JP6669006B2 - Brush roller and charging device - Google Patents

Description

  The present invention relates to a brush roller as a cleaning member, a charging device provided with the brush roller, and an image forming apparatus provided with the charging device.

  In an electrophotographic image forming apparatus, a charging device for charging an image carrier such as a photosensitive drum includes a charging roller for performing contact charging. On the surface of the charging roller that comes into contact with the image carrier, toner and toner external additives, fibers derived from paper, fillers, and the like may adhere. The charging roller may cause a partial current decrease due to a local resistance increase or a discharge hindrance due to contamination of a discharge site due to such deposits. As a result, poor charging of the image carrier may occur. I will. Therefore, the charging device is provided with a brush roller on which a large number of brush hairs are planted in order to remove deposits on the surface of the charging roller, and cleans the surface of the charging roller.

  Since the brush roller rotates with a speed difference from the charging roller while the tip of the brush bristles is in contact with the surface of the charging roller, the so-called bristle that the brush bristles in the rotating direction with use may occur. . When the bristle falls, the amount of the bristle biting into the charging roller and the rigidity of the bristle due to the tendency of the bristle to fall are reduced, and the cleaning property of the brush roller deteriorates.

  The brush roller disclosed in Patent Literature 1 is a brush roller in which the outer peripheral surface of a shaft is covered with a pile (brush bristle) in which electrostatic flocking is performed. The pile includes a plurality of types of piles having different fiber lengths, Plural kinds of piles are planted almost uniformly. For example, the shaft is covered with a first type of pile having a first fiber length and a second type of pile having a fiber length shorter than the first fiber length, and the rigidity of the second type of pile is reduced. It is equal to or higher than the stiffness of the first type of pile.

JP 2008-122484 A

  When long brush bristles and short brush bristles are mixed in the brush roller, the rigidity of the short brush bristles is higher than that of the long brush bristles. The brush roller formed of the same material and having long and short brush bristles has a higher rigidity than a brush roller including only long brush bristles because long brush bristles are supported by short brush bristles. I have. Further, if the rigidity of the short brush bristles is made higher than that of the long brush bristle, the rigidity of the brush roller is further increased.

  However, when the rigidity of the brush roller is increased, the contact load between the brush roller and the charging roller increases, and the driving load of the charging roller also increases. Since the charging roller rotates following the rotation of the image carrier, the charging roller may slip with respect to the rotation of the image carrier due to an increase in driving load. If the charging roller and the image carrier slip, uneven charging occurs locally, resulting in image defects. In addition, if the contact load is reduced by reducing the amount of bite of each brush bristle of the brush roller with respect to the charging roller, the cleaning property is reduced.

  In view of the above circumstances, an object of the present invention is to prevent brush hairs from falling down and reduce the contact load of the brush hairs.

  The brush roller of the present invention includes a core bar and two or more types of brush bristles implanted on the outer peripheral surface of the core bar, and the two or more types of brush bristles have at least a first bristle length. A first brush bristle formed; and a second brush bristle formed with a second bristle length shorter than the first bristle length and lower rigidity than the first brush bristle. I do.

  By adopting such a configuration, the brush roller supports the long first brush bristles with the short second brush bristles, thereby preventing the bristle of each brush bristles and increasing the rigidity of the short second brush bristles. By making it lower than the first brush bristle, the rigidity of each brush bristle can be reduced. Accordingly, the contact load of each brush bristle on the member to be cleaned can be reduced without reducing the amount of each brush bristle biting into the member to be cleaned. Therefore, the cleaning performance by the brush roller can be maintained high, and the driving load on the member to be cleaned can be suppressed.

  The second brush bristles may be formed of a material having a smaller Young's modulus than the first brush bristles, so that the second brush bristles are formed with lower rigidity than the first brush bristles.

  By adopting such a configuration, the rigidity of each short bristle can be reduced by making the rigidity of the short second bristle lower than that of the long first bristle with a simple configuration.

  The second brush bristles may be formed with a smaller fiber thickness than the first brush bristles, and thus may be formed with a lower rigidity than the first brush bristles.

  By adopting such a configuration, the rigidity of each short bristle can be reduced by making the rigidity of the short second bristle lower than that of the long first bristle with a simple configuration.

  The charging device of the present invention includes the above-described brush roller, and a charging roller that contacts the surface of the image carrier and charges the surface of the image carrier to a predetermined potential. The brush bristles are arranged so as to contact the surface of the charging roller to clean the surface of the charging roller.

