JP2007193031A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stabilized electrostatic charging and cleaning properties over a long period of time by suppressing the degradations of the properties of the electrifying roll and cleaning roll to follow. <P>SOLUTION: The gap G between the holder 120 and the photoreceptor drum 12 is blocked by attaching a cover 130 to the upper edge 127 of the holder 120 covering the electrifying roll 14 and the cleaning roll 100. Since the toner and dust floating inside the image forming device are prevented from entering the holder 120 to accumulate between the support 14a of the electrifying roll 14 and the support 100a of the cleaning roll 100 and a bearing member 110, the degradations of the properties are suppressed for the electrifying roll 14 to follow the photoreceptor drum 12, and for the cleaning roll 100 to follow the electrifying roll 14. <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 image carrier 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 a problem, a cleaning member constituted by a brush attached to a support member in a radial manner is brought into contact with the charging roll, and the foreign matter on the surface of the charging roll is removed by sliding in the longitudinal direction of the charging roll. (For example, see Patent Document 1), or a cleaning roll made of a brush or an elastic material is brought into contact with the charging roll, and the cleaning roll is rotated at a relative speed with respect to the charging roll, so that the charging roll is excellent. A cleaning technique has been proposed (see, for example, Patent Document 2).

In addition, by covering the periphery of the charging roll provided with the cleaning member with a housing, toner that is scattered from the developing device and floats inside the apparatus is prevented from adhering to the charging roll, and stable charging performance is obtained. Technology has been proposed (see, for example, Patent Document 3)
JP-A-5-265307 Japanese Patent Laid-Open No. 7-140763 Japanese Patent Laid-Open No. 8-110685

  However, in the configuration of Patent Document 3, although the charging roll is covered with a housing, the effect of preventing floating toner and dust entering the housing through the gap between the housing and the photosensitive member is insufficient. . For this reason, floating toner and dust are likely to accumulate between the shaft (support) of the charging roll or cleaning roll and the bearing member, and the followability of each roll is reduced, resulting in stable charging performance and cleaning performance over a long period of time. There is a problem that cannot be maintained.

  In view of the above-described facts, it is an object of the present invention to provide an image forming apparatus capable of suppressing a decrease in followability of a charging roll and a cleaning roll and maintaining stable charging performance and cleaning performance over a long period of time.

  In order to achieve the above object, the invention described in claim 1 supports a rotating image carrier, a charging roll that contacts and rotates the image carrier and charges the image carrier, and supports the charging roll. A cleaning member that contacts the charging roll to clean the charging roll; and a sealing member that covers at least the first supporting part outside the image forming area of the image carrier. It is said.

  In the present invention, by covering the first support portion that supports the charging roll with the seal member, for example, toner or the like that scatters from the developing device and floats inside the device can be prevented from accumulating in the first support portion of the charging roll. . Further, by disposing the seal member outside the image forming area of the image carrier, adverse effects on image formation can be avoided. As a result, a decrease in the followability of the charging roll with respect to the image carrier is suppressed, and stable charging performance can be maintained over a long period of time.

  According to a second aspect of the present invention, the cleaning member includes a cleaning roll that rotates following the charging roll, and includes a second support portion that supports the cleaning roll, and the second support portion is also sealed by the seal member. It is characterized by being.

  In the present invention, by covering the second support portion that supports the cleaning roll with the seal member, accumulation of floating toner or the like in the second support portion of the cleaning roll can also be prevented. As a result, a decrease in the followability of the cleaning roll relative to the charging roll is suppressed, and stable cleaning performance can be maintained over a long period of time.

  According to a third aspect of the present invention, there is provided a rotating image carrier, a charging roll that contacts and rotates the image carrier, and charges the image carrier, and a cleaning that contacts the charging roller and cleans the charging roller. A member, a covering member that covers the periphery of the charging roll and the cleaning member excluding the image carrier side, and a first support portion that supports at least the charging roll outside the image forming area of the image carrier. And a sealing member that seals a gap formed between the image carrier and the covering member.

