JP2692801B2 - Vibration type actuator device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a drive circuit of a vibration wave motor as a vibration type actuator device, and more particularly to a drive circuit of a vibration wave motor for frictionally driving a moving body by a progressive vibration wave. is there. BACKGROUND OF THE INVENTION An electromechanical conversion element for detecting vibration is provided in a vibration wave motor as a drive circuit of a vibration wave motor driven by a progressive vibration wave generated by applying a frequency voltage to a drive electromechanical conversion element, The drive circuit that drives the vibration wave motor most efficiently by automatically setting the frequency of the frequency voltage applied to the drive electromechanical conversion element according to the change in the impedance of the detection electromechanical conversion element as the resonance wave number It has been proposed by the applicant as Japanese Patent Application No. Sho 59-276962. However, in the case of such a conventional technique, the voltage generated from the electromechanical conversion element for detection is a high voltage almost equal to the voltage applied to the electromechanical conversion element for driving, and therefore a circuit that withstands the high voltage is prepared as the vibration detection circuit. Must. Further, since the high withstand voltage detecting circuit may cause a phase change, there is a drawback that a circuit having a high input resistance must be used as the detecting circuit in order to reduce the phase change. Further, the detection circuit has a voltage of a frequency from the electromechanical conversion element for detection, that is, a frequency corresponding to the frequency applied to the electromechanical conversion element for driving (generally, 50 to 10).
A voltage of 0 KHZ) is applied, but the detection circuit must be able to respond to an input signal of such frequency. Therefore, a current of about several mA is applied to the detection circuit. The current flowing through the detection circuit is such a small current, but the voltage level input to the detection circuit is a high level as described above, so the power consumed by the high withstand voltage detection circuit becomes a large value, and the small capacity However, it has a drawback that it is difficult to apply it to small portable devices such as cameras in which the batteries described above are used. [Object of the Invention] An object of the present invention is to provide a drive circuit for a vibration wave motor that solves the above-mentioned drawbacks of the conventional device and does not require a high breakdown voltage circuit and has low power consumption. The point is that a capacitive element is connected in parallel with the vibration detecting element. [Embodiment] FIGS. 2 to 6 are views for explaining the structure of a vibration wave motor applied to the present invention. FIG. 2 is a sectional view of the vibration wave motor, and FIG. 3 is shown in FIG. FIG. 4 is a perspective view of a stator composed of a vibrating body 1 that constitutes a vibration wave motor and an electrostrictive element 2 as an electromechanical conversion element that is bonded to the vibrating body 1 as seen obliquely from above, and FIG. 4 is a side view of the stator. FIG. 5 is a diagram in which three diagrams of the electrode pattern are vertically arranged 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. The electrostrictive element 2 is, for example, PZT (lead zirconate titanate) and is bonded to the vibrating body 1. The electrostrictive element 2 is composed of an annular electrostrictive element that is polarized in a pattern shown in FIG. 6 in a plane, or a plurality of electrostrictive elements arranged in an annular shape.
In the embodiment, a polarized annular electrostrictive element is used. The polarization pattern of the electrostrictive element 2 is, as shown in FIG. 6, an electrode 2-1 and an electrode 2-2 to which a frequency voltage having a predetermined frequency is applied, and an electrode 2 for vibration detection forming a vibration detection element.
-3, the electrode 2-2 is arranged with a pitch shifted by 1/4 of the wavelength λ of the vibration wave to be excited with respect to the electrode 2-1. "+" And "-" shown in FIG. 6 are reference numerals indicating the directions of polarization processing. In FIG. 2, 60 is a moving body that makes frictional contact with the vibrating body 1, 70 is a fixed body of the motor, 80 is a central shaft that supports the moving body, and 90 is provided at a contact portion between the central shaft 80 and the moving body 60. It is a bearing. Reference numeral 100 denotes a spring provided so that the moving body 60 and the vibrating body 1 are brought into pressure contact with each other by a predetermined force by exerting a force on the central shaft 80 in the downward direction in FIG. 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 described above,
Reference numerals -2 and 2-3 are electrodes shown in FIG. 5, 10 and 11 are coils, and 7 and 8 are amplifiers. Reference numeral 17 is a comparator that is connected to the electrode 2-1 and shapes the sine wave of the electrode 2-1 and converts it into a logic level pulse. 2A is an output waveform of the detection electrode 2-3 (sine wave).
Is a comparator for converting to a logic level pulse. Reference numeral 12 denotes a phase comparator (phase comparator circuit) having one input end thereof connected to the output of the comparator 2A and the other input end thereof connected to the inverter 18, which is well known in, for example, USP 4,291,274. Although the detailed description thereof is omitted, the phase difference between the input signals is detected and the output is generated only when the phase difference exists. The block configuration and the input output characteristics of the comparator 12 are as shown in FIGS. 7 and 8, and when the input pulse (rising signal) to the input terminal R is input before the rising signal to the input terminal S. Output is Vc only during the rising signal difference
When the rising signal is input to the input terminal S, the output becomes an open state (high impedance state). Also, the input pulse (rising signal) to the input end S is the input end R
If the signal is input before the rising signal to, the rising signal period output is at the ground level (hereinafter referred to as low level and referred to as L).
