JPS61221585A - Drive circuit of vibration wave motor - Google Patents

Abstract

PURPOSE:To enable to drive an ideal vibration wave motor by automatically generating a resonance frequency in response to the signal of an electromechanical converter provided in a vibrator for detecting the vibration, thereby automatically starting the motor. CONSTITUTION:A Meacham circuit 13 generates the frequency that the impedance of an electrostrictive element provided with electrodes 5 for detecting a vibration, i.e., the frequency voltage of the resonance frequency of a stator with the vibrator or the electrostrictive element to vary to follow the external condition change, and the output of the circuit 13 is applied through a band pass filter 14 to a phase shifter 15. The output shifted in the prescribed amount by the shifter 15 is applied through a 90 deg. phase shifter 16, an amplifier 11 and a switch 18 to electrodes 4, and through an amplifier 10 and the switch 18 to electrodes 3 without intermediary of the shifter 16. When the circuit 13 does not generate the output of a resonance frequency, a pulse voltage from a starting pulse generator 17 is applied to the circuit 13.

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 achieved unless the frequency of the voltage is set to the resonant frequency of the elastic body and electrostrictive element, and there are generally multiple resonant frequencies that generate traveling surface waves, each corresponding to a unique drive mode. 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 resonant frequency corresponding to the most efficient vibration mode among the plurality of resonant frequencies. 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, a vibration detection element is provided in the drive wave motor to detect the drive state of the vibration wave motor, that is, whether or not the vibrating body is vibrating in a resonant state, and the oscillation frequency of the oscillation circuit is determined according to the signal from the element. A driving circuit for a vibration wave motor has been proposed that automatically changes the frequency and applies only a desired frequency to a driving electrostrictive element.

By the way, in the drive circuit proposed in the above-mentioned application, once the oscillation frequency of the circuit matches the resonant frequency, the resonant frequency remains unchanged even if the resonant frequency changes due to external conditions, such as load fluctuations or temperature changes applied to the vibrating body. The oscillation frequency of the circuit also has the characteristic of changing according to changes in the resonant frequency, but if it is not within the resonant frequency band in the initial state, it will not be possible to oscillate at the resonant frequency, and the frequency fluctuation will change. I turned the adjustment volume and fumbled around to match the resonance frequency.

Therefore, such a circuit has the disadvantage that it cannot be activated automatically.

(Object of the Invention) In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide a drive circuit that automatically generates a resonant frequency even in the initial state and does not require a single touch to generate the resonant frequency.

<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.

Figures 1 (a) to (C) are diagrams explaining the structure of the vibration wave motor, and Figure 1 (&) is a sectional view of the vibration wave motor.
Figure (b) shows the stator, which consists of the vibrating body l and the electrostrictive element 2, which constitute the vibration wave motor shown in Figure 1 (a), viewed diagonally from above, from the side, and from diagonally below. FIG. 4 is a diagram in which four diagrams, a diagram showing the polarization pattern of the electrostrictive element and a diagram showing the electrode pattern, are arranged vertically 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(a) to 1(C), reference 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 an annular electrostrictive element polarized in a pattern as shown in the plane shown in FIG. 1(C).
Alternatively, it is configured by arranging a plurality of electrostrictive elements in an annular shape. The polarization pattern of the electrostrictive element 2 is shown in FIG. 1(b).
, as shown in (C), it is divided into a 2c group to which a frequency voltage is applied by the electrode 3, a 2b group to which a frequency voltage is applied by the electrode 4, and a 2c group for vibration detection, but the 2b group is divided into the 2c group. They are arranged at a pitch shifted by 1/4 of the wavelength λ of the vibration wave to be excited. The electrostrictive element in each group is 1/4λ
The device is arranged so that the polarities of adjacent elements are opposite to each other at a pitch of ing.

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° to the electrostrictive elements 2a and 2b via the electrodes 3.4. The moving body that is brought into frictional contact with the vibrating body is driven by this traveling surface wave.

Further, when the frequency voltage is at the resonant frequency, the vibration wave motor is driven 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 (C) 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(C), 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 is a 90" phase shifter. 13 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. 17
is a starting pulse generation circuit that generates a starting pulse.

Next, the operation of the embodiment configured as above will be explained.

