JPH04360133A - Camera - Google Patents

Abstract

PURPOSE:To provide a camera in which the stable polarization state of a piezoelectric body is maintained for a long time and a piezoelectric actuator is always in an action feasible state. CONSTITUTION:This camera is provided with the piezoelectric body 103, the actuator driven by the piezoelectric body 103, a maximum driving voltage impressing means 102 for impressing maximum driving voltage for forming polarization on the body 103, and a maximum driving voltage impressing signal generating means 101 for allowing the means 102 to act in accordance with at least either specified time or specified operation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, and more particularly, to a camera using an actuator driven by a piezoelectric body.

0002

2. Description of the Related Art In recent years, it has been proposed to drive actuators of cameras, such as shutters, with piezoelectric bodies.

[0003] Since this piezoelectric body normally exhibits maximum displacement with an applied voltage of several hundred volts, a high-voltage power source of several hundred volts and a means for controlling this high-voltage power source are required to drive it. It is also required to finely control the amount of displacement of the piezoelectric body.
Correspondingly, high resolution and high precision are also required for the applied voltage.

[0004] Incidentally, the electrical control systems of small precision instruments such as cameras are designed to be operable with low voltage batteries. Furthermore, most cameras in recent years have a built-in strobe, and many use the low-voltage battery as a power source for the strobe to obtain a high-voltage power source of several hundred volts. Therefore, in some cases, this strobe power source of several hundred volts is used to apply a high voltage to the piezoelectric body to drive the actuator of the camera.

FIG. 10 shows the displacement vs. drive voltage characteristics of a typical stack-type (laminated) piezoelectric actuator using the electrostrictive effect, with the vertical axis representing the strain amount and the horizontal axis representing the applied voltage. This is a characteristic diagram for each.

In FIG. 10, point A indicates a state where no polarization has occurred in the piezoelectric material (for example, immediately after production). When a driving voltage is applied to the piezoelectric body in this state, the voltage VB
Until then, no dipole polarization occurs in the piezoelectric material, so no deformation strain occurs (between A and B). When a higher voltage is applied to this piezoelectric body, the piezoelectric body deforms and the maximum drive voltage V
The maximum deformation occurs at max (between B and C). After that, when the applied voltage is gradually lowered, the deformation becomes smaller and 0V
At the same time, it passes through point D and the amount of distortion becomes 0 at voltage -VB (C-
between D and E). By applying this voltage -VB, the polarity of the dipole polarization of the piezoelectric body becomes opposite to that when voltage VB was applied, and by applying a negative voltage up to voltage -Vmax, the amount of distortion becomes
Shows the same value as when max is applied (between E and F). Furthermore, this time, when the applied voltage is increased in the positive direction, it passes through point D at 0V and reaches point B at voltage VB. Furthermore, by applying the voltage Vmax, the aforementioned maximum deformation point C is reached.

[0007] Here, when the applied voltage is lowered to 0V, it reaches point D along the solid line CD. When the applied voltage is increased from this point D to Vmax, the maximum displacement point C is reached along the dotted line DC. Thereafter, when applied voltages from 0 to Vmax are applied alternately, the amount of displacement decreases along the solid line CD, and further increases along the dotted line DC.

The relationship between the amount of displacement of the piezoelectric body and the applied voltage depends on the state of dipole polarization inside the piezoelectric body. Generally, once a piezoelectric material is polarized, it maintains a certain degree of stability until a reverse voltage is applied. However, it is also known that even if no reverse voltage is applied, polarization gradually decreases due to spontaneous discharge and disappears in a few years. Further, in order to restore the piezoelectric material to a completely polarized state, it is necessary to apply the maximum driving voltage to the piezoelectric material for several minutes.

[0009] Considering the use of piezoelectric actuators in cameras based on these circumstances, it is important to maintain stable dipole polarization of the piezoelectric material because the lifespan of the camera is from several years to several decades. proves difficult.

0010

[Problems to be Solved by the Invention] As described above, in a camera using the conventional piezoelectric actuator described above, it is difficult to maintain a stable polarization state of the piezoelectric material for a long period of time, and after the polarization is resolved, it is difficult to maintain the stable polarization state of the piezoelectric body for a long period of time. It becomes difficult to operate accurately and instantaneously.

