JP4730058B2 - Image forming apparatus and process cartridge - Google Patents

Description

  The present invention relates to an image forming apparatus and a process cartridge.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers that employ an electrophotographic system, those using a corona discharge phenomenon such as a scorotron charger have been frequently used as a charging device.

  However, in such chargers, the generation of ozone and nitrogen oxides that are harmful to the human body and the global environment is a problem.

  As another charging device used in an electrophotographic image forming apparatus, there is a contact charging type device in which an image bearing member is charged by directly contacting a conductive charging member. Contact-type charging devices have recently become mainstream because they generate much less ozone and nitrogen oxides and have good charging efficiency.

  By the way, the biggest problem of the charging device of the contact charging system is contamination due to adhesion of foreign matters to the surface of the charging member, which is caused when the charging member is always in contact with the image carrier.

  In the charging step, after the surface of the image transfer member is charged by the charging member, the surface of the image carrier is exposed in the exposure step to form an electrostatic image. In the developing step, toner is attached to the electrostatic image to form a toner image. In the transferring step, the toner image formed on the surface of the image carrier is transferred to a transfer medium. The toner remaining without being transferred to the transfer medium is removed from the surface of the image carrier in a cleaning process.

  However, particles that are smaller than the toner adhering in the development process, such as crushing toner and toner external additives that are crushed during use, remain on the surface of the image carrier without being removed in the cleaning process. Adhere to the surface. When foreign matter such as particles adheres to the surface of the charging member, the surface resistance value of the charging member becomes uneven, causing abnormal discharge or unstable discharge, and the image carrier is not uniformly charged.

  Accordingly, a cleaning method has been devised in which the charging member is cleaned by scraping off dirt such as foreign matter adhering to the surface of the charging member with a blade or a pad.

  In order to maintain the charging ability of the charging member over a long period of time, the charging member and the blade or pad need to be in strong contact. However, if the blade or pad is always in contact with the charging member, the surface of the charging member may be damaged. In order to shorten the life of the charging member, a retract type cleaning device in which a blade or a pad is intermittently brought into contact with the charging member has been put into practical use.

  However, in the retract type cleaning device, since the cleaning operation becomes intermittent, there is a concern that the surface of the charging member may not be sufficiently cleaned if the surface of the charging member becomes extremely dirty during the cleaning operation.

In view of this, as a cleaning device that can always clean the charging member, there has been proposed a cleaning device in which a roller-shaped cleaning member is driven while being in contact with the charging member (Patent Document 1). Further, in the cleaning device, there has been proposed one in which the cleaning member is bitten into the charging member by a specific biting amount, and at the same time, the cleaning member is driven by driving means to prevent the cleaning member from slipping (Patent Document). 2).
JP-A-2-272594 JP-A-8-062948

  However, in these cleaning apparatuses, if the cleaning member is increased in contact area with the charging member to improve the cleaning performance, the pressing force of the cleaning member against the charging member becomes excessive. There arises a problem that slip occurs between the cleaning members and the cleaning member does not rotate.

  If driving means is provided on the charging member or the cleaning member in order to solve the slip or rotation failure, the configuration around the charging member becomes complicated, leading to an increase in cost and a great hindrance to downsizing.

  In addition, since the cleaning member and the charging member are always in contact as described above, high cleaning performance is exhibited in a low-temperature environment where the releasability of dirt such as external additives is good, but the releasability of dirt. In a high-temperature and high-humidity environment with poor quality, filming in which dirt adheres to the surfaces of the cleaning member and the charging member tends to occur. In particular, when a circumferential speed difference is provided between the cleaning member and the charging member when the pressing force is high, the occurrence of filming becomes significant, and thus high cleaning performance is maintained for a long time in various environments. It was difficult.

  The present invention has been made in order to solve the above-described problems. There is no rotation failure of the charging member and the cleaning member, and no filming occurs even in a high-temperature and high-humidity environment. An object of the present invention is to provide an image forming apparatus capable of exhibiting a cleaning property and a process cartridge attached to and detached from the image forming apparatus.

