Patent Grant
8081912
The present invention relates to an image forming apparatus for forming a color image, the apparatus having at least two image bearing members, wherein toner images formed on image bearing members are overlaid sequentially on a transfer material carried on a transfer material feeding member, by a transfer member.
Recently, color image forming apparatuses of an electrophotographic type are widely used, and there is a demand for high speed production of the color images in addition to the quality of the color images. To meet such a demand, some proposals have been made. For example, Japanese Laid-open Patent Application 2001-109325 discloses an apparatus, wherein toner images are formed by respective image forming units and are overlaid by transfer means sequentially on a transfer material carried on a transfer material feeding belt (transfer material feeding means) into a color image (tandem color image forming apparatus). In addition, there is an increasing demand for a marginless print as in film photography as a result of wide use of a digital image recording device, such as a digital still camera. Such a marginless print has been put into practice with an ink jet type image forming apparatus disclosed in Japanese Laid-open Patent Application Hei 10-337886, for example, and is desired in the electrophotographic type image forming apparatus.
With such an image forming apparatus of an electrophotographic type capable of a marginless print, no blank need appear on the transfer material even if the transfer material is fed to the transfer station with some positional deviation and even if the transfer material is not completely uniform in size.
It has been proposed that the size of the toner image is made larger than the size of the transfer material, that is, the toner image is larger to extend beyond a first region corresponding to the size of the transfer material, that is, it extends into a second region outside the first region. This result in that toner is transferred onto the transfer material feeding member such as a transfer material feeding belt in the second region, that is, the toner is transferred onto the belt in the second region outside the transfer material.
The size of the outside transferred toner is about 2 mm×210 mm along the short sides in the case of A4 size transfer material.
The size of the outside transferred toner is about 2 mm×297 mm along the long sides in the case of A4 size transfer material.
The excessive toner outside the second area is collected by cleaning means such as a blade, a brush or a roller provided downstream of the transfer portion with respect to the feeding direction of the transfer material feeding belt. In a proposal, the cleaning means is provided with a toner collection container, and the toner is reverse-transferred from the transfer material feeding belt onto the image bearing member, and the toner is collected by the cleaning means.
Such cleaning means is effective to collect a small amount of the toner assuredly, but it may not collect a large amount of toner in a short period. For the case in which a large amount of the toner is to be removed, such as a case immediately after paper jam occurrence or a case in which a control toner image for image density adjustment or for print position adjustment is formed on the transfer material feeding belt, it would be considered to carry out the belt cleaning operation twice or more, with the result of increased number of belt rotations.
It is tolerable to increase the number of rotations of the transfer material feeding belt, for the abnormal cases.
However, in the case of a marginless print, the occurrence of the excessive toner is normal.
In view of continuous printing operations, however, the increase of the number of rotations of the transfer material feeding belt would result in reduction of productivity.
According to an aspect of the present invention, there is provided an image forming apparatus, comprising a transfer material feeding member for feeding a transfer material; a first image bearing member for carrying a first toner image; a second image bearing member, provided downstream of the first image bearing member with respect to a feeding direction of the transfer material feeding member, for carrying a second toner image; a first transfer member for transferring the first toner image carried on the first image bearing member onto a transfer material; and a second transfer member, provided downstream of the first transfer member with respect to the feeding direction, for transferring the second toner image carried on the second image bearing member onto the transfer material. The apparatus is operable in a marginless print mode in which the toner image is formed on the first region on the first image bearing member corresponding to a size of the transfer material and a second region on the first image bearing member outside the first region, and wherein a reverse-transfer efficiency TR1=(P2/P1)×100(%) and a reverse-transfer efficiency TR2=(E2/E1)×100(%) satisfy:
TR1<TR2
These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings.
The color image forming apparatus of the present embodiment is the color image forming apparatus of the in-line type. It has four image forming stations (the image formation stations S (Sa, Sb, Sc, Sd)) which are perpendicularly arranged in the present embodiment (the so-called color image forming apparatus of the tandem type). The four image formation stations Sa, Sb, Sc, and Sd are the yellow (Y), magenta (M), cyan (C), and black (Bk) image formation stations arranged in the order named from upstream with respect to the transfer material carrying direction of the transfer material conveying belt 1 as the transfer material feeding member. The image formation stations Sa, Sb, Sc, and Sd have the same structures.
