Abstract: A color laser printer is configured to fulfill Qmin<Qs for suppressing occurrence of reverse transfer of toner. Qmin designates the minimum amount of transfer electric charge per unit area required to transfer a toner image of the maximum amount of toner onto a sheet (hereinafter referred to as a “per-unit-area required transfer electric charge level”). Qs designates the maximum amount of transfer electric charge per unit area which can prevent occurrence of reverse transfer (hereinafter referred to as an “transfer prevention per-unit-area electric charge level”). The transfer prevention per-unit-area electric charge level Qs is represented by Qs=a/(Md)2. Md designates the maximum quantity of developing agent on a toner image per unit area thereof transferred onto a sheet immediately before being transferred, and “a” designates a proportional constant.

Abstract: A transfer device includes a transfer roller that is rotatably provided facing an image carrying member, an urging device that urges the transfer roller in a direction that the transfer roller presses the image carrying member, and a regulating roller that is provided to a shaft commonly used with the transfer roller and presses the image carrying member to regulate a pressing force of the transfer roller that presses the image carrying member. The regulating roller is made of an elastic material.

Abstract: A color image forming apparatus is described. The color image forming apparatus may includes: a belt that travels in a prescribed direction; a plurality of image carriers arranged in parallel in the prescribed direction, and opposed to the belt and carrying developing agent images of different colors respectively; a backup roller arranged in opposed relation to the belt; a cleaning roller arranged in opposed relation to the backup roller with the belt sandwiched therebetween, and adsorbing an adherent to the belt by a potential difference produced between the backup roller and the cleaning roller; and a discharge member opposed to the belt between a position more downstream in the prescribed direction than a position where the cleaning roller is opposed to the belt and a position more upstream in the prescribed direction than a position where the image carrier arranged on the most upstream side in the prescribed direction is opposed to the belt, for discharging the belt.

Abstract: Provided is an image forming apparatus including an image forming section forming images on image forming faces of a recording medium, a condition setting section individually setting an operating condition of the image forming section for forming the image on a first image forming face of a recording medium and another operating condition of the image forming section for forming the image on a second image forming face of the recording medium opposite to the first image forming face in the manual duplex mode, and a control section controlling the image forming section on the basis of each operating condition set by the condition setting section.

Abstract: A control section sets the transfer bias level applied between a transfer roller and a photosensitive drum in the printer to a “ghost generation level.” The control section forms a test pattern on the recording medium by applying a transfer bias set to the ghost generation level in order to transfer a toner image onto the recording medium. A density sensor detects the density of the toner image deposited in a non-image-forming region when the test pattern is formed. The control section estimates a transfer bias level, at which ghosts will not occur, based on the ghost generation level and the density level of the toner image in the non-image-forming region, and sets this estimated value as the transfer bias level for forming images.

Abstract: An image forming apparatus comprises: a photosensitive element; a charger electrostatically charging a surface of the photosensitive element uniformly at a voltage of a polarity; an exposure device exposing the charged surface of the photosensitive element, to a light, to form an electrostatic latent image; a developing device depositing a developer on the latent image, to form a developer image; a device for transferring the developer image onto a transfer object; and a developer removing device comprising a cleaning member, to which a voltage is applied to generate a cleaning bias between the cleaning member and photosensitive element, to remove a waste developer adhering to the photosensitive element after the developer image is transferred, and which is disposed to act on a part of the surface of the photosensitive element having been charged by the charger and at which the developer image is not formed yet.

Abstract: An apparatus for forming a multi-color image is disclosed which includes a controller that performs an anti reverse-transfer control such that a surface potential of a previously-formed separated-developer-image subset of a plurality of single-color separated-developer-images which has been previously transferred onto an image transferred medium is reduced, prior to a subsequent transfer in which a remainder of the plurality of separated-developer-images is transferred onto the image transferred medium after a previous transfer of the previously-formed separated developer-image subset onto the image transferred medium, to thereby prevent a reverse transfer of a part of a developer material on the image transferred medium from the image transferred medium onto a photoconductor at the subsequent transfer.

