JPH05183209A - Laminated piezoelectric element - Google Patents

Abstract

PURPOSE:To obtain prescribed displacement in a short time through simple turning on/off control. CONSTITUTION:The displacement of each piezoelectric body (5-0)-(5-N) of the title element 5 when the same voltage is applied across each piezoelectric body (5-0)-(5-N) is set in advance so that the displacement of the body 5-1 can become 2X and that of the body 50-N can become 2<n>X, with X representing the displacement of the body 5-0. Therefore, when a command from an operation instructing signal outputting means 1 is impressed upon each piezoelectric body through a drive circuit section 4 after A/Dconverting the command at a drive control circuit 2, the displacement of the element 5 can digitally be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element, and more particularly to a laminated piezoelectric element capable of easily controlling the displacement amount in an actuator using a piezoelectric body.

[0002]

2. Description of the Related Art Since a piezoelectric body has a good responsiveness to an applied input, a drive device for driving a driven body by an actuator using the piezoelectric body has conventionally been required to operate at high speed especially in electronic devices of various fields. It is widely used as an actuator for a driven body and is recently proposed to be used for opening / closing control of a shutter, a diaphragm mechanism, etc. in the field of cameras.

However, the change of the deformation amount with respect to the applied voltage has a hysteresis as shown in FIG. 7, and since the deformation of the piezoelectric member is not linear, the minute deformation amount and the deformation speed of the piezoelectric member are small. There was a problem that it was difficult to control.

In view of the above-mentioned problems, the present applicant has previously proposed Japanese Patent Application No. 03-147625 to correct hysteresis and non-linearity, which are characteristics of a piezoelectric material.
A technical means has been proposed in which the characteristic curve of the voltage-displacement of the piezoelectric body is made into a ROM table in advance and stored in the camera, and the generated displacement amount of the piezoelectric body is controlled by referring to this table as needed. According to this means, since all the drive control of the piezoelectric body is performed based on the table table stored in this ROM, position information such as the current position of the piezoelectric body is not necessary in principle, This is significant because it does not require a position detecting means of resolution.

[0005]

However, the above-mentioned conventional example has the following problems. That is,
The voltage-displacement characteristic curve of the piezoelectric body is stored in the camera as a ROM table, and the control is performed by referring to this table as needed. According to this method, the table is always stored. Since the piezoelectric body is controlled while referring to it, processing time is required for "data reading", "calculation", and "output".

Further, a movement different from the movement on the stored characteristic curve, for example, starting from the "0" point in FIG. 7 and returning to the "G" point and returning to the "0" point, that is, on the way In the case of folding back at, the characteristic curve of the piezoelectric body is considered to shift to a similar shape, an approximate shape of the characteristic curve is obtained, and the piezoelectric body is controlled based on this data. However, this requires more processing time than that described above and is not suitable for an operation requiring a fast response.

Further, a method of reducing the stored data in order to reduce the data storing the characteristic curve, and interpolating between them to obtain the data is also described in the above conventional example.
However, also in this case, another time is required for the interpolation calculation, and another problem occurs that the accuracy of the characteristic data obtained by the "interpolation" is reduced.

Therefore, an object of the present invention is to solve the above problems and to provide a laminated piezoelectric element which can obtain a predetermined displacement amount in a short time by simple on / off control in an actuator using a piezoelectric body. ..

[0009]

According to the laminated piezoelectric element of the present invention, a plurality of piezoelectric elements having different dimensional changes due to the application of the same voltage are laminated, and the voltage applied to the plurality of piezoelectric elements is changed. It is characterized in that a desired dimensional change is obtained by controlling on / off.

[0010]

This laminated piezoelectric element comprises a plurality of piezoelectric elements having different dimensional changes, and the displacement amount of each element is determined by the signal corresponding to the coded digit. Then, each piezoelectric element is on / off controlled based on a signal from the operation command signal output means. Therefore, the displacement amount can be determined without being affected by the hysteresis inherent in the piezoelectric body.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing the basic concept of the present invention. Reference numeral 1 is an operation command signal output means for outputting a signal for performing a camera operation, for example, when operating a shutter or a diaphragm mechanism in a camera. The signal output part of is equivalent to this. Next, the signal from the operation command signal output means 1 is sent to the drive control circuit 2. The drive control circuit 2 is a part that outputs a drive signal to the laminated piezoelectric element 5 as an actuator described later. The detailed operation will be described later, and thus the description thereof is omitted here.

