JPS61221584A - Drive circuit of vibration wave motor - Google Patents

Abstract

PURPOSE:To always improve a drive by providing phase means for bringing the phases of a signal corresponding to the vibration of a vibrator and a frequency voltage applied to an electromechanical converter into in-phase to efficiently drive a vibration wave motor. CONSTITUTION:The output of Meacham circuit 13 is passed through a band pass filter 14, and its output is shifted by a phase shifter 15 in the prescribed angular phase. The output of the shifter 15 is applied through a 90 deg. phase shifter 16, an amplifier 11 and a switch 17 to an electrode 4, and through an amplifier 10 and the switch 17 to an electrode 3 without intermediary of the shifter 16. The shifter 15 sets the phase of a counterelectromotive current to the output current of the circuit 13 to the prescribed relationship to apply the frequency voltage of the resonance frequency of the highest efficiency to an electrostrictive element 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drive circuit for a vibration wave motor that drives an object using progressive surface waves.

(Prior art) In a vibration wave motor, an electrostrictive element is attached to an elastic body such as a metal, and a frequency voltage is applied to the electrostrictive element to excite it and generate a progressive surface wave in the elastic body. Efficient excitation cannot be performed unless the frequency of the above-mentioned frequency 1 pressure is set to the resonant frequency of the elastic body and the electrostrictive element, and the resonant frequency that generates the traveling surface wave generally corresponds to each unique drive mode. Although there are a plurality of them, in order to increase the efficiency, it is necessary to apply a voltage to the electrostrictive element from an oscillation circuit that oscillates at a resonance frequency corresponding to the most efficient vibration mode among the plurality of resonances and cycles. Furthermore, since the above-mentioned resonant frequency generally fluctuates according to changes in the environment such as temperature and load, the oscillation circuit is It is necessary to make the oscillation frequency always follow the resonant frequency.

Therefore, the patent application No. 59-2769 filed by the present applicant
In No. 62, the driving state of the vibration wave motor, that is, the vibrating body is in a resonant state! A vibration detection element that detects whether or not it is vibrating is installed in the drive wave motor, and the oscillation frequency of the oscillation circuit is automatically changed according to the signal from the element, and a bandpass filter is also installed to adjust the oscillation frequency to the desired frequency. A driving circuit for a vibration wave motor has been proposed that applies only the output of 1 to a driving electrostrictive element.

By the way, when using the above-mentioned drive circuit, depending on the position where the vibration detection element is installed, there may be a time delay until the progressive surface waves generated by the excitation of the driving electrostrictive element propagate to the vibration detection element. Therefore, there is a drawback that a phase shift occurs between the input and output of the oscillation circuit, and oscillation cannot be performed stably.

<Object of the Invention> An object of the present invention is to provide a drive circuit for a vibration wave motor that eliminates the above-mentioned conventional drawbacks. The phase shift means has a phase shift characteristic according to the phase difference between the vibration due to the propagation of the progressive surface wave at the position where the driving electrostrictive element is placed and the vibration of the progressive surface wave at the position where the driving electrostrictive element is placed. It is characterized by being provided in the motor drive circuit.

<Example> Before describing an example of a drive circuit for a vibration wave motor of the present invention, a vibration wave motor according to the present invention will be described.

1(a) to 1(C) are diagrams explaining the structure of a vibration wave motor, and FIG. 1(a) is a sectional view of the vibration wave motor.
FIG. 1(b) shows the vibrating body 1 constituting the vibration wave motor shown in FIG. 1(a). Four diagrams of the stator consisting of the electrostrictive element 2 are shown vertically: a diagram viewed diagonally from above, a diagram viewed from the side, a diagram showing the polarization pattern of the electrostrictive element when viewed diagonally from below, and a diagram showing the electrode pattern. This is a diagram that shows them side by side for easy understanding.

FIG. 1(C) is a plan view showing the polarization pattern of the electrostrictive element and the wiring of the electrostrictive element.

