Information
-
Patent Grant
-
6813468
-
Patent Number
6,813,468
-
Date Filed
Wednesday, August 21, 200221 years ago
-
Date Issued
Tuesday, November 2, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Grimley; Arthur T.
- Gleitz; Ryan
Agents
-
CPC
-
US Classifications
Field of Search
US
- 399 357
- 399 71
- 399 123
- 399 149
- 399 34
- 399 343
- 399 353
- 399 354
- 399 98
- 399 99
- 399 100
- 399 349
- 015 151
- 015 25652
- 430 125
-
International Classifications
-
Abstract
A cleaner includes a first roller and a second roller. The first roller is for removing foreign matter from a photosensitive body of an image forming device. The second roller is disposed in confrontation with the first roller. An electric field developed between the first roller and the second roller moves foreign matter having a predetermined charge polarity from the surface of the first roller to the surface of the second roller.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a corona charger used in an electrophotographic imaging device, such as a laser beam printer.
2. Description of the Related Art
A conventional image forming device, such as a laser beam printer, includes a photosensitive drum and a process unit. The process unit includes a charger, a scanner unit, a developing roller, and a transfer roller, which are disposed in the stated order around the periphery of the photosensitive drum in confronting relation with the peripheral surface of the photosensitive drum. As the photosensitive drum rotates, the drum is uniformly charged by the charger and then exposed to a laser beam emitted from the scanner unit. The laser beam, which is modulated in accordance with image data, scans the charged surface of the photosensitive drum at a high speed to form an electrostatic latent image on the photosensitive drum.
The process unit further includes a toner box holding toner. The toner contained in the toner box is supplied to the developing roller to form a thin film of toner on the surface of the developing roller. Rotation of the developing roller brings the toner into confrontation with the photosensitive drum. The toner is attracted to the static-electric latent image formed on the surface of the photosensitive drum, so that the static-electric latent image is developed into a visible toner image. When the visible toner image moves into confrontation with the transfer roller, the visible toner image is transferred onto a sheet that passes between the photosensitive drum and the transfer roller.
In a “cleanerless” image forming device, toner that remains on the photosensitive drum after transfer of toner onto the sheet is collected by the developing roller. Because the residual toner is collected in this manner, there is no need to provide a blade or other components for cleaning the photosensitive drum or a waste-toner box for holding the toner that was cleaned off from the photosensitive drum. As a result, “cleanerless” image forming devices have a simpler configuration, are more compact, and less expensive.
Sometimes a “cleanerless” image forming device cannot collect all of the residual toner using the developing roller when a great deal of toner remains on the photosensitive drum after visible image transfer. As a result, the residual toner can influence the next visible toner image formed on the photosensitive drum and appear as a ghost image. Therefore, “cleanerless” process units usually also include a cleaning roller in contact with the photosensitive drum at a position downstream with respect to the rotational direction of the photosensitive drum. The cleaning roller is made from a resilient and conductive material. During image forming processes, the cleaning roller is applied with a bias (negative bias) that is lower than the bias at the surface of the photosensitive drum when the visible toner image is transferred onto the sheet, so that the toner remaining on the photosensitive drum is temporarily collected onto the cleaning roller. At periods of non-image transfer, that is, in between successive sheets, the cleaning roller is applied with a bias (positive bias) that is higher than the bias at the surface of the photosensitive drum. Toner that was temporarily collected by the cleaning roller is returned back to the photosensitive drum and the returned toner is then collected by the developing roller.
Japanese Patent-Application Publication No. 9-127844 discloses a conductive brush member for removing paper dust that clings to the photosensitive drum during printing operations. The brush member is disposed in sliding contact with the surface of the cleaning roller and removes paper dust that is mixed in with toner that was temporarily collected by the cleaning roller. The brush member is applied with the same bias as the cleaning roller or applied with a voltage having the same polarity as the toner that was temporarily collected by the cleaning roller.
However, the brush member has a coarse fiber density so that tips of the brush fibers do not uniformly contact the entire outer peripheral surface of the rotating cleaning roller. Therefore, paper dust is not efficiently removed.
SUMMARY OF THE INVENTION
The present invention has been made to solve the aforementioned problems, and accordingly it is an object of the invention to provide an image forming device that can efficiently remove paper dust by abutting a secondary roller against the cleaning roller and maintain a high printing quality.
To achieve the above and other objects, there is provided a cleaner that includes a first roller and a second roller. The first roller is for removing foreign matter from a photosensitive body of an image forming device. The second roller is disposed in confrontation with the first roller. An electric field developed between the first roller and the second roller moves foreign matter having a predetermined charge polarity from the surface of the first roller to the surface of the second roller.
With this configuration, after foreign objects are completely removed from the photosensitive member by the first roller, the electric field operating between the first roller and the second roller selects only those foreign objects that have the predetermined charge polarity and moves them to the second roller. This ensures that only desired foreign objects of two types of different-polarity foreign objects are reliably removed.
It is desirable to further provide a slide-contact member that contacts the surface of the second roller and scrapes foreign matter from the surface of the second roller. With this configuration, the foreign objects moved to the second roller can be mechanically removed by the slide-contact member. Therefore, foreign objects will not accumulate on the second roller. A clean surface of the second roller, free of foreign objects, will always confront the first roller so that foreign objects will not be returned back to the first roller. Object removal can be more efficiently performed. It is desirable that the slide-contact member includes a porous material made from at least one of sponge and unwoven fabric. With this configuration, the porous portion of the slide-contact member can mechanically trap and hold foreign objects. The foreign objects can be reliably prevented from returning back to the second roller. Moreover, slide-contact member has a large capacity for holding foreign objects, and so can be used for a long time, which proves to be economical.
It is desirable to further comprising a first voltage application unit for applying voltage to the first roller, a second voltage application unit for applying voltage to the second roller, and a control unit. The control unit controls the first voltage application unit to change polarity of voltage applied to the first roller to one polarity when toner is to be drawn from the photosensitive body and to the opposite polarity when toner is to released onto the photosensitive body. The control unit further controls the second voltage application unit to apply voltage to the second roller that does not change the direction of the electric field between the first roller and the second roller, even if the second voltage application unit changes voltage applied to the first roller.
With this configuration, toner that remained in image regions of the photosensitive member after image transfer is once collected on the first roller and then returned back to the non-image regions for the photosensitive member. As a result, toner is not wasted. Moreover, because the voltage applied to the second roller is controlled so as to not change the electric field between the first roller and the second roller, even if the voltage applied to the second roller is switched. Therefore, when the foreign objects have a different polarity than the toner, the foreign objects that are collected on the first roller with the toner can be selectively removed by the electric field to the second roller. Therefore, the configuration for removing foreign objects is a simple configuration that adds only the second roller to the first roller. Production cost can be reduced.
