JP2009282247A - Image forming unit and image forming apparatus - Google Patents

Abstract

[Objective] An image that can maintain good image quality developed on a recording medium by absorbing and removing external additives that are difficult to remove with a conventional cleaning member by a cleaning member having bubbles on the surface. An object is to provide a forming unit and an image forming apparatus.
An image forming unit according to the present invention includes a rotatable image carrier on which a developer image is formed, a charging member that contacts the image carrier and charges the image carrier, and the image carrier. And a cleaning unit that removes the developer remaining on the image carrier by contact, and the cleaning member is a first cleaning member provided upstream of the charging member in the rotation direction of the image carrier. And a second cleaning member having air bubbles on a surface provided between the first cleaning member and the charging member.
[Selection] Figure 10

Description

  The present invention provides an image forming unit having a cleaning member for removing a toner as a developer remaining on a photosensitive drum by charging a photosensitive drum as an image bearing member with a charging roller as a charging member, and the above image forming unit. The present invention relates to an image forming apparatus that develops and outputs input image data to a recording medium based on a certain control.

  Conventionally, in image forming apparatuses such as printers, copiers, facsimile machines, and electrophotographic color recording apparatuses, an image forming unit corresponding to each color of toner as a developer is arranged along the conveyance direction of the recording medium. is there. Each image forming unit is provided with a photosensitive drum and the like, and after developing an electrostatic latent image based on image information by an exposure source on the surface of the photosensitive drum uniformly charged by a charging roller as a charging member. A toner image is formed by adhering toner as an agent. After the toner image is transferred to the recording medium, the toner image is formed on the recording medium by fixing the toner image on the recording medium using a fixing device.

  Further, the image forming unit is provided with a cleaning member for removing toner remaining on the surface of the photosensitive drum without being transferred to the recording medium. Here, there is an image forming unit in which two cleaning members are provided to sufficiently remove the toner remaining on the photosensitive drum, and the toner remaining in different regions of the photosensitive drum is removed by each cleaning member (for example, (See Patent Document 1).

JP 2006-201591 A

  However, with the above-described configuration, due to the recent improvement in image quality of image forming apparatuses, it has become difficult to sufficiently remove the external additive detached from the toner with a cleaning member. Specifically, in order to achieve high image quality of the image forming apparatus, it is necessary to make the toner particle size smaller. However, if the toner particle size is made small, the fluidity of the toner deteriorates, so Defects such as image fading occur in the developed printed image.

  For this reason, by adding an external additive made of a material such as silica to the toner, the fluidity of the toner is maintained. However, the size of the external additive that is detached from the toner and adheres to the surface of the photosensitive drum is from 15 nm. Since the thickness is about 100 nm, it is difficult to remove the external additive by scraping it off with a cleaning member. Due to such external additives, there has been a problem that drum filming called white spots occurs in a printed image developed on a recording medium.

  In view of the above technical problems, the present invention is an image forming unit that can maintain the image quality of a developed image by removing external additives that are difficult to remove with a conventional cleaning member. And an image forming apparatus.

  In order to solve the above-described problems, an image forming unit according to the present invention includes a rotatable image carrier on which a developer image is formed, a charging member that contacts the image carrier and charges the image carrier, A cleaning unit that contacts the image carrier and removes the developer remaining on the image carrier, and the cleaning member is provided upstream of the charging member in the rotation direction of the image carrier. It comprises a first cleaning member and a second cleaning member having air bubbles on the surface provided between the first cleaning member and the charging member.

  According to the image forming unit of the present invention, the second cleaning member having bubbles on the surface absorbs and removes the external additive that was difficult to remove with the conventional cleaning member. With such a structure, it is possible to prevent white spots from occurring in the printed image developed on the recording medium and maintain the image quality of the printed image.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments according to an image forming unit and an image forming apparatus of the invention will be described with reference to the drawings. The image forming unit and the image forming apparatus of the present invention are not limited to the following descriptions, and can be appropriately changed without departing from the gist of the present invention.

[First embodiment]
The image forming unit according to the first embodiment absorbs and removes external additives that are difficult to remove with a cleaning blade by bringing a cleaning sponge provided in the image forming unit into contact with the photosensitive drum. Thus, the occurrence of drum filming is prevented.

  First, the image forming apparatus 1 of the present embodiment will be described. FIG. 1 shows a configuration diagram of the image forming apparatus 1. The image forming apparatus 1 includes image forming units 2C, 2M, 2Y, and 2K that print on a recording medium 4 based on image information corresponding to cyan, magenta, yellow, and black, and a tray 5. A substantially S-shaped paper transport path 3 having a stacker 19 from which the recording medium 4 on which image information is printed as a start point is discharged is provided.

  The image forming unit 2 in the image forming apparatus 1 includes image forming units 2C, 2M, 2Y, and 2K that develop image information corresponding to cyan, magenta, yellow, and black colors. Since they have substantially the same configuration, they are referred to as an image forming unit 2 in the following description. Details of the image forming unit 2 will be described later.

  The sheet conveyance path 3 in the image forming apparatus 1 starts from a tray 5 containing a recording medium 4 and starts from a hopping roller 6, a pressure registration roller 7, a feed registration roller 8, an idle roller 11, a transfer roller 9, a transfer belt 10, and a drive. The roller 12, the fixing device 15, and the discharge roller 18 are passed through a path having a stacker 19 as an end point. Hereinafter, each component included in the sheet conveyance path 3 will be described in detail with reference to FIG.

  The recording medium 4 is a recording paper having a predetermined size for developing monochrome or color image information, and is generally made of paper such as recycled paper, glossy paper, and high-quality paper, or an OHP film. The paper feed cassette 5 stores a plurality of recording media 4 and supplies the recording media 4 into the image recording apparatus 1 when a printing operation is started. The paper feed cassette 5 is configured to be detachable from the image recording apparatus 1. The hopping roller 6 rotates in a state of being pressed against the recording medium 4 accommodated in the paper feeding cassette 22 to remove the recording medium 4 taken out from the paper feeding cassette 5 one by one. This is for supplying to the roller 8. Further, the pressure registration roller 7 and the feed registration roller 8 take the recording medium 4 supplied from the hopping roller 6, remove the screw, etc., and convey it to the transfer belt 10.

