Abstract: An image forming apparatus includes a photosensitive member, a charging member for electrically charging the photosensitive member to a first polarity, an intermediary transfer belt, a transfer member, a constant-voltage element, a voltage source, and a controller for executing an adjusting operation for applying at least a voltage of a second polarity, opposite to the first polarity from the voltage source to the transfer member during non-image formation in which both of primary transfer and secondary transfer are not effected. When the voltage of the second polarity is applied from the voltage source to the transfer member in the adjusting operation, the controller continuously applies the voltage for a time corresponding to a substantially integer multiple of a time required for one full turn of the photosensitive member.

Abstract: In an image forming apparatus including a power source for forming a secondary-transfer electric field at a secondary-transfer position and for forming a primary-transfer electric field at a primary-transfer position by applying a voltage to a transfer member to pass a current through a constant-voltage element, a potential of an image portion is controlled depending on a detection result of a detecting member.

Abstract: In a constitution in which a power source exclusively for primary-transfer is omitted and a predetermined voltage is generated in an intermediary transfer member, in a test mode in which a test voltage is applied to a secondary-transfer member in advance in order to obtain a proper secondary transfer voltage, in the case where the test voltage is low, a proper secondary-transfer voltage cannot be obtained in some cases. In a period of the test mode, the power source is controlled in order to maintain a Zener breakdown voltage, so that the proper secondary-transfer voltage can be obtained.

Abstract: In a constitution of primary-transfer-high-voltage-less in which a power source dedicated to primary-transfer, in the case where voltage applications for determining primary-transfer and secondary-transfer voltages are carried out concurrently, there is a possibility of improper primary-transfer. The possibility is decreased by controlling a power source so that a voltage drop of a Zener diode maintains a Zener breakdown voltage.

Abstract: In a constitution of primary-transfer-high-voltage-less in which a power source dedicated to primary-transfer, in the case where voltage applications for determining primary-transfer and secondary-transfer voltages are carried out concurrently, there is a possibility of improper primary-transfer. The possibility is decreased by controlling a power source so that a voltage drop of a Zener diode maintains a Zener breakdown voltage.

Abstract: In a constitution in which a power source exclusively for primary-transfer is omitted and a predetermined voltage is generated in an intermediary transfer member, in a test mode in which a test voltage is applied to a secondary-transfer member in advance in order to obtain a proper secondary transfer voltage, in the case where the test voltage is low, a proper secondary-transfer voltage cannot be obtained in some cases. In a period of the test mode, the power source is controlled in order to maintain a Zener breakdown voltage, so that the proper secondary-transfer voltage can be obtained.

Abstract: In a constitution in which a power source exclusively for primary transfer is omitted and a predetermined voltage is generated in an intermediary transfer member by a constant-voltage element, a high power source voltage more than necessary is applied in order to avoid primary transfer defect, so that a transfer member is deteriorated by energization in some cases. By detecting a current flowing into the constant-voltage element, it becomes possible to obtain a minimum power source voltage at which the intermediary transfer member is capable of maintaining a predetermined voltage, so that it is possible to avoid the energization deterioration of the transfer member.

Abstract: An image forming apparatus includes a movable intermediary transfer member, a first photosensitive member contacting an outer surface of the intermediary transfer member to form a first nip, a second photosensitive member provided in a downstream direction of the first photosensitive member and contacting the outer surface of the intermediary transfer member to form a second nip, a first transfer roller contacting an inner surface of the intermediary transfer member to form a first contact portion, and a second transfer roller contacting the inner surface of the intermediary transfer member to form a second contact portion. A length of the second contact portion is longer than a length of the first contact portion, measured in the moving direction.

Abstract: An image forming apparatus includes: an image bearing member; an electrostatic image forming unit; a developing unit; an intermediary transfer member; a rotatable secondary transfer member; a constant voltage element; a voltage source; and a controller. The apparatus is operable in a lowering mode in which a secondary transfer electric field in a trailing end region of a recording material passing through a secondary transfer position with respect to a recording material feeding direction is made lower than the secondary transfer electric field in a region from a leading end to the trailing end region of the recording material. The controller sets a toner image distance so as to be longer than the toner image distance when the operation in the lowering mode is not performed to prevent a toner image from being primary-transferred in a period in which the secondary transfer electric field is lowered.

Abstract: An image forming apparatus includes a photosensitive drum for bearing a toner image, a rotatable endless belt provided so that its outer surface opposes the drum, and a rigid transfer roller, provided so as to contact an inner surface of the belt, for transferring the toner image from the drum onto the belt or a recording material conveyed by the belt. A coefficient of static friction of a surface of the transfer roller is smaller than that of the inner surface of the belt. In addition, a stretching roller is provided so as to contact the inner peripheral surface of the belt for stretching the belt, with a coefficient of static friction of a surface of the stretching roller being larger than that of the inner peripheral surface of the belt. A cleaning member cleans the surface of the stretching roller.

