JP2007178612A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stable cleaning performance by excellently removing a stuck foreign matter while restraining damage given to a cleaning roll. <P>SOLUTION: A projected loosening member 144 provided in a casing 140 is provided to contact with/separate from a cleaning roll 100 for cleaning a charging roll 14 and made of sponge. The loosening member 144 is made to bite at the outer peripheral surface of the cleaning roll 100 and presses it partially when it approaches thereto. Since the foreign matter stuck to the cleaning roll 100 is loosened and its sticking force is weakened by the pressing of the loosening member 144, foreign matter discharging property is improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method, and more particularly, a contact charging method that charges the surface of an image carrier while rotating in contact with the rotationally driven image carrier. The present invention relates to an image forming apparatus having a charging roll and a cleaning member for the charging roll.

  In recent years, as a charging device for an image forming apparatus such as a copying machine or a printer using an electrophotographic method, in order to suppress ozone emission, reduce the size of the apparatus, and reduce the high-voltage power supply cost, a conventional scorotron or the like can be used. Instead of the non-contact type charger, a roller charger (BCR) that is in contact with or close to the photoreceptor is used.

  In such a contact charging type charging device, since the charging roll is always in contact with the image carrier, there is a problem that the surface of the charging roll is liable to be contaminated by foreign matter. The surface of the image carrier on which the image forming operation is repeatedly performed passes through a cleaning process for removing foreign matter such as residual toner after transfer on the downstream side of the transfer process, and then enters the charging process area. Even after the process, a part of the toner and an external additive of the toner, such as finer particles than the toner, remain on the image carrier without being cleaned and adhere to the surface of the charging roll. The foreign matter adhering to the surface of the charging roll causes unevenness in the surface resistance value of the charging roll, resulting in abnormal discharge or unstable discharge, which deteriorates charging uniformity.

Therefore, in order to improve such problems, the surface of the charging roll is brought into contact with a surface of the rotating charging roll by rotating a cleaning roll made of a roll-shaped sponge member or the like, or by rotating the brush roll in contact with the surface of the charging roll. A technique for satisfactorily cleaning the dirt is proposed (see, for example, Patent Documents 1 and 2). In the configuration using the brush roll, the edge of the scraper is brought into contact with the brush roll, so that foreign matters such as toner staying on the brush roll are scraped off and forcedly discharged.
JP-A-5-297690 Japanese Patent Laid-Open No. 4-60660

  However, even if the scraper as described above is used for a cleaning roll formed of a member having elasticity or foaming properties such as sponge, foreign matter cannot be removed well, and further, the cleaning roll is formed by the edge of the scraper. There is a problem that the cleaning performance is deteriorated.

  In consideration of the above-described facts, the present invention provides an image forming apparatus capable of satisfactorily removing attached foreign matter while suppressing damage to a cleaning roll for cleaning a charging roll and maintaining stable cleaning performance. Is an issue.

  In order to achieve the above object, an invention according to claim 1 is directed to an image carrier, a charging roll for charging the image carrier, a cleaning roll for cleaning the charging roll, and an axis of an outer peripheral surface of the cleaning roll. And a loosening member that is disposed across the direction and loosens foreign matter adhering to the cleaning roll.

  In the present invention, in the charging roll for charging the image carrier in image formation, foreign matters such as toner adhering to the roll surface are cleaned by the cleaning roll. In this cleaning roll, the outer peripheral surface is pressed in the axial direction by the loosening member, so that the foreign matter such as the adhered toner is loosened and the adhesion force is weakened. As a result, even when the cleaning roll is formed of an elastic or foaming member such as a sponge, the foreign matter can be satisfactorily removed from the cleaning roll using, for example, another foreign matter collecting means without damaging the cleaning roll as in a scraper or the like. The cleaning performance for the charging roll can be stably maintained. Therefore, the charging performance to the image carrier by the charging roll is improved, and with this image forming apparatus, image defects due to poor charging of the image carrier can be suppressed and high-quality image formation can be realized.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the foreign matter is reversely transferred from the cleaning roll to the image carrier through the charging roll and collected.

  In the present invention, the foreign matter that has been loosened by the loosening member and weakened its adhesion to the cleaning roll is reversely transferred from the cleaning roll to the charging roll, and further reversely transferred from the charging roll to the image carrier, for example, an image carrier. Is collected by an image carrier cleaning means such as a blade for cleaning the image. Thereby, it is not necessary to provide a dedicated foreign material collecting means for collecting and removing foreign materials from the cleaning roll, and the configuration can be simplified.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect of the present invention, the image forming apparatus further comprises contact / separation means for contacting and separating the loosening member with respect to the cleaning roll.

  In the present invention, for example, when the rotation of the cleaning roll is pressed against the loosening member when the image forming apparatus is stopped, the pressing portion may be deformed and the cleaning performance may be deteriorated. On the other hand, if the loosening member is moved by the contacting / separating means and is in contact with / separating from the cleaning roll, by separating the loosening member from the cleaning roll at the time of non-image formation or when the rotation of the cleaning roll is stopped, The deterioration of the cleaning performance due to such deformation of the cleaning roll can be prevented.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the loosening member includes a convex portion, and the convex portion is provided on the outer peripheral surface of the cleaning roll. It is characterized by being arranged to bite in.