  The transfer roller 9 is a transfer member that transfers a toner image formed on the surface of the photosensitive drum 21 to be described later to the recording medium 4. The transfer roller 9 is positioned below the photosensitive drum 21 and is recorded by the transfer roller 9 and the photosensitive drum 21. It is rotatably provided in contact with the medium 4 so as to sandwich the medium 4. Such a transfer roller 9 is made of a foaming elastic body. In addition, the transfer belt 10 is a conveying unit that sucks the recording medium 4 and conveys the recording medium 4 to a position facing the image forming unit 2, and is an endless belt. The developer image is transferred onto the photoconductive drum 21 by the electric field between the transfer roller 9 and the photoconductive drum 21 with respect to the recording medium 4 attracted and conveyed by the transfer belt 10. The idle roller 11 stabilizes the drive of the transfer belt 10, and the drive roller 12 drives the transfer belt 10. The idle roller 11 and the drive roller 12 are provided at both ends of the endless transfer belt 10 and apply a certain tension to the transfer belt 10. Such idle roller 11 and drive roller 12 are provided with a high wear member on the surface. When the idle roller 11 and the drive roller 12 are rotated by a drive system (not shown), the transfer belt 10 is driven in conjunction with the idle roller 11 and the drive roller 12.

  The transfer belt cleaning member 13 is configured to remove deposits such as toner 24 and paper dust attached to the surface of the transfer belt 10 in the image forming apparatus 1. The transfer belt cleaning member 13 is in contact with the surface of the transfer belt 10 with a certain pressure applied. The toner collection container 14 is a container for collecting the toner 24 that has been wiped off by the transfer belt cleaning member 13. The toner collection container 14 is provided near the transfer belt cleaning member 13 and below the transfer belt 10. The fixing device 15 includes a fixing roller 16 and a pressure roller 17. The fixing roller 16 and the pressure roller 17 are arranged so as to sandwich the recording medium 4 conveyed by the transfer belt 10, and fix the toner image developed on the recording medium 4 by the image forming unit 2 to the recording medium 4. Specifically, the toner image adhering to the recording medium 4 is dissolved using heat supplied from a heat source such as a halogen lamp (not shown) disposed in the fixing roller 16, and then the pressure roller 17 is applied. The toner image is fixed on the recording medium 4 by pressure. The discharge roller 18 is for discharging the recording medium 4 on which the toner image is fixed by the fixing device 15 to the stacker 19. The stacker 19 is a loading space for loading the recording medium 4 that has been developed and discharged from the image information.

  The image forming apparatus 1 includes a print control unit including a microprocessor, a ROM, a RAM, an input / output boat, a timer, and the like as constituent members (not shown) related to the control of the image forming apparatus 1 and a host computer or the like. An interface (I / F) control unit that receives print data and a control command from the apparatus and controls the sequence of the entire image forming apparatus 1 to perform a printing operation, and print data input through the interface (I / F) control unit A receiving memory that temporarily stores data, an image data editing memory that stores image data formed by receiving and processing print data stored in the receiving memory, and each component of the image forming apparatus 1 Each control unit, each control power supply unit for supplying power to each component of the image forming apparatus 1, and image formation A display unit for displaying an operating state of the apparatus 1, an operation unit having a switch or the like for giving an instruction from the operator to the image forming apparatus 1, and a sheet position detection sensor for monitoring the operating state of the image forming apparatus 1. And various sensors such as a temperature / humidity sensor and a concentration sensor.

  Next, the image forming unit 2 that prints a toner image on the recording medium 4 based on image information corresponding to each color of cyan, magenta, yellow, and black will be described. FIG. 2 is a configuration diagram of the image forming unit 2, and FIGS. 3 to 9 are diagrams showing the cleaning sponge unit 31 according to the present invention provided in the image forming unit 2. For ease of explanation, FIG. 2 shows a transfer roller 9 in addition to the image forming unit 2. Hereinafter, each component constituting the image forming unit 2 will be described in detail.

  The image forming unit 2 includes a photosensitive drum 21 that carries an electrostatic latent image based on image information, a charging member 22 that stores charges on the surface of the photosensitive drum 21, and light corresponding to the image information. An exposure source 23 that irradiates the surface of the toner, a toner 24 that is a developer, a toner cartridge 25 that contains the toner 24, a stirring member 26 that stirs the toner 24 in the toner cartridge 25, and a toner 24 The toner supply roller 27, the developing roller 28 for developing the electrostatic latent image on the surface of the photosensitive drum 21 with the toner 24, the developing blade 29 for regulating the thickness of the toner 24 to be uniform, and the residual on the photosensitive drum 21 A cleaning blade 30 for scraping off the toner 24 and a cleaning blade for adsorbing and removing the toner 24 remaining on the photosensitive drum 21. Having a Nji unit 31, a cleaning spiral 35 for conveying toner 24 scraped off by the cleaning member 31, and a waste toner storing portion 36 for storing toner 24 conveyed by the cleaning spiral 35. The image forming unit 2 is detachably attached to the image forming apparatus 1. Hereinafter, each component included in the image forming unit 2 will be described in detail with reference to FIG. The cleaning sponge unit 31 according to the present invention will be described in detail with reference to FIGS. 3 to 9 in addition to FIG.

  The photosensitive drum 21 is an image carrier and carries a developer image which is an electrostatic latent image and a developer image attached to the electrostatic latent image, and carries an electrostatic latent image based on image information. It is possible to store charges on the surface. The photosensitive drum 21 is formed of a cylindrical portion having an outer diameter of 40 mm and is rotatably provided. The linear velocity of the photosensitive drum 21 is 178 mm / sec. In such a photosensitive drum 21, a photosensitive layer made of a photoconductive layer and a charge transport layer is formed on a conductive base layer made of aluminum or the like. Further, the charging member 22 applies a predetermined positive voltage or negative voltage to the surface of the photosensitive drum 21 using a power source (not shown), so that the charge is uniformly stored on the surface of the photosensitive drum 21. Is for. The charging roller 22 is a charging member, and is provided so as to be rotatable while being in contact with the surface of the photosensitive drum 21 with a constant pressure. Such a charging roller 22 is configured by coating a conductive metal shaft with a semiconductive rubber such as silicon. The exposure source 23 is configured to be able to form an electrostatic latent image on the surface of the photosensitive drum 21 by irradiating the surface of the photosensitive drum 21 with light corresponding to the image information. It is provided above the drum 21. Such an exposure source 23 is composed of a combination of a plurality of LED elements, a lens array, and LED driving elements.

