JP5982768B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus, and more particularly to a cleaning mechanism for a charging roller used in a charging device.

In an image forming layer using an electrophotographic method, an electrostatic latent image is formed by a writing process after uniform charging is performed on a photosensitive member as a latent image carrier using a charging device.
The electrostatic latent image is subjected to a visible image processing by a developing device, and then transferred to a recording medium such as recording paper, and the transferred visible image is fixed to form a copy.

  A plurality of photoconductors may be provided so that different color images can be formed. In this case, a visible image formed by each photoconductor is superimposed and transferred onto the recording medium during the movement of the recording medium. In some cases, the superimposed image may be collectively transferred to a recording medium after being superimposed on the intermediate transfer member.

  As described above, a plurality of color images such as a full color image can be formed by superimposing and transferring visible images from a plurality of photoconductors.

Since untransferred toner may remain on the photoconductor after image transfer, the untransferred toner is cleaned by a cleaning device.
For the cleaning of the photoconductor, a configuration in which untransferred toner is scraped off by a cleaning blade that contacts the photoconductor is known.

Conventionally, for the purpose of protecting the photoreceptor surface and improving the cleaning blade performance, the lubricity on the photoreceptor surface has been improved.
As a method for improving the lubricity, there is a method of scraping a solid lubricant with a brush roller or the like and supplying it to the surface of the photoreceptor, in addition to the method of externally adding the lubricant particles to the toner in the developer.

  As the above-described lubricant, a method of supplying a lubricant containing zinc stearate and boron nitride has been proposed (for example, Patent Document 1).

  On the other hand, a configuration is known in which a charging bias is applied to the charging member in which DC alternating current is superimposed in a state of being close to the surface of the photoreceptor. In this configuration, the photosensitive member can be uniformly charged, but the toner or the external additive of the toner may slightly fly and adhere to the charging member depending on the bias polarity when the charging bias is applied. .

  Therefore, as a simple configuration for removing the toner and foreign matters adhering to the charging member and maintaining the charging characteristics appropriately, a configuration for removing the toner by bringing the cleaning member into contact with the surface of the charging member is known. .

  In the case of a charging member using a configuration that contacts the surface of the latent image carrier, the charging member moves while contacting the surface of the latent image carrier, so that the toner that has still adhered even after cleaning is scraped off the charging member. May be. When the toner adhering to the charging member is deposited, the surface characteristics of the charging member may change, and the charging characteristics may be deteriorated.

  Conventionally, as a configuration for solving the above-described problems, a configuration in which the cleaning member can be brought into contact with and separated from the charging member, and a realistic toner based on the history of use of the photosensitive member, the history of use of the apparatus, the history of the image area, etc. A method has been proposed in which the removal amount of the cleaning member is indexed and the contact / separation interval of the cleaning member to the charging member is changed in accordance with the indexing amount (for example, Patent Document 2).

  Among the components used as a lubricant, zinc stearate has an excellent protection function for the photoconductor, and can reduce the wear of the photoconductor even when an AC bias executed on a nearby charging member is superimposed. .

  On the other hand, when boron nitride is used as the lubricant, when the cleaning blade is used for cleaning the photoreceptor, the contact state of the cleaning blade can be stabilized, and the cleaning performance for the photoreceptor can be maintained. Can do.

  For these reasons, a lubricant having the advantages of both can be constituted by using a component containing zinc stearate and boron nitride as the lubricant supplied to the photoreceptor.

  However, when the lubricant containing the above-described components is used, there is a problem that the consumption variation of the lubricant is large.

FIG. 9 is a diagram for explaining the transition of the lubricant consumption with respect to the travel distance of the photoreceptor.
In the figure, A shows a change in consumption for a lubricant composed only of a fatty acid metal salt mainly composed of zinc stearate, and B represents 95 parts by weight of a fatty acid metal salt mainly composed of zinc stearate. On the other hand, the change in lubricant consumption is shown by setting boron nitride to 5 parts by weight and mixing both.

  The lubricant is intended for a case where the lubricant is scraped off and supplied by a brush roller made of PET (polyethylene terephthalate) in which the hair density is 3 mm, the fiber system is 200 μm, and the flocking density per square inch is set to 150,000.

  In the case of the lubricant indicated by A in FIG. 9, although there is a slight decrease, it tends to stabilize while gradually decreasing, but in the case of the lubricant indicated by B, the initial consumption is very high. Many tend to stabilize while gradually decreasing from this state.

  The cause of such fluctuations in consumption transition is not clear, but according to the inventor's consideration, there is a difference in the state of adhesion to the brush fibers depending on the type of lubricant, and this difference changes the amount of lubricant scraped off. Was found to occur.

  If the amount of lubricant consumed is reduced, the protective function of the photoconductor cannot be obtained sufficiently, and the amount of wear of the photoconductor increases, or there is a filming phenomenon in which toner or toner external additives adhere to the surface of the photoconductor. There is a risk that it is likely to occur. Usually, in order to fully exhibit the function of the lubricant, it is necessary to maintain a consumption amount of at least 0.2 g / km or more.

  Therefore, when using a lubricant of B, which is a mixture of zinc stearate and boron nitride, the amount of lubricant consumed is very high at the initial stage, and the amount of lubricant supplied (consumption) increases. If the lubricant supplied to the photosensitive member flies to the charging member side through an AC bias superimposed on the charging member, the degree of contamination on the charging member side may be increased. .

  The object of the present invention is to solve the above-described problems in the conventional charging device, in particular, the contamination of the charging member due to the consumption tendency of the lubricant supplied to the latent image carrier. It is an object of the present invention to provide a charging device having a configuration capable of preventing dirt on the surface and maintaining a stable charged state.

