JP2009116373A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent charging property by holding a charging roll and a cleaning member for the charging roll with high relative positional accuracy with simple constitution. <P>SOLUTION: The supporting part 14a of the charging roll 14 charging a photoreceptor drum 12, and the supporting part 100a of a sponge member 100 cleaning the charging roll 14 are respectively directly supported by a single bearing member 110, and also the bearing member 110 is energized to the photoreceptor drum 12 side by a compression coil spring 128 so as to bring the charging roll 14 into press-contact with the photoreceptor drum 12. Influence by variance of parts for supporting the charging roll 14 and the sponge member 100 is restrained and relative positional accuracy between them is improved, and variance of load received by the charging roll 14 from the sponge member 100 is restrained and following ability to the photoreceptor drum 12 is improved, so that the charging property of the photoreceptor drum 12 by the charging roll 14 becomes excellent. <P>COPYRIGHT: (C)2009,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.

  Conventionally, as a charging device for an image forming apparatus such as a copying machine or a printer adopting an electrophotographic method, a device using a corona discharge phenomenon such as a scorotron charger has been widely used, but a charging device using a corona discharge phenomenon is used. In this case, the generation of ozone and nitrogen oxides that have a negative effect on the human body and the global environment is a problem. In contrast, the contact charging method in which a conductive charging roll is brought into direct contact with the image carrier to charge the image carrier has significantly reduced generation of ozone and nitrogen oxides and has good power supply efficiency. Then it has become mainstream.

  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 technique has been proposed in which a cleaning member made of a plate-like sponge or brush is pressed (slidably contacted) on the surface of the rotating charging roll to clean the surface of the charging roll. (For example, refer to Patent Document 1).

  Further, as shown in FIG. 7, in a non-contact charging type charging device that charges the charging roll 202 without contacting the photosensitive drum 200, a roll-shaped cleaning member has been conventionally provided on the surface of the rotating charging roll 202. In some of the conventional configurations, both ends of the charging roll 202 and the cleaning member 204 are rotatably supported by a single support member 206. .

JP 2005-134760 A

  However, in the configuration of Patent Document 1, since the cleaning member is urged and pressed by the urging member against the charging roll supported by the casing (case), the charging roll directly supported by the casing, The relative positional accuracy with the cleaning member indirectly attached to the housing via the biasing member is deteriorated, and the followability of the charging roll with respect to the photosensitive member is reduced due to the variation in the load received from the cleaning member. It tends to occur. Further, since it is necessary to provide two urging members, ie, an urging member for bringing the cleaning member into pressure contact with the charging roll and an urging member for bringing the charging roller into pressure contact with the photosensitive member, the structure is complicated and the assembly is easy. There is also a problem of increasing costs and increasing costs.

  On the other hand, in the conventional support structure shown in FIG. 7, since the charging roll 202 and the cleaning member 204 are pivotally supported by the support member 206 via the sintered bearings 208 and 210, respectively, the charging roll 202 inserted into each bearing. The outer diameters of the shaft 202A and the shaft 204A of the cleaning member 204 must be reduced. As described above, when the shaft has a small diameter and is disadvantageous against bending, when applied to the contact charging method, the charging roll cannot be strongly pressed against the photosensitive drum, and a follow-up failure tends to occur, or When pressed strongly, the shaft bends, and the pressure contact state of the charging roll against the photosensitive drum changes, and charging failure tends to occur. Further, if each shaft is made thicker in order to increase the rigidity, the bearing and the support member are enlarged, and the entire apparatus is enlarged. Furthermore, since the number of parts is large, there are many factors that are affected by component variations, and similarly to Patent Document 1, there is a problem that a charging failure due to a decrease in the relative positional accuracy between the charging roll and the cleaning member is likely to occur. .

  In consideration of the above-described facts, the present invention keeps the charging roll for charging the charged body by being in contact with the rotating charged body and rotating it and the cleaning member with a simple configuration with high relative positional accuracy. It is an object of the present invention to provide an image forming apparatus that can obtain good chargeability.

