Ricoh Company, Ltd.

Takahiro Tamiya

Hajime Oyama

Katsuhiro Echigo

Tsuyoshi Deki

Nobuo Iwata

Mitsuru Takahashi

Hiromi Ogiyama

Akihiro Sugino

Yuuji Sawai

Katsuya Kawagoe

Kohki Katoh

Takeshi Motohashi

Tomonori Yabuta

Shigeru Watanabe

Shigeo Kurotaka

Shinichi Namekata

Eiichi Sasaki

Yutaka Shio

Ayako Iino

Shingo Katou

Koichi Irie

A transfer device for use in an image forming apparatus includes at least two belt members constituting a secondary nip portion therebetween. The transfer device electrostatically transfers a toner image from one of the belt members onto a recording medium when the recording medium passes through the secondary nip portion. The transfer device includes a mechanism that supports the belt members such that the secondary nip portion is substantially linear; and a bias applying member that applies a secondary transfer bias at a substantially center portion of the secondary nip portion.

Transfer device and image forming apparatus

An exit blade is arranged on a downstream side of a transfer nip formed between a photosensitive element and a primary transfer roller, with an intermediate transfer belt being put therebetween, and brought into contact with an internal surface of the intermediate transfer belt. A neutralizing bias of the same polarity as that of the toner is applied to the exit blade, rather than a primary transfer bias voltage.

Image forming apparatus having a neutralizing member of determined resistivity

An intermediate transfer belt and a photosensitive member form a transfer nip. An electrode is arranged close to an inner surface of the intermediate transfer belt in a portion on an upstream side of a direction of endless movement of the intermediate transfer belt with respect to a downstream-side exit of the transfer nip and on a downstream side of the direction of endless movement with respect to a position at which a transfer roller charges the intermediate transfer belt. A voltage of same polarity as the polarity of a toner is applied to the electrode, so that there is no movement of an electric charge between the electrode and the intermediate transfer belt.

Image forming apparatus

An image forming apparatus includes at least one image forming unit, a primary transfer belt, and a secondary transferer. The image forming unit includes an image carrier and a primary transfer bias applicator. The secondary transferer includes a secondary transfer nip, a secondary transfer bias applicator, and a facing member facing the second transfer bias applicator. The secondary transfer bias applicator forms a secondary transfer electric field. The image forming apparatus further includes a bias applicator, a contact start site, and an electrode. The bias applicator applies a bias voltage having a same polarity as the normal charge polarity of the toner to the primary transfer belt, downstream of the primary transfer bias applicator. The recording medium starts to contact the toner image at the contact start site, located upstream of the secondary transfer nip, where the electrode forms an electric field.

An image forming method of the present invention sequentially transfers toner images formed on image carrier to an intermediate image transfer body one above the other to thereby form a multicolor toner image. An image transfer roller faces the inside surface of the intermediate image transfer body for applying an image transfer bias when a toner image is transferred from the image carrier to the intermediate image transfer body. Rollers are positioned at both sides of the image transfer roller in the axial direction of the image transfer roller in order to control a nip width over which the image carrier and intermediate image transfer body contact each other during image transfer.

Image forming method and apparatus with reduced reverse toner transfer

In an electrophotographic image forming apparatus of the type including a plurality of image carriers arranged along an image transfer belt and an image transferring device configured to transfer toner images of different colors from the image carriers to a sheet being conveyed by an image transfer belt or by way of the image transfer belt by applying a bias to the belt, a bias applying method of the present invention can measure a current leaking between a plurality of high-tension power supply sections or to the ends thereof as AC resistances between respective terminals and therefore to accurately measure the leak currents of DC components. Therefore, when relatively high DC components are selected, a difference in current between a plurality of power supply sections can be maintained constant.

Transfer bias applying method for an image forming apparatus and device for the same

An image forming apparatus comprises a latent image support which supports an electrostatic latent image. A charging unit charges a surface of the image support. A latent image formation unit forms an electrostatic latent image on the image support surface. A developing unit develops the latent image with toner to form a toner image. A transfer unit transfers the toner image from the image support to a recording medium. A transport unit transports the recording medium so that the image support surface is countered to a surface of the recording medium. The surface of the image support has a coefficient of friction ranging from 0.1 to 0.7 according to Euler belt method, and a difference between a speed of the image support and a speed of the recording medium is below 1%, and the image support has an outermost surface containing a filler and a binder resin.