  The toner 24 is a developer, and image information can be visualized by adhering to the electrostatic latent image formed on the surface of the photosensitive drum 21. An external additive is externally added to the toner 24 in order to ensure the fluidity of the toner 24. The toner cartridge 25 is a container that stores the toner 24, and is disposed above the toner supply roller 27. In the toner cartridge 25, a cylindrical portion having a substantially rectangular side surface and a long circular shape in the direction perpendicular to the conveyance direction of the recording medium 4 is bonded to a lower portion of a rectangular portion having a substantially rectangular side surface and extending in a direction perpendicular to the conveyance direction of the recording medium 4. It is formed to do. Since the joint portion is open, the rectangular portion and the cylindrical portion are formed from a single chamber and accommodate the toner 24. The toner cartridge 25 is configured to be detachable from the image forming apparatus 1 so that it can be replaced when the toner 24 is consumed. The agitating member 26 is rotatably provided in the toner cartridge 25 and agitates the toner 24. The stirring member 26 is made of a hard material, and for example, the side surface portion is formed from a substantially circular rod-shaped portion, or the side surface portion is formed from a substantially rectangular plate-shaped portion.

  The toner supply roller 27 is provided so that the toner 24 can be supplied to the developing roller 28 by contacting the developing roller 28 while rotating. Such a toner supply roller 27 is configured, for example, by covering a conductive metal shaft with rubber added with a foaming agent. The developing roller 28 is configured to be rotatable while contacting the surface of the photosensitive drum 21 with a constant pressure. The developing roller 28 conveys the toner 24 to the photosensitive drum 21 while rotating, and develops the electrostatic latent image formed on the surface of the photosensitive drum 21 with the toner 24. Such a developing roller 28 is composed of a cylindrical portion having an outer diameter of 20 mm, and is configured by covering a conductive metal shaft with a semiconductive urethane rubber material or the like. Further, the developing blade 29 is provided so that the tip thereof slightly contacts the surface of the developing roller 28, and the toner 24 that has been supplied from the toner supply roller 27 to the surface of the developing roller 28 exceeds a certain amount. By scraping, the thickness of the toner 24 formed on the surface of the developing roller 28 is regulated to be always uniform. Such a developing blade 29 is formed of a plate-like elastic member such as stainless steel.

  The cleaning blade 30 is a first cleaning member, and is configured to remove the toner 24 remaining on the photosensitive drum 21 after transferring the toner image formed on the photosensitive drum 21 to the recording medium 4. Yes. Such a cleaning blade 30 is formed in a plate shape, is disposed upstream of the charging roller 22 in the rotation direction of the photosensitive drum 21, and applies a constant pressure to the surface of the photosensitive drum 21. It is in contact with. Table 1 shows typical examples of physical property values related to the cleaning blade 30. For example, the cleaning angle [°] representing the contact angle of the cleaning blade 30 with respect to the photosensitive drum 21 is preferably set to 10 ° or more in order to effectively remove the toner 24 remaining on the photosensitive drum 21. Further, the rebound resilience representing the elastic modulus of the cleaning blade 30 with respect to the photosensitive drum 21 is 40% or less in order to suppress the amount of wear of the cleaning blade 30 and to remove the external additive detached from the toner 24. It is preferable that In addition, although the shape of the cleaning blade 30 has been described as a plate shape, a roller shape such as a fur brush may be used.

  The toner 24 scraped off from the photosensitive drum 21 by the cleaning blade 30 is conveyed by the cleaning spiral 35 to the end of the waste toner container 36. Such a cleaning spiral 35 prevents the toner 24 from adhering to and clogging in the vicinity of the entrance of the waste toner container 36. Further, the waste toner storage unit 36 stores the toner 24 conveyed by the cleaning spiral 35. The waste toner container 36 is formed of a rectangular portion having a substantially rectangular side surface and long in the direction perpendicular to the conveyance direction of the recording medium 4. The waste toner container 36 is provided so that the side surface of the toner cartridge 25 is substantially rectangular and is parallel to a rectangular portion that is long in the direction perpendicular to the conveyance direction of the recording medium 4.

  The cleaning blade 30 described above is configured to remove the toner 24 remaining on the surface of the photosensitive drum 21 after the toner image formed on the photosensitive drum 21 is transferred to the recording medium 4. However, with the recent increase in image quality of image forming apparatuses, it has become difficult to sufficiently remove the external additive detached from the toner 24 with the cleaning blade 30. Here, the external additive externally added to the toner 24 will be described. In order to realize high image quality of the image forming apparatus, it is necessary to make the particle size of the toner 24 smaller. However, if the toner 24 is made to have a small particle size, the fluidity of the toner 24 is deteriorated. If the fluidity of the toner 24 deteriorates, defects such as image fading occur in the printed image developed on the recording medium 4. As a countermeasure against this, by adding an external additive made of a material such as silica to the toner 24, The fluidity of the toner 24 is maintained. Table 2 shows the relationship of the external additive content [%] to the particle size of the toner 24. As the particle size of the toner 24 is reduced, the content rate [%] of the external additive added to the toner 24 needs to be increased.