Furthermore, requiring application of the maximum drive voltage for several minutes prior to use risks impairing timely use. In other words, in the case of a camera, there is a risk of missing a valuable photo opportunity.

An object of the present invention is to provide a camera that focuses on the characteristics of the piezoelectric actuator, maintains a stable polarization state of the piezoelectric body for a long period of time, and allows the piezoelectric actuator to always perform instantaneous and accurate operations. It is.

[0013]

[Means for Solving the Problems] In order to achieve the above object, a camera according to the present invention has the following features as shown in the conceptual diagram of FIG.
A piezoelectric body 103, an actuator 104 driven by the piezoelectric body 103, and a maximum drive voltage applying means 102 that applies a maximum drive voltage for forming polarization to the piezoelectric body 103.
and maximum drive voltage application signal generation means 101 for operating this maximum drive voltage application means 102 in accordance with at least one of a predetermined timing and a predetermined operation.

[0014]

[Operation] In the present invention, the maximum drive voltage application signal generating means 101 operates the maximum drive voltage application means 102 in accordance with at least one of a predetermined timing and a predetermined operation,
A maximum driving voltage is applied to the piezoelectric body 103 to form polarization, and the piezoelectric body 103 drives the actuator 104 .

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2(a) is a block diagram of a first embodiment of the present invention.

The actuator 104 that drives the shutter of the camera, etc. is driven by a piezoelectric body 103 such as a piezoelectric ceramic, and the piezoelectric body 103 has a maximum drive voltage applying means 1.
02, the maximum driving voltage for forming polarization is applied, and when a switch 101a constituted by a power switch of a camera or the like is turned on, the maximum driving voltage applying means 102 operates, and the piezoelectric body A maximum drive voltage is applied that causes polarization to occur at 103.

FIG. 3 shows the first embodiment of the present invention shown in FIG. 2(a) above.
FIG. 2 is a specific electrical circuit diagram of an example.

The high voltage source 1 is a power source for the built-in strobe of the camera, and this power source includes a booster circuit 11 that boosts the low voltage of a built-in battery, and a main capacitor 1.
2. Further, the circuit 11 becomes activated when a power switch SW92 in the piezoelectric control signal generating section 2, which will be described later, is turned on, and outputs a high voltage, for example, about 330V.

The piezoelectric control signal generating section 2 includes a power switch SW92, a control CPU 20, and a control CPU 20.
a decoding section 21 controlled by the piezoelectric body 5, a drive voltage limiting section 22 that limits the application of voltage exceeding the maximum rated value to the piezoelectric body 5, and a constant current injection section 3 and a constant current discharge section 4, which will be described later.
It has a constant current injection control section 23 and a constant current release control section 24, which respectively control.

The constant current injection section 3 and the constant current discharge section 4 are circuits that control the amount of displacement of the piezoelectric body 5, and are controlled by the constant current injection control section 23 and the constant current discharge control section 24, respectively. It has become so.

The piezoelectric body 5 is a piezoelectric element that utilizes a piezoelectric effect in which displacement occurs when a voltage is applied, and an actuator (not shown) is driven by this displacement. Further, this piezoelectric body 5 is attached with an applied voltage detection section 6 that detects the applied voltage, and a displacement amount detection section 7 that detects the amount of displacement of this piezoelectric body 5. Note that Cp in FIG. 3 represents an equivalent capacitor component of the piezoelectric body 5.

Vcc in FIG. 3 is a constant voltage source for the CPU 20, logic circuits such as the decoder 21, drive voltage limiter 22, etc., and is set to 5V in this embodiment.

The control CPU 20 has a power switch S.
It operates when W92 is turned on, and the applied voltage detection section 6
, a CPU that transmits a control signal to the decoding unit 21 according to information obtained from the displacement amount detection unit 7 and the like. That is, in accordance with the above information, a direction signal indicating the direction in which the piezoelectric body 5 is driven and a drive control signal controlling the driving speed are transmitted to the decoding unit 21 via the signal lines 2a and 2b, respectively. It has become. This drive control signal is a pulse wave modulation (PWM) signal called duty drive, and is a pulse wave modulation (PWM) signal.
This is a method of adjusting the drive amount by allocating the time at the "H" level and the time at the "L" level.

