JP2000253679A - Drive method for ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive method for an ultrasonic motor which can perform the smooth rotation. SOLUTION: This ultrasonic motor is equipped with the first frequency divider 16D1 which divides the signal of frequency(f) into (n), a phase comparator 16D2 which has this divided signal and a feedback signal inputted, an integrator 16D3 which integrates the output of the phase comparator 16D2, a voltage control oscillator 16D4 which has the output of the integrator 16D3 inputted, and the second frequency divider 16D5 which divides the frequency of the output of the voltage control oscillator 16D4 into N and feeds it back as the above feedback signal to the phase comparator 16D2. Here, the signal of the frequency(f) is inputted into the first frequency divider 16D1, and a drive signal fOUT is generated from the signal of the frequency f.N/n outputted from the voltage control oscillator 16D4. The maximum value of N is under A, and 10×f/n is set to be larger than one-Ath as large as natural frequency F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for driving an ultrasonic motor.

[0002]

2. Description of the Related Art A conventional ultrasonic motor is disclosed in
No. 4981. In this ultrasonic motor, a vibrator made of piezoelectric ceramic is provided on both the stator and the mover, and the vibrator is vibrated to generate a vibration wave, that is, a surface acoustic wave, on their opposing surfaces. In this ultrasonic motor, the vibration wave is generated by applying a drive signal to the vibrator, but a frequency difference is given to both drive signals, thereby changing the position where the vibration wave meshes between the stator and the mover. Let's move the mover. According to the publication, an ultrasonic motor based on such a principle has an accurate speed control and can increase a driving torque without depending on a rotation speed.

[0003]

The present inventors have independently developed such an ultrasonic motor and its driving circuit. In this circuit, in order to achieve high-precision driving, the frequency difference Δf of the driving signal is set to 1 / A of the natural frequency (resonance frequency) of the stator or the moving element. For example, when the natural frequency is 50 kHz, the frequency difference Δ
f is set to 50 Hz or less (A = 1000). The drive signal f + Δf (or −Δf) is generated by inputting a signal of frequency f to a frequency synthesizer using a phase locked loop.

A preferred frequency synthesizer comprises a first frequency divider for dividing the frequency f signal by n, a phase comparator to which the frequency-divided signal and the feedback signal are inputted, and an output of the phase comparator. , A voltage-controlled oscillator to which the output of the integrator is input, and a second frequency divider that divides the output of the voltage-controlled oscillator by N and feeds it back to the phase comparator as the feedback signal.

When a signal of a frequency f is input to a first frequency divider of a frequency synthesizer, a signal of a frequency f · N / n is output from a voltage controlled oscillator. Or a drive signal of -Δf).

When an input signal frequency f is set to 50 kHz and a signal which is increased (or decreased) by 1 / A is generated from the input signal frequency f, if A is set to 1000, the output signal frequency becomes f · N /
Usually, N is 1001 and n is 1000
Output signal frequency = 50 kHz · 1001/10
00 is obtained. That is, when the frequency difference Δf of the drive signal is set to 1 / A to perform high-precision drive, it is considered that N needs to be equal to or more than A.

However, when N is equal to or larger than A in the frequency synthesizer having the above configuration, a noticeable jitter occurs in the output of the voltage controlled oscillator, and this jitter suppresses the smooth movement of the moving element.

When the values of N and n are greatly changed,
There is also a problem that the operation stability of the frequency synthesizer using the phase locked loop becomes low. In order to secure the operation stability, the circuit constant of the integrator must be changed according to the values of N and n, which is not practical.

The present invention has been made in view of the above problems, and has as its object to provide a method of driving an ultrasonic motor capable of smoothly moving a moving element.

[0010]

In the method of driving an ultrasonic motor according to the present invention, a driving signal for forming a vibration wave on each surface is applied to each of a stator and a moving member which are opposed to each other in a pressed state. The frequency difference between the drive signals is set within 1 / A of the natural frequency of the stator or the mover, and the moving position of the mover is changed by changing the meshing position of the vibration wave according to the frequency difference. In the method for driving an acoustic wave motor, a first frequency divider that divides a frequency f signal by n, a phase comparator to which the frequency-divided signal and a feedback signal are input,
An integrator for integrating the output of the phase comparator, a voltage-controlled oscillator to which the output of the integrator is input, and a second for dividing the output of the voltage-controlled oscillator by N and feeding it back to the phase comparator as the feedback signal.
A first frequency divider of a frequency synthesizer having a frequency divider;
Inputting a signal having a frequency f and generating a drive signal from a signal having a frequency f · N / n output from a voltage controlled oscillator, wherein the maximum value of N is less than A and 10 × f
/ N is set to be larger than 1 / A of the natural frequency.

As described above, when N is equal to or larger than A, noticeable jitter occurs in the output of the voltage controlled oscillator, and this jitter suppresses the smooth movement of the moving element. Therefore, the occurrence of jitter is suppressed by setting N to be less than A. Since N is less than A, 10 × f / n is set to be larger than 1 / A of the natural frequency, and the resulting frequency difference between the drive signals is reduced by the natural vibration of the stator or the movable element. High-precision driving is performed with setting within 1 / A of the number. As described above, in the driving method of the ultrasonic motor according to the present invention, the moving element can be rotated with high precision and smoothly.

Preferably, the difference between n and N is set to one. In this case, the frequency difference between the drive signals can be finely varied.

When Δf is a small positive frequency, a second frequency synthesizer for generating an output frequency f _IN −Δf or f _IN + Δf in accordance with an input frequency f _IN is provided before the first frequency synthesizer. The frequency synthesizer has fixed transform coefficients, and n and N in the first frequency synthesizer are set so as to satisfy n <N when the output frequency of the second frequency synthesizer is f _IN −Δf, In the case of f _IN + Δf, it is preferable to set n> N.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic motor according to an embodiment and a driving method thereof will be described below. The same reference numerals shall be used for the same elements or elements having the same functions,
Duplicate description will be omitted.

FIG. 1 is a configuration diagram showing an ultrasonic motor according to the present embodiment. This ultrasonic motor includes an ultrasonic motor main body 1 composed of a mechanical drive mechanism and an electric control unit 2 that controls the driving of the ultrasonic motor main body 1.

First, the ultrasonic motor body 1 composed of a mechanical drive mechanism will be described.

The ultrasonic motor body 1 has a circular outer edge stator 5 and a rotor 6 provided opposite to each other on a rotating shaft 4 penetrating the center of the fixing base 3. The rotor 6 rotates by displacing the phase of one displacement wave from the other in a state where the displacement waves generated in the circumferential direction of the opposing contact surfaces of the stator 5 and the rotor 6 mesh with each other.

The displacement wave described here is a wave of a physical displacement constituted by a physical deformation of the opposing surfaces of the stator 5 and the rotor 6, and a conventional drive signal having a phase difference of 90 degrees is applied to each vibration. When applied to the probe, the displacement wave constitutes a traveling wave.

More specifically, the displacement wave is a mesh surface formed by ultrasonic waves formed on the opposing surfaces of both the stator 5 and the rotor 6. And the relative movement between the rotor 6 displacement waves is restricted. As described above, when a displacement wave is generated on the opposing surfaces of both the stator 5 and the rotor 6 and one displacement wave as the ultrasonic meshing surface is moved with respect to the other while the relative movement between the displacement waves is regulated. The rotor 6 rotates relative to the stator 5, and when the stator 5 and the moving element 6 are a stator and a slider, the slider performs a linear motion. Hereinafter, a driving method for moving the moving element by meshing such a displacement wave is referred to as a “displacement lock drive”. Although various types of displacement waves can be considered,
In the following description, the displacement wave is a traveling wave.

The fixing base 3 is for fixing the ultrasonic motor to a fixed side of a main unit such as a camera to which the ultrasonic motor is applied. A through hole 3h is formed in the center of the fixing base 3 so as to penetrate the fixing base 3 in the vertical direction.

The stator 5 includes an annular vibrator 5v made of a ceramic piezoelectric element, and an annular elastic body 5e made of a metal with the vibrator 5v adhered to the outer periphery of the back surface. An inner peripheral portion 5i of the elastic body 5e is fixed to the fixing base 3 by, for example, screwing, and an annular intermediate portion 5m between the outer peripheral portion 5o and the inner peripheral portion 5i is thin.
m facilitates the vibration of the outer peripheral portion and the inner peripheral portion 5i.
Vibration transmission between the motor and the outer peripheral portion 5o is suppressed. A through hole 5h penetrating the stator 5 in the up-down direction is also formed in the center of the stator 5.

The rotor 6 has the same structure as the stator 5, and has an annular vibrator 6v made of a ceramic piezoelectric element.
And a vibrator 6v having an annular elastic body 6e made of a metal adhered to the outer peripheral portion of the upper surface. The inner peripheral portion 6i of the elastic body 6e is fixed to the rotating shaft 4, and the elastic body 6e is fixed to the outer peripheral portion 6o.
An annular thin intermediate portion 6m is provided between the inner peripheral portion 6i and the inner peripheral portion 6i.

The rotating shaft 4 is inserted through the fixing base 3 and the through holes 3h and 5h of the stator 5. Rotary axis 4
Is rotatably supported by a bearing 7 fitted and fixed in the through hole 3h of the fixing base 3. The bearing 7 of the rotating shaft 4
A boss 8 having a diameter larger than that of the rotary shaft 4 is provided above the supporting position of the boss 8. Inner peripheral portion 6i of rotor side elastic body 6e
Is located between the boss 8 and the stator-side elastic body 5e, and is press-fitted and fixed to the boss 8. A snap ring 9 such as a C-ring is attached to the lower portion of the rotary shaft 4. A compression spring 11 is inserted between the snap ring 9 and the bearing 7 via a spacer 10. I have. The rotating shaft 4 and the boss 8 are constantly urged downward by the compression spring 11.

The stator-side elastic member 5e has a narrow annular convex portion 5p on the upper surface of the outer peripheral portion 5o.
Has a narrow annular convex portion 6p on the back surface of the outer peripheral portion 6o.
When the elastic bodies 5e and 6e are brought into full contact with each other, most of the vibration on the excitation side is transmitted to the other side and the displacement of the displacement wave is attenuated. However, the elastic bodies 5e and 6e have the convex portions 5p and 6p. Since the contact surface becomes narrow, the elastic members 5e, 6e
Can hold a displacement wave.

Between the rotor-side protrusion 6p and the stator-side protrusion 5p, an annular cushioning friction member 1 made of, for example, resin is provided.
2 intervenes, and the cushioning friction member 12 is in pressure contact with them. That is, the rotor-side convex portion 6p is formed by the stator-side convex portion 5
p is pressed.

The cushioning friction member 12 functions as a kind of vibration low-pass filter that makes it difficult to transmit the displacement wave generated in the convex portion 5p or the convex portion 6p to the other side. Mutual interference between the displacement wave on the body 5e side and the displacement wave on the rotor side elastic body 6e side is prevented, and a normal displacement wave is generated in both. That is, for example, the oscillator
When the displacement wave is generated at both sides by vibrating at 0 kHz, the vibration of 50 kHz is hardly transmitted to the other party, and the vibration of the rotation frequency of the displacement wave, for example, 100 Hz, is transmitted to the other party. Further, the cushioning friction member 12
Prevents direct contact between metals (projections 5p, 6p) to prevent generation of abnormal noise, and further improves durability of the press contact portion. The cushioning friction member 12 may not be fixed to any of the protrusions 5p and 6p, but may be interposed between the protrusions 5p and 6p or may be fixed to one of them.

A slip ring 13 composed of three rings 13a, 13b, and 13c that are disconnected from each other is fixed to the upper portion of the rotating shaft 4. For these rings 13a, 13b, 13c, the energizing brushes 15a, 15 for the rotor provided on the upper part of the fixing base 1.
b and 15c are arranged so as to be in contact with each other.

The energizing brushes 15a and 15b are a brush for supplying the first component of the rotor drive signal and a brush for supplying the second component of the rotor drive signal, respectively.
3c is a ground brush. Here, the first component and the second component preferably have a 90 ° phase difference and are sine waves, but they may be square waves.

An electric control unit 2 applies a stator driving signal having two mutually related components to the stator-side vibrator 5v to generate a displacement wave in the stator-side elastic body 5e along the circumferential direction. The two components of the stator drive signal preferably have a 90 ° phase difference and are sine waves, but they may be square waves.

The displacement wave generated in this manner has a form as if the displacement wave is rotating on a ring, and will be hereinafter described as a "rotational displacement wave". That is, when the two-phase stator drive signal is applied from the electric control unit 2 to the stator-side vibrator 5v, a rotational displacement wave traveling in the circumferential direction of the stator-side elastic body 5e is generated.
When another drive signal is applied, the stator-side elastic body 5
A standing wave or the like is generated in e.

On the other hand, the electric control unit 2 is attached to the rotor-side vibrator 6v.
, A rotor drive signal having two mutually related components is applied via the slip ring 13 to generate a displacement wave traveling in the circumferential direction of the rotor-side elastic body 6e. That is, when the two-phase drive signal is applied to the rotor-side vibrator 6v from the electric control unit 2 via the slip ring 13, a rotational displacement wave traveling in the circumferential direction of the rotor-side elastic body 6e is generated. . When another drive signal is applied, a standing wave or the like is generated in the rotor-side elastic body 6e.

In the ultrasonic motor according to the present embodiment, the phase of one displacement wave is shifted from the other while the rotational displacement waves serving as the displacement waves of the stator-side elastic member 5e and the rotor-side elastic member 6e are engaged. By doing so, the meshing rotation position of the rotor side elastic body 6e and the rotating shaft 4 shifts, and the continuation of the shift amount becomes rotation. Therefore, if the continuity of the shift amount is lost, the rotor 6 does not rotate while the displacement wave meshing is performed. The details are described below.

FIG. 2 shows the above-described piezoelectric vibrator 5v or 6v.
FIG. 3 is a plan view of one surface side of FIG. The vibrators 5v and 6v each include an annular piezoelectric ceramic plate CM and four first electrode portions S1 to S4 formed on one surface of the piezoelectric ceramic plate CM.
S4 and second electrode portions C1 to C4. The first electrode units S1 to S4 and the second electrode units C1 to C4 are equally arranged at a mechanical angle of 36 ° so that the vibrator can generate a standing wave of five wavelengths (5λ) in the entire circumferential direction. First electrode units S1 to S
4. The second electrode portions C1 to C4 are preliminarily polarized so that the polarization directions in the thickness direction are opposite to each other (see + and-in the drawing) in the adjacent regions. In addition, each electrode S1
S4 and C1 to C4 are provided without leaving a gap between the inner edge and the outer edge of the annular piezoelectric ceramic plate CM.

FIG. 3 is a plan view of the other side of the vibrator 5v or 6v. On the other surface of the annular piezoelectric ceramic plate CM, a first side electrode portion SS opposed to the entire formation region of the first electrode portions S1 to S4 on one surface of the piezoelectric ceramic plate CM.
And a second side electrode portion CC facing the entire formation region of the second electrode portions C1 to C4. First side electrode section SS
The feedback electrode portions FB and FB 'which are opposed to each other at a mechanical angle of 18 ° and an electrical angle of 90 ° are provided between the first and second side electrode portions CC.

Referring again to FIG. 1, the entire surface of the one side of the stator-side vibrator 5v is bonded to the upper surface of the metal elastic body 5e with an adhesive or a conductive adhesive. In general, even when a non-conductive adhesive is used, a small portion of the machined surface comes into contact because of the small thickness of the adhesive, and electrical conduction is achieved. The metal elastic body 5e is electrically connected to the fixing base 3 and has an electrode S formed on one surface of the stator-side vibrator 5v.
1 to S4, FB and C1 to C4 are connected to the ground. On the other hand, the first side electrode portion SS of the stator side vibrator 5v
The second side electrode section CC is connected to the drive circuit 16.

The drive circuit 16 applies a sine wave voltage signal (sine wave), which is the first component of the drive signal for the stator, between the ground and the first side electrode portion SS of the stator-side vibrator 5v. 90 ° between this and the second side electrode part CC
Sine wave voltage signal (co
(s wave) is applied to generate a displacement wave in the circumferential direction of the stator-side vibrator 5v and the elastic body 5e attached thereto, thereby forming a rotational displacement wave. A piezoelectric voltage signal is input to the drive circuit 16 as a displacement detection signal generated between the feedback electrode portions FB and FB ′ according to the displacement amount of the vibrator 5v.
Stator-side vibrator 5 based on the input displacement detection signal
The frequency and phase of the sinusoidal voltage signal supplied to v are kept constant.

The one surface of the rotor-side vibrator 6v is entirely bonded to the upper surface of the metal elastic body 6e using an adhesive or a conductive adhesive. The metal elastic body 6e includes an internal wiring 14c and a ring 13 electrically connected thereto.
c, the electrodes S1 to S4, FB, and C1 to C4 formed on one surface of the rotor-side vibrator 6v are electrically connected to the fixing base 3 via the conductive brush 15c. I have.

On the other hand, the first side electrode portion SS of the rotor-side vibrator 6v is connected to the internal wiring 14 electrically connected thereto sequentially.
a, a ring 13a, and an energizing brush 15a. The second side electrode portion CC of the rotor side vibrator 6v is connected to the internal wiring 1 electrically connected thereto sequentially.
4b, the ring 13b, and the energizing brush 15b are connected to the drive circuit 16.

The drive circuit 16 applies a sine wave voltage signal (sine wave) as a first component of the rotor drive signal between the ground and the first side electrode portion SS of the rotor side vibrator 6v, and 90 ° between this and the second side electrode part CC
A sinusoidal voltage signal (cos wave) is applied as a second component of the rotor drive signal having the phase difference described above to generate a displacement wave in the circumferential direction of the rotor-side vibrator 6v and the elastic body 6e attached thereto. Then, a rotational displacement wave is formed. In this embodiment,
Using the feedback displacement detection signal from the stator-side vibrator 5v, the frequency of the drive signal supplied to the stator-side vibrator 5v is automatically controlled so that the stator 5 can generate an appropriate displacement wave. In the description, the frequency of a pulse or a rectangular wave means its repetition frequency.

FIG. 4 is a graph for explaining the relationship between the drive signal and the displacement of the vibrator. Note that the physical displacement V in the transducer thickness direction is proportional to the voltage V of the drive signal,
The three axes indicating the orthogonal coordinate system in the graph are time (t), circumferential length (L) of the vibrator, and displacement (voltage) V, respectively.
Is shown. In the stator or rotor-side vibrators 5v and 6v, adjacent electrodes S1 (SS) and C1 (CC)
Drive voltages of Vs = V ₀ sinωt and Vc = V ₀ cosωt are given, respectively. Here, V ₀ indicates the voltage amplitude of the drive signal, ω indicates the angular frequency, and T indicates the cycle. Assuming that the displacement at each electrode position is represented at its center, as shown in the figure, the point P which gives the minimum value of the physical displacement by the application of the two-phase drive signals Vs and Vc is changed with time. In the −L direction, the driving signal is applied to form a rotational displacement wave as a traveling wave, and the electrical phase of the driving signal and the physical phase of the traveling wave (the phase is both θ)
Changes proportionally.

More specifically, in this example, the total circumferential length of the vibrator is set to be an even number (10 times) the circumferential length (λ / 2) of the individual electrode (for example, S1). , Five wavelengths (5) by applying the single-phase voltage Vs to the individual electrode (S1).
λ) is generated, and the above-mentioned phase difference (λ / 4 or −3λ /) is applied by applying the single-phase voltage Vc to the individual electrode (C1).
4) is set so as to generate a standing wave of five wavelengths (5λ), and the stator and rotor-side vibrators 5v, 6
When the respective drive signals v are simultaneously supplied, a rotational displacement wave due to a synthetic wave is formed on the surface of each of the stator and the rotor-side elastic bodies 5e and 6e.

In order to perform the displacement lock drive, the traveling directions of the displacement waves traveling in the circumferential direction of the stator 5 and the rotor 6 are adjusted to be the same as viewed from the rotating shaft 4. For this purpose, one electrode SS of the stator 5 or the rotor 6,
Reverse the polarity of the drive power supply input to CC or
Alternatively, one input phase may be inverted by 180 °.

FIG. 5 is a cross-sectional view taken along the circumferential direction of the stator / rotor contact portion when such displacement waves are engaged, and the phase of the stator drive signal (Vs) is shown. This shows how the rotor is rotated by an amount corresponding to θ when it differs from the rotor drive signal (referred to as Vs) by θ. As described above, the electrical phase of the drive signal Vs and the physical phase of the traveling wave change in proportion.

As shown in FIG. 5A, the frequency of the two-phase stator drive signal as two mutually related drive signals supplied from the drive circuit 16 to the stator-side vibrator 5v is f, and the rotor-side vibration is The control circuit 17 controls the drive circuit 1 so that the frequency of the two-phase drive signal serving as the two related rotor drive signals supplied to the child 6v is also f.
6 (ie, Δf = 0 (relative phase change = 0), the rotational displacement wave A generated at the convex portion 5p of the stator-side elastic member 5e and the rotational displacement wave B generated at the convex portion 6p of the rotor-side elastic member 6e However, the gears are rotated and displaced in the same phase, and the gears are engaged and locked as if they were meshing. The position where the displacement occurs also advances in the circumferential direction, and the position is constantly changing. The shaft 4 does not rotate, and the rotor 6 becomes stationary.

As shown in FIG. 5B, the frequency of a two-phase stator drive signal as two mutually related drive signals supplied from the drive circuit 16 to the stator-side vibrator 5v is f, and the rotor-side vibration is The control circuit 17 controls the frequency of the rotor drive signal supplied to the element 6v to (f + Δf).
Controls the drive circuit 16, since the minute frequency difference Δf is equivalent to the continuous change of the phase difference θ, the rotational displacement wave A of the meshed rotational displacement waves A and B becomes the rotational displacement wave B. On the other hand, there is a relationship in which the position is relatively advanced by an amount corresponding to the continuously changing θ.

As shown in FIG. 5 (c), a pressing force is applied between the stator 5 and the rotor 6 to maintain the meshing state between the stator 5 and the rotor 6, and the meshing is maintained at this time. The rotating shaft of the rotor 6 rotates by the amount of the phase change so that the rotational displacement waves A and B mesh with each other in a state where the stator 5 is not moved and the relative positional relationship between them is locked. When a specific phase difference θ is given between the drive signals, the rotor 6 rotates by an amount corresponding to θ and then stops.

In the displacement lock drive type ultrasonic motor according to the present embodiment, even if the traveling direction of the displacement wave is fixed in one direction, the rotation direction is determined by the phase relationship between the displacement waves A and B. The rotation direction is determined from the relationship between the traveling direction of the displacement wave and the phase difference, and is not determined only by the traveling direction of the displacement wave.

The rotation direction of the rotating shaft 4 when (f + Δf) is applied to the rotor 6 is the same as the rotation direction of the rotational displacement wave, and when (f−Δf) is applied, the rotational direction of the rotational displacement wave is The direction is opposite to the direction. That is, the frequency of the two-phase stator drive signal supplied to the stator-side vibrator 5v from the drive circuit 16 is f, and the frequency of the rotor drive signal supplied to the rotor-side vibrator 6v is (f−Δf). When the control circuit 17 controls the drive circuit 16 as described above, the rotational displacement wave A of the meshed rotational displacement waves A and B has a positional relationship relatively delayed with respect to the rotational displacement wave B. Is stationary, and the rotational displacement waves A and B mesh with each other,
Both relative positions are locked. In this case, in order to maintain the meshing state, the rotor 6 responds to the phase delay,
It rotates in the direction opposite to (f + Δf), and the rotor 6 rotates in the reverse direction.

Further, when the variable amount of the frequency ± Δf is increased or decreased, the rotation speed of the rotor 6 is increased or decreased. The rotation speed (rpm) based on the ± Δf value indicates a synchronous rotation speed determined by 60 × Δf / wave number. For example, in the case of the 5-wave type shown in FIG. 2, when Δf is 1 Hz, 60 ×× = 12 rpm.

Next, the electric control unit 2 according to the above-described embodiment will be described.
Will be described in more detail.

FIG. 6 is a system configuration diagram of the electric control unit 2 including a drive circuit 16 connected to the stator 5 and the rotor 6 and a control circuit 17 for controlling the drive circuit 16.

The drive circuit 16 applies the first drive voltage signal (Vs, Vc) having the first frequency f to the stator-side vibrator 5v to generate the displacement wave A on the opposing surface of the stator-side elastic body 5e. And the second drive voltage signal (Vs, Vc) having the second frequency f + Δf or f−Δf is applied to the rotor-side vibrator 6v to generate the displacement wave B on the opposing surface of the rotor-side elastic body 6e. .

The driving circuit 16 applies an oscillator section 16 _A for generating a signal of the first frequency f, and a signal of the first frequency f output from the oscillator section 16 _A to the stator-side vibrator 5 v to cause the stator 5 to operate. Stator-side drive signal generator 16 to be vibrated
And _B, and a phase difference detecting unit 16 _C for detecting a phase difference between the drive signal of the first frequency f which is applied a feedback displacement detection signal generated by the stator-side transducer 5 v.

Further, the drive circuit 16 receives the rotor rotation speed instruction information from the control circuit 17 and, from the first frequency f to the second frequency f + △ f or f- △, according to the inputted information.
a frequency conversion unit 16 _D to generate an f signal, the second frequency f + △ f, or output from the frequency conversion unit 16 _D f- △
The f signal is applied to the rotor side transducer 6v and a rotor-side drive signal generator 16 _E vibrating the rotor 6. Note that Δf can be set to zero.

Oscillator section 16_AOutputs a signal of frequency f
Voltage controlled oscillator (VCO) 16_{A 1}Having. here
And the frequency f is_ARather than the output frequency of
Is rather the natural frequency of the stator 5 in the circumferential direction,
This is the frequency at which the stator 5 itself resonates most. Oscillator section
16_AThe signal of frequency f output from the
16_BIs input to Frequency divider 16 in the present embodiment
_A2The signal of frequency f output from is a square wave signal
However, this signal is a sine wave if the fundamental wave is frequency f.
You may.

