JP2007241106A - Cleaning roll and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the cleaning performance of a charging roll. <P>SOLUTION: In a cleaning roll 100 for cleaning the charging roll 14, a sponge layer 100B is made to come into contact with the charging roll 14 is formed of a first sponge material 102 and a second sponge material 104 which are different in foam hardness, and also each sponge material is arranged alternately in the circumferential direction of the cleaning roll 100. Two cleaning conditions are set in one cleaning roll 100, by using two kinds of sponge materials which are different in the foam hardness thereof, so that each contaminant, such as, toner and external additives or various oils deposited on the charging roll 14 can be removed properly. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a contact charging method that is mounted on an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method and charges the surface of the image carrier while rotating in contact with the image carrier that is driven to rotate. The present invention relates to a cleaning roll for cleaning a charging roll and an image forming apparatus provided with the cleaning roll.

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

  In such a contact charging type charging device, since the charging roll is always in contact with the image carrier, the surface of the charging roll is likely to be contaminated with foreign matter, and recently the image quality has been improved. However, the following image quality failure caused by the charging roll is a problem.

  For example, when a minute foreign substance adheres to the charging roll, charging failure occurs on the image carrier and appears on the image quality as a white point or a color point of the charging roll pitch. Further, filming occurs in which the external additive contained in the toner adheres to the surface of the charging roll in a thin layer, and the charging performance changes. Depending on the pattern of the image, the filming state may change in the axial direction due to a difference in toner density, and charging unevenness may occur.

Therefore, for the purpose of reducing such image quality defects, a technique for cleaning dirt on the surface of the charging roll by rotating a cleaning roll formed of a roll-shaped sponge member or the like on the surface of the charging roll has been proposed. (For example, refer to Patent Document 1). Further, a contact / separation mechanism for separating the cleaning roll from the charging roll is provided (see, for example, Patent Document 2), or the cleaning roll is driven to rotate to create a peripheral speed difference with respect to the charging roll (see, for example, Patent Document 3). Alternatively, a technique is also proposed in which the cleaning roll is configured by a spiral elastic member extending in the axial direction (see, for example, Patent Document 4).
JP-A-2-272594 JP-A-5-297690 JP-A-8-62948 JP-A-8-137208

  In such a cleaning roll, usually, only one type of sponge member is used, and the roll surface has a circumferential surface shape without irregularities. However, it is difficult to remove all the contaminants well because, for example, the optimum foam hardness of each sponge that removes each of them is different from the contaminants of the charging roll such as toner, external additives and various oils. It is.

  In view of the above facts, the present invention has an object to provide a cleaning roll capable of improving the cleaning performance of the charging roll, and an image forming apparatus capable of realizing high-quality image formation by including the cleaning roll. To do.

  In order to achieve the above object, the invention described in claim 1 is a cleaning roll for cleaning by contacting and rotating a charging roll for charging an image bearing member, and a cleaning condition is applied to an outer peripheral surface in contact with the charging roll. A plurality of different parts are provided.

  In the present invention, in the charging roll for charging the image carrier in image formation, the foreign matter (contaminant) adhering to the roll surface is cleaned by the cleaning roll. In this cleaning roll, a plurality of parts having different cleaning conditions are provided on the outer peripheral surface, so that contaminants such as toner, external additives, and various oils attached to the charging roll can be satisfactorily removed. it can.

  According to a second aspect of the present invention, in the cleaning roll according to the first aspect, the cleaning conditions of the plurality of portions are changed depending on a material, a contact load with respect to the charging roll, or a difference in biting amount with respect to the charging roll. It is characterized by having.

  In the present invention, a plurality of parts are formed of different materials, are formed so that the contact load on the charging roll is different, or are formed so that the amount of biting into the charging roll is different, so that the cleaning conditions of each part are set. It can be changed easily. In addition, by utilizing such a difference in material, contact load, and biting amount, it is possible to easily and inexpensively produce a cleaning roll that exhibits high cleaning performance against a plurality of types of contaminants attached to the charging roll. it can.

  According to a third aspect of the present invention, in the cleaning roll according to the first or second aspect, the plurality of portions extend along the axial direction and are arranged in the circumferential direction.

  In the present invention, each portion extending along the axial direction and arranged in the circumferential direction and having different cleaning conditions sequentially contacts the charging roll as the cleaning roll rotates, so that the charging roll is cleaned well. can do.

  According to a fourth aspect of the present invention, in the cleaning roll according to the first or second aspect, the plurality of portions are arranged in a spiral shape.

  In the present invention, each of the spirally disposed portions having different cleaning conditions comes into contact with the charging roll while moving in the circumferential direction and the axial direction as the cleaning roll rotates. The vibration generated sometimes is suppressed and the charging roll can be cleaned well without unevenness.

  According to a fifth aspect of the present invention, in the cleaning roll according to the second aspect, the material difference is hardness.

  In the present invention, by utilizing the difference in material such as hardness, it is possible to easily and inexpensively produce a cleaning roll that exhibits high cleaning performance against a plurality of types of contaminants attached to the charging roll.

  According to a sixth aspect of the present invention, in the cleaning roll according to the first aspect, the plurality of portions include a first foam material and a second foam material having different foam hardness.

  In the present invention, at least two cleaning conditions are set for one cleaning roll by configuring the plurality of portions including the first foam material and the second foam material having different foam hardness (foam hardness). Using two types of foam materials having different foam hardnesses, a cleaning roll that exhibits high cleaning performance against a plurality of types of contaminants attached to the charging roll can be easily and inexpensively manufactured.

  A seventh aspect of the invention is characterized in that, in the cleaning roll of the sixth aspect, the first foam material and the second foam material are alternately arranged in the circumferential direction.

  In the present invention, since the first foam material and the second foam material are alternately brought into contact with the charging roll by the rotation of the cleaning roll, the charging roll can be cleaned better.

  The invention according to claim 8 is characterized in that, in the cleaning roll according to claim 7, the widths of the first foam material and the second foam material in the axial direction are substantially uniform.

  In the present invention, since the first foam material and the second foam material that alternately contact the charging roll by rotation of the cleaning roll always come into contact with each other in the axial direction at the contact portion, the charging roll is made uniform. It can be cleaned well.

  A ninth aspect of the present invention is the cleaning roll according to any one of the sixth to eighth aspects, wherein the first foam material and the second foam material are both disposed in contact with the charging roll. It is characterized by being.

  In the present invention, since both the first foam material and the second foam material are in contact with the charging roll and perform cleaning simultaneously under each condition, the charging roll can be cleaned well, and in particular, the charging roll surface filming (contaminant) Occurrence of thin layer adhesion) is effectively suppressed.

  A tenth aspect of the present invention is the cleaning roll according to the sixth aspect, wherein the first foam material and the second foam material are arranged in a spiral shape.

  In the present invention, the rotation of the cleaning roll causes the first foam material and the second foam material arranged in a spiral to come into contact with the charging roll while moving in the circumferential direction and the axial direction. Can be satisfactorily cleaned without unevenness.

  The invention according to claim 11 is the cleaning roll according to any one of claims 6 to 10, wherein the first foamed material has a foam hardness S1 of 250N ≦ S1 ≦ 400N, and the second foamed material. Is characterized in that the foam hardness S2 is 100N ≦ S2 <250N.

  In the present invention, by using the first foam material having a foam hardness S1 of 250N ≦ S1 ≦ 400N and the second foam material having a foam hardness S2 of 100N ≦ S2 <250N, sufficient cleaning conditions are provided between the two foam materials. A difference in (performance) can be provided, and each foaming material can exhibit high cleaning performance against a plurality of types of contaminants.