The decoding section 21 is a logic circuit formed of, for example, a NAND circuit and an inverter circuit, and decoding the direction signal and drive control signal sent from the CPU 20. Its output signal is on signal lines 2c, 2
d to the constant current injection control section 23 and the constant current discharge control section 24, respectively. The signal passing through the signal line 2c is limited by the drive voltage limiter 22 and processed so that the voltage applied to the piezoelectric body 5 does not exceed the maximum rated value.

The driving voltage limiting section 22 includes a limit voltage generating section 22a, a comparator 22b, a NAND circuit,
The voltage applied to the piezoelectric body 5 is divided by the applied voltage detection unit 6, which is composed of an inverter circuit, etc., and the reference voltage 2e generated by the limit voltage generation unit 22a.
A comparison is made by the comparator 22b. Only when the divided voltage is lower than the reference voltage 2e, an injection signal is allowed to be sent from the decoder 21 to the constant current injection controller 23 via the signal line 2i. This results in
The piezoelectric body 5 is controlled so that a voltage higher than necessary is not applied to the piezoelectric body 5.

The constant current injection control section 23 includes a transistor Q
23 and resistors R23a, R23b, and R23c, the switching circuit is configured to perform a switching operation based on the signal on the signal line 2i, and to control the constant current injection section 3 via the output signal line 2g.

The constant current release control unit 24 includes a transistor Q
24a, Q24b and resistors R24a, R24b, R24
c, R24d, and R24e are connected as shown in the figure.Similar to the constant current injection control section 23, it performs switching operation based on the signal on the signal line 2d, and outputs the signal via the output signal line 2h. The constant current emitting section 4 is controlled.

In the applied voltage detection section 6, the voltage applied to the piezoelectric body 5 is divided by the resistor R6a and the resistor R6b, and the divided voltage is input to the comparator 22b and the A/D converter 61. It looks like this. When this partial voltage is f and the voltage applied to the piezoelectric body 5 is Vp, the partial voltage f is expressed as f=Vp·(R6b/(R6a+R6b)). Furthermore, the partial voltage f input to the A/D converter 61 is converted into a digital signal by this converter and transmitted to the control CPU 20 as an applied voltage signal.

The displacement amount detection section 7 measures the amount of displacement of the piezoelectric body 5 directly, or measures the amount of movement of a shutter sector, etc. driven by this piezoelectric body 5, and then generates a displacement amount detection signal converted into a digital signal. is transferred to the control CPU 20.

Note that when there is no current applied to the piezoelectric body 5, that is, when the residual capacitance component Cp of the piezoelectric body 5 spontaneously discharges, the resistors R6a,
Since current is discharged through R6b, the potential difference of the piezoelectric body 5 is caused by the capacitance component Cp and the resistor R6a.
, R6b, and becomes 0V with a time constant determined by R6b.

The constant current injection section 3 turns on and off the transistor Q3 in response to a signal sent from the piezoelectric control signal generating section 2 via the signal line 2g. The above signal is low active and turns on the above transistor Q3, but in this case, this transistor Q
The potential difference VR3a applied across the resistor R3a on the emitter side of the transistor Q3 is the difference between the potential difference across the series circuit consisting of the diodes D3a and D3b and the potential difference between the base and emitter of the transistor Q3. Further, the current value flowing through the resistor R3a is determined as (VR3a/R3a), and this current value, the current value flowing through the signal line 2g, and the current value flowing through the resistor R3b are determined by the constant current injection part
The value of the current flowing through the output line 3a is determined. By determining circuit constants such that the current value of the resistor R3a is sufficiently larger than the current value of the resistor R3b and the signal line 2g, the characteristics of the transistor Q3, diodes D3a, D3b, and resistor R3a are determined. It is possible to make the current constant by using only Note that when the signal from the signal line 2g is at the "H" level, the transistor Q3 is turned off, the circuit is cut off, and no current is injected into the output line 3a.

The constant current emitting section 4 turns on and off the transistor Q4 in response to a signal sent from the piezoelectric control signal generating section 2 via the signal line 2h. The signal is high active and turns on the transistor Q4, but in this case, as in the case of the constant current injection section 3, the resistor R on the emitter side of the transistor Q4
The potential difference VR4a applied across 4a is the potential difference across the series circuit consisting of diodes D4a and D4b, and
This is the difference from the potential difference generated between the base and emitter of transistor Q4. Further, the current value flowing through the resistor R4a is determined as (VR4a/R4a), and this current value, the current value flowing through the signal line 2h, and the current value flowing through the resistor R4b form the input line of the constant current discharge section 4. The value of the current flowing through 4a is determined. By determining circuit constants such that the current value of the resistor R4a is sufficiently smaller than the current value of the resistor R4b and the signal line 2h, the characteristics of the transistor Q4, the diodes D4a, D4b, and the resistor R4a are determined. It is possible to make the current constant by using only In addition,
When the signal from the signal line 2h is at the "L" level, the transistor Q4 is turned off, the circuit is cut off, and no current is injected from the input line 4a.