  In the present invention, in the charging roll that charges the image carrier in image formation, the foreign matter adhering to the roll surface is cleaned by the cleaning member, so that a reduction in charging performance can be suppressed. In addition to the cleaning member and the periphery except for the image carrier side being covered with the covering member, it is possible to prevent toner, dust, and the like floating in the apparatus from adhering to the charging roll. Further, in the gap formed between the image carrier and the covering member, the position corresponding to the first support portion that supports the charging roll outside the image forming area of the image carrier is sealed by the seal member. Intrusion of floating toner and dust through the seal portion into the covering member is prevented without adversely affecting image formation. As a result, accumulation of floating toner and dust in the first support portion of the charging roll is prevented, a decrease in the followability of the charging roll with respect to the image carrier is suppressed, and stable charging performance can be maintained over a long period of time.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the cleaning member includes a cleaning roll that is driven to rotate by the charging roll, and is located at a position corresponding to a second support portion that supports the cleaning roll. The gap is also sealed by the seal member.

  In the present invention, when the cleaning member is a cleaning roll that rotates following the charging roll, good cleaning performance can be obtained with a simple configuration without providing a drive source for rotationally driving the cleaning roll. Further, in the gap formed between the image carrier and the covering member, the position corresponding to the second support portion that supports the cleaning roll is also sealed by the seal member, so that the floating in the second support portion of the cleaning roll is suspended. Accumulation of toner and dust is prevented. Thereby, a decrease in the followability of the cleaning roll with respect to the charging roll is suppressed, and a stable cleaning performance can be maintained over a long period of time.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, a base end portion of the seal member is attached to the covering member, and a distal end portion is slidable to the image carrier. It is characterized by having.

  In the present invention, the seal member is attached to the covering member at the base end portion, and the distal end portion is in sliding contact with the image carrier to seal a gap formed between the image carrier and the covering member. With such a seal member, it can be arranged between the image carrier and the covering member with a simple configuration, and can exhibit high sealing performance against the rotating image carrier.

  According to the image forming apparatus of the present invention, a decrease in the followability of the charging roll and the cleaning roll can be suppressed, and stable charging performance and cleaning performance can be maintained for a long time.

  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.

(Configuration of support structure, holder, and seal member)
Next, the support structure for the charging roll 14 and the cleaning roll 100 according to the present embodiment, the holder that covers them, and the seal member that seals the gap formed between the holder and the photosensitive drum 12 will be described in detail. .

  As shown in FIG. 3, in this embodiment, the charging roll 14 and the cleaning roll 100 are assembled to a box-shaped holder 120 via a pair of bearing members 110, and are accommodated in the holder 120 together with the holder 120. It is unitized and arranged at a predetermined position with respect to the photosensitive drum 12.

  As shown in FIG. 4, 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 bearing grooves 112 and bearing holes 114 arranged at predetermined intervals along the longitudinal direction (vertical direction in FIG. 4). The bearing groove 112 is formed in a U-shaped cross-section that opens the upper end surface of the bearing member 110, and the inner diameter of the inner circumferential surface that is a semicircular surface is provided at the end of the shaft 14 </ b> A of the charging roll 14. The shaft diameter of the portion 14a is substantially the same. In the bearing groove 112, a support portion 14a of the shaft 14A of the charging roll 14 is rotatably fitted. Further, since the bearing groove 112 is opened on the photosensitive drum 12 side, which is the upper side of the drawing, when the support portion 14a is abutted and supported by the inner peripheral surface portion, the support portion 14a is moved to the photosensitive drum 12. It is set as the shape which gives a freedom degree to the press-contact direction (arrow 8 direction). On the other hand, a support portion 100a provided at the end of the shaft 100A of the cleaning roll 100 is rotatably inserted into the bearing hole 114.

  As shown in FIG. 3, the holder 120 has the pair of bearing members 110 at both ends (left and right side ends in FIG. 3) 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 be 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.

  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 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. In a state where 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 distance between the axes is 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 FIG. 5, the holder 120 covering the periphery of the charging roll 14 and the cleaning roll 100 is open on the photosensitive drum 12 side (upper side in FIG. 5), and the upper edge 127 and the photosensitive drum 12 are separated from each other. A gap G is formed between them.

  As shown in FIG. 6, each end position in the longitudinal direction (left-right direction in FIG. 6 / depth direction in FIG. 5) at the upper edge 127 of the holder 120 is formed into a thin long rectangular shape by an elastic material. A total of four formed seal members 130 are attached. Each seal member 130 is outside the image forming area (non-image forming area) on the photosensitive drum 12, and supports the support part 14 a and the bearing groove 112 of the charging roll 14, and the support part 100 a and the bearing hole of the cleaning roll 100. The base end portion is fixed to the outer surface of the upper end edge portion 127 of the holder 120 by adhesion or the like, and the front end portion contacts the surface of the photosensitive drum 12 to be curved outward. It is elastically deformed. Further, the front end portion of the seal member 130 in contact with the photosensitive drum 12 can be slidably contacted with the rotating photosensitive drum 12 and is in close contact with the photosensitive drum 12 without being separated even when the photosensitive drum 12 is rotated.

