JP2009139529A - Charging device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device capable of preventing degradation in image quality caused by charging failure and nonuniform charging, by sufficiently cleaning the surface of a charging member, and to prevent degradation in image quality caused by charging failure and non-uniform charging, by sufficiently cleaning the surface of a gap holding member, thereby highly accurately maintaining a gap (separation distance) for a long time. <P>SOLUTION: The charging device includes a first cleaning roller whose surface is formed from a continuous foam body, and a second cleaning roller whose surface is formed from an elastic body. The first cleaning roller is disposed so as to be rotated in the normal direction of the rotation of the charging member in contact with the electric resistance adjustment layer of the charging member and a gap holding member. The second cleaning roller is disposed downstream of the first cleaning roller in the rotating direction of the charging member so as to be rotated slower than the charging member in the opposite direction of the rotating direction of the charging member in firm contact with the surface electric resistance adjustment layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charging device mounted on an image forming apparatus such as a copying machine, a printer, or a facsimile. Specifically, the present invention relates to cleaning of the charging member. The present invention also relates to a process cartridge and an image forming apparatus having such a developing device.

  FIG. 1 is a schematic view of an electrophotographic image forming apparatus. In the figure, reference numeral 11 denotes an image carrier on which an electrostatic latent image is formed (electrostatic latent image carrier, photoconductor), and 12 is in contact with the image carrier or arranged close to the image carrier to perform charging processing. A charging member (charging roller), 13 is exposed to laser light or reflected light of a document, 14 is a toner carrier (developing roller) for adhering toner 15 to an electrostatic latent image on the image carrier, and 16 is on the photoreceptor. A transfer member (transfer roller) for transferring the toner image to the recording medium 17, and a cleaning member (blade) 18 for cleaning the photoconductor after the transfer process. Reference numeral 19 denotes waste toner from which the toner remaining on the photosensitive member is removed by the cleaning member, 20 denotes a developing device, and 21 denotes a cleaning device.

  In FIG. 1, functional units normally required in other electrophotographic processes are omitted because they are not required in this case.

In the image forming apparatus, an image is formed by the following means.
1. A charging roller charges the surface of the photoreceptor to a desired potential.
2. An exposure device projects image light onto the photoconductor to form an electrostatic latent image corresponding to a desired image on the photoconductor.
3. The developing roller develops the electrostatic latent image with toner and forms a toner image (developed image) on the image carrier.
4). The transfer roller transfers the toner image on the image carrier onto the recording paper.
5). A cleaning device cleans the toner that is not transferred and remains on the image carrier.
6). The recording paper onto which the toner image has been transferred by the transfer roller is conveyed to a fixing device (not shown). The fixing device heats and pressurizes the toner to fix it on the recording paper.

  By repeating the above steps 1 to 6, a desired image is formed on the recording paper.

  Here, as a charging method using a charging roller, a proximity charging method has been devised in which the charging roller is brought close to the photosensitive member.

  In the technique described in Japanese Patent Application No. 2005-24830 (Patent Document 1), a gap holding member is press-fitted into both end portions of the electric resistance adjusting layer portion. The configuration (relationship) of the electrical resistance adjustment layer portion and the gap holding member is such that a gap holding member is formed at the end of the electrical resistance adjustment layer portion, and the gap holding member includes the end surface of the electrical resistance adjustment layer portion and the conductive support. It is in contact with the body. As a result, long-term reliability is improved as compared with the tape-shaped gap holding member, and in the technique described in Japanese Patent Application Laid-Open No. 2005-91818 (Patent Document 2), the gap holding member and the electric resistance adjusting layer portion are simultaneously processed (removed) ) Makes it possible to precisely control the air gap.

  A method of charging an image carrier to form an electrostatic latent image on the surface of the image carrier using a roll-shaped charging member is large, and a DC charging method and an AC charging method are currently mainstream.

  The AC withstand voltage charging method is a charging method in which an oscillating voltage obtained by superimposing an AC voltage on a DC voltage corresponding to a desired charging position is applied to a charging member. However, when the AC charging method is used continuously, the surface of the image carrier deteriorates, and the durability is inferior to that of the DC charging method. In addition, generation of ozone is also observed. Further, due to the AC electric field, the toner and the toner additive and the like are retained by the electric and mechanical vibrations due to the vibration voltage between the image carrier and the charging member. The carrier contamination proceeds. Further, when used over time, dirt such as a toner additive may enter the gap holding member.

