Abstract: A Zener diode contacts an inner periphery surface of an intermediate transfer belt, and an opposing roller which opposes a detecting member is electrically insulated, in a configuration where transfer is performed at multiple photosensitive drums while an electrical current is applied in a peripheral direction of the intermediate transfer belt.

Abstract: Wheels configured to be supported by a metallic roller on an outside of end portions of a contact area and inside of end portions of the transfer belt in terms of a width direction are provided, and the wheels are formed of a non-conductive resin.

Abstract: A voltage maintenance element is connected to a contact member that contacts a primary transfer surface area of an intermediate transfer belt to which toner images are transferred from a plurality of image carriers between stretch members, in such a way as to prevent the electric potential of the intermediate transfer belt from varying between respective stations.

Abstract: In an image forming apparatus that performs primary transfer by allowing a current to flow to an intermediate transfer belt in the circumferential direction of the belt, the image forming apparatus has a control unit that can execute a second mode in which a second current amount which is larger than a first current amount is supplied from a current supply unit to an intermediate transfer belt and a toner image is primarily transferred only from a first photosensitive body to the intermediate transfer belt. The control unit can adjust surface potentials of the first photosensitive body and a second photosensitive body, and makes the absolute value of the surface potential of the second photosensitive body less than the absolute value of the surface potential of the first photosensitive body when the second mode is executed.

Abstract: A voltage maintenance element is connected to a contact member that contacts a primary transfer surface area of an intermediate transfer belt to which toner images are transferred from a plurality of image carriers between stretch members, in such a way as to prevent the electric potential of the intermediate transfer belt from varying between respective image forming stations.

Abstract: An image forming apparatus includes a resistor in a sheet shape configured to ground a sensor member electrically; a first contact member configured to form a current path between the resistor and the sensor member; and a second contact member configured to form a current path between the resistor and an electrical ground portion. A first contact portion and a second contact portion are arranged so as not to overlap in a thickness direction of the resistor.

Abstract: An image forming apparatus includes a resistor in a sheet shape configured to ground a sensor member electrically; a first contact member configured to form a current path between the resistor and the sensor member; and a second contact member configured to form a current path between the resistor and an electrical ground portion. A first contact portion and a second contact portion are arranged so as not to overlap in a thickness direction of the resistor.

Abstract: An image forming apparatus that adjusts the electric current supplied from a second transfer member to suppress acceleration of abrasion of a photoconductor drum while maintaining the second transfer efficiency at a desired level.

Abstract: An image forming apparatus includes a main body of the apparatus, a plurality of cartridges each including a photosensitive member, and a transfer unit detachably mounted on the main body of the apparatus. The transfer unit includes an endless belt opposing the photosensitive member, a plurality of stretching members configured for stretching the belt, and a frame configured to axially support a plurality of rollers. The frame is provided with a plurality of positioning portions configured to allow abutment of the plurality of cartridges and determine the positions of the plurality of cartridges in the main body of the apparatus.

Abstract: In an image forming apparatus that performs primary transfer by allowing a current to flow to an intermediate transfer belt in the circumferential direction of the belt, the image forming apparatus has a control unit that can execute a second mode in which a second current amount which is larger than a first current amount is supplied from a current supply unit to an intermediate transfer belt and a toner image is primarily transferred only from a first photosensitive body to the intermediate transfer belt. The control unit can adjust surface potentials of the first photosensitive body and a second photosensitive body, and makes the absolute value of the surface potential of the second photosensitive body less than the absolute value of the surface potential of the first photosensitive body when the second mode is executed.

Abstract: A control unit is provided which controls at least one of a first power supply unit (a secondary transfer power supply connected to a secondary transfer roller) and a second power supply unit (high-voltage power supplies connected to a conductive brush and a conductive roller) so that a current supplied to a primary transfer region from a beginning of primary transfer until a beginning of secondary transfer has a magnitude larger than a magnitude of a current supplied to the primary transfer region from a beginning of image formation until the beginning of the primary transfer.