Referring to
Furthermore, a developing device 15 (15a, 15b, 15c, 15d) is provided downstream with respect to the rotational direction of the photosensitive drum around the photosensitive drum 11. In addition, a transfer member 3 (3a, 3b, 3c, 3d) and a cleaning device 17 (17a, 17b, 17c, 17d) are provided downstream with respect to the photosensitive drum rotational direction around the photosensitive drum 11.
The photosensitive drum 11 as the image bearing member may comprise a cylindrical drum of aluminum, and an OPC (organic optical semiconductor) layer as a photosensitive layer on the surface thereof. The charging roller 12 is contacted to the surface of the photosensitive drum 11, and it is supplied with a charging bias voltage from an unshown charging bias voltage applying source. By this, the surface of the photosensitive drum 11 is uniformly charged to a predetermined potential in a predetermined polarity. The exposure device 13 includes a scanner unit or an LED array for deflecting the laser beam oscillated in response to the image information by a polygon mirror. The exposure device 13 scans the surface of the charged photosensitive drum 11 by the scanning beams 14 (14a, 14b, 14c, 14d) modulated on the basis of the 8-bit image signals (00h-FFh (h expresses the hexadecimal)). By this, the charge of the portion exposed to the beam is removed, so that an electrostatic latent image is formed. In this embodiment, when the image signal is 00h, the solid white image is formed, and the solid black image is formed when it is FFh.
Each developing device 15 deposits the toner on the developing sleeve 19 (19a, 19b, 19c, 19d) which is the developer carrying member on the electrostatic latent image on the photosensitive drum 11 surface to develop it into a visualized toner image of each color.
Each transfer roller 3 which constitutes the transfer member has the function of electrostatically transferring, onto the transfer material P on the transfer material conveying belt 1, the toner image formed on the photosensitive drum 11. As the material of the transfer roller 3, rubber materials, such as EPDM, urethane, NBR, epichlorohydrine, and silicone, are usable. In this embodiment, the transfer roller 3 includes the core metal having 6 mm in diameter, and the elastic layer having a thickness of 3 mm thereon. As the elastic layer, NBR and epichlorohydrine are blended so that the six kinds of elastic layers which have volume resistivities of (ρT) 105.5, 106, 106.5, 107, 107.5, 108, and 108.5 Ω-cm, respectively were prepared. They have Asker C hardnesses of 30 degrees.
The transfer roller 3 is disposed inside of the transfer material conveying belt 1, presses the transfer material conveying belt 1 to the photosensitive drum 11 surface with pressure, so as to form a transfer nip N (Na, Nb, Nc, Nd) between the photosensitive drum 11 and the transfer material conveying belt 1. In this embodiment, a contact pressure to the photosensitive drum 11 of the transfer roller 3 is 2.0 g/mm. In this embodiment, each transfer roller 3 is connected with a transfer bias application voltage source 4 (4a, 4b, 4c, 4d) as a constant voltage source. It may be a constant-current source. A photosensitive drum cleaning device 17 (17a, 17b, 17c, 17d) as a cleaning member has a cleaning blade 18 (18a, 18b, 18c, 18d) for removing the toner which remains on the surface of the photosensitive drum 11 without transferring onto transfer material P.
In each of the above-described image formation stations S, the developing device 15 is in the form of a developing unit, and the cleaning device 17 is constituted as the drum unit with the photosensitive drum 11 and the charging roller 12. These developing units and the drum unit may be in the form of a cartridge which can be detachably mountable to the main assembly of the image forming apparatus, respectively. The developing unit and the drum unit can also be constituted as one process cartridge.
The transfer material conveying belt 1 as a transfer material conveyance member is extended around the four rollers 6, 7, 8, and 9, and is rotated at a predetermined speed (process speed of 100 mm/s in the present embodiment) in the arrow R2 direction. In this manner, the transfer material conveying belt 1 feeds the transfer material P carried by the surface thereof sequentially to the image formation station S (Sa, Sb, Sc, Sd).
