Electrophotography – Cleaning of imaging surface – Including lubricant
Reexamination Certificate
2000-07-19
2001-09-25
Chen, Sophia S. (Department: 2852)
Electrophotography
Cleaning of imaging surface
Including lubricant
C399S299000, C399S349000
Reexamination Certificate
active
06295438
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, a facsimile, a printer, etc., and more particularly to an image forming apparatus capable of preventing a lifetime of an electrostatic latent image bearing member from being decreased by friction with an appropriate supply of a lubricant to the electrostatic latent image bearing member such as a photoconductive element.
2. Discussion of the Background
In an electrophotographic image forming apparatus, such as a copying machine, a facsimile, a printer, etc., such an image forming apparatus is well known that includes an image forming section having an electrostatic latent image bearing member to form an electrostatic latent image on its surface, a charging device to uniformly charge the electrostatic latent image bearing member, a developing device to develop the electrostatic latent image formed on the surface of the electrostatic latent image bearing member into a visible image and a cleaning device to remove developer adhered to the electrostatic latent image bearing member.
FIG. 9
is a schematic drawing illustrating an exemplary construction of an image forming section
1
in an electrophotographic image forming apparatus in the art. A part having the reference numeral of
10
in
FIG. 9
is a photoconductive element, for example an electrostatic latent image bearing member, and a surface of the photoconductive element
10
is uniformly charged by a charging roller
11
. A desired electrostatic latent image is formed on the surface of the charged photoconductive element
10
with an exposure light
12
irradiated from an optical writing device (not shown). The electrostatic latent image is then developed into a visible toner image with toner in a developing device
13
. The toner image formed on the surface of the photoconductive element
10
is transferred onto a transfer sheet carried on a transfer sheet conveying belt
14
with a transfer bias applied by a transfer brush
15
. The transfer sheet having the transferred toner image is conveyed to a fixing device (not shown) where the toner image is fixed onto the transfer sheet by being heated and pressed. A part having the reference numeral of
16
is a cleaning device including a cleaning blade
17
. The cleaning device
16
is provided so as to remove residual toner remaining on the surface of the photoconductive element
10
with the cleaning blade
17
. The removed toner is conveyed to a used toner container (not shown) by a used toner conveying screw
19
. Further, a cleaning brush roller
18
, which is a cleaning support member, to roil and remove toner on the surface of the photoconductive element is disposed at an upstream side of the cleaning blade
17
in the moving direction of the photoconductive element.
An image forming apparatus illustrated in
FIG. 10
includes four image forming sections. Each of which has the same construction as that illustrated in FIG.
9
and is located in parallel to form images of different colors. The image forming apparatus also includes a transfer sheet conveying belt
14
to convey a transfer sheet to the four image forming sections
1
B,
1
C,
1
M and
1
Y. Reference numerals
12
Y,
12
C,
12
M and
12
B represent exposure light irradiated in the four image forming sections
1
Y,
1
C,
1
M and
1
B respectively. In the back surface side of the transfer sheet conveying belt
14
, transfer brushes
15
B,
15
C,
15
M and
15
Y, which transfer a toner image formed at each image forming section
1
B,
1
C,
1
M and
1
Y, are provided opposing to the respective photoconductive elements
10
B,
10
C,
10
M and
10
Y so as to transfer the toner image formed at each image forming section
1
B,
1
C,
1
M and
1
Y onto a transfer sheet carried on the transfer sheet conveying belt
14
one after another superimposing each color toner image on each other. In an image forming apparatus illustrated in
FIG. 10
, a desired full color image can be obtained when each color of toner; black (B), cyan (C), magenta (M) and yellow (Y) is used at respective developing devices
13
B,
13
C,
13
M and
13
Y of the image forming sections
1
B,
1
C,
1
M and
1
Y. Such an image forming apparatus as described above is commonly known as a tandem color image forming apparatus.
A technology is widely known which suppresses an abrasion of a surface of a photoconductive element caused by a cleaning blade, etc., by supplying the photoconductive element with a lubricant and thereby preventing a lifetime of the photoconductive element from being decreased due to the abrasion, and various systems for supplying a lubricant are proposed. Two systems are known to supply a lubricant. A first type supplies the lubricant by pressing it directly against a surface of a photoconductive element (for example, in Japanese Patent Laid-Open Publication No. 9-62163). A second type supplies the lubricant by abutting a rotatable brush roller on the photoconductive element while abutting the lubricant on the rotatable brush roller (for example, in Japanese Patent Laid-Open Publication No. 6-324603). In the latter system, since a cleaning device to remove residual toner remaining on the surface of the photoconductive element is often configured to include a cleaning brush roller, such a system has been proposed that utilizes the cleaning brush roller as the above-described brush roller.
A plurality of image forming sections in the above-described tandem image forming apparatus are configured to have the same structure as to each other. However, a supply of a lubricant to a photoconductive element has to be adjusted to a proper amount in each image forming section.
An electrical action for a lubricant in a transfer section will now be discussed. Fluorine-containing resins polytetrafluoroethylene (four fluoridation ethylene resin) and PVDF (polyvinylidene fluoride) used as a lubricant electrically have negative characteristics. In a reverse development that uses negatively charged toner, positive bias is applied to a transfer section. Consequently, a force is exerted that electrically removes the lubricant adhered to a photoconductive element.
FIG. 11
explains a change in an amount of a removed lubricant over a lapse of time according to a different voltage level of a transfer bias. In this explanation, a coefficient of friction on a photoconductive element is measured as substitutive characteristics of an amount of a lubricant on a surface of the photoconductive element. It is observed that the higher a voltage of the transfer bias to be supplied, the larger the amount of the lubricant is removed when the apparatus is operated by varying the voltage level of the transfer bias with using a photoconductive element possessing a nearly constant coefficient of friction.
In the above-described tandem color image forming apparatus having four image forming sections, a technology is commonly known in which a smooth transfer is achieved by intensifying a transfer bias to be applied to an image forming section in order of image forming section from an upstream to a downstream in a moving direction of a transfer sheet conveying direction. In the configuration that intensifies the transfer bias in order of the image forming section from the upstream to the downstream, a lubricant will be easier to be removed from a surface of a photoconductive element in order of the image forming section from the upstream to the downstream, and an application of a lubricant to increase a lifetime of a photoconductive element will become less effective.
A proper amount of a lubricant must be supplied so as not to be inconvenienced by a mixture of a foreign substance due to an accumulated lubricant on a surface of a photoconductive element. It is preferable that the lubricant on the surface of the photoconductive element is removed completely before the next supply of lubricant is made after the lubricant has been supplied so that a fresh lubricant layer is always formed on the surface of the photoconductive element
Fujishiro Takatsugu
Takehara Atsushi
Ueda Masayuki
Umezawa Nobuhiko
Yokokawa Nobuto
Chen Sophia S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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