JP2006317746A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a long life and printing a stable and high-quality image by preventing the uneven deterioration of a cleaning blade for cleaning an intermediate transfer belt or the like so as to prolong the service life of the cleaning blade. <P>SOLUTION: The image forming apparatus is equipped with the intermediate transfer belt 60 to which a toner image from a photoreceptor 11 is transferred, and a cleaning device 85 having a blade 86 and a brush 87 for cleaning the intermediate transfer belt 60. After a toner mark pattern for controlling density or controlling alignment is transferred to the intermediate transfer belt 60 and is detected by a detection means, the density or positional deviation is controlled to be corrected. The length of the bristles of the brush is made longer only at a part equivalent to the toner mark pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to an image forming apparatus including a cleaning device that scrapes residual toner on an intermediate transfer belt with a cleaning blade.

When a toner mark is transferred to an intermediate transfer belt, which is an intermediate transfer body, for the purpose of density correction, belt position detection, or color misregistration correction in an image forming apparatus, the load on the blade of the cleaning device as a cleaning unit is Concentrate on the toner mark. As a result, toner slips out of the cleaning blade at the toner mark portion, which adversely affects image formation. In order to prevent this, it is obvious that increasing the contact pressure of the cleaning blade to the intermediate transfer belt is effective. However, if this is done, the wear of the cleaning blade is accelerated, and the blade cleaning performance is prematurely deteriorated. In addition, increasing the amount of biting of the brush to improve brush cleaning performance is also effective, but the rotational torque of the brush increases, causing problems such as deterioration of color misregistration due to uneven rotation of the belt or step-out of the drive motor. May cause. With respect to these problems, in Patent Document 1, in a cleaning device including a brush roller that performs cleaning by contacting the surface of a charging roller that is an object to be cleaned, the cross-sectional shape of the brush roller in the rotational axis direction is a polygon. Since the distance from the center of the brush roller to the tip of the brush varies around the roller, the contact pressure of the brush with the object to be cleaned fluctuates as the brush roller rotates, A technique that facilitates sweeping out foreign matter on a cleaning body is disclosed.
However, since the above-described technique uniformly abuts against the axial direction of the object to be cleaned, the cleaning blade is unevenly deteriorated at a portion where the toner is partially concentrated, such as a toner mark, and is effective. There was a problem of not going up.

JP 20042333652 A

  In view of the above problems, the present invention prints a long-life and stable high-quality image by preventing uneven deterioration of the cleaning blade for cleaning the intermediate transfer belt and the like and extending the life of the cleaning blade. An object of the present invention is to provide an image forming apparatus.

In order to solve the above problems, the present invention is characterized by the following.
An image forming apparatus of the present invention includes an intermediate transfer belt to which a toner image on an image carrier is transferred, and a cleaning unit having a blade and a brush for cleaning the intermediate transfer belt, and density control is performed on the intermediate transfer belt. Alternatively, in the image forming apparatus in which the toner mark pattern for alignment control is transferred and detected by the detection unit, and the density or positional deviation correction control is performed, only the portion corresponding to the toner mark pattern is bristled on the brush. It is characterized by a longer length.

  The present invention provides an image forming apparatus that prints a long-life and stable high-quality image by preventing uneven deterioration of a cleaning blade for cleaning an intermediate transfer belt and the like and extending the life of the cleaning blade. can do.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The following description is an example of the best mode of the present invention, and it is easy for those skilled in the art to make other embodiments within the scope of the claims by making changes and modifications within the scope of the claims. However, this does not limit the scope of the claims.

One embodiment in which the present invention is applied to an electrophotographic direct color transfer color laser printer (hereinafter referred to as “laser printer”) as an image forming apparatus will be described with reference to FIGS.
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. In addition, the arrangement of the toner image forming units 1Y, 1M, 1C, and 1K is set so that the rotation axes of the photosensitive drums are parallel 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, 4, the resist roller pair 5, and the transfer paper 100, and each toner image forming unit. A transfer unit 6 as a belt driving device having a transfer conveyance belt 60 as a transfer conveyance member that conveys the sheet so as to pass through the transfer position, a belt fixing type fixing unit 7, a paper discharge tray 8, and the like. 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 image data. To do.