For the cleaning of the transfer material conveying belt 1, a transfer material feeding belt cleaning device 20 as the means to remove unnecessary toner on the surface thereof is provided. The transfer material feeding belt cleaning device 20 is provided with a scraping blade 21 and a container 22 which stores the toner collected by the blade 21 shown in
The transfer material feeding belt cleaning device 20 is not limited to the scraping type of the present embodiment which uses the blade 21. The rollers, such as a fur-brush roller and a sponge roller, may be used in place of the blade 21, for example, and a peripheral speed difference may be provided relative to the transfer material conveying belt 1 (rubbing-off type). In order to utilize the potential difference, these toner recovery means may be supplied with the bias.
The transfer material conveying belt 1 may be made of resin film, such as PVdF, ETFE, polyimide, PET, polycarbonate or the like resin material, which have about 50-300 micrometers in thickness. Alternatively, it may include a base layer of the EPDM or the like rubber, for example, which has about 0.5-2 mm in thickness, and a urethane rubber surface layer in which fluorinated resin material, such as PTFE, for example, is dispersed, thereon. An electroconductive filling material of carbon, ZnO, SnO2, and TiO2 or the like may be dispersed in this material to adjust the volume resistivity. In this embodiment, the six kinds of the volume resistivities (pH) 106, 108, 1010, 1012, and 1014 and 1016 Ω-cm are prepared, and they are made of PVdF or the like which has a thickness of 100 micrometers.
The volume resistivity of the transfer material conveying belt 1 is measured by the method stipulated in JIS-K6911. The satisfactory contact property between the electrode and the belt surface is provided by using the electrode of electroconductive rubber. A Resistivity Meter (available from Mitsubishi Chemical Analytech Co., Ltd, Hiresta UP) is used. The measuring condition is such that the applied voltage=100V, the voltage applying duration=10 s.
Transfer material P is fed to the transfer material conveying belt 1 by supplying and feeding device 30. The attraction roller 5 electrostatically attracts the transfer material P fed from the supplying and feeding device 30 to the transfer material conveying belt 1 surface. The attraction roller 5 includes a metal core, for example, and an electroconductive elastic member of EPDM, urethane rubber, and NBR or the like, which have a volume resistivity of about 105 to 108 Ω-cm thereon. It further includes an intermediate layer, such as a urethane layer with a thickness of about 200-600 micrometers, thereon. It further includes a surface layers layer, such as the styrene layer of about 250-micrometer thickness.
The attraction roller 5 is urged toward the roller 7 through the transfer material conveying belt 1 by pressing metal core portions provided in opposite ends of the attraction roller 5 by the spring with about 0.04-0.5-N line pressure. By this, it is rotated by the movement of the transfer material conveying belt 1. In this manner, an attraction nip is constituted between the attraction roller 5 and the roller 7.
In this embodiment, the attraction roller 5 is connected with an attraction bias voltage applying source 13 as the constant voltage source.
In a further downstream part, with respect to the transfer material carrying direction, of the roller 6 disposed at the most downstream side of the transfer material conveying belt 1, a fixing device 14 for fixing the toner image transferred onto the surface of transfer material P is disposed.
When an image forming operation starts in the image forming apparatus having the above-described structure. The photosensitive drum 11 (11a, 11b, 11c, 11d) and the transfer material conveying belt 1 begin rotating in the arrow R1 direction and the arrow R2 direction with the predetermined process speed, respectively. Simultaneously, the exposure device 13 (13a, 13b, 13c, 13d) starts. The photosensitive drum 11 is uniformly charged to the predetermined potential of the predetermined polarity by the charging roller 12.
On the other hand, the transfer material P contained in a sheet feeding cassette 30 as the supplying and feeding device is fed to the attraction roller 5 by the sheet feeding cassette. The transfer material P is electrostatically attracted on the transfer material conveying belt 1 surface by the voltage applied between the attraction roller 5 and the roller 7. At this time, in the yellow image forming station Sa, the electrostatic latent image is formed on the surface of a photosensitive drum 11a in accordance with image information by scanning beam 14a from the exposure device 13a synchronized with the feeding of transfer material P. With the further rotation of the photosensitive drum 11a, the electrostatic latent image is developed with toner by the developing sleeve 19a, and is visualized into a yellow toner image. The toner image on the photosensitive drum 11a is transferred by the transfer bias voltage for the image formation applied to the transfer roller 3a by the transfer bias application voltage source 4a onto the transfer material P attracted and fed by the transfer material conveying belt 1.