Abstract: In a color laser printer, the amount of reversely transferred developing agent on the surface of a developing roller is estimated based on the operating time of the color laser printer, the surface area of an image, and the charging amount of developing agent. When the estimated amount of reversely transferred developing agent reaches a predetermined value, a solid image is formed on a photoconductor drum. By transferring the solid image onto recording paper, a conveyer belt, or an intermediate transfer belt, the reversely transferred developing agent is removed. Alternatively, by rotating the developing roller in a state in which the developing roller is separated from the photoconductor drum, the reversely transferred developing agent on the surface of the developing roller is collected into a developing agent hopper.

Abstract: An apparatus for forming a multi-color image is disclosed which includes a controller that performs an anti reverse-transfer control such that a surface potential of a previously-formed separated-developer-image subset of a plurality of single-color separated-developer-images which has been previously transferred onto an image transferred medium is reduced, prior to a subsequent transfer in which a remainder of the plurality of separated-developer-images is transferred onto the image transferred medium after a previous transfer of the previously-formed separated developer-image subset onto the image transferred medium, to thereby prevent a reverse transfer of a part of a developer material on the image transferred medium from the image transferred medium onto a photoconductor at the subsequent transfer.

Abstract: Whether or not a density of black is a predetermined value or more is judged, and when it is judged to be the predetermined value or more, a resolution characteristic is changed to an improved resolution characteristic compared to the resolution characteristic used in a case in which a judgment result shows a value under the predetermined value. When the density of black is deeper, the resolution characteristic is improved, and therefore black is prevented from becoming in a so-called void state. Accordingly, the color close to black such as four-color black can be stably and excellently formed. In addition, when the density of black is the value under the predetermined value, the resolution characteristic lower than this value is used, and therefore dots can be stably formed and an excellent gradation property can be achieved.

Abstract: An image forming device measures calibration patterns printed on a conveying belt and stores the measurement data, which includes data for the density and position of the patterns. Measurement data is deleted from memory when the position of the pattern matches positional data stored in a flash memory for indicating unusable or abnormal positions on the conveying belt. Next, the density data and positional data in each measurement data is checked. If either the density or positional data falls outside of a specified range, then the measurement data is considered abnormal. In this case, the pattern forming position in the measurement data is stored as positional data and the measurement data is deleted. Subsequently, color registration correction is performed based on the remaining normal measurement data.

Abstract: A color laser printer is configured to fulfill Qmin<Qs for suppressing occurrence of reverse transfer of toner. Qmin designates the minimum amount of transfer electric charge per unit area required to transfer a toner image of the maximum amount of toner onto a sheet (hereinafter referred to as a “per-unit-area required transfer electric charge level”). Qs designates the maximum amount of transfer electric charge per unit area which can prevent occurrence of reverse transfer (hereinafter referred to as an “transfer prevention per-unit-area electric charge level”). The transfer prevention per-unit-area electric charge level Qs is represented by Qs=a/(Md)2. Md designates the maximum quantity of developing agent on a toner image per unit area thereof transferred onto a sheet immediately before being transferred, and “a” designates a proportional constant.

Abstract: A transfer device includes a transfer roller that is rotatably provided facing an image carrying member, an urging device that urges the transfer roller in a direction that the transfer roller presses the image carrying member, and a regulating roller that is provided to a shaft commonly used with the transfer roller and presses the image carrying member to regulate a pressing force of the transfer roller that presses the image carrying member. The regulating roller is made of an elastic material.

Abstract: An image-forming device includes 1st to Nth image bearing members, 1st to Nth developing units provided in one-to-one correspondence with the 1st to Nth image bearing members, and a transfer unit. N is an integer number equal to or greater than two. The 1st to Nth image members have 1st to Nth surfaces respectively. The 1st to Nth electrostatic latent images are formable on the 1st to Nth surface respectively. The 1st to Nth developing units have 1st to Nth monochromatic developers respectively. The 1st monochromatic developer is of monochromatic black and has a toner particle substantially spherical in shape. The 1st to Nth developing units develop the 1st to Nth electrostatic latent images with the 1st to Nth monochromatic developers respectively in order to form 1st to Nth developer images respectively. The transfer unit transfers sequentially the 1st to Nth developer images to a recipient in a superimposed manner in order of the 1st to Nth developer image.

