Photography – With film drive – Mechanical detail
Reexamination Certificate
1999-06-30
2001-04-24
Gray, David M. (Department: 2851)
Photography
With film drive
Mechanical detail
C396S087000
Reexamination Certificate
active
06220769
ABSTRACT:
This application is based on Application No. 10-185862 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to rotation detection in a speed reduction mechanism using a planet gear mechanism in a drive force transmission mechanism or an apparatus using same.
2. Description of the Related Art
Various drive force transmission mechanisms provided with the differential gear mechanism using a planet gear disclosed, for example, in U.S. Pat. No. 5,640,636 have been proposed to obtain a high deceleration ratio in a compact space.
In speed reduction mechanisms achieved through a differential gear mechanism using a planet gear, however, it is difficult to assure a space for the because the gears occupy most of the space within the deceleration unit. Even assuming the detection member is installed, the deceleration unit is disadvantageously enlarged by an amount equal to the size of the detection member.
Furthermore, when rotation detection is accomplished at fine resolution outside the speed reduction mechanism achieved through a differential gear mechanism, the number of parts used increases which is a great demerit from the perspectives of cost and space due to the need to add an acceleration transmission system separated from the output shaft of the speed reduction mechanism, or arrange the detection member on the motor shaft on the side opposite the deceleration unit. The detection accuracy is disadvantageously reduced by gear backlash particularly when an acceleration transmission system is added.
SUMMARY OF THE INVENTION
In view of the aforesaid disadvantages, an object of the present invention is to provide a rotation detection mechanism of fine resolution which is compact and does not increase the number of parts within in a speed reduction mechanism achieved through a differential gear mechanism using a planet gear. Another object of the invention is to provide an apparatus provided with such a rotation detection mechanism.
To attain these objects, one aspect of the present invention comprises a planet gear which rotates in engagement with a sun gear that itself rotates integratedly with the output shaft of a rotation drive source such that the planet gear rotates around the periphery of the output shaft, a carrier which rotates integratedly to match the rotation of the planet gears while supporting the planet gears in free rotation, a first rotation detector provided on the exterior surface of the carrier or the sun gear, and a second rotation detector for detecting rotation by detecting the first rotation detector.
One example of the second rotation detector comprises a photoreflector. The first rotation detector comprises a reflecting surface for reflecting a light flux projected from a light projector of the photoreflector toward a photoreceptor, and a non-reflecting surface having different reflection angle than the reflecting surface so as to not reflect light flux toward the photoreceptor. A secondary reflecting surface is provided to again reflect the light flux projected from the light projector of the photoreflector and reflected by the non-reflecting surface so as to not impinge the photoreceptor.
Alternatively, another example of the first rotation detector comprises a reflecting surface for reflecting a light flux projected from the light projector of the photoreflector toward a photoreceptor, and a non-reflecting surface having a lower reflectivity than the reflecting surface so as to not reflect the light flux toward the photoreceptor.
An optical path regulator is provided to regulate the optical path of the light flux from the photoreflector. Furthermore, a protuberance extends from the vicinity of the photoreflector toward the interior diameter of the first rotation detector.
Alternatively, another example of the second rotation detector comprises an MR element.
The rotation detector mechanism is used in a drive force transmission mechanism for accomplishing a focusing operation or a zoom operation of the lens barrel of a camera.
These and other objects, advantages, and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings, which illustrate specific embodiments of the invention.
REFERENCES:
patent: 4615600 (1986-10-01), Nakajima et al.
patent: 4958177 (1990-09-01), Akitake
patent: 5025277 (1991-06-01), Inoue et al.
patent: 5602608 (1997-02-01), Asakura et al.
patent: 5634148 (1997-05-01), Kunishige et al.
patent: 5640636 (1997-06-01), Yokoyama et al.
patent: 6039476 (2000-03-01), Katagiri et al.
patent: 9-060716 (1997-03-01), None
Hirota Toshihiko
Kojima Kazuhiko
Burns Doane , Swecker, Mathis LLP
Gray David M.
Minolta Co. , Ltd.
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