Ricoh Company, Ltd.

Yuko Harasawa

Satoshi Takano

Itaru Matsuda

Hirokazu Ishii

Mitsuru Takahashi

Takashi Bisaiji

Yasunori Kawaishi

Toshiaki Motohashi

Hideo Yu

Hideki Kamiyama

Hitoshi Ishibashi

Masumi Sato

Akio Kutsuwada

Itaru Matsuta

Megumi Otoshi

An image transferring device incorporated in an image forming apparatus and capable of surely preventing a sheet from wrapping around a photoconductive element. The image transferring device includes a transfer belt contacting an image bearing member to form a nip portion and which is supported by first and second rollers. A contact electrode connected to a power source contacts the inner surface of the belt and is located downstream of the nip for applying a transfer bias to the belt. A discharge electrode is located downstream of the contact electrode and separate from the first and second rollers for dissipating transfer charge on the belt. A controller controls the power source such that a relation: I.sub.1 -I.sub.2 =I.sub.out is satisfied, where I.sub.1 is the transfer current, 1.sub.2 is the feedback current flowing from the discharge electrode and I.sub.out is constant.

Image transferring device for image forming equipment

An image transferring device incorporated in an image forming apparatus and capable of surely preventing a sheet from wrapping around a photoconductive element. The image transferring device includes a transfer belt contacting an image bearing member to form a nip portion and which is supported by rollers one which is made from insulating material. A contact electrode contacts the inner surface of the belt and is located downstream of the nip for applying a transfer bias to the belt. A power source is connected to the contact electrode. A discharge electrode is located downstream of the contact electrode for dissipating transfer charge on the belt. A controller controls the power source such that a relation: I.sub.1 -I.sub.2=I.sub.out is satisfied, where I.sub.1 is the transfer current, I.sub.2 is the feedback current flowing from the discharge electrode and I.sub.out is constant.

The apparatus includes a photoconductive element and a transfer belt, with an electrode or bias applicator located downstream from a nip formed between the photoconductive element and the transfer belt. Upstream from the nip, a roller is provided which can also act as an electrode, or which can be held in an electrically floating state. A bias voltage can be provided to the roller upstream from the nip, with the voltage equal to or less than the voltage applied to the downstream electrode so as form a potential gradient. In addition, the applied voltages can be varied based upon the position of a sheet of paper, or in response to changes in humidity.

Image transferring device and medium separating device for an image

An image transferring device for image forming equipment and capable of insuring desirable image transfer by obviating premature image transfer, print, and the leak of transfer bias. A belt causes a toner image to be transferred from an image carrier to a transfer medium while conveying it. A bias member applies a charge to the belt. A feedback current from the belt flows through a feedback electrode. A constant current control device executes constant current control such that the difference between a current to flow from the bias member to the belt and the feedback current to flow from the belt to the feedback electrode remains constant. The constant current control is based on PWM having a spatial frequency of either lower than 0.5 cycles/mm or higher than 1.5 cycles/mm. In addition, a current sensing resistor is disposed between a first and second node wherein the first node is connected to a power source for applying current to the bias member and the feedback electrode and the second node is connected to the image carrier.

An image transferring device incorporated in an image forming apparatus and capable of surely preventing a sheet from wrapping around a photoconductive element and from being incompletely separated from a transfer belt. A transfer bias and discharge are effected to prevent changes in the resistances of the transfer belt and sheet ascribable to changes in environment from translating into changes in a current to flow to the photoconductive element, and to efficiently dissipate a charge deposited on the belt. Various members constituting the device are positioned relative to one another such that the discharging effect is achievable most effectively while preventing the transfer bias from causing dielectric breakdown in any constituent part. For example, if a discharge member is spaced from a transfer electrode by L.sub.3 and if the transfer electrode is spaced from a nip portion between the transfer belt and image bearing member by a distance L.sub.2, than L.sub.3 .gtoreq.L.sub.2. Additionally, if the vokage applied to the transfer electrode is V.sub.O, than L.sub.2 .gtoreq.a.vertline.V.sub.O .vertline., where a is 1.0 (mm/kv); if a distance between the nip and an upstream roller entraining the belt is L.sub.1, than L.sub.1 .gtoreq.a.vertline.V.sub.O .vertline.; and if the distance between to discharge members is L.sub.4, the transfer belt has a time constant of .tau., and a process speed is .nu., than .tau..ltoreq.L.sub.4 /.nu.. Finally, the transfer belt has a double layer structure made up of an outer layer having a surface resistivity of 1.times.10.sup.9 to 1.times.10.sup.12 .OMEGA. and an inner layer having a surface resisitivity of 8.times.10.sup.6 to 8.times.10.sup.8 .OMEGA. and a volume resisitivty of 5.times.10.sup.8 to 5.times.10.sup.10 .OMEGA.cm.

