JP4839080B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus capable of maintaining the temporal quality of an intermediate transfer member cleaning apparatus.

  Conventionally, a cleaning device for cleaning an object to be cleaned has been widely used in machines and devices in various technical fields. For example, in an image forming apparatus configured as a copying machine, a printer, a facsimile, or the like, a cleaning device that cleans the surface of an image carrier, a cleaning device that cleans the peripheral surface of a charging roller that charges the image carrier, or a transfer A cleaning device for cleaning the surface of the transfer belt, which is a body, is used.

  As such a cleaning device, a cleaning device having a brush roller on the surface of an object to be cleaned is widely used (for example, see Patent Document 1). A method of applying a solid lubricant to a transfer body or the like with a brush roller has also been proposed (see, for example, Patent Document 2).

  In this type of cleaning device, a brush roller is driven to rotate by a driving device, and a brush that contacts the surface of the object to be cleaned applies a solid lubricant to the transfer member. In Patent Document 2, a mechanism for adjusting the amount of solid lubricant applied is provided so that the amount of lubricant is neither too much nor too little.

  As described above, in Patent Document 2, a mechanism for adjusting the coating amount of the solid lubricant is provided, but the toner mark is transferred onto the transfer body for the purpose of correcting the density and the transfer position of the toner image. There are many. In such a case, since the toner mark is intermittently transferred to the same position, the toner input amount to the cleaning device is increased only in that portion. As a result, the solid lubricant is scraped by the toner, and the consumption of the solid lubricant is initially increased. As a result, the solid lubricant becomes a concave portion at the position where the toner mark is transferred (the measurement result is shown as the toner mark position in FIG. 6). There was a problem that the amount would decrease. Since the solid lubricant has a concave portion in this way, the lubricant consumption amount varies between the region including the toner mark and the other region as shown in FIG. This becomes non-uniform in the sub-scanning direction, causing a cleaning failure.

Japanese Patent Laid-Open No. 7-140763 JP-A-2005-77717

  Therefore, the present invention solves the problems of the conventional one, and the amount of solid lubricant applied does not decrease over time, and the amount of lubricant consumed differs between the region including the toner mark and the other regions. An object of the present invention is to provide an image forming apparatus capable of ensuring good cleaning performance without causing the occurrence of the above.

In order to solve the above-mentioned problems, the invention according to claim 1 is an image forming apparatus comprising : a transfer body to which a toner image from an image carrier is transferred; and a cleaning device for cleaning the toner image on the transfer body. in the device, the cleaning device comprises a brush roller, together with the solid lubricant is applied to the transfer member is in contact with the said brush roller, the height of the brush of the brush roller, the transfer member The region including the width of the toner mark transferred above is lower in the axial direction than the other regions .

According to a second aspect of the invention, in the image forming apparatus according to claim 1, wherein, in the portion where the height of the brush is low, the amount of bite into the solid lubricant of the brush, than other regions characterized in that it also has less of at least 0.5mm or more.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the average circularity of the toner is 0.90 to 0.99.

The present invention is as described above, and the cleaning device has a brush roller. The brush roller is in contact with the solid lubricant applied to the transfer body, and the brush roller height of the brush roller is in contact with the brush roller. However, in the region including the width of the toner mark transferred onto the transfer body, it is lower in the axial direction than in other regions, so that the consumption amount of the solid lubricant can be changed in the axial direction. it can. Therefore, the amount of solid lubricant applied does not decrease over time, and the amount of lubricant consumed does not deviate between the area including the toner mark and the other areas as in the prior art. An excellent effect of ensuring the cleaning performance can be expected.

  An embodiment in which the present invention is applied to an electrophotographic color laser printer (hereinafter referred to as “laser printer”) as an image forming apparatus will be described with reference to the drawings.

  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 toner image forming units 1Y, 1M, 1C, and 1K are arranged so that the rotation axes of the photosensitive drums 11Y, 11M, 11C, and 11K are parallel to each other and at a predetermined pitch in the transfer sheet moving direction. Is set to do.

  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, and each of the toner image forming units. A transfer unit 6 as a belt driving device having a transfer conveyance belt 60 as a transfer conveyance member that conveys the transfer position so as to pass through the transfer position, a belt fixing type fixing unit 7, a paper discharge tray 8, and the like are provided. In addition, a manual feed tray MF and a toner supply container TC are provided, and a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like (not shown) are also provided in a space S indicated by a two-dot chain line.

  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 conveyance belt 60 is wound around support rollers 61 to 68 so as to pass through the transfer positions that are in contact with and face the photosensitive drums 11Y, 11M, 11C, and 11K of the toner image forming units.

  Among these support 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 80a is opposed. Yes. The transfer paper 100 that has passed between the two rollers 61 and 80 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.

  Transfer bias applying members 67Y, 67M, 67C, and 67K are provided as transfer electric field forming means for forming a transfer electric field at each transfer position so as to be in contact with the back surface of the transfer conveyance belt 60 at a position facing the photosensitive drum. It has been. 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. Further, a backup roller 68 is provided in order to keep the contact between the transfer paper and the photoconductor in an 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 around the 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 swing of the swing bracket 93. Due to the clockwise rotation of the brackets 90 and 93, the bias applying members 67Y, 67M, and 67C and the backup roller 68 disposed in the vicinity thereof are separated from the photoreceptors 11Y, 11M, and 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.

  On the other hand, 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 the transfer unit 6 is attached to or detached from the main body, the transfer unit 6 is rotated clockwise by a handle (not shown) to transfer the transfer bias applying member 67K and the backup roller 68 adjacent thereto from the black image forming photosensitive member 11K. Are separated from each other.

