JPS60170473A - Drive circuit of vibration wave motor - Google Patents

Abstract

PURPOSE:To enhance the drive efficiency by oscillating a frequency voltage by the variation in the impedance of an electrostrictive element by the resonating vibration of elongation and contraction. CONSTITUTION:Positive input terminal voltage of an operational amplifier OP1 in an oscillator 11 becomes a value divided from an output voltage of the amplifier OP1 via resistors R2, R3. Negative input terminal voltage of the amplifier OP1 becomes a value divided by the impedances of resistor R1 and an electrostrictive element 1a from the output voltage of the amplifier OP1. The impedance of the element 1a is varied by the vibration frequency. 90 deg. phase shifter 12 is delayed by 90 deg. in phase of the output frequency voltage of the amplifier OP1, and applied to an electrostrictive element 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a vibration wave motor that frictionally drives a moving body using progressive vibration waves, and particularly to a drive circuit suitable for vibrating the vibration waves into a stable resonance state.

FIG. 1 shows 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 figure, 1a and 1b are electrostrictive elements made of, for example, PZT (lead zirconium titanate), and 2 is a vibrating body made of an elastic material, to which the electrostrictive element 1aslb is bonded. The vibrating body 2 is held on the stator (not shown) side together with the electrostrictive element 1aelb.

Reference numeral 3 denotes a moving body which is in pressure contact with the vibrating body 2 and forms a rotor. A plurality of electrostrictive elements 1a and lb are each bonded to each other, and one group of electrostrictive elements 1a and another group of electrostrictive elements ib are arranged at a pitch shifted by a % wavelength of the wavelength of the vibration wave. Ru. Each electrostrictive element 1aφ1 in the group
a, 1a, . . . are the pitches of the wavelengths, and the polarities of adjacent ones are opposite to each other. Electrostrictive element 1b・
Similarly, for lb, 1b..., the pitch of the station wavelength is
Neighbors have opposite polarity. Also, the electrostrictive element 1a/1
Although not shown, electrode films are provided on the front and back sides of b, respectively, so that an alternating current voltage can be applied to each of the electrostrictive elements 1a and lb.

With the vibration wave motor having such a configuration, an AC voltage of VoSinωT is applied to one group of electrostrictive elements 1a, and an AC voltage of voCosωT is applied to the other group of electrostrictive elements 1b. Therefore, each electrostrictive element undergoes stretching vibration by applying alternating current voltages with opposite polarities and a 90' phase shift between the two groups. This vibration is transmitted and the vibrating body 2 undergoes electrostrictive vibration. Illllll eye movements vibrate according to the arrangement pitch of the element 1aslb.

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 is
% wavelength shift, bending vibration progresses. 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), (b), and (c).
It is shown in (d). Now, the progressive bending vibration wave is pointing to arrow X.
Suppose it moves in one direction. If 0 is the central plane of the vibrating body in the static 1 state, then in the vibrating state it will be in the state shown by the chain line, and the stress due to bending is balanced on this neutral plane 6. Middle 1γ plane 6
A cross section perpendicular to 7. If we look at it, no stress is applied to the intersection line 5 of these two surfaces, and there is only vertical vibration.

At the same time, the cross section 71 is pendulum vibrating left and right about the intersection line 51.

Similarly for the cross section 72 or 73, the intersection line 52 or 5
The pendulum oscillates left and right with L7 as the center.

In the state shown in FIG. 5A, point P1 of the intersection line ``-'' between the cross section 71 and the surface of the vibrating body 2 on the movable body 3 side is the right dead center of left-right vibration, and is only directionally linked.

This pendulum vibration is caused by stress in the left direction (opposite to the wave traveling direction (Similarly when it is on the lower side) stress is applied in the right direction. That is, the same figure (
In a), when the intersection line 52 and the cross section 72 are in the former state, stress is applied to the point P2 in the direction of the arrow. Intersection line 53 and cross section 7
In state F) when 3 is the latter, stress is applied to point P3 in the direction of the arrow. As the wave progresses and the intersection line 51 comes to the positive side of the wave as shown in (b), point P1 moves to the left and at the same time.
Exercise in one direction. In (C), point P1 only moves in the left direction at the top dead center of the -1-down vibration. In (d), point P1 moves leftward and downward. The wave progresses further, moving to the right and downwards, moving to the right and moving in one direction (
Return to state a). When this series of movements is synthesized, the point P,
is in spheroidal motion. On the other hand, the moving body 3 is the vibrating body 2.
As shown in FIG. 2C, the spheroidal movement of point 'P1 on the vibrating body 2 frictionally drives the movable body 3 in the X2 direction.

Point P2 ・P3 and all other points on the vibrating body 2 are point P
The movable body 3 is driven by friction in the same manner as in 1.

The vibration wave motor driven in this manner is efficiently driven when the vibration is in a resonant state. The resonance frequency is determined by the dimensions and temperature of the electrostrictive tube vibrating body, the contact pressure of the moving body, and the like. Therefore, conventionally, for example, the vibration frequency of the vibrating body is detected by a sensor and fed back to a drive voltage oscillation circuit to control the drive voltage frequency to the resonance frequency. However, with this indirect control method that involves sensors, etc., there is a delay in response speed and it takes time for the resonant frequency to oscillate, during which time different frequencies may be superimposed and cause "beating". , control tends to be inaccurate.

As a result, not only is the noise generated, but the drive efficiency is also poor. In addition, the sensor and its signal processing circuit complicate the component configuration of the motor and the drive circuit configuration, which is an obstacle to lowering production costs.

