JP3790830B2 - Drive device for vibration wave motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive device for a vibration wave motor.
[0002]
[Prior art]
FIG. 4 is a diagram showing a general configuration of a conventional vibration wave motor.
FIG. 4A is a cross-sectional view of the vibration wave motor 100, and a moving element composed of a rotor 100-1 and a sliding material 100-2 bonded to each other, and an elastic body 100 − similarly bonded to each other. 3 and a stator composed of the vibrating body 100-4. These movers and stators are driven by being brought into pressure contact with pressure means (not shown).
[0003]
FIG. 4B is a plan view showing the arrangement of electrodes of the vibrating body 100-4. The electrodes 100-4a and 100-4b are input electrodes, and a frequency voltage having a frequency determined for each vibration wave motor and having a phase difference of 90 ° or 270 ° is applied to these electrodes. Causes the stator to vibrate. The electrode 100-4c is a common electrode that is grounded. On the other hand, the electrode 100-4d is an electrode used for taking out the monitor voltage, but does not directly contribute to the vibration of the vibrating body 100-4.
[0004]
FIG. 4C shows an equivalent circuit between the input electrode 100-4a or 100-4b of the vibrating body 100-4 and the ground electrode. As shown in the drawing, the equivalent circuit is represented by a self-capacitance C ₀ and a series resonance circuit of L, C, and R connected in parallel with C ₀ .
The driving amount (rotational speed) of the vibration wave motor is considered to change depending on the value of the current (motional current) flowing through the series resonance circuit of L, C, and R of the vibration body equivalent circuit. That is, a large driving amount can be obtained by increasing the current value by increasing the frequency voltage applied to the vibrating body or by bringing the frequency of the frequency voltage close to the resonance frequency of the series resonance circuit.
[0005]
Next, a driving device for the conventional vibration wave motor 100 will be described. FIG. 5 is a block diagram showing a driving device of the vibration wave motor of FIG.
A conventional vibration wave motor driving apparatus includes a driving frequency setting circuit 101, a phase shift circuit 102, a piezoelectric body driving circuit 103 (103A, 103B), and the like. The drive frequency setting circuit 101 is a circuit that outputs a frequency signal, and the frequency is set corresponding to the drive frequency determined for each vibration wave motor, and the output is connected to the phase shift circuit 102. The phase shift circuit 102 is a circuit that outputs two frequency signals whose phases are different from each other by 90 ° or 270 ° from the output of the drive frequency setting circuit 101, and outputs the same to the piezoelectric body drive circuit 103 (103A, 103B). It is connected. The piezoelectric body drive circuit 103 (103A, 103B) is a circuit that inputs a sine wave voltage obtained by amplifying the frequency signal from the phase shift circuit 102 to the electrodes 100-4a and 100-4b of the vibrating body 100-4. The vibrating body 100-4 is excited by the input of a sine wave voltage, and drives the moving element.
[0006]
[Problems to be solved by the invention]
However, in the conventional vibration wave motor driving device described above, a sinusoidal voltage must be generated and applied to the electrode of the vibrating body, which complicates the circuit of the driving device and reduces the energy of the driving device. There was a problem that the loss increased.
Furthermore, the complexity of the circuit of the driving device leads to an increase in the volume of the circuit itself, which makes it difficult to apply the vibration wave motor to portable devices.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an invention according to claim 1 is directed to a vibration wave motor driving apparatus that drives using an oscillating motion of an electric / mechanical energy conversion element that converts electric energy into mechanical energy. / Charging circuit (10, 11, 14, 15, 16) for supplying electrical energy by applying a predetermined voltage to the mechanical energy conversion element, and an inductive element for the electrical / mechanical energy conversion element supplied with the electrical energy A discharge circuit (12, 13) for generating mechanical energy in the electrical / mechanical energy conversion element by discharging through
The electrical / mechanical energy conversion element is connected to the discharge circuit after the charging circuit is connected to the electrical / mechanical energy conversion element, and the electrical / mechanical energy conversion element is connected to the discharge circuit. when applied potential approaches the elevated potential at the start of discharging after the drop, characterized in that it comprises a number of recurrence control circuit (1,2,17) to re-connect the charging circuit.