  However, since the external diameter of the external additive that is detached from the toner 24 and adheres to the surface of the photosensitive drum 21 is about 10 nm to 100 nm, it is difficult to remove the external additive by removing it with the cleaning blade 30. . Further, the external additive remaining and deposited on the surface of the photoconductive drum 21 is fixed to the surface of the photoconductive drum 21 by being pressure-bonded to the surface of the photoconductive drum 21 by the developing roller 28, and the fixed external additive is cored. As a result of the wax added to the toner 24 being fused to the external additive, a spot-like fixing portion is formed on the surface of the photosensitive drum 21. Since the toner 24 cannot be adhered to the fixing portion generated on the photosensitive drum 21 by the toner supply roller 27, white spots occur in the printed image developed on the recording medium 4. This white spot phenomenon is called drum filming.

  Therefore, in the case of the image forming apparatus using the toner 24 having a small particle diameter, it is necessary to sufficiently remove the external additive attached to the surface of the photosensitive drum 21 in order to prevent drum filming. Therefore, conventionally, the cleaning blade 30 is brought into contact with the photosensitive drum 21 by applying a strong pressure. In this case, the effect of removing the toner 24 itself is improved. However, when the cleaning blade 30 is brought into strong contact with the photosensitive drum 21, wear of the cleaning blade 30 becomes intense, so that the external additive attached to the photosensitive drum 21 passes through the worn portion of the cleaning blade 30.

  Therefore, in the present invention, external additives that are difficult to remove with the cleaning blade 30 are absorbed and removed using a cleaning sponge unit 31 formed of a foamed member such as silicone and urethane and having a large number of bubbles on the surface. This prevents the occurrence of drum filming. Hereinafter, the configuration of the cleaning sponge unit 31 according to the present invention will be described in detail with reference to FIGS. 3 to 9.

  The cleaning sponge unit 31 is provided between the cleaning blade 30 and the charging roller 22. As shown in FIG. 3, the cleaning sponge unit 31 includes a cleaning sponge 32, a joining member 33, and a cleaning sponge mounting plate 34. The cleaning sponge 32 biased by the cleaning sponge mounting plate 34 has a constant pressure. Is arranged so as to be in contact with the surface of the photosensitive drum 21. In order to sufficiently adsorb and remove the external additive separated from the toner 24 remaining on the photosensitive drum 21, the cleaning sponge 32 is preferably in contact with the photosensitive drum 21 in a compressed state of 1 mm or more. It is most preferable that the cleaning sponge 32 is compressed by about 2 mm. Further, FIG. 4 shows a side view of the cleaning sponge unit 31 when viewed from the direction A shown in FIG. 3, and FIG. 5 shows a bottom view of the cleaning sponge unit 31 in the same manner. The cleaning sponge 32 is bonded and fixed to the cleaning sponge mounting plate 34 using a joining member 33 such as a double-sided tape. The cleaning sponge unit 31 is screwed to the image forming apparatus 1 using the round holes 34A and the long holes 34B provided in the cleaning sponge mounting plate 34.

  Next, the cleaning sponge 32 will be described in detail with reference to FIGS. The cleaning sponge 32 is a second cleaning member and is provided in the cleaning sponge unit 31. Such a cleaning sponge 32 is formed of a sponge made of silicone, urethane, or the like, and has a large number of bubbles on the surface. The sponge material is preferably non-hydrolyzed. A large number of bubbles are formed on the surface of the cleaning sponge 32, and the external additive detached from the toner 24 remaining on the surface of the photosensitive drum 21 without being transferred to the recording medium 4 is adsorbed and removed. The cleaning sponge 32 is formed in a plate shape having a length L1 = 300 mm, a lateral width W1 = 10 mm, and a thickness H1 = 5 mm, for example. The length L1 is preferably about 5 mm to 10 mm longer than the length of the cleaning blade 30 in order to ensure the effect of collecting the external additive. Similarly, the width W1 is preferably 10 mm or more in consideration of the collection efficiency of the external additive of the toner 24. Similarly, the thickness H1 is preferably 5 mm or more considering that the cleaning sponge 32 is brought into contact with the photosensitive drum 21 using the elasticity. The cleaning sponge 32 is fixed by adhering to a cleaning sponge mounting plate 34 to be described later by engaging a joining member 33 such as a double-sided tape with a flat surface having a length L1 = 300 mm and a lateral width W1 = 10 mm. To do. Table 3 shows typical examples of physical property values related to the cleaning sponge 32 described above.

  Next, the cleaning sponge mounting plate 34, which is a constituent member of the cleaning sponge unit 31, will be described in detail with reference to FIGS. The cleaning sponge mounting plate 34 is an urging member for disposing the cleaning sponge 32 in the image forming unit 2 in a state where the cleaning sponge 32 is in contact with the photosensitive drum 21. Such a cleaning sponge mounting plate 34 is made of a hard material such as stainless steel. The cleaning sponge mounting plate 34 is, for example, a plate-like flat portion that engages with the cleaning sponge 32 with a length L2 = 310 mm and a lateral width W2 = 12 mm, and a plate with a round hole 34A with a length L3 = 60 mm and a lateral width W2 = 12 mm, for example. And a plate-shaped bottom surface portion having a length L4 = 70 mm and a lateral width W2 = 12 mm and having a long hole 34B. The plate-like flat surface portion and the two plate-like bottom surface portions described above are integrally formed by, for example, joining at right angles to a plate-like side surface portion having a thickness H2 = 25 mm. The total length of the cleaning sponge mounting plate 34 is length L5 = 440 mm. The cleaning sponge mounting plate 34 is screwed to the image forming apparatus 1 using the round holes 34A and the long holes 34B.

  Next, the function and effect of the cleaning sponge unit 31 according to the present invention will be described in detail with reference to Table 4 and FIG. First, Table 4 shows the state of the printed image for each drum filming level when printing on the recording medium 4 with a duty of 100%. For example, when the drum filming level is 3, white spots of 0.5 mm or less occur in 50% or more of the print image area in the print image developed on the recording medium 4.