In order to achieve the above object, the invention described in claim 1 is characterized in that a charged roll for charging a charged body by being driven to rotate while being pressed against the rotating charged body, and a surface of the charging roll for contacting the charged roll. A pair of cleaning members for cleaning the charging roll, a pair of support portions provided at both ends of the charging roll, and a pair of support portions provided at both ends of the cleaning member are provided. A single holding member that directly supports the supporting portion of the cleaning member and the supporting portion of the cleaning member to hold the charging roller and the cleaning member in a substantially constant position, and urges the pair of holding members toward the charged object side. Biasing means for pressing the charging roll against the member to be charged, and the pair of holding members are movably attached to a single casing along the biasing direction of the biasing means. Vignetting, the cleaning member is characterized in that in pressure contact with said charging roller which rotates a roll-shaped rotating body is driven to rotate.

  In the present invention, a pair of support members provided at both end portions of the charging roll and a pair of support members provided at both end portions of the cleaning member, and a pair of holding members each having a single configuration. The charging roll and the cleaning member are held at a substantially constant relative position in a state where the cleaning member is in contact with the surface of the charging roll by directly supporting the support portions at both ends by the pair of holding members. The Further, the charging roll is pressed against the charged body by the pair of holding members being urged to the charged body side by the urging means, and is rotated following the rotation of the charged body to charge the charged body. The roll surface is cleaned by the cleaning member.

  In this way, by directly supporting the charging roll and the cleaning member by the single holding member, the number of elements affected by component variations is reduced and the relative positional accuracy of the charging roll and the cleaning member is improved. The variation in the received load is suppressed and the followability to the charged body is improved. Thereby, the charging property of the member to be charged by the charging roll becomes good. Further, the structure is simplified, the assemblability is improved, and the cost is reduced. Therefore, the charging roll and its cleaning member can be held with high relative positional accuracy with a simple configuration, and good chargeability can be obtained.

  In addition, since the charging roll is not pivotally supported via a bearing as in the past, for example, even if the shaft diameter of the charging roll is increased to ensure the necessary rigidity, the increase in the size of the holding member can be suppressed. Is advantageous against deflection. As a result, the charging roll can be strongly pressed against the member to be charged, the follow-up failure is suppressed, and the shaft is not easily bent even if it is strongly pressed, so that the pressure contact state of the charging roll with respect to the member to be charged is stable. The contact is almost uniform in the axial direction, and the occurrence of charging failure is suppressed. Moreover, the whole apparatus can be reduced in size by suppressing the enlargement of a holding member as mentioned above.

In addition, by attaching the pair of holding members to a single housing, for example, the relative positional accuracy of the charging roll and the cleaning member can be further improved as compared with a configuration in which the pair of holding members are respectively attached to separate attachment portions. In particular, the axial alignment accuracy can be maximized.
In addition, since the cleaning member is a roll-shaped rotating body that is driven to rotate while being pressed against the charging roll, it is possible to provide a simple drive without providing a drive source for rotationally driving the cleaning member formed of the roll-shaped rotating body. Depending on the configuration, good cleaning performance can be obtained.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the object to be charged is rotatably supported by the single casing.

  In the present invention, the relative position accuracy between the charged body and the charging roll can be maximized by supporting the charged body on the single casing.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the charging roll is disposed vertically below the member to be charged, and the cleaning roller is disposed vertically below the charging roll. A member is arranged.

  According to the image forming apparatus of the present invention, the charging roll for charging the charged body by being driven to rotate while being pressed against the rotating charged body and the cleaning member are held with high relative position accuracy with a simple configuration. And good chargeability can be obtained.

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 sponge member mounted on the image forming apparatus in FIG. 1. It is a fragmentary sectional side view which shows the structure of the attachment structure of the charging roll and sponge member which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the state by which the charging roll and sponge member which concern on the 1st Embodiment of this invention were supported by the bearing member. It is a partial cross section side view which shows the structure of the attachment structure of the photoconductive drum, charging roll, and sponge member which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the state by which the charging roll and sponge member which concern on 3rd Embodiment as a reference example were pivotally supported by the bearing member. It is a perspective view which shows the state by which the charging roll and cleaning member of the conventional non-contact charging system were pivotally supported by the support member.

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

  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 drum made of a conductive cylinder having a diameter of about 47 mm and coated on a surface with a photosensitive layer made of OPC or the like is used. It is rotationally driven at a process speed of 150 mm / sec.