  In particular, in the non-contact charging method, the roller surface contamination, the progression of image carrier contamination, and the non-uniform charging due to the roller contamination are greatly affected by the non-uniformity of the gap between the gap holding member and the resistance adjusting layer.

  In a conventional cleaning mechanism, an open-cell foam that is rotatable and rotatable is disposed in contact with the rotating mechanism as in the technique described in Japanese Patent Laid-Open No. 2002-049220 (Patent Document 3), and is rotated with respect to the nip between the charging member and the photosensitive member. In the longitudinal direction of the contact charging member, such as one that is positioned downstream of the direction and rotates in the opposite direction to the rotation direction of the contact charging member to absorb and remove, or the technique described in JP-A-2004-54141 (Patent Document 4). The cleaning member made of a flexible organic polymer compound disposed so as to be in contact with each other has a plurality of gaps along the longitudinal direction of the charging member, and is in contact with the contact charging member. There are things that are movably provided so as to displace and scrape off the contamination source. In either case, cleaning with a single cleaning member is insufficient, and over time, due to deterioration, slipping occurs at the deteriorated portion, and stain on the streaks occurs. In the technique described in JP 2004-184934 A (Patent Document 5) and the like, durability is improved by a mechanism that repeats intermittent, contact, and non-contact. However, the durability is improved, but the cleaning property is lowered.

  In the technique described in Japanese Patent Application Laid-Open No. 2002-341718 (Patent Document 6), a cleaning roller that removes the toner that comes into contact with and adheres to the carrier, an image carrier, and a cleaning brush roller that rubs the surface of the cleaning roller. There is a combination of cleaning devices that aim to improve stain resistance.

  According to such a technique, although the cleaning performance is improved as compared with the cleaning by one cleaning member, it is not sufficient for deterioration due to use over time and abrasion at a deteriorated portion.

  In the technique described in Japanese Patent Application Laid-Open No. 2006-259628 (Patent Document 7), in combination with a cleaning brush roller, in a cleaning device that abuts against an image carrier and removes an object to be cleaned, the image carrier is pressed against the image carrier. There has been proposed a cleaning mechanism that forms a nip portion, stops rotation during cleaning, and can rotate intermittently during non-cleaning.

This technique also improves the cleanability compared to cleaning with a single cleaning member, but does not provide sufficient countermeasures against abrasion between brushes.
Japanese Patent Application No. 2005-24830 JP-A-2005-91818 JP 2002-49220 A JP 2004-54141 A JP 2004-184934 A JP 2002-341718 A JP 2006-259628 A

  The present invention has been made in view of the above problems, and its purpose is to sufficiently clean the surface of the charging member to prevent image quality deterioration due to poor charging or non-uniform charging, and Charging with a highly durable cleaning mechanism that thoroughly cleans the gap holding member surface, maintains a high-precision gap (separation distance) over time, and prevents deterioration of image quality due to poor charging or uneven charging An apparatus is provided to improve the durable life of a roller and provide stable image quality over a long period of time.

  In order to solve the above-described problems, the charging device of the present invention provides an electric resistance adjusting layer portion for charging the image carrier and the image carrier and the electric carrier in contact with the image carrier. In a charging device provided with a charging member that has a gap holding member for holding a gap between the resistance adjustment layer portion and is driven to rotate, in order to clean the charging member in contact with the charging member, Two cleaning rollers, a first cleaning roller whose surface is made of a continuous foam and a second cleaning roller whose surface is made of an elastic body, are provided, and the surface of the first cleaning roller has an electric resistance of the charging member. The second cleaning roller is provided so as to be driven to rotate in the forward direction with respect to the rotation direction of the charging member while being in contact with the adjustment layer portion and the gap holding member. While being in pressure contact with the layer portion, the charging member is driven downstream in the rotation direction of the charging member in a direction opposite to the rotation direction of the charging member and slower than the rotation of the charging member. A charging device is provided.

  According to a second aspect of the present invention, the charging device according to the first aspect is characterized in that the rotation of the second cleaning roller is intermittent.