  In the present invention, a convex portion such as a rib provided on the loosening member, or a convex portion provided on the end portion of the loosening member formed in a bar shape or the like is bitten into the outer peripheral surface of the cleaning roll and pressed. As a result, the loosening force against the foreign matter is strengthened, and the foreign matter dischargeability from the cleaning roll is enhanced.

  A fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, further comprising a casing that covers the charging roll and the cleaning roll, wherein the loosening member is arranged in the casing. It is characterized by being installed.

  In the present invention, the loosening member installed in the vicinity of the cleaning roll is disposed in the casing that covers the charging roll and the cleaning roll, so that installation in a space-saving manner is possible.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the distance between the casing and the surface of the image carrier is reduced as the loosening member moves closer to the cleaning roll. It is said.

  In the present invention, as the loosening member moves closer to the cleaning roll, the distance between the casing covering the charging roll and the cleaning roll and the surface of the image carrier is reduced, so that the foreign matter can be discharged from the cleaning roll due to the loosening effect. Along with the improvement, entry of the toner cloud into the casing can be suppressed, and toner contamination of the charging roll and the cleaning roll can be prevented.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the loosening member has irregularities in the axial direction.

  In the present invention, by pressing the outer peripheral surface of the cleaning roll with the loosening member having an unevenness in the axial direction, the pressing force to the cleaning roll is changed, and the loosening force is strengthened.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the image forming apparatus further includes a moving unit that reciprocally moves the loosening member relative to the cleaning roll. It is a feature.

  In the present invention, the unwinding member is reciprocated in the axial direction with respect to the cleaning roll, whereby the pressing force to the cleaning roll is changed and the unwinding force is strengthened. In particular, when the present invention is applied to the configuration of the seventh aspect, the entire outer peripheral surface of the cleaning roll can be pressed evenly with the loosening member having the unevenness in the axial direction, and the foreign matter can be discharged from the cleaning roll. Further enhanced.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the pressing force of the loosening member that presses the cleaning roll is directed upstream in the rotation direction of the cleaning roll. It is characterized by adding.

  In the present invention, by applying the pressing force of the loosening member toward the upstream side in the rotation direction of the cleaning roll, the loosening force is strengthened and the foreign matter discharging property from the cleaning roll is further enhanced.

  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the pressing force of the loosening member that presses the cleaning roll is directed downstream in the rotation direction of the cleaning roll. It is characterized by adding.

  In the present invention, the load torque applied to the cleaning roll can be reduced by applying the pressing force of the loosening member toward the downstream side in the rotation direction of the cleaning roll. For example, the cleaning roll is configured to rotate following the charging roll. In this case, the decrease in followability is suppressed.

  According to the image forming apparatus of the present invention, damage to the cleaning roll for cleaning the charging roll can be suppressed, and the adhered foreign matter can be satisfactorily removed to maintain stable cleaning performance.

  An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

(Configuration of image forming apparatus)
An image forming apparatus 10 according to the present embodiment shown in FIG. 1 is a four-cycle full-color laser printer. As shown in the drawing, a photosensitive drum 12 can be rotated in the apparatus at a position slightly upper right from the center. It is arranged. As this photosensitive drum 12, for example, a photosensitive cylindrical body whose surface is coated with a photosensitive layer made of OPC or the like is used, and is rotated at a predetermined process speed along the direction of an arrow by a motor (not shown). Driven.

  The surface of the photosensitive drum 12 is charged to a predetermined potential by a charging roll 14 disposed almost directly below the photosensitive drum 12, and then exposed to a laser beam LB by an exposure device 16 disposed below the charging roll 14. Image exposure is performed, and an electrostatic latent image according to image information is formed.

  The electrostatic latent image formed on the photosensitive drum 12 has yellow (Y), magenta (M), cyan (C), and black (K) developing devices 18Y, 18M, 18C, and 18K in the circumferential direction. The toner is developed by a rotary developing device 18 disposed along the toner image to form a toner image of a predetermined color.

  At this time, charging, exposure, and development processes are repeated a predetermined number of times on the surface of the photosensitive drum 12 in accordance with the color of the image to be formed. In the developing process, the rotary developing device 18 rotates, and the corresponding color developing devices 18Y, 18M, 18C, and 18K move to a developing position facing the photosensitive drum 12.

  For example, when a full-color image is formed, the charging, exposing, and developing processes are performed on the surface of the photosensitive drum 12 in yellow (Y), magenta (M), cyan (C), and black (K) colors. The toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is sequentially formed on the surface of the photosensitive drum 12. When the toner image is formed, the number of rotations of the photosensitive drum 12 varies depending on the size of the image. For example, in the case of A4 size, one image is obtained by rotating the photosensitive drum 12 three times. It is formed. That is, a toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the surface of the photosensitive drum 12 every time the photosensitive drum 12 rotates three times. Is done.