In FIGS. 1(&) to (C), numeral 1 denotes a vibrating body made of an elastic body made of brass, for example. Reference numeral 2 denotes an electrostrictive element which is connected to the vibrating body 1 using, for example, PZT (lead zirconium titanate). Such an electrostrictive element is constituted by an annular electrostrictive element polarized in a pattern as shown in the plan view in FIG. 1(C), or by a plurality of electrostrictive elements arranged in an annular shape. Furthermore, the polarization pattern of the electrostrictive element 2 is shown in FIG.
), (e), the 2a group is divided into the 2a group to which the frequency voltage is applied by the electrode 3, the 2b group to which the frequency voltage is applied by the electrode 4, and the 2C group for vibration detection.
They are arranged at a pitch shifted by 1/4 of the wavelength of the vibration wave to be excited with respect to the group. The electrostrictive element in each group is 1/4
The device is set up so that the polarities of adjacent elements are opposite to each other at the human pitch. The + and - shown in the figure are signs that indicate the direction of polarization processing, so that the electrode side is negative and the vibrator side is positive. It is polarized. Incidentally, FIG. 1(d) is a diagram showing the correspondence between the polarization position and the sign of the electrostrictive element in order to explain the driving principle of the vibration wave motor, and the details will be described later.

Reference numeral 6 denotes a movable body that comes into frictional contact with the vibrating body l, 7 a fixed body of the motor, 8 a central shaft that supports the movable body, and 9 a bearing provided at a contact portion between the central shaft 8 and the movable body. 10 applies a force downward in the figure to the central axis 8,
This is a spring provided so that the moving body 6 and the vibrating body 1 come into contact with each other with a predetermined force.

In the vibration wave motor configured as described above, progressive surface waves are applied to the vibrating body by applying frequency voltages whose phases are shifted by 90'' from each other to the electrostrictive elements 2a and 2b via the electrodes 3.4. A moving body that is brought into frictional contact with a vibrating body is driven by the traveling surface waves.

Further, when the frequency of the frequency voltage is the resonant frequency, the motor is driven as a vibration wave motor with the highest efficiency.

Next, a first embodiment of the drive circuit of the present invention for driving the vibration wave motors shown in FIGS. 1(a) to (e) will be described with reference to FIG.

In Fig. 2, 3 and 4.5 are Fig. 1(b).

This is the electrode shown in FIG. 1(e), and is arranged at the position shown in FIGS. 1(b) and 1(C) of the electrostrictive element 1.

10.11 connects the input voltage to the electrostrictive element 2. An amplifier 13 that amplifies the voltage to a voltage sufficient to excite the vibrating body 1 is a Meacham circuit, and a variable resistor 12 in the Meacham circuit is used for fine adjustment of the resonant frequency. 14 is a bandpass filter that passes only the output of the resonant frequency necessary for driving among the outputs of the Meacham circuit; 15 is a phase shifter for adjusting the phases of the output current of the Meacham circuit and the back electromotive current to a predetermined relationship; and 16 17 is a 90" phase shifter. 17 is a changeover switch that reverses the rotational direction of the motor by reversing the phase relationship of the frequency voltage applied to the electrodes 3.4.
@Next, the operation of the drive circuit configured as above will be explained.

In this drive circuit, the frequency at which the impedance of the electrostrictive element for vibration detection on which the electrode 5 is provided is minimum, that is, the vibrating body 1. The Meacham circuit 13 generates a frequency voltage at the resonant frequency of the stator including the electrostrictive element 2.

By the way, the stator including the vibrating body 1 and the electrostrictive element 2 generally has a plurality of resonance vibration modes, and has a plurality of resonance frequencies corresponding to the plurality of resonance vibration modes. The output of the resonant vibration mode does not always have the frequency of the most efficient vibration mode among the vibrations of the resonance vibration mode, and may end up having the frequency of another vibration mode. In order to prevent such a phenomenon, the band pass filter 14 is provided, so that the frequency of the output of the Meacham circuit becomes a resonant frequency corresponding to the most efficient resonant vibration mode.