  The invention according to claim 12 is the cleaning roll according to any one of claims 6 to 11, wherein the first foam material and the second foam material have a cell density of 20 to 125 pieces / 25 mm. It is characterized by that.

  In the present invention, by using a foam material having a cell density of 20 to 125 cells / 25 mm, agglomeration of foreign matter taken in and collected in the foam material cell, and a foreign matter cell having an appropriate size due to this agglomeration The discharge from the inside can be maintained and maintained well. Thereby, stable cleaning performance can be maintained over a long period of time.

  A thirteenth aspect of the present invention is the cleaning roll according to the second aspect, wherein the difference between the contact load and the amount of biting is formed by the outer peripheral surface being a non-circumferential surface. It is said.

  In the present invention, the outer peripheral surface of the cleaning roll is a non-circumferential surface, and a change in shape is formed in the circumferential direction, thereby forming a difference in contact load and biting amount. By utilizing such a change in shape, the charging roll It is possible to easily and inexpensively produce a cleaning roll that exhibits high cleaning performance for a plurality of types of contaminants attached to the surface.

  According to a fourteenth aspect of the present invention, in the cleaning roll according to any one of the second to fourth aspects and the thirteenth aspect, the contact load / the amount of bite is changed in a circumferential direction or a circumferential direction by the rotation. It changes in direction and axial direction.

  In the present invention, the rotation of the cleaning roll causes each part having a different contact load / biting amount to come into contact with the charging roll while changing in the circumferential direction, or in the circumferential direction and the axial direction. It can be cleaned well.

  According to a fifteenth aspect of the present invention, in the cleaning roll according to the fourteenth aspect, the amount of biting that varies in the circumferential direction is in the range of 0.1 to 0.8 mm.

  In a sixteenth aspect of the present invention, in the cleaning roll according to the fourteenth aspect, the amount of biting that varies in the axial direction is in a range of 0.1 to 0.8 mm.

  In the inventions of the fifteenth and sixteenth aspects, the amount of biting in the circumferential direction / axial direction is set to 0.1 mm or more, so that the prevention of contamination of the toner / external additive of the charging roll can be satisfied. By setting the biting amount to 0.8 mm or less, it is possible to ensure the rotational speed stability of the charging roll and the cleaning roll in a low temperature and low humidity environment.

  The invention according to claim 17 is characterized in that the cleaning roll according to any one of claims 13 to 16 is configured to reciprocate in the axial direction.

  In the present invention, since the cleaning roll reciprocates in the axial direction while rotating, each portion having a different contact load / biting amount comes into contact with the charging roll while moving in the circumferential direction and the axial direction. The charging roll can be cleaned well without unevenness.

  The invention according to claim 18 is the cleaning roll according to any one of claims 1 to 17, wherein at least one of the plurality of portions is a high hardness portion having a hardness higher than that of the charging roll. In the contact state with the charging roll, the high hardness portion is arranged so as to always contact the charging roll.

  In the present invention, the high-hardness portion having a hardness higher than that of the charging roll is always brought into contact with the charging roll, whereby the charging roll can be cleaned well and the occurrence of filming on the surface of the charging roll can be more effectively suppressed. .

  The invention according to claim 19 is characterized in that, in the cleaning roll according to any one of claims 1 to 18, an abrasive is mixed in at least one of the plurality of portions. .

  In the present invention, by mixing an abrasive to at least one of the plurality of portions, the charging roll can be cleaned well and filming on the surface of the charging roll can be effectively suppressed.

  According to a twentieth aspect of the present invention, in the cleaning roll according to the nineteenth aspect, the abrasive is composed of a Si-based hard abrasive or a component contained in a toner external additive.

  In the present invention, the effect of suppressing filming on the surface of the charging roll is further enhanced by using the above abrasive as a component contained in the Si-based hard abrasive grains or the external additive of the toner.

  According to a twenty-first aspect of the present invention, in the cleaning roll according to any one of the first to twentieth aspects, the circumference is set to a non-integer multiple of the circumference of the charging roll. .

  In the present invention, the circumferential length of the cleaning roll is set to a non-integer multiple with respect to the circumferential length of the charging roll, so that the charging roll and the cleaning roll always come in contact at different locations. Cleaning can be performed without any problems, and the occurrence of filming can be suppressed.

  According to a twenty-second aspect of the present invention, in the cleaning roll according to any one of the first to twenty-first aspects, the contact load on the charging roll is self-weight.

  When cleaning a charging roll with a contact-type cleaning roll, in order to reduce damage to the charging roll and maintain stable charging performance in the long term, it is necessary to reduce the load of the cleaning roll that is in contact with the charging roll. . On the other hand, in the present invention, the load can be reduced with a simple configuration by bringing the cleaning roll into contact with the charging roll under its own weight without using a biasing means such as a spring.

  According to a twenty-third aspect of the present invention, in the image forming apparatus, the cleaning roll according to any one of the first to twenty-second aspects is provided.

  In the image forming apparatus of the present invention, high-quality image formation can be realized by improving the cleaning performance of the charging roll.

  According to a twenty-fourth aspect of the present invention, in the image forming apparatus according to the twenty-third aspect, at least one of the plurality of portions of the cleaning roll is in contact with an area corresponding to an image forming area of the charging roll. The load is a low load portion that is lower than a predetermined load, and a contact / low load contact state with respect to the charging roll is switched by the rotation.

  In the present invention, at least the image forming area of the charging roll rotates the cleaning roll to switch between a contact state and a low load contact state. As a result, the contact / low load contact state can be switched instantaneously with a simple configuration, and the charging roll damage (decrease in durability) due to friction with the cleaning roll can be suppressed, and the charging roll can be stably charged over a long period of time. Can be maintained.

  According to a twenty-fifth aspect of the present invention, in the image forming apparatus according to the twenty-third aspect, at least one of the plurality of portions of the cleaning roll is in contact with an area corresponding to an image forming area of the charging roll. The non-contact portion is released from the state, and a contact / non-contact state with respect to the charging roll is switched by the rotation.

  In the present invention, at least the image forming area of the charging roll rotates the cleaning roll to switch between a contact state and a non-contact state. As a result, the cleaning state at the time of contact and the non-cleaning state at the time of non-contact (non-cleaning state) can be switched instantly with a simple configuration, and the charging roll is damaged (decreasing durability) due to friction with the cleaning roll. And stable charging performance of the charging roll can be maintained over a long period of time.

  According to a twenty-sixth aspect of the present invention, in the image forming apparatus according to the twenty-fourth or twenty-fifth aspect, the cleaning roll is brought into a low load contact / non-contact state at least when the rotation of the charging roll is stopped. It is said.

  In the present invention, the charging roll in the rotation stop state is not strongly pressed against the cleaning roll for a long time (low load contact state) or not pressed at all (non-contact state). And the occurrence of charging defects can be suppressed.

  According to a twenty-seventh aspect of the present invention, in the image forming apparatus of the twenty-fifth or twenty-sixth aspect, the contact / non-contact state of the cleaning roll with respect to the charging roll is determined by rotating / stopping the charging roll and changing the applied voltage. It is characterized by being able to be switched.

  In the present invention, the contact / non-contact state of the cleaning roll with respect to the charging roll can be switched using the rotation / stop of the charging roll and the change of the applied voltage, so that switching with a simple configuration is possible.

  The cleaning roll of the present invention improves the cleaning performance of the charging roll, and the image forming apparatus of the present invention can realize high-quality image formation.

