Abstract: A developing unit which forms an image on a photosensitive medium, includes a housing which accommodates a developer, a magnetic cylinder having a catch pole which picks up the developer in the housing by a magnetic force, and a main pole which couples a carrier among the picked-up developer, a sleeve rotatably installed on a circumference of the magnetic cylinder to form a magnetic brush having a predetermined width on the circumference by the developer picked up by the catch pole, and a sealing member provided at opposite end parts in an axial direction of the sleeve to prevent a leak of the developer, wherein a width Ws of the sleeve, a magnetized width WM of the main pole, a magnetized width Wc of the catch pole, and a width WB of the magnetic brush satisfy WS>WM>WB>WC.

Abstract: An electrophotographic image forming apparatus and a developing method thereof are provided. The electrophotographic image forming apparatus includes an image carrier body on which an electrostatic latent image is formed, a developing roller which faces the image carrier body and supplies toner to the electrostatic latent image formed on the image carrier body, and an anti-toner-dispersion element which faces an outer circumferential surface of the image carrier body between an exposing section where the electrostatic latent image is formed and a developing section where the electrostatic latent image is developed by the developing roller. A collection bias is applied to the anti-toner-dispersion element to collect dispersed toner from the developing roller.

Abstract: A toner density estimating method for a two-component developer is provided. The toner density estimating method includes: sensing photo-reflectance of a test pattern having a plurality of grayscales formed by using toner; calculating a rate of change of the photo-reflectance according to the grayscales of the test pattern; and estimating a toner density based on the rate of change. Accordingly, it is possible to accurately estimate the toner density irrespective of the influence of changes in temperature, humidity, or other external factors.

Abstract: An electrophotographic image forming device is provided which includes an image holder on which an electrostatic latent image is formed. A magnetic roller has a magnetic brush including nonmagnetic toner and a magnetic carrier using a magnetic force. Donor rollers are provided which have toner layers that are received from the magnetic roller on an outer circumference of each of the donor rollers. The donor rollers are located opposite to the image holder to develop the toner onto the electrostatic latent image.

Abstract: A hybrid type developing apparatus and method forms a magnetic brush of non-magnetic toner and a magnetic carrier on a circumference of a magnetic roller forms a uniform toner layer on the circumference of a donor roller using only toner from the magnetic roller, and develops an electrostatic latent image on an image receptor. The hybrid type developing apparatus includes: a plurality of electrodes on the circumference of the donor roller; first and second brush electrodes in an upstream area and a downstream area, respectively, of the donor roller facing the magnetic roller with respect to a direction of rotation; and a bias applying device for applying a recovery bias to the first brush electrode to remove toner from the donor roller and a supply bias to the second brush electrode to supply toner from the magnetic roller to the donor roller.

Abstract: A developing unit which forms an image on a photosensitive medium, includes a housing which accommodates a developer, a magnetic cylinder having a catch pole which picks up the developer in the housing by a magnetic force, and a main pole which couples a carrier among the picked-up developer, a sleeve rotatably installed on a circumference of the magnetic cylinder to form a magnetic brush having a predetermined width on the circumference by the developer picked up by the catch pole, and a sealing member provided at opposite end parts in an axial direction of the sleeve to prevent a leak of the developer, wherein a width Ws of the sleeve, a magnetized width WM of the main pole, a magnetized width Wc of the catch pole, and a width WB of the magnetic brush satisfy WS>WM>WB>WC.

Abstract: A toner density estimating method for a two-component developer is provided. The toner density estimating method includes: sensing photo-reflectance of a test pattern having a plurality of grayscales formed by using toner; calculating a rate of change of the photo-reflectance according to the grayscales of the test pattern; and estimating a toner density based on the rate of change. Accordingly, it is possible to accurately estimate the toner density irrespective of the influence of changes in temperature, humidity, or other external factors.

Abstract: A color image forming apparatus which, in a sequential order for each of plural colors of a composite color image, charges plural photosensitive bodies, exposes electrostatic latent images on the plural photosensitive bodies, develops latent images on the photosensitive bodies into color images, and transfers the color images to sequentially form images of each of the plural colors one on another to form the composite color image and transcribing the composite color image onto a printing medium. The color image forming apparatus includes: plural charging units which perform the charging process for each of the plural colors; plural exposing units which perform the exposing process for each of the plural colors; plural developing units which perform the developing process for each of the plural colors; and plural transfer units which perform the transfer process for each of the plural colors.

Abstract: An electrophotographic image forming apparatus and a developing method thereof are provided. The electrophotographic image forming apparatus includes an image carrier body on which an electrostatic latent image is formed, a developing roller which faces the image carrier body and supplies toner to the electrostatic latent image formed on the image carrier body, and an anti-toner-dispersion element which faces an outer circumferential surface of the image carrier body between an exposing section where the electrostatic latent image is formed and a developing section where the electrostatic latent image is developed by the developing roller. A collection bias is applied to the anti-toner-dispersion element to collect dispersed toner from the developing roller.

Abstract: An apparatus for applying a voltage across an image carrying member carrying a toner image and a print medium, the toner image being transferred from the image carrying member to the print medium during an image transfer process. The apparatus includes a first voltage receiver disposed on a first side in reference to the print medium, a second voltage receiver disposed on a second side opposite the first side, a voltage supply unit adapted to apply the voltage selectively to the first voltage receiver and to the second voltage receiver, and a voltage adjustment unit adapted to compensate for variations of the voltage.

