Abstract: A developing device uses a two-component developer including at least carriers and toners. The toners are supplied to an image bearing member bearing an electrostatic latent image so that a toner image is developed from the electrostatic latent image. The developing device has a developing roller arranged to oppose the image bearing member; and a magnetic roller arranged to oppose the developing roller. The magnetic roller retains the two-component developer to supply toners to the developing roller. The developing roller and the magnetic roller are rotationally driven in directions to be opposite from one another at an opposed position, and a magnetic pole of the magnetic roller and a magnetic pole of the developing roller have magnetic polarities different from one another at the opposed position. A surface roughness of the magnetic roller is greater than a surface roughness of the developing roller.

Abstract: An image forming apparatus is characterized in that an absolute value of a difference between a first coefficient of variation in a number distribution of the particle diameter of a toner carried on a developing roller and a second coefficient of variation in a number distribution of the particle diameter of a toner in a two-component developer carried on the magnetic roller is within 5% and an absolute value of a difference between a third coefficient of variation in a number distribution of the particle diameter of a toner of a toner image developed on the outer surface of an image bearing member and the second coefficient of variation is within 6%. With such an image forming apparatus, high-quality images can be stably formed over a long term.

Abstract: An image forming apparatus is provided with a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image formed on the photoconductive member by a first bias, and a magnetic roller for forming a magnetic brush thereon with a two-component developer and forming a thin toner layer on the developing roller by a second bias. If (D1) denotes the duty ratio of a first alternating-current bias included in the first bias and (D2) denotes the duty ratio of a second alternating-current bias included in the second bias, the duty ratios (D1, D2) satisfy the following relationship: D1>100?D2.

Abstract: An image forming apparatus has a photoconductive member, and a developing roller develops a latent image on the photoconductive member by a first alternating-current bias in the form of a rectangular wave. The following relationships are satisfied in calculating the duty ratio (D1) of the first alternating-current bias using an application period of voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: a CV value in the number particle size distribution of the toner is ?25%, 4 ?m?Dt?7 ?m, 105 ?·cm?pv?109 Q?cm, 0.4 ?m?Ra?1.5 ?m, and 35%?D1?75%. where Dt denotes the volume average particle diameter of the toner, pv denotes the intrinsic resistance value of a developing roller surface, Ra denotes the arithmetic average roughness of the developing roller surface.

Abstract: An image forming apparatus has a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image on the photoconductive member by a first bias. A magnetic roller forms a magnetic brush thereon with a two-component developer and forms a thin toner layer on the developing roller by a second bias. The developing roller is aluminum with a surface treated for high resistance. The thickness (T) of the toner layer and the duty ratio (D1) of the first alternating-current bias satisfy relationships of the following equations for calculating the duty ratio (D1) using an application period of a voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: 7 ?m?T?13 ?m, and 35%?D1?70%.

Abstract: A developing unit has a voltage-applicator (80) to apply a developing bias voltage to a developing roller (72). The voltage-applicator (80) applies the developing bias voltage for a first duration to apply an AC voltage having a rectangular waveform, and a second duration to stop applying the AC voltage. The AC voltage has a duty ratio of 50% or more in a direction for causing toner to develop an electrostatic latent image. The number of cycles of the AC voltage in the first duration is two or more, and the AC voltage has a voltage in a direction for pulling the toner back to the developing roller, just before transition to the second duration. The developing unit suppresses occurrence of image unevenness due to a fluctuation in developing gap. Thus, an image forming apparatus equipped with the developing unit forms a high-quality image while suppressing image unevenness.

Abstract: A developing unit includes a development roller and a magnetic roller. Sleeves of the development roller and the magnetic roller are driven to rotate in the same circumferential direction. A first magnet is provided on the roller shaft in the sleeve of the development roller and a second magnet is provided on the roller shaft in the sleeve of the magnetic roller. The first and second magnets are opposed to each other so that opposite polarities face each other, and are supported non-rotatably in circumferential directions. The first magnet is supported so that the peak of the magnetic force of the first magnet is positioned upstream in the direction of rotation of the sleeve of the development roller from the straight line connecting the center of the roller shaft of the development roller to the center of the roller shaft of the magnetic roller.

Abstract: An image forming apparatus which adjusts toner density in a developing device according to humidity. However, an image quality may decrease if the humidity changes between the time when a power source is turned off and the time when the power source is turned on. Accordingly, the image forming apparatus includes an absolute humidity calculator and a toner density controller for changing the toner density in the developing device in accordance with a difference between the absolute humidities. A storage controller controls the storing of an absolute humidity in a storage portion; and a toner removal controller controls the removal of residual toner particles from the developing device if a difference between an absolute humidity detected by the humidity detector when the power source is turned on and an absolute humidity stored in the storage portion is more than a predetermined value.

Abstract: A developing unit in an image forming device is disclosed which includes a first agitation transport member, a second agitation transport member, a bulkhead, and a housing. The second agitation transport member is arranged to be parallel to the first agitation transport member in the horizontal direction, and configured to simultaneously agitate and transport developer in cooperation with the first agitation transport member and mix developer with the externally supplied toner. The bulkhead has a partition member arranged between the first agitation transport member and the second agitation transport member, and a guide member that is formed to be integrated with the partition member and guide developer peeled off from the developing roller to the first agitation transport member. The bulkhead can arranged in the housing such that there is no space between first and second ends of the bulkhead and the housing.

Abstract: A developing unit in an image forming device is disclosed in which developer peeled off from a developing roller can be reliably retrieved to an agitation transport member and avoid being directly drawn thereto. A developing unit has a drawing magnetic pole and a peel-off magnetic pole. A first agitation transport member is arranged below a developing roller and agitates and transports the developer in the axial direction simultaneously and supplies it to the developing roller. A guide member has a sloping surface guiding the developer torn off from the developing roller to the first agitation transport member. The magnetic pole is arranged between horizontal positions of the sloping surface, and the magnetic pole is arranged horizontally outward of the lower end of the sloping surface.