  By adopting such a configuration, using a brush roller that reduces the stiffness of each brush bristle while preventing the bristle of each brush bristle, without reducing the amount of bite of each brush bristle into the charging roller, The contact load of each brush bristle on the charging roller can be reduced. Therefore, the cleaning performance of the brush roller can be maintained high, and the driving load of the charging roller can be suppressed. Along with this, it is possible to prevent charging unevenness of the charging roller and prevent image defects of the image carrier.

  An image forming apparatus according to the present invention includes the charging device described above.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to prevent the brush bristle falling down and to reduce the contact load of a brush bristle.

FIG. 1 is a cross-sectional view schematically illustrating a configuration of a color printer according to an embodiment of the invention. FIG. 1 is a cross-sectional view illustrating a photosensitive drum and its periphery in a color printer according to an embodiment of the present invention. FIG. 1 is a cross-sectional view schematically showing a charging device in a color printer according to an embodiment of the present invention.

  First, the overall configuration of a color printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. Hereinafter, for convenience of explanation, the front side of the paper in FIG. 1 is referred to as the front side of the color printer 1.

  The color printer 1 includes a box-shaped printer main body 2 (apparatus main body), a paper feed cassette 3 storing paper is provided at a lower portion of the printer main body 2, and a paper output tray 4 is provided at an upper portion of the printer main body 2. Provided.

  In the center of the printer body 2, an intermediate transfer belt 5 is provided between a plurality of rollers. Below the intermediate transfer belt 5, an exposure device 6 including a laser scanning unit (LSU) is disposed. . Below the intermediate transfer belt 5, four image forming units 7 are provided for each toner color (for example, four colors of yellow, cyan, magenta, and black). A secondary transfer roller 8 is provided at a right end of the intermediate transfer belt 5, and a belt cleaning device 9 is provided at a left end of the intermediate transfer belt 5. The secondary transfer roller 8 is arranged to face the bridge roller on the right side with the intermediate transfer belt 5 interposed therebetween, and forms a secondary transfer unit.

  As shown in FIGS. 1 and 2, a photoreceptor drum 10 (image carrier) is rotatably provided in each image forming unit 7. A charging device 11 is provided around the photoreceptor drum 10, The developing device 12, the primary transfer roller 13, the static eliminator 14, and the cleaning unit 15 are arranged in the order of the primary transfer process.

  On the right side of the printer main body 2, a paper transport path 16 is provided in a vertical direction. A paper feed unit is provided at an upstream end of the transport path 16, and a secondary transfer roller 8 is provided at a middle part of the transport path 16. A fixing device is provided at a downstream portion of the transport path 16, and a paper discharge section is provided at a downstream end of the transport path 16.

  Next, an image forming operation of the color printer 1 having such a configuration will be described. The color printer 1 starts an image forming operation when image data is input from an external computer or the like and an instruction to start printing is given. First, after the surface of the photoconductor drum 10 is charged by the charging device 11, an electrostatic latent image is formed on the surface of the photoconductor drum 10 by the laser beam (see the arrow P) from the exposure device 6. Next, the developing device 12 develops the electrostatic latent image into a toner image of a corresponding color. This toner image is primarily transferred onto the surface of the intermediate transfer belt 5 by the primary transfer roller 13. The above operation is sequentially repeated by each image forming unit 7 to form a full-color toner image on the intermediate transfer belt 5. The charge and toner remaining on the photosensitive drum 10 are removed by the charge remover 14 and the cleaning unit 15.

  On the other hand, the paper stored in the paper feed cassette 3 is taken out by the paper feed unit and transported on the transport path 16. This sheet is conveyed to the secondary transfer roller 8 at a predetermined timing, and the full-color toner image on the intermediate transfer belt 5 is secondarily transferred to the sheet by the secondary transfer roller 8. The sheet on which the toner image has been secondarily transferred is conveyed to a fixing device, and the toner image is fixed on the sheet by the fixing device. The sheet on which the toner image has been fixed is discharged to the sheet discharge tray 4 from the sheet discharge section. Note that toner and the like remaining on the intermediate transfer belt 5 are removed by the belt cleaning device 9.

  Next, each image forming unit 7 will be described with reference to FIG. Since the four image forming units 7 corresponding to the four color toners have the same configuration, one image forming unit 7 will be described below.