FIG. 2 is an enlarged view showing a schematic configuration of the transfer unit. 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 paper moving direction is disposed on the outer peripheral surface of the transfer conveyance belt 60 so as to face the electrostatic adsorption roller 80 to which a predetermined voltage is applied from the power source 80a. . The transfer paper 100 that has passed between the two rollers 61 and 80 is electrostatically adsorbed 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, a transfer bias applying member 67Y, at a position facing the photosensitive drums 11Y, 11M, 11C, 11K so as to be in contact with the back surface of the transfer conveyance belt 60, 67M, 67C, and 67K are 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 around 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 shown in 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 photoconductors 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.

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 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 including a cleaning brush roller 86 and a cleaning blade 87 is disposed on the outer peripheral surface of the transfer / conveying belt 60 wound around the driving 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.

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 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 embodiment of this invention is demonstrated. FIG. 3 is a sectional view of the cleaning brush, and FIG. 4 is a plan view of the cleaning brush.
As shown in FIG. 3, the cleaning brush 86 is installed so as to bite into the transfer belt that is stretched around the opposing roller by about 0.5 to 2 mm, and has an action of scraping off the toner on the transfer belt.
In this embodiment, as shown in FIG. 4, the length of the bristle of the cleaning brush 86 is increased to increase the amount of biting in accordance with the position of the toner mark written on the transfer belt. The width of the hair lengthening part is about 10-20 mm longer than the width of the toner mark, and the hair length is about 0.5-1 mm longer than the other part.
In FIG. 4, the position of the toner mark is shown as one place. However, when it is applied to a plurality of places, a portion where the hairs are lengthened correspondingly may be set at a plurality of places. Furthermore, the length and width of the hair can be set to arbitrary values depending on the frequency of writing the toner mark or the image area.
As described above, when a toner mark or the like is transferred onto the transfer member, the toner amount input to the cleaning blade 87 increases only in that portion, and the toner amount input to the cleaning device 85 in the belt axial direction is uniform. Don't be. Therefore, by increasing the length of the bristle of the cleaning brush 86 at the portion corresponding to the toner mark position, the cleaning load of the cleaning blade 87 is made uniform in the axial direction, thereby extending the life of the cleaning blade 87. It becomes possible.

  Further, as described above, in the embodiment of the present invention, 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, the transfer sheet 100 is transferred at each transfer nip. The present invention is applied to the transfer unit 6 that is superimposed on the transfer unit 6 and transferred onto the transfer paper 100 under the action of the transfer electric field and nip pressure. However, the printer and the belt driving device to which the present invention can be applied are limited to this configuration. It is not a thing. 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 cleaning brush, a cleaning blade, The present invention is applicable to any image forming apparatus provided with a process for cleaning a toner mark by a cleaning apparatus having

1 is a schematic configuration diagram of a laser printer according to the present invention. It is a figure which shows the transfer unit which concerns on this invention. It is sectional drawing of the cleaning brush which concerns on this invention. It is a top view of the cleaning brush which concerns on this invention.

Explanation of symbols

1Y, 1M, 1C, 1K Image forming unit 2 Optical writing unit 3, 4 Paper feed cassette 5 Registration roller pair 6 Transfer unit 7 Fixing unit 8 Paper discharge trays 9Y, 9M, 9C, 9K Transfer bias power supplies 11Y, 11M, 11C, 11K photosensitive drum 60 transfer belt 61-68 support rollers 67Y, 67M, 67C, 67K transfer bias applying member 80 electrostatic adsorption roller 85 cleaning device 86 cleaning brush 87 cleaning blade 88 shaft 90 entrance roller bracket 91 shaft 92 pin 93 swing Bracket 94 Rotating shaft 95 Hole 96 Cam 97 Cam shaft 98 Exit bracket 99 Shaft 100 Transfer paper 101 Toner mark A Belt running direction B First paper discharge direction C Second paper discharge direction S Space MF Manual feed tray G Switching guide

Claims (1)

An intermediate transfer belt onto which the toner image on the image carrier is transferred;
A cleaning means having a blade and a brush for cleaning the intermediate transfer belt;
After transferring the toner mark pattern for density control or alignment control onto the intermediate transfer belt and detecting it by the detecting means,
In an image forming apparatus that performs density or positional deviation correction control,
An image forming apparatus, wherein the length of the bristle of the brush is increased only in a portion corresponding to the toner mark pattern.

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