The present invention was made in view of the above situation, and it is an object of the present invention to provide a drive circuit suitable for a vibration wave motor that is noiseless, has good drive efficiency, and can be produced at low cost. be.

In order to achieve this object, the present invention provides a drive circuit for a vibration wave motor that drives a moving body using progressive vibration waves generated by the expansion and contraction vibration of an electrostrictive element to which a frequency voltage is applied.
The drive circuit is characterized in that the frequency of the frequency voltage is oscillated by a change in impedance of the electrostrictive element due to resonance vibration of the expansion and contraction.

The embodiments shown in the drawings will be described in detail below to clarify the structure of the present invention.

FIG. 3 shows a drive circuit to which the present invention is applied.

In the figure, 10 is a voltage power supply, 11 is an oscillation unit, and 12 is 9
This is a 0' phase shift section. OPI/OF2 is an operation multiplier [1],
R1-R4 are resistors, C1 is a capacitor, and 1a and 1b are the aforementioned electrostrictive elements.

In the oscillator 11, the input terminal voltage V+ of the operational amplifier OPI is
is the value v+=(R3/(R2+
R3))・Vout , , becomes (1). Similarly,
The voltage at one input terminal f of the operational term IJ device OP1 is the resistor R1
The voltage divided by the impedance 2 of the electrostrictive element 1a is V - = (z / (z + R1)l Vout ,,
, , , , (2).

The impedance Z of the electrostrictive element changes depending on the vibration frequency f, and its characteristics are shown in FIG. fr is the resonant frequency, and a is the anti-resonant frequency.

Now -12 Differentiating equation (2) with respect to the frequency f, therefore,
The potential difference between input terminal voltages Vin=(V+) (V-) is
Depending on the change in frequency f, it increases or decreases as shown in the table below.

As can be seen from this table, the input potential difference Vin reaches its maximum value when the resonance frequency fr of the electrostrictive element is reached. Therefore, resistors R1-R3 that satisfy the above relationship are determined. Note that the Q at that time becomes Ao'Qo, if the Q of the electrostrictive element is Qo.
AO is the increase of the operational amplifier OF1 (11] degrees).

In the 90° phase shifter 12, an integrating circuit including an operational amplifier OP2, a resistor R4, and a capacitor C delays the phase of the output frequency voltage of the operational term +l amplifier OPI by 90' and applies it to the electrostrictive element 1b.

FIG. 5 is a block diagram showing a circuit of another embodiment. In the figure, only the oscillation section is shown, and the phase shift section is omitted because it can be constructed in the same manner as in the previous example. In this embodiment, various modifications can be made by forming blocks z13 to z16 into various impedance circuits. Each modification example is listed below.

Example 1. Block z14 is an electrostrictive element that should resonate,
Block z12 life z13 resist fist z15, block z1
Short 6.

Example 2. Block z12 is an electrostrictive element that should resonate,
The block z13 is made up of a series inductance L1 and a capacitor C2 as shown in FIG. 6(a). In this case, 2πfr=1
/L l eC2. Blocks Z14-z15 are resistors, and block z16 is also a parallel inductance L1 and capacitor C2 shown in FIG. 6(a). At this time, the apparent amplification dust of the operational amplifier OPI becomes Ao at the resonance frequency fr. As the distance from the resonance frequency fr increases, the block z16
Since the impedance of OPI increases and the feedback voltage at the input terminal of the operational amplifier OPI decreases, the amplification dust appears to decrease. This suppresses oscillation at a resonance point far from the vicinity of the preset resonance frequency f.The impedance of block z13 also approaches the resonance frequency fr.
, the voltage applied to the block 12, which is an electrostrictive element, is increased until it corresponds to the maximum output of the operational term 11 unit OPI.

Example 3. Block z12 is made up of parallel inductance L3, capacitor C4, and electrostrictive element 1a shown in FIG. 6(c). At this time, 2πfr=I/L 3·C4. Blocks z13 to z15 are connected to resistors, and block z16 is shorted. At the resonant frequency fr, the impedance of the block z12 is maximum and decreases with distance. As a result, voltage is applied only near the resonance frequency fr.

As explained above, since the drive circuit to which the present invention is applied oscillates at the resonant frequency of the electrostrictive element, the vibration wave motor driven by this circuit can prevent noise (1) and improve drive efficiency. Moreover, since it does not require sensors or the like, it can be produced at low cost.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the main parts of the vibration wave motor, Fig. 2 is a diagram explaining the driving principle of the vibration wave motor, Fig. 3 is a drive circuit diagram of an embodiment to which the present invention is applied, and Fig. 4 is the same. Characteristic diagram, 5th
FIG. 6 is a circuit diagram of another embodiment. la*lb is an electrostrictive element, 2 is a vibrating body, 3 is a moving body, 10
is a voltage power supply, 11 is an oscillation unit, 12 is a 9°0 phase shift unit, OP
I・OF2 is an operational amplifier, R1 to R4 are resistors, Cl-
C5 is a capacitor, Ll-L3 is an inductance, z1
2 to z16 are impedance circuit blocks. Patent applicant Canon Co., Ltd. Agent Fuku 1) 1 -377- IN N

Claims (1)

[Claims] (1) A progressive vibration wave that is generated by being excited by the stretching vibration of an electrostrictive element to which a frequency voltage is applied. A drive circuit characterized in that the frequency of the frequency voltage is oscillated by changing the impedance of an element.