JP4193456B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine, or a facsimile using an electrophotographic system or an electrostatic recording system, and in particular, removes foreign matters adhering to a charging roller that rotates in contact with the surface of an image carrier. The present invention relates to an image forming apparatus provided with a cleaning brush.
[0002]
[Prior art]
Conventionally, in surface image forming apparatuses such as printers and copying machines using this type of electrophotographic system or electrostatic recording system, the surface of an image carrier such as a photosensitive drum is uniformly charged to a predetermined potential. The electrostatic latent image is formed on the surface of the image carrier by performing image exposure, and the electrostatic latent image is visualized and developed by fixing and developing the electrostatic latent image with toner. A toner image is formed thereon, and the toner image is transferred to a recording medium such as paper and fixed, whereby an image is formed on the recording medium.
[0003]
In such an image forming apparatus, a charging roller that uniformly applies a charge to the surface of an image carrier that carries a toner image is used. Since this charging roller is brought into contact with the image carrier, dirt such as toner, discharge products, dust in the air, paper dust, etc. is likely to adhere, and abnormal or unstable discharge occurs when such dirt adheres. However, it tends to cause image defects such as fog.
[0004]
Therefore, in a conventional image forming apparatus, a rotating image carrier, a charging roller that contacts the image carrier and charges it while rotating, and a surface of the charging roller that contacts the image carrier are cleaned. In an image forming apparatus provided with a cleaning member that performs cleaning, the cleaning member is normally held away from the surface of the charging roller, and is brought into contact with the surface of the charging roller for a certain period of time at predetermined timing intervals. There exists what comprised so that a member moving means might be provided (for example, refer patent document 1).
[0005]
In addition, in a conventional image forming apparatus, there is a technique in which a cleaning roller having a rotatable roller shape and made of the same material as a charging roller is brought into contact with the charging roller (see, for example, Patent Document 2).
[0006]
[Patent Document 1]
JP-A-7-128956 [Patent Document 2]
Japanese Patent Laid-Open No. 7-140762
[Problems to be solved by the invention]
However, the technique of Patent Document 1 has the following problems. In other words, this technique is configured to provide a cleaning member moving means for bringing the cleaning member into contact with the surface of the charging roller for a certain period of time at a predetermined time interval. The stain is mainly made from an external additive such as titanium oxide (TiO ₂ ), which is a component of the toner. The amount of adhesion varies greatly depending on the type of image actually formed, such as the print area and image density, and the predetermined time interval is set. At each opening timing, there is a problem that cleaning of the charging member becomes defective.
[0008]
In the image forming apparatus disclosed in Patent Document 1, since a cleaning member made of a felt material or a sponge material is used, titanium oxide having a particle size of about 50 nm, which is a main cause of contamination attached to the charging member. There is a problem that external additives such as (TiO ₂ ) cannot be efficiently removed, and cleaning defects still occur.
[0009]
In the technique of Patent Document 2, since the cleaning roller is made of the same single material as the charging roller, cleaning failure is liable to occur due to uneven wiping due to brush falling or deterioration of flicking performance. In order to avoid this, strict management of releasability, surface roughness, peripheral speed difference, friction coefficient, and the like is necessary, and there is a problem that the cost of the apparatus increases.
[0010]
In view of the above circumstances, an object of the present invention is to provide an image forming apparatus that can reliably remove external additives and other deposits with a simple configuration.
[0011]
[Means for Solving the Problems]
The image forming apparatus of the present invention that achieves the above object is a toner fixed on a recording medium by forming a toner image on an image carrier and finally transferring and fixing the toner image on the recording medium. In an image forming apparatus for forming an image consisting of an image,
A charging roller for charging the image carrier;
A brush that contacts the charging roller and removes toner adhering to the charging roller;
The brush is composed of a mixed hair material of a conductive first fiber material having flexibility and a second fiber material having higher rigidity than the first fiber material.
