terminals of the magnitude comparators 22, 25. The value set in the latch 26 is 23
Is set higher than the value set in.

Magnitude comparators 22 and 25
Compares the two input data and outputs H to the output terminal when the data output from the counter 21 becomes smaller. 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, a phase difference corresponding to the frequency set in the oscillator OSC8 is input to the input terminal of the phase comparator 20. Is 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 is later than in the resonance state, and the period during which the output of the phase comparator 20 is H becomes longer. That is, the period during which the counter 21 is enabled becomes longer, and the output data becomes larger. The CPU sets certain data in the data latches 23 and 26 in advance. When the driving frequency is higher than the resonance frequency, the data output from the counter 21 is higher 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, the operation of the circuit of FIG. 1 relating 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, the driving is started from a high frequency, and the frequency is gradually reduced. Then, it reaches the frequency f1 shown in FIG.
The output OUT1 of the magnitude comparator 25 becomes H as shown in FIG. This signal OUT1 is C
It acts for the PU 24 to stop lowering the drive frequency. That is, at this time, the CPU 24
Stop lowering 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 has a meaning that the set frequency is too low,
It acts on the CPU 24 to slightly increase the frequency set in the OSC 8. That is, when the UT2 becomes H, the CPU 24 raises the frequency set in the OSC 8 by one step. As a result, the rotation speed of the vibration wave motor is slightly reduced, so that the vibration wave motor is normally driven stably at a high speed, 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 held in that state, and when H is output from the comparator 22, the frequency is shifted slightly higher to change the driving frequency of the motor. Is set lower than the resonance frequency.

However, since the driving state of the vibration wave motor is unstable within a certain time immediately after the application of the driving frequency to the vibration wave motor, the comparator 22
25 may output an erroneous signal. The CPU 24 receiving this erroneous signal performs the operation of maintaining the frequency or the operation of shifting the frequency to a higher direction as described above. Then, when the vibration wave motor is started, the drive frequency should be shifted smoothly from high to low, but not shifted or conversely shifted to higher. Therefore, the vibration wave motor may start moving slowly or become jerky.

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

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

Hereinafter, the control operation and functions of the vibration wave motor drive circuit of this embodiment will be described with reference to FIG.

<Step 1> Initial settings such as resetting the frequency f _O of the drive frequency signal applied to the vibration wave motor to the initial value f _S and resetting the counter 27 are performed.

<Step 2> It is determined whether or not to drive the vibration wave motor. If the drive is to be performed, the process proceeds to step 4; otherwise, the process 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> Judgment of acceleration / deceleration of the driving speed of the vibration wave motor is performed.
If the vehicle is decelerating, the process proceeds to step 14, and if the speed is unchanged, the process proceeds to step 13.

<Step 6> The drive frequency f _O is compared with the lowest drive frequency f _L. 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, the process proceeds to step 9; if not, the process proceeds to step 8.

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

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

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

[0032] to <Step 11> magnitude read the output of the comparator 22, step 13 it is determined that L if the current phase difference theta is greater than the set value theta _2, H
If so, it is determined to be small and the process proceeds to step 12.

<Step 12> Change the driving frequency f _O to fΔ ′
Only update to a higher value.

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

<Step 14> The drive frequency f _O is compared with the maximum drive frequency f _H. 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 above control, within a predetermined time after the start of the application of the frequency voltage to the vibration wave motor, the operation of maintaining the drive frequency and ignoring the output of the magnitude comparators 22 and 25 to the higher side is ignored. , And the motor can be started smoothly. In addition, when the motor starts to rotate after the predetermined time has elapsed or within the predetermined time, the signals of the magnitude comparators 22 and 25 are immediately received to enable the operation of holding the driving frequency and the operation of shifting to a higher frequency. Therefore, it is possible to drive the vibration wave motor stably without being driven at a frequency lower than the resonance frequency.

<Correspondence between the invention and the embodiment> The "frequency varying means" of the first embodiment includes the "oscillator OSC8" and "C
PU24 ", and the" first detection means "of 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 for generating 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 shifting means" in claim 1 is also the "means configured in the CPU 24" in the embodiment. .

The "second detecting means" of claim 1 is the "photo interrupter 28" of the embodiment, and the "time measuring means" of claim 1 is the "counter 27" of the embodiment. The "restriction means and restriction release means" of No. 1 is "C
Means formed in the PU 24 ”.

[0040]

According to the present invention, as described above ,
Disables the prohibition means and shift means for a predetermined time from the time of operation
Prevents malfunctions as a status, and at a specified time after startup
Detects that the motor is rotating even if the time has not elapsed
The prohibition means and the shift means are activated.
Therefore, even if the specified time has not
If it is determined that is rotating, the prohibition means and shift
Activating the means allows the motor to rotate
Frequency becomes lower than resonance and motor stops
Drive frequency is close to resonance
Sometimes prevents the frequency from dropping below the resonance frequency.
Obtained .

[Brief description of the drawings]

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

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

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 elimination filter 4 ... Voltage control 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 ... Magnetic comparator 23,26 ... Data latch 24 ... CPU 27 ... Counter 28 ... Photo interrupter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (1)

(57) [Claims] An arrangement for controlling 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 frequency changing means for changing the frequency of the alternating voltage, vibration
A signal from a detection electrode provided on a moving body and the alternating voltage
And a first output is generated when the vibration state of the vibrating body becomes a first state close to resonance, and a second state closer to the resonance state than the first state. A first detecting means for generating a second output when the first output, a prohibiting means for prohibiting a frequency changing operation by the frequency varying means in accordance with the first output, and a frequency in response to the second output. A frequency shift means for shifting the output frequency of the variable means by a predetermined value, wherein a second output is generated by detecting that the vibration wave motor is in a rotating state. Detecting means, timing means for detecting that a predetermined time has elapsed since the start of applying the alternating voltage to the element, and time elapsed from when the alternating voltage was applied to the element is within the predetermined time Is detected by the timing means. A limiting means for disabling the prohibiting means and the frequency shifting means when the voltage is applied, and detecting that the time elapsed from the time when the alternating voltage is applied to the element is within the predetermined time by the timing means. Even when the third output is generated from the second detecting means, the regulating means is deactivated and the restriction canceling means for operating the prohibiting means and the frequency shift means, A vibration wave motor drive circuit, comprising: