JPS61221583A - Drive circuit of vibration wave motor - Google Patents

Abstract

PURPOSE:To substantially eliminate generation of an audible sound by gradually varying the amplitude of a frequency voltage applied to an electromechanical energy converter. CONSTITUTION:The outputs of an oscillator 8 and a function generator 9 are input to a multiplier 10 to multiply both. The generator 9 applies a voltage E to the input of an integrator made of an operational amplifier OP2 by the ON of a switch SW to operate to gradually vary the vibration of a frequency voltage applied to drive electrostrictive elements 1a, 1b. The output of the multiplier 10 is input to a filter phase shifter 11, and its output is applied through an amplifier 13 to the element 1a and through a phase shifter 12 and an amplifier 14 to the element 1b.

Description

[Detailed Description of the Invention] <Industrial Application> The present invention provides a drive circuit for a vibration wave motor that frictionally drives a moving body by progressive vibration waves, and a special method for controlling the start, stop, acceleration and deceleration of a Kl vibration wave motor. Relating to something suitable for smooth operation without producing audible sounds.

<Prior Art> FIG. 1 is a schematic diagram of an embodiment of a vibration wave motor driven by progressive vibration waves, which has recently been put into practical use. In the same figure, la, 11) is an electrostrictive element, for example, PZT (
2 is a vibrating body made of an elastic material], and the electrostrictive elements 1a and 1b are bonded together. The vibrating body 2 is held on the stator (not shown) side together with the electrostrictive elements 1a, 11).

The 5Fi moving body is in pressure contact with the vibrating body 2 to form a rotor. A plurality of electrostrictive elements 1a and 1b are each glued together, and one group of electrostrictive elements 1a and the other group of electrostrictive elements 1b are arranged at nine pitches with a difference of one wavelength of the vibration wave wavelength λ. be done. Each electrostrictive element 1a in the group,
la, la, . . . are pitches of wavelength A, and are arranged so that adjacent ones have opposite polarities. As for the electrostrictive elements 1b, tb, 1b, . Further, although not shown in the drawings, electrode films are provided on the front and back surfaces of the electrostrictive elements 1a and Ib, respectively, so that an alternating current voltage can be applied to the electrostrictive elements 1a and 1b, respectively.

In a vibration wave motor having such a configuration, a group of electrostrictive elements t a
An alternating current voltage of K vostnωT is applied, and an alternating voltage of tl K To Cog (alT is applied to the electrostrictive element 1 of the other group. Therefore, each electrostrictive element has polarities opposite to each other, and the two groups are connected to each other. AC voltages with a phase shift of 90 degrees are applied to cause stretching vibrations.This vibration is transmitted to the vibrating body 2 to cause bending vibrations in accordance with the arrangement pitch of the electrostrictive elements 1a and tb.

When the vibrating body 2 protrudes at the position of every other electrostrictive element, the position of every other electrostrictive element retracts. On the other hand, as described above, the electrostrictive element 1a undergoes a bending vibration at a position shifted in wavelength from that of the electrostrictive element 1bK. While the alternating current voltage is applied, vibrations are excited one after another and propagate through the vibrating body 2 as progressive bending vibration waves.

The progress state of the wave at this time is shown in Figure 2 (a) (bl ra+
(a) IC diagram. Now, assume that the progressive bending m@ wave advances in the direction of arrow x1. If 0 is the central plane of the vibrating body in the resting state, then in the vibrating state, the state is 1J#, and
The stress due to bending K is balanced on this neutral plane 6. Cross section 7 perpendicular to the neutral plane 6. If we look at it, no stress is applied at the intersection 1i151 of these two surfaces, and it only vibrates vertically. At the same time, the cross section 71 is vibrating left and right about the intersection line 51. Even if the cross section is 72 or 7sK, the pendulum oscillates in the same way from side to side centering on the intersection i%$52 or 5s.