Next, the output of the bandpass filter 14 is shifted by a predetermined angular phase by a phase shifter 15. As mentioned in the above description of the prior art, the phase of the vibration excited in the vibration detection electrostrictive element 2C is different from the driven phase generated when a frequency voltage is applied to the electrostrictive element groups 2a and 2b. In other words, after the time delay required for the withdrawal excited by the frequency voltage applied to the electrostrictive element groups 2a and 2b to propagate to the vibration detection electrostrictive element 2C,
Since the vibration propagates to C, if the time delay is not an integral multiple of the period of the vibration, the phases mentioned above will not match, and the oscillation of the oscillator will not continue stably, but one The phase shifter 16 of the embodiment ensures stable oscillation at all times by bringing the above-mentioned phases into a predetermined relationship.

In addition, the output of the phase shifter 15 is 90". The output of the phase shifter 16 and the amplifier 11
, applied to the electrode 4 via the switch 17, and 90″
A traveling surface wave is applied to the electrode 3 through the amplifier 10 and the switch 17 without going through the phase shifter 16, as shown in FIG. 1(a).

The movable body 6 is excited by the electrostrictive element 2 and the vibrating body 1 shown in FIG. A frequency voltage at a resonant frequency can be applied to the electrostrictive element.

Next, the optimum phase shift characteristic of the phase shifter 15 in the above-described embodiment will be explained using FIG. 1(d).

First, a progressive vibration wave excited when frequency voltages having a 90° phase difference are applied to the electrostrictive element groups 1a and lb will be described.

When the distribution of polarization P of the electrostrictive element 2 is approximated by a trigonometric relationship, it becomes as shown in equation (1).

ps, :';'65in(ntc-π/2)
)nmi! :/2)) Formula (1) where n is a variable that represents the position, and as shown in Figure 1 (d), it is 0. For example, a
The points are n=1.5. The subscript P is the number of the electrode to which the excitation voltage is applied.

Further, the voltage applied to the two electrostrictive element groups is expressed as in equation (2). The subscript ``■'' is the number of the electrode shown in fs1 diagram (b).

￥l::￥65in(:t□72)) Equation (2) In the resonance state, assuming that there is a time delay of π/2 in the response to the voltage applied to the electrostrictive element, the vertical displacement Z is No. (
3) Given by the equation (when there is a delay of π/2, all the applied electrical energy is converted into mechanical energy).

Z=P6 sin nwXV6 5in(ωt-π
/2) + Po 5in (ntc -π/2)
xvosin ta t= P(, V6 gin((
n+1) tc+ωt ) --- First equation (3) Here, the amount of vertical displacement Z in the detection electrode 5 shown in FIG. 1(C)
can be obtained from the above equation (3).

As mentioned above, the response of the amount of displacement to the voltage applied to the electrostrictive element has a phase delay of π/2 in the co-grip state, but the response of the back electromotive force generated to the amount of displacement of the electrostrictive element It can be assumed that the delay in 2 is not present when the resistance value of the resistor 12 is larger than the impedance of the electrostrictive element 5 (at resonance), that is, due to the polarization of the electrostrictive element of the detection electrode, the vertical displacement 2 and the electromotive force V , will be a car whose phases match. Therefore, the back electromotive force v5 of the electrostrictive element generated in the detection electrode is as follows.

yVd sin (wt+135”) Here, Vo is a constant.

Note that when the resistance value of the resistor 12 is smaller than the impedance of the electrostrictive element 5, the voltage at the input terminal of the operational amplifier advances further by 90@.

Therefore, the above-mentioned phase shifter 15 may be any phase shifter that delays the input phase by 135 degrees and outputs the input when the resistance value of the resistor 12 is larger than the impedance of the electrostrictive element (at resonance). When the resistance value is small, input 2
Any phase shifter that outputs with a 25° phase delay may be used.

Furthermore, in the above explanation, the phase lead or lag occurring in the Meacham oscillator circuit, bandpass filter, and amplifier has been ignored, but in an actual circuit, the phase lead or lag occurring in such a circuit is also taken into account and the phase shifter 15 is shifted. What is necessary is to determine the phase characteristics.

