Driving device, light amount controller and shutter

Details Driving device, light amount controller and shutter Driving device, light amount controller and shutter

2002-03-11

2004-03-23

Leykin, Rita (Department: 2837)

Electricity: motive power systems

Phasing or angular or linear positional control of movable...

C318S685000, C318S696000, C318S640000, C318S254100, C310S049030, C359S227000, C359S230000

Reexamination Certificate

active

06710563

ABSTRACT:

BACKGROUND OF THE PRESENT INVENTION
1. Field of the Present Invention
The present invention relates to a driving device having an extremely compact size, and a light amount controller and a shutter using the driving device.
2. Description of the Related Art
Conventionally, motors that can be designed compact in size include a brushless motor. Brushless motors with simple driving circuits include a stepper motor, described below.
FIG. 17
shows an example of a small-sized hollow cylindrical stepper motor. The stepper motor includes two stators
102
each comprised of a bobbin
101
having a stator coil
105
concentrically wound thereon, two stator yokes
106
axially fixedly holding the bobbin
101
in a sandwiching fashion, the stator yokes
106
each having stator teeth
106
a
and
106
b
alternately arranged circumferentially of an inner peripheral surface of the bobbin
101
, and a casing
103
to which are secured the stator yokes
106
formed integrally with the respective stator teeth
106
a
and
106
b
. One of the two casings
103
has a flange
115
and a bearing
108
fixed thereto, while the other casing
103
has another bearing
108
fixed thereto. A rotor
109
is comprised of a rotor magnet
111
rigidly fitted on a rotor shaft
110
. The rotor magnet
111
defines radial gaps between the same and the stator yokes
106
of the stators
102
. The rotor shaft
110
is rotatably supported by the two bearings
108
on opposite ends thereof.
A light controller using a variation of the stepper motor constructed as above has been proposed in Japanese Patent Publication (Kokoku) No. 53-2774. The light controller controls the quantity of passing light by opening and closing shutter blades connected to the stepper motor, in a stepwise fashion. Another variation is a hollow motor proposed in Japanese Laid-Open Patent Publication (Kokai) No. 57-166847. The hollow motor is a ring-shaped stepper motor which allows light to pass through a cavity formed in a central portion thereof.
There are known digital cameras of a kind which use a CCD or the like as an image pickup device for photoelectrically converting an object image to thereby record the image on a storage medium as information of a still image. The digital cameras of this kind include a type having a diaphragm blade and a shutter blade, and actuators for actuating the respective blades.
Operations related to exposure of the digital camera of the above-mentioned type are as follows.
First, when the main power supply is turned on to make the image pickup device operative before photographing, the shutter blade is held in its open position which allows the image pickup device to be exposed to light. The image pickup device repeatedly accumulates, discharges, and transfers electric charge to allow an object field to be observed on an image monitor. When a release button is depressed, a diaphragm value and an exposure time are determined according to an output from the image pickup device at this time point. Judging from the determined diaphragm value and exposure time, if it is necessary to reduce the diameter of an exposure aperture, first, the diaphragm blade is operated into a position providing a predetermined diaphragm value. Then, the image pickup device from which the stored electric charge has been discharged is caused to start storage or accumulation of electric charge in response to a storage start signal. At the same time, an exposure time control circuit is started in response to the storage start signal serving as a trigger signal, and when the lapse of the predetermined exposure time has been counted up, the shutter blade is actuated into a closed position for blocking light to the image pickup device. After the blocking of light to the image pickup device, the stored electric charge is transferred, whereby image information is recorded onto a storage medium via an image writing device. The exposure of the image pickup device is inhibited during the transfer of the electrical charge because it is necessary to prevent the charge from being changed by extra light.
Another type of digital camera has been proposed in Japanese Laid-Open Patent Publication (Kokai) No. 11-305285, in which a diaphragm blade and a shutter blade are driven by a single actuator. In this digital camera, the actuator can assume any of three states, i.e. a deenergized state, a normally energized state, and a reversely energized state. When the actuator is in the deenergized state, the camera is placed in an intermediate aperture state. When the actuator is in the normally energized state, the camera is placed in a maximum aperture state, while when the actuator is in the reversely energized state, the camera is placed in a fully closed state.
In the above conventional small-sized stepper motor shown in
FIG. 17
, however, the cases
103
, the bobbins
101
, the stator coils
105
and the stator yokes
106
are concentrically arranged around the rotor
109
, which inevitably results in increased outer dimensions of the motor. Further, magnetic flux generated by energization of the stator coils
105
mainly flows between the end faces
106
a
1
of the stator teeth
106
a
and the end faces
106
b
1
of the stator teeth
106
b
as shown in
FIG. 18
, and hence the magnetic flux does not effectively act on the rotor magnet
111
.
Similarly, the light controller proposed in Japanese Patent Publication (Kokoku) No. 53-2774 and the hollow motor proposed in Japanese Laid-Open Patent Publication (Kokai) 57-166847 each have stator coils and stator yokes arranged around a rotor magnet, so that the outer dimensions of the motor are increased, and magnetic flux generated by energization of the stator coils does not effectively act on the rotor magnet.
Further, a coin-shaped brushless motor as shown in
FIG. 19
has been proposed e.g. in Japanese Laid-Open Patent Publications (Kokai) No. 7-213041 and No. 2000-50601. The brushless motor is comprised of a plurality of coils
301
,
302
,
303
and a disk-shaped magnet
304
. As shown in
FIG. 19
, each of the coils has a thin coin-like shape, and is disposed such that the axis thereof extends parallel with that of the magnet. The disk-shaped magnet is magnetized in the axial direction thereof, and is disposed such that the magnetic surface (inner peripheral surface) of the magnet faces in a direction perpendicular to the axis of each of the coils.
In this motor, as illustrated by arrows in
FIG. 20
, magnetic flux generated by the coils cannot fully effectively act on the magnet. Further, the center of a rotational force or torque generated by the magnet is away from the outer periphery of the motor by a distance of L, so that the torque generated by the motor is small for the size of the motor. In addition, a central portion of the motor is occupied by the coils and the magnet, it is difficult to utilize this portion for some other purposes.
Further, some shutter devices for digital cameras have diaphragm blades and shutter blades incorporated therein. In view of costs and space, it is preferable that these blades are actuated by a single actuator. Japanese Laid-Open Patent Publication (Kokai) No. 11-305285 discloses a shutter device of this type in which a single actuator actuates a shutter blade which also serve as a diaphragm blade. However, in the shutter device, a magnetic neutral point thereof is utilized to control the position of the shutter blade for an intermediate aperture, which makes it difficult to operate the blade with high accuracy.
SUMMARY OF THE PRESENT INVENTION
It is a first object of the present invention to provide a small-sized and slim driving device which is easy to manufacture and capable of producing high output.
It is a second object of the present invention to provide a light amount controller using a small-sized and slim driving device which is easy to manufacture and capable of producing high output.
It is a third object of the present invention to provide a shutter using a small-sized and slim driving device which is capable of changing a diaphragm value and capable o

Affiliated with

Also associated with

Rating

Driving device, light amount controller and shutter does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Driving device, light amount controller and shutter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driving device, light amount controller and shutter will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3252503