The output from the drive control circuit 2 is sent to each of the piezoelectric drive circuits 4-0 to 4-N. Piezoelectric bodies 5-0 to 5-N are connected to the drive circuits 4-0 to 4-N, respectively, and these piezoelectric bodies change their displacements when a voltage is applied from the drive circuit section 4. Occur. Here, the drive circuit unit 4 and the laminated piezoelectric element 5 have at least 2
Although it is composed of more than N pieces, this will be described next with reference to FIG.

FIG. 2 is a block diagram of a circuit for driving the laminated piezoelectric element according to the first embodiment of the present invention. The CPU 13 incorporates the operation command signal output means 1 and the signal conversion
A drive control circuit 2 including an arithmetic unit 10, a storage unit 11, and an execution control unit 12, and a drive circuit 4-described later with reference to FIG.
.., 4-N, and a laminated piezoelectric element 5 composed of piezoelectric bodies 5-0, 5-1 ,. Has been done.

The signal conversion / calculation means 10 in the drive control circuit 2 performs various calculations after A / D conversion of the operation command signal from the operation command signal output means 1 based on a command from the CPU 13 and digitization. Perform processing. The storage means 11 also stores the (n + 1) -bit data output from the means 10. Execution, stop, data transfer, etc. of the operation for each of these means 10 and 11 are performed by the execution control unit 12 based on a command from the CPU 13.

In FIG. 2 constructed in this way, first, when a signal for operating the diaphragm mechanism is applied from the operation command signal output means 1 to the signal converting / calculating means 10, the signal converting / calculating means 10 Information such as how much the aperture value is set is obtained from the CPU 13. Upon receiving this information, the signal conversion / operation means 10 performs A / D conversion to convert the aperture value information into a (N + 1) -bit digital signal. Then, in response to an instruction from the execution control unit 12, the (N + 1) -bit digital signal is transferred to the storage unit 11. The transfer method here may be serial transfer or parallel transfer.

By this transfer, (N +
1) Bit digital signal data is set, but the drive circuit 4 is stored in the storage means 11 for each bit.
-0 to 4-N are connected to the piezoelectric bodies 5-0 to 5-N, respectively.

Returning to the above description, the storage means 11
Although there is data of the (N + 1) -bit digital signal set in (1), when the execution control unit 12 outputs a data discharge signal (OUT) to the storage unit 11, (N + 1) of the storage unit 11 is output. The contents of the storage means 11 are transferred to the drive circuits 4-0 to 4-N corresponding to the respective bits, and the drive circuits 4-0 to 4-N operate, whereby the piezoelectric bodies 5-0 to 5-N. Will generate displacement.

Here, the drive circuits 4-0 to 4-N are composed of (N + 1) identical drive circuits which will be described later with reference to FIG. The piezoelectric bodies 5-0 to 5-N are well-known piezoelectric bodies, but the amount of displacement X generated by the piezoelectric body with respect to a predetermined applied voltage corresponds to the (N + 1) bit of the storage means 11 described above. It is a thing.

That is, letting X be the generated displacement amount corresponding to the predetermined applied voltage E of the piezoelectric body 5-0 corresponding to the 0th bit (minimum bit) of the storage means 11, the Nth bit of the storage means 11 is assumed. The generated displacement amount corresponding to the same predetermined applied voltage E as the 0th bit on the corresponding piezoelectric body 5-N is (X · 2 ^N ).

Considering that the above-described piezoelectric bodies 5-0 to 5-N use the same predetermined applied voltage, the piezoelectric bodies 5-0 to 5-N are laminated type piezoelectric bodies. When considered, its effective length (that is, the stack length that defines the amount of displacement generated for the same predetermined applied voltage) is X ′ · 2 ^N, where X ′ is the stack length of the minimum bit. In other words, the piezoelectric body corresponding to a higher bit position in the storage means 11 has a larger stack length.