[0012]
In the image forming apparatus of the present invention, the image carrier is charged by the charging roller, a toner image is formed on the image carrier, and the toner image is finally transferred and fixed on the recording medium. An image consisting of a toner image is formed.
[0013]
The brush contacts the charging roller and removes toner adhering to the charging roller. This brush is composed of a mixed hair material of a conductive first fiber material having flexibility and a second fiber material having rigidity higher than that of the first fiber material, and is used for the toner adhering to the surface of the charging roll. Fine particles such as external additives are triboelectrically charged by the flexible conductive first fiber material and electrostatically adsorbed, and deposits that cannot be adsorbed are scraped and removed by the rigid second fiber material. . Moreover, the rigid 2nd fiber material plays the role of support, and prevents the fall of a hair-mixing material.
[0014]
It is preferable that the hair-mixing material has a hair length of the first fiber material longer than that of the second fiber material.
[0015]
It is preferable that the mixed hair material has a density of 10 to 60 T, and a number of filaments including the first fiber material and the second fiber material is 5 to 20 fibers / mm ² .
[0016]
It is preferable that the hair-mixing material has a tip formed in a tapered shape.
[0017]
It is preferable that the hair-mixing material has a rounded shape at an outer peripheral edge portion of the tapered surface.
[0018]
The brush preferably has a hair density of 10 to 50 hairs / cm ² of the mixed hair material.
[0019]
The brush is preferably one in which the hair-mixing material is coated with fluorine or a Teflon (registered trademark) material.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0021]
FIG. 1 shows a tandem type digital color copying machine as an embodiment of the image forming apparatus of the present invention.
[0022]
As shown in FIG. 1, the digital color copying machine includes an automatic document feeder (ADF) 3 that automatically feeds documents 2 one by one on the top of a main body 1 and the automatic document feeder 3. A document reading device 4 for reading an image of the document 2 being conveyed is provided. Except for the automatic document feeder (ADF) 3 and the document reading device 4, a digital color printer is constructed.
[0023]
The document reader 4 illuminates a document 2 placed on a platen glass 5 with a light source 6, and a reflected light image from the document 2 includes a full-rate mirror 7, half-rate mirrors 8 and 9, and an imaging lens 10. Scanning exposure is performed on an image reading element 11 composed of a CCD or the like via a reduction optical system, and the color material reflected light image of the original 2 is read at a predetermined dot density (for example, 16 dots / mm) by the image reading element 11. It is like that.
[0024]
The color material reflected light image of the document 2 read by the document reading device 4 is, for example, IPS (red (R), green (G), blue (B) (8 bits each) as document reflectance data of three colors. Image processing system) 12, and in this IPS 12, predetermined reflectivity data such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, frame deletion, color / movement editing, etc. are applied to the reflectance data of the document 2. Image processing is performed. The IPS 12 also performs predetermined image processing on image data sent from a personal computer or the like.
[0025]
The image data that has been subjected to the predetermined image processing by the IPS 12 as described above is also four colors of yellow (Y), magenta (M), cyan (C), and black (K) (each 8 pits) by the IPS 12. As described below, the image forming units 13Y, 13M, 13C, and 13K for each color of yellow (Y), magenta (M), cyan (C), and black (K) are converted. The ROS (Raster Output Scanner) 14 is used, and the ROS 14 as the image exposure apparatus performs image exposure with the laser beam LB in accordance with the original reproduction color material gradation data of a predetermined color.
[0026]
As shown in FIGS. 1 and 2, the main body 1 has four image forming units 13Y, 13M, 13C, and 13K of yellow (Y), magenta (M), cyan (C), and black (K). Are arranged in parallel at regular intervals in the horizontal direction.