First, a case will be described in which the Meacham circuit 13 has already generated an output at the resonant frequency in the drive circuit.

The frequency at which the impedance of the vibration detection electrostrictive element provided with the electrode 5 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 and changes it in accordance with changes in external conditions, and the output of the Meacham circuit 13 is passed through the bandpass filter 1.
Only the resonance frequency necessary for driving is applied to the phase shifter 15 via the phase shifter 4. A phase shifter 15 shifts the phase of the output of the band-pal filter by a predetermined amount so that the oscillation of the Meacham circuit 13 continues stably.

In addition, the output of the phase shifter 15 is transferred to the 90° phase shifter 16 and the amplifier 11.
, is applied to the electrode 4 via the switch 17, and also 90°
The amplifier lO and the switch 17 do not pass through the phase shifter 16.
A traveling surface wave is generated by being applied to the electrode 3 via the waveform shown in FIG. 1(a).

Electrostrictive element 2 shown in (b). The movable body 6 is moved by being excited by the vibrating body 1.

Next, a case will be described in which the output of the resonant frequency is not generated in the Meacham circuit 13. In this circuit, when the power is turned on, it oscillates at a frequency determined by the constant of the Meacham circuit and the impedance of the piezoelectric or electrostrictive element, but it is generally not the resonant frequency at this stage. Therefore, as mentioned above, conventionally the volume 12 was turned to adjust to the resonant frequency, but in this embodiment, the resonant frequency is adjusted by applying a pulse voltage containing a broadband frequency component output from the starting pulse generation circuit. There comes a moment when it is applied momentarily and strongly vibrates the stator. At this time, a strong back electromotive voltage is generated at the detection terminal 5, and this is applied again to the Meacham circuit with an appropriate phase relationship processed by the phase shifter 11, so a positive return path is applied, and the amplitude further increases from then on, until finally maintains the resonant frequency where the amplitude is maximum.

If the pulse voltage output from the starting pulse generation circuit at this time is a low voltage, even if the pulse voltage continues to be applied, it will not be affected once the output of the Meacham circuit 13 reaches the resonant frequency, so the voltage will always be low. The pulse voltage may remain applied.

In this embodiment, the pulsed oscillating voltage was applied to the impedance detection terminal of the Meacham circuit 13 (the inverting input terminal of the operational amplifier constituting the Meacham circuit 13), but similar effects can be expected at other locations as well. This point is shown in Figure 3(a).
It is shown in (b).

The present invention can also be applied to the startup of vibration feedback type drive circuits that do not have an internal oscillator, such as Meacham circuits, and improves startup reliability and
This has the effect of increasing restartability when oscillation stops.

In the above embodiments, the starting pulse generation circuit generated pulses containing broadband frequency components;
Of course, such a pulse has a square wave shape, but it may have another shape.

Furthermore, in the embodiments described above, an electrostrictive element is shown as the electro-mechanical energy conversion element, but it goes without saying that other piezoelectric elements may be used. Although a rotary type motor has been shown as the vibration wave motor, it may be a linear type motor, or any other type of motor can be applied as long as it uses a vibrating body to resonate.

(Effects of the Invention) As explained above, according to the present invention, resonant frequency adjustment immediately after power is turned on is automated, and furthermore, it is possible to drive an ideal vibration wave motor with followability of the resonant frequency thereafter. becomes. Further, according to the present invention, the circuit can be configured in a very simple manner by simply adding a pulse generation circuit, and there is an effect that the motor does not require any adjustment and does not lose its small size and light weight, which are the characteristics of this motor.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view of a vibration wave motor. FIG. 1(b) shows the vibrating body 1 of the vibration wave motor shown in FIG. 1(a). An explanatory diagram of a stator consisting of an electrostrictive element 2, FIG. 1(C) is a plan view showing the polarization pattern and arrangement of the electrostrictive element, and FIG. 2 is a circuit diagram of a drive circuit according to a 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.

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 by being excited by the expansion and contraction movement of an electro-mechanical transducer to which a frequency voltage is applied, a vibration detecting electric circuit provided in the vibrating body is used. 1. A drive circuit for a vibration wave motor, comprising: an oscillation circuit that automatically generates a resonant frequency according to a signal from a mechanical transducer; and a pulse generation circuit that applies a starting pulse to the oscillation circuit.