Next, a second embodiment of the drive circuit of the present invention will be described with reference to FIG.

FIG. 3 shows an elementary amplifier circuit having the same function as that in FIG. 2. In the embodiment shown in FIG. 2, the drive circuit is constructed using a Meacham circuit, but in the second embodiment, a so-called vibration return type drive circuit is disclosed.

In this embodiment, the phase shifter 11 is similar to the embodiment shown in FIG.
is provided so that the phase of the input end and the phase of the output end of the drive circuit satisfy a predetermined relationship. Here, the predetermined relationship means that the vibration of the electrostrictive element groups 2a and 2b driven by the output of the drive circuit propagates to the electrostrictive element 2c for vibration detection, as in the embodiment shown in FIG. This is a phase relationship that compensates for time.

In the above configuration, by adjusting the phase shift amount of the phase shifter 15, the phase shift that occurs before the resonant frequency voltage (current) input to the amplifier 14 reaches one output terminal (electrode 3) of the drive circuit is compensated. can do. In other words, if the input impedance of the signal from the electrostrictive element for vibration detection (resistance value of resistor 15 in Fig. 3) is sufficiently high (during voltage detection), a phase delay of 135° will occur. 225° when low (when detecting current)
so that a phase delay occurs. In other words, as in the embodiment shown in FIG. 2, the frequency voltage applied to the electrode 3 is V6s.
When expressed in inwt, the input voltage from the electrode 5 to the amplifier is V, sin (wt+135°) when the resistance value of the resistor 15 is larger than the impedance of the electrostrictive element 5, and when it is smaller, the input current is Io ain (wt+22
5@).

Compared to the embodiment shown in FIG. 2, this embodiment eliminates the resonant frequency adjustment resistor 12, resulting in a simpler configuration. Also, compared to the conventional vibration feedback type oscillator, phase compensation is performed to improve resonant frequency followability and excitation. The output that can be extracted from the voltage increases. Also, in this embodiment, similar to the embodiment shown in FIG. 2, the phase lead or lag caused by the bandpass filter, amplifier, etc. is ignored, but in an actual circuit, the phase shifter is 15 phase shift characteristics may be determined.

As explained above, in this embodiment, the phase shifter 15 is provided in the drive circuit of the vibration wave motor to eliminate the conventional drawbacks. How to shift the phase using the phase shifter 15 will be explained using FIGS. 4 and 5.

In FIG. 4, (A) to (D) are plan views showing examples of arrangement of electrostrictive elements for vibration detection, of which FIG.
In (C), the electrostrictive element groups 2a and 2b are arranged in exactly the same way as in the embodiment shown in Fig. 1 (C), and examples of the arrangement of electrostrictive elements for vibration detection are shown in (a) and (b). .

They are shown as (c), (e), CD, and (g). Also, FIG. 4(D) shows electrostrictive element groups 2a, 2b, and FIG. 1(C).
Examples of the arrangement of electrostrictive elements for vibration detection in the case where they are arranged in a pattern different from the embodiment shown in (C) and (d) are shown. Note that (C) showing the arrangement of the electrostrictive elements is commonly used in FIGS. 4(A) to (D), but 184
All (C) shown in FIGS. (A) to (D) vibrate in the same phase, so they are indicated by common symbols.

In addition, in Fig. 5 (A) and (B), the phase of the electromotive force generated in the electrostrictive elements for vibration detection placed at the locations shown in Fig. 4 (h) to (g) is applied to the electric ai3.4. This figure shows the result of calculating the relationship with the phase of the frequency voltage using the same method as described above. Note that FIGS. 5A and 5B show a case where the resistance value of the load resistance of the electrostrictive element for vibration detection is larger than the impedance of the electrostrictive element. Figure 5 (A) shows a case where the frequency voltage applied to electrode 4 leads the frequency voltage applied to electrode 3 by 90°.
Figure (B) shows a case where the frequency voltage applied to the electrode 3 leads the frequency voltage applied to the electrode 4 by 90°.