Also in the image formation stations Sb, Sc, and Sd, the respective color toner image is formed on the photosensitive drums 11b, 11c, and 11d similarly to the image formation station Sa of the yellow. The toner images on the photosensitive drums 11b, 11c, and 11d are superimposedly transferred by the transfer member onto the transfer material P in synchronism with the feeding by the transfer belt 1 of the transfer material P. In this manner, a toner image which has the yellow, magenta, cyan, and black images superimposedly on the transfer material P is formed. The transfer material P after the transferring of the toner image is separated from the transfer material conveying belt 1, and, thereafter, is heated and pressed by the fixing device 14, and the toner image is fused and fixed on the surface.
On the other hand, the toner which remains on the surface without transferring onto the transfer material P is removed by the respective photosensitive drum cleaning devices 17 from the photosensitive drums 11 (11a, 11b, 11c, 11d) after the toner image transferring. Thereafter, the photosensitive drums 11 are prepared for the next image formation.
From the transfer material conveying belt 1, the unnecessary toner which remains is removed by the cleaning blade 21 of the transfer belt cleaning device 20, and is prepared for the feeding of the next transfer material P.
The image forming apparatus of the present embodiment is operable in a marginless print mode which can form a marginless image which does not have a blank at least at one edge of the transfer material P. As shown in
In other words, by extending the toner image beyond the region of the transfer material P, the toner image can be formed to the extent of the edges of the transfer material P eve even with some positional deviation of the transfer material P.
In this embodiment, the second region M in the marginless print mode is defined at 2 mm outside of the each of the four edges of the transfer material P.
In the marginless print mode, the toner image formation area of the image bearing member is wider than usual, it is necessary to enlarge the image data. This is accomplished by the user making the image having a size larger than the size of the transfer material using a software application.
Alternatively, it is accomplished by the controller enlarging the image data with the predetermined magnification or repeating the data of the outermost periphery of the image data to provide the enlarged portion.
In this manner, the marginless print is possible by increasing the toner image area on the image bearing member than the region corresponding to the transfer material.
On the other hand, as for the toner transferred on the transfer material conveying belt 1 without transferring onto the transfer material from the 2nd region on the image bearing member, it is desired to remove assuredly by the transfer material feeding belt cleaning device 20, in the marginless print mode operation. Otherwise, it appears as toner soiling the back side and the edge portion of the next transfer material. In order to carry out the cleaning assuredly, the present embodiment selects the volume resistivities of the transfer roller 3 and the transfer belt 1, by which before reaching the cleaning device 20, a part of the toner on the transfer belt 1 is collected by the photosensitive drum 11. By this, the load of the cleaning device 20 is reduced.
In the Case A shown with the solid-black dots and the solid line, the volume resistivity of the transfer material conveying belt 1 is 108 Ω-cm, and the volume resistivity of the transfer roller 3 is 107 Ω-cm.
In the Case B shown with the hollow dots and the broken line, the volume resistivity of the transfer belt 1 is 1012 Ω-cm, and the volume resistivity of the transfer roller 3 is 108 Ω-cm. This graph shows that there is no large difference between Case A and Case B. In the case of the combination of the volume resistivities in Case A, the volume resistivities of the transfer material conveying belt 1 and the transfer roller 3 are significantly low as compared with volume resistivity 1011 Ω-cm of the transfer material. Therefore, the large transfer current tends to flow in the area outside the transfer material.
In the case of the combination of Case B, the volume resistivity of the transfer roller is high, and the volume resistivity of the transfer material conveying belt is also high as compared with volume resistivity 1011 Ω-cm of the transfer material. Therefore, the transfer current equivalent to the portion with the transfer material flows through the area outside the transfer material. In
On the other hand,
The following is understood from the result of
On the other hand, in Case A, the image does not have the defect and there is a smaller amount of the toner transferred onto the transfer material conveying belt 1 than in Case B. In addition, the amount which will be collected by the photosensitive drum from the toner transferred onto the transfer material conveying belt 1 by the time it passes the fourth station is larger than the amount in Case B, and therefore, the duty of the cleaning device 20 is significantly small.
In this manner, the structure of Case A provides the low transfer efficiency to the transfer material conveying belt 1, wherein the toner is easily transferred inversely onto the photosensitive drum 11 from the transfer material conveying belt 1 at the time of passing the downstream transferring station. The reason therefor will be described referring to
In
On the other hand, in the case of the plots shown by the broken line, the highest transfer efficiency to the transfer material conveying belt 1 occurs at the set point Y, and the transfer efficiency is relatively low at the set point X.
