An image forming apparatus includes a member-to-be-cleaned, a first cleaner unit including a first attracting member, a first rotatable member and a first blade member, a second cleaner unit including a second attracting member, a second rotatable member and a second blade member, and a feeding member. The feeding member rotates around its rotational axis and is provided vertically below a first position where a toner drops by gravitation and a second position where the toner drops by gravitation. The feeding member is disposed such that vertical lines passing through the first position and the second position cross the feeding member.

A tension applying device that applies tension to a strip-shaped body supported on a support member, the tension applying device is provided with a moving body that supports the support member, a holding body movably supporting the moving body in a direction in which the tension is applied to the strip-shaped body, a tension spring exerting the tension to the strip-shaped body, a first spring support portion disposed in the holding body and supporting one end of the tension spring, a second spring support portion disposed in the moving body in order to support the other end of the tension spring and disposed on an upstream side from the first spring support portion in the direction in which the tension is applied, and an opening formed in the holding body and in a position corresponding to the second spring support portion.

An application voltage to a conveyance auxiliary roller is controlled to have a polarity opposite to a charged polarity of toner before a front end of a sheet makes contact with the conveyance auxiliary roller, and the application voltage to the conveyance auxiliary roller is switched to a ground voltage before a rear end of the sheet is separated from the conveyance auxiliary roller after being separated from a conveying belt.

A belt device for an image forming apparatus, includes an endless belt; a first and second support rollers, each including a rotary shaft, that support the belt with tension; a contacted member that contacts the belt; a shaft displacement device to displace any of the rotary shafts of the support rollers; and a main rotary shaft disposed at a side of the rotary shaft of the first support roller moved by the shaft displacement device along a stretching direction of the stretched surface of the endless belt that the contacted member contacts, relative to a contact portion between the endless belt and the contacted member, and at an opposite side of the contacted member in a direction perpendicular to the stretching direction of the endless belt. As the first support roller and the second roller rotate about the main rotary shaft, the endless belt is separated from the contacted member.

A fixing portion is provided with a fixing roller, a heating roller having a heat source, a fixing belt stretched between the fixing roller and the heating roller, and a pressurizing roller that is brought into pressure contact with the fixing roller across the fixing belt and forms a nip portion into which a sheet of paper is conveyed between the fixing belt and the pressurizing roller. The fixing portion is further provided with a pad that has a contact surface portion in contact with the inner peripheral surface of the fixing belt, and a biasing member that biases the pad in a direction in which the contact surface portion is brought into pressure contact with the inner peripheral surface of the fixing belt. The pad is configured so as to pivot about the rotating shaft of the heating roller.

A first stretch roller stretches a secondary transfer belt at a position where a tip in a conveying direction of a recording medium being conveyed through a secondary transfer portion can reach. The first stretch roller has a circumferential surface formed into a normal crown shape in which a straight area where a diameter of the first stretch roller is constant is provided at a center part in a direction of axis of rotation. A second stretch roller has a circumferential surface formed into an inverse crown shape in which a straight area where a diameter of the second stretch roller is constant is provided at a center part in a direction of axis of rotation.

A transfer device includes an intermediate transferor and primary transfer sections. The primary transfer sections each includes a primary transferor. The primary transfer sections include a most-upstream primary transfer section and a most-downstream primary transfer section. One of the primary transfer sections is a special-color primary transfer section switchable between the most-upstream primary transfer section and the most-downstream primary transfer section. The primary transferor of each of the most-upstream primary transfer section and the most-downstream primary transfer section is switchable between a contact position at which the primary transferor contacts the latent image bearer and a separation position at which the primary transferor is separated from the latent image bearer. With only the primary transferor of the special-color primary transfer section at the separation position, the primary transferor of any other primary transfer section than the special-color primary transfer section is arranged at the contact position to transfer an image.

A transfer device includes: an endless transfer belt that circulates and receives an image; one image carrier that carries an image and is in contact with an outer circumferential surface of the transfer belt from above; another image carrier that carries an image and is in contact with the outer circumferential surface of the transfer belt from below; one transfer roller that holds the transfer belt with respect to the one image carrier to transfer the image carried on the one image carrier to the transfer belt, the one transfer roller including one cylindrical roller part; and another transfer roller that holds the transfer belt with respect to the other image carrier to transfer the image carried on the other image carrier to the transfer belt, the other transfer roller including another cylindrical roller part. The one roller part and the other roller part protrude at central portions thereof in the axial direction with respect to ends thereof in the axial direction. The amount of protrusion at the central portion of the other roller part is smaller than the amount of protrusion at the central portion of the one roller part.

Provided is a belt driving roller for a belt driving device configured to drive and rotate an endless belt with at least one driving roller of a plurality of rollers over which the belt is hung by its internal surface, wherein the belt driving roller includes an electroviscosity retaining member of which surface viscosity force reversibly changes under an effect of an electric field.

An image forming apparatus includes: an image bearing member; a toner image forming unit; an endless transfer belt; a transfer roller urged from an inner peripheral surface of the transfer belt toward the image bearing member via the transfer belt; a feeding surface forming roller, provided downstream of the transfer roller with respect to a traveling direction of the transfer belt, having such a shape that a diameter at each of end portions is smaller than a diameter at a central portion with respect to a rotational axis direction; and a stretching roller, downstream of the feeding surface forming roller with respect to the traveling direction of the transfer belt, having such a shape that a diameter at each of end portions is larger than a diameter at a central portion with respect to the rotational axis direction.