Ricoh Company, Ltd.

Tomokazu Takeuchi

Hiromi Ogiyama

Hiroyoshi Haga

Kenji Sengoku

Shinya Tanaka

Masahide Nakaya

Katsuhito Suzuki

Shinji Aoki

Keigo Nakamura

Yasunobu Shimizu

Junpei Fujita

Haruo Iimura

Yasuhiko Ogino

Yuusuke Kohri

Tomonori Maekawa

Shohgo Miura

A transfer device includes a power supply control unit, a direct-current (DC) power supply, an alternating-current (AC) power supply, and a transfer unit. The power supply control unit controls a first control signal for controlling a DC voltage and a second control signal for controlling an AC voltage based on a condition relating to image formation. The DC power supply outputs the DC voltage based on the first control signal. The AC power supply selectively outputs, with a particular waveform, either of the DC voltage output from the DC power supply or a superimposed voltage obtained by superimposing the AC voltage determined based on the second control signal on the DC voltage output from the DC power supply. The transfer unit transfers a developer onto a sheet using a voltage output from the AC power supply.

Transfer device, image forming apparatus, and power supply control method

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

According to an aspect of the present invention, a power supply device includes: a DC power supply that outputs a DC voltage; an AC power supply that outputs any one of the DC voltage and a superimposed voltage being the DC voltage with an AC voltage superimposed thereon; and a bypass capacitor that charges a part of a voltage that is output from the AC power supply. The DC power supply starts outputting the DC voltage in a constant voltage mode and, when a predetermined condition is satisfied, switches from the constant voltage mode to a constant current mode to output the DC voltage in the constant current mode.

Power supply device, image forming apparatus, and voltage output method

A transfer device includes a direct-current (DC) power supply configured to output a DC voltage; an alternating-current (AC) power supply configured to selectively output a superimposed voltage in which an AC voltage is superimposed on the DC voltage output from the DC power supply or the DC voltage output from the DC power supply; and a transfer unit configured to transfer a developer to a sheet using the voltage output from the AC power supply.

Power supply device to selectively output power and transfer device to transfer a toner image to a sheet

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.

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.

Image forming apparatus

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.

Transfer device including a selectively outputting power supply, image forming apparatus including the same, and method of transferring developer to sheet

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.

Power supply module and image forming apparatus including same

An image forming apparatus includes a transfer unit configured to transfer a toner image onto a recording medium; a power supply unit configured to apply one of a superimposed voltage in which an alternating-current voltage and a first direct-current voltage are superimposed and a second direct-current voltage to the transfer unit; and a power supply control configured to, when the power supply unit outputs the superimposed voltage, instruct the power supply unit to output the first direct-current voltage at a first timing, and, when the power-supply unit outputs the second direct-current voltage, instruct the power-supply unit to output the second direct-current voltage at a second timing which is later than the first timing.

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Tokyo, Japan

Tomokazu Takeuchi