[0008]
According to a second aspect of the present invention, in the vibration wave motor drive device according to the first aspect, the control circuit has at least a voltage application period during which the charging circuit applies a voltage to the electric / mechanical energy conversion element. The charging control signal is output so that the charging time is longer than the charging time required for charging, and the discharging period of the discharging circuit acting on the electrical / mechanical energy converting element is determined by the energy converting element and the inductive element. The discharge control signal is output so as to have a period substantially equal to the period of the resonance vibration of the circuit constituted by:
[0009]
According to a third aspect of the present invention, in the vibration wave motor drive device according to the second aspect, the control circuit changes the drive period of the electrical / mechanical energy conversion element by changing the output period of the charge control signal. It is characterized by.
[0010]
The invention according to claim 4 is the vibration wave motor drive device according to claim 3, further comprising a current detection circuit (5) for detecting a current supplied from the charging circuit to the electrical / mechanical energy conversion element. The control circuit controls the output period of the charge control signal so that the current value detected by the current detection circuit is less than or equal to a predetermined value.
[0011]
The invention according to claim 5 is the vibration wave motor drive device according to claim 3, further comprising a voltage detector that detects the voltage of the electrical / mechanical energy conversion element immediately before the charging circuit is connected, The control circuit controls the output period of the charging control signal so that the voltage value detected by the voltage detection unit is driven at a driving frequency higher than a driving frequency at which the voltage value is a predetermined value.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram showing an embodiment of a vibration motor driving apparatus according to the present invention, and FIG. 2 is a diagram for explaining the operation thereof.
[0013]
As shown in FIG. 1, the present embodiment includes a drive signal generator 1, a phase shift circuit 2, drive circuits 3 </ b> A and 3 </ b> B, and a high-voltage power supply 10.
The drive signal generator 1 is connected to the drive circuit 3A and the phase shift circuit 2 and outputs _a frequency signal Sa to each of them. Here, frequency signal S _a is a logic signal to the driving cycle period T _a, as shown in FIG. 2 (A) the upper. In the present embodiment, the f _a driving frequency of the vibration body 100-4 and T _a, having a relationship given by T _a = 1 / f _a.
Phase shift circuit 2 inputs the frequency signal S _a which is output from the drive signal generator 1, the same phase 90 ° or a circuit for outputting the 270 ° different frequency signals S _b to the drive circuit 3B.
[0014]
The drive circuits 3A and 3B are respectively connected to the input electrodes 100-4a and 4b of the vibrating body 100-4. When receiving the frequency signal S _a or S _b from the drive signal generator 1 or the phase shift circuit 2, the drive circuits 3A and 3B vibrate. This circuit outputs a drive signal to the body 100-4. In the present embodiment, the drive circuits 3A and 3B having the same circuit configuration are used. Therefore, in the following description, the circuit configuration and operation of only the drive circuit 3A will be described.
[0015]
The drive circuit 3A includes switching elements 11a and 12a, an inductive element 13a, resistors 14a and 15a, a transistor 16a, a phase inverter 17a, and rectifier elements 18a and 19a such as diodes inserted as necessary.
One end of the switching element 11a is connected to the high-voltage power supply 10 via the current detection circuit 5, and the other end is connected to the switching element 12a via the inductive element 13a. The switching element 12a is grounded at one end different from that connected to the switching element 11a via the inductive element 13a. In the present embodiment, for example, a MOS type FET is used as a switching element. However, this is not particularly limited to a MOS type FET, and other switching elements may be used.
[0016]
The input electrode 100-4a of the vibrating body 100-4 is connected to the contact A between the switching element 11a and the inductive element 13a. On the other hand, the input electrode 100-4b of the vibrating body 100-4 is connected to the contact B of the switching element 11b and the inductive element 13b in the drive circuit 3B.
Drive signal output from the generator 1, the drive signal S _a inputted to the drive circuit 3A is split into two in the driving circuit 3A. One of the branched signals is input to the switching element 12a via the phase inverter 17a, and the other is input to the transistor 16a.
[0017]
The switching element 11a is closed, that is, is switched on only when the drive signal _Sa is at the logic level “H” (charge control signal) due to the action of the circuit including the resistors 14a and 15a and the transistor 16a. On the other hand, the switching element 12a is closed only when the drive signal _Sa is at the logic level “L” (discharge control signal) by the signal from the phase inverter 17a.
[0018]
When the drive signal S _a is at logic level "H", the voltage V _d of the high-voltage power source 10 is applied through the switching element 11a to the input electrode 100-4a of the vibration body. Accordingly, the equivalent capacitance of the vibration body 100-4, the voltage V _d is charged. The time required for charging, since the ON resistance of the switching element is small, a very short compared to T _a.
