Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-12
2001-12-18
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156010, C310S216006, C396S463000
Reexamination Certificate
active
06331741
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic driving device having a construction adapted for driving the diaphragm blades of a diaphragm device of, for example, a camera or the like.
2. Description of Related Art
Heretofore, electromagnetic driving devices using electromagnetic driving motors as drive sources, such as an electromagnetic driving diaphragm device which uses a stepping motor as a drive source, have been arranged, as disclosed in Japanese Laid-Open Patent Application No. HEI 3-207254, for example, to have a stator yoke and a coil arranged in one unit to extend in two radial directions with respect to the rotation axis of a rotor (two-phase type). Such a stepping motor has a shape that protrudes with respect to the diaphragm device.
In the stepping motor, a rotor shaft which is a motor output shaft protrudes from the stepping motor. A rotation output member such as a gear is provided on the protruding rotor shaft. Generally, the electromagnetic driving diaphragm device is thus arranged to drive a working member which drives diaphragm blades by the rotation of the gear on the rotor shaft.
In the above-stated example of conventional arrangement, the electromagnetic driving motor, i.e., a stepping motor, is arranged to protrude with respect to the diaphragm device. The protruding arrangement, however, hinders efforts to reduce the size of products and is thus against the recent trend of reduction in size. In other words, in the case of the stepping motor of the type disclosed in Japanese Laid-Open Patent Application No. HEI 3-207254, the stator yoke and the coil are arranged to extend in two radial directions with respect to the axis of rotation of the rotor (two-phase type). Therefore, the motor part flatly protrudes over a wide area for the diaphragm device. In a case where the layout of a camera or like product necessitates some other part to be also disposed in the motor space, therefore, the design of the camera or the like must be changed to avoid the use of the motor space for the part. Then, the change tends to cause the structural arrangement of the product to become complex or hinder reduction in size of the product.
In respect to the structural arrangement of the electromagnetic driving motor, the motor is of the type having a rotor shaft protruding therefrom. Therefore, the protruding part of the motor is supported only on its one side in a cantilever-like (or in an overhanging-impeller-like) manner, although the rotor is supported on its two sides within the electromagnetic driving motor (in a center impeller-like manner). Since the working member is under some amount of load, when a rotation force is transmitted to the working member under such a condition, some force is applied to the gear of the rotor shaft in its radial direction by a reaction to the load. This force exerts some lateral pressure on the rotor shaft to warp the free end side of the cantilever-like-supported rotor shaft.
Meanwhile, a force acts to restore the rotor shaft to its normal state against the warping force caused by the load of the working member. When the rotor shaft is caused to rotate under this condition, the rotor shaft comes to rotate in a whirling manner. Then, vibrations are transmitted to the working member within the diaphragm device. As a result, a chattering sound or chattering vibration arises there.
Such a chattering sound or chattering vibration has an adverse effect on the recent trend of arranging cameras or the like to make no sound and deteriorates the quality of the products. Besides, since a concentrated stress is applied to the bearing of the rotor by the lateral pressure on the rotor shaft, the performance of the motor is lowered by the stress.
Further, since the working member which drives the diaphragm blades within the diaphragm device rotates at high speed, the lateral pressure on the rotor shaft becomes very large to make the above-stated problems more serious.
BRIEF SUMMARY OF THE INVENTION
The present invention is made to solve the problems of the prior art described above. It is, therefore, an object of the invention to provide an electromagnetic driving device advantageously arranged for driving diaphragm blades of a diaphragm device of a camera or the like.
Another object of the invention is to provide an electromagnetic driving device which is arranged to be capable of maintaining a stable output without causing any vibration and noise.
To attain the above objects, in accordance with an aspect of the invention, there is provided an electromagnetic driving device comprising a first permanent magnet, a second permanent magnet arranged to be opposed to the first permanent magnet, a rotation shaft arranged to interconnect the first permanent magnet and the second permanent magnet, the rotation shaft constituting a rotor in conjunction with the first permanent magnet and the second permanent magnet, a first stator yoke having magnetic poles opposed to a peripheral part of the first permanent magnet, the first stator yoke being arranged to extend from the peripheral part of the first permanent magnet toward an outside thereof, a second stator yoke having magnetic poles opposed to a peripheral part of the second permanent magnet, the second stator yoke being arranged to extend from the peripheral part of the second permanent magnet toward an outside thereof in the same direction as the extending direction of the first stator yoke, a first coil arranged to excite the first stator yoke, the first coil being disposed at the first stator yoke, and a second coil arranged to excite the second stator yoke, the second coil being disposed at the second stator yoke.
In accordance with another aspect of the invention, there is provided an electromagnetic driving device comprising a rotor having a rotation output part arranged to allow a rotation output to be externally taken out, a first stator yoke opposed to a peripheral part of the rotor, a second stator yoke opposed to the peripheral part of the rotor, the second stator yoke being arranged to extend from the peripheral part of the rotor toward an outside thereof together with the first stator yoke and being disposed to be superposed on the first stator yoke, a first coil arranged at the first stator yoke to excite the first stator yoke, a second coil arranged at the second stator yoke to excite the second stator yoke, energization of the first coil and the second coil being controlled to control rotation of the rotor, a first fixing member arranged to support the first stator yoke and the first coil, the first fixing member having an aperture part formed on an inner circumferential side thereof to allow photo-taking light to pass therethrough, a plurality of diaphragm blades arranged to adjust a quantity of the photo-taking light, a second fixing member arranged to hold the plurality of diaphragm blades between the first fixing member and the second fixing member, and a working member for driving the plurality of diaphragm blades, the working member being arranged between the first fixing member and the second fixing member to be driven by the rotation output part of the rotor.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in connection with the accompanying drawings.
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patent: 5757108 (1998-05-01), Suzuki
patent: 5969444 (1999-10-01), Kamitani
patent: 3-207254 (1991-09-01), None
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lam Thanh
Ramirez Nestor
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