JPS6344642A - Shutter driving device - Google Patents

Abstract

PURPOSE:To shorten a release lag by determining the current value based upon a 2nd charging path forming means according to desired shutter aperture characteristics as to a shutter driving device which drives a shutter by using an electrostrictive element generating a driving force by being applied with a voltage as a driving element. CONSTITUTION:When the shutter is controlled by using a bimorph element Bi to perform exposure control, variation (movement quantity of shutter blade) in the aperture quantity of the shutter using the bimorph element Bi is not so large to a charging voltage in the beginning of charging. This results from that a driving force against the stationary frictional force of a driving mechanism is not generate at the bimorph element Bi unless the bimorph element Bi is charged above a certain constant voltage. For the purpose, a charging current is increase only for a constant time T1 in the beginning of the charging to perform rapid charging. Consequently, the time from release operation almost to the opening of the blade is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a shutter drive device using an electrostrictive element such as a bimorph.

Conventional technology This type of shutter drive device η is disclosed in, for example, Japanese Patent Application Laid-Open No. 1986-1.
- Already proposed in No. 19033, the bimorph is charged and displaced in response to the release operation to obtain shutter driving force. In this conventional example, in order to achieve accurate shutter speed, only consideration is given to keeping the charging speed constant using a pulse current with a negative radio waveform.

C9 Problems to be Solved by the Invention As a characteristic of the bimorph, while the charged S pressure is low, the displacement is small and the driving force is small, and static frictional force acts when the shutter starts driving. In a configuration in which charging is started immediately after the shutter is driven, there is a problem in that the time (release lag) from when the shutter is driven to when the shutter aperture actually starts to be formed becomes long. One possible solution to this problem is to set a large current value to charge the bimorph, but if this method is simply adopted, the speed of change of the shutter opening will be determined by the charging speed, that is, the set current value. As a result, the desired shutter aperture characteristics cannot be obtained.

The present invention solves the problem of long release lag while maintaining desired shutter characteristics. Solution) +'I.

(2) Means for Solving Problems In a shutter driving device that uses an electrostrictive element as a shutter driving means, the electrostrictive element is charged with a first current until a predetermined time point before the start of forming a shutter aperture in response to a release operation. a first charging circuit means and a second charging circuit means for charging the electrostrictive element 3 with a second current after the predetermined time; I set it larger than .

E1 Effect The present invention focuses on the fact that the shutter drive speed at the time before the start of shank-opening formation l7i4 does not affect the shutter opening characteristics. The electrostrictive element for driving the shunter is charged by the current of 1 and then by the second current of a small value. Sign. As a result, the electrostrictive element is displaced from a relatively early point after the release operation. Shutter for the first time
f! : Drive. On the other hand, the shutter opening-if characteristics can be maintained at desired characteristics by appropriately setting the current value of the second TL flow.

Fig. 2 shows the mechanical part of the present invention! 8 @ Show an example. This embodiment is a shutter device in which the shutter also serves as an aperture and opens at a constant speed to an aperture value determined by the brightness of the subject. The shutter blades 2.4 are simultaneously rotated in opposite directions, and the light detection element 10 at the rear detects the coincidence of the small holes for shutter opening detection provided in the shutter blades 2.4, and the specified shutter opening position is detected. is detected based on the number of times the photodetecting element 10 detects light.

In other words, when the number of light detections reaches a predetermined number, it is determined that the shutter opening has reached the specified opening, the shutter blades are stopped opening, and the shunter blades are returned to their initial positions. It is.

Next, we will explain the functions of the individual parts,
In FIG. 2, the shutter blades 2 and 4 are rotatably held on a shaft S fixed to a shutter plate 6.
The shape is symmetrical with respect to a line connecting the center of the exposure opening 6a and the center of the shaft 8. The long holes 2b and 4b provided in the shunter blades 2 and 4 are connected to the engagement pin 1 provided in the opening/closing lever 12.
2a.

12b, and the shutter blades 2 and 4 are rotated by the movement of the engagement pins 12a and 12b.

The single-shaped notch openings 2a and 4a provided in the shutter blades 2 and 4 open and close the exposure opening 6a by the above rotation. A plurality of small holes 2A, 2B in the shutter blades 2 and 4,
2C, 2D, 2E and 4A.

