U.S. patent application number 11/873920 was filed with the patent office on 2008-06-05 for manufacturing method of transfer unit.
Invention is credited to Takahiro IWASAKI.
Application Number | 20080127493 11/873920 |
Document ID | / |
Family ID | 39474112 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080127493 |
Kind Code |
A1 |
IWASAKI; Takahiro |
June 5, 2008 |
MANUFACTURING METHOD OF TRANSFER UNIT
Abstract
A diameter of middle section of at leas one of rollers, which
are spanned by an intermediated transfer substance, is increased in
respect to the diameter of end sections thereof by an amount which
is determined in accordance with a degree of sub-scanning curvature
of an image transferred onto a sheet.
Inventors: |
IWASAKI; Takahiro; (Tokyo,
JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
39474112 |
Appl. No.: |
11/873920 |
Filed: |
October 17, 2007 |
Current U.S.
Class: |
29/890.1 |
Current CPC
Class: |
G03G 15/1605 20130101;
Y10T 29/49401 20150115 |
Class at
Publication: |
29/890.1 |
International
Class: |
B21D 53/76 20060101
B21D053/76 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2006 |
JP |
JP2006-326903 |
Claims
1. A manufacturing method of a transfer unit to transfer a
plurality of toner images transferred from a photo conducive
substance onto a sheet, having a endless belt and a plurality of
rollers which are spanned by the endless belt, the method
comprising: determining an increasing amount of a diameter of a
middle section of at least one of a plurality of the rollers in
respect to end sections thereof, in accordance with a degree of
sub-scanning curvature of an image transferred onto the sheet.
2. The manufacturing method of claim 1, wherein the rollers are
produced by machining.
3. The manufacturing method of claim 1, wherein the rollers are
produced by casting.
4. The manufacturing method of claim 1, wherein the increasing
amount of the diameter of the middle section of the roller is
determined based on a measurement value of the degree of
sub-scanning curvature of the image transferred onto the sheet.
5. The manufacturing method of claim 1, wherein the increasing
amount of the diameter of the middle section of the roller is
determined based on a measurement value of the degree of
sub-scanning curvature of the image transferred onto the sheet
measured by an image sensor.
6. The manufacturing method of claim 1, wherein the increasing
amount of the diameter of the middle section of the roller is
determined by presumption of the degree of sub-scanning curvature
in case the image is transferred onto the sheet based on a rigidity
calculation of the endless belt and the rollers.
7. The manufacturing method of claim 1, wherein the increasing
amount of the diameter of the middle section of the roller is
determined by presumption of the degree of sub-scanning curvature
in case the image is transferred onto the sheet based on
measurement amounts of distortion of the endless belt and the
rollers.
8. The manufacturing method of claim 1, wherein the increasing
amount of the diameter of the middle section of the roller is
determined by presumption of the degree of sub-scanning curvature
in case the image is transferred onto the sheet based on a
measurement circumferential speed of the endless belt.
9. The manufacturing method of claim 1, wherein the photoconductive
substance is in a shape of a drum.
10. The manufacturing method of claim 1, wherein the
photoconductive substance is in a shape of a belt.
11. The manufacturing method of claim 1, wherein the end less belt
is an intermediate transfer substance on which the toner image
developed, by developer is transferred.
12. The manufacturing method of claim 1, wherein the end less belt
is a conveyance belt to convey the sheet.
Description
[0001] This application, is based on Japanese Patent Application
No. 2006-326903 filed on Dec. 4, 2006, in Japanese Patent Office,
the entire content of which is hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a manufacturing method of a
transfer unit used in an image forming apparatus such as an
electro-photographic copying machine, a facsimile machine and a
printer.
[0003] There are known various color image forming methods for the
image forming apparatus. A method called tandem method is one of
them. An image forming apparatus employing this tandem method is
provided with, a photoconductive substance, light scanning device
to write image data on the photoconductive substance, a plurality
of image forming sections having a developing device to develop an
electrostatic latent image formed on the photoconductive substance
and a transfer units to transfer a toner image formed by each image
forming section on the photoconductive substance onto a sheet.