[0034] Here, the operation when applying voltage to the piezoelectric body 5 and increasing the voltage will be explained with reference to FIGS. 3 and 4.

In FIG. 3, under the control of the CPU 20, the direction signal transmitted to the signal line 2a is set to "L".
In addition, when the drive control signal transmitted to the signal line 2b is set to the "H" level, the output signal lines 2d and 2c of the decoder 21 are set to the "L" level and "L" level, respectively.
It becomes H” level.

Now, when the voltage applied to the piezoelectric body 5 is lower than the limit value determined by the limit voltage generating section 22a, that is, the output of the comparator 22b is "H".
" level, the signal line 2i becomes "H" level. As a result, the input of transistor Q23 of constant current injection control section 23 changes from "L" level to "H" level, so that this transistor Q23 is turned on, and the signal on the signal line 2g becomes "L" level. Therefore, the input of the constant current injection section 3 becomes "L" level, so that the current (VR3a/R
3a) flows into the piezoelectric body 5.

As shown in FIG. 4, the current flowing through the signal line 5a is i3a (=VR3a/R3a), and the signal line 5a is
The currents flowing through b and 5c are respectively ib and ic, and resistance R6
The current ib flowing through the signal line 5b is expressed as shown in FIG. Assuming that no current is consumed in the applied voltage detection section 6 shown by, the voltage Vp is

[0038]

[Math 1]

From [0039], Vp=i3a・R6+(V0−i3a・R
6)×
EXP(-
t/Cp・R6) Vp=i3a・R6+K
・EXP(-t/Cp・R6) (K is a constant).

Now, the voltage at time t=0 is V0
Then, K = V0-i3a・R6, and Vp= i3a・R6+(V0-i3a
・R6) ×
E
It becomes XP(-t/Cp・R6).

Here, if the duty ratio of the drive control signal of the control CPU 20 is d, then Vp=d・i3a・R6(1−EXP
(-t/Cp・Vp)+
V
It can be expressed as 0.EXP(-t/Cp.R6), and the voltage applied to the piezoelectric body 5 is determined by time and duty ratio.

[0042] Also, the voltage change rate when t=0 is:
dV/dt= (-1/Cp・R6)×(V0-d・
i3a・R6) ×

From EXP(-t/Cp・R6), (dV/dt)t=0 = d(i3a/Cp
) - (V0/Cp・R6). Also, even if t≠0,

[0043]

[Math 2]

Then, the above voltage change occurs.

[0045] Here,

[0046]

[Math 3]

If the relationship between Cp, R6, and i3a is determined as follows,

[0048]

[Math 4]

It is also possible to approximate as follows.

As can be seen from the above, by changing the duty ratio d, it is possible to arbitrarily control the rate of change of the applied voltage Vp applied to the piezoelectric body 5.

By the way, when the voltage Vp exceeds the limit value determined by the limit voltage generating section 22a, the output of the comparator 22b becomes "L" level. Therefore, the output of the drive voltage limiting section 22 is
It is always at the "L" level regardless of the output of 1, and the constant current injection limiting section 23 and the constant current injection section 3 are in an OFF state. This operation prevents the applied voltage Vp from exceeding the limit value.

Next, the operation when lowering the voltage of the piezoelectric body 5 will be explained with reference to FIGS. 3 and 5.

In FIG. 3, under the control of the CPU 20, the direction signal transmitted to the signal line 2a is set to "H".
In addition, when the drive control signal transmitted to the signal line 2b is set to the "H" level, the output signal lines 2c and 2d of the decoder 21 are set to the "L" level and "L" level, respectively.
It becomes H” level.

