Patent Application
20250208532
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2023-217122, filed on Dec. 22, 2023, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Embodiments of the present disclosure relate to a cleaning device, a process cartridge, and an image forming apparatus.
In an electrophotographic image forming apparatus, a surface of a photoconductor serving as an image bearer is charged, the charged surface of the photoconductor is exposed to light to form an electrostatic latent image, and toner is supplied to the electrostatic latent image to form a toner image. The toner image formed on the photoconductor is transferred onto a recording sheet and is fixed on the recording sheet by receiving heat and pressure. Untransferred toner remains on the surface of the photoconductor after the toner image is transferred. The surface of the photoconductor is cleaned by a cleaning blade before the next charging process starts. When untransferred toner remaining on the surface of the photoconductor after the transfer of the toner image is not completely removed in a cleaning process and reaches a region in which the untransferred toner is close to or contacts a charging roller, the untransferred toner may adhere to the charging roller and a transfer belt.
In an embodiment of the present disclosure, a cleaning device includes a cleaner to contact a surface of a rotator to clean the surface of the rotator. The cleaner is a roller that includes a foam layer to contact the surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
In another embodiment of the present disclosure, an image forming apparatus includes a latent image bearer, a charger, a developing device, and a cleaning device. The latent image bearer bears a latent image. The charger includes a rotator to charge a surface of the latent image bearer. The developing device develops the latent image to form a toner image. The cleaning device includes a cleaner to contact a surface of the rotator to clean the surface of the rotator. The cleaner is a roller including a foam layer to contact the surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
In still another embodiment of the present disclosure, a process cartridge detachably attachable to a body of an image forming apparatus includes a latent image bearer, a charger, and a cleaning device. The latent image bearer bears a latent image. The charger includes a rotator to charge a surface of the latent image bearer. The cleaning device includes a cleaner to contact a surface of the rotator to clean the surface of the rotator. The cleaner is a roller including a foam layer to contact the surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:
The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
With reference to the drawings, a description is given below of a cleaning device, a process cartridge, and an image forming apparatus according to the present embodiment of the present disclosure. The present disclosure is not limited to the following embodiments, but can be changed within the range that can be conceived of by those skilled in the art, such as other embodiments, additions, modifications, deletions, and the scope of the present disclosure encompasses any aspect as long as the aspect achieves the operation and advantageous effect of the present disclosure.
The image forming apparatus of the present embodiment includes at least a latent image bearer that bears a latent image, a charger that charges a surface of the latent image bearer by a charging member formed of a rotator, and a cleaning device including a cleaner that contacts a surface of the charging member to clean the surface of the charging member. The cleaner is a roller. The roller has a foam layer that contacts a surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
The process cartridge of the present embodiment includes at least a latent image bearer that bears a latent image, a charger that charges a surface of the latent image bearer by a charging member formed of a rotator, and a cleaning device including a cleaner that contacts a surface of the charging member to clean the surface of the charging member. The process cartridge is detachably attached to a body of an image forming apparatus. The cleaner is a roller. The roller has a foam layer that contacts a surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
The image forming apparatus 1 illustrated in
The charging device 22 includes a charging roller 22a disposed with a clearance (gap) from the photoconductor 21, and a cleaning device according to the present embodiment that removes stain on the charging roller 22a. The cleaning device includes a cleaner 22b that is a roller. The developing device 23 includes a developing roller 23a, a stirring roller 23b, and a stirring roller 23c.
In the image forming apparatus 1, the optical writing device 11 writes laser light modulated based on image data to be formed on the photoconductor 21, which is a latent image bearer having a surface charged to a specified potential by the charging device 22, to form a latent image on the photoconductor 21. The electrostatic latent image is developed by the developing device 23 to form a toner image. The toner image is primarily transferred onto the intermediate transfer belt 17 by the primary transfer device 18. Each of the process cartridges 10Y, 10M, and 10C as image forming units for the colors other than black also performs primary transfer, so that four color toner images are superimposed on the intermediate transfer belt 17 to form a full-color toner image.
The secondary transfer device 13 collectively transfers the full-color toner image formed on the intermediate transfer belt 17 onto a sheet fed from any one of sheet trays 12a in the sheet feeding device 12. A registration roller pair 12b feeds the sheet to a vertical conveyance passage 12c at a timing at which the sheet can receive the full-color toner image on the intermediate transfer belt 17. The fixing device 14 applies heat and pressure to the full-color toner image transferred onto the sheet to fix the full-color toner image onto the sheet, and the sheet ejecting device 15 ejects the sheet to the sheet ejection tray 16.