  According to a third aspect of the present invention, in the charging device according to the first or second aspect, the first cleaning roller and the second cleaning roller are in contact with each other. Features.

  According to a fourth aspect of the present invention, there is provided a process cartridge comprising the charging device according to any one of the first to third aspects.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising the process cartridge according to the fourth aspect.

According to the charging device of the present invention, an electric resistance adjustment layer for charging the image carrier and the gap between the image carrier and the electric resistance adjustment layer in contact with the image carrier are maintained. In the charging device provided with a charging member that has a gap holding member and is driven to rotate,
In order to clean the charging member in contact with the charging member, there are provided two cleaning rollers, a first cleaning roller having a surface made of continuous foam and a second cleaning roller having a surface made of an elastic body, The first cleaning roller is provided such that the surface thereof is driven to rotate in the forward direction with respect to the rotation direction of the charging member while being in contact with the electric resistance adjusting layer portion and the gap holding member of the charging member. The first cleaning roller is driven to rotate in a direction opposite to the rotation direction of the charging member and slower than the rotation of the charging member while the surface of the cleaning roller is pressed against the electric resistance adjusting layer portion. The first cleaning roller effectively absorbs the dirt on the surface of the charging member and is thus provided on the downstream side in the rotation direction of the charging member. Perform cleaning of the electrical resistance adjusting layer portion and the space holding members of members, and, a second cleaning roller to remove contaminants deposited while preventing slipping of the contaminants. In addition, the cleaning ability is prevented from deteriorating over time by changing the nip position formed by the second cleaning roller that rotates slower than the rotation of the charging member in pressure contact with the charging member. For this reason, the surface of the charging member is sufficiently cleaned to prevent deterioration of image quality due to poor charging or non-uniform charging, and the surface of the gap holding member is sufficiently cleaned to form a high-precision gap (separation distance) over time. The image quality can be prevented from being deteriorated due to poor charging or non-uniform charging.

  Further, according to the charging device of the present invention described in claim 2, since the nip position of the second cleaning roller is intermittently changed due to the intermittent rotation of the second cleaning roller, the cleaning capability is improved. Can be more effectively prevented.

  In the charging device according to the third aspect of the present invention, since the first cleaning roller and the second cleaning roller are in contact with each other, the surface of the second cleaning roller is covered by the first cleaning roller. Cleaning is also possible, and the surface of the second cleaning roller is always kept clean.

  According to the process cartridge of the present invention described in claim 4, since the charging device is provided, it is possible to provide a process cartridge in which deterioration of image quality due to poor charging or non-uniform charging is prevented. .

  According to the image forming apparatus of the present invention described in claim 5, since the process cartridge is provided, the image forming apparatus can be prevented from being deteriorated in image quality due to poor charging or non-uniform charging. it can.

  Below, an example of an embodiment of the present invention is described based on a drawing.

<About image forming apparatus>
FIG. 2 is a schematic diagram illustrating a configuration of an image forming apparatus using a charging device and a process cartridge. FIG. 3 is a schematic diagram illustrating a configuration of an image forming unit of the image forming apparatus of FIG. The image forming apparatus 1 is a drum having a photoreceptor layer on the surface, and is equivalent to the number of images corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K). A carrier 61, a charging device 100 that charges each image carrier 61 almost uniformly, an exposure device 70 that forms an electrostatic latent image by exposing the charged image carrier 61 with laser light, yellow, A developing device 63 that contains developers of four colors, magenta, cyan, and black, and forms a toner image corresponding to the electrostatic latent image on the image carrier 61, and 1 that transfers the toner image on the image carrier 61 A secondary transfer device 62; a belt-like intermediate transfer member 50 to which a toner image on the image carrier 61 is transferred; a secondary transfer device 51 to transfer the toner image of the intermediate transfer member 50; and a toner of the intermediate transfer member 50. Fixing device for fixing a toner image on a recording medium to which an image is transferred 80, further includes a cleaning device 64 for removing the toner remaining after transfer on the image carrier 61. The recording medium is conveyed from one of the paper feeding devices 21 and 22 that store the recording medium one by one to the registration roller 23 by a conveyance roller through the conveyance path. Here, the recording medium is synchronized with the toner image on the image carrier 61. To the transfer position.

