Image forming apparatus, transfer unit thereof, and method of shifting transfer rollers thereof

An image forming apparatus comprising:

• a first photoconductive drum configured to carry a first toner image;
• a second photoconductive drum configured to carry a second toner image;
• a third photoconductive drum configured to carry a third toner image;
• a transfer belt configured to carry the first toner image transferred from the first photoconductive drum at a first nip;
• a first roller configured to take a first position and a second position to regulate the transfer belt;
• a first transfer member configured to contact with the transfer belt to transfer the first toner image from the first photoconductive drum to the transfer belt at the first nip;
• a second roller configured to regulate the transfer belt between the first roller and the first transfer member;
• a second transfer member configured to contact with the transfer belt between the first roller and the second roller to transfer the second toner image from the second photoconductive drum to the transfer belt when the first roller takes the second position, and configured to separate by a distance from the transfer belt regulated between the first roller and the second roller without loosening when the first roller takes the first position;
• and
• a third transfer member configured to contact with the transfer belt between the first roller and the second transfer member to transfer the third toner image from the third photoconductive drum to the transfer belt when the first roller takes the second position, and configured to separate by the distance from the transfer belt regulated between the first roller and the second roller without loosening when the first roller takes the first position.