  Next, FIG. 10 shows the state of occurrence of the drum filming level with respect to the operation time of the conventional image forming apparatus 1 according to the present invention. Note that the printing speed of the image forming apparatus 1 in FIG. 10 is 30 PPM, and the image printing density is 5%. Further, the replacement life of the image forming unit 2 is equivalent to 20000 sheets when converted to the recording medium 4 of A4 size. Specifically, the printing conditions are 9000 sheets in an operating environment of 20 ° C. and 60%, 5000 sheets in an operating environment of 28 ° C. and 80%, and finally 6000 sheets in an operating environment of 10 ° C. and 20%. As shown in FIG. 10, in the image forming apparatus 1 of the present invention, since the drum filming occurs later and the drum filming level is lighter than in the conventional case, the image forming unit 2 has a cleaning sponge. The effect of providing the unit 31 is shown. Specifically, in the conventional image forming apparatus, drum filming at level 4 occurs when the number of printed sheets of the recording medium 4 exceeds 10,000, and similarly deteriorates to level 3 when the number exceeds 14,000. Furthermore, when it exceeds 18,000 sheets, it has deteriorated to level 2. Compared to the conventional example, in the image forming apparatus 1 of the present invention, drum filming does not occur until the number of prints of the recording medium 4 reaches 20000. Accordingly, it can be understood that the drum filming can be prevented because the external additive attached to the photosensitive drum 21 is sufficiently absorbed and removed by the cleaning sponge 32.

  As described above, according to the first embodiment, the cleaning sponge unit 31 is brought into contact with the photosensitive drum 21 to absorb and remove the external additive that is difficult to remove with the cleaning blade 30. Since the occurrence of filming can be prevented, the quality of the printed image developed on the recording medium 4 can be maintained.

[Second Embodiment]
The image forming unit according to the second embodiment reduces the bubble diameter of the cleaning sponge unit provided in the image forming unit, and improves the collecting ability of external additives that are difficult to remove with a cleaning blade. With such a configuration, the external additive is more effectively absorbed and removed by the cleaning sponge, and drum filming is prevented from occurring.

  The image forming unit according to the second embodiment of the present invention will be described below. In this embodiment, the configuration relating to the image forming unit other than the cleaning sponge is the same as the configuration of the image forming unit 2 described in the first embodiment. Therefore, in the present embodiment, for the sake of simplicity, a duplicate description will be omitted, and only the cleaning sponge will be described. Hereinafter, the cleaning sponge will be described in detail with reference to Table 5 and FIG.

  The removal efficiency of the external additive by the cleaning sponge greatly depends on the printing speed and the printing duty of the image forming apparatus 1 in addition to the operation time of the image forming apparatus 1. Here, FIG. 11 shows an example of the drum filming occurrence state when the printing speed of the image forming apparatus 1 is changed. The printing conditions excluding the printing speed are the same as the printing conditions of the present invention according to the first embodiment shown in FIG. FIG. 11 shows the transition of the drum filming level when the printing speed is 30 PPM and 36 PPM.

  As shown in FIG. 11, when the printing speed is set to 30 PPM, drum filming does not occur until the replacement life of the image forming unit. However, when the printing speed is set to 36 PPM, before the replacement life of the image forming unit. Drum filming occurs when the number exceeds 18000 sheets. This is because when the printing speed is increased, the amount of the external additive that passes through the cleaning blade 30 increases and the total amount of the external additive that adheres to the cleaning sponge per unit time increases. Specifically, if the allowable amount of the external additive that can be collected in the bubbles on the surface of the cleaning sponge is exceeded, the external additive remaining without being collected by the cleaning sponge is deposited on the surface of the photosensitive drum 21 and drum filming is performed. Will occur. That is, as the printing speed increases, the efficiency of removing the external additive by the cleaning sponge decreases. The printing duty is 5%. Note that the printing duty when black printing is performed on the entire printable area of the recording medium 4 is defined as 100%. As the printing duty increases, the amount of toner 24 supplied to the surface of the photosensitive drum 21 increases, so that the performance of removing external additives contained in the toner 24 decreases.

  In order to maintain the cleaning performance of the cleaning sponge described above, the surface area of the cleaning sponge may be increased, but the space in the image forming unit is limited. Therefore, by reducing the size of the bubbles in the cleaning sponge, the area occupied by the bubbles per unit surface area of the cleaning sponge is increased, and the collection amount of the external additive in the cleaning sponge is increased. In the following description, the size of the bubbles in the cleaning sponge is referred to as the cell diameter. The cell diameter is specified as follows. When the major axis of the cell is A and the minor axis of the cell is B, the cell diameter is calculated by Equation 1. When a plurality of cells are connected and formed, the cell outline is estimated for each cell, and the cell diameter is calculated by regarding each cell as an independent cell.

[Formula 1] Cell diameter [μm] = (A × B) ^1/2 ÷ 2

  Table 5 shows the occurrence of drum filming related to each printing speed with respect to each cell diameter. When there is no drum filming, it is indicated by using a symbol ◯, when there is a slight occurrence, Δ, when it occurs, and a symbol X. For example, when the printing speed is 40 PPM, if the cell diameter of the cleaning sponge is in the range of 50 μm to 200 μm, the occurrence of drum filming can be suppressed until the replacement life of the image forming unit.

  As described above, according to the second embodiment, the collection capacity of the external additive by the cleaning sponge is increased by reducing the cell diameter of the cleaning sponge. With such a configuration, drum filming can be prevented from occurring without depending on the printing speed and printing duty, so that the quality of the printed image developed on the recording medium 4 can be maintained.

[Third embodiment]
In the image forming unit 40 according to the third embodiment, the sponge portion of the cleaning roller sponge 42 provided in the cleaning cleaning sponge sponge unit 41 is formed into a cylindrical shape and rotated depending on the photosensitive drum. With such a configuration, the surface area of the sponge portion can be increased as compared with the rectangular cleaning sponge 32. For this reason, it is characterized in that drum filming is more effectively prevented by absorbing and removing external additives that are difficult to remove with a cleaning blade. Further, the cleaning roller sponge 42 rotates depending on the photosensitive drum, whereby the driving torque of the photosensitive drum can be reduced. Further, compared with the first embodiment and the second embodiment, the photosensitive drum is photosensitive. It is characterized in that the wear of the photosensitive drum, that is, the wear associated with the reduction in the thickness of the photosensitive layer on the surface of the photosensitive drum is reduced.