[0027]
These four image forming units 13Y, 13M, 13C, and 13K are all configured in the same manner, and roughly divided, a photosensitive drum 15 as an image carrier that is rotationally driven at a predetermined speed, and the photosensitive drum. A charging roller 16 for primary charging that uniformly charges the surface of the drum 15 and an image exposure apparatus that forms an electrostatic latent image by exposing an image corresponding to a predetermined color on the surface of the photosensitive drum 15. The image forming apparatus includes a ROS 14, a developing device 17 that develops an electrostatic latent image formed on the photosensitive drum 15 with a predetermined color toner, and a cleaning device 18 that cleans the surface of the photosensitive drum 15. These photosensitive drums 15 and image forming members disposed in the periphery are integrally unitized, and can be individually replaced from the printer and the copying machine main body 1.
[0028]
The ROS 14 is configured in common to the four image forming units 13Y, 13M, 13C, and 13K, and modulates four semiconductor lasers (not shown) according to the original reproduction color material gradation data of each color, and these semiconductors. Laser light LB-Y, LB-M, LB-C, and LB-K are emitted from the laser in accordance with the gradation data. The ROS 14 may be individually configured for each of a plurality of image forming units. The laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the semiconductor laser are applied to the polygon mirror 19 through an f-theta lens (not shown), and are deflected and scanned by the polygon mirror 19. The The laser beams LB-Y, LB-M, LB-C, and LB-K deflected and scanned by the polygon mirror 19 are passed to an exposure point on the photosensitive drum 15 through an imaging lens (not shown) and a plurality of mirrors. Scanning exposure is performed obliquely from below.
[0029]
Since the ROS 14 scans and exposes an image on the photosensitive drum 15 from below, the ROS 14 receives toner from the four image forming units 13Y, 13M, 13C, and 13K, which are located above. Etc. may fall and be damaged. Therefore, the periphery of the ROS 14 is hermetically sealed by a rectangular parallelepiped frame 20, and four laser beams LB-Y, LB-M, LB-C, and LB-K are placed on the upper portion of the frame 20, Transparent glass windows 21Y, 21M, 21C, and 21K as shield members are provided for exposure on the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K.
[0030]
From the IPS 12, the image of each color is supplied to the ROS 14 provided in common to the image forming units 13Y, 13M, 13C, and 13K of each color of yellow (Y), magenta (M), cyan (C), and black (K). Data is sequentially output, and the laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the ROS 14 in accordance with the image data are scanned and exposed on the surface of the corresponding photosensitive drums 15 to statically. An electrostatic latent image is formed. The electrostatic latent images formed on the photosensitive drum 15 are respectively developed in yellow (Y), magenta (M), cyan (C), and black (K) colors by developing units 17Y, 17M, 17C, and 17K. Developed as a toner image.
[0031]
The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K are as follows. On the intermediate transfer belt 25 of the transfer unit 22 disposed over the image forming units 13Y, L3M, 13C, and 13K, the images are transferred in multiple by the four primary transfer rolls 26Y, 26M, 26C, and 26K. These primary transfer rolls 26Y, 26M, 26C, and 26K are disposed on the back side of the intermediate transfer belt 25 corresponding to the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K. The volume resistance values of the primary transfer rolls 26Y, 26M, 26C, and 26K in this embodiment are adjusted in resistance to 10 ⁵ to 10 ⁸ Ωcm. The primary transfer rolls 26Y, 26M, 26C, and 26K are connected to a transfer bias power source (not shown), and a transfer bias having a polarity opposite to a predetermined toner polarity (positive polarity in this embodiment) is predetermined. It is applied at the timing.
[0032]
The intermediate transfer belt 25 is wound around the drive roll 27, the tension roll 24, and the back-up roll 28 with a constant tension, and is a dedicated drive motor (not shown) having excellent constant speed. By the drive roll 27 that is rotationally driven by the rotation, it is circulated and driven at a predetermined speed in the direction of the arrow. The intermediate transfer belt 25 is made of, for example, a belt material (rubber or resin) that does not cause charge-up, and the volume resistance value of which is adjusted to about 10 ⁵ to 10 ¹² Ωcm is used. ing.
