Photography – Camera detail – Shutter
Reexamination Certificate
2002-07-19
2004-11-23
Mahoney, Christopher (Department: 2851)
Photography
Camera detail
Shutter
C310S256000
Reexamination Certificate
active
06821033
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electromagnetic actuator having a rotor that rotates within a predetermined angular range and relates to a camera shutter device that uses such an electromagnetic actuator as its drive source.
BACKGROUND ART
Electromagnetic actuators used as drive sources for a camera shutter devices, particularly focal-plane type camera shutter devices are known from, for example, Unexamined Japanese Patent Gazettes No. 1-310329, No. 8-190123 (corresponding to U.S. Pat. No. 5,749,014), No. 8-254729, No. 9-329827, and No. 10-20364 (corresponding to U.S. Pat. No. 6,071,019), and U.S. Pat. Nos. 5,822,629 and 6,000,860.
The electromagnetic actuators disclosed in the gazettes or the like comprise a rotor with a cylindrical permanent magnet that outputs a rotational driving force, a frame member that rotatably supports the rotor, and a coil wound around the outside of the frame member.
These electromagnetic actuators are arranged on the base plate as drive sources for camera shutter devices so that the actuators are set correspondingly with before-moving (or first-moving) and after-moving (or second-moving) shutter blades, and open and close the aperture for exposure by driving the before-moving and after-moving shutter blades respectively through a complex interlocking mechanism including a drive lever.
The shutter devices are also provided with a stopper mechanism that positions the shutter blades at the operation start position before the shutter blades start moving for the exposure operation and a brake mechanism that prevents bounds or the like of the shutter blades at the completion of the movement.
In the conventional electromagnetic actuator, the coil is wound around the outside of the rotor in the direction of the rotation axis of the rotor so as to surround the axis, thereby increasing the height or the thickness of the electromagnetic actuator.
Therefore, if the actuator is used as a drive source for a focal-plane camera shutter device to be incorporated particularly in a camera or the like required for thinness, the freedom of its arrangement is limited due to its great height (thickness). As a result, it is difficult to produce a thin camera with the actuator.
The camera shutter devices disclosed in Unexamined Japanese Patent Gazettes No. 8-190123 (corresponding to U.S. Pat. No. 5,749,014) and No. 10-20364 (corresponding to U.S. Pat. No. 6,071,019) adopt an electromagnetic actuator composed of flat yokes, a coil wound around the yokes and a rotor placed between the yokes, and use the actuator as a trigger mechanism to release the before-moving and after-moving shutter blades engaged and stopped. The devices are designed to move the before-moving and after-moving shutter blades by releasing the spring force charged by the complex charging mechanism.
Therefore, the devices use complex mechanisms such as a charging mechanism, a trigger mechanism (engagement and stop release mechanism) or the like, thereby increasing the number of parts used and complicating their structures. As a result, the device becomes large and the cost is increased accordingly.
The present invention is made in view of the problems. The purpose of the present invention is to provide an electromagnetic actuator that enables the simplification of the structure, low power consumption and thinning of the device as well as a camera shutter device with such an actuator and even a camera shutter device that gives a desired stable exposure operation.
DISCLOSURE OF THE INVENTION
The electromagnetic actuator in the present invention comprises an exciting coil, a yoke forming a magnetic circuit and a rotatable rotor which is magnetized with different polarities, rotates within a predetermined angular range through the supply of current to the coil, and has an output portion to output the driving force externally. The yoke comprises flat plate-like yokes provided with first and second magnetic pole parts formed to be opposed to the circumference surface of the rotor. The coil comprises first and second coils wound in such a manner that different polarities are generated in the first and second magnetic pole parts and the coils become flat in the same direction as the plate-like yoke when the current is turned.
According to this configuration, when the first and second coils are supplied with electricity, generated lines of magnetic force pass through the plate-like yokes and cause the generation of different poles (north pole in one part and south pole in the other part) in the first and second magnetic pole parts, and then, by the relationship between the rotor's magnetic pole (north pole and south pole) and the generated poles, the rotor rotates within the predetermined angular range and outputs the driving force externally.
As shown above, the electromagnetic actuator is composed of a flat plate-like yoke and first and second coils wound flat, thereby increasing the driving force and at the same time, making the device thin (flat).
Herein, the plate-like yoke may be laminated with a plurality of magnetic plates in the direction of the rotation axis of the rotor.
According to this configuration, a plate-like yoke whose thickness conforms to various specifications by selecting the suitable number of magnetic plates for lamination as required can be formed.
In addition, the plate-like yoke may be divided into two parts, which are of a first yoke having a first magnetic pole part and a second yoke having a second magnetic pole part, in the direction substantially perpendicular to the rotor's rotation axis. The first and second coils may be wound around the joint areas of the first and second yokes, respectively.
According to this configuration, the assembly efficiency is improved by dividing the plate-like yoke into two parts. The bobbin, etc. that winds the coils can also serve as a member for joint by winding the first and second coils around the joint areas of the first and second yokes. Furthermore, the number of part types is decreased by making the divided first and second yokes identical in shape, whereby the management cost, etc. can be reduced.
The first and second yokes may be jointed at least on the planes overlapping in the direction of the rotor's rotation axis.
If a yoke whose thickness in the direction of the rotor's rotation axis is thin is used and the two divided yokes are jointed in the direction perpendicular to the rotor's rotation axis, enough joint area can not be obtained due to the thin plate. According to this configuration, however, the enough joint area for the two yokes can be obtained by jointing them on the planes overlapping in the direction of the rotor's rotation axis. That is to say, the magnetic efficiency on the interface of the two-divided yokes can be enhanced while the yokes can be thinned.
The first and second yokes may be jointed to get engaged with each other on the planes alternately overlapping in the direction of the rotor's rotation axis.
According to this configuration, the magnetic efficiency on the interface can be enhanced while the yokes can be thinned, as shown above. Moreover, since the first and second yokes are jointed to engage with each other by overlapping them alternately, sufficient joint strength can be obtained even though a thin plate is used as the laminated magnetic plate.
The first and second coils are arranged opposite each other with the rotor sandwiched therebetween. The first and second magnetic pole parts are arranged opposite each other in the direction substantially perpendicular to the direction that the first and second coils are arranged opposite each other, and have a constricted portion formed by narrowing down the cross section as the magnetic circuit, compared with the other portions.
According to this configuration, the lines of magnetic force generated by the first and second coils affect the first and second magnetic pole parts differently with the constricted portion as the boundary of their influence. By this effect, an efficient magnetic circuit is formed an
Inoue Nobuyoshi
Sekizawa Koji
Toma Kiyosi
Mahoney Christopher
Nidec Copal Corporation
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