Image forming apparatus, and process cartridge for use in image forming apparatus

An image forming apparatus of the present invention includes a latent image forming device for forming a latent image on an image carrier and a developing device for developing the latent image with toner to thereby form a corresponding toner image. The surface of an intermediate image transfer body is movable and includes an high-resistance layer having a volume resistivity of 10 &OHgr;&middot;cm or above. A primary image transferring device transfers the toner image from the image carrier to the intermediate image transfer body. Secondary image transferring device transfers the toner image from the intermediate image transfer body to a sheet. A polarization uniforming device uniforms, at the beginning of an image forming operation, polarization left in the high-resistance layer while preserving the polarity of the polarization after the surface of the intermediate image transfer body has started moving, but before the toner image is transferred from the image carrier to the secondary image transfer body.

Image forming apparatus including an image carrier and a polarization uniforming structure

A color image forming apparatus capable of superposing toner images of respective colors in accurate register by preventing an exposing position from being displaced in the subscanning direction. The rotation phase of a polygonal mirror is controlled on the basis of the mark detection timing of a mark sensor. Hence, the exposing position in the subscanning direction is prevented from being displaced without regard to irregularities in the circumferential length and feed speed of an intermediate image transfer belt.

Color image forming apparatus with polygonal mirror rotation phase control

An image forming apparatus, such as a color image forming apparatus using a transfer roller or similar transfer electrode, and a constant current power source. The transfer roller is made of a material to which ion agents are added. The constant current power source applies the electric current to the transfer electrode so as to implement an image transfer operation. An electric resistance of the material satisfies a formula log R (Va)-log R (10.times.Va).ltoreq.0.5, such that a quality of the image transfer operation is not corrupted when a relatively little amount of toner is transferred, or a relatively large amount of toner is transferred.

Image forming apparatus having a transfer electrode

A color image forming apparatus is provided with an intermediate transfer belt to transfer thereupon an image of each of a plurality of colors carried on a photoconductive member, sequentially superposing one image on top of another, to form a full color image, and to further transfer the full color image to a copysheet. The intermediate transfer belt is passed over supporting rollers and a plurality of marks are printed on the intermediate transfer belt for indicating a position on the belt. A detector is provided for detecting the marks on the belt to generate a detect signal to start an image forming operation for each of the colors. The detector is controlled to start detection of a mark when a predetermined length of time is elapsed after a start or a termination of an operation of a driving element of the apparatus. The detector is provided at a position facing one of the support rollers around which the intermediate transfer belt is passed. A distance between the adjoining marks is equal to an integral multiple of at least one of a circumference of the roller the detector faces. The provision of an improved color image forming apparatus realizes a capability of accomplishing an accurate image registration for each of the plurality of colors.

Color image forming apparatus

In a paper conveyer of an image forming apparatus, a transfer operation is performed by a transfer roller and an unfixed image in the transfer operation is carried onto the lower side of a transfer paper sheet. The transfer paper sheet is conveyed to a fixing device constructed by a fixing roller and a pressurizing roller. A hardness of the fixing roller is smaller than that of the pressurizing roller, while a nipping portion of the fixing and pressurizing rollers is formed in a concave shape. The fixing and pressurizing rollers are arranged such that a nipping inlet port point of the fixing and pressurizing rollers is located in the vicinity of a line of a conveying locus of a thin transfer paper sheet. A paper guide plate guides the transfer paper sheet to the nipping inlet port. In this construction, a transferred paper sheet is conveyed such that this transferred paper sheet is reliably fed into the nipping portion of the fixing device, and it is possible to prevent an image rub, wrinkles, a jam, etc. from being caused.

Paper conveyer of image forming apparatus which conveys paper to a

In an image forming apparatus of the type sequentially forming powder images of different colors on an image carrier, and sequentially transferring them to an acceptor one above the other (primary transfer), an image transfer method is disclosed which prevents transfer dust from being transferred to the acceptor at the time of the primary transfer. During the primary transfer, a bias potential V.sub.1 is applied to one of two conductors located at an upstream side. The potential V.sub.1 has the same polarity as the charged powder carried on the image carrier. A potential V.sub.2 is applied to the other conductor at a downstream side and provided with a polarity opposite to the polarity of the charged powder. Every time the primary transfer is repeated, the potentials V.sub.l and V.sub.2 are respectively sequentially shifted toward the polarity of the powder and toward the polarity opposite to the polarity of the powder.

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Tokyo, Japan

Takahiro Tamiya