  Hereinafter, an image forming unit 40 according to a third embodiment of the present invention will be described with reference to FIG. However, the image forming unit 40 of the present embodiment differs from the image forming unit 2 described in the first embodiment in that a cleaning roller sponge unit 41 is provided instead of the cleaning sponge unit 31. The other structures are almost the same. In addition, in this embodiment, since it is simple, the overlapping description is abbreviate | omitted and only a different component is demonstrated. Hereinafter, the configuration of the cleaning roller sponge unit 41 will be described in detail with reference to FIGS. 13 to 18 in addition to FIG.

  The cleaning roller sponge unit 41 is provided between the cleaning blade 30 and the charging roller 22. As shown in FIG. 13, the cleaning roller sponge unit 41 includes a cleaning roller sponge 42, a cleaning roller sponge bearing 43, and a cleaning roller sponge mounting plate 44. The cleaning roller sponge unit 41 is biased by the cleaning sponge mounting plate 44. The sponge 42 is arranged to rotate while contacting the surface of the photosensitive drum 21 with a constant pressure. In order to sufficiently adsorb and remove the external additive separated from the toner 24 remaining on the photosensitive drum 21, the cleaning roller sponge 42 needs to be brought into contact with the photosensitive drum 21 in a compressed state of 1 mm or more. is there. It is most preferable that the cleaning roller sponge 42 is compressed by about 2 mm. Further, FIG. 14 shows a side view of the cleaning roller sponge unit 41 when viewed from the direction B shown in FIG. 13, and FIG. 15 shows a top view of the cleaning roller sponge unit 41 in the same manner. By attaching cylindrical cleaning roller sponge bearings 43 to shaft portions 42A provided at both ends of the cleaning roller sponge 42, the cleaning roller sponge mounting plate 44 is rotatably arranged. The cleaning roller sponge unit 41 is screwed to the image forming apparatus 1 using the round hole 44A and the long hole 44B provided in the cleaning roller sponge mounting plate 44.

  Next, the cleaning roller sponge 42 will be described in detail with reference to FIG. The cleaning roller sponge 42 is a second cleaning member and is provided in the cleaning roller sponge unit 41. Such a cleaning roller sponge 42 is formed of a sponge made of silicone, urethane, or the like, and has a large number of bubbles on the surface. The sponge material is preferably non-hydrolyzed. A large number of bubbles are formed on the surface of the cleaning roller sponge 42, and the external additive detached from the toner 24 remaining on the surface of the photosensitive drum 21 without being transferred to the recording medium 4 is adsorbed and removed. The cleaning roller sponge 42 is formed in a cylindrical shape having a length L6 = 300 mm and a diameter D2 = 15 mm, for example, and has shaft portions 42A made of a cylindrical shape having a length L7 = 30 mm and a diameter D1 = 5 mm, for example. For this reason, the total length of the cleaning roller sponge 42 is L8 = 360 mm, for example. Further, the length L8 of the sponge portion of the cleaning roller sponge 42 is preferably about 5 mm to 10 mm longer than the length of the cleaning blade 30 in order to ensure the effect of collecting external additives. Similarly, the diameter D2 is preferably 15 mm or more in consideration of contact with the photosensitive drum 21 using the elasticity of the cleaning roller sponge 42. The cleaning roller sponge 42 is rotatably arranged on a bearing portion 44C of a cleaning roller sponge mounting plate 44 described later by attaching cleaning roller sponge bearings 43 to shaft portions 42A provided at both ends of the cleaning roller sponge 42. Established. The physical property values of the cleaning roller sponge 42 described above are the same as the physical property values of the cleaning sponge 32 according to the first embodiment shown in Table 3.

  Next, the cleaning roller sponge mounting plate 44, which is a component of the cleaning sponge unit 41, will be described in detail with reference to FIGS. The cleaning roller sponge mounting plate 44 is an urging member for disposing the cleaning roller sponge 42 in the image forming unit 40 in a state where the cleaning roller sponge 42 is in contact with the photosensitive drum 21. Such a cleaning roller sponge mounting plate 44 is made of a hard material such as stainless steel. The cleaning roller sponge mounting plate 44 is integrally formed in a U-shape. Specifically, for example, a plate-like flat part having a length L9 = 330 mm and a lateral width W3 = 12 mm and having a round hole 44A and an elongated hole 44B, and a plate-like part having a bearing part 44C having a thickness H3 = 25 mm and a lateral width W3 = 12 mm, for example. The plate-shaped flat surface portion and the two plate-shaped bottom surface portions are formed at a right angle and are integrally formed in a U-shape. The cleaning roller sponge mounting plate 44 is screwed to the image forming apparatus 1 using a round hole 44A and a long hole 44B.

  As described above, according to the third embodiment, the sponge portion of the cleaning roller sponge 42 provided in the cleaning cleaning roller sponge unit 41 is formed into a cylindrical shape, and then rotated depending on the photosensitive drum 21 to obtain a rectangular shape. Compared with the cleaning sponge 32, the surface area of the sponge portion is increased. With such a configuration, the occurrence of drum filming can be more effectively prevented, so that no white spots occur in the printed image developed on the recording medium 4, and the image quality can be maintained. Further, since the cleaning roller sponge 42 rotates depending on the photosensitive drum 21, the driving torque of the photosensitive drum 21 can be reduced.

[Fourth Embodiment]
In the image forming unit 50 according to the fourth embodiment, the cleaning sponge of the cleaning sponge unit 50 provided in the image forming unit is brought into contact with the photosensitive drum and the charging roller, so that it is difficult to remove by the cleaning blade. It is characterized by absorbing and removing the additive. That is, in the first embodiment, the cleaning sponge is brought into contact only with the photosensitive drum to prevent drum filming. In the fourth embodiment, the cleaning sponge is also brought into contact with the charging roller. Thus, the external additive attached to the charging roller is also removed.

