JPH0624817Y2 - Shutter for camera using electrostrictive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a camera shutter that utilizes the electrostrictive action of an electrostrictive element as a driving force.

[Conventional technology]

BACKGROUND ART Electrostrictive elements have been widely used in, for example, microphones and receivers, but recently, as disclosed in Japanese Patent Publication No. 45-15192, for example, application to blade driving means in camera shutters has been proposed. There is.

In addition, the applicant of the present invention, for example, as described in Japanese Utility Model Publication No. 63-101925 and Japanese Utility Model Publication No. 63-105125,
An example applied to a blade driving means of a camera shutter is proposed.

This is, as shown in FIG. 7, a shutter base plate 21 having an exposure opening 21a, and a pair of shutter blades 23 pivotally supported by a support shaft 22 on the back surface of the base plate 21 to open and close the exposure opening 21a. 23 and a fork portion 25a which is pivotally supported on the surface of the main plate 21 by a support shaft 24 and which engages with the tip of an electrostrictive element described later at one end side thereof, and arc-shaped holes 21b, 21b of the main plate 21 at the other end side thereof. Pins 25b, 25b which penetrate through the shutter blades 23, 23 and engage with the slots 23a, 23a of the shutter blades 23, 23, respectively.
Is fixed to the open / close lever 25, and the base portion is fixed and supported by a bracket 26 attached to the main plate 21, and the distal end portion is inserted into and engaged with the fork portion 25a of the open / close lever 25, and has an elongated rectangular plate-like electric shape. And the strain element 27.

Here, the structure and properties of the electrostrictive element 27 will be described. For example, in the case of a series type, the electrostrictive element 27 has a structure in which piezoelectric ceramic plates having opposite polarization directions are laminated with an insulating plate sandwiched therebetween, When a voltage is applied to both insulated ceramic plates, electric charge is accumulated between the insulated ceramic plates in the same manner as a so-called parallel plate capacitor, and one of the insulated ceramic plates corresponds to the potential difference between the insulated ceramic plates. Has the property of being distorted by stretching and contracting the other ceramic plate. And even after the application of voltage is stopped, the potential difference continues to be maintained by the accumulated charge, so the above-mentioned distorted state is maintained, and the charge is discharged and distorted from the distorted state only when the two insulated ceramic plates are short-circuited. It has the property of returning to the initial state.

The distortion characteristic of the electrostrictive element is represented by the following formula (1).

Where: electrostrictive element length V: drive voltage d: electrostrictive constant Th: electrostrictive element thickness Then, in the above equation (1), It is understood that the equation (1) is converted into the following equation (2), and the displacement amount is directly proportional to the applied voltage.

Displacement amount = KV (2) Therefore, in this example, by increasing the voltage applied to the electrostrictive element 27 at the same time as the shutter release, the amount of distortion of the electrostrictive element 27 is gradually increased. Exposure opening 21 by shutter blades 23 and 23
By gradually increasing the opening diameter of a and short-circuiting both terminals of the electrostrictive element 27 at the timing when an appropriate exposure amount is given, the electrostrictive element 27 is returned to the initial state and the exposed opening 21a is instantaneously opened. I'm trying to close it.

[Problems to be solved by the device]

However, in the above-mentioned conventional example, in order to increase the displacement amount of the electrostrictive element 27, it is clear from the above equation (1) that the electrostrictive element 27 is
However, the shape of the electrostrictive element 27 could not be unnecessarily increased in order to satisfy the market demand for miniaturization of the camera. For example, if the length of the electrostrictive element 27 (length in the direction orthogonal to the optical axis) is increased,
It was limited by the diameter of the lens barrel. Therefore, in the structure in which the displacement direction of the electrostrictive element 27 is set in the direction orthogonal to the optical axis as in the above conventional example, miniaturization of the shutter and obtaining a large displacement amount conflict with each other.

An object of the present invention is to provide a camera shutter in which the electrostrictive element has a sufficiently large amount of displacement, which does not conflict with the downsizing of the shutter.

[Means for Solving the Problems]

In order to achieve the above object, in a camera shutter according to the present invention, an electrostrictive element is such that a pair of piezoelectric ceramic plates are laminated with an intermediate electrode plate interposed therebetween, and outer electrode plates are respectively provided on the surfaces of both piezoelectric ceramic plates. The blade working member for driving the blade working member having a laminated structure and arranged in parallel or substantially parallel to the vane member and having a size that does not cover the exposure opening, the fixed end portion, and the blade working member. And a free end portion engaged with a part of the free end portion on one side of the center line of the free end portion, and one piezoelectric ceramic plate and the outer electrode plate are notched. On the side, the other piezoelectric ceramic plate and the outer electrode plate are notched to form a flexible structure in which the center line portion is composed only of the intermediate electrode plate, and the blade operating member is contacted with the blade operating member during forward and backward movements. Above to be treated Each portion of the magnetostrictive element is configured to be positioned on both sides of the flexible structural part.

