JPS6151779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a rotor in which a sector ring is made of an insulating plate and a conductor coil pattern is formed on it by etching or the like, and the rotor is generated by energizing the radial component of the coil in a magnetic field. The present invention relates to an improvement of the conductor coil pattern in an electromagnetic drive shutter in which the rotor drives the shutter blades to open and close using the Lorentz force.

For example, in an electromagnetic drive shutter for cameras, in which a sector ring is rotated by electromagnetic drive to open and close shutter blades linked to this, a coil print pattern is formed on the front and back surfaces of the sector ring made of an insulating plate, and the sector ring is driven by a coil print pattern. It uses a method of rotating the sector ring by passing an electric current through it. In such an electromagnetic drive shutter, in order to obtain rotational force by placing a rotor made of a sector ring or the like in a magnetic field, a stator with multiple pairs of magnets placed on a yoke in a radial direction centered on the optical axis is used. use The effective portion of the conductor coil pattern printed on the rotor that receives the rotational force is a component in the radial direction centered on the optical axis of the coil, and therefore the ratio of the length of the effective portion to the total length of the coil conductor is large. The smaller the electric power, the greater the driving force that can be obtained.

The present invention has been made in view of the above points, and is aimed at obtaining a pattern in which the radial component of the conductor coil pattern printed on the sector ring is as long as possible, and the circumferential component is short. belongs to.

The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a front view showing an example of an electromagnetically driven shutter, which is used as an aperture shutter. FIG. 2 is a sectional view taken along the line AA in FIG. 1. In the figure, reference numeral 3 denotes a shutter blade which also serves as an aperture, and is made of a non-conductive material made of a light-shielding thermoplastic resin or thermosetting resin. The figure shows only two of the plurality of sheets, one of which is provided with a sub-diaphragm section.

2 is a sector ring made of non-conductive material such as non-magnetic glass epoxy or plastic. Linear conductor patterns 2a and 2b are printed on the front and back surfaces of the sector ring 2, and when a driving current is applied to these, the sector ring 2 is rotated by a fixed magnet, and the shutter blade 3 is driven. It's summery. That is, the printed patterns 2a and 2b generate a rotational force on the sector ring according to Fleming's law within the magnetic field of the fixed magnetic pole. Also this sector ring 2
is biased in the direction in which the shutter is closed by a closing spring 6, and normally the shutter blade 3 is held in the closed state. The shutter blade 3 rotates around a fixed shaft 8 fixed to the base plate 10. The rotational force of the sector ring 2 is transmitted to the shutter blade 3 by a dowel 5 made of a conductive material fixed thereto. A plurality of dowels 5 are fixed to the sector ring 2 by crimping or soldering, and one of the dowels 5 electrically connects the conductor patterns on the front and back surfaces of the sector ring. Reference numeral 9 denotes a sub-diaphragm that controls incident light to the light receiving element 50 for exposure control. A yoke 4 constitutes a magnetic flux path from the magnet and is made of a soft magnetic material.

1a and 1b are stationary magnets that are arranged in sequence in the circumferential direction, facing the printed pattern on the sector ring, with N and S poles alternately adjacent to each other as shown in the figure, and the magnetic flux generated by these magnets is directed in the radial direction of the pattern. The conductor section is penetrated through the conductor section.

Next, the operation of the electromagnetically driven shutter shown in FIGS. 1 and 2 will be explained. When a release button (not shown) is operated, a drive circuit is activated, and the coil consisting of a conductive pattern is connected from the first terminal 7a to the second terminal 7.
Current flows in the direction b. As a result, coil 2a
and 2b, a rotational force F ₁ as shown in FIG. 1 is generated according to Fleming's law by a current component flowing in the radial direction of the conductor pattern within the magnetic field of fixed magnets 1a and 1b. This force _F1 causes the sector ring 2 to rotate against the urging force of the closing spring 6, and this rotation is transmitted to the shutter blade 3 by the sector pin 5, so that the shutter blade 3 is gradually opened. As the shutter blades open, the amount of light passing through the sub-diaphragm 9 and entering the light receiving element 50 increases, and when this reaches a predetermined amount, the current from the drive circuit, which will be described later, is turned off. As a result, the sector ring 2 is rotated counterclockwise by the restoring force of the closing spring 6, and the shutter blade 3 is closed.

In the electromagnetic drive shutter described above with reference to FIGS. 1 and 2, in the present invention, the length of the effective portion of the coil for obtaining Lorentz force is minimized by changing the shape of the conductor coil pattern disposed on the sector ring. This is to obtain an improved pattern that becomes longer. FIG. 3 is an explanatory diagram showing the shape of a conductor coil pattern having two pairs of fan-shaped coil parts, FIG. 3a shows one used in a conventional device, and FIG. 3b shows an example of a pattern according to the present invention. . That is, the actual coil pattern consists of a group of conductors drawn many times on a plane as shown in FIG. 1 according to the pattern shape shown in FIG. In the figure, O is the optical axis, and the conductor pattern has an inner diameter of φ22 and an outer diameter of φ48, centering around this axis, forming a fan shape of 30° symmetrical to the axis.