To this end, the present invention is at least capable of a charging device having a charging member for charging the image bearing member to be supplied with lubricant on the front surface, the image forming having said latent image bearing member The image forming apparatus includes a single image forming unit and a control unit that controls the charging device, and the charging device can contact and separate from the charging member to remove transfer residual toner and foreign matters adhering to the charging member. such a cleaning means, and a drive for moving parts contacting and separating said cleaning means to said charging member, the control unit may contact the cleaning means with respect to the charging member by controlling the drive state position of the drive unit The separation condition can be changed , and the lubricant includes zinc stearate and boron nitride, and when the traveling distance of the latent image carrier exceeds the traveling distance threshold, the controller The cleaning In the image forming apparatus characterized by increasing the number of passed paper for up to abut the timber to the charging member.

  According to the present invention, when the consumption amount of the lubricant on the latent image carrier side fluctuates, the cleaning unit contacts the charging member so that the transfer residual toner and foreign matter are prevented from adhering to the charging member. Change the release condition. This prevents the transfer residual toner from adhering to the charging member even when the lubricant consumption tends to increase, preventing the charging member from deteriorating due to the transfer residual toner adhering to the charging member. The state can be maintained.

1 is a schematic diagram for explaining an overall configuration of an image forming apparatus using a charging device according to an embodiment. FIG. 2 is a schematic diagram illustrating an example of a charging device used in the image forming apparatus illustrated in FIG. 1. FIG. 6 is a schematic diagram illustrating another example of a charging device used in the image forming apparatus illustrated in FIG. 1. It is sectional drawing for demonstrating the structure of the charging member used for a charging device. It is a figure for demonstrating the structure of the cleaning means used for a charging device. It is a figure for demonstrating the structure of the charge cleaning member used for a charging device. It is a block diagram for demonstrating the structure of the control part used for an image forming apparatus. It is a flowchart for demonstrating the effect | action of the control part shown in FIG. It is a diagram for demonstrating the consumption transition based on the component used for a lubrication agent.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an example applied to a tandem intermediate transfer type full-color copying machine.

  In FIG. 1, the full-color copying machine includes an apparatus main body 100, a paper feed table 200 on which the main body is mounted, a scanner 300 mounted on the copying apparatus main body, an automatic document feeder (ADF) 400 mounted on the scanner, and the like.

The full-color copying machine is configured as a tandem image forming apparatus 20 in which image forming units 18Y, 18C, 18M, and 18Bk used as four image forming units Y, C, M, and Bk are arranged side by side in the center of the main body. Yes.
Each image forming unit of the tandem image forming apparatus 20 includes photoreceptors 40Y, 40C, 40M, and 40Bk on which toner images of respective colors Y, C, M, and Bk are formed.

An exposure device 21 is provided above the tandem image forming apparatus 20.
The exposure device 21 is arranged in four laser diode (LD) light sources prepared for each color, a pair of polygon scanners composed of a six-sided polygon mirror and a polygon motor, and the optical path of each light source. It is composed of a lens such as an fθ lens, a long WTL, or a mirror.
Laser light emitted from the LD in accordance with the image information of each color is deflected and scanned by a polygon scanner and irradiated to the photoreceptors 40Y, 40C, 40M, and 40Bk of each color.

Below the tandem image forming apparatus 20, an endless belt-like intermediate transfer belt 10 is installed.
In the illustrated example, the intermediate transfer belt 10 is wound around three support rollers 14, 15, 16 and can be rotated and conveyed in the clockwise direction in the figure. The support roller 14 is a driving roller that drives the intermediate transfer belt 10 to rotate.

  Further, between the first support roller 14 and the second support roller 15, a primary transfer roller 62Y is used as a primary transfer unit for transferring a toner image from the photoreceptors 40Y, 40C, 40M, and 40Bk of the respective colors to the intermediate transfer belt 10. , C, M, and Bk are provided to face the photoreceptors 40Y, 40C, 40M, and 40Bk with the intermediate transfer belt 10 interposed therebetween.

  An intermediate transfer belt cleaning device 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is provided downstream of the third support roller 16.

  As a material of the intermediate transfer belt 10, a resin material such as polyvinylidene fluoride, polyimide, polycarbonate, polyethylene terephthalate, etc. can be formed into a seamless belt and used. These materials can be used as they are, or the resistance can be adjusted with a conductive material such as carbon black.

  Further, using these resins as a base layer, a surface layer may be formed by a method such as spraying or dipping to form a laminated structure.

A secondary transfer device 22 is provided below the intermediate transfer belt 10.
In the illustrated configuration, the secondary transfer device 22 is disposed between two rollers 23 with a secondary transfer belt 24, which is an endless belt, being stretched over. The secondary transfer device 22 is disposed so as to be pressed against the third support roller 16 via the intermediate transfer belt 10 and transfers an image on the intermediate transfer belt 10 to a transfer material.
As the secondary transfer belt 24, the same material as that of the intermediate transfer belt 10 can be used.

Next to the secondary transfer device 22, a fixing device 25 for fixing an image on the transfer material is provided.
The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.

  The secondary transfer device 22 described above is also provided with a sheet transport function for transporting the transfer material after image transfer to the fixing device 25. Of course, a transfer roller or a transfer charger may be disposed as the secondary transfer device 22, and in such a case, it is necessary to provide this transfer material conveying function separately.

  In the illustrated example, a transfer material is disposed below the secondary transfer device 22 and the fixing device 25 in parallel with the above-described tandem image forming device so as to reversely discharge the transfer material or to form an image on both sides of the transfer material. And a reversing device 28 for re-feeding and refeeding.

  When performing a copying operation using such a tandem image forming apparatus, an original is set on the ADF original table 30. Alternatively, the ADF is opened, a document is set on the contact glass 32 of the scanner 300, the ADF is closed, and the document is pressed.