After a toner image is primarily transferred onto the photoconductor 21, the photoconductor cleaning device 24 cleans the surface of the photoconductor 21 to remove residual toner T, which is not transferred from the photoconductor 21 to the intermediate transfer belt 17 and remains on the surface of the photoconductor 21, from the surface of the photoconductor 21. Then, the charge elimination device discharges the surface of the photoconductor 21. The photoconductor cleaning device 24 includes a cleaning blade 24a and a waste-toner conveyor 24b. The cleaning blade 24a scrapes off the residual toner T on the photoconductor 21. The waste-toner conveyor 24b conveys and collects the scraped residual toner T. The intermediate transfer belt 17 is stretched between a driving roller and a driven roller. A belt cleaner 17a for cleaning the intermediate transfer belt 17 is disposed with respect to the driving roller.
Each of the process cartridges 10Y, 10M, and 10C for yellow, magenta, and cyan has similar configuration as the process cartridge 10K for black.
The lubricant application device 27 includes a lubricant 27a, a brush roller 27b, a compression spring 27c, and an application blade 27d. The lubricant application device 27 is disposed downstream from the photoconductor cleaning device 24 in the rotation direction R of the photoconductor 21. The lubricant 27a is solid. The brush roller 27b contacts the lubricant 27a and the photoconductor 21 to rotate, and thus scrapes the lubricant 27a to apply the lubricant 27a to the photoconductor 21. The lubricant 27a is pressed against the brush roller 27b by the compression spring 27c to maintain contact with the brush roller 27b.
A rotator as a cleaning target of the cleaner 22b according to the present embodiment is, for example, a charging member (charging roller 22a). The charging roller 22a is formed of a conductive member and a conductive supporting member that rotatably supports the conductive member. As the conductive member, a known material can be used, but a material to which foreign substance is less likely to adhere to the surface thereof and from which the adhered foreign substance can be efficiently removed is preferable, and for example, a hard resin member is preferable. The charging roller 22a that includes the conductive member made of a hard resin member is combined with the cleaning device according to the present embodiment, so that a significant effect of removing foreign substance and reducing the occurrence of an abnormal image can be obtained.
The material used for the resistance adjustment layer 222 may be a thermoplastic resin and is not limited to any particular material as long as the JIS-D hardness of 45 degrees or more can be maintained after molding. However, a material that is easily molded is preferable, and examples thereof include general purpose resins such as polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS), and copolymers thereof (e.g., acrylonitrile styrene (AS) and acrylonitrile butadiene styrene (ABS)).
The resistance adjustment layer 222 is formed of a thermoplastic resin composition in which a polymeric ion conductive agent is dispersed. The volume resistivity of the resistance adjustment layer 222 is preferably 106 to 109 Ω·cm. This is because when the volume resistivity exceeds 109 Ω·cm, the charge amount is insufficient, and the photoconductor 21 is unlikely to obtain a sufficient charge potential for obtaining an image without unevenness. On the other hand, when the volume resistivity is smaller than 106 Ω·cm, leakage to the entire photoconductor 21 occurs.
The polymeric ion conductive agent to be dispersed in the thermoplastic resin is preferably a compound that has a volume resistivity of about 106 to 1010 Ω·cm as a single substance and easily lowers the resistance of the resin, and contains, for example, a polyether ester amide component. In this case, the amount of the polymeric ion conductive agent to be blended is preferably set to a ratio of 30 to 70 parts by weight with respect to 100 parts by weight of the base material in order to set the volume resistivity of the resistance adjustment layer 222 to a desired value. On the other hand, a compound containing a quaternary ammonium salt group can also be used as the polymeric ion conductive agent, and examples of the resistance adjustment layer include a polyolefin containing a quaternary ammonium salt group. In this case, the amount of the polymeric ion conductive agent to be blended is preferably set to a ratio of 10 to 40 parts by weight with respect to 100 parts by weight of the base material in order to set the volume resistivity of the resistance adjustment layer 222 to a desired value.
The polymeric ion conductive agent can be easily dispersed in the thermoplastic resin by using, for example, a twin-screw kneader. Since the ion conductive material is uniformly dispersed at a molecular level in the matrix polymer, the resistance adjustment layer 222 does not have a variation in volume resistivity due to poor dispersion of the conductive substance, which is observed in a resistance adjustment layer in which a conductive pigment is dispersed. The ion conductive material that is a polymer compound is uniformly dispersed and fixed in the matrix polymer, and bleed-out is unlikely to occur.