The drive signal generation unit 16 _B receives the input first
An amplifier 16 that removes the high-frequency component of the square wave voltage signal of the component, amplifies the sine wave voltage signal (sin wave) generated thereby, and applies the amplified signal between the first side electrode portion SS of the stator-side vibrator 5v and the ground. _B1 , a phase shift circuit 16 _B2 that shifts the phase of the first component of the first drive signal by 90 ° to generate a second component (cos wave), and a second phase shift circuit 16 _B2 output from the phase shift circuit 16 _B2 .
It consists of an amplifier _B3 which removes the high-frequency component of the square wave voltage signal of the component, amplifies the sine wave voltage signal generated thereby, and applies it between the second side electrode portion CC of the stator side vibrator 5v and the ground. When voltage signals having these phase differences are applied to the vibrator 5v, the vibrator 5v vibrates at substantially its natural frequency, and the elastic member 5 adhered integrally to the vibrator 5v.
The displacement wave A is generated at e. At this time, a displacement detection signal is generated between the feedback electrode portion FB ′ and the ground based on the piezoelectric effect. Let the frequency of this displacement detection signal be f
θ ′. Displacement detection signal output from the electrode portions FB 'feedback is input to the phase difference detecting unit 16 _C.

The phase difference detecting section 16 _C includes a limiter 16 _C3 for converting the sine wave displacement detection signal into a square wave, and a limiter 1
It has a phase difference detector (PD) 16 _C1 cascaded to 6 _C3 and a low-pass filter 16 _C2 cascaded to the phase difference detector 16 _C1 . The phase detector 16 _C1 has a square wave signal of a frequency fθ ′ which is a displacement detection signal as a feedback signal from the oscillator 5v and a square wave signal of a stage before amplification of a drive signal of a frequency f which is an applied voltage to the oscillator 5v. Is input, and a detection signal corresponding to the phase difference is output. The detection signal is to be smoothed direct current by the low-pass filter 16 _C2, the phase difference detecting unit 16 _C outputs a control signal corresponding to the phase difference between these input signals. This control signal is fed back to the VCO 16 _A1 . Note that when there is a small difference between the input frequencies f and fθ ′, a phase difference occurs, so that the control signal changes according to the small frequency difference.

The VCO 16 _A1 varies the output frequency according to the input voltage. When the frequency fθ ′ of the feedback signal is higher than the frequency f of the drive signal, which is the reference frequency, the VCO 16 _A1 lowers the output signal frequency f _OUT to lower the frequency f of the drive signal, and vice versa. In this case, the output signal frequency f is increased to increase the frequency f of the drive signal. Here, lower than the level of the reference value of the control signal output from the low pass filter 16 _C2 in the former case, and is set to be higher in the latter case.

As described above, the circuits 16 _{A to} 16 _C constitute a phase locked loop (PLL), control the output frequency f so that the input frequencies f and fθ ′ coincide, and change the frequency f and phase of the drive signal. Lock.

Frequency converter 16_DFrom the control circuit 17
Rotor rotation speed instruction information is input through terminal S,
The first frequency f to the second frequency f + according to the input information.
Generates a signal of Δf or f−Δf to continuously rotate the rotor 6
Let it. Note that the frequency conversion unit 16_DFrequency output from
Number f_OUT(= F + Δf or f−Δf) is the driving signal
Signal signal generator 16_BAmplifier 16 having the same configuration as_E1, Phase shift
Road 16_E2And amplifier 16_{E Three}Drive signal generator 16 comprising
_EPhase drive with 90 ° phase difference
Applied to the electrodes SS and CC of the rotor as signals
Is done.

[0061] Here, generation of f ± Delta] f is Okonawaru the frequency conversion unit 16 _D. Hereinafter, the frequency conversion unit _16D will be described.

FIG. 7 shows the frequency converter 16_DCircuit configuration
FIG. Frequency converter 16_DAre in phase
It consists of a frequency synthesizer using a periodic loop. Sand
The frequency converter 16_DDivides the signal of frequency f by n
First frequency divider 16_D1And the divided signal and the feedback signal
Phase comparator 16 to which the signal is input_D2And the phase comparator 16 _D2
Integrator 16 that integrates the output of_D3And the integrator 16_D3Output
Is input to the VCO 16_D4And VCO16_D4Output of N
The frequency is divided and the phase comparator 16_D2Return to
Second frequency divider 16_D5Frequency synthesizer comprising
You. Note that n and N are natural numbers.

The signal of the frequency f is input to the first frequency divider _16D1 . At this time, from the VCO 16 _D4 , the frequency f _OUT =
A signal of f · N / n is output, and a drive signal is generated from this signal.

FIG. 8 is a circuit diagram showing a detailed configuration of the integrator _16D3 . The integrator 16 _D3 includes resistors R ₁ and R ₂ and a capacitor C ₁ connected as shown. Here, resistors R ₁ ,
The resistance and capacitance of R ₂ and capacitor C ₁ are 1
20 kΩ, 10 kΩ, and 1 μF. An edge discrimination type phase comparator was used as the phase comparator 16 _D2 , and a BCD programmable counter (TC9122p) was used as the frequency dividers 16 _D1 and 16 _D5 . In addition, PLL
Used was 14046 manufactured by Motorola.

Here, in order to achieve high-precision driving, the frequency difference Δf of the driving signal is set to 1 / A of the natural frequency (resonance frequency) F of the stator 5 or the rotor 6. That is, it is set so that the displacement of the vibration wave does not occur. For example, when the natural frequency F is 50 kHz, the frequency difference Δ
f is set to 50 Hz or less (A = 1000). Drive signal f + Delta] f (or -.DELTA.f) is generated by inputting a signal of a frequency f to the frequency synthesizer 16 _D using a phase locked loop.