When the start switch of the operation unit (not shown) is pressed, when the document is set on the ADF, the document is transported and moved onto the contact glass, and when the document is set on the other contact glass, the scanner is immediately 300 is driven to travel on the first traveling body 33 and the second traveling body 34.
The first traveling body 33 irradiates light from the light source and further reflects reflected light from the document surface toward the second traveling body 34, reflects off the mirror of the second traveling body 34, and passes through the imaging lens 35 to read the sensor. 36 to read the contents of the document.

  Thereafter, when the mode setting is set in the operation unit or the automatic mode selection is set in the operation unit, the image forming operation is started in the full color mode or the monochrome mode according to the reading result of the original.

  When the full color mode is selected, each photoconductor rotates in the counterclockwise direction in FIG. The surface of each photoconductor is uniformly charged by a charging roller 70 as a charging device.

  Laser light corresponding to the image of each color is irradiated from the exposure device 21 to each color photoconductor (for convenience, omitting alphabets indicating the type of color) 40, and a latent image corresponding to the image data of each color is formed. Is done. Each latent image is developed with toner of each color by developing device 60Y, C, M, Bk of each color as photoreceptor 40 rotates.

  The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 10 along with the conveyance of the intermediate transfer belt 10 to form a full color image on the intermediate transfer belt. After the transfer, the photosensitive member 40 is subjected to light neutralization by a static elimination lamp (a member denoted by reference numeral 72 in FIG. 2), and residual toner is removed by a cleaning unit.

  On the other hand, one of the paper feed rollers 42 is selectively rotated, the transfer material is fed out from one of the paper feed cassettes 44 provided in multiple stages in the paper feed unit 43 in the paper feed table 200, and one sheet is fed by the separation roller 45. The paper is separated and put into a paper feed path 46, transported by a transport roller 47, guided to a paper feed path 48 in the main body, and abutted against a registration roller 49 and stopped.

  When paper is fed from the manual feed tray 51, the paper feed roller 50 is rotated to feed the transfer material on the manual feed tray 51, separated one by one by the separation roller 52, and put into the manual feed path 53. Stop against the roller 49.

  Then, the registration roller 49 is rotated in synchronization with the full-color image on the intermediate transfer belt 10, the transfer material is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A toner image is collectively transferred onto a transfer material.

  The transfer material onto which the toner image has been transferred is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where it is fixed to the transfer material by applying heat and pressure in the fixing device 25. The paper is switched and discharged by a discharge roller 56 and stacked on a discharge tray 57.

  At the time of image formation on both sides of the transfer material, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and fed again to the transfer position. The paper is discharged onto the paper discharge tray 57. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

After the formation of a predetermined number of images, the rotation of the photoconductor 40 is stopped after post-image forming processing is performed.
In the post-image processing, the photosensitive member is rotated one or more times with the charging bias and transfer bias turned off. At that time, the charge on the surface of the photosensitive member is discharged by the discharging means, and the photosensitive member 40 is left discharged. Prevents the photoreceptor from deteriorating.

  When the monochrome mode is selected, the support roller 15 moves downward to separate the intermediate transfer belt 10 from the photoreceptors Y, C, and M. Only the Bk photoconductor 40Bk rotates counterclockwise in FIG. 1, the surface of the Bk photoconductor is uniformly charged by the charging roller 70, and a laser beam corresponding to the Bk image is irradiated to form a latent image. Then, the toner image is developed with Bk toner.

  This toner image is transferred onto the intermediate transfer belt 10. At this time, the three-color photoconductors 40Y, C, and M other than Bk, and the developing devices 60Y, C, and M are stopped, and unnecessary consumption of the photoconductor 40 and the developer is prevented.

On the other hand, the transfer material is fed from the paper feed cassette 44 and conveyed by the registration roller 49 at a timing that coincides with the toner image formed on the intermediate transfer belt 10.
The transfer material onto which the toner image has been transferred is fixed by the fixing device 25 as in the case of a full-color image, and is processed through a paper discharge system corresponding to a designated mode.
Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

  Next, the image forming unit will be described in detail. Since the image forming units 18Y, C, M, and Bk (hereinafter also referred to as reference numeral 18 for the sake of convenience) have the same configuration except for the color of the accommodated toner, the subscripts Y, C, and M will be described below. , Bk is omitted for explanation.

FIG. 2 is a schematic configuration diagram of the image forming unit.
In the figure, around the photoconductor 40, a charging roller 70 as a charging means for uniformly charging the photoconductor 40, a potential sensor 71 for detecting the potential of the photoconductor 40, and an electrostatic latent image formed on the photoconductor 40 A developing device for developing the toner (for the sake of convenience, the alphabet indicating the type of color is omitted) 60, a charge removing lamp 72 for discharging the surface of the photosensitive member 40 after the toner image is transferred, and a photosensitive member for cleaning the transfer residual toner. A body cleaning device is arranged.
The case of the image forming unit 18 is provided with an opening for allowing the exposure light 76 from the exposure device 21 to pass therethrough.

  The photoreceptor 40 shown in FIG. 2 is a stacked organic photoreceptor provided with a charge generation layer and a charge transport layer constituting a photosensitive layer provided on a conductive support.

The conductive support has a volume resistance of 10 ¹⁰ Ωcm or less, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum, or a metal oxide such as tin oxide or indium oxide. The film is formed by vapor deposition or sputtering, film- or cylindrical plastic, paper-coated, pipes such as aluminum, aluminum alloy, nickel, and stainless steel are subjected to surface treatment by cutting, superfinishing, polishing, or the like.

The charge generation layer is a layer mainly composed of a charge generation material.
As the charge generation material, an inorganic or organic material is used, and typical examples include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squarics. Examples include acid dyes, phthalocyanine pigments, naphthalocyanine pigments, azulenium salt dyes, selenium, selenium-tellurium alloys, selenium-arsenic alloys, and amorphous silicon. These charge generation materials may be used alone or in combination of two or more.