That is, in FIG. 5(A) and FIG. 5CB), when a traveling wave is generated in the stator consisting of the vibrating body 1 and the electrostrictive element 2,
The traveling directions of the traveling waves are opposite to each other. That is, the rotation direction of the motor is reversed in FIG. 5(A) and FIG. 5(B). In FIGS. 5(A) and 5(B), the counterclockwise direction of the diagram represents the advance of the phase. As can be seen by comparing FIG. 5(A) and FIG. 5(B), if the electrostrictive element for vibration detection is placed at the location shown in (C), (d), and (e), the electrode 3.
Even if the direction of rotation of the motor is changed by switching the frequency voltage applied to the element, the phase of the electromotive force generated in the element does not change. When the rotation direction of the motor is changed by arranging the elements, it is not necessary to change the amount of phase shift of the phase shifter 14.

On the other hand, when placing electrostrictive elements for vibration detection at locations (a), (b), CD, and (g) other than (c), (d), and (e) in Figure 4, It is necessary to switch the amount of phase shift of the phase shifter 14 every time the rotation direction of the motor is changed.

Note that the phase of these electromotive voltages is in a no-load state (load resistance is infinite), and when the load resistance is reduced, the detector becomes a current source as shown in the above example, and is detected as an electromotive current. In this case, the phase will lead the phase of the electromotive force by 90°.

In this example, an electrostrictive element was used as the electro-mechanical energy conversion element, but other piezoelectric elements may be used.

Of course, a magnetostrictive element may be used.

<Effects of the Invention> As explained above, according to the great invention, there is a detecting means for detecting the vibration of a vibrating body and outputting a signal corresponding to the vibration, and a detecting means for detecting the vibration of a vibrating body and outputting a signal corresponding to the vibration, and a vibration wave motor for controlling the vibration wave motor according to the signal of the detecting means. An oscillation means for applying a frequency voltage at a resonant frequency to an electro-mechanical conversion element that is a driving force source, and a phase of a signal from the detection means and a phase of the frequency voltage so that the vibration wave motor can be driven efficiently. Since the matching phase means is provided, it is possible to always drive the vibration wave motor satisfactorily.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of the vibration wave motor, and FIG. 1(b) is an explanatory diagram of the stator consisting of the vibrating body l and the electrostrictive element 2 of the vibration wave motor shown in FIG. 1(a). FIG. 1(C) is a plan view showing the polarization pattern and wiring of the electrostrictive element. FIG. 1(d) is a diagram showing the correspondence between polarization positions and signs of an electrostrictive element. FIG. 2 is a circuit diagram of a drive circuit according to the first embodiment of the present invention, FIG. 3 is a circuit diagram of a drive circuit according to a second embodiment of the present invention, and 4r111(A) to (D) are vibration detection Figures 5(A) and 5(B) are diagrams showing the arrangement of the electrostrictive elements for vibration detection and the phase of the electromotive force generated in the electrostrictive elements for vibration detection shown in Figures 4(A) to (D) and the electrode 3. ．．
4 is a diagram showing the relationship between the voltage applied to the voltage and the phase thereof. l-1--Vibrating body 2--1 Electrostrictive element 13--Meacham circuit 15--1 Phase shifter

Claims (1)

[Claims] In a drive circuit for a vibration wave motor that drives a moving body by vibration waves generated in a vibrating body excited by the expansion and contraction movement of an electro-mechanical transducer to which a frequency voltage is applied, a vibration wave motor detects the vibration of the vibrating body and responds accordingly to the vibration. a detection means for outputting a signal that outputs a signal, a means for making the frequency of a frequency voltage applied to the electro-mechanical conversion element a resonance frequency in accordance with the signal of the detection means, and a means for outputting a signal of the frequency voltage applied to the electro-mechanical conversion element according to the signal of the detection means; What is claimed is: 1. A drive circuit for a vibration wave motor, comprising: a phase shift means for setting a phase in a predetermined relationship.