Although the operation of FIG. 2 has been described above, in actual use, a moving object (for example, a shutter or a blade of a diaphragm) is connected to the piezoelectric bodies 5-0 to 5-N. Therefore, the signal from the operation command signal output means 1 is converted into a predetermined form by the signal conversion / operation means 10, and the converted data is set in the storage means 11. Then, the execution control unit 12 controls the output timing of the stored data and the conversion method in the signal conversion / calculation unit 10, and as a result, the moving object is controlled.

FIG. 3 is a circuit diagram of one of the piezoelectric body driving circuits 4-0, 4-1, ..., 4-N shown in FIG. 2, in which a high voltage source 3 and a constant current injection unit 24 are provided. Constant current emission unit 2
5, a constant current injection control unit 26 and a constant current emission control unit 27 that control the injection unit 24 and the emission unit 25, respectively, are the main components.

The high voltage source 3 is a power source for the built-in strobe of the camera, and this power source is a booster circuit 21 for boosting the low voltage of the built-in battery as well known, and the main capacitor 2.
2 and. Further, the circuit 21 outputs a high voltage, for example, about 330V. The constant current injection unit 24 and the constant current emission unit 25 are circuits that control the amount of deformation of the piezoelectric body 5, and are controlled by the constant current injection control unit 26 and the constant current emission control unit 27, respectively. Is becoming
Cp of the piezoelectric body 5 represents the equivalent capacitor component of the piezoelectric body 5.

The constant current injection control unit 26 includes a transistor Q
26 and resistors R26a, R26b, R26c, a switching circuit performs a switching operation according to the signal on the signal line 2i, and controls the constant current injection unit 24 via the output signal line 2g.

The constant current emission control unit 27 includes a transistor Q
27a, Q27b and resistors R27a, R27b, R27
c, R27d, R27e are connected as shown in the drawing, and like the constant current injection control unit 26, the switching operation is performed by the signal of the signal line 2d, and the constant voltage is supplied via the output signal line 2h. Current emission part 2
5 is controlled.

The constant current injection section 24 is adapted to turn on / off the transistor Q24 by a signal sent from the corresponding bit of the storage means 11 via the signal line 2g. The signal is low active and turns on the transistor Q24. In this case, the potential difference V _R24a applied across the resistor R24a on the emitter side of the transistor Q24 is equal to the potential difference across the series circuit including the diodes D24a and D24b. , Transistor Q24
It becomes the difference from the potential difference generated between the base and the emitter.
Therefore, the value of the current flowing through the resistor R24a is (V _R24a
/ R24a), the current value flowing through the signal line 2g, and the current value flowing through the resistor R24b determine the current value flowing through the output line 24a of the constant current injection unit 24.

In this case, the current value of the resistor R24a is
If the circuit constant is determined to be sufficiently larger than the current value of the resistor R24b and the signal line 2g, the transistor Q24, the diodes D24a and D24b, and the resistor R24.
A constant current can be obtained only by the characteristics of 24a. In addition,
When the signal from the signal line 2g is at "H" level, the transistor Q24 is turned off and the circuit is cut off, so that current is not injected into the output line 24a.

The constant current emitting section 25 is adapted to turn on / off the transistor Q25 in response to a signal sent from the corresponding bit of the storage means 11 via the signal line 2h. The signal is high active and turns on the transistor Q25. In this case, as in the case of the constant current injection unit 24, the potential difference V _R25a applied across the resistor R25a on the emitter side of the transistor Q25 is _equal to the diode D25a, It is the difference between the potential difference across the series circuit of D25b and the potential difference between the base and emitter of the transistor Q25. In addition, the resistor R25
The current value flowing through a is determined as ( _VR25a / R25a), and this current value and the current value flowing through the signal line 2h are:
The value of the current flowing through the resistor R25b determines the value of the current flowing through the input line 25a of the constant current emission unit 25.