  An intermediate transfer belt 20 is wound around the outer periphery of the photosensitive drum 12 for yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drum 12. At the primary transfer position, the images are transferred onto the intermediate transfer belt 20 by the primary transfer roll 22 while being superimposed on each other.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 20 are recorded on a recording sheet 24 fed at a predetermined timing. The images are collectively transferred by the secondary transfer roll 26.

  On the other hand, the recording paper 24 is fed out from a paper feed cassette 28 disposed at the lower part of the image forming apparatus 10 by a pickup roll 30 and is fed in a state of being fed one by one by a feed roll 32 and a retard roll 34. The toner image is transferred to the secondary transfer position of the intermediate transfer belt 20 in synchronization with the toner image transferred onto the intermediate transfer belt 20 by the registration roll 36.

  The intermediate transfer belt 20 includes a wrap-in roll 38 that specifies the wrap position of the intermediate transfer belt 20 on the upstream side in the rotational direction of the photosensitive drum 12 and a toner image formed on the photosensitive drum 12 as an intermediate transfer belt. A primary transfer roll 22 that is transferred onto the intermediate transfer belt 20, a wrap-out roll 40 that specifies the wrap position of the intermediate transfer belt 20 on the downstream side of the wrap position, and a backup that contacts the secondary transfer roll 26 via the intermediate transfer belt 20. The roll 42, the first cleaning backup roll 46 facing the cleaning device 44 of the intermediate transfer belt 20, and the second cleaning backup roll 48 are stretched with a predetermined tension and circulated at a predetermined process speed. For example, it is driven as the photosensitive drum 12 rotates so as to move.

  Here, in order to reduce the size of the image forming apparatus 10, the intermediate transfer belt 20 is configured such that a cross-sectional shape on which the intermediate transfer belt 20 is stretched is a flat and elongated substantially trapezoidal shape.

  The intermediate transfer belt 20 includes a photosensitive drum 12, a charging roll 14, an intermediate transfer belt 20, a plurality of rolls 22, 38, 40, 42, 46, and 48 that stretch the intermediate transfer belt 20, and an intermediate transfer belt. The cleaning device 44 for 20 and the cleaning device 78 for the photosensitive drum 12 described later integrally form an image forming unit 52. Therefore, the entire image forming unit 52 can be removed from the image forming apparatus 10 by opening the upper cover 54 of the image forming apparatus 10 and lifting the handle (not shown) provided on the upper part of the image forming unit 52 by hand. It has become.

  On the other hand, the cleaning device 44 for the intermediate transfer belt 20 includes a scraper 58 disposed so as to come into contact with the surface of the intermediate transfer belt 20 stretched by the first cleaning backup roll 46, and a second cleaning backup roll 48. And a cleaning brush 60 disposed so as to be in pressure contact with the surface of the stretched intermediate transfer belt 20. Residual toner and paper dust removed by the scraper 58 and the cleaning brush 60 are contained in the cleaning device 44. It has come to be collected.

  The cleaning device 44 is disposed so as to be able to swing counterclockwise in the drawing with the swing shaft 62 as the center. Until the secondary transfer of the final color toner image is completed, the intermediate transfer belt is provided. It is configured to retreat to a position separated from the surface of the surface 20 and to contact the surface of the intermediate transfer belt 20 when the secondary transfer of the final color toner image is completed.

  Further, the recording paper 24 onto which the toner image has been transferred from the intermediate transfer belt 20 is conveyed to a fixing device 64 and is heated and pressurized by the fixing device 64 to fix the toner image on the recording paper 24. Thereafter, in the case of single-sided printing, the recording paper 24 on which the toner image has been fixed is discharged as it is onto a discharge tray 68 provided at the top of the image forming apparatus 10 by a discharge roll 66.

  On the other hand, in the case of double-sided printing, the recording paper 24 on which the toner image is fixed on the first surface (front surface) by the fixing device 64 is not directly discharged onto the discharge tray 68 by the discharge roll 66 but is discharged by the discharge roll 66. With the rear end portion of the recording paper 24 being held, the discharge roller 66 is reversed, the conveyance path of the recording paper 24 is switched to the double-sided paper conveyance path 70, and the double-sided paper conveyance path 70 is disposed. In the state where the front and back of the recording paper 24 are reversed by the transport roller 72 thus transferred, the recording paper 24 is again transported to the secondary transfer position of the intermediate transfer belt 20 and the toner image is transferred to the second surface (back surface) of the recording paper 24. . Then, the toner image on the second surface (back surface) of the recording paper 24 is fixed by the fixing device 64, and the recording medium 24 is discharged onto the discharge tray 68.

  Furthermore, a manual feed tray 74 can be attached to the side surface of the image forming apparatus 10 so as to be freely opened and closed. An arbitrary size and type of recording paper 24 placed on the manual feed tray 74 is fed by a paper feed roll 76, and a secondary transfer position of the intermediate transfer belt 20 via a transport roll 73 and a registration roll 36. The image can be formed on the recording paper 24 of any size and type.

  The surface of the photosensitive drum 12 after the toner image transfer process is completed is cleaned by the cleaning blade 80 of the cleaning device 78 disposed obliquely below the photosensitive drum 12 every time the photosensitive drum 12 rotates once. Residual toner, paper dust, and the like are removed to prepare for the next image forming process.