  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. As described above, the charging roller 14 for charging the photosensitive drum 12 in image formation is cleaned of foreign matter adhering to the surface of the roller by the cleaning roller 100, so that a decrease in charging performance can be suppressed. Further, since the periphery of the cleaning roller 100 except for the photosensitive drum 12 side is covered by the holder 120, it is protected from toner, dust, and the like that are scattered from the developing units 18Y, 18M, 18C, and 18K and floating in the apparatus. Adherence of these foreign matters is prevented. Further, in the gap G formed between the photosensitive drum 12 and the holder 120, outside the image forming area of the photosensitive drum 12, the support portion 14 a of the charging roll 14, the bearing groove 112, and the cleaning roll 100. Since the positions corresponding to the support portion 100a and the bearing hole 114 are sealed by the seal member 130, entry of floating toner and dust into the holder 120 through the seal portion can be prevented without adversely affecting image formation. . Thereby, accumulation of floating toner and dust between the support portion 14a of the charging roll 14 and the bearing groove 112 of the bearing member 110 is prevented, and a decrease in the followability of the charging roll 14 with respect to the photosensitive drum 12 is suppressed. Thus, stable charging performance can be maintained over a long period of time. Further, accumulation of floating toner and dust between the support portion 100a of the cleaning roll 100 and the bearing hole 114 of the bearing member 110 is prevented, and a decrease in the followability of the cleaning roll 100 with respect to the charging roll 14 is suppressed. Stable cleaning performance can be maintained for a long time.

  Therefore, with this image forming apparatus 10, image defects due to poor charging of the photosensitive drum 12 and poor cleaning of the charging roll 14 can be suppressed, and high-quality images can be formed over a long period of time.

  Further, the seal member 130 according to the present embodiment has a base end portion attached to the covering member, and a tip portion that is in sliding contact with the rotating photosensitive drum 12, and a gap formed between the photosensitive drum 12 and the holder 120. G is sealed. Such a sealing member 130 can be disposed between the photosensitive drum 12 and the holder 120 with a simple configuration, and can exhibit high sealing performance with respect to the rotating photosensitive drum 12.

(Configuration of Example)
Hereinafter, the charging roll 14, the cleaning roll 100, and the seal member 130 used in the examples will be described. As the charging roll 14 of this embodiment, φ12 mm × 314 mm, volume resistance 10 ^ 6Ω, hardness 65 ° (ASK-C) is used, and the photosensitive drum 12 is nipped with a pressing load of 9.3 N. The photosensitive drum 12 is driven to rotate.

  Further, as the cleaning roll 100 of this example, φ10 mm × 314 mm in which the sponge layer 100B is formed of foamed urethane rubber is used, and the number of cells is 40/25 mm. The amount of biting into the charging roll 14 is set to 0.75 mm. The roll 14 is driven and rotated.

  In addition, as the sealing member 130 of this embodiment, a 0.1 mm thick and 10 mm free length formed of an ester polyurethane foam is used, the nip width with respect to the photosensitive drum 12 is 1.0 mm, and the image forming area +2 mm. From the position to the end of the holder 120 is sealed. The actual length of the seal member is set to 28 mm on the IN side and 21 mm on the OUT side.

(Followability evaluation method)
Below, the evaluation method of followability is demonstrated. In the evaluation apparatus having a full-color tandem configuration, when the photosensitive drum 12, the charging roll 14, the cleaning roll 100, and the seal member 130 of this embodiment are arranged as shown in FIGS. When not attached (conventional example), running is performed at a process speed of 165 mm / s, and the relative speed between the photosensitive drum 12 and the charging roll 14 and the relative speed between the charging roll 14 and the cleaning roll 100 are measured. It was.

(Following evaluation results)
From the evaluation results shown in FIGS. 7A and 7B, in the conventional example, each relative speed starts to decrease from around 60 kpv and decreases by about 10% at 100 kpv, whereas in this example, each relative speed is 100 kpv. It turns out that it is maintaining favorable, without falling.

  As mentioned above, although this invention was demonstrated in detail by the specific embodiment mentioned above, this invention is not limited to it, Various other forms can be implemented within the scope of the present invention.

