JPH064337Y2 - Electrostrictive element drive shutter mechanism - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to an electrostrictive element driving shutter mechanism, and more particularly to a shutter mechanism driven by distortion generated in the electrostrictive element when a voltage is applied to the bimorph structure electrostrictive element, in which an initial stage caused by hysteresis of the electrostrictive element is used. The present invention relates to a novel electrostrictive element drive shutter mechanism capable of removing an error in an aperture position due to a difference in distortion amount.

[Prior art]

It is well known that when one end of an electrostrictive element having a bimorph structure is fixed and a voltage is applied, the free end of the electrostrictive element is distorted according to the applied voltage. An electrostrictive element drive shutter mechanism is known which is driven by a distortion generated when a voltage is applied to the distortion element as a drive source.

[Problems to be solved by the device]

By the way, the electrostrictive element acts equivalently to a capacitor in terms of a circuit, and once the electric charge is accumulated, the distortion state is maintained by the accumulated electric charge and the accumulated electric charge is released even after the application of the voltage is stopped. However, when the shutter mechanism is driven by using this electrostrictive element as a drive source, it is pointed out that there is a hysteresis characteristic as an undesirable property, and charge is stored even if the inter-electrode voltage is equal. Distortion amount is different between when the charge is discharged and when the charge is discharged. Therefore, in the case of the conventional electrostrictive element drive shutter mechanism, particularly when continuously operated, the initial distortion amount varies depending on the length of the operation interval, and as a result, the obtained aperture position is not constant even if a desired voltage is applied. Problem has occurred.

[Means for solving problems]

The present invention has been made in view of these problems,
It is an object of the present invention to provide a novel electrostrictive element driving shutter mechanism that can always obtain a desired aperture position without being affected by a difference in initial distortion amount due to hysteresis of an electrostrictive element. In summary, the electrostrictive element driving shutter mechanism according to the present invention is configured to determine the opening amount of the shutter blade that also serves as the diaphragm blade in accordance with the distortion amount of the electrostrictive element that is distorted according to the applied voltage. An electrostriction in which the applied voltage to the electrostrictive element is increased with the passage of time, and both ends of the electrostrictive element are short-circuited at the timing when a desired time has elapsed to release the electric charge accumulated in the electrostrictive element. In the element driving shutter mechanism: An origin switch is provided which is activated when the amount of distortion of the electrostrictive element reaches a reference amount of distortion in a region where the ratio of the amount of change in applied voltage and the amount of change in amount of distortion is approximately constant. : The timing at which the electrostrictive element is short-circuited is determined by using the timing at which the origin switch is operated as a starting point, and the shutter blade blades are irrelevant regardless of the difference in the initial distortion amount due to hysteresis. It has been made so as to be able to control the mouth characteristics.

[Action]

That is, according to the present invention, since the initial restoration timing of the electrostrictive element is timed from the timing when the amount of distortion of the electrostrictive element becomes a constant value, the influence of the initial amount of distortion of the electrostrictive element is measured. It is possible to remove it at all.