The first frequency divider 16 of the frequency synthesizer
_When a signal having a frequency f is input to _D1 , a signal having a frequency f · N / n is output from the VCO 16 _D4 . In this circuit, this signal is used as a drive signal having a frequency f + Δf (or −Δf).

FIG. 9 is a graph showing the relationship between N and jitter (μs) in the frequency synthesizer. The input signal frequency f is set to 50 kHz, and the
When a signal having the following increase (or decrease) (50 Hz or less) is generated, if A is 1000, the output signal frequency is f · N / n.
1 and n = 1000, output signal frequency = 50 k
Hz.1001 / 1000 is obtained. That is, in order to perform high-precision driving, the frequency difference Δ
If f is set to 1 / A, N seems to need to be greater than or equal to A.

However, according to this graph, when N is set to 1000 or more, the jitter is 0.5 μs
Increase beyond. In other words, in the frequency synthesizer having the above configuration, when N is equal to or more than A, the VCO
_Significant jitter occurs in the output of 16D4, and this jitter suppresses the smooth rotational movement of the rotor 6. Note that N is 7
When the value is less than 00, the jitter hardly occurs.

Therefore, in the circuit according to the present embodiment, the maximum value of N is less than A and 10 × f / n
Is set to be larger than 1 / A of the natural frequency F (= F / A).

As described above, when N is equal to or larger than A, significant jitter occurs in the output of the VCO 16 _D4 , and this jitter suppresses the smooth movement of the mover. Therefore,
By making N less than A, generation of jitter is suppressed. Since N is less than A, 10 × f / n is set to be larger than 1 / A (= F / A) of the natural frequency, and the resulting frequency difference Δf between drive signals is set to 5 or within 1 / A (= F / A) of the natural frequency F of the stator 6 to perform high-precision driving. As described above, in the driving method of the ultrasonic motor according to the present embodiment, the rotor 6 can be rotated accurately and smoothly.

It is desirable that the difference between n and N is set to 1. In this case, the frequency difference Δf of the drive signal can be finely varied.

[0072] Figure 10 is a block diagram showing a preferred circuit configuration of the frequency controller 16 _D. Frequency converter 16 _D consists of cascade has been pre-stage frequency converter 16 _DF and a subsequent stage frequency converter 16 _DB. The configuration of the _post- stage frequency converter 16DB is the same as that shown in FIG. The configuration of the former-stage frequency converter 16 _DF is the same as that of the latter-stage frequency converter 16 _DB except for the frequency division ratio of the frequency divider. The first frequency divider 16 _D1 ′, the phase comparator 16 _D2 ′, and the integrator 16 _D3 'and VCO16 _D4 '.

Note that, in the following description, the post-stage frequency
Conversion unit 16_DBF is the frequency of the signal input to
Number converter 16_DFIs the frequency of the signal input to_INage,
Post-frequency converter 16_DBThe frequency of the signal output from
f_OUT(= F_IN+ Δf or f_{I N}−Δf), and FIG.
Shall correspond to those shown in (1).

Each frequency divider 16_D1’, 16_D5’, 16_D1,1
6_D5Are n 'division, N' division, n division, and N division, respectively.
Shall be performed. Input signal frequency f_INAnd output signal frequency
Number f _OUTSatisfies the following relationship:

[0075]

(Equation 1)

The output frequency f _OUT (= f _IN ± Δf)
Are the above formulas (a) to (a-1 to a-
4), can be obtained by substituting (b-1 to b-4).

To satisfy such conditions, the switches SW1, SW2, and SW3 in FIG. 10 are switched in conjunction with each other as follows.

In the case (a), the switches SW1 and S
W2 and SW3 are connected to an adder AD via an information input terminal S.
₁ , k + ₁ , ₁ , 0 are input to one input terminal of each of the adder AD ₂ and the adder AD ₃ , and the other input terminal
Switching is performed so that 0, k + Δk, and k + Δk are input. Here, n 'and k are fixed values, and N' is a fixed value unless the case is switched.

In the case (b), the switches SW1 and S
W2 and SW3 are connected to an adder AD via an information input terminal S.
₁ , k−1, 0, and 1 are input to one input terminal of each of the adder AD ₂ and the adder AD ₃ , and the other input terminal is
Switching is performed so that 0, k + Δk, and k + Δk are input.

Note that the slide switches SW10 and SW
20 moves in conjunction with each other to change the value of Δk, and consequently k
The value of + Δk is varied.

In the above description, the occurrence of jitter is suppressed by setting N to be less than A. Accordingly, 10 × f / n becomes larger than 1 / A (= F / A) of the natural frequency. And the resulting frequency difference Δf between the drive signals is set to 1 / A of the natural frequency F of the rotor 5 or the stator 6 (= F
/ A) to perform high precision driving. In this example, f = (N ′ / n ′) · f _IN .

In both cases (a) and (b), since the difference between n and N is always set to 1, the frequency difference Δf of the drive signal can be finely varied.