The invention of claim 1 includes an image bearing member, a roller-shaped charging member by rotating with contact charging the image bearing member to said image bearing member, is rotated in contact with said charging member And a roller-shaped cleaning member having an elastic layer formed on the surface, and the charging member has a surface hardness measured in accordance with JIS K 7312 of 50 degrees or more and 85 degrees or less. the size of the total runout is at 0.4mm or less, the ratio S10 / S50 in the load S10 in the time the elastic 10% the load of S50 at 50% compression of the layer compression of the cleaning member is not less than 0.4, the cleaning the elastic layer of the member is a polyurethane foam, the cleaning member, to characterized in that the compressibility of the elastic layer are pressed against the charging member to be less than 1% to 50% An image forming apparatus.

  The cleaning member rotates at a high speed while being constantly compressed and in contact with the charging member. If the cleaning member is highly accurate, in other words, if the deflection is small and straightness is high, and if the cleaning member is attached with high accuracy, the cleaning member contacts the charging member with a constant compressive load. Is obtained.

  As the cleaning member, a member having a structure in which a shaft is inserted and fixed at the center of a cylindrical cleaning member is often used. The cleaning member having such a structure is generally formed by forming an insertion hole in a foam material formed in an appropriate shape and fixing the outer periphery of the insertion hole fixed through a shaft with a cylindrical grinder or the like. It is made by polishing.

  However, in the manufacturing method, it is difficult to achieve high outer diameter accuracy and runout accuracy, and if high outer diameter accuracy and runout accuracy are to be achieved, the processing becomes complicated and the yield decreases. Therefore, the cleaning member becomes expensive.

  Since the cleaning member used in the image forming apparatus has a ratio S10 / S50 of the load S50 to the load S10 of 0.4 or more, the charging member can be used without extremely increasing the outer diameter accuracy and the deflection accuracy. Since the compression load applied to the charging member is substantially constant, even if the charging member is compressed and contacted with the charging member and rotated at a high speed, the change in the pressing force is small and good cleaning performance can be obtained.

  Therefore, the surface of the charging member is less likely to leave dirt and image quality defects such as streaks.

  When the load S50 and the load S10 are obtained by compressing at a constant speed of 10 mm / s in a vertical direction with a disk having a diameter of 200 mm using a material having a thickness of 50 mm, a vertical width and a horizontal width of 390 mm based on the JIS-K6400 specification. Of the load when the compression rate is 50% and the compression rate is 10%.

  When the magnitude of the total deflection of the cleaning member is 0.4 mm or less, the change in the compressive load exerted from the cleaning member to the charging member is reduced, and defective cleaning of the charging member is prevented. The total runout is preferably 0.35 mm or less. Here, as shown in FIG. 3, the magnitude of the total deflection is determined by measuring the displacement amount of the distance from the reference plate to the cleaning member while rotating the cleaning member, and measuring the maximum and minimum values of the displacement amount. This value is defined as the maximum value of the deflection of the measurement points measured repeatedly, for example, 3 to 10 points along the longitudinal direction of the cleaning member.

  In the image forming apparatus, since the cleaning member is brought into contact with the charging member at a constant compression rate, the cleaning action of the cleaning member is stable.

  The compression ratio is particularly preferably in the range of 5 to 40%.

  According to the polyurethane foam, a porous foam having a three-dimensional structure can be obtained, but the porous foam having a three-dimensional structure often takes in external additives and pulverized toner adhering to the surface of the charging member. Easy to wear and resistant to wear. Furthermore, filming does not occur on the surface of the charging member even under high temperature and high humidity.

  If the Asker C hardness of the surface of the charging member is within the above range, the charging member is appropriately deformed by being nipped between the cleaning member and the image carrier, and therefore the rotation of the image carrier is cleaned via the charging member. Effectively transmitted to the member, rotation failure of the charging member and the cleaning member is prevented. In addition, since the charging member is not significantly deformed by the nip, it is possible to prevent the cleaning property of the cleaning member from being deteriorated and the charging failure of the image carrier due to the non-uniform nip between the charging member and the image carrier. The

According to a second aspect of the present invention, there is provided a roller-shaped charging member that rotates while being in contact with an image carrier, and charges the image carrier, an exposure unit that forms an electrostatic image on the image carrier, and the image carrier Developing means for developing a toner image by developing an electrostatic image formed on the body with toner, and the toner image on the image carrier remaining on the image carrier after being transferred to a transfer body or an image recording medium 2. A process cartridge according to claim 1, further comprising at least one of image bearing member cleaning means for removing the toner that has been removed.