Becomes The output is in an open state except when it shows H or L. Therefore, when the phase difference is zero, the output is kept open. A low-pass filter 4 smoothes the output of the comparator 12. Reference numeral 5 is a voltage controlled oscillator (VCO) that outputs a signal with a duty ratio of 50% at a frequency according to the input voltage, and its input is connected to the output of the low-pass filter 4. The
The input voltage and output frequency of VCO5 have a linear relationship, and the higher the voltage, the higher the output frequency. Reference numeral 19 is a frequency dividing circuit for dividing the output of the VCO 5 by 32, and the output of the frequency dividing circuit is applied to the electrode 2-1 via the amplifier 7 and the coil 10. Further, the output of the frequency dividing circuit 19 is an 8-stage shift register 20.
Are connected to the D input terminal of The output of the VCO5 is input as a clock pulse to the clock terminal of the register 20. Since the frequency of VCO5 with respect to the output pulse of the frequency dividing circuit 19 is 32 times, the relationship between the D input to the register 20 and the clock pulse is also 32 times. Therefore, the outputs Q _{1 to} Q ₈ of the shift register 20 are pulses which are shifted (delayed) by 11.25 ° from 0 ° to 90 ° with respect to the D input signal. The oscillation frequency of VCO5 is set to 32 times the resonance frequency of the vibration wave motor. The outputs Q _{1 to} Q ₈ of the shift register 20 are speed selection switches.
The output of the register 20 connected to the terminals 30-1 to 30-8 of the amplifier 30 and selected via the switch 30 is the amplifier 8 and the coil 11
Is applied to the electrode 2-2 via. Reference numeral 25 is an 8-stage shift register. The output of the comparator 17 is input to the D input terminal of the register, and the output of the VCO5 is input to the clock input.
A pulse delayed by 90 ° with respect to the signal input to the D input terminal is output from Q ₈ . 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 input as the D input and the output of the VCO 5 is input as the clock. Output Q ₈ is a pulse delayed by 90 ° with respect to the D input signal, that is, the signal of the electrode 2-1. The output Q ₈ of the shift register 25 is input to the S input of the phase comparator 12 via the inverter 18. It is assumed that the electrodes 1-1 and 1-3 are in a positional relationship of being displaced by 90 °. 32
Is a capacitor externally connected as a capacitive element connected in parallel to the detection electrode 2-3.
3 has a function of lowering the voltage generated. Next, the operation of the embodiment shown in FIGS. 1 to 8 will be described. When a power switch (not shown) is turned on, power is supplied to the circuit and VCO5 starts oscillating at a certain frequency. The output of the VCO 5 (Fig. 9 (a)) becomes the shift clock of the shift registers 20 and 25, and at the same time, it is transmitted to the frequency dividing circuit 19, so that a pulse divided by 32 (Fig. 9 (b) is output as the frequency dividing circuit 19). The pulse is input to the amplifier 7. The pulse becomes a sine wave in the resonance circuit including the coil 10 and the electrode 2-1 and is applied to the drive electrode 2-1. A sine wave having the same phase and the same frequency as the pulse shown in 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 so as the Shifutokurotsuku of the register 20 output pulse of VCO5 being applied, Q ₁ to Q ₈ output of the shift register 20 is first As shown in FIGS. 9 (c) to 9 (j), the output of the frequency divider 19 is delayed by one VCO output pulse. As described above, the frequency divider circuit 19 is 3 for the VCO output.
Since the frequency is divided by two, each output of register 20 is delayed 360 ° / 32 = 11.25 ° with respect to the output of the previous stage, and output Q ₈
From the above, the frequency divider circuit output is also 11.25 with respect to Fig. 9 (b).
× 8 = pulse delayed by 90 °. Assuming that the switch 30 is selectively connected to the contacts 30-8, a pulse of the output Q ₈ of the register 20 is the amplifier 8 is applied as a sine wave to the electrodes 2-2 via the coil 11.
Therefore, in this state, 90 between electrode 2-1 and electrode 2-2.
The frequency voltages having different phases are applied. On the other hand, in the vibration wave motor, the first group (electrode 2-1)
When the phase angle between the applied voltage to the electrostrictive element of and the applied voltage to the electrostrictive element of the second group (electrode 2-2) is 90 °, the electro-rotation conversion efficiency is highest and the phase angle becomes narrow. The higher the value, the lower the efficiency becomes, and at 0 °, the efficiency becomes 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 contacts the contact 30-8.