  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 have a predetermined process speed (about 150 mm / sec), for example, as the photosensitive drum 12 rotates. It is driven Te.

  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 the discharge roll 66 In this state, the discharge roll 66 is reversed while the rear end portion of the recording paper 24 is nipped, and the conveyance path of the recording paper 24 is switched to the double-sided paper conveyance path 70. With the conveyance roller 72 provided, the recording paper 24 is reversed and conveyed to the secondary transfer position of the intermediate transfer belt 20 again, and the toner image is transferred to the second surface (back surface) of the recording paper 24. To do. 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 openable and closable as an option. 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 14 so as to be in contact with the photosensitive drum 14. The charging roll 14 has a conductive layer 14B formed around a conductive shaft 14A, and the shaft 14A is rotatably supported. A roll-like sponge member 100 that is in contact with the surface of the charging roll 14 is provided at a lower portion of the charging roll 14 opposite to the photosensitive drum 12. This sponge member 100 has a sponge layer 100B formed around a shaft 100A, and the shaft 100A is rotatably supported.

  The sponge member 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 sponge member 100 is driven to rotate in the direction of the arrow 6 by the rotation of the charging roll 14.

  As the sponge member 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 sponge member 100. When the foreign matter is taken into the foam cell of the sponge member 100 and the foreign matter collected in the cell aggregates to an appropriate size, it is transferred from the sponge member 100 to the photosensitive drum 12 via the charging roll 14. It is considered that the cleaning performance is maintained and maintained by returning to the cleaning device 78 that cleans the photosensitive drum 12.

  With respect to the sponge member 100 as a cleaning member for the charging roll 14, free cutting steel, stainless steel, or the like is used as the material of the shaft 100A, and the material and surface treatment method may be selected depending on applications such as slidability. Selected in a timely manner. In addition, a non-conductive material may be processed by a general process such as a plating process and subjected to a conductive process, or may be used as it is. Further, since the sponge member 100 is in contact with the charging roll 14 with an appropriate nip pressure via the sponge layer 100B, the shaft diameter having a sufficient rigidity with respect to a material having a strength that does not bend at the time of nip or a shaft length is sufficient. Selected.

  The sponge layer 100B is made of a foam having a porous three-dimensional structure. The sponge layer 100B is selected from those made of a foamable resin or rubber such as polyurethane, polyethylene, polyamide, or polypropylene. The sponge layer 100B efficiently cleans foreign substances such as external additives by driven sliding rubbing with the charging roll 14, and at the same time does not damage the surface of the charging roll 14 due to rubbing of the sponge layer 100B. In order to prevent tearing and breakage, it is particularly preferable to use polyurethane that is strong in tearing and tensile strength.

  The charging roll 14 is formed by sequentially forming a conductive elastic layer and a surface layer as a charging layer 14B on a conductive shaft 14A.

  As the material of the shaft 14A, free-cutting steel, stainless steel or the like is used, and the material and the surface treatment method are appropriately selected according to the use such as slidability, and the material having no conductivity is generally plated. It may be processed by an appropriate process and a conductive process may be performed.

  The conductive elastic layer constituting the charging layer 14B of the charging roll 14 may be, for example, an elastic material such as rubber having elasticity, a conductive material such as carbon black or ionic conductive material for adjusting the resistance of the conductive elastic layer, or the like. Accordingly, materials that can be usually added to rubber, such as softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, anti-aging agents, and fillers such as silica and calcium carbonate, may be added. It is formed by coating the peripheral surface of the conductive shaft 14 </ b> A with a mixture in which materials usually added to rubber are added. As a conductive agent for the purpose of adjusting the resistance value, a material in which a material that conducts electricity using electrons and / or ions as a charge carrier, such as carbon black or an ionic conductive agent blended in a matrix material, is used. it can. The elastic material may be a foam.

  The surface layer constituting the charging layer 14B is formed for the purpose of preventing contamination by foreign matters such as toner, and the surface layer material may be any of resin, rubber, etc. It is not limited. Polyester, polyimide, copolymer nylon, silicone resin, acrylic resin, polyvinyl butyral, ethylene tetrafluoroethylene copolymer, melamine resin, fluoro rubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride, polyvinyl chloride, polyethylene And ethylene vinyl acetate copolymer.