Here, a transfer efficiency, to the transfer material, of the toner image formed on the photosensitive drum 11 by the developing device 15 is TRP1. A transfer efficiency, to the outside area of the transfer material on the transfer material conveying belt 1, of the toner image formed on the second region of the photosensitive drum 11 is TRE1.
The toner mass (g/cm2) per unit area of the toner image formed on first region and second region of the photosensitive drum 11 is P0. The toner mass (g/cm2) per unit area of the toner image transferred onto the transfer material from the first region of the photosensitive drum 11 is P1. The toner mass per unit area of the toner image transferred onto the outside area of the transfer material on the transfer material conveying belt 1 from the second region of the photosensitive drum 11 is E1 (g/cm2).
Then,
Transfer efficiency TRP1=(P1/P0)×100(%)
Transfer efficiency TRE1=(E1/P0)×100(%)
In this embodiment, the transfer efficiency TRP1 and the transfer efficiency TRE1 satisfy the following relation:
The reason will be described.
With the volume resistivity setting of the transfer roller 3 and the transfer belt 1 of Case A in
In the downstream transferring station formed with the second photosensitive drum and the second transfer roller on the other hand, the toners transferred onto the transfer material from the first photosensitive drum hardly reverse-transfer to the photosensitive drum 11. This is because the correct current flows in the portion in which the transfer material presents.
However, the optimal transfer bias voltage relative to the transfer material causes abnormal discharge relative to the toner on the transfer material conveying belt 1. Therefore, the potential of the toner on the transfer material conveying belt 1 further attenuates, or the reversion is promoted, and as a result, reverse transfer is promoted further.
Here, the toner P1 transferred onto the transfer material by the upstream first transfer roller 3 with respect to the transfer material carrying direction of the transfer material conveying belt 1 is reverse-transferred onto the second photosensitive drum 11 by the downstream second transfer roller 3 (toner P2) according to a reverse transfer ratio TR1. The toner E1 transferred onto the outside area of the transfer material by the upstream first transfer roller 3 with respect to the feeding direction of the paper on the transfer belt 1 is reverse-transferred onto the second photosensitive drum 11 by the downstream second transfer roller 3 (toner E2) according to a reverse transfer ratio TR2. In other words, P1, P2, E1, and E2 are the masses (g/cm2) of the toner per unit area, and the reverse transfer ratios TR1 and TR2 are,
TR1=(P2/P1)×100(%)
TR2=(E2/E1)×100(%).
According to this embodiment, the reverse transfer ratio TR1 and the reverse transfer ratio TR2 satisfy the following relation:
With this structure, even when the toner image on the second region of the first image bearing member is transferred onto the transfer material conveying belt by the first transfer roller, the toner transferred onto the transfer material conveying belt is easy to reverse-transfer onto the second image bearing member by the second transfer roller. Therefore, the high-quality image not having the contamination due to improper cleaning can be continuously outputted without the reduction of the speed.
Here, the image defect in
<Memory>
In
<Interference>
In
<Insufficient Image Density>
In
As a result, the light image is particularly roughened, or the dark image also becomes lighter in the worst case.
<“G” Part>
Referring to
This is a range surrounded by the solid line in
More particularly, in the case of the volume resistivity (ρT) of the transfer roller 3 and the volume resistivity (ρH) of the transfer material conveying belt 1 being lower than the volume resistivity of the transfer material, it is easy to flow the abnormal current into the portion which does not have the transfer material. Therefore, it becomes easier to produce the reverse-transfer onto the second photosensitive member.
In other words, the second photosensitive drum can collect easily the toner image transferred onto the transfer material conveying belt from the first photosensitive drum 11.
More particularly, by using the transfer material conveying belt 1 and the transfer roller 3 which are set to the volume resistivity within the limits surrounded with the solid lines in
As a result, the amount of the toner which is not removed by the cleaning member 21 in operation in marginless print mode is reduced, and the toner on the transfer material conveying belt 1 is assuredly removed by one cleaning operation. Therefore, the high-quality image not having the contamination attributable to the improper cleaning can be continuously outputted without the reduction of the speed.