The charge generation layer is obtained by dispersing the charge generation material together with a binder resin, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, 2-butanone, dichloroethane, or the like by a ball mill, an attritor, a sand mill, or the like, and applying a dispersion. Can be formed.
The charge generation layer can be applied by dip coating, spray coating, bead coating, or the like.

  Examples of the binder resin used as appropriate include resins such as polyamide, polyurethane, polyester, epoxy, polyketone, polycarbonate, silicone, acrylic, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polyacryl, and polyamide. The amount of the binder resin is suitably 0 to 2 parts with respect to 1 part of the charge generating material on a weight basis.

The charge generation layer can also be formed by a known vacuum thin film manufacturing method.
The film thickness of the charge generation layer is usually 0.01 to 5 μm, preferably 0.1 to 2 μm.

The charge transport layer can be formed by dissolving or dispersing the charge transport material and the binder resin in an appropriate solvent, and applying and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added as needed.
Among charge transport materials, low molecular charge transport materials include electron transport materials and hole transport materials.

Examples of the electron transport material include chloroanil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide.
These electron transport materials may be used alone or as a mixture of two or more.

  Examples of hole transport materials include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane. , Styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials may be used alone or as a mixture of two or more.

  Examples of the binder resin used in the charge transport layer together with the charge transport material include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, and vinyl chloride. Vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy, polycarbonate, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic, silicone, epoxy, melamine, urethane, phenol, alkyd, etc. A thermoplastic or thermosetting resin is mentioned.

Examples of the solvent include tetrahydrofuran, dioxane, toluene, 2-butanone, monochlorobenzene, dichloroethane, methylene chloride and the like.
The thickness of the charge transport layer may be appropriately selected in accordance with desired photoreceptor characteristics within a range of 10 to 40 μm.
Examples of the plasticizer that is optionally added to the charge transport layer include dibutyl phthalate, dioctyl phthalate, and other general-purpose plasticizers. The amount used is 0 to 30% based on the weight of the binder resin. The degree is appropriate.
Leveling agents added to the charge transport layer as desired include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in the side chain. About 0 to 1% is appropriate for the binder resin on the basis.

In the present invention, the amount of the charge transport material contained in the photosensitive layer is preferably 30% by weight or more of the charge transport layer. If it is less than 30% by weight, a sufficient light decay time in a high-speed electrophotographic process cannot be obtained in pulsed light exposure in laser writing on the photoreceptor 40, which is not preferable.
In the photoreceptor 40 shown in FIG. 2, an undercoat layer can be formed between the conductive support and the photosensitive layer. In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is applied using a solvent, the resin is a resin having high resistance to general organic solvents. Is desirable.

  Such resins include water-soluble resins such as polyvinyl alcohol, casein, sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine, alkyd-melamine, epoxy, etc., three-dimensional Examples thereof include a curable resin that forms a network structure.

Further, fine powder of metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the undercoat layer in order to prevent moire and reduce residual potential.
This undercoat layer can be formed using an appropriate solvent and coating method, as in the above-described photosensitive layer.
Furthermore, it is also useful to use a metal oxide layer formed by, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like as the undercoat layer. In addition, the undercoat layer is formed by anodizing Al2O3, organic matter such as polyparaxylylene (parylene), inorganic matter such as SiO, SnO2, TiO2, ITO, Ce02 by a vacuum thin film manufacturing method. The formed one is also effective. The thickness of the undercoat layer is suitably from 0 to 5 μm.

A protective layer may be formed on the photosensitive member 40 on the photosensitive layer for the purpose of protecting the photosensitive layer and improving durability.
This protective layer has a structure in which metal oxide fine particles such as alumina, silica, titanium oxide, tin oxide, zirconium oxide, and indium oxide are added to the binder resin for the purpose of improving wear resistance. Binder resins include styrene-acrylonitrile copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, olefin-vinyl monomer copolymer, chlorinated polyether, allyl, phenol, polyacetal, polyamide, polyamide Imide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethine, polyethylene terephthalate, polyimide, acrylic, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polyurethane, polyvinyl chloride, polyvinylidene chloride And resins such as epoxy.

  The amount of metal oxide fine particles added to the protective layer is usually 5 to 30% on a weight basis. If the amount of the metal oxide fine particles is less than 5%, the wear is large and the effect of improving the wear resistance is small and the durability is inferior. If it exceeds 30%, the bright portion potential is significantly increased during exposure, and the sensitivity is lowered. Is not desirable because it cannot be ignored. As a method for forming the protective layer, a normal coating method such as a spray method is employed. The thickness of the protective layer is 1 to 10 μm, preferably about 3 to 8 μm.

  If the protective layer is too thin, the durability will be poor, and if the protective layer is too thick, not only will the productivity at the time of photoconductor production decrease, but the residual potential will increase significantly over time. . The particle size of the metal oxide particles added to the protective layer is suitably 0.1 to 0.8 μm. When the particle size of the metal oxide fine particles is too large, the unevenness on the surface of the protective layer becomes large and the cleaning property is deteriorated, and the exposure light is easily scattered by the protective layer, so that the resolution is lowered and the image quality is inferior. If the particle size of the metal oxide fine particles is too small, the wear resistance is poor.

Further, a dispersion aid can be added to the protective layer in order to improve the dispersibility of the metal oxide fine particles in the base resin. As the added dispersion aid, those used in paints and the like can be used as appropriate, and the amount thereof is usually 0.5 to 4%, preferably 1 to 2 with respect to the amount of metal oxide fine particles contained on a weight basis. %.
Further, by adding a charge transport material to the protective layer, the movement of charges in the protective layer can be promoted. As the charge transport material added to the protective layer, the same material as the charge transport layer can be used.
Further, the photoreceptor 40 used in the present invention has an antioxidant, a plasticizer, an ultraviolet absorber, and a leveling agent for each layer in order to improve environmental resistance, particularly for the purpose of preventing a decrease in sensitivity and an increase in residual potential. Etc. can be added.