As described above, since the signal on the signal line 2c that controls constant current injection, that is, voltage rise, is at the "L" level, the operation of the transistor Q3 of the constant current injection section 3 is turned off. On the other hand, since the signal on the signal line 2d for controlling constant current discharge is at the "H" level, both transistors Q24a and Q24b of the constant current discharge limiting section 24 are turned on, and the output line of the constant current discharging limiting section 24 is turned on. 2
The signal h becomes "H" level. As a result, the transistor Q4 of the constant current emitting section 4 is turned on, and the signal line 4a
will cause a constant current to flow to the ground side.

Now, with reference to FIG. 5, the applied voltage Vp will be determined in the same manner as in the case where a voltage is applied to the piezoelectric body 5 described above.

As shown in FIG. 5, similarly to FIG. 4, the current flowing through the signal line 5a is expressed as i4a (=VR4a/R4a).
, the currents flowing through the signal lines 5b and 5c are respectively ib,
ic, R6 is the combined resistance of resistor R6a and resistor R6b, Q is the charge accumulated in the capacitance component Cp of piezoelectric body 5, and Vp is the voltage applied to piezoelectric body 5, and the current ib flowing through the signal line 5b is , assuming that no current is consumed in the applied voltage detection section 6 shown in FIG.

[0057]

[Math 5]

From [0058]

[0059]

[Math 6]

Then, the rate of change of the applied voltage Vp is also as in the above case,

[0061]

[Math 7]

It can be expressed as follows.

From the above, in this case as well, the rate of change of the applied voltage Vp applied to the piezoelectric body 5 can be arbitrarily controlled by changing the duty ratio d, as in the case of voltage increase described above. becomes possible.

Now, the constants of the circuit shown in FIG.
c=560KΩ, R24e=8.2KΩ, R3b=R4
b=100KΩ, R3a=R4a=27Ω, R6a=1
MΩ, R6b=27KΩ, diodes D3a, D
The voltage drops of 3b, D4a, and D4b are each 0.5
V, the base-emitter voltages of the transistors Q3 and Q4 are each 0.6 V, and the equivalent capacitance component of the piezoelectric body 5 is 1 μF.

When the constant current injection section 3 is turned on, the voltage applied to R3a is VR3a=(0.5+0.5)-0.6=0.4ViR
3a= VR3a/R3a =14.8mA

00
66]

[Math. 8]

Therefore, almost no current flows through R3b. In addition, when the voltage of high voltage source 1 is 330V, R23
The current flowing through c is approximately 330V/560kΩ=0.6mA, so i3a=14.2mA.

Similarly, VR4a=0.4V iR3a=14.8mA

[0069]

[Math. 9]

Therefore, almost no current flows through R4b, and the current flowing through R24e is approximately 5V/R24e=0.6mA, so i4a=-14.2mA.

[0071] Also,

[0072]

[Math. 10]

[0073] Therefore,

[0074]

[Math. 11]

[0075], V0 is in the range of 0 to 150V, and from i3a/Cp = 14200,

[0076]

[Math. 12]

If it is within the range of

[0078]

[Math. 13]

It can be considered as follows.

[0080] Also, the rate of change of applied voltage (dV/d
t), measure the voltage of the piezoelectric body 5,
(dV/dt)=(d・i3a/Cp)−V0/Cp
・It can be calculated as R6.

Next, the operation of applying the maximum voltage to the piezoelectric body 5, that is, applying the maximum driving voltage to the piezoelectric body, is shown in FIG.
This will be explained with reference to FIG.

First, the control CPU 20 increases the voltage applied to the piezoelectric body 5 according to the procedure described above. At this time, the duty ratio is at its maximum, and the voltage is increased efficiently. Then, after a certain period of time, when the voltage applied to the piezoelectric body 5 reaches the voltage value limited by the drive voltage limiting section 22, further voltage application is stopped. This is as described above. Further, the applied voltage may be limited by the CPU 20 detecting the applied voltage signal, which is an output signal of the A/D converter 61 in the applied voltage detection section 6.

Now, if we calculate the time t for the applied voltage Vp to go from, for example, 0V to 150V, with reference to the above formula, Vp=i3a・R6+(V0−i3a・R
6)×
EXP(-
t/Cp・R6), V0=0, Vp=i3a・R6(1-EXP(-t/
Cp・R6)) Therefore, t=−Cp・R6・log(1
-V/i3a·R6), and if the circuit constants mentioned above are adopted in the circuit of FIG. 3, the above-mentioned time t becomes t=0.0106 seconds.

