JP2005122037A - Transferring unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transferring unit which prevents poor cleaning caused by sticking of foreign matters onto a roller member facing a cleaning member. <P>SOLUTION: The transferring unit 6 has an endless transferring belt 60 which is laid across a plurality of roller members 61 to 68 and which has predetermined electric resistance and a cleaning device 85 equipped with cleaning members 87, 88 which are arranged at the roller member 63 by facing each other while holding the transferring belt 60 therebetween and which clean a belt surface by coming into contact with the transferring belt. Further a cleaning member which is made of Mylar 21 (R) or a fiber flocked roller 22 for cleaning a surface 63A of the roller member 63 is provided in the transferring unit 6 such that the cleaning member is brought into contact with the surface 63A to remove the foreign matters stuck thereon. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a FAX, or a multifunction machine of these, and a transfer unit using them.

  A typical method for forming a color image is to transfer toner images of different colors formed on a plurality of image carriers while being superimposed on an intermediate transfer member as described in Patent Document 1, and then collectively onto a transfer sheet. There are an intermediate transfer system for transfer and a direct transfer system for transferring toner images of different colors formed on a plurality of image carriers while directly superimposing them on a transfer sheet. In an image forming apparatus having these transfer methods, a plurality of image carriers are arranged in parallel facing a transfer paper or an intermediate transfer member. Therefore, this is called a tandem method, and each image carrier is yellow (Y). , Magenta (M), cyan (C), and black (K) are each subjected to an electrophotographic process such as electrostatic latent image formation and development. In the direct transfer method, intermediate transfer is performed on a running transfer paper. In this method, the image is transferred onto the running intermediate transfer member.

  In the tandem color image forming apparatus using each of these methods, in the case of the direct transfer method, an endless transfer belt that runs while supporting the transfer paper is used. In general, an endless belt that receives and carries the belt is employed. An image forming unit including an image carrier corresponding to each color is arranged side by side on one traveling side of the belt.

  In the tandem color image forming apparatus, a cleaning member such as a blade and a cleaning brush is generally installed to clean the transfer residual toner and the background toner on the endless belt. In addition, when it is necessary to draw an image directly on an endless belt and monitor the density of the image with an optical sensor or the like, this image must also be cleaned.

JP 2000-137386 A

  In the case where such an endless belt cleaning member is disposed, the endless belt is generally brought into contact with one of the roller members stretching the endless belt through the endless belt. However, if foreign matter such as minute dust in the apparatus adheres to the roller member, the foreign matter enters between the cleaning member and the belt or between the roller member and the endless belt, and the cleaning member is locally There is a problem that cleaning failure occurs in one rotation cycle of the roller member. In particular, this phenomenon occurs remarkably when the roller member is a driving roller and the cleaning member is a blade.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a transfer unit capable of preventing a cleaning failure caused by foreign matter adhering to a roller member facing a cleaning member, and an image forming apparatus capable of preventing a cleaning failure and obtaining a stable image. To do.

  According to the first aspect of the present invention, an endless transfer belt that is stretched by a plurality of roller members and has a predetermined electric resistance is disposed opposite to the transfer belt with one of the roller members interposed therebetween, and is in contact with the transfer belt. Thus, a transfer unit having a cleaning device provided with a cleaning member for cleaning the belt surface includes a cleaning member for cleaning the surface of the roller member facing the cleaning member.

  The invention of claim 2 is characterized in that the cleaning member is made of mylar, and the invention of claim 3 is characterized in that the cleaning member is a brush member.

  The invention of claim 4 is characterized in that the cleaning member is a blade, and the roller member cleaned by the cleaning member is a drive roller.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier; and a transfer unit provided with an endless transfer belt on which the toner image formed on the image carrier is opposed to the image carrier. The transfer unit according to any one of claims 1 to 4 is used as the transfer unit.

