Charging roller cleaning device and image forming apparatus including the same

A charging roller cleaning device is provided for removing impurities attached on a charging roller that charges a photosensitive medium to a uniform electric potential. Such a cleaning device includes: a cleaning roller arranged to rotate, while contacting the charging roller to remove the impurities attached on the charging roller; and a cleaning member arranged to scrap off impurities attached on the cleaning roller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 from Korean Patent Application No. 2006-50460, filed on Jun. 5, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a charging roller cleaning device and an image forming apparatus including the charging roller cleaning device, and more particularly, to a charging roller cleaning device removing impurities attached on a charging roller and preventing the charging roller from being contaminated by the removed impurities and an image forming apparatus including the charging roller cleaning device.

2. Related Art

Image forming apparatuses using an electro-photographic process, such as laser beam printers, photo-copiers, facsimile machines and multi-functional products, are apparatuses for forming images by charging a photosensitive medium to have a uniform electric potential using a charging roller, scanning light modulated to correspond to image information onto the photosensitive medium using an optical scanning unit to form an electrostatic latent image on the photosensitive medium, supplying a toner to the electrostatic latent image using a developing unit to form a toner image, transferring the toner image to a printable medium, and fusing the toner image onto the printable medium by heating the toner image to form an image on the printable medium.

After performing the above charge, exposure, development, and transferring processes, waste toner remaining on a photosensitive drum is removed by a cleaning device. In this process, impurities such as silica having small particle diameters and paper dust included in the toner may not be removed. When these impurities are attached onto the charging roller, the photosensitive drum cannot be charged uniformly and a defective printing can occur. In addition, the impurities attached on the charging roller may become securely fused on the photosensitive drum.

SUMMARY OF THE INVENTION

Several aspects and example embodiments of the present invention provide a charging roller cleaning device that is capable of removing impurities attached on a charging roller and preventing the charging roller from being contaminated by the removed impurities, and an image forming apparatus including the charging roller cleaning device.

In accordance with an example embodiment of the present invention, there is provided a charging roller cleaning device for removing impurities attached on a charging roller that charges a photosensitive medium to a uniform electric potential. Such a charging roller cleaning device comprises: a cleaning roller arranged to rotate, while contacting the charging roller to remove the impurities on the charging roller; and a cleaning member arranged to scrape off impurities attached on the cleaning roller.

According to an aspect of the present invention, the cleaning device may further include: a blocking member located between the cleaning member and the charging roller to block the impurities that are scattered by the cleaning member so as not to contaminate the charging roller. The blocking member may be formed of a material having lower elasticity than the material forming the cleaning member.

According to an aspect of the present invention, the cleaning device may further include: a housing, in which the cleaning member is installed, forming a first receiving space receiving the impurities. The blocking member may form a second receiving space receiving the impurities with an outer circumference of the cleaning roller and the housing.

According to an aspect of the present invention, the cleaning member may be installed so that a front edge of the cleaning member contacting the outer circumference of the cleaning roller is angled towards a forward direction of rotation of the cleaning roller.

In accordance with another example embodiment of the present invention, there is provided an image forming apparatus including: a charging roller for charging a photosensitive medium to a uniform electric potential; a light scanning unit for forming an electrostatic latent image on the photosensitive medium; a developing unit for supplying a toner to the electrostatic latent image to develop the image; and a charging roller cleaning device for cleaning the charging roller, wherein the charging roller cleaning device includes: a cleaning roller arranged to rotate, while contacting the charging roller to remove impurities attached on the charging roller; and a cleaning member arranged to scrape off impurities attached on the cleaning roller.

According to an aspect of the present invention, the developing unit may develop the electrostatic latent image using a two-component developing method.

In accordance with yet another example embodiment of the present invention, a removable cartridge for use in an image forming apparatus is provided to remove impurities attached on a charging roller disposed in the image forming apparatus. Such a removable cartridge comprises a housing; a cleaning roller disposed in the housing to rotate along with the charging roller, while contacting the charging roller so as to remove the impurities on the charging roller; and a cleaning member disposed in the housing to scrape off impurities attached on the cleaning roller.

