Ricoh Company, Ltd.

Hiromi Ogiyama

Yasunobu Shimizu

Hiroyoshi Haga

Kenji Sengoku

Tomokazu Takeuchi

Yuuji Sawai

Shinya Tanaka

Junpei Fujita

Keigo Nakamura

Hirokazu Ishii

Mitsuru Takahashi

Ken Yoshida

Katsuya Kawagoe

Shin Kayahara

Akihiro Sugino

Kohki Katoh

Shinji Kato

Yoshihiro Fujiwara

Atsushi Takehara

Takahiro Tamiya

Ryuuichi Mimbu

Ryuuichi Minbu

Junroh Uda

Hiroshi Ono

Shinji Aoki

Kazuo Kobayashi

Akio Kosuge

Koji Sakamoto

Jun Yura

Ryuta Takeichi

Naoyuki Ozaki

Toshiharu Hachisuka

Toshiaki Motohashi

Wataru Yasuda

Satoru Uchida

Fuchio Kanno

Yuji Sawai

Emiko Ishikawa

Masako Yoshii

Hideki Kamiyama

Ichiro Maeda

An image forming apparatus includes an image bearing member to bear a toner image charged with a predetermined polarity, and a power source to apply a bias to a transfer portion to transfer the toner image from the image bearing member to a recording medium, a polarity of the bias being changed alternately. The toner image formed with toner of a plurality of colors is transferred in a color mode and the toner image formed with toner of a single color is transferred in a monochrome mode. The bias includes a peak voltage with a polarity that returns toner from the recording medium to the image bearing member. An absolute value of the peak voltage in the color mode is equal to or greater than an absolute value of the peak voltage in the monochrome mode.

Image forming apparatus with a controller to set transfer bias

An image forming apparatus includes an image carrier that carries an electrostatic latent image; a developing unit that develops the electrostatic latent image using a toner; an intermediate transfer body onto which toner image is transferred; a secondary transfer member that comes in contact with a surface of the intermediate transfer body; a power supply that outputs a voltage for transferring the toner image on the intermediate transfer body onto a recording member; and a protective agent supply unit that applies a protective agent including zinc stearate and boron nitride onto a surface of the image carrier. The voltage is alternatively switched in a transfer direction and an opposite direction. The voltage in the transfer direction enables transfer of the toner image from the intermediate transfer body to the recording member, and the voltage in the opposite direction has polarity opposite to polarity of the voltage in the transfer direction.

Image forming apparatus

An image forming apparatus includes a transfer device to transfer a toner image from an image bearing member onto a recording medium, disposed opposite the image bearing member, a transfer bias power source to apply, between the image bearing member and the transfer device, a superimposed transfer bias in which a direct current (DC) component and an alternative current (AC) component are superimposed to transfer the toner image borne on the image bearing member to the recording medium, and a controller to change the superimposed bias that the transfer bias power source applies. The controller changes the levels of the DC component and the AC component of the superimposed transfer bias in a color mode from that in a monochrome mode to secure a return electric field in the superimposed transfer bias by which the toner is returned from the recording medium to the image bearing member.

An image forming apparatus includes an image bearing member to bear a toner image on a surface thereof, a transfer device to transfer the toner image onto a recording medium, and a transfer bias power source to apply to the transfer device a superimposed transfer bias in which an alternating current (AC) component is superimposed on a direct current (DC) component in a superimposed transfer mode to transfer the toner image. The superimposed transfer bias has a waveform in which a first polarity in a direction of transferring the toner image onto the recording medium and a second polarity opposite the first polarity switch alternately. The superimposed transfer bias is output such that a standard value of each of the DC component and the AC component is multiplied by a respective correction ratio, and the correction ratio of the DC component is different from that of the AC component.

An image forming apparatus includes an image bearing member, a transfer member disposed facing the image bearing member to form a transfer region therebetween, a transfer bias application device to apply to the transfer region a transfer bias including a direct current (DC) component and an alternating current (AC) component to transfer the toner image onto the recording medium as the recording medium passes through the transfer region, and a controller operatively connected to the transfer bias application device to allow, during a bias change period in a sheet absent period in which the image bearing member rotates and no recording medium passes through the transfer region, the transfer bias application device to selectively apply to the transfer region one of the transfer bias without the AC component and the transfer bias with a peak-to-peak voltage of the AC component less than that applied in image formation.

Image forming apparatus and transfer bias application device therein

A transfer device includes a transfer bias power source, a switching device, and a sheet dependent condition setting device. The transfer bias power source applies to a transfer member, based on sheet dependent conditions for a recording medium onto which a toner image is transferred, one of a DC transfer bias and a superimposed transfer bias including an alternating current (AC) component superimposed on a DC component. The switching device switches a transfer mode between a DC transfer mode in which the DC transfer bias is applied to the transfer device and a superimposed-bias transfer mode in which the superimposed transfer bias is applied to the transfer device. The sheet dependent condition setting device sets arbitrarily at least one of the sheet dependent conditions for the recording medium at the superimposed-bias transfer mode. The sheet dependent conditions include a DC component value and an AC component value.

