Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-12-26
2003-12-02
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000
Reexamination Certificate
active
06655774
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a color copying machine, a color laser printer, or the like.
2. Related Background Art
An example of a conventional tandem type image forming apparatus is shown in FIG.
16
.
The image forming apparatus
401
includes a transferring belt
405
being a transferring material bearing body for bearing and conveying a material to which an image is transferred (hereinafter referred to as a transferring material P), and process cartridges (hereinafter simply referred to as “cartridges”) for yellow Y, magenta M, cyan C and black Bk
414
,
415
,
416
and
417
are arranged in tandem along the transferring material bearing surface of the transferring belt
405
. Above the cartridges
414
to
417
, optical units
418
,
419
,
420
and
421
are disposed correspondingly to each of the cartridges
414
to
417
. Moreover, transferring rollers
410
,
411
,
412
and
413
are disposed in a state of being correspondingly opposed to photosensitive drums
406
,
407
,
408
and
409
being image bearing bodies of the respective cartridges
414
to
417
with the transferring belt
405
put between them.
In the aforesaid structure, toner images of yellow, magenta, cyan and black obtained by being processed by well known electrophotographic processes are transferred one over another on the transferring material P fed on the transferring belt
405
by a pickup roller
403
and feeding/conveying rollers
429
from a sheet cassette
402
, and the toner images are fixed by a fixing unit
422
. And then, the transferring material P is delivered to the outside of the image forming apparatus
401
through a delivery sensor
424
and a paper path
423
.
Moreover, when a toner image is formed also on the backside of the transferring material P, the transferring material P is again conveyed to the transferring belt
405
through another paper path
425
after exiting the fixing unit
422
, and then the image is formed also on the backside after undergoing similar processes.
Incidentally, the transferring belt
405
is driven to rotate by a transferring belt driving roller
404
.
Moreover, the optical units
418
to
421
of each color expose to scan the surface of each of the photosensitive drums
406
to
409
with laser beams L
1
, L
2
, L
3
and L
4
for forming an latent image, respectively, and a series of these image-forming operations are controlled to scan the surfaces of the photosensitive drums
406
to
409
in order that images are transferred from a predetermined position on each conveyed transferring material P by being synchronized with one another.
Furthermore, the image forming apparatus
401
includes a feeding motor for driving the feeding/conveying rollers
429
, a transferring belt driving motor for driving the transferring belt driving roller
404
, a drum driving motor for driving each color photosensitive drum
406
to
409
, and a fixing roller driving motor for driving fixing rollers
422
a
in the fixing unit
422
. For the acquisition of a good quality image, these motors are controlled to rotate at a fixed number of revolutions.
However, the conventional image forming apparatus
401
has a problem of the remarkable deterioration of the image quality of a formed image that is caused by the following reason. That is, the controlled temperature of a heater built in the fixing unit
422
and the heat evolution by each driving motor make the temperature in the image forming apparatus
401
rise. The rise of the temperature causes the thermal expansion of the transferring belt driving roller
404
, which makes the rate of the transferring belt
405
faster. Then, the so-called color aberration is produced when each color toner image is transferred from a specific position on a transferring material P one over another. Namely, the color aberration brings about the remarkable deterioration of image quality. That is, because the photosensitive drums
406
to
409
and the transferring belt driving roller
404
are controlled to rotate at a fixed rate, the peripheral velocity of the transferring belt
405
becomes faster when the diameter of the transferring belt driving roller
404
becomes large. That causes the color aberration.
As a measure for resolving such a problem, there is a method of performing registration correction. The method is performed as follows. That is, a pattern for color aberration detection is formed on the transferring belt
405
. The pattern is read in with a sensor to detect the amount of the relative color aberration of each color. On the detection results, the position at which the writing of each color image with the laser beam of each color L
1
to L
4
starts is corrected. However, the method has the following problems.
(1) Although the image writing starting positions immediately after the registration correction can be accorded to one another, in the case where temperature rise in the image forming apparatus
401
becomes large, for example, in case of continuous printing, the peripheral velocity of the transferring belt
405
gradually becomes faster, and the amount of the color aberration becomes large after the processing for a predetermined number of sheets.
(2) For resolving the problem, for example, an idea to perform the registration correction each performance of the printing of a certain fixed number of sheets has been proposed. However, the more frequently the registration correction is performed, the less the throughput of the image forming apparatus
401
becomes.
The resist correction also has the following problem. That is, because a pattern for registration correction is formed on the transferring belt
405
at a time of the registration correction, the consumption amount of toner becomes large, which makes the economical efficiency of the image forming apparatus
401
deteriorate for a user.
Moreover, as another measure of the correction of the color aberration, a method is disclosed in Japanese Patent Application Laid-Open No. 2000-071522. In the method, registration reference marks are formed on the transferring belt
405
in advance, and the reference marks are detected with a charge coupled device (CCD) sensor. The method corrects the image writing starting positions on the results.
However, this method requires to form the reference marks on the transferring belt
405
in advance, which brings about the problems such that the manufacturing costs of the transferring belt
405
rise and the width of the image forming apparatus
401
becomes large for securing the spaces for forming the reference marks.
Such problems are produced in an image forming apparatus equipped with an intermediate transferring body.
Furthermore, the conventional image forming apparatus includes the feeding/conveying rollers
429
for feeding and conveying the transfer material P. In this case, when the peripheral velocity of the transferring belt
405
becomes faster as the temperature rise in the image forming apparatus
401
, the difference between the transferring material conveyance force of the feeding/conveying rollers
429
and the transferring material conveyance force of the transferring belt
405
becomes large to produce color aberration and image blurring. That is, when the transferring material conveyance force of the feeding/conveying rollers
429
becomes larger than the transferring material conveyance force of the transferring belt
405
, the inclination of pushing the transferring material P into the conveyance direction becomes large. In such a case, when the transferring material P is a stiff transferring material such as a thick paper or the like, image blurring is produced in the trailing edge part of the transferring material P.
On the other hand, when the transferring material conveyance force of the transferring belt
405
is larger than the transferring material conveyance force of the feeding/conveying rollers
429
, there is a problem such that image blurring or color aberration is produced at the leading ed
Fitzpatrick ,Cella, Harper & Scinto
Meier Stephen D.
Stewart Jr. Charles W.
LandOfFree
Image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3181579