In this case, the current value of the resistor R25a is
If the circuit constant is determined to be sufficiently larger than the current value of the resistor R25b and the signal line 2h, the transistor Q25, the diodes D25a and D25b, and the resistor R25.
A constant current can be obtained only by the characteristics of 25a. In addition,
When the signal from the signal line 2h is at "L" level, the transistor Q25 is turned off and the circuit is cut off, so that the current is not discharged from the input line 25a.

Here, the operation in the case of increasing the applied voltage to a certain piezoelectric body in the laminated piezoelectric element 5 will be described. First, the setting data of the storage means 11 is either "0" or "1". Here, "1", that is, "H".
In the case of the level, the signal line 2i becomes the "H" level.
As a result, the transistor Q2 of the constant current injection control unit 26
Since the input of 6 changes from "L" level to "H" level, this transistor Q26 turns on and the signal line 2
The signal of g becomes "L" level. Therefore, the constant current injection unit 2
As described above, the current (V _R24a / R24a) is applied from the output line 24a to the piezoelectric body 5 because the input of 4 is at "L" level.
Flow to.

Here, the current flowing through the signal line 5a is i
24a (= _VR24a / R24a), signal lines 5b and 5c
Where ib and ic are currents, virtual resistances applied to both ends of the piezoelectric body 5 are R5, electric charge accumulated in the equivalent capacitance component Cp of the piezoelectric body 5 is Q, and an applied voltage of the piezoelectric body 5 is Vp. The voltage Vp is

[Equation 1] Therefore, if the voltage at time t = 0 is V0, then Vp = i24a.R5 + (V0-i5a.R5) * EXP (-t / Cp.R5) Vp = i24a.R5 + K.EXP (-t / Cp. R5). Here, K is a constant and K = V0-i24a.R5 and Vp = i24a.R5 + (V0-i5a.R5) .times.EXP (-t / Cp.R5).

Now, the setting data of the storage means 11 is "1".
That is, since the constant current is continuously injected at the “H” level, the voltage Vp rises, and the generated displacement amount X of the piezoelectric body with respect to this voltage is determined. Therefore, it is sufficient to continue injecting the constant current until the voltage Vp reaches the desired generated displacement amount, and this time control is performed by the execution control unit 12 in FIG. 2 or by switching the digital data of the signal conversion / calculation means 10. Done.

Next, the case where the voltage of a certain piezoelectric material in the laminated piezoelectric element 5 is dropped will be described. In this case, since the setting data of the storage means 11 is "0", that is, "L" level, that is, the line 2i is "L" level, the transistor Q26 of the constant current injection control unit 26 described above is not turned on. Therefore, since the constant current injection into the piezoelectric body 5 is not performed, the voltage Vp across the piezoelectric body 5 does not rise. On the other hand, since the line 2i is at "L" level, the line 2d via the inverter 28 becomes "H" level. Therefore, the transistors Q27a and Q27b of the constant current emission control unit 27 are both turned on, and the output line 2h of the constant current emission control unit 27 is turned on.
Signal level becomes "H" level. As a result, the transistor Q25 of the constant current emitting unit 25 is turned on, and the signal line 25a causes a constant current to flow to the ground side.

Now, the applied voltage Vp will be calculated in the same manner as in the case of applying a voltage to the piezoelectric body 5 described above. In FIG. 3, the current flowing through the signal line 5a is represented by i25a (= V _R25a
/ R25a), the currents flowing through the signal lines 5b and 5c are ib and ic, respectively, the virtual resistance applied to both ends of the piezoelectric body 5 is R5, the charge accumulated in the capacitance component Cp of the piezoelectric body 5 is Q, and the piezoelectric body 5 is If the applied voltage of Vp is
The voltage Vp is

[Equation 2] From this, the following formula is obtained.