【Example】

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a principle diagram of an electrostrictive element which is a premise of the present invention. One end of an electrostrictive element 1 having a bimorph structure is fixed, and a power supply circuit 2 is connected to the fixed end. Then, when the voltage V is applied from the power supply circuit 2, the free end thereof is distorted, and the distortion amount ρ generated at the free end is determined corresponding to the applied voltage V. Next, FIG. 2 is a characteristic diagram showing the relationship between the applied voltage V to the electrostrictive element 1 and the distortion amount ρ of the electrostrictive element 1.
When the applied voltage V to V is increased from 0 V to the maximum allowable voltage Vmax, the electrostrictive element 1 is distorted along the curve a in FIG. 2, and the applied voltage V to the electrostrictive element 1 is changed from the maximum allowable voltage Vmax to 0V. When lowered, the distortion of the electrostrictive element 1 is restored along the curve b in FIG. Although the distortion characteristic of the electrostrictive element 1 exhibits a hysteresis phenomenon as shown in FIG. 2, the voltage region (that is, the variation dV of the applied voltage V in which the curve a and the curve b in FIG. 2 are in a substantially parallel state). There is a voltage region in which the amount of change dρ of the distortion amount ρ with respect to is approximately constant, and this region is referred to as a linear region in the present specification.) In the present invention, the electrostrictive element 1 is operated in this linear region. A target distortion amount ρ by applying a voltage to the electrostrictive element 1
_{In order} to obtain ₂ , the voltage V ₂ finally applied to the electrostrictive element 1
Is not constant due to the difference in the initial distortion amount ρ ₀ due to hysteresis, but in the linear region, the reference voltage V ₁
(This reference voltage V _{1 is} also not constant because of the initial distortion amount ρ ₀ ) and the constant addition voltage eV is superimposed on the electrostrictive element 1 which has already shown the constant reference distortion amount ρ ₁ . In this case, since the added distortion amount eρ of the electrostrictive element 1 is proportional to the added voltage eV, it is apparent from FIG. ₂ that the finally obtained distortion amount ρ ₂ has a constant value. Therefore, in the electrostrictive element driving shutter mechanism of the present invention, the opening position of the shutter blade that also serves as the diaphragm blade is controlled in accordance with the distortion generated at the free end when a voltage is applied to the electrostrictive element 1. In addition, an origin switch that operates when the amount of distortion of the electrostrictive element 1 reaches the above-described constant reference distortion amount ρ ₁ is provided, and the voltage already applied to the electrostrictive element 1 at the time when the origin switch operates. was a reference voltage V _1, further allowed distortion by adding distortion amount eρ electrostrictive element 1 by applying by superimposing the added voltage eV to the reference voltage V _1, and the manner to obtain a desired opening characteristics. FIG. 3 is a mechanism diagram showing a driving mechanism of a program shutter according to one embodiment of the present invention. In the figure, reference numeral 1 is the electrostrictive element already described, and one end of the electrostrictive element 1 is fixed by a fixing member 200 to the shutter base plate. It is fixed at 3. Also, 4 is an aperture chair perforated in the shutter base plate 3, 5
Are shutter blades, which also function as diaphragm blades, are swingably supported by a shaft 6a on the back side of the shutter base plate 3. Although only one shutter blade 1 is shown in FIG. 3 in order to avoid complication of the drawing, the shutter base plate 3
A shutter blade (not shown), which is bilaterally symmetrical to the shutter blade 5, is also supported on the shaft 6b on the back side of the. Reference numeral 7 denotes an interlocking lever for transmitting the distortion generated at the free end of the electrostrictive element 1 to the shutter blade 5. The interlocking lever 7 is swingably supported by the shutter base plate 3 by a shaft 7a, and a holding groove 7b formed in the interlocking lever 7 holds the contact 1a at the tip of the electrostrictive element 1. A boss 7d is formed on the back side of the operating arm 7c of the interlocking lever 7, and the boss 7d is the long hole 3 formed in the shutter base plate 3.
It penetrates through a and engages with a long hole 5a formed in the shutter blade 5. Then, when the electrostrictive element 1 is not distorted, the shutter blade 5 shields the aperture chair 4 as shown in the figure, but if the tip of the electrostrictive element 1 is distorted to the right in FIG. Since the boss 7d at the tip of the operating arm 7c pushes up the long hole 5a by turning counterclockwise, the shutter blade 5 turns counterclockwise about the shaft 6a and opens the aperture chair 4. The aperture of the aperture chair 4 at this time is determined by the amount of distortion of the electrostrictive element 1. Next, 8 shows an origin switch which is a feature of this embodiment,
In the origin switch 8, the amount of distortion of the electrostrictive element 1 is the reference amount of distortion ρ ₁
It is designed to break when it reaches. In this embodiment, the amount of distortion of the electrostrictive element 1 reaches the reference distortion amount ρ ₁ in the process of increasing the applied voltage to the electrostrictive element 1 with the passage of time, and the origin switch 8 breaks.