FIG. 11 is a table showing the relationship between the values of n and N and the frequency difference Δf in such a case. In addition,
A is set to 1000, f _IN and F are set to 50 kHz, and n ′
= 700 and N '= 701. As shown in the figure, by changing Δk in the frequency divider,
Δf changes in very small units (frequency steps in units of 0.1 Hz), and changes so that the increasing rate becomes substantially equal in the variable frequency band. In this example, if 1 / A of F, that is, Δf is within 50 Hz, the same effect is obtained. In this example, the switch and the slide switch have been described.
Needless to say, it can be realized by inputting a numerical value directly from 7 and changing the value.

When the moving element 6 performs a linear motion, it can function as a slider.

As described above, in the above-described method of driving the ultrasonic motor, the drive signal for forming the vibration wave on each surface is applied to each of the stator 5 and the mover 6 which are opposed to each other in a pressed state. And the frequency difference Δf between the driving signals is set to 1 / A of the natural frequency F of the stator 5 or the moving element 6.
In the driving method of the ultrasonic motor that moves the movable element 6 by changing the meshing position of the vibration wave according to the frequency difference Δf, the first frequency divider 16 that divides the signal of the frequency f by n and _D1, a phase comparator 16 _D2 that this divided signal and the feedback signal is input, the integrator 16 _D3 for integrating the output of the phase comparator 16 _D2, the voltage output of the integrator 16 _D3 are input A first frequency divider of a frequency synthesizer 16 _{D including} a control oscillator 16 _D4 and a second frequency divider 16 _D5 which _divides the output of the voltage controlled oscillator 16 _D4 by N and feeds back the feedback signal to the phase comparator 16 _D2 . A signal of frequency f is input to 16 _D1 and a frequency f · N output from the voltage controlled oscillator 16 _D4
/ N generating a drive signal f _OUT from the signal
The maximum value of N is set to be smaller than A, and 10 × f / n is set to be larger than 1 / A of the natural frequency F.

In the above ultrasonic motor, Δf
Is the first minute frequency synthesizer
16_DBBefore the input frequency f_INOutput frequency f according to
_IN-Δf or f_IN+ Δf generating second frequency synthesizer
Isa 16_DFAnd the second frequency synthesizer 16_DFIs solid
A first frequency synthesizer having a constant conversion factor
16_DBAre the second frequency synthesizer 1
6_DFOutput frequency is f _INIn case of -Δf, n <N
Is set to_INIn the case of + Δf, n> N is satisfied
It is set as follows.

In the driving method of the ultrasonic motor,
The mover can be rotated with high precision and smoothness.

[0088]

As described above, according to the driving method of the present invention, the maximum value of N given by the frequency divider is less than A and the input frequency is set to a predetermined value. Can be rotated accurately and smoothly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an ultrasonic motor according to an embodiment.

FIG. 2 is a plan view of one side of a piezoelectric vibrator 5v or 6v.

FIG. 3 is a plan view of the other side of the piezoelectric vibrator 5v or 6v.

FIG. 4 is a graph for explaining a relationship between a drive signal and a displacement of a vibrator.

FIG. 5 is a sectional view taken along a circumferential direction of a stator / rotor contact portion when a traveling wave is generated.

FIG. 6 is a system configuration diagram of the electric control unit 2.

FIG. 7 is a block diagram of a frequency conversion section 16 _D.

FIG. 8 is a circuit diagram of an integrator.

FIG. 9 is a graph showing a relationship between N and jitter.

[10] Suitable block diagram of a frequency conversion section 16 _D.

FIG. 11 is a table showing calculation results of the circuit shown in FIG. 10;

[Explanation of symbols]

5 ... stator, 6 ... mover, 16 _D1 ... 1st frequency divider, 16 _D2
... phase comparator, 16 _D3 ... integrator, 16 _D4 ... voltage-controlled oscillator, 16 _D2 ... phase comparator, 16 _D5 ... second frequency divider, 16 _D
... frequency synthesizer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference)

Claims (3)

[Claims] 1. A driving signal in which an oscillating wave is formed on each surface is applied to each of a stator and a moving member which are opposed to each other in a press-contact state, and a frequency difference between the driving signals is applied to the stator or the moving member. A method for driving an ultrasonic motor for moving the movable element by changing the meshing position of the vibration wave according to the frequency difference, wherein the signal having the frequency f is set to within 1 / A of the natural frequency of the element. a first frequency divider for dividing by n, a phase comparator to which the frequency-divided signal and the feedback signal are input, an integrator to integrate the output of the phase comparator, and an output of the integrator The first frequency synthesizer of the first frequency synthesizer, comprising: a voltage-controlled oscillator; and a second frequency divider that divides the output of the voltage-controlled oscillator by N and feeds the feedback signal back to the phase comparator. Inputting the signal of the frequency f,
Generating the drive signal from a signal of a frequency f · N / n output from the voltage controlled oscillator, wherein the maximum value of N is less than A and 10 × f / n is the natural frequency. A method for driving an ultrasonic motor, wherein the setting is made to be larger than 1 / A. 2. The method of driving an ultrasonic motor according to claim 1, wherein the difference between n and N is set to 1. 3. A frequency synthesizer for generating an output frequency f _IN −Δf or f _IN + Δf in accordance with an input frequency f _IN in a case where Δf is a positive minute frequency is provided before the first frequency synthesizer. , The second frequency synthesizer has a fixed transform coefficient, and n and N in the first frequency synthesizer are n <N when the output frequency of the second frequency synthesizer is f _IN −Δf. 3. The method of driving an ultrasonic motor according to claim 1, wherein the setting is made such that n> N is satisfied when f _IN + Δf.