In this case, it is desirable that the first roller has a higher peripheral speed than the photosensitive body. The first roller and the second roller contact each other at their outer peripheral surfaces at a contact portion and move in the same direction at the contact portion. With this configuration, even if the toner and foreign objects are mixed on the first roller, the electric field can selectively remove only foreign objects without having to mechanically scrape toner off the second roller using a difference in peripheral speed between the first and second rollers. Toner will not be wasted.
When the outer surface of the first roller is a resilient and porous member, then the first roller will have a large surface area that enhances the capacity to remove foreign objects and toner using the electric field. Further, the first roller contacts the photosensitive member with a larger surface area so that the effects of mechanical removal of toner and foreign objects is enhanced.
When the second roller is conductive and has a smooth surface, there is no need to mechanically scrape toner and foreign objects, which have different polarities, from the first roller using the second roller. The foreign objects cling to the second roller by the electric field and the mechanical removal of foreign objects by the slide-contact member can be enhanced.
It is desirable that the first roller removes foreign objects from the photosensitive member using a combination of mechanical scraping-off force and electrostatic drawing force. The second roller selectively draws only paper dust from the first roller using mainly electrostatic drawing force. With this configuration, toner that was collected on the first roller can be returned to the photosensitive member without moving to the second roller and foreign objects that cling to the first roller can be moved to the second roller.
An image forming device that includes a photosensitive body and the inventive cleaner has a more compact size and simpler configuration. Also production costs are reduced.
It is desirable that the image forming device further include a charge unit that develops a uniform charge on the photosensitive member, a developing unit that develops images on the photosensitive member using toner into visible images, and a transfer member that transfers the visible images from the photosensitive member onto sheets. The charge unit, the developing unit, the transfer member, and the first roller of the cleaner device are disposed around the photosensitive drum in this order starting from an upstream side with respect to rotational direction of the photosensitive body. When the image forming device has this configuration, a cleanerless type process unit can be configured. Toner will not be wastefully used. Also, the image forming device is more compact and reasonably priced.
BRIEF DESCRIPTION OF THE DRAWINGS
The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which:
FIG. 1
is a cross-sectional view showing a laser beam printer according to an embodiment of the present invention;
FIG. 2
is an enlarged cross-sectional view showing essential portions of a process unit of the printer;
FIG. 3
is a block diagram showing a power source arrangement of the process unit; and
FIG. 4
is a timing chart for describing the operation of the power source arrangement.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A laser beam printer according to a preferred embodiment of the invention will be described with reference to the accompanying drawings.
FIG. 1
is a cross-sectional view showing the laser beam printer.
FIG. 2
is an enlarged cross-sectional view showing essential portions of a process unit.
FIG. 3
is a block diagram showing a power source arrangement of the process unit.
FIG. 4
is a timing chart for describing the operation of the power source arrangement.
The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath” and the like will be used throughout the description assuming that the laser beam printer is disposed in an orientation in which it is intended to be used.
Referring first to
FIG. 1
, the laser beam printer
1
has a housing
2
in which a sheet feed section
4
and an image forming section
5
are disposed. The image forming section
5
forms images on paper sheets supplied by the sheet feed section
4
.
The sheet feed section
4
includes a sheet feed tray
6
, a sheet urging plate
7
, a sheet feed roller
8
, a sheet feed pad
9
, a pair of paper dust removing rollers
10
, a pair of sheet feed rollers
11
, and a pair of registration rollers
12
. The sheet feed tray
6
is detachably provided on the bottom portion of the housing
2
. The sheet urging plate
7
is disposed in the sheet feed tray
6
. The sheet feed roller
8
is rotatably disposed above one end of the sheet feed tray
6
. The paper dust removing rollers
10
are disposed downstream from the sheet feed roller
8
with respect to a sheet transport direction in which the sheets of paper are transported. The registration rollers
12
are disposed downstream from the sheet feed rollers
11
with respect to the sheet transport direction.
The sheet urging plate
7
is pivotally movably supported about its end portion remote from the sheet feed roller
8
and is upwardly biased by springs (not shown) provided on the lower side of the urging plate
7
. A stack of sheets
3
is adapted to be placed on the urging plate
7
. The free end portion of the urging plate
7
moves downward against the biasing force of the springs to an extent that depends upon how many sheets of paper are stacked in the sheet feed tray
6
.
The sheet feed roller
8
and the sheet feed pad
9
are disposed in confronting relation with each other. The sheet feed pad
9
is pressed against the sheet feed roller
8
by a spring
13
disposed in the rear surface of the sheet feed pad
9
. The tip end of the uppermost sheet
3
stacked in the sheet feed tray
6
is pressed against the sheet feed roller
8
by the spring biasing the sheet urging plate
7
upward, is gripped by the sheet feed roller
8
and the sheet feed pad
9
, and then is transported by rotation of the sheet feed roller
8
. The sheet of paper fed by the sheet feed roller
8
passes through the nip between the paper dust removing rollers
10
. At this time, the paper dust removing rollers
10
remove paper dust from the sheet to a certain extent. Then, the sheet of paper is further transported by the sheet feed rollers
11
to the registration rollers
12
, where the sheet of paper is subjected to registration, and then fed to the image forming section
5
.
The sheet feed section
4
further includes a multi-purpose tray
14
, a multi-purpose sheet feed roller
15
, and a multi-purpose sheet teed pad
25
. The multi-purpose sheet feed roller
15
and the multi-purpose sheet feed pad
25
supply sheets
3
that are stacked on the multi-purpose tray
14
. The multi-purpose sheet feed roller
15
and the multi-purpose sheet feed pad
25
are disposed in mutual confrontation with each other. A spring disposed to the undersurface of the multi-purpose sheet feed pad
25
presses the multi-purpose sheet teed pad
25
toward the multi-purpose sheet feed roller
15
. Rotation of the multi-purpose sheet feed roller
15
sandwiches sheets
3
that are stacked on the multi-purpose tray
14
between the multi-purpose sheet feed roller
15
and the multi-purpose sheet feed pad
25
and then feeds the sheets
3
one at a time to the registration rollers
12
.
The image forming section
5
includes a scanner unit
16
, a process unit
17
, and a fixing unit
18
.
The scanner unit
16
is provided in the upper section of the casing
2
and includes a rotating driven polygon mirror
19
, lenses
20
and
22
, and a reflection mirror
21
. A laser emitting portion emits a laser beam modulated based on image data. As indicated by single-dot chain line in
FIG. 1
, the laser beam is reflected by the polygon mirror
19
, passes through the lens
20
, is reflected by the reflection mirror
21
, and passes through the lens
22
to scan across the surface of a photosensitive drum
27
in the process unit
17
at a high speed.