  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 this embodiment shown in FIG. 1 is a four-drum tandem color copier, and as shown in the drawing, yellow (Y), magenta (M), cyan (C), and black (K). Image forming units 11 (11Y, 11M, 11C, and 11K) that form toner images of the respective colors are arranged in parallel along the moving direction of the intermediate transfer belt 30.

  The image forming unit 11 is provided with a photosensitive drum 12 (12Y, 12M, 12C, 12K) as an image carrier. The photosensitive drum 12 has a photosensitive layer made of, for example, OPC on the surface. A coated conductive cylinder is used, and is driven to rotate at a predetermined process speed in the direction of the arrow in the figure (right rotation direction) by a motor (not shown).

  A charging device including a charging roll (contact charger) 14 (14Y, 14M, 14C, 14K) for charging the surface of the photosensitive drum 12 is disposed almost directly above the photosensitive drum 12, and further, the photosensitive drum. Above 12 is an exposure device 13 (13Y, 13M, 13C, 13K) that irradiates the surface of the photosensitive drum 12 charged by the charging device with laser light L to form an electrostatic latent image. .

  A developing device 15 (15Y, 15M, 15C, 15K) is disposed adjacent to the right side of the photosensitive drum 12, and the electrostatic latent image formed on the photosensitive drum 12 is transferred to the developing device 15 as Y. , M, C, and K are provided with developing rolls 16 (16Y, 16M, 16C, and 16K) for developing toner images of respective colors.

  An endless intermediate transfer belt 30 to which the toner image visualized by the developing device 15 is transferred is disposed below the photosensitive drum 12, and the primary transfer roll 18 (18Y) is further sandwiched between the intermediate transfer belt 30. , 18M, 18C, 18K) are arranged to face each other. Each contact portion between the photosensitive drum 12 and the intermediate transfer belt 30 is a primary transfer portion T1, and a primary transfer bias having a positive polarity is applied to the primary transfer roll 18.

  On the left side of the photoconductive drum 12, a cleaning device as a photoconductive cleaner that removes transfer residual toner remaining on the photoconductive drum 12 after the primary transfer is disposed adjacent to the photoconductive drum 12. There are provided brush rolls 20 (20Y, 20M, 20C, and 20K) that are pressed against the outer peripheral surface of the photosensitive drum 12 and driven to rotate in a direction opposite to the rotation direction of the photosensitive drum 12 and scrape off transfer residual toner from the photosensitive drum 12.

  The intermediate transfer belt 30 is wound around a drive roll 32, a tension roll 33, and a secondary transfer backup roll 34, and rotates in the same direction in synchronization with the rotation of the photosensitive drum 12. The image forming units 11Y, 11M, 11C, and 11K are arranged in series in that order with respect to the moving direction of the intermediate transfer belt 30. As a result, the toner image on the photosensitive drum 12 is primarily transferred onto the intermediate transfer belt 30 in the order of yellow, magenta, cyan, and black by the primary transfer roll 18 in each primary transfer portion T1, and this primary transferred toner is transferred. The image is conveyed toward the following secondary transfer portion T2 (secondary transfer roll 36).

  On the right side of the intermediate transfer belt 30, a secondary transfer roll 36 is disposed to face the sheet conveyance path 40. A contact portion between the secondary transfer roll 36 and the intermediate transfer belt 30 is a secondary transfer portion T2, and a negative secondary transfer bias is applied to the secondary transfer roll 36. As a result, the secondary transfer roll 36 is assisted by the secondary transfer backup roll 34 and secondarily transfers the toner image primarily transferred to the intermediate transfer belt 30 onto the paper P at the secondary transfer portion T2. Further, an intermediate transfer belt cleaner 38 for removing residual toner remaining on the intermediate transfer belt 30 after the secondary transfer is provided on the upper right side of the secondary transfer backup roll 34 that rotatably supports the intermediate transfer belt 30. .

  Below the intermediate transfer belt 30, a paper feed tray 42 for storing paper P is disposed, and in the vicinity of the right side of the paper feed tray 42, a feed roll 44 that feeds the paper P from the paper feed tray 42 to the paper transport path 40. In addition, a retard roll 46 is provided for separating the paper P to be fed one by one.

  In addition, a fixing device 50 including a heating roll 52 and a pressure roll 54 facing each other is disposed on the downstream side of the secondary transfer portion T <b> 2 in the paper conveyance path 40, and a pair of discharges is provided on the downstream side of the fixing device 50. A roll 56 is provided. The paper conveyance path 40 extends from the feed roll 44 and the retard roll 46 to the discharge roll 56 via the secondary transfer portion T2 and the fixing device 50.

(First embodiment)
Next, the charging roll 14 mounted on the image forming apparatus 10 having the above configuration and the cleaning roll 100 according to the first embodiment of the present invention for cleaning the charging roll 14 will be described in detail.

  As shown in FIG. 2, a charging roll 14 is disposed above 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 that is a roll-shaped cleaning member that comes into contact with the surface of the charging roll 14 is provided on the upper right portion of the charging roll 14. 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 in the direction of arrow A (clockwise direction) in FIG. 2 by a motor (not shown), and the charging roll 14 is driven to rotate in the direction of arrow B (counterclockwise direction) as the photosensitive drum 12 rotates. . Further, the rotation of the charging roll 14 causes the cleaning roll 100 to rotate following the direction of arrow C (clockwise direction).

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

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

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

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

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

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

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

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

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

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

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

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

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

  In such a cleaning roll 100, in this embodiment, as shown in FIGS. 5A and 5B, a sponge layer 100 </ b> B is formed of a first sponge material 102 and a second sponge material 104. The first and second sponge materials 102 and 104 have different foam hardness (foaming hardness), and the foam hardness S1 of the first sponge material 102 is higher than the foam hardness S2 of the second sponge material 104 ( Foam hardness S1> foam hardness S2).

  Here, regarding the foam hardness of each sponge material, the first sponge material 102 preferably has a foam hardness S1 of 250N ≦ S1 ≦ 400N, and the second sponge material 104 has a foam hardness S2 of 100N ≦ S2 <250N. It is preferable. The cell density is preferably set in the range of 20 to 125 cells / 25 mm. Further, the first sponge material 102 having a high foam hardness is preferably higher in hardness than the hardness of the charging layer 14 </ b> B of the charging roll 14.

  In this embodiment, a relatively soft polyurethane foam: EP70 (manufactured by INOAC) is used as the sponge layer, and the foam hardness for this polyurethane foam is measured by the following measuring method.

[EP-70 measurement method]
−Specifications−
・ Sample (urethane) size: 390 x 390 x 50t (mm)
・ Compression jig: φ200 (mm) disk ・ Compression method: Partial compression ・ Pre-compression: Available (75% of original thickness)
・ Compression amount: 25% of original thickness (recompression)
-Procedure-
-Place a compression jig on the center of the sample set on the horizontal surface, apply a load of 4.9 N, measure the thickness of the compression part, and use it as the original thickness.
・ Compress the original thickness by 75%.
-After unloading, compress 25% of the original thickness again, measure the load after 20 seconds, and set it as hardness (N).

  The first and second sponge materials 102 and 104 are alternately arranged in the circumferential direction of the cleaning roll 100, and the widths in the axial direction are substantially uniform, and are arranged at substantially equal pitches. Further, as shown in FIG. 5B, the first and second sponge materials 102 and 104 are each set to a predetermined width dimension so that both are always in contact with the charging roll 14.

(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 the present embodiment, the charging roll 14 and the cleaning roll 100 are assembled to a single frame 120 via a pair of bearing members 110, and are accommodated in the frame 120 together with the frame 120. It is unitized and arranged at a predetermined position with respect to the photosensitive drum 12.