Abstract: In an image forming apparatus including a power source for forming a secondary-transfer electric field at a secondary-transfer position and for forming a primary-transfer electric field at a primary-transfer position by applying a voltage to a transfer member to pass a current through a constant-voltage element, a potential of an image portion is controlled depending on a detection result of a detecting member.

Abstract: In a constitution provided with no primary-transfer roller, in order to ensure a contact length between each of photosensitive drums and an intermediary transfer belt, the photosensitive drums are disposed in entering amounts at a plurality of levels with respect to a stretching surface of the intermediary transfer belt, and therefore an apparatus is upsized in a height direction. In order to avoid this, four image bearing members are arranged, along the intermediary transfer belt, in the same entering amount with respect to the stretching surface of the intermediary transfer belt, and a depressing member for depressing a belt surface between two central image bearing members toward an outside is provided.

Abstract: In a constitution in which a power source exclusively for primary transfer is omitted and a predetermined voltage is generated in an intermediary transfer member by a constant-voltage element, a high power source voltage more than necessary is applied in order to avoid primary transfer defect, so that a transfer member is deteriorated by energization in some cases. By detecting a current flowing into the constant-voltage element, it becomes possible to obtain a minimum power source voltage at which the intermediary transfer member is capable of maintaining a predetermined voltage, so that it is possible to avoid the energization deterioration of the transfer member.

Abstract: In a constitution in which a power source exclusively for primary-transfer is omitted and a predetermined voltage is generated in an intermediary transfer member, in a test mode in which a test voltage is applied to a secondary-transfer member in advance in order to obtain a proper secondary transfer voltage, in the case where the test voltage is low, a proper secondary-transfer voltage cannot be obtained in some cases. In a period of the test mode, the power source is controlled in order to maintain a Zener breakdown voltage, so that the proper secondary-transfer voltage can be obtained.

Abstract: In a constitution of primary-transfer-high-voltage-less in which a power source dedicated to primary-transfer, in the case where voltage applications for determining primary-transfer and secondary-transfer voltages are carried out concurrently, there is a possibility of improper primary-transfer. The possibility is decreased by controlling a power source so that a voltage drop of a Zener diode maintains a Zener breakdown voltage.

Abstract: A charge elimination needle is set at a predetermined position (first position) when a recording material is separated by utilizing the curvature of a separation stretching roller without using a separation assist roller, and at a position (second position) higher than the first position when the recording material is separated by using the separation assist roller.

Abstract: An image forming apparatus includes an image bearing member; toner image forming portion for forming a toner image on the image bearing member; a transfer member for transferring the toner image from the image bearing member onto a transfer material; a cleaning blade for removing a toner remaining on the image bearing member after transfer while being contacted to the image bearing member; a rotatable member, provided upstream of the cleaning blade, for carrying the toner and rotationally sliding on the image bearing member; a separating mechanism for removing the toner from the rotatable member in contact with the rotatable member, wherein the separating mechanism includes a toner sump for accumulating the toner in an area adjacent to the rotatable member so that the toner removed from the rotatable member is suppliable to the rotatable member; and a controller for controlling at least one of the toner image forming portion and rotatable member so that an amount of the toner in the toner sump is estimated an

Abstract: An image forming apparatus includes: a photosensitive drum for bearing a toner image; a rotatable endless belt provided so that its outer surface opposes the drum; a rigid transfer roller, provided so as to contact an inner surface of the belt, for transferring the toner image from the drum onto the belt or a recording material conveyed by the belt by being supplied with a transfer bias, wherein a coefficient of static friction of a surface of the transfer roller is smaller than that of the inner surface of the belt; a stretching roller, provided so as to contact the inner peripheral surface of the belt, for stretching the belt, wherein a coefficient of static friction of a surface of the stretching roller is larger than that of the inner peripheral surface of the belt; and a cleaning member for cleaning the surface of the stretching roller.

Abstract: An image forming apparatus includes a movable intermediary transfer member; a first photosensitive member forming a first nip with the intermediary transfer member; a second photosensitive member forming a second nip with the intermediary transfer member; a first transfer roller contacting the intermediary transfer member to form a first contact portion at a position away from the first nip toward downstream; and a second transfer roller contacting the intermediary transfer member to form a second contact portion at a position away from the second nip toward downstream; wherein a length of the second contact portion is longer than a length of the first contact portion, measured in the moving direction.

Abstract: A charge elimination needle is set at a predetermined position (first position) when a recording material is separated by utilizing the curvature of a separation stretching roller without using a separation assist roller, and at a position (second position) higher than the first position when the recording material is separated by using the separation assist roller.