On the other hand, if a logic level "L" of the drive signals S _a, one end of the inductive element 13a is grounded by the switching element 12a. As a result, an electrical resonance vibration is generated due to the equivalent capacitance of the vibrating body 100-4 and the inductance of the inductive element 13a.
[0019]
Now, from time t _0, as shown in FIG. 2 (B) the upper, when the driving signal S _a is assumed to hold the state of the logical level "L", the change of the voltage V _A of the contact A is drawing the lower As shown by the solid line waveform in FIG. 2, the oscillation period and the initial potential are T _r and V _d , respectively, and the damped resonance vibration has the amplitude center at the ground potential. Here, it is considered that the vibration period T _r is determined by the magnitude of the inductance of the inductive element 13a and the equivalent circuit constant (L, C, R, C ₀ ) of the vibrating body.
[0020]
In the present embodiment, as shown in the upper part of FIG. 2 (A), the period T _a (which is “H” for a predetermined time T _c and thereafter becomes “L” corresponding to one period of the vibration period T _r. A frequency signal S _a of T _a = T _c + T _r ) was input to the drive circuit 3A. By using such a frequency signal S _a , the voltage difference δV between the power supply voltage Vd at the moment when the drive signal S _a becomes “H” and the voltage V _{A at} the contact A is minimized, and the equivalent capacitance of the vibrating body is reduced. The amount of charge to be charged is minimized. Therefore, the average current supplied from the high-voltage power supply 10 to the vibrating body through the drive circuit 3A is minimized.
[0021]
As described above, in the present embodiment, the frequency voltage as shown in the lower part of FIG. 2A is applied from the drive circuit 3A to the input electrode 100-4a of the vibrating body 100-4. On the other hand, the frequency voltage applied to the input electrode 100-4a and the frequency voltage whose phase is different by 90 ° or 270 ° are applied to the input electrode 100-4b by the drive circuit 3B. As a result, a traveling wave is formed in the elastic body 100-3, and the moving element is driven.
[0022]
Next, a method for adjusting the drive amount (rotational speed) of the vibration wave motor in this embodiment will be described.
As already described in the prior art, as a method of changing the drive amount of the vibration wave motor, a method of increasing or decreasing the voltage of the frequency voltage applied to the input electrode of the vibrating body (hereinafter referred to as “first method”). And a method of increasing or decreasing the frequency of the frequency voltage (hereinafter referred to as “second method”). In the present embodiment, the first method can be realized by changing the voltage value Vd of the high-voltage power supply 10. However, a high-voltage power supply whose output voltage is generally variable has drawbacks such as a complicated circuit configuration.
[0023]
Therefore, in the present embodiment, the driving amount of the vibration wave motor is adjusted using the second method. That is, by changing the frequency f of the drive signal generator 1 and changing the repetition period T _a (= 1 / f) of the drive signals S _a and S _b , the frequency voltage frequency applied to the vibrator is changed. To make it happen.
Here, the period T _r of the period T _a is determined by the electrical oscillation period is a period that can not be arbitrarily increased or decreased. Therefore, the change of the cycle T _a is the output period of the charge control signal output from the drive frequency generator 1, that is, the period T _c where the drive signal _Sa is at the logic level “H”, T _c = T _a −T _r This is realized by changing so as to satisfy the relationship. However, the period T _c must be longer than the time required to charge the equivalent capacitance of the vibrator.
[0024]
Here, the inventor has experimentally obtained the knowledge that the drive amount of the vibration wave motor can be adjusted from the stop to the maximum amount by changing the drive frequency in the range of 30 kHz to 32 kHz, for example. According to this, the variable amount of the period T _c is about 6% of T _a . Therefore, if it is assumed the charge time 4% of T _a, so that the period T _r may be selected inductive element 13 having an appropriate inductance value of so as to be 90% or less of the T _a .
[0025]
Next, the drive frequency characteristic of the vibration wave motor driven using this embodiment will be described.