According to the present invention, since the foreign material adhering to the roller member facing the cleaning member and the transfer belt is removed by the cleaning member, the foreign material is sandwiched between the cleaning member and the belt or the roller member and the belt. The cleaning defect which arises can be prevented, and the stable image without back stain | pollution | contamination is obtained.
According to the present invention, since the surface of the roller member is removed by the mylar, the foreign matter attached to the roller member facing the cleaning member and the transfer belt is generated, and the foreign matter is sandwiched between the cleaning member and the belt or the roller member and the belt. It is possible to prevent poor cleaning at a low cost, and a stable image free from backside contamination can be obtained.
According to the present invention, since the surface of the roller member is removed by the brush member from the foreign material adhering to the roller member facing the cleaning member and the transfer belt, the foreign material is sandwiched between the cleaning member and the belt or the roller member and the belt. The cleaning failure which arises can be prevented stably over time, and the stable image without back dirt is obtained. Also

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment applied to an electrophotographic color laser printer (hereinafter referred to as “laser printer”) as an image forming apparatus.

  FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer includes four toner image forming units 1Y, 1M, 1C, 1K (hereinafter referred to as “yellow” (Y), magenta (M), cyan (C), and black (K)). The subscripts Y, M, C, and K of the reference numerals indicate yellow, magenta, cyan, and black members, respectively, and the direction of movement of the transfer paper 100 (the belt 60 along the arrow A in the figure). In the traveling direction) from the upstream side. Each of the toner image forming units 1Y, 1M, 1C, and 1K includes photosensitive drums 11Y, 11M, 11C, and 11K as image carriers and a developing unit. The arrangement of the toner image forming units 1Y, 1M, 1C, and 1K is set so that the rotation axes of the respective photosensitive drums are parallel to each other and arranged at a predetermined pitch in the transfer paper moving direction.

  In addition to the toner image forming units 1Y, 1M, 1C, and 1K, the laser printer carries the optical writing unit 2, the paper feed cassettes 3 and 4, the registration roller pair 5, and the transfer paper 100 to transfer each toner image forming unit. The image forming apparatus includes a transfer unit 6 having a transfer belt 60 as a transfer conveying member that conveys the sheet so as to pass the position, a belt fixing type fixing unit 7, a paper discharge tray 8, and the like. The laser printer includes a manual feed tray MF and a toner replenishing container TC, and a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like (not shown) are also provided in a space indicated by a symbol S.

  The optical writing unit 2 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each of the photosensitive drums 11Y, 11M, 11C, and 11K while scanning the laser beam based on the image data. .

FIG. 2 is an enlarged view showing a schematic configuration of the transfer unit 6. The transfer conveyance belt 60 used in the transfer unit 6 is a high-resistance endless single-layer belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, and the material thereof is PVDF (polyvinylidene fluoride). The transfer / conveying belt 60 is wound around rollers 62 to 68 as a plurality of roller members so as to pass through the transfer positions that contact and face the photosensitive drums 11Y, 11M, 11C, and 11K of the toner image forming units. Yes.

  Among these rollers, the entrance roller 61 on the upstream side in the transfer sheet moving direction is disposed on the outer peripheral surface of the transfer conveyance belt 60 so that the electrostatic adsorption roller 80 to which a predetermined voltage is applied from the power source 65a is opposed. . The transfer paper 100 that has passed between the two rollers 61 and 65 is electrostatically attracted onto the transfer conveyance belt 60. A roller 63 is a drive roller that frictionally drives the transfer conveyance belt 60, and is connected to a drive source (not shown) and rotates in the direction of the arrow.

  As a transfer electric field forming means for forming a transfer electric field at each transfer position, transfer bias applying members 67Y, 67M, 67C, and 67K are provided at positions facing the respective photosensitive drums so as to contact the back surface of the transfer conveyance belt 60. Is provided. These are bias rollers provided with a sponge or the like on the outer periphery, and a transfer bias is applied to the roller core from each transfer bias power source 9Y, 9M, 9C, 9K. Due to the action of the applied transfer bias, a transfer charge is applied to the transfer conveyance belt 60, and a transfer electric field having a predetermined strength is formed between the transfer conveyance belt 60 and the surface of the photosensitive drum at each transfer position. In addition, a backup roller 68 is provided to keep the contact between the transfer paper and the photoconductor in the area where the transfer is performed, and to obtain the best transfer nip.

