JPS63161882A - Drive circuit for oscillatory wave motor - Google Patents

Abstract

PURPOSE:To reduce power consumption by connecting a capacitive element in parallel with a vibration detecting element. CONSTITUTION:An oscillatory wave motor has an electrostrictive element 2, and a driver circuit for the motor is constituted of a low-pass filter 4, a voltage controlled oscillator 5, a comparator 12, a frequency dividing circuit 19, shift registers 20, 25, a speed selecting switch 30, etc. An externally attached capacitor 32 as a capacitive element is connected in parallel with detecting electrodes 2-3 for the electrostrictive element 2 at that time. The capacitor 32 lowers voltage generated from the detecting electrodes 2-3. Consequently, voltage generated from the detecting electrodes 2-3 can be reduced apparently without changing the phase of output voltage from the detecting voltages 2-3, thus eliminating the need for a detector for a high input resistor by a high withstanding voltage part. When the switch 30 is connected to a contact 30-8, the motor is turned in maximum efficiency, the efficiency of revolution is lowered by changing over and connecting the switch 30 to contacts 30-7, 30-6, 30-5 in succession, thus decreasing the speed of revolution of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a drive circuit for a vibration wave motor, and particularly to a drive circuit for a vibration wave motor that frictionally drives a moving body using progressive vibration waves.

[Background of application] As a drive circuit for a vibration wave motor that is driven by progressive vibration waves generated by applying a frequency voltage to an electromechanical conversion element for driving, an electromechanical conversion element for vibration detection is provided in a vibration wave motor. A drive circuit that drives a vibration wave motor most efficiently by automatically setting the frequency of a frequency voltage applied to a drive electromechanical transducer as a resonance frequency in response to a change in impedance of the detection electromechanical transducer. It has been proposed by the applicant as Japanese Patent Application No. 59-276962.

However, in the case of such conventional technology, since the voltage generated by the electromechanical transducer for detection is a high voltage that is almost equal to the voltage applied to the electromechanical transducer for drive, the vibration detection circuit must be a circuit that can withstand the high voltage. Must be prepared. Further, since the high withstand voltage detection circuit may cause a phase change, there is a drawback that a circuit with a high input resistance must be used as the detection circuit in order to reduce the phase change. Furthermore, the detection circuit has a voltage of a frequency from the electromechanical transducer for detection, that is, a voltage of a frequency corresponding to the frequency applied to the electromechanical transducer for drive (generally 50 to
If a voltage of 100K+12) is applied, the detection circuit must be able to respond to an input signal of such frequency. Therefore, a current of about several mA is passed through the detection circuit.

Because the current flowing through the detection circuit is such a small current, or because the voltage level input to the detection circuit is high as described above, the power consumed by the high withstand voltage detection circuit is large, and the capacitance is small. However, it has the disadvantage that it is difficult to apply it to small portable devices such as cameras that use batteries.

[Object of the Invention] The object of the present invention is to provide a drive circuit for a vibration wave motor that solves the drawbacks of the above-mentioned conventional devices, does not require a high voltage circuit, and has low power consumption. The problem lies in that a capacitive element is connected in parallel to the vibration detection element.

[Example 2, 1 to 6 are diagrams explaining the structure of a vibration wave motor to which the present invention is applied, FIG. 2 is a sectional view of the vibration wave motor, and FIG. FIG. 4 is a perspective view of a stator consisting of a vibrating body l constituting a vibrating wave motor and an electrostrictive element 2 as an electromechanical conversion element bonded to the vibrating body l, as seen diagonally from above, and FIG. 4 is a side view of the stator. , FIG. 5 is a diagram in which three diagrams showing electrode patterns are arranged vertically for easy understanding. FIG. 6 is a plan view showing the polarization pattern of the electrostrictive element 2 and the wiring of the electrostrictive element 2.