Vp = i25a.R5 + (V0-i25a.R5) .times.EXP (-t / Cp.R5) Here, the setting data of the storage means 11 is "0", that is, "L".
Since the constant current is continuously emitted when the voltage is at the level, the voltage Vp drops, and the generated displacement amount X of the piezoelectric body with respect to this voltage.
Is determined. Therefore, it is sufficient to continue discharging the constant current until the voltage Vp that reaches the desired generated displacement amount is reached, and this time control is performed by the execution control unit 12 in FIG. 2 or by switching the digital data of the signal conversion / calculation means 10. Done. Further, by outputting the RESET signal from the execution control unit 12 to the storage unit 11, all the bits of the storage unit 11 become “0”, that is, “L” level, and all the piezoelectric bodies 5-0 to 5-N are output. It is also possible to emit a constant current.

Next, each of the piezoelectric bodies 5 described above will be described.
The relationship between the generated displacement amounts of 0 to 5-N and the sum of the generated displacement amounts substantially obtained will be described with reference to FIG. First, when the number of piezoelectric bodies to be used is four, the relationship of the laminated length is as described above. For example, the piezoelectric bodies 5-N and 5- shown in FIG.
It becomes like N-1,5-N-2,5-N-3. In addition,
Since the operation of FIG. 6 will be described later, the description thereof will be omitted here.

First, regarding the memory means 11 corresponding to each of the four piezoelectric bodies, the 0th bit (minimum bit) is the piezoelectric body 5-.
N-3, 1st bit is 5-N-2, 2nd bit is 5-N
-1, and the third bit is 5-N. Further, since the respective piezoelectric bodies have different effective lengths, as shown in FIG. 6, if the sectional areas S are the same, the equivalent capacitance Cp is naturally different. Therefore, in order to obtain a desired amount of generated displacement for a given applied voltage, the injection in FIG.
The resistors R24a and R25a that define the constant current values i24a and i25a for discharging are respectively determined. This allows
It becomes possible for four piezoelectric bodies to simultaneously generate desired displacements within a predetermined time.

Here, the desired generated displacement amount X ⁿ of the piezoelectric body 5-N is twice the desired generated displacement amount X ^n-1 of the piezoelectric body 5-N-1, and the desired generated displacement amount X ^{n of} the piezoelectric body 5-N-1. The desired amount of generated displacement X ^n-1 is
Twice the piezoelectric element 5-N-2 of the desired generation displacement X ^n-2, the desired occurrence displacement X ^n-2 of the piezoelectric element 5-N-2, the piezoelectric element 5
It is set to twice the desired generated displacement amount ^Xn-3 of -N-3.

Next, an actual operation example will be described with reference to FIG. First, it is assumed that operation control is performed by a 4-bit signal,
The operation command signal output means 1 outputs a piezoelectric body operation command signal to the signal converting / calculating means 10. In addition, the CPU 13
Also, a signal indicating how much amount to operate is output to the signal converting / calculating means 10. If the content is “to operate with a full stroke”, binary data (right edge is LSB) such as “1111” is created in the signal conversion / calculation unit 10. In addition, here, CPU1
When a signal indicating an operation amount is sent as an analog signal from a place other than 3 to the signal converting / calculating means 10, A / D conversion may be performed here.

Next, when binary data such as "1111" is created, the execution control unit 12 stores this data in the storage means 1.
Set to 1. When the execution control unit 12 outputs the output command signal to the drive circuit 4, the drive circuits 4-N and 4-N- connected corresponding to each bit of the storage unit 11 are connected.
Signals of each bit are sent to 1,4-N-2 and 4-N-3, respectively.

If the bit signal is "1", the line 2i in FIG. 3 becomes "H" level, a constant current is injected into the piezoelectric body 5 to increase the voltage Vp, and if it is "0", the line 2i.
Becomes "L" level and a constant current is emitted from the piezoelectric body 5 to decrease the voltage Vp.

