A belt unit according to an embodiment may include: an endless belt including a first surface and a second surface opposite to the first surface; and a drive roller in contact with the second surface and configured to drive the endless belt. A surface potential of the first surface of the belt is a voltage of not more than 20 volts, 0.1 seconds after an application of a voltage of 6000 volts.

An image forming apparatus employs a constitution in which, in a case that a relative position between an inner roller and an outer member with respect to a circumferential direction of the inner roller is changed in a period after a preceding recording material passes through a transfer portion and until a recording material subsequent to the preceding recording material reaches the transfer portion during execution of a job for forming and outputting images on a plurality of recording materials, a controller controls a position changing mechanism and a contact and separation mechanism so that a separating operation for separating the outer roller from a belt is performed and then the above described relative position is changed.

An intermediate transfer medium onto which a toner image is transferred is provided. The intermediate transfer medium comprises a base layer and an elastic layer overlying the base layer. The elastic layer contains spherical fine particles to form an irregular surface, and the spherical fine particles have a volume resistivity of 1×10.sup.−4 Ω.Math.cm or more and less than 1×10.sup.0 Ω.Math.cm.

A belt driving device includes plural rotating members around which a belt member extends, each rotating member rotating about a rotating shaft; and contact members disposed at both sides of the belt member in a width direction. The rotating members include a first rotating member, having a dimension less than a width of the belt member in a direction of the rotating shaft. Each contact member has a first contact point at which the contact member contacts the belt member and a second contact point closer to a corresponding one of the end portions in the width direction than the first contact point and at which the contact member contacts the belt member such that an angle between the contact member and the rotating shaft at the second contact point is greater than an angle between the contact member and the rotating shaft at the first contact point.

An image forming apparatus which includes a rotary member and a detecting member configured to detect light from a surface of the rotary member. A controller is configured to acquire information relating to a position on the rotary member in a moving direction thereof based on a detection result obtained by the detecting member. The surface of the rotary member has, in a part of the rotary member in its moving direction, an area with a different detection result obtained by the detecting member based on a shape of the surface of the rotary member. The controller acquires the information relating to the position on the rotary member in the moving direction based on the detection result of detecting light from the surface of the rotary member by the detecting member.

A belt driving device includes plural rotating members around which a belt member extends, each rotating member rotating about a rotating shaft; and contact members disposed at both sides of the belt member in a width direction. The rotating members include a first rotating member, having a dimension less than a width of the belt member in a direction of the rotating shaft. Each contact member has a first contact point at which the contact member contacts the belt member and a second contact point closer to a corresponding one of the end portions in the width direction than the first contact point and at which the contact member contacts the belt member such that an angle between the contact member and the rotating shaft at the second contact point is greater than an angle between the contact member and the rotating shaft at the first contact point.

An endless belt includes either a single-layer body including a layer including an imide resin and conductive particles, or a multilayer body including the layer as an outermost layer. The ratio y/x of the layer is 0.8992 or more and 1.0157 or less, where x [log /] is the common logarithm of the surface resistivity of the outer peripheral surface of the layer measured with a ring probe when a voltage of 100 V is applied to the layer for 3 seconds at a load of 1 kg, and y [log .Math.cm] is the common logarithm of the volume resistivity of the layer measured with a ring probe when a voltage of 100 V is applied to the layer for 5 seconds at a load of 1 kg.

A belt unit according to an embodiment may include: an endless belt including a first surface and a second surface opposite to the first surface; and a drive roller in contact with the second surface and configured to drive the endless belt. A surface potential of the first surface of the belt is a voltage of not more than 20 volts, 0.1 seconds after an application of a voltage of 6000 volts.

An image forming apparatus includes: an attachment table to which an object is attached; a transfer unit that transfers an image onto the object; and a transport unit that transports the attachment table along a transport path that has a transport start position on one side relative to the transfer unit and has a transport end position on a same side as the transport start position relative to the transfer unit, the transport path extending beyond the transfer unit and the attachment table being transported so as to turn back at a position beyond the transfer unit.

An image forming apparatus includes: a transport unit that transports a recording medium; a transfer unit that transfers an image formed with particles onto an image formation surface of the recording medium transported by the transport unit by an electric field formed between the transfer unit and the image formation surface by making contact with the image formation surface; and a support unit that supports the recording medium, is transported to the transfer unit together with the recording medium by the transport unit, and is not directly conductive with the transfer unit.