-7, 30-6, 30-5, 30-4, 30-3, 30-2, 30-
By switching and connecting to 1, rotation efficiency becomes low and SSM
Rotation speed will decrease. In the present invention, the switch 30 and any of the contacts 30-1 to 30-8 are connected to form an SS.
The rotation speed of M is variable. The rotation speed of the SSM is adjusted by the above operation, and in the present embodiment, the frequency control is performed so that the SSM is always driven at the resonance frequency. The frequency control operation will be described below. Generally, in SSM, the drive electrode 2 is in the resonance state.
-1 or 2-2 and the detection electrode 2-3 depending on the positional relationship between the detection electrode 2-3 and the electrode 2-1 or 2-2.
The phase of the signal from 3 has a specific relationship, that is, the positional phase relationship between the electrodes and the phase relationship of the signal at the electrodes show the same phase difference relationship, and the above phase relationship is maintained in order to drive the SSM in resonance. If it is not made, resonance drive can always be performed. In the embodiment, the electrodes 2-1 and 2-3 are
Since they are arranged 90 ° apart from each other, in this embodiment, resonance drive can be performed by controlling the waveform of the electrode 2-1 and the waveform of the output of the electrode 2-3 by 90 °. In this embodiment, the comparator 12 has electrodes 2-3.
Then, the phase of the waveform at the electrode 2-1 is detected, and the phase is controlled so as to be always shifted by 90 °. The operation will be described in detail below. The output of the electrode 2-3 is converted into a pulse by the comparator 2A and transmitted to the R input of the comparator 12. At this time, assuming that the external capacitor 32 is not provided, the configuration of the electrode portion on the electrostrictive element 2 is as shown in FIG. 11, and the voltage V ₁ is generated from the detection electrode 2-3. Incidentally, the detection electrode 2- in FIG.
The equivalent circuit of 3 can be shown in FIG. Where 2-
3A is a current source that generates a current i (t) according to the vibration of the vibrating body 1, and cd is a braking capacity. Therefore, when the output voltage V ₁ is expressed using the equivalent circuit, Where i (t) = ie ^jωt , ω: angular frequency of vibration of the vibrating body 1. Becomes On the other hand, in this embodiment, the external capacitor 32 is connected in parallel to the detection electrode 2-3 as described above. Therefore, the equivalent circuit of the detection electrode 2-3 portion in this embodiment is as shown in FIG. Here, C is the capacity of the external capacitor.
Therefore, the output voltage in the embodiment, that is, the voltage V ₂ applied to the input of the comparator 2A forming the detection circuit is Becomes Therefore, from equations (1) and (2), V ₂ / V ₁ is And V ₂ is in phase with V ₁ and It becomes a low output voltage divided by the ratio of. Therefore, The output voltage of the detection element 2-3 can be apparently lowered to the voltage level (for example, 5V) of the logic circuit by appropriately selecting the ratio of the above. 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. The register
Since the shift clock pulse of 25 is the output of the VCO 5, the output Q ₈ of the shift register 25 is a pulse whose phase is delayed by 90 ° with respect to the waveform of the electrode 2-1. The pulse from the output Q _{8 of the} register 25 is inverted by the inverter 18 and transmitted to the S input of the phase comparator 12.
As described above, the pulse 2 of the output Q ₈ of the register 25 is a pulse delayed by 90 ° as shown in FIG. 10 (b) when the pulse applied to the amplifier 7 is shown in FIG. 10 (a), and the pulse is output by the inverter 18. Since the signal is inverted and transmitted to the S input of the comparator 12, the pulse to the S input of the comparator 12 is shown in Fig. 10 (c).
The pulse advances 90 ° with respect to the pulse in Fig. 10 (a). Therefore, if the phase of the pulse to the S input of the comparator 12 and the phase of the pulse to the R input of the comparator 12 match, it means that there is a 90 ° phase difference between the electrode 2-3 and the electrode 2-1. The state is detected.
Also, the comparator 12 holds its output open if the input signal phases to its input terminals R and S match, so the VCO 5 will continue to hold its oscillating state and will be driven at the resonance frequency. to continue. Further, when the SSM is not in the resonance state, the signal from the electrode 2-3 is shifted from the state in which the signal is 90 ° in phase with respect to the signal of the electrode 2-1 to the front and back. 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.
When the rising signal of the pulse to the input terminal is generated before the rising signal of the pulse to the S input terminal, the output of the rising signal difference comparator 12 becomes H, and conversely, the rising signal to the S input terminal. Is generated before the rising signal to the R input terminal, the output of the rising signal difference comparator 12 becomes L. Therefore, the pulse of the comparator 2, that is, the phase of the waveform from the electrode 2-3 is the inverter.