[0004] As the image forming apparatus provided with the transfer
unit, there is known an apparatus in which the toner image formed
on the photoconductive substance is transferred onto an
intermediate transfer substance (hereinafter call a transfer belt
as well) in a shape of an endless belt of the transfer unit, then
the toner image on the intermediate transfer substance is
transferred onto the sheet. Since the image forming apparatus
employing the intermediate transfer substance is able to
superimpose the toner images formed on the photoconductive
substance on the intermediate substance, it is popularly used in
color image forming apparatus, which forms a color image on the
sheet. In the color image forming apparatus, the color images of
three colors i.e. yellow (Y), magenta (M) and cyan (C), or four
colors where black (Bk) is added, are transferred and superimposed
on the intermediated transfer substance, thereafter this
superimposed toner image is transferred onto the sheet in a lump
using an electrostatic force.
[0005] The toner images for respective colors formed on the
photoconductive substance are transferred onto the intermediated
transfer substance with predetermined timings so that color shifts
do not occur when each color image is superimposed.
[0006] However, a plurality of rollers are spanned with the
intermediate transfer substance with a certain tension, a distorted
occurs in the rollers in a direction of a roller axis.
[0007] FIG. 1 shows an example of the image forming apparatus, FIG.
2 is a partial view of a transfer unit 60 in FIG. 1. FIG. 3 is a
view showing a frame format of rollers 61 and 62 as seem from an
arrow X1 in FIG. 2, which indicates a state where the rollers 61
and 62 spanned by the intermediate transfer substance 6 are
distorted as mentioned above. Meanwhile, FIG. 3 shows that the
rollers 61 and 62 in FIG. 3 are both straight rollers having the
same diameter throughout entire width.
[0008] As FIG. 2 shows, if the rollers 51 and 62 distort in the
axis direction, there is occurred a difference of a circumferential
length between both ends sections and a middle section. Thus moving
distances of the toner image transferred from the photoconductive
substance to the intermediated transfer substance 6, until the
toner image is transferred onto the sheet P differ between the both
end sections and the middle section of the intermediated transfer
substance 6, therefore a sub-scanning curve occurs in a
sub-scanning direction (sheet conveyance direction) when the toner
image transferred onto the intermediate transfer substance 6 is
transferred onto the sheet P.
[0009] FIG. 4(a) is a diagram showing states of sub-scanning curves
by respective colors, using line images as examples of the images
of respective colors to be transferred, onto the sheet P, in case
the photoconductive substances 1Y, 1M, 1C and 1K, and the
intermediate transfer substance 8 are arranged as FIG. 1 shows.
Here the sheet P is conveyed in an arrow W direction. The toner
image, transferred onto the intermediated transfer substance 6 via
the photoconductive substance 1Y is transferred onto the sheep P as
a yellow toner image YL in FIG. 4(a). In the same manner, a cyan
toner image CL, a magenta toner image ML and a black toner image Bk
are transferred. As above understanding, the toner image
transferred onto the intermediate transfer substance has more
tendency to be effected in a portion near the rollers 61 and 62 and
the sub-scanning curve is tend to occur.
[0010] As above, there was a problem that a high quality image can
not be obtained due to color shift if the images of respective
colors are transferred onto the sheet P in a state where the
sub-scanning curve occurs for each color. FIG. 4(b) shows a state
where the ends images are superimposed. Here a toner image CL for
cyan color and toner image ML for magenta color are omitted. As the
figure show, even if the end sections are matched in this manner,
there is occurred color shift at the middle section.
[0011] Contrarily, there is disclosed a method that the curving of
a scan line, a position of the scan line or inclination of the scan
line are corrected by controlling a posture of an imaging element
based on information from a color shift sensor arranged near the
intermediated transfer substance through an actuator (for example
Patent Document 1).