  In the image forming section 7, the photosensitive drum 10 is formed in a cylindrical shape that is long in the front-rear direction. The photoreceptor drum 10 is composed of, for example, a single-layer type photoreceptor having a photosensitive layer in which a charge generating agent and a charge transporting agent are contained in the same layer. The photoconductor coating liquid for forming the photoconductive layer of the photoconductor drum 10 is, for example, a binder of 5 parts by mass of a charge generating agent (metal-free phthalocyanine), 50 parts by mass of a hole transport agent, 35 parts by mass of an electron transport agent It is adjusted by mixing and dispersing 100 parts by mass of a resin (viscosity average molecular weight 67000) with 800 parts by mass of tetrahydrofuran in a ball mill for 50 hours. Then, this coating solution is applied on a conductive substrate by dip coating, and then dried with hot air at 100 ° C. for 40 minutes to obtain a photosensitive layer having a thickness of 36 μm (diameter: 30 mm).

  The charging device 11 is provided below the photosensitive drum 10 in the image forming unit 7 as shown in FIGS. 1 and 2, and as shown in FIGS. 2 and 3, a housing 20, a charging roller 21, And a brush roller 22. The charging device 11 is configured to apply a predetermined charging bias supplied from a charging bias power supply (not shown) to the charging roller 21. Hereinafter, an example of the charging device 11 provided below the photosensitive drum 10 will be described. However, the charging device 11 may be configured such that the opening 20 a of the housing 20 faces the peripheral surface of the photosensitive drum 10. 10 may be provided at any position. Hereinafter, details of the charging device 11 will be described.

  In the charging device 11, the housing 20 is formed in a box shape that is long in the axial direction (front-back direction) of the photosensitive drum 10. The housing 20 has an opening 20a at the upper end, and the opening 20a is arranged so as to face the lower side of the photosensitive drum 10. The housing 20 has, for example, a capacity capable of housing the charging roller 21 and the brush roller 22 arranged vertically.

  The charging roller 21 includes a cylindrical core 23 that is long in the front-rear direction, and a charging layer 24 provided on the outer peripheral surface of the core 23. The charging roller 21 is rotatably mounted near the upper opening 20a in the housing 20 with the core metal 23 as a rotation axis. The charging roller 21 is arranged so that a part (upper side) of the peripheral surface of the charging layer 24 is exposed to the outside (upper side) from the opening 20 a and is brought into contact with the lower side of the photosensitive drum 10. The charging roller 21 rotates in a counterclockwise direction in front view following the rotation of the photosensitive drum 10 (clockwise direction in front view). The core metal 23 of the charging roller 21 has, for example, an outer diameter of 8 mm. The charging layer 24 is made of, for example, a rubber containing epichlorohydrin rubber as a main component, and is laminated around the cored bar 23 with an outer diameter of 12 mm.

  The brush roller 22 includes a cylindrical metal core 25 that is long in the front-rear direction, and a number of bristles 26 provided on the outer peripheral surface of the metal core 25. The brush roller 22 is rotatably attached to the lower part in the housing 20 around the core metal 25 as a rotation axis. Further, as shown in FIG. 3, the brush roller 22 is spaced apart from the charging roller 21 by a predetermined center distance D (for example, 10.5 mm), and is a tip of a part (upper side) of a large number of brush bristles 26. Is arranged to contact the lower side of the charging roller 21.

  The brush roller 22 is connected to a driving unit (not shown) such as a motor, and the driving unit drives the brush roller 22 at a surface speed of 80% of the rotation speed of the charging roller 21 and in a direction opposite to the rotation direction of the charging roller 21. It is rotationally driven in the direction (clockwise in front view). The brush roller 22 has improved cleaning properties by providing a surface speed difference with respect to the charging roller 21.

  In the brush roller 22, the core metal 25 is formed, for example, with an outer diameter of 5 mm. A large number of brush bristles 26 are uniformly implanted on the core metal 25 coated with the adhesive by electrostatic flocking. The large number of brush bristles 26 has two or more types of brush bristles 26, and as shown in FIG. 3, at least a first brush formed with a first bristle length La (for example, a fiber length of 2.5 mm). It has bristles 26a and second brush bristles 26b formed with a second bristle length Lb (for example, a fiber length of 2.2 mm) shorter than the first bristle length La.