  The developing device 60 contains a two-component developer composed of toner and carrier. The developing device 60 includes a developing roller 61 facing the photoreceptor 40, screws 62 and 63 for conveying and stirring the developer, a toner concentration sensor 64, and the like.

The developing roller 61 is composed of an outer rotatable sleeve and an inner magnet.
The developer frictionally charged by being agitated by the screws 62 and 63 is carried by the magnetic force of the developing roller 61, conveyed to a portion facing the photoreceptor 40, and supplying toner to the latent image on the photoreceptor 40. Develop it.
Further, the toner concentration of the developer that has consumed the toner is detected by the toner concentration sensor 64, and a necessary amount of toner is supplied from a toner supply device (not shown) provided at the upper portion of the developing device 60 according to the detection result.

The toner supply device transports and stores toner from a toner storage container (not shown) that stores toner.
The toner supply device is provided with a supply port communicating with the developing device 60 and a screw (not shown) for moving the stored toner to the supply port.

  At the time of toner supply, when a toner supply command to the developing device 60 is issued by the toner concentration sensor 64, a clutch (not shown) is turned on to operate the screw, and an amount of toner corresponding to the rotation time is directed to the supply port. The toner is supplied by being moved and dropped into the developing device 60 from the supply port.

The toner used in the developing device 60 includes a binder resin, a colorant, and a charge control agent as main components, and other additives are added as necessary.
Specific examples of the binder resin include polystyrene, styrene-acrylic acid ester copolymer, polyester resin, and the like. As the colorant (for example, yellow, magenta, cyan and black) used for the toner, those known for toner can be used. The amount of the coloring material is suitably 0.1 to 15 parts by weight with respect to 100 parts by weight of the binder resin.

  Specific examples of the charge control agent include a nigrosine dye, a chromium-containing complex, a quaternary ammonium salt, and the like, which are properly used depending on the polarity of the toner particles. The amount of the charge control agent is 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  It is advantageous to add a fluidity imparting agent to the toner particles. Examples of the fluidity-imparting agent include fine particles of metal oxides such as silica, titania and alumina, and those obtained by surface-treating these fine particles with a silane coupling agent, titanate coupling agent, etc., polystyrene, polymethyl methacrylate, polyvinylidene fluoride. Polymer fine particles such as are used. These fluidity imparting agents have a particle size in the range of 0.01 to 3 μm. The addition amount of these fluidity-imparting agents is preferably in the range of 0.1 to 7.0 parts by weight with respect to 100 parts by weight of the toner particles.

As a method for producing a toner for two-component developer, it can be produced by various known methods or a combination thereof.
For example, in the kneading and pulverization method, a binder resin, a colorant such as carbon black, and the necessary additives are dry-mixed, heated and melt-kneaded with an extruder or two-roll, three-roll, etc., and after cooling and solidification Then, the toner is pulverized by a pulverizer such as a jet mill and classified by an airflow classifier. In addition, a toner can be directly produced from a monomer, a colorant, and an additive by suspension polymerization or non-aqueous dispersion polymerization.

  The carrier is generally composed of the core material itself, or a carrier provided with a coating layer on the core material. The core material of the resin-coated carrier that can be used in the present invention is ferrite or magnetite. An appropriate particle size of the core material is about 20 to 60 μm.

  Examples of the material used for forming the carrier coating layer include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinyl ether substituted with a fluorine atom, and vinyl ketone substituted with a fluorine atom. As a method for forming the coating layer, a resin may be applied to the surface of the carrier core material particles by a spraying method, a dipping method, or the like, as in the conventional case.

  The photoconductor cleaning device includes two brush rollers 73 and 74 and a cleaning blade 75. Further, a solid lubricant 78 is in contact with the brush roller 74, and has a function as a lubricant supply member.

  Examples of solid lubricants 78 include zinc stearate, barium stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, magnesium stearate, zinc oleate, olein Fatty acid metal salts such as cobalt oxide, magnesium oleate, and zinc palmitate, natural wax such as carnauba wax, and fluorine-based resin such as polytetrafluoroethylene can be used. Further, other materials can be mixed as required. The solid lubricant 78 can be produced by melting and solidifying lubricant particles or compression molding.

  The toner scraped off from the photoreceptor 40 by the brush rollers 73 and 74 and the cleaning blade 75 made of polyurethane rubber is collected by the toner transport coil 79 and transported to a waste toner storage unit (not shown).

  The image forming unit 18 is configured to clean the photoreceptor 40 that has been neutralized after the transfer, but may be configured to neutralize the photoreceptor 40 that has been cleaned after the transfer.

In the image forming unit 18 of FIG. 2, the lubricant supply member is disposed in the photosensitive member cleaning device. However, in this configuration, the supply of the lubricant 78 is easily affected by the amount of toner input to the cleaning. There were drawbacks.
In contrast, by arranging a lubricant supply member downstream of the photoconductor cleaning device as shown in FIG. 3, even if the input amount of transfer residual toner or reverse transfer toner changes depending on the image area to be formed, the photoconductor The lubricant 78 can be stably supplied to 40.

FIG. 4 shows a schematic configuration of the charging roller 70.
In the figure, the charging roller 70 includes a cored bar 70A that is a conductive support, a resin layer 70B as a charging member, and a gap holding member 70C that holds a gap between the photosensitive member 40. A metal such as stainless steel is used for the core metal 70A.

  If the core metal 70A is too thin, the influence of the deflection when the charging member is cut or when the photosensitive member 40 is pressed cannot be ignored, and the required gap accuracy is difficult to obtain. Further, when the cored bar 70A is too thick, there is a problem that the charging roller 70 becomes large or the mass becomes heavy. For this reason, the diameter of the cored bar 70A is preferably about 6 to 10 [mm].