FIG. 3 shows the drive amount N of the moving element (rotational speed of the vibration wave motor) when the drive frequency f is scanned from the high frequency f _H to the low frequency f _L , and the current value I _d supplied from the high-voltage power supply. It is a figure which shows a change. The vibration wave motor starts driving at a frequency lower than the driving frequency f ₀ , and the driving amount N increases as the frequency decreases. Further, the drive amount N rapidly decreases at f _{2 when the} drive frequency is further lowered. This is a phenomenon peculiar to a vibration wave motor, and is considered to be a phenomenon that occurs due to a decrease in stability due to excessive vibration of a vibrating body.
[0026]
On the other hand, the current value I _d does not show a large change in the range of the drive frequency f _{H to} f ₁ (f ₂ <f ₁ ) and remains small, but the drive frequency decreases in a frequency range lower than f _1. Increasing gradually. Further, when the drive frequency is further lowered, the current value I _d returns to the initial current value in synchronization with the decrease in the drive amount N at f ₂ or less.
Such a frequency characteristic of the current value I _d is described as follows. The current (motional current) flowing through the L, C, R series resonance circuit of the vibrating body increases as the drive frequency decreases. For this reason, the damped resonance vibration indicated by the voltage V _A at the contact A increases the degree of attenuation as shown by a voltage waveform indicated by a dotted line in the lower part of FIG. As a result, the voltage difference δV (see FIG. 2A) when the drive signal Sa becomes the logic level “H” increases, and the current value I _d supplied from the power source for charging increases. .
[0027]
As described above, in the present embodiment, when the drive frequency f is decreased too much in order to obtain a large drive amount N (f <f ₂ ), the drive amount N is rapidly decreased. In order to avoid this problem, it is necessary to determine the minimum frequency so that the drive frequency f does not become f ₂ or less. However, since the frequency f ₂ varies depending on conditions such as temperature, the minimum frequency cannot be determined unconditionally. Therefore, in this embodiment, it was decided that the current value I _d is not to lower the driving frequency f to the lower value when exceeding the predetermined value I _s.
Specifically, the drive amount N is increased while gradually decreasing the drive frequency f from f _H, and the vibration wave is generated from the high voltage power supply 10 by the current detection circuit 5 connected between the high voltage power supply 10 and the vibration wave motor 100. The current value I _d supplied to the motor 100 is monitored. When the current detection circuit 5 detects that I _d exceeds the predetermined value I _s (I _d ≧ I _s ), the drive frequency generator 1 generates a vibration wave motor at a frequency equal to or higher than the drive frequency f _{s at} that time. Is controlled, the output period (T _c ) of the charge control signal is controlled. Thereby, it is possible to prevent the drive amount N from rapidly decreasing.
[0028]
As described above, the driving device of the present embodiment supplies electric energy by applying a predetermined voltage to the vibrating body based on the rectangular wave logic signal output from the driving frequency generator, and then the vibrating body. Is periodically and repeatedly discharged through the inductive element. Here, since the vibrating body is discharged via the inductive element, the inductance of the inductive element and the equivalent circuit of the vibrating body are included in the vibrating body even though the signal output from the drive frequency generator is rectangular. oscillating voltage of sinusoidal are marked pressurized accordance resonance frequency determined from the constants. Thereby, conversion of electric energy into mechanical energy occurs in the vibrating body, and the vibration wave motor is driven. Therefore, in this embodiment, it is not necessary for the driving device itself to output a sinusoidal signal in order to cause the vibrating body to vibrate, thereby making the circuit configuration of the driving frequency generator simple and compact. Is possible.
[0029]
In this embodiment, the period during which the vibrating body is discharged, that is, the period during which the drive signal Sa is at the logic level “L” is made to coincide with the resonance frequency determined from the inductance of the inductive element and the equivalent circuit constant of the vibrating body. ing. As a result, when the vibrating body is charged again, the amount of current supplied to the vibrating body can be minimized, and the driving efficiency of the vibration wave motor is also improved from this point.
[0030]
On the other hand, the period during which the driving device charges the vibrating body can be set independently of the resonance frequency of the inductive element and the vibrating body, unlike the discharge period. In view of this, the present embodiment pays attention to this characteristic and makes it possible to easily adjust the driving amount of the vibration wave motor by changing the vibration frequency of the vibrating body by increasing or decreasing the charging period.
In addition, the driving device of the present embodiment further monitors the amount of current supplied from the high-voltage power source to the vibrating body by a current detection circuit, and adjusts the frequency for driving the vibration wave motor so that the current value does not exceed a predetermined value. Therefore, it is possible to prevent a sudden decrease in the driving amount, which is a phenomenon peculiar to this type of vibration wave motor.