  The surface layer can contain a conductive material to adjust the resistance value. The conductive material preferably has a particle size of 3 μm or less.

  In addition, as a conductive agent for the purpose of adjusting the resistance value, it electrically conducts electrons and / or ions as charge carriers, such as carbon black, conductive metal oxide particles, or ionic conductive agent blended in the matrix material. What disperse | distributed material etc. can be used.

  The conductive metal oxide particles, which are conductive particles for adjusting the resistance value, are conductive particles such as tin oxide, tin oxide doped with antimony, zinc oxide, anatase titanium oxide, and ITO. Any conductive agent using electrons as charge carriers can be used without any particular limitation. These may be used alone or in combination of two or more. Any particle size may be used as long as the present invention is not inhibited. From the viewpoint of resistance value adjustment and strength, tin oxide, antimony-doped tin oxide, and anatase-type titanium oxide are preferable. Tin oxide and antimony-doped tin oxide are preferred.

  By performing resistance control with such a conductive material, the resistance value of the surface layer does not change depending on environmental conditions, and stable characteristics can be obtained.

  Further, a fluorine-based or silicone-based resin is used for the surface layer. In particular, it is preferably composed of a fluorine-modified acrylate polymer. Further, fine particles may be added to the surface layer. As a result, the surface layer becomes hydrophobic and acts to prevent the adhesion of foreign matter to the charging roll 14. In addition, insulating particles such as alumina and silica are added to give unevenness to the surface of the charging roll 14, thereby reducing the burden at the time of rubbing against the photosensitive drum 12, and the charging roll 14 and the photosensitive drum. It is also possible to improve the mutual wear resistance.

(First embodiment)
Next, the first embodiment of the present invention will be described in detail.

  As shown in FIG. 3, in the present embodiment, the charging roll 14 and the sponge member 100 are assembled to a single frame 120 via a pair of bearing members 110, and are housed in the frame 110 together with the frame 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 flat 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 14a provided at the end of the shaft 14A of the charging roll 14 is rotatably inserted into one bearing hole 112, and the other bearing hole 114 is provided at the end of the shaft 100A of the sponge member 100. The support part 100a is rotatably inserted.

  The charging roller 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 sponge member 100 in which the support portions 100a at both ends of the shaft 100A are pivotally supported have a substantially constant relative position. As described above, the sponge member 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).

  As shown in FIG. 3, the frame 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 sponge member 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. Accordingly, when the photosensitive drum 12 rotates, the charging roll 14 is driven to rotate with the rotation of the photosensitive drum 12 to charge the photosensitive drum 12, and further, the sponge member 100 is driven to rotate with the rotation of the charging roll 14. Then, the charging roll 14 is cleaned.

  As described above, in the present embodiment, the charging roll 14 and the sponge member 100 are directly supported by the single bearing member 110, so that the number of elements affected by component variations is reduced, and the relative positional accuracy thereof is reduced. And the variation in the load that the charging roll 14 receives from the sponge member 100 is suppressed, and the followability to the photosensitive drum 12 is improved. Thereby, the charging property of the photosensitive drum 12 by the charging roll 14 is improved. Further, the structure is simplified, the assemblability is improved, and the cost is reduced. Therefore, the charging roll 14 and the sponge member 100 can be held with high relative positional accuracy with a simple configuration, and good chargeability can be obtained.

  Further, since the charging roll 14 is not pivotally supported through a bearing as in the conventional case, the bearing member 110 can be enlarged even if the outer diameter of the shaft 14A of the charging roll 14 is increased to ensure the required rigidity. Therefore, the shaft 14A is advantageous against bending. As a result, the charging roll 14 can be pressed strongly against the photosensitive drum 12 to suppress the follow-up failure, and the shaft 14A is not easily bent even when pressed strongly, so that the charging roll 14 is pressed against the photosensitive drum 12. Is stable, that is, the pressure is almost uniformly pressed in the axial direction, and the occurrence of charging failure is suppressed. In addition, since the increase in diameter of the bearing member 110 is suppressed as described above, the entire apparatus can be reduced in size.