  As shown in FIG. 4, the bearing member 110 is formed with two bearing holes 112 and 114 arranged at a predetermined interval. A support portion provided at the end of the shaft 14A of the charging roll 14 is rotatably inserted into one bearing hole 112, and a support provided at the end of the shaft 100A of the cleaning roll 100 is inserted into the other bearing hole 114. The part is inserted rotatably. The bearing member 110 according to the present embodiment 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.

  As described above, the charging roll 14 in which the support portions 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 at both ends of the shaft 100A are pivotally supported are as described above. 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 pressing 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 fitted in the guide groove 126 and disposed on the front end side (lower end side). The bearing member 110 is guided by the guide groove 126 and extends in the extending direction of the mounting portion 124 (contact / separation with respect to the photosensitive drum 12). Slidable along the direction).

  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 D), and the charging roll 14 is in pressure contact with the photosensitive drum 12.

(Operation of image forming apparatus)
Next, a color image forming operation by the image forming apparatus 10 of the present embodiment will be described.

  When an image forming signal is input to the image forming apparatus 10 and the photosensitive drum 12 is driven to rotate, the charging roll 14 is driven to rotate as the photosensitive drum 12 rotates, and the surface (outer peripheral surface) of the photosensitive drum 12 is charged. The roll 14 is uniformly charged. Subsequently, the surface of the photosensitive drum 12 is irradiated with laser light L from the exposure device 13 based on the image forming signal. With the laser light L, the surface of the photosensitive drum 12 is exposed to form an electrostatic latent image.

  The electrostatic latent image formed on the photosensitive drum 12 is developed with yellow, magenta, cyan, and black toner images by the developing roll 16 of the developing device 15, and is superimposed on the intermediate transfer belt 30 by the primary transfer portion T1. The primary transfer. Further, the transfer residual toner remaining on the photosensitive drum 12 after the primary transfer is scraped off and removed by the brush roll 20 of the cleaning device.

  On the other hand, the paper P stored in the paper feed tray 42 is sent out by the feed roll 44, and is fed by the retard roll 46 so that only the uppermost paper P is guided to the paper transport path 40, and the secondary transfer is performed at a predetermined timing. It is fed between the roll 36 and the secondary transfer backup roll 34, that is, into the secondary transfer portion T2. The toner image that is primarily transferred to the intermediate transfer belt 30 is secondarily transferred to the paper P at the secondary transfer portion T2. The sheet P to which the toner image is transferred is conveyed downstream in the sheet conveyance path 40 and guided to the fixing device 50, and the toner image is fixed by the thermal pressure of the heating roll 52 and the pressure roll 54. The paper P on which the image is formed by fixing the toner image is discharged to a paper discharge tray (not shown) by a discharge roll 56.

  Further, the transfer residual toner remaining in the image area of the intermediate transfer belt 30 after the secondary transfer is scraped off and removed by the intermediate transfer belt cleaner 38. Further, as the charging roll 14 rotates, the cleaning roll 100 is driven to rotate, and 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. When the foreign matter is taken into the cell of the sponge layer 100B of the cleaning roll 100 and the foreign matter collected in the cell is aggregated to an appropriate size, the photosensitive drum 12 is passed from the cleaning roll 100 through the charging roll 14. Then, the cleaning is performed by the brush roll 20 that cleans the photosensitive drum 12, and the cleaning performance is continuously maintained. With the above operation, a color image is formed on the paper P by the image forming apparatus 10.

  Next, the operation of this embodiment will be described.

  As described above, in the cleaning roll 100 according to the present embodiment for cleaning the charging roll 14, the sponge layer 100B is composed of the first sponge material 102 and the second sponge material 104 having different foam hardness, so that one cleaning is performed. Two cleaning conditions are set for the roll 100. By using two types of sponge materials having different foam hardnesses, it is possible to satisfactorily remove contaminants such as toner, external additives, and various oils attached to the charging roll 14.

Table 1 shows the results of evaluating the cleaning performance based on the image quality when the cell density and foam hardness (EP-70 measuring method) of the sponge material are changed. Here, 16 types of sponge materials (A to P materials) having different cell densities and foam hardnesses are used to prepare cleaning rolls, and each cleaning roll is mounted on an image forming apparatus (evaluator) and has a life equivalent. After use, an evaluation method was adopted to check image quality degradation due to adhesion of toner and external additives to the charging roll and image quality degradation due to oil adhesion. The evaluation criteria for image quality are three levels: good image quality (◯), occurrence of poor image quality only in a specific environment (Δ), and occurrence of poor image quality (×).

  As shown in Table 1, the deterioration of image quality due to oil adhesion is not seen in the BG and P materials having a relatively low hardness in which the cell density is in the range of 20 to 125 cells / 25 mm and the foam hardness is in the range of 128 to 226N. Not (◯), image quality deterioration due to adhesion of toner / external additive was observed (Δ or ×). Also, with H and J and L materials having a relatively high hardness in which the cell density is in the range of 45 to 65 cells / 25 mm and the foam hardness is in the range of 300 to 441 N, image quality deterioration due to adhesion of toner and external additives is observed. (○), image quality deterioration due to oil adhesion was observed (×). Furthermore, oil adheres to sponge materials with a relatively high cell density, such as A material with a cell density of 130 cells / 25 mm and foam hardness of 300 N, or M material with a cell density of 125 cells / 25 mm and foam hardness of 230 N. Image quality deterioration (x) due to toner and image quality deterioration (△) due to adhesion of toner / external additive in a specific environment, cell density 65/25 mm, foam hardness 21N K material, cell density 65 / In the case of a sponge material having a very low hardness, such as an O material having a foam hardness of 20 N at 25 mm, or a sponge material having a very high hardness, such as a N material having a cell density of 150 cells / 25 mm and a foam hardness of 500 N, toner Image quality degradation was observed for both external additives and oil adhesion (×).

  From the above evaluation results, in order to improve the cleaning performance for the toner and external additives and suppress the deterioration of the image quality, it is preferable that the foam hardness of the sponge material is about 250 to 400 N, and the cleaning performance against the oil is improved to improve the image quality deterioration. In order to suppress it, the foam hardness of the sponge material is preferably about 100 to 250N. In order to exhibit high cleaning performance in each of these hardness ranges, the cell density of the sponge material is preferably about 20 to 125 cells / 25 mm.

  Therefore, in the cleaning roll 100 of the present embodiment, the first sponge material 102 in which the foam hardness S1 by the EP-70 measurement method is 250N ≦ S1 ≦ 400N, and the second sponge material in which the foam hardness S2 is 100N ≦ S2 <250N. When 104 is used, toner and external additives are mainly removed well by the first sponge material 102 having high hardness, and oil and the like are mainly well removed by the second sponge material 104 having low hardness. Thus, each sponge material can exhibit high cleaning performance with respect to each contaminant.

  Further, when the cell density of the first sponge material 102 and the second sponge material 104 is set to 20 to 125/25 mm, the aggregation of the foreign matters taken in and collected in the cells of each sponge material and the aggregation It is possible to maintain and continue to discharge the foreign matter having an appropriate size from the cell. Thereby, more stable cleaning performance can be maintained over a long period of time.

  In the present embodiment, the first and second sponge materials 102 and 104 are alternately brought into contact with the charging roll 14 by the rotation of the cleaning roll 100, and in the axial direction at the contact portion (nip portion) with the charging roll 14. Since the contact is always substantially uniform, the charging roll 14 can be cleaned well without unevenness. Further, since the first and second sponge materials 102 and 104 are both arranged to contact the surface of the charging roll 14 at the nip portion (see FIG. 5B), the first sponge material 102 is always in the nip portion. Thus, a high contact load is applied, and the occurrence of filming on the surface of the charging roll can be effectively suppressed.