The process unit
17
is disposed below the scanner unit
16
. As shown in
FIG. 2
, the process unit
17
includes the photosensitive drum
27
, a developing cartridge
28
, a scorotron charge unit
29
, a transfer roller
30
, and a cleaning unit
50
. These components of the process unit
17
are housed in a drum case
26
, which is freely detachably mounted on the casing
2
.
The developing cartridge
28
is detachably mounted with respect to the drum case
26
. The developing cartridge
28
includes a developing roller
31
, a layer-thickness regulating blade
32
, a supply roller
33
, and a toner box
34
.
The toner box
34
is filled with non-magnetic single-component toner having a positively charging nature. In the present example, the toner filling the toner box
34
is a polymer toner obtained by co polymerization of a monomer with a polymerizing nature. The co polymerization can be performed by a well-known polymerization method such as suspension polymerization. Examples of monomers that can be used include a styrene monomer, such as styrene, or an acrylic monomer, such as acrylic acid, alkyl (C1-C4) acrylate, and alkyl (C1-C4) meta acrylate. The polymer toner particles are spherical so that the toner has extremely high fluidity. Also, coloring agents, such as carbon black, and wax are dispersed in the toner. Also, an external additive such as silica is added to increase fluidity of the polymer toner. The toner particles have a particle size of between about 6 to 10 micrometers.
A rotation shaft
35
is provided in the center of the toner box
34
. An agitator
36
is supported on the rotation shaft
35
. The agitator
36
rotates in the counterclockwise direction as indicated by an arrow in FIG.
2
. This stirs up the toner in the toner box
34
and also pushes the toner out through a toner supply opening
37
that is opened in the side of the toner box
34
. A window
38
is formed in the side wall of the toner box
34
. The window
38
is for detecting how much toner remains in the toner box
34
. Also, a cleaner
39
is supported on the rotation shaft
35
for cleaning the window
38
.
The supply roller
33
is disposed at the side of the toner supply opening
37
. The supply roller
33
is rotatable in the clockwise direction as indicated by an arrow in FIG.
2
. The developing roller
31
is disposed in confrontation with the supply roller
33
and is rotatable in the clockwise direction as indicated by an arrow in FIG.
2
. The supply roller
33
and the developing roller
31
abut against each other so that each is compressed by a certain extent.
The supply roller
33
is a conductive foam roller that covers a metal roller shaft. The developing roller
31
is a conductive rubber roller that covers a metal roller shaft. In more concrete terms, the foam roller portion of the developing roller
31
includes a roller body with a coat layer covering its surface. The roller body is made from conductive silicone rubber or urethane rubber including carbon particles. The coat layer is silicon rubber or urethane rubber including fluoride. The developing roller
31
is applied with a developing bias by a developing bias application power source (not shown).
The layer-thickness regulating blade
32
is disposed next to the developing roller
31
. The layer-thickness regulating blade
32
includes a blade body and a pressing portion
40
. The blade body is made from a metal plate spring member. The pressing portion
40
is provided on the free tip of the blade body. The pressing portion
40
has a half circle shape in cross section and is made from silicone rubber with electrically insulating properties. The layer-thickness regulating blade
32
is supported on the developing cartridge
28
at a position near the developing roller
31
. The resilient force of the blade body presses the pressing portion
40
against the surface of the developing roller
31
.
The toner pushed out from the toner supply opening
37
is supplied to the developing roller
31
by rotation of the supply roller
33
. The toner is charged to a positive charge by friction between the supply roller
33
and the developing roller
31
. As the developing roller
31
rotates, the toner on the developing roller
31
enters between the developing roller
31
and the pressing portion of the layer-thickness regulating blade
32
. The toner is further charged by friction between the developing roller
31
and the layer-thickness regulating blade
32
and regulated into a thin layer of uniform thickness on the developing roller
31
.
The photosensitive drum
27
serves as an example of a photosensitive body and is disposed to the side and in confrontation with the developing roller
31
. The photosensitive drum
27
is rotatable in the counterclockwise direction as indicated by an arrow in FIG.
2
. The photosensitive drum
27
includes a drum body and a photosensitive layer with a positively charging nature. The drum body is connected to ground. The photosensitive layer covers the outer surface of the drum body and includes polycarbonate. The photosensitive drum
27
is driven to rotate by drive force from a main motor (not shown).
The scorotron charge unit
29
is disposed above the photosensitive drum
27
and separated from the photosensitive drum
27
by a predetermined distance so as not to contact the photosensitive drum
27
. The scorotron charge unit
29
is a positively-charging scorotron type charge unit that generates a corona discharge from a charge wire made from tungsten, for example. The scorotron charge unit
29
uniformly charges the surface of the photosensitive drum
27
to a uniform positive polarity. The scorotron charge unit
29
is turned ON and OFF by a charge power source (not shown).
In association with rotation of the photosensitive drum
27
, first the scorotron charge unit
29
charges the surface of the photosensitive drum
27
to a uniform positive charge. Then, the laser beam emitted from the scanner unit
16
scans across the photosensitive drum
27
at a high speed. The bias at the surface of the photosensitive drum
27
drops at portions of the uniformly charged surface that are exposed by the laser beam based on image data. The portions with bias lowered in this way form a static-electric latent image on the surface of the photosensitive drum
27
based on the image data.
When rotation of the developing roller
31
brings the positively charged toner borne on the developing roller
31
into confrontation with and contact with the photosensitive drum
27
, the toner selectively clings to the static-electric latent image on the surface of the photosensitive drum
27
, thereby developing the static-electric latent image into a visible toner image. As a result, inverse development is achieved.
The transfer roller
30
is disposed below the photosensitive drum
27
at a position in confrontation with the photosensitive drum
27
. The transfer roller
30
is supported on the drum case
26
so as to be rotatable in the clockwise direction as indicated by an arrow in FIG.
2
. The transfer roller
30
is a roller made from an ion conducting rubber material covering a metal roller shaft. As will be described later, a transfer bias application power source
54
applies a transfer bias (a regular transfer bias) to the transfer roller
30
when toner is to be transferred from the photosensitive drum
27
. As a result, the visible toner image borne on the upper surface of the photosensitive drum
27
is transferred onto a sheet
3
that passes between the toner supply opening
37
and the transfer roller
30
.