[0033]
The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 25 in multiple layers are pressed against the backup roll 28 as shown in FIG. The recording sheet 30 that has been secondarily transferred onto a recording sheet 30 as a recording medium by a pressing force and an electric field by the secondary transfer roll 29 and onto which the toner image of each color has been transferred is transferred to a fixing device 31 positioned above. It is conveyed. The secondary transfer roll 29 is in pressure contact with the side of the backup roll 28, and secondary-transfers each color toner image onto a recording paper 30 conveyed upward from below. The recording paper 30 to which the toner images of the respective colors are transferred is subjected to a fixing process with heat and pressure by a fixing device 31 and then discharged onto a discharge tray 33 provided on the upper portion of the main body 1 by a discharge roll 32. The
[0034]
The recording sheets 30 having a predetermined size are separated one by one by a nudger roll 35 and a sheet separating / conveying feed roll 36 from a sheet feeding device 34 disposed inside the apparatus main body 1. In this state, the paper is once transported to the registration roll 38 via the paper transport path 37 and stopped. The conveyance path 37 of the fed recording paper 30 is directed upward in the vertical direction. The recording paper 30 supplied from the paper feeding device 34 is sent to the secondary transfer position of the intermediate transfer belt 35 by a registration roll 38 that rotates at a predetermined timing.
[0035]
In the digital color copying machine (or printer), when full-color double-sided copying is performed, the recording paper 30 with the image fixed on one side is not discharged onto the discharge tray 33 as it is by the discharge roll 32. The conveyance direction is switched by a switching gate (not shown), and the sheet is conveyed to the duplex conveyance unit 40 via a pair of sheet conveyance rollers 39. In the double-sided conveyance unit 40, the recording paper 30 is conveyed again to the registration roll 38 with the front and back sides of the recording paper 30 reversed by a pair of conveyance rollers (not shown) provided along the conveyance path 41. Is discharged onto the discharge tray 33 after the image is transferred and fixed on the back surface of the recording paper 30.
[0036]
To the upper part of the main body 1, toner cartridges 44Y, 44M, 44C, and 44K that supply toner of a predetermined color to the developing device 17 of each color of yellow (Y), magenta (M), cyan (C), and black (K). Is provided.
[0037]
FIG. 2 shows details of each image forming unit of the digital color copying machine (or printer).
[0038]
The four image forming units 13Y, 13M, 13C, and 13K of yellow, magenta, cyan, and black are all configured similarly (only 13Y and 13M are shown here), and these four image forming units are formed. As described above, the units 13Y, 13M, 13C, and 13K are configured so that yellow, magenta, cyan, and black toner images are sequentially formed at predetermined timings. As described above, the image forming units 13Y and 13M are provided with the photosensitive drums 15 (15Y and 15M in this case), and the surfaces of these photosensitive drums 15 are uniformly provided by the charging roll 16 for primary charging. Charged.
[0039]
The surface of the photosensitive drum 15 is scanned and exposed to image forming laser light LB emitted from the ROS 14 according to the image data, and an electrostatic latent image corresponding to each color is formed. The laser beam LB that is scanned and exposed on the photosensitive drum 15 is set so as to be exposed from an obliquely lower side slightly to the right side immediately below the photosensitive drum 15. The electrostatic latent image formed on the photosensitive drum 15 is yellow, magenta, cyan, and black by the developing roll 17a of the developing unit 17 of each image forming unit 13Y, 13M, 13C, and 13K. The visible toner images are developed with the toners of the toner, and the visible toner images are sequentially transferred in multiple onto the intermediate transfer belt 25 by the charging of the primary transfer roll 26.
[0040]
Residual toner, paper dust, and the like are removed from the surface of the photosensitive drum 15 after the toner image transfer process by the cleaning device 18 to prepare for the next image forming process. The cleaning device 18 includes a cleaning blade 42, and the cleaning blade 42 removes residual toner, paper dust, and the like on the photosensitive drum 5. Further, as shown in FIG. 1, residual toner, paper dust, and the like are removed from the surface of the intermediate transfer belt 25 after the toner image transfer process is completed as shown in FIG. 1 to prepare for the next image forming process. The cleaning device 43 includes a cleaning member 43a and a cleaning blade 43b. The cleaning member 43a and the blade 42 remove residual toner and paper dust on the intermediate transfer belt 25.
