Electrophotography – Image formation – Transfer
Reexamination Certificate
2000-03-28
2001-12-04
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S043000, C399S049000
Reexamination Certificate
active
06327453
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and specifically relates to an image forming apparatus having a plurality of image forming units, and which performs a registration correction process to correct dislocation of images formed by the plurality of image forming units.
DESCRIPTION OF THE RELATED ART
Digital copiers are known which form full color images by supporting a recording medium used for image formation on an endless belt, and sequentially forming images with toner of different colors as the recording medium is transported. Such a digital copier forms images using toners of four colors, i.e., cyan (C), magenta (M), yellow (Y), black (K), and is provided with image forming units for forming images in each of the colors. An image of each color is formed as the recording medium passes the image forming units, such that images of four colors are overlaid by passing four image forming units.
Since the full color image is formed by overlaying images of four colors formed by four image forming units, it is necessary to prevent dislocation of the four overlaid images. For this reason, the amount of dislocation of registration patterns actually formed on an endless belt by the respective four image forming unit is detected, and a registration correction value for correcting the images is determined based on the detected dislocation. Then, the image is subjected to a registration correction process based on this determined registration correction value.
The registration pattern has a shape determined beforehand, and is formed on an endless belt by the four image forming units. The amount of dislocation of the registration pattern actually formed on the endless belt is detected by reading the registration pattern formed on the endless belt.
The registration correction value used in the registration correction process is updated at predetermined time intervals, or when a predetermined number of images have been formed in the color image forming mode.
The registration correction value update process requires a predetermined amount of time for execution since the registration pattern is actually formed on the endless belt by the four image forming units. Accordingly, when the registration correction value update process is executed at predetermined time intervals, this registration correction value update process may be executed while the digital copier is being used. In this instance, the user must wait until the registration correction value update process is completed, thereby lengthening the time necessary for the copy operation and adversely affecting efficiency. Furthermore, when the registration correction value update process is executed after a predetermined number of images have been formed in the color image forming mode, the user must similarly wait until the registration correction value update process is completed, thereby lengthening the time necessary for the copy operation.
When the amount of residual toner is low, the registration correction value cannot be accurately determined because the registration pattern is not reliably formed by the image forming units.
DISCLOSURE OF THE INVENTION
An object of the present invention is to eliminate the previously described disadvantages by providing an image forming apparatus capable of reducing the time required for copying in an image forming apparatus which performs a registration correction process.
Another object of the present invention is to provide an image forming apparatus capable of reliably performing a registration correction process.
These objects are attained by an aspect of the image forming apparatus of the present invention comprising: a plurality of image forming units for respectively forming images on a recording medium; a fixing unit for fusing the images formed on the recording medium to the recording medium; a fixing temperature detecting unit for detecting a temperature of the fixing unit; a registration pattern detecting unit for detecting registration patterns formed by the plurality of image forming units; and a calculating unit connected with the registration pattern detecting unit and the image forming units, said calculating unit determining registration correction values for correcting deviance of the images based on output from the registration pattern detecting unit and requesting an update of the registration correction values based on the temperature detected by the fixing temperature detecting unit.
It is desirable that the update request means of the image forming apparatus requests the registration correction value update when the temperature detected by the fixing temperature detecting means is less than a predetermined value.
Another aspect of the image forming apparatus of the present invention comprises: a plurality of image forming units for respectively forming images on a recording medium; a receiving unit for receiving input from outside the apparatus; a registration pattern detecting unit for detecting registration patterns formed by the plurality of image forming units; and a calculating unit including a first timer for measuring the passage of time from the reception of final input by the receiving unit and a second timer for measuring the passage of time from the point the plurality of image forming units stop, said calculating unit being connected with the registration pattern detecting unit and the plurality of image forming unit, said calculating unit determining a registration correction values for correcting deviance of the images based on an output from the registration pattern detecting unit and requesting an update of the registration correction values based on a value of the first timer and/or the second timer.
Another aspect of the image forming apparatus of the present invention comprises: a plurality of image forming units for respectively forming images on a recording medium; a fixing unit for fusing the images formed on the recording medium to the recording medium; a fixing temperature detecting unit for detecting a temperature of the fixing unit; a registration pattern detecting unit for detecting registration patterns formed by the plurality of image forming units; a receiving unit for receiving input from outside the apparatus; and a calculating unit including a first timer for measuring the passage of time from the reception of a final input by the receiving unit and a second timer for measuring the passage of time from the point the plurality of image forming units stop, the calculating unit determining registration correction values for correcting deviance of the images based on an output from the registration pattern detecting unit and requesting an update of the registration correction value based on at least one of 1) the temperature detected by the fixing temperature detecting unit and 2) a value of the first timer and/or the second timer, wherein the calculating unit does not request an update based on the temperature detected by the fixing temperature unit when an update has already been requested the value of the first timer and/or the second timer.
Another aspect of the image forming apparatus of the present invention comprises: a plurality of image forming units for respectively forming images on a recording medium; a remainder detecting unit for detecting an amount of remaining recording media remaining in a recording media accommodating unit; a registration pattern detecting unit for detecting registration patterns formed by the plurality of image forming units; a calculating unit connected with the remainder detecting unit and the registration pattern detecting unit, said calculating unit determining a registration correction values for correcting deviance of the images based on an output from the registration pattern detecting unit and requesting an update of the registration correction value when the amount of remaining recording media detected by the remainder detecting unit is less than a predetermined value.
The present invention provides an image forming apparatus
Ideyama Hiroyuki
Imaizumi Shoji
Kawabata Kazuyuki
Kuno Takatsugu
Grimley Arthur T.
McDermott & Will & Emery
Minolta Co. , Ltd.
Tran Hoan
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