Oki Data Corporation

Tsutomu Yamane

Kuniharu Hayashi

Tatsuya Murakami

Mitsuru Kishimoto

Takao Mizutani

Hirokazu Ando

Masamitsu Nagamine

Shigeru Tsunoda

Akihito Onishi

Masahiko Shimosugi

Hiroyuki Yajima

Masao Isoda

Satoshi Ishikawa

Hirotomo Nonaka

An image forming apparatus includes an image supporting member; a developer supporting member for attaching developer to a static latent image formed on a surface of the image supporting member; a developer layer forming member for forming a developer layer on the developer supporting member; a developer supply member for supplying developer to the developer supporting member; a developer supporting member voltage applying unit for applying a voltage to the developer supporting member; a developer supplying member voltage applying unit for applying a voltage to the developer supplying member; and a reset operation processing unit for setting a reset mode over a specific period of time, so that a bias difference in the reset mode between the voltage applied with the developer supporting member voltage applying unit and the voltage applied with the developer supplying member voltage applying unit becomes smaller than that in a printing mode.

Image forming apparatus with reset operation processing unit

An image forming apparatus includes: an image carrier on which an electrostatic latent image is formed; a developer carrier being in contact with the image carrier and configured to develop the electrostatic latent image on the image carrier with a developer; a temperature humidity measurement unit configured to measure the temperature and humidity around the developer carrier; a pressure changing mechanism configured to change a pressure of a contact between the image carrier and the developer carrier; and a pressure controller operable to change, based on the temperature and humidity measured by the temperature humidity measurement unit, the pressure by controlling the pressure changing mechanism.

Image forming apparatus

An image forming apparatus includes a process including at least a developing section and an image bearing body. A calculating section calculates a number of the dots formed on the image bearing body. A rotation calculating section calculates a number of rotations of the image bearing body for forming the number of dots on the image bearing body in accordance with the print data. A controller makes a decision to determine whether the number of dots formed on the image bearing body is larger than a first reference when the number of rotations is larger than a second reference. If the answer is YES, then the controller forms a developer image formed of dots equivalent to a difference between the first reference and the number of dots. Then, the developer image is discarded.

Image forming apparatus having an image bearing body

The present invention is an image forming apparatus containing an image holding body, a developer holding body for holding developer that forms a developer image by being affixed to the electrostatic latent image formed on the image holding body, a transfer unit for transferring the developer image to a medium, a fusion apparatus for fusing the transferred developer image onto the medium, an idle time judgment process section for making a judgment as to whether an idle time, from when printing is completed to when printing is initiated, of the image forming apparatus is long, and a surface potential setting process section for changing and setting a surface potential of the image holding body to a reference value at which fogging is not generated in a case where the idle time is long.

Image forming apparatus with surface potential adjustment based on idle time

A developing roller supplies toner to an image on an image bearing body, the image being formed in accordance with image data. A toner supplying member supplies developer material to the developer bearing member. A computing section computes a dot population density in corresponding one of a plurality of sub data areas. The plurality of sub data areas are obtained by dividing the image data such that the plurality of sub data areas are aligned in a printable area of a print medium in a direction perpendicular to the direction of travel of the print medium. A controller performs a developer material removing process based on the dot population density, in which the toner deposited on the developing roller is removed from the developing roller in an area corresponding to a low dot population density of image data.

Image forming apparatus with improved quality on image of low dot population

An image forming apparatus in which a toner layer is formed onto a developing roller which is restricted by a toner restricting member and rotated, toner is supplied to a photosensitive drum by the toner layer, and a toner image is formed onto the drum and transferred onto a print medium, thereby forming an image. The apparatus has: a counter which counts the toner image, on a dot unit basis, formed on the drum and a control unit which stops the rotation of the developing roller for a predetermined time and intermittently executes a series of image forming operation when a count value is equal to or larger than a predetermined reference value. The occurrence of filming is prevented by preventing an increase in toner temperature.

Image forming apparatus including a counting section for counting the toner image

A fixing device capable of improving printing speed without increasingly the size of rollers, and making the surface temperature of the heating roller quickly reach a target temperature. The heating roller, which comes into contact with recording sheet having unfixed toner adhering to it, includes an elastic body of low heat conductivity and high heat resistance, and has metal foil formed tightly to the external circumferential surface thereof. This meal foil with a small heat capacity, by direct contact on its surface with the heating source, helps the surface of the heating roller quickly rise in temperature.