  The transfer bias applying members 67Y, 67M, and 67C and the backup roller 68 disposed in the vicinity thereof are integrally held by the swing bracket 93 so as to be rotatable, and can be rotated about a rotation shaft 94. This rotation is clockwise when the cam 96 fixed to the cam shaft 97 is rotated in the direction of the arrow.

  The entrance roller 61 and the suction roller 80 are integrally supported by the entrance roller bracket 90, and can be rotated clockwise from the state of FIG. A hole 95 provided in the swing bracket 93 and a pin 92 fixed to the entrance roller bracket 90 are engaged with each other, and rotate in conjunction with the rotation of the swing bracket 93. By the clockwise rotation of these brackets 90, 93, the bias applying members 67Y, 67M, 67C and the backup roller 68 disposed in the vicinity thereof are separated from the photoreceptors 11Y, 11M, 11C, and the entrance roller 61 and the suction roller 80 also moves downward. It is possible to avoid contact between the photoconductors 11Y, 11M, and 11C and the transfer conveyance belt 60 when forming a black-only image.

  The transfer bias applying member 67K and the backup roller 68 adjacent to the transfer bias applying member 67K are rotatably supported by the outlet bracket 98, and are rotatable about a shaft 99 coaxial with the outlet roller 62. When attaching / detaching the transfer unit 6 to / from the main body, the transfer unit 6K is rotated clockwise by operating a handle (not shown), and the transfer bias applying member 67K and the backup roller 68 adjacent thereto are moved from the black image forming photosensitive member 11K. They are separated.

  A cleaning device 85 having a brush roller 87 and a cleaning blade 86 is disposed on the outer peripheral surface of the transfer / conveying belt 60 wound around the drive roller 63. The cleaning device 85 removes foreign matters such as toner adhering to the transfer conveyance belt 60.

  A roller 64 is provided downstream of the driving roller 63 in the traveling direction of the transfer / conveying belt 60 in a direction to push the outer peripheral surface of the transfer / conveying belt 60, and a winding angle around the driving roller 63 is secured. A tension roller 65 that applies tension to the belt with a pressing member (spring) 69 is provided in the loop of the transfer conveyance belt 60 further downstream from the roller 64.

  A two-dot chain line in FIG. 1 indicates a conveyance path of the transfer paper 100. The transfer paper 100 fed from the paper feed cassettes 3 and 4 or the manual feed tray MF is transported by transport rollers while being guided by a transport guide (not shown), and is transported to a temporary stop position where the registration roller pair 5 is provided. The transfer paper 100 delivered at a predetermined timing by the registration roller pair 5 is carried on the transfer conveyance belt 60, conveyed toward the toner image forming portions 1Y, 1M, 1C, and 1K, and passes through the transfer nips. .

  The toner images developed on the toner drums 11Y, 11M, 11C, and 11K of the toner image forming portions 1Y, 1M, 1C, and 1K are superimposed on the transfer paper 100 at the transfer nips, respectively, and transferred electric fields and nip pressures. Is transferred onto the transfer paper 100 in response to the above action. By this superposition transfer, a full-color toner image is formed on the transfer paper 100.

  The surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K after the toner image transfer are cleaned by a cleaning device, and are further discharged to prepare for the formation of the next electrostatic latent image.

  On the other hand, the transfer paper 100 on which the full-color toner image is formed is fixed in the first paper discharge direction B or the second in accordance with the rotation posture of the switching guide G after the full-color toner image is fixed by the fixing unit 7. In the paper discharge direction C. When the paper is discharged from the first paper discharge direction B onto the paper discharge tray 8, it is stacked in a so-called face-down state with the image surface down. On the other hand, when the paper is discharged in the second paper discharge direction C, it is conveyed toward another post-processing device (such as a sorter or a binding device) (not shown), or is registered again for double-sided printing via a switchback unit. It is conveyed to the roller pair 5.

  Next, the characteristic part of this embodiment is demonstrated. FIG. 3 is a cross-sectional view of the cleaning portion of the transfer conveyance belt 60, which is a characteristic portion of the present embodiment. A transfer conveyance belt 60 is stretched around the driving roller 63, and a cleaning device 85 is in contact with the driving roller 63 as an opposing roller. In the cleaning device 85, a cleaning blade 86, a cleaning brush 87, a toner discharge coil 88, and the like are disposed in a casing, and the toner adhering to the transfer conveyance belt 60 is removed by the cleaning blade 86 and the cleaning brush 87. The removed toner is conveyed by a toner discharge coil 88 to a waste toner bottle (not shown) in which waste toner is stored.