In FIGS. 2 to 5, the vibrating body 1 is composed of an elastic body made of brass, for example. Further, the electrostrictive element 2 is made of, for example, PZT (lead zirconium titanate) and is bonded to the vibrating body l. Such an electrostrictive element 2 is composed of an annular electrostrictive element polarized in a pattern as shown in the plane in FIG. 6, or a plurality of electrostrictive elements arranged in an annular shape. A polarized annular electrostrictive element is used. In addition, the polarization pattern of the electrostrictive element 2 is as shown in FIG. Alternatively, the electrodes 2-2 are arranged at a pitch shifted by 1/4 of the wavelength of the vibration wave to be excited with respect to the electrode 2-1. + and - shown in FIG. 6 are signs indicating the direction of polarization treatment. In FIG. 2, 60 is a moving body that comes into frictional contact with the vibrating body l, 70 is a fixed body of the motor, and 80
9 is a central shaft that supports the moving body, and 90 is a bear link provided at the contact portion between the central shaft 80 and the moving body 60. 100
is a spring provided on the center shaft 80 so that it can be moved downward in FIG. 2 so that the movable body 60 and the vibrating body 1 come into pressure contact with each other with a predetermined force.

FIG. 1 is a circuit diagram showing a drive circuit of the second illustrated vibration wave motor.

In FIG. 1, 2 is the electrostrictive element mentioned above, and 2-1.2
-2.2-3 is the electrode shown in the fifth figure, 10.11 is a coil,
7 and 8 are amplifiers.

A comparator 17 is connected to the electrode 2-1 and shapes the sine wave of the electrode 2-1 to convert it into a logic level pulse. Further, 2A is a comparator that converts the output waveform (sine wave) of the detection electrode 2-3 into a logic level pulse.

12 is a phase comparator (phase comparison circuit) having one input terminal connected to the output of the comparator 2A and the other input terminal connected to the inverter 18, which is well known in, for example, US Pat. No. 24.291,274. The detailed explanation will be omitted, or the phase difference between the input signals is detected and an output is generated only when the phase difference exists.

The flock configuration and input/output characteristics of the comparator 12 are as shown in FIGS. In this case, the output becomes Vcc (high level signal hereinafter referred to as H) only during the period of the rising signal difference, and when the rising signal is input to the input terminal S, the output becomes an open state (high impedance state).

Further, when the input pulse (rising signal) to the input terminal S is inputted earlier than the rising signal to the input terminal R, the output during the rising signal period becomes the ground level (referred to as lower than the low level).

Also, it is in an open state except when the output indicates an H-cross. Therefore, when the phase difference is zero, the output is held open.

4 is a low-pass filter that smoothes the output of the comparator 12. 5 is a voltage controlled oscillation H (vco) that outputs a signal with a duty ratio of 50% at a frequency according to the input voltage,
Its input is connected to the output of the low pass filter 4. The input voltage and output frequency of the VCO 5 are in the relationship of the first-order rJJ number, and the higher the voltage, the higher the frequency output.

Reference numeral 19 denotes a frequency dividing circuit that divides the output of the VCO 5 by 32, and the output of the frequency dividing circuit is sent to the electrode 2 through the amplifier 7 and the coil IO.
1. Further, the output of the frequency dividing circuit 19 is connected to the D input terminal of an eight-stage shift register 20. The output of the VCO 5 is inputted to the clock terminal of the register 20 as a clock pulse. Since the frequency of VC05 is 32 times higher than the output pulse of the frequency dividing circuit 19, the relationship between the D input to the register 20 and the clock pulse is also 32 times higher. Therefore, shift register 2
0's output Q, ~Q8 is 0° to 90° with respect to the D input signal.
A pulse shifted (delayed) by 11.25 degrees up to ' is output. The oscillation frequency of the VCO 5 is set to 32 times the resonance frequency of the vibration wave motor. The outputs Q, -QA of the shift register 20 are respectively connected to terminals 30-1 to 30-8 of a speed selection switch 30, and the output of the register 20 selected via the switch 30 is connected to the amplifier 8. It is applied to the electrode 2-2 via the coil 11.

