Image forming apparatus

An image forming apparatus comprising:

• an image forming unit configured to form an image on a sheet;
• a conveyance roller configured to convey, after inverting a front and a back of the sheet with a first surface on which the image forming unit has formed an image, the sheet to the image forming unit;
• a motor configured to drive the conveyance roller;
• a gear train configured to transmit driving force of the motor to the conveyance roller;
• a detection unit configured to detect driving current flowing through a wound wire of the motor;
• a phase determination unit configured to determine a rotation phase of a rotor of the motor based on the driving current detected by the detection unit;
• and
• a control unit having a first control mode in which vector control for controlling driving current flowing through the wound wire of the motor is performed based on a torque current component which generates torque in the rotor and is expressed in a rotating coordinate system with the rotation phase determined by the phase determination unit as a reference, and a second control mode in which driving current flowing through the wound wire is controlled based on current with a magnitude determined in advance,
• wherein the control unit rotates the conveyance roller in a predetermined direction by rotating the rotor in a first direction, and rotates the conveyance roller in a direction opposite to the predetermined direction by rotating the rotor in a second direction opposite to the first direction,
• wherein the control unit starts controlling the driving current in the second control mode, and then switches, in response to a value corresponding to a rotation speed of the rotor having reached a target speed, a control mode for controlling the driving current from the second control mode to the first control mode, and
• wherein the target speed is a speed which corresponds to a speed when the conveyance roller conveys the sheet and is a constant value.