  Further, in the present embodiment, the pair of bearing members 110 are attached to the single frame 120, so that the charging roll 14 and the sponge are compared with a configuration in which the pair of bearing members are attached to separate attachment portions, for example. The relative positional accuracy of the member 100 can be further improved, and in particular, the axial alignment accuracy can be improved to the maximum.

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

  As shown in FIG. 5, in this embodiment, the charging roll 14 and the sponge member 100 are assembled to a single frame 130 via a pair of bearing members 110, and the photosensitive drum 12 is also assembled to the frame 130. They are unitized.

  The frame 130 is formed such that the outer surface side of the pair of attachment portions 124 is thick and the distal end side is extended, and a pair of bearing portions 132 that pivotally support the photosensitive drum 12 is provided at the distal 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 sponge member 100 are assembled to the frame 130.

  Thereby, in this embodiment, the relative positional accuracy of the photosensitive drum 12 and the charging roll 14 can be improved to the maximum.

(Third embodiment)
Next, a third embodiment as a reference example will be described.

  As shown in FIG. 6, in this embodiment, a sponge member (cleaning member) 140 for cleaning the charging roll 14 includes a bar-shaped substrate 140 </ b> A extending along the axial direction of the charging roll 14, and the substrate 140 </ b> A. It is composed of a pad-like sponge layer (elastic body) formed on one side.

  In the sponge member 140, like the sponge member 100 of the first embodiment, the support portions 140a provided at both ends of the substrate 140A are rectangular support holes 152 formed in the bearing member 150 having a single configuration. Are supported by a pair of bearing members 150 together with the charging roll 14. Further, the relative position between the charging roll 14 and the sponge member 140 is kept substantially constant, the sponge member 140 is pressed against the charging roll 14 with a predetermined load, and the sponge layer 140B is elastically deformed along the peripheral surface of the charging roll 14. A nip portion is formed.

  Thereby, when the charging roll 14 is driven to rotate along with the rotation of the photosensitive drum 12, the roll surface is brought into sliding contact with the sponge layer 140B of the sponge member 140 and cleaned.

  As described above, in this embodiment, the sponge member 140 that cleans the charging roll 14 is provided with the pad-like sponge layer 140B that is in sliding contact with the rotating charging roll 14, so that the charging roll 14 has a simple and inexpensive configuration. Can be cleaned well.

  The present invention has been described in detail with reference to the first to third 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 embodiment, the charging roll 14 is brought into contact with the lower part of the photosensitive drum 12 and the sponge members 100 and 140 are brought into contact with the lower part of the charging roll 14. The positional relationship between the roll 14 and the sponge members 100 and 140 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 sponge member is brought into contact with the upper portion of the charging 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.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (charged body)
14 Charging roll 14A Shaft 14a Supporting part 100 Sponge member (cleaning member / rotating body)
100A shaft 100a support part 100B sponge layer 110 bearing member (holding member)
120 frames
128 compression coil spring (biasing means)
130 frames
140 Sponge member (cleaning member)
140A Substrate 140B Sponge layer (elastic body)
150 Bearing member (holding member)

Claims (3)

A charging roll for charging the member to be charged by being in contact with the rotating member to be rotated and driven to rotate;
A cleaning member that contacts the surface of the charging roll to clean the charging roll;
A pair of support portions provided at both ends of the charging roll, and a pair of support portions provided at both ends of the cleaning member, corresponding to the pair of support portions provided at both ends of the cleaning member. And a single holding member that directly supports each of the charging roll and the cleaning member to hold the relative position of the cleaning member substantially constant;
A biasing means for biasing the pair of holding members toward the member to be charged to press the charging roll against the member to be charged;
Have
The pair of holding members are attached to a single housing so as to be movable along a biasing direction by the biasing means,
The image forming apparatus according to claim 1, wherein the cleaning member is a roll-shaped rotating body that rotates in contact with the rotating charging roll .   The image forming apparatus according to claim 1, wherein the member to be charged is rotatably supported by the single casing.   The charging roll is disposed vertically below the member to be charged,
  The image forming apparatus according to claim 1, wherein the cleaning member is disposed vertically below the charging roll.

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