When the origin switch 8 breaks, the added voltage eV is superposed on the reference voltage V ₁ applied to the electrostrictive element 1 to apply the added voltage eV to further distort the electrostrictive element 1 by the added distortion amount eρ, and a desired opening is obtained. I try to get the characteristics. FIG. 4 shows an example of a circuit for controlling the voltage applied to the electrostrictive element as described above, and the electrostrictive element 1 acts equivalently to a capacitor in terms of circuit. Further, in FIG. 4, 10 is an electrostrictive element drive circuit,
Shows the exposure control circuits, respectively. Since the electrostrictive element drive circuit 10 shown in FIG. 4 increases the aperture diameter of the shutter blade that also serves as the diaphragm blade substantially linearly with time, a voltage that linearly increases with time is applied to the electrostrictive element 1. It is designed to be applied. That is, in FIG. 4, the capacitor 11 and the transistor T
A constant current is supplied to the parallel circuit of R ₁ through a transistor TR ₂ which is a constant current source, and the transistor TR ₁ is switched by a shutter release switch 12 (B contact operation) connected to its base. Then, by turning off the transistor TR _1, the charging of the capacitor 11 is started. Next, 13 FETs, the FET 13 and the resistor R ₁ are connected in series to the high-voltage power supply 14, and the drain current flowing in this series circuit is controlled by the charge level of the capacitor 11 applied to the gate of the FET 13, and at this time the resistor R ₁ Is applied to the electrostrictive element 1 via the transistor TR ₃ and the FET 13 and the resistor R ₁ constitute a voltage amplifier circuit. Note that TR ₄ is a switching transistor for short-circuiting both ends of the electrostrictive element 1, and the operation timing of the transistor TR ₄ is controlled by the exposure control circuit 20 described in detail below. Next, the exposure control circuit 20 is a CdS which is an example of a photometric element.
(Cadmium sulfide) 21, this CdS 21 and power supply 2
2 has a field brightness integration circuit composed of a capacitor 23 connected in series to the capacitor 2. Since the capacitor 23 is charged by the photocurrent flowing through the CdS 21 in accordance with the field brightness, the charge level of the capacitor 23 is It indicates the integrated value of the field light. In addition, reference numeral 24 is a comparator, the reverse phase input level of which is, for example, a variable resistor VR which is linked to a film sensitivity setting mechanism or the like.
Is determined by the voltage division ratio of the resistor R ₂ and the positive phase input level thereof is determined by the charge level of the capacitor 23. Then, the switching transistors TR ₅ and TR ₄ are activated by the inversion of the output of the comparator 24 to the H level at the timing when the charge level of the capacitor 23 reaches the voltage division level of the variable resistor VR and the resistor R ₂ , and the electrostriction occurs. Both ends of the element 1 are short-circuited. A switching transistor TR ₆ connected in parallel with the capacitor 23 is for starting the integration operation of the field light by the capacitor 23. A characteristic point of this embodiment is that the transistor TR ₆
The base of is connected to the ground side of the origin switch 8 (B contact operation) via the resistor R ₃ . The origin switch 8 is for detecting the amount of distortion of the electrostrictive element 1 when it reaches a reference amount of distortion, and is constituted by, for example, a mechanical contact arranged at a passage point near the tip of the electrostrictive element 1. The electrostrictive element 1 is mechanically operated when the amount of distortion of the electrostrictive element 1 reaches the reference amount of distortion ρ ₁ . Next, the operation of this embodiment will be described with reference to the above matters. First, in the initial state, the origin switch 8 is made, so that the switching transistor TR ₆ is turned on and the condenser 23 for integrating the field brightness does not start the integration operation. Therefore, the output of the comparator 24 becomes L level, the transistor TR ₅ is cut off, and the base of the transistor TR ₄ becomes H level. Therefore, the transistor TR ₄ is cut off, and the electrostrictive element 1 is in a chargeable state. The amount of distortion of the electrostrictive element 1 at this time, that is, the initial amount of distortion ρ ₀ is not constant due to hysteresis. Now, in this state, when the shutter release switch 12 breaks in conjunction with the operation of a shutter button (not shown),
The base input of the switching transistor TR ₁ is cut off due to the L level, the capacitor 11 is charged by the current flowing through the transistor TR ₂ , and the charge level thereof rises substantially linearly. When the capacitor 11 is charged in this way, FET1
The gate level of 3 also rises, and the drain current flowing through the FET 13 also rises. Then, the voltage V corresponding to the voltage generated across the resistor R ₁ corresponding to the drain current flowing through the FET 13 is applied to the electrostrictive element 1 via the transistor TR ₃ , and the electrostrictive element 1 corresponds to the applied voltage V. Then, its free end is distorted to the right in FIG. The distortion amount ρ of the electrostrictive element 1 also rises as the capacitor 11 is charged. Now, when the free end of the electrostrictive element 1 is distorted to the right in FIG. 3 in this manner, the boss 7d at the tip of the interlocking lever 7 is caused by the contact 1a at the tip of the elongated hole 5 of the shutter blade 5.
