JPS6370233A - Electromagnetic program shutter - Google Patents

Abstract

PURPOSE:To obtain a shutter of simple constitution which has high accuracy and operates electromagnetically by installing a columnar permanent magnet rotatably and opening and closing shutter sectors with the rotational force of the magnet generated when a fixed coil provided at the periphery of the magnet is fed with electricity. CONSTITUTION:An arithmetic circuit 10 feeds electricity to the fixed coil 5 according to object brightness measured by a photodiode 9, and then the columnar permanent magnet 3 rotates as shown by an arrow together with a rotary shaft 4. The shutter is opened by said rotation through an arm and a link lever 7. Then the value of a current supplied from a constant current output circuit 11 to the coil 5 is set previously that the opening speed of the shutter sectors 1 and 2 is proper. Then the electricity to the coil 5 is ceased, the magnet 3 is rotated with the attractive force operating between a magnetic body piece 8 and the magnet 3 and its N pole stops opposite the magnetic body piece 8. The sectors 1 and 2 close the opening of the shutter at the return position of the magnet 3.

Description

TECHNICAL FIELD The present invention relates to a program shutter used in a still camera, and more particularly to an electromagnetic program shutter whose driving force is obtained electromagnetically.

"Prior Art and its Problems" A program shutter is a shutter that also serves as an aperture, and automatic exposure is performed using a preset combination of aperture value and shutter speed.

In conventional program shutters, for example, a shutter drive spring is charged during a film winding operation, and when the shutter release operation is performed, the shutter drive spring causes the shutter sector to open, and when the shutter sector is opened during or after opening, the closing spring is activated. A shutter is known in which the shutter sector is closed by releasing the latch of the shutter. However, a programmable shutter based on a mechanical structure like this requires a link mechanism for spring charging, a latch release mechanism, etc.
I couldn't avoid having a complicated structure.

"Objective of the Invention" An object of the present invention is to obtain an electromagnetically actuated program shutter that has a simple mechanical configuration, is low in cost, and has high precision.

"Summary of the Invention" The electromagnetic program shutter of the present invention has a cylindrical permanent magnet rotatably installed, and utilizes the rotational force of the permanent magnet generated by energizing a snow-proof fixed coil around the cylindrical permanent magnet. It is configured to open and close a shutter sector linked to a permanent magnet. The fixed coil is energized for a predetermined period of time depending on the brightness of the subject, and is controlled by a control circuit whose output stage has constant current output characteristics. Furthermore, since the shutter must remain closed when the fixed coil is not energized, a return means is provided that biases the permanent magnet to rotate in the direction in which the shutter is closed.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIG. 1 illustrates a mechanical part of an electromagnetic program shutter according to the present invention. 1.2 are shutter sectors, each with axis 1
It is rotatable around a and 2aa. This shutter sector 1.2 is provided with elongated holes 1b, 2b located in the middle of its shafts 1a, 2a and overlapping with each other,
The shutter sector 1.
2, the shirt opening is opened and closed. ○ indicates the optical axis.

3 is a cylindrical permanent magnet, and a rotating shaft 4 is integrally attached to the central axis of the magnet.
is provided. A fixed coil 5 is installed within the magnetic field of this cylindrical permanent magnet 3. When this fixed coil 5 is energized, the permanent magnet 3 is moved to the rotating shaft 4.
Throws snow by rotating it around the center. FIG. 4 specifically shows how the permanent magnet 3 and fixed coil 5 are installed.

An arm 6 is integrally provided on the rotating shaft 4, and a drive pin 6a implanted in the free end of the arm 6 engages with an interlocking notch 7b of a link lever 7. The link lever 7 is rotatable around the rotation axis 7a%, and is fitted into the interlocking pin 7c provided at the end opposite to the interlocking notch 7b or into the long holes 1b and 2b of the shutter sector 1.2. waiting.

Reference numeral 8 denotes a piece of magnetic material such as soft iron, which is fixed within the magnetic field of the permanent magnet 3. This magnetic piece 8 attracts the permanent magnet 3 and holds the cylindrical permanent magnet 3 in a position where the shutter is closed when the fixed coil 5 is not energized. Also, when the fixed coil 5 is energized to rotate the permanent magnet 3 and open the shutter, and then the fixed coil 5 is de-energized,
The cylindrical permanent magnet 3 is returned to its original position. That is, this magnetic one-piece piece 8 is a means for returning the permanent magnet 3. Note that the rotation angle range of the link lever 7 is regulated by a stopper (not shown) so that it does not rotate more than necessary.

FIG. 2 shows an energization time control circuit for controlling the energization time to the fixed coil 5 of FIG. 9 is a photodiode that measures the subject brightness; 10 is a photodiode 9
11 is a constant current output circuit that supplies a constant current to the fixed coil 5 in accordance with the output of the arithmetic circuit 10.

The present electromagnetic program shutter having the above configuration operates as follows.