  Since the process cartridge can be attached to and detached from the image forming apparatus, mounting the charging member or the like on the process cartridge side facilitates replacement when the charging member or the like is consumed or damaged.

  As described above, according to the present invention, there is no charging unevenness or filming of the charging member due to rotation failure, and an image forming apparatus capable of obtaining good image quality over a long period of time, and the image forming apparatus can be attached to and detached from the image forming apparatus. A process cartridge is provided.

1. Embodiment 1
A full-color image device that is an example of the image forming apparatus of the present invention will be described below.

1-1 Overall Configuration The image forming apparatus 10 according to the first embodiment is a four-cycle full-color image forming apparatus, and as illustrated in FIG. A photosensitive drum 12 corresponding to a carrier is rotatably disposed. As the photosensitive drum 12, for example, a drum made of a conductive cylinder having a diameter of about 47 mm and having a surface coated with a photosensitive layer made of OPC or the like is used. It is rotationally driven at a process speed of about 150 mm / sec.

  The surface of the photosensitive drum 12 is charged to a predetermined potential by a charging roller 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 roller 14. Image exposure is performed, and an electrostatic latent image according to image information is formed. The charging roller 14 corresponds to a charging member in the present invention.

  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, and becomes 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 by the primary transfer roller 22 while being superimposed on the intermediate transfer belt 20. The intermediate transfer belt 20 is an example of a transfer body.

  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 roller 26.

  On the other hand, the recording paper 24 is fed from a paper feed cassette 28 arranged at the lower part of the image forming apparatus 10 by a pickup roller 30 and is fed in a state where it is rolled one by one by a feed roller 32 and a retard roller 34. Then, the toner image is conveyed 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 roller 36.

  The intermediate transfer belt 20 includes a wrap-in roller 38 that specifies the wrap position of the intermediate transfer belt 20 on the upstream side in the rotation direction of the photosensitive drum 12, and a toner image formed on the photosensitive drum 12 as an intermediate transfer belt. A primary transfer roller 22 to be transferred onto the intermediate transfer belt 20, a wrap-out roller 40 for specifying 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 roller 26 via the intermediate transfer belt 20. The roller 42, the first cleaning backup roller 46 facing the cleaning device 44 of the intermediate transfer belt 20, and the second cleaning backup roller 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 the photosensitive drum 12, the charging roller 14, the intermediate transfer belt 20, a plurality of rollers 22, 38, 40, 42, 46, and 48 that stretch the intermediate transfer belt 20, and the 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 contact the surface of the intermediate transfer belt 20 stretched by the first cleaning backup roller 46, and a second cleaning backup roller 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, and 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 is fixed is discharged as it is onto a discharge tray 68 provided on the upper part of the image forming apparatus 10 by a discharge roller 66.

  On the other hand, in the case of double-sided printing, the recording sheet 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 roller 66, but the discharge roller 66 In this state, the discharge roller 66 is reversed while the rear end portion of the recording paper 24 is pinched, and the conveyance path of the recording paper 24 is switched to the double-sided paper conveyance path 70. In a state where the front and back of the recording paper 24 are reversed by the transport roller 72 provided, 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. 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 freely opened and closed. The recording paper 24 of an arbitrary size and type placed on the manual feed tray 74 is fed by a paper feed roller 76, and the secondary transfer position of the intermediate transfer belt 20 via a transport roller 73 and a registration roller 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, the charging roller 14 is in contact with the photosensitive drum 12 below the photosensitive drum 12. The charging roller 14 has a charging layer 14B formed around a conductive shaft 14A.

  A roller-shaped cleaning roller 100 that is in contact with the surface of the charging roller 14 is provided at a lower portion of the charging roller 14 opposite to the photosensitive drum 12. The cleaning roller 100 has an elastic layer 100B formed around the shaft 100A.