As shown in
FIG. 1
, the fixing unit
18
is disposed at the downstream of the process unit
17
. The fixing unit
18
includes a thermal roller
41
, a pressing roller
42
, and a pair of transport rollers
43
. The pressing roller
42
presses against the thermal roller
41
. The transport rollers
43
are disposed at the downstream side of the thermal roller
41
and the pressing roller
42
. The thermal roller
41
is made from metal and includes a halogen lamp for heating up. After toner is transferred onto a sheet
3
in the process unit
17
, the sheet
3
passes between the thermal roller
41
and the pressing roller
42
. Heat from the thermal roller
41
melts and fixes the toner onto the sheet
3
. Afterward, the transport rollers
43
transport the sheet
3
to a discharge path
44
. The sheet
3
transported to the discharge path
44
is transported to sheet-discharge rollers
45
and discharged onto a sheet-discharge tray
46
.
The laser printer
1
uses the “cleanerless” method to collect residual toner from the surface of the photosensitive drum
27
. That is, the developing roller
31
collects the toner that remains on the photosensitive drum
27
after toner is transferred onto the sheet
3
. Because the cleaning unit
50
uses the “cleanerless” method to collect toner, there is no need to provide a means for holding waste toner. Therefore, the printer can be made with a simpler configuration, more compact, and less expensive.
The cleaning unit
50
enhances the effects of the “cleanerless” method. Next, the configuration of the cleaning unit
50
will be described in detail. As shown in
FIGS. 2 and 3
, the cleaning unit
50
includes a cleaning roller
51
, a secondary roller
52
, and a sliding contact member
53
provided in the drum case
26
of the process unit
17
.
The cleaning roller
51
is supported in the drum case
26
and located at the side of the photosensitive drum
27
at a position downstream from the transfer roller
30
, and upstream from the scorotron charge unit
29
, with respect to rotational direction of the photosensitive drum
27
. The cleaning roller
51
is supported in contact with the photosensitive drum
27
and is rotatable in the clockwise direction as indicated by an arrow in FIG.
2
. As can be seen in
FIG. 2
, contacting surfaces of the cleaning roller
51
and the photosensitive drum
27
move in the same direction where they are in sliding contact with each other. The cleaning roller
51
is rotated so as to have a faster peripheral speed than the peripheral speed of the photosensitive drum
27
, that is, 1.5 times that of the photosensitive drum
27
in the present embodiment. As a result, the cleaning roller
51
slidingly contacts the surface of the photosensitive drum
27
at a high speed so as to mechanically scrape foreign objects, such as paper dust and other objects other than toner, off the photosensitive drum
27
. It should be noted that bias is selectively applied to cleaning roller
51
during image forming operations to enhance mechanical cleaning operation (of toner and paper dust) performed by the cleaner roller, and to selectively electrically draw toner to and from the cleaner roller
51
.
The cleaning roller
51
is a roller covering a metal roller shaft. The roller portion is made from conductive rubber or other soft and porous material. For example, the roller portion can be made from a sponge rubber material such as conductive silicone rubber, urethane rubber, or Ethylene Propylene Diene Monomer (EPDM). The hardness of the sponge rubber material is about Asker C 35. By using such a sponge rubber, the surface area of the cleaning roller
51
increases, thereby enhancing the effects of removing foreign objects, such as paper dust, both mechanically and by difference in bias.
As shown in
FIG. 3
, a cleaning bias application power source
55
is provided for selectively applying the cleaning roller
51
with a positive bias, which serves as a reference bias, and a negative bias. The negative bias is applied during transfer periods, that is, while toner is being transferred from the photosensitive drum
27
to the sheet
3
during image forming operations. Therefore, during transfer periods, residual toner is continuously electrically drawn to the cleaning roller
51
. On the other hand, the positive bias is applied during non-transfer periods, that is, periods in between sheets to be formed with toner images one after the other. When the positive bias is applied, toner that was electrically drawn to the cleaning roller
51
is electrically returned to the photosensitive drum
27
. In this way, residual toner generated during image forming operations can be temporarily collected electrically. The residual toner electrically returned to the photosensitive drum
27
during non-transfer periods is charged to a positive polarity by the scorotron charge unit
29
when rotation of the photosensitive drum
27
moves the residual toner into confrontation with the scorotron charge unit
29
and then collected by the developing roller
31
when brought into confrontation with the developing roller
31
.
Changes in transfer conditions, such as environmental and durability changes, can result in large amounts of toner remaining on the photosensitive drum
27
after transfer. The developing roller
31
will be unable to collect all of the residual toner by itself. By providing the cleaning roller
51
, the residual toner can be temporarily recovered by the cleaning roller
51
. The influence of the residual toner on the next visible toner image formed on the photosensitive drum
27
can be reduced so that ghosts and the like are not generated in the image.
The secondary roller
52
is aligned in parallel with the cleaning roller
51
. The cleaning roller
51
and the secondary roller
52
are driven to rotate so that the outer peripheral surfaces of the cleaning roller
51
and the secondary roller
52
move in the same direction where the cleaning roller
51
and the secondary roller
52
contact each other. The secondary roller
52
removes and collects foreign objects such as paper dust that are mixed in with the toner that was moved from the photosensitive drum
27
to the cleaning roller
51
, and also prevents the paper dust from being returned to the photosensitive drum
27
with toner that is returned from the cleaning roller
51
to the photosensitive drum
27
.
The secondary roller
52
is made from a metal rotation shaft mounted with a material having conductive properties such as a metal roller portion plated with nickel on its surface. The cleaning roller
51
and the secondary roller
52
are rotated so as to rotate together in the same direction at their mutual contact surface. In this example, the cleaning roller
51
rotates in the clockwise direction of
FIG. 2
, so the secondary roller
52
is rotated in the counterclockwise direction, and also at the same peripheral speed. If the cleaning roller
51
and the secondary roller
52
were driven to rotate with a different peripheral speed where they contact, the secondary roller
52
would scrape off both paper dust and toner from the cleaning roller
51
so that the toner could not be returned from the cleaning roller
51
to the photosensitive drum
27
. However, because the cleaning roller
51
and the secondary roller
52
have the same peripheral speed in the present embodiment, no scraping occurs between the cleaning roller
51
and the secondary roller
52
. As will be described later, the biases applied to the cleaning roller
51
and the secondary roller
52
constantly result in the secondary roller
52
having a higher bias than the cleaning roller
51
. As a result, negatively-charged paper dust can be easily and constantly moved from the cleaning roller
51
to the secondary roller
52
.
