JP4760313B2 - Image forming apparatus - Google Patents

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 that charges the surface of an image carrier while rotating in contact with or in close proximity to a rotationally driven image carrier. The present invention relates to an image forming apparatus having a charging-type 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 a problem, there is a technique for satisfactorily cleaning the surface of the charging roll by bringing a cleaning roll made of a roll-shaped sponge member or the like into contact with the surface of the rotating charging roll and rotating it in a driven manner. It has been proposed (see, for example, Patent Document 1).

  In such a cleaning roll, in order to obtain stable cleaning performance, it is desirable to secure a certain amount of the cleaning roll to the charging roll, for example, about 0.3 to 1.0 mm. However, when the amount of biting is increased, a load on the driven rotation of the charging roll increases, and a new problem occurs that the charging roll slips and charging unevenness occurs. In addition, in order to meet the recent demand for downsizing of the apparatus, there is a particular problem when, for example, a charging roll or a cleaning roll having a reduced outer diameter ≦ φ12 is used. In the case of the contact charging method, the charging roll obtains a driving torque (driving force) for rotation by friction and electrostatic attraction with the photosensitive member (image carrier). Frictional force + adsorptive force) × charged roll radius. Therefore, as the charging roll becomes smaller in diameter, the driving torque becomes smaller and slipping tends to occur.

On the other hand, a configuration is disclosed in which a charging roll is driven at the same speed as a photosensitive member using a driving mechanism including a driving gear and a driven gear (see, for example, Patent Document 2). In this prior art, by using the same drive mechanism, the cleaning roll is driven to rotate in the direction of rotating with the charging roll, thereby suppressing the occurrence of slip between the cleaning roll and the charging roll, thereby preventing the charging roll from being poorly cleaned. It has been proposed to prevent.
JP-A-5-297690 JP-A-8-62948

  However, when rotationally driving the charging roll or cleaning roll, it is extremely difficult to make the peripheral speeds of the charging roll, cleaning roll, and photoconductor completely equal in consideration of variations in the outer diameter of the roll. A speed difference of about several to 10% occurs. Therefore, a “shearing force” is exerted between the charging roll and the photoconductor or between the charging roll and the cleaning roll to stretch the contaminants attached to the surface of the photoconductor or the charging roll. Adhesion) is likely to occur. In addition, the cost increases by providing the drive mechanism for each roll, and the increase in size of the apparatus by securing the installation space is also a problem.

  On the other hand, as a method for increasing the driving torque, it is conceivable to increase the pressing load (pressing force) of the charging roll to the photosensitive member. However, if the load is increased too much, the charging roll may be deformed during storage, and the pressing load may be suppressed to, for example, about 10 N / 300 mm or less, depending on the material of the charging roll. desirable. Therefore, it is difficult to increase the driving torque only by increasing the load.

  In particular, a cleaning roll with a small diameter is likely to bend due to the influence of the pressure contact force, and this bending causes the end portion (support portion) of the rotating shaft of the cleaning member to be galled between the bearing portion and locally. Since they come into strong contact, there is a problem that the rotational resistance increases, the followability with respect to the charging roll is deteriorated, and the cleaning property is deteriorated. Further, due to an increase in the load received from the cleaning roll, the followability of the charging roll with respect to the photoconductor also deteriorates, so that charging failure is likely to occur.

  In view of the above-described facts, an object of the present invention is to provide an image forming apparatus capable of obtaining a good cleaning performance of a charging roll by a cleaning roll and a good charging performance to an object to be charged by the charging roll. .

According to the first aspect of the present invention, a charging roll for charging the object to be charged by being driven and rotated while being pressed against the rotating member to be charged, and a charging roll being cleaned by being driven and rotated by being pressed against the charging roll. A cleaning roller, a first receiving portion that rotatably supports a shaft end support portion of the charging roll, and a shaft end support of the cleaning roller so that the relative positions of the charging roller and the cleaning roller are held substantially constant. A support means for supporting both ends of the charging roll and the cleaning roll by a pair of bearing members each comprising a single member having a second receiving part for rotatably supporting the part; and A pair of urging means for urging the charged roll side against the charged body by urging the charged roll side, and the supporting means is provided by the urging means The charged body and the charging roll, and the charging roll and the cleaning roll are pressed against each other by a load from the pair of bearing members, and the central portion of the cleaning roll is bent in a direction away from the charging roll. Accordingly, the bearing member is tilted so that the charged member side of the bearing member is positioned on the inner side in the axial direction of the cleaning roll with respect to the opposite side to the charged member side .