  As shown in FIG. 4, the cleaning roller 100 and the charging roller 14 are both supported by a pair of conductive bearing members 15 on the shaft 100A and the shaft 14A, respectively. In FIG. 4, one of the conductive bearing members 15 is omitted. The conductive bearing member 15 is configured so that a DC voltage from a high-voltage power source is applied and the shaft 100A can move with respect to the shaft 14A. Thereby, the distance between the shafts of the cleaning roller 100 and the charging roller 14 is increased. Can be adjusted.

  The cleaning roller 100 is pressed against the charging roller 14 with a predetermined repulsive load, and the elastic layer 100 </ b> B is elastically deformed along the peripheral surface of the charging roller 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 roller 14 is driven to rotate in the direction of arrow 4 as the photosensitive drum 12 rotates. Further, the roller-shaped cleaning roller 100 is driven to rotate in the direction of the arrow 6 by the rotation of the charging roller 14.

  As the cleaning roller 100 is driven to rotate, dirt such as toner and external additives on the surface of the charging roller 14 is cleaned by the cleaning roller 100. Further, the charging roller 14 and the cleaning roller 100 have a physical property of scraping off dirt such as toner and external additives attached to the surface of the charging roller 14 by the contact of the cleaning roller 100. This physical property adjusts the material, surface microhardness, elastic modulus, and the like of the charging roller 14, and also adjusts the material of the cleaning roller 100, the number of foam cells, the amount of biting into the charging roller 14, and the like. It is a property obtained by this. These physical properties will be described later.

1-2 Cleaning Roller In the elastic layer 100B of the cleaning roller 100, the ratio S10 / S50 between the load S50 at 50% compression and the load S10 at 10% compression is 0.4 or more.

  Since the cleaning roller 100 is constantly compressed and in contact with the charging roller 14 and rotates at a high speed, in order to obtain a high cleaning performance, the cleaning member must be highly accurate, specifically, the shake is small and straight. And high mounting accuracy of the cleaning roller 100 is required.

  Here, the cleaning roller 100 has an insertion hole formed in a central portion of a foamed material such as polyurethane foam formed in an appropriate shape, and the outer periphery of a shaft that is fixed by inserting the shaft 100A into the insertion hole is cylindrical. It is produced by polishing in a cylindrical shape with a grinding machine or the like.

  If it is intended to achieve high outer diameter accuracy and runout accuracy in the manufacturing method, the processing becomes complicated and the yield decreases, so that the cleaning roller 100 becomes expensive.

  However, if the ratio S10 / S50 between the load S10 and the load S50 is set to 0.4 or more, the cleaning roller 100 can be charged to the charging roller even if the outer diameter accuracy and the deflection accuracy of the cleaning roller 100 are not extremely increased. Since the compression load applied to 14 is substantially constant, even if the cleaning roller 100 is rotated at high speed while being compressed and in contact with the charging roller 14, the change in the pressing force is reduced, and good cleaning performance can be obtained. Therefore, the surface of the charging member is less likely to leave dirt and image quality defects such as streaks.

  The loads S50 and S10 are made of a material having a thickness of 50 mm, a vertical width and a horizontal width of 390 mm based on the JIS-K6400 specification as described in the section “Means for Solving the Problems”. It is a value obtained by compressing in the vertical direction at a constant speed of 10 mm / s.

  Further, from the viewpoint of preventing the rotation failure of the cleaning roller 100 and exhibiting good cleaning properties, the magnitude of the total runout of the cleaning roller 100 is preferably 0.4 mm or less, and particularly preferably 0.35 mm or less. Here, as shown in FIG. 3, the magnitude of the total shake is measured by measuring the displacement of the distance between the reference plate and the cleaning roller 100 while rotating the cleaning roller 100, and the maximum value of the displacement. A value obtained by taking a difference between the minimum value and the minimum value is measured, and this is repeatedly measured along the longitudinal direction of the cleaning roller 100 at several points, for example, 3 to 10 points. Defined.

  Further, the cleaning roller 100 is preferably pressed against the charging roller 14 so that the compression rate of the elastic layer 100B is 1 to 50%, particularly 5 to 40%.