4B, 4C, 4D, and 4E are provided on the same circumference centering on the axis 8 and symmetrically with respect to the line connecting the center of the exposure opening 6a and the center of the axis 8, and the rotation of the shutter blades 2 and 4 is At the same time, the group of small holes moves, and at the measurement position 10a of the installed photodetecting element 1o, the small holes 2A and 4A are located just before the blade opening, and the small holes 2B and =1B are at the minimum. When the aperture is opened to the maximum aperture, the small holes 2E and 4E are arranged so that they overlap when the aperture is opened to the maximum aperture.
The other small holes 2C and 4C, 2D and 4D are arranged so as to overlap when the shaft blades are opened to a predetermined aperture between the minimum and maximum apertures. Note that an appropriate number of small holes may be provided at appropriate positions corresponding to the aperture value to be detected.The shutter plate 6 has an exposure opening 6a, a notch 6b for installing the photodetecting element 10, Elongated holes 6c and 6d are provided to prevent the bottle 12a212b placed upright on the opening/closing lever 12 from coming into contact with it and interfering with the movement of the lever.

The shutter opening/closing lever 12 is rotatably held by a shaft 16 on the shutter base plate 6, and a long hole 12e provided at the right end in the figure so as not to contact the shaft 8 and a long hole 2 of the shutter blade.
b, 4b (insert the bins 12a and 12b into the long holes 12
The bottles 12c and 12de are provided almost symmetrically with respect to e, and the left end in the figure is formed into a U-shape, and the bins 12c and 12de are provided so as to sandwich the tip of the bimorph 14. bimorph 1
4 has one end held between the bins 12c and 12d, and the other end t! - fixed by a retaining plate 18;

In the shutter closed state shown in No. 221I, when a voltage is applied to the bimorph 14, the bimorph 14 rotates clockwise with the end on the holding plate 18 side as the fixed end,
This generates driving force. When the im lock lever 12 is rotated clockwise by the driving force, the bin 12a
and 12b, the elongated hole 2b of the shutter blades 2, 4,
4b is pushed, and the shutter blades 2 and 4 are rotated in a direction in which they are mutually opened.

As the shutter blade 2.4 rotates, the small holes 2A, 4A, 2
The photodetecting element 10 is located at the measurement position 10a, where B and 4B, 2C and 4C, 2D and 4D, and 2E and 4E overlap each other in sequence.
The control circuit detects the overlap and outputs a signal, and when the number of outputs of the detection signal reaches a predetermined number of times, the control circuit determines that the specified shutter opening has been reached, and the bimorph 1
4, the opening movement of the shutter blade 2.4 is stopped, and an operation is performed to return the shutter blade 2.4 to its initial position.

Next, an embodiment of a control circuit for controlling the above-mentioned operation will be explained.One control circuit shown in FIG. B11) - Insert into the collector circuit of Runsister Tr 3 and utilize the transistor's amplification characteristic that if the base voltage is constant and the base-emitter voltage is constant, the collector current is almost constant regardless of the collector voltage. This circuit allows the bimorph B1 to be charged with a constant current. The control circuit shown in FIG. 1 has a two-layer structure with a transistor Tr6 connected in parallel to the transistor Tr3 and a transistor Tr5 for controlling the transistor Tr6, and an initial charging circuit arranged in parallel.

21 is a photometry circuit that measures the brightness Bv value of the subject; 22 is a film sensitivity reading circuit that reads the film sensitivity Sv value;
23 is an aperture position detection circuit incorporating the photodetection element 10 of FIG. 2 into the circuit. 2-1 is a calculation circuit that calculates an exposure value Ev from the brightness Bv value and film sensitivity Sv, and outputs it to the exposure control circuit 25. The exposure control circuit 25 outputs a charging signal for the bimorph Bi to the bimorph charging circuit 27 by closing the switch S2, which is closed by the shutter release Jifj, and the pulse signal input from the aperture position detection circuit 23 to the exposure control circuit 25 detects the exposure. When the number corresponds to the value Ev, the charging signal is stopped and a signal for discharging the bimorph charge is outputted. The bimorph charging circuit 27 is a circuit that charges the bimorph Bi with a constant current based on a control signal from the exposure control circuit 25, and instantly discharges the charged electric charge.