First, the calculation circuit 10 calculates an appropriate energization time for the fixed coil 5 in accordance with the subject brightness measured by the photodiode 9 shown in FIG. The constant current output circuit 11 supplies a constant current to the fixed coil 5 according to the output of the arithmetic circuit 10.

Since the fixed coil 5 is within the magnetic field influence area of the permanent magnet 3, energization of the fixed coil 5 causes the cylindrical permanent magnet 3 to rotate together with the rotating shaft 4 in the direction of the arrow in FIGS. 1 and 4 (A). . The rotation of the cylindrical permanent magnet 3 is transmitted to the shutter sector 2 via the arm 6 and the link lever 7.
Open the shutter. The constant current value given from the constant current output circuit 11 to the fixed coil 5 is set in advance so that the opening speed of the shutter sector 1.2 is appropriate. When the magnetic poles are arranged as shown in Figure (A), the rotation angle is 90 degrees, but the shutter sector 1.2 can be sufficiently opened and closed with this rotation angle or less.

Then, when the power to the fixed coil 5 is cut off, the permanent magnet 3 rotates in the direction shown by the arrow in FIG. 4(B) due to the attractive force acting between the magnetic piece 8 and the cylindrical permanent magnet 3. Permanent magnet 3 N
The pole stops at a position facing the magnetic piece 8. In this return position of the cylindrical permanent magnet 3, the shutter sector 1.2 closes the shutter opening.

The cylindrical permanent magnet 3 can of course be returned to its original state by a commonly used spring means, but according to this embodiment,
It is more compact than when a spring is used, and since the permanent magnet 3 and the magnetic piece 8 are not in contact, there is no friction or frictional resistance, and there are fewer failures.

FIG. 3 schematically shows the opening action 'P1' of the shutter of the present invention. In this example, the maximum aperture f is set to F'@F2.8. In the figure, A shows the opening operation when the fixed coil 5 is energized and reaches the maximum opening.The dotted line in B shows the opening/closing operation when the fixed coil 5 is energized for a time t1 before reaching the maximum opening. The exposure amount is the area of the triangle surrounded by A, 8, and the horizontal axis. Therefore fixed coil 5
By controlling the energization time, the amount of exposure can be controlled by a combination of E value and shutter speed. If the constant current value is changed, the slope of the aperture characteristic at the time of opening changes, and the amount of exposure can be controlled with a different combination of F value and shutter speed.

As mentioned above, if the fixed coil 50 is de-energized, the shutter sector 1.2 is closed due to the action of the magnetic piece 8.
If it is desired to obtain a high-speed shutter, it is possible to supply a reverse current to the fixed coil 5 or to separately provide a fixed coil exclusively for closing.

Further, the shutter structure itself shown in the above embodiments shows an example of the position, and the present invention can of course be applied to other shutter structures.

"Effects of the Invention" As described above, the electromagnetic program shutter of the present invention has an extremely simple structure compared to conventional products. Also, since the fixed coil is supplied with current from the constant current output circuit,
Even if the resistance value of the fixed coil changes due to a temperature change, the rotational speed of the cylindrical permanent magnet does not change, so a highly accurate programmable shutter can be achieved with a wide temperature range. Additionally, since the cylindrical permanent magnet rotates while the coil is fixed, there is no need to worry about the power supply wire breaking, unlike coil-rotating actuators such as ammeters.

[Brief Description of the Drawings] Fig. 1 is an exploded perspective view of the main parts showing an embodiment of the electromagnetic program shutter of the present invention, Fig. 2 is a block diagram of a control circuit for controlling energization to a fixed coil, and Fig. 2 is a block diagram of a control circuit for controlling energization to a fixed coil. Figure 3 is a graph showing the program operation of the shutter of the present invention, Figure 4 (A)
, (B) is a sectional view showing the relationship between a cylindrical permanent magnet and a fixed coil. 1.2...Shutter sector, 3...Cylindrical permanent magnet, 5...Fixed coil, 6...Arm, 7...Link lever, 9...Photodiode, 10...Calculation Circuit, 11... Constant current output circuit. Patent applicant: Asahi Optical Industry Co., Ltd. Agents: Kunio Miura, Shigeto Matsui, Yoshimi Sasayama Figure 1 Figure 3 (A) (B)

Claims (2)

[Claims] (1) A cylindrical permanent magnet that is rotatably installed around a central axis; a shutter sector that opens and closes in conjunction with the rotation of this cylindrical permanent magnet; and the influence of the magnetic field generated by the cylindrical permanent magnet. a fixed coil that is installed within the area and rotates the cylindrical permanent magnet in the direction of opening the shutter sector when energized; and a fixed coil that rotates the cylindrical permanent magnet in a direction opposite to the direction of rotation when energized to close the shutter. An electromagnetic program shutter comprising: a return means for returning to the position; and an energization time control circuit including a constant current output circuit that controls the energization time to the fixed coil. (2) In claim 1, the return means for the cylindrical permanent magnet is a magnet that is fixedly provided within the influence area of the magnetic field generated by the cylindrical permanent magnet and that attracts the cylindrical permanent magnet to each other. Electromagnetic program shutter made of wood.