Image forming apparatus

An image forming apparatus comprising:

• an image forming unit configured to form an image on a sheet at an image forming position;
• a registration roller pair positioned upstream of the image forming position in a conveyance path of the sheet, and configured to convey the sheet to the image forming position such that the image is formed on the sheet;
• an upstream roller pair positioned upstream of the registration roller pair in the conveyance path, and configured to convey the sheet to the registration roller pair;
• a detection unit configured to detect a leading edge of the sheet at a detecting position between the registration roller pair and the image forming position in the conveyance path;
• a driving device configured to drive the registration roller pair and the upstream roller pair;
• and
• a control unit configured to control the driving device,
• wherein the control unit is configured to execute an accuracy priority mode and a speed priority mode selectively,
• wherein, in the accuracy priority mode,
• after the leading edge of the sheet conveyed by the upstream roller pair has abutted against the registration roller pair that was stopping, the control unit is configured to start rotation of the registration roller pair to convey the sheet while accelerating a conveyance speed of the sheet to a first speed within a range slower than a process speed of the image forming unit, and
• after the leading edge of the sheet has been detected by the detection unit, the control unit is configured to accelerate the conveyance speed from the first speed to a second speed faster than the first speed to convey the sheet to the image forming position,
• wherein, in the speed priority mode,
• after the leading edge of the sheet conveyed by the upstream roller pair has abutted against the registration roller pair that was stopping, the control unit is configured to start rotation of the registration roller pair to convey the sheet while accelerating the conveyance speed to a third speed faster than the process speed, and
• after the leading edge of the sheet has been detected by the detection unit, the control unit is configured to decelerate the conveyance speed from the third speed to a fourth speed that is slower than the third speed and is the process speed or faster to convey the sheet to the image forming position, and
• wherein, during execution of the accuracy priority mode,
• in a case where a time from start of the rotation of the registration roller pair to detection of the leading edge of the sheet by the detection unit is a first time, a time from the detection of the leading edge of the sheet by the detection unit to reach of the conveyance speed to the second speed is a second time, and,
• in a case where a time from the start of the rotation of the registration roller pair to the detection of the leading edge of the sheet by the detection unit is a third time, the time from the detection of the leading edge of the sheet by the detection unit to the reach of the conveyance speed to the second speed is a fourth time,
• the third time is longer than the first time and the fourth time is shorter than the second time.