  As shown in FIG. 2, a charging roll 14 is disposed below the photosensitive drum 12 so as to be in contact with the photosensitive drum 12. The charging roll 14 has a conductive layer 14B formed around a conductive shaft 14A, and the shaft 14A is rotatably supported. A cleaning roll 100, which is a roll-shaped cleaning member that contacts the surface of the charging roll 14, is provided on the lower side of the charging roll 14 opposite to the photosensitive drum 12. The cleaning roll 100 has a sponge layer 100B formed around a shaft 100A, and the shaft 100A is rotatably supported.

  The cleaning roll 100 is pressed against the charging roll 14 with a predetermined load, and the sponge layer 100 </ b> B is elastically deformed along the peripheral surface of the charging roll 14 to form the nip portion 101. The photosensitive drum 12 is driven to rotate clockwise (in the direction of arrow 2) in FIG. 2 by a motor (not shown), and the charging roll 14 is driven to rotate in the direction of arrow 4 as the photosensitive drum 12 rotates. Further, the roll-shaped cleaning roll 100 is driven to rotate in the direction of the arrow 6 by the rotation of the charging roll 14.

  As the cleaning roll 100 is driven to rotate, dirt (foreign matter) such as toner and external additives attached to the surface of the charging roll 14 is cleaned by the cleaning roll 100. Then, when the foreign matter is taken into the foam cell of the cleaning roll 100 and the collected foreign matter aggregates to an appropriate size, the cleaning roll 100 passes the charging roll 14 to the photosensitive drum 12. Returned and recovered by the cleaning device 78 for cleaning the photosensitive drum 12, the maintenance of the cleaning performance is continued.

(Configuration of charging roll and cleaning roll)
Here, the charging roll (BCR) 14 and the cleaning roll 100 of this embodiment will be described.

  As described above, the charging roll 14 is disposed in contact with the surface of the photosensitive drum 12 and applies a DC voltage or an AC voltage to the DC voltage to charge the surface of the photosensitive drum 12. Further, the shape is a roll shape in which a resistance elastic layer constituting the charging layer 14B is provided around the core constituting the shaft 14A, and the resistance elastic layer is formed from the outside and the elastic layer supporting them. A configuration in which the layers are divided in order is also possible. Furthermore, a protective layer can be provided on the outside of the resistance layer as needed to impart durability and contamination resistance to the charging roll 14.

  Hereinafter, the case where an elastic layer, a resistance layer, and a protective layer are provided on the core material will be described in more detail.

  The core material is conductive and generally used is iron, copper, brass, stainless steel, aluminum, nickel, or the like. Also, a material other than metal can be used as long as it has conductivity and appropriate rigidity. For example, a resin molded product in which conductive particles are dispersed, ceramics, or the like can be used. In addition to the roll shape, a hollow pipe shape can also be used.

  The elastic layer is made of a material having conductivity or semiconductivity, and generally is a material in which conductive particles or semiconducting particles are dispersed in a resin material or a rubber material. Polyester resin, acrylic resin, melamine resin, epoxy resin, urethane resin, silicon resin, urea resin, polyamide resin, etc. are used as the resin material, and ethylene-propylene rubber, polybutadiene, natural rubber are used as the rubber material. Polyisobutylene, chloroprene rubber, silicon rubber, urethane rubber, epichlorohydrin rubber, fluorosilicone rubber, ethylene oxide rubber, or a foamed material obtained by foaming them is used.

  Conductive particles or semiconductive particles include carbon black, zinc, aluminum, copper, iron, nickel, chromium, titanium and other metals, ZnO-Al2O3, SnO2-Sb2O3, In2O3-SnO2, ZnO-TiO2, MgO-Al2O3, Metal oxides such as FeO-TiO2, TiO2, SnO2, Sb2O3, In2O3, ZnO, MgO and ionic compounds such as quaternary ammonium salts can be used. These materials can be used alone or in combination of two or more. May be used. Furthermore, you may mix the 1 type (s) or 2 or more types of organic fillers, such as inorganic fillers, such as a talc, an alumina, and a silica, and the fine powder of a fluororesin or a silicon rubber, as needed.

  As the material of the resistance layer and the protective layer, conductive particles or semiconductive particles are dispersed in a binder resin to control the resistance. The resistivity is 10 ^ 3 to 10 ^ 14 Ωcm, preferably 10 ^ 5 10 ^ 12Ωcm, more preferably 10 ^ 7-10 ^ 12Ωcm. Moreover, as a film thickness, 0.01-1000 micrometers, Preferably it is 0.1-500 micrometers, More preferably, 0.5-100 micrometers is good. As binder resin, acrylic resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxymethylated nylon, polyurethane resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin, PFA, FEP, A polyolefin resin such as PET, a styrene butadiene resin, a melamine resin, an epoxy resin, a urethane resin, a silicon resin, a urea resin, or the like is used.

  As the conductive particles or the semiconductive particles, one or more of ionic compounds such as carbon black, metal, metal oxide, and quaternary ammonium salt exhibiting ionic conductivity, which are the same as those of the elastic layer, may be used. Mixed. If necessary, antioxidants such as hindered phenols and hindered amines, inorganic fillers such as clay, kaolin, talc, silica and alumina, organic fillers such as fine powder of fluororesin and silicon resin, silicone oil, etc. 1 type (s) or 2 or more types, such as a lubricant, can be added. Further, a surfactant, a charge control agent and the like are added as necessary.