  As shown in FIG. 3, a cleaning device 85 including a brush roller 85a and a cleaning blade 85b is disposed on the outer peripheral surface of the transfer conveyance 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 conveyance belt 60 in a direction of pushing the outer peripheral surface of the transfer conveyance belt, and a winding angle around the drive roller 63 is ensured. A tension roller 65 for applying tension to the belt with a pressing member 69 made of a spring or the like is provided in the loop of the transfer conveyance belt 60 further downstream from the roller 64.

  The one-dot chain line in FIG. 1 shown above indicates the 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 units 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 units 1Y, 1M, 1C, and 1K are superimposed on the transfer paper 100 at the transfer nips, respectively. It is transferred onto the transfer paper 100 under the action of pressure. 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 the cleaning device 85, and are further neutralized 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 (not shown) (such as a sorter or a binding device) or again for double-sided printing via a switchback unit. It is conveyed to the registration roller pair 5.

  In the cleaning device 85, as shown in FIG. 3, the cleaning blade 85b abuts against the transfer belt 60 stretched around the drive roller 63, and a brush roller 85a is provided on the upstream side thereof. A solid lubricant 86 is brought into contact with the brush roller 85a by a compression spring 87, and the lubricant once adhered to the brush is applied to the transfer belt 60. At this time, since the toner on the transfer belt 60 also adheres to the brush, the toner is interposed between the solid lubricant 86 and the brush in an area where the toner input is large, and the toner acts as an abrasive. The consumption of 86 becomes active. As a result, as described in paragraph 0005, in the time-lapse state, the contact of the solid lubricant 86 is reduced as shown in FIG. 4, and the amount of lubricant applied to the transfer belt 60 in that region becomes insufficient.

  However, the shape of the brush of the brush roller 85a in the present embodiment is as shown in FIG. 5, and initially the amount of lubricant consumed in the portion where the brush is low (position corresponding to the toner mark) is suppressed. In the aging state, the brush shape and the solid lubricant shape are synchronized, and as a result, the consumption amount of the lubricant in the aging state is made uniform. Moreover, the effect in this plan can be expected by changing the amount of biting into the lubricant by 0.5 mm or more than other portions. In consideration of brush fall, about 1 mm is desirable. On the other hand, the same effect was confirmed when the amount of biting of the brush toward the transfer belt 60 was in the range of 0.5 to 2 mm in this embodiment. This is also preferably about 1 mm in consideration of brush falling.

  As the lubricant in the present embodiment, for example, a fluorine-based material, zinc stearate, or the like can be used as appropriate. Also, as shown in FIG. 3, a block-shaped solid lubricant 86, a compression (pressurization) spring 87, and a brush roller 85a constitute an agent application unit that applies lubricant to the surface of the transfer belt 60. However, the compression spring 87 is not necessarily required, and the same effect can be expected in the form of contacting the brush by the weight of the solid lubricant 86 or the like.

  In the above embodiment, in the tandem printer in which the photosensitive drums 11Y, 11M, 11C, and 11K are arranged side by side on the transfer conveyance belt 60, the transfer electric field is superimposed on the transfer paper 100 at each transfer nip. Although the present invention is applied to the transfer unit 6 that is transferred onto the transfer paper 100 under the action of the nip pressure, a printer and a belt driving device to which the present invention can be applied are not limited to this configuration. In a transfer body in which an endless belt stretched around a plurality of rollers is rotationally driven by at least one of the rollers, a toner mark is transferred onto the transfer body, and finally a blade and a brush are provided. Any image forming apparatus having a process for cleaning a toner mark by a cleaning device can be applied.

Next, a characteristic effect of the invention described in claim 2 and the following claims will be described. According to the second aspect of the present invention, the amount of biting of the brush into the solid lubricant at the portion where the height of the brush is low is reduced by 0.5 mm or more than that in the other regions. Can be expected more reliably. According to the third aspect of the present invention, since it is difficult to maintain the cleaning performance in a time-dependent state with respect to the toner having an average circularity of 0.90 to 0.99, , The reliability of the cleaning performance can be improved.

1 is a schematic configuration diagram of a laser printer according to an embodiment of the present invention. It is an enlarged view which shows schematic structure of the transfer unit same as the above. It is an enlarged view which shows schematic structure of the cleaning apparatus same as the above. It is drawing which shows contact | abutting of the solid lubricant and brush of an aging state same as the above. It is drawing which shows a brush same as the above. It is a graph which shows the surface profile of the solid lubricant in the conventional aging state. It is a graph which shows the consumption transition of the conventional lubricant.

Explanation of symbols

1Y, 1M, 1C, 1K Toner image forming unit 6 Transfer unit 11Y, 11M, 11C, 11K Photosensitive drum (image carrier)
60 Transfer conveyor belt 85 Cleaning device 85a Brush roller 85b Cleaning blade 86 Solid lubricant 87 Compression spring 100 Transfer paper

Claims (3)

In the image forming apparatus having a transfer member to which the toner image from the image bearing member is transferred, a cleaning device for cleaning the toner image on said transfer Utsushitai, a,
The cleaning device comprises a brush roller, together with the solid lubricant is applied to the transfer member is in contact with the said brush roller,
The height of the brush of the brush roller is lower in the axial direction in the region including the width of the toner mark transferred onto the transfer body than in other regions. . The image forming apparatus according to claim 1, wherein, in a portion where the height of the brush is low, the amount of bite into the solid lubricant of the brush, become less of at least 0.5mm or more than other regions image forming apparatus characterized by there. 3. The image forming apparatus according to claim 1, wherein an average circularity of the toner is 0.90 to 0.99.

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