[Action]

The electrostrictive element with a hole in the center has a length from the fixed point to the point of action along the arc, which is longer than a rectangular plate with the same length in the longitudinal direction. The amount is large enough. Furthermore, since a part of the free end of the electrostrictive element that engages with the blade actuating member has a flexible structure, the torsional deformation of the electrostrictive element is reduced, and the displacement amount at the point of action is further increased. Further, since the respective portions of the electrostrictive element that should come into contact with the blade operating member during the forward and backward movements of the blade operating member are arranged on both sides of the flexible structure portion, the freedom of the electrostrictive element is reduced. Although the end portion has a flexible structure, the displacement can be surely transmitted to the blade operating member.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

First, in FIGS. 1 to 3, 1 is a substantially circular plate-shaped electrostrictive member, one end of which is held by a fixing member 2 and the other end of which is displaced in a direction along an optical axis passing through the center of an exposure opening described later. Element, 3
Is a point of action of the driving force to be provided at the free end of the plate-like electrostrictive element 1, and 4 is a hole formed in the central portion of the plate-like electrostrictive element 1 so as to taper from the fixed end toward the point of action 3. The teardrop-shaped hole 5 formed in the above is a driven member formed as, for example, a lever, which is engaged with the free end of the plate-shaped electrostrictive element 1 from the inner peripheral side of the hole 4. Reference numeral 6 denotes a shutter substrate which cooperates with the fixing member 2 to hold one end of the plate-shaped electrostrictive element 1 and which is provided with an exposure opening 6a and slots 6b, 6c and 6d, and 7 is a pin implanted in the shutter substrate 6. , 8 and 9 have pin 7 at the base
A pair of shutter blades, which are rotatably fitted to each other and formed to open and close the exposure opening 6a,
Reference numeral 0 denotes an opening 10a and slots 6b, 6c, 6d which are fixed to the shutter substrate 6 so as to form a space capable of accommodating the shutter blades 8 and 9 and which are aligned with the exposure opening 6a.
A cover plate 11 having slots 10b, 10c, and 10d aligned with each other is rotatably supported by a pin 12 on the back surface of the shutter substrate 6, and has a slot 11a at one end and slots 6c and 6d at the other end. The blade opening / closing lever has a pair of pins 11b and 11c which extend through the respective shutter blades and which are connected to the shutter blades 8 and 9 by pin-slot connection.

The plate-shaped electrostrictive element 1 is of a so-called parallel type, and as shown in FIG. 4, a pair of piezoelectric ceramic plates 13 and 13 having the same polarization direction are laminated with an intermediate electrode plate 14 interposed therebetween. The outer electrode plates 15 and 15 are provided on the respective surfaces of both piezoelectric ceramic layers 13 and 13, and the piezoelectric ceramic layer 13 and the outer electrode plate 15 on the upper side are cut out on one side from the center line of the free end of the outer electrode plates 15 and 15. On the side of, the lower piezoelectric ceramic layer 13 and the outer electrode plate 15 are cut out to form a flexible structure in which the center line portion is composed only of the intermediate electrode plate 14. The driven member 5 is configured as a crank lever supported by a bracket 16 mounted on the cover plate 10 (see FIGS. 1 to 3), and the flexible end portion of the plate-shaped electrostrictive element 1 is flexible. A pair of arms 5a, 5a that come into contact with the opposite side of the notch from both sides of the structural part, respectively, a pair of arms 5a penetrating through the slots 10b, 6b, and a slot 11 of the blade opening / closing lever 11.
It has a spherical lower end portion 5c fitted to a. In this embodiment, when the opposite voltages are applied to the pair of piezoelectric ceramic layers 13, one expands and the other contracts so that the free end of the plate-shaped electrostrictive element 1 is curved downward. Assume that it is configured.

Since this embodiment is configured as described above, when a voltage is applied between the outer electrode plates 15 and 15 of the plate-shaped electrostrictive element 1 and the intermediate electrode plate 14, the action point 3 is displaced downward, The driven member 5 is rotated right at the position shown in FIG. Therefore, the blade opening / closing lever 11 is turned counterclockwise from the position shown in FIG. 1 to the position shown in FIG. 3 with the pin 12 as a fulcrum, thereby opening the shutter blades 8 and 9. In that state, the outer electrode plates 15, 15
If a short circuit is made between the intermediate electrode plate 14 and the intermediate electrode plate 14 or a reverse voltage is applied, the plate-shaped electrostrictive element 1 returns to its original shape, so that the driven member 5 is rotated counterclockwise, and as a result, the blade opening / closing lever 11 again moves to the first position.
Returning to the position shown in the figure, the shutter blades 8 and 9 are brought to the closed position to complete one exposure operation.