  As a means for forming these layers, a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like can be used.

  The cleaning roll 100 is formed of a core material constituting the shaft 100A and a porous elastic layer constituting a sponge layer 100B formed on the peripheral surface of the core material, and contacts the surface of the charging roll 14 as described above. Arranged.

  As a material of the core material, a material that supports the porous elastic layer and has a rigidity that can maintain a contact state with an appropriate pressure contact force to the charging roll 14 is used. Generally, iron, copper, brass, In addition to metals such as stainless steel, aluminum, and nickel, resin molded products, ceramics, and the like in which conductive particles are dispersed, and inorganic fillers are dispersed. In addition to the roll shape, a hollow pipe shape can also be used.

  The porous elastic layer is a roll-like sponge formed at a predetermined cell density. For example, ether-based urethane foam, polyethylene foam, polyolefin foam, melamine foam, micropolymer, or the like can be used.

  Taking a polyurethane foam as an example, the production method will be briefly described. It is produced using a polyol, isocyanate, water, a catalyst (amine catalyst, metal catalyst, etc.) and a foam stabilizer (surfactant). Additives such as are used. When these raw materials are mixed and stirred, a chemical reaction occurs, and a urethane resin foam can be obtained.

(First embodiment)
Next, the support structure for the charging roll 14 and the cleaning roll 100 according to the first embodiment and the loosening member for loosening the foreign matter attached to the cleaning roll 100 will be described in detail.

  As shown in FIGS. 3 and 4, in this embodiment, the charging roll 14 and the cleaning roll 100 are assembled to a single frame 120 via a pair of bearing members 110 and accommodated in the frame 120, and further photosensitive. The body drum 12 is also assembled to the frame 120 and unitized.

  As shown in FIG. 7, one bearing member 110 is formed in a rectangular parallelepiped shape (block shape) and has a single configuration. The bearing member 110 is formed of a synthetic resin material such as polyacetal or polycarbonate having high rigidity, high slidability, and excellent wear resistance. In order to further improve the wear resistance, the synthetic resin material may contain glass fibers, carbon fibers, or the like.

  The bearing member 110 is formed with two bearing holes 112 and 114 arranged at predetermined intervals along the longitudinal direction (vertical direction in FIG. 4). A support portion 14 a provided at the end of the shaft 14 </ b> A of the charging roll 14 is rotatably inserted into one bearing hole 112, and is provided at the end of the shaft 100 </ b> A of the cleaning roll 100 in the other bearing hole 114. The support part 100a is rotatably inserted.

  As described above, the charging roll 14 in which the support portions 14a at both ends of the shaft 14A are pivotally supported by the pair of bearing members 110 and the cleaning roll 100 in which the support portions 100a at both ends of the shaft 100A are pivotally supported are as described above. The cleaning roll 100 is pressed against the charging roll 14 with a predetermined load, and the sponge layer 100B is elastically deformed along the peripheral surface of the charging roll 14 to form the nip portion 101 (see FIG. 2). The relative distance in the pressure contact direction is kept constant. Furthermore, the positional relationship in the direction orthogonal to the pressure contact direction (substantially tangential direction of the contact portion (nip portion 101)) is also kept constant, and the relative position is kept constant, thereby keeping the nip width constant. .

  As shown in FIGS. 3 and 4, the frame 120 has the above-described pair at both ends (the left and right side ends in FIGS. 3 and 4) along the axial direction of the charging roll 14 and the cleaning roll 100 in the main body 122. A pair of attachment portions 124 to which the bearing member 110 is attached are integrally provided.

  A guide groove 126 is formed in the attachment portion 124 along the extending direction of the attachment portion 124. The bearing member 110 is inserted into the guide groove 126 and disposed on the tip end side thereof. The bearing member 110 is guided by the guide groove 126 and extends in the extending direction of the mounting portion 124 (the direction in which it is in contact with and away from the photosensitive drum 12). It is possible to slide along.

  The outer surface sides of the pair of attachment portions 124 are thick and the front end side is extended, and a pair of bearing portions 132 that pivotally support the photosensitive drum 12 is provided at the front end portion. A bearing hole 134 is coaxially formed in the pair of bearing portions 132, and the support portion 12 a provided at the end of the shaft 12 </ b> A is rotatably inserted into each bearing hole 134. The charging roll 14 and the cleaning roll 100 are assembled to the frame 120.

  A compression coil spring 128 that urges the bearing member 110 toward the photosensitive drum 12 is provided on the base end side in the guide groove 126. The bearing member 110 is biased toward the photosensitive drum 12 by the spring force of the compression coil spring 128 (in the direction of arrow 8), and the charging roll 14 is in pressure contact with the photosensitive drum 12.

