A combination of a fixing device and a sheet jamming determination device comprising:
- the fixing device comprising:
- a frame;
- a pair of conveyer rollers including an upper roller and a lower roller;
- a pair of fixing rollers rotatably supported to the frame, and positioned upstream of the pair of conveyer roller in a sheet feeding direction;
- a lower holding member vertically movably supported to the frame and rotatably supporting the lower roller
- an upper holding member pivotally movably supported to the frame and movable to either one of a first position and a second position in synchronism with movement of the lower holding member, the upper holding member rotatably supporting the upper roller maintaining a contact of the upper roller with the lower roller;
- and
- a sheet guide section having an upstream end portion pivotally movable relative to the frame and a downstream end portion pivotally movable about an axis of the upper roller to change a posture of the sheet guide section;
- and
- the sheet jamming determination device comprising:
- a position detector that detects a position of the upper holding member;
- a first sheet sensor that detects passing of the sheet at a first fixed position upstream of the pair of fixing rollers in the sheet feeding direction;
- a second sheet sensor that detects arrival of the sheet at a second fixed position downstream of the pair of fixing rollers in the sheet feeding direction;
- and
- a control unit to which the position detector, the first sheet sensor and the second sheet sensor are connected, the control unit comprising:
- a processing unit;
- a non-transitory medium, having instructions stored thereon that, when executed by the processing unit, cause the control unit ot function as
- a retrieving part that retrieves a first threshold time period when the position detector detects the first position of the upper holding member, or retrieves a second threshold time period different from the first threshold time period when the position detector detects the second position of the upper holding member;
- and
- a determination part that determines whether or not a first time period starting from a timing of detection by the first sheet sensor and ending at a timing of detection by the second sheet sensor is within the first threshold time period when the position detector detects the first position, or determines whether or not a second time period starting from a timing of detection by the first sheet sensor and ending at a timing of detection by the second sheet sensor is within the second threshold time period when the position detector detects the second position.