In the conventional pattern shown in FIG. 3a, the conductor in the radial direction of the fan-shaped pattern completely coincides with the radial direction centered on the optical axis, and in the conductor pattern of the present invention shown in FIG. The conductor patterns are each offset by 7.5 degrees in the direction of the center line of the sector. It is shown that using the pattern of FIG. 3b, the length of the sector-shaped circumferential conductor pattern is shorter than that of FIG. 3a. As shown in Figure 3 a and b, the magnetic field starts from R12.25mm.
Assuming that it is added between R22.75mm,
The total length of one coil shown in Figure a is 200.3 mm, and the effective length is 10.5 mm x 8 = 84 mm.
In figure b, the length of the conductor in the peripheral direction becomes shorter, so the total length at one time is 191.6, and the effective length is a
The same as in the case of 10.5mm x 8 = 84mm. Therefore, the ratio of the effective portion of the conductor coil to the total length in the patterns shown in Figures a and b is 41.9% in a, and 41.9% in b.
Then it becomes 43.8%. Here, the motion component of the Lorentz force in the case of the pattern shown in Figure b is the deviation angle
Since the cos of 7.5° is 0.9914, Figure a and Figure B
The ratio of effective rate is 43.8×0.9914/41.9=1.03
6, and by using the pattern in figure b, it becomes 3.6
% efficiency improvement.

As the above deviation angle increases, the length of the coil in the peripheral direction becomes shorter, but this increases the difference in direction between the motion direction and the Lorentz force, and during that time the value of cosθ, which is the effective component, decreases. Therefore, efficiency improvement will not progress. Therefore, this deviation angle has a certain limit, and it is effective to set it within a range of approximately 0° to 15°.

In the embodiments shown in Figures 1 to 3, the angle formed by adjacent fan-shaped pattern parts is set to 30 degrees, but this angle is set in consideration of the stroke to prevent the conductor of the radial component from entering the adjacent magnetic field. and this angle is
Any angle of about 30° can be selected.
The reason why the conductor coil pattern in the embodiment shown in FIGS. 1 to 3 lacks a fan-shaped pattern in the vertical direction is that mechanical parts such as those related to driving the lens barrel are arranged in this part. FIG. 4 is a circuit connection diagram showing an embodiment of the electromagnetic shutter control circuit according to the present invention. In the figure, 100 is the power battery, 101 is the main switch that is always open, and the first release button.
Operated by strokes. A release switch 102 is always closed and is operated by the second stroke of the release button or a focusing completion signal from an autofocus camera. A resistor 103 and a capacitor 104 constitute a time-fixing circuit, and 105 is a timer circuit for preventing chattering upon release, which is operated by this time-fixing circuit.
110 is a constant voltage circuit, and 50 is a light receiving element for photometry, in which a silicon photocell SPC is used.
The SPC is connected between both input terminals of operational amplifier 112. 133 is a switching transistor for shorting both ends of the capacitor 119;
Its collector side is connected to the non-inverting input terminal of the comparator 121.

A variable voltage source for generating a film ASA sensitivity signal is connected to the inverting input terminal of the comparator 121. Reference numerals 131 and 132 are switching transistors that control the transistor 129 for turning on and off the supply of electricity to the printed pattern coil 20.

The operation of the circuit shown in FIG. 4 constructed as above will now be described.

First, when the main switch 101 is turned on, the release switch 102 is closed, so the output of the timer circuit 105 is low level (L) and the transistor 108 remains off. Therefore, since the transistor 133 is on, the voltage at the non-inverting input terminal of the comparator 121 is approximately zero, and the output of the comparator 121 is at L level. Further, since the transistor 108 is off, the switching transistor 132 is turned on and the transistor 129 is turned off, so that the printed pattern coil 20 is not energized and the electromagnetic device does not operate.

Next, when the release switch 102 is opened by the shutter release operation, the resistance is determined by the resistor 103 and the capacitor 104. After a certain period of time, the timer circuit 105 turns on and its output changes from L level to H level.
To invert the level, transistor 108 is turned on.

This turns off switching transistors 132 and 133. At this stage, the output of the comparator 121 remains at the L level, so the transistor 131 remains off.
Therefore, since the transistor 129 is turned on, a current is applied to the printed pattern coil 20, and the shutter starts to open. At the same time, light enters the SPC 50 through the sub-diaphragm aperture, and a current proportional to the amount of incident light flows into the capacitor 119. When the terminal voltage of the capacitor 119 reaches the voltage set by the voltage source 120 according to the ASA sensitivity of the film, the output of the comparator 121 is inverted from the L level to the high level (H). As a result, the switching transistor 13
2 is turned off, the transistor 129 is turned off, and the current to the printed pattern coil is cut off.

As described above, in the electromagnetic drive shutter according to the present invention, the conductor coil pattern in the radial direction centered on the optical axis is tilted to some extent in the direction of the center line of the fan-shaped pattern, thereby shortening the length of the peripheral portion of the coil and increasing the effective length. The efficiency can be increased by increasing the ratio of It is suitable.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of an electromagnetic drive shutter to which the present invention is applied, and FIG. 2 is an A in FIG.
3 is an explanatory diagram illustrating the improvement of the coil pattern in the shutter shown in 1. FIG. 3 a is a conventional pattern, and FIG. 3 b
4 is a circuit connection diagram showing an embodiment of a drive circuit for an electromagnetic shutter according to the present invention. 1a, 1b...Magnet, 2...Sector ring,
3...Shutter blade, 4...Yoke, 5...Dowel, 6...Return spring, 7a, 7b...Coil lead wire, 8...Shutter blade rotation shaft, 9...Sub-diaphragm, 10...Shutter board .

Claims (1)

[Claims] 1. A rotor that controls the opening and closing of the blade member, a first conductor that is fixed to this rotor and that allows current to flow outward from the center of rotation of the rotor, and a current that is flown by the first conductor. In the electromagnetic drive shutter, the electromagnetic drive shutter comprises a second conductor for causing the current to flow again toward the rotation center, and a stator for forming a magnetic field for generating a driving force in the rotor via these conductors. The effective straight portions of the first conductor and the second conductor that generate a rotational driving force in the rotor are arranged closer to each other than when the effective straight portions are formed in the radial direction. An electromagnetic drive shutter, characterized in that the shutters are arranged at a predetermined angle, and magnetic fields in different directions are applied to the effective straight portions by the stator.