  In particular, when the first sponge material 102 has a higher hardness than the charging layer 14 </ b> B of the charging roll 14, the high-stiffness first sponge material 102 always contacts the charging roll 14 when the cleaning roll 100 rotates. Thus, high cleaning performance can be exhibited, and filming on the surface of the charging roll 14 can be more effectively suppressed.

  In such a cleaning roll 100, an abrasive may be mixed with at least one of the first and second sponge materials 102 and 104. In this case, the charging roll 14 can be cleaned well, and filming on the charging roll surface can be more effectively suppressed. Further, the effect of suppressing filming on the surface of the charging roll can be further enhanced by using the abrasive as a component contained in the Si-based hard abrasive grains or the external additive of the toner.

  Further, by utilizing the difference in foam hardness (material) of the sponge layer 100B, the cleaning roll 100 that exhibits high cleaning performance against a plurality of types of contaminants attached to the charging roll 14 can be easily and inexpensively manufactured. can do.

  In the image forming apparatus 10 of this embodiment provided with the cleaning roll 100, the cleaning performance of the charging roll 14 is improved, so that an image defect due to poor cleaning of the charging roll 14 or poor charging of the photosensitive drum 12 is caused. Therefore, a high-quality image can be formed over a long period of time.

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

  As described in the first embodiment, when a charging roll is cleaned with a contact-type cleaning roll, in order to reduce damage to the charging roll and maintain stable charging performance for a long period of time, contact the charging roll. The problem is how to reduce the load of the cleaning roll. In the second embodiment, in order to solve this problem, the above-described cleaning roll 100 is brought into contact with the charging roll 14 by its own weight.

  As shown in FIG. 6, in the bearing member 130 of the present embodiment, the bearing hole 134 that supports the cleaning roll 100 is a long hole whose longitudinal direction is the longitudinal direction. The end of the shaft 14A is inserted into the bearing hole 134, and the cleaning roll 100 is rotatably supported and given a degree of freedom to move somewhat in the vertical direction.

  In addition, a bearing groove 132 having an inverted U-shaped cross-section opening the lower end surface of the bearing member 130 is formed for the charging roll 14. The end of the shaft 14A is fitted into the bearing groove 132 of the charging roll 14, and the bearing member 130 is urged toward the photosensitive drum 12 (in the direction of arrow D) by the compression coil spring 128, whereby the photosensitive drum 12 is loaded. While being in pressure contact, the bearing groove 132 is rotatably contacted and supported.

  As described above, the cleaning roll 100 supported by the bearing member 130 of the present embodiment approaches the charging roll 14 and moves the peripheral surface of the sponge layer 100B by lowering by its own weight (in the direction of arrow E) without using a spring or the like. Since the charging roll 14 is in contact with the peripheral surface, the contact load can be reduced with a simple configuration. In particular, when the shaft 100A is formed of an insulating resin material, it is possible to reduce the weight as compared with the metal shaft, so that the load reduction effect is enhanced.

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

  As shown in FIG. 7, in the cleaning roll 140 of this embodiment, the sponge layer 140 </ b> B is formed of the same first and second sponge materials 102 and 104 as in the first embodiment. However, here, the first and second sponge materials 102 and 104 are alternately arranged in a spiral at substantially equal pitches.

  Accordingly, when the cleaning roll 140 of the present embodiment rotates, the first and second sponge materials 102 and 104 arranged in a spiral form come into contact with the charging roll 14 while moving in the circumferential direction and the axial direction, respectively. Therefore, the charging roll 14 can be cleaned well without unevenness.

  Also, as described in the first embodiment, at least one of the first and second sponge materials 102 and 104 is made harder than the charging roll 14 for the cleaning roll 140, or Further, at least one of them may be mixed with an abrasive, or the abrasive may be used as a component included in an Si-based hard abrasive or an external additive of the toner. Can be satisfactorily cleaned, and filming on the surface of the charging roll can be effectively suppressed.

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

  In the fourth embodiment, the thickness of the cleaning roll (sponge layer) in the circumferential direction is changed, so that the amount of biting into the charging roll changes with rotation. FIG. 8 and FIG. Two types of modifications according to the present embodiment are shown.

  First, in the cleaning roll 150 shown in FIGS. 8A and 8B, a substantially cylindrical sponge layer 150B is formed eccentrically on the peripheral surface of the shaft 150A. Therefore, the sponge layer 150B has one maximum thickness portion and one minimum thickness portion in one circumference, and a difference in thickness in the circumferential direction is provided. The circumferential length of the cleaning roll 150 (sponge layer 150B) is set to a non-integer multiple with respect to the circumferential length of the charging roll 14.

  In the cleaning roll 160 shown in FIGS. 9A and 9B, a sponge layer 160B having a substantially star-shaped cross section and a non-circumferential outer peripheral surface is formed on the peripheral surface of the shaft 160A. In the sponge layer 160B, a plurality of irregularities are alternately arranged at substantially equal pitches in the circumferential direction, and a plurality of maximum thickness portions and minimum thickness portions are formed in one circumference, and the thickness in the circumferential direction is increased. A difference is provided. The circumferential length of the cleaning roll 160 (sponge layer 160B) is also set to a non-integer multiple with respect to the circumferential length of the charging roll 14.

  In these cleaning rolls 150 and 160, the sponge layers 150 </ b> B and 160 </ b> B are provided with a plurality of shapes with different amounts of biting into the charging roll 14 by changing the thickness in the circumferential direction. Multiple cleaning conditions are set. As a result, it is possible to remove foreign substances and external additives that could not be removed from the charging roll 14 under the same cleaning conditions, and these contaminants can be removed satisfactorily. In particular, in the case of the cleaning roll 160, the sponge shrinks within the circumference of the roll, and thus the effect of preventing the sticking by floating dirt on the charging roll 14 can be obtained.

  In addition, the sponge layer 100B is decentered in this way, or the outer peripheral surface is formed into a deformed shape such as a non-circumferential surface, and a plurality of shapes with different amounts of biting into the charging roll 14 are configured, thereby simplifying the cleaning conditions for each part Can be changed. By utilizing such a difference in shape (biting amount), it is possible to easily and inexpensively manufacture the cleaning rolls 150 and 160 that exhibit high cleaning performance against a plurality of types of contaminants attached to the charging roll 14. it can.

Table 2 shows the results of evaluating the charging roll rotation and cleaning properties when the amount of biting of the cleaning roll with respect to the charging roll is changed. Here, the cleaning roll is mounted on an image forming apparatus (evaluator), and the amount of biting into the charging roll is set to 0.05 / 0.1 / 0.2 / 0.5 / 0.8 / 1.0 mm. An evaluation method was adopted in which the rotation property was confirmed by the presence or absence of slippage of the charging roll in a low-temperature and low-humidity environment, and the cleaning property was confirmed by the image quality after each life equivalent. In addition, the evaluation criteria for the charging roll rotation are two stages: no slip (O) and slip occurrence (X), and the evaluation criteria for the cleaning property (image quality) are good image quality (O) and poor image quality. (X), two stages.

  As shown in Table 2, both the rotation property and cleaning property (image quality) of the charging roll were good when the biting amount was in the range of 0.1 to 0.8 mm. In addition, when the biting amount was as small as 0.05 mm, the rotating property of the charging roll was good, but poor image quality was seen, and when the biting amount was as large as 1.0 mm, the charging roll slipped. As a result, image quality defects due to filming were observed.