The resin layer 70B of the charging roller 70 is preferably made of a material having a volume resistance of 10 ⁴ to 10 ⁹ [Ω · cm].
If the resistance is too low, charging bias leaks easily when there is a defect such as a pinhole in the photoconductor 40. If the resistance is too high, the discharge is not sufficiently generated and a uniform charging potential cannot be obtained.
A desired volume resistance can be obtained by blending a conductive material with a resin as a base material.

  As the base resin, resins such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, and polycarbonate can be used.

  Since these base resins have good moldability, they can be easily molded. As the conductive material, an ion conductive material such as a polymer compound having a quaternary ammonium base is preferable.

  Examples of polyolefins having a quaternary ammonium base include polyethylene, polypropylene, polybutene, polyisoprene, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene- Polyolefins such as propylene copolymer and ethylene-hexene copolymer.

As described above, the polyolefin having a quaternary ammonium base is exemplified, but a polymer compound other than the polyolefin having a quaternary ammonium base may be used. The ion conductive material is uniformly blended with the base resin by using means such as a biaxial kneader or a kneader. The blended material can be easily molded into a roller shape by injection molding or extrusion molding on the core metal 70A.
The blending amount of the ion conductive material and the base resin is desirably 30 to 80 parts by weight of the ion conductive material with respect to 100 parts by weight of the base resin.

  The thickness of the resin layer 70B of the charging roller 70 is desirably 0.5 to 3 [mm]. If the resin layer 70B is too thin, it is difficult to mold and there is a problem in terms of strength. If the resin layer 70B is too thick, the charging roller 70 is increased in size and the actual resistance of the resin layer 70B is increased, so that the charging efficiency is lowered.

  After the resin layer 70B is formed, the gap holding member 70C previously formed on both ends of the resin layer 70B is fixed to the core metal 70A by press-fitting, bonding, or both. In this way, after the resin layer 70B and the gap holding member 70C are integrated, the outer diameter of the charging roller 70 is adjusted by performing processing such as cutting and grinding, so that the phase of the flare between the resin layer 70B and the gap holding member 70C is obtained. And the fluctuation of the charging gap can be reduced.

  As the material of the gap holding member 70C, a resin such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, and polycarbonate can be used as in the case of the base member of the charging member. However, since the gap holding member 70C is brought into contact with the photoconductor 40, it is desirable to use a grade having a lower hardness than the charging member in order to prevent the photoconductor 40 from being damaged.

  Resin materials that are excellent in slidability and hardly damage the photoreceptor 40 include polyacetal, ethylene-ethyl acrylate copolymer, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene Resins such as copolymers can also be used. In addition, the resin layer 70B and the gap holding member 70C can be formed with a surface layer with a thickness of about several tens [μm] to which toner or the like is difficult to adhere by coating or the like.

  A gap is formed between the resin layer 70 </ b> B of the charging roller 70 and the photoconductor 40 by applying the gap holding member 70 </ b> C outside the image area of the photoconductor 40.

  In the charging roller 70, the gear attached to the end of the metal core 101 is engaged with the gear formed on the flange of the photoconductor 40. When the photoconductor 40 is rotated by a photoconductor drive motor (not shown), the charging roller 70 is also in the photoconductor. Rotate in the follower direction at a linear speed approximately equal to 40.

  Since the resin layer 70B and the photoconductor 40 are not in contact with each other, even when a hard resin material and an organic photoconductor are used as the charging roller 70, the photoconductor 40 in the image region is not damaged. Further, if the gap is too wide, abnormal discharge occurs and it becomes impossible to uniformly charge, so the maximum gap needs to be suppressed to about 100 [μm] or less. When such a charging roller 70 having a gap between the photoreceptor 40 and the charging roller 70 is used, it is desirable to superimpose an AC voltage on a DC voltage as a charging bias. Details of problems that occur in the charging roller 70 will be described later.

  By the way, when the charging roller 70 is disposed in contact with the photoreceptor 40, dirt on the surface of the photoreceptor 40 is rubbed against the charging roller 70 when the charging roller 70 rotates with the photoreceptor 40. Dirt such as toner is likely to adhere and more easily adhere.

  On the other hand, by disposing the charging roller 70 close to the photoreceptor 40 in a non-contact manner, the surface of the charging roller 70 is not rubbed against the photoreceptor 40, so that the contamination of the charging roller 70 can be greatly reduced. it can.

However, since the AC voltage is superimposed to uniformly charge the photoconductor 40, a slight amount of toner, toner external additive, and the like on the photoconductor 40 fly to the charging roller 70 even when arranged in a non-contact manner. Will adhere.
For this reason, it is necessary to provide the charging cleaning member 77 as a cleaning unit for cleaning the charging roller 70 and remove the contamination of the charging roller 70 even in the charging roller 70 in the close arrangement, as well as the charging roller 70 in the close arrangement.

  However, when such a charging cleaning member 77 is always brought into contact with the charging roller 70, the surface of the charging roller 70 can be removed initially, but accumulated on the surface of the charging cleaning member 77 over a long period of time. The toner or the like is rubbed against the surface of the charging roller 70, and the charging roller 70 is soiled.

  On the other hand, since an AC bias is applied to the charging roller 70, dirt on the photosensitive member 40 is attracted electrostatically, but conversely, dirt attached to the charging roller 70 is electrostatically returned to the photosensitive member 40. Power also works.

  Due to the phenomenon described above, the amount of dirt such as toner accumulated on the charging cleaning member 77 can be reduced by intermittently contacting the charging cleaning member 77 to the charging roller 70, so that the charging roller 70 is always charged. Unlike the case where the cleaning member 77 is brought into contact, the deterioration of the charging cleaning member 77 can be suppressed, and the lifetimes of both the charging roller 70 and the charging cleaning member 77 can be extended.

