A semiconductive roller is provided, which includes a tubular main body having a multiplicity of concavities (2) provided in an outer peripheral surface (1) thereof in at least one of circumferentially overlapping relation and axially overlapping relation. The concavities are each gently concave toward a center thereof from an outer periphery thereof. A semiconductive roller production method is also provided, which includes the step of forming the concavities by a laser processing method.

A rotation apparatus includes a first rotating body rotatable; a second rotating body movable to a contact position at which the second rotating body contacts an outer circumferential surface of the first rotating body and a separation position at which the second rotating body is separated from the first rotating body outward in a radial direction of the first rotating body and rotatable in a reverse direction to the rotation direction; a first drive mechanism that rotationally drives the first rotating body at a first circumferential speed and rotates the second rotating body at the contact position; and a second drive mechanism that generates a driving force, rotationally drives the second rotating body at a second circumferential speed lower than the first circumferential speed at the separation position, and applies a resistance force to the first rotating body via the second rotating body at the contact position.

A fixing device includes a fixing belt, a nip pad, a press roller, a driving portion, and a heat generation source. The fixing belt has an endless shape. The nip pad is located on an inner circumferential side of the fixing belt. The nip pad presses the fixing belt. The press roller presses the fixing belt along with the nip pad. The driving portion moves the press roller toward the nip pad. The heat generation source causes the fixing belt to generate heat. A control section controls an image forming section and the fixing device. The nip pad includes a protrusion. The protrusion protrudes toward an outer circumference of the fixing belt and a downstream side of the nip. The control section changes a movement amount of a protrusion to the press roller.

A fixing device includes a heating member configured to heat a toner image on a front surface of a recording medium; a pressing member having an outer circumferential surface formed with a concave portion into which a gripping portion configured to grip a front end side of the recording medium enters, the pressing member being configured to rotate and press the recording medium together with the heating member; a moving portion configured to cause the heating member and the pressing member to relatively move between a position where the heating member comes into contact with the outer circumferential surface of the pressing member directly or via the recording medium and a position where the heating member moves away from the outer circumferential surface of the pressing member when the concave portion passes; and a switching portion configured to switch, between high and low, a load to be applied to a contact portion between the heating member and the outer circumferential surface of the pressing member in accordance with a type of the recording medium or a selection by a user.

A fixing device includes a first rotary body, a second rotary body to contact the first rotary body, and a plain bearing that supports the first rotary body or the second rotary body. One rotary body of the first rotary body and the second rotary body has an outer diameter increasing, while the other rotary body has an outer diameter decreasing, in a curved line from an axial center portion to axial end portions of the first rotary body and the second rotary body at least between the first rotary body and the second rotary body. A recording medium passes between the first rotary body and the second rotary body with a circumferential component of a shear force generated between the first rotary body and the second rotary body by use of the plain bearing being in a range of from 15N to 25N.