  Based on the above evaluation results, the lower limit of the amount of cleaning roll biting into the charging roll is 0.1 mm that satisfies the prevention of contamination of the toner and external additives of the charging roll at a level at which image defects do not occur, and the upper limit is It was found that 0.8 mm, which can ensure the rotational speed stability that prevents the charging roll and the cleaning roll from slipping in a low temperature and low humidity environment, is optimal. Therefore, by changing the amount of biting in the range of 0.1 to 0.8 mm, it is possible to satisfy the prevention of contamination of the toner and the external additive of the charging roll 14, and the charging roll 14 and the cleaning roll 150 in a low temperature and low humidity environment. , 160 can be secured.

  Further, if the rotation of the charging roll 14 and the cleaning rolls 150 and 160 is not stable and the speed difference becomes too large, a filming phenomenon occurs in which toner stains are rubbed and fixed on the charging roll 14 and the photosensitive drum 12. . On the other hand, in the present embodiment, the circumferential length of the cleaning rolls 150 and 160 and the circumferential length of the charging roll 14 are non-integer multiples, so that the same amount of biting in the same location on the surface of the charging roll. Is prevented from being repeatedly contacted, that is, parts having different biting amounts come into contact with each other sequentially, so that dirt can be dispersed and cleaned evenly, and the occurrence of filming can be suppressed.

  Further, these cleaning rolls 150 and 160 may be supported so as to be reciprocally movable in the axial direction, for example, and may be configured to reciprocate in the axial direction using a driving unit such as an actuator. In this case, each part having a different biting amount comes into contact with the charging roll 14 while moving in the circumferential direction and the axial direction, so that the charging roll 14 can be cleaned well without unevenness.

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

  In the fifth embodiment, the shape of the outer peripheral surface of the cleaning roll described in the fourth embodiment is further changed. FIG. 10 shows two types of modifications according to the present embodiment.

  First, in the cleaning roll 170 shown in FIG. 10 (A), a sponge layer 170B formed in a substantially cylindrical and eccentric manner is spirally arranged on the peripheral surface of the shaft 170A.

  In the cleaning roll 180 shown in FIG. 10B, a sponge layer 180B having a substantially star-shaped cross section and a non-circumferential outer peripheral surface is spirally arranged on the peripheral surface of the shaft 180A. .

  In these cleaning rolls 170 and 180, vibrations generated during rotation are suppressed, and the respective portions with different biting amounts arranged in a spiral form contact with the charging roll 14 while moving in the circumferential direction and the axial direction, respectively. Therefore, the charging roll 14 can be cleaned satisfactorily with a simple configuration without unevenness.

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

  As described above, in the configuration in which the charging roll is cleaned by the contact type cleaning roll, if the cleaning roll is always in contact, there is a problem that durability is lowered due to damage to the surface of the charging roll due to friction during rotation. In particular, there is also a problem that the surface of the roll is deformed to cause uneven charging due to partial pressing for a long time when rotation is stopped.

  Therefore, as described above, a technique (Japanese Patent Laid-Open No. 5-297690) for separating the cleaning roll from the charging roll using a contact / separation mechanism such as a cam has been proposed, but a configuration using such a contact / separation mechanism is proposed. However, there is a drawback that it takes time to contact and separate, and the apparatus becomes large. Also known is a cleaning roll (JP-A-8-137208) in which a cleaning member (elastic member) is spirally extended in the axial direction. In this case, although the contact area of the cleaning member is reduced, Since the structure is always contacted, deformation of the surface of the charging roll and poor charging due to pressing for a long time cannot be avoided.

  Based on these problems, the sixth embodiment has a simple configuration that utilizes the rotation of the cleaning roll, and enables switching between a contact / non-contact state with respect to the charging roll, suppresses a decrease in durability and deformation of the charging roll, It maintains stable charging performance over a long period of time.

  As shown in FIGS. 11A and 11B, in the cleaning roll 200 of this embodiment, a cylindrical sponge layer 200B is concentrically formed on the peripheral surface of the shaft 200A. The shape is formed by removing both sides in the axial direction and removing a part in the circumferential direction, and the thinned portion forms a concave portion 202 as a non-contact portion in a predetermined region of the circumferential surface. A convex portion 204 is formed as a contact portion.

  As shown in FIGS. 12 and 13, the cleaning roll 200 is supported by a pair of bearing members 110 having the same configuration as that of the first embodiment together with the charging roll 14, and is assembled to the frame 120 while being pressed against the charging roll 14. ing. In addition, the concave portion 202 formed on the peripheral surface of the sponge layer 200 </ b> B is an image forming area G on the charging surface of the charging roll 14, that is, the charging roll 14 corresponding to the image (toner image) forming area on the photosensitive drum 12. The length in the axial direction is slightly larger than the width of the image forming area G (length in the charging roll axial direction). Then, in the rotation range where the peripheral surface portion excluding the concave portion 202 faces the charging roll 14 side, the cleaning state comes into contact with the charging surface including the image forming area G of the charging roll 14, and the concave portion 202 contacts the charging roll 14. In the rotation range facing each other, the non-cleaning state in which the image forming area G is not contacted is obtained.

  Next, the operation of the image forming apparatus 10 (see FIGS. 1 and 2) provided with the cleaning roll 200 will be described.

  When the image forming apparatus 10 is stopped, as shown in FIG. 13, the concave portion 202 of the cleaning roll 200 is positioned on the charging roll 14 side and is not in contact with the charging surface (image forming area G). In this state, when a print instruction is received, the photosensitive drum 12 is rotationally driven to start the above-described charging / exposure / development / transfer processes, and in the charging process, a voltage is applied to the charging roll 14 to rotate. While charging, the photosensitive drum 12 is charged.

  By applying a voltage to the charging roll 14, a suction force acts on the sponge layer 200B of the cleaning roll 200. Further, due to the rotation of the charging roll 14, a mechanical frictional force is generated in the convex portions 204 (charging roll contact portions) provided on both sides in the axial direction of the sponge layer 200B. With these suction force and friction force, the cleaning roll 200 is given a rotational force and starts rotating. Then, while the charging roll 14 is rotated and voltage is applied, the cleaning roll 200 is driven to rotate by following the charging roll 14, and the contact (cleaning state) shown in FIG. 12 and the non-contact (non-cleaning state) shown in FIG. repeat.

  As described above, the rotation of the charging roll 14 and the application of voltage cause the cleaning roll 200 to start rotating instantaneously and move to a cleaning operation. The charging roll 14 periodically moves at an appropriate interval according to the rotation period of the cleaning roll 200. Since cleaning is performed, a decrease in durability of the charging surface due to friction with the cleaning roll 200 is suppressed, and stable charging performance can be maintained over a long period of time.

  When the printing is completed, the voltage applied to the charging roll 14 is stopped. Here, when the cleaning roll 200 is in contact with the charging roll 14, the rotation is continued by a mechanical frictional force, and the cleaning roll 200 stops rotating at a position where the concave portion 202 faces the charging roll 14. Thereafter, the charging roll 14 also stops rotating, and the operation of the image forming apparatus 10 ends. After this operation is completed, the charging roll 14 and the cleaning roll 200 are maintained in a substantially non-contact state until the next print instruction is received. As a result, the rotation of the charging roll 14 in a stopped state is not strongly pressed against the cleaning roll 200 for a long time, the deformation of the charging roll 14 is prevented, and the occurrence of rotation failure or charging failure is suppressed.

  Further, as described above, the switching of the contact / non-contact state of the cleaning roll 200 with respect to the charging roll 14 is performed by rotating / stopping the charging roll 14 and changing the applied voltage. It is possible to perform switching with a simple configuration without using a special means or the like.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described.