Abstract: A developing unit is disclosed in which replenished toner is smoothly transported and efficiently agitated into the developing unit by an agitation transport member provided therein having a supply region formed upstream from a transport region. A first agitation transport screw installed in a developing unit includes a developer transport region to transport developer downstream thereof, and a toner supply region that is formed coaxially with the developer transport region and upstream of the developer transport region, and supplies the externally replenished toner to the developer transport region. Moreover, a gap formed between the toner supply region and a region of the housing in the toner supply region is smaller than a gap formed between the developer transport region and a region of the housing in the developer transport region.

Abstract: An image forming apparatus is able to maintain an image density at a constant level. The apparatus has a FC mode selecting key for allowing a user to selectively designate a low FC mode indicating that the apparatus is in a less-used state where the number of times of image formation is smaller than a predetermined value and a high FC mode indicating that the apparatus is in a highly-used state where the number of times of image formation is not smaller than the predetermined value, and a CPU for correctively setting a target value of toner density at a value higher than a target value of toner density at the low FC mode when the apparatus is in the high FC mode.

Abstract: Disclosed is an image forming apparatus that enables to maintain an image density at a constant level. The apparatus has a FC mode selecting key for allowing a user to selectively designate a low FC mode indicating that the apparatus is in a less-used state where the number of times of image formation is smaller than a predetermined value and a high FC mode indicating that the apparatus is in a highly-used state where the number of times of image formation is not smaller than the predetermined value, and a CPU for correctively setting a target value of toner density at a value higher than a target value of toner density at the low FC mode when the apparatus is in the high FC mode.

Abstract: An aid tool used for aiding in replacement operation of a part to be replaced in an image forming apparatus. This aid tool includes: a part holding unit for holding a part to be replaced; and a mounting portion for removably mounting the part holding unit on an image forming apparatus. The part holding unit is for example a part housing container for housing a part, and may also serve as a packaging container which houses a new replacing part. The part housing container may include, for example, a main body for receiving the part to be replaced, and a lid for openably closing the main body.

Abstract: An image-forming machine has a sheet member conveying passage extending through a transfer zone and a fixing zone, a sheet member-feeder for feeding a sheet member to the sheet member conveying passage, and a sheet member conveyor for conveying the sheet member through the sheet member conveying passage. A housing of the image-forming machine has a lower surface defined by an intermediate lower wall and an upper surface defined by an intermediate upper wall, and has a space of which the front surface is opened. The downstream end portion of the sheet member conveying passage extends along one side portion of the intermediate lower wall on the lower side thereof. That one side portion of the intermediate lower wall is defined by an opening/closing member which is brought to the open position to open the downstream end portion of the sheet member conveying passage. The sheet member conveyer includes a pair of register rollers.

Abstract: An image-forming machine comprises a sheet member conveying passage extending through a transfer zone and a fixing zone, a sheet member-feeding means for feeding a sheet member onto the sheet member conveying passage, and a sheet member conveying means for conveying the sheet member through the sheet member conveying passage. A housing of the image-forming machine has a lower surface defined by an intermediate lower wall and an upper surface defined by an intermediate upper wall, and forms a space of which the front surface is opened. The downstream end portion of the sheet member conveying passage extends along a one side portion of the intermediate lower wall on the lower side thereof. The one side portion of the intermediate lower wall is defined by the opening/closing member, and opening/closing member is brought to the open position to open the downstream end portion of the sheet member conveying passage. The sheet member conveying means includes a pair of register rollers.

Abstract: An image forming machine having a transfer roller comprises a rotatably disposed photoconductor drum, a transfer roller disposed opposite the photoconductor drum with a predetermined gap provided therebetween, a register roller pair for feeding a transfer sheet toward a transfer area where the photoconductor drum and the transfer roller are opposed to each other, transfer sheet guide means disposed between the register roller pair and the transfer area, and a fixing roller pair for fixing a toner image transferred to the transfer sheet passing through the transfer area. The transfer sheet guide means comprises an inner guide plate and an outer guide plate, and the inner guide plate has a linear guide portion extending toward a predetermined position on the peripheral surface of the photoconductor drum. The predetermined position is set in an angular range (.theta.) covering 12.degree. to 23.degree.

Abstract: An imaging unit includes a developer unit which is supported rotatably about a predetermined rotation axis thereof by means of a drum unit. Spacing regulation sleeves are respectively fitted around opposite ends of a support shaft of a developer roller for regulating a spacing between the photoreceptor drum and the developer roller. A driven gear is engaged with one end of the support shaft of the developer roller for integral rotation thereof, and adapted to be driven by a drive transmission gear. By utilizing a driving force applied to the driven gear, the developer unit is biased about the rotation axis to press one spacing regulation sleeve fitted around one end of the support shaft of the developer roller against the photoreceptor drum. The other spacing regulation sleeve fitted around the other end of the support shaft of the developer roller is resiliently pressed against the photoreceptor drum by means of a resilient member.

Abstract: A device for developing an electrostatic latent image includes a developing roller disposed in a developing housing and a developing agent-limiting device for limiting the amount of the developing agent held on the peripheral surface of the developing roller. The developing agent-limiting device includes a flexible blade brought into pressed contact with the peripheral surface of the developing roller, a flexible support plate that is mounted on the blade and supports the blade in a predetermined positional relationship with respect to the developing roller, and a resilient urging device that is constituted by a plurality of spring members arranged on the back surface of the support plate at a distance in the direction of width thereof and pushes the blade in a direction in which it comes into pressed contact with the peripheral surface of the developing roller via the support plate.