Belt conveyor unit and image forming apparatus including same

A belt conveyor unit, comprising:

• a belt formed into an endless loop;
• a plurality of rollers around which the belt is rotatably entrained, the plurality of rollers including at least a first roller, a second roller disposed opposite the first roller via the belt, and a third roller other than the first roller and the second roller;
• and
• a belt alignment device including a shaft moving device to tilt a rotary shaft of the third roller upon receiving a moving force of the belt moving in a width direction of the belt in an axial direction of the rotary shaft to adjust displacement of the belt within a permissible range,
• the shaft moving device including
• an axial-direction displacement member disposed at an end of the rotary shaft of the third roller to move to a first side in the width direction of the belt along the rotary shaft of the third roller upon receiving the moving force of the belt, the axial-direction displacement member including a slanted surface, and
• a fixation member to contact the slanted surface from the first side in the width direction of the belt,
• wherein as the axial-direction displacement member receives the moving force of the belt moving in the width direction of the belt and moves in accordance with the slanted surface relative to the fixation member, the end of the rotary shaft of the third roller is displaced so as to tilt the rotary shaft of the third roller,
• wherein a maximum amount of belt displacement in the width direction of the belt is adjusted by the axial-direction displacement member such that the maximum amount of belt displacement is substantially the same as a width of the slanted surface in the width direction of the belt, and the following relation is satisfied:
• Z>2X+Y,
• where X is the maximum amount of the belt displacement on one side in the width direction of the belt, Y is a width of the belt in the axial direction of the rotary shaft, and Z is a width of the second roller in the width direction of the belt.