  In the present invention, the charging roll and the cleaning roll are rotatably supported by the support member, respectively, and the relative positions are held substantially constant while the cleaning roll is in pressure contact with the charging roll. The charging roll is pressed against the charged body by the supporting member being urged toward the charged body by the urging means, and is driven to rotate as the charged body rotates to charge the charged body and rotate. Accordingly, cleaning is performed by a cleaning member that is driven to rotate.

With this configuration , when the cleaning roll is pressed against the charging roll to bend, and the support part is displaced, the support member tilts following the displacement of the support part, so the support part strongly contacts the support member. In this case, it is possible to prevent a failure of the cleaning roll from following the charging roll. Further, by suppressing increase in the load received from the cleaning roll, it is possible to prevent the follow-up failure of the charging roll relative to the charged body.

  Furthermore, when the charging roll bends due to the influence of the pressure contact force, the rotational resistance increases due to an increase in the contact pressure between the support part and the support member, and the followability deteriorates. Since the support member also follows and tilts with respect to the displacement, an increase in contact pressure is suppressed and followability is improved. Therefore, it is possible to obtain a good cleaning performance of the charging roll by the cleaning roll and a good charging performance to the member to be charged by the charging roll.

  In addition, by supporting the charging roll and the cleaning member with a common support member in this way, for example, the support structure and the power supply structure for applying a voltage can be simplified compared to a configuration in which they are individually supported by separate members. Can be

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the support portion of the cleaning roll is disposed on an inner side in the axial direction than an action line in which the biasing unit applies a biasing force to the support unit . It is characterized by being.

  In the present invention, the support portion of the cleaning roll supported by the support member is positioned axially inward of the action line where the urging means applies the urging force to the support member, that is, the action point (load point) at which the urging force acts. By disposing the support member on the inner side in the axial direction with respect to the straight line along the direction in which the urging force is applied, the support member is easily inclined following the displacement (inclination) of the support portion due to the deflection of the cleaning roll. Accordingly, the support member can be tilted by following the displacement of the support portion with a simple configuration without using a special tilt mechanism or electrical means, and the good followability of the cleaning roll and the charging roll ( (Rotatability) can be ensured.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the support portion of the charging roll is disposed on an action line that causes the urging unit to exert a urging force on the support unit . It is a feature.

  In the present invention, the supporting portion of the charging roll supported by the supporting member is placed on the line of action where the urging means applies the urging force to the supporting member, that is, through the action point (load point) at which the urging force acts. By arranging them on a straight line along the direction in which the charging roll is applied, a pressing force (biasing force) for pressing the charging roll against the member to be charged can be efficiently transmitted to the charging roll via the support member. Thereby, the pressure contact state of the charging roll with respect to the member to be charged becomes almost uniform in the axial direction and becomes stable, and the followability can be further improved.

  According to the image forming apparatus of the present invention, it is possible to obtain good cleaning performance of the charging roll by the cleaning roll and good charging performance to the member to be charged by the charging roll.

  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. It is considered that the cleaning performance is maintained and maintained by returning to the cleaning device 78 that cleans the photosensitive drum 12.

(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. 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)
Next, the support structure for the charging roll 14 and the cleaning roll 100 according to the present embodiment will be described in detail.

  As shown in FIG. 3, in this embodiment, the charging roll 14 and the cleaning roll 100 are assembled into a single frame 120 via a pair of bearing members 110 and housed in the frame 120, and further, the photosensitive drum 12. Are also assembled into the frame 120 and unitized.

  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 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 provided at the end of the shaft 100A 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 FIG. 3, the frame 120 includes 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. In addition, a predetermined gap is provided between the guide groove 126 and the bearing member 110 along the axial direction of the charging roll 14 and the cleaning roll 100, so that the bearing member 110 is placed in the guide groove 126. It can be inclined with respect to the sliding direction.

  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.

  Further, in the present embodiment, the support portion 100a of the cleaning roll 100 supported by the bearing member 110 is located on the inner side in the axial direction from the action line L where the compression coil spring 128 applies the spring force to the bearing member 110, that is, the spring force. Is arranged on the inner side in the axial direction from the straight line along the direction in which the spring force is applied through the point of action (load point P). Further, the support portion 14a of the charging roll 14 supported by the bearing member 110 passes through an action point (load point P) where the spring force of the compression coil spring 128 acts on the action line L, that is, its spring force. It is arrange | positioned on the straight line along the direction which adds.