In the case of this embodiment, the length from the fixed point of the plate-shaped electrostrictive element 1 to the point of action becomes the length along the arc, which is longer than that of the rectangular plate having the same length in the longitudinal direction. The amount of displacement is sufficiently large.

Further, in the case of the present embodiment, since a part of the free end of the plate-shaped electrostrictive element 1 which engages with the driven member 5 has a flexible structure,
Torsional deformation of the plate-shaped electrostrictive element 1 is reduced, and the amount of displacement at the point of action is further increased.

Further, since the respective portions of the plate-shaped electrostrictive element 1 that should come into contact with the arms 5a of the driven member 5 are arranged on both sides of the flexible structure portion when the driven member 5 moves forward and backward. While the free end of the plate-shaped electrostrictive element 1 has a flexible structure, its displacement can be reliably transmitted to the driven member 5.

Further, in the plate-shaped electrostrictive element 1, only the center line portion of the free end thereof is composed of only the intermediate electrode plate 14, and the other parts are composed of at least the intermediate electrode plate 14, the piezoelectric ceramic plate 13, and the outer electrode plate 15. Therefore, the free end has a flexible structure, but its strength is maintained.

FIG. 5 shows an essential part of the second embodiment, in which the arm 5a of the driven member 5 is made into two pairs and is cut on both sides of the flexible structure part of the free end of the plate-shaped electrostrictive element 1. A pair of arms 5a from above and below respectively come into contact with the portion excluding the notch portion, and this has the advantage that the displacement of the free end portion can be transmitted to the driven member 5 more reliably.

FIG. 6 shows an essential part of the third embodiment, in which the pair of arms 5a of the driven member 5 are vertically moved to the notches on both sides of the flexible structure part of the free end of the plate-like electrostrictive element 1, respectively. Since the abutment is performed from the above, there is an advantage that the length of the entire shutter in the optical axis direction can be shortened as compared with the other embodiments.

[Effect of device]

As described above, the camera shutter according to the present invention has the practically important advantage that the electrostrictive element has a sufficiently large displacement amount, which does not conflict with the downsizing of the shutter.

[Brief description of drawings]

FIG. 1 is a plan view of a main part showing a normal state of a first embodiment of a camera shutter according to the present invention, FIG. 2 is an explanatory vertical sectional view showing a relation of components shown in FIG. 1, and FIG. FIG. 4 is a plan view showing a blade open state of the first embodiment, FIG. 4 is a perspective view of an essential part of the first embodiment, and FIGS. 5 and 6 are perspective views of an essential part of the second and third embodiments, respectively. The figure is a plan view of a conventional example. 1 ... plate-like electrostrictive element, 2 ... fixing member, 3 ... action point,
4 ... Hole, 5 ... Driven member, 5a ... Arm, 5b ...
Arm part, 5c ... Lower end part, 6 ... Shutter substrate,
7,12 ... Pin, 8,9 ... Shutter blade, 10 ...
… Cover plate, 11 …… Blade opening / closing lever, 13 ……
Piezoelectric ceramic layer, 14 ... Intermediate electrode plate, 15 ... Outer electrode plate, 16 ... Bracket.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Innovator Nobuyoshi Inoue 2-16-20 Shimura, Itabashi-ku, Tokyo Copal Co., Ltd. (72) Inventor Kazuyuki Nemoto 2-16-20 Shimura, Itabashi-ku, Tokyo Copal Co., Ltd. In (72) Inventor Hichiya Toriho Shimura 2-16-20 Itabashi-ku, Tokyo Copal Co., Ltd. (56) Reference JP-A 64-939 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A blade member for opening and closing an exposure opening to adjust an exposure amount, a blade operating member for operating the blade member, and a pair of piezoelectric ceramic plates which are laminated with an intermediate electrode plate interposed therebetween. An outer electrode plate is provided on the surface of each of the piezoelectric ceramic plates, and the piezoelectric ceramic plates have a laminated structure and are arranged in parallel or substantially in parallel with the vane member and have a size that does not cover the exposed opening and a fixed end portion. An electrostrictive element having a free end engaged with the vane actuating member for driving the vane actuating member, wherein a portion of the free end of the electrostrictive element is in the center of the free end. One center side of the line is formed by notching one piezoelectric ceramic plate and the outer electrode plate, and the other side is notched by the other piezoelectric ceramic plate and the outer electrode plate. Along with the structure, wings A camera using an electrostrictive element, wherein each portion of the electrostrictive element that should come into contact with the blade operating member during forward and backward movement of the operating member is arranged on both sides of the flexible structure portion. Shutter.