In the embodiment of the present invention, when the charging cleaning member 77 is intermittently contacted with the charging roller 70, the charging cleaning member 77 is brought into contact with and separated from the photosensitive member 40 in accordance with the variation of the lubricant consumption amount. The condition is set.
In particular, the contact / separation conditions are for contact conditions of the charging cleaning member 77 that can suppress contamination on the charging roller 70, that is, adhesion of lubricant and toner to the charging roller 70.

As the contact / separation condition described above, when the consumption amount of the lubricant 78 increases, the contact frequency of the charging cleaning member 77 with the charging roller 70 is increased.
In order to increase the contact frequency, the contact interval and contact time of the charging cleaning member 77 with respect to the charging roller 70 are used.

The reason for increasing the contact frequency is as follows.
When the consumption amount of the lubricant 78 on the photoconductor side increases, the amount of toner that passes through the cleaning blade 75 also increases, so that the contamination on the charging roller 70 side due to the lubricant 78 is likely to occur. For this reason, the cleaning by the charging cleaning member 77 is frequently or for a long time when the contamination of the charging roller 70 increases, thereby facilitating removal of the lubricant and toner adhering to the charging roller 70.
As a result, contamination on the charging roller 70 can be suppressed, and the life of the charging roller 70 and the cleaning blade 75 can be extended.

FIG. 5 is a schematic configuration diagram of a contact / separation mechanism that contacts and separates the charging cleaning member 77 from the charging roller 70.
The charging cleaning member 77 has a roller shape and is supported by arms 80 at both ends.
The arm 80 is swingably provided with the support shaft 80A as a fulcrum, and the state where the charging cleaning member 77 is separated from the charging roller 70 due to the behavior of an urging member (not shown) other than during cleaning is the initial state. Has been.

  When the arm 80 is in the initial state, when a solenoid (not shown) installed on the main body side is excited, the arm 80 pushes down the protrusion 82 located on the swing end side of the arm 80 (in the direction opposite to the arrow A in FIG. 5). Thus, the charging cleaning member 77 is brought into contact with the charging roller 70.

Thereby, the charging cleaning member 77 cleans the surface of the charging roller 70 while rotating around the charging roller 70.
After the cleaning is finished, a solenoid (not shown) installed on the main body side is released to move the protrusion 82 of the arm 80 in the direction of arrow A in FIG. 5 and the charging cleaning member 77 is separated from the charging roller 70. In FIG. 5, reference numeral 70 </ b> A <b> 1 indicates a charging frame that supports the charging roller 70.

  Since the state in which the charging cleaning member 77 is separated from the charging roller 70 is the initial state, the chance of toner adhesion from the charging roller 70 to the charging cleaning member 77 is reduced. It is possible to suppress the toner accumulation amount at 77 and prevent the charging roller 70 from being soiled.

  If such a contact / separation operation of the charging cleaning member 77 is executed during the image forming operation, vibrations due to the operation of the solenoid may be transmitted to the exposure device 21 or the like to disturb the image. For this reason, it is necessary to perform the charging roller cleaning operation by the charging cleaning member 77 other than during the image forming operation. Further, if the charging roller cleaning operation is frequently executed, the waiting time of the user increases. Therefore, it is desirable to reduce the execution frequency of the charging roller cleaning operation as much as possible.

  Various materials such as sponges and brushes can be used as the charging cleaning member 77. However, when the charging cleaning member 77 is fixedly brought into contact with the charging roller 70, the toner or the like accumulated on the contact surface is changed. Therefore, it is desirable that the charging cleaning member 77 be rotated with the charging roller 70 as a roller shape.

FIG. 6 is a schematic configuration diagram of the roller-shaped charging cleaning member 77.
The charging cleaning member 77 has a configuration in which a core metal 86 is covered with a melamine resin foam (porous material) 87, and the melamine resin foam (porous material) 87 is brought into contact with the surface of the charging roller 70 to charge the charging roller. Remove 70 stains.
Melamine resin foam 87 is superior in strength to other sponge-like materials, and since there are many spaces in the foam, it is possible to retain a large amount of dirt such as toner and maintain cleaning performance over a long period of time. .

In the charging cleaning member 77 having the above-described configuration, the contact / separation condition of the charging cleaning member 77 is set by the control unit 1000 shown in FIG. 7 based on the fluctuation of the lubricant consumption.
FIG. 7 is a block diagram for explaining the configuration of the control unit 1000. In the figure, the control unit 1000 uses a processor that executes an image forming process sequence program.

The control unit 1000 sets the contact frequency of the charging cleaning member 77 with respect to the charging roller 70 based on a change in image forming history that affects the lubricant consumption.
For this reason, the input side of the control unit 1000 is connected to a memory 1001 that stores and stores image forming histories in the respective image forming units, so-called use histories of the photoconductors 40Y, C, M, and Bk. A solenoid driving unit 1002 used as a contact / separation driving source for the charging cleaning member 77 is connected to the motor.
The use history described above also stores information about the amount of toner attached to the photosensitive drum, in other words, the image area that affects the residual toner amount.

  In the control unit 1000, for the case where the lubricant 78 in which zinc stearate and boron nitride are mixed is used as the lubricant 78, the image forming history in which the fluctuation of the lubricant consumption is captured in the memory 1001 described above. In addition, when it is determined from the image area and it is determined that the consumption has changed in an increasing trend, control is performed to increase the contact frequency of the charging cleaning member 77 in accordance with the increasing trend.

The amount of lubricant consumption tends to increase as the image forming history and the image area increase. In this case, the travel distance of the photoconductor 40 is used as the image formation history.
The control unit 1000 sets a threshold value for the travel distance of the photosensitive member 40 that affects the accumulated amount, and sets the number of excitation times or the excitation time of the solenoid according to the result of determining the travel distance based on this threshold value. The contact frequency of the charging cleaning member 77 with respect to 70 is increased.