  As shown in FIGS. 5 and 6, a casing 140 covering the charging roll 14 and the cleaning roll 100 is disposed around the charging roll 14 and the cleaning roll 100 except for the photosensitive drum 12 side (the upper side in the drawing). Yes. The casing 140 has a substantially U-shaped cross-section with an open top surface, and includes a casing body 142 that extends along the axial direction of the cleaning roll 100 (see FIGS. 3 and 4). A loosening member 144 for loosening foreign matter adhering to the cleaning roll 100 is provided at the approximate center. The loosening member 144 has a substantially triangular cross-section projecting upward from the bottom surface and extends in parallel with the axial direction of the cleaning roll 100. The top surface portion is formed in a circumferential surface shape, and the convex surface portion is formed by the top surface portion. It is configured.

  As shown in FIGS. 3 and 4, the casing 140 (casing body 142) is slidable in the direction of coming into contact with and separating from the cleaning roll 100 on the inner side surfaces of the pair of attachment portions 124 provided on the frame 120. A plurality of eccentric cams 146 are arranged on the lower side of the casing 140. Each eccentric cam 146 is attached to a cam shaft 148 disposed in parallel with the axial direction of the cleaning roll 100 at a predetermined interval and in the same phase, and the cam shaft 146 rotates to a plurality of bearing portions 150 provided on the bottom surface of the frame 120. The cam surface 146A is in contact with the lower surface of the casing 140 in this state (see FIGS. 5 and 6). A rotating gear 152 is attached to the camshaft 148, and a driving gear 156 of a driving motor 154 attached on the bottom surface of the frame 120 is engaged with the rotating gear 152 gear.

  When the drive motor 154 is rotationally driven, a rotational force is transmitted to the cam shaft 148 via the drive gear 156 and the rotational gear 152, and each eccentric cam 146 rotates. When the image forming apparatus 10 forms an image, as shown in FIGS. 3 and 5, the casing 140 is pushed up by the eccentric cam 146, and the loosening member 144 is loosened on the outer peripheral surface of the sponge layer 100 </ b> B of the rotating cleaning roll 100. The top surface portion (convex shape portion) of the material bites in the axial direction and partially presses the outer peripheral surface of the sponge layer. Further, as the casing 140 moves upward, that is, as the loosening member 144 moves closer to the cleaning roll 100, the gap between the casing 140 and the surface of the photosensitive drum 12 is reduced, and a gap is formed between them. Is reduced.

  Further, when the rotation of the cleaning roll 100 is stopped during non-image formation or when the apparatus is stopped, the eccentric cam 146 is substantially half-rotated from that state as shown in FIGS. 4 and 6, and the casing 140 is lowered to clean the cleaning roll. The partial pressing of the outer peripheral surface of the sponge layer by the loosening member 144 is released.

  Next, the operation of this embodiment will be described.

  In the image forming apparatus 10 of the present embodiment, when the photosensitive drum 12 rotates during the image forming operation, the charging roll 14 is driven to rotate with the rotation of the photosensitive drum 12 to charge the photosensitive drum 12, and the charging roll 14 is further charged. The rotation of the cleaning roll 100 is driven to rotate and the charging roll 14 is cleaned. In the rotating cleaning roll 100, the outer peripheral surface of the sponge layer 100 </ b> B is partially pressed across the axial direction by the loosening member 144, so that foreign matter such as attached toner is loosened and the adhesion force is weakened. In particular, in the loosening member 144 of the present embodiment, the top surface portion (convex portion) is pushed into the outer peripheral surface of the sponge layer 100B of the cleaning roll 100 and pressed, so that the loosening force against the foreign matter is strengthened and the foreign matter discharge property. Is increased.

  Thereby, even if it is the cleaning roll 100 made from sponge like this embodiment, the damage received by being pressed by the loosening member 144 is suppressed, and a foreign material comes to be removed favorably, and the charging roll 14 The cleaning performance against is stably maintained. Therefore, in this image forming apparatus 10, the charging performance to the photosensitive drum 12 by the charging roll 14 is improved, and image defects due to poor charging of the photosensitive drum 12 are suppressed, and high-quality image formation can be realized. it can.

  Further, the foreign matter loosened by the loosening member 144 and weakened in adhesion force is reversely transferred from the cleaning roll 100 to the charging roll 14, and further reversely transferred from the charging roll 14 to the photoconductive drum 12. It is collected by a cleaning device 78 for cleaning. Therefore, the configuration can be simplified without providing a dedicated foreign matter collecting means for collecting foreign matter from the cleaning roll.

  In addition, when the image forming apparatus 10 is stopped or during non-image formation, the pressing of the cleaning roll 100 by the loosening member 144 is released. Therefore, in the cleaning roll 100 in the rotation stopped state, a certain portion of the outer peripheral surface is extended to the loosening member 144. A concave partial deformation caused by pressing for a period of time is avoided. Therefore, the deterioration of the cleaning performance due to such deformation is prevented. As another aspect, at the time of image formation, the pressing of the cleaning roll 100 by the loosening member 144 may be released, and a cleaning mode may be provided before and after image formation, and in that case, the cleaning roll 100 may be pressed. While suppressing excessive external pressure (stress), the adhered foreign matter can be loosened efficiently.

