Image forming apparatus and transfer device thereof

An image forming apparatus, comprising:

• a plurality of developing units, each of the plurality of developing units including a photosensitive member respectively and being configured to supply developer to the corresponding photosensitive member so as to form visible images;
• a transfer belt arranged to come into contact with the plurality of photosensitive members to allow the visible images formed on the plurality of photosensitive members to be transferred to and overlap one another on the transfer belt, an inner surface of the transfer belt being rotatably supported by at least two rollers;
• at least one sensor to sense a mark formed on the transfer belt;
• and
• a supporting unit to support the transfer belt at a position corresponding to the at least one sensor so as to apply a tensile force to the transfer belt,
• wherein the supporting unit includes a first supporting portion arranged to press and support the inner surface of the transfer belt, and a second supporting portion spaced apart from the first supporting portion in a rotating direction of the transfer belt and protruding farther toward the transfer belt than the first supporting portion to press and support the inner surface of the transfer belt simultaneously with the first supporting portion.

A transfer device to be mounted in an image forming apparatus including at least one sensor, the transfer device comprising:

• at least two rollers;
• a transfer belt including a sensing region to be sensed by the at least one sensor and rotatably supported by the at least two rollers;
• and
• a supporting plate arranged to support an inner surface of the transfer belt so as to apply a tensile force to the transfer belt,
• wherein the supporting plate includes a first supporting portion arranged to come into contact with the transfer belt at a position upstream of the sensing region in a rotating direction of the transfer belt, a second supporting portion arranged to come into contact with the transfer belt at a position downstream of the sensing region in the rotating direction of the transfer belt, and a non-contact portion spaced apart from the inner surface of the transfer belt between the first supporting portion and the second supporting portion, and
• wherein the second supporting portion protrudes farther toward the transfer belt than the first supporting portion.