In this embodiment, although the blade 21 is used as the cleaning device 20 for the transfer material conveying belt 1, the toner may be physically scratched by a known brush and known roller.
As the cleaning device 20 of the transfer material conveying belt 1, the means for collecting the toner onto the photosensitive drum 11 by charging the toner on the transfer belt 1 by the known charging means may be employed.
Alternatively, the peripheral speed difference may be provided between the photosensitive drum 11 and the transfer material conveying belt 1, and the toner may be collected onto the photosensitive drum 11 by applying the transfer bias voltage in the opposite direction. The toner collected onto the photosensitive drum 11 is removed from the photosensitive drum 11 by the cleaning device 17 for the photosensitive drum. These means may be combined properly.
Also in this embodiment, the image forming apparatus has the structure similar to the forgoing embodiment described referring to
The toner amount which remains on the transfer material conveying belt 1 after all the transferring station passages is controlled by controlling the volume resistivity of the transfer member, and the volume resistivity of the transfer feeding member in Embodiment 1. In this embodiment, the toner amount which remains on the transfer material conveying belt 1 is controlled by controlling the hardness of the transfer roller 3 and the contact pressure against the transfer material conveying belt 1.
The value of the width (nip width NW) of a nip N shown in
The image forming apparatus is once stopped in the state where the solid black toner image is formed on the photosensitive drum 11. Then, in the state where the transfer material conveying belt 1 is spaced from the photosensitive drum 11, the photosensitive drum 11 is rotated until the phase in which the toner on the photosensitive drum 11 contacts to the transfer material conveying belt 1 is reached. The transfer material conveying belt 1 is contacted to the photosensitive drum 11, and then only the transfer belt 1 is moved. The width on the photosensitive drum 11 with which the toner was scratched by the transfer material conveying belt 1 is measured. This value is determined as the transfer nip width (NW).
The respective cases in
<“N” (Solid Dot)>
In the range which contains solid dots in
The width (NW) of the transfer nip in the range which contains the solid dots was measured through the above described method. They are less than 0.5 mm. Thus, in the case of the width (NW) of the nip being very small, the contact pressure is uneven with respect to the longitudinal direction of the transfer roller, and vertical stripe-like non-uniformity and density difference tends to appear. On the other hand, the transfer material conveying belt 1 and the photosensitive drum 11 separate from each other by the distance corresponding to the thickness of the transfer material in the range which is outside the transfer material and in which the photosensitive drum 11 contacts directly to the transfer belt 1. Therefore, the transfer efficiency onto the transfer material conveying belt 1 reduces, and therefore, the transfer nip width (NW) further reduces. Therefore, the remainder amount of the toner on the transfer material conveying belt 1 after passing all the transferring station decreases.
<“G” (Hollow Dot)>
The hardness of the transfer roller 3 and the pressure of the transfer roller 3 are proper in the range which contains hollow dots in
<“F” (Triangle Mark Area)>
It is satisfactory in the image on paper in the range which contains triangle marks in
On the other hand, since the transferring pressure in the paper-present-area is also sufficiently high, the setting of the transfer bias voltage is slightly low.
On the other hand, since the transferring pressure in the paper-present-area is also sufficiently high, the setting of the transfer bias voltage is slightly low.
As a result, the difference between the optimal transfer bias voltages for the transfer material and the transfer material conveying belt is small. Even if the transfer bias voltage is set to the optimal voltage for the transfer material, the abnormal discharge does not occur in the transfer-material-absent-area. In addition, the reverse-transfer of the toner does not occur. Moreover, since the amount of the toner transferred by the transferring pressure onto the belt is large, the remainder amount of the toner on the belt after passing all the transferring stations is large.
<“N” (Cross Mark Area)>
In the range which contains x in
On the basis of the above-described result, as shown by hollow dots in
In this manner, the high image quality of the image on the transfer material transferred can be maintained. And, simultaneously, the load of the cleaning means 20 for the transfer belt 1 is reduced, and after carrying out the marginless print mode, it is not necessary to add the special cleaning operation. In addition, it is not necessary to provide an additional cleaning means for the edge portion where the remainder amount of the toner on the belt is particularly large.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modification or changes as may come within the purposes of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 029744/2008 filed Feb. 8, 2008 which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-029744 | Feb 2008 | JP | national |
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| Number | Date | Country | |
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| 20090202279 A1 | Aug 2009 | US |