  In the present embodiment, the loosening member 144 installed in the vicinity of the cleaning roll 100 is disposed in the casing 140 that covers the charging roll 14 and the cleaning roll 100, so that the space-saving member 144 can be installed. Further, as the casing 140 moves upward and the unraveling member 144 moves closer to the cleaning roll 100, the distance between the casing 140 and the surface of the photosensitive drum 12 is narrowed. In addition to the improved foreign matter discharge, the toner cloud can be prevented from entering the casing 140, and toner contamination of the charging roll 14 and the cleaning roll 100 can be prevented.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  As shown in FIGS. 8 and 9, in this embodiment, a casing 160 that covers the charging roll 14 and the cleaning roll 100 and moves up and down by the same drive mechanism as that of the first embodiment is provided. A plurality of loosening members 164 protrude from the bottom surface of the casing main body 162 constituting the. As shown in the figure, each loosening member 164 is formed in a substantially hemispherical shape, and the top surface portion is formed in a substantially spherical shape, and each is arranged in a line (linear shape) at equal intervals parallel to the axial direction of the cleaning roll 100. ing.

  As described above, when the outer peripheral surface of the rotating cleaning roll 100 is pressed by the plurality of loosening members 164 configured to have unevenness in the axial direction, the pressing force applied to the cleaning roll 100 is changed and the loosening is performed. You can strengthen your power.

(Third embodiment)
Next, a third embodiment of the present invention will be described.

  As shown in FIGS. 10 and 11, in this embodiment, a plurality of loosening members 164 configured in the same manner as in the second embodiment are provided on the bottom surface of the casing main body 162 constituting the casing 170. It is arranged in two rows parallel to the direction. In addition, as shown in FIG. 10, each row of loosening members 164 does not overlap in the direction orthogonal to the axial direction of the leaning roll 100, and each row of loosening members 164 is provided between each row of loosening members 164. 164 are arranged and arranged alternately (staggered).

  As described above, when the plurality of loosening members 164 are arranged in a staggered manner to form the unevenness, the entire outer peripheral surface of the cleaning roll 100 is increased while increasing the loosening force by changing the pressing force to the cleaning roll 100. Since pressing can be performed with almost no unevenness, the foreign matter discharge performance from the cleaning roll 100 is further enhanced.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.

  As shown in FIG. 12, in this embodiment, the casing 170 described in the second embodiment is configured to reciprocate in the axial direction of the cleaning roll 100 by driving the actuator 180.

  As described above, the casing 170 is reciprocated by the actuator 180, and the loosening member 164 is reciprocated in the axial direction with respect to the cleaning roll 100, whereby the pressing force to the cleaning roll is changed in the circumferential direction (rotating direction) and the axial direction. Changes are given and the unraveling power is further strengthened. Moreover, even when the axial irregularities are arranged in a line as in the present embodiment, the entire outer peripheral surface of the cleaning roll 100 can be pressed almost uniformly, as in the third embodiment. It is possible to improve the foreign matter discharge performance from 100.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described.

  As shown in FIG. 13, in this embodiment, a loosening member 165A having the same configuration as that of the second embodiment protrudes from the bottom surface of the casing main body 162 constituting the casing 190. Although illustration is omitted, also in this embodiment, a plurality of loosening members 165A are arranged in a line at equal intervals in parallel with the axial direction of the cleaning roll 100. Each loosening member 165A is inclined so as to protrude toward the upstream side in the rotation direction of the cleaning roll 100.

  As described above, when the cleaning roll 100 is pressed by the loosening member 165A whose protruding direction is inclined to the upstream side in the roll rotation direction, the pressing force is applied toward the upstream side in the rotation direction of the cleaning roll 100. This enhances the foreign matter dischargeability from the cleaning roll.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described.

  As shown in FIG. 14, in this embodiment, a loosening member 165B having the same configuration as that of the second embodiment projects on the bottom surface of the casing body 162 constituting the casing 200 in the opposite direction to that of the fifth embodiment. It is installed. That is, the loosening member 165B is inclined so as to protrude toward the downstream side in the rotation direction of the cleaning roll 100. Although illustration of this embodiment is also omitted, a plurality of loosening members 165B are arranged in a line at equal intervals in parallel with the axial direction of the cleaning roll 100.

  As described above, when the cleaning roll 100 is pressed by the loosening member 165B whose protrusion direction is inclined toward the downstream side in the roll rotation direction, the pressing force is applied toward the downstream side in the rotation direction of the cleaning roll 100. The load torque applied to 100 is reduced, and a decrease in the followability of the cleaning roll 100 with respect to the charging roll 14 is suppressed.

  The present invention has been described in detail with reference to the first to sixth embodiments. However, the present invention is not limited thereto, and various other modes can be implemented within the scope of the present invention. is there.

  For example, in the above-described embodiment, the charging roll 14 and the cleaning roll 100 are both supported by the bearing member 110 so as to be in a pressure contact state, and the bearing member 110 is biased by the compression coil spring 128 so that the charging roll 14 is photosensitive. Although the structure in which the body drum 12 is press-contacted is adopted, the support structure and press-contact structure of each roll are not limited to this, and the charging roll 14 and the cleaning roll 100 are supported by individual bearing members, and individual urging means are provided. It may be energized and pressed.