  As shown in FIG. 2, the exposure device 70 in the image forming apparatus 1 irradiates the image carrier 61 charged by the charging device 100 with light, and the electrostatic latent image on the image carrier 61 having photoconductivity. Form.

  The developing device 63 has a developer carrying member, and the toner stored in the developing device 63 is conveyed to a stirring unit by a supply roller, mixed and stirred with a developer containing a carrier, and faces the image carrying member 61. To the developing area. At this time, the positively or negatively charged toner is transferred to the electrostatic latent image on the image carrier 61 and developed.

  The primary transfer device 62 transfers the developed toner image on the image carrier 61 to the intermediate transfer member 50 by forming an electric field having a polarity opposite to the polarity of the toner from the back side of the intermediate transfer member 50. The primary transfer device 62 may be any one of a corotron, a scorotron corona transfer device, a transfer roller, and a transfer brush. Thereafter, in synchronization with the recording medium conveyed from the paper feeding device 22, the toner image is transferred onto the recording medium again by the transfer by the secondary transfer device 51. Here, the first transfer may be performed directly on the recording medium instead of the intermediate transfer member 50.

  The fixing device 80 heats and / or pressurizes the toner image on the recording medium to fix and fix the toner image on the recording medium. Here, the toner is passed through a pair of pressure / fixing rollers, and at this time, heat / pressure is applied to fix the toner while the toner binder resin is melted. The fixing device 80 may be in the form of a belt instead of a roller, or may be fixed by heat irradiation with a halogen lamp or the like. The cleaning device 64 for the image carrier 61 cleans and removes the toner remaining on the image carrier 61 without being transferred, thereby enabling the next image formation.

  The cleaning device 64 may be any system such as a blade made of rubber such as urethane or a fur brush made of fiber such as polyester.

<About process cartridges>
Here, the case where it is used as a charging member will be described in detail with reference to the charging device 100. FIG. 4 is a schematic diagram showing the configuration of the charging device and the process cartridge of the present invention. The process cartridge includes at least the image carrier 61, the charging device 100, and the cleaning device 64, and may include a developing device 63 as shown in FIG. The process cartridge is an integral unit and can be freely attached to and detached from the image forming apparatus. Referring to FIG. 3, the surface of the image carrier 61 is uniformly charged by a charging member in which an image forming area is arranged in a non-contact manner, and is visualized by development after forming an image (latent image), and a toner image is recorded. Transferred to the medium. The toner remaining on the image carrier without being transferred to the recording medium is collected by the auxiliary cleaning member 64d. Thereafter, in order to prevent toner and toner constituent materials from adhering to the surface of the image carrier, the solid lubricant 64a is uniformly applied on the image carrier by the application member 64b to form a lubricant layer. Thereafter, the toner that could not be collected by the auxiliary cleaning member by the cleaning member 64c is collected and conveyed to the waste toner collecting unit. The auxiliary cleaning member has a roller shape and a brush shape, and solid lubricants such as fatty acid metal salts such as zinc stearate, polytetrafluoroethylene, etc., reduce the coefficient of friction on the image carrier, and make it non-adhesive. Anything can be given. Examples of the cleaning member include a blade made of rubber such as silicon and urethane, and a fur brush made of fiber such as polyester.

<Regarding the charging device and its cleaning device>
As shown in FIG. 5A, the charging member (charging roller) 101 of this example has gaps at both ends of the electric resistance adjusting layer portion on which the electric resistance adjusting layer 104 formed on the conductive support 106 is formed. A holding member 103 is disposed. Further, a protective layer 105 is formed on the surface of the electric resistance adjusting layer so that the toner and the toner additive are difficult to adhere.

  The shape of the charging member 101 is preferably cylindrical so that the contact surface can always be changed with respect to the rotation of the image carrier, and both ends may be rotatably supported by gears or bearings. As described above, when the charging member 101 is formed with a curved surface that gradually separates from the closest part to the image carrier 61 in the moving direction of the image carrier 61, the image carrier 61 is more uniformly charged. Can be made. If the charging member 101 facing the image carrier 61 has a sharp portion, the electric potential of that portion becomes high, so discharge is preferentially started, and it becomes difficult to uniformly charge the image carrier 61. Accordingly, the image carrier 61 can be charged uniformly by having a cylindrical shape and a curved surface. Further, the discharging surface of the charging member 101 is subjected to strong stress. Since the discharge always occurs on the same surface, its deterioration is promoted and may be scraped off. Since the entire surface of the charging member 101 can be used as a discharging surface, it can be used over a long period of time by preventing the early deterioration by rotating.