  If the compression rate of the elastic layer 100B is 50% or less, the cleaning roller 100 can be stably rotated by being driven by the charging roller 14, so that rotation failure does not occur. Further, since the foam cell of the elastic layer 100B is not crushed, dirt such as an external additive is sufficiently taken into the foam cell. Therefore, the dirt adhering to the charging roller 14 is not rubbed against the surface of the charging roller 14, and the occurrence of filming is also prevented. On the other hand, if the compressibility of the elastic layer 100B is 1% or more, sufficient cleaning properties can be obtained.

  For the elastic layer 100B, foamed materials made of various resin materials such as polyethylene, polyamide, polyurethane, and polypropylene can be used, and external additives can be effectively removed, and the surface of the charging roller 14 is not damaged. In addition, a porous foam having a three-dimensional structure is preferable from the point that tearing and breakage do not occur over a long period of time.

  The number of foam cells of the foam is preferably 30 to 80 cells / 25 mm. The cleaning roller 100 using the foam material having the number of foam cells as the elastic layer 100B is preferable because dirt such as an external additive is easily taken into the elastic layer 100B. Polyurethane foams are particularly preferred because of their excellent tear strength and tensile strength.

  As the polyurethane used as the polyurethane foam, polyols such as polyester polyol, polyether polyester, acrylic polyol, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, Reaction products with diisocyanates such as tolidine diisocyanate and 1,6-hexamethylene isocyanate can be used. Moreover, what mixed and reacted chain extenders, such as 1, 4- butanediol and a trimethylol propane, to the reaction mixture of the said diol and diisocyanate can also be used. The reaction mixture is mixed with a foaming agent such as water, an azo compound such as azobisdicarbonamide or azobisisobutyronitrile, and foamed while reacting the diol, diisocyanate and chain extender in the reaction mixture. Thereby, a polyurethane foam is obtained. A polyurethane foam may be produced by blending the reaction mixture with an auxiliary agent such as a foaming aid, a wrapping agent, or a catalyst that controls foamability as necessary.

  When a polyurethane foam is used as the elastic layer 100B, the diol, diisocyanate, foaming agent, type and amount of the foaming aid in the reaction composition, and selection of a catalyst for promoting the reaction, etc. Cell number and cell density can be controlled. By controlling the number of cells and the cell density in this manner, the repulsive load at a compression rate of 50% and 10% of the elastic layer 100B, the ratio thereof, and the like can be set within a predetermined range.

  As the polyurethane foam used for the polyurethane foam, the outer diameter of the cleaning roller 100 is preferably in the range of 8 to 15 mm, particularly preferably in the range of 9 to 14 mm.

  If the outer diameter of the cleaning roller 100 is within the above range, the number of contacts per surface of the charging roller 14 is neither too much nor too little, so that the surface of the charging roller 14 is effectively removed. In addition, sufficient long-term stability is obtained.

1-3 Charging Roller Hereinafter, the charging roller 14 will be described in detail.

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

  The charging roller 14 preferably has a surface Asker C hardness of 50 to 85 degrees, particularly preferably 60 to 85 degrees. Here, the Asker C altitude is a value obtained by measuring the hardness of the surface of the charging roller 14 with an Asker (trade name) C-type hardness meter in accordance with JIS K 7312.

  If the Asker C hardness of the surface of the charging roller 14 is 50 or more, the charging roller 14 is significantly deformed at the contact portion between the cleaning roller 100 and the photosensitive drum 12 when the cleaning roller 100 is pressed against the charging roller 14. Therefore, the cleaning property of the cleaning roller 100 is not deteriorated, and the nip formation between the photosensitive drum 12 and the charging roller 14 is not uniform, and the charging failure of the photosensitive drum 12 does not occur. If the Asker C hardness is 85 or less, the charging roller 14 is sufficiently nip-deformed by contact with the photosensitive drum 12, so that the rotational force from the photosensitive drum 12 is sufficiently transmitted to the charging roller 14. The Therefore, rotation failure does not occur.