  FIG. 8 is a flowchart for explaining a control procedure executed by the control unit 1000. The control procedure shown in FIG. 8 is based on the conditions of the first embodiment described below.

Using an experimental machine in which the charging cleaning member of the Ricoh printer “Imagio MPC600” is modified so as to be able to contact and separate, an image forming unit for the configuration of the lubricant supply device shown in FIG. 3 is used.
The charging cleaning member 77 uses the roller structure shown in FIG. 6, which is composed of a metal cored bar 86 and a melamine resin foam 87.

  As the lubricant 78, 95 parts by weight of a fatty acid metal salt containing zinc stearate as a main component and 5 parts by weight of boron nitride are mixed and compression-molded. A brush roller having a fiber diameter of 200 μm and a flocking density of 150,000 pieces per square inch was used.

  A sheet passing test was performed under the condition of 25 sheets of A4 size transfer paper per job with an image area of 5% for each color.

  The test starts from a state in which all the image forming units including the photosensitive member 40 are new, and the traveling distance is 10 every 200 sheets until the traveling distance of the photosensitive member 40 (photosensitive member linear speed × photosensitive member rotating time) reaches 10 km. Cleaning of the charging roller (a member indicated by reference numeral 70 in FIG. 2) was performed every 500 sheets up to 30 km and every 1000 sheets after the traveling distance of 30 km. The charging roller was cleaned by rotating the photosensitive member 40 and the charging roller while the charging roller cleaner was in contact with the charging roller for 10 seconds.

The procedure is described as follows based on the above conditions.
In FIG. 8, an image formation history (travel distance) is captured (ST1), and it is determined whether or not the result has reached a preset threshold (less than 10 km, 10 to 30 km, 30 km or more) (ST2, 3). 4).
In accordance with the comparison result between the travel distance and the threshold value, the contact interval of the charging cleaning member 77 is set (every 200 sheets for less than 10 km, every 500 sheets for 10 to 30 km, and every 1000 sheets for 30 km and later) (ST5, 6). 7) The time for which the charging cleaning member 77 is brought into contact with the charging roller 70 at each contact interval timing is set as the excitation time of the solenoid (ST8). If the distance between the travel distance and the threshold cannot be determined to be 30 km or more, it is determined that the apparatus is abnormal and error processing such as an alarm is executed (ST9).

  In the above embodiment, when an experiment was performed up to a traveling distance of 120 km (corresponding to 300,000 sheets in a normal temperature and humidity environment), an abnormal image caused by an increase in the coefficient of friction with the cleaning blade or contamination of the charging roller. The occurrence of was not observed.

The comparative example with respect to the above Example is given next.
(Comparative Example 1)
Of the conditions in the above-described embodiment, the experiment was performed except that the charging cleaning member 77 was brought into contact with the charging roller 70 every 1000 sheets.
When a paper passing test was conducted in a room temperature and humidity environment, vertical streak-like density unevenness occurred in the halftone image after about 10 km (25,000 paper passing) in the running distance, and the charging roller There was streak-like dirt. Since the leakage of the lubricant 78 was large and the charging roller was not completely cleaned, an abnormal image due to contamination of the charging roller occurred early.

(Comparative Example 2)
A paper passing test was performed under the same conditions as in Comparative Example 1 except that the lubricant was changed to a fatty acid metal salt mainly composed of zinc stearate.
Longitudinal stripe-like density unevenness began to occur in the halftone image due to charging roller contamination after the travel distance of 60 km (150,000 sheets passed). As the wear of the coating blade progressed and the slipping of the lubricant from the coating blade increased, the leakage of the lubricant increased with time, and an abnormal image due to contamination of the charging roller occurred.

10 Intermediate transfer bell 18Y, C, M, Bk Image forming unit 40CY, C, M, Bk Photoconductor 70 Charging roller 70A Core metal 70B Resin layer 70C Gap holding member 77 Cleaning member 78 Lubricant 80 Arm 82 Arm protrusion 87 Melamine Resin foam 100 Image forming apparatus main body 1000 Control unit 1001 Image forming history storage memory 1002 Solenoid drive unit

JP 2009-300861 A JP 2009-58559 A

Claims (6)

A charging device having a charging member for charging a latent image carrier to which a lubricant is supplied on the surface;
At least one image forming unit having the latent image carrier and capable of image formation;
A control unit for controlling the charging device,
The charging device includes: a cleaning unit that can come into contact with and separate from the charging member in order to remove transfer residual toner and foreign matters adhering to the charging member; and a drive unit that brings the cleaning unit into contact with and separated from the charging member. With
The control unit can change a contact / separation condition of the cleaning unit with respect to the charging member by controlling a driving state of the driving unit,
The lubricant includes zinc stearate and boron nitride,
When the travel distance of the latent image carrier exceeds the travel distance threshold, the control unit increases the number of sheets that pass until the cleaning member contacts the charging member by the drive unit. Image forming apparatus.   The control unit sets the contact / separation condition so that a contact ratio of the cleaning unit to the charging member increases when a supply amount of the lubricant to the latent image carrier is large. The image forming apparatus according to claim 1. The lubricant includes zinc stearate and boron nitride mixed in a ratio of 95 parts by weight of a fatty acid metal salt mainly composed of zinc stearate and 5 parts by weight of boron nitride. There the image forming apparatus according to claim 1 or 2, wherein the Rukoto. Before SL cleaning means, the image forming apparatus according to one of claims 1 to 3, characterized in that chromatic melamine resin foam core metal and cleaning. 5. The image forming apparatus according to claim 1, wherein the charging member has a roller shape, and at least a charging region is arranged in a non-contact manner with the latent image carrier . 6. One of said image bearing member is an organic photoreceptor having a protective layer as the outermost layer, the said protective layer, according to claim 1 or 5 metal oxide particles is characterized that you have been distributed The image forming apparatus described in 1.

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