The charging roller 22a is coupled with a power supply, and a specified voltage is applied to the charging roller 22a. The specified voltage may be a direct current (DC) voltage alone. However, the specified voltage is preferably obtained by superimposing an alternating current (AC) voltage on the DC voltage. The AC voltage is applied to more uniformly charge the surface of the photoconductor 21. The charging roller 22a may contact the photoconductor 21. However, in the present embodiment, the charging roller 22a is preferably disposed with a minute clearance with respect to the photoconductor 21. The minute clearance can be set by winding spacers around non-image forming regions at both ends of the charging roller 22a and contacting the surfaces of the spacers against the surface of the photoconductor 21.
The material of the core 223 is not limited to any particular material and may be appropriately selected according to the purpose. Examples of the material of the core 223 include, but not limited to, plastic and metal. Examples of the resin include, but not limited to, an epoxy resin and a phenol resin. Examples of the metal include, but not limited to, iron, aluminum, and stainless steel.
The foam layer 224 is formed on an outer circumference of the core 223. In the cleaning device of the present embodiment, the coefficient of static friction of the surface of the foam layer 224 is 0.5 or more by the Euler belt method.
A description is given of a method for measuring the coefficient of static friction of the surface of the foam layer 224 by the Euler belt method with reference to
A description is given of the reason why the coefficient of static friction measured by the Euler belt method can be an index indicating the cleanability based on the experimental result using an observation apparatus of
When the contact state between the cleaner 22b having a roller shape and the glass plate 58 at the nip portion was observed by the observation apparatus of
It was also observed that the higher the tackiness (adhesiveness) of the surface of the cleaner 22b, the more active the movement of the cells in the foam forming the surface of the cleaner 22b. It is considered that the more active the movement of the cells, the more the adhesive material on the surface of the charging roller 22a can be removed by more random movements. As a result, the cleanability is enhanced, and at the same time, stain is less likely to accumulate on the same circumferential region. Thus, the occurrence of streaky stain can be reduced.
At the time point illustrated in
As a result of detailed studies of the examples described below, it has been found that, when the value of the coefficient of static friction by the Euler belt method is 0.5 or more, preferable cleanability can also be obtained for the actual charging roller 22a. The upper limit of the coefficient of static friction is not limited, and the higher the coefficient of static friction, the better the cleanability is obtained. However, the value that can be achieved by a resin foaming member is generally 1.5 or less. In the cleaning device according to the present embodiment, the coefficient of static friction of the surface of the foam layer 224 is preferably 0.5 or more, and more preferably 0.6 or more, by the Euler belt method. In the cleaning device according to present embodiment, the coefficient of static friction of the surface of the foam layer 224 is preferably 0.5 or more and 0.79 or less by the Euler belt method.
The average thickness of the foam layer 224 is not limited to any particular thickness and may be appropriately selected depending on the purpose. The average thickness is preferably 1 to 4 mm. If the average thickness of the foam layer 224 is less than 1 mm, the foam layer 224 is likely to receive the influence of the core 223 (shaft). If the average thickness exceeds 4 mm, the size of the component increases and the flexibility in layout decreases. The “average thickness” is an average value of values obtained by measuring the thickness of the foam layer 224 at any three points.
Examples of the structure of the foam forming the foam layer 224 include a form having closed cells (see
The number of cells included in the foam forming the foam layer 224 is not limited to any particular number and may be appropriately selected depending on the purpose. The number of cells is preferably 30 cells/inch to 150 cells/inch and is more preferably 50 cells/inch to 100 cells/inch. When the number of cells is less than 50 cells/inch, the area of the cells that contact the cleaning target is too small, and thus the cleanability may not be sufficiently obtained. When the number of the toner particles is more than 100 particles/inch, the removed adhesive material is likely to remain on the surface of the cleaning member, and thus the cleanability may deteriorate over time.
The number of cells in the present embodiment is an average value of values measured by the following method.
Each of the determined measurement points is photographed using a microscope, and the number of cells is measured from the obtained image.
The hardness of the foam forming the foam layer 224 is not limited to any particular hardness and may be appropriately selected depending on the purpose. The hardness is preferably from 50 to 600 N, more preferably from 100 to 500 N. If the hardness of the foam is less than 100 N, the wall surface forming the cells is not strong enough and the effect by cleaning is slightly reduced. On the other hand, if the hardness of the foam exceeds 500 N, the polishing force of the individual cells increases and the surface of the cleaning target may be unevenly worn. The hardness of the foam is an average value of values measured at any three points on the surface of the foam layer in accordance with JIS K 6400.
The coefficient of static friction of the surface of the foam layer, the form of the foam (closed-cell type/open-cell type), the number of cells contained in the foam, and the hardness of the foam can be controlled by appropriately adjusting, for example, the raw materials used in the production of the foam, the type and amount of the foaming agent, and the reaction conditions during the production. The foam is preferably a resin foam, and particularly preferably a polyurethane foam.