  The diameter of the charging roller 14 is from φ8 mm to φ15 mm, more preferably from φ9 mm to φ14 mm, and the thickness of the charging layer 14B is preferably from 2 mm to 4 mm. If the diameter is 15 mm or more, the number of times of contact with the external additive per location on the peripheral surface is reduced, and the number of discharges is reduced. This is disadvantageous from the viewpoint of miniaturization, although it has excellent long-term stability against dirt and charging performance. . If the diameter is 8 mm or less, the image forming apparatus 10 can be downsized, which is advantageous, but the number of times of contact with the external additive per peripheral surface increases and the number of discharges increases, which is disadvantageous for long-term stability. It becomes.

  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 roller 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 elastic material constituting the conductive elastic layer is formed, for example, by dispersing a conductive agent in a rubber material. Rubber materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide. -Allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber, natural rubber and the like, and blended rubbers thereof. Among these, silicone rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, acrylonitrile-butadiene copolymer rubber, and blended rubbers thereof are preferably used. These rubber materials may be foamed or non-foamed.

  As the conductive agent, an electronic conductive agent or an ionic conductive agent is used. Examples of electronic conductive agents include carbon blacks such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; tin oxide, indium oxide, titanium oxide Examples thereof include fine powders such as various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals Can be mentioned.

  These conductive agents may be used alone or in combination of two or more. The amount of addition is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 to 60 parts by mass with respect to 100 parts by mass of the rubber material. Is preferably in the range of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the rubber material.

  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.

  Of these, polyvinylidene fluoride, a tetrafluoroethylene copolymer, polyester, polyimide, and copolymer nylon are preferably used from the viewpoint of contamination of the external additive. The copolymer nylon includes one or more of 610 nylon, 11 nylon, and 12 nylon as polymerized units, and the other polymer units contained in the copolymer include 6 nylon. 66 nylon and the like. Here, the proportion of polymer units composed of 610 nylon, 11 nylon, and 12 nylon contained in the copolymer is preferably 10% or more in terms of weight ratio. When the above polymerized unit is 10% or more, it is excellent in liquid preparation and film-forming properties at the time of coating the surface layer, and in particular, there is little abrasion of the resin layer and adhesion of foreign matter to the resin layer during repeated use, and durability of the roll Is excellent, and changes in properties due to the environment are reduced.

  The above polymer materials may be used alone or in combination of two or more. Further, the number average molecular weight of the polymer material is preferably in the range of 1,000 to 100,000, and more preferably in the range of 10,000 to 50,000.

  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.

  Specifically, carbon black as a conductive agent includes “Special Black 350”, “Special Black 100”, “Special Black 250”, “Special Black 5”, “Special Black 4” manufactured by Degussa, "Special Black 4A", "Special Black 550", "Special Black 6", "Color Black FW200", "Color Black FW2", "Color Black FW2V", "MONARCH1000" manufactured by Cabot, Cabot “MONARCH1300” manufactured by the company, “MONARCH1400” manufactured by Cabot, “MOGUL-L”, “REGAL400R”, and the like.

  The carbon black has a pH of 4.0 or less, and has better dispersibility in the resin composition due to the effect of the oxygen-containing functional group present on the surface compared to general carbon black. By blending, it is possible to improve the charging uniformity and further reduce the fluctuation of the resistance value.

  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 roller 14. In addition, insulating particles such as alumina and silica are added to provide irregularities on the surface of the charging roller 14, thereby reducing the burden at the time of rubbing against the photosensitive drum 12, and the charging roller 14 and the photosensitive drum. It is also possible to improve the mutual wear resistance.

  The charging roller 14 is not limited to the above configuration as long as it has sufficient charging performance.

1. Example 1
(1) Preparation of Cleaning Roller A round bar of SUS303 with a diameter of 6 mm was used as the shaft 100A.

  A hot melt adhesive (manufactured by Nisshin Chemical Co., Ltd., BR4301) was applied as an adhesive on the shaft 100A.

