Electrophotography – Control of electrophotography process – Responsive to copy media characteristic
Reexamination Certificate
2000-01-12
2001-07-10
Grainger, Quana M. (Department: 2852)
Electrophotography
Control of electrophotography process
Responsive to copy media characteristic
C399S384000
Reexamination Certificate
active
06259868
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus which can automatically measure a width of a recording medium such as paper, facilitate determination of an image formation width, improve image transfer quality and further improve a control characteristic of an image formation start position.
2. Description of the Related Art
In an image forming apparatus, such as a printer, for forming an image including characters on a recording medium such as paper, an image formation width, such as a print width, is determined depending on a width of paper. Therefore, an operator uses a given setting means to set the paper width in advance so as to indirectly set the print width.
There is available such an image forming apparatus, wherein for automatically setting a paper width, sensors are disposed in a paper width direction near a paper feed means for detecting the paper width. However, printing is carried out with a given print width regardless of the detected paper width.
With the foregoing arrangement, no problem may be raised when an image is formed on only one side of the paper. This is because, in this case, a print start position (image formation start position) is unchanged even if a paper width is changed (the paper width is used only for determining a print end position).
On the other hand, in case of forming images on both sides of the paper, a change of the paper width cannot be dealt with. This is because a print start position is changed on the reverse of the paper depending on the paper width.
Further, in an image forming apparatus wherein toner is adhered to a charged drum and the paper is pressed thereupon to carry out image transfer, charging is caused from an end of the paper (in case of continuous paper, also via paper feed holes of the paper formed near the end thereof) to deteriorate the transfer quality (print quality). This is significant particularly in such an image forming apparatus wherein the paper width is changed.
Further, when high-priced photosensors are used as the foregoing sensors, the sensors are minimized in number and disposed only at positions corresponding to paper widths to be used. Thus, if a paper width which is not expected is used, the paper width cannot be detected.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an image forming apparatus, wherein an image formation start position can be set to a predetermined position even when a width of a recording medium is changed, particularly in the apparatus which forms images on both sides of the recording medium.
It is another object of the present invention to provide an image forming apparatus whose transfer quality is excellent.
It is another object of the present invention to provide an image forming apparatus which can automatically detect a width of a recording medium having any width in a certain range with a simple structure.
According to one aspect of the present invention, there is provided an image forming apparatus comprising an image transfer assembly for performing image transfer onto a recording medium; and a controller which, based on a width of the recording medium, determines an image formation start position on the recording medium so as to control the image transfer onto the recording medium performed by the image transfer assembly.
With this arrangement, not only an image formation end position but also the image formation start position (print start position) are determined by the controller based on the detected width of the recording medium so that the image transfer onto the recording medium is implemented. Therefore, particularly in case of both-side printing wherein image transfer mechanisms of the image transfer assembly are provided at both sides of the recording medium, at least one of the image transfer mechanisms (reverse image transfer mechanism) performs the image transfer onto the recording medium from the image formation start position determined by the controller. Thus, even if the width of the recording medium is changed, the image formation start position can be set to a predetermined position.
According to another aspect of the present invention, there is provided an image forming apparatus comprising an image transfer assembly for performing image transfer onto a recording medium; a width detecting mechanism for detecting a width of the recording medium; a transfer inhibitor for preventing the image transfer onto the recording medium; and a controller which, based on the width of the recording medium detected by the width detecting mechanism, moves the transfer inhibitor from one end to the other end of the recording medium in a width direction thereof.
With this arrangement, the controller moves the transfer inhibitor to the other end of the recording medium in the width direction based on the detected width of the recording medium, so that the image transfer onto the recording medium at the other end thereof is prevented by the transfer inhibitor. Thus, even if the width of the recording medium is changed, the transfer inhibitor can always be moved to the other end of the recording medium to prevent charging at the other end thereof, thereby to avoid deterioration of the transfer quality.
According to another aspect of the present invention, there is provided an image forming apparatus comprising a home position detecting means for detecting a width detection start point of a recording medium, the home position detecting means provided at a fixed feed means for conveying one side of the recording medium; an end detecting means for detecting one end of the recording medium remote from the width detection start point in a width direction of the recording medium, the end detecting means provided at a movable feed means which is movable in the width direction and conveys the other side of the recording medium; and a measuring means which is moved between the home position detecting means and the end detecting means so as to measure a distance therebetween, the distance corresponding to a width of the recording medium.
With this arrangement, a width of a recording medium having any width in a certain range can be automatically detected with the simple structure.
If the measurement of the distance is carried out by moving the measuring means from the home position detecting means to the end detecting means, the end detecting means can always be reached finally. If the measuring means is moved in one of the directions from an arbitrary position, there is no guarantee that the end detecting means can be always reached. Further, even if the power once goes off, since the measuring means is moved from the width detection start point (home position), the accurate width measurement can be ensured after the power goes on.
If the power goes off, a change during the power being off is unknown. Thus, it is preferable that the measuring means is moved to measure the width of the recording medium when the power goes on.
It is preferable that the measuring means is moved to measure the width of the recording medium when the fixed feed means and the movable feed means are operated to automatically feed the recording medium. This is because it is possible that the width of the recording medium has been changed.
It is preferable that the measuring means is moved to measure the width of the recording medium when a change of a recording medium width is notified. It is possible that an operator changes a recording medium width for adjusting the tension of the recording medium after an automatic loading operation. It is also possible that the operator carries out manual setting of the recording medium. In these cases, it is necessary that the operator notifies the apparatus of the width change of the recording medium by, for example, pushing an automatic loading switch. In response to the notification, the measuring means is moved to measure the width of the recording medium.
It may be arranged that the measuring means continues to detect the end detecting means and, when the
Chihara Amiko
Chinzei Kiyoshi
Fujii Daisuke
Hirao Naoto
Yoshida Hiroaki
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Grainger Quana M.
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