  Thus, 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 cleaning roll 100 is driven to rotate with the rotation of the charging roll 14. Then, the charging roll 14 is cleaned.

  Next, the effect | action of this embodiment is demonstrated with reference to FIGS.

  FIG. 5A shows an outline of driving torque and rotational load acting between the photosensitive drum 12 and the charging roll 14 and between the charging roll 14 and the cleaning roll 100.

  As shown in FIG. 5A, the charging roll (BCR) 14 receives a conveying force from the photosensitive drum 12, and receives a rotational load due to its own rolling resistance and shaft sliding resistance. Further, a rotational load is received from the cleaning roll (CLN-R) 100, which includes the rolling resistance of the cleaning roll 100 and the shaft sliding resistance of the cleaning roll 100. In addition to these, there are forces that form a rotational load, but these are omitted.

  Since the above-described transport force depends on the frictional force between the photosensitive drum 12 and the charging roll 14, it greatly depends on the spring load that presses the charging roll 14 and the cleaning roll 100 against the photosensitive drum 12. On the other hand, when this spring load changes, the load applied to the bearing member 110 changes and the sliding resistance changes, so that the rotational load also has spring load dependency. Therefore, the spring load dependency of the conveying force and the rotational load is as shown in FIG. 5B, and the charging roll 14 and the cleaning roll 100 are stably driven and rotated in a region where the conveying force exceeds the spring load exceeding the rotational load. You can see that

  The load applied to the bearing member 110 will be described with reference to FIG. FIG. 6 shows the force applied to each of the photosensitive drum 12, the charging roll 14, and the cleaning roll 100.

  The balance equation for the charging roll 14 and the cleaning roll 100 is as shown in FIG. 6, and the balance equation when the charging roll 14, the cleaning roll 100, and the bearing member 110 are regarded as one body is also shown in FIG. 6. Indicated.

  When the load applied to the bearing portion (bearing hole 112) of the charging roll 14 and the bearing portion (bearing hole 114) of the cleaning roll 100 is obtained from these three balance equations, the bearing portion of the cleaning roll 100 is determined as the cleaning roll. The nip load between the roller 100 and the charging roll 14 is applied as it is, whereas the bearing portion of the charging roll 14 has a nip load between the photosensitive drum 12 and the charging roll 14 and a nip load between the cleaning roll 100 and the charging roll 14. It can be seen that only the difference is applied. Therefore, the sliding resistance of the cleaning roll 100 is remarkably larger than the sliding resistance of the bearing of the charging roll 14, and when considering the followability, the sliding resistance of the cleaning roll 100 is sufficiently considered. It is necessary to.

  Further, from the consideration of how the bearing load is applied, the charging roll 14 obtains a pressure contact force with the cleaning roll 100 and the photosensitive drum 12 close to a uniform load, whereas the cleaning roll 100 is supported at both ends. It can also be seen that it is loaded and easily bent.

  On the other hand, in order to keep the contact state between the photosensitive drum 12 and the charging roll 14 and between the charging roll 14 and the cleaning roll 100 in a good and uniform nip, both rolls have a certain thickness, for example, about 2 to 3 mm. An elastic layer is required. In order to make the outer diameter ≦ φ12 small, the diameter of the cored bar must be about φ4-6 or less, but with such a thin cored bar, for example, a cored bar of about φ4, When the axial length is about 300 mm, when the pressure contact is performed with a load of about 10 N, the cleaning roll 100 side may bend about 0.5 mm at the center even if a stainless alloy such as SUS303 is used.

  When the cored bar (shaft 100A) is bent in this manner, the cored bar is galling in the bearing part (bearing hole 114) of the cleaning roll 100 as shown in FIG. Will rise significantly. In this case, as shown in FIG. 7A, the spring load, which is the main component of the force applied to the bearing member 110A, and the cleaning roll shaft load act on substantially the same line, so that the bearing is tilted. The force is suppressed (the charging roll axial load is small compared to both).

  On the other hand, if the positional relationship between the load point and the bearing surface is as shown in FIG. 7C, it acts on the point where the spring load and the cleaning roll shaft load are separated from each other. A couple force to be bent is generated, and the bearing member 110B can be tilted appropriately. Thereby, since the cored bar (support part 100a) and the bearing surface 115 substantially coincide, the above-described galling of the cored bar is suppressed, and an increase in sliding resistance can be prevented.