[0012] Patent Document 1: Tokkai 2004-286981
[0013] As above, the image forming apparatus using the
intermediated transfer substance is popularly used as the color
image forming apparatus which forms the color image of the sheet,
since the toner images formed on the photoconductive substance can
be superimposed on the intermediate transfer substance. However,
since the sub-scanning curve occurs in the image, there was a
problem that a high quality image can not be obtained due to the
color shift at the time of color imposing. The method in the Patent
Document 1 is to correct the sub-scanning curve of the image by
correcting a writing beam to write the image data by controlling
the pasture of the imaging element equipped in a light scanning
device in the sub-scanning direction based on detected color
shift.
[0014] Therefore, a device to control posture of the imaging
element, device to correct the sub-scanning curve and the sensor to
detect the sub-scanning curve were necessary, therefore the
apparatus became complicated which increases the cost.
SUMMARY OF THE INVENTION
[0015] An object of the present invention is to provide a transfer
unit, which can inhibit the sub-scanning curve with a simple
structure, capable of forming the high quality image without having
color shift.
[0016] The above object can be achieved by the following. A
manufacturing method of a transfer unit to transfer a plurality of
toner images onto a sheet, having a endless belt and a plurality of
rollers which are spanned by the endless belt, the method having
determining an increasing amount of a diameter of a middle section
of at least one of a plurality of the rollers in respect to end
sections thereof, in accordance with a degree of sub-scanning
curvature of an image transferred onto the sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an image forming apparatus where a manufacturing
method of a transfer unit, of the present invention is
adaptable.
[0018] FIG. 2 is a partial view of a transfer unit shown in FIG.
1.
[0019] FIG. 3 is a frame format of the transfer unit shown in FIG.
2 as seen from an arrow X1 in FIG. 2.
[0020] FIG. 4(a) a diagram showing states of sub-scanning curves by
respective colors, using line images as examples of images of
respective colors to be transferred onto a sheet P, in case
photoconductive substances 1Y, 1M, 1C and 1K, and a intermediate
transfer substance 8 are arranged as FIG. 1 shows.
[0021] FIG. 4(h) is a diagram where states of sub-scanning curve
transferred onto a sheet are indicated by respective colors, where
a cyan toner image and a magenta toner image are omitted.
[0022] FIG. 5 is a diagram where states of sub-scanning curve
transferred and superimposed onto a sheet are indicated.
[0023] FIG. 6 is a view where an endless belt is used for a
photoconductive substance in a shape of a belt.
[0024] FIG. 7 is a view where an endless belt of a transfer unit is
used as a sheet conveyance belt.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] The following describes an embodiment of a manufacturing
method of a transfer unit related to the present invention with
reference to drawings, without the present invention being
restricted thereto:
[0026] FIG. 1 is a view showing an example of an image forming
apparatus to which the manufacturing method of transfer unit
related to the present invention can be adapted.
[0027] The image forming apparatus related to the present invention
is configured with an image forming apparatus main body GH and an
image reading apparatus YS. The image forming apparatus main body
GH, so called tandem type color image forming apparatus includes a
transfer unit 60 having a plurality of sets of image forming
sections 10Y, 10M, 10C and 10K, and an intermediated transfer
substance 6 in a shape of an endless belt; a sheet feeding section
said a fixing device 9.
[0028] Above the image forming apparatus main body GH, the image
reading apparatus YS configured with an automatic document feeding
device 201 and a scanning exposing device 202 is disposed. A
document d placed on a document table of the automatic document
feeding device 201 is conveyed through conveyance rollers and the
image on a single side or both sides of the document d is light
scanned through an optical system of scanning exposing device 201
and read by a line image sensor CCD.
[0029] Signals formed by photoelectric conversion through the line
image sensors CCD are processed by analogue processing, shading
correction, A/D conversion and image compression thereafter sent to
exposing sections 3Y, 3M, 3C and 3K.