In a charging device (corresponding to the charging device 22 in
A process cartridge in which a cleaner having a foam layer formed of the foam A was used as a cleaning device for a charging device was mounted on a black (K) station of an image forming apparatus (RICOH IM C5000), and evaluation was performed by an actual machine as follows. In each case, the black station was used alone.
In a cleaning process of the charging roller, the larger the consumption of the lubricant in the process cartridge, the greater the risk of the cleaning failure, the experiment was performed by setting the pressing force of a compression spring (corresponding to the compression spring 27c in
The occurrence of the cleaning failure was determined by feeding a blank sheet every 50,000 sheets and checking whether a vertical black streak (abnormal image) caused by stain of the charging roller was found on the image. When a vertical black streak was generated on the image, the process cartridge was taken out, and the cleaning failure was determined by checking that a streak-like stain was found on the charging roller at a portion corresponding to the vertical black streak on the image. The degree of the vertical black streak was evaluated, and the cleanability was ranked into five levels. The best level was set to five, the acceptable level in practical use was set to three or more, and the unacceptable level in practical use was set to two or less. The results are illustrated in Table 2.
The evaluation was performed in the same manner as in the first example except that the foam forming the foam layer of the cleaner was changed to the foams B to M. The results are illustrated in Table 2.
The evaluation was performed in the same manner as in the first example except that the conductive member of the charging roller as a cleaning target was a rubber roller containing epichlorohydrin rubber as a main component. The electrical characteristics were adjusted so that elements other than the surface properties of the charging roller do not affect the evaluation results. The results are illustrated in Table 2.
The evaluation was performed in the same manner as in the first example except that the foam forming the foam layer of the cleaner was changed to the foam N and the foam O. The results are illustrated in Table 2.
The evaluation was performed in the same manner as in the fourteenth example except that the foam forming the foam layer of the cleaner was changed to the foam N and the foam O. The results are illustrated in Table 2.
From the above-described results, it was indicated that the cleaning device according to the present embodiment, the process cartridge including the cleaning device, and the image forming apparatus including the process cartridge can uniformly and efficiently remove the stain attached to the charging roller and can reduce the occurrence of an abnormal image mainly including the vertical black streak for a long period of time. On the other hand, in a comparative example using a cleaner having a coefficient of static friction of the surface of a foam layer measured by the Euler belt method of less than 0.5, the occurrence of an abnormal image was observed at an early stage.
In the above-described examples, the charging roller was evaluated as a cleaning target, but the cleaning target of the cleaning device according to the present embodiment is not limited as long as the cleaning target is a rotator that can contact the surface of the cleaning target to clean the surface of the cleaning target. The cleaning device can also be applied to cleaning of the surface of a belt such as a transfer belt, cleaning of the surface of a photoconductor drum, and cleaning of the surface of a roller such as a conveying roller.
In recent years, demands for high image quality and high definition of images have increased, and toners having a small particle diameter and a spherical shape have been used in a developing step. By using such a toner, the toner is caused to adhere to the electrostatic latent image in a dense manner. However, such a toner having a small particle diameter and a spherical shape is likely to pass through a cleaning blade in a cleaning step, and thus cleaning failure is likely to occur.
On the other hand, many attempts have been made to enhance the cleaning property by applying a lubricant such as zinc stearate to the surface of the image bearer to reduce the friction coefficient of the surface and reduce the frictional force acting between the surface of the image bearer and a member in contact with the surface. However, if there is powder of the lubricant that cannot be sufficiently formed into a film, the powder passes through the cleaning blade and may adhere to the charging roller similarly to the toner.
When the toner or the lubricant adheres to the charging roller, the resistance of the surface of the charging roller locally increases. Accordingly, the charging ability of the charging roller is partially reduced in the axial direction, and the image bearing member may not be uniformly charged. As a result, vertical black streaks (abnormal image) are likely to appear in an image particularly in a low-temperature and low-humidity environment.
To deal with such a failure, as a cleaning unit for a charging roller, a cleaning roller provided with a resin foam has been proposed. In a cleaning member using a foam on the outer periphery, the same portion in the axial direction continuously contacts a rotator to be cleaned, and thus the contamination is likely to be accumulated only in the portion.
The occurrence of an abnormal image due to the adhesion of foreign substance to a rotating member such as a charging roller or a transfer belt is fundamentally caused by the occurrence of uneven resistance due to a large local difference in the amount of foreign substance adhered. In order to prevent such a failure, it is preferable to efficiently remove the foreign substance on the rotator to prevent the accumulation of the foreign substance and to uniformly remove the foreign substance.