The shutter blade 5 starts the opening operation of the aperture 4 while rotating a while rotating a. In this way, in the process of starting the opening operation of the aperture chair 4, the distortion amount of the electrostrictive element 1 reaches the reference distortion amount ρ ₁ at the timing before the shutter blade 5 that also serves as the diaphragm blade becomes the pinhole state, and at that timing. The origin switch 8 breaks. Then, when the origin switch 8 breaks, the base of the transistor TR ₆ is cut off at the ground level, and the capacitor 23 for integrating the field brightness can be charged. In this way, the amount of distortion of the electrostrictive element 1 is changed to the reference amount of distortion ρ ₁
It goes without saying that the reference voltage V ₁ applied to the electrostrictive element 1 at the time when the voltage reaches the maximum value varies depending on the initial distortion amount of the electrostrictive element 1 due to the influence of hysteresis. The distortion amount of the distortion element 1 is the reference distortion amount ρ
_When it reaches ₁ , the reference voltage V ₁ applied to the electrostrictive element 1 becomes low. Now, as the aperture 4 is opened, CdS2
A photocurrent corresponding to the brightness of the object field starts to flow in 1, and the capacitor 23 is charged by the photocurrent flowing in CdS21. Then, the output of the comparator 24 is inverted to the H level at the timing when the charge level of the capacitor 23 exceeds the level determined by the distribution ratio of the variable resistor VR and the resistor R ₂ . The time required for the output of the comparator 24 to be inverted is determined according to the field brightness and the film sensitivity, and when the field brightness and the film sensitivity are constant, the time is fixed after the origin switch 3 breaks. After the elapse of time, the output of the comparator 24 is inverted. Then, when the output of the comparator 24 is inverted to the H level, the transistor TR ₅ becomes conductive and the transistor TR ₄
Since it also conducts, the electrostrictive element 1 is short-circuited via the transistor TR ₄ and releases the accumulated charges to restore the distorted state. When the electrostrictive element 1 is restored to the initial state, the interlocking lever 7 is moved to the boss 7d at its tip by the contact 1a at the tip of the electrostrictive element 1.
Rotates clockwise while locking the elongated hole 5a of the shutter blade 5, and the shutter blade 5 closes the aperture 4 and ends the exposure operation. As described above, the time until the output of the comparator 24 is inverted after the origin switch 8 is actuated is uniquely determined by the field brightness and the film sensitivity. Further, since the capacitor 11 that determines the applied voltage to the electrostrictive element 1 is charged with a constant current, the time until the output of the comparator 24 is inverted after the origin switch 3 is activated (this time is the same as the object field as described above). The amount of change in the applied voltage to the electrostrictive element 1, that is, the addition voltage eV is also uniquely determined according to the field brightness and the film sensitivity. In the linear region, the amount of change dρ of the distortion amount of the electrostrictive element 1 is proportional to the amount of change dV of the applied voltage, and therefore the added distortion amount eρ corresponding to the added voltage eV also corresponds to the field brightness and the film sensitivity. Is uniquely determined. Therefore, according to this embodiment, the initial distortion amount ρ of the electrostrictive element 1 is
_Irrespective of the difference of ₀ , the final distortion amount ρ of the electrostrictive element 1
₂ is always uniquely determined corresponding to the field brightness and the film sensitivity. Next, FIG. 5 is a circuit diagram showing a modification of the present invention. Specifically, in the embodiment of FIG. 4, an example in which mechanical contacts are used as an example of the origin switch 8 is assumed.
In the illustrated embodiment, as an example of the origin switch 8, the phototransistor 8a uses a photointerrupter having a light emitting diode 8b. In FIG. 5, reference numeral 25 denotes an optical path opening / closing member that opens / closes the optical path from the light emitting diode 8b to the phototransistor 8a in conjunction with the distortion operation of the electrostrictive element 1.
Reference numeral 5 is composed of, for example, the vicinity of the free end of the electrostrictive element 1, a part of the shutter blade 5 also serving as a diaphragm blade, or a part of the interlocking lever 7. In the initial state, the component opening / closing member 25 shields the optical path from the light emitting diode 8b to the phototransistor 3a, and when the distortion amount of the electrostrictive element 1 reaches the reference distortion amount ρ ₁ , the light emitting diode 8b moves to the phototransistor. 8a to form an optical path. The embodiment shown in FIG. 5 is also constructed in exactly the same manner as the embodiment shown in FIG. 4 with respect to the elements other than the origin switch 8,
After the amount of distortion of the electrostrictive element 1 reaches the reference amount of distortion ρ ₁ , an optical path from the light emitting diode 8b to the phototransistor 8a is formed, the phototransistor 8a becomes conductive, and the condenser 23 starts the integration operation to the field light. To be done. Although the example in which the capacitor 23 is charged with a current corresponding to the brightness of the field is shown above, a strobe tuning circuit in which the CdS21 of the exposure control circuit 20 is replaced with a variable resistor linked to the shooting distance is used. By providing it, it is possible to determine the strobe synchronization timing in so-called flashmatic photography. Also, in the above, an example is shown in which one end of the electrostrictive element is fixed and the mechanical member is driven by its free end, but both ends of the electrostrictive element are fixed and the mechanical member is driven by the central portion. You may choose to do it.