That is, for example, when a maximum driving voltage of 150V is applied to the piezoelectric body 5 for about 0.5 seconds, the voltage of about 0.4
It is possible to apply the voltage for 9 seconds (0.5-0.0106).

Although not shown, a confirmation circuit is provided to confirm that the strobe current has been increased to a predetermined voltage, and when there is an output from this confirmation circuit, the above maximum drive voltage is applied. You may also have them do this.

FIG. 6 is a schematic flowchart of the control CPU 20 when performing the above-described operations.

As shown in FIG. 6, this operation is performed in conjunction with power-on, and the maximum drive voltage is applied. The CPU first performs initial settings such as memory clear in step S61. Next, in step S62, the camera is controlled and driven to be in a state where it can take pictures. Specifically, these operations include moving the lens position from a so-called sinking area to a normal area, and opening a built-in lens cover. Next, in step S63, the operation of applying the piezoelectric maximum drive voltage described above is performed. Thereafter, in step S64, the piezoelectric drive voltage application described above is turned off, and in step S65, key input, optical measurement,
Performs normal camera operations such as shooting mode settings and exposure settings.

FIG. 2(b) is a block diagram of a second embodiment of the present invention.

The piezoelectric body 103 is a piezoelectric element that drives an actuator (not shown). Note that this actuator is the same as that in the first embodiment. The maximum drive voltage applying means 102 is an application means that applies a maximum drive voltage that causes the piezoelectric body 103 to form polarization. The switch 101b is a specific operation switch for a camera or the like, and when this switch is turned on, the maximum drive voltage applying means 102 operates so that the maximum drive voltage for forming polarization on the piezoelectric body 103 is applied. It has become.

The electric circuit of this second embodiment has the same configuration as the first embodiment described above, and has a power switch SW92 (
(see Figure 3) instead of a specific operating switch, e.g.
It operates in conjunction with the first (1st) release switch, etc., and the other configurations and operations are the same as those of the first embodiment described above.

FIG. 7 is a schematic flowchart of the control CPU 20 in the second embodiment.

As shown in FIG. 7, the CPU is
As in the embodiment, first, in step S71, initial settings such as memory clear are performed, and then in step S7
In step 2, the camera is controlled and driven so that it is in a state where it can take pictures. Next, in step S73, switch data is read, and in step S74, various calculation modes are set. Next, in step S75,
It is checked whether the 1st release switch is on or not, and if it is on, in step S76, the operation of applying the maximum drive voltage to the piezoelectric body is performed in the same manner as in the first embodiment. Thereafter, in step S77, the application of the piezoelectric drive voltage is turned off, and then, in step S78a, it is checked whether the 2nd release switch is on.

[0093] In step S75, if the first release switch is off, the process returns to step S73. If the second release switch is on in step S78a, the exposure sequence is operated in step S79, and then the process returns to step S73. If the second release switch is off in step S78a, it is checked in step S78b whether the first release switch is on, and if it is on, the process returns to step S78a. In step S78b, if the first release switch is off, the process returns to step S73 again.

In the case of this second embodiment, the maximum drive voltage is applied to the piezoelectric body 5 (see FIG. 3) every time the first release switch is operated.

FIG. 2(c) is a block diagram of a third embodiment of the present invention.

Piezoelectric body 103, maximum drive voltage application means 10
2 has the same structure and operation as the first and second embodiments. The timer 101c is controlled by the control CPU 2.
Under the control of this timer, the maximum drive voltage applying means 102 operates to apply the maximum drive voltage that causes polarization to be formed in the piezoelectric body 103.

The electric circuit of the third embodiment is similar to that of the first embodiment, and as shown in FIG. The circuit configuration is such that the maximum drive voltage is applied to the piezoelectric body 5 at regular intervals using a timer or counter inside the CPU 20.
The operation is similar to the first embodiment described above. The external timer T90 is connected to the port P91 on the control CPU 20.
It is designed to connect to.

FIG. 8 is a schematic flowchart of the control CPU 20 when controlled by the external timer T90 in the third embodiment.