25 is an 8-stage shift register, and the output of the comparator 17 is input to the D input terminal of this register, and the output of the VCO 5 is input to the clock input.
90″ from the output terminal Qo to the input signal to the D input terminal
A delayed pulse is output. That is, since the output pulse of the frequency dividing circuit 19 and the output pulse of the comparator 17 have the same phase relationship, the pulse is inputted as the D input, and the output of the VCO 5 is inputted as the clock at the 8th stage of the shift register 25. The output Q8 of is the D input signal, i.e. electrode 2
The pulse is 90°'lI with respect to the -1 signal. The output Q8 of the shift register 25 is inputted to the S input of the phase comparator 12 via the inverter 18. The arrangement relationship between electrode 1-1 and electrode 1-3 is 9.
It is assumed that the positions are shifted by 0°. Reference numeral 32 denotes an external capacitor as a capacitive element connected in parallel to the detection electrode 2-3, and the capacitor 32 has the function of dropping the voltage generated from the detection electrode 2-3.

Next, the operation of the embodiment shown in FIGS. 1 to 8 will be explained.

When a power switch (not shown) is turned on, power is supplied to the circuit and the VCO 5 starts oscillating at a certain frequency. The vcos
The output (FIG. 9(a)) serves as the shift clock for the shift register 20.25 and is simultaneously transmitted to the frequency dividing circuit 19, so the pulse whose frequency is divided by 32 (FIG. 9(b)) is the output of the frequency dividing circuit 19 and is transmitted to the frequency dividing circuit 19. 7. The pulse is input to the coil lO
A sine wave is applied to the drive electrode 2-1 in the resonant circuit consisting of one electrode 2-1, etc., and as a result, the electrode 2-1 is applied to the drive electrode 2-1.
1, a sine wave having the same phase and frequency as the pulse shown in FIG. 9(b)) is applied.

On the other hand, the output of the frequency dividing circuit 19 is transmitted to the D input terminal of the shift register 20, and since the output pulse of the VCO 5 is applied as the shift clock of the register 20, the Q, to Q8 outputs of the shift register 20 are Figure 9(c)-(
j), the outputs of the frequency dividing circuit 19 are respectively vCO output l.
The pulse is delayed by the pulse amount. As mentioned above, frequency divider circuit 1
9 is divided by 32 for the vCO output, so each output of the register 20 is 360°/32=360°/32 for the output of the previous stage.
I+, will move by 25 degrees, and -1- will be output from output Q8.
The distribution circuit output is also 11.25 x for Fig. 9(b).
The pulse is delayed by 8-90'.

Now, assuming that the switch 3o is selectively connected to the contact 3o-8, the pulse of the output QO of the resistor 20 is applied as a sine wave to the 'Ju pole 2-2 via the amplifier 8 and the coil 11. . Therefore, in this state, frequency voltages having a phase difference of 90° are applied between the north pole 2-1 and the electrode 2-2.

On the other hand, in a vibration wave motor, the phase angle between the voltage applied to the electrostrictive elements of the first group (electrode 2-1) and the voltage applied to the electrostrictive elements of the second group (quasi-pole 2-2) is 900°. In other words, the electrical one-rotation conversion efficiency is the highest, and the narrower the phase angle, the lower the efficiency is, and when it is 0°, the efficiency is 0, that is, the vibration wave motor (hereinafter referred to as SSM) stops.

Therefore, when the switch 30 is connected to the contact 30-8 as described above, the SSM rotates with maximum efficiency, and the switch 30 is connected to the contact 30-7.30-6.30-5.30-4.30-
By switching connection to 3.30-2.30-1, the rotational efficiency becomes low and the rotational speed of the SSM decreases. In the present invention, the rotation speed of the SSM is varied by connecting the switch 30 to any one of the contacts 30-1 to 30-8.

The rotational speed of the SSM is adjusted through the above operations, and in this embodiment, frequency control is performed so that the SSM is always driven at the resonant frequency.

The frequency control operation will be explained below.

Generally, in SSM, the resonance state of the drive electrode 2
The phase of the drive signal to electrode 2-1 or 2-2 and the detection electrode 2- according to the positional relationship between -1 or 2-2 and the detection electrode 2-3.
This indicates a specific relationship between the phases of the signals from 3, that is, the positional phase relationship between the electrodes and the phase relationship or the same phase difference relationship between the signals at the electrodes, and in order to drive the SSM resonantly, the above phase relationship must be maintained. If you do this, you can always drive it resonantly. In this embodiment, electrode 2-1 and electrode 2-3 are 9
Since they are arranged with a 0° deviation, in this embodiment, resonance driving can be achieved by controlling the waveform of the electrode 2-1 and the waveform of the output of the electrode 2-3 to be deviated by 90'.