  If foreign matter such as toner, paper dust, or a damaged member adheres to the surface of the charging member 101, abnormal electric discharge that preferentially generates discharge occurs because the electric field concentrates on the foreign matter portion. On the contrary, when an electrically insulating foreign material adheres to a wide range, no discharge occurs in that portion, and thus charging spots occur on the image carrier 61. For this purpose, the charging device 100 includes two types of cleaning rollers 102 a and 102 b for removing contamination of the charging member 101. As shown in FIG. 5B, these two cleaning rollers 102 a and 102 b are arranged so that the shaft is parallel to the shaft of the charging member 101 and is in contact with the charging member 101.

  The first cleaning roller 102 a is a second cleaning roller so that the cleaning members 102 a and 102 b are fitted into bearings provided in a housing (not shown) of the charging device 100, are rotatably supported, and come into contact with the charging member 101. It is installed upstream of the charging member 101 in the rotation direction with respect to 102b. The surface of the first cleaning roller 102a is made of a porous material, and a resin foam is used in this embodiment. In particular, it is preferable to use an open-cell foam if the absorbability of the soil component is taken into consideration. The hardness (JIS-A) of the first cleaning roller is preferably 20 degrees or less. The first cleaning roller 102a is in contact with the second cleaning roller 102b, absorbs contaminants present on the outer peripheral surfaces of the first cleaning roller 102a, and cleans each other. In particular, the first cleaning roller is sufficiently applied to the electric resistance adjusting layer portion provided with the electric resistance adjusting layer 104 and the gap holding member 103 installed at both ends thereof and having a diameter larger than that of the electric resistance adjusting layer portion. Length.

  In this example, the first cleaning roller 102a rotates in the forward direction with respect to the rotation direction of the charging member 101. At this time, the first cleaning roller 102a may rotate with a linear velocity difference from the charging member 101, or intermittently. It may be rotated in various forms such as being separated. In the case of the present embodiment, the rotation was performed by gear driving in conjunction with driving of the charging roller. When the first cleaning roller 102a is rotated in the direction opposite to the rotation direction of the charging member 101, there is a possibility that dust collected on the upstream side of the first cleaning roller may be scattered.

  The second cleaning roller 102b is pressed against the charging member 101 by a pressure spring (not shown) and is brought into pressure contact with the electric resistance adjusting layer portion. At this time, the second cleaning roller 102b is deformed to form a nip portion. Such a nip prevents the contaminants from slipping through.

  Further, the second cleaning roller 102b is in contact with the first cleaning roller 102a at the same time. Therefore, the first and second cleaning rollers 102a and 102b clean each other.

  In addition, since the nip portion is formed by pressure contact as described above, the surface portion of the second cleaning roller 102a is an elastic material, such as a urethane-based, silicone-based, fluorine-based, styrene-based, or olefin-based elastic material. Formed from.

  The hardness (JIS-A) of the second cleaning roller is preferably 50 to 85 degrees. If the hardness is less than 50, deformation of the elastic body is increased and uneven wear is promoted to cause problems in durability. If the hardness is greater than 85, wear of the image carrier progresses.

  The second cleaning roller 102b rotates in a direction opposite to the rotation direction of the charging member 101 (forward direction with respect to the first cleaning roller 102a) and slower than the rotation of the charging member. Accordingly, since the second cleaning roller 102b is not worn unevenly, it has a long life and can be cleaned with the first cleaning roller 102a as described above, so that the cleaning effect is great. Such a second cleaning roller 102b can be driven by an ultra-low speed rotation motor, or a rotation mechanism that combines such a motor and gear, and a one-way clutch as required.