[Effect of device]

As described above, according to the present invention, the voltage that increases with time is applied to the electrostrictive element in the region where the ratio of the change amount of the applied voltage and the change amount of the distortion amount has a substantially constant value. Distort the electrostrictive element, and drive the shutter blade that also serves as the diaphragm blade by distorting the electrostrictive element. As, since the voltage corresponding to the difference between the target distortion amount and the reference distortion amount is superimposed on the reference voltage and applied to the electrostrictive element, the electrostrictive element caused by the hysteresis of the electrostrictive element Regardless of the difference in the initial distortion amount, the desired distortion amount can always be obtained, so that the ideal aperture characteristic can always be obtained.

[Brief description of drawings]

FIG. 1 is a principle diagram of an electrostrictive element driving device, FIG. 2 is a characteristic diagram showing a relationship between an applied voltage to an electrostrictive element and a distortion amount, and FIG. 3 is a mechanism showing an example of a shutter mechanism to which the present invention is applied. Figure,
FIG. 4 is a circuit diagram showing one embodiment of the present invention, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. 1 ... Electrostrictive element, 8 ... Origin switch 11 ... Capacitor, 13 ... FET

Claims (3)

[Scope of utility model registration request] 1. An opening amount of a shutter blade that also serves as a diaphragm blade is determined according to a distortion amount of an electrostrictive element that distorts according to an applied voltage, and the applied voltage to the electrostrictive element is changed with time. In the electrostrictive element drive shutter mechanism, the both ends of the electrostrictive element are short-circuited at a timing when the desired time has increased, and the electric charge accumulated in the electrostrictive element is released. An origin switch is provided which is activated when a reference distortion amount is reached in a region showing substantially constant distortion with respect to a change in applied voltage without being affected by a difference in initial distortion amount, and the origin switch is operated. The electrostrictive element driving shutter mechanism is characterized in that the timing at which the electrostrictive element is short-circuited is determined by using the timing as a starting point. 2. The electrostrictive element driving shutter mechanism according to claim 1, wherein the time until the electrostrictive element is short-circuited after the origin switch is actuated is the film sensitivity and the field of view. An electrostrictive element drive shutter mechanism characterized in that it measures time corresponding to brightness. 3. The electrostrictive element drive shutter mechanism according to claim 1 of the utility model registration, wherein the time until the electrostrictive element is short-circuited after the origin switch is actuated is defined as film sensitivity and shooting distance. An electrostrictive element drive shutter mechanism characterized by being adapted to measure time.