  The image forming unit 50 according to the fourth embodiment of the present invention will be described below with reference to FIG. However, the image forming unit 50 of the present embodiment is different from the image forming unit 2 described in the first embodiment in that a cleaning sponge unit 51 is provided instead of the cleaning sponge unit 31. The other structures are almost the same. In addition, in this embodiment, since it is simple, the overlapping description is abbreviate | omitted and only a different component is demonstrated. Hereinafter, the cleaning sponge unit 51 will be specifically described with reference to FIGS. 20 to 26 in addition to FIG.

  Since the external additive adhering to the photosensitive drum 21 is adsorbed by the cleaning sponge, the occurrence of drum filming can be prevented. However, not all external additives attached to the photosensitive drum 21 can be removed. For this reason, a part of the external additive that has not been removed by the cleaning sponge adheres to the charging roller 22 in contact with the photosensitive drum 21. The external additive attached to the charging roller 22 has a high resistance value. For this reason, when an external additive adheres to the surface of the charging roller 22, charging failure occurs in the photosensitive drum 21, and black streaks occur in the printed image developed on the recording medium 4. Therefore, the external additive adhering to the charging roller 22 is removed by bringing the cleaning sponge into contact with the charging roller 22 to absorb and remove the external additive that is difficult to remove with the cleaning blade 30. Do. Hereinafter, the configuration of the cleaning sponge unit 51 according to the present invention will be described in detail with reference to FIGS.

  The cleaning sponge unit 51 is provided between the cleaning blade 30 and the charging roller 22. Further, as shown in FIG. 20, the cleaning sponge unit 51 includes a cleaning sponge 52, a joining member 33, and a cleaning sponge mounting plate 53. The cleaning sponge 52 biased by the cleaning sponge mounting plate 53 has a constant pressure. Is arranged so as to be in contact with the surface of the photosensitive drum 21. In order to sufficiently adsorb and remove the external additive separated from the toner 24 remaining on the photosensitive drum 21, the cleaning sponge 52 is preferably in contact with the photosensitive drum 21 in a compressed state of 1 mm or more. It is most preferable that the cleaning sponge 52 is compressed about 2 mm with respect to the photosensitive drum 21. Similarly, the cleaning sponge 52 is preferably in contact with the charging roller 22 while being compressed by 1 mm or more. The state in which the cleaning sponge 52 is compressed about 2 mm with respect to the charging roller 22 is most preferable. Further, FIG. 21 shows a side view of the cleaning sponge unit 51 when viewed from the direction C shown in FIG. 20, and FIG. 22 shows a bottom view of the cleaning sponge unit 51 in the same manner. The cleaning sponge 52 is bonded and fixed to the cleaning sponge mounting plate 53 using a joining member 33 such as a double-sided tape. The cleaning sponge unit 51 is screwed to the image forming apparatus 1 using the round hole 53A and the long hole 53B provided in the cleaning sponge attachment plate 53.

  Next, the cleaning sponge 52 will be described in detail with reference to FIGS. 21 and 22. The cleaning sponge 52 is a second cleaning member and is provided in the cleaning sponge unit 51. Such a cleaning sponge 52 is formed of a sponge made of silicone, urethane, or the like, and has a large number of bubbles on the surface. The sponge material is preferably non-hydrolyzed. A large number of bubbles are formed on the surface of the cleaning sponge 52, and the bubbles are separated from the toner 24 remaining on the surfaces of the photosensitive drum 21 and the charging roller 22 without being transferred to the recording medium 4. The external additive adhering to the surface of the charging roller 22 is adsorbed and removed. The cleaning sponge 52 is formed, for example, from a plate shape having a length L10 = 300 mm, a lateral width W4 = 10 mm, and a thickness H4 = 5 mm. The length L10 is preferably about 5 to 10 mm longer than the length of the cleaning blade 30 in order to ensure the collection of the external additive. Similarly, the width W4 is preferably 10 mm or more in consideration of the collection efficiency of the external additive of the toner 24. Similarly, the thickness H4 is preferably 5 mm or more in consideration of the contact with the photosensitive drum 21 using the elasticity of the cleaning sponge 52. The cleaning sponge 52 is bonded and fixed to a cleaning sponge mounting plate 53 described later by engaging a joining member 33 such as a double-sided tape with a flat surface having a length L10 = 300 mm and a lateral width W4 = 10 mm. . In order to bring the cleaning sponge 52 into contact with the charging roller 22, the cleaning sponge 52 is fixed while protruding from the cleaning sponge mounting plate 53. The protrusion amount is, for example, W6 = 3 mm. The physical property values of the cleaning sponge 52 described above are the same as the physical property values of the cleaning sponge 32 according to the first embodiment shown in Table 3.

  Next, the cleaning sponge mounting plate 53, which is a constituent member of the cleaning sponge unit 51, will be described in detail with reference to FIGS. The cleaning sponge mounting plate 53 is an urging member for disposing the cleaning sponge 52 in the image forming unit 50 in a state where the cleaning sponge 52 is in contact with the photosensitive drum 21 and the charging roller 22. Such a cleaning sponge attachment plate 53 is made of a hard material such as stainless steel. The cleaning sponge mounting plate 53 is, for example, a plate-like flat portion that engages with the cleaning sponge 52 with a length L11 = 310 mm and a lateral width W5 = 7 mm, and a plate having a round hole 53A with a length L12 = 60 mm and a lateral width W5 = 7 mm, for example. And a plate-like bottom surface portion having a length L13 = 70 mm and a lateral width W5 = 7 mm and having a long hole 53B. The plate-like flat surface portion and the two plate-like bottom surface portions described above are integrally formed by, for example, joining at right angles to a plate-like side surface portion having a thickness of H5 = 25 mm. The total length of the cleaning sponge attachment plate 53 is length L14 = 440 mm. Further, the cleaning sponge attachment plate 53 is screwed to the image forming apparatus 1 using a round hole 53A and a long hole 53B.

  As described above, according to the fourth embodiment, the cleaning sponge unit 51 is brought into contact with the photosensitive drum 21 and the charging roller 22 to absorb and remove the external additive attached to the photosensitive drum 21 and the charging roller 22. To do. With this configuration, drum filming can be prevented, and black streaks due to the charging roller 22 can be prevented, so that the quality of the printed image developed on the recording medium 4 can be maintained. can do.