  In addition, the second cleaning roller 102b contacts the charging member 101 by micro-rotation when non-cleaning is performed at regular intervals, that is, when image formation (sheet passing) is completed and the drive system related to image formation is stationary. A mechanism for changing the contact surface may be provided and rotated intermittently. At this time, for example, the micro-rotation is performed at the time of non-cleaning for every 5000 processed sheets, and the mechanism rotates once every 100,000 sheets. Such a mechanism records the number of sheets to be passed, and is set so that the predetermined angle is changed by a pulse motor that operates in synchronization with the pulse power after the predetermined number of sheets has been reached and image formation (sheet passing) has been completed. Can be configured.

  Note that the second cleaning roller 102b is rotated during non-cleaning as described above because the nip pressure with respect to the charging member 101 is changed when the drive system related to image formation is rotated during driving. This is because the dirt component may slip through.

  As described above, the first cleaning roller 102a on the upstream side in the rotation direction of the charging member 101 rotates in the forward direction with respect to the rotation of the charging member 101, and pollutants in the electric resistance adjusting layer portion of the charging member and the gap holding member. The second cleaning roller 102b catches contaminants (contamination sources) that have not been absorbed by the first cleaning roller 102a, or slipped through the second cleaning roller 102b, and are placed in contact with each other. The contamination source accumulated between the first cleaning roller 102a and the second cleaning roller 102b is supplied to the first cleaning roller 102a by the cleaning roller 102b and absorbed and removed by the first cleaning roller 102a. Further, the second cleaning roller rotates slowly in order to improve durability. At this time, the dirty surface of the second cleaning roller moves to the first cleaning roller, so that the second cleaning roller is also cleaned.

  FIG. 5 is a schematic diagram showing the positional relationship between the charging member, which is a conductive member, the photosensitive layer area of the image carrier, the image area, and the non-image area.

  The charging device 100 is opposed to the image carrier 61 and is provided with a minute gap G, a cleaning roller 102a, 102b for cleaning the charging member, and a voltage not applied to the charging member 101 (not shown). And a pressure spring (not shown) that pressurizes and contacts the charging member 101 to the image carrier 61. As shown in FIGS. 4 and 5, the charging member 101 is disposed to face the image carrier 61 with a minute gap G therebetween. The gap G between the charging member 101 and the image carrier 61 is formed by bringing the gap holding member 103 into contact with the non-image forming area of the charging member 101. By bringing the gap holding member into contact with the photosensitive layer region, variation in gaps can be prevented even if the coating thickness of the photosensitive layer varies.

<About the gap holding member>
A necessary characteristic of the gap holding member 103 is to form a gap with the photoreceptor stably over the environment and for a long time (time). For this purpose, a material having low moisture absorption and wear resistance is used. desirable. In addition, it is important that the toner and the toner additive do not easily adhere to each other, and that the photosensitive member is not abraded because it contacts and slides on the photosensitive member, and is appropriately selected according to various conditions. Is. Specifically, general-purpose resins such as polyethylene (PE), polypropylene (PP), polyacetal (POM), polymethyl methacrylate (PMMA), polystyrene (PS) and copolymers thereof (AS, ABS), polycarbonate (PC ), Urethane, fluorine (PTFE), and the like. In particular, in order to securely fix the gap holding member, an adhesive can be applied and bonded. The gap holding member is preferably an insulating material, and preferably has a volume resistivity of 10 ¹³ Ωcm or more. The reason why insulation is necessary is to eliminate the occurrence of leakage current with the photoreceptor. The gap holding member is formed by a molding process.

<About surface layer (protective layer)>
As a material for forming the surface layer, fluorine-based resin, silicone-based resin, polyamide resin, polyester resin and the like are excellent in non-adhesiveness, and are preferable in terms of preventing toner sticking. The surface layer is formed on the resistance adjusting layer by dissolving the surface layer constituting material in an organic solvent to prepare a paint, and various coating methods such as spray coating, dipping, and roll coating. About a film thickness, about 10-30 micrometers is desirable.
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Examples and Comparative Examples>
As a resistance adjusting layer, ABS resin (Denka ABS GR-3000, manufactured by Denki Kagaku Kogyo Co., Ltd.) 50% by weight, polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals) 50% by weight, polycarbonate-glycidyl methacrylate-styrene-acryloyl A resin composition obtained by mixing 4.5 parts by weight of a tolyl copolymer (Modiper CL440-G, manufactured by NOF Corporation) with 100 parts by weight of a total of polyether ester amide and ABS resin, and then melt-kneading the mixture. The resin composition was molded by injection molding on a core shaft (outer diameter 8 mm) made of nickel-plated stainless steel (SUM (Ni plating)).