As described above, according to at least one embodiment of the present disclosure, a cleaning device can uniformly and efficiently remove contamination adhering to a rotator and reducing the occurrence of an abnormal image mainly including a vertical black streak for a long period of time.
A description is given below of some aspects according to the present disclosure.
A cleaning device includes a cleaner (e.g., the cleaner 22b) that contacts a surface of a rotator (e.g., the charging roller 22a) to clean the surface of the rotator. The cleaner is a roller and has a foam layer (e.g., the foam layer 224) that contacts the surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
In the cleaning device according to the first aspect, the foam of the foam layer (e.g., the foam layer 224) has a plurality of cells. The number of the plurality of cells per inch in the foam layer is 30 to 150.
In the cleaning device according to the first aspect, the foam of the foam layer (e.g., the foam layer 224) has a plurality of cells. The number of the plurality of cells per inch in the foam layer is 50 to 100.
In the cleaning device according to the first or second aspect, the hardness of the foam of the foam layer (e.g., the foam layer 224) is 100 to 500 N.
In the cleaning device according to any one of the first to fourth aspects, the foam of the foam layer (e.g., the foam layer 224) is made of foamed polyurethane.
In the cleaning device according to any one of the first to fifth aspects, the foam has a plurality of adjacent cells that communicate with each other.
In the cleaning device according to any one of the first to sixth aspects, the rotator is a charging member. The charging member is a charging roller (e.g., the charging roller 22a) that includes a conductive member (e.g., the resistance adjustment layer 222) made of a hard resin member and a conductive support member (e.g., the core metal 221) that rotatably supports the conductive member.
In the cleaning device according to any one of the first to seventh aspects, the coefficient of static friction of the surface of the foam layer (e.g., the foam layer 224) measured by the Euler belt method is 0.5 or more and 1.5 or less.
In the cleaning device according to any one of the first to seventh aspects, the coefficient of static friction of the surface of the foam layer (e.g., the foam layer 224) measured by the Euler belt method is 0.5 or more and 0.79 or less.
An image forming apparatus (e.g., the image forming apparatus 1) includes a latent image bearer (e.g., the photoconductor 21), a charger, a developing device (e.g., the developing device 23), and a cleaning device (e.g., the photoconductor cleaning device 24). The latent image bearer bears a latent image. The charger charges a surface of the latent image bearer with a charging member formed of a rotator. The developing device develops the latent image to form a toner image. The cleaning device includes a cleaner (e.g., the cleaner 22b) that contacts a surface of the charging member to clean the surface of the charging member. The cleaner is a roller. The roller has a foam layer (e.g., the foam layer 224) that contacts a surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
In the image forming apparatus (e.g., the image forming apparatus 1) according to the tenth aspect, the coefficient of static friction of the surface of the foam layer (e.g., the foam layer 224) measured by the Euler belt method is 0.5 or more to 1.5 or less.
In the image forming apparatus (e.g., the image forming apparatus 1) according to the tenth aspect, the coefficient of static friction of the surface of the foam layer (e.g., the foam layer 224) measured by the Euler belt method is 0.5 or more and 0.79 or less.
A process cartridge (e.g., the process cartridge 10Y, 10M, 10C, 10K) detachably attachable to a body of an image forming apparatus (e.g., the image forming apparatus 1) includes a latent image bearer (e.g., the photoconductor 21), a charger, and a cleaning device (e.g., the photoconductor cleaning device 24). The latent image bearer bears a latent image. The charger charges a surface of the latent image bearer with a charging member (e.g., the charging roller 22a) formed of a rotator. The cleaning device includes a cleaner (e.g., the cleaner 22b) that contacts a surface of the charging member to clean the surface of the charging member. The cleaner is a roller. The roller has a foam layer (e.g., the foam layer 224) that contacts a surface of the rotator. A coefficient of static friction of a surface of the foam layer measured by an Euler belt method is 0.5 or more.
In the process cartridge (e.g., the process cartridge 10Y, 10M, 10C, 10K) according to the thirteenth aspect, the coefficient of static friction of the surface of the foam layer (e.g., the foam layer 224) measured by the Euler belt method is 0.5 or more and 1.5 or less.
In the process cartridge (e.g., the process cartridge 10Y, 10M, 10C, 10K) according to the thirteenth aspect, the coefficient of static friction of the surface of the foam layer (e.g., the foam layer 224) measured by the Euler belt method is 0.5 or more and 0.79 or less.
The above-described embodiments are illustrative and do not limit the present disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-217122 | Dec 2023 | JP | national |