Now, in the present case, since the binary data of "1111", the voltage Vp of all four piezoelectric bodies is increased, and a desired amount of generated displacement can be obtained. This is shown in Figure 4A.
It rises with the characteristic curve of. As described above, the four piezoelectric bodies have the same sectional area S and are arranged as shown in FIG.
Therefore, the sum X ₀ of the generated displacement is

[Equation 3] And X ₀ = X ⁿ + X ^n-1 + X ^n-2 + X ^n-3 . Further, the piezoelectric body has a good responsiveness due to its characteristics, and it can be used in such a manner that it is activated all at once in a predetermined time t _{1 as} shown in FIG. Note that t ₁ is about several tens of [nSEC], which is a sufficient speed for use in a camera. When the execution control unit 12 outputs the "RESET" signal to the storage unit 11 as described above, the data "1111" in the storage unit 11 becomes "0000".
A constant current is emitted to all the two piezoelectric elements, and the voltage V
As p falls, the amount of displacement generated becomes zero at time t ₂ .

Further, the signal converting / calculating means 10 uses the data "1".
When "0111" is set instead of 111 ", a locus like the characteristic curve shown by the broken line B in FIG. 4 is obtained by the same operation as above.

Next, the series of operations described so far are
This will be described with reference to the flowchart of FIG. First, in step # 1, initialization is performed, and then in step # 2, the operation command signal output means 1 and the CPU
The initial position of the moving body is judged by receiving a command from the control unit 13, and this data is set in the signal converting / calculating means 10 by the "PRESET" signal from the execution control unit 12. Next, in step # 3, the execution control unit 1 stores this data in the storage unit 11.
2, and the drive circuit 4 and the piezoelectric body 5 are operated in a direction in which the voltage Vp increases in step # 4.

At step # 5, it is judged whether or not there is an operation end signal from the operation command signal output means 1 and the CPU 13. If there is no operation end signal here, step # 6.
And a new operation command signal is sent to the operation command signal output means 1
Also, it is determined whether or not the data is output from the CPU 13.
If there is no new operation command signal here, the above step #
Return to 5.

On the other hand, if there is a new operation command signal, the process proceeds to step # 7 and the signal conversion / calculation means 10 performs conversion. Then, the process proceeds to step # 8 and the above step #
The data converted in step 7 is transferred to the storage means 11, and it is determined whether or not the storage means 11 can be discharged. O here
In the case of K, the process proceeds to step # 9, and the drive circuit 4 and the piezoelectric body 5 operate in the direction of increasing or decreasing to the voltage Vp.
After that, the process returns to step # 5 to repeat the series of loops described above.

If there is an operation end signal after returning to the step # 5, the execution control section 12 outputs a "RESET" signal to the storage means 11 in step # 10. As a result, all the data set in the storage means 11 becomes zero as described above, and the voltage Vp of the drive circuit 4 and the piezoelectric body 5 operates in the decreasing direction in step # 11,
To return.

FIG. 6 is a front view of an example in which the laminated piezoelectric element according to the first embodiment is applied to a diaphragm driving unit of a camera. The fixed portion 61 is an immovable member inside a device such as a camera, and the laminated piezoelectric element 5 is provided on one side of the fixed portion 61.
Is mounted, and a supporting portion 61a that supports the fulcrum 62c of the lever 62 is provided in the vicinity of the position where the piezoelectric element 5 is mounted. The fulcrum 62c of the lever 62 is swingably supported by the top end of the support portion 61a.
The lever 62 is swingable in the direction of arrow M in the figure, one arm end of which is on the upper surface of the piezoelectric body 5, the other arm end is on a driven body 60 which will be described later, and its end portion. Has been inserted.

The fulcrum 62c is provided on the piezoelectric element 5 side with respect to the longitudinal center of the lever 62, and the distance from the fulcrum 62c to the end of one arm extending toward the piezoelectric body 5 side. The distance 62a and the distance to the driven body 60 are distance 62b. This lever 62 and the piezoelectric body 5
The enlarged displacement mechanism including the driven body 60 and the support portion 61a has a displacement enlargement ratio A = 62b / 62a which is the ratio of the distances 62a and 62b.

On the other hand, a cylinder portion 61b is formed on the other side of the fixed portion 61, and the driven body 60 is slidably arranged in the direction of arrow N in the drawing inside the cylinder portion 61b. There is. A diaphragm mechanism of a camera, for example, is connected to the upper portion of the driven body 60 so as to interlock with the driven body 60.