Abstract: A control section sets the transfer bias level applied between a transfer roller and a photosensitive drum in the printer to a “ghost generation level.” The control section forms a test pattern on the recording medium by applying a transfer bias set to the ghost generation level in order to transfer a toner image onto the recording medium. A density sensor detects the density of the toner image deposited in a non-image-forming region when the test pattern is formed. The control section estimates a transfer bias level, at which ghosts will not occur, based on the ghost generation level and the density level of the toner image in the non-image-forming region, and sets this estimated value as the transfer bias level for forming images.

Abstract: In a color laser printer, the amount of reversely transferred developing agent on the surface of a developing roller is estimated based on the operating time of the color laser printer, the surface area of an image, and the charging amount of developing agent. When the estimated amount of reversely transferred developing agent reaches a predetermined value, a solid image is formed on a photoconductor drum. By transferring the solid image onto recording paper, a conveyer belt, or an intermediate transfer belt, the reversely transferred developing agent is removed. Alternatively, by rotating the developing roller in a state in which the developing roller is separated from the photoconductor drum, the reversely transferred developing agent on the surface of the developing roller is collected into a developing agent hopper.

Abstract: An image forming apparatus comprises: a photosensitive element; a charger electrostatically charging a surface of the photosensitive element uniformly at a voltage of a polarity; an exposure device exposing the charged surface of the photosensitive element, to a light, to form an electrostatic latent image; a developing device depositing a developer on the latent image, to form a developer image; a device for transferring the developer image onto a transfer object; and a developer removing device comprising a cleaning member, to which a voltage is applied to generate a cleaning bias between the cleaning member and photosensitive element, to remove a waste developer adhering to the photosensitive element after the developer image is transferred, and which is disposed to act on a part of the surface of the photosensitive element having been charged by the charger and at which the developer image is not formed yet.

Abstract: An apparatus for forming a multi-color is disclosed which includes a controller that performs an anti reverse-transfer control such that a surface potential of a previously-formed separated-developer-image subset of a plurality of single-color separated-developer-images which has been previously transferred onto an image transferred medium is reduced, prior to a subsequent transfer in which a remainder of the plurality of separated-developer-images is transferred onto the image transferred medium after a previous transfer of the previously-formed separated developer-image subset onto the image transferred medium, to thereby prevent a reverse transfer of a part of a developer material on the image transferred medium from the image transferred medium onto a photoconductor at the subsequent transfer.

Abstract: An image forming device measures calibration patterns printed on a conveying belt and stores the measurement data, which includes data for the density and position of the patterns. Measurement data is deleted from memory when the position of the pattern matches positional data stored in a flash memory for indicating unusable or abnormal positions on the conveying belt. Next, the density data and positional data in each measurement data is checked. If either the density or positional data falls outside of a specified range, then the measurement data is considered abnormal. In this case, the pattern forming position in the measurement data is stored as positional data and the measurement data is deleted. Subsequently, color registration correction is performed based on the remaining normal measurement data.

Abstract: The pressure between a developing roller and a photosensitive drum is set to 0.24 MPa. Because the pressure is smaller than 0.31 MPa, if the potential difference &Dgr;V between the non-image forming part on the photosensitive drum and the electrically-charged polymer toner on the surface of the developing roller is at the preset proper voltage (300 volts), pressure fogging will be prevented. Because the pressure is 0.24 MPa or less, even if the potential difference varies within the range of 200 volts to 400 volts that occurs in practice, pressure fogging will be prevented. By resetting the pressure to 0.22 MPa, even if the potential difference &Dgr;V varies in a wider voltage range of 100 to 400 volts, pressure fogging will be prevented. In this way, by setting the pressure between the developing roller and the photosensitive drum appropriately, pressure fogging can be prevented even when using the opposite-direction developing method and polymer toner.