According to an aspect of the present invention, the cleaning member is a thin plate-shaped member having a rear edge supported by the housing and a front edge in contact with an outer circumference of the cleaning roller, and is arranged at an angle toward a rotating direction of the cleaning roller so as to form a first receiving space in the housing for receiving the impurities removed from the charging roller.

According to an aspect of the present invention, a blocking member is further disposed between the cleaning member and the charging roller, to block the impurities that are scattered by the cleaning member, so as not to contaminate the charging roller. Such a blocking member is a thin plate-shaped member having a rear edge supported by the housing and a front edge in proximity with an outer circumference of the cleaning roller, and is arranged at an angle toward a rotating direction of the cleaning roller so as to form a second receiving space in the housing for receiving the impurities scattered from the cleaning member.

According to another aspect of the present invention, the cleaning member is installed so that a front edge of the cleaning member contacting the outer circumference of the cleaning roller is angled towards a forward direction of rotation of the cleaning roller.

According to another aspect of the present invention, the blocking member may be formed of a material having lower elasticity than the material forming the cleaning member. Both the cleaning member and the block member may be formed of a rubber, a polyethylene terephthalate (PET), or an urethane.

In addition to the example embodiments and aspects as described above, further aspects and embodiments will be apparent by reference to the drawings and by study of the following descriptions.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a cross-sectional diagram of an image forming apparatus according to an example embodiment of the present invention. Referring toFIG. 1, a photosensitive drum110is an example of a photosensitive medium, and is obtained by forming a photosensitive layer of a predetermined thickness on an outer circumferential surface of a cylindrical metal pipe. Alternatively, a photosensitive belt can also be used as another example of the photosensitive medium. A charging roller150is a charger that rotates by contacting the photosensitive drum110to charge a surface of the photosensitive drum110to a uniform electric potential. A charge bias (Vc) is applied to the charging roller150.

A light scanning unit300scans a light that is modulated according to image information onto the photosensitive drum110that is charged to have the uniform electric potential. As a result, an electrostatic latent image is formed. A laser scanning unit (LSU) including a laser diode (LD) as a light source can be used as the light scanning unit300.

A developing unit100includes the photosensitive drum110and a developing roller120. The developing roller120rotates, while facing the photosensitive drum110. In a developing unit adopting a one-component developing method, the developing roller120may contact the photosensitive drum110or may be separated a predetermined distance from the photosensitive drum110. In a developing unit adopting a two-component developing method, the developing roller120is separated a predetermined distance (for example, a few hundreds of μm) from the photosensitive drum110. The above distance is referred to as a developing gap. In the current example embodiment of the present invention, the developing unit100adopting the two-component developing method will be described. The developing roller120includes a sleeve121rotating around a magnet122, and thus, is referred to as a magnet roller.

A toner supplied from a toner unit200to the developing unit100is agitated with a magnetic carrier using an auger140and a mixer130installed in the developing unit100and is charged by friction. Shapes of the auger140and the mixer130are not limited to the examples shown inFIGS. 1 and 2; however, such an auger140and a mixer130can be any type, size or shape, as long as they can move and agitate the toner and the magnetic carrier. The carrier is attached onto a surface of the sleeve121by the magnetic force of the magnet122, and the toner is attached onto a surface of the magnetic carrier by the electrostatic force. A developing bias (Vd) is applied to the developing roller120. When the sleeve121rotates, a magnetic brush formed by the magnetic carrier and the toner is moved to the developing gap where the photosensitive drum110and the developing roller120face each other. The toner is then separated from the carrier by the developing bias Vd and attached to the electrostatic latent image formed on the photosensitive drum110.

A transfer roller700is located to face the photosensitive drum110to form a transfer nip. A transfer bias (Vt) is applied to the transfer roller700for transferring the toner image attached on the photosensitive drum110onto a printable medium, such as a sheet of paper R A crona transfer device may be used instead of the transfer roller700. Each sheet of paper P is picked up by a pickup roller501from a feed cassette500and then conveyed, via a feed roller600to the photosensitive drum110at a predetermined printing speed. When the paper P passes through the transfer nip between the transfer roller700and the photosensitive drum110, the toner image is transferred from the photosensitive drum110to the paper P by the transfer bias Vt.