  As described above, in the present embodiment, when the cleaning roll 100 is pressed against the charging roll 14 to bend and the support portion 100a of the shaft 100A is displaced, the bearing member follows the displacement of the support portion 100a. Since 110 inclines, it is avoided that the support part 100a is galling between the bearing hole 114 and strongly contacts locally. As a result, an increase in rotational resistance is suppressed, and a poor follow-up of the cleaning roll 100 with respect to the charging roll 14 can be prevented. Further, by suppressing an increase in the load received from the cleaning roll 100, it is possible to prevent the charging roll 14 from being poorly driven with respect to the photosensitive drum 12.

  Furthermore, when the charging roll 14 bends due to the influence of the pressure contact force, the rotational resistance increases due to an increase in the contact pressure between the support portion 14a of the shaft 14A and the bearing hole 112, and the followability deteriorates. Since the bearing member 110 also tilts following the displacement of the support portion 14a of the roll 14, an increase in contact pressure is suppressed, and the followability is improved. Therefore, good cleaning performance of the charging roll 14 by the cleaning roll 100 and good charging performance to the photosensitive drum 12 by the charging roll 14 can be obtained.

  In addition, as described above, the charging roll 14 and the cleaning roll 100 are supported by the common bearing member 110, so that, for example, compared to a configuration in which they are individually supported by separate members, a support structure and power supply for applying a voltage are applied. The structure can be simplified.

  Further, the support member 100a of the cleaning roll 100 supported by the bearing member 110 is disposed on the inner side in the axial direction from the action line L in which the compression coil spring 128 applies a spring force to the bearing member 110, whereby the bearing member 110 is provided. Becomes easy to incline following the displacement (inclination) of the support part 100a due to the bending of the cleaning roll 100. Accordingly, the bearing member 110 can be tilted by following the displacement of the support portion 100a with a simple configuration without using a special tilting mechanism or electrical means, and the cleaning roll 100 and the charging roll 14 are excellent. Secure followability.

  Further, the support portion 14a of the charging roll 14 supported by the bearing member 110 is disposed on the action line L, so that the charging roll 14 is pressed against the photosensitive drum 12 via the bearing member 110. This pressure contact force (spring force) can be efficiently transmitted to the charging roll 14. As a result, the pressure contact state of the charging roll 14 with respect to the photosensitive drum 12 becomes almost uniform in the axial direction and becomes stable, and the followability is further improved.

(Configuration of Example)
Hereinafter, the charging roll 14 and the cleaning roll 100 used in the examples will be described. As the charging roll 14 used in this example, as shown in FIG. 8A, a conductive core layer 15A, a resistance layer 15B, a surface, a surface of a metallic core bar that forms a shaft 14A A roll having an outer diameter of 12 mm in which the protective layer 15C was laminated in this order was used.

  As the metal core, a SUS303 stainless alloy with a diameter of 8 mm is used, and a conductive elastic layer having a thickness of 2 mm containing carbon black (CB) is coated on the periphery thereof, and epichlorhydrin rubber is coated with CB on the outer periphery. A 0.1 mm thick resistive layer containing SiO2 was coated. Further, finally, a coating layer having a thickness of 5 to 50 μm was formed as a surface layer using a coating agent containing CB and SiO 2 in a nylon resin.

  In addition, as shown in FIG. 8B, the cleaning roll 100 used in this example is an outer cover in which a polyurethane foam constituting the sponge layer 100B is coated around a metal core constituting the shaft 100A. A roll with a diameter of 10 mm was used.

  As the metal core, a SUS303 stainless alloy having a diameter of 6 mm was used. As the polyurethane foam, ether-based polyurethane having a thickness of 2 mm and having a hardness adjusted so that a load necessary to push a φ50 disk-like member by 0.5 mm is about 0.8 to 1.5 N was used.

(Followability evaluation method)
Below, the evaluation method of followability is demonstrated. The φ30 photosensitive drum 12, the charging roll 14 and the cleaning roll 100 of this embodiment were arranged as shown in FIG. The amount of biting between the cleaning roll 100 and the charging roll 14 contributes to the rotational load, but is fixed at 0.75 mm in this embodiment. Further, since the contact state of the photosensitive drum / charging roll / cleaning roll changes depending on the temperature and the frictional force changes, the test was performed under a constant temperature. In addition, since the synthetic resin used for the bearing member 110 and the like has a temperature change in dimensions, the inner diameter of the bearing portion (bearing holes 112 and 114) is reduced and the sliding resistance is increased in a low temperature environment (10 ° C.). And measured.