The booster circuit 26 is a booster circuit that boosts the battery voltage to the maximum voltage required for bimorph charging, and the booster circuit used in electronic flash devices is commonly used. In addition, bimorph 14 (
As shown in IZ(B), the center electrode is connected to the booster circuit side, the both side electrodes are connected to the collector side of the transistor Tr3, and a positive voltage is applied between the center electrode and both side electrodes. Particularly, in FIG. 2(A), the retaining plate 1
8 (turning and displacing clockwise with one end of ltll as a fixed end).

In the above circuit configuration, transistor Tr5.
The circuit will be explained assuming that Tr6 is not present. When the main switch (not shown) is turned on, power is supplied to the booster circuit 26 of the electronic flash device, and the booster circuit 26 increases the main capacitor C to a predetermined voltage. It will be charged. Next, by pressing the first stage of the release button (not shown), the switch (not shown) supplies power to the battery circuits except for the ONL booster circuit 26.
1 is performed. As a result, the photometry circuit 21 operates and outputs the brightness of the subject as a Bv value to the arithmetic circuit 211. The film sensitivity reading circuit 22 automatically reads the film sensitivity from the DX code on the film cartridge and outputs it as an Sv value to the calculation circuits 2 and 4. The arithmetic circuit 24 calculates the exposure fa from the input luminance Bv value and film sensitivity Sv.
Ev is calculated and output to the exposure control circuit 25. In this step, the exposed 91131 circuit 25 outputs a high level signal at both output terminals a and b, and as shown in FIG. The transistors Tr3 and Tr4 that perform initialization are in an OFF state, and the charge of the immorph Bi is O.

Next, the Lelys River (not shown) was used as the second stage (first
When the release switch S2 is pressed down to a stroke deeper than the stroke, the release switch S2 is turned on. As a result, the exposure control circuit 25 outputs a 0-level signal to the output terminal a and a high-level signal to the terminal A, and as shown in No. 11!1<C>, the transistor T r 2 of the bimorph charging circuit 27 is activated. OF'FL
, turns on the transistor Tr3. Transistor 'r
3 is constant current I.

A diode D1 is connected between the base and emitter to allow a constant current to flow through the diode D1 from a constant current power supply (2).

Therefore, the base-emitter voltage of the transistor T r 3 is kept constant, and the collector voltage a 11 of the transistor T r 3 is kept constant.
becomes constant. In addition, VR is a constant "Ji current l11 (variable resistance for adjustment. As mentioned above, when bimorph Bi is charged with constant current I, f: driving force is proportional to the charging voltage of bimorph Bi. This driving force causes the shunter to open as described above.
As the shutter opens, the opening position detection circuit 23 sequentially outputs pulses to the exposure control circuit in accordance with the opening of the shutter. When the exposure control circuit 25 receives the number of pulses corresponding to the calculated exposure value Ev, it outputs a high level signal to the output terminal a and a 0 level signal to the output terminal
As shown in Figure (C), the l-run transistor Tr2 is turned on and the transistor TrB is turned off to stop the shutter opening.5 At the same time, the transistor Tri that controls shutter closing is turned off and the transistor Tr4 is turned off. Turn on for a short time to short-circuit bimorph Bi. Due to this short circuit, the bimorph Bi moves to return to its initial position and closes the shutter. FIG. 1(C) shows an operating signal diagram of each of the above transistors.

As described above, exposure is controlled by controlling the shutter using bimorph Bj, but the change in the opening area of the shutter (the amount of movement of the shutter blades) using bimorph BE depends on the charging voltage at the initial stage of charging. It doesn't change much. This is thought to be because unless the bimorph Bi is charged to a certain voltage or higher, the driving force that resists the static friction force on the side of the drive R is not generated in the bimorphs 1 and 7Bi. This situation is shown in Figure 3. In Figure 3, the left scale of the vertical axis shows the rotation angle (travel amount) of the shutter blade, the right scale shows the charging voltage of the bimorph, and the horizontal axis shows the control time of the shutter blade. , curve xi, and VBI are transistor T, respectively.
r5. It shows the rotation angle of the shutter blade and the charging voltage required for the rotation in the above-described state where Tr6 is not provided. Also, A, .

Note that the charging voltage is shown by the voltage at the collector of transistor T r 3 in Figure 1, so the actual charging voltage is the voltage obtained by subtracting the collector voltage of 'r' r 3 from the output voltage of the booster circuit. The charging voltage increases from top to bottom.