[0030] The image forming section 10Y to form a yellow color image
is provided with a charging section 2Y, an exposing section 3Y, a
developing device 4Y and a cleaning section 8Y at a peripheral of
the photoconductive substance in a shape of a drum. The image
forming section 10M to form a magenta color image is provided with
a charging section 2M, an exposing section 3M, a developing device
4M and a cleaning section 8M at a peripheral of the photoconductive
substance in a shape of a drum. The image forming section 10C to
form a cyan color image is provided with a charging section 2C, an
exposing section 3C, a developing device 4C and a cleaning section
8C at a peripheral of the photoconductive substance in a shape of a
drum. The image forming section 10K to form a black color image is
provided with a charging section 2K, an exposing section 3K, a
developing device 4K and a cleaning section 8K at a peripheral of
the photoconductive substance in a shape of a drum.
[0031] Meanwhile, each of the developing devices 4Y, 4M, 4C and 4K
contains each of yellow (Y), magenta (M), cyan (C) and black (K)
binary developing agent including toner and carrier of small
particle diameters.
[0032] The intermediated transfer* substance 6 trains about a
plurality of the rollers, being supported rotatably.
[0033] The fixing device 9 includes a first pressure roller 93
having an elastic layer over a core steel; a heating roller 92
having a heater inside; a endless fixing belt training about the
first pressure roller 93 and the heating roller 92, a second
pressure roller 94 arranged in a position opposite to the first
pressure roller 93 in a way that a second pressure roller 94 is in
contact with the fixing belt 91 with pressure so as to form a
fixing nip section; and fixes toner not yet fixed onto the sheet P
with a heat and a pressure when the sheet F passes through the
fixing nip section in a direction where the a toner surface of the
sheet P before fixing comes in contact with the fixing belt 91.
[0034] Thereby, the toner images of respective colors formed
through the image forming sections 10Y, 10M, 10C and 10K are
subsequently superimposed on the intermediate transfer substance 6
in rotation motion so as to be primary transferred, thus a color
toner image where the toner images of respective colors are
superimposed is formed. The sheet P stored in a cassette 20 is fed
by a sheet feeding section 21 and goes through the sheet feeding
rollers 22A, 22B, 22C, 22D and resist roller 23 then is conveyed to
a transfer section 7A so as to the color toner image is secondary
transferred onto the sheet P. The sheet P on which the color image
has been transferred is heated and pressed at a fixing device 9 so
that the color image is fixed onto the sheet P. Thereafter, sheet P
is grasped by a discharging rollers 24 and loaded on a discharge
sheet tray 25 outside the apparatus.
[0035] On the other hand, after the color toner image is
transferred onto the sheet P through the transfer section 7A, the
intermediate transfer substance 6 from which the sheet P is
separated by curvature is cleaned by the cleaning section 8A to
remove remaining toner.
[0036] The following will describe a manufacturing method related
to the present invention employing the transfer unit.
[0037] FIG. 5 is a frame format of the intermediate transfer
substance 6 and rollers 61 and 62 of the transfer unit 60 as seen
from an arrow X1 in FIG. 2. The roller 61 is a straight roller and
the roller 62 is so-called crown roller where a diameter Dc at
middle section is larger than a diameter Ds of the end sections. A
crown of the roller 62 is formed in a shape of a straight line or
in a shape of a circular arc. In the embodiment of the present
invention, a roller 62 is machined in order to realize high
accuracy of dimension. However, it is preferable to cast the roller
62 from a view point of the cost, in case a highly accurate steel
molding can be used thanks to a large number of the rollers 62 are
produced.
[0038] An increasing amount of the diameter of the meddle section
of the roller 62 in respect to the end sections (Dc-Ds) is
determined in accordance with a degree of sub-scanning curvature of
the image transferred onto the sheet P.
[0039] As FIG. 4 shows, to measure the degree of the sub-scanning
curvature, a largest distance of each image in the middle part of
the image is measured. The above measurement is carried out by
actually measuring the aforesaid largest distance with measuring
instruments such as a scale and a magnifier. In the present
embodiment, a distance h between the yellow color image and the
black color image both having a large sub-scanning curvature is
measured.
[0040] The measured distance h is assigned as a standard value for
the increasing amount of the diameter at the middle section of the
roller 62. Using the roller 62 having the standard value, printing
test, is further carried out with trimming so as to determine an
optimum value.