When the phase of the pulse from 18 is advanced, that is, when the phase difference between the waveforms of the electrodes 2-1 and 2-3 becomes 90 ° or more, the output of the comparator 12 becomes H for the phase difference period. Is input to VCO5 through the low pass filter 4 and VC
The input voltage to O5 increases, and the oscillation frequency of VCO5 increases accordingly. The higher the oscillation frequency of VCO5, that is, the driving frequency to the electrodes 2-1 and 2-2, the higher the phase of the signal input to the electrode 2-1 becomes than that of the signal generated at the electrode 2-3. Because of the characteristics, the phase difference between the electrodes 2-1 and 2-3 is controlled in the 90 ° direction. On the contrary, if the phase difference between the electrodes 2-1 and 2-3 is within 90 °, the rising signal to the S input terminal of the comparator 12 occurs earlier than the rising signal to the R input terminal. ,
The output of the phase difference comparator 12 becomes L, and the oscillation frequency of VCO5 decreases, so the drive frequency to the electrodes 2-1 and 2-2 also decreases, and the phase of the waveform of the electrodes 2-1 and 2-3 increases and the electrode The phase difference between 2-1 and 2-3 shifts toward 90 °. In this way, the phase difference between the waveforms of the electrodes 2-1 and 2-3 is detected, the drive frequency of the SSM is controlled so that this phase difference is always 90 °, and the drive control of the SSM is always in the resonance state. Becomes FIGS. 15 to 17 show another embodiment in which the capacitance of the external capacitor 32 in the first embodiment shown in FIG. 1 can be reduced, and FIG. 14 shows the detection electrode 2-3 and the driving electrode 2 shown in FIG.
It is a partially enlarged view of -1. Normally, in the SSM, the circumferential length 1 and the radial length ω are determined from the wavelength of the vibration wave, the phase detection sensitivity, the signal-to-noise ratio, and the condition for not shifting to another vibration mode. From the relationship between l and ω, the capacitance C of the external capacitor 32 may increase when a low output voltage V ₂ is obtained when the detection electrode as shown in FIG. 14 is configured. FIGS. 15 to 17 show an embodiment in which such a problem is solved and a detection voltage of a low output level can be obtained with the external capacitor 32 having a small capacity. 15 and 16 show the same function (l, ω) as the embodiment shown in FIG.
This is an example in which the area of the detection electrodes 2-33, 2-34 is reduced while holding the above), and FIG. 17 is an example in which the detection electrode 2-35 is divided into a plurality of parts. Since the portions other than the detection electrodes of the embodiment shown in FIGS. 15 to 17 are the same as those of the first embodiment, the description thereof will be omitted. [Effect] As described above, according to the present invention, since the capacitive element is connected in parallel to the detecting element, it is possible to apparently reduce the output voltage of the detecting element without changing the phase of the output voltage. The advantage is that the detection circuit for high input resistance due to the high withstand voltage component is not required, the drive circuit can be provided at low cost, and the output voltage of the detection element is reduced, so that the power consumption is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drive circuit diagram 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 FIG. 1, and FIG. FIG. 4 is a perspective view of a stator of the vibration wave motor, FIG. 4 is a side view of the stator shown in FIG. 3, FIG. 5 is a view showing a pattern of electrodes provided under the starter of the motor shown in FIG. 2, and FIG. Fig. 7 is a plan view showing the wiring of the electrostrictive element of the motor, Fig. 7 is a block diagram of the comparator 12 shown in Fig. 1, Fig. 8 is an input / output characteristic diagram of the comparator shown in Fig. 7, and Figs. Output waveform diagram of each part of the drive circuit, FIG. 11 is a circuit diagram of main parts of the drive circuit shown in FIG. 2, FIGS. 12 and 13 are equivalent circuit diagrams of the circuit shown in FIG. 11, and FIG. Partially enlarged views, FIGS. 15 to 17 are enlarged views of electrode portions in another embodiment of the present invention. In the figure, 2 ... Electrostrictive element as electromechanical conversion element, 2-1 and 2-2 ... Driving electrode, 2-3 ... Detection electrode 2A ... Comparator 32 ... Capacitor as capacitive element

Claims (1)

(57) [Claims] A frequency signal having different phases is applied to the driving electro-mechanical energy conversion element portion arranged on the vibrating body to excite the vibrating body to obtain a driving force, and a voltage corresponding to the vibration due to the vibration of the vibrating body. A vibration-type actuator device for detecting a drive state by providing a vibration detection electric-mechanical energy conversion element section on the vibrating body and monitoring a voltage from the vibration detection electric-mechanical energy conversion element section. A capacitive element is connected in parallel to the vibration detecting electric-mechanical energy conversion element section, and the phase of the voltage generated in the vibration detecting electric-mechanical energy conversion element section is changed by the capacitive element. Without vibrating, the voltage dropped by the capacitive element is input to a monitor circuit to detect a vibration state. Eta apparatus.