  Further, the charging roll 14 is brought into contact with the lower part of the photosensitive drum 12, the cleaning roll 100 is brought into contact with the lower part of the charging roll 14, and the loosening member 144 is brought into contact with the lower part of the cleaning roll 100. The positional relationship among the photosensitive drum 12, the charging roll 14, the cleaning roll 100, and the loosening member 144 is not limited to this. For example, the charging roll is brought into contact with the upper part of the photosensitive drum, the cleaning roll (sponge member) is brought into contact with the upper part of the charging roll, and the loosening member is brought into contact with the upper part or the side part of the cleaning roll. The present invention can also be applied. Furthermore, the loosening member of the present invention can also be applied to a form in which charging is performed by the charging roll 14 disposed in a non-contact state on the photosensitive drum 12.

  In addition, the loosening member is not limited to a single rib shape provided in the casing as in the first embodiment or a plurality of protrusions as in the second to sixth embodiments, for example, Press the cleaning roll directly with a bar-shaped member such as a columnar or elliptical column, or bite the surface (convex portion) of the bar-shaped member into the cleaning roll, or form multiple irregularities on the bar-shaped member The cleaning roll may be pressed by the convex portion, or the convex portion may be bitten into the cleaning roll.

  The image forming apparatus to which the present invention is applied has a four-cycle configuration in which the toner image is formed on the photosensitive drum 12 four times using the rotary developer 18 as in the above-described embodiment. It is not limited to. For example, even if the yellow, magenta, cyan, and black image forming units are arranged side by side along the moving direction of the intermediate transfer belt, the present invention is applied to the photosensitive drum, the charging roll, and the sponge member of each image forming unit. Can be applied.

1 is a configuration diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a configuration of a photosensitive drum, a charging roll, and a cleaning roll mounted on the image forming apparatus of FIG. 1. FIG. 3 is a partial cross-sectional side view illustrating the configuration of the photosensitive drum, the charging roll, the cleaning roll, and the pressing member in a pressed state according to the first embodiment of the present invention. FIG. 3 is a partial cross-sectional side view illustrating the configuration of the photosensitive drum, the charging roll, the cleaning roll, and the loosening member in a separated state according to the first embodiment of the present invention. It is a longitudinal cross-sectional view corresponding to FIG. It is a longitudinal cross-sectional view corresponding to FIG. It is a perspective view which shows the state by which the charging roll and cleaning roll which concern on one Embodiment of this invention were pivotally supported by the bearing member. It is a partial cross section side view which shows the structure of the loosening member which concerns on the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view corresponding to FIG. It is a partial cross section side view which shows the structure of the loosening member which concerns on the 3rd Embodiment of this invention. It is a longitudinal cross-sectional view corresponding to FIG. It is a fragmentary sectional side view which shows the structure of the loosening member which concerns on the 4th Embodiment of this invention, and the moving means for reciprocation. It is a fragmentary sectional side view which shows the structure of the loosening member which concerns on the 5th Embodiment of this invention. It is a fragmentary sectional side view which shows the structure of the loosening member which concerns on the 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (Image carrier)
14 Charging roll 100 Cleaning roll 100B Sponge layer 140 Casing 142 Casing body 144 Unraveling member 146 Eccentric cam (contacting / separating means)
148 Camshaft (contact / separation means)
152 Rotating gear (contact / separation means)
154 Drive motor (contact / separation means)
156 Drive gear (contact / separation means)
160 Casing 162 Casing body 164 Unraveling member 165A Unraveling member 165B Unraveling member 170 Casing 180 Actuator (moving means)
190 Casing 200 Casing

Claims (10)

An image carrier;
A charging roll for charging the image carrier;
A cleaning roll for cleaning the charging roll;
A loosening member that is disposed along the axial direction of the outer peripheral surface of the cleaning roll and loosens foreign matter adhering to the cleaning roll;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the foreign matter is reversely transferred from the cleaning roll to the image carrier via the charging roll and collected.   The image forming apparatus according to claim 1, further comprising a contact / separation unit that contacts and separates the loosening member with respect to the cleaning roll.   4. The image forming apparatus according to claim 1, wherein the loosening member includes a convex portion, and the convex portion is arranged to bite into an outer peripheral surface of the cleaning roll. 5. .   The image forming apparatus according to claim 1, further comprising a casing that covers the charging roll and the cleaning roll, wherein the loosening member is disposed in the casing.   6. The image forming apparatus according to claim 5, wherein a distance between the casing and the surface of the image carrier is reduced as the loosening member moves closer to the cleaning roll.   The image forming apparatus according to claim 1, wherein the loosening member has irregularities in the axial direction.   The image forming apparatus according to claim 1, further comprising a moving unit that reciprocally moves the loosening member in an axial direction with respect to the cleaning roll.   The image forming apparatus according to claim 1, wherein a pressing force of the loosening member that presses the cleaning roll is applied toward the upstream side in the rotation direction of the cleaning roll.   The image forming apparatus according to claim 1, wherein a pressing force of the loosening member that presses the cleaning roll is applied toward the downstream side in the rotation direction of the cleaning roll.

Images