  And the ring-shaped space | gap holding member (High density polyethylene resin (Novatech PP HY540, Nippon Polychem company make) was press-fit in the both ends of the said electrical resistance adjustment layer.

  Next, by cutting, the outer diameter of the gap holding member was 12.5 mm and the outer diameter of the resistance adjusting portion was finished to 12.4 mm by simultaneous processing.

  Next, a mixture of an acrylic silicone resin (3000 VH-P, manufactured by Kawakami Paint), an isocyanate curing agent (manufactured by Kawakami Paint Co., Ltd.), and carbon black (30% by weight based on the total solid content) is formed on the surface of the resistance adjusting portion. Was spray-coated to form a surface layer having a thickness of about 10 μm. Thereafter, the coating resin was heated and cured in an oven at 80 ° C. for 1 hour to obtain a conductive member having a step difference of about 40 μm between the gap holding member and the resistance adjusting layer.

  The charging device according to the present invention is completed by installing two types of cleaning rollers for cleaning the charging member obtained by the above method.

<Example 1>
As a first cleaning roller, a diameter of 6 mm provided by insert-molding an open-cell foam layer of melamine foam on the side surface of a core material having a diameter of 4 mm (a stainless steel base plated with nickel (SUM (Ni plating))) Got Laura. The axial length of the open cell foam layer of the melamine foam is the length of the electric resistance adjusting layer portion and the electric resistance adjusting layer portion of the charging member, and the first cleaning roller is arranged so that the open cell foam layer is in contact with them. Built into the charging device.

  As a second cleaning roller, urethane rubber having a hardness of 70 was extruded on the side surface of a core material having a diameter of 6 mm (stainless steel base plated with nickel (SUM (Ni plating))). Thereafter, the outer diameter was processed by a cylindrical grinder to make the diameter 11 mm. The length of the rubber part at this time was the same as the electric resistance adjusting layer part of the charging member.

  The first cleaning roller is rotated while the melamine foam portion is in contact with the electric resistance adjusting layer portion and the electric resistance adjusting layer portion of the charging roller by gear driving in the forward direction of the charging roller in conjunction with the driving of the charging roller. I tried to make it.

  For the second cleaning roller, the rotation direction is the reverse rotation with respect to the rotation of the charging roller, the forward direction with respect to the first cleaning roller, and the rubber portion is pressed against the electric resistance adjusting layer portion of the charging roller, Further, while contacting the first cleaning roller, the contact surface is changed by slightly rotating (1/20 rotation) in the rotation direction at the time of non-cleaning for every 5000 processed sheets.

  The charging device equipped with such a cleaning device was incorporated into the positive process cartridge shown in FIGS.

<Example 2>
As in Example 1, except that the open-cell foam layer of cellulose, which is a vegetable fiber, was used instead of the open-cell foam layer of melamine foam, a charging device using a first cleaning roller was incorporated in a process cartridge.

<Comparative Example 1>
As in Example 1, however, a charging device that does not use the second cleaning roller was incorporated in a process cartridge.

<Comparative example 2>
As in the first embodiment, however, instead of the second cleaning roller, an elastic blade-shaped cleaning member formed by molding urethane rubber having a hardness of 70 is provided downstream of the first cleaning roller in the rotation direction of the charging roller. The charging device was installed on the side so as to be in contact with the surface of the charging roller for cleaning, and was incorporated into a process cartridge. There is no mechanism for changing the contact surface of the cleaning member with respect to the charging roller, and the same surface always contacts the charging roller.

<Comparative Example 3>
As in Example 1, except that the first cleaning roller is formed by insert molding a single foam layer of polystyrene foam instead of the open cell foam layer of melamine foam on the surface of the core material. The device was obtained and assembled into a process cartridge.

<Comparative example 4>
As in Example 1, except that the length of the open cell foam layer of the melamine foam of the first cleaning roller is the same as the length of the electric resistance adjusting layer, and the open cell foam layer of the first cleaning roller is electrically The charging device was assembled so as to be in contact with the resistance adjusting layer portion and not on the gap holding member, and this was assembled into the process cartridge.