The sliding contact member
53
is for removing paper dust that clings to the outer peripheral surface of the secondary roller
52
. The sliding contact member
53
is disposed in sliding contact with the outer peripheral surface of the secondary roller
52
at one side of the secondary roller
52
and substantially parallel with the axial line of the secondary roller
52
. The sliding contact member
53
is made from a soft material with a large surface area in a porous condition such as sponge or unwoven fabric. The sliding contact member
53
scrapes off paper dust that clings only by static electricity to the hard and smooth surface of the secondary roller
52
. After the paper dust is caught up in the sliding contact member
53
, it is returned from the sliding contact member
53
to the secondary roller
52
.
FIG. 3
shows power source configuration for the process unit
17
of the laser printer
1
. As shown in
FIGS. 2 and 3
, the process unit
17
includes the scorotron charge unit
29
, the developing roller
31
, the transfer roller
30
and the cleaning roller
51
disposed around the photosensitive drum
27
in this order following the rotational direction of the photosensitive drum
27
.
The power source configuration of the laser printer
1
includes a charge power source
56
, a development bias application power source
57
, a transfer bias application power source
58
, the cleaning bias application power source
55
, a secondary roller bias application power source
59
, and a control circuit
54
. The control circuit
54
is connected to and controls the charge power source
56
, the development bias application power source
57
, the transfer bias application power source
58
, the cleaning bias application power source
55
, and the secondary roller bias application power source
59
.
FIG. 4
is a timing charge showing timing at which the various power sources are controlled.
The charge power source
56
is connected to the scorotron charge unit
29
. The control circuit
54
controls the charge power source
56
to turn the scorotron charge unit
29
ON and OFF. When the charge power source
56
is turned ON, the scorotron charge unit
29
is turned ON and charges the surface of the photosensitive drum
27
to a bias of about 900 volts.
The development bias application power source
57
is connected to the roller shaft of the developing roller
31
. The control circuit
54
controls the development bias application power source
57
to turn ON and OFF the developing bias applied to the developing roller
31
.
The transfer bias application power source
58
is connected to the roller shaft of the transfer roller
30
. The control circuit
54
controls the transfer bias application power source
58
to selectively switch the transfer bias applied to the transfer roller
30
between a regular transfer bias and an inverse transfer bias. The regular transfer bias is applied to the transfer roller
30
to transfer visible toner images from the photosensitive drum
27
to a sheet
3
that passes between the photosensitive drum
27
and the transfer roller transfer roller
30
. The inverse transfer bias is applied to the transfer roller
30
before image transfer starts in order to electrically transfer toner from the transfer roller
30
to the photosensitive drum
27
.
The transfer bias application power source
58
includes a switching switch
60
, a constant current power source
61
, and a constant voltage power source
62
. The switching switch
60
is connected to the roller shaft of the transfer roller
30
and selectively connected to either the constant current power source
61
or the constant voltage power source
62
. That is, the control circuit
54
controls the switching switch
60
to selectively connect the transfer roller
30
to the either the constant current power source
61
or the constant voltage power source
62
. As a result, the transfer bias applied to the transfer roller
30
is selectively switched between the regular transfer bias from the constant current power source
61
and the inverse transfer bias from the constant voltage power source
62
.
The regular transfer bias applied by constant current control of the constant current power source
61
is set to produce a bias at the surface of the transfer roller
30
that is lower than the surface electric potential of the photosensitive drum
27
directly before the photosensitive drum
27
comes into confronting contact with the transfer roller
30
. When the regular transfer bias is applied to the transfer roller
30
, then the visible toner image formed on the photosensitive drum
27
will be properly transferred to a sheet
3
that passes between the photosensitive drum
27
and the transfer roller
30
. In the present example, the regular transfer bias is set to a constant current of −12 μA. Because the scorotron charge unit
29
charges the surface of the photosensitive drum
27
to about +900V, then the surface electric potential of the photosensitive drum
27
will be about 900V directly before the photosensitive drum
27
confronts and contacts the transfer roller
30
. Portions of the photosensitive drum
27
that contact the transfer roller
30
while the transfer roller
30
is being applied with the regular transfer bias will be rendered to a surface electric potential of about +50V to +400V just before confronting and contacting the cleaning roller
51
. This surface electric potential of the photosensitive drum
27
will be referred to as the first surface electric potential, hereinafter.
The inverse transfer bias applied by constant voltage control of the constant voltage power source
62
is set to produce a bias at the surface of the transfer roller
30
that is higher than the surface electric potential of the photosensitive drum
27
directly before the photosensitive drum
27
comes into confronting contact with the transfer roller
30
. Therefore, by applying the inverse transfer bias to the transfer roller
30
, toner that clings to the transfer roller
30
during image forming operations can be electrically transferred back to the photosensitive drum
27
. In the present example, the regular transfer bias is set to a constant voltage of 1.6 kV. Because of the charging operation of the scorotron charge unit
29
, a bias of about +900V exists at the surface of the photosensitive drum
27
directly before the photosensitive drum
27
confronts and contacts the transfer roller
30
. Therefore, the surface electric potential of the photosensitive drum
27
is rendered to a second surface electric potential of about +900V to +1,000V after photosensitive drum
27
confronts and contacts the transfer roller
30
that is being applied with the regular transfer bias.
The cleaning bias application power source
55
is connected to the roller shaft of the cleaning roller
51
. The control circuit
54
controls the cleaning bias application power source
55
to selectively apply a positive cleaning bias or a negative cleaning bias to the cleaning roller
51
.
The negative bias is applied to electrically draw and temporarily collect toner that remains on the photosensitive drum
27
after visible images are transferred onto sheets. The negative bias is applied while the regular transfer bias is being applied to the transfer roller
30
, that is, at transfer periods during image forming operations when a visible toner image is being transferred to a sheet
3
. In this example, the negative bias is set to about −200V so as to be lower than the first surface electric potential (+200V to +400V).
The positive bias is applied to electrically return residual toner that was electrically drawn onto the transfer roller
30
back to the photosensitive drum
27
. The positive bias is set to +700V so as to be higher than the first surface electric potential (+50V to +400V) and is applied during non-transfer periods of an image forming operation, that is, while the regular transfer bias is being applied to the transfer roller
30
and in between consecutive sheets
3
formed with images.
The secondary roller bias application power source
59
is connected to the roller shaft of the secondary roller
52
. The control circuit
54
controls the secondary roller bias application power source
59
to apply to the secondary roller
52
a bias that maintains the direction of the electric field between the cleaning roller
51
and the secondary roller
52
unchanged even if the voltage applied to the cleaning roller
51
is switched. In this example, the control circuit
54
controls the secondary roller bias application power source
59
to apply a bias of about +750V to +800V to the secondary roller
52
while the cleaning roller
51
is applied with the positive bias (+700V) to return toner from the cleaner roller
51
back to the photosensitive drum
27
, and to apply a bias of about 0V to −100V to the secondary roller
52
while the cleaning roller
51
is being applied with the negative bias (−200V) to draw residual toner from the photosensitive drum
27
to the cleaner roller
51
.