In this embodiment, in the comparator 12, the electrode 2-3
The phase of the waveform at the electrode 2-1 is detected and controlled so that this phase is always shifted by 90 degrees.

The operation will be explained in detail below. The output of the electrode 2-3 is converted into a pulse by the comparator 2A and is transmitted to the R input of the upper comparator I2. At this time, if the external capacitor 32 is not provided, the configuration of the electrode portion on the electrostrictive element 2 will be as shown in FIG. 11, and the detection electrode 2-
3, a voltage V is generated. Incidentally, the equivalent circuit of the detection electrode 2-3 in FIG. 11 can be shown in FIG. 12. Here, 2-3A is the current i (
t), and cd is the braking capacitance. Therefore, if the output voltage v1 is expressed using a nuclear equivalent circuit, then: ■ Angular frequency.

bawl.

On the other hand, in this embodiment, as described above, an external capacitor 32 is connected in parallel to the detection electrode 2-3. Therefore, the equivalent circuit of the detection electrode 2-3 portion in this embodiment is as shown in FIG.

Here, C is the capacitance of the external capacitor. Therefore, the output voltage in this embodiment, that is, the voltage V2 applied to the input of the comparator 2A forming the detection circuit, is 7.
It will be 21.

This results in a low output voltage that is divided compared to .

The detection element 2-3 is connected to the voltage level of the logic circuit (for example, 5V).
It is possible to apparently lower the output voltage of the

Further, the explanation of FIG. 1 will be continued.

On the other hand, the waveform of the electrode 2-1 is converted into a pulse by the comparator 17 and transmitted to the D input of the register 25. Since the shift clock pulse of the register 25 is the output of the VCO 5, the output Q8 of the shift register 25 is connected to the electrode 2.
The pulse is delayed in phase by 90° with respect to the −1 waveform.

The pulse from the output Q8 of the register 25 is sent to the inverter 1.
8 and transmitted to the S input of the phase comparator 12. As mentioned above, if the pulse 2 of the output Q8 of the register 25 is the pulse applied to the amplifier 7 as shown in FIG.
As shown in Figure 1 (b), the pulse is delayed by 906 seconds, and the pulse is inverted by the inverter 18 and transmitted to the S input of the comparator 12, so the pulse to the S input of the comparator 12 is delayed by 906 as shown in Figure 1 (C). The pulse is advanced by 90° with respect to the pulse in Figure 1O (a).

Therefore, if the phase of the pulse to the S input of the comparator 12 and the pulse to the R input of the comparator 12 match, it means that a 90° phase difference has occurred between the electrode 2-3 and the electrode 2-1, and resonance occurs. The condition will be detected and detected. Also, if the input signal phases to the input terminals R and S of the comparator 12 match, the output is held in the open state, so the VCO 5 continues to maintain its oscillation state, and is driven at the resonant frequency. continues to be.

Further, if the SSM is not in a resonant state, the signal from the electrode 2-3 will be shifted back and forth from the state where the signal is out of phase by 90 degrees with respect to the signal from the electrode 2-1. Therefore, in this case, the pulse phases to the R and S input terminals of the comparator 12 do not match, and for example, as shown in FIG.
If the pulse rising signal to the R input terminal of 2 is generated before the pulse rising signal to the S input terminal, the output of the rising signal difference comparator 12 becomes H, and conversely to the S input terminal. If the rising signal is generated before the rising signal to the R input terminal, the output of the rising signal difference comparator 12 becomes L. Therefore, when the pulse of the comparator 2, that is, the phase of the waveform from the electrode 2-3 leads the phase of the pulse from the inverter 18, that is, the phase difference between the waveforms of the electrodes 2-1 and 2-3 becomes When the phase difference is 90° or more, the comparator 12
The output of is H, and this H is passed through the low-pass filter 4 to v
input to cos.