In the state shown in FIG. 4A, a point P1 on the intersection line between the cross section 71 and the surface of the vibrating body 2 on the movable body s side is the right dead center of left-right vibration, and the vibrating body 2 moves only in the upward direction.

In this pendulum vibration, when the intersection line 51 + 52 or 53 is on the positive side of the wave (when it is above the center plane 0), stress is applied to the left (opposite to the wave traveling direction x1), and on the negative side of the wave (also (when it is on the lower side) stress is applied in the right direction. That is, in the same figure (al), when the intersection line 52 and the cross section 72 are in the former state, the point P
2, stress is applied in the direction of the arrow. When the intersection line 55 and the cross section 75 are in the latter state, stress is applied to the point P3 in the direction of the arrow.

As the wave progresses, the intersection line 51 is on the positive side of the wave as shown in (1)).
When the point P1 comes, it moves to the left and at the same time moves upward. At (0), point P1 moves only in the left direction at the top dead center of vertical vibration. (At (L), point P1 moves leftward and downward. Furthermore, the wave advances, moves rightward and downward, moves rightward and upward, and returns to the state of (al). When this series of movements is combined, the point P1 is moving in a spheroidal motion.On the other hand, the moving body 5 is in pressure contact with the vibrating body 2, and as shown in FIG. point P
The rotational elliptical motion of 1 frictionally drives the moving body 3 in the x2 direction. Point P2゜Ps and all other points on the vibrating body 2 are point P
Move the moving body 3 in the same way as in step 1.

Although this is a vibration wave motor driven in this way, the moving body 3
In addition to the mode of vibration that is generated by applying the most preferable resonant frequency that excites the vibration that most efficiently drives friction, there are other modes that are generated by resonance. These modes are unnecessary to drive a vibration wave motor, so vibrations in such unnecessary modes should not be excited as much as possible, and furthermore, vibrations in unnecessary modes with low resonant frequencies should be avoided. It generates audible sounds and feels uncomfortable. In general, the most preferable resonant frequency is set in the audible range (20 Hz to 20 KHz 3 or higher).

Also, when the voltage value of the frequency voltage applied to the electrostrictive element changes during starting, stopping, acceleration/deceleration, etc., K is the electrostrictive voltage that contains components of other frequencies in addition to the frequency of the frequency voltage. The voltage applied to the element becomes K.

Frequency voltage waveform at startup f(t) as shown in Figure 3 (a)
= eg Bin ωOt (t≧0).

0g is the maximum value of the applied voltage ω0 is the resonance angular frequency of the applied voltage. If we transform this into Fourier transform, we get ? (ω) =+J': f(t)e−j”at;−[π
δ(ω angle)−πδ(ω+ωoDj; 碩−■=1]j. If this is shown in a graph, it will be busy as shown in Fig. 3(b) and (0). Fig. 3(1)) is , the horizontal axis is the angular frequency ω, and the vertical axis is the real part of the function (5ω). In addition, in FIG. 3(0), the horizontal axis represents the angular frequency ω, and the vertical axis represents the imaginary part of the function F11.1).

In this way, the transient waveform shown in Figure 3(a) contains other angular frequency components of the resonance angular frequency ω0 as shown in Figure 3(b), and the transitional waveform shown in Figure 5(a) ) If you apply a waveform like this, it will excite vibrations in unnecessary modes,
The problem is that it generates audible sounds and is noisy. Further, it is an object of the present invention to eliminate the drawback of the defective path that an audible sound similarly occurs when there is a change in the voltage value of the applied frequency voltage, such as when stopping or accelerating/decelerating. Gradually changing the amplitude of the frequency voltage applied to the electro-mechanical energy conversion element in the drive circuit of a wave motor.
It is characterized by ik.

<Example> In the practical examples described below, an electrostrictive element is used as the electro-mechanical energy conversion element, but other elements, magneto-electric elements,
Needless to say, piezoelectric elements can also be used.

