An image forming apparatus includes the following, a pair of first conveying rollers, a pair of second conveying rollers, a driver which rotates and drives the second conveying rollers by a command value; and a controller which is able to control the driver to perform constant speed control to rotate the pair of second conveying rollers at a constant speed and to perform constant torque control to rotate the pair of second conveying rollers at a constant torque. When the constant torque control is performed, the controller starts the constant torque control with a predetermined initial torque. Based on sheet interval torque detected in a sheet interval term in which the pair of second conveying rollers do not sandwich and convey a sheet after the first sheet reaches the pair of second conveying rollers, the controller corrects the initial torque and calculates a command value for the next sheet.

A printing apparatus comprises a conveyance control unit which controls conveyance of printing sheets so that a trailing edge of a preceding sheet as a printing sheet precedingly fed from the stacking unit and a leading edge of a succeeding sheet as a printing sheet succeedingly fed from the stacking unit overlap each other; and a skew correction unit which performs skew correction of the succeeding sheet while the succeeding sheet overlaps the preceding sheet by the conveyance control unit. The skew correction unit makes the leading edge of the succeeding sheet abut against the conveyance roller during a time from an end of a last line feed operation by the conveyance roller for printing on the preceding sheet by the printing unit to start of a next conveyance operation.

A sheet conveyance device includes a conveyance roller pair to convey a sheet, a skew correction roller pair to correct a skew of the sheet in a state in which the skew correction roller pair is being stopped, first and second conveyance guides, and a protrusion. The first conveyance guide includes a bend contact portion to come into contact with a portion forming a bend on the first surface of the sheet. The second conveyance guides the sheet. The protrusion is disposed between the skew correction roller pair and the bend contact portion to come into contact with the first surface of the sheet. The protrusion protrudes toward the second conveyance guide from the first conveyance guide in a manner as to intersect with a straight line connecting two nip portions and the bend contact portion in a cross section perpendicular to a width direction.

A sheet conveyance device includes a conveyance roller pair. A skew correction roller pair conveys the sheet after contacting two nip portions, and a sheet skew is corrected in a state in which the skew correction roller pair is being stopped. The sheet having a toner image is bent by a first conveyance guide such that a sheet first surface becomes an inside surface. The sheet is bent by the first and second conveyance guides to cause the sheet first surface to be the inside surface and a sheet second surface to be an outside surface. The skew correction roller pair includes two first rotary members of a first roller. A second roller and the two first rotary members form the two nip portions. The second roller and the first conveyance guide contact the sheet first surface. The first roller and the second conveyance guide contact the sheet second surface.

When an open hole is detected at the front end of a sheet at a conveyance start position, a registration operation to correct a tilt posture of the sheet is avoided, and the present velocity is retrained to convey the sheet without temporarily stopping the sheet having the tilt posture.

A sheet conveying device includes a first sheet conveyance passage, a second sheet conveyance passage, a pair of sheet conveying rollers, and a movable member. The second sheet conveyance passage is different from the first sheet conveyance passage. The pair of sheet conveying rollers includes two rollers configured to hold a sheet passing the first sheet conveyance passage. The movable member is configured to convey the sheet passing the second sheet conveyance passage. The two rollers are configured to be separated from each other along with movement of the movable member.

A test chart is obtained by printing a test chart image using an image forming apparatus for skew measurement of the image forming apparatus. The test chart includes a first scale image that includes a scale along a secondary scanning direction and a second scale image that includes a scale along the secondary scanning direction. The first and second scale images are arranged along a primary scanning direction. When a top-end part of the test chart is folded back, a top end of the test chart indicates different values from each other on the first and second scale images in accordance with a skew angle.

A printing apparatus can be downsized while degradation in the print quality can be suppressed. To perform skew correction on a second print medium on which printing is to be performed subsequent to a first print medium, a first conveying unit disposed upstream of the printing position where the printing unit performs printing on the print medium is stopped. Then, driving and stopping of third conveying unit disposed downstream of a second conveying unit is controlled, depending on whether the first print medium after printing has already passed by the second conveying unit when the first conveying unit is stopped, the second conveying unit being driven by the same driving source as that for the first conveying unit and being disposed downstream of the printing position.

A cleaning device cleans a surface of a sheet conveyance member which conveys a sheet in an image forming apparatus that executes image forming processing using a recording material, the surface carrying a solid substance that originates from the recording material and that adheres to the surface. The cleaning device includes a cleaning member including a contact surface configured to come in contact with the surface of the sheet conveyance member. The contact surface is an irregular surface rougher than the surface of the sheet conveyance member. At cleaning of the surface, the cleaning member makes a relative movement to the surface of the sheet conveyance member. The irregular surface is an irregular surface configured to take away the solid substance adhering to the surface of the sheet conveyance member when the cleaning member makes the relative movement.

A sheet conveyance device includes a conveyance roller pair to convey a sheet, a skew correction roller pair to correct a skew of the sheet in a state in which the skew correction roller pair is being stopped, first and second conveyance guides, and a protrusion. The first conveyance guide includes a bend contact portion to come into contact with a portion forming a bend on the first surface of the sheet. The second conveyance guides the sheet. The protrusion is disposed between the skew correction roller pair and the bend contact portion to come into contact with the first surface of the sheet. The protrusion protrudes toward the second conveyance guide from the first conveyance guide in a manner as to intersect with a straight line connecting two nip portions and the bend contact portion in a cross section perpendicular to a width direction.