  As shown in FIGS. 14A and 14B, in the cleaning roll 210 of the present embodiment, a substantially cylindrical sponge in which a partial area in the circumferential direction is thinned over the entire area in the axial direction on the peripheral surface of the shaft 210A. Layer 210B is formed. By this thinned portion, a circumferential surface portion 214 as a contact portion and a flat surface portion (thin wall portion) 212 as a non-contact portion thinner than the circumferential surface portion 214 are formed in the sponge layer 210B.

  As shown in FIGS. 15 and 16, the cleaning roll 210 is also supported on the pair of bearing members 110 together with the charging roll 14, and is assembled to the frame 120 so as to be in a relative positional relationship capable of being pressed against the charging roll 14. However, here, the gear 216 attached to one end of the shaft 210 </ b> A meshes with the gear 217 attached to one end of the shaft 14 </ b> A of the charging roll 14. A gear 218 is attached to one end of the shaft 14 </ b> A of the charging roll 14, and the gear 218 meshes with a gear 219 attached to one end of the shaft 12 </ b> A of the photosensitive drum 12.

  As described above, in the image forming apparatus 10 provided with the cleaning roll 210, when the photosensitive drum 12 is rotationally driven during printing, the rotational force is transmitted to the charging roll 14 via the gear 219 and the gear 218. Rotate. Further, when the charging roll 14 rotates, the rotational force is transmitted to the cleaning roll 210 via the gear 217 and the gear 216, and the cleaning roll 210 rotates to contact the sponge layer 210B with the charging roll 14 shown in FIG. The cleaning when facing the peripheral surface portion 214 and the non-contact (non-cleaning when facing the flat surface portion 212) shown in FIG. 16 are repeated.

  As described above, the cleaning roll 210 is rotated by the rotational driving of the photosensitive drum 12, and the charging roll 14 is cleaned at the rotation cycle of the cleaning roll 200. Therefore, in the present embodiment, a decrease in durability is suppressed, and a long-term operation is achieved. And stable charging performance can be maintained.

  In addition, as in this embodiment, the cleaning roll 210 that does not contact the charging roll 14 at the time of rotation also uses a rotational force transmission mechanism including a plurality of gears without using a complicated contact / separation mechanism. With a simple configuration, the cleaning roll 210 can be smoothly rotated by the rotational force of the photosensitive drum 12, and a periodic cleaning operation in contact / non-contact with the charging roll 14 can be performed.

  Further, when the operation of the image forming apparatus 10 is stopped, the rotation stop position of the photosensitive drum 12 is controlled, and the cleaning roll 210 is stopped in a non-contact state with respect to the charging roll 14 in the rotation stop state. Deformation of the charging roll 14 due to strong pressing for a long time can be avoided, and rotation failure and charging failure can be prevented.

(Eighth embodiment)
Next, an eighth embodiment of the present invention will be described.

  As shown in FIGS. 17A and 17B, in the cleaning roll 220 of this embodiment, an elliptical cylindrical sponge layer 220B is formed on the peripheral surface of the shaft 220A. The thick part 224 as a contact part and the thin part 222 as a non-contact part are provided in two places in one circumference.

  As shown in FIGS. 18 and 19, the cleaning roll 220 is also supported by the pair of bearing members 110 together with the charging roll 14, and is assembled to the frame 120 in a relative positional relationship capable of being pressed against the charging roll 14. Here, an electromagnetic clutch 226 is attached between the shaft 220A and the gear 216. The electromagnetic clutch 226 is locked by energization during the printing operation of the image forming apparatus 10, and is de-energized when the operation is stopped. Is done. Further, the gears 218 and 219 between the charging roll 14 and the photosensitive drum 12 described in the seventh embodiment are removed.

  As described above, when the image forming apparatus 10 including the cleaning roll 220 rotates following the photosensitive drum 12 during printing, the rotational force is applied to the cleaning roll 210 via the gear 217, the gear 216, and the electromagnetic clutch 226. Then, the cleaning roll 210 rotates, and the sponge layer 210B comes into contact with the charging roll 14 shown in FIG. 18 (cleaning when facing the thick portion 224) and non-contact shown in FIG. 19 (non-cleaning when facing the thin portion 222) )repeat.

  As described above, also in this embodiment, since the charging roll 14 is periodically cleaned by the cleaning roll 220, a decrease in durability can be suppressed and stable charging performance can be maintained over a long period of time.

  In addition, the cleaning roll 220 that is not in contact with the charging roll 14 at the time of rotation also has a simple configuration using a rotational force transmission mechanism including the gears 216 and 217 and the electromagnetic clutch 226, and the cleaning roll 220 becomes the charging roll 14. It is possible to perform a periodic cleaning operation in contact / non-contact with the charging roll 14 by smoothly rotating and rotating.

  When the operation of the image forming apparatus 10 is stopped, the cleaning roll 220 stops in a non-contact state with respect to the charging roll 14 in the rotation stopped state by the rotation stop position control of the cleaning roll 220 by unlocking the electromagnetic clutch 226. Even in the configuration, deformation of the charging roll 14 due to the pressing of the cleaning roll 220 for a long time can be avoided, and rotation failure and charging failure can be prevented.

(Ninth embodiment)
Next, a ninth embodiment of the present invention will be described.

  As shown in FIG. 20, in the cleaning roll 230 of the present embodiment, an elliptical cylindrical sponge layer 230B is formed on the peripheral surface of the shaft 230A, and there are two sponge layers 230B in the circumferential direction. One of the thick portions is thinned over the entire area in the axial direction, and a flat portion 232 as a non-contact portion is formed by the thinned portion.

  The thick portion 234 located on the opposite side of the flat portion 232 across the shaft 230A has a large bite amount with respect to the charging roll 14, and has a high hardness with a foam hardness higher than that of the charging layer 14B of the charging roll 14. It is made of sponge material. Further, the two thin portions 236 located between the thick portion 234 and the flat portion 232 in the circumferential direction have a small bite amount with respect to the charging roll 14, and the foam hardness is made lower than that of the thick portion 234. It is made of a low hardness sponge material.

  As described above, the cleaning roll 230 according to the present embodiment is in contact with the charging roll 14 and the thick-walled portion 234 and the thin-walled portion 236 having different foam hardness and the amount of biting into the charging roll 14 as a plurality of portions having different cleaning conditions. Accordingly, a flat portion 232 that does not perform cleaning is provided, and as a result, an effect of improving the cleaning property against a plurality of types of contaminants attached to the charging roll 14, an effect of suppressing filming on the surface of the charging roll 14, and the charging roll 14 As a result, it is possible to maintain the stable charging performance of the charging roll 14 over a long period of time.

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

  For example, in the seventh to ninth embodiments, a non-contact portion that does not contact the charging roll at all is provided in the sponge layer of the cleaning roll in order to prevent deterioration and deformation of the charging roll. Instead of the non-contact portion, a low load portion in which a contact load in an area corresponding to at least the image forming area of the charging roll is made lower than a predetermined load (for example, a load at which the charging roll starts to deform) may be used. The above effect can also be obtained by a low load portion.

  Further, in the above-described embodiment, the charging roll and the cleaning roll are both supported by the same bearing member so that they are in a pressure contact state, and the bearing member is urged by the compression coil spring to press the charging roll against the photosensitive drum. However, the support structure and pressure contact structure of each roll are not limited to this, and a charging roll that is in contact with or close to the photosensitive drum and a cleaning roll that is driven to rotate while being pressed against the charging roll. The present invention can also be applied to a configuration in which the bearing is supported by an individual bearing member and is urged and pressed by an individual urging means.