Fixing device, method for temperature control of the same, and method for manufacturing rollers of the same

An image forming apparatus an electrophotographic image forming section and a controller. The image forming section forms a toner image on a print medium. When a cumulative operation reaches a predetermined value, the controller causes the image forming section to form the toner image of a pattern image on the print medium. The pattern image is at least one of a number of pattern images aligned in an advance direction, the number of pattern images being increased in accordance with a cumulative print duty. The cumulative operation includes a number of print jobs, a number of printed pages, and a number of rotations of an image drum. The number of printed pages has a print duty less than a predetermined value.

Image forming apparatus that periodically discharges waste toner and method of operation thereof

An image forming apparatus has a fixing unit. A heat roller heats a toner image on a print medium to fuse the toner image. A first temperature detector is in contact with a longitudinal end portion of the heat roller, and generates a first temperature data. A second temperature detector opposes the heat roller and is in proximity to a substantially middle portion of the heat roller. The second temperature detector generates a second temperature data. Depending on the first temperature data and the second temperature data, a controller performs temperature control either in a first mode where the heater is energized such that the first temperature data is equal to a first target value, or in a second mode where the heater is energized such that second temperature data is equal to a second target value.

A method for cleaning an image-forming apparatus. Toner is charged to the first polarity prior to transferring the toner image to the print medium and accidentally inverted from the first polarity to a second polarity opposite to the first polarity during the transfer of the toner image to the print medium. When performing a cleaning operation, a first voltage of a first polarity is applied to at least one of a charging roller and a cleaning roller in contact with a surface of a photoconductor. The surface of the photoconductor is charged to a second voltage. The second voltage has a smaller value than the first voltage and is of the same polarity as the first voltage. Therefore, the toner of the second polarity sandwiched between the charged surface of the photoconductor and the at least one of the charging roller and cleaning roller is inverted in polarity, i.e., from the second polarity to the first polarity by triboelectric charging. If the first voltage is applied to the cleaning roller, the photoconductor may be charged to the second voltage by a transfer device or by a charging device. Alternatively, if the first voltage is applied to the charging roller, the photoconductor may be charged to the second voltage by a cleaning device or by the transfer device.

Method of cleaning residual toner from drum and rollers of image forming

An electrophotographic printer includes a photosensitive drum, charging roller, image writing device, developing roller, and controller. The controller controls the operations of the image writing device and the developing roller so that a difference in potential between the surface of the photosensitive drum and the developing roller is below a firing potential. The controller causes the image writing device to fully emit light for a first predetermined time period immediately before completion of a printing operation, and for a second predetermined time period immediately after the printing operation starts, thereby bringing the surface of the drum to a potential nearly zero volts. The photosensitive drum stops rotating after the first predetermined time period and the photosensitive drum starts rotating immediately before the first predetermined time period. The photosensitive drum does not necessarily stop at exactly the same angular position after each printing operation. Likewise, the rising time and falling time of the bias voltage V.sub.B vary to some extent. In order to accommodate such variations, the controller compares an elapsed time after a preceding print operation has completed with a predetermined reference value. Then, the developing roller receives a bias voltage for the following print operation, the bias voltage being the same polarity as the surface oft he photosensitive drum charged by the charging device if the elapsed time is shorter than the predetermined value.

Electrophotographic printer having image writing timed to prevent toner

An electrophotographic printing apparatus has two charging bodies that are held at different potentials. The first charging body makes contact with the surface of a photosensitive drum; the second charging body makes contact with the first charging body. Toner particles that have acquired an electrostatic charge opposite to their normal charge are attracted from the drum surface to the first charging body. These toner particles are then attracted from the first charging body to the second charging body, whereby the first charging body is kept clean and able to charge the surface of the photosensitive drum to a uniform potential.

Electrophotographic printing apparatus with two charging bodies

A method of cleaning is used to remove residual toner in an electrophotographic printer. After a printing operation, some amount of normally-charged toner and reversely-charged toner is left on the photoconductive drum and rollers such as charging rollers, transfer roller, and cleaning roller in contact with the photoconductive drum. A potential difference is applied between two members, for example, the cleaning roller and the photoconductive drum in electrical contact with each other so as to cause the residual toner to migrate from one member to the other. The potential differences are applied at specific timings so that the residual toner migrates properly onto the rotating photoconductive drum and is carried to the developing section for reuse.

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Tokyo, Japan

Tsutomu Yamane