The first brush bristles 26a and the second brush bristles 26b are configured such that the rigidity of the second brush bristles 26b is lower than the rigidity of the first brush bristles 26a. For example, the first brush bristles 26a are formed of a material having a large Young's modulus (for example, conductive acrylic fiber having a fiber diameter of 4 dtex, Young's modulus: 3350 N / mm ² ). The second brush bristles 26b are formed of a material having a small Young's modulus (for example, conductive nylon fiber having a fiber diameter of 4 dtex, Young's modulus: 1700 N / mm ² ). As described above, the second brush bristles 26b are formed of a material having a smaller Young's modulus (about ２ Young's modulus) than the first brush bristles 26a, that is, a soft material, so that the second brush bristles 26b The rigidity is suppressed to be lower than the rigidity of the first brush bristles 26a.

  When the distance D between the charging roller 21 and the brush roller 22 whose outer diameter φ1 is 12 mm (that is, the distance from the shaft center to the outer peripheral surface is 6 mm) is set to 10.5 mm, the outer diameter φa at the tip is 10 mm ( That is, the first brush bristles 26a whose distance from the shaft center to the tip is set to 5 mm) bite into the charging roller 21 by 0.5 mm. In this case, the second brush bristles 26b whose outer diameter φb at the tip is set to 9.4 mm (that is, the distance from the axis center to the tip is 4.7 mm) bite into the charging roller 21 by 0.2 mm.

  The developing device 12 is provided below the photosensitive drum 10 on the downstream side of the charging device 11 in the rotation direction of the photosensitive drum 10. The developing device 12 includes, for example, a housing, a first stirring screw, a second stirring screw, a magnetic roller, a developing roller, and a developer regulating blade. It is arranged in contact with the drum 10.

  The primary transfer roller 13 is provided above the photosensitive drum 10 on the downstream side of the developing device 12 in the rotation direction of the photosensitive drum 10. The primary transfer roller 13 is disposed, for example, opposite to the photosensitive drum 10 with the intermediate transfer belt 5 interposed therebetween, and forms a primary transfer unit.

The static eliminator 14 is provided downstream of the primary transfer roller 13 in the rotation direction of the photoconductor drum 10 and on the right side of the photoconductor drum 10. The static eliminator 14 includes, for example, a static elimination lamp or the like in which a plurality of (for example, 12) LED chips are arranged at equal intervals in the front-rear direction. The static eliminator 14 is configured such that static elimination light from a plurality of LED chips of the static elimination lamp is uniformly irradiated in the longitudinal direction (front-back direction) of the photoconductor drum 10 so that the photoconductor surface light amount satisfies ² to 10 μJ / cm ^2. Is done.

  The cleaning unit 15 is provided downstream of the static eliminator 14 in the rotation direction of the photoconductor drum 10 and on the right side of the photoconductor drum 10. The cleaning unit 15 includes, as a cleaning blade, a rubber blade in which urethane rubber having a thickness of 2.0 mm and a free length of 11 mm is adhered onto a sheet metal with an adhesive, for example, and the tip of the cleaning blade is applied to the outer peripheral surface of the photosensitive drum 10. It is arranged in contact.

  According to the present embodiment, as described above, the brush roller 22 of the charging device 11 of the color printer 1 includes the core bar 25, two or more types of brush bristles 26 implanted on the outer peripheral surface of the core bar 25, Is provided. The two or more types of brush bristles 26 have at least a first brush bristles 26a formed with a first bristle length La, a second bristle length Lb shorter than the first bristle length La, and And second brush bristles 26b formed with lower rigidity than the first brush bristles 26a.

  The charging device 11 includes the brush roller 22 described above and a charging roller 21 that contacts the surface of the photosensitive drum 10 (image carrier) and charges the surface of the photosensitive drum 10 to a predetermined potential. The brush roller 22 is arranged so that two or more types of brush bristles 26 are brought into contact with the surface of the charging roller 21 to clean the surface of the charging roller 21.

  As described above, in the brush roller 22, the long first brush bristles 26a are supported by the short second brush bristles 26b, thereby preventing the bristle of each of the brush bristles 26 and increasing the rigidity of the short second brush bristles 26b. By making the bristles lower than one bristles 26a, the rigidity of each bristles 26 can be reduced. Thereby, the contact load of each brush bristle 26 on the member to be cleaned (charging roller 21) can be reduced without reducing the amount of bite of each brush bristle 26 into the member to be cleaned (charging roller 21). Therefore, the cleaning performance by the brush roller 22 can be maintained high, and the driving load on the member to be cleaned (charging roller 21) can be suppressed. Along with this, it is possible to prevent charging unevenness of the charging roller 21 and to prevent an image defect of the photosensitive drum 10.