  On the other hand, polyether-polyol foamed urethane (manufactured by INOAC Corporation, RR90) is used as the polyurethane foam, and the ratio S10 / S50 between the load S50 at the time of 10% compression and the load S50 at the time of 50% compression becomes 0.4. Thus, the elastic layer 100B was obtained. The obtained elastic layer 100B was hollowed with a penetrating drill, passed through the shaft 100A coated with the hot melt adhesive, and heated in an oven at 90 ° C. to adhere the elastic layer 100B to the shaft 100A.

Next, the outer periphery of the elastic layer 100B was polished into a cylindrical shape having a diameter of 12 mm and a wall thickness of 3 mm using a cylindrical polishing machine, whereby the cleaning roller 100 was obtained. The total runout of the obtained cleaning roller was 0.4.
(2) Production of Charging Roller A mixture having the composition shown in Table 1 was kneaded with an open roller, and the kneaded mixture was coated on a round bar of SUS416 with a diameter of 8 mm so as to have a thickness of 3 mm.

  Next, the round bar coated with the mixture was placed in a mold having an inner diameter of 14.5 mm and vulcanized at 170 ° C. for 30 minutes.

  After vulcanization, the round bar is taken out from the mold and polished so as to have a diameter of 14.0 mm and a rubber layer thickness of 3 mm to obtain a charging roller 14 in a state where a charging layer 14B is formed on the surface of the shaft 14A. It was.

  The charging roller 14 with the charged layer 14B formed on the surface of the shaft 14A has the composition shown in Table 2, and a dispersion A obtained by dispersing each component in a solvent by a bead mill is diluted with methanol. The surface of the charging layer 14B was dip coated and dried by heating at 140 ° C. for 15 minutes to form a surface layer having a thickness of 10 μm.

(3) Performance evaluation The Docu Center 1450 (trade name, manufactured by Fuji Xerox Co., Ltd.) was modified, and the cleaning roller 100 and the charging roller 14 manufactured in the above procedure were mounted. The conductive bearing member 15 was adjusted so as to come into contact with the charging roller 14 at a compression rate to adjust the inter-axis distance, and a charging unit was manufactured.

  The prepared charging unit is mounted on the Docu Center 1450, and 50,000 sheets are printed in a high temperature and high humidity (28 ° C, 85% humidity) environment, and then printed in a low temperature and low humidity (10 ° C, 15%) environment. Tested. In the image quality evaluation, the low-temperature, low-humidity environment image after running 50,000 sheets was visually evaluated based on the criteria shown in Table 3 for the presence or absence of density unevenness and color streaks in the halftone image.

  Regarding the dirt on the surface of the power failure roller 14, the surface of the charging roller 14 was visually evaluated based on the criteria shown in Table 4 after running 50,000 sheets.

  The results are shown in Table 5.

2. Examples 2-5
The same operation as in Example 1 was performed except that the compression rate of the cleaning roller 100 was changed as shown in Table 5. The results are shown in Table 5.

3. Example 6
Example 1 except that RR80 (manufactured by Inoac Corporation) was used as the polyether-polyol foamed urethane, and the elastic layer 100B was formed so that the ratio S10 / S50 of the load S10 to the load S50 was 0.45. Implemented. The results are shown in Table 5.

4). Example 7
The same operation as in Example 6 was performed except that the compression rate of the cleaning roller 100 was changed to 1%. The results are shown in Table 5.

5. Example 8
Example 1 except that RR26 (manufactured by Inoac Corporation) was used as the polyether-polyol foamed urethane and the elastic layer 100B was formed so that the ratio S10 / S50 of the load S10 to the load S50 was 0.5. Implemented. The results are shown in Table 5.

6). Example 9
The same operation as in Example 8 was performed except that the compression rate of the cleaning roller 100 was changed to 1%. The results are shown in Table 5.

7). Example 10
Example 1 except that RMM (manufactured by Inoac Corporation) was used as the polyether-polyol foamed urethane and the elastic layer 100B was formed so that the ratio S10 / S50 of the load S10 to the load S50 was 0.77. Implemented. The results are shown in Table 5.

8). Example 11
The same operation as in Example 1 was performed except that the total runout of the cleaning roller 100 was 0.35 mm. The results are shown in Table 5.