As shown in FIG. 8, the CPU
As in the embodiment, first, in step S81, initial settings such as memory clear are performed, and then in step S8
2, it is checked whether the external timer T90 is activated. When activated by the external timer T90, in step S83, the operation of applying the maximum drive voltage to the piezoelectric body is performed in the same manner as in the first embodiment, and then in step S8
In step 4, the piezoelectric drive voltage application is turned off. In the above step S82, if the activation is not by the external timer T90, that is, in the case of normal activation, the camera is controlled and driven in step S85 to be in a state where it can take pictures, and in step S86, key input,
Performs normal camera operations such as light measurement, shooting mode settings, and exposure settings.

Note that it is appropriate that the operation of applying the maximum drive voltage to the piezoelectric body by the external timer T90 be performed, for example, once a month.

FIG. 9 is a schematic flow chart of the control CPU 20 when controlled by the internal timer or counter of the control CPU 20 in the third embodiment.

As shown in FIG. 9, the CPU
As in the embodiment, first, in step S91, initial settings such as memory clear are performed. Next, in step S92, the camera is controlled and driven to be in a state where it can take pictures, and in step S93, normal camera operations such as key input, light measurement, shooting mode setting, exposure setting, etc. are performed. Next, in step S94, it is checked whether the internal timer or counter of the control CPU 20 has timed out. Here, if the time is up, in steps S95 and S96, the operation of applying the piezoelectric body maximum drive voltage is performed in the same manner as in the first embodiment, and after turning off the piezoelectric body drive voltage application, step S9
Return to step 3 and proceed to normal camera operation. Further, in step S94, if the time is not up, the process returns to step S93 and continues normal camera operation. In this example, it is preferable that the power supplied to the control CPU 20 is not turned off, and that the timer or counter continues to operate even when the camera is not in use.

[0103] In this way, by applying a high voltage to the piezoelectric body during certain camera operations or at certain intervals, it is possible to maintain the polarization state of this piezoelectric body in a stable state. By applying a predetermined voltage, it is possible to always obtain a stable displacement amount and response according to the voltage.

[0104] Furthermore, since a high voltage is applied periodically or at a certain frequency, the effect can be expected even if the application time per time is shortened, and rapid imaging becomes possible.

Now, the first to third embodiments described above are as follows:
It is not limited to only one type, but may be used in combination in order to make the effect obtained by each more efficient.

Furthermore, these embodiments can be applied not only to cameras but also to other electrical products, such as video equipment.

[0107]

[Effects of the Invention] As explained above, according to the present invention, since a high voltage is applied to the piezoelectric body periodically or at a certain frequency,
It is possible to provide a camera in which a stable polarization state of a piezoelectric body can be maintained for a long period of time, and a piezoelectric actuator can always operate instantaneously and accurately.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing the concept of the present invention.

FIG. 2 is a configuration block diagram of first to third embodiments of the present invention.

FIG. 3 is an electric circuit diagram showing a specific configuration of first to third embodiments of the present invention.

FIG. 4 is an explanatory circuit diagram for determining the state of the applied voltage when the voltage applied to the piezoelectric body 5 of the present invention increases.

FIG. 5 is an explanatory circuit diagram for determining the state of the applied voltage when the voltage applied to the piezoelectric body 5 of the present invention drops.

FIG. 6 is a schematic flowchart showing the operation of the control CPU 20 in the first embodiment of the present invention.

FIG. 7 is a schematic flowchart showing the operation of the control CPU 20 in the second embodiment of the present invention.

FIG. 8 is a schematic flowchart showing the operation of the control CPU 20 when controlled by an external timer in the third embodiment of the present invention.

FIG. 9: Control CPU 2 in the third embodiment of the present invention.
Control CPU when controlled by 0 internal timer
20 is a schematic flowchart showing the operation according to No. 20.

FIG. 10 is a displacement vs. drive voltage characteristic diagram of a general stack type (laminated type) piezoelectric actuator using an electrostrictive effect.

[Explanation of symbols]

101... Maximum drive voltage application signal generation means 102... Maximum drive voltage application means 103... Piezoelectric body 104... Actuator

Claims (1)

[Claims] 1. A piezoelectric body, an actuator driven by the piezoelectric body, a maximum drive voltage applying means for applying a maximum drive voltage for forming polarization to the piezoelectric body, and a maximum drive voltage applying means for applying a maximum drive voltage to the piezoelectric body at a predetermined level. 1. A camera comprising: maximum drive voltage application signal generating means for operating in response to at least one of the timing and a predetermined operation.