<Comparative Example 5>
As in Example 1 above, however, a charging device that does not use the first cleaning roller was assembled and incorporated into the process cartridge.

<Evaluation and results>
The process cartridge was mounted on the image forming apparatus shown in FIGS. 2 and 3 and image evaluation was performed. The voltage applied to the charging roller was DC = −700 V and AC = 2200 Vpp (frequency = 2 kHz). The evaluation environment was 23 ° C. and 60% RH. In addition, image streaks due to abnormalities of rollers after passing 40000, 80000, and 120,000 sheets, or the presence or absence of abnormal images, and the surface condition of the charging roller (presence of fixed matter on the charging roller), The presence or absence of toner entering the gap holding member was evaluated.

The evaluation is performed visually. In each case, “◎” indicates that the product can be used satisfactorily (“No”), “○” indicates that there is no problem in practical use, and “Permissible” if it is not practical. It was set as “x” as outside. In addition, as a comprehensive evaluation, after passing 120,000 sheets, “◎” indicates that an abnormal image is not good, and “○” indicates that the abnormal image is within an allowable range after passing 120,000 sheets. After passing 120,000 sheets, the case outside the allowable range was evaluated as “x” as impractical.
These evaluation results are shown in Table 1.

When the charging device according to the present invention was used, good images were obtained up to 120,000 sheets.
However, in Comparative Example 1, contaminants that could not be removed by the first cleaning roller adhered to the roller surface over time. In Comparative Example 2, chipping of the blade occurred, the dirt component slipped from the portion, and was fixed in a circumferential shape. When such a blade is used, the blade chip often occurs over time, and there is a disadvantage that it is inferior in reliability and durability.

  In Comparative Example 3, since the single foam layer of the first cleaning roller is strong in absorbing power, it is considered that the result was inferior because the limit of the absorbing capacity was exceeded after time.

  In Comparative Example 4, it is considered that the toner entered the gap holding member, and as a result, an abnormal image was generated due to the non-uniform gap between the charging roller and the rebound itself.

  In Comparative Example 5, there is no mechanism for absorbing and removing the accumulated dirt, and it is considered that the result was inferior because slipping occurred from the part where the dirt concentrated over time.

  In the above description, the charging roller is used as the charging member. However, the present invention can be applied not only to the charging roller but also to the charging belt.

1 is a schematic view of an electrophotographic image forming apparatus. 1 is a schematic diagram illustrating a configuration of an image forming apparatus using a charging device and a process cartridge. FIG. 3 is a schematic diagram illustrating a configuration of an image forming unit of the image forming apparatus in FIG. 2. FIG. 2 is a schematic diagram illustrating a configuration of a charging device and a process cartridge according to the present invention. It is a model diagram which shows a charging device and its cleaning device. (A) It is a front view. (B) It is a surface view.

Explanation of symbols

61 Image carrier 101 Charging member 103 Gap holding member 104 Electric resistance adjusting layer 105 Protective layer 106 On conductive support 102a First cleaning roller 102b Second cleaning roller

Claims (5)

An electric resistance adjusting layer for charging the image carrier and a gap holding member for contacting the image carrier and holding a gap between the image carrier and the electric resistance adjusting layer. In a charging device including a driven charging member,
In order to clean the charging member in contact with the charging member, there are provided two cleaning rollers, a first cleaning roller having a surface made of continuous foam and a second cleaning roller having a surface made of an elastic body,
The first cleaning roller is provided such that the surface thereof is driven to rotate in the forward direction with respect to the rotation direction of the charging member while being in contact with the electric resistance adjusting layer portion and the gap holding member of the charging member.
The second cleaning roller is driven to rotate in the direction opposite to the rotation direction of the charging member and slower than the rotation of the charging member while the surface thereof is pressed against the electric resistance adjusting layer portion. The charging device is provided on the downstream side in the rotation direction of the charging member with respect to one cleaning roller.   The charging device according to claim 1, wherein the second cleaning roller is driven to rotate intermittently.   The charging device according to claim 1, wherein the first cleaning roller and the second cleaning roller are in contact with each other.   A process cartridge comprising the charging device according to any one of claims 1 to 3.   An image forming apparatus comprising the process cartridge according to claim 4.

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