  Further, according to the present embodiment, the second brush bristles 26b are formed of a material having a smaller Young's modulus than the first brush bristles 26a, and thus are formed with lower rigidity than the first brush bristles 26a. Thereby, the rigidity of the short second brush bristles 26b can be made lower than that of the long first brush bristles 26a with a simple configuration, and the rigidity of each brush bristles 26 can be reduced.

  In the present embodiment, the configuration of the brush roller 22 in which the second brush bristles 26b are formed of a material having a smaller Young's modulus than the first brush bristles 26a has been described, but the configuration of the brush roller 22 is not limited thereto. For example, in another embodiment, the brush roller 22 uses the first brush bristles 26a and the second brush bristles 26b of the same material (the same Young's modulus) to make the second brush bristles 26b thinner than the first brush bristles 26a. It may be formed with a thickness.

  Specifically, in another embodiment, the large number of brush bristles 26 are, as described above, at least first brush bristles formed with at least a first bristle length La (for example, a fiber length of 2.5 mm). 26a, and second brush bristles 26b formed with a second bristle length Lb (for example, a fiber length of 2.2 mm) shorter than the first bristle length La. Also, unlike the above, the first brush bristles 26a are formed of thick fibers (for example, conductive nylon fibers having a fiber diameter of 4 dtex), and the second brush bristles 26b are formed of thin fibers (for example, a fiber diameter of 2 dtex). (Conductive nylon fiber).

  In this manner, the second brush bristles 26b are formed with a thinner fiber thickness (about 1/2 fiber thickness) than the first brush bristles 26a, so that the rigidity of the second brush bristles 26b is increased by the first brush bristles. The stiffness of the bristles 26a can be reduced. Thereby, the rigidity of the short second brush bristles 26b can be made lower than that of the long first brush bristles 26a with a simple configuration, and the rigidity of each brush bristles 26 can be reduced.

  In addition, the first brush bristles 26a and the second brush bristles 26b may be configured with the same number, but may be adjusted by changing the number to change the rigidity. For example, the rigidities of the two may be made to differ greatly depending on the different Young's modulus or the different fiber thickness, and the rigidity of each may be finely adjusted by changing the number.

  In the present embodiment, the configuration in which the large number of brush bristles 26 of the brush roller 22 have the first brush bristles 26a and the second brush bristles 26b having different bristle lengths has been described. It is not limited to. For example, in other embodiments, the multiple bristles 26 may have three or more types of bristles 26 of different bristle lengths. In this case, the rigidity of the other bristles 26 is set to be smaller than that of the longest bristles 26 among the three or more types of bristles 26.

  In the present embodiment, the example in which the brush roller 22 is applied to the charging device of the image forming unit 7 has been described, but the application example of the brush roller 22 is not limited thereto. For example, in another embodiment, the brush roller 22 may be applied to a belt cleaning device 9 that cleans the rotating intermediate transfer belt 5 or a cleaning device that cleans another rotating member to be cleaned.

  In the present embodiment, the case where the configuration of the present invention is applied to the color printer 1 has been described. However, in another different embodiment, the present invention is applied to other image forming apparatuses such as a monochrome printer, a copier, a facsimile, and a multifunction peripheral. A configuration may be applied.

1 color printer (image forming device)
Reference Signs List 5 intermediate transfer belt 7 image forming section 9 belt cleaning device 10 photoconductor drum (image carrier)
DESCRIPTION OF SYMBOLS 11 Charging device 20 Case 20a Opening 21 Charging roller 22 Brush roller 23 Core bar 24 Charging layer 25 Core bar 26 Brush bristles 26a First brush bristles 26b Second brush bristles

Claims (4)

A brush roller for cleaning a charging roller of a charging device provided in the image forming apparatus,
A cored bar,
And two or more types of brush bristles implanted on the outer peripheral surface of the cored bar,
The two or more types of brush bristles are at least a first brush bristles made of conductive acrylic fibers formed with a first bristle length, a second bristle length shorter than the first bristle length, and A second brush bristle made of conductive nylon fiber, formed with lower rigidity than the first brush bristle,
A brush roller, wherein the two or more types of brush bristles are arranged to contact the surface of the charging roller to clean the surface of the charging roller.   The brush roller according to claim 1, wherein the second brush bristles are formed of a material having a smaller Young's modulus than the first brush bristles.   2. The brush roller according to claim 1, wherein the second brush bristles are formed with the same fiber thickness smaller than the first brush bristles. 3. A brush roller according to any one of claims 1 to 3,
A charging roller that contacts the surface of the image carrier and charges the surface of the image carrier to a predetermined potential.

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