[0031]
(Other embodiments)
In addition, this invention is not limited to the said embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0032]
For example, in the above-described embodiment, an annular vibration wave motor has been described. However, the technical idea according to the present invention can also be applied to a linear vibration wave motor.
In the above embodiment, in order to ensure stable driving of the vibration wave motor, a current detection circuit is used to monitor the current value supplied from the high voltage power source to the vibrating body. This may be to directly monitor the voltage difference δV between the oscillating voltage and the power supply voltage V _d just before the period T _c or the oscillating voltage value just before the period T _c instead of the current value I _d . In this case, the voltage detection circuit is connected to the electrode 100-4a of the vibration wave motor 100, the frequency when the detected voltage value reaches a predetermined value is f _s, and the drive frequency of the vibration wave motor is less than f _s. The output period (T _c ) of the charge control signal is appropriately adjusted so as not to occur.
[0033]
【The invention's effect】
As described above in detail, according to the invention according to claim 1 or claim 2, it is possible to provide a drive device for a vibration wave motor having a simple circuit configuration and high energy efficiency.
According to the third aspect of the present invention, it is possible to provide a vibration wave motor drive device that can easily control the drive amount of the vibration wave motor.
Furthermore, according to the invention which concerns on Claim 4 or Claim 5, it became possible to provide the drive device of the vibration wave motor which can drive a vibration wave motor in the always stable state.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of a vibration wave motor driving apparatus according to the present invention.
FIG. 2 is a diagram for explaining the operation of the embodiment shown in FIG. 1;
FIG. 3 is a diagram showing a drive amount characteristic of a vibration wave motor driven by the embodiment shown in FIG. 1 and a drive frequency characteristic of a supply current.
FIG. 4 is a diagram showing a general configuration of a conventional vibration wave motor.
FIG. 5 is a block diagram showing a conventional vibration wave motor driving apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Drive frequency generator 2 Phase shifter 5 Current detection circuit 10 High voltage power supply 11, 12 Switching element 13 Inductive element 14, 15 Resistance 16 Transistor 17 Phase inverter 18, 19 Rectifier 100 Vibration body

Claims (5)

In a drive device for a vibration wave motor that drives using the vibration motion of an electrical / mechanical energy conversion element that converts electrical energy into mechanical energy,
A charging circuit for supplying electrical energy by applying a predetermined voltage to the electrical / mechanical energy conversion element;
A discharge circuit for generating mechanical energy in the electric / mechanical energy conversion element by discharging the electric / mechanical energy conversion element supplied with electric energy through an inductive element;
The electrical / mechanical energy conversion element is connected to the discharge circuit after the charging circuit is connected to the electrical / mechanical energy conversion element, and the electrical / mechanical energy conversion element is connected to the discharge circuit. when applied potential approaches the elevated potential at the start of discharging after the drop, and a control circuit to repeat that again connecting the charging circuit,
A drive device for a vibration wave motor, comprising: In the vibration wave motor drive device according to claim 1,
The control circuit is configured so that a voltage application period in which the charging circuit applies a voltage to the electric / mechanical energy conversion element is longer than at least a charging time required for charging the electric / mechanical energy conversion element. Output a charge control signal to
The discharge circuit outputs a discharge control signal so that a discharge period acting on the electrical / mechanical energy conversion element is substantially equal to a period of resonance vibration of a circuit constituted by the energy conversion element and the inductive element. To
A drive device for a vibration wave motor. In the drive device of the vibration wave motor according to claim 2,
The control circuit changes the drive amount of the electrical / mechanical energy conversion element by changing the output period of the charge control signal,
A drive device for a vibration wave motor. In the drive device of the vibration wave motor according to claim 3,
And a current detection circuit for detecting a current supplied from the charging circuit to the electrical / mechanical energy conversion element,
The control circuit controls an output period of the charge control signal so that a current value detected by the current detection circuit is a predetermined value or less;
A drive device for a vibration wave motor. In the drive device of the vibration wave motor according to claim 3,
Furthermore, it has a voltage detector for detecting the voltage of the electrical / mechanical energy conversion element immediately before the charging circuit is connected,
The control circuit controls an output period of the charge control signal so that the voltage value detected by the voltage detection unit is driven at a drive frequency higher than a drive frequency at which the voltage value is a predetermined value.
A drive device for a vibration wave motor.

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