Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
2002-10-09
2004-04-20
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Photoconductive member
Reexamination Certificate
active
06725005
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image forming apparatus for forming a toner image on a rotating photoreceptor drum by an electrophotographic method to carry out image formation and to a method of controlling the rotational peripheral speed of said rotating photoreceptor drum to make it constant.
In an image forming apparatus based on an electrophotographic method, it is put into practice that a toner image is formed on a rotating image carrying member made up of a photoreceptor drum or a photoreceptor belt and the formed toner image is directly or indirectly transferred onto a sheet of recording paper and fixed. In forming an image, image exposure is carried out by an image exposure means on an image carrying member which has been uniformly charged by a charging means, to form a latent image; in forming a latent image, if the peripheral speed of the image carrying member which is rotating at a constant speed fluctuates, some distortion of the formed image is brought about. Further, in a color image forming apparatus of a tandem type, a plurality of monochromatic images formed by the respective monochromatic image forming units are superposed together to form a color image on a sheet of recording paper, it is regarded as an essential condition for obtaining a good-quality color image that the image carrying members in the respective monochromatic image forming units have the same speed and have no speed fluctuation.
As regards the speed control of a photoreceptor drum, control methods using various kinds of speed detecting means have been proposed; however, if it is intended to control the angular speed of a photoreceptor drum in real time to make it constant, a rotational speed control method for practicing the control of rotational speed using an angular speed detecting means based on an encoder is used.
In the publication of the unexamined patent application H6-327278, for the angular speed control of a photoreceptor drum, it is proposed that the profile of the rotational fluctuation of a photoreceptor drum at a certain timing is measured by the use of a feedback control method or a feed-forward control method, and the angular speed control is carried out until the next specified sampling timing by using the data. This proposal has been done by taking it into consideration to control a factor of a rotating photoreceptor drum having no reproducibility by using a feedback control process. However, in the above-mentioned proposal, the control is such that only the factor of rotational fluctuation which happens to be generated during the sampling timing is suppressed. Further, as regards the feedback control, if it is intended to suppress a wide-range rotational fluctuation, a high-priced CPU, a high-resolution encoder, etc. are required, which makes the feedback control not realistic.
On the other hand, if a peripheral speed detecting means based on an encoder is used for the detection of the peripheral speed of an image carrying member, the structure becomes mechanically complex, and the speed detecting means becomes high in price. For a tandem-type color image forming apparatus, because a plurality of speed detecting means are required, this problem becomes more remarkable.
It is also an object of this invention to provide a rotational speed control method in which a speed detecting means based on an encoder is not used, marking is made on a rotary body such as an image carrying member by a writing means, and the speed control of the rotary body is performed by carrying out a low-cost high-precision peripheral speed detection based on the detection of the marking.
Further, in an image forming apparatus employing the above-mentioned speed control method, marking toner particles of the marking adhere to the circumferential surface of the image carrying member, and a problem of toner consumption being of large amount and a problem of the surface of the image carrying member being smudged are produced.
SUMMARY OF THE INVENTION
To overcome the abovementioned drawbacks in conventional image-recording apparatus, it is the first object of the present invention to provide a drive control method of a photoreceptor drum to actualize that rotational fluctuation of a photoreceptor drum is suppressed at a high-precision by the use of a repetition control method, and an image forming apparatus which carries out image formation using this drive control method.
Further, it is the second object of the present invention to provide an image forming apparatus by which the problem to be produced in employing a rotational speed control method is eliminated.
Accordingly, to overcome the cited shortcomings, the abovementioned objects of the present invention can be attained by motor controlling methods and image-forming apparatus described as follow.
(1) A method of controlling a motor for driving a photoreceptor drum, comprising the steps of: detecting angular velocity signals by means of angular velocity detecting device disposed on an axis of the photoreceptor drum, which is driven by the motor to form a latent image on its circumferential surface; finding deviations from a reference angular velocity, based on the angular velocity signals detected by the angular velocity detecting device; storing a profile of the deviations within a one-revolution of the photoreceptor drum in a storage section, while revising the profile already stored in the storage section in real-time base; applying an arithmetic processing to an angular velocity signal, being one of the angular velocity signals, detected at a current rotational-position of the photoreceptor drum currently rotating, by referring data included in the profile obtained in a preceding one-revolution of the photoreceptor drum; and controlling the motor, based on results of the arithmetic processing for the angular velocity signals, so as to compress the deviations from the reference angular velocity as small as possible.
(2) The method of item 1, wherein the data correspond to a same position as the current rotational-position or a position near the current rotational-position.
(3) The method of item 1, wherein the detecting step of detecting the angular velocity signals is commenced, after a rotational velocity of the motor reached to a target value, and then, a waiting time interval for stabilizing mechanical fluctuations of the motor has elapsed.
(4) An apparatus for forming an image, comprising: a photoreceptor drum to form a latent image on its circumferential surface; a motor to drive the photoreceptor drum; an angular velocity detecting device to detect angular velocity signals, the angular velocity detecting device being disposed on an axis of the photoreceptor drum; a controlling section to control the motor and to find deviations from a reference angular velocity, based on the angular velocity signals detected by the angular velocity detecting device; a storage section to store a profile of the deviations within a one-revolution of the photoreceptor drum in it, while revising the profile already stored in the storage section in real-time base; and an arithmetic processing section to apply an arithmetic processing to an angular velocity signal, being one of the angular velocity signals, detected at a current rotational-position of the photoreceptor drum currently rotating, by referring data included in the profile obtained in a preceding one-revolution of the photoreceptor drum; wherein the controlling section controls the motor, based on results of the arithmetic processing for the angular velocity signals, so as to compress the deviations from the reference angular velocity as small as possible.
(5) The apparatus of item 4, wherein the data correspond to a same position as the current rotational-position or a position near the current rotational-position.
(6) The apparatus of item 4, wherein the angular velocity detecting device commences detecting the angular velocity signals, after a rotational velocity of the motor reached to a target value, and then, a waiting time interval for stabilizing mechanical fluctuat
Izumiya Kenji
Kishi Shinobu
Maruyama Hiroyuki
Nishikawa Eiji
Ogata Satoshi
Frishauf Holtz Goodman & Chick P.C.
Konica Corporation
Pendegrass Joan
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