Next, with reference to
FIG. 4
, pre-image formation cleaning operations performed by the cleaning roller
51
and the transfer roller
30
before image formation starts, temporarily toner collecting operations performed by the cleaning roller
51
during image formation, and paper dust removal operations performed by the cleaner device
50
both before and during image formation will be explained.
First, pre-image formation cleaning operations are performed when power of the laser printer
1
is turned ON and include cleaning collected residual toner from the cleaning roller
51
and toner from the transfer roller
30
and removing paper dust. When the power source is turned ON, then the main motor and the scorotron charge unit
29
are turned ON. The transfer roller
30
is maintained in a float condition wherein the switching switch
60
is connected to neither the constant current power source
61
nor the constant voltage power source
62
, so that the transfer roller
30
has the same electric potential as the electrical potential of the photosensitive drum
27
because it is in contact with the photosensitive drum
27
. While maintaining the float condition of the transfer roller
30
, the negative bias (−200V) is applied to the cleaning roller
51
and the negative bias with a higher electric potential (−100V) is applied to the secondary roller
52
.
Of the foreign objects (both toner and paper dust) clinging to the cleaning roller
51
, only the negative-polarity paper dust moves to the high potential of the secondary roller
52
. The positive-polarity toner remains on the cleaning roller
51
. Because the cleaning roller
51
and the secondary roller
52
rotate together in the same direction and with the same peripheral speed, the secondary roller
52
does not mechanically scrape against the surface of the cleaning roller
51
so toner will not be scraped off the cleaning roller
51
by the secondary roller
52
. Because the sliding contact member
53
, which is made from unwoven fabric for example, abuts against the secondary roller
52
, foreign objects such as paper dust on the smooth-surfaced secondary roller
52
can be scraped off and captured by the sliding contact member
53
. Therefore, foreign objects can be properly removed from the secondary roller
52
. It should be noted that in the present embodiment the electric potential at the secondary roller
52
is maintained higher than at the cleaner roller
51
until the power of the laser printer
1
is turned OFF, so that foreign objects such as paper dust are continuously removed from the cleaning roller
51
and the secondary roller
52
as long as the cleaning roller
51
and the secondary roller
52
are rotating.
Next, the inverse transfer bias is applied to the transfer roller
30
. When the portion of the photosensitive drum
27
that contacted the transfer roller
30
when the inverse transfer bias was first applied to the transfer roller
30
arrives at the cleaning roller
51
, then at this timing the positive bias (+700V) is applied to the cleaning roller
51
and the positive bias (+800V) with a higher electric potential is applied to the secondary roller
52
. It should be noted that the electric potential at the secondary roller
52
is still higher than at the cleaner roller
51
, so that negative polarity paper dust will continue to move to the secondary roller
52
and the positive polarity toner will remain clinging to the cleaning roller
51
. Also, the sliding contact member
53
continues to scrape off and capture foreign objects so that the foreign objects can be reliably removed from the secondary roller
52
.
As mentioned above, the scorotron charge unit
29
charges the surface of the photosensitive drum
27
to about +900V from the time that power of the laser printer
1
is turned ON. The inverse transfer bias is higher than the electric potential at the surface of the photosensitive drum
27
directly before contacting the transfer roller
30
. Therefore, when the charged surface of the photosensitive drum
27
contacts the transfer roller
30
while the transfer roller
30
is being applied with the inverse transfer bias, toner that clings to the transfer roller
30
is electrically moved onto the photosensitive drum
27
, resulting in a cleaning operation being performed on the transfer roller
30
. The electric potential at the surface of the photosensitive drum
27
is increased to the second surface electric potential (about +900V to +1,000V) after contacting the transfer roller
30
while the transfer roller
30
is being applied with the inverse transfer bias.
Because the second surface electric potential (about +900V to +1,000V) at the photosensitive drum
27
is higher than the positive bias (+700V) applied to the cleaning roller
51
, the toner that was electrically drawn from the transfer roller
30
onto the photosensitive drum
27
is further electrically drawn onto the cleaning roller
51
when the photosensitive drum
27
contacts the cleaning roller
51
while the cleaning roller
51
is being applied with the positive bias, and so is temporarily collected by the cleaning roller
51
.
Then, the switching switch
60
is switched to connect the transfer roller
30
with the constant current power source
61
to develop the regular transfer bias at the transfer roller
30
, while continuing to apply the positive bias to the cleaning roller
51
. Because the regular transfer bias is lower than the surface electric potential of the photosensitive drum
27
directly before contact with the transfer roller
30
, the surface of the photosensitive drum
27
that is charged by the scorotron charge unit
29
to about +900V is rendered to the lower first surface electric potential (+50V to +400V) directly after contact with the transfer roller
30
while the transfer roller
30
is being applied with the regular transfer bias. Because the first surface electric potential (+50V to +400V) of the photosensitive drum
27
directly before the photosensitive drum
27
confronts and contacts the cleaning roller
51
is lower than the positive bias (+700V) that is being applied to the cleaning roller
51
, toner that was temporarily collected by the cleaning roller
51
is electrically drawn to the surface of the photosensitive drum
27
when the surface portions of the photosensitive drum
27
that were rendered to the first surface electric potential (+50V to +400V) contact the cleaning roller
51
as the cleaning roller
51
is being applied with the positive bias. As a result, a cleaning operation is performed on the cleaning roller
51
.
Then, the transfer bias of the transfer roller
30
is again switched from the regular transfer bias to the inverse transfer bias while the cleaning roller
51
is still applied with the positive bias. In the same way as described above, the toner clinging to the transfer roller
30
is electrically drawn to the photosensitive drum
27
, so that a cleaning operation is performed on the transfer roller
30
. Further, the surface electric potential of the photosensitive drum
27
is rendered to the second surface electric potential (about +900V to +1,000V). Therefore, when the portion of the photosensitive drum
27
at the second surface electric potential (about +900V to +1,000V) reaches the cleaning roller
51
, the toner that was electrically drawn from the transfer roller
30
onto the photosensitive drum
27
is again electrically drawn onto the cleaning roller
51
.
When the transfer bias of the transfer roller
30
is switched from the inverse transfer bias back to the regular transfer bias while the cleaning roller
51
is being applied with the positive bias, the toner that was temporarily collected by the cleaning roller
51
is electrically drawn onto the surface of the photosensitive drum
27
after the surface of the photosensitive drum
27
is rendered to the first surface electric potential (about +50V to +400V), Therefore, a cleaning operation of the cleaning roller
51
is performed. It should be noted that toner that was electrically drawn from the cleaning roller
51
to the surface of the photosensitive drum
27
is collected by the developing roller
31
after being charged to a positive charge by the scorotron charge unit
29
.
