Ricoh Company, Ltd.

Itaru Matsuda

Satoshi Takano

Yuko Harasawa

Hirokazu Ishii

Ryoh Tanoue

Yuji Suzuki

Mitsuru Takahashi

Hiroshi Saitoh

Takashi Bisaiji

Yasunori Kawaishi

Toshiaki Motohashi

Akio Kutsuwada

Hideo Yu

Hiroyuki Ohkaji

Hideki Kamiyama

Eiji Shimojo

Noboru Onodera

Hidenori Nihei

Hiroshi Itoh

Hitoshi Ishibashi

Masumi Sato

Masato Yanagida

Haruji Mizuishi

Takayuki Maruta

Mitsuo Hasebe

Akio Katsumata

Hiroshi Hosaka

Chiemi Kaneko

Yoshihiro Mitekura

Kazuaki Tagawa

Izumi Tagoku

Yuko Hayama

Masaaki Kogure

Ryou Tanoue

Kotaro Yonenaga

Megumi Otoshi

An image forming apparatus in which a visible image is transferred to a transfer material includes a pre-transfer exposing unit that makes only a portion of a latent image carrier that corresponds to a leading edge of the transfer material expose, and a transfer-bias applying unit that applies a bias for transferring the visible image. The transfer-bias applying unit starts applying the bias to the transfer material, at least step-by-step, when a predetermined time is passed from a point of time at which the leading edge of the transfer material comes into a contact with the latent image carrier by controlling the pre-transfer exposing unit and a bias applying timing of the transfer-bias applying unit.

Image forming apparatus with improved separability of transfer material

Image forming apparatus with improved separatability of transfer material

An image transferring and recording medium conveying device, for an image forming apparatus, which includes a nip between a belt and an image carrier for image transfer to a recording medium. A bias applying device applies a bias for image transfer to the nip. An image transfer bias Tb is applied during a leading edge interval, in which the leading edge portion of the recording medium between the leading edge and a preselected position in the direction of medium conveyance moves away from the nip. An image transfer bias Ta is applied to the nip during a remaining interval, in which the remaining portion of the recording medium moves away from the nip. A controller switches the image transfer bias Tb within a range lower than the image transfer bias Ta and greater than an image transfer bias Tc.

Image transferring and recording medium conveying device and image forming apparatus including the same

An image forming apparatus of the present invention includes a developing device including two developing rollers arranged in parallel in a direction in which an image carrier moves each for forming a magnet brush thereon. The magnetic poles of the developing rollers for effecting hand-over of a developer between the rollers are provided with the same polarity. An optical writing device optically writes an image on the image carrier in accordance with tonality data of four levels or less for a single dot. The developing device prevents the developer from moving through a gap between the developing rollers and bringing about irregular image density and background contamination. In addition, the optical writing device successfully obviates ghosts, which are likely to appear when a uniform halftone image including solid portions or bold characters is reproduced.

Image forming apparatus having developing device including developing rollers with differing flux density and optical writing device using xonality data of four levels or less

An image forming apparatus is provided with an image carrier that carries a visible image thereon, a transfer support element that conveys a sheet to which the visible image is transferred from the image carrier at a transfer nip portion, and a transfer member that applies a transfer bias to the transfer support element. The transfer member is in contact with an inner layer of the transfer support element at an edge of the transfer nip portion. The transfer member has a medium inherent volume resistance which is less than an inherent volume resistance of the inner layer of the transfer support element. Further, a plurality of transfer members may be provided, in which case the transfer member closest to the transfer nip portion has the medium inherent volume resistance.

Image forming apparatus with a transfer member having an inherent volume resistance less than that of an inner layer of a transport support element

A belt cleaning device included in an image forming apparatus for transferring a toner image from an image carrier to a recording medium and conveying the medium while electrostatically retaining it thereon is disclosed. The device allows its belt to be surely cleaned over the entire circumference even when electrostatic cleaning and image transfer share a single power source. The device therefore prevents the rear of the recording medium from being smeared.

Belt 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. 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.

In an image forming apparatus, a lubricant is fed to an image carrier on which a toner image is to be formed. An endless rotatable transfer member conveys a recording medium to which the toner image is to be transferred from the image carrier. The transfer member is capable of contacting the surface of the image carrier to which the lubricant has been applied. As a result, an adequate amount of lubricant is evenly applied to the transfer member to reduce the coefficient of friction of the surface of the transfer member, thereby enhancing the cleanability of the transfer member.

Image transferring device for an image forming apparatus

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 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.

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Yokohama, Japan

Itaru Matsuda