Transfer device and image forming apparatus including same

An image forming apparatus includes a transfer device to transfer a toner image formed on an image bearing member onto a recording medium, a sheet separation device to separate the recording medium from the image bearing member, a sheet separation bias application device to apply to the sheet separation device a sheet separation bias in which an alternating current (AC) component is superimposed on a direct current (DC) component, and a transfer bias application device to selectively apply to the transfer device one of a DC transfer bias having a DC component and a superimposed transfer bias in which an AC component is superimposed on a DC component. Upon application of the superimposed transfer bias to the transfer device, the sheet separation bias applied to the sheet separation device is changed from the sheet separation bias applied upon application of the DC transfer bias to the transfer device.

A transfer device including an image carrier; a transfer member disposed facing the image carrier; a transfer electrical field generator including a direct-current (DC) power source to generate a DC voltage and an alternating current (AC) power source to generate an AC voltage; and a controller. The transfer electrical field generator forms the transfer electrical field between the image carrier and the transfer member using the DC voltage and the AC voltage, to transfer the toner image on the image carrier, charged to a predetermined polarity, onto the recording medium. The controller controls the AC voltage source so that, the AC voltage output from the AC voltage source when a leading edge of the recording medium is positioned in the transfer electrical field is set larger than the AC voltage when the portion of the recording medium other than the leading edge is positioned in the transfer electrical field.

Transfer device and image forming apparatus

An image forming apparatus includes an image bearing member, an image forming unit for forming a toner image and a toner pattern comprising toner not to be transferred onto a recording medium for adjustment of a density of toner on a surface of the image bearing member, a nip forming member contacting the surface of the image bearing member to form a transfer nip therebetween, a transfer bias applicator for applying a transfer bias in which an alternating current component and a direct current component are superimposed to transfer the toner image onto the recording medium in the transfer nip, a first cleaning device to mechanically remove toner remaining on the image bearing member after passing through the transfer nip. The transfer bias applicator applies a charge eliminating bias to remove charge from toner in the toner pattern when the toner pattern passes through the transfer nip.

An image forming apparatus includes an image carrier; a facing member facing the image carrier via a transfer position; a power supply to output a voltage between a first position on the image carrier side and a second position on the facing member side; a resistance detector to detect electrical resistance between the first position and the second position via the transfer position; and a controller to switch between a first transfer mode in which the power supply outputs a direct current voltage, and a second transfer mode in which the power supply outputs a superimposed voltage. When a toner image on the image carrier is transferred onto a recording medium at the transfer position, the controller selects either the first transfer mode or the second transfer mode. When the resistance detector detects the electrical resistance, the controller selects the first transfer mode.

An image forming apparatus includes a transfer unit configured to transfer a toner image onto a recording medium; a power supply unit configured to output one of an alternating-current-based voltage including at least an alternating-current voltage and a direct-current voltage to the transfer unit; and a power supply control unit configured to cause the power supply unit to start switching to the alternating-current-based voltage a first time after the power supply unit stops outputting the direct-current voltage in the case that output of the power supply unit is switched to the alternating-current-based voltage, and cause the power supply unit to start switching to the direct-current voltage a second time after the power supply unit stops outputting the alternating-current-based voltage in the case that output of the power supply unit is switched to the direct-current voltage. The second time is longer than the first time.

Image forming apparatus, image forming system, and transfer method

An image forming apparatus, includes an image bearer to bear a toner image; a transfer member to transfer the toner image; a transfer bias applicator to apply a transfer bias to the transfer member, the transfer bias applicator including a direct current voltage source to apply a direct current transfer bias constituted by a direct current voltage to the transfer member; and a superimposed voltage source to apply a superimposed transfer bias in which an alternating current voltage is superimposed on a direct current voltage to the transfer member; and a controller to switch between a direct current transfer mode during which the direct current transfer bias is applied to transfer the toner image and a superimposed transfer mode during which the superimposed transfer bias is applied to transfer the toner image while the direct current voltage source and the superimposed voltage source are off.

An image forming apparatus includes a controller and a transfer device including a power source to output a superimposed bias in which an AC voltage is superimposed on a DC voltage, a first electrode, a second electrode disposed opposite the first electrode with an image bearing member interposed therebetween to form a transfer electric field to transfer a toner image on the image bearing member to a recording medium. The controller including a CPU adjusts the transfer electric field and a transfer speed. One of the first electrode and the second electrode is connected to the power source, and the other is grounded. The controller adjusts the transfer speed such that in a case in which an oscillating electric field of the transfer electric field is strong, a maximum transfer speed is slower than the maximum transfer speed in a case in which the oscillating electric field is weak.

Image forming apparatus which uses an AC voltage and/or a DC voltage at a transfer nip depending on a surface roughness of a recording sheet

An image forming apparatus includes an image bearing member to bear a toner image on a surface thereof, a transfer unit including a transfer device to transfer the toner image onto a recording medium, disposed opposite the image bearing member, a direct current (DC) power source to apply, between the image bearing member and the transfer device, a DC bias to form a first transfer electric field to transfer the toner image onto the recording medium, and a power supply module detachably attachable relative to the image forming apparatus. The power supply module includes an AC-DC superimposed bias power source to apply, between the image bearing member and the transfer device, a superimposed bias in which an alternating voltage is superimposed on a DC voltage to form a second transfer electric field to transfer the toner image onto the recording medium.

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Tokyo, Japan

Hiromi Ogiyama