A fusing unit400applies heat and pressure onto the paper P and the toner image to fuse the toner image on the paper P. The paper P is discharged by a discharge roller800. In a case where a duplex-printing is performed, before an edge of the paper P, a surface of which includes a printed image, passes the discharge roller800after passing through the fusing unit400, the discharge roller800is reversely rotated. The paper P is conveyed to the feed roller600along a duplex-printing path900. Here, a rear surface of the paper P faces the photosensitive drum110. Therefore, when the paper P passes through the transfer nip and the fusing unit400, the image is printed on the rear surface of the paper P. The paper P is discharged by the discharge roller800.

Referring toFIG. 1, the toner that is not transferred to the paper P remains on the surface of the photosensitive drum110that passes through the transfer nip. The remaining toner is removed by a cleaning member170that contacts the surface of the photosensitive drum110, and the removed toner is conveyed to a waste toner container (not shown) by a waste toner conveying unit180.

Various kinds of external additives are contained in the toner. External additives having small particles, such as small-particle silica, may not be completely removed by the cleaning member170. In addition, paper dust or fine dust may not be completely removed by the cleaning member170. In particular, the performance of the cleaning member170is degraded due to a long time usage. As a result, it is much more difficult to completely remove the fine dust. The impurities on the photosensitive drum110are attached onto the charging roller150that rotates while contacting the photosensitive drum110, and thus, contaminate the surface of the charging roller150. When the surface of the charging roller150is contaminated, it is difficult to charge the surface of the photosensitive drum110uniformly. That is, portions of the photosensitive drum110contacting the contaminated charging roller150cannot be charged to sufficient electric potential, and thus, a printing quality may be degraded.

In order to prevent the charging roller150from being contaminated, a cleaning roller160is disposed to remove the impurities on the charging roller150. The cleaning roller160is arranged to rotate, while contacting the surface of the charging roller150. A porous cleaning layer formed of a sponge, or a foam, is formed on a surface of the cleaning roller160. The impurities removed from the charging roller150are received in the porous cleaning layer of the cleaning roller160.

However, if the toner contains a large amount of external additives of small particles or the toner is used for a long time, the amount of impurities removed from the charging roller150increases and exceeds the impurity receiving capacity of the porous cleaning layer on the cleaning roller160. Then, the impurities are moved from the cleaning roller160to the charging roller150, thus contaminating the charging roller150. In addition, the impurities may be moved to the photosensitive drum110through the charging roller150, and thus, the photosensitive drum110may be contaminated. The contamination of the charging roller150or the photosensitive drum110due to the impurities results in a defective printed image quality.

Therefore, the image forming apparatus according to the current example embodiment of the present invention includes a charging roller cleaning device that can remove the impurities on the cleaning roller160. Specifically,FIG. 2is a cross-sectional diagram of a charging roller cleaning device according to an example embodiment of the present invention, andFIG. 3is a diagram illustrating an example arrangement of a cleaning member and a blocking member in the cleaning device shown inFIG. 2.

Referring toFIGS. 2 and 3, the charging roller cleaning device includes a cleaning member10arranged to scrape off the impurities contained in, or deposited on the cleaning roller160. Such a cleaning member10can be a cleaning blade, or alternatively can be a thin plate shape member formed of a rubber, a polyethylene terephthalate (PET), or an urethane. A front edge11of the cleaning member10contacts an outer circumference162of the cleaning roller160. A rear edge12of the cleaning member10is supported by a housing101. Referring toFIG. 3, a length of the cleaning member10can be formed so that the front edge11of the cleaning member10may slightly overlap with the outer circumference162of the cleaning roller160. In addition, the cleaning member10may not be in parallel with a straight line L1that connects an end portion (the rear edge12shown inFIG. 3) of the cleaning member10to a center161of the cleaning roller160. Also, the front edge11of the cleaning member10may be angled toward a rotating direction of the cleaning roller160from the straight line L1. That is, the front edge11may be angled toward a forward direction of the rotating direction of the cleaning roller160. As shown inFIG. 3, if the front edge11of the cleaning member10faces a backward direction of the rotating direction of the cleaning roller160, it may damage the surface of the cleaning roller160.

According to the structure shown inFIG. 2, the impurities removed from the cleaning roller160by the cleaning member10are received or deposited in a first receiving space102formed by the housing101. Therefore, the impurity containing capacity of the cleaning roller160can be maintained for a long time, and thus, the contaminations of the charging roller150and the photosensitive drum110and the defective printing can be prevented.