[0041] In the present embodiment, the distance h of the
sub-scanning curve is 100 .mu.m, thus 100 .mu.m is assigned to the
increasing amount at the roller middle section to inhibit the color
shift.
[0042] In the above measurement, distance measuring devices such as
an image sensor can be used. With the image sensor, a measuring
error can be eliminated and an accurate measurement can be easily
realized.
[0043] Also, in advance, the distortion amount of the rollers 61
and 62 when the intermediate transfer substance 6 is spanned is
calculated by means of rigidity calculation. Then a degree of
sub-scanning curvature is estimated based on the distortion amount
so as to determine a standard value of the increasing amount of the
diameter of the middle section of the roller 62. Thus printing test
is further carried out with trimming so as to determine the optimum
value.
[0044] Presumption of the degree of sub-scanning curvature can be
carried out by measuring amounts of deformation of the rollers 61
and 62 or the intermediate transfer substance 6 while the rollers
are spanned by the intermediate transfer substance 6. Also it can
be carried out by measuring a circumferential speed of the
intermediate transfer substance 6. As above by presumption of the
degree of sub-scanning curvature based on measurement of the actual
apparatus, more realistic presumption can be possible.
[0045] According to the above embodiment, it is possible to
equalize the moving distances of the toner image, which is
transferred from the photoconductive substance onto the
intermediate substance 6, until the toner image is transferred onto
the sheet P at the both ends and at the middle section of the
intermediate transfer substance 6, thus the color shift due to
sub-scanning curve of the image can be inhibited. Thereby there can
be provided a transfer unit 60 capable of forming the high quality
image, without having the color shift, using simple parts and the
structure with low cost.
[0046] In the present embodiment, a photoconductive substances (1Y,
1M, 1C and 1K) have a drum shape, however, they can be in a shape
of an endless belt. FIG. 6 shows an example. Since the structure of
each color is the same, here yellow color will be described.
Rollers 1Y2 and 1Y3 are spanned with a photoconductive substance
1Y1 in the shape of a belt. At a peripheral of the photoconductive
substance. 1Y1 training about the roller 1Y3, an unillustrated
charging section 2Y, exposing section 3Y, developing section 4Y and
cleaning section 8Y are arranged. The configuration conforms to the
photoconductive drum shown by FIG. 1. FIG. 6 shows an example where
two rollers are spanned by the photoconductive substance 1Y1, and
number of the rollers can be more than two. The above structure
expands a possibility of arranging the charging section 2Y, the
exposing section 3Y, the developing section 4Y and the cleaning
section 8Y.
[0047] Also, in the present embodiment, the endless belt of the
transfer unit 60 was used as the intermediate transfer substance,
however in other embodiment, the endless is not used as the
intermediate transfer substance, the belt can be used as a sheet
conveyance belt. FIG. 7 shows an example of other embodiment of the
transfer unit. A transfer section is configured with transfer
rollers (7Y, 7M, 7C and 7B) which are arranged opposite to the
photoconductive substances via a conveyance belt 6b. A sheet P is
conveyed on the conveyance belt and goes through from a right
direction of FIG. 7 so as to transfer an image formed on a
photoconductive drum onto the sheet P. In this case, since the
sheet P is nipped and conveyed by the photoconductive substances
(1Y, 1M, 1C and 1K) and the transfer rollers (7Y, 7M, 7c and 7k)
via the conveyance belt 6b, the color shift due to the distortion
of rollers 61b and 62b occurs in the same manner as above.
Therefore, by conforming to the embodiment of the transfer unit
shown by FIG. 7, and by increasing the diameter of the middle
section of the roller 62b in respect to the diameters of the end
sections in the above method, the color shift due to the
sub-scanning curve of image can be inhibited.
[0048] According to the above embodiments of the present invention,
there can be manufactured a transfer unit, which can inhibit the
sub-scanning curve with a simple structure capable of forming the
high quality image without having the color shift.
* * * * *