9. Example 12
The charging layer 14B of the charging roller 14 was carried out in the same manner as in Example 1 except that Asahi # 60 was 45 parts by mass as carbon black, dioctyl phthalate was 40 parts by weight, and the Asker C hardness of the charging roller 14 was 50. . The results are shown in Table 5.

10. Example 13
The same operation as in Example 12 was performed except that the compression rate of the cleaning roller 100 was set to 40%. The results are shown in Table 5.

11. Example 14
The charging layer 14B of the charging roller 14 was carried out in the same manner as in Example 1 except that Asahi # 60 was 60 parts by mass as carbon black, dioctyl phthalate was 30 parts by weight, and the Asker C hardness of the charging roller 14 was 85. . The results are shown in Table 5.

12 Comparative Example 1
The same procedure as in Example 1 was performed except that EXROTH-BB (trade name: manufactured by Inoac Corporation) was used as the polyurethane resin and the cleaning roller 100 having a ratio S10 / S50 of the elastic layer 100B of 0.32 was produced. The results are shown in Table 5.

13. Comparative Example 2
The same operation as in Example 1 was performed except that the compression rate of the cleaning roller 100 was changed to 60%. The results are shown in Table 5.

14 Comparative Example 3
The same operation as in Example 1 was performed except that the compression rate of the cleaning roller 100 was changed to 0%. The results are shown in Table 5.

15. Comparative Example 4
The charging layer 14B of the charging roller 14 was carried out in the same manner as in Example 1 except that the charging roller 14 having Asker C hardness 45 was prepared by using 42 parts by weight of Asahi # 60 as carbon black and 40 parts by weight of dioctyl phthalate. . The results are shown in Table 5.

16. Comparative Example 5
In the charging layer 14 </ b> B of the charging roller 14, except that Asahi # 60 was 63 parts by mass as carbon black and the plasticizer dioctyl phthalate was increased to 30 parts by weight to prepare the charging roller 14 with Asker C hardness 91. 1 was carried out. The results are shown in Table 5.

17. Comparative Example 6
The same operation as in Example 1 was performed except that the total runout of the cleaning roller 100 was set to 0.5. The results are shown in Table 5.

18. Comparative Example 7
The same operation as in Example 1 was performed except that a melamine foam material was used as the elastic layer 100B of the cleaning roller 100. The results are shown in Table 5.

FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of the image forming apparatus according to the first embodiment. FIG. 2 is an enlarged view showing a configuration around the charging roller and the cleaning roller of the image forming apparatus according to the first embodiment. FIG. 3 is an explanatory diagram illustrating a procedure for measuring the forward deflection of the cleaning roller in the image forming apparatus according to the first embodiment. FIG. 4 is an enlarged view showing the positional relationship between the charging roller and the cleaning roller of the image forming apparatus according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photoconductor drum 14 Charging roller 14A Shaft 14B Charging layer 15 Conductive bearing member 18 Rotary developing device 20 Intermediate transfer belt 44 Cleaning device 78 Cleaning device 100 Cleaning roller 100A Shaft 100B Elastic layer

Claims (2)

An image bearing member, a charging member in contact with the image bearing member rotation to form roller for charging said image bearing member, while rotating in contact with the charging member, the elastic layer is formed on the surface A roller-shaped cleaning member,
The charging member has a surface hardness measured according to JIS K 7312 of 50 degrees or more and 85 degrees or less.
The total deflection of the cleaning member is 0.4 mm or less,
The ratio S10 / S50 in the load S10 in the time the elastic 10% the load of S50 at 50% compression of the layer compression of the cleaning member is not less than 0.4,
The elastic layer of the cleaning member is a polyurethane foam;
The image forming apparatus , wherein the cleaning member is pressed against the charging member such that the compressibility of the elastic layer is 1% or more and 50% or less . A roller-shaped charging member that rotates while being in contact with the image carrier and charges the image carrier, an exposure unit that forms an electrostatic image on the image carrier, and an electrostatic image formed on the image carrier Developing means for developing a toner image with toner, and image carrier cleaning for removing the toner remaining on the image carrier after transferring the toner image on the image carrier to a transfer body or an image recording medium 2. A process cartridge comprising at least one of means and detachable from the image forming apparatus according to claim 1 .

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