Here, the cleaning operations performed before image forming operations will be reviewed. The control circuit
54
controls the switching switch
60
to switch to apply the inverse transfer bias to the transfer roller
30
while the cleaning roller
51
is being applied with the positive bias. As a result, the toner that clings to the transfer roller
30
is electrically drawn to the photosensitive drum
27
so that a cleaning operation can be performed on the transfer roller
30
. On the other hand, the transfer roller
30
is then applied with the regular transfer bias so that the toner that was collected and remains on the cleaning roller
51
is electrically drawn onto the photosensitive drum
27
, so that a cleaning operation can be performed on the cleaning roller
51
.
Accordingly, the cleaning bias applied to the cleaning roller
51
does not need to be selectively switched between a positive bias and a negative. That is, the surface electric potential of the photosensitive drum
27
is changed by only switching the transfer bias applied to the transfer roller
30
, so that the toner can be selectively electrically drawn toward or away from the cleaning roller
51
. Therefore, cleaning operations can be reliably performed while simplifying the configuration of the power sources and reducing production costs.
It is conceivable to selectively electrically draw toner to or away from the cleaning roller
51
by switching the cleaning bias that is applied to the cleaning roller
51
. However, in this case, in order to insure that the toner moves toward or away from the cleaning roller
51
in the desired manner, the surface electric potential of the photosensitive drum
27
directly before contact with the cleaning roller
51
needs to be at a fixed level. Therefore, a charge removing lamp is an essential component of such a conceivable configuration in order to lower the surface electric potential to a constant level. However, in the present embodiment, the surface electric potential of the photosensitive drum
27
directly before the photosensitive drum
27
confronts and contacts the cleaning roller
51
is switched in order to electrically draw toner toward and away from the cleaning roller
51
, so there is no need to use a configuration that requires a charge removing lamp. Therefore, the configuration can be simplified and the costs can be reduced.
After cleaning operations have been performed on the cleaning roller
51
, image operations are performed for forming images on sheets
3
.
Next, temporarily toner collecting operations performed by the cleaning roller
51
during image formation will be described. As shown in
FIG. 4
, during image forming operations while the main motor and the scorotron charge unit
29
are in an ON condition, the developing bias is applied to the developing roller
31
and the regular transfer bias is applied to the transfer roller
30
. A negative bias (−200V) is applied to the cleaning roller
51
and a negative bias (−100V) is applied to the secondary roller
52
during image transfer to the first sheet
3
, that is, while the first sheet
3
is passing between the photosensitive drum
27
and the transfer roller
30
. As a result, portions of the photosensitive drum
27
just about to contact the cleaning roller
51
are rendered to the first surface electric potential. In this case, the first surface electric potential is about +50V to +100V at regions of the photosensitive drum
27
exposed by laser light and about +50V to +400V at unexposed regions of the photosensitive drum
27
. Further, because the negative bias (−200V) is applied to the cleaning roller
51
, toner remaining on the photosensitive drum
27
after image transfer is electrically drawn to and temporarily collected onto the cleaning roller
51
when the photosensitive drum
27
contacts the cleaning roller
51
. That is, as described above, the cleaning roller
51
continues to electrically draw residual toner from the surface region of the photosensitive drum
27
that comes into contact with the sheet
3
as long as the cleaning roller
51
contacts the surface of the photosensitive drum
27
.
On the other hand, the cleaning roller
51
is applied with the positive bias (+700V) while the portion of the photosensitive drum
27
that corresponds to a non-developed region, that is, in between successive sheets
3
that are formed with images one after the other, is contacting the developing roller
31
. In this particular example, the cleaning roller
51
is applied with the positive bias (+700V) while the region of the photosensitive drum
27
that corresponds to between the end of the toner-developed image for the first sheet
3
and the start of toner-developed image for the second sheet
3
is located where the transfer roller
30
and the photosensitive drum
27
contact each other. At this time, the surface electric potential of the photosensitive drum
27
at portions just about to confront and contact the cleaning roller
51
is at the first surface electric potential because the regular transfer bias is still applied to the transfer roller
30
while the positive bias (+700V) is applied to the cleaning roller
51
. Because both the cleaning roller
51
and the secondary roller
52
are applied with positive bias (+700V and +800V, respectively) that is higher than the first surface electric potential, the positively-charged toner that was electrically drawn to the cleaning roller
51
is in turn electrically discharged back to the surface of the photosensitive drum
27
. That is, residual toner that was temporarily collected by the cleaning roller
51
is electrically discharged back to the photosensitive drum
27
while the surface portion of the photosensitive drum
27
where no image is developed, such as in between sheets, contacts the cleaning roller
51
.
By controlling the cleaning roller
51
to electrically draw and discharge residual toner in this way, toner remaining on the photosensitive drum
27
after visible image transfer onto sheets can be temporarily collected using the cleaning roller
51
. Even when toner remains on the photosensitive drum
27
in large amounts that cannot be completely collected by the developing roller
31
alone, the temporarily collection by the cleaning roller
51
will enhance the collecting ability of the developing roller
31
so that even large amounts of residual toner on the photosensitive drum
27
can be reduced to levels that have little influence on the subsequent visible image formed on the photosensitive drum
27
. Subsequent images will therefore be free of ghosts.
After a desired number of sheets
3
have been formed with images using the above-described processes, the developing bias is turned OFF and the cleaning roller
51
is again applied with the positive bias (+700V). As a result, residual toner that was electrically drawn onto the cleaning roller
51
during visible image transfer for the last sheet
3
is electrically discharged back onto the photosensitive drum
27
. Then, the regular transfer bias and the cleaning bias are turned OFF in this order and then the main motor and the scorotron charge unit
29
are turned OFF. As a result, operations of the laser printer
1
are completed.
In this way, the laser printer
1
uses the cleanerless method to collect toner, wherein the developing roller
31
collects toner that remains on the surface of the photosensitive drum
27
after the transfer roller
30
transfers a visible toner image onto a sheet
3
. In addition, during cleaning operations performed using the cleaning roller
51
, the surface electric potential of the photosensitive drum
27
is switched between the first surface electric potential and the second surface electric potential, in order to electrically attract and discharge toner to and from the cleaning roller
51
. In other words, cleaning operations are performed using the cleaning roller
51
without selectively applying a cleaning bias to the cleaning roller
51
. For this reason, the power source configuration can be simplified and costs can be reduced. Also, the cleaning operation performed by the cleaning roller
51
can be reliably performed. Further, there is no need to provide a charge removing lamp, so costs can be simplified because the device configuration is simpler. The simpler configuration translates not only into a more compact device configuration and reduced costs, but also to a device capable of properly forming images over a long period of time.