  For example, in the above-described embodiment, the seal member 130 is attached to the holder 120 and the gap G formed between the holder 120 and the photosensitive drum 12 is sealed, but the seal member mounting structure and shape are the same. For example, the seal member is configured so as to directly cover the support portion 14a of the charging roll 14 and the support portion 100a of the cleaning roll 100 by covering the upper side and the periphery of the bearing member 110. You can also

  Further, both the charging roll 14 and the cleaning roll 100 are supported by the bearing member 110, and the bearing member 110 is urged by the compression coil spring 128 to bring the charging roll 14 into pressure contact with the photosensitive drum 12, so that the cleaning roll 100 is charged. However, 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 applied by individual urging means. You may make it press-contact.

  In addition, the charging roll 14 is brought into contact with the lower part of the photosensitive drum 12 and the cleaning roll 100 is brought into contact with the lower part of the charging roll 14, but the photosensitive drum 12, the charging roll 14, and the cleaning roll 100 The positional relationship is not limited to this. For example, the present invention can be applied to a configuration in which a charging roll is brought into contact with an upper portion of the photosensitive drum and a cleaning roll is brought into contact with the upper portion of the charging roll.

  The cleaning member that cleans the charging roll 14 is configured in a roll shape that is driven to rotate by the charging roll 14. However, the present invention is also applied to a configuration such as a pad shape that slides on the charging roll 14. Can do.

  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 in a full-color tandem configuration in which yellow, magenta, cyan, and black image forming units are juxtaposed along the moving direction of the intermediate transfer belt, the photosensitive drum, charging roll, and cleaning roll of each image forming unit The present invention can be applied to the holder. In particular, in the case of such a tandem configuration, in the magenta and cyan image forming units arranged inside the four units arranged side by side, since the developing devices exist on the upstream side and the downstream side, The floating toner enters the holder from the gap, and adverse effects are likely to occur. However, by applying the configuration of the present invention, it is possible to satisfactorily prevent the toner from entering from both the gaps, and it is possible to suppress a decrease in the followability of the charging roll and the cleaning roll. Cleaning performance can be maintained over a long period of time.

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 a photosensitive drum, a charging roll, a cleaning roll, and a holder according to an embodiment of the present invention. 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. FIG. 4 is a partial cross-sectional front view showing a state in which a gap formed between the holder and the photosensitive drum is sealed by a seal member attached to the holder according to an embodiment of the present invention. It is an enlarged view which shows the attachment position of the sealing member which concerns on one Embodiment of this invention corresponding to FIG. (A), (B) is a graph which shows the evaluation result of the followability of the charging roll and cleaning roll in one Example of this invention, and a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (Image carrier)
14 Charging roll 14A Shaft 14a Support part (first support part)
100 Cleaning roll (cleaning member)
100A shaft (second support part)
100a Support part 110 Bearing member 112 Bearing groove (first support part)
114 Bearing hole (second support part)
120 Holder (Coating material)
130 Seal member G Clearance

Claims (5)

A rotating image carrier;
A charging roll for contacting and rotating the image carrier and charging the image carrier;
A first support for supporting the charging roll;
A cleaning member for cleaning the charging roll in contact with the charging roll;
A seal member that covers an area outside the image forming area of the image carrier and at least covers the first support;
An image forming apparatus comprising:   The cleaning member includes a cleaning roll that rotates following the charging roll, and includes a second support portion that supports the cleaning roll, and the second support portion is also sealed by the seal member. Item 2. The image forming apparatus according to Item 1. A rotating image carrier;
A charging roll for contacting and rotating the image carrier and charging the image carrier;
A cleaning member for cleaning the charging roll in contact with the charging roll;
A covering member that covers the periphery of the charging roll and the cleaning member excluding the image carrier side;
A seal member that is disposed outside the image forming area of the image carrier and at a position corresponding to at least the first support portion that supports the charging roll, and seals a gap formed between the image carrier and the covering member. When,
An image forming apparatus comprising:   The said cleaning member consists of a cleaning roll which rotates following the said charging roll, The said clearance gap of the position corresponding to the 2nd support part which supports this cleaning roll is also sealed by the said sealing member. The image forming apparatus described.   5. The image forming apparatus according to claim 3, wherein a base end portion of the seal member is attached to the covering member, and a tip end portion thereof is slidably contactable with the image carrier.