In addition, referring toFIGS. 2 and 3, a blocking member20may be installed between the cleaning member10and the charging roller150. An end portion22of the blocking member20is supported by the housing101. A front edge21of the blocking member20may contact the outer circumference162of the cleaning roller160, or may be separated a predetermined distance from the outer circumference162of the cleaning roller160. In a case where the front edge21of the blocking member20contacts the outer circumference162of the cleaning roller160, the blocking member20may not be parallel to a straight line L2that connects an end portion (end portion22shown inFIG. 3) to the center161of the cleaning roller160. In addition, the front edge21of the blocking member20may be located toward the rotating direction of the cleaning roller160based on the straight line L2. That is, the front edge21of the blocking member20faces a forward direction of the rotating direction of the cleaning roller160. A thin plate shape member formed of a rubber, a PET, or a urethane can be used as the blocking member20. In addition, in order to prevent any impurities from scattering due to the blocking member20, an elasticity of the blocking member20may be sufficiently smaller than that of the cleaning member10.

During the process of removing the impurities of the cleaning roller160using the cleaning member10, the impurities can be scattered. Most of the impurities can be received in the first receiving space102in the housing101. However, some of the impurities can be scattered toward the charging roller150. The blocking member20is located between the cleaning member10and the charging roller150to prevent the scattered impurities from contaminating the charging roller150. The arrangement of the blocking member20relative to the cleaning member10forms a second receiving space103with the outer circumference162of the cleaning roller160and the housing101. The scattered impurities are received in the second receiving space103. Therefore, contamination of the charging roller150by the impurities that are scattered during the removing process by the cleaning roller160can be prevented.

In the above example embodiment, one cleaning member10is installed; however, the present invention is not limited thereto, and two or more cleaning members10can be installed to remove impurities on the cleaning roller160. In addition, a plurality of blocking members20can also be installed to prevent scattered impurities from contaminating the charging roller150. Also, in the above example embodiment, the image forming apparatus including the developing unit100adopting the two-component developing method is described; however, the charging roller cleaning device according to an example embodiment of the present invention can be applied to the image forming apparatus adopting the developing unit of the one-component developing method. In addition, in the above example embodiment, the developing unit100and the toner unit200are separated each other so that the toner unit200can be replaced; however, the charging roller cleaning device can be applied to an image forming apparatus, in which the developing unit and the toner unit are formed integrally with each other. Furthermore, the cleaning member10and the blocking member20included in the charging roller cleaning device, shown inFIG. 2, can be arranged in a removable cartridge having a housing101, as described in connection withFIG. 2andFIG. 3, for use in an image forming apparatus, shown inFIG. 1. In addition, the charging roller110may also be included in the removable cartridge, shown inFIG. 2.

In the charging roller cleaning device and the image forming apparatus including the cleaning device according to an example embodiment of the present invention, the cleaning performance of the cleaning roller that cleans the charging roller can be maintained for a long time. As a result, the contamination of the charging roller due to the impurities can be prevented effectively, and a good printing quality can be maintained. The present invention helps increase the lifespan of the developing unit in the image forming apparatus adopting the two-component developing method, by which the developing unit can be used for a long time while replacing the toner unit. That is, costs for replacing supplies can be reduced, and thus, costs for printing each sheet of paper can be reduced. Then, higher competitiveness in the market of the image forming apparatuses can be obtained.

While there have been illustrated and described what are considered to be example embodiments of the present invention, it will be understood by those skilled in the art and as technology develops that various changes and modifications, may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. Many modifications, permutations, additions and sub-combinations may be made to adapt the teachings of the present invention to a particular situation without departing from the scope thereof. For example, a charging roller150, as shown inFIG. 2, may be arranged differently relative to a photosensitive body. As a result, a housing of a charging roller cleaning device, as shown inFIG. 2, may be arranged and structured differently, as long as a cleaning mechanism is utilized herein. In addition, as previously discussed, one or more cleaning members and block members can be arranged differently, as long as impurities on the charging roller are contained in the manner as described. Accordingly, it is intended, therefore, that the present invention not be limited to the various example embodiments disclosed, but that the present invention includes all embodiments falling within the scope of the appended claims.