  In addition, the charging roll is brought into contact with the upper part of the photosensitive drum and the cleaning roll is brought into contact with the upper part of the charging roll. However, the positional relationship between the photosensitive drum, the charging roll, and the cleaning roll is limited to this. It is not something. For example, if the cleaning roller contact load is not set to its own weight, the present invention is also applied to a configuration in which the charging roll is brought into contact with the lower part of the photosensitive drum and the cleaning roll is brought into contact with the lower part of the charging roll. can do.

  The image forming apparatus to which the present invention is applied has a tandem configuration in which yellow, magenta, cyan, and black image forming units are arranged in parallel along the moving direction of the intermediate transfer belt as in the above-described embodiment. It is not limited. For example, the present invention can be applied to cleaning means for a charging roll that charges a photosensitive drum, even in a four-cycle configuration in which a toner image is formed on a photosensitive drum four times using a rotary developing device. 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. It is a partial cross section side view showing composition of a support structure of a charging roll and a cleaning roll concerning a 1st embodiment of the present invention. It is a front view which shows the state by which the charging roll and cleaning roll which concern on the 1st Embodiment of this invention were supported by the bearing member. (A) is a front view which shows the cleaning roll which concerns on the 1st Embodiment of this invention, (B) is a partial cross section side view which expands and shows the state which the cleaning roll of (A) contacted the charging roll. It is a front view which shows the state by which the charging roll and cleaning roll which concern on the 2nd Embodiment of this invention were supported by the bearing member. It is a front view which shows the cleaning roll which concerns on the 3rd Embodiment of this invention. (A) which shows the eccentric cleaning roll which concerns on the 4th Embodiment of this invention is a perspective view, (B) is a side view. (A) which shows the cross-sectional substantially star-shaped cleaning roll which concerns on the 4th Embodiment of this invention is a perspective view, (B) is a side view. (A), (B) is a perspective view which shows two types of cleaning rolls concerning the 5th Embodiment of this invention. (A) which shows the cleaning roll concerning the 6th Embodiment of this invention is a front view, (B) is a side view. It is a front view which shows the contact state with respect to the charging roll of the cleaning roll which concerns on the 6th Embodiment of this invention. It is a front view which shows the non-contact state with respect to the charging roll of the cleaning roll which concerns on the 6th Embodiment of this invention. (A) which shows the cleaning roll concerning the 7th Embodiment of this invention is a front view, (B) is a side view. It is a front view which shows the contact state with respect to the charging roll of the cleaning roll which concerns on the 7th Embodiment of this invention. It is a front view which shows the non-contact state with respect to the charging roll of the cleaning roll which concerns on the 7th Embodiment of this invention. (A) which shows the cleaning roll which concerns on the 8th Embodiment of this invention is a front view, (B) is a side view. It is a front view which shows the contact state with respect to the charging roll of the cleaning roll which concerns on the 8th Embodiment of this invention. It is a front view which shows the non-contact state with respect to the charging roll of the cleaning roll which concerns on the 8th Embodiment of this invention. It is a side view which shows the contact state with respect to the charging roll of the cleaning roll which concerns on the 9th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (Image carrier)
14 Charging roll 100 Cleaning roll 100B Sponge layer 102 First sponge material 104 Second sponge material 140 Cleaning roll 140B Sponge layer 150 Cleaning roll 150B Sponge layer 160 Cleaning roll 160B Sponge layer 170 Cleaning roll 170B Sponge layer 180 Cleaning roll 180B Sponge layer 200 Cleaning roll 200B Sponge layer 202 Concave portion 210 Cleaning roll 210B Sponge layer 212 Flat portion 220 Cleaning roll 220B Sponge layer 222 Thin portion 230 Cleaning roll 230B Sponge layer 232 Flat portion 234 Thick portion 236 Thin portion

Claims (27)

A cleaning roll that contacts and rotates with a charging roll that charges the image bearing member,
A cleaning roll, wherein a plurality of parts having different cleaning conditions are provided on an outer peripheral surface in contact with the charging roll.   The cleaning roll according to claim 1, wherein cleaning conditions of the plurality of portions are changed depending on a material, a contact load with respect to the charging roll, or a difference in amount of biting into the charging roll.   The cleaning roll according to claim 1, wherein the plurality of portions extend along the axial direction and are arranged in the circumferential direction.   The cleaning roll according to claim 1, wherein the plurality of portions are arranged in a spiral shape.   The cleaning roll according to claim 2, wherein the difference in material is hardness.   The cleaning roll according to claim 1, wherein the plurality of portions include a first foam material and a second foam material having different foam hardness.   The cleaning roll according to claim 6, wherein the first foam material and the second foam material are alternately arranged in a circumferential direction.   The cleaning roll according to claim 7, wherein widths in the axial direction of the first foam material and the second foam material are substantially uniform.   The cleaning roll according to any one of claims 6 to 8, wherein both the first foam material and the second foam material are disposed so as to contact the charging roll.   The cleaning roll according to claim 6, wherein the first foam material and the second foam material are arranged in a spiral shape.   The foam foam hardness S1 of the first foam material is 250N ≦ S1 ≦ 400N, and the second foam material has a foam hardness S2 of 100N ≦ S2 <250N. The cleaning roll according to item 1.   The cleaning roll according to any one of claims 6 to 11, wherein a cell density of the first foam material and the second foam material is 20 to 125 cells / 25 mm.   The cleaning roller according to claim 2, wherein the difference between the contact load and the biting amount is formed by making the outer peripheral surface a non-circumferential surface.   14. The cleaning according to claim 2, wherein the contact load / the amount of biting is changed in the circumferential direction, or in the circumferential direction and the axial direction by the rotation. roll.   The cleaning roll according to claim 14, wherein the amount of biting that varies in the circumferential direction is in the range of 0.1 to 0.8 mm.   The cleaning roll according to claim 14, wherein the amount of biting that varies in the axial direction is in the range of 0.1 to 0.8 mm.   The cleaning roll according to any one of claims 13 to 16, wherein the cleaning roll is configured to reciprocate in an axial direction.   At least one of the plurality of portions is a high-hardness portion having a hardness higher than that of the charging roll, and the high-hardness portion is always in contact with the charging roll when in contact with the charging roll. The cleaning roll according to any one of claims 1 to 17, wherein:   The cleaning roll according to any one of claims 1 to 18, wherein an abrasive is mixed in at least one of the plurality of portions.   20. The cleaning roll according to claim 19, wherein the abrasive is composed of Si hard abrasive grains or a component contained in an external additive of toner.   The cleaning roll according to any one of claims 1 to 20, wherein the circumference is set to a non-integer multiple of the circumference of the charging roll.   The cleaning roll according to any one of claims 1 to 21, wherein a contact load on the charging roll is self-weight.   An image forming apparatus comprising the cleaning roll according to any one of claims 1 to 22.   In the cleaning roll, at least one of the plurality of portions is a low load portion in which a contact load in an area corresponding to an image forming area of the charging roll is set lower than a predetermined load, and is charged by the rotation. 24. The image forming apparatus according to claim 23, wherein a contact state / low load contact state with respect to the roll is switched.   In the cleaning roll, at least one of the plurality of portions is a non-contact portion in which a contact state at least in an area corresponding to an image forming area of the charging roll is released. The image forming apparatus according to claim 23, wherein the non-contact state is switched.   26. The image forming apparatus according to claim 24, wherein the cleaning roll is brought into a low load contact / non-contact state at least when the rotation of the charging roll is stopped.   27. The image forming apparatus according to claim 25, wherein the cleaning roll is brought into contact / non-contact with the charging roll by rotating / stopping the charging roll and changing the applied voltage.

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