While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims.
For example, the embodiment describes that during the pre-image forming cleaning operation performed by the cleaning roller
51
before image formation starts, the surface electric potential of the photosensitive drum
27
is switched between the first surface electric potential and the second surface electric potential by switching the transfer bias that is applied to the transfer roller
30
between the regular transfer bias and the inverse transfer bias. However, the surface electric potential of the photosensitive drum
27
could instead be switched between the first surface electric potential and the second surface electric potential by turning the laser beam from the scanner unit selectively ON and OFF. That is, while scorotron charge unit
29
is turned ON, the switching switch
60
is switched out of connection with both the transfer bias application power source
58
or the secondary roller bias application power source
59
. As a result, no transfer bias is applied to the transfer roller
30
, so that the transfer roller
30
is placed in a “float” condition. The first surface electric potential is achieved by scanning the laser light is scanned across the surface of the photosensitive drum
27
to reduce the electric potential at the surface of the photosensitive drum
27
. The second surface electric potential is achieved by turning the laser light OFF.
The embodiment describes using positively charging toner. However, negatively charging toner can be used instead. In this case, the polarity of voltage applied to the scorotron charge unit
29
, the developing roller
31
, the transfer roller
30
, the cleaning roller
51
, and the secondary roller
52
would need to be reversed. Also, when negatively charging toner is used, then the secondary roller
52
would only be capable of removing positive polarity paper dust.
Claims
- 1. A cleaner, comprising:a first roller for removing foreign matter from a photosensitive body of an image forming device; and a second roller disposed in confrontation with the first roller, wherein an electric field developed between the first roller and the second roller moves foreign matter having a predetermined charge polarity from the surface of the first roller to the surface of the second roller, wherein the first roller and the second roller contact each other at their outer peripheral surfaces at a contact portion and move in the same direction at the contact portion, and wherein the first roller and the second roller move in the same speed at the contact portion.
- 2. A cleaner as claimed in claim 1, further comprising a slide-contact member that contacts the surface of the second roller and scrapes foreign matter from the surface of the second roller.
- 3. A cleaner as claimed in claim 2, wherein the slide-contact member includes a porous material made from at least one of sponge and unwoven fabric.
- 4. A cleaner as claimed in claim 1, further comprising:a first voltage application unit for applying voltage to the first roller; a second voltage application unit for applying voltage to the second roller; and a control unit that controls the first voltage application unit to change polarity of voltage applied to the first roller to one polarity when toner is to be drawn from the photosensitive body and to the opposite polarity when toner is to be released onto the photosensitive body, and controls second voltage application unit to apply voltage to the second roller that does not change the direction of the electric field between the first roller and the second roller, even if the second voltage application unit changes voltage applied to the first roller.
- 5. A cleaner as claimed in claim 4, wherein the first roller has a higher peripheral speed than the photosensitive body.
- 6. A cleaner as claimed in claim 1, wherein an outer surface of the first roller is a resilient and porous member.
- 7. A cleaner as claimed in claim 1, wherein the second roller is conductive and has a smooth surface.
- 8. A cleaner as claimed in claim 1, wherein the first roller removes foreign objects from the photosensitive body using a combination of mechanical scraping-off force and electrostatic drawing force, the second roller selectively drawing only paper dust from the first roller using mainly electrostatic drawing force.
- 9. A cleaner as claimed in claim 1, further comprising a toner supply unit that supplies non-magnetic single-component toner having a positively charging nature to the photosensitive body.
- 10. A cleaner as claimed in claim 9, further comprising:a bias application unit that selectively applies a positive bias and a negative bias to the first roller; and a control unit that controls the bias application unit to apply the positive bias to the first roller to draw the toner that was supplied by the toner supply unit away from the photosensitive body to the first roller and to apply the negative bias to the first roller to return the toner from the first roller to the photosensitive body.
- 11. A cleaner as claimed in claim 10, wherein the bias application unit, while applying the positive bias to the first roller to draw the toner away from the photosensitive body, further applies a bias that is higher than the positive bias to the second roller and, while applying the negative bias to the first roller to return the toner to the photosensitive body, further applies a bias that is higher than the negative bias to the second roller.
- 12. An image forming device comprising:a photosensitive body; and a cleaner including: a first roller for removing foreign matter from the photosensitive body of an image forming device; and a second roller disposed in confrontation with the first roller, wherein an electric field developed between the first roller and the second roller moves foreign matter having a predetermined charge polarity from the surface of the first roller to the surface of the second roller, the first roller and the second roller contact each other at their outer peripheral surfaces at a contact portion and move in the same direction at the contact portion, and the first roller and the second roller move at the same speed at the contact portion.
- 13. An image forming device as claimed in claim 12, further comprising:a charge unit that develops a uniform charge on the photosensitive body; a developing unit that develops images on the photosensitive body using toner into visible images; and a transfer member that transfers the visible images from the photosensitive body onto sheets, wherein the charge unit, the developing unit, the transfer member, and the first roller of the cleaner device are disposed around the photosensitive body in this order starting from an upstream side with respect to a rotational direction of the photosensitive body.
- 14. An image forming device as claimed in claim 12, further comprising a developing unit that supplies non-magnetic single-component toner having a positively charging nature to the photosensitive body to develop images on the photosensitive body.
- 15. An image forming device as claimed in claim 14, further comprising:a bias application unit that selectively applies a positive bias and a negative bias to the first roller; and a control unit that controls the bias application unit to apply the positive bias to the first roller to draw the toner that was supplied by the developing unit away from the photosensitive body to the first roller and to apply the negative bias to the first roller to return the toner from the first roller to the photosensitive body.
- 16. An image forming device as claimed in claim 15, wherein the bias application unit, while applying the positive bias to the first roller to draw the toner away from the photosensitive body, further applies a bias that is higher than the positive bias to the second roller and, while applying the negative bias to the first roller to return the toner to the photosensitive body, further applies a bias that is higher than the negative bias to the second roller.
Priority Claims (1)
Number |
Date |
Country |
Kind |
P2001-253404 |
Aug 2001 |
JP |
|
US Referenced Citations (5)
Foreign Referenced Citations (4)
Number |
Date |
Country |
A 9-127844 |
May 1997 |
JP |
A 9-292809 |
Nov 1997 |
JP |
A 9-319278 |
Dec 1997 |
JP |
A 10-39705 |
Feb 1998 |
JP |