Further, the driven body 60 has a force Fs (V) (hereinafter (V) represents a vector) due to the biasing spring 63 disposed between the bottom surface of the driven body 60 and the cylinder portion 61b.
Then, Hirao presses the one arm end of the lever 62 toward the piezoelectric body 5, and the one arm end of the lever 62 is in pressure contact with the piezoelectric body 5.

Now, there is no loss at each point and the efficiency is 10
It is assumed that the piezoelectric body 5 is extended by the force Fp (V) with 0%.
At this time, a force of F (V) = Fp (V) × 1 / A is applied to the driven body 60 by the displacement magnifying mechanism, whereby the driven body 60 moves downward in the figure. In this case, the driven body 60 receives the load Fi (V) due to inertia, the load Ff (V) due to friction, and the load Fs (V) due to the biasing spring 63. Therefore, in order for the driven body 60 to actually move, the condition of F (V) + Fi (V) + Ff (V) + Fs (V) ≠ 0 is satisfied.

Here, it is assumed that the constant of the biasing spring 63 is set so that the load Fs (V) does not change due to the movement of the driven body 60. In this case, the signs of the inertial load Fi (V) and the frictional load Ff (V) change when the piezoelectric body 5 expands and contracts, but the signs of the spring load Fs (V) do not change. If the absolute value of each load is Fi, Ff, and Fs, Fi
(V) + Ff (V) + Fs (V) means that when the piezoelectric body 5 extends (the direction of the force F (V) in this extension direction is the plus direction),-(Fi + Ff + Fs) when the piezoelectric body 5 contracts. Is-(-Fi-Ff + Fs).

The above is the description of the essential parts of the diaphragm drive mechanism of the camera utilizing the present invention.

In the first embodiment, as shown in FIG. 6, the laminated piezoelectric element 5 to be used has the structure shown in FIG.
The lengths of the respective piezoelectric bodies are set so that the generated displacement amounts when applying the same predetermined voltage to each of N, 5-N-1, 5-N-2, and 5-N-3 are in a multiple of 2. However, in contrast to this, the laminated piezoelectric element 5 shown in FIG.
The same shape (that is, the effective length and the amount of displacement generated with respect to a predetermined voltage are substantially the same) may be used, and the setting of the constant current value described above may correspond to each bit of the storage means 11. This is described here as a second embodiment of the invention. Also in the second embodiment, the first described above
The same effect as that of the embodiment can be obtained, and moreover, since a plurality of products having the same shape are used, the variation can be reduced.

According to the above-mentioned embodiment, since the piezoelectric bodies are arranged in series and the ON / OFF operation is simply performed as necessary, a predetermined displacement amount can be obtained in a short time with good reproducibility. .. Therefore, there is no need for complicated and time-consuming calculations that have been performed conventionally, and it becomes unnecessary to store a huge amount of characteristic curve data.

[0058]

As described above, according to the present invention, a plurality of piezoelectric elements having different dimensional changes due to the application of the same voltage are laminated, and the voltage applied to the plurality of piezoelectric elements is turned on. Since the desired dimensional change is obtained by controlling the off state, a remarkable effect that a predetermined displacement amount can be obtained in a short time is exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the basic concept of the present invention.

FIG. 2 is a block configuration diagram of a circuit for driving the laminated piezoelectric element according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of the piezoelectric body drive circuit in FIG.

FIG. 4 is a diagram showing a displacement characteristic in the first embodiment.

FIG. 5 is a flowchart of the operation of the first embodiment.

FIG. 6 is a front view when applied to the diaphragm drive unit of the camera of the first embodiment.

FIG. 7 is a diagram showing a hysteresis characteristic of a piezoelectric body.

[Explanation of symbols]

 5 ... Multilayer piezoelectric element

Claims (1)

[Claims] 1. A desired dimensional change is obtained by stacking a plurality of piezoelectric elements having different dimensional changes caused by applying the same voltage to each other and controlling ON / OFF of a voltage applied to the plurality of piezoelectric elements. A multi-layer piezoelectric element, which is obtained.