FIG. 4 is a circuit diagram of an embodiment of the present invention, in which 8 is an oscillation section, 9 is a function generation section, 10 is a multiplication section, 11 is a filter phase shift section, 1
2 is a 90' phase shift section, 13.14 d is an amplification section, ta is an electrostrictive element of an oscillation electrode section, and 1a.

tb is an electrostrictive element of the driving electrode section, R1-R5 is a resistance element, Of is a capacitor, sw is a switch, mt is a power supply, O
Pt・OI'2 Fi operation intensifier.

The function generator 9 is a switch swomJc! j7 It performs the operation of adding a voltage reference to the input of the integrating circuit consisting of operational amplifier OP2. At this time, the output voltage VO2 of the integrating circuit consisting of the operational amplifier OP2 is expressed as follows when expanded into a Fourier series.

However, Mu. p2 is the increase in clearing amplifier OP2 @t is the time after turning on the switch It is possible to obtain an output voltage 702 that is (
t, << ol-Ft4), to2 is as follows.

If the input of the multiplier 100 is saturated with this output voltage Voz(to), then the input voltage of the multiplier t'' Vmil(t)
.

When Vmi2(t) and the output voltage are Vmo(t), their respective characteristics are shown as in Figure 5 (a), (b) ((i.
The output does not increase after the ninth point where it becomes saturated. Figure 5 (a
l is the input voltage TI on the oscillation unit 8 side! 1it(t),(b)
is the input voltage on the function generator 9 side “iml 2 (t),
(0) This is the output Vmo(t) of the Fi multiplier 1o.

In this way, when the frequency voltage applied to the electrostrictive element is gradually increased, the absolute value of the frequency components including other unnecessary modes that occur decreases, reducing the sound pressure level of the audible sound and making it virtually invisible. can do.

If we show this using a formula, we get: This Fourier transform becomes: [πδ(ω−ω0)−πδ(ω+ωo))2j]. In this way, it can be seen that the peak value of energy decreases because all terms including frequency components including unnecessary modes are divided by to.

6 ports (7 ports [πδ(ω-Q)O)-πδ(ω+ωo)1 is the frequency component necessary for vibration).

Also, according to this embodiment, even when the switch SW is turned on, the output of the function generator 9 gradually decreases. can be reduced. 1+ Even when the motor is accelerated or decelerated, the amplitude of the frequency voltage applied to the electrostrictive element is gradually changed by the integrating circuit as described above, so that this audible sound can be reduced.

FIG. 6 is a diagram showing another embodiment. In the embodiment of FIG. 4, the time constant is set to a large value, whereas in this embodiment, the time constant is set to a small value using the same circuit as that of FIG. I'm taking it. vmll(t) is the input voltage from the oscillation unit 8 of the multiplication unit 10, Vmt2(t) is the input voltage from the function generation unit 9 of the multiplication unit 10, and Two(t) is the output voltage of the multiplication unit 10. Here, to2 is almost equal compared to C1R4K.

(Constant) Another way to obtain a voltage that gradually increases the applied frequency voltage over one hour is to use a function (for example, Hanning, /), mi/ It is also possible to use a t-generating circuit (eg, half-cosine, Gaussian, Blackman, etc.).

FIG. 7 shows another embodiment. FIG. 7(a) is a block diagram in which 8 is an oscillation section, 11 is a filter phase shift section, and 12 is 90@
A phase shifter 15.16 is an amplifier whose amplification degree changes depending on the power supply voltage, 17 is a power supply of 15.16, and la and tb are driving electrostrictive elements. Figure 7(b) is a diagram showing an amplifier 15.16 whose amplification degree changes depending on the power supply voltage.
R7 is a resistance element, 0dL8 is a cadmium sulfide element, LI
CD is a light emitting diode, and 18 is a power amplifier. 7th
Figure (0) is a diagram showing the power supply 17, B2 is the power supply (battery, etc.),
Tr is a transistor, - is a diode, C2 is a capacitor, T is a transformer, and 19 is a variable pulse width oscillator.