Now, if the rotational angle position of the shutter blade just before the shutter blade opening is A, it takes time To to displace by this rotational angle.

Considering that this time To has no effect on exposure, it is nothing more than a release time lag from the release operation (S2.ON), and is a useless time. If you want to correct this, that is, shorten the above-mentioned time, you can increase the charging current, but this current value is determined by the shutter blades (including the drive mechanism) as the shutter opening speed (shutter speed). , which is uniquely determined and cannot be changed freely.

Therefore, in this embodiment, in order to shorten the above-mentioned time, it was decided to perform charging (increase the current by the amount of current and perform rapid charging) for a certain period of time T1 at the initial stage of charging. This result is added to the 3rd M as X2. VB2 indicates the rotation angle of the shutter blade and the charge required to drive it. ! ! Shows voltage.

As is clear from the figure, the time from the release operation to just before the blade opens is T. GaraT. You can see that it has been shortened to °.

The circuit configuration and time chart for realizing these are shown in FIG. 1, and this control circuit is the main part of the present invention.
Transistor T connected in parallel with transistor T r 3
r 6 and this? A bypass charging circuit is configured by the controlling transistor 1r5, and the release operation is performed to charge the bimorph for a certain period of time T1 by the charging circuit consisting of the transistor Tr3 and the resistor VR, and this bypass charging circuit. (32ON), the exposure control circuit 25 normally outputs a high level output terminal C.
It outputs an O level signal for a certain period of time T1 to control the transistor Tr6@○N and the +-run transistor Tr5.

As a modified embodiment, rapid charging may be performed until just before the blade opening instead of the fixed time T1, and the same effect as the above-mentioned embodiment can be obtained. In this case, the exposure control port i25 is
The output signal of the output terminal C is set to the ○ level until the signal detecting the overlap of the small holes A is input from the 1-use opening position detection circuit 23 from 2ON.

In addition, in order to increase the charging current by a predetermined time Tl after the release switch 92 is turned ON, a method of connecting the transistor Tr6'g in parallel with the resistor VR [Fig. 4 (A)] is available.
1 and the method of increasing the base current of transistor ``r3'' by turning on transistor Tr6 [Figure 11 (B
) E is also considered, and in these methods, both the output terminals a and c of the exposure control circuit 25 are changed from high-high level to 0 level by turning on the release switch 32, and the output terminals are turned on for a predetermined time T1.
After the elapsed time, only the output terminal C needs to be returned to the 3 high level.Furthermore, the transistor Tr3. It is also possible to switch the charging circuit in which the resistor VR roars to a completely separate charging circuit with a large current value. For example, by turning on the release switch 82, the output terminal C
is changed from high level to O level, output terminal a is kept at high level, and then when a predetermined time Tl has elapsed, output terminal a is changed to 0 level, while output terminal C is returned to high level. In this case, the transistor T r 6 can be used as a separate charging circuit that allows a large current to flow.

G. Effects According to the present invention, in a shutter driving device that drives a shutter using an electrostrictive element that generates a driving force by applying a voltage as a driving element, the current value by the second charging path forming means is adjusted to a desired shutter opening. By determining the value according to the characteristics, the shunter opening characteristics can be deepened, and during the release operation, the electrostrictive element is powered by the first current from the first charging path forming means until a predetermined time immediately before the shutter opening is formed. Rapid charging reduces release lag.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 shows a concave 28 configuration according to an embodiment of the present invention, (A) is a circuit diagram, (B) is a bimorph wiring diagram, and (C) is a time chart of circuit operation. , FIG. 2 shows the mechanism of the above embodiment, (A) IIJ is a plan view, (B) is a sectional view, FIG. 3 is a time chart for charging and driving the bimorph, and FIG. 4 (
A) and (B) are circuit diagrams showing main parts of different modifications of the charging circuit. 21...Photometering circuit, 22...Film sensitivity reading circuit. 23...Opening position detection circuit, 211...Arithmetic circuit. 25... Exposure control circuit, 26... Boost circuit. 27... Charging circuit.

Claims (1)

[Claims] In a shutter driving device using an electrostrictive element as a shutter driving means, first charging circuit means charges the electrostrictive element with a first current to a predetermined time point before the start of shutter aperture formation in response to a release operation; and second charging circuit means for charging the electrostrictive element with a second current after a predetermined time, and the current value of the first current is set to be larger than the current value of the second current. Shutter drive device.