In an image transfer device for an image forming equipment, a bias for image transfer is applied from a power source to an endless transfer belt via a bias roller. A current from the Transfer belt is released to ground via a ground electrode. Transfer control means variably controls a current I.sub.1 output from the power source that the difference between the current I.sub.1 and a current I.sub.2 flowing from the power source to the ground via the transfer belt, i,e., I.sub.out =I.sub.1 -1.sub.2 remains at a preselected target current. Setting means sets the target current on the basis of a set condition or conditions.

Image transfer device for an image forming apparatus

An image transferring device incorporated in an image forming apparatus and capable of surely preventing a sheet from wrapping around a photoconductive element and from being incompletely separated from a transfer belt. A transfer bias and discharge are effected to prevent changes in the resistances of the transfer belt and sheet ascribable to changes in environment front translating into changes in a current to flow to the photoconductive element, and to efficiently dissipate a charge deposited on the belt. Various members constituting the device are positioned relative to one another such that the discharging effect is achievable most effectively while preventing the transfer bias from causing dielectric breakdown in any constituent part. A bias roller is held in contact with the transfer belt which is made of a dielectric material. A current I.sub.OUT to flow frown the bias roller to ground via a nip portion between the belt and an image carrier and the image carrier is maintained greater than or equal to a current I.sub.2 to flow from the contact electrode to ground via the belt without the intermediary of the nip portion.

An image forming device incorporated in an image forming apparatus and capable of cleaning a residual toner on a transfer belt. A transfer belt transports a sheet to a nip portion of an image carrier and the transfer belt. A transfer bias current It1 is applied to the transfer belt from a power source, so that a toner image on the image carrier is transferred to the sheet at the nip portion. A cleaning bias current It2 is applied to a cleaning bias roller which is held in contact with the transfer belt so as to transfer the residual toner and paper particles from the transfer belt to the cleaning bias roller. An electric current Ir is returned from the transfer belt to a transfer control board which is also connected to the power source. The transfer control board controls the current It1 to satisfy an equation '(It1+It2)-Ir=IOUT' where IOUT is constant.

Apparatus and method for cleaning a belt of an image forming apparatus

An image transfer device for a copier, printer, facsimile apparatus or similar image forming apparatus. A transfer belt is rotated and applied with a charge from a first electrode in contact with the transfer belt to transfer a toner image from an image carrier to a transfer medium carried on the transfer belt or to the transfer belt itself. A second electrode contacts the transfer belt. A variable resistance element is connected between the second electrode and ground. A controller produces a ratio of a current applied from the first electrode to the transfer belt and a current from the transfer belt to the second electrode and controls a resistance of the variable resistance element such that the ratio has a predetermined value. Additionally, the resistance of the transfer belt to the variable resistance element is one of 1:1-100, 10:1-100 and 100:1-100.

An image forming apparatus includes a photoconductive element and a transfer belt, with an electrode or bias applicator located downstream from a nip formed between the photoconductive element and the transfer belt. Upstream from the nip, a roller is provided which can also act as an electrode, or which can be held in an electrically floating state. A bias voltage can also be provided to the roller upstream from the nip, with the voltage equal to or less than the voltage applied to the downstream electrode. In addition, the applied voltages can be varied based upon the position of a sheet of paper, or in response to changes in humidity.

Growing community of inventors

Hayama-machi, Japan

Yuko Harasawa