  The follow-up performance was evaluated by measuring the peripheral speed of the charging roll when the photosensitive member was rotated at a peripheral speed of 165 mm / s while changing the pressure spring load of the charging roll. The circumferential speed is measured by attaching a reflective member of about 5 mm square to the surface of the charging roll and using a non-contact type tachometer (Hi-tachometer 3403) manufactured by Hioki Electric Co., Ltd. It was done by measuring.

(Following evaluation results)
The followability was evaluated for the comparative example shown in FIGS. 10 (A) and 10 (B) and the example shown in FIGS. 11 (A) and 11 (B). As shown in FIG. 12, in the comparative example, the rotation due to the sliding resistance of the cleaning roll was large, and a load of about 13 N was required to obtain stable followability. On the other hand, in Example, the rotational load was reduced, and stable followability could be obtained with a load of about 7.5N.

  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 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. However, the structure for supporting and pressing the rolls is not limited to this, and the charging roll 14 that is in contact with or close to the photosensitive drum 12 and the charging roll 14 are pressed. Thus, the present invention can also be applied to a configuration in which the cleaning roll 100 that is driven and rotated is supported by an individual bearing member and is urged and pressed by an individual urging means.

  Further, the charging roll 14 is brought into contact with the lower part of the photosensitive drum 12 and the cleaning rolls 100 and 140 are brought into contact with the lower part of the charging roll 14. However, the photosensitive drum 12, the charging roll 14, and the cleaning roll are arranged. The positional relationship between 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.

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 a configuration of a support structure for a photosensitive drum, a charging roll, and a cleaning roll according to an embodiment of the present invention. 1 is a perspective view showing a state where a charging roll and a cleaning roll according to an embodiment of the present invention are pivotally supported by a bearing member. (A) is explanatory drawing for demonstrating the drive torque and rotational load which act on a photosensitive drum, the charging roll 14, and a cleaning roll, (B) is a graph which shows the spring load dependence of conveyance force and rotational load. FIG. It is explanatory drawing for demonstrating the force concerning a photoconductor drum, the charging roll 14, and a cleaning roll. (A)-(C) is explanatory drawing for comparing and explaining the improvement effect of the support structure which concerns on one Embodiment of this invention with respect to the support structure of the conventional charging roll and sponge member. (A) is sectional drawing which shows the cross section of the charging roll which concerns on the Example of this invention, (B) is sectional drawing which shows the cross section of the cleaning roll which concerns on the Example of this invention. FIG. 3 is a partial cross-sectional side view illustrating a configuration of a support structure for a photosensitive drum, a charging roll, and a cleaning roll according to an embodiment of the present invention. (A), (B) is a partial cross section side view which shows the structure of the support part and bearing member of a charging roll and a cleaning roll which concern on the comparative example of this invention. (A), (B) is a partial cross section side view which shows the structure of the support part and bearing member of a charging roll and a cleaning roll which concern on the Example of this invention. It is a graph which shows the evaluation result of the followability of the support structure of the comparative example shown in FIG. 10, and the support structure which concerns on the Example of this invention shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (to-be-charged body)
14 Charging roll 14A Shaft 14a Support part 100 Cleaning roll 100A Shaft 100a Support part 100B Sponge layer 110 Bearing member (support member)
112 Bearing hole 114 Bearing hole 128 Compression coil spring (biasing means)

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 roll for cleaning the charging roll by being driven and rotated against the charging roll;
The first receiving portion for rotatably supporting the shaft end support portion of the charging roll and the shaft end support portion of the cleaning roll can be rotated so that the relative position between the charging roll and the cleaning roll is held substantially constant. Supporting means for supporting both ends of the charging roll and the cleaning roll with a pair of bearing members each composed of a single member provided with a second receiving portion supported by
A pair of urging means for urging the support means toward the member to be charged and pressing the charging roll against the member to be charged;
Have
The supporting means presses the charged body and the charging roll, and the charging roll and the cleaning roll, respectively, with a load from the pair of bearing members provided by the biasing means, and a central portion of the cleaning roll Is tilted so that the charged member side of the bearing member is positioned on the inner side in the axial direction of the cleaning roll with respect to the opposite side to the charged member side. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the support portion of the cleaning roll is arranged on an inner side in an axial direction than an action line in which the biasing unit applies a biasing force to the support unit.   The image forming apparatus according to claim 2, wherein the supporting portion of the charging roll is disposed on a line of action in which the urging unit applies an urging force to the supporting unit.

Images