  The surface of the driving roller 63 (hereinafter referred to as “roller surface 63A”) is in contact with the mylar 21 as a cleaning member so as to scrape off foreign matters such as dust adhering to the roller surface 63A. The mylar 21 is attached to a bracket 101 provided on a frame (not shown) of the transfer unit 6. The foreign matter scraped off by the mylar 21 moves again together with the transfer belt 60 and does not adhere to the driving roller 63 again by adhering to other rollers or dropping into the unit. For this reason, it is possible to prevent a cleaning failure caused by foreign matter sandwiched between the cleaning blade 86 and the transfer / conveying belt 60 belt or the roller surface 63A and the transfer / conveying belt 60, and a stable image free from backside contamination can be obtained.

  FIG. 4 shows another embodiment of this configuration. The cleaning member made of the mylar 21 has the advantage of being simple and inexpensive, but there are also concerns about side effects such as generation of rubbing noise and torque increase of the driving torque due to rubbing resistance. Therefore, in the embodiment shown in FIG. 4, the flocking roller 22 as a brush member is brought into contact with the driving roller 63 as a cleaning member instead of the mylar 21. The flocking roller 22 is a roller in which a pile is electrostatically flocked on the surface of a metal roller. Both ends of the flocking roller 22 are supported by bearings 102 attached to the bracket 101 and abut against the driving roller 63 by its own weight. Or it rotates by the drive of the gear etc. which are not shown in figure. By using the flocking roller 22 as the cleaning member, the cost is slightly higher than that of the mylar 21, but there are no side effects such as rubbing noise and torque increase, and stable performance over time can be obtained. Further, it is possible to prevent a cleaning failure caused by a foreign matter being sandwiched between the cleaning blade 86 and the transfer / conveying belt 60 belt or the roller surface 63A and the transfer / conveying belt 60, and a stable image without back-staining can be obtained.

  In the above embodiment, the present invention is applied to the transfer unit 6 in the tandem printer in which a plurality of the photosensitive drums 11Y, 11M, 11C, and 11K are arranged on the transfer conveyance belt 60. However, the present invention is applied. The possible printer and transfer unit 6 are not limited to this configuration. In a printer having a transfer unit that rotates an endless belt stretched around a plurality of rollers by at least one of the rollers, the present invention can be applied to any transfer unit.

1 is a schematic diagram illustrating a configuration of an image forming apparatus illustrating an embodiment of the present invention. It is an enlarged view showing a configuration of a transfer unit. It is an enlarged view which shows the structure of the cleaning part using the mylar used as the principal part of this invention. It is an enlarged view which shows the structure of the cleaning part using the brush used as the principal part of this invention.

Explanation of symbols

6 Transfer unit 11Y, 11M, 11C, 11K Image carrier 21 Cleaning member (mylar)
22 Cleaning member (brush)
60 Transfer belt 61 to 68 Multiple roller members 63 One roller member (drive roller)
63A Roller surface 85 Cleaning device 86 Cleaning member (blade)
87 Cleaning member (brush)

Claims (5)

An endless transfer belt stretched by a plurality of roller members and having a predetermined electric resistance is disposed opposite to the roller member with the transfer belt interposed therebetween, and the belt is brought into contact with the transfer belt. In a transfer unit having a cleaning device provided with a cleaning member for cleaning the surface,
A transfer unit comprising a cleaning member for cleaning a surface of a roller member facing the cleaning member.   The transfer unit according to claim 1, wherein the cleaning member is made of Mylar.   The transfer unit according to claim 1, wherein the cleaning member is a brush member.   4. The transfer unit according to claim 1, wherein the cleaning member is a blade, and the roller member cleaned by the cleaning member is a drive roller. In an image forming apparatus comprising: an image carrier; and a transfer unit provided with an endless transfer belt that is disposed opposite to the image carrier and onto which a toner image formed on the image carrier is transferred.
An image forming apparatus using the transfer unit according to claim 1 as the transfer unit.

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