[0041]
FIG. 3 shows a detailed view of the periphery of the photosensitive drum.
[0042]
As shown in the figure, a brush 45 for cleaning the surface of the charging roll 16 is provided. The brush 45 is swingably mounted about a fulcrum 50 positioned at one end in the width direction, and an eccentric cam 51 is provided on the back side of the brush 45 for each image forming unit 13. It is arranged. The eccentric cam 51 is attached so as to be swingable about a fulcrum 52. The eccentric cam 51 provided for each of the image forming units 13 is connected to a link 53 disposed so as to be movable in the horizontal direction. The link 53 is connected to a drive motor 54 with a reduction gear 55, It is connected to a rotating arm 57 that is rotationally driven through 56.
[0043]
By rotating the drive motor 54 in a predetermined direction by a predetermined amount, the link 53 is moved along the horizontal direction via the rotary arm 57, and the eccentric cams 51 connected to the link 53 are rotated. It is like that. Thus, when the eccentric cam 51 rotates, the back side of the brush 45 is pushed up by the eccentric cam 51, and the brush 45 comes into contact with the surface of the charging roll 16.
[0044]
As shown in FIG. 4, the brush 45 has a hair mixture 46 of a first fiber material (indicated by a solid line) 46 a and a second fiber material (indicated by a dotted line) 46 b, which is planted in a base cloth 47. Is affixed to the resin table 48.
[0045]
The first fiber material 46a is a flexible conductive fiber material, and the second fiber material 46b is a fiber material having higher rigidity than the first fiber material 46a (whether conductive or non-conductive). The hair-mixing material 46 is composed of stranded wires. In FIG. 4, a schematic diagram in which the first fiber material 46a and the second fiber material 46b are twisted one by one is shown, but actually the first fiber material 46a and the second fiber material 46b are composed of a plurality of fibers. It is configured.
[0046]
As described above, as the brush 45, the mixed hair material 46 in which both of the conductive first fiber material 46a having flexibility and the second fiber material 46b having higher rigidity than the first fiber material 46a are mixed as a stranded wire is used. As a result, fine particles such as toner external additives attached to the surface of the charging roll 16 are triboelectrically charged by the flexible conductive first fiber material 46a and electrostatically adsorbed. The kimono can be reliably removed by scraping with a rigid second fiber material 46b. Further, the rigid second fiber material 46b serves as a support, and prevents the hair mixture material 46 from falling down.
[0047]
In the mixed hair material 46, the first fiber material 46a is also longer than the second fiber material 46b, that is, the second fiber material 46b is up to the chain line L in FIG. 4, and the first fiber material 46a extends above the chain line. Yes. By comprising in this way, the effect | action of the triboelectric charging by the electroconductive 1st fiber material 46a which has a softness | flexibility, and the effect | action of the scraping by the 2nd fiber material 46b work more effectively, and it is more reliable. Can be removed.
[0048]
More preferably, the first fiber material 46a is preferably a belt (trade name) fiber made of PET (polyethylene terephthalate), and the second fiber material 46b is preferably a fiber made of 6-6 nylon. Further, the hair mixture 46 preferably has a density of 10 to 60 T (tex: 1000 m / g), and has a number of filaments of 5 to 20 including the first fiber material 46a and the second fiber material 46b. preferable. In addition, although the ratio of the fiber amount of the 1st fiber material 46a and the 2nd fiber material 46b is arbitrary, the 1st fiber material 46a is combined in 30 to 80%, and the 2nd fiber material 46b is combined in the range of 70 to 20%. And good results.
[0049]
Moreover, the hair-mixing material 46 has good cleaning properties when coated with fluorine or a Teflon-based material.