  As described above, in the first embodiment, by bringing the cleaning sponge 32 into contact with the photosensitive drum 21, it is possible to absorb and remove external additives that are difficult to remove with the cleaning blade 30. Further, in the second embodiment, the collection capacity of the external additive by the cleaning sponge can be increased by reducing the cell diameter of the cleaning sponge. Furthermore, in the third embodiment, the cleaning roller sponge 42 provided in the cleaning roller sponge unit 41 is formed into a cylindrical shape, and then rotated depending on the photosensitive drum 21 to thereby form a rectangular cleaning sponge. Compared with 32, the surface area of the sponge part can be increased. In the fourth embodiment, the cleaning sponge 52 is brought into contact with the photosensitive drum 21 and the charging roller 22 to absorb and remove external additives attached to the photosensitive drum 21 and the charging roller 22. it can. With the configuration described above, drum filming can be prevented and black streaks due to the charging roller 22 can be prevented, so that the quality of the printed image developed on the recording medium 4 can be maintained. .

  In the first to fourth embodiments described above, the image forming apparatus is described as a printing apparatus. However, the image forming apparatus according to the present embodiment may be provided in a copying machine, a facsimile apparatus, an MFP apparatus, or the like.

1 is a configuration diagram illustrating an image forming apparatus according to a first exemplary embodiment of the present invention. 1 is a configuration diagram illustrating an image forming unit according to a first embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a state in which a cleaning sponge unit is in contact with a photosensitive drum in the image forming unit according to the first exemplary embodiment of the present invention. It is a side view which shows the cleaning sponge unit of the 1st Embodiment of this invention. It is a bottom view which shows the cleaning sponge unit of the 1st Embodiment of this invention. It is a bottom view which shows the cleaning sponge of the 1st Embodiment of this invention. It is a side view which shows the cleaning sponge of the 1st Embodiment of this invention. It is a side view which shows the cleaning sponge attachment plate of the 1st Embodiment of this invention. It is a bottom view which shows the cleaning sponge attachment plate of the 1st Embodiment of this invention. It is a figure which shows transition of the drum filming level in the image forming apparatus of the 1st Embodiment of this invention. It is a figure which shows transition of the drum filming level which concerns on the printing speed in the image forming apparatus of the 2nd Embodiment of this invention. It is a block diagram which shows the image forming unit of the 3rd Embodiment of this invention. FIG. 10 is a schematic diagram illustrating a state in which a cleaning roller sponge unit is in contact with a photosensitive drum in an image forming unit according to a third embodiment of the present invention. It is a side view which shows the cleaning roller sponge unit of the 3rd Embodiment of this invention. It is a top view which shows the cleaning roller sponge unit of the 3rd Embodiment of this invention. It is a side view which shows the cleaning roller sponge of the 3rd Embodiment of this invention. It is a side view which shows the cleaning roller sponge attachment plate of the 3rd Embodiment of this invention. It is a top view which shows the cleaning roller sponge attachment plate of the 3rd Embodiment of this invention. It is a block diagram which shows the image forming unit of the 4th Embodiment of this invention. FIG. 10 is a schematic diagram illustrating a state in which a cleaning sponge unit is brought into contact with a photosensitive drum in an image forming unit according to a fourth embodiment of the present invention. It is a side view which shows the cleaning sponge unit of the 4th Embodiment of this invention. It is a bottom view which shows the cleaning sponge unit of the 4th Embodiment of this invention. It is a bottom view which shows the cleaning sponge of the 4th Embodiment of this invention. It is a side view which shows the cleaning sponge of the 4th Embodiment of this invention. It is a side view which shows the cleaning sponge attachment plate of the 4th Embodiment of this invention. It is a bottom view which shows the cleaning sponge attachment plate of the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2,2C, 2M, 2Y, 2K Image forming unit 3 Paper conveyance path 4 Recording medium 5 Tray 6 Hopping roller 7 Pressure registration roller 8 Feed registration roller 9 Transfer roller 10 Transfer belt 11 Idle roller 12 Drive roller 13 Transfer Belt cleaning member 14 Toner recovery container 15 Fixing device 16 Fixing roller 17 Pressure roller 18 Discharge roller 19 Stacker 21 Photosensitive drum 22 Charging roller 23 Exposure source 24 Toner 25 Toner cartridge 26 Stirring member 27 Toner supply roller 28 Developing roller 29 Developing blade 30 Cleaning blade 31 Cleaning sponge unit 32 Cleaning sponge 33 Joining member 34 Cleaning sponge mounting plate 34A Round hole 34B Long hole 35 Cleaning spiral 36 Waste Toner container 40 Image forming unit 41 Cleaning roller sponge unit 42 Cleaning roller sponge 42A Shaft portion 43 Cleaning roller sponge bearing 44 Cleaning roller sponge mounting plate 44A Round hole 44B Long hole 44C Bearing portion 50 Image forming unit 51 Cleaning sponge unit 52 Cleaning sponge 53 Cleaning sponge attachment plate 53A Round hole 53B Long holes L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12,
L12, L13, L14 Length W1, W2, W3, W4, W5, W6 Width H1, H2, H3, H4, H5 Thickness D1, D2 Diameter

Claims (6)

A rotatable image carrier on which a developer image is formed;
A charging member that contacts the image carrier and charges the image carrier;
Cleaning means for removing the developer remaining on the image carrier in contact with the image carrier;
The cleaning member is
A first cleaning member provided upstream of the charging member in the rotational direction of the image carrier;
An image forming unit comprising: a second cleaning member having air bubbles on a surface provided between the first cleaning member and the charging member. 2. The image forming unit according to claim 1, wherein the bubble size of the second cleaning member is in the range of 50 μm to 500 μm. The image forming unit according to claim 1, wherein the second cleaning member is formed in a cylindrical shape. The image forming unit according to claim 3, wherein the second cleaning member is rotatably supported. 2. The image forming unit according to claim 1, wherein the second cleaning member contacts the image carrier and the charging member to remove the developer remaining on the image carrier and the charging member. An image forming apparatus comprising the image forming unit according to claim 1.