Here, the operation of the power supply 17 will be explained. Power supply 17 is power supply E
The voltage of the transistor TrJf-2 is increased by the pulse I [chopped with a 1fJ variable oscillator, converted to AC, and converted to AC]. On the secondary side of the transformer 70, it is rectified by a diode m and a capacitor C2.

Depending on the load, you may need to change capacitor C2.
The rise characteristics of voltage V can be changed.

Next, the 15.16 K amplifier whose amplification degree changes depending on the power supply voltage shown in FIG. 7(1)) will be explained. power amplifier 1
The amplification factor of 8 is the resistance of the cadmium sulfide element Ca5O element CdS, which is determined by the voltage V of the power supply 17 and the resistance Ry.
Vc and light emitting diode (IJI) K vary depending on the flowing current. Therefore, as the voltage V of the power supply 17 becomes higher, the resistance Reds becomes smaller and the degree of amplification also increases.

With these functions, it is possible to gradually increase the amplitude of the frequency voltage applied to the microdistortion element as the voltage of the power supply 17 rises. On the other hand, when the power supply voltage starts to fall, the light emitting diode Lm! ! D
Since the light emission gradually decreases, the applied voltage can be gradually reduced. Therefore, the generation of audible sounds can be suppressed as in the previous embodiment. The same applies to the acceleration and deceleration of cheeks.

Alternatively, this can be realized by appropriately providing a time constant in a power supply using a series regulator or the like.

The present invention also provides a method using a main oscillator (MOPA method).
K can also be applied to self-oscillation systems.

<Effects of the Invention> By gradually increasing the amplitude of the frequency voltage applied to the vibration wave motor, it has become possible to reduce unnecessary vibration mode frequency components. For this reason, the number of shots in the audible range has decreased.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the main parts of a vibration wave motor, and Figure lJ2 is:
FIG. 3 is a diagram illustrating the driving principle of a vibration wave motor. FIG. 3 is a diagram showing the time waveform of a transient external sine wave and its frequency spectrum obtained by Fourier transformation. FIG. 4 is a circuit diagram of an embodiment of the present invention. 6 is a diagram showing the operating principle of the present invention, FIG. 6 is a diagram showing the operating principle of another embodiment, and FIG. 7 is a diagram showing another embodiment. la, l...Driving electrostrictive element 1C...Oscillating electrostrictive element 2...Vibrating body 5...Moving body 8...Oscillating section 9...Function generating section 1a...Multiplication Section 11...Filter/phase shift section 12...90' phase shift section 13.14...Power amplification section! 5.16... Amplifier whose amplification degree changes depending on the power supply voltage 17... Power supply 18... Power amplifier 19... Variable pulse width oscillator R1-R6... Resistance elements 01-02-, Capacitor SW. ... Switches M1 to x2 ... DC power supply QPMP2 ... Operational amplifier LIlfD ... Light emitting diode 04 day ... Cadmium sulfide element Tr, φ, Transistor T ... Transformer Dl ... Diode Fig. 2 Figure 4

Claims (4)

[Claims] (1) In a drive circuit for a vibration wave motor that drives a moving body by vibration waves generated by applying a frequency voltage to an electro-mechanical conversion element and being excited by the expansion and contraction movement generated in the element, the electro-mechanical conversion element is A drive circuit for a vibration wave motor, comprising means for gradually changing the amplitude of the applied frequency voltage so as not to substantially generate an audible sound in the motor. (2) The drive circuit for a vibration wave motor according to claim 1, wherein the means for gradually changing the frequency voltage is a means for making the amount of change of the frequency voltage with respect to time match an exponential function. (3) The drive circuit for a vibration wave motor according to claim 1, wherein the means for gradually changing the frequency voltage is a means for making the amount of change of the frequency voltage with respect to time match a linear function. . (4) The vibration wave motor according to claim 1, wherein the means for gradually changing the frequency voltage is a means for making the amount of change of the frequency voltage with respect to time the same as a window function used in fast Fourier transform. drive circuit.