[0050]
As shown in FIG. 5, it is preferable to form a tapered surface 49 at the tip of the hair mixture 46. In this case, it is preferable to form a rounded portion 49 a at the outer peripheral edge portion of the tapered surface 49. By attaching the taper surface 49 in this way, the deposit on the charging roller 16 is scraped off at the pointed portion, and cleaning can be performed more effectively. Further, by rounding 49a at the edge of the taper surface 49, it is possible to prevent the edge from being chipped and sticking to the charging roller 16 and becoming an adhering substance.
[0051]
FIG. 6 shows the result of testing the cleaning property of the charging roller 16 by the brush 45.
[0052]
FIG. 6A shows the relationship between the density (T: tex) of the hair-mixing material 46 and the cleaning property. The density is 10 to 50 T and the cleaning property is good. If the density is outside this range, the cleaning property is deteriorated. .
[0053]
FIG. 6B shows the relationship between the density (f: the number of filaments) of the hair-mixing material 46 and the cleaning property. The density is 5 to 20 f, and the cleaning property is good. Yes.
[0054]
FIG. 6 (c) shows the relationship between the flocking density (k pieces / cm ² ) of the hair mixing material 46 and the cleaning property. The flocking density is 10 to 50 and the cleaning property is good. It is getting worse.
[0055]
FIG. 6 (d) shows the relationship between the running volume by the coating of the hair mixture 46 and the cleaning performance. The fluorine coating A and the Teflon-based material coating B have a cleaning performance at the same running volume as compared with the uncoated C. It is good.
[0056]
【The invention's effect】
As described above, according to the present invention, the mixed hair material obtained by mixing the conductive first fiber material having flexibility and the second fiber material having higher rigidity than the first fiber material is used as the brush. As a result, fine particles such as toner external additives adhering to the surface of the charging roll are electrostatically adsorbed by triboelectric charging by the flexible conductive first fiber material, and the adhering matter that cannot be adsorbed is rigid. It can be reliably removed by scraping with a second fibrous material. In addition, since the rigid second fiber material serves as a support, it is possible to prevent the hair mixture from falling down and to improve the durability.
[Brief description of the drawings]
FIG. 1 is a side view showing a main part of a tandem type digital color copying machine according to an embodiment of an image forming apparatus of the present invention.
FIG. 2 is a side view showing an image forming unit of the digital color copying machine shown in FIG.
FIG. 3 is an enlarged view of a photosensitive drum and a charging roller portion of the digital color copying machine shown in FIG.
FIG. 4 is a sectional view of a charging roller cleaning brush.
5A is an enlarged perspective view of a hair-mixing material for a cleaning brush, and FIG. 5B is a cross-sectional view taken along the line bb of FIG. 5A.
FIG. 6 is a graph showing the results of testing the cleaning performance of a brush with different hair mixing materials.
[Explanation of symbols]
15 Photosensitive drum (image carrier)
16 Charging roll (charging member)
30 Recording paper (recording medium)
45 Brush 46 Mixed Hair Material 46a First Fiber Material 46b Second Fiber Material 49 Tapered Surface 49a Roundness

Claims (1)

In an image forming apparatus for forming a toner image on an image carrier, and finally transferring and fixing the toner image on a recording medium to form an image composed of the toner image fixed on the recording medium.
A charging roller for charging the image carrier;
A brush that contacts the charging roller and removes toner adhering to the charging roller;
The brush is planted with a plurality of mixed hair materials obtained by twisting and mixing a conductive first fiber material having flexibility and a second fiber material having higher rigidity than the first fiber material ,
The first fiber material and the second fiber material that are twisted together in the hair mixture material are arranged such that the first fiber material extends to the charging roller side than the second fiber material, While the charging roller and the second fiber material are not in contact with each other and the charging roller and the first fiber material are in contact with each other, the adhering matter adhering to the surface of the charging roller is frictionally charged and electrostatically adsorbed. ,
The charging roller and the second fiber material are in contact with each other on the downstream side, and deposits that cannot be adsorbed by the first fiber material are scraped and removed by the second fiber material. apparatus.

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