Abstract: It has been difficult to ensure satisfactory secondary transfer performance while ensuring satisfactory primary transfer performance by passing a current in the circumferential direction of an intermediate transfer belt from a current supply member. To satisfy a relationship of Rv>Rs, where Rv is resistance in the thickness direction of an intermediate transfer belt and Rs is resistance in the circumferential direction of the intermediate transfer belt over the distance between an image carrier located most upstream and an image carrier located most downstream in the movement direction of the intermediate transfer belt.

Abstract: A voltage maintenance element is connected to a contact member that contacts a primary transfer surface area of an intermediate transfer belt to which toner images are transferred from a plurality of image carriers between stretch members, in such a way as to prevent the electric potential of the intermediate transfer belt from varying between respective stations.

Abstract: When secondary-transfer residual toner adheres to a brush member, the secondary-transfer residual toner is concentrated on an end of the brush member and it is difficult to uniformly charge the secondary-transfer residual toner. The secondary-transfer residual toner can be recovered to the roots of conductive fibers of the brush member by satisfying the relationship Rb?Ri, where Rb (?) is a resistance value of the brush member and Ri (?) is a resistance value of an intermediate transfer member in an area where the intermediate transfer member is in contact with the brush member.

Abstract: A voltage maintenance element is connected to a contact member that contacts a primary transfer surface area of an intermediate transfer belt to which toner images are transferred from a plurality of image carriers between stretch members, in such a way as to prevent the electric potential of the intermediate transfer belt from varying between respective image forming stations.

Abstract: In an image forming apparatus, a current supply member comes into contact with a belt at a position different from a position of the transfer section in a rotational direction of the belt, and a control unit performs constant current control on the current flowing through the current supply member by setting a predetermined value to a target current value, and can change a first state in which a part of the current supplied to the current supply member flows to a ground side via a constant voltage element, and a second state in which the current supplied to the current supply member does not flow to the ground side via the constant voltage element, by maintaining the constant current control by the predetermined value.

Abstract: An image forming apparatus includes a main body of the apparatus, a plurality of cartridges each including a photosensitive member, and a transfer unit detachably mounted on the main body of the apparatus. The transfer unit includes an endless belt opposing the photosensitive member, a plurality of stretching members configured to stretch the belt, and a frame configured to axially support a plurality of rollers. The frame is provided with a plurality of positioning portions configured to allow abutment of the plurality of cartridges and determine the positions of the plurality of cartridges in the main body of the apparatus.

Abstract: An image forming apparatus includes an apparatus main body, an image bearing member capable of bearing a toner image, a current supply member, and an intermediate transfer unit which is removably mounted to the apparatus main body. When the intermediate transfer unit is attached to the apparatus main body, the intermediate transfer unit includes an endless belt whose outer peripheral surface is configured to contact the current supply member, onto which the toner image is transferred from the image bearing member by current supplied from the current supply member, a contact member configured to contact an inner peripheral surface of the endless belt at a position opposed to the image bearing member through the endless belt, an opposing member configured to contact the inner peripheral surface of the endless belt at a position opposed to the current supply member through the endless belt, and a voltage maintaining element which is connected to the opposing member and the contact member.

Abstract: A high-voltage power source can change a set value of a current to be supplied to an electroconductive brush from a first set current that has been set when the image formation has been started, to a second set current smaller than the first set current, at a previously set timing after the image formation for a recording material has been started. An absolute value of a potential difference between potentials of a photosensitive drum and an intermediate transfer belt, when a secondary transfer residual toner that has been charged by the electroconductive brush to which the second set current has been supplied is positioned in a primary transfer portion, is not larger than an absolute value of a potential difference which is shown when a toner image formed on the photosensitive drum is primarily transferred in the primary transfer portion.

Abstract: In existing image forming apparatuses, it is difficult to maintain each of a primary transfer member and a secondary transfer member at an optimum potential. An image forming apparatus includes a voltage maintenance element connected to a secondary transfer counter roller and a primary transfer member. The voltage maintenance element maintains each of the secondary transfer counter roller and the primary transfer member at a predetermined potential or higher. By using the voltage maintenance element, each of a secondary transfer roller and the primary transfer member is set to an optimum potential by a single transfer power supply.