The input voltage to the VCO 5 increases, and the oscillation frequency of vcos increases accordingly. The higher the oscillation frequency of vcos, that is, the drive frequency to electrodes 2-1 and 2-2, the more the signal input to electrode 2-1 changes in phase to advance the signal generated at electrode 2-3. Because of this characteristic, the phase difference between the electrodes 2-1 and 2-3 is controlled in the 90' direction.

Conversely, if the phase difference between electrodes 2-1 and 2-3 is within 90 degrees, the rising signal to the S input terminal of the comparator 12 is generated earlier than the rising signal to the R input terminal. , the output of the phase difference comparator 12 becomes L and VC
Since the oscillation frequency of O5 decreases, the driving frequency to electrodes 2-1 and 2-2 also decreases, the phase of the waveforms of electrodes 2-1 and 2-3 increases, and the position of electrodes 2-1 and 2-3 increases. The phase difference shifts toward 90''.

In this way, the phase difference between the waveforms of electrodes 2-1 and 2-3 is detected, and the drive frequency of the SSM is controlled so that this phase difference is always 90°, so that the SSM is always driven and controlled in a resonant state. becomes.

15 to 17 are other embodiments in which the capacitance of the external capacitor 32 in the first embodiment shown in the first embodiment can be reduced, and FIG. It is a partially enlarged view of electrode 2-1. Normally, in SSM, the circumferential length and radial length ω are determined from the wavelength of the vibration wave, phase detection sensitivity, signal-to-noise ratio, and conditions to prevent transfer to other vibration modes. When a detection electrode is configured as shown in FIG. 14 based on the relationship between this value and ω, there is a possibility that the capacitance C of the external capacitor 32 becomes large when trying to obtain a low output voltage v2.

FIGS. 15 to 17 show embodiments in which this problem is solved by using a small external capacitor 32, and a detection voltage of a low output level can be obtained.

Figures 15 and 16 show the detection electrode 2-33.
Fig. 17 shows an example in which the area of the detection electrode 2-3 is reduced.
5 is divided into multiple parts. Note that the parts other than the detection electrodes in the embodiment shown in FIGS. 15 to 17 are the same as in the first embodiment, so their explanation will be omitted.

[Effects] As described above, according to the present invention, since the capacitive element is connected in parallel to the detection element, the detection element output voltage can be reduced by 2 (apparently) without changing the phase of the output voltage. As a result, there is no need for a detection circuit with a high input resistance using high withstand voltage components, making it possible to provide a drive circuit at a low cost, and since the output voltage of the detection element is lowered, there are advantages in that power consumption is also reduced.

[Brief explanation of the drawing]

Fig. 1 shows a drive circuit 1 of a vibration wave motor to which the present invention is applied, Fig. 2 is a sectional view of a main part of the structure of the vibration wave motor shown in the first drawing, and Fig. 3 shows a stator of the vibration wave motor shown in the second drawing. FIG. 4 is a side view of the stator shown in the third drawing; FIG. 5 is a diagram showing the pattern of electrodes provided at the bottom of the starter in the motor shown in the second drawing; FIG. 6 is a diagram showing the electrostrictive element of the motor shown in the second drawing. A plan view showing wiring, FIG. 7 is a block diagram of the first illustrated comparator 12, FIG. 8 is an input/output characteristic diagram of the seventh illustrated comparator, and FIGS. 9 and 10 are outputs of each part of the first illustrated drive circuit. Waveform diagram, Figure 11 is a circuit diagram of the main part of the drive circuit shown in the second diagram, Figure 12,
FIG. 13 is an equivalent circuit diagram of the circuit shown in FIG. 11, and an enlarged view of the electrode portion. In the figure, 2... an electrostrictive element as an electromechanical conversion element, 2-1.
2-2... Drive electrode, 2-3... Detection electrode 2A... Comparator

Claims (1)

[Claims] (1) A drive electromechanical transducer that expands and contracts in response to an applied frequency voltage; a movable body that is moved by vibration waves generated in a vibrating body by the expansion and contraction of the element; 1. A vibration wave motor drive circuit comprising a vibration detection element provided to adjust to the resonant frequency of a body, characterized in that a capacitive element is connected in parallel to the vibration detection element.