Abstract: There are provided a hybrid type developing apparatus and method.

Abstract: An electrophotographic image forming apparatus includes: an image receptor on which an electrostatic latent image is formed; a magnetic roller for forming a magnetic brush having a non-magnetic toner and a magnetic carrier by magnetic force; a donor roller facing the image receptor and receiving a toner from the magnetic roller to form a toner layer on an outer circumference thereof; bias applying device for applying a bias voltage to the donor roller to develop the electrostatic latent image by supplying the toner from the toner layer; and toner removing device which contacts the donor roller and removes at least a portion of the toner layer from a surface of the donor roller after developing. A method of developing the latent image on the image receptor is provided by the apparatus.

Abstract: A hybrid type developing apparatus of an electrophotographic image forming apparatus includes: an image receptor on which an electrostatic latent image is formed; a magnetic roller for forming a magnetic brush of non-magnetic toner and magnetic carrier by using magnetic force; a donor roller which faces the image receptor and has a circumference for supporting a toner layer formed by receiving toner from the magnetic roller; a bias voltage applying device for applying a development bias voltage to the donor roller to develop toner of the toner layer to the electrostatic latent image; an electrode positioned at an upstream side at a point closest and most adjacent position between the donor roller and the image receptor and at a downstream side at a point closest and most adjacent position between the donor roller and the magnetic roller and an applied bias voltage of weakening adhesive force of the toner layer to the donor roller and cohesive force of toner to each other.

Abstract: A developing device for a liquid electrophotographic image forming apparatus is provided. The developing device may have a developing roller, which supplies ink to a photosensitive body on which an electrostatic latent image is formed and develops the electrostatic latent image. The apparatus may include an ink reservoir in which ink supplied to the developing roller is accommodated, and an ink removal unit, which removes ink remaining in the ink reservoir after a development operation is performed. The ink removal unit may comprise an ink removal member rotatably installed in the ink reservoir that exhausts ink through a through hole formed under the ink reservoir. A driving member rotates the ink removal member. An ink cartridge stores ink exhausted through the through hole.

Abstract: An electrophotographic image forming apparatus is provided which includes a first developing unit which forms a monochrome image in a two-component development method and includes a photosensitive medium on which an electrostatic latent image is formed by a first exposure unit. Additionally, a plurality of second developing units are provided which form a color image in a one-component development method and include a photosensitive medium on which an electrostatic latent image is formed by a second exposure unit. A control unit generates control signals to independently control the operations of the first and second exposure units and the first and second developing units.

Abstract: Provided is an image forming device performing hybrid development that uses magnetic carriers and nonmagnetic carriers. An electrical potential of a non-image portion on an image holder and an electrical potential of a direct current component of a developing bias voltage applied to a developing roller are determined so that a difference between the electrical potentials are less than or equal to a value at which a developing rate of the non-image portion is saturated.

Abstract: An electrophotographic image forming device is provided which includes an image holder on which an electrostatic latent image is formed. A magnetic roller has a magnetic brush including nonmagnetic toner and a magnetic carrier using a magnetic force. Donor rollers are provided which have toner layers that are received from the magnetic roller on an outer circumference of each of the donor rollers. The donor rollers are located opposite to the image holder to develop the toner onto the electrostatic latent image.

Abstract: A transfer power supply apparatus of an image forming machine which can maintain a predetermined degree of the quality of an image on a print medium even when the temperature of the surrounding environment varies. The image forming machine includes a voltage computation unit computing an appropriate voltage corresponding to resistance of an intermediate transfer medium, an output voltage generator generating a transfer voltage according to a signal output from the voltage computation unit, and a switching unit selectively applying a voltage output from the output voltage generator, wherein the switching unit connects a voltage output from the output voltage generator to a transfer roller when the image created on the intermediate transfer medium is transferred to a print medium, and connects a voltage output from the output voltage generator to a transfer backup roller when the image is not transferred to the print medium.

Abstract: A color image forming apparatus which, in a sequential order for each of plural colors of a composite color image, charges plural photosensitive bodies, exposes electrostatic latent images on the plural photosensitive bodies, develops latent images on the photosensitive bodies into color images, and transfers the color images to sequentially form images of each of the plural colors one on another to form the composite color image and transcribing the composite color image onto a printing medium. The color image forming apparatus includes: plural charging units which perform the charging process for each of the plural colors; plural exposing units which perform the exposing process for each of the plural colors; plural developing units which perform the developing process for each of the plural colors; and plural transfer units which perform the transfer process for each of the plural colors.

Abstract: A color image forming apparatus which, in a sequential order for each of plural colors of a composite color image, charges plural photosensitive bodies, exposes electrostatic latent images on the plural photosensitive bodies, develops latent images on the photosensitive bodies into color images, and transfers the color images to sequentially form images of each of the plural colors one on another to form the composite color image and transcribing the composite color image onto a printing medium. The color image forming apparatus includes: plural charging units which perform the charging process for each of the plural colors; plural exposing units which perform the exposing process for each